AWE_APR_1929 .pdf - JumpJet .info

AMATEUR WIRELESS, APRIL 6, 1923

"BRITAIN'S FAVOURITE THREE -1929 MODEL

Every Azsr

Thursday()

Vol. XIV. No. 356 Saturday, April 6, 1929

RITA1N'SAVOURITE

Registered at the G.P.O. as a Nel...3-ttr

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that thereis only

a differenceof natne

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valveand.

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tor the Ventoneis a perfected

inadeonly

by Nkullard,with,

the wholeNiullard

tradition.arta reptaation

behindit.

"(beeryand practice

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resultsin an increase

in.

volumeequal

to that obtainedby adding,

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-valve.

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call it the Ventooejust to be different,

beatbecause

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brothers.N.B.MullaYd

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The Mallard Wireless Service Co, Ltd., Mullard House, Denmark Street, London, W.C.Z.

Advertisers Appreciate Mention of "A.W." with Your Order

APRIL 6, 1929

THE AINvict1 it I EXPEpts,

LEWCOS COI LS

SIX -PIN COILS

USE THEM

IN

" BRITAIN'S

FAVOURITE

THREE"

ULTRA -SHORT-

WAVE COIL

FIXED POTENTIOMETER

RADIO PRODUCTS

LEWCOS RADIOPRODUCTS FORBETTER RECEPTION.

THE LONDON ELECTRIC WIRE

COMPANY AND SMITHS, LIMITEDCHURCH ROAD, LEYTON, LONDON, E.10

Telephone : Telegrams:Waltharnstow 2531 "Lewcos, Phons. London."

Trade Coanter and Calle Sales :7, PLAYHOUSE YARD, GOLDEN LANE, E.C.1

513 amour Wtraluj.

ENGINEERINGPRECISION . . .Engineering Precision has once againresulted in J.B. Condensers being chosenfor yet another Star Circuit-in fact, it'sno easy matter to -day to find a reallyhigh-class set which does not includethese precision instruments.

This time J.B. Logarithmic Condensers(Plain Type), are used in " Britain'sFavourite Three " De Luxe, as describedin this issue of " Amateur Wireless."These Condensers are the last word inhigh-class design, possessing greatmechanical strength combined with thehighest possible electrical efficiency. Animportant feature of this model is theVariable Friction Brake, by means ofwhich the turning tension of the rotormay be varied to suit individual require-ments, while at the same time the move-ment of this condenser is extraordinarilysmooth.

Prices, complete, 4 in. Bakelite Dial :-.0005 . 11/6.00025

.000310/- .00015

INSTRUMENTS

. 10/610/

Advt. of Jackson Brothers , 72, St. Moms' Street, London, Telephone: flop. 1.637.

To Ensure Speedy Delit4ry, Mention `.`A.W." to Advertisers

entatew Wire65.3 514 APRIL 6, 1929

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Advt.of The Ever Ready Co. (G.B.), Ltd., Hercides Place, London, N.7.You will Help Yourself and Help Us by Mentioning "A.W." to Advertisers

St 50,-,,-.,,,-,,,,,,--),,,,,--..-,,,,,,.,-,,-,--,,,,,,,--,,,,,,t.e73..c_<-.:Itc.-...--1,t,_..-,)-1c,-)Iate7)w-1--)c),--4te7ir.v.._>ttel:1C APRIL 6, 1929 No. 356, Vol. XIV C

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§The Leading Radio Weekly for the Constructor, Listener and Experimenter

= --- Editor : BERNARD E. JONESTechnical Editor : J. H. REYNER, B.Sc., A.M.LE.E. :: Research Consultant: W. JAMES :: Assistant Editor: H. CORBISHLEY §

ricete7)---)clec7.1e-lca-)t,:7)tc)t.4:7)e)--7-1-. t.')r--)t.--)t71wle-.)t--1t.:ItIte7Ite7).+ctoit%)t-oc,tclte%)t-v.,.ett7)c-)t4.2)r---7it.&>0.4n.,.)0

Is There Jamming ?-Fultograph Filmed !-" Hot" News-Exit Jeffrey-The General-Don't Swear !-Next Week

Is There Jamming ?-Why is it thatwhen thinking of towns with "broad-casters in every block" one always startswith New York? Apparently the U.S. hasnot the monopoly of jamming, for theevening paper in Toronto, Ontario, givesevery day the programme of five stationsin Toronto itself, nine stations elsewherein Canada, together with a schedule of theprogrammes of seventy stations in theUnited States.

Fultograph Filmed!-A film entitled:The Fultograph Story has been incor-porated in Pathe Pictorial No. 571. Thishas been booked by over, a thousand'cinemas throughout the country, and isexpected to be showing in most districts,within a week. Incidentally, perhaps allbroadcast picture enthusiasts are not'aware of the fact that experimental testsare being made at the Royal Airship[Works at Carclington in the course of,which weather maps are being trans-mitted by the Fultograph system andreceived in a number of places in thesouth of England. There is obviously a

[big future for this sphere of picture broad-casting.

" Hot" News-And, while on thesubject of Fultographs, a word of praise'must be given to the Wireless Picturespeople for the way in which they arestarting to fulfil their promise about givinglisteners real news pictures. Boat -race photographs were broadcastwithin an hour and a half of therace, you may remember, and even-ing papers contained pictures of theGrand National wired, via Fulto-graph, from Aintree.

Exit Jeffrey-A loss to broad -'casting and a gain to "talkies" isMr. R. E. Jeffrey, who, we learn,has resigned from the staff of theB.B.C. in order to take charge ofthe sound production departmentof British International Pictures,Ltd. Mr. Jeffrey has, of course,been associated with broadcaStingfor the past six years, and the factof his leaving the sphere in whichhe is at present best known will be

The Genera/-A broadcast which willbe of particular interest to all members ofthe Salvation Army is that from 2L0 and

tic471cce7iciw-icar.e7o.ce7icace,lece7ne7e.e7lote7i0§ PRINCIPAL CONTENTS Page §5 515§ 5165

§ 551187 15 519 5§ 523 5ci 524 5

§ 525 §

5 527 §

§ 528 §

§ 531

§ 532 §

§ 534 §

5 537 5

Before its time-a spark transmitter and receiverin use, in 1902, at Streatham Fire Station. A

telephone is now used.

regretted by all listeners. Nevertheless,he should be able to do some good workfor the "talkie" people, and they are cer-tain to be congratulated on the initiativethey show in getting good men like Jeffreywith ready-made experience.

5 \ X on April 7, when General Higgins,the new leader of the Army, will conducta service to be relayed from the CongressHall, Clapto,n, London, E.

Don't Swear!-Has it ever occurredto you when listening to the running com-mentaries, such as the. football broadcastsand the Boat Race relay, what a tempta-tion it is for the commentator to makeejaculations which the microphone andsome of the millions of listeners might notlike? After all we are only human, andit is very natural that a keen sport enthu-siast should forcibly and fiercely vent hisfeelings in ungentlemanly style when, say,a good pass is dropped ! The B.B.C. makesthoughtful provision for this, often, byplacing a large notice, "Don't Swear !" infront of the running commentator's"mike."

A New Rela y!-A clever skit is to begiven on April 9, under the fascinatingtitle of "A relay from the National RadioStation in Erewhonia." This programme,which consists of typical scenes from Britishlife, is said to be founded on a study ofB.B.C. methods made by a NorthernErewhonian representative during a visitto London!

" The Proms."-The B.B.C. has de-cided to hold an eight weeks' season ofPromenade concerts again this year, start-ing on Saturday, August 17, and conclud-

ing on October 12. Sir HenryWood will be the conductor. The" Proms." series is one muchappreciated by listeners-" high,"" mezzo " and " low -brow."

Next Week-So many peoplelike reasonably simple and self-con-tained sets, particularly if electric -light mains can be used, that theAm ATEUR WIRLLESS Technic alStaff is sure next week's set will bea winner. It is a "simplicity" two-valver, working entirely from A.C.mains and using the new directly -heated Valves and a simple rectifierfor H.T. No H.T. batteries to rundown or accumulators to "gophut" just when there is a good

Clcev.lcoicacatoitoice:macatatacac,at&vlwIcioie,.7)0 Programme to be beard

Current Topics ..14 Audiences at Once ..Improving Your PortableElectrical Recording at Home ..On Your Wavelength ..Cutting Out Needle Scratch ..My Wireless Den ..Points About Exponential HornsWithout Fear or FavourBritain's Favourite Three Up-to-dateThe "Arcadian Portable " Afield"A:W." Tests of ApparatusRadiogramsOur Information Bureau

(imam WireiT

RECENTLY I described in AMATEURWIRELESS how land -lines were used

for a giant political" S.B." of speeches fromNewcastle simultaneously to a number ofother towns. From this, shall we say,"modest," beginning the scheme hasgrown until when Mr. Lloyd George spokelast week at the Albert Hall, in London, hiswords were carried to thirteen other towns

DERBY

WOLVERom.

SOUTH,

BOURN

NOITINGHAM

LEICESTER

NORTHAMPTON

FENNY STRRTFORD

MANNIW,TREE

HA LES WORG4

ST ALSRNS

RP MSGATE

0 REPEATERSRELAYS

Map showing the towns in which Mr. LloydGeorge's speech was simultaneously heard

and over L000 miles of special P.O. trunk -lines. Great care was taken to preventinterference or "cross -talk, and repeaters(special valve amplifiers) were inserted atland -line points en route.

The repeaters used on long-distanceland -line are the outcome of workdone on valves and low -frequency amplifiers-another example of the manner in whichthe requirements of broadcasting havestimulated improvements in the techniqueof allied sciences.

In the old days, when there were norepeaters, it would have been practicallyimpossible to relay a speech over morethan a moderate distance and amplify it fora large audience with any degree of success.In the first place, a long line is bound topick up interference from electrical sourcesand tends therefore to be "noisy," clicks

516 APRIL 6, 1929

I AUDIENCESI AT ONCE !

Political Broadcasts Made Possible by WirelessBy An " A.W. " CORRESPONDENT

and other sounds similar to atmosphericsbeing introduced. Now, it is a curiousfact that noises one would hardly noticewhen listening to speech on headphonesassume serious proportions when the wholeis raised to loud -speaker level. This mayeasily be confirmed on any wireless set.Unless, therefore, the input is strongenough to ensure an output intensity wellabove that of any interference, the amplifiedresults are rather like those obtained whentrying to receive a distant station duringa thunderstorm

Repeaters solve the problem, as withthem we are able to start with a moderateinput; send this over a limited distance,at the end of which it is still well abovethe noise level; then amplify again to theallowable limit, pass on over the nextsection and so on, finally feeding it into thepower banks and loud -speakers at the hall.This, then, is the procedure adopted in allthe great political relays.

A RecordAt Mr. Lloyd George's relay, which

creates a record for this type of "wiredbroadcasting," the firststage was, of course, themicrophone, a Marconi-Reisz, followed by aspecial double micro-phone amplifier placedimmediately below theplatform. The ampli-fier incorporates twostages, resistance -capa-city coupled, withvolume control and apitch -raising device,necessary because thecapacity of a long tele-phone line acts like acondenser across thecircuit and cuts off thehigher frequencies. Byartificially distorting theinput - over -emphasis-ing the high notes andharmonics-it is possible to counterbalancethe effect and obtain a natural output,The entire amplifier panel is duplicated,and in the event of a fault in either thechange over may be accomplished in afraction of a second by means of twoswitches.

Following this comes the "distributor "panel, 'consisting of fourteen valves inparallel-one feeding each line and one theamplifier in the Albert Hall itself. The

grids are connected together to the second-ary of a special to to i Marconi Ideal trans-former, but the output circuits are inde-pendent. It is therefore possible to controlthe input to individual lines and a fault onany one line will not affect the others. Alistening point and volume control are alsofitted to each circuit.

Twenty-six Trunk Lines!The final unit at the trunsmitting end

was a thirteen -way change -over and moni-toring panel from which radiated twenty-six trunk lines, each of the thirteen circuitsthus being duplicated again. The sparelines were used for communication betweenengineers at the input and output stations,enabling the engineer in charge, to watchthe whole system from his position at theAlbert Hall itself.

At each receiving end there were one ortwo engineers in charge of a standard " B"amplifier and power bank of from four tosixteen LS5A's, depending on the size ofaudience and number of loud -speakers.The latter were of the well-knOwn Marconi -phone moving -coil type with rubber dia-

The distributing panel for twelve of the fourteen circuits

phragm, this equipment being standardfor public speech and music reproduction.

No fewer than 191 trawlers and drifterscarry wireless apparatus. This evidence ofthe value of wireless in small ships wasfurnished by Mr. Kellaway at the recentmeeting of the Marconi Company. Thisfigure is about one -fifth of all the trawlerswhich might be fitted.

APRIL 6, 1929 517 rnaterx Wirc.14s)

IMPROVINGYouRPORTABLE

Here is a Series of Hints Showing Howthe Utility of a Portable May Be Greatly

IncreasedIT is probably safe to state that portable

and transportable receiving sets at thepresent time are used as much in the homeas out of doors, in fact, this type is takingthe place of the more conventional patternto a greater and greater extent.

There are, however, one or two difficultiesthat arise in the use of a portable in thehome due to certain limitations in thedesign. For instance, the H.T. batteryincorporated in most portable sets is-dueto the necessity of keeping down the weightand bulk to a minimum-of small capacityand is therefore an uneconomical proposi-tion when used on other than out-of-dooroccasions.

Use a Super -capacity BatteryFor continuous indoor working with a

portable receiver it is an excellent planTO H.T.1-1TAPPINGON INTERNALN.T. HATT Efiy

11:T.+ I

WIRIKof

SET1

H:T.+2

TO H.T.+2TAPPING ONINTERNAL

BATTERY

SOCKET ON PANEL FORN.T.1-1 TAPPING FROMEXTERNAL H.T. SUPPLY

JACK :WITCH

SOCKET ON PANEL JOINEDTO MT -WIRING IN SET

SOCKET on PANEL FORH.T. +2 TAPPING FROMEXTERNAL H.T. SUPPLY

Fig. 1. External H.T. supply may be usedin this manner

SOCKETS ONPANEL FOR "f-CONNECTion OF

L,W EXTERNAL L.T.ACCUMULATOR

TO LT -WIRINGIN SET

CONNECT TO WIRETHAT WAS, ORIGINALLYJOINED TO L.T.+TERMINAL OF INTERNAL

ACCUMULATOR.

JACKON PANEL

TO L.T.+ TERMINALOF INTERNALACCUMULATOR.

Fig. 2. This diagram shows how externalL.T. may be obtained

for both economical and efficient workingof the set to use an external H.T. batteryof the power or super -power type particu-larly where, as is the case with manypresent-day portable receivers, a super-power valve is fitted in ,the last stage.Naturally there arises the difficulty ofconnecting up the external H.T. batteryand disconnecting the internal batterywithout interfering with the wiring of theset with its attendant risks every time onewishes to transport the receiver.

TOLOUD-SPEAALR

NEC. TERMINAL IN SET

TO ANODE OF LASTVALVE IN SET

PLUG

TO LIMO -SPEAKER -IS rLT+ I ri SET

JACK

TO EXTERNAL PHONES,LOUD -SPEAKER,, PICTURERECENER OR AMPLIFIER

Fig. 3. Method of wiring jack for use ofexternal loud -speaker or picture receiver

There is, however, as shown by Fig.a simple method of permanently alteringthe wiring by the addition of a small jack -switch and two or three valve leg socketswhich enables either the internal H.T.battery or any external H.T. supply suchas a power type battery, H.T. accumulatoror mains unit to be connected into thecircuit by pushing in the jack -switch andplugging the leads from the external H.T.source into the sockets on the panel. Thephotograph in the heading, for instance,shows a mains unit used in this manner.

To enable the receiver to be used foroutdoor work the external supply leads aresimply removed from the panel of the setand the jack -switch is pulled out.

An Alternative AccumulatorIn cases where the frequent recharging of

the small internal accumulator is a' diffi-culty, a jack -switch and socket may befitted on the panel, in.a similar way to thatfor connecting the external H.T. supply;the wiring alterations in this case should bemade as shown in Fig. 2. To connect up anexternal accumulator the leads from thisshould be plugged into the socket on the

panel and the jack -switch placed in the"in" position. To reconnect the internalaccumulator the foregoing procedure isreversed.

Additional Loud -speakerOne of the most useful improvements

which can be made to an existing portableor transportable receiver is a provision forthe quick connection of external head-phones, loud -speaker, picture receiver oramplifier. The necessary requirements inthis case are very simple and merelynecessitate the fitting of a jack and twovalve sockets to the panel and slightalterations to three wires as shown byFig. 3. When this is carried out the act ofplugging in any external piece of apparatus,automatically cuts out the existing loud-speaker which is fitted to the receiver.

Provision for MetersAmong the minor improvements which

may be made is the fitting of points on the(Continued at foot of next page)

VALVE. LEC SOCKETS III

TO HT - -PANEL OF SET

To HT.- - -

TO LT.+0R-WRiCHEVER IS -*4NOT CONNECTEDTO NT. -

TO C.ES- - -

7E51

LT. VOLTS TEST

.\-:TO SOCKET ,LOWED TOGS+

GRID BIASBATTERY TEST

Fig. 4. Arrangement of testing points forvoltmeter

Ri*A'

08/S/NIILIV/R/Ya

PLUGS FORSHOAT/NS SDCATT.S!P/HENNOTI/S//Yonf/a/ANNETE:9 I

701-17:+INSET

socierTrayPNNEL FORCONNECT/ON

OF19/L149/14117 -AP

TOL.S+TERMIWil INSET

Fig. 5. This diagram shows how a milliam-meter may be inserted in the anode circuit of

the last valve

master WireLzSi 518

ELECTRICALRECORDING at HOME

ANEW system of gramophone record -in& particularly devised for home use,

has been developed in the laboratories ofthe Stuttgart Broadcasting Co. The paten-tee is Oberregierungsrat Rammelsberg, ofWernigerode, in Central Germany, and hisinvention has been developed by Mr.Formis, who probably will introduce it atthe Berlin Wireless Exhibition this comingSeptember.

The new process opens up many hithertounthought of possibilities and briefly is asfollows : A microphone, in the case of music'a high-class Reisz microphone, will haveto be used, but for ordinary speech it is -quite sufficient if one earpiece of a head-phone be used as a microphone. Thecurrents coming from this microphone arepassed through an eight -stage amplifier.From here the impulses drive the usualcommercial gramophone pick-up. Theaction of the pick-up is thus reversed or,in other words, the pick-up becomes amotor. A small diamond takes the place of the pick-up needle and, in operation, this

diamqnd is pressed or hammeredinto the substance of the recorddisc and forms the grooves,without previous preparation ofthe disc. The disc material isnon - inflammable ,celluloid,about L in. thick, both' sides ofwhich can be used. Immediate-ly after recording, any ordinarygramophone using an electricalpick-up, an amplifier and loud-speaker can play whatever hasjust been impressed On thecelluloid. The record can beplayed sixty or seventy times beforewearing out. The record disc, while therecording is being done, is carried by agramophone table in the usual way, exceptthat a special rubber -pad is interposedbetween table and disc.

For making a number of records it isnecessary to use copper or zinc instead ofcelluloid discs and to use the metal recordas a master. For playing the celluloidrecord it is necessary to use a fibre needle

PRIL 6, 1929

Making gramophone records at homeRammelsberg System

and, as in recording, to use aunder the record.

by the

rubber disc

Long RecordsFor records that will last longer than

ten minutes or a quarter of an hour, Mr.Formis proposes using an endless non-inflammable celluloid band which will bepassed under the recording diamond bymeans of two rotating cylinders some dis-tance apart. G. DONALD.

"IMPROVING YOUR PORTABLE"(Continued from page

panel to which a voltmeter may be appliedfor determining H.T., L.T., and gridbias voltage, or for temporarily, connecting

milliammeter into the anode circuit ofthe last valve in order to determine whetherthat valve is working at its best.

These testing "points" may take theform of valve sockets fitted near one sideof the panel, as shown in Figs. 4 and 5respectively. As the use of a milliammeternecessitates the actual breaking of thecircuit a "bridge" or re -connecting attach-ment formed by fixing two small wanderplugs to each end of a short length of flexmust be utilised to re -make the circuit afterusing the milliammeter.

Two Loud -speakers at OnceIncidentally this "break" in the anode

circuit may be employed for the connectionof an external loud -speaker in series with,and, of course, additional to, the internalinstrument. This means, of course, thatboth internal and external loud -speakerswill be operating at the same time and ifdesired the extra instrument may besituated in another room. In cases wherethe leads to the second loud -speaker are ofany considerable length, however, it willbe advisable to employ an output trans-former for feeding this instrument, so thatthere will be no possibility of H.T. leakage,or unwanted capacity to earth or-in theevent of a mains H.T. supply unit beingused with the set-to prevent the possi-

bility of dangerous shocks being receivedterminals.

Outdoor AerialsWhere no provision is made on

OUTPUTTRANSFORMER

the set

TO Dlf,TANT,LOUD-5PE4KE.R

SOCKETS Oft PANELOF SET

Fig. 6. Output transformer connections fordistant loud -speaker

OUTDOORAERIAL

VARIABLECONDENSER

EARTH

Fig. 7. How to add external aerial and earth

for connecting up an outdoor aerial andearth the method of using the outdooraerial and earth without interfering withthe wiring of the portable set shown byFig. 7 may be used.

A small frame aerial containing about15 turns wire (the bestnumber of turns should be found byexperiment) wound in a square with 1 -2 -in.sides is connected up to the outside aerialand earth and shunted by a .0005 -micro -farad variable condenser. This frame aerialand condenser is then brought to withina fciot or so of the frame aerial in the port-able set and the latter tuned in the ordinarymanner ; the external frame condenSershould also be adjusted until best resultsare obtained. Stations which previouslycame in weakly will now be heard at con-siderably increased volume, without appre-ciable reduction of selectivity.

Obtaining Directional EffectsFinally mention should be made of that

little -used component the turn -table. Goodturn -tables can now be obtained quitecheaply and are easily fitted to an existingportable or transportable receiver. Theadvantages of a turn -table are twofold asits use enables the set to be placed on apolished table without risk of damage tothe surface and at the same time the wholereceiver can easily be turned round to anydesired position.

A dispatch from Prague states that atPoderbrady, where the main wirelessreceiving station in Czecho-Slovakia islocated, the Czecho-Slovak Post Office isinstalling a short-wave transmitting stationfor telegraphic communication withAmerica.

APRIL 6, 1929 519

("114 - Kiasile.e&s.e/eAn Unexpected Emergency

T WONDER how many readers have had1 the delight of arranging to give a displayof how to receive a musical programme, andthen at the last moment to find that theset, which worked so well the previousnight, has developed a subtle fault? Imyself have had this occur on two occa-sions. The first instance was when I hadpromised a special concert to somemusical high -brows. As the time for theconcert to begin drew near, the set de-veloped crackles and in a very short spaceof time the signals could only just be heardwith the ear close to the loud -speaker.Hasty tests with instruments showed thatone of the intervalve resistance couplingshad ceased its useful functions owing to aburn out or fault in the wire.

A Bright IdeaIt was then a few minutes to the time

when the concert was due to begin. Threecritical musicians were wagging their headsin a knowing fashion and the nearest radiodealer's shop, a mile away, was closed forthe evening. It was an emergency whichcaught me napping, for it is rarely that awire anode resistance gives up theghost after a couple of month's service.Resistance bobbins from the junk box onlytotalled about 4,000 ohms, and everythingseemed lost when a bright idea struck me.In less than five minutes a high -resistancemoving -coil milliammeter was in the anodecircuit of that valve, and 200,000 ohms ofresistance did service as an anode couplingthat night. It was an interesting, experience,and the moral is that a high -resistanceinstrument has more uses than one.

A SurpriseA somewhat astounding announcement

is that in future provincial main stationsare to rely upon local artistes to supply themajority of their star turns. It is said thatthe local spirit must be encouraged, andthis is held to be the way to do it. Con-sidering that as soon as an artiste, whetherhe be instrumentalist, vocalist, ventrilo-quist, entertainer or whatnot, makes a beeline for London and higher pay as soon asever he has begun to attract any attentionin his own home town, I am rather afraidthat provincial stations are going to comeoff rather worse than 2L0 over the deal.

I am hoping that somebody has got holdof the wrong end of the stick in makingsuch an announcement, for I can really

" hardly see how such a silly course could betaken. Actually it is quite on the cardsthat though the B.B.C. is striving to givethe public alternative programmes bymeans of the regional scheme and in otherways, the provincial public does not wantalternative programmes: what it wants is

London. At any rate, I nearly always findin talking to people from distant parts ofthe country that they consider the Londonprogrammes far better than their own, andfrequently say what a shame it is that theycannot always have them. So far as I cansee, two completely different programmessent out simultaneously from variouspoints would be absolutely sufficient forthe whole country's requirements. If onlytwo programmes had to be provided eachday good fees could be paid the artistesand the very best talent in all departmentscould be secured.

Life in the Old Joke YetYou remember the story of the joke?

I have referred to it on several occasionsin these columns. In case you have joinedthe great band of AMATEUR WIRELESSreaders since it was last mentioned, here isthe history. In one of the very earliestnumbers of AMATEUR WIRELESS I per-petrated a joke about Adam having pos-sessed a loud -speaker made from his spareparts. This spread all over the world inthe most astonishing way, appearing withor without an illustration in papers ofpractically every European country, aswell as those of distant parts of the world.A reader sent me a Japanese paper con-taining it and others reported its outbreakin the most astonishing places. About threeyears ago the joke won a prize in anAmerican paper which had previouslyannounced that it was not the slightestuse sending in anything that was notabsolutely original ! It hadn't cropped up,though, for quite a long time; in fact,I had begun to think that the dear oldthing was at last dead. Not a bit of it,though; I happened to switch on 5GB or2LO-I forget which it was now-theother night when an entertainer was atwork, and sure enough out it came I

Why Have Anonymity?The B.B.C. new dramatic producer has

not been long in the saddle, yet his per-sonality is beginning to be felt. His latestdecision, that'of not publishing the namesof artistes speaking the lines of plays, hascaused severe heart burnings among thosewho take part in radio productions. Nowwhat is the position?

Some years back the B.B.C. laboriouslybuilt up a repertoire company of playerschosen for their voices and ability to speaklines clearly and well and with a certainamount of meaning. Not content with thatbright idea, they proceeded to fix up awhole string of plays for months ahead tobe played by these chosen people, who, nodoubt, had a comfortable little contract.So far, so good, but their next step waspossibly the worst. They hired photo-

(1,LPtir wire

graphers who took them in every possibleattitude with absurd backgrounds, and, of 'course, always with the camel -like affairon which was supported a very ludicrousbusiness which held the microphone.

After this well -thought-out campaign,which some wireless papers are suggestingshould be repeated, it was discovered thatMiss Dulcet's voice was always the same,whether she was Mrs. Wiggins or Joan ofArc, and also that her very comfortablefigure was firmly embeded. in the mindsof listeners. It became irritating to hearthe same voice one day as the fat girl ofPeckham and next evening as Melisande.

A Stage ParallelTo return to the anonymity edict. There

is much to be said for it. If an artiste hasa flexible voice-and how few have-it ismuch better to leave the listener his orher own mind picture of the character thanto picture some very worthy, but veryordinary, person speaking the words of theplay. There are some cases where it woulddo no harm, but it must be rememberedthat on the stage the dress and make-updivest the artiste of much of his very ownappearance. Seldom in a costume playdoes the artiste put up outside the theatrea picture of himself as, for example,Shylock unless he is dressed for the part.The same should apply to radio drama;but, of course, it can't be done.

There is, of course, another point whichmight be stated. So many of our well-known actresses and actors mumble theirwords that really anonymity is in theirfavour. They must realise this. However,I don't suppose the projected boycott bymany of these famous artistes will ma-terially affect radio drama. Anonymity isvery interesting.

SundayDull and dreary Sunday broadcasting

continues. Having educated a large sectionof the public to expect entertainment onSundays, the B.B.C. now proceeds to driveits converts out of their homes to places ofrefreshment and those evil cinematographpalaces I True, Sandler sometimes comesto the rescue with a bright spot of musicand there are occasional symphony con-certs; but, in the main, the Sundayprogrammes save such a lot of filamentcurrent ! Religious broadcasts can beinteresting, we all know, but this type ofbroadcast rapidly reaches the saturationpoint unless there is some powerful micro-phone personality to hold the attention.As it is, the Sunday programmes seem tohave degenerated into a repetition ofhymns just as irritating as the " plugging "of popular songs. On Sunday, Savoy Hilltakes its finger off the pulse of the nation

emateur Wirelesi 5'2.0 APRIL 6, 1929

C 04 0 On Your Wavelength ! (continued) *

order to gratify a few "extremists." Whois responsible ?

Pictures and SqueaksSunday is usually the field -day for the

experimenter. There must be hundreds ofthousands of wireless gentry who lookupon Sunday afternoon as being sacred tothe soldering iron. Aerials are pulled downand put up again, new sets are tried out,new loud -speakers put on, and moderncomponents put in. Therefore, Sundayafternoon, after the concert transmissionwould be an ideal time for prolongedFultograph transmissions and "squeak"tests. In regard to "squeak" or low -frequency note tests, I find that individualB.B.C. engineers have peculiar ideas as totheir utility. Their attitude is that theyconsider very few people could make use ofsuch tests and that the remainder would becompletely mystified and probably ledastray into the ranks of oscillators. Thesuccess of such tests would, of course,depend on the manner in which they wereput over. The B.B.C. can rest assuredthat all AMATEUR WIRELESS readers willknow how to make use of "squeak" tests.

Our Good SetsTruth to tell, our receiving sets are

getting so good that we want something alittle more scientific than broadcast musicfor making comparisons between trans-formers, chokes, and loud -speakers. Thebroadcast of individual pure notes onvarious parts of the musical scale is the onlymethod which will enable us to make furtherprogress towards perfection. Therefore, letus have a weekly half-hour of low -frequencycalibration tests and let that hall -hour be atthe time most convenient to us-Sunday.

The Grand NationalTemporary sets were erected in thou-

sands of offices for the reception of therunning commentary on the Grand National.I penetrated into one West End office intime to hear this most successful broadcaston a real "Heath Robinson " crystal set. Awire had been slung out of a window for anaerial and the set consisted of a few turnsof bell -wire on a roll of cardboard, and acrystal detector. Someone had forgottento bring a "pukka" set, and as everybodyelse had brought their headphones some-thing had to be done about it. Bell -wirewas produced from an old store cupboardand some bright youth found a small pieceof crystal in his pocket ! A drawing pin anda couple of paper clips completed the set,which gave satisfactory signals on six pairsof headphones !

-and PicturesA triumph was scored by the still -

picture people by the transmission ofphotographs illustrating both the BoatRace and Grand National. Pictures of thelatter were sent from the course over the

land -line and were. received in the MorningPost office within twenty minutes of theirhaving been taken. Anyone who saw thereproductions in the Saturday issue of thepaper must have been astonished by theirexcellent quality. This, of course, opens upa wonderful field, for the Fultographtransmitter is quite portable, so that it canbe taken to the scene of almost any import-ant event. All that is needed then is a smallemergency dark room in which to developthe films. The negatives are then putstraight on to the photo -electric transmitterand sent over the land -line to their destina-tion. No less than eight pictures of theBoat Race were sent out within a little overan hour of the finish and those who receivedthem had a splendid piece of wirelessentertainment. I think that a prophecy Imade some months .ago is likely to be ful-filled this year. I said then that we shouldhave a picture of the finish of the Derbybroadcast the same evening.

Heating by WirelessOne of the lay papers rather went in off

the deep end the other day by giving itsreaders to understand that they mightshortly warm their houses by means ofwireless. The actual facts are that inlaboratory experiments, heat transmissionshave been made over very short distances,and that it has been proved quite possibleto carry out this kind of thing on a verysmall scale. There is considerable differencethough, between producing in a coil of wirea degree of heat that can be measured onlyby the most delicate instruments, andcreating in a living -room the lkind of fugthat you and I like on a cold winter's night.The transmission of heat by wireless is oneof the things that will probably come in thefar away future, but it is most unlikelythat something of the sort will happen nextweek, or anything of that kind. So there isno need for you to rush off and sell yourfire -grates and gas -stoves, just at once.

A Pentode PointI am very fond of the pentode valve

myself, though I come across from time totime numbers of people who have triedthem and given them up in disappoint-ment, since they have been unable toobtain from them the kind of quality thatthey want. The whole trouble with thepentode is to obtain exactly the rightimpedance in the output circuit. Get thisand quality is beautiful; fail to get it andit may be very much lacking. Outputtransformers are now available whichexactly suit the pentode valve. One thatI am very pleased with has a tappedsecondary, so that it may be adapted tosuit the particular loud -speaker which isto be used with the valve. With theMoving -coil loud -speaker it is essentialto wind the coil exactly to fit the

pentode. Too few turns mean poor signalstrength; too many spell poor quality.

American Sets To -dayLooking through advertisements in the

catalogues of 'American wireless manufac-turers, one cannot fail to be struck by thesize of the receiving sets in use in theStates to -day. It may come as a surpriseto some readers to know that the averageAmerican set nowadays contains no lessthan six _valves, whilst many have sevenor eight. They are not super -heterodyned,for that type of set is not greatly used now;most of them, in fact, are absolutelystraight receivers, containing two or threeH.F. stages, a rectifier, and two or threenote -magnifiers. The American wants hisset to be able to bring in a big number ofstations at full loud -speaker strength, andit must be also sufficiently selective to cutout a local station at very short range.

The high -frequency side is not, as a rule,designed for big magnification per stage;what the makers aim at is comparativelysmall magnification from each valve.

What of Television?I am writing my notes earlier this week

under orders from the Editor, who informsme that, owing to Easter, this issue goes topress two days earlier than usual, and Ishould not be surprised if, before my readerssee these words, _the Postmaster -Generalhas not publicly..annnunced the results ofthe B.B.C.'s recent tests of Baird television.While I have been unable to obtain officialinformation, I learn from a number ofspecial sources that the tests were successfulfrom the Baird point of view and verysignificant to the P.M.G. and to the broad-casting authorities. Indeed, I rather expectthe P.M.G. to announce his personal faithin the system and to explain his proposalsfor giving it further broadcasting facilitiesof an experimental nature. I believe mostof the witnesses were impressed by theextraordinary improvements made by Mr.Baird in recent months and by the amountof detail and degree of illumination dis-played by the transmitted image. Doubt-less there is a big difficulty to be overcome-not so much in the system itself, but in thegreat width of the frequency band whichwould be occupied by the transmission andthe consequent risk of general interruptionof speech transmission-and this difficulty,I expect, has delayed the P.M.G.'s an-nouncement. Mr. Baird will have ourhearty congratulations and those of allreasonable people should it be found thatthe test's were of such a nature as to causethe B.B.C. to change its attitude, and Ishall be the first to congratulate the B.B.C.themselves on what I hope will be anannouncement of their goodwill to theBaird system. And, between ourselves,AMATEUR WIRELESS ought to come in fora good word, too. THERMION.

APRIL 6, 1929 521

SHOCK -PROOF!When you buy your Screened Grid Valve insiston the one which will give you the longestservice-choose Cossor. These illustrationsshow why the Cossor Screened Grid Valve isthe most robust-the most dependable-andthe most uniform Screened Grid Valve madein Great Britain. Remember that this wonder-ful new system of Interlocked constructionis to be found only in the Cossor ScreenedGrid Valve. No other make of Valve hasthese outstanding features of design.

NOISE -PROOF!Noises are generally due to loose elements ina valve. In the Cossor Screened Grid Valve theelements are interlocked. Even under thehardest blow individual movement is impos-sible. The Cossor Screened Grid Valve is builtlike a bridge. Every joint is scientifically weld.ed to ensure long life and complete rigidity.

BREAK -PROOF!Never before has such a wonderful system ofconstruction been used in any Screened GridValve. Even the hardest blow cannot disturbthe perfect alignment of the elements whichare rigidly held at top and bottom. As aresult every Cossor Screened Grid Valveretains its characteristics throughout its ab-normally long life. For any Screened GridReceiver choose Cossor. Accept no substitute-for there is no adequate substitute for theCossor system of Interlocked- construction.

Technical Data.Cossor 220 S G (2 volts, .2 amps.) and 415 S.C. (4 volts, .15 amps.)Max Anode Volts 150, Impedance 200,000, Amplification Factor200, Grid Bias 1.5 volts at max. anode Volts. Price teach)

Demand the

Here you see thedouble length ofCossor filamentfamed for itscolossal emis-sion. Note theseonite bridgeholding it rigidlyin position.

Around the twostout grid sup-ports is woundthe first grid,electrically weld-ed at twenty-fivepoints.

Note the enor-mous siren thand rigidity ofthe screen. Seehow it is builton four stoutsupports andcapped by ametal bridge -piece anchoredto seonite insu-lator.

Finally, obsertethe constructionof the anode.Actually two rec-tangular nickelplates are usedand for greaterrigidity each isdiagonallyribbed.

2216

Cossor &G.Valveo //The only Screened Grid Valve with Moi4OCKED construction

A. C. Cossor. Ltd.. Highbztry Grove, London, N.5.

Pease Mention "A.W." When Corresponding with Advertisers

M 8103

&attarWelts,' 522

You may save pounds by reading the AprilNumber of the " Wireless Magazine," now onsale. The following contents list indicates thewealth of really useful and interesting features(illustrated with over 130 photos and diagrams)offered to readers :

Valves to Use in Your Set. '

Start Radio with the ClipperTwo for £51 ;

A Broadcast Revolution.Under My Aerial.If Your Set Starts Motor -boat-

ing. By W. James.More About the Lodestone Loud-

speaker. By W. James.

GRAMO-RADIO SECTIONCan You Cut Out Needle Scratch ?Where to Place a Volume Control.Is Gramo-Radio at a Standstill ?If I Were Bass Deaf. By H. T.

Barnett.A Good Pich-up. By W. James.Designing Scratch Filters. By

J. H. Reyner, B.Sc.,A.M.I.E.E.

The University of the Ether.By B.B.C. Officials.

Our Cartoonists f` Review "Some Broadcasters.

"Show Me the Way to CoHome." Verse.

A Safe H.T. Unit for D.C.Mains. By W. James.

Is the Aerial Doomed?Studio Audiences. By Tommy

Handley.A Visit to Savoy Hill.My Radio Week -end. By

J. Godchaux -Abrahams.Wavelengths of the European

Stations.Wireless Fallacies,What Readers Think of Our Sets.The Dominions Four. Can, be

Converted into -a Short-waveSuper -het.

Full-size Blueprints of all sets described in thisissue -are available at half-price until April 30th

Continental Appreciation.What You Want to Know About

Wired Wireless.Short-wave Relays from

Colombo.Wiring Your New House for

Radio.Seeing When Distortion Occurs.Hints for Success on the Short

Waves.A Wireless Fictionary.The Letters of Priscilla Playne-

Smythe.Radio Quarrels in the United

States.The Dynamic Three. A Set

for A.C. Mains.It's Better with a Baffle !When Air -liners Talk by Radio IHalf Hours with the Professor.-

Amp Solves the TuningProblem.

Japan's Pirate Listeners.Broadcast Music of the Month.

By Studius.In Tune with the Trade !Leaves from a Listener's Log.

By Jay Coote.Loud -speakers from a New

Angle. By Kenneth Ullyett.The Drum -Major. A Four-

valver for Quality.A Cone Loud -speaker.4eaders' Questions Answered.Using the Melody Maker on- the

Short Waves.New System of Focused Radio.Reference Sheets. Compiled by

J. H. Reyner, B.Sc.,A.M.I.E.E.

A Free Broadcast Map.

APRIL 6, 1929

APRIL 6, 1929

OPINION is divided as to the desira-bility of fitting special filters to cut

out the noise of the scratch on recordswhich are reproduced through the mediumof the wireless set. One of the advantagesof electrical reproduction is that one canjuggle with the frequency response fromthe record as one wishes. For example, itis well known that the bass on a gramo-phone record cannot correctly be repro-duced because the movement of the needle

/000 MVO 1000 NWFig. L Effect of Shunt Condenser

to reproduce frequencies below 200 cyclesbecomes so large as to be -impracticableunder ordinary conditions. We can, how-ever, if we wish, put in an amplifier whichhas a rising characteristic at the bass endto compensate for this defect. Whetherthe results would be altogether desirable isentirely a different story, but the instanceserves to illustrate the flexibility of elec-trical reproduction.

The problem of scratch is more con-cerned with the upper end of the frequencyspectrum, for it is here that the noises con-stituting the scratch predominate. It isnot possible to say that scratch onlyoccurs at or above any definite frequency,for in point of fact it is due to a con-glomeration of noises occurring throughoutthe whole of the audible range, but there islittle doubt that scratch does predominatein the upper registers.

The question is whether we, can mini-mise scratch by cutting off a, certain pro-portion of the upper frequencies. At firstsig1kAhislseems heresy, and indeed nit4anvindividuals claim that the whole idea of ascratch filter is impracticable and unwork-able. I myself do 'not hold this view, for,as in most other aspects of wireless, a greatdeal depends upon the personal factor, andalso upon the amount of compromise whichis deemed advisable. At any rate, I haveconducted a number of tests at Elstree

523 emaw Wirere.5

Cutting Out //EEDLE SCRATCH

/ One of the advantages of Gramo-Radio Reproduction is that surfacenoises associated with all Gramophones can be almost eliminated. Inthis article our Technical Editor describes various filter systems

which are used to this end.which have given a distinct measure ofsuccess.

One of the complications of the problemis that the average loud -speaker is by no

VVVVVVVVVVVVR

I

4

AIMPLIPER

Fig. 2. Simple R.C. Filter

means a good reproducer in the upperfrequencies. The taking of response curveson loud -speakers is quite a fascinating sub-ject. . The difficulties in the way of pro-ducing a true response curve to which onecould swear are so large as to render theproblem almost impossible, but it is afairly easy matter to obtain a comparisonof the relative radiation at different fre-quencies, and the number of loud -speakerswhich commence to cut off in the regiohof 2,000 to 3,000 cycles per second is quitesurprising. There are few loud -speakersindeed of the average cone type which willreproduce faithfully about 4,000 cycles persecond, and in the average case the responseis falling gradually the whole time for

t0002csv

P/C/(-a'C

Fig. 4. A better form of Filter

r,000 1,50o cycles before this point isreached.

Now tests actually made with a verysharp cut-off filter indicated that if fre-

NUA/PDUETDRESONANCE

f00 /000 2000 icoo wooFig. 5. Cut off with L.C. Filter

quencies above 4,000 to 5,,000 cycles petsecond were cut off, quite an appreciableportion of the scratch was removed. Thescratch, in fact, ceased to be evidentduring the playing of the record, and onlybepame apparent when the music ceased,which, after all, is sufficient for our purpose.These tests, incidentally, were taken on amoving -coil speaker which had beendefinitely proved to go up to frequenciesabove 8,000. Moreover, aural tests con-ducted from opinions given by independentlisteners indicated that there was little

500 /000 2000 1000 wooFig. 3. Cut off with R.C. Filter

loss of brilliance if frequencies above 5,000were omitted. Indeed, it takes a verycritical ear to distinguish the difference.

Consequently, if we can retain the fre-quencies up to this limit and cut them ofiabove, we shall obtain a certain measureof elimination of the scratch, resulting ita greater clarity of tone. With the ordinaryloud -speaker, as has been pointed out, wecan reduce this limit somewhat and com-mence our cut-off in the neighbourhood of4,000 cycles per second, since the loud-speaker itself is not likely to give usvery much above this point. This was theprinciple which was adopted in makingthe tests, and it has met with quite a goodmeasure of success. We now have to con-sider the methods by which we can achievethis cutting -off of the upper frequencies.

The simplest method is to connect acondenser across the pick-up or some suit-able portion of the amplifying circuit.This, however, is not a satisfactory method,because it causes a gradual reduction ofthe output, so that not only shall wereduce the frequencies above the cut-offpoint, but also considerably affect the fre-quencies below. It is indeed difficult toconsider this as a cut-off in the ordinary

(Continued on page 538)

Weekly Tips,Constructional

end

Theoretical-fl Neutralising Snag

Ihad a rather interesting experience theother day in connection with a

neutralised receiver which was suppliedwith high tension from an A.C. mains unit.

It was pointed out to me that with thepower plug one way round in the socket theet could not be stabilised, but yet normal

working was obtained when the plug wasreversed ! I tried neutralising the receivermyself. I had not the time to spend onmaking numerous tests, but the trouble wascompletely cured by connecting a high fre-quency choke in one of the wires to theprimary of the transformer. This chokewas afterwards fitted in the mains unit.

It should be noted that an ordinarychoking coil may become too hot and

eventually burn out if used in this manner.

Low Notes and Motor -boatsIn order that the low notes may be

magnified by a resistance -capacity -coupledamplifier, or one of the popular types havinga resistance stage and a transformer stage,it is necessary that the coupling condenserbe of suitable capacity in comparisonwith the resistance of the grid leak.

The condenser is marked c in the diagramFig. 2 and the grid -leak R. Usual values are.005-microfarad and 2 megohms, but whenthe very best quality of reproduction isdesired the coupling condenser c may be of

microfarad and the grid leak R have aresistance of f megohm.

There is a disadvantage, however, inemploying components which pass the verylow notes; and this is that motor -boating islikely to be troublesome in the absence ofspecial filters. It is therefore just as well soto design the low -frequency amplifier thatthe very low notes which the loud -speakeris not capable of reproducing correctlyshall not be amplified.

Ordinary horn type loud -speakers andcertain cone types, too, do not reproduce thevery low notes, and it is therefore hardlyworth while employing an amplifier whichwill magnify them. The low notes may bereduced by cutting down the capacity ofthe coupling condenser or the grid leak'sresistance, and it is sometimes possible toemploy a value as low as .00r microfaradwith a .I-megohm grid leak

G.B. from A.C.The grid bias for power valves supplied

with high-tension of zoo volts or more mayamount to as much as 40 or 5o volts, anddry batteries are often employed. But whena mains high-tension unit is used it is notvery difficult to arrange a rectifier andsmoothing circuit for the grid bias.

Troisicomer 'Mho*

Fig. 1. An A.C. Grid Bias Unit

When the rectifier is of the Westinghousetype only one additional transformerwinding is required and, of course, a smooth-ing circuit. A suitable arrangement issketched in Fig. I, which shows a half -waverectifier, a resistance -capacity filter, and atapped resistance. The amount of the A.C.voltage to be delivered by the transform'eris dependent upon the type of rectifierand the grid bias required, but will usuallynot be more than 40 or 5o volts. Condenserc may have a capacity of 2-microfarads,

L.S.

1Z+

KT -

Fig. 2. A typical R.C. arrangement

resistance R.I, a value of f o,000 ohms andR.2 of 3o,000 ohms. A choking coil may beemployed instead of resistance R.I, but aresistance is, of course, much cheaper.

A Mysterious HowlIt is surprising how the results to be

obtained from receiver fitted with an

APRIL 6, 1929

W JAMESFor the

WirelessAmateur

H.F. stage may be affected by small mattersthat are apt, at least for a time, to passunnoticed.

I have in mind the case of a quite ordinaryreceiver having three valves. The firstwas of the shielded type, and it was followedby a detector and power valve in the usualstraightforward manner. But the com-plaint was made that the expected resultswere not being obtained because squeals andhowls were produced- sometimes evenbefore the reaction was adjusted to thepoint where the anode circuit of the high -frequency stage would oscillate.

Now the loud -speaker usually stood onthe cover of the receiver, and if high -fre-quency currents were passing through theloud -speaker Ord there would be trouble.There would be coupling between the inputand output circuits, in this instance theaerial connecting wire and the loud -speakercord.

Tests were therefore made, and showedthat the strength of the. howl could be variedby altering the position of the loud -speakercord, which seemed to prove that high -frequency currents were flowing in thespeaker circuit.

Buzzing Chokes!Iron cored components such as low -fre-

quency inter -valve transformers or chokingcoils are liable to buzz unless the iron or steellaminations fit accurately together and arewell bolted in position. It is not unusual tocome across an output choke, for example,which is so constructed that it is actuallypossible to hear the broadcast by placingthe ear within a foot or so of it. Obviouslysuch a component must introduce distor-tion, and it is, therefore, desirable to guardagainst looseness or poorly fitting parts bytightening all fixing bolts and, whennecessary, by jamming together looselaminations with pieces of cardboard orwood.

It is sometimes rather difficult to locatethe particular lamination which is vibrating.A cure may, however, sometimes be effectedby varnishing the core sheets in order thatthey shall tend to -stick together, but onoccasion it is found that an odd piece hasbeen built into the core and is the cause ofthe trouble. Thi.: piece must be removed.

APRIL 6, 1929

Points RhoTHERE is no doubt but that the

exponential horn is an excellent formof reproductive amplifier, but many con-structors are disappointed in the resultsobtained owing to the fact that the generaldesign has not been well considered. Thesecret of perfection lies in the correct shapeof the horn.

The best horn for tonal reproduction isthe wood horn, but good hard ply -woodshould be used. Soft wood will absorbsound instead of reflecting it. Then, again,the seams must be made a perfect fit and

A logarithmic ex-ponential horn madeby the ScientificSupply Stores. Theactual model is

5 ft. 6 in. long

well pinned andglued with nocracks or crevices.When the hornis housed in acabinet it shouldbe padded withfelt where contactis made betweenthe external sidesand the points ofcontact with thecabinet in order toisolate the hornentirely as a sound -reproducingchamber.

Now as regardsthe design forobtaining the bestacoustical pro-perties. The shapeshould be such asto give an equalratio of cut-off

By H. BRAMFORDfrequencies, and the size of the mouthof the flare will govern the total range ofthose frequencies. The best way to plot outa shape for any given purpose is first todecide the space available for the mouth,which should be as large as possible, andthen determine the overall length. Wherethe horn is to be folded in any manner,decide upon the formation of the fold,which is of no great importance providingthe curves are graceful, and from thiscalculate what the overall length will be,allowing for bends.

Plotting the HornNow plot on paper, as shown in the sketch,

the straight horn, and divide it into anumber of equal parts, each of which istermed a pitch. Now the width or diameterat each pitch should be directly proportionalto the distance, as will be noticed, andwhatever size horn is made, these propor-tions will ensure thatthe horn will possessfairly good acousticalproperties. One can-not give any par-ticular hard and fastrule, as so many willwish to house thehorn in some existingcabinet. The idea isthat at each alternatepitch the diameter,or width, should bedoubled, getting asmuch length to thehorn as possible, andstarting, of course,from a small neck.For a 2 -ft. squaremouth the length

4

Cmateur Wtrelersi

ores4R

matched impedance type it is only neces-sary to form the double flare merging atthe input, as shown, and this may have someadvantage over the single outlet, but bothsections must be perfectly alike in shapeand construction. The square section horn,of course, is easier to make in wood thanone of round section.

Readers who do not wish to go to thetrouble of constructing a horn of the typedescribed will be' interested to know thatan excellent range of non-metallic ex-ponential horns are marketed by Messrs.Scientific Supply Stores. These horns aremade in both straight and folded patterns,the latter type being particularly usefulwhen space is a primary consideration.

By reason of the good general design,approximately even response to all fre-quencies above 13o cycles is obtained withvery little falling off down to 6o cycles.

On fitting a well -designed exponentialhorn to a loud -speaker base in place of theordinary short metal horn, one is imme-diately impressed by the fullness and"body" of the reproduced music, while

SON

pitch-4- 24"-

/2.1111 III

24'1

Dimensions of straight and folded types of exponential hornsshould not be lessthan five feet, and this may be taken asa fair basis upon which to work.

Having plotted the straight horn in thismanner to the best advantage possible forgiven conditions, the rest of the job merelyamounts to plotting a corresponding shapeto any curvature, and this should be quiteeasy to do, as the main essential is to watchthat the ratio of increase is the same atequal pitch distances along the entirecurve. For an exponential horn of the

there is a total lack of the "blare" and" tinniness" usually associated with hornloud -speakers.

The fitting of the unit, which may beeither a horn loud -speaker base or of thegramophone attachment type, should becarefully carried out, as a really airtightjoint is essential for good results. Suitableunits for use with these exponential hornsare the Brown, Amplion, Nissen, andBullphone gramophone units.

natew W raT 526

THE BATTLE OF THE GIANTS4PF: IL 6, 1929

JOTTINGS FROM MY LOGIEITHER the title of a silent film nor

that of a talkie, but merely a recordof the nightly struggle which is takingplace between high -power stations and theforecast of the general battle which mustinevitably take place in 1930-!

For some clays I have been trying to geta good reception from Lahti, and up toquite recently at every attempt the EiffelTower has baulked my efforts. Not thatanyone, I believe, wants to hear the Paristransmitter, for its programmes are verypoor in comparison with those offered tous by other studios, but the fact remainsthat its power (some 15 kilowatts) and itsposition in the long -wave band greatlyinterfere with the 13roadcasts of the Finnishstation.

LahtiFortunately, at times, the Eiffel Tower

wavelength is subject to variations; onone or two nights, as it wavered from itscourse, so Lahti was effectively captured.On March 23 I was able to hold the Finnfor more than half an hour at full loud-speaker strength, and during that periodgleaned a mass of information. The call isgiven out now by a male, now by a ladyannouncer; it varies from Lahti, Lahti, toa longer announcement, for sometimes atthe end of an item you may hear "Huomio !Huomio ! Suomen Yleis Radio Lahti Hel-sinki"; but on days when a Swedish trans-mission is given (on Fridays from the high -power station, on Tuesdays from Helsing-fors only) you will pick up words in theScandinavian language, namely : "Givakt ! Giv akt Finlands Rundradio LahtiHelsingfors."

Apparently the station puts out nointerval signal, but preceding the main

:: By JAY COOTEtransmission I heard a series of faint noteswhich to my mind would coincide with anautomatic broadcast of .a very thin buglecall. This was repeated at intervals ofabout ten seconds before speech was heard.Generally speaking, the station is off theair by, latest, 9 p.m. G.M.T., except onspecial nights, when an operatic trans-mission is given; but the best time tosearch for it is towards 7.3o to 8 p.m. Ifyou happen to hear the Swedish language-an easy one to recognise in view of theopportunities offered to us by Motala-do not jump to the conclusion that youhave necessarily tuned in to a Scandinaviantransmitter, for at 7.45 p.m. nightly Lahtiputs out a news bulletin in both Finnishand Swedish, in view of its mixed popula-tion., The high -power station is rated at20 kilowatts, and on favourable nights thesignals are very powerful. Possibly, withan outside aerial the nearer Eiffel Towermay swamp them, but with a frame youcan make use of its directional propertiesand cut out the French broadcasts. Lahtion an air line must be roughly 1,15omiles from London; it is worth tryingto get.

More CrowdingThis tussle to disentangle two powerful

stations from one another, although per-haps not the ideal aim of a wavelengthplan, if not carried too far breaks themonotony of "you press the button, we dothe rest" class of reception and leaves onewith the feeling that something has beenaccomplished. But you can have toomuch of a good thing, and this is what Iforesee for 193o.

At present, of the high -power stations

we have Moscow, Motala, Zeesen, 5XX,Lahti, and Eiffel Tower working daily inan already crowded corner of the ether.Do you know that Zeesen now threatensto increase its power to zoo kilowatts; 'thatEiffel Tower, still on a nominal 55, con-templates pushing up to roo kilowatts;and that Warsaw has decided to erect a;" super " with 5o kilowatts in the aerial? I

No special mention has been made ofHilversum, Kalundborg, Leningrad, Huizenor Kovno, which do not come within theaffected broadcast band limits; yet theseare all transmitters of which the concerts'are easily capturable in the United King-!dom. It is unfortunate, however, thatthey fall within the areas of spark inter -Iference.

On the Medium BandIn the medium band the menace is even'

greater, for on any evening now we mayexpect experimental tests from the new,Oslo transmitter with actually 6o kilowatts:in the aerial, and Bucharest in the near,future will also contribute a 24 -kilowattvoice. Turin, it was officially stated at the,opening ceremony, is eventually to become,one of the largest stations in Europe; yetiRome contemplates the erection of al50-kilowatter and Prague is imbued with!the same ambition. Add to these Langen-1berg and Daventry 5GB, which are no!weaklings, a threat by France to put upia super -power station in Strasbourg as alcounter -blast to Freiburg and Stuttgart,Ithe new Bratislava station, two furtheradditions to Czecho-Slovakia, and Switzer-land's intention to build twin semi -giantsat Gros de Vaud, and Suhrental, and you'have a fair picture of what 193o maybring us-the Battle of the Giants !

LOUD -SPEAKER VARIETIES

ANextraordinary amount of ingenuity

has been expended upon loud -speakerdevelopment. In addition to such standardmodels as horn, cone, and moving -coilspeakers, with their many modifications indesign, one notes the appearance of theelectrostatic type in which 'variations inVoltage, as distinct from current, are usedto set a large diaphragm into audiblevibration.

Another ingenious application of theelectrostatic principle is the so-called"corona" speaker in which voltages derivedfrom a low -frequency amplifier are appliedto a surface which has initially been chargedup to a point just short of that at which asilent brush or corona discharge occurs.The additional low -frequency voltagescreate disturbances in the air moleculesadjacent to the charged surface, and inthis way set up sound waves. B.A.R. Lilian Braithwaite-An Impression by Lissenden

FREQUENCY MODULATION;THE increasing congestion on the ether,1

particularly in the zones reserved for;broadcasting, draws attention to a newmethod of modulation which has recentlybeen developed with the object of reducing:the width of the sideband fringe accompany-ing the wavelength allotted to each station.;

In the new system of transmission,instead of varying the amplitude of thetransmitted carrier wave, the latter is keptat a constant height or level, but the wavesare more crowded together in certain partgithan in others, the relative "spacing" beingcontrolled by the applied microphonecurrents. By using this method of frequency,modulation it is possible to confine the'width of the resultant side -bands to approxi-imately ioo cycles, as compared with normalwidths of 5,000 cycles and upwards'required in " amplitude" modulationsystems. M. N.

APRIL 6, 1929

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A Weekly Programme Criticism by Sydney A. Moseley

T' week of sports commentaries wasnot bad, although the Grand National

did not sound as thrilling as it was lastyear.. Difficult to find the real reason.Possibly the number of horses participatingmade the job of impromptu descriptionhard. Messrs. Lyle and Hobbis coped withthe task like stalwarts, but the odds wereagainst them.

"I am glad to see that you have all ofa sudden 'got religion'," writes H.B.(Who said I had?) "But I am sure that,devout churchman as you must now be,you cannot be in favour of the kind ofSunday broadcast which Was given us from5GB recently." He gees on to enumeratethe items thus : "5-5.30, Children's Ser-vice; 5.30-5.45, Old Testament Reading;5.45-6.55, Church Cantata; 6.3o ReligiousService in Welsh; 8-8.45, Religious Ser-

Charity Appeal; then anhour of Handel's music."

Well, if H.B.-reads my notes as closelyas he pretends, he would know (1) that Iam' not a devout churchman (being merelycontent to be devout) and (2) that I havedone, and am still doing, my best for brightSunday broadcasts.

Are not we getting rather too muchTeddy Brown? There is a sameness abouthim. His tinkly bits all sound alike andhis "stunt" endings are sterotyped, if notidentical. Moreover, he is hardly an expertsaiiophonist-his tone is too fuzzy to beagreeable. Why doesn't he give us a goodprogramme on his xylophone alone? Heis quite capable of doing this.

A reader "views with apprehension" thethreatened return of -Schubert's UnfinishedSymphony " twice nightly." He was"forced to complain" about it not longago, and now finds that after a lull it isbeing served up again. "Although amasterpiece, it does not stand constantrepetition, and I solemnly assure theB.B.C. that in putting it over so 'Oftenthey are helping to ruin it as a classic."After which solemn warning there is onlyone thing for the B.B.C. to do-give itonce nightly 1

Joseph Szigeti gave us a pleasing violinrecital. His playing is of the kind I admire

-more expression and less tricks. Oneitem in particular-De Falla's "SpanishDance "-was rendered by him in such anunderstanding manner that the melodyseemed to live; in fact, it did live.

Are the provincial dance bands up tobroadcasting standards ? _I was listeningto Paul Raffman's band from Birmingham,and one could not fail to make a comparisonbetween this and London bands. Roffmanmay sound well enough in a dance hall, butit does not follow that what serves well ina dance hall will broadcast well. I shouldimagine that Raffman's band is quite goodto dance to "in the flesh," but there aren'tenough instruments in this combination tomake it a success over the ether.

The Count of Como was spoilt by mumb-ling. The music was tuneful enough, butthe continuity was absolutely lost. Thefew words I heard lead me to believe thatI didn't miss much

J. H. Squire has indeed a flair for findingor personally arranging tasteful musicalmedleys. Let us hear the octet play againthese arrangements of excerpts from well-known and well -liked selections and songs.For instance, "Everybody's Melodies"and "A Potted Concert in One Item" areingeniouslyarranged.

Julian Roseexcels himself asan announcer.Well-somewhatof a contrast toour "refaned"announcers, sothat one mustlaugh with him.

All Aboardfrom Birming-ham was anotherof those self-praisedselfrevueswhich turn -outto be common-place variety.In the officialprogramme itwas stated that.

the book was "by accident," and I canwell believe it. I am sure that no onewould sit down and dish up such stuffdeliberately.

4. 4*

Ann Penn-although good-has a faultwhich I dislike. It is staleness. She failsto vary her programme sufficiently, andone tires of even the best material. Thisfault is certainly not confined to Ann.Others need pulling up for the same reason.Wish Wynne, for instance.

"The-shall I say?-abdication of FredElizalde's Savoy Band has given us theopportunity of hearing regularly what isadjudged by the experts to be 'the finestdance band in the country,' " writes"Harold," my adviser on matterssyncopated. "The band in questionis that led by Ambrose at the MayfairHotel."

Well, I don't like to be too dogmaticmyself about dance orchestras, but thereseems to be something in what "Harold"says. Ambrose's band has a quiet rhythmicway about it which is a relief from theblaring crudities of other orchestras. Igather, by the way, that in Ambrose welisten to the highest paid violinist inEngland

Broadcasting Takes the Place of the Newspapers.-The photographshows a crowd outside a London wireless dealer's listening to the

result of the Grand National

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RITAKS "FAVOURITE fiREf

NEITHER apology nor explanationis needed in deseribing - this newversion of Britain's " Favourite

Three," one of the most successful threesvalvers which has been described by theAMATEUR WIRELESS Technical Staff.

There is an interesting little bit ofhistory behind the original version of the" Favourite.'. It will be remembered that it

The wiring isparticularly

simple

was described only last year in "AMATEURWIRELESS," No. 294, and its special pointof interest was that it embodied the circuitvoted first in an AMATEUR WIRELESScompetition which had been organised alittle time before the publication of the" Favourite Three."

-" Choose your circuit" was the theme ofthe competition and the " Favourite " wasthe material, form of the most popular

P T ilIMF DATDual Wavelength Range :: No Coil Changing :: Selectivity Control

oMotor-boatStopper :: For Long orztSh rt Waves

voting. There is no reason to suppose thatalthough developments in wireless are saidto move quickly the voting would be anydifferent to -day, and the fact which will bemost obvious to present owners of the" Favourite" or to those who were interestedin its design on first publication is that thepresent receiver bears very much the sameoutward appearance. Indeed, the end in

view with which this set was designedwas, first, to present owners of Brit-ain's " Favourite Three " a chance toadd and incorporate just those refine-ments which a year's progress hasmade possible, and not entirely tomodify the set to gratify some new

craze; and, second, in the light ofour readers' voting in 1928 and

subsequent technicaldevelopments, to present toall readers the opportunityto make up a really good

practical three, with-out any unnecessary,frills or limitations ofperformance.

ModificationsAs it is expected

that a large number of set con-structors who perhaps have an entirelydifferent type of set will want to makeup this " 1929 Favourite Three," it isnecessary to describe it with the object ofexplaining the whole set to these new-comers. Present owners of " FavouriteThrees" will readily see the additions whichhave been incorporated and can modifytheir own receivers accordingly. There isnot the slightest need to make up anentirely new set and only the minimum ofparts will have to be scrapped.

By far the most obvious feature is that asix -pin coil has taken the place of theprevious plug-in coil arrangement. All set

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owners can see that this is a good point,because, although plug-in coils are by nomeans as dead as the proverbial dodo, in aIII

along the winding, listeners close to apowerful station may have cause to com-plain of lack of selectivity. 'Well, this

A GREAT FAVOURITE.This set was first produced at the beginning of 1928 as a result of an "A.W."competition to decide the most popular circuit. So satisfactory have been theresults obtained by constructors of the "Favourite," and' so insistent has beenthe demand for new facts about this set, that we considered a 1929 edition of the"Favourite" advisable. So here is Britain's "Favourite Three" with all the

latest improvements, and it is one of the best " threes" you can make.114.01111 011111

general-purpose set of this nature coilchanging is nothing better than a bother.The six -pin -coil can be of the dual rangetype and a simple push-pull switch on thepanel allows of either the long or the shortwavebands to be received. Alternatively,the very short waves can easily be received.

With a plain coil arrangement, even if atapping is taken to an intermediate point

difficulty has been overcome in this newedition by the incorporation of a smallvariable condenser of the pre-set type, whichcan, if desired, be placed in series with theaerial lead.

There is a flex connection from the aerialterminal of the panel, to the other end ofwhich is attached a spade tag. This can beshifted from one side of the pre-set con -

WAVE -CHANGE SWITCH ON PANEL

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ANT1-MOTOR BOATING UNIT

This photograph shows the modifications that have been made to bring Britain's" Favourite Three " Up-to-date

denser to the other so that forlocal reception, when the verygreatest strength is needed, and selectivitydoes not matter very much, the series con-denser can be cut out of circuit.

For the reception of the more distanttransmissions adjacent to the wavelengthof the local station, however, judicious useof .the series pre-set condenser will be foundan almost complete cure for inter -station lamming.

Simple' TuningThis will not be found an extra com-

plication when tuning, because formost purposes the condenser can bepre-set at one intermediate valuebetween the possible extremes(say .000r-microfarad), andthis will be suitable for alldistant station reception,while the condenser can becut out altogether bychanging over thepasition of the spadetag for local stationreception. There isample space avail-able on the panel forthe mounting of apre-set condenser if the design reallynecessitated it, but the job is adjustedat such infrequent intervals that thereis no real point in disfiguring the lay-out of the panel and complicating thew:ring by shifting the pre-set conden-ser from the baseboard to the panel.

A common H.T. lead for the anodes of allthree valves is a feature which will beobvious from the circuit diagram, and this,of course, makes for simplicity, since itmeans that only one H.T: potential has tobe applied. The voltage on the detectorvalve anode is, of course, cut down by theresistance of the R.C. coupler, while the

D.C. resistance of the primary of the L.F.transformer cuts down the H.T. voltageto a suitable value for the first L.F. valve.

A trouble which is likely to arise when apower valve taking a large H.T. currentis employed is that motor -boating may beset up, or the tendency to L.F. oscillation

Ample space isallowed for the

components

accentuated. The same trouble is likely toarise if a mains eliminator is employed and,in rare instances, builders of the originalBritain's "Favourite Three" (and inciden-tally of many other receivers having acommon H.T. tapping) may have haddifficulty in preventing motor -boatingwhen working from the mains.

Well, any such troubles are now obviated

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['Air WtreleD 530 AMR/I, 6, 19.29

" BRITAIN'S FAVOURITE THREE UP-TO-DATE" (Continued)in the 1929 edition by the incorporation of amotor -boating stopper in the H.T. circuit.This consists simply of a fixed condenserand 20,000-ohni resistance in series withthe primary winding of the L.F. trans-former. This is a complete cure for motor -boating in a receiver of this type. It will beseen from the photographs that the con-

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denser is placed on the baseboard quiteclose to the R.C. coupler.

Long and Short WavesFor the benefit of those who are making

up the " Up-to-date Three " as a newreceiver, it must be explained that in itsnew guise, or rather with the addition ofits latest improvements, it is a very goodreceiver for general work. In practicallyevery part of the country it should becapable of giving good loud -speaker recep-tion of 5XX, 5GB, and a local station. Inmost cases a healthy batch of foreignersshould also be easily receivable on the loud-speaker, provided, of course, that a goodaerial is employed and there should reallybe no need to use phones in order to get aproper amount of enjoyment from the set.

If you are making up the set as anentirely new venture you will require forits construction the parts mentioned in theappended list. Comparison of this listwith existing receivers will see what needsto be purchased by present possessors of a"Favourite Three" who wish to bring itup to date.

ComponentsEbonite or Bakelite panel, 16 in. by 8 in.,

and strip, 4 in. by 2 in. (Becol, Raymond,Paxolin, Radion).

.0005-mfd. variable condenser, log mid -line type (J.B., Polar, Ormond, Burton,Burndept).

.00025-mfd. variable condenser, log mid -line type (J.B., Polar, Ormond, Burton,Burndept).

7 -ohm panel -mounting rheostat (Lissen,Igranic, G.E.C., R.I. & Varley).

68.-2

Push-pull switch (Lotus, Lissen, Trix, 50,000 -ohm resistance (Graham-Farish,Wearite). Lissen, Dubilier, Mullard, R.I. & Varley).

Panel brackets (Bulgin, Cameo). 2-mfd. fixed condenser (Lissen, DOilier,Dial indicator (Bulgin). T.C.C., Ferranti, -Mullard).Three anti-microphonic valve holders how -frequency tratisfOrmer (R.I. and

(Benjamin, Lissen,- Burton, Wearite). Varley, Lissen, Philips, Mullaid, Cossor.0003-.000025-mfd. pre:set condenser Igra.nic).

(Forniodeiiser type J, Igranic). ' . Grid -bias battery clips (Bulgin): Two,.0003-mfd: fitted con- black and one red wander plugs (Clix).

denser with series clip Baseboard, 16 in. by gin. (Pickett,0 HT+(Dubilier, Lissen, Gra- Clarion, Camco).ham-Farish, Mullard).

2-megohm grid leak(Dubilier, Lissen, Gra-ham-Farish, Mullard).

Six -pin coil base(Tunewell, Lissen, Lew -cos, Peto-Scott).

High -frequency choke(Lissen, R.I. and Varley,Burndept, Polar, Tune -

o L.T+ well, Trik).Resistance - capacity

coupling unit (Dubilier,Lissen, R.I. & Farley,Graham-Farish, M u 1 -Imid).

LT-T -

Connecting wire (Glaaite). One yard ofthin flex (Lewcoflex).

Seven terminals, marked : Aerial, Earth,L.T.-I-, L.T.-, L.S.-, L.S.(Belling -Lee, Eelex, Igranic).

The following constructional details willbe of interest to those who are making up theset, while those who are simply adding thetit -bits, as it were, may pass on to theoperating details which will be given.

A new blueprint is available, and can beobtained, price Is., post free, from Blue-print Department, AMATEUR WIRELESS,58-61 Fetter Lane, London, E.C.4. This is agreat help in building up the set, because

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APRIL 6, 1929entaleurWixel2

The ARCADIAN PORTABLEAFIELD

WITH the instructions for building the"Arcadian Portable" published last

week and in the previous week, AMATEURWIRELESS Nos. 354 and 355, readersinterested in portable sets have had anopportunity to make up this excellent1929 portable. In last week's issuesufficient operating notes were givento enable those listeners who had com-pleted the construction of the receiverand loud -speaker unit to get the wholeportable working as soon as possible.Thumb Control

As stated in the specification of the" Arcadian," the fact that it is to tallintents and purposes a one -thumb controlreceiver is a great operative advantage;it is interesting to note how this works.If you take an ordinary H.F. and detectorreceiver it will be found that if logarithmiccondensers are employed for tuning, the dialsettings will be approximately the same overthe middle portions of the scales, andany variation between the settings ofthe H.F. and aerial condensers will benoticed only at the extreme ends of thescale. This is simply because one circuit

531

-gets a little " behind " or "ahead" of theother, and this can be corrected quiteeasily simply by placing a small correctingor balancing condenser across one circuit.

This is just what has been done in thepresent receiver. Thus, when operatingthe "Arcadian" the knob of the gangingcondenser (which, as a matter of fact, is apre-set condenser mounted on. a woodenpanel) should be adjusted in conjunctionwith a thumb control, and at the extremeends of the Main condenser scale the gang-ing condenser will be found to be relativelyimporfhnt.

The circuit of this portable is a veryefficient four-valver, and if used as anindoor transportable the receiver can bemade to give Some very startling results inthe way of DX getting.

Full Volunie Oat -of -doorsAs a portable, however, only the stations

which can be received at full volume arereally of interest, because when out of doors,and for dancing at picnics, and so on, fullloud -speaker strength is an asset., As amatter of interest it may be stated that the

SOME HINTS ONITS OPERATIONdial readings of the stations whichan average London amateur willwish to receive when working the

"Arcadian" out of doors, are asfollows : On the short waves-London, 98 degrees, Daventry5GB, 140 degrees; on the long

waves-Croydon, 8o degrees; Hil-versum, ioo; Daventry 5XX, 145degrees and Radio Paris, 170.

As the main condenser dial isgradually turned from zero to 180 degreesby means of the thumb control, the knobof the pre-set condenser should be slowlyscrewed in a little at a time, in order tocorrect for inaccuracies of ganging.

If, for any reason, it is desired to get atthe "internals" of the receiver while it is inoperation it is better to move the loud-speaker side of the cabinet rather than theset side, for the loud -speaker can be removedwithout disturbing the batteries. It maybe necessary to do this, for instance, in orderto adjust the reed movement of the loud-speaker or to vary the H.T. or screen -gridvoltages.

One little point which may be mentionedas the result of an extended practical testof the "Arcadian" is that it is wise to seethat' all the battery plugs are a tight fitin their sockets before closing up the sidesof the receiver. Loose plugs and faultyconnections can cause a deal of bother inportable sets, and troubles of this kind aregreatly accentuated if the receiver is usedin a car, and in consequence the "works"are severely jolted about before the set isput into operation.

"BRITAIN'S FAVOURITE THREE UP TO DATE" (Continued fronz preceding page)on the one sheet are incorporated a wiringdiagram, drilling guide, and layout template.When drilling the panel do not forget theholes for the mounting brackets and thosethrough which wood screws are passed inorder to attach the panel to the baseboard.

The blueprint can be used in a veryconvenient fashion for showing the exactpositions of the baseboard components. Itis rather important to adhere as closely aspossible to the dimensions given in thisoriginal design and no difficulty will befound in doing so, for there is ample spaceto spare on the baseboard and panel.Wiring -up should be carried out with rigidwire, and in this particular instance in orderto make the job of wiring -up as simple aspossible, bare wire, and not insulated wire,such as Glazite, has been employed.

For the variable connections, such as thelead from the aerial terminal to the pre-setcondenser, and the three leads to the gridbias battery, thin rubber -covered flexiblewire, such as Lewcoflex, is best employed.The grid bias connections are taken asfollows : One from the moving arm of thefilament rheostat to the positive batterysocket; one from the G.B. terminal on theR.C. coupler to about the 3 -volt tapping onthe G.B. battery; and finally one from theG.B. negative terminal on the L.F. trans-former to the 71/2 or 9 -volt tapping.

A wiring point which will be of interestto owners of existing "Favourite's" is thatthe connection which formerly made con-tact with all the one -hole fixing devices onthe panel has now been dispensed with asit is possible that some constructors did not

manage to make a very good job of "com-moning" the framework of the two.condensers and the moving arm of therheostat with this one connection fixedbetween the components and the panel. Inthe present design this busbar has beentransferred to a more accessible position, aswill be seen by the photographs.

As usual, this receiver can be seen in theSomerset Street windows of Messrs. Self-ridge, Ltd., and London listeners shouldtake advantage of this excellent opportunityto see the way in which this very popularthree has been brought up to date.

The Radio Corporation of Americarecently issued its annual report for 1928,showing total gross income of $101,851,603and net income of $23,661,990,

Mateur Wtreig.D 5-32 APRIL 6, 1929

"A.W." TESTS OF APPARATUSConducted by our Technical Editor. J. H. REYNER. B.Sc. (Hons.). A.M.I.E.E.

Grawor Loud.speakerALOUD-SPEAKR of a novel cone

type is the Grawor and ari instrumentof this type has been received for test from.Messrs. Henry Joseph, II, Red Lion Square,High Holborn, London, W.CA. A cone ofa resultant rectangular form is employed inthe Grawor and the diaphragm itself iscomposed of four damp -impervious sectorsjoined together by strips of pliable material.Each strip has a maximum width' equidis-tant between the apex and the edge of thediaphragm, and this gives a useful degie-eeof elasticity.

The edges of the diaphragm are attachedby means of a Pliable surround to a lightwooden chassis which is really capable ofproducing a sufficient baffle effect withoutfurther enclosing of the back of the dia-phragm. Nevertheless, for domestic reasonsit is usually desired to operate the instru-ment in a cabinet and an attractive rangeof loudspeakers complete in cabinets isobtainahha The chassis are made in threesizes, namely I2.1 in.., 16 in. and r6 in..square, and each is fitted with a Graworreed movement.

The resultant tone is very pleasing andnot unnaturally deep.. Speech is verynatural and not tinged with that "boom-inesS" so often produced by cone -typelend-speakers.Which appear to give a very

"rel3irecluction ofthe ordinary musicalfrequ ey ran v. '

'

Grawor Loud -speaker

Potar Reaction CondenserTN these days of high -magnification screen-'. grid valves, it seems almost unnecessaryto fit a slow motion control to thereaetioa;but, having used such a condenSer; in difa;ee-.eat types of circuit, we are conireenced thatit forms an aid to tuning and adds pleasureto this operation. This is particularlytrue in the case of 'portable receivers whenthe reaction ematxol is of 'far greater im-par lance.

The construction of the new Polar Idealreaction condenser which we have receivedfor test is particularly robust. The mov-ing plates are held in position by an insu-lated moulding at the panel end in whicha cone and ball bearing is fixed : the bearing

- at the farther end and the slow-motiondevice are clamped to insulated supportswhich form part of the main moulding.Although the fixed plates are clamped at

Poen- Reaction Condenser

one end only, they are amply rigid add eamnot be appreciably distorted even weeconsiderable pressure is applied to them.

Two small knobs are lifted, the outer ofwhich is fired to a spindle mounted to themain spindle and controlling the slow mo-tion ball gearing. The slow motion ratiois approximately 20 to t. The second knobis attached to the main spindle and givesa t : t ratio. The motion is smooth andfree from stiff spots.

Complete with one hole fixing device andterminals OA component makes a mostuseful reaction condenser. The total lengthof tire; component is 2 Y2 in., whilst itswidth is in. We found the maximumcapacity was aa micro-microlarads.

The makers are Wingrove and Rogers,Ltd., Mill Lane, Old Swan, Liverpool.

Siemen's Grid -bias Battvy -

TH.ERE are many points in a receiverat which it is very convenient to place

a small r 1/2 volt grid -bias battery in orderto obviate the need for taking' G.B. leadsout to tappings on an external battery.

For example, a midget r I/2 -volt cell canconveniently be incorporated in the screen -grid H.F. stage in order to provide thenecessary bias, while in the case of ananode -bend detector, it is a. good point tosee that the necessary biasing voltage isgenerated fairly close to the valve itself andthat lengthy grid leads are not trailed aboutthe receiver.

A convenient little bias battery whichfulfils all these requirements is manu-factured by Messrs. Siemens Bros. !Se Co.,Ltda..' of Woolwich, London. Exter-nally the cell is rectangular and, roughly

speaking, has thh overall dimensions of 3 in.by ra in., while at the base are attachedtwo cardboard flaps which facilitate thetacking of the battery to the baseboard, orother methods of fixing. Convenient term-inals are provided and the polarity indica-tions are clearly moulded on the insulatingcompound at the top of the cell.

It may be remembered that cells of thistype have been used in AMATEUR WIRELESSreceivers and we have found them entirelysatisfactory and very convenient in use.

G.E.C. Reed MovementGENERAL .ELECTRIC CO.,

Magnet House, Kingswa.y, London, W.are well known as manafacturers of high-class loud -speakers of the cone type; it istherefore to be expected that the new conewhich has been recently -ffitroduced by theG.E.C. would be a well -designed article.Actually this is aninexpensive unit andu di sea a straightforward magnetic system.

E eery effort is made to keep the com-ponent compact : the electro-magnet andarmature are mounted in a metal cradlewith dimensions of 312 in. by OA in. by

1/2 in. high : these dimensions do not takeinto account the length of the reed, theadjusting knob or the terminals. It ispossible when building portable sets, tomount the unit inside the cone, even if thecone angle is somewhat obtuse. Thearmature, comprises a strip of metal firmly

G. E.C. Reed Movement

fixed at one end and lying over an electro-magnet at the other.

We tested the unit in conjunction withseveral cones including a good qualityfloating cone. The results were quite good,music and speech being reproduced withclarity and pleasing tone. Although thestrength of reproduction was not quite ashigh as some expensive units we have testedthe overall performance is satisfactory andthe unit may be recommended,

APRIL 6, 1929 533

ARCADIAN PORTABLE(Described in "A.W." March 23)

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(i maw Wirete5 534

R(TDIOGR(IMSPHOTOGRAPHS

takn during the BoatRace were transmitted experimentally

by the Fultograph process from Daventry5XX between -2 and 2.45 p.m. on the sameafternoon.

The Glasgow Bach Society's concert onApril 8 in the Stevenson Hall is to be put"on the air." The broadcaSt will includethe Concerto in C major for three pianosand strings, the Concerto in D minor forsolo violin and strings, which is a trans-cription of the Concerto in D minor for solopianoforte andsstrings, and one item riot byBach-a suite for strings from the sym-phonies of William BoYce.

Northern listeners will be interested tohear that "George." and "Wullie" are toretuili to the Aberdeen studio on April 12.Some twoyears ago a meeting of these two"worthies" (created by Arthur Black)was 'a weekly feature of Aberdeen pro-grammes.

The French P.T.T. has now definitelydecided on the site of the new high -powerStrasbourg transmitter; the station is to beerected at Brumath, some 14 miles fromthe city.

Anthony Hope's famous novel " ThePrisoner of Zenda," which scored so greata success both on stage and screen, is being

adapted for the microphone and will bebrOadcast from London and Daventrysome time in May.

" That the broadcast play is not a satis-fact'ory form of art" is the subject of adiscussion which will take place betweenMiss Naomi Royde Smith and Mr. ComptonMackenzie at the 5GB studio on April 19.Savoy Hill is providing the disputantswith microphone facilities to enable themto decide whether the broadcast play canever "get over."

The Foden Motor Works Band havebeen declared eight times chafinpions ofthe Belle Vue Contest at Manchester; lastyear they were awarded the challenge cupoutright. On April 8 both London andManchester, will broadcast their concert.

Square Pegs, a polite satire by CliffordBax, and The Dear' Departed, by StanleyHoughton, will be found in the varietyprogramme given to 5GB listeners onApril 20; as usual; Clapham and Dwyerwill contribute their spot of bother.

On April 18 the Newcastle studio willpresent a new revue entitled Tyney Trifles,from the pen of the Gateshead humorist,E. A. Bryan; the cast will include SalSturgeon, Doris Miller, Tom Heenan, andHarold Earnshaw, all popular favourites.

APRIL 6, 1929

In order to reduce serious interference,,the French broadcasting authorities areendeavouring to obtain permission for theEiffel Tower to lower ,its ivaVelength to1,47o metres; in the meantime -the trans-mitter suspended the broadcast of the mid-day concerts for"one week in order to carryout a shortening of the aerial.

Russia is holding its first radio lotteryon April 15. The broadcasting authoritiesrecently received authority from theSoviet Union to organise a national lotteryin which the prizes to be won consisted ofwireless transmitters, loud -speakers, andother radio material. Two million ticketshave been issued at 5o copecks each (about6d.); all profit derived from this under-taking is used for the development ofwireless instruction in schools and work-men's clubs.,

From a Continental source it is reportedthat the Baird International TelevibionCompany, Limited, has now concludedcontracts with some seven European sta-tions for the transmission of. living pic-tUres; Berlin will be one of the first Con-tinental cities to be so equipped-to beclosely followed by Radio Paris.

Test transmissions have been satisfac-torily carried out with the new Viennashort-wave transmitter, and it is statedthat details of the official times of broad-cast, wavelength, and power will be shortlyissued. The station will relay the Viennaentertainments.

The high -power short-wave Dutch wire-less station at 'Huizen (PCL) works on18.4 metres between it a.m. and 5 p.m.,and on 38.8 metres from 3 p.m. to I a.m.G.M.T., thus giving daily a fotirteen-hour'public telephony; service.

MR. FLEX RECEIVES A CALLER-I WAS PASSING

V\,...,s/114.........._-4THETHIS WAY

DOG, OLDMAN), AND

1,, THOUGHT. I'D JUST

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APRIL 6, 1929 535

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736

LETTERS TOTHE EDITOR

The Editor does not necessarily agree withthe views expressed by correspondents.

Round the World with an "A.W." SetSIR,-Having had your "Home and

Abroad" set during my trip round theworld, I felt I ought to write and let youknow the excellent results obtained at thedifferent places we visited.

When off watch at night I used to listenregularly to 2)(AF all along.the Mediterlranean. 5SW and PCJJ were easily ob-tained in Australia. Melbourne was heardin the Suez Canal, and now with coils2, 4, and 6 or 7, according to the type ofdetector valve in use, Huizen comes in on16.88 metres. I added one stage L.F. forgood speaker results, and feel quite dis-appointed if unable to listen for some sta,tion about 2,000 miles away. The chiefdifficulty, however, is the difference intime, but the other morning, quite onehour after sunrise, 2XAF was comingthrough on the loud -speaker.

B. (Annan).

Foreign ValvesSIR,-I entirely agree with J.D.B.

(Ulster) that the cheaper foreign valveslack " pep.'! I must explain that my pre-vious letter was only written in the samestrain as the article which prompted it,i.e., valves were being compared solely bytheir mutual conductance valui.s: and assuch the particular make of Austrian valvementioned was- equal to English. It willbe remembered, however, that I mentionedthat the Part of a valve which is of 'para-mount importance is the filament, thequality of which,. I admit, is doubtful inthe cheaper valves.

As he appears to have been unfortunatewith the foreign valves he has bought, Iwould suggest that J.D.B. should trythose made by the Dutch firm Philips,which are .sold in France at 37.5o and55 francs (ordinary and power respectively).

J. S. (London, S.W.).

A Linen Speaker ControversySeveral letters have appeared in

your correspondence columns latelyfrom readers who have constructed linen -diaphragm loud -speakers. While makingallowances for the exuberance developedwhen suddenly becoming the possessors ofloud -speakers 'very imich superior in per-forncance to anything they may have pre-viously owned, such remarks as "equal to,or better than, any moving -coil speaker Ihave heard" Cannot be allowed to passwithout comment.,

-The plain- fact is that, to people with amusically trained ear (and they are com-paratively -few), the M.C. speaker, operatedunder correa) conditions, is hi -comparablyin a- -class by itself. One wonders whatconditions obtained when your enthusiastic

APRIL 6, 1929

"linen -diaphragm" construct-ors formedtheir opinions of M.C. reproduction. Theymust have been pretty ghastly ! The con-ventional " Det,, 2 L.F." or " H.F.,2 L.F.,' With 120 volts H.T., will mostdecidedly not cope with a M.C. speaker,

To the many "plodder"" in the searchfor quality reproduction, via M.C. speakers,the extravagant claims of some of your" linen-ites " must be somewhat amusing.

I have bifilt ydur "linen" speaker, andagree that it is good-exceptionally good.But in moving -coil class-no, decidedlynot.

,1'o conclude, it is an established medicalfact that a very high percentage of theinhabitants of these islands is partly orwholly-" tone-deaf " !

F. S. (London, N.).

Mr. Frank NewmanCIR,-I was pleased to see my photo-

graph among "Broadcast Artistes ofthe Month" itt No. 354 of your excellentpaper (page 444), but must beg you, ifpossible, for the insertion of a correction.

I left Lozells Picture House, Birming-ham, on February 7 (when I gave my lastbroadcasf) to go to the New EmpireTheatre, Leicester Square, as one of thetwo solo organists there. At the EmpireI have the largest cinema organ in thiscountry-a Wurlitzer organ.

FRANK NEWMAN (London, W.).

5XX QualitySIR,-I have followed the correspondence

in AMATEUR WIRELESS for a consider-able time and note that W. J. F., (Redruth)experiences the same trouble that one hears°mall sides in Penzance. 'No one can denythat the quality of 5X X varies considerablyin such short periods as twenty-four hours.The programmes are only comparable tomincemeat, especially when from 8 p.m.to 8.3o p.m. "Daventry only" a talk issandwiched in on any subject.

Why we should be penalised, -I really amat a loss to understand. Thus, again thetit -bit Of the evening is usually 9135 toti.o, which is after country listeners havegone to bed.

I imagine that A. M. H. (Coventry) hasa number of stations at his disposal, andis not a 5XX listener only. Should thiscorrespondent visit ' Cornwall, he will bewelcome to try the experiment of listeningto 5XX for one week.

Perhaps A. M. H. would be interested toknow that 5GB is not comparable withsuch stations as Turin, Toulouse, Nurembergand Stuttgart at one quarter of the power,and as an alternative programme it is uselessto us here. BRITISH Six (Penzance).

NEXT WEEK

An All -from -the -Mains "Two"Don't Miss It!

APRIL 6, 1929 537 ittrifc ur

ilefilliiils60,"

0010011400

ddl1111111111100

RULES .-Please write distinctly and keep to the point. We reply promptly by post. Please give all necessary details. Ask oner,tiestion at a time to ensure a prompt reply, and please put sketches, layouts, diagrams, etc., on separate sheet; containing your narn End address. See announcement below. Address Queries-Alta:mutt Wzavr rss Information Bureau, 58/61 Fetter Lane`, London, E.C.4 -

Aerial Types.Q.-Why is it that most amateurs use a single -

wire aerial for their receiving stations when,according to what can be seen from photographsof professional stations and warships, the use ofa multi -wire aerial of the cage or " sausage "type appears to be the type most favoured bythe people who should know which is the bestaerial.-A. P. (Godalming).

A.-Multi-wire aerials of the type you referto possess a large capacity and as a fairly largecapacity aerial is required for transmittingpurposes it explains why such aerials as youhave seen in photographs are in common usein professional circles. The receiving aerialsof these stations and ships, however, are of thesingle wire type and if it were possible to seemore detail in the photographs in question oreven to visit the stations or ships themselves itwould be seen that quite a small single wireaerial is in use in addition to the large mainaerial.-L. C.

QVVVVVWVVVVVVVVP> When Asking

Technical QueriesPLEASE write brieflyand to the point

A Fee of One Shilling (postal orderor postage stamps) must accompanyeach question and also a stampedaddressed envelope and the couponwhich will be found on the last page.Rough sketches and circuit diagramscan be provided, but it will be neces-sary to charge a special fee (which willbe quoted upon request) for detail

o> layouts and designs.

MMAAAA

0

0

0

AAA.A.A A

Damaged Valve.Q.-Recently one of my valves was dropped

from a height of about 3 ft. to the floor and,although the filament is intact, the valve nolonger works. Can you suggest what has happened?

A.-It is possible that th.e electrodes havebecome misplaced and either ,the filament istouching the grid or the latter is touching theanode. A defect of this kind can be traced bytesting with a battery and meter, between thegrid and filathent or grid and plate legs of thevalve for short-circuits. If no reading isobtained in either case the valve is all right onthis score, and probably one of the wires. mayhave broken off between the electrodes and thelegs.. This can be remedied by removing thebase and completing the broken wire. If theelectrodes themselves are damaged, or theirpositions altered, it is improbable that thisvalve will work properly again ; in any case itscharacteristics will be materially altered.-B.

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533

"CUTTING OUT NEEDLE SCRATCH"(Continued from page 523)

sense of the word, since all that is happen-ing is the gradual diminution of the outputin a manner somewhat similar to thatindicated in Fig. i.

An improved form of filter can beobtained by connecting a resistance inseries with the condenser. This acts as apotentiometer arrangement. At the lowerfrequencies the reactance of the condenseris very high compared with the resistance,and therefore nearly all the voltage isdeveloped across the condenser. At thehigher frequencies the reactance of thecondenser becomes small, and we moverapidly down the potentiometer, as it were,so reducing the output. The form of cut-offobtained with an arrangement of this sortis illustrated in Fig. 2. It will be seen tohave some form of cut-off point, althoughthis is not very great.

A Better SystemA better form of filter is that shown in

Fig. 4, where we have an inductance inseries with a condenser. This again acts asa sort of potentiometer. At low frequenciesthe inductance has little effect, while thecondenser presents a high impedance, sothat most of the voltage is developedacross the condenser. At high frequencies,on the other hand, the inductance has alarge effect, while the condenser has onlya small impedance and most of the voltageis developed across the inductance. As ouroutput is connected across the condenser,we are only left with quite a small amountand we obtain a cut-off.

The cut-off here, however, is accen-tuated because a resonance occurs at sometransitional point between the two effectsjust considered. Without this .resonancethe cut-off would be somewhat as indicatedby the dotted line in Fig. 5. The resonanceoccurs, however, at a point where thecurve is beginning to fall away, and thishas the effect of increasing the voltage onthe output. The voltage developed acrossthe condenser, indeed, may even exceedthat on the input, so that not only do wemaintain the curve level, but we actuallycause it to rise slightly. As soon as thisartificial boosting effect has finished, how -

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THE LATEST SCIENTIFICDEVELOPMENT IN CONE UNITSSpecially Recommended for the Linen DiaphragmThe Lassophone Triangle Fork Reed Balanced Armature ConeUnit is a triumph of British inventive genius ant work-manship.Reproduces all frequencies equal to a moving coil speaker onany set.Guaranteed not to overload on the most powerful set.Specialty recommendel for use with The Linen Diaphragmand i5 unequalled by any other unit.

The LASSOPHONEFork Reed Balanced Armature Cone Unit

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H. H. LASSMAN, F.R.A., A.M.I.R.E.(Dept. A.W.), 429 Barking Road, East Ham, E.6

ememmillewilivellelemmoolicumaM.B.

ever, we. fall very rapidly down to thenormal curve indicated by the dotted line,after which the frequencies are cut off moreor less uniformly to an increasing extent.

It will be seen that the effect of thisresonance has sharpened up the cut-off veryconsiderably. It is still not a really sharpcut-off, and such a result can only be obtained by:the use of a number of sectionsall made up in a similar manner. ' This,combined with the proper design of thevalue of inductance and capacity to accen-tuate the resonance effect, enables particu-larly sharp cut-off filters to be made up.The reader, however, who wishes to experi-ment can do this by using an arrangementsuch as that shown in Fig. 4, using high -frequency chokes for the inductances andvarious values of condenser until he obtainsthe required cut-off. It is preferable to usechokes having a really high inductance,such as the Lewcos, Bulgin SG type, or theBurne-Jones. With such chokes a capacityof the order of .005 will, be found to givethe required results.

WIRELESS IN PARLIAMENT(From Our Own Correspondent)

MAJOR OWEN asked whether therewas any provision in the regulations

relating to wireless licences whereby totallyincapacitated persons might be excused thepayment of the annual licence.

Lord Wolmer said the answer was in thenegative. The only wireless licences issuedfree of charge were those issued to blindpersons under the provisions of the WirelessTelegraphy (Blind Persons Facilities) Act,1926.

We are to hear a Kennedy -Fraser recitalfrom all Scottish Stations on April rr. Thiswill be given from two studios. From Glas--gow the Station Orchestra will play aselection of the Kennedy -Fraser melodiesand the Rev. Kenneth MacLeod will tellsome of the island legends on which thesongs are based. From the Edinburghstudio, Mrs. Kennedy -Fraser, MargaretKennedy, and Patuffa Kennedy -Fraser,will give a recital of the songs. Some ofMiss Patuffa Kennedy-Fraser's songs willbe sung to her own accompaniment on anold Celtic harp.

The completion of the new big broad-casting station in Prague, which is beinginstalled by the Standard Electric Com-pany, will be in operation during the courseof the year.

In the Royal. Gazette, which is the officialpublication of the Spanish Gbvernment,appears an order approving the project putforward by the Radio Society of Argentinefor the establishment of wireless com-munication between Spain and theArgentine.

Picture transmissions on the Fultographsystem are shortly to be carried out dailyby the Prague and Bratislava broadcastingstations.

H.F. ChokeMassive All Purpose

5/9 each.MULLARDDUALCOILS7/9 &10/6

TWO - PINCOILS

all typesfrom1/6

APRIL 6, 1929

" GRAWOR "Comes to your aid !

THE " SECTORPHONE "LOUD - SPEAKER CHASSISembodying the famous" Grawor " Double MagnetUnit and an entirely new andPatented design of diaphragmhas set a new standard inreproduction.Every independent test has provedthese statements.The " Grawor" Unit fitted has apowerful double' Magnetic System.

Balanced armaturemovement. PerfectReed adjustment.Carries full loadswithout a vestige ofdistortion.SECTORPHONE'

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Price. With Double Magnet Unit 53/ -With Single Magnet Unit 48/ -

Obtainable from all Dealers, or direct.

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MINIIMMMEMM,

TUNEWELLwith our DUAL RANGE COILS

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Illustr,tion of our Cossor Circuit DualAerial Coil, showing base mounting

and switch control.

TURNER & CO 54 STATION RD., LONDON : N.I I

539

RADIO -EQUIPPEDTRAINS

MOST of the long-distance expresses inAustria are now equipped with receiv-

ing apparatus for the reception of broadcastconcerts, special carriages being reservedfor passengers desirous of passing away thetime with these entertainments. A chargeof roughly sixpence per hour over andabove the railway fare is made; andstatistics show that the service has rapidlygained in popularity; whereas from Septem-ber to December, 1926, io,000 travellershad paid fees to listen to the concerts, fir1928 the figure had increased to loo,000.It has been proved that some 70 per cent.of the passengers carried on trains at sometime during the journey now visit theradio compartment. Generally speaking,only transmissions from the Vienna stationare tuned in, but as occasions arise, solisteners are given opportunities of hearingmany of the German entertainments. Inorder to avoid any possible interferencethe carriages containing both the receivingsets and headphones are lighted by gasonly. Arrangements are now being madewith neighbouring countries to provide asimilar service on international trains.

The San Francisco studio of the NationalBroadcasting Company (U.S.A.) reportsthat its musical library, consisting of some0,000 pieces of music, is valued at about

,65,000

efisoieurWtrdez,

DOMINION

BROWNIE are now producing 2,000Dominion Vernier Dials a day.

That is why it is possible to offer thishigh-grade dial at the wonderfulprice of 3/6.The mechanism is a special non -backlash design with a reductionratio which makes fine tuning easywithout becoming tedious.Obtainable from all wireless dealersin beautifully finished plain black orlovely grained mahogany bakelite.

1:LSON Sc. WORKS

ESS.

LONDON, N.W.

RADIOpRODUCTS

THE NEWTHREE SPRING

WAVECHANGE SWITCHHere is another line at a popular price.

Made with the same precision and finish as all BulginProducts which have made them world famous. Willfit all panels from paper thickness metal to a" Eboniteby the unique method of design. Highly polishedknob, plating, and fitted with 3 terminals.

SEND FOR OUR FREE 56 PAGE CATALOGUE & WIRELESS .11.1 'JU:7 LA. F. BULGIN & CO., 9-10-11 CURSITOR ST., CHANCERY LANE, LONDON, E.C.4

Amateur Wireless HANDBOOKS each 2/6 net.

TIIE

The Shielded Four -elec-trode Valve.

Loud -speaker Crystal Sets.Wireless -controlled Mechan-

ism for Amateurs.The Wireless Man's Work-

shop.

The Practical " Super -het "Book.

Perfect Broadcast Reception.'The Short-wave Handbook.The Practical Wireless Data

Book.BOOK OF THE NEUTRODYNE, by J. H. Reyner, B.Sc. (Hotrs.), A.M.I.E.E.

Price 1/6 net, or post free for 1,9

Of all Newsagents and Booksellers or by pmt, 3d.extra, from Cassell& Co., La Belle Saavage, E.C.4.

so UNIV.V.,0411.CIIMI004041=1,0M041.0411M00.4041M104MEN,EMPNIAM.Ii0101.0.11.0.11.1MO.G.I.F0.11111.1141M

ti mating' Wireless 540 APRIL 6, 1929

04)00.0*****.00.4+41104440.04,4:404.*.*Itto.0400040.4041.43.044).4).0404).0

FULL-SIZE BLUEPRINTSFOR EVERY REQUIREMENT

Each blueprint shows the position of each component and every wire, and makes construction a simplematter. Copies of " Amateur Wireless" and of " Wireless Magazine" containing descriptions ofall these sets can be obtained at 4d. and Is. 3d. respectively, post free. Index letters "A.W." refer

to" Amateur Wireless" sets and" W.M." to Wireless Magazine" sets.

N.uper Set,`Best -yet" Set ..rezo Crystal ReceiverTwo -programme SetCentre -tap Set .. 4

ONE -VALVE SETSAll these is. each, post free.

rHartley DXEconomy OneLoud -speaker SpecialUltra -sensitive Hartley OneSuper Reinartz One ..Beginners' One-valverLong-range Hartley ..Reflexed One for the Loud -speakerSpecial OneReinartz One ..

CRYSTAL SETSAll these 6d. each, post free.

TWO -VALVE SETSAll these Is. each, post free.

;Wide -World Short-wave (D, Trans) ..Empire Short-waveNext Step z (D, Trans) ..Centre -tap 2 (D, Trans) ..Rover 2 (HF, D)General-purpose_ 2 (D, Trans) ..3o/- 2 (D, Trans),Trapped Reinartz (D, Trans) .."Q" 2 (D, Trans)Long Distance Two (HF, b,) .Three Two (D, Trans).DX Headphone Two (HF, D)

;Ace of Twos (D, Pentode) ..Home Two (D, Trans) . _ ,Chapman Reinartz Two (D, Trans -4d. with

copy of "A.W.") .

'Globe DX Two (SG, D.jEast to West Short-wave Two (D, Trans) ..Beginner's Two (D. Trans.) ..'Auto Two (D, Trans)British Broadcast z (D, Trans),Two -programme 2 (D, Trans) ..Q -coil 2 (D, Trans)Crusader (D, Trans) ..Flat -dweller's 2 (HF, D)Two-Daventry Two (D, Trans)Tetrode Short-wave Two (SG, D)Key -to -the -Ether Two (D, Pentode)Meteor Two (D, Trans) .

Clipper Two (D. Trans) ..

THREE -VALVE SETSAll these Is. each, post free.

Short-wave (D, RC Trans)Ether -searcher (D, RC, Trans)Standard (D, 2 Trans)Hartley DX (D, RC, Trans) Broadcast 3 (D, RC, Trans) .Selectus 3 (HF, D, Trans)Q -coil 3 (D, RC Trans)Clarion 3 (D, z Trans)Miniature Hartley ThreeSummer -time DX Three (HF, D, Trans) ..

.Three -valve Mains Receiver (HF, r), Trans) ..British Station Three (HF, D, Trans) ..Optional Two -three (D, zLF)"Simpler Wireless" Mains Three (D, 2"LF)Simplicity Screen -grid Three (HF, D, Trans)"Proms" Three (D, RC) ;

Adaptable Three (D, z Trans) ..New -style Baffle Three (D, RC, Push-pull-

Price 1/6) ..

AW64AW154AW165WMz5WM50

AW27AW7iAW78

AW1o3AW1 27AWt4oWM54WM6

WMt 16WMI27

AWiIAWz8AW34AW42AW53AW55AW6AW92AW99

AW1 soAWis2AWI34AW143AWs46

AM's 48AW157AW159AWs7iAW174WM44WM56WM62WM69WM76WM97WM99

WMio7WM114WM135

AW5oAW52AW56AW63AW76AW8iAM+AW88

AW vasAW io6AWto9AW122AWs24AW126AVV132AWr37AW139-

AWt4t

ALLBLUEPRINTSOF SETS AREFULL-SIZE

All -wave Mains Three (HF, D, Trans, Rectifier-Price 1/6)

All-purpose Short-wave Three (D, RC, Trans) AAWW:447

Screen -grid Q -Coil Three (HF, D, Trans) .. AWisoNew -style Mains Three (HF, D, Trans-Price

1/6) .. AW151All -Round Three ( RC, Trans) AWi55James Special Three(HF, D, Trans) .. AWs56All Britain Three (HF, D, Trans) .. AW158Bantam Three (D, RC, Trans) .. AWI6oHartley, Dual -range Three (D, RC Trans) .. AWi66Listener's Three (HF, D, Trans) Price 4c1. free

with copy of "A.W." . .. AW169Binowave Three (D, RC, Trans) .. AW172Clarion Three (SG, D, Trans) .. .. AW 755929 Favourite Three (D, RC. Trans) .. AW:79Five -guinea 3 (HF, D, Trans) .. . WM29Mains Three-valver (D, zLF) WM34Tuned -anode from the Mains (HF, D, LF) WM43Metropolitan (D, zLF) .. WM413Everyday (D, 2 Trans) .. WM5zMusic Charmer (D, R.C, Trans) WM6oBritannia (0, RC; Trans) WM67Pole -to -Pole Short -waver (D, RC, Trans) .. WM89Glee -singer Three (D, 2 RC) .. WM92Aladdin Three (HF, D, LF) . WM95Inceptor Three (SG, D, Pentode) Price is. 3d.

with copy of "W.M." WMto5All -wave Screened -grid Three (HF, D, Pentode WMs soGramophone Three (D, 2RC) WM115Standard Coil Three (HF, D, trans) WM' t7Festival Three (D, 2 LF-Dual Imp) .. WM118Wide -world Short -waver (SG, D, Trans) .. WMtzoNew Year Three (SG, D, Pentod..e) WMiz3wm:24

The Q3 (D, RC, Trans) ..Lodestone Three (HF, D, Trans) .. WIV1129Simple Screen Three (HF, D, Trans) .. WM131Dynamic Three (SG, D, Trans) WMI36

FOUR -VALVE SETSAll these Is. 6d. each, post free.

"Q" 4 (HF, D, RC) _ _ . AW98Explorer Four (HF, D, RC, Trans) .. . ANVizo

Overseas Shortwaver (HF, D, 2 Trans)Ranger Four (SG, D, RC, Trans) .. .. AWI45

.. AW133Summertime Searcher (2HF, D, Trans)

Facility Four (HF, D, 2 RC-Q-coil)

The Orchestra Four (D, RC, Push-pull) .. AWi67Broadcast Picture Four (HF, D, 2RC) .. ' .. AW163

All Europe Four (2FIF, D, Trans) .. .. AWI73Revelation (HF, D, RC, Trans)Simplicity (HF, D, 2 Trans) .. . WM49Astral (HF, D, 2 RC) .. .. .. .. w_ M53Trapped 3-4 (D, zRC Paralleled) - .. WM6tGramo Radio 4 (D, RC, 2 Trans Push -Pull) .. WM7oQ-coi[4 (HF, Trans, RC) - .. .. WM71Screened grid 4 (HF, D, zRC) .. .. . WM77Five -pounder Four (HF, D, RC, Trans) .. WM91Frame -aerial Four (HF, 0, 2RC) .. .

...wWm,0)M8,5

Touchstone (HF, D, RC, Trans) ..Reyner's Furzehill Four (SG, D, 2 Trans) .. WWIJI2Economy Screen -grid Four (SG, D, RC, Trans) WMII3Binowave Four (SG, D, RC, Trans) .. .. WM119Standard -coil Four (HF, D, zRC) .. .. WMI22Dominions Four (zSG, D, Trans) .. .. WMI34The Drum Major (HF, D, RC, Trans) .. .. WIVI137

FIVE -VALVE SETSAll these Is. 6d. each, post free.

Individual 5 (2HF, D z Trans)School 5 (HF, D, zRC)"Q" Gang -control Five (zHF, D, z Traria)Exhibition 5 (zHF, D, RC, Trans) ..Phoenix (2HF, D, 2LF)1928 Five (zHF, D, 2 Trans) ..All -the -world 5 (zHF, D,.211C)Cataract 5 (HF, D, RC, Push-pull)Empire Five (zSG, D, RC, Trans)Fidelity Five (HF, D, RC) ..

SIX -VALVE SETSls. 6d. each, post free.

Short-wave Super -6 (Super -het, Trans)Adaptor for above (see miscellaneous list)Nomad (zHF, D, RC, Push-pull, Trans)Connoisseur's Six (zHF, D, RC, Push-pull)Eagle Six (3HF, D, RC, Trans)

+11.,41,+#.41...+411.041.+4100,04.0.444.....****41.60.440000.0.060.00.

AW25AW85

AWx6iWM33WM4z.. WM46

.. WM63

WM796VVM9

SEVEN -VALVE SETSis. 6d. each, post free.

Simpladyne (Super -het) WM22

PORTABLE SETSHoliday 3 (D, 2 Trans) ..Table Grand 4 (HF, D, 211C)Attaché Portable 2 (HF, D)Daventry Portable (D, Trans) ..Daventty Loud -speaker Portable (211i,

D, RC, Trans) . . .Town and Country .(HF, 'D, RC, 'Trans)House and Garden (SG, HF, D, RC,

Trans) .."Best -yet" Portable (SG, D, z Trans) ..House Portable (SG, D, RC, Trans) ..Arcadian Portable with Linen -diaphragm

Loud -speaker (half -scale)Springtime 2 (D, Trans)Countryside 4 (HF, D, z Trans)Chummy 4 (HF, D, RC, Trans)Chummy 4 (with modification fc r LS and

H ..Pilgrim Portable (D, Trans) ..

AW3 zAW93AW96AWto5

5-1116

sl-

AWt o7 /6AWt t 1/6

AW116 z/6AW136 1/6AWs 68 /6

AW177 s/6WMiz

1/6WMSo 1/6

WM8oa 1/6 -WM94 1/6

AM PLI FIERSAll these Is. each, post free.

Utility (RC, Trans)Screened -grid HF Unit .:One -valve LF Unit ..Super -power Push-pull ..Hook on Short-wave ..Purity Amplifier ..Add-on Distance -getter ..Screened -grid HF Amplifier .."A.W." Gramophone Amplifier (3RC)Searcher Unit (HF) .Gramo-radio Amplifier (2 v.) .Super -power Unit (a v.) .Signal Booster (HF Unit)Auditrol Amplifier .

MISCELLANEOUSAdaptor for Short-wave Super 6H.T. from A.C. Mains .."A.W." Moving -coil Loud -speaker ..H.T. Eliminator for A.C. (r)o v. output)L.T. and H.T. Mains Unit (DC)Knife-edge WavetrapAll -metal Eliminator for 1-.; T. ..Duplex:diaphragm Loud -speak& ..Power -plus Loud -speakerLinen -diaphragm Loud -speaker with

BafflePedestal Cone Loud -speakerListener's Speaker, price 4d. with copy of

AW68AW75

7AW9AW86

AWio4AWioS

.. AWL 17AWi38

.. AWi6zAW176 WM72

WMso3WMt28WM132

AW6ra -16AW73 sl-AW97 ii-AWrozAW123 51-AWi3t -/6AWt35 1)-AWI42 if-AW149

AWt 52 I-T-AW:64

AW 170 -14Arcadian Linen -diaphragm Loud -speaker

(full-size) AW177a 5/-D.C. Unit (H.T.) AWt78 if-Wavetrap WM64 if --Portable Cone Loud -speaker .. WM73 th"Junior" Moving -coil Loud -speaker .. WM8t 1/ -Universal Short-wave Adaptor WM8z 1/ -Linen -diaphragm Loud -speaker WM90 I/ -Valveless A.C. Power Unit for L.T. WMioo -/6Valveless A.C. Power Unitior H.T. ., WM tot -16Simple Cone .. . ,WMist if --Buzzer Wavemeter . .. WM121 -/6James H.T. Unit for A.C. Mains .. WM125 if -Lodestone Loud -speaker WM' 26's /-James H.T. Unit for D.C. Mains .. WMI33 11 -

Send, preferably, a postal order(stamps over sixpence in value

unacceptable) to

Amateur WirelessAW67

AW67a.. WM31

WM88WM106

Blueprint Dept., 58/61Fetter Lane - E.C.4

APRIL 6, 1929 541

ROADCAST TELEPHONY(Broadcasting stations classified by country and in order of wavelengths)

Kilo- Station and PowerMetres cycles Call An (Kw.)

GREAT BRITAIN25.5311,752 Chelmsford

(5SW) 15.0243.9 1,230 Newcastle (5NO) 1.0258.6 .2,260 *Leeds (2LS) 0.13270.3 2,209 *Sheffield (6LF) 0.13288.5 1,040 *Bournemouth

(313M) 1.0288.5 1,040 *Bradford (2LS) 0.13288.5 .7,o4o *Edinburgh

(2EH) 0.35288.5 1,040 *Hull (6KH) 0.2288.5 1,540 *Dundee (2DE) 0.13294.1 2,02o *Liverpool (6LV) 0.13294.1 1,020 *Stoke-on-Trent

(5ST) 0.13294.1 1,020 *Swansea (5SX) 0.13302.6 991.1 Belfast (2BE) 1.0311 964 Aberdeen (2BD) .1.0.323 928 Cardiff (5WA) 1.0358.9 838- London (2L0) 2.0378 793 Manchester

(2ZY) 1.0303 757 *Plymouth (5PY) 0.13401 748.3 Glasgow (5SC) 1.0482 622 Daventry Ex.

(5GB) 25.01,562.5 z52 (Daventry

(5XX) 25.0* Relay stations. tRelays 2L0.

AUSTRIA248 1,209 Linz277.8 1,080 Salzburg (under

construction) 0.5354.2 847 Graz 0.5

Klagenfurt 0.5456 t94 Innsbruck 0.5510 577 Vienna 20.0

BELGIUM220 2,360 Chatelineau 0.25250 1,200 Schaerbeek-

Brussels 0.5275 7,4290 Ghent 0.5.

280 1,070 Liege 0.5312 91 o Arlon 0.25612 e85 Brussels 10.0

CZECHO-SLOVAKIA265 1,130 Kosice 2.0r93.7 1,004 Bratislava 4 0142 873 Prague (Praha) 5.0432.3 694 Brunn (Brno) 2.4

DENMARK839 883 Copenhagen

(Kjobenhavn)p 1.01,155 r59 Kalundborg 7.5

456 694

0.5

ESTHONIA408 735 Royal (Tallinn) 1.3

FINLAND371 e00 Helsingfors

(Helsinki) 0 81,504 49 Lahti 20.0

FRANCE80.75 9,755 Agen 0.25200 9,50o Fecamp 0.3211.3 1,420 Heziers 0.1233 2,260 Bordeaux(Radio

Sud-Ouest) 2.0245 1,224 Lille (PTT) 0.8252.1 1,190 Juan-les-Pins 0.4253 1,185 Montpellier 0,25254 1,180 Rennes (PTT) 1.0255 2,275 Toulouse (PTT) 1.0268 1,2228 Strasbourg 0.3274 1,592 Limoges (PTT) 0.5

Kilo- Station and PowerMetres cycles Call Sign (Kw.)

291.3 2,030 Radio Lyons 1.5301 997 Bordeaux (PTT) 0.5305 982 Agen 0.3105.6 981 Marseilles (PTT) 0.5322 930 Vitus (Paris) 2.0536 892 Petit Parisien 0.5351 846.7 Algiers (PTT)._ 2.0370 811 Radio LL, Paris LO382.2 785 Toulouse (Radio) 9.0400 749 Mont de Marsan 0.1914 724 Radio Maroc

(Rabat) 2.0427 Tor Grenoble (PTT) 1.5430 697 Radio Flandre

Lille 0.25448 C68 Paris (Ecole

Sup., PTT) 0.7473 635.1 Lyons (PTT) 5.0

1,487 201 Eiffel Tower 8.01,748 .r7r Radio Paris 8.0

GERMANY219 2,370 Flensburg 1.5240 1,250 Nfirnberg 4.0250 x,aoo Kiel 0.7250 1,200 Cassel 0.7263.2 1,140 Cologne 4.0267.8 1,120 Muenster 1.5272.7 1,100 Kaiserslautern 1.5280.4 r,o7o Konigsberg 4.0283 1,o6r.Berlin (E) 0.7283 r,o6r Stettin ... 0.7283 z,o6r Magdeburg 0.7317.5 945 Dresden 0.75321.2 937 Breslau 4.0326.4 gig Gleiwitz 6.0329.7 9ro Bremen 0.75361.9 829 Leipzig 4.0374.1 8o2 Stuttgart 4.0891.6 766 Hamburg 4.0421.3 712 Frankfurt 4.0455.9 654 Danzig 0.75458 654 Aachen 0.75462.2 649 Langenberg 25.0975.4 631 Berlin 4.0537 559 Munich 4.0566 53o Augsburg 0.5565 530 Hanover 0.7577 520 Freiburg 0.7

1,650 182 Zeesen 20.01,650 18/ Norddeich 10.0

GRAND DUCHY OFLUXEMBOURG

1,280234.2 Radio Luxembourg 0.25

HOLLAND81.4 9,554 Eindhoven

(PCJ) 25.038.8 - Kootwijk

(PCL) 32.0(Wed. 12.40 G.M.T.)

337 889 Huizen (until5.40 p.m.) 5.0

1,073 279.5 Hilversum(ANRO) 5.0

1,152 262 Huizen (after5.40 p.m. and on

Sundays) 5.01,152 262 Scheveningen -

haven 5.0

HUNGARY548 548 Budapest 15.0

ICELAND333.3 goo Reykjavik 10

IRISH FREE STATE2212 1,352 Cork (5C K) 1.5411 730 Dublin(2RN) 1.5

Kilo. Station and PowerMetres cycles Call Sign (Kw.)

ITALY277 2,084 Turin 0.5333 900 Naples (Napoli) 1.5387 775 Genoa 3.0443.8 676 Rome (Roma) 3.0456 658 Bolzano 0.3604.2 595 Milan 7.0

JUGO-SLAVIA308.3 973 Zagreb (Agram) 1.25582 515 Ljubljana 5.0

LATVIA529 567 Riga 2.0

LITHUANIA2,020 748.4 Kovno 15.0

NORWAY242 1,240 Rjukan 1.0297 1,010 Notodden 0.7365 820 Bergen 1.0387 775 Fredriksstad387 775 Aalesund 1.0459 653 Porsgrund 1.0496 604 Oslo ... ...... . 1.5500 600 Tromso 1.0560 350 Hamar ...... 0.7

POLAND314 95,5 Cracow 1.5336 890 . Posen 1.5416 72x Rattowitz 10.0456 658 Wilno 1.5

1,395 215 Warsaw 10.0

317.5PORTUGAL945 Lisbon CTIAA (Wed.and Sat.: 10 -midnight)

ROUMANIA896.3 757 Bucharest 4.0

RUSSIA825 363.5 Moscow (PTT) 25.0925 323 Homel ...... 2.5

1,000 30o Leningrad ... 20.01,44 208 Moscow 30.01,635 278 Kharkov 15.0

SPAIN277.8 r,o8o Barcelona

(EAJ13) 2.0309 97o Oviedo (EAJ19) 0.5348 857 Barcelona(EAJ1) 3.5370 8or Seville (EAJ5) 0.5400 75o Radio Espana LO404 744 San Sebastian(A

426.7 703 Madrid (EAJ71 5.0456 658 Salamanca

(EAJ22) 0.55

SWEDEN281 1,149 Horby 10.0265 1,230 Trollhattan 0.4833 goo Falun 0.5346.8 865 Goteborg 0.0438 655 Stockholm 1.5645.5 550 Sundsvall770 390 Ostersund

1,200 250 Boden1,825 223 Motala

SWITZERLAND408 739 Berne 1.0489.4 613 Zurich 0.6080 441 Lausanne 0.6760 395 Geneva 0.5

1,010 297 Basle ..... 0.25

TURKEY1,232 243 Stamboul 5.01,840 163 Angora 5.0

2.02.0

30.0

CHIEF EVENTSOF THE WEEK

LONDON AND DAVENTRY, 5XXApril 8 Roumanian national programme.

9 British national programme, a burlesque.ro The Cherry Orchard, a comedy by Anton

Chekov, arranged by Dulcima Glasby.A vaudeville programme.

ix B.B.C. symphony concert, relayed from theQueen's Hall.

The Glasgow Orpheus Society Concert,relayed from the Queen's Hall.

It 13

DAVENTRY EXPERIMENTAL, 5GBApril 9 The Cherry Orchard, a comedy by Anton

Chekov, arranged by Dulcima Glasby.to A vaudeville programme.11 R.B.C. popular orchestral concert, from the

People's Palace,lz " Requests," an orchestral and vocal pro-

gramme.

f t

ff

April 13 Hip-Hip-Hoo-Radio, a revue. Books andlyrics by Graham Squiers: music by ShirleyGoodall.

CARDIFFApril 9 The second concert of the Newport Choral

Society (31st season).

MANCHESTERApril 13 The Conquering Hero, a play by Allan Monk -

house, arranged by Victor Smythe.

NEWCASTLEApril 13 Alibis, a play by Harold Melvill.

GLASGOWApril 13 Running commentary on the Scotland v. Edin-

burgh Association Football International,from Hampden Park, relayed to Londonand Daventry.

BELFASTApril 13 A concert by prizewinners in the Belfast"

Musical Competitions (1929).

enuauirWintit:

BRITAIN'S FAVOURITETHREE DE LUXE

OUR -KIT OF SPECIFIED PARTS as advocatedin this issue of " AM:"Supplied for . 82/ -or 15/4 down and co monthly payments of 8/-.This includes a full-size blue -print. Cabinet in Oak,17/6 extra. MULLARD, MARCONI, or COSSORValves for this set 33/6 extra. SPECIFIED KIT,COMPLETE with MULLARD valves, OAKCabinet, reo-Volt EVER -READY Battery,EXIDE Accumulator, and AMPLION CONESPEAKER -Cash Price £8 18s. 6d. or can besupplied on our gradual payment system, 33/ -down and ro payments of 16/6.

The H. IL KIT FOR','FAVOURITE THREE"

Containing only first-class ALL -BRITISH parts,and will give first-class results. Complete withpanel drilled, baseboard wire and 60/-screwsor 11;6 down and 5 payments of 11/6.DID YOU BUILD THE " CLARION

THREE" 2 -PROVED A TREMENDOUS SUCCESS.

Our customers report wonderful success from thisset. Twenty stations obtained on loud -speaker.OUR KIT OF PARTS, cash price, £4 4s.or 15/- down and 5 payments of 15/-. Completekit with MULLARD Valves, £6 9s. 6d., or 18/ -down and, so payments of 12/-. Oak Cabinet,14 X 7 in., 14/6 extra.CLARION THREE Coils (Tunewell) 21/- per pair.TITAN COILS-BULGIN, WEARITE, 15/- each.DUNHAM Tuners, 9/6; switch for same, 2/9.

GRADUAL PAYMENTSAny Kits, Speakers, Valves, Batteries, etc., suppliedon terms. All transactions are financed by ourselves,and that alone will assure you of courteous treatment.Write us, state your requirements; it gives us pleasureto supply you on our GRADUAL PAYMENT

SYSTEM.Carriage Paid on all cash orders.

Terms Cash, C.O.D. or Gradual payments as desired.

H. f3 B. RADIO CO.34 BEAK ST., REGENT ST., London, W.I.

Ger.: 2834

VVYVVVYVVVVVVVVVVVVVVVYVVYYVV

Do You Want to Know About -?Wireless symbols and contrac-tions? Accumulators? Laws ofA.C. circuits? Current -carryingcapacities and resistances ofwires? Details of coil windings?The Reinartz circuit? Whatvalves to use ? What " blueglow " means?These are only representative ofthe thousands of questions youcan "ask " the

Letts' Amateur Wireless1929 Notebook Diary

1 /9 (Post Free) from this office 2/9AAAAAAAAAAAAAAAA.AAAA.AAAAAAAILAA

QMAW' Wireig5 542

WIRELESS & HEALTHEACH fresh scientific discovery plays its

own part directly or indirectly in thehealth and longevity of the human race.Mention need only be made of the Roentgenrays, Finsen's light therapy, the Curiediscovery of Radium, etc., in order to seehow far-reaching and beneficial legitimateuse of such scientific phenomena are insuch diseases as commonly affect thehuman anatomy.

One's thoughts turn naturally to thesense of hearing when wireless is men-tioned, for instance, for it is with our audit-ory apparatus that we appreciate the trans-missions sent over the ether for our enter-tainment or education. It is remarkablehow one finds in active practice such a largepercentage of adults, say over the age offorty-five or so, who suffer from deficientsensitiveness in one or other ear, at timesin both; a simple experiment is easily. madeby those of, or over, the age mentioned ifthey will test the hearing of each earalternately with a watch which has apronounced " tick."

A Help to the DeafThe chances are that by testing by placing

the watch near the ear, then graduallydrawing it away, it will be noticed that oneorgan is more sensitive than the other.

Nov, it has been found that in many casesof diminished sensitivity, not actual or evenpartial deafness, the use of the ear -phoneswhile listening to transmissions havebrightened up and stimulated the .hearingconsiderably. The vibrations received bythe drum of the ear have apparently actedas a stimulant with- satisfactory results,these being demonstrated when the audit-ory apparatus is put to ordinary use-in other words the patient finds that 11.0 orshe " hears " better. As we reach middlelife there are few who retain the specialsenses at normality; glasses may berequired for reading for example. Tissuesharden, become less elastic-, less sensitive,and by the, same method as correctiveglasses are used in mild eye cases, so wehave at hand a very pleasant remedy inheadphones and loud -speakers of a mildcorrective for incipient ear trouble.

There. is a further advantage in somecases as well. One patient complainingof an oversupply of the natural wax of theear canal has found a considerable improve-ment since using a wireless set; in this easeit is likely that the offending wax is notpermitted to "ball up" as it did previously,the vibrations received preventing this.Anyhow there is no other reason one canthink' of, for the patient does not require

APRIL 6, 1929

SOME BENEFICIAL EF-FECTS OF WHICH YOUMAY NOT BE AWARE

to visit his surgeon so frequently as before.That wireless will tend to longevity will

be admitted by all I think; one of the mosttroublesome conditions which a doctor iscalled upon to treat is that of persons whodeplore the fact that old age is creeping onand that the world has no further use forthem.

A New InterestMany a piteous sight has been noted.

prior to the wireless age, of people ofseventy years or over, practically awaitingtheir end, with most interest in life gone.

One of the neatest sets I have seen forquite a time was a five-valver constructedby a retired clergyman who had decidedthat he was of no further use on this sphere.Here was an old man who did not know thedifference between a hacksaw and a chiselwho had acquired the art of " keepingyoung."

It might be said that this old ministerwould have found similar benefit fromother hobbies . . . this I question verymuch, however, for sustained interest inwireless construction and use seems to beillimitable, more especially as the date isnot far distant when the other importantsense . . seeing moving objects will bebrought into play. Doc PAGE.

wwwwwwwwwwwww

`74 wsule of the new

661.1.134G- LE E.and Socket

FAME

ISNNFRAY

GRIPPED

COPPER(RIPPED

CURET WELLERCIDED

PLUG WELLSHROUDED

This eagerly awaited product incor-porates several unique advantages.High -voltage and loty-voltage plugsare a different size- a safety devicewhich prevents any possibility of.valves being burnt out. The wholeproduct is beautifully finished ahlinsulated throughout. Made by themakers of the famous Belting -Leeterminals. Price 9d. (Panel portion3c1. each; Rex portion Ed. each).Ask for the new Belling -Lee WanderPlug-the first insulated WanderIlug on the market to be engraved.

Choice of 14 engravings,

Pray. Pa..NAME

NO SOLDERING

BELLING LEEAdvt. of BELLING & LEE, Ltd., Queensway Works, Ponders End, Middlesex

HELLESENDRY BATTERIES

PRICESStandard Capacity

" Wiray " 9 -volt GridBias Type ... 2/-

" Wirin " 60 -volt H.T.Type ... 10/8

" Wirup " 99 -volt HT.Type .. 18/.

Wisol " 108 -volt H.T.Type ...

Tsoble Capacity.20/.

" Kolin " 60 -voltType ... 1-

" Kolup " 99 -volt H.T9/.

Type 32/3

DON'T SPECULATE"A little flutter now andthen is relished by the wisestmen," but I cannot und1r-stand why people shouldwish to gamble where H.T.Batteries are conctHellesen Batteries are soconsistent, so reliable andthey bring you in so great areturn in ampere -hours forthe money you spend, that-as Ridley remarked-theyjustify the gilt edge whichappears round the container.Next time you need a newH.T. Battery ask your dealerfor a Hellesen, rememberingthat the Triple capacity bat-teries do not even cost twiceas much as the correspond-ing Standard capacities ; aninvestment, not a speculation.

/HURT'S3-fELLESEN DRY BATTERIES INSTRUMENTS

POLYMET4 MICA &.PAPER CONDENSERSHAND & CYCLE LAMPS, TORCHES, ETC

A. Ii. HUNT, LTD., CROYDON, SURREY

APRIL 6, 1929

INCREASING YOUR RANGEWITH the coming of summer, H.F.

amplification is more than everimportant in order to get winter -time rangefrom a set; and one of the best ways ofgetting to know about H.F. amplificationis to read "The Book of the Neutrodyne,"by J. H. Reyner, B.Sc. (Hons.), A.M.I.E.E.(Cassell & Co., Ltd.). This is not a technic-ally worded text book, but is in every wayunderstandable by the man in the street;and in the hundred -and -twenty -odd pagesof the book are contained some most help-ful hints and information on neutralisedH.F. amplification, making the whole wellworth the price of is. 6d.

HOW H.T. IS MADE !RECENTLY an AMATEUR WIRELESS

representative had the opportunityof seeing a novel film which has been pro-duced for Siemens Bros. & Co., Ltd., ofWoolwich, showing the whole process ofmanufacturing H.T. batteries. It reallyis most interesting to see the deal of careexpended in the manufacture of small drycells, and it is to be noted that a represen-tative of Messrs. Siemens will be pleased toshow the film at any wireless club meeting.Club secretaries should communicate directto Messrs. Siemens.

A WORLD TIME INDICATORVEANY DX enthusiasts will have found-VI the need for some form of chi rt orindicator which will show them the exacttime at any part of the world correspondingto Greenwich time. This demand has'nowbeen supplied by Messrs. J. H. Willis & Co.,Iiisivich Road, Norwich, who have pro-.duced a world time indicator. The chart,which is of stiff board, carries a rotatablecentral disc which' is simply turned roundand the times can be read off direct withoutany calculation.

Another Russian broadcasting stationhas been installed at Turuchansk on theborders of the Polar circle. Placed, as it isin the wild and dreary Tundra of theNorthern Jenissei district, it is the onlymeans of communication the trappers andthe explorers have with the outside world.

"Amateur Wireless and Radiovision." PriceThreepence. Published on Thursdays and bear-ing the date of Saturday immediately following.Post free to any part of the world : 3 months,4s. 6d.; 6 months, 8s. 9d.; 12 months, 17s. 6d.Postal Orders, Post Office Orders, or Chequesshould be made payable to " Bernard JonesPublications, Ltd."General Correspondence is to be brief andwritten on one side of the paper only. Allsketches and drawings to be on separate sheets.Contributions are always welcome, will bepromptly considered, and if used will be paid for.Queries should be addressed to the Editor, andthe conditions printed at the head of " Ourinformation Bureau" should be closely observed.Communications should be addressed, accord-ing to their nature, to The Editor, The Adver-tisement Manager, or the Publisher, "AmateurWireless," 58-61 Fetter Lane, London, E.C.4.

543 entateurWireie

K. RAYMOND27 & 28a, LISLE ST., LONDON, W.C.2

Come to LEICESTER SQUARE TUBE.This address is at the back of Daly'sTheatre. Phones: Gerrard 4637 and 2821

HOURS OFBUSINESS

EVERY DAY 9 to 8SATURDAY 9 to 9SUN. MORN. 11 to 1

CLARION THREEKIT OF PARTS (" A.W." 9-3-29)

Any other nanoenser, H.F. Choke, or L.F. Transformer.supplied by adding balance.

2 Polar .0005, No. 3, at 5/9. .0001 Reaction 4/-.2 Dual range C.T. Coils, with Reaction (Tunewell),Anode, 10/6; Aerial, 10/6. 3 Lotus or Formo V.H. at 1/3.Formodenser, "J," Dubilier 1 mfd., 2/6. .01 Fixed.T.C.C., 1/9. 3-meg. Lissen or Edison Bell, 1/, S.O. B.F.Choke, I'eto - Scott, 5/.. H.F. Choke, Lissen, 5/6.L.F. Transformer, R.I. & Varley, 15/-. Ebonite Strips.14x7 Ebonite Panel. Screen, 81)(6. 8 Engraved Terminals.Push-pull Switch, Flex, Plugs, 16-g. Wire, 2 S.M. Dials.

The Lot 70/- Post Free.0002 Fixed and Series Clip 16 extra.The above Kit withAMERICAN TYPE

CABINET, POLISHED OAKCOLOUR, BASEBOARD,H.T. 120v., L.T. 2v. 45.

£4 . 17 . 6Carriage 4/- up to 200 miles,6/- over (U.K.), pass. train.

ALL PREVIOUS OFFERS CANCELLED.

VALVES 2v.S.G. 22'6. D 10/6. P 12/6.

(Mallard or Six -Sixty)

CLEARTRONS.G., 2v. 12/6C.T.15, L.F. or H.F. . 41.

TRADERSDON'T FORGET OUR

WHOLESALEDEPT.

QUICKSERVICE

ALL LINESSTOCKED.

OPEN :9 to 8 EVERY DAY9 to 9 Saturdays11 to 1 Sunday Morn,

CLEARTRON

VALVESl'creen Grid 2v. 12/6Usual Types 4/- eachR.C. and Power 6/- ea.

TUNEWELLCLARION

COILSANODE or AERIAL

10/6 eachPush-pull panel mtg.

HANDSOME OAK POLISHEDSPEAKER CABINETS 13 x 13 x 6

Cannot guarantee exactpattern of front panel,

but all good designs.

Post1/3

BLUESPOT 25661i (101)4 POLE ADJUSTABLEBALANCED ARMATURE,

GENUINE 66K.

OR

CABINET

BLUESPOT

12" CONE

Carr. Pd. The Lot.

12/11

TRIOTRON UNIT4 - Pole Balanced With Cabinet asArmature 17/ Cone 27/66 011shown above and 12"

EestCarr. paid. Free.

EK CO H.T.UNIT 3F12For use with S.G. Valves.A.C. with Valve and

Royalty ... 78/6D.C. 3F12 37/6D.C. 3F12 S.G. 39/6

GENUINEBLUE SPOT

66 K (101)25/ -

Adjustable 4 PoleBalanced Armature.

OSRAM MUSIC MAGNETKit of Parts and ValvesES :12 :6

BOOKLET FREE.

TITAN COILS15/- TRADE SUPPLIED

S.G. VALVESMULLARD 22/6SIX -SIXTY 22/6COSSOR 2216OSRAM 22/6

MULLARD, SIX -SIXTY. MARCONI,OSRAM, COSSOR,EDISWAN VALVES

Lewcos Q CoilsQ.A. 15/- Q.A.M. 21/-Q.A.R.21/.. Q.S.P. 21 /.

Q.S.G. 21/.LOTUS Q.A. 1 5/.

Q.S.P. 21/. Q.3 Star 151.

LEADING HOUSE for KITS OF PARTSSee weekly Advts. all wireless papers.

WE STOCK, WHOLESALEAND RETAIL

BULGIN FERRANTIEKCO AMI'LIONCELESTION IGRANICLISSEN M.P.A.EDISWAN COSSORSIX -SIXTY COLVERNCYLDON Melt -IMAMWATMEL LEWCOSPOLAR CLIMAXORMOND J.B.PYE POLYMETT.C.G. DUBILIERLOTUS W.B.PHILIPS MULLARDand all standard components,valves, etc. Ever -Ready,Siemens, Exide Batteries.

TUNEWELLMassive All Pur-

pose H.F. Choke 59Dual Range Coil 7,9Master 3 Star - 3/115XX do. - 5/9Globe DX pr. - 21/-B. Picture 4 pr. - 21/ -Dual Range for ex-

isting Cossor,Lissen Sets, each 10,6

No alteration needed.

LISSEN PARTSALWAYS IN STOCK.

Bulgin All -wave Tuner 15/6British General All -

wave Tuner ... 18/6Wates' 3 in 1 Test

Meters ... 8/6Lotus Cond., .0005 ... 5/9Lotus Cond., .0003 ... 5/6Colvern Master 3 Star

Dual Coil ... ... 17/6Wearite Dual Wave

Tuner ... 15/-Wearite Standard Load-

ing Coil ... 7/6Dubilier B.C. Cond.,

friction control, .0005and .0003, each ... 12/ -

Ditto, thumb control 15/6Telsen Radio grand ... 12/6Telsen Ace ... 8/6Brown H.Q. Speaker... 6t71-Amplion A.C.2, 39/6

model for ... 21/-M.P.A. Popular Plaque

Speaker ... 29/6Ormond Turn -table for

Portables ... 6/-

BULLPHONEGRAMO UNITS, 15/ -CONE do. 15/ -WONDER L.F., 10/6

ORMONDlatest 5 -valvePORTABLES

£ 1 5TRADE SUPPLIED.

TRIOTRONVALVES

H.F., Det., R.C., 5/2 each ;Power, 6/9. 2-v. or 4-v.

Post 4d. (10/- Free).

DARIO RADIO -MICRO2-v. or 4-v. G.P. 5,'6Super Power .. .. 7/6Super H.F., 2-v. or 4-v. 7/6

Post 3d. each.

140p. CATALOGUEILLUSTRATEDALL LATESTCOMPONENTS

Price 1/-, which is creditedon first 10/- order.

Special Price forSETS OF PARTS

over 25/- givenwhere possible.

Kindly forward list ofgoods required (or call).

BRITAIN'S FAVOURITE 3(DE LUXE) A.W. 6/4;29

Ormond Leg .0005, 61.; .00025, 56; 7 -ohm panel Rheo2 6 ; 3 Benjamin V.H., 416; Formodenser Type "J,"2/-; .0003 and series clip, 2/-; 2-meg. Leak, 1/-;Tunewell All purpose H.F. Choke, 5/9; R.C.C. UnitDubilier, 7/-; 50,000 ohm wire wound, 5/6; 2-mfd.Mansbridge, 3/6 ; L.F. Transformer R.I. Varley 15/- ;(add balance any other). Push-pull &witch, 1'3, com-plete with Panel Brackets, Indicator, G.B. Clips,6 -pin Base, Connecting Wire, Thin Flex, 7 EngravedTerminals, EBONITE Panel 16 x 8, and 16 x 9 Base-board.

The above lot 63/° Cash with order.Carriage and Packing, 2,'6

SIEMENS, Ever Ready, LISSEN, HellesenH.T. Batteries. Large stocks.

Goods despatched Cash on DeliveryC.O.D. (pay postman) at slightly increased

charge.

&W. SPECIAL COUPON (64)FOR EVERY 30/- you spend retailYOU CAN buy ONE of the following for

3d. each extra (on this Coupon)IPF. Choke, Silk Loud -Speaker Cord, 9 -volt GridBias, Pair Panel Brackets, .0001 Reaction, 2 mfd.Mansbridge, 100 ft. Insulated Aerial, 4- or 5 -wayBattery Leads, 30 ft. Coloured Connecting Wire.

:e!tieforlittnie.3

THE LARGEST -WIRELESSSTATION IN ASIA.

JAPAN,JAPAN, with its recently opened high -power telegraphy station at Nagoya,

now possesses the largest long -wave trans-mitter in the world. The gigantic electricalplant is capable of putting 550,000 milli -amps in the aerial.

The Nagoya transmitter and the receiv-ing station at Yokkaichi keep Japan inconstant touch with all corners of the globe

The Rolls-Royce of Radiois the 50 Range

DIX-ONEMETERThe High-grade Radio Tester

Low Price High Value Worth ILO

Instrument in Case 55, -Multipliers each 6'6Complete Radio Outfit

E.4 : 10 : 0LOUD -SPEAKERS. R. K. Cones fitted B.T.H. Mov-ing Coil, 100 surplus at only 76 each. MarconiMoving Coil Magnet Pots, 6 volt, 20 -. GRAMO.MOTORS. Genuine Panatrope Gramophone Motors,run direct off mains supply, fitted Turntable, etc.Few only, 37'6 each. Worth £4 10s. CHOKES.Round's Output L.F. Chokes by Marconi, for feedfrom power amplifiers. Latest model, 756. CON-DENSERS. New Sterling, 2 mfd., genuine MansbridgeCondensers to 940 volts, at reduced price of 2 10 only.Capacity Meters £8 ; Wheatstone Recorders £12 ;Multi -Micro Galvos. 60/- ; Res. Boxes 17;6 ;Hydrometers 1!6 ; Relays 6/6 ; Remote Switches 15'- ;12 in. Spark Coils £10. Weston 601.; Micro

Ammeters for Grid bias testing, 35/- only.Fine! Edition of our Surplus Bargain, in Radio and Electrical

(1.4 ready. Send stamped addres,ed enreroye for largesale lest. SAVES RADIO USERS POUNDS

ELECTRADIX RADIOS,218, Upper Thames St.,Blackfriars Stn, Underground Rly, City 0191

WET H.T. BATTERIESSolve all H.T. troubles

SELF -CHARGING, SILENT, ECONOMICALJARS (wand) 21" li" sL 113 doz.Zincs, New Type, 10.1. doz. SACS 1/2 doz.Sample do, (18 volts), complete with bandsand electrolyte 411, post 9d. Sample unit,6d. Illustrated booklet free. Bargain list tree.AMPLIFIERS, 30/- 3 -VALVE SET, £5.A. TAYLOR, 57 Studley Rd.,

Stockwell, London.

22 in. LINEN SPEAKERALL COMPONENTS, comprising-

Wood Lengths (drilled), 4 61" x r 8/6 Post Free.Brass Stretching Screws (far super- Cash withfor to Meccano strip), 8 Wing Nuts order.and Washers, Linen, Dope, Screws, With 66K "Blueetc., Extension Rod with Sleeve. Spot" Unit 41/6

Rubber 2/- extraSpeaker made up complete, less unit and baffle 36i -

ARCADIAN PORTABLELinen Speaker Kit (or made up) supplied.

LOWNE ELECTRIC CLOCK CO.Boone. St., Lee, London, S.E.13.- 'Phone Lee Green or43

Buy "THE ALL EUROPE THREE"A book of clear instructions for 6d.making this efficient 3 -valve Set net.From a bookseller, or PITMAN'S, Parker St., W.C.2

544

. on wavelengths varying toe4eeti7i0boand 2o,00p metres.

The aerial is' supported on eight -mastseach 825 ft. high, Which, in view of therisks of earthquakes in that country, havebeen specially constructed for the purpose.Equipped with the latest automatic tele-graph transmitters, this new giant stationcan deal with wireless traffic at the rate ofone hundred and twenty words per minute.

WORTH WRITING FORAMOST attractive illustrated booklet,

describing Eloden loud -speakers ofvarious types, can be obtained from Messrs.F. L., Lesingham, 53 Victoria Street, West-minster, S.W.I.

Pentodes and screen -grid valves arefully described, together with somehelpful operating notes, in a new bookletissued by the Edison Swan Electric Co.,Ltd., 123-5 Queen Victoria Street, E.C.I.Copies can be obtained on application(meniionink :AMATEUR WIRELESS), and willbe found very useful when operating Edis-win pentodes and screen -grid valves.

AN interesting experiment recently tookplace in Moscow when a short-wave

telephony transmitter was taken up by anengineer in an ordinary gas balloon. Com-munication with the earth was easily estab'-li-thecl even at heights exceeding 4,00ometres (13,000 feet). Two-way communi-cation was maintained continuously fortwo days and two nights on a wavelengthof 43 metres, the transmissions beingsimultaneously picked up by Odessa,Vladivostock, Minsk, and Leningrad.

Senator Marconi and Mr. David Sarnoff,head of the Radio Corporation of America,have been elected to the board of directorsof the Gramophone Co., Ltd. (His Master'sVoice).

W. D. Terrell, chief of the U.S. RadioDivision of the Department of Commerce,in his annual report to the Federal RadioCommission states that ,during the yearending December, 5928, 9,093 inspectionswere made of the radio installations onAmerican and foreign vessels clearing P.S.ports. These inspections showed 235 casesof defective apparatus and lack of properequipment or personnel.

Let "Amateur Wirelesssolve your problems

1 PAUL 6, 1929

PREPAID ADVERTISEMENTS.Advertisements under this head are chargedTHREEPENCE PER WORD, minimum chargeTHREE SHILLINGS.

DEPOSIT SYSTEMAs the Publishers cannot accept responsibility for the

bona tides of advertisers in this publication, they haveintroduced a system of deposit which it is recommendedshould be adopted by readers when dealing with personswith whom they are unacquainted. It i3 here explained.

Intending purchasers should forward to the Publishersthe amount of the purchase money of the article advertised.This will be acknowledged to both the Depositor and theVcndor, whose names and addresses must necessarily begiven. The deposit is retained until advice is received olthe completion of the purchase, or of the article havingtcen returned to and accepted by the Vendor. In additionto the amount of the Deposit, a Fee of 6d. for sums of 61and under, and is. for amounts in excess of El, to coverpostage, etc., must bo remitted at the same time. In casesof persons not resident within t:1-3 United Kingdom, doubleIces arecharged.

The amount of the Deposit and Fee must be remitted byPostal Order or Registered Letter(Cheque; cannot bovocepted), addressed to

"AMATELlIt WIRELESS," ADVERT ISFIIENT DEPARTMENT,58/61, FETTER LANE, LONDON, E.C.4.

PATENTS,-Trade Starke, Advice' Handbook free.-S. T. King, Regd./Vent Agent, 146 Queen Victoria 'Street, London.

EARN MONEY AT HOME. You can earn money at home in wholeor spare time writing Show -Cards for us. No canvassing. we train Yonby poet by our new simple method and furnlah the Outfit free. We'imply both men and women with steady work at home, no mattera here you live, and pay yon cash for all work completed each week,under our legal guarantee. Fnll particulars and Booklet free. Writezt once or call. Show Card Service, Hitchin.

EBORITIt PANELS-Special offer at greatly reduced prices inblahoganite and Polished Black. guaranteed .12 x 3, 117; 12 x 6, 3/2:12 x 8, 4/2; 14 x 7, 4/:'; 18 X 7, 5/6: 16 x 5/8: 'M TO, 6/4; post free.1 rade invited. Bannister and Fltton,27 Milurow Read, Rochdale.

FREE: INVENTOR'S GUIDE ON PATENTS. T.A.A., 253(A'.Gray's Inn Road, London, W.C.1.

WIRELESS OPERATING APPOINTMENTS: fees payab'e after qua'ityinq ticar boarding students.) Morse Lasses. Wire esti School, ManorGardens, Honoway, N.7.

CENTREPARALLEL

CLIXTHE PIN WITHMANY PURPOSESThe ideal fitment for all types ofhome -constructed coils, for wall -plugs and connectors generally.The resilient principal on which theplug is constructed, guarantees per-fect contact, The shank is providedwith two nuts and allows connec-tions to be made with ease. The

whole is nickel -plated.

CLIX COIL PIN2d.

each. From all Dealers.Write for Clis Catalogue.

LECTRO LINX LTD.254 Vauxhall Bridge Rd., London, S.W.1

SATISFACTIONand Quick Service

We give you BOTH!Our large Stocks and extensive range include Sets andAccessories of every des:I-lotion, and which enables usto give almost immediate delivery of anyth.ng you mayr quire for Cash or on the. EASIEST DEFERREDTERMS. Send us a list of your requirements and let113 quote you by retu n. Lists Free.

Cirainaphones and Records on Easy Palmeri, Tenn*

V V '.

'Q

WIRELESS STORESWALLINGTON - . - SURREY

SUPPLY UNITS' HIGH TENSION

For Multi. -Valve ReceivereGuaranteed silent: No valves.No expensive replacements.

computing fromuaranteed47/6 7 DAYS' FREE TRIAL AGAINST CASH.

THE TULSEMERE-MANIG. CO., Dalton Street, West Norwood, S.E.27.

FOR A.C. MAINSLOW TENSION

Incorporating Westinghouse MetalRectifier.

2, 4 or 6 volts .at an amp.No renewals: No attention

Complete Units from

47/6'Phone: Streatham 673s:

mutat:- Wirele5COUPON

Available until Saturday,

APRIL 13th, 1929

APRIL 6, 1929

DUBILIERFIXED

CONDENSERS

Type 610

MICACONDENSERS

Types 610 and 620.00005 to .0009 - 2/6.00 I to .006 - 3/-.007 to .009 - 3:6

Type B 775.0I - 4/- - 8/6

.5 ' 37/6Intermediate Capacities at pro-

portionate prices.

Type 620

PAPERDIELECTRIC

CONDENSERSAll capacities from

.ot upwards..ot to .1, each 2/-.125 and .2, each 2/3.25 and .3, each 2/54 and .5, each 2/6

.o, each 2/62 .0 , each 3/6

Other prices onapplication.

DUBILIER for DURABILITY"TOREADOR SCREEN -GRID FOUR"

This set incorporates the latest dm,elopments in Receiver I

I design-full constructional details free on request.

DUMMERCONDENSERS

If unobtainable from your dealer,write direct to us giving his name

and address. 3:;IC;44"W." 44444 1/1.1 MARA

Advt. of Dubil ter Condenser Co.,(192 5)Ltd. , Ducon Works, Victoria

Road, N. Acton, London,' W.3

Don't Forget to Say That You Saw it in "A.W."

111

Lotus Condensersfrom 5,-.

Lotus Dual WaveCoil, 16/-, 16.6, ZU,Lotus Valve

Holders, 1/3.Lotus RemoteControl, from 30/ -

for 2 rooms.

mauls- Wirek

Build yourSet withLotus

Components

The best of circuitscannot produce agood set if you usecheap shoddy com-ponents. Ask yourdealer for Lotus.

Every Lotus Com-ponent is a well con-structed, reliable unitbuilt to do its partic-ular job, accuratelyand without fail fora long life.Don't forget - getLotus.

From all RadiG Dealers.

1E00E1DMcoistoositsis

Made by Garnett, Whiteley and Co., Ltd.Lotus Works, Broadgreen Rd., Liverpool

Onugatuviin4

V orLow -Vrequency

Intervalve

Conpling,.you

can bnd no bettet

coobistation.than. the R. 1. and V atley

tv:Verrninal

StraiglnLine

`tralls=

forraeran of

CapacityCony

-

le. Bothof tb.ese

farrousproducts

ate the 01.1tCOVCIC

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vesearcb,and both can boast

d crag,-

1:tcallystraight

linearapli.bcation

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by vaaeverldeslt

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VaysicalLaboratory

APRIL 6 , 1929

On the oneside

our4j-carnival

rcransforraer

ell-sloesall the volurne

that colldpossibly

bethee.. under

noroalcoTtdittorts,

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out 'ResistanceCaCacity

Couple

wire-woundon the a°farla3

Bi-clARIelt.

system---results

ID.quality

and

parityof torte

whichadd beauty

and

-realtso

to receptionin a degree

TheR. 1. and

V arley4-:r errninal

rarelyfootla to

-day .

StraightLine Transformer

is usedin

the De" Britain's

Favourite

Three"-_-_-another

tributeto its effici-

encyand high-clas's

clesign.

THE MARK OF BET -TER 'RADIOKingszvay House, 103 lingsway, London, IV .C.2 Telephone-Holborn 5303'

Printed in England: Published by Bernard Jones Publications, Ltd., 58/61 Fetter Lane, London, E.C.4Sole Agents for South Africa: CENTRAL NE WS AGENCY, LI USED. Sole Agents for Australasia; GORDON & GOTCH, Lxaeiiao, Saturday, April 6, 1929,

AMATEUR WIRELESS, APRIL 11, 1321

TWO FINE SETS IN THIS ISSUE

Every AzqThursdayki

ol. XIV. No. 357 Saturday, April 13, 1929

oelliii, *sum

BRITAP4

BLUEPRINTofthis

FAMOUS

SET nOWAVAILABLE

1 29/YodelRegistered at the G.P.O. as G Newtattast

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APRIL 13, 1929

-211M11111=M:INI==1211.

THERE'S ONLY ONEWORD FOR EVERY GOOD

RADIO PRODUCT-

DUBILIERH.F.

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lf unobtainable front your dem'er,write direct to us giving his nume

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Mention of "Amateur Wireless" to Advertisers will Ensure Prompt Attention

11111111111111111111121.141111ININIIMM11111111111111111111111111111111

Your set will do allthat the designerclaims for it if you useLotus Components.Every Lotus unit youuse is a sturdy, ac-curate link towardsperfection. The bestbakelite, t he bestmetals and the bestBritish workmanshipgo into all LotusComponents a n devery one is severelytested before it comesto you.When you buy yourcomponents ask forLotus Componentsand ensure your set'ssuccess.

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APRIL, 13, 1929 545 matey Wirtle5

The ever popular 66K unit

The Blue Spot Chassiscarries the Unit

Blue Spot 66K 4 -pole balanced arma-ture unit : (adjustable), Price 25/ -

Blue Spot Metal Chassis (completewith cone), Price 1216

Build up your own cone speaker using thefamous Blue Spot 66K unit. To make a conespeaker equal to any you have yet heard _be-comes simplicity itself if you follow the instruc-tions given with every Blue Spot unit-and youwill be delighted with the reproduction of anyand every programme.

Here is the Blue Spot Metal Chassis, completewith cone in position ready for affixing theunit-simplicity itself-and takes five minutesto assemble.

To bolt the chassis to a baffle board, whichyour dealer can supply cut to size, or toa cabinet of your own choice completes aninexpensive speaker giving results little shortof amazing.

F. A. HUGHES & CO., LTD., 204-6 Great Portland Street, LONDON, W.xDistributors for Northern England. Scotland and North Wales: H. C. RAWSON (SHEFFIELD & LONDON) LTD.,

zoo LONDON ROAD, SHEFFIELD; 183 PRINCESS STREET, MANCHESTER.

Don't Forget to Say That You Saw it in "A. W."

onetime Wirel.e;" 546 APRIL 13, 1929

Grannysays:"NOWthat'swhatI callrealmusic!"Everyone is thrilled whenfirst they hear a Set withCossor Valves. CossorValves give loud, clearmusic-real melody thatcharms the ear. Changenow to Cossor Valves-there are types to suitevery Receiver foruse with 2, 4 or 6volt Accumulators.

CossorBRITAIN'S FIN EST VALVES

Adv . A. C. Ccssor. Ltd.. Highbury Grove. Londa2. NJ.

Please Mention !VIM." When Corresponding with Advertisers

M 8219

547)tc.e71t-)w,,ecce,lcatezte7)ce71c5Pr....c-ocIte,:;,&)ca

-C APRIL 13, 1929

That B.B.C. Ban-There is still much'ado about nothing-namely, the B.B.C.ban on the announcement of names of dancetunes. It has been suggested, We know,that this ban is the result of interestedpeople having used the microphone as ameans of publicity. However this may be,we are rather inclined' to agree with a'correspondent who says that it is not a'coincidence that there is more variety in theprogrammes while the ban -is in action !

No. 357. Vol. XIV,

,5 5

5 5

55

5Lr s

s5 55 and . 5

5 The Leading Radio Weekly for the Constructor, Listener and Experimenter 5S

5.--- Editor : BERNARD E. JONES ---=

5§ Technical Editor : J. H. REYNER, B.Sc., A.M.LE.E. :: Research Consultant : W. JAMES :: Assistant Editor : H. CORBISHLEY 5

0,,,,,,,,,,,,,,,,,..3,,,,,,,,,,,,,,,,),,,,,,),,,,,,,,,,),....,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,--,..),7,0That B B C Ban-A Radio Hero-Radio at 103 !-" Talkies Pit areBooming-The Unseen Five Hundred-" Threes,' and " Fours pl

1 bringing Wagner up to date, and by meansof microphones and loud -speakers "thereare brought on the stage the voices of achorus of 500 (sic !) for whom there wouldbe no room in front, of the footlights."With the unlimited possibilities of electricalpublic address and gramo-radio, what giantoperas Wagner could have produced !

Wireless and. Weather-So the oldrumour that wireless causes bad weather isstill afoot ! We have never seen any

A Radio Hero-1.'et another wireless statistics to prove the point but here areoperator hero. In this case he is R. Osbjorn- some figures from the Royal Meteorologicalson, the operator of the ill-fated cargo Society, which, if you are a lover ofsteamer Selje. He remained at his post in statistics, may kill the old rumour once andthe sinking vessel, sending out calls for help for all. "The average rainfall in Englanduntil the generator room was flooded, and requires for its production roughly 330,000the transmitter went out of action. He then horse power per square mile, night and daywent up on deck to find that the other throughout the year. The total horse -members of the crew had gone to the power used by all broadcasting stations insteamer Kaituna (with which the Selje was Gt. Britain and Northern Ireland is underin collision) without realising he was left The City of Glasgow leaving Croydon, with 55 horse -power; the corresponding figure forbehind. He managed 'to sound the ship's which it will be in radio communication, on Europe being about .400 horse -power. Anysiren just as the vessel sank in shark -infested the first trip of the Air Mail Service to India effect of broadcasting on weather wouldwater. filna of Boris Godounov. If technical develop- -therefore be due to sub -homoeopathic

Radio at 103 !-At Chelmsford, Essex, ments keep pace with these giant artistic doses of less than one in r,,000,000,000 Iis what the newspapers call " a wonderful and commercial forecasts, then there should Applying the same arithmetic to domesticyoung woman"-she celebrated -her io3rd be a great deal in . " talkies " to interest affairs one finds that to produce a year'sbirthday last week ! In a recent interview wireless fans. rain for the tennis court by means of anthe good lady, after airing her views on The Unseen Five Hundred-Incident- electric kettle, would cost over L800." Wemodern girls and short skirts, said that she ally a new use is being found for loud- cannot vouch for these figures, but theyhas only two interests in life. One is pre- speakers on the stage. At the Chavlotten- sound convincing !paring for the ' celebration of her 1 o4th burg Opera House in Berlin, they are Radio at Brooklands-An "A.W."birthday and the other is listening- cief..ce7)w.3wIce7o.acce7o.acaf.acolt.ace%ne2lf.e0 Correspondent who ,was at Brook -in. We wish her many More years § lands at the recent openingin which to enjoy her hobby.

§- PRINCIPAL CONTENTS Page §meeting of the season, had his

g, Talkies " are Booming-If § ' Current Topics .. .. .. 547 § ardour damped by the rain, butone is to believe what one is told

5Policing the Ether .. .. .. 548 was cheered to find' the old familiar

by film stars themselves, soon no5

Baird Television-Facilities at Last ! .. 548 loud -speaker "putting" over gramo.cinema in any civilised country will An All -mains Two549 5 music during intervals.be showing "silent" films. " Talkies" 5 Circuits for You to Try

..551 § "Threes " and " Fours " -

will be all the rage. Douglas Fair- § My Wireless Den . . 552 § This week we deal at greater length i

banks and Mary Pickford (his wife) § On Your Wavelength .. .. 555 § with the up-to-date version of i

are talking about a giant combina-5

Wireless Control of Mode':,' ....... ,

.. 5575

"Britain's Favourite Three "-ation in which Warner Bros. are to For the Newcomer .. 558 really good " three" -for broadcasttake part. Charlie Chaplin has not

§Without Fear or Favour .. .. ' 559 5 reception. Next week we are to have

yet definitely "fallen," but Chalia- " Britain's Favourite Three " .. .. 560 5 an efficient four-valver designed bypine, the: famous singer, is a new- § "A.W." Tests of Apparatus .. .. 562 § our Technical Editor, Mr. J. H.corner to the cinema and will prob- § Experiments with Neon Tubes .. .. 563 - 5 - Rey- ner, witli dual -range, simplicityably appear in talking films this C Can We Amplify on Short Waves? .. .. 566 C of control, and "super" perform -summer. Irfcidentally he has been ' Radiograms .. .. .. .. .. 568 ance. In Coto, a "four" worth,offered Lroo,000 to make a talking 1:1t,nte'etatocit~.stoatenti.e,von~itafoicaloiter743§' waiting for I

el:mien( WiretT

An interior view of Dr. Reisser's Ether -policing Station

T HAD, of course, been acquainted with the1 excellent work done by Dr. Reisser forthe Reichsrundfunk-Gesellschaft (GermanBroadcasting Corporation) in policing theether, superintending the activities ofGerman transmitting stations and perform-ing a number of other useful duties. His"den" turned out to be the snuggest, mostup-to-date, and best equipped wirelesslaboratory I have yet come across.

There, all around the walls, could be found

548

POLICINGTHE ETHER

APRIL 13, 1929

An Accountof Dr.Reisser'sStationin Germany

By Dr. ALFRED GRADEKIWITZan imposing arrayof the most effi-c ie n t wirelessreceivers, bymeans of whichany wirelessstation in Ger-many or else-where in Europeor beyond theseas could at a

moment's notice, be heard.Apart from superintending what is going

on in the ether, checking, controlling andpolicing the German stations and comparingtheir performance with the working offoreign stations, this laboratory is intendedfor the occasional re -transmission of Germanor foreign broadcasting stations to thetransmitters of Berlin and stations con-nected up to Berlin.

The equipment of the laboratory corn -

prises a large number of receiving sets forwave ranges of from 12 to 2,000 metres.

These receivers are accurately calibratedso that any station can ube identified withabsolute certainty.

Two lines connected with the preliminaryamplifier room , at the . Voxhaus head-quarters of the Berlin broadcasting stationserve for transmission and telephonecommunication respectively.

All connections between sets on the onehand and the switchboard on the other arelaid out permanently under the tablecarrying the apparatus. Switch panels areprovided at every operator's seat. A 4 -voltcircuit serves to supply the heating current,alternating -current mains supply the anodecurrent, and H.T. accumulators are alsoavailable.

There are in all, four outdoor aerials,4o, 3o, J5, and so metres in length respec-tively, in addition to frame aerials.

BAIRD TELEVISION FACILITIES AT LAST!A Letter from the Postmaster -General to the Baird Television Development Co., Ltd.

Sir,The Postmaster -General has considered

the results of the recent television demon-stration, in conjunction with the BritishBroadcasting Corporation, and his techni-cal advisers, and he has reached the follow-ing conclusions which accord generallywith the opinions of those who witnessedthe demonstration. The demonstrationshowed that the Baird system was capableon that occasion of producing with suffi-cient clearness to be recognised the featuresand movements of persons posed for thepurpose at the transmitting point. It isnot at present practicable to reproducesimultaneously more than perhaps two orthree individuals or to exhibit any scene orperformance which cannot be staged withina space of a few feet in very close proximityto the transmitting apparatus.

In the Postmaster -General's opinion thesystem represents a noteworthy scientificachievement ; but he does not consider thatat the present stage of development tele-vision could be included in the broadcastingprogrammes within the broadcasting hours.He bases this view not so much upon thequality of the reproduction which furtherexperiments may be expected to improve,as upon the present limited scope of theobjects which can be reproduced.

The Postmaster -General is, however,anxious that facilities should be afforded,

so far as is practicable without impairingthe broadcasting service, for continued andprogressive experiments with the Baird ap-paratus and he would assent to a stationof the British Broadcasting Corporationbeing utilised for this purpose outsidebroadcasting hours. He understands thatthe Corporation would agree in principle tothis course, provided satisfactory termswere negotiated between the Corporationand the Baird Company.

It will probably be essential that anyexperimental demonstrations of televisionshould be accompanied by the broadcastingof speech and, in consequence, two wave-lengths and two transmitters would berequired. It will not be possible to providea second transmitter in a suitable localitywhich will avoid interference with impor-tant wireless services in Central Londonuntil the completion of the new station ofthe British Broadcasting Corporation atBrookmans Park, which is expected to beready in July. In the meantime, it issuggested that the Company should opennegotiations with the Corporation as to thefinancial and other arrangements whichmay be necessary, and it would probablybe advantageous to them to enter upon dis-cussions of the technical aspects with theCorporation's Chief Engineer.

In order to find room for a televisionservice in broadcasting hours it will

probably be necessary to utilise for thereproduction of vision wavelengths out-side the bands now being used for speechtroadcasting. These Lands, as you aredoubtless aware, are already highly con-gested and it is important therefore, thatthe Company should press on with ex-periments on a much lower band whichwill be notified to the Company in duecourse.

In conclusion, it is necessary to empha-sise that in granting facilities for experi-mental demonstrations in which the publiccan if they so desire take part, neither thePostmaster -General nor the British Broad-casting Corporation accept any responsi-bility for the quality of the transmission orfor the results obtained. The object of thedemonstrations is to afford the Baird Com-pany a wider opportunity than they atpresent possess for developing the possibili-ties of their system of television and forextending the scope and improving thequality of the reproductions. While the,Company will not be precluded from sellingapparatus to anyone who desires to pur-chase it, the purchaser must understandthat he buys at his own risk at a time whenthe system has not reached a sufficientlyadvanced stage to warrant its occupying aplace in the broadcasting programmes.

(Signed) G. E. P. MURRAY.General Post Office March 27, 1929.

APRIL 13, 1929 549 Ornate= Wirete-

AYEAR or so ago people used tosay how nice it would be if bat-teries could be dispensed with

altogether in wireless Sets, and how thescope of radio would be widened if thewhole business of operating a receivercould be reduced simply to the simple jobof tuning -in and switching on and off.

Well, since then mains eliminators havebeen developed, and the lucky possessorsof either A.C. or D.C. mains, of any normalvoltage, can now work their sets directfio:n the public supply. Thus they candispense with the high-tension battery-a costly article, particularly if thereceiver is a large one-the accumulator,which formerly required laboured journeysto the charging station at all -too -frequentintervals, and even the grid -bias batteryif desired.

High- and Low-tension fromthe MainsThis set is a "two," entirely self-con-

tained, and takes both H.T. and L.T."juice" from A.C. mains. In this par-ticular instance the grid bias is obtainedfrom an ordinary 9 -volt battery, becausein a receiver of this type the extra corn-plication in order to obtain smooth D.C.,G.B. from A.C. mains is hardly worthwhil3. Grid -bias batteries are so cheap

=1\2NA-a

2Acc2

A No -trouble Receiver for those who have A.C.Mains-Sale and Simple

and last until their initialcost, of a shilling or so, isforgotten !

_ This receiver will find awarm reception from twoclasses Of AMATEURWLRELESSreaders. First, there arethe experienced people whorealise the difficulties which

attend obtaining H.T. and L.T. from A.C.mains and in working a two-valver fromalternating current without any hummingor motor -boating.

Second, there are those programmeenthusiasts who do not care very muchabout the technical side of their sets, butwho have always wantedsomething which has nobattery bothers. A largenumber in this latter classwill possibly get thereceiver made up for themby one of their more tech-nical friends.

Just what this "two"will do is this. It willgive ample loud-speake rstrength from a mainbroadcasting station up toabout twenty-five miles orso distant. At greaterdistances than this it willstill give satisfactory loud-speaker strength, but therewill not be that amountof volume in hand whichis . always dictated bypurity critics.

There is no reason why,if the mains are fairly quiet in working,headphones should not be used and quite

a respectable D.X.reception log obtained..Loud -speaker workingat normal distancesfrom B.B.C. stationsis, however, the " dailybread!' of this two-valver, and it has beendesigned primarily for,those who want broad-cast programmes with-out battery troubles.It, has-been designed as

Co

aim

ZAN? 4/11172

6.8- caoThe circuit diagram of the All -Mains Two

a two-valver becausequite a large numberof those who makeup this receiver willhave to keep economy

in view, and for ordinary broadcast recep-tion a really good two-valver is as much asmany folk require.

If you glance at the photographs youwill see that the whole receiver is verycompact, when the fact is taken intoaccount it is all complete and that noexternal batteries or accumulators haveto be housed. The one lengthy flex leadto a convenient lighting plug does thetrick !

To beginners the baseboard may seemto present a rather fearsome appearance,and this is perhaps because, in addition tothe normal components necessitated bythe circuit, the baseboard carries the few

Receiver section

Mains section

The receiver section and the mains section are entirely separateas this picture shows

extra " gadgets " which provide both H.T.and L.T. --

Of course, to constructors of AMATEURWIRELESS sets, one set can hardly everbe more "difficult" to construct thananother, because it is child's play to mountthe components and just as simple to wirethem up with the aid of a combined blue-print and wiring diagram. And, whiletalking of blueprints, don't forget that onecan be obtained for this receiver, price is.,post free, from AMATEUR WIRELESS,58-61 Fetter Lane, London, E.C.4.

Technical readers will be anxious tounderstand the working of this all-from-A.C. "two:' and the rather less technicalenthusiasts must forgive the followingbrief description and analysis of the cir-cuit. They can pass on direct to theyconstructional details.

ITICLUItt

" AN ALL -MAINS TWOBasically, and leaving out the mains

eliminator part, the set is of the ever -popular "det. and one L.F. (trans.)" type,and transformer coupling has, of course,been employed in order to give a satisfac-

Constructionis quite Simple

tory degree of loud -speaker strength.Semi-Reinartz type reaction is employed

and the tuner is of the dual -range typewith incorporated moving reaction.

From the circuit diagram you will see

'BLUEPRINTMA W/80

BIT

TUNER

ro nnyp la

BASEBOARD14.rxrx Of

L.F.0

0 05 0

MA INS TRANS

("W8,454T;"Vf PANEL .9.4'

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24"

ThAra -Az

.0002 mfdme 0/47

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VALVE

00020262

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A C MAINS

The wiring diagiam. Blueprint available,price 1/ -

/7002

(Continued from preceding page)

that the dual -range scope is obtainedsimply by short-circuiting one section ofthe winding for the short waves, bothsections being in series for the long waves.There are two tappings on that portion of

the winding which isnot short-circuited onthe medium waveband,and by means of a flexconnection which makescontact with either oneor other of the tappingsthe degree of selectivitycan be very easilycontrolled.

A leaky grid detectoris employed with thelower end of the gridleak taken to a tappingon a potentiometer

winding across the filaments. The reasonfor this will be obvious when it is explainedthat both the valves employed are of thenew A.C. directly -heated type, and it istherefore important to get a propermedium tapping for the grid leak.

Aeanti-motor-boating unit is inserted inseries with the primary of the L.F. trans-former, and will be found of inestimableadvantage in getting the best out of theset without any tendency whatsoevertowards uncontrolled L.F. oscillation. Theunit consists simply of a 20,000 -ohm fixedresistance in series with the primary wind-ing of the L.F. transformer and a 2 -micro -farad fixed condenser between this junc-tion point and earth.

The Mains SectionNow for the mains -supply section. In

the present set a Marconiphone powertransformer (type M) is used and is ar-ranged to provide double -wave rectifica-tion (in conjunction with a suitablerectifier valve) for H.T.; a separate wind-ing with a centre tapping, gives the neces-sary "juice" for lighting the filament ofthe rectifier, while yet a third windingprovides .8 volts of A.C., which is takendirect to the filament of the receivingvalves.

There is really nothing to go wrong, andthe combination of power transformer,rectifier valve, and smoothing choke andcondensers is comparatively cheap (muchcheaper in the long run than batteries),and entirely safe and foolproof.

So far as the operation of the set is con-cerned, the panel carries a .0005 -micro -farad tuning condenser, the knob of thereaction control with which is mountedconcentrically the wave -change switch,and terminals for aerial, earth, and loud-speaker.

At the back of the set is a flex connectionwhich is taken to any convenient lightingpoint. No switching is needed, for thereis no ." juice" to waste. When you insert

APRIL 13, 1929

the plug in the lighting socket the setworks and when you remove it it stopsworking If you care to do so, you cancontrol the receiver by the ordinarylighting switch. The current consumptionis not worth considering, for it is very small.

The only difference which --the con-structor should make when building upthis set, as distinct from an ordinarybattery -operated " two," is to take themost particular care to get the connectionsright first time. Of course, if you are care-ful to check the wiring over with a full-size blueprint, marking off in pencil eachwire as its actual counterpart in the set ischecked as O.K., you can't go wrong.

For the construction of this "two" youwill require the following components, andfor the guidance of those who want tomake up the receiver exactly as describedit should be explained that in each casethe first -mentioned component is thatused and illustrated in the original set.

-and the wiring is no more complicatedthan w;th an ordinary receiver

The alternatives are those which have, asnear as possible, the same electrical charac-teristics and (in most cases) very similardimensions.

Ebonite or bakelite panel, 9 in. by 6 in.(Raymond, Becol, Ebonart, Paxolin).

.0005-microfarad variable condenser(Igranic, J.B., Lissen, Polar, OrmondBurton).

All -wave tuner (Wearite, type WG2).Baseboard, 13 in. by 9 in. (Pickett,

Clarion, Camco).Three valve holders (Burton, Lissen,

Benjamin, Wearite)..0002-microfarad fixed condenser with

grid -leak clips (T.C.C. S.P. type, Dubilier,Mullard, Graham-Farish).


APRIL 13, 1925 551

CIRCUITS FOR YOUTO TRY

111111111111111111111Inun1I11111111111111111114.

From time to time our TechnicalEditor has described various cir-cuits of particular interest to

I RECEIVED an inquiry a few days agofrom a reader who was anxious to try

one screen -grid valve. and one ordinaryH.F. valve in conjunction with "Q " coils.He said that he felt that a circuit such asthis ought to give him good selectivitywith comfortable signal strength,which' it undoubtedly will do.Moreover, if the apparatus is fairlywell spaced there should be littledanger of trouble from instability.

At any rate, a 'circuit of thisnature is an interesting one to .1".hook up, and the details given inFig. i will Make it clear as to' howsuch an arrangement could beadopted. The aerial circuit con-tains one of the latest type ofaerial coils, the QAA. This, asreaders will remember, -is a' newform of tapped aerial coil, whichgives better selectivity and betterwavelength range than the olderform of QA coil. The only 'differ-ence in its use is that the aerialis connected to terminal No. 4instead of to terminal No. r,the same .000r or a pre-set con-denser being used in the aerialcircuit.

.. . ......................

an L.F. valve or one of the new special,

detector valves made by the MullardCompany. The reason for this is that theheavy negative grid bias causes consider-able increase in the resistance of the valve,and this is liable to affect quality unless

;00:05 Fool

Fig. 1.

This circuit feeds the screen -grid valve.This has been placed first in the circuit inorder to avoid coupling between the latercircuits and the aerial. It is sometimesfound that alteration of the aerial or itscapacity has an effect upon the neutralisingof the ordinary form of H.F. circuit, andfor this reason the neutralised stage hasbeen placed second. Following the screen -grid valve is a QSG coil, a screen -grid trans-former giving rather more selectivity thanthe tuned -anode arrangement.

The neutralising stage is placed thirdand feeds an anode -bend detector. It isbecoming an axiom-as, indeed, it shouldbe-that any receiver employing an appre-ciable measure of high -frequency ampli-fication should utilise an anode -bend de-tector, because the grid detector overloadsseriously if the signal strength is at all large.The L.F. stages are not shown. Thedetector may be followed by a resistance -coupled arrangement or, if desired, bytransformer -coupled circuit, in which lattercase it will be preferable to use either

90K

1256 QSP

WIN

those who are experimentally in-clined; on this page are two morewhich will repay' investigation

arrangement pure and simple, and is adevelopment of the well-known dual -impedance system. Dual -impedance coup-ling is a system in which high-tension issupplied to the anode through a low -fre-quency choke. The L.F. voltages are by-

passed to the next grid through/2" a coupling with a choke, it

will be understood, the usualleak being replaced with a choke.The values of the coupling con-denser and choke are so chosenthat a resonance, occurs betweenthe two in the bass regions, inconsequence of which the ordinarytendency of the curve to fallaway at about zoo cycles is ar-rested, and in place a slight reson-ance peak is introduced whichkeeps the curve fairly level downto quite low values of frequency.

1.(.1"Such an arrangement suffers

from the disadvantage that nostep-up is obtained, and thecircuit shown in Fig. 2 illustratesa system in which the advantagesof the dual -impedance couplingare retained together with a step -

,up effect. The H.T. supply tothe valve is fed through a good

make of low -frequency choke, while thelow -frequency impulses are passed throughthe coupling condenser on to the primaryof a 6-i transformer. For this purpose agood form of 6-i transformer, such as theIgranic type J, should be used.

If the coupling condenser is made of theorder of .05 rnicrofarad we shall obtain aresonance between this coupling condenserand the primary inductance in the neigh-bourhood of ioo cycles per second. Thiswill result in the bass being very well main-tained, perhaps even slightly, boosted,which will allow for the defects in theremainder of the amplifying system, in-cluding the loud -speaker. At the sametime, owing to the fact that we have a6-1 transformer, we shall obtain a largestep-up so that the system, althoughapparently a 'little cumbersome at firstsight, is one having considerable promise.

The arrangement can be used followinga valve having quite a high resistance,with a correspondingly high amplificationfactor.

6A combination of screen -grid H.F. and ordinaryvalves used in conjunction with a " Q " coil

arrangements are so made that the actualresistance of the valve under working -conditions is approximately that for whichthe transformer has been designed.

A Dual -impedance SystemAnother circuit which is of interest is

that shown in Fig. 2. This is an L.F.

Fig. 2. A development of the dual -impedancesystem

H.F.

nuitem Wiry] 0, 552 APRIL 13, 1929


and

Theoretical-Metal-panel Matters

WHEN a metal front panel is used it isnecessary to take steps which will en-

sure that only parts which are earthed shallmake contact with the metal and that allother parts are insulated.

It is usually not very difficult to arrangethat the various switches and tuning con-densers shall have the side which makescontact with the panel at earth potential,but in an endeavour to effect this one ortwo weak points may be left. As anexample I will take the case of a tunedanode circuit (Fig. 1).

Plates A of the variable condenser areconnected to earth and plates B (the fixedones) are joined to the anode of the shieldedvalve. The full voltage of the H.T. batteryis, therefore, across this variable condenser,and the battery would be short circuitedwere the plates 4 touch.

This arrangement may correctly betermed a dangerous one, although when agood component is employed the chancesof a short-circuit taking place are remote.Nevertheless, one would feel better satis-fied with the circuit were a protectingcondenser included in series (Fig. 2).

0604

RN0.05;COIL

E li

0+Fig. 1. A simple circuit for a metal panel

The safety condenser may have a valueof .002-microfarad or more, and it neednot necessarily be of the type havingmica insulation. If this condenser has toosmall a capacity the tuning range of thecircuit would be restricted and a poorcondenser would reduce the amplificationand have the effect of broadening the

tuning. Ordinary mica condensers havereasonably low losses, however, and maybe used in this position.

Cutting out the " Stray "Tuning coils having a small stray field

are popular just now and, indeed, I havefound this type of coil to be practicallyessential for use in circuits with shieldedvalves. There are several forms of con-struction, and a particularly simple one isshown in Fig. 3.0

Fig. 3. Scheme of coil with small strayfield

Here, one half of the coil is wound in thereverse direction from the other and thetwo halves have an equal number of turns.The efficiency of such a coil is naturallyless than that of a coil having a straight-forward winding and of the same bulk,but this is usually a matter of no greatimportance. What is important, however,is the distance separating the two halves.

It will be clear that if the two parts werewidely separated the coil would have arelatively large stray field which is thereforereduced as the two parts are broughttogether. In practice a separation of abouta r/4 -inch is often employed with goodresults although it should not be thoughtthat such a coil has no stray field. It iscertainly small, and would be smallerstill were the two parts Wound even closertogether. There is a practical side to thequestion, however, and a designer so adjuststhe various factors that the best of all-round results are obtained.

A Soldering TipThere are occasions when, either because

of lack of space or the need for economy,one is tempted to solder connecting wiresto anode resistances or grid leaks insteadof employing suitable holders. The prac-tice of soldering wires is, however, not,always to be recommended for the reason'that unless great care is taken the heat

ENc2Q=W JAMES

For theWirelessAmateur

from the soldering iron will loosen thecap of the resistance or grid leak, or evendisconnect the '`internals" of the com-ponent. Grid leaks in particular shouldbe handled carefully.

That H.T. SparkMany a beginner has felt there was

perhaps something wrong with the wiringof his newly constructed receiver becausea small spark is produced by brushing thehigh tension lead across the positive ter-minal of the battery. The spark is quiteharmless, and is dye to the large condensersin the receiver charging or discharging.

It is not unusual for three or four con-densers of one or two microfarads each, tobe included in an ordinary three -valvereceiver, and, collectively, they will storequite a fair amount of electricity.

Anyone who has connected a 2-microfaradcondenser across an H.T. battery and thenplaced a screwdriver between the terminalsof the condenser will be familiar with thespark created. It is only to be expectedthat when the high-tension wire is drawnacross the terminal of the battery sparkswill be prochiced and they may give the

RAWECO/1 Nr+teo

PROTECT/YEI CONDsz,.

Fig. 2. A protecting Condenser for Fig. 1

novice quite a surprise until it is realisedto what they are due.

NEXT WEEK :

A FINEFOUR-VALVERBy J. H. REYNER

APRIL 13, 1929

SENDFORONE

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FOR ONE WEEK'S TRIALTest it at your leisure against ANY Speaker atANY price. WE KNOW it is the equal of any.Talking won't convince you, but hearing it onyour set will. If you are not fully satisfied, packit up and return it to us within a week, and yourmoney and postage will be refunded.If you decide to keep it-Remember your judg-ment is final-remit the balance 30/- or, if youprefer it, 2/6 a week for fourteen weeks. C .0.D . 5 /6.

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APRIL 13, 1919 555

2A Wonderful Broadcast

THE broadcast of the funeral cere-monies of the late Marshal Foch was,

I think, one of the most impressive wirelessoccasions that we have ever had. Onething, though, struck me as a very greatpity. The commentator was absolutelyfirst-rate, making one see every scene andevery incident; but he spoke in. French,and thousands of those who listened inthis country must have been unable on thisaccount to follow closely what was going on.On such an occasion one would havethought that the B.B.C. would have hadits own commentator and have conductedits own broadcast of the proceedings. Sofar as I can make out, they simply relayedthe broadcast by Radio -Paris, picking it upby wireless at Keston. I am almost surethat this was the case, since when I tunedin Radio -Paris direct I found C.W. inter-ference in the background, and this sameC.W. was distinctly audible when oneturned to 2LO, 5GB, and 5XX.

Try for TheseThere are some wonderful stations at

work just now below 30o metres. If youhave not a set of coils that will drop downto the lower portion of the broadcast bandlet me counsel you to beg, borrow, buy, ormake them at once, if not sooner. I am notexaggerating in the least when I say thatTurin, Hoerby (the big Swedish station),Cologne, and Nuremberg are receivable onfavourable nights with the quality and, ifthe set is reasonably, well furnished in theway of H.F. amplification, all the strengthof the local. So powerful are Turin andHoerby on good nights that full loud-speaker strength is obtainable with a three -valuer, and if the first valve is of the screen -grid kind you probably won't have anyneed to use reaction. Other stations thatcan be quite marvellous below 30o metresare Flensburg, Kaiserslautern, Limoges,and Cork. Taking the broadcast band as awhole, the number of quality stations nowreceivable is wonderfully big.

-and Some OthersIn addition to those mentioned I find

that- real alternative programmes-that is,those providing music that can be listenedto with genuine pleasure-are obtainablefrom Huizen (especially when he is usingthe long waves), Radio -Paris, Kalundborg,Motala, Hilversum, Budapest, Vienna,Brussels, Langenberg, Frankfurt, Stutt-gart, and Barcelona. I don't mean thatyou will hear every one of these stationson any night of the week, but you will cer-tainly find in normal circumstances thatyou have half a dozen or more first-rateforeign transmissions from which to choose.Fit a good high -frequency stage, if you

iclv,e4 eie dowt..01.0%%°^1.0."%0

haven't already got one, and you can haveail the variety that you want.

Economy in DXFor real efficiency combined with

economy in long-distance work I canstrongly recommend a set of the type thatI am using now, which contains only threevalves. The first is a screen -grid H.F.amplifier, the second an anode -bend recti-fier, and the third a pentode. The totalfilament consumption at 4 volts is only.35 ampere, whilst the H.T. drain is17 milliamperes. This may seem a gooddeal, but it must be remembered that theset is used for producing a big volume ofsound, and I don't know that you canmanage with much less nowadays if youwant first-rate quality.

I find that the pentode will take moregrid bias than the characteristic curvewould lead one to expect, which meansthat one can cut down the H.T. currentconsiderably. Normally a pentode withi5o volts on the plate and screen grid, andgiven a bias of about 71/2 volts negative,takes something over 20 milliamperes toits own cheek. Experiment shows that agood deal mofe grid bias can be appliedwithout producing any trace of overloadingor distortion..

Another SavingWith a three -valve set of this kind one

saves also in other ways. Screen -gridvalves and pentodes are rather expensive,but if the whole set contains only three" toobs" there is clearly a big economy incomponents. In fact, all that one wants istwo pairs of coifs (one for the medium andone for the long waves), two .0005 -micro -farad variable condensers and one midgetsa pair of H.F. chokes, three valve holders,a good low -frequency transformer, an out-put transformer, the usual fixed condensers,and an on -and -off switch. In addition tothese, a volume control is also desirable,for the huge amplification available is oftenconsiderably more than one needs. Thepentode is a delightful valve to use, since,owing to its enormous amplifying powers,quite a small applied grid swing producesa big output in the plate circuit. It is per-fectly stable and gives a dead quiet back-ground.

An ErrorI was very sorry to find the B.B.C.

allowing the talk recently given on foreignaffairs to include certain rather scathingremarks about the policy of a very dis-tinguished man who is the leader of one ofthe great allied nations. "No politics " issupposed to be the rule of the B.B.C., andexcept that our own domestic affairs maybe dealt with at election time this ruleshould be strictly adhered to. Everyone is

entitled to his own opinions about thegovernments of other nations, but it is cer-tainly quite out of place to broadcastcriticisms, especially as the B.B.C. is nowa Government department. People some-times forget that broadcasting knows nofrontiers. Actually 5GB and 5XX areregularly tuned in by dwellers in countriesall over Europe, and criticisms such asthat referred to must give widespreadoffence.

A Good SelectionThe B.B.C. did us very well indeed in

the matter of holiday programmes atEaster. Those responsible are to be con-gratulated on the way in which theyexactly matched the holiday spirit by thechoice -of programme items. I am surethat the big output of light entertainment,variety,- tuneful music, and humour wasappreciated far and wide.

"A Noteworthy ScientificAchievement "

The Postmaster -General is to be con-gratulated on his excellent summing up ofthe recent official tests carried out betweenthe Baird Television Development Co.,Ltd, and the B.B.C. The purport of hiscommunication to the Baird Company in-dicates that we can look forward to real"seeing -in" in a relatively short time.With television as an ally, broadcastingwill take on a new interest.

The other day I read an article in anAmerican paper which questioned whetherwireless broadcasting would be so effectiveif it were accompanied by television.Summing up the situation, the writer heldthat he who travels by the wireless withimagination for his guide may enter intothose realms of gold which are closed tothose who, seeing all, blindly seek acertainty.

Doubly GirdedI am afraid, however, that the arguments

put forward were far from convincing.Imagination is a wonderful asset to theindividual when applied in the right direc-tion, but to use that as an excuse for dis-counting television is certainly whollywrong. To the amateur this new scienceopens up what may be regarded as a virginfield of investigation, and for that reason-alone we shall welcome its appearance.Of late, I have been making a careful studyof the problems involved and find thatonce the elementary principles are thor-oughly understood "seeing by wireless" isreally only slightly more complicated thansound reception.

"Listening " With Your Eyes!Have you ever seen speech or music?

No, I am not taking flights into the realms

moleur Wireko 556 APRIL 13, 1929

S. On Your Wavelength ! (continued) 41 of fancy, but am perfectly serious. Mythoughts over the week -end had beencentred round that very absorbing sciencewhich has been so much in the public eyeof late, to whit television, and I was won-dering how long we should have to waitbefore regular transmissions took place, sothat it would then be in the public eye inmore senses than one. I therefore turnedon my favourite set (perhaps one of thesedays I shall let you into the secret as towhich one this is), and having tuned in afairly strong signal I substituted anordinary neon lamp, just a simple beehivepattern, for the loud -speaker.

You should try this for yourself, as thepreviously audible signals now becomevisible, inasmuch as you can see theflickerings of the lamp in place of hearingthe vibrations of the diaphragm. Whereasin this instance the flickerings were due topassages of music interspersed with speech,I knew that if I had been able to tune inthe characteristic television note, the lampflickerings would then have been repro-ducing the reflected light from the objectbeing televised. Actually, this providesthe gradations of light and shade thatenable us to distinguish form, and all thatremains is to arrange the series of lightflashes over a surface or area correspondingto that occupied by the object we desireto see.

A Glowing Plate for a CanvasPut into more familiar language, this is

the same as saying that a picture must beformed- out of the succession of light andshade in just the same way as the artistforms his picture by a succession of brushtouches on a canvas. In actual teleVisionpractice this is effected at the receiver byemploying a scanning disc having the samenumber of holes and running in syn-chronism with the disc at the transmitter.What we may regard as the canvas is theglowing plate of the neon lamp, it beingborne in mind, of course, that the actualneon lamp is not like those we use as nightlights, but has a comparatively large, flat,rectangular -shaped positive plate. Now,when the first hole of the transmitter discexplores a line across the object and letsthe reflected beams of light fall in successionupon the "photo -electric microphone" sothe receiver disc has a hole which exploresa line across the glowing plate of the lamp,and it is seen bright in one spot and darkin another as it flickers.

Creating the FormWith perfect synchronism between the

transmitter and receiver discs the successionof lines build up an image identical in lightand shade to the original form, the spreadof the light impulses over a surface creatingthis form. Naturally, this process must beeffected at sufficient speed to prevent theeye from dwelling on the mechanics of the

scheme, as thereby the light flashes areseen in their proper place, and not actuallyas a sequence. That is why the minimumnumber of complete picture scans is usuallygiven as fifteen per second, correspondingto a disc speed of 90o revolutions perminute. Images viewed under these condi-tions are really excellent.

Needle ScratchThe general use of electric gramophone

pick-ups has created two great new"schools of thought." One huge section ofpick-up users is in favour of the abolitionof the irritating background noise causedby needle scratch. The other section, theminority movement, agrees with all theseadmirable sentiments, but expresses theview that any electrical or mechanical" damping " introduced for cutting outneedle scratch must inevitably reduce thestrength of high notes, harmonics, andsibilants of speech. The "minority move-ment" resigns itself to the awful presenceof needle scratch, rejoicing in the moreeven response of their gear to all themusical frequencies.

Cutting it OutNaturally, the decision as to whether

you will cut out needle scratch or notdepends on the type of pick-up you use andits particular resonances in relation to theband of frequencies carrying* the scratch.The use of a fairly "blunt" filter circuitwhich will shunt frequencies of the orderof 6,000 cycles is the most effective weaponfor cutting down the scratch withoutinjuring the tone values too much. Butthe design of such a circuit is tricky, andthe capacities of the condensers employed,etc., will vary according to the type ofpick-up used and other factors. The easiestway is to shunt a condenser in series witha variable resistance across the pick-upleads, respective values being about.t microfarad and o-5,000 ohms. Variationof the resistance will then alter the amountof "damping" on the needle scratch asrequired.

Another RemedyPersonally, I have used neither filter nor

" integration" (shunt condenser) for sometime in connection with my own pick-up.I don't buy any but the best records andendeavour to reproduce them as well aspossible, neglecting the question of needlescratch. The blare of the brass and thehigh harmonics of the violin, as well asspeech sibilants, come out very well andI am satisfied. Any kind of filter circuit isbound to cut these down; and I'd soonerhave the scratch than that ! If the gramo-phone companies made their records witha terrific resonance on musical notes around6,000 cycles, then one could employ afilter on the reproducer to diminish thisresonance, which would at the same time

cut out the needle scratch. But I aip afraidthat there are too many mechanicalgramophones in use for the gramephonecompanies to do anything like this.

Sound FilmsThe boom in talking pictures has resulted

in a steady flow of engineers and programmebuilders from the B.B.C. to the film studios.R. E. Jeffrey, the B.B.C.'s chief dramaticproducer, has moved his tent to Elstree,quickly followed by K. V. Wright, "0.C.Noises," and about half a dozen engineers:All these people have been absorbed byone producing concern only ! Meanwhile,there is keen competition for the servicesof some of the leading B.B.C. engineers inboth sound film and gramophone recordingstudios.

Fieldless Coils and ReactionIn many sets nowadays astatic coils are

used to prevent interaction effects and tominimise eddy current losses where screen-ing is employed. A difficulty sometimespresents itself when the grid coil of thedetector valve is of this kind and it isdesired to make use of reaction. Thetrouble is, of course, that one half of thecoil is wound in one direction and one inthe other. The reaction coil tends, there-fore, to ginger up one half of the coil andto do just the opposite to the other. I havecome across several cases where friendswho had made their own coils were very,much puzzled by failure to obtain properreaction effects. Investigation showed thatthe end of the grid coil remote from thereaction coil had been wound clockwiseand the other end anti -clockwise, thereaction .coil itself being wound clockwise.If the usual plate and grid connections aremade, the reaction coil then exercises areverse effect upon the end of the grid coilto which it is coupled and rather queerresults occur. The rule is always to windthe reaction coil in the same direction asthat of the grid coil to which it is nearest.If this is done and capacity control is useda short series of experiments will serve todetermine the position for the reaction coilwhich gives the optimum degree of coupling.

An Unexpected EmergencyDoubtless I had the sympathy of readers

last week when I described how I was "letdown" by the burning out of an anoderesistance just when I had promised- aspecial concert to some musical high-brows. I told you how I used a moving -coilmilliammeter in the plate circuit, in placeof the resistance. Well, I must crave stillfurther sympathy-this time for a slip ofthe pen ! Of course, I meant to say that Iused a voltmeter, and not a milliammeterin place of the defective and now defunctanode resistance. It is certainly a tipworth remembering, for most enthusiastshave a high -resistance voltmeter.

THERMION.

APRIL 13. 1929 557

THE WIRELESSCONTROL OF MODELS'Part Two-

By MAJOR RAYMOND PHILLIPS

THE RECEIVING GEARr - 1-1E last article dealt with the con -

1 struction of a simple "spark" trans-mitter arranged to function each timeselected words are spoken into a specialmicrophone. As there may be enthusiastswho would like to possess a radio trans-mitter fitted with a special microphone, andmorse key, the latter can be inserted in theprimary circuit of the small spark coil asshown in Fig. i. When using the morse keyit is advisable (for some experiments) todisconnect the microphone circuit, other -

0SPRRK CRP

SPRRI( 60/4

NORSE;TY

MITCH

4tRallArrRIWYGEMINCT

Fig. 1. Circuit for key control of transmitter

wise there would be a risk of signals beingtransmitted when not required.

Such a method is useful where a numberof controls have to be effected in "and where it is necessary quickly to passover contacts on a selector drum whichmay not at the time be required. Forinstance, the writer often found it necessarywhen manoeuvring his well-known wire-less controlled airship quickly to pass a

Fig. 2. Photograph showing under -carriage ofmodel locomotive

series of contacts in order to select circuitsconnected with the different electric motors,so that steering and general control couldrapidly be effected.

Alternative UseIt will be necessary to construct special

receiving apparatus for use with the micro-phone transmitter already described, but

the circuits of the receiver are so arrangedthat a morse key can if desired be used withthe transmitter. Before giving construc-tional details of the special receivingapparatus, it will be well briefly to referto various types of model electric locomc-tives suitable for wireless control. Manymodel electric locomotives are fitted withpermanent -magnet type electric motor.This only involves the necessity of reversingthe flow of electric current to the "con-ductor," and " outer " rails of a modelrailway in order to cause a model locomo-tive to run forwards, or backwards, asdesired. It sounds like a fairly simpleoperation, but unfortunately it means intro-ducing slight complications in a selector,or distant -control switch fitted in receivingapparatus.

Sequence ControlFor simplicity of control the better plan

is to have a model electric locomotive (asshown in Fig. fitted with " sequence" re-versing mechanism. This involves switch-ing electric current "on " and "off." Thereversing mechanism fitted to such a modellocomotive functions in "sequence," sothat each time electric current is switchedon to a model railway the locomotive willrun forwards, or backwards in sequence.As the mechanism acts very rapidly, it is nota difficult matter to cause the model torun in the same direction on two successiveoccasions if desired, as it is only necessaryto switch electric current "on," "off," and"on" again quickly. This type of locomo-

tive is also fitted with a lockinglever, so that the running positioncan be fixed if desired.

The construction of special re-ceiving apparatus suitable for usewith the microphone transmitterwill now be described. The follow-ing components (some of whichcan be purchased "ready-made")will be required : coherer, de-coherer, relay, special selector, twoordinary electric -light switches

(5 -amp.), pneumatic dashpot device, eightlarge terminals, and about four yards offlexible electric -light wire.

The coherer can be purchased ready-made. A de-coherer simply comprises themovement of a 3 -in. electric bell. A suitablerelay can be purchased from almost anydealer in wireless apparatus, but an oldG.P.O. type rewound with No. 36 -gauge

Cmaw:Wu-Q-1T

The Complete Receiving Gear

enamelled copper instrument wire to aresistance of too ohms gives excellentresults. A pneumatic magnetically -operateddashpot will have to be made specially.The device shown by Fig. 3 functions per-fectly, and is fairly simple to make. Anordinary wooden block (such as is used formounting electric light switches) gin. by3 in. will provide a base, and the electro-magnet shoskrn should have cores r 1/2 in.long by % in. diameter, and the bobbinsbe wound with No. 25 -gauge enamelledcopper wire.

The armature of the electro-magnet

Fig. 3. The pneumatic " dashpat "

should be made of soft iron, 6,in. long byr in. wide by -116- in. thick, and at one end(which should be bent at right angles) thereshould be fitted a piece of vulcanised fibreI% in. square by It in. thick. Two screw-

threaded holes should be made in the fibreto accommodate two % in. No. 6B.A. brassscrews, the latter to form contacts. Thetwo spring contacts shown in Fig. 3 shouldbe made of No. 26 gauge hard brass sheet,each contact being % in., wide. The maincontact should be 3 in. long. The shorterone (de-coherer contact) should be 3 in.long.

(To be continued)

tRI MOLESe

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-(1)-Fig. 4. Base for Selector

entaitur wt 558........._... ....................__- ........_., .............._

I

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ill For the Newcomer to Wireless : TRANSFORUENCYMERS Iii

LOW-FREQ 111

WOULD you mind clearing up -' smaller the inductance of that winding.matters about low -frequency - I think -I see what you are driving at.,

APRIL 13, 1929

1111

111

lit

I.

111

111

II

III111

transformers ? I was told the other claythat they can give perfect reproduction,but in a book that I have just beenreading, I find that they must alwayslead to distortion.

When was your book published?Three or four years ago.Then the writer was quite correct, for

at that time even the best transformerswere a long way from perfect.

And can we obtain real quality fromthem to -day ?

Certainly we can, if we purchase first-rate components and use them as theyshould be used.

How do you mean?The secondary of a transformer cannot

contain more than a certain number ofturns for various reasons; and obviouslyif we want a step-up ratio the primarymust have a smaller number of turns.

That's quite clear.Since you cannot increase the number

of secondary turns it's plain I think thatthe only way of obtaining a big step-upratio is to have a few turns on theprimary.

That seems obvious.The fewer the primary turns the

It comes to this; the bigger the step-upratio the smaller must be the inductanceof the primary.

Exactly, and this means that youcannot use a transfornier with a bigstep-up to couple a high- or even amedium -impedance valve to the nextone,

I don't quite follow that.If there's not to be a suppression of

certain notes the impedance of theprimary winding must be kept highat all frequencies. Now the impedanceof a transformer primary depends verylargely upon its inductance and if theinductance is not big enough the imped-ance will be too small at low frequencies,with the result that there will be asuppression of the bass notes, for theywill not be properly amplified.

Can you give me any kind of rule togo by?

Several!Well, please fire away.In the first place don't use transformer

coupling after an anode -bend rectifier.You will find that the resistance -capa-city method is better here. Next, ifthe makers state the inductance of the

primary when a normal current ispassing I can give you a good rule ofthumb.

What is that?The minimum inductance value for

good results is five times as manyhenries as there are thousands of ohmsin the valve impedance. That is to say,if the rectifier has an impedance of20,000 ohms you want a transformerwith 5 by go or ioo-henry inductance tofollow it. Supposing that you want tocouple note-mag. number one to note-mag. number two by means of a trans-former and that the first has an imped-ance of 6,000 ohms, then a 3o -henryprimary is needed.

But supposing that they don't statethe inductance value?

Then you are pretty safe in taking itthat a 2o,000 ohm valve is the highestthat can be used satisfactorily withtransformer coupling and that for thisclass you must not use a bigger step-upthan about 3 to 1. For the 8,000 -ohmtype of valve a 4 -to -I transformer maybe used whilst a 6 -to -1 may follow valvesof 5,000 to 6,000 ohms impedance. Areally big step-up such as 8 to r can beused with advantage only after quite lowimpedance valves.

FROM ACROSS THE "DITCH "JOTTINGS FROM MY LOG ;: By JAY COOTE

HAS it ever struck you to what extentradio has annihilated distance?

Recently, during a period when theChannel was blotted out by a bank of fog,it took some friends of mine almost anentire day to cross from Calais to Dover;on the same evening, when they called onme, I was able to switch them over toBrussels (their native city) by the mereturn of a wrist. Through the loud -speaker,the news bulletin which interested themwas received as if the announcer had beenin the same room, yet he was on the otherside of the "ditch" I

On many evenings, instead of potteringaround in an aimless manner, I devotesome time to individual stations. In viewof the fact that Radio Belgique is nowplaying with a higher powered transmitter,I have followed its programmes more care-fully than hitherto. At the end of whatis usually an excellent musical programme,you will be treated to a very remarkableseries of announcements, inasmuch as theycomprise the latest news items, political,social, or commercial, interlarded withadvertisements and puffs. - On one occa-sion following the details of a particularlygruesome murder, the announcer ended upwith : "If you want -to sleep soundly to-

night, drink a large glass of -" andfolloWed the name of a well-known Belgianbeer !

In this bulletin one finds references totinned tomatoes, radio components, thenames of seaside resorts at which you areinvited to spend your holidays, and appa-rently cofitracts are made with advertisingfirms, for the same publicity is given outnightly.

Radio Belgique receives no subsidy fromthe State, and relies entirely on voluntarycontributions. For this reason appeals aremade to listeners to buy listening cards,the cost of which is 25 francs per annum(under 3s.) or entreats them to becomepatrons at the cost of ioo francs yearly.

By the way, all the transmissions fromBrussels regularly close down to the playingof " La Brabanconne " on a gramophonerecord.

-Another station to which I listened

regularly during the last few nights is thatof Frankfurt, of which, for some reason orother, the reception has gradually become' weaker. 'Although the studio has a very' full day, when I was last in that city, Iascertained that the bulk of the work isdone by one announcer whose call, Frank-

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III

furt-artz-Main and Kassel must now befamiliar to you all.

" CUTTING OUT THEHIGH-TENSION BATTERY"

A Patented CircuitWHEN our Te.chnical Staff prepared'

the article "Cutting Out the High-:Tension Battery" that appeared on pages,485 and 486 of our March 3o issue, webelieved that the circuit on which thearticle was based was common property.'Since publication of the article, however,'Messrs. E. K. Cole, Limited, "Ekco"Works, London Roads Leigh -on -Sea, havecourteously drawn our attention to thefact that the circuit in question is fully,covered by their patent 'No. 262567. Itfollows, therefore, that readers may only,construct the D.C. mains unit described inthe article for purely experimental pur-poses, since only the patentees and theiragents have the right to make and sell aunit built in accordance with that circuit.

We express to Messrs. E. K. Cole, Limited,our regret that, being unaware of theirpatent, we quite inadvertently used thecircuit as the basis of our article.

APRIL 13, 1929

WITHOUI 1/

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559

A Weekly Programme Criticism by Sydney A. MoseleyWHAT beautifully expressive music is

Grieg's ! The holiday programme ofthe great Norwegian composer's workswas incomparably rendered by the Wire-less Symphony Orchestra, Kate Winter,and Maurice Cole. What poetry, whatlonging there is in "First Spring." Andwhat grotesqueness in the "March of theDwarfs." In pre -wireless days the multi-

. tude knew only "Peer Gynt." Now these

11 SS Ge.--ipeammti,

Miss Jessie Matthews-as our artist sees her

and other musical treasures are being dis-closed to people whose musical souls werehalf-starved.

Song recital by Olga Haley good."Serenade" by Strauss has become a bestsinger. Oh, by the way, where did EstherColeman get her translation of " I LoveThee "?

Interesting, isn't it, to watch jokesgrow?

"What's your name? "'"Watt !"" That's what I asked you. What's

your name?""Watt !"And now the variation."Where do you live ?"" Ware I"

" That's what I asked you. Where doyou live? "

" Ware !"How the music -hall audience roared I

It's quite a useful thing to barge intopeople whose work you criticise, or peoplewell up in the world of wireless whocriticise you ! For instance, I had some-thing to say about Lance Sieveking's pro-duction recently.

"I don't forget you wrote, 'Keep yourhand out of the till,' " he said as we walkedaway from Savoy Hill, "but my. next pro-duction will have an equally big caste."

Well, if the money's worth it, Lance,we'll break no more lances. (Oh, cheap Icheap !)

Sieveking, by the way, made a spiriteddefence of those at the B.B.C. who workseriously and conscientiously on behalf ofthe listener. Productions that go overbadly apparently hurt the producers asmuch as they hurt listeners. I have, how-ever, paid tribute to the type of earnestworker at Savoy Hill.

I was glad to hear from such an eminentexpert as Professor Appleton that he andothers supported my "clean radio" cam-paign. Apparently the comments in thispage ha've been closely followed.

We shall have to mind our pros andcons, for the wife of another radio pro-fessor tells me she reads us "first" eachweek. Frank criticism may rub some ofthe victims up the wrong way. Honesty isnot the best policy if you desire to " keepin" with everybody. As it happens, I don'twish to keep in-or out-with anybodyexcept the bulk of my readers. And thissort of unexpected tribute helps me in myattitude.

Professor d'Andrade is another interest-ing personality who told me he had keptcertain cuttings of mine. But the subjectturned out to be-spiritualism ! I wonder,by the way, whether we shall hear anymore of those spirited and well-informedtalks of his.

nuuctsr Wt J

A young author who is doing enter-prising work in the production line is HoltMarvel. He tells me that I "gave away"his identity. Did I? He ought to be proudof it if I did. He is certainly brimful ofideas, and I gather we shall soon be listen-ing to more of his work.

And, yea, verily, among others, whosenames are familiar to readers, whom I metin the flesh was my old tried and trustedfriend, Captain Eckersley. As a matter offact, I got him to televise for the first timein history ! But about all this I shall haveto refer readers to my " secret history "book which I hope to write one day.

Another chat I had was with R. E.Jeffrey. He believes a visual audience isessential to the temperamental radioartiste. I think Eckersley would dissent.So do I. Still, R. E. J. is frightfully keenon the future of "sight and sound" enter-tainment, and I wish him luck.

Sullivan's Ivanhoe is little known. Why?Because it was "grand opera" and unlikethe rollicking Sullivan airs that helped topack the Savoy Theatre. Still, it is abeautiful opera, and one is grateful for theopportunity of hearing it.

An impression of Jack Hobbs

malkur Wtretesi 560

FOR the benefit of those who did nothave the opportunity of reading theconstructional article last week which

dealt with an up-to-date version of thatever -popular receiver " Britain's FavouriteThree," it must be explained that soinsistent has been the demand for newfacts about this set that it was deemedadvisable to produce an absolutely up-to-date version.

You may remember that the "Favour-ite" owed its inception to a competitionwhich was held in AMATEUR WIRELESS inorder to decide the most popular circuit.The "Favourite" was the result, and waspublished at the beginning of 1928 andit embodied everything that an amateurrequired for general-purpose reception:

4 Popular CombinationAt the time when it was produced high -

frequency amplification had not beendeveloped to the extent which it has beento -day. As most readers of AMATEURWIRELESS will be aware, high -frequencystages, once the playthings of more or lessexperienced set operators, can now safelybe included in the specification of general-purpose receivers.

Some very popular three-valvers havebeen described in AMATEUR WIRELESS,and these, while designed for the "wirelessman in the street," have included whatwould once have been considered a difficult

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RITAIN'S4 6

Further Details Hon) to (

both in outlay and in the continued expense,month by month, between a three-valverand ,a four-valver; in very many cases thenecessity to own a " three " is quite clearlydictated. Well, if it is to be a "three," thenext question which automatically arisesis : is it to be used mainly for "family"work or for DX reception ?

A Double -purpose ReceiverIf the set has as its main duty to receive

5XX, 5GB, and the local station at goodloud -speaker strength, but when the restof the family has gone to bed pater-familias likes to put up a good showingagainst some of the neighbours' super-hetsand multi -stage screen -grid job postes, thenan H.F. stage is essential. This, of course,means that there is only one low -fre-

quency stage, and unless thecircuit is carefully designedand the very best compon-ents are used, the home -broadcasting results maysuffer.' On the other hand, if the

three - valver is used just asan alternative to the gramo-phone and only Daventryand the local station are tobe received at adequatevolume, then two L.F. stagesand no high -frequency stageis the obvious arrangement.

This is just what is doneiri the:case of " Britain's Fav-ourite Three," and, as wehave said, when it was voted

(in 1928) ,to be themost popular circuit,screen -grid stages were not such aneveryday matter as they now are.

With the additions described in the 1929model it is in every sense an up-to-datethree, capable of giving a good show withoutany unnecessary frills.

A Popular TypeAs even the least technically -minded

reader will gather from a cursory inspectionof the photographs and theoretical circuitdiagram, " Britain's Favourite Three " isof the ever -popular detector, R.C., andtransformer -coupled L.F. type.

The Circuit of " Britain's Favourite Three "

stage to operate, namely, a stage of screen -grid H.F. amplification.

But there are still many reasons whythree-valvers with two stages of amplifica-tion on the low -frequency side, and withno H.F. boosting whatsoever, are verypopular, and why, if the votingwere taken again, three -valuers with-out H.F. might conceivably not beswamped by their more distance -gettingcounterparts with one H.F. stage.

The whole question resolves itself on thepoint of economy, both as regards valvesand running costs.

There is quite a big step of difference

ivThose who take an interest in the work..-

ing of their receivers will perhaps care toexamine the various features obvious fromthe circuit diagram. The detector operateson the leaky -grid principle, andthis is because at normal rangesand owing to the fact that there isno high -frequency amplifier pre-ceding the detector, there is notendency for the leaky-gridgsystem to be over -loaded.

As is well-known, the greatadvant a g eof employ-ing theanode -bendsystem,insteadof leaky -grid rec-tification, is to befound when the inputto the detector isalready fairly large,and there is adanger that theproper functioning of the condenser andleak, in the leaky:grid system, might beupset by the comparatively heavy gridvoltage.

COMPONENTS REQUIREDEbonite or bakelite panel, 16 in. by 8 in., and strip,

4 in. by a in. (Becol, Raymond, Paxolin, Radion)..000s-mfd. variable condenser, log mid -line type

(J.B., Polar, Ormond, Burton, Burndept)..00023-mfd. variable condenser, log mid -line type

(J.B., Polar, Ormond, Burton, Burndept).7 -ohm panel -mounting rheostat (Lissen, Igranic,

G.E.C., R.I. & Varley).Push-pull stvitch (Lotus, Lissen, Trix, Wearite).Panel brackets (Bulgin, Camco).Dial indicator (Bulgin).Three antimicrophonic valve holders (Benjamin,

Lissen, Burton, Weaiite)..0003-.ocio023-mfd. pre-set condenser (Formo-

denser type J, Igranic)..0003-mfd. fixed condenser with series clip (Dubilier,

Lissen, Graham-Farish, Mullard).a-megohm grid leak (Dubilier, Lissen, Graham-

Farish, Mullard).Six -pin coil and base (Tunewell, Lissen, Lewcos,

Peto-Scott).High -frequency choke (Lissen, R.I. and Varley,

Burndept, Polar, Tunewell, Trix).Resistance -capacity coupling unit (Dubilier, Lissen,

R.I. & Varley, Graham-Farish, Mullard).50,000 -ohm resistance (Graham-Farish, Lissen,

Dubilier, Mullard, R.I. & Varley).z-mfd. fixed condenser (Lissen, Dubilier, T.C.C.,

Ferranti, Mullard).Low -frequency transformer (R.I. & Varley, Lissen,

Philips, Mullard, Cossor, Igranic).

561

Amszalcrutammimuclaiis

VOURITESATE'et `Kest Results

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The various technical merits and de-merits of each system have been discussedin the pages of AMATEUR WIRELESS, butit may be taken for granted that in a

general- purpose receiver,such as this "Britain'sFavourite Three," a n dwhere there is no ampli-fication preceding the rec-tifier, the grid condenserand leak system is prefer-able. The values for thecondenser and leak are con-ventional, being . o o o 3 -microfarad and 2-megohm

respectively.A little hint which

may be appreciatedis that with somedetector valves andunder certainworking conditionsslightly better sen-sitivity, thoughsometimes at the

expense of purity, is ob-tained if the value of the

grid leak is raised somewhat-to, say, 3or even 5 megohms.

The values of the condenser and leakin the R.C. coupling system are also

Grid -bias battery clips (Bulgin). Two black andone red wander plugs (Clix).

Baseboard, z6 in. by q in. (Pickett, Clarion, Cameo).Connecting wire (Glazite). One yard of thin flex

(Lewcoflex).Seven terminals, marked : Aerial, Earth, L.T.+,

L.T.-, H.T.±, L.S.-, L.S.-{- (Belling -Lee, Eelex,Igraine).

Six -volt Valves to Use with thelip -to -date " Favourite Three"

Make Det. 1st L.F. Potter

Cleartron .. CT25F CTz5

DE5o

CT25X

Cosmos ..

Cossor . . MoRC 6ioLF 6i oP

Ediswan .. RC6io LF6io P V610

Marconi . . DEHM o DEL6i o DEP6 1 o

Mazda .. RC6o7 GP6o7 P615

Mullard .. PM5B PM6D PM6

DEP6 1 oOsram . . DEHM o DELM o

Six -Sixty . . 6o75RC 6o75fIF 6 x oP

FIRE19

conventional, that is, for an R.C.stage immediately following a detectorvalve.

The anode resistance used in conjunctionwith these components has a value of.25 megohm, and in series with this is the50,00o -ohm resistance, which forms partof the anti -motor -boating unit.

1929 Modifications:The additions to the original 1928

"Favourite" are the following : The plug-incoils are scrapped in favour of a six -pindual -range coil, and the wave -changeswitch is placed on the panel just belowthe centre tuning condenser; a pre-setcondenser is incorporated in order to givethe very best selectivity; this condenseris mounted on the baseboardand can be put in or out ofcircuit as required, simply bychanging over a flex con-nection from one termind:to another ; the third additionis an anti -motor -boating unitwhich enables a high valueof H.T., a large power -valveor a mains eliminator to beemployed without any fearof motor -boating.

As a matter of fact, pos-sessors of old "Favourites"will find very little differencebetween the operation of thenew set and the 1928 edition.Valves and battery detailsare, of course, relatively im-portant. For the guidance of new con- in somestructors of the "Favourite" a table is foreigners.given showing a selection of six -volt -valves If interference from thewhich will work very well in combination. seems to cover an unduly large section of theAs in most other receivers, 2- and 4 -volt tuning scale, the knob of the pre-set con -equivalents can be used and the final denser can be slacked off, thus reducing thedecision with regard to type rests almost capacity until the required selectivity isentirely with the set user and the type obtained.of accumulator he has available. The simple push-pull switch on the panel

It is recommended that about 12o -volts changes over from the long- to the short-H.T. should be used, in conjunction with a waves and this is a convenient point9 -volt grid bias battery, and about 3 -volts -Which will be most appreciated by users ofnegative G.B. being applied to the first the former edition of the set and who mayL.F. valve. have had cause to grouse at the job of

It is opportune at this point to note that changing over the coils.

&attar Wire!5

131

in the accompanying valve table, valvessuitable only for ordinary requirementsare given ; that is to say, the last valve isof the normal power or large L.F. type,capable of dealing with a reasonably exten-sive grid swing, and giving an output forone of the larger cone type or smallermoving -coil loud -speakers.

There are, however, still larger powervalves on the market, and in cases whereexceptionally large output is required oneof these may be used, provided that acorresponding alteration in H.T. and grid -bias voltage is effected.

A glance at any list of typical two-voltersin this super -power class shows such valvesas the Cossor 23oXP, the Marconi orOsram DEP24o, Mullard PM252, EdiswanPV225, Mazda P227, and Six -Sixty 23oSP.

For a preliminary test, tune in the localstation. To do this fully screw in the knobof the pre-set condenser and with thereaction condenser at practically zero,slowly rotate the main tuning condenseruntil the desired station is heard.

Then reaction may be adjusted untilvolume is at the required degree and theknob of the pre-set condenser can beslacked off a little, if desired, though thereis really no need to do this in the case oflocal station reception, which is generallyfree from interference. H.T. and G.B.values can then be adjusted to a nicetyand an attempt may then be made to tune

:NAVE -CHANGE SWITCH ON PANEL

PRE-SETCONDENSERFOR SELECT-IVITY

-PINDUAL RANGECOIL

ANT I-NICTOR BOATING UNIT

This picture shows the 1929 modifications

of the more easily receivable

local station

entatentWireLz..,5 562 APRIL 13, 1929

UMW

"A.W." TESTS OF APPARATUSConducted In our Technical Editor. I. H. REYNER. B.Sc. (Hons.), A.M.I.E.E.

New Wearite H.F. Choker -r HE Wearite H.F. choke has, since its

1 inception, earned a good name foritself because it will operate in a reliablemanner from below 20 metres up to wave-lengths exceeding 2,000 metres. Thisshows that the value of inductance issufficiently great and the self -capacitysufficiently small for efficient choking bothon the high and the low wavelengths.

A new model of this popular componenthas recently been put on the market. Thisdiffers from the older form in that the twoterminals are placed on the base instead ofone being on the base and the other at thetop of the former. Tests which we con-ducted on the old and the new type ofchoke indicate that the new type has aslightly higher self -capacity owing to thepositioning of the terminals. This, however,is scarcely noticeable, being less than onemicro-microfarad and in practice no differ-ence in the operation of the instrument

New Wearite H.F. Choke

could be discerned over the entire workingrange.

As before, the finish and appearance ofthis choke are excellent. The makers, ofcourse, are Messrs. Wright and Weaire, Ltd.,of 74o High Road, London, N.x 7.

An Automatic Time SwitchIT is very annoying to miss the beginning

of a much -desired programme simplybecause one forgets to switch on the set atthe proper time. Also, if a set is to be leftin non -technical hands it is satisfying toknow that it can automatically be switchedon and off without any chance of the othercontrols being upset.

These two needs are supplied by theSetalite, which is an automatic time switch,manufactured by Setalite, Ltd., MorleyHouse, Regent Street, London, W.I. Itincorporates a clock -work mechanism whichneeds no special winding.

All that it is necessary to do in order tomake the set operative in, say an hour and

a half's time, is to turn the knob on thefront of the Setalite unfit the setting of1-3o is obtained on the dial. This is all thewinding that is needed, and the instrumentthen goes on ticking, until the properperiod has elapsed, when two contacts areclosed and the set is -switched on.

Setalite Time Switch

The Setalite is capable of switchingeither on or off at any predetermined time,and a simple push-pull switch on the sideof the case arranges for it to switch on oroff as required. We have tried one of theseswitches in conjunction with an ordinaryset and have found, that it gives a verysatisfactory degree of accuracy.Floating -cone Unit

THE advent of the moving -coil speakerwith its floating diaphragm has

demonstrated the advantages of using afloating diaphragm with magnetic vibratingarmature units. If a diaphragm is free to

A. W. Knight's Floating Cone

move at the periphery there is more chancethat the motion will take place as a wholerather than in small segments.

We have recently tested a floating cone,marketed and submitted by Messrs. A. W.Knight and Co., of r8o Tower Bridge Road,S.E.r. This is simply and inexpensivelymade but is an efficient article of its kindand capable of giving good reproduction.

A 7 i2 in. cone is attached at the peripheryto circular pieces of chamois leather and isfinally clamped to a small baffle boardhaving overall dimensions of loin. square.The baffle board is covered on the outsidewith green baize, so that it can be fitted ifdesired to a larger baffle without loss ofsignal strength or tendency to rattle.

During our tests we connected severalunits in position, in turn, and affixed anextra 2 ft. baffle; the results obtained werequite pleasing, the reproduction from high-class units being good and free from unde-sirable rattle, even when large volume out-puts were obtained. This cone assemblycan be recommended.

Polar Ideal CondenserTHE Polar Ideal variable condenser is

well-known as a robust instrument ofhigh-class design fitted with a reliable andsmooth slow-motion device working on aninteresting and practical system of ball -bearing.

Readers will probably be interested to

Polar Ideal Condenser

know that this condenser may now heobtained with a drum dial, a form of controlwhich has recently become popular owingto the neatness of such a fitment.

The drums of the Polar condenser consistof two insulated mouldings having a dia-meter of 23/4 in.; these are knurled to afforda suitable finger grip. l3etween ,the twodrums a cylindrical ivorine scale is fixedand this rotates directly with the left-handdrum. The right-hand drum is attached tothe slow-motion spindle giving a reductionof approximately 20 to 1.

Fitting this condenser to a' panel presentsno difficulty whatsoever. A portion of thepanel must be cut away to take the neatescutcheon plate and allow the drum to,project slightly. The actual condenser isheld in position by drilling two holes on thepanel on the left of the drum and placingscrews through these into two bracketsprovided on the instrument.

The makers are Messrs. Wingrove andRogers, Arundel Street, Strand.

APRIL 13, 1929 563 =tear wire

rEXPERIMENTSWITH NEONMBEScrhatYou Can Make

The Neon Tube has many peculiarcharacteristics which will well

A MATEURS who have. experimentedZ:1, with neon tubes have found that theycan successfully be used for many purposesformerly only served by the more costly

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HO 115Fig. 1.

/20 /2S /Y.0 /SS HO /15 /50 /51Characteristic curve of neon lamp

three -electrode or two -electrode valve. Itis intended here to give an outline of theproperties and characteristics of neon

tubes with a view tohelping the amateurto form an idea ofwhat can be donewith these lamps. Itshould be understoodthat the results areobtainable using anymake of neon tubewhich operates onabout 200 volts, theelectrodes being ofiron and situated fair-ly wide apart. Thereare several makeson the market, suchas Philips and Osram,and a slight variationof the characteristicwill, of course, beproduced by usingdifferent types. Thisvariation may beeasily met by an ad-justment of the re-sistance and capacityvalues in the figuresof circuits shown.

In the neon tube aluminous ionised gas

The Raytheon neontube as used for tele-

vision purposes

repay investigation. This articlegives some suggestions for its use

By H. F. LEECH

discharge takes place between two metallicelectrodes in a rarefied atmosphere of neongas, which latter possesses a remarkablylow -ionising potential and a comparativelyhigh electrical conductivity. TM neonlamp requires about 200 volts across itsterminals-. According to modern standards,the vacuum is an extremely soft one, pres-sure being equal to several millimetres, oreven a centimetre of mercury. A slighttrace of helium is also contained in the"space," and possibly also a very slighttrace of hydrogen.

Contained in the brass cap of the lampis a safety resistance, usually consisting ofa quantity of fine wire wound on an earthen-ware or cardboard bobbin. This resistancemust be removed before experiments areundertaken, as its presence would seriouslyinterfere with the action of the lamp, par-ticularly when dealing with high -frequencycurrents.

There is no need to damage the brasscap in removing the resistance : the cap isconvenient for plugging the lamp into thestandard bayonet ldmpholder. The bestprocedure is as follows : Grasp the glassbulb firmly in the left hand and carefullyheat the brass cap in a small fiame, beingcareful not to allow the flame to play onthe glass. This has the double effect ofmelting the solder which secures the lead-inwires to the contacts, and of softening thecement which holds the bulb in the cap;so that it is a simple matter to grasp the

HAVE YOU NOTICED-that the standard values forleaky grid rectification are, inEngland : Condet.ther, .0003mfd. ; leak, 2 megohms ; inFrance : condenser, .00015mfd. ; leak, 3 megohms ? Itwould be interesting to knowwhat are the standard values inother countries, why there shouldbe differences, and on whatreckoning, the decision of therespective values has been ar-rived at.

cap with a pair of pliers and pull off thecap gently, thus revealing the resistance.Remove the resistance, and after makingsuitable connections between the lead-inwires and contact lugs, fix the cap onagain. If it is afterwards required to usethe lamp across the ordinary lighting

0 o-vvvvvw4- Hr -WO K

A detector circuit using a neon tube

mains, an ordinary lamp should be used inseries, since after removal of the resistanceany overload in the current would blowthe neon lamp if connected alone.

Characteristics of the Neon LampFig. i gives the characteristic curve of

a typical neon lamp. No two lamps havethe same characteristic curve. The un-steadiness of the discharge position giveskinks in the curve. The extinction andlighting-up potentials are not identical, inthat the discharge will not commencebefore a certain minimum potential isapplied, but once the lamp glows thepotential necessary to keep it alight maybe lower than that required for startingthe discharge.

In a lamp containing electrodes ofunequal size the conductivity is not thesame both ways, the lamp conducting

Fig. 3. Arrangement for production ofoscillations

better when the larger, electrode is thecathode. Should the lamp. be _inserted inits socket the wrong. way round,, the glowappears at the, smaller electrode, and less

makur WiretT

current passes through the lamp thanwhen it is connected in the normal manner.A typical lamp tested in this manner, usingabout 200 to 220 volts, passed about15.4 milliamps in the normal direction,but only 12.8 milliamps in the reversedirection. A neon lamp requires a smallerminimum ignition voltage when the smallerelectrode is used as the cathode.

Rectification by Means ofa Neon Lamp

The propertieS already explained are alldue to the fact that a neon lamp does notobey Ohm's law, and this fact, together

L2 L/Fig. 4. Arrangement of neon lamp oscillator

for a 300 -metre wavelength

1-11117___NTERRUPTERFig. 7. Method of obtaining rectified H.T.

from spark coil

with the power of partial unilateral con-ductivity, makes it possible to rectify, toa- certain extent, oscillations occurring ina circuit. The rectification, however, isincomplete and is really inferior to a goodcrystal rectifier, and thus this use will not -find a very extended application.

Fig. 2 shows a circuit suitable as adetector circuit. In series with a pair oftelephones, a high variable resistance a,and a H.T. supply of 200 volts, is a neonlamp. c is a large capacity by-pass con-denser. This condenser is absolutely essen-tial. The resistance should be adjusteduntil the lamp glows very feebly and thereceiver then tuned in the usual manner.

Production of OscillationsA neon lamp is capable of converting a

D.C. supply into regularly pulsating cur-rent. Fig. 3 gives a suitable arrangement.

When the supply is switched on a rapidseries of pulses will -pass through the lamp,when the resistance is adjusted so as tocause the lamp just to glow. The frequencyof the discharges depends on the rate atwhich the supply current through theresistance R. can charge up the condenser cto the ignition potential of the lamp. Itwill be readily seen that decreasing theresistance increases the frequency of thepulsations, and, also, the smaller thecapacity of c, the higher will be the dis-charge frequency. Any frequency may beobtained from. say, one pulse every two

564

or three seconds up to about 20,000 persecond by suitably adjusting R and c. Thepotential drop in R should be approximatelyequal to the potential drop in the lamp forbest results.

These pulsations are really detacheduni-directional surges, and not sinusoidaloscillations ; therefore, we must expect anenormous number of harmonics to bepresent. Cause a lamp to pulsate at about15,000 per second, and listen on a hetero-dyne receiver, and a strong C.W. note willbe heard on a wavelength of about 20,000Metres; then tune the receiver down, andwe come to harmonics of two, three, four,and five times the fundamental wavelength.The higher the fre-quency tuned-i.e., thelower wavelengths-themore congested theseharmonics become. Be-low 400 metres the har-monics are feeble, butcome in in very rapidsuccession.

Maintenance ofOscillations

If an oscillatory cir-cuit, coupled to theneon lamp circuit, be tuned to one of theshort -wave -harmonics, this harmonic willpredominate more strongly than the others.Fig. 4 gives an excellent arrangement for aneon lamp oscillator to generate oscilla- Fig. 6.tions of 300 metres wavelength. Connectthe neon lamp to produce the pulsations,as in Fig. 3, except that an inductance LIis put in series with the lamp. Adjust Rand ct so as to cause the lamp to pulsateat as high a frequency as possible. Theinductance LI must be of such a valuethat in conjunction with cf it will tune tothe desired frequency-I,000,000 persecond-although, strictly speaking, thecircuit LIcr is not really a tuned cir-cuit owing to the inclusion of the lamp.

APRIL 13, 1929

-a tuned -aerial circuit should replace L2 -c2. Each aperiodic discharge from thelamp gives a kick to the circuit L2C2,which oscillates in its own natural perioduntil the next kick is produced to keepthe oscillations going. If the lamp is dis-charging at the rate of 20,000 per secondand, the circuit L2c2 is tuned to a fre-quency of L000,000, a kick is administeredto L2C2 once every fifty oscillations, and so,if L2c2 possesses low H.F. losses, prac-tically undamped oscillations will be sus-tained in it.

The Neon Lamp Transmitter,Only vety, small power is available with

0601

O

Fig. 5. Neon lamp as modulatorOnce the circuit L2C2 has been tuned to

,000,000 per second a slight adjustmentof c1 or a will briag a harmonic into exactsynchronisation with L2C2. The couplingbetween LI and L2 must be tight. High -frequency chokes may be inserted in thesupply leads as shown. in Fig. 4, though theresistance R may be high enough to keepthe oscillations out of the supply leads.

To use the arrangement as a transmitter

THIRD

ELECTRODE

a

220KAnother modulator circuit

a neon lamp circuit, as standard lampsconsume only 5 watts; since they pulsateonly at almost extinction point:about only

watt is available for use. If the lamp isoverrun on -about 400 volts the glow willchange to a- pale violet colour. This en-ables the lamp subsequently to pulsate onhigher power, 1pecause once the lamp hasbeen overrun it requires a considerablyhigher voltage to work it afterwards, andalso this overrunning causes it to pulsateon a higher fundaniental frequency and togive stronger harmonics. The oscillatoryproperties of a neon lamp, then, are greatlyimproved by about twenty minutes' over-running.

It is highly important that the supplycurrent be absolutely regular and constant.The frequency is not determined, by atuned circuit the fundamental lamp fre-quency, that is-but is chiefly a function

of the supply circuit and the large con-denser in the lamp circuit. Should smallvariations occur in the supply current, thefundamental pulsation frequency of thelamp will vary. These variations areenormously magnified in the selected har-monic, and hence the necessity of keepingthe supply constant.

The Neon Lamp as aSpeech Modulator

The susceptibility of the oscillations toany variations has a great advantage in


Small, neat, and handsome, but with a straight lineperformance and a purity and constancy of amplifica-tion far above any transformer in its price class.The wonderful results from this instrument are onlypossible because of its special windings and ultra -permeable iron core enabling bulk and cost to bereduced without any sacrifice of efficiency.Ratio 3:1 for use after valves of 10,000 to 20,000ohms impedance, or 6:1 after valves of 5,000 to10,000 ohms impedance.

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inateia Wirdes1 566 APRIL 13, 1929

Some Considerations of aPossible New Method

MATHEMATICS are troublesomethings to the average man at the

best of times, and indeed the amateurprefers, as a rule, to leave such mattersstrictly alone, confining his attention tothe actual practical' results obtained.Nevertheless, there are undoubtedly occa-sions on which a mathematical analysisserves a very valuable purpose.

Perhaps one of the most interestingexamples of this is that of Maxwell'stheory of light. Long before the end oflast century, Clerk Maxwell evolved hiswave theory of light, which he worked outto fit in with the facts known in thosedays. Having decided the general prin-ciple upon which he thought light radia-tions were operating, he investigated thesubject and made a complete mathe-matical analysi. This went far ahead ofpractice in those days, and not only pre-dicted numerous effects concerning lightwaves which were ultimately found to betrue; but also foretold the existence ofwireless waves.

He said we should find that such ethervibrations which we now know as wirelesswaves would be capable of production,that they would obey the same laws aslight vibrations, due allowance being madefor the difference in frequency, and hegave various estimated theories regardingtheir operation. It was notuntil the beginning of thiscentury, many yearS after thefirst predictions, that wire-less waves were actuallyproduced and found to con-form to the laws whichClerk Maxwell had laid doWnfor them. Still, in those daysthe full signifiCance and theenormous applications of thenew vibrations were notrealised, and it remained forMarconi to make the firstpractical utilisation of thenew discoveries.

So to an increasing ex-tent the pure mathematicianshave started the engineersthinking. The mathematicalmind is quite distinct fromthat of the engineer orphysicist. A mathematician

can deal entirely in symbols and- formulae,and can deduce from them other forintlaewhich upon examination may indicate anentirely unsuspected state of affairs. Theengineer or physicist in his turn investigatesthe practical way of carrying out the newmethods disclosed, and in general he pre-fers to carry a mental physical picture ofwhat is happening, using mathematicsmore as an aid than as a primary structureon which to build his ideas. The net re-sult, however, is generally progress, foreven if the mathematics prove incorrect,owing to insufficient knowledge regardingthe assumptions or for some other unfore-seen cause, a train of thought is startedwhich usually results in an interestingdevelopment.

Divided OpinionsThe problem of amplification of the very

' short wavelengths has been exercising theminds of radio engineers for some consider-able time past. Opinion is very muchdivided on this subject. One school stoutlyaffiwns that,' although a high -frequencyvalve can be made to hand on high -fre-quency energy with no serious loss ofvolume-i.e., so that it is not definitelyworse than a simple detector arrange-ment-it cannot be made to give anyappreciable amplification effect over a

By J. H. REYNER,B.Sc., A. '.I.E.E.

reasonable wavelength band. Others, on,-the. other hand, claim that with correcjdesigned apparatus and careful construc-tion, real amplification is possible,although this may not be of a very- highorder. Even an amplification of 2 or .3serves to give a margin of reserve over andabove the ordinary detector circuit, whichmakes tuning easier and tends to minimisethe disadvantages of fading.

Possibilities-Any suggestion that an amplification of

the order of io to 15 is possible would seem,on the face of it, ludicrous. Yet a recentdetailed analysis on the, operation of thestandard three -electrode valve, publishedby F. M. Colebrook (Journal I.E.E.,vol. 57, page 157), indicates that there arecertain unsuspected effects taking placeby the utilization of which we may obtaina distinct amplification on these highfrequencies.

The first thing that emerges from theanalysis is that the maximum amplifica-tion is obtained from a valve not quite atthe point where the anode circuit is tunedto resonance, but at a point where theimpedance of the anode circuit is slightlyinductive. This effect is almost negligibleat- ordinary broadcast frequencies, but onshort waves the difference is appreciable.

This does not mean that

American Broadcasters you may have heard on the short waves fromKDKA-The Happy Wonder Bakers

thereare two tuning points,for the apparent tuning pointwill be that where maximumsignal strength is. Obtained,and one automatically tunesthe condenser until this max-imum amplification is pro-duced. The fact remains,however, that at this pointthe circuit is not really tuned,but is slightly undertuned, sothat the impedance isinductive.- When this is, -the case aresonance effect occurs be-tween the anode circuit andthe internal capacity of thevalve, and, due to this, thevoltage developed on the out-put may be more than intimes the input, in being the

. . .. -


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568

R DIOGR(INISa 4.,

ISTENERS to 2L0 and 5XX will begiven anopportunity of bearing Mrs.

Baldwin on April 28, when she is to makean appeal on behalf of the National Birth-day Fund, for Maternity Services.

The concert to be given at Queen's Hallon April 12 and to be conducted by SirHenry Wood will consist entirely of Wagnermusic. The soloists for the evening areWalter Widdop and Tatiana Makuschina.

On April i8 a special broadcast versionof the Nine O'Clock Revue is to be givenfrom 5GB. Morris Harvey, part -authorand one of the principal stars in theoriginal production at the Little Theatre,London, will be responsible for its presenta-tion before the microphone. The perform-ance will be repeated on April 20 for thebenefit of listeners to 2L0 and 5XX.

Act I of Richard Strauss's opera, DerRosenkavalier; which opens the CoventGarden opera season on April 22, will berelayed to 2L0 and 5XX. During thefollowing weeks 5GB listeners will also begiven opportunities of hearing excerptsfrom some of the performances.

Mr. George Allison on April 13 willdeliver a running commentary on theinternational football match, Scotland v.England, which is being played on thatdate at Hampden Park, Glasgow; it is tobe relayed to both 2L0 and 5XX.

A polite satire, entitled Square Pegs, byClifford Bax, is the title of one of the shortplays to be found in the 5GB eveningentertainment on April 20; it will precedeThe Dear Departed, a comedy of lowermiddle-class life, by Stanley Houghton.

Wagner's romantic , opera, The "FlyingDutchman, has been chosen as the work tobe broadcast from the London studio onApril 24; the cast includes Miriam Licette,Harry Brindle, Hughes Macklin, JohnArmstrong, Arthur Fear, and Evelyn Arden,The performance will be conducted byPercy Pitt.

Spanish Shawls, a novel entertainmentspecially written for the "mike" byEdmund Wynschenk, a Birmingham solici-tor, will be presented at the 5GB studio onApril 17. To use the author's own words,"the book with lyrics has been takenfrom the Spaniards when they weren'tlooking "

Short-wave experimenters should beinterested in the programme offered by theCardiff station on April 13, for on thatevening they will hear E. U. Ridgway, andhis partner, Frances Gayton, who arebelieved to be the first artistes to broadcastacross the Atlantic on five metres !

Mabel Constanduros is responsible foranother comedy en casserole, entitled The

APRIL 13, 1929

Dragon's Bride; it is to be heard fromBelfast on April 22. In this short play shewill herself take the part of Ju-Jube, avillage maiden, and will be supported byHarold Clements as Liquorice, a deep-dyedvillain, and Olive Groves as a princess.

The Belfast Wireless Orchestra is prob-ably making more appearances in outsidehalls than any other B.B.C. orchestra. Ona recent visit to Londonderry to give aconcert in the local Guildhall, a journeyof nearly one hundred miles had to beundertaken by road through some of thewildest parts of Ulster.

In Scotland it is necessary to employat least one stage of H.F. amplification it5XX is to be received at loud -speakerstrength. The B.B.C. admits that indistricts where there is no preponderingsignal from 5XX, it is not possible,without some form of directive aerialsystem, to render a set sufficiently selectiveto receive 5XX free from interference byZeesen without seriously impairing thequality of reproduction.

An idea which is proving popular inScottish broadcast programmes is that of a"musical tour" of the country north of theTweed, each town, village, or districtvisited being marked by the rendering ofsome song or melody closely associatedwith it.

Some districts on the south side etGlasgow are being troubled just now by apeculiar fading of the transmissions fromthe local B.B.C. station. No solution of theproblem has yet presented itself, but it isnoticed that the fading is usually at itsworst between 6 and 8 p.m., while there isno trace of it during the morning trans-missions.

A dispatch from Rome states : plans fora powerful wireless station which v illtransmit and receive has been approvedby a commission which is acting as aprovisory Government of the Vatican.The Papal wireless will enable the Vaticanto communicate with the whole worldand have a power equal to the Italianstation at Saint -Paul.

On March 29 the wireless station of theEiffel Tower began to broadcast on a shorterwavelength, 1,47o metres, in the hope thatits reception would be improved and RadioParis and Daventry would not be impededin their service. The new wavelength willbe used until the Ministry of Posts, Tele-graphs and Telephones publishes its studyof the most suitable wavelengths for theEiffel Tower.

According to a report issued recently byGeorge Engles, director of the American

National Broadcasting and Concert Bureau,musicians in the United States owe morethan a third of their income to wireless.Out of a total of £6,000,000 spent on musicin the United States during the past year,his statements show that the broadcastingcompanies have contributed fully Z2,5oo,000.

APRIL 13, 1929

" CAN WE AMPLIFY ON SHORTWAVES ?"

(Continued from page 566)amplification factor of the valve. Inother words, we can obtain a greateramplification from the circuit than thatgiven by the valve itself. It should beremembered that we are dealing withordinary three -electrode valves, whichhave an appreciable capacity betweenanode and grid, and it is due to this thatthe resonant effect is obtained.

There is nearly always some qualifyingfactor which has to be taken into account.In this case it is a fairly serious one, apartfrom any question of stability and avoid-ance of self -oscillation. The anode circuitof the valve has a very marked effect uponthe input circuit. We are accustomed toregard the input circuit, i.e., the grid -fila-ment circuit, of the valve as of practicallyinfinite impedance. Where grid current isactually flowing, as in the detector circuit,this, of course, is not the case, as has beenpointed out in certain recent articles, butfor pure amplification, where we bias thevalves if necessary with a negative voltageto avoid any flow of grid current, we usuallyassume that the input impedance isinfinite.

This, however, is not the case, the inputimpedance being not only finite, but 'rela-tively low under normal conditions. Atthe point where the maximum amplifica-tion occurs on short waves the effect is tointroduce a relatively low resistance acrossthe grti circuits. In a particular instanceconsidTred of amplification at 28.3 metresthe shunt was as low as 300 ohms, thedamping effect of which would be enormousand would prevent the tuned circuit con-nected across the grid and filament fromdeVeloping any appreciable voltage what-ever,

A Cause of Failure?Indeed, it is probable that this unsus-

pected shunt -resistance effect has beenthe cause of the failure to obtain satisfac-tory amplification on short waves hitherto.Not only would it prevent any develop-.ment of the resonance effect just dis-cussed, but it would prevent the first cir-cuit from tuning satisfactorily, and thusnullify the effect of the amplification fromthe valves, if any, right at the commence-ment.

The difficulty may be combated bymethods ordinarily used to minimise theeffect of shunt -resistance across tunedcircuits, but such methods usually resultin such a loss of signal strength as torender the gains of other causes of no avail.Whether this is the case or not in thepresent instance remains to be seen, but ifit does not prove to be so, then we canlook forward to a new system of short-wave amplification which may conceivablygive results superior to any yet obtained.

"A.W." Solves Your Wireless Problems

569 0 =tau WitviT

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ETTERS TO THE EDITOR

The Editor Les not necessarily agree Withthe views expressed by correspondents.

Linen Speaker ImprovementsSIR,-Very many congratulations on the

linen -diaphragm loud -speaker. It iswonderful. Your readers might be in-terested to hear how I overcame its twodefects, namely ugliness and ungainlysize. I screwed four twisted oak legs tothe inside of the large frame and made thespeaker into a table! Five -inch boardsplaced round the inside of the same framebetween the legs act as a good baffle. Thetop was covered with fine -mesh wire net-ting to make a levelsurface. Over the topis then placed .a "table cloth" of darkbrown velvet. Light objects, such as avase of flowers, can then be put on the"table," and the speaker is entirelydisguised. K. L. D. (Richmond).

Organ BroadcastsSIR,I would ask your permission to---

support your contributors, Mr. SydneyMoseley and also Mr. J. B. Ingles, ofHawick, in their endeavour to get betterbroadcast organ music.

W. E. C. in his recent letter raises seriousdoubts as to whether he really knows any-thing about organs and organ music, inspite of his forty years of critical listeningall over the world.

Recently I heard the Stoll organ, andthis, in my opinion, would be far moresuitable to broadcast. The gentleman whoplays this organ is undoubtedly a musician,not a musical conjurer. The organ itself,too, is really an organ-unlike most cinemainstruments.

I might add that I hold no brief what-ever for the Stoll apart from expressingmy appreciation of the performance oftheir organ and its player.

G. H. G. (Croydon).

Sunday ProgrammesSIR, Regarding " Thermion's " sugges-

tion re church services via wireless, Imaintain (I) that all licence -holders underthe present conditions are really entitledto alternative programmes or a return of5s. on their licences; (2) if we are to havealternative programmes they should bereally alternative.

It naturally follows, then, that althoughany who may be so inclined may have abroadcast church service on the one wave-length, those who are not so inclined neednot at the same time be obliged to listento it, but instead may be amused withouthaving to seek this from foreign stations orgo withott.

Nor do I favour too much broadcasting

Correspondence should be brief and to thepoint and written on one side of the paper.

by the local stations on Sunday, as thiswould seriously interfere with the small -setowner searching abroad.

H. S. H. (London, W.)

SIR,-I am glad to see that AMATEURV.-.7 WIRELESS is at last taking up thecudgels on behalf of the Sunday listener.I hope you will get Mr. Moseley interestedin the subject, because his views arenoticed even by those at Savoy Hill. I amone of thousands who don't want to' listento religion at all, and I object most stronglyto the best part of Sunday evening beingdevoted to it. Fortunately, I possess fivevalves, and have all Europe -to choosefrom; therefore, I have least right togrowl; but, then, if I hadn't been drivenout of my own country to find entertain-ment I wouldn't need five valves.

C. S. (Birkenhead).

SIR,-The Sunday programmes are verygood as they are. To be of any use a

service must come from a church. Studioservices are paltry. 5GB and 2L0 neednot have them simultaneously, however.What about a little real organ music (notcinema piffle) that the B.B.C. often givewhen the breadwinners are at work ! But,for heaven's sake, don't give the B.B.C. achance to inflict Jack Payne's pains on us.Let us have one day of comparative peace !

P. P. P. (London, N.).

Linen -diaphragm SpeakersSIR,-Allow me, as one of your regular

AMATEUR WIRELESS readers, to con-gratulate you on the huge success of the" Linen -diaphragm Loud -speaker." I builtone a week after it was published inAMATEUR WIRELESS. Previously I hadbeen using a good make of horn -type loud-speaker, which. I exchanged for a Blue Spotunit. As soon as I connected the unit andswitched on I was quite satisfied at partingwith my horn speaker. Volume, as well asthe fine bass, is a 'credit to this fine speaker.I used' three-ply oak for the baffle, andcompleted the speaker by adding a fret-work front. No more horn loud -speakersfor me. W. H. G. (Newport).

AppreciationSIR,-Thanks for information re ampli-

fier. The trouble is now remedied.Let me also thank you for the great helpyour excellent articles have given me.They are just what the amateur wants.

S. F. (Altrincham).

April 16. De Courville's Hour.17. A Military Ceremonial by the and Battalion,

the Norfolk Regiment, relayed from Aldershot.18. A Symphony Concert, relayed from the Queen's

"Hall.19. A Vaudeville Programme.

DAVENTRY EXPERIMENTAL (5GB)

April 17. Spanish Shawls, a revue by EdmundWynschenk.

18. A Programme of Selections from the MusicalComedies.A Discussion on Broadcast Drama.

CARDIFFApril is. "Young Wales," a programme contributed by

some of the Winners at the Annual Inter -Collegiate Eisteddfod, 1929.

APRIL 13, 1929

OA571

CAST TELEPHONY(Broadcasting stations classified by country and in order of wavelengths)

Kilo- Station and PowerMetres cycles Call Sign (Kw.)

GREAT BRITAIN25.53 11,751 Chelmsford

(5SW) 15.0243.9 1,230 Newcastle (5NO) 1.0258.4 1,i61 *Leeds (2LS) 0.13270.3 1,109 'Sheffield (6LF) 0.13268.5 2,040 'Bournemouth

(6BM) 1.0288.5 r,o4o 'Bradford (2LS) 0.13288.5 r,o4o 'Edinburgh

(2E11) 0.85288.5 2,040 'Hull (8KH) 0.2288.5 1,040 'Dundee (2DE) 0.13294.1 1,020 *Liverjeaol (6LV) 0.139.94.1 .1,020 'Stoke-on-Trent

(5ST) 0.13294.1 r,oao 'Swansea (5SX) 0.13302.6 99/./ Belfast (2BE) 1.0311 964 Aberdeen (2BD) 1.0323 928 Cardiff (5WA) 1.0858.9 838 London (2L0) 2.0378 793 Manchester

(2ZY) 1.0398 ;57 'Plymouth (SPY) 0.13401 748.3 Glasgow (5SC) 1.0482 622 Daventry Ex.

(5GB) 25.01,562.5 192 fDaventry

(5XX) 25.0 Relay stations. tRelays 2L0.

AUSTRIA248 2,209 Linz 0.5277.8 1,478o Salzburg (under

construction) 0.5Graz 0,5KlagenfurtInnsbruck 0.5Vienna 20.0

354.2 847456 694456 694520 577


Brussels 0.5275 2,090 Ghent 0.5280 1,070 Liege 0.5312 9i o Arlon 0.25612 t8o Brussels 10.0

CZECHO-SLOVAKIA265 1,230 Kosice 2.0278 z,o8o Feriby (testing) 12.0299.3 1,060 Bratislava 4.0342 873 Prague (Praha) 6.0432.3 694 Drums (Brno) 2.4


(Kjobenbavn) 1.01,155 259 Kalundborg 7.5

ES'THONIA408 935 Reval (Tallinn) 1.3

FINLAND371 too Helsingfors

(Helsinki) 0 81,101 199 Lahti 20.9

FRANCE30.75 9,755 Agen 0.25200 1,500 Fkamp 0.3211.3 1,420 Beziers 0.1233 1,260 Bordeaux (Radio

Sud-Ouest) 2.0245 1,224 Lille (PTT) 0.8252.1 1,190 Juan-les-Pins 0.4253 1,./85 Montpellier 0,25254 r,./8o Rennes (PTT) 1.0255 1,775 Toulouse (PTT) 1.0268 1,//8 Strasbourg 0.3274 1,692 Limoges (PTT) 0.5

Kilo- Station and PowerMars cycles Call Sign (Kw.)

291.3 r,o3o Radio Lyons 1.5301 997 Bordeaux (PTT) 0.5805 982 Agen 0.3505.6 98% Marseilles (PTT) 0.5322 93o Vitus (Paris) 2.0336 892 Petit Parisien 0.5854 846.7 Algiers (PTT) 2.0870 8/r Radio LL, Paris 1.0382.2 785 Toulouse (Radio) 9.0400 749 Mont de Marsan 0.4414 724 Radio Maroc

(Rabat) 2.0428 7oz Grenoble (FM") 1.5430 '697 Radio Flandre

Lille 0.25448 168 Paris (Ecole

Sup., PIT) 0.7973 635.r Lyons (PTT) 5.0

1,470 203 Eiffel Tower 8.01,748 271 Radio Paris 8.0

GERMANY219 z,376 Flensburg 1.5240. 1,250 Nurnberg 4.0250 1,200 Kiel 0.7250 .7,200 Cassel 0.7263.2 1440 Cologne 4.0267.8 2,120 Muenster 1.5272.7 1,100 Kaiserslautern 1.5280:4 1,070 Konigsberg 4.0283 1,061 Berlin (5) 0.7283 z,o6r Stettin 0.7283 2,06z Magdeburg 0.7817.5 945 Dresden 0.75821.2 937 Breslau 4.0$26.4 919 Gleiwitz 6.0230 909 Bremen 0.75361.9 829 Leipzig 4.0374.1 802 Stuttgart 4.0891.6 766 Hamburg 4.0421.3 712 Frankfurt 4.0455.9 654 Danzig 0.75458 654 Aachen 0.75462.2 649 Langenberg 25.0476 630 Berlin 4.0

4.00.50.70.7

90 0Norddeich 10.0

537 559 Munich566 53o Augsburg566 530 Hanover677 520 Freiburg

1,650 182 Zeesen1,650 182


1,280 234.2 Radio Luxembourg 0.25


(PCJ) 25.088.8 - Kootwijk

(PCL) 32.0(Wed. 12.40 G.M.T.)

337 889 Huizen (until5.40 p.m.) 5.0

1,073 279.5 Hilversum(ANRO) 5.0

1,152 rfa Huizen (after5.40 p.m. and on

Sundays) 5.01,152 262 Scheveningen -

haven 6.0



1.51.5

IRISH FREE STATE222.2 1,35 Cork (5GE)411 73) Dublin(2RN)

cyclesKi CallStation andPower

Metres (Kw.)

ITALY276 2,08o Turin 7.033:1 goo Naples(Napoli) 1.5

3.0443.8 676 Rome (Roma) 3.0456 658 Bolzano 0.3504.2 Milan 7.0

308.3452582

LATVIA529 567 Riga 2.0

LITHUANIA2,000 150 Kovno 15.0

NORWAY242 1,240 Rjtikan 1.0297 r,oro Notodden 0.7365 82o Bergen 1.0387 775 Fredriksstad 1.0387 775 Aalesund 1.0959 653 Porsgrund 1.0496 604 Oslo . . 1.5500 boo Tromso 1.0566 35o Hamar 0.7

POLAND314 955 Cracow 1.5336 890 Posen 1.5416 721 Kattowitz 10.0456 658 Wilno. 1.5

1,305 215 Warsaw 10.0

PORTUGAL317.5 945 Lisbon CTIAA (Wed.

and Sat.: 10 -midnight)

ROUMANIA395 757 Bucharest 4.0

RUSSIA825 363.5 Moscow (PTT) 25.0925 323 Homel 2.5

1,000 300 Leningrad 20.01,444 207 Moscow 30.01,6e5 178 Kharkov 15.0

SPAIN277.8 z,o8o Barcelona

(EAJ13) 2.0309 970 Oviedo (EA J19) 0.5348 857 Barcelona(EAJD 3.5370 8or Seville (EAJ5) 0.5400 75o Radio Espana... 1.040/ 744 San Sebastian

(EAJS) 0.5426.7 103 Madrid (EAJ7) 3.0456 658 Salamanca

(EAJ22) 0.55

SWEDEN261 2,149 Herby 10.0265 1,130 Trollhattan 0.4333 goo Falun 0.5346.8 865 Goteborg 6.0438 655 Stockholm 1.5545.5 550 Sundsvall770 390 Ostersund 2.0

1,200 25o Boden 2.01,325 223 Motala 30.0

SWITZERLAND406 739 Berne 1.0489.4 613 Zurich 0.6680 44r Lausanne 0.8760 395 Geneva 0.5

1,010 297 Basle 0.25



LONDON AND DAVENTRY (5XX)

'PP

Of 19.

595

JUGO-SLAVIA073 Zagreb (Agram) 1.25664 Belgrade 4.0515 Ljubljana.........5.0

POLITICAL BROADCASTST is welcome news for those who take anI interest in politics, to note the number

of political speeches to be given before thedissolution of Parliament. Each speechlasts about half -an -hour, and the startingtime is 9.15 p:m. The programme. of futurespeeches is as follows : April 16, Govern-ment; April 19, Opposition, Liberal; April22, Government; April 25, Opposition,Labour; April 3o, Government; May 3,Opposition, Liberal. During the time ofthe General Election one opportunity willbe given to each of the three politicalparties to broadcast a speech.

sugargligoogBritish Materials. BritishCraftsmen. British Through-out. Thorough testing. Sucha combination is essentialto produce an instrumentwhich can definitely rankas "Incomparably Superior"

CELESTIONTHE VERY SOUL OF MUSIC

The only Pier Proof e our State-ment if to bear Celestims MuriaYou ran do so without obligation at

any good Wireless Dealers, or at ourShowrooms. Models range from.0.10.0 in oak or mahogany.

Made under Licence.

The new Celestion Booklet is free andgiirs you briefly and interestingly allparticulars. Mail the coupon below

for your copy now!

CELESTION LTD. (DEPT.. 4KiNOSTON - ON THAMES.

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WHEN A BETTER LOUD -SPEAKERIS MADE -- CELESTION WILL

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ECPlease send me a copy of the Niw Celestion Book- .--M--

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Why the tens of k3thousands who listen -in praise Celestion.

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WHICH MAINS WIRE ISEARTHED?

IEADERS may recall that informationwas given under the above heading in

a recent issue, regarding the testing of themains for polarity and earthing. It shouldhave been stated that when testing for thepolarity of the mains, one wire of the lampadaptor should be connected to one wireof the lamp -holder, thus leaving one wirefrom the adaptor free and one wire fromthe lamp -holder free. These two wiresshould be kept well apart and after plugginga suitable lamp in the lamp -holder theadaptor should be inserted into one of thelamp sockets of the house. The two freewires should then be dipped into a glassof ordinary tap water. Bubbles will be seento rise from the ends of both wires, but morebubbles will be seen to rise from the endof the wire which is negative.

Having determined the polarity andmarked the house -lamp socket accordingly,the next step is to find out which main isearthed.

Negative or Positive?One wire of the lamp socket should be

connected to an earthed object such as thelead covering of the mains or a water pipe,whilst the other wire should be connectedto the negative main of the house. Pro-vided there is a lamp in the holder and thelamp does not light the negative main isearthed. If the lamp lights then possiblythe positive main is earthed. To make sure,connect the unearthed wire to the positivemain, leaving the other flex still connectedwith earth. If the lamp does not light thenthe positive main is earthed. If the lampdoes light, then it may safely be assumedthat neither main is earthed. In every casethe lamp should be rated at the full voltageof the mains and should light up at fullbrilliancy.

If ,the lamp only lights up at half brilli-ancy the mains should be treated as thoughneither main is earthed. If the lamp lightsat full brilliancy on one wire and very dullyon the, other, then there is a faulty earthon the mains at the time of testing, and themains should still be treated as thoughneither main were earthed. If your nega-tive main is earthed you may certainly con-sider yourself lucky to a -certain degree,but when in doubt treat them as thoughneither main were earthed. This meansplacing a large capacity fixed condenser -between the earth terminal of your receiverand the actual earth wire. The condensershould beeither..5 or 1 microfarad capacityand should be capable of withstandingdouble the voltage of the house mains.

Finally, when testing or using the housemains always work on the house side ofthe house fuses, and not on the supply sideof the house fuses.

Let "Amateur Wireless"solve your problems

APRIL 13, 1929

EVERY VALVE SETUSER HEEDS A

NvATEsvoLT -AMPRADIO TEST METER

You may have a baseboard full of components-BUT you can-not hope to obtain really perfect QUALITY in reception unlessyou have that perfect set control ensued by accurate Volt andAmp readings! All you want is a Wates Mater. With its threereadings on one dial feature it has an immensely withr range ofusefulness-yet it costs no more than single purpose instrum ,nts.Obtain one now and let it reveal what a world of difference liesin the expert handling of your sat. Obtainable from your dealer

or direct, complete with explanatory leaflet.

Stocked by Halford's Stores, Curry's Stores, and all radixdealers.

a

READINGS0-150 VOLTS0- 6 VOLTS0- 30 MILLIAMPS

11-5 5,C00 ohms.Can be used asa Pole Finder

PRICE

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P". IMPERIAL RADIO CO..1P 72 VICTORIA STREET, LONDON, S.W.1. IsAlsisIkisAskAA.AA.AA/ds.AAAAAskAA.A.IsA

Messrs. A. F. Bulgin & Co., of 9-11Cursitor Street, London, E.C.4, haveissued an interesting booklet illustratingand describing a selection of foreign -madecomponents which Messrs. Bulgin importdirect from all parts of the world. Thelist number of this booklet is 125, andreaders can obtain copies on application.

APRIL 13, 1929

80/1/1/111111111111110,

573 mateur Wtre

.0\0"1","&iliz,

RULES .-Please write distinctly and keep to the point. We reply promptly by post. Please give all necessary details. Ask onstmestion at a time to ensure a prompt reply, and please put sketches, layouts, diagrams, etc., on separate sheets containing your namsand address. See announcement below. Address Queries-Amaxitun WIRELESS Information Bureau, 58/6r Fetter Lane, London, E.C4

Indoor versus Outdoor Aerials.Q.-I have been informed that if I erect and

use an indoor .aerial I shall stand a better chanceof getting distant stations than I do at presentwith an outdoor. aerial. I have a finer -valve set,with one stage. of what is known as K.F. ampli-fication, and was assured by those from whom theset iris purchased that this set would be capableof getting foreign stations on my speaker. I canonly get about two foreign stations and onlythree British stations, the latter being London,5GB, and 5XX. . Can you account for theapparent paradox regarding an in, aerialbeing better for foreign stations when my outdooraerial will not get them P-F. K. (Fulham).

A.-This " apparent paradox " is easilyexplained. When using an outdoor aerial closeto a broadcasting station the amount of energyactually picked up by the outdoor aerial fromthe local station is sufficient to swamp out allweaker signals. By using an indoor aerial theamount of pick-up from the local station isconsiderably reduced, thus permitting theselection of signals from more distant stations.This is" practicable only in sets having at leastone H.F. stage to offset the reduced pick-up ofthe aerial. In some cases quite good resultscan be obtained with a plain detector set and

an indoor aerial, but most satisfactory resultsare obtained when a stage of H.F. is used.-A. L.

0

0

0

0

o )1/40, 0V0

When AskingTechnical Queries

PLEASE write brieflyand to the point

A Fee of One Shilling (postal orderor postage stamps) must accompanyeach question and also a stampedaddressed envelope and the couponwhich will be found on the last page.Rough sketches and circuit diagramscan be provided, but it will be neces-sary to charge a special fee (which willbe quoted upon request) for detaillayouts and designs.

Wavemeter Calibrating.Q.-I have a buzzer wavemeter covering

from 25o to 50o metres. Will you tell me how

to calibrate and use it?-S. M. (Blackheath).A.-Tune in any -station working between

the wavelength limits you mention, and setthe wavemeter buzzer in operation. Turn thetuning dial of the wavemeter until the soundof the buzzer is heard in the phones or loud-speaker with the greatest intensity. If thebuzzer can be heard over a great range ofadjustments, move it farther away from theset. When you have decided with whichwavemeter setting the buzzer is heard atthe greatest strength make a note of the read-ing. Do this with as many stations as practic-able. Now either .make a table showing,therelation between the wavemeter readings andwavelength or draw a graph showing this. Inorder to pick up a station with the aid of thewavemeter, set the latter to the reading corres-ponding to the wavelength of the desiredstation, and set the buzzer in operation. Thenalter the tuning of the set until the buzzeris heard most strongly, when the set will betuned to the station. Cut off the buzzer andlisten for the station itself. To find the wave-length of an unknown transmission whichhas been tuned in, adjust the wavemeter untilit is most strongly heard, and then find thewavelength corresponding to the wavemeterreading.-R.

8E09 149 1.510/1.

N C C 207

574 APRIL 13, 1929rnateur Wig tle.1

DISPOSAL SALEof High Grade Electrical andWireless Apparatus by the

R.A.F. and C.P.O.METERS -Milli -ammeters, all ranges, 15'. to 2216.

0 to 500 volts, 451.. Weston Meters. all ranges to 1,600volts. Elliott, etc., Testing Sets. E.108, 4 ranges, amps.and volts, 45/- A.C. Hot Wire, f amp., 4/.. FrequencyMeters, various ranges Capacity Meters, ES; WheatstoneRecorders, £12; Multi -Micro Galvos, 60/-; Res. Boxes,17/6; Hydrometers, 1/6; Relays, 6/6; Remote Switches,15!-; 12 in. Spark Coils, £10. Anode Converters fromA.C. or D.C. Mains for outputs of 400 to 800 volts.H.T. Generators in stock, 50 watts to 2 kw. Weston 90/ -Micro Ammeters for Grid Bias testing, 35/. only.

TRANSMITTERS. R.A.F. I in. Spark with A.T.1. andall fittings, in polished mahogany case. Cost £15. Sale,15/. each; 100 watts, 25/-; 250 watts, 50/.. 2 -ValveAircraft ditto, with Osram valves. Speech or Morse,40/- each. No. 1 Tapping Keys, open type, with mas-sive contacts, 6/- each. Transmitting No. 51 KD, withaluminium cover, double contact, fine work, 7/6 each.Morse Practice Sets, with Buzzer and Key on Mahoganypanel, 8/6 each. Morse Recorders, for making picturemachines, 35/- each. Spark Gaps, 2/- ArtilleryElectric Torches and Battery, 2'6.

TRANSMITTING VALVES. 6 volt 40, 100, 200, and250 watts, from 4'6.

WAVEMETERS by Townsend, Paul, Silver town, Gam-brel!, and Marconi, from 151..

LOUD -SPEAKERS. R.K. Cones fitted B.T.H. MovingCoil, 100 surplus at only 7/6 each. Marconi L.S. Mag-nets, 6v. for moving coil cones, 20/-. Gramo. Motors,Genuine Panatrope Motors, run direct off mains supply,fitted Turntable, etc. Few only. 3716 each. Worth£4 10s. Chokes. Round's Output L.F. Chokes byMarconi, for feed from power amplifiers. Latest model,7/6. Condensers. New Sterling, 2 mfd., genuineMansbridge Condensers to 440 volts, at reduced price of2/10 only.

L.T. ACCUMULATORS. Celluloid, 2 volt 20 amp..3/.; 4 volt 20 amp., in case, 6/3; H.T., in Ebonite, 1,000m/a hours: 60 -volt, 19/6; 90 -volt, MI.; 120 -volt, 39/-;3-v. Inert Dora, 1/3. Cell Fillers, 1/6. Hydrometers,1/.. Petrol Testers, 2/6.

NEW CINEMA ARC LAMPS, 50/-. Leitz Lab. ArcLamps, 5 a., 55,'-.

INSULATORS. H.T., in porcelain and ebonite, from6d. each. Empire, Insulating Cloth for Coils, Chokes.etc., 1/. roll of 100 sq. in, 4 -Pin Plug and Sockets, Ed.pair. 2 -Pin do., Wall Plug and Baser, 5 amp., 10d.

MARCONI AERIAL ADJUSTERS, 30 to 300 Micro -henrys, 4/6.

If eavy Rubber Insulated Lead-in Wire, copper strand coil.2i- doz. yards. 3/22 VIR Cable, 50 ft. coils, 1/-. SilkFlex, 1/6 doz. yards.

52 PETROL -ELECTRIC GENERATING SETS. AirForce Portable, 1 kw. 50/70 volts 20 amps. from £20.150 Electric Bench and Portable, 110 and 2210 v. Drills,from £3 10s. Electric Hand Blowers, 220 v., 17/6.Immersion Heaters, 110 and 250 v., 3/6. Electric Sauce-pans, 5/.. 12 v. Carburetter Heaters, 2/6.

RECEIVERS. New R.A.F. Aircraft 3 -Valve semi -portable, I Det., 2 L.F., 3 anti-pong Holders, RemoteControl, Variable Condenser, and Rheostat. All testedon Broadcast, 27/6. R.A.F., 5 -valve ditto, with Valves£4. Or fitted in polished Mahogany Cabinet with S.M.Dials, £6 10s. Burndept 6 -valve Super -Het, with valvesand 2 frame aerials. New and O.K., TN 10s. Lht£45. 3 -valve L.F. Amplifiers, 30/, Twin Loud-speaker Wire, per 100 yds., 3/.. 2 -Pin Wall Plugs andSockets, 10d. Remote Tuning Controls, fitted 2 varia.condensers and rheo., 21- each.

ELECTRIC POCKET TORCHES, with new " Ever -Ready " Battery, 2/6. Hand Lanterns, ditto. 4/6. Airs1Safety Lamps, 2 volts, 7/6. 25 volts Candle Lamps, 6 .each. Radiator 250 watt 110 -volt Lamps for Charging,24.

ELECTRIC BELLS. G.P.O. Circular, 2/.. Outdoor,1/6. Sounders, 10/-. Ironclad Bells, 5/-. Pushes,6d.; Multiple Pushes, 2/6; A.C. Bell Transformers, 12/6.

SWTICHGEAR. Every description of radio and electricpower switch and fuse gear at lowest prices; 6 -wayswitch boxes by Lucas, 3/6; 2 -pin wall plug and base.250 v., 10d. 10 amp. porcelain switch fuses, with baseand handle, 1/2 pair; small 250 v, 3 amp, porcelain fuses,3d.: twin bell wire, 1/6 per 50 yard run; 1-18 V.I.R.cable, 5/6 per 100 yds.; test thermometers, 1/6; petrolgravity testers, 2/6; battery acid testers, 716; Morserecorders, minus ink -well and wood base, make fine autounits for home-made picture machines, W..

Final Milian of our Surp:us Bargains in Radio and EtecfrionGoods ,eady. Send stamped addressed enverope. SAVESRADIO USERS POUSDS.

ELECTRADIX RADIOS218 Upper Thames St., London, E.C.4Blackfriars Station, Underground Railway. City 0191.

" EXPERIMENTS WITH NEONTUBES

(Continued from page 564)that one can obtain extremely sensitivemodulation by inserting the secondary ofa modulation transformer in series withthe supply leads. Fig. 5 gives a suitablecircuit for neon lamp modulation. Althoughthe neon lamp may be no better as amodulator than the ordinary three -elec-trode valve, yet it is certainly much cheaperand is capable of giving excellent results.

How It ModulatesAcross the aerial circuit is shunted the

lamp in series with the secondary of amodulation transformer m and a high-tension supply. Adjust the resistance Runtil the lamp glows feebly. When themicrophone is spoken into the potentialsset up across the transformer vary theconductivity of the lamp, owing to its non-linear characteristic, causing a varyingdamping effect on the aerial circuit.Another and preferable circuit arrange-ment is shown in Fig. 6. Here a thirdelectrode is formed by neatly sticking acoat of tinfoil to the outside of the bulb bymeans of shellac varnish. The tinfoilshould cover the whole of the bulb, but onno account must it be allowed to touchthe cap of the lamp or any other conductorat earth potential. Bind a piece of copperwire round the bulb so as to make goodcontact with the tinfoil. This wire shouldthen be connected to the grid of theoscillator valve.

When the lamp glows the bulb -space- becomes semi -conductive, and the capacityeffect of the outer coating with the interior,forms an excellent conducting path forH.F. currents. The most effective modula-tion is obtained by using a tuned grid cir-cuit and shunting the absorption modula-tor across this. By adjustment of the gridcircuit tuning condenser a very flexiblecontrol of the extent of modulation isobtained. The polarising potential for theneon lamp may be derived from theoscillator high-tension if desired.

Rectified H.T. from a Spark CoilFig. 7 gives the connections for obtain-

ing H.T. supply from a spark coil, and issuitable for use with C.W. and telephonytransmitters. The condensers should bebuilt to stand very high peak voltages.When the interrupter of the coil " makes"the circuit only a low voltage of a certainpolarity is set up in the secondary, and,this is insufficient to drive any -currentthrough the lamp. At "break,'' however,a high potential is set up across the secon-dary, and this easily passes through thelamp and charges up condensers c r andC2. Since only tlui " break" currents getthrough the lamp, and these are always ofthe same polarity, it follows that the con,densers are charged with D.C. Probablytwo neon lamps will have to be connectedin series, as one lamp may not stand aback -voltage of more than 200. _

TO PERFECT RADIO

In addition to their own extensive range,PETO SCOTT offer YOU Every KnownRadio Receiver or Component -all on

EASY TERMSThe following list is merely representative, andwe ask you to fill in the coupon below or send us

a list of your requirements.COSSOR MELODY MAKER. Send on'y 1.01., balance

in 11 monthly instalments of 14/7.MULLARD MASTER THREE STAR. Send only 10/-,

balance in 11 monthly payments of 15/3.LEADING MAKES OF H.T. ELIMINATORS from

917 down. Balance in 11 monthly payments of 417.ARCADIAN PORTABLE. Kit of parts (see "A.W."

March 30), Send only 20/-, balance in easy payments.ETUDE 120 -VOLT H.T. ACCUMULATOR, 2,500 m'a

hours. Send only 6/11, balance in 11 monthly paymentsof 6/11.

ALL MAINS TWO. Kit of parts (see this issue), sendon'y 15,'-, balance in easy in ta'ments.

OSRAM MUSIC MAGNET. Send only 20,'-, balancein 11 monthly payments of 21/9.

Build your own set the Easy Way NOW !Our Catalogue contains all leading makes of Re.ceivers, Accessories, Kits of Components for theHome Constructor.

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Please send me your big Iliustratel Lists.

NAME

ADDRESS

'A. W. 1114

Free Demonstrations and Advice ty Qualified Engineers atoar Shops

77 City Road, London, E.C.12, HIGH HOLBORN, LONDON, W.C.1.

4, MANCHESTER STREET, LIVERPOOL.33 WHITELOW RD., CHORLTON.CUM.HARDY,

MANCHESTER.

Burndeptradio receivers

THE CHOICE OF EXPERTS"NIKOLA" CONES

For PURITY, VOLUME and. ADAPTABILITYStandard Chassis, cone floating in kid on felt -frontedclamping -board, with screw -clamp to take any unit,

Read Mr. Reyner's test report in this issuePosT 14/6 FREE

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" A.W." Solves Your Wirelesi Problems

a

APRIL 13, 1929

BLUEPRINTS IVeitg,=".97:=7=',.;::'d-criptions of all these sets can be obtainedat ls. 3d. and 4d, respectively, poet free.

Index letters "A.W-" refer to "Amateur Wireless " sets and " W ,M."to " Wireless Magazine " sets.

All Post Free

CRYSTAL SET (6d.)Z929 Crystal Receiver .. AW165

ONE -VALVE SETS (1s.each)Beginners' One -valve AW 140Reinartz One .. WM127

TWO -VALVE SETS (IS. each)East to West Short-wave Two (D. Trans.)Beginner's Two (D, Trans) Auto Two (ID, Trans) ...All -Mains Two (D, Trans) "Q "-coil (D, Trans) ..

Key -to -the -Ether Two (D, Trans)Meteor Two (D. Trans) ..Clipper Two (D, Trans)

-AW1.59AVV17t

.; AW174AW t8oWM6z

WMto7WMx14.WM135

THREE -VALVE SETS (Is. each)All -wave Mains Three (HF, D, Trans, Rectifier) AW144All-purpose Short-wave Three (D, RC, Trans) AWI47Screen -grid Q Cuil Three (HF, D, 'Frans) .. AWI5oAll -Britain Three (HF, D, Trans) AW158Bantam Three (D, RC, Trans) .. AWitioHartley Dual -range Three (D, RC, Tram) .. AW 166Listener's Three (HF, D, Trans) price 4d. free

with copy of "AW" AW169The Binowave Three (D, RC, Trans) . AW172Clarion Three (SG, D, Trans) AW1751929 Favourite Three (D, RC, Trans) , . AV( -179Everyday (D, 2 Trans) . WM52All -wave Screen -grid Three (H17, 13, Trans.) WMItoStandard Coil Three (HF, D, Trans) WM1 17Festival Three (D, aLF-dual Imp.) _ WM118Wide -world Short -waver (SG, D, 'Trans) WM12oNew Year Three (SG, D, Pentode) .. WM123The Q3 (D, RC, Trans) WMx24Lodestone Three (HF, D, Trans) WM129Simple Screen Three (HF. D, Trans) .. W0413:Dynamic Three (SG, D, Trans) .. WMI36

FOUR -VALVE SETS (1s. 6d. each)Overseas Short -waver (HF, D, zTrans) AWi33The Ranger( SG, D, RC Tram) AW145Broadcast Picture Four (HF, D, 211C) . .. AW163Orchestra Four (D. RC, Push-pull) AWt67All Europe Four (2 HF, D, Trans) .. AW173

-coil 4 (HF,D, RC,Trans).. WM7IFive -pounder Four (HF, D, RC, Tram) WM9tTouchstone (BF, D, RC, Trans) WMIo9Reyner's Furzehill Four (SG, D, 2Trans) .. WM112Economy Screen -grid Four (SG, D, RC, Trans) WM113Binowave Four (SG, D, RC, Tram) WM119Standard -coil Four (HF. D. 2 RC) .. .. WM x 22Dominions Four (2SG, D, Trans) .. W1V1134.The Drum Major (HF, D, RC, Trans) WMx 37

FIVE -VALVE SETS (1s. 6d. each)" Q " Gang -control Five (2HF, D, zTrans) AW161Empire Five (2 SG, D, RC, Trans) .. WM96Widelity Five (HF, D, a RC) . WM13o

SIX -VALVE SETS (1s. 6d. each)Short-wave Super -6 (Super -het, Trans).. AW 67Eagle Six (3 HF, D, RC, Trans) .. WMto6

AMPLIFIERS (Is. each)Screened -grid HF Amplifier" A.W." Gramophone Amplifier (311C)Searcher Unit (1 -IF)True -tone (3. valves) (Trans, RC)Grarno-radio Amplifier (20 (Trans)Signal Booster (HF Unit) .. . Auditrol Amplifier

AW138AWi 62AVV176 WM47

.. W0472.. WM128

WMx32

MISCELLANEOUS (h. -each)H.T. Eliminator for A.C.. (zoo v. output) AWtozL.T. and H.T. Mains Unit (D.C.) - AW /23Listener's Speaker, price 4d. free with copy of

"AW" - AW170Arcadian Linen -diaphragm Loud -speaker (Fu

size) AW177AD.C. Unit(HT) AW 7 8"Junior':Moving-coil Loud-speak:1r StUniversal Short:waVe Adaptor WM82Buzzer Wavemeter (6d.) _H.T. Unit for A.C. Mains ..Lodestone Loud -speaker ..James H.T. Unit for D.C. Mains

WIMI2t WMx25

WMI26WM133

PORTABLE SETSHouse Portable (SG, D, RC, Trans) AW163 1/6Arcadian Portable (SG, D. z Trans) with

linen -diaphragm loud -speaker (half -scale) AWx 77 1/6Chummy 4 (with Modifications for LS

and HT) wms04 i/o

Send, preferablY, a Postal Order (stamps over sixpencein value unacceptable) to Blueprint Service

AMATEUR WIRELESS55-61 FETTER LANE

LONDON E.C.4

575 outuoriltwele

LEADING HOUSE FORKITS OF PARTS

See Weekly Advts.Any list of components over 25/- quoted

for at a special price, where possible.

K. RAYMOND'27 & 28a, LISLE ST., LONDON, W.C.2

Come to LEICESTER SQUARE TUBE.This address Is at the back of Daly'sTheatre.. Phones: Gerrard 4837 and 2821

HOURS OF EVERY DAY 9 to 8SATRDAY 9 to 9BUSINESS SUN.U MORN. 11 to 1

GENUINE IDEAL BLUE SPOTAdjustable Power 66K (101)4 -pole Balanced Armature 25Complete with Cord /-HANDSOME OAK POLISHEDSPEAKER CABINETS 13 x 13 x 6

12/11

Cannot guarantee exactpattern of front panel,but all good designs.

BLUE "SPOT la

Post1/3

5/-66K (101) Shown above.4 POLE ADJUSTABLEBALANCED ARMATURE,

GENUINE 66K.

OR

CABINET

BLUESPOT

12" CONE

Carr. Pd. The Lot.

DON'T FORGET OURWHOLESALE DEPT. ro CTN.

HOURS OF BUSINESS AS ABOVE.WE STOCK, WHOLESALE AND RETAIL

BULGIN FERRANTI WATMEL LEWCOSEKCO AMPLION POLAR CLIMAXCELESTION IGRANIC ORMOND 3.B.LISSEN M.P.A. PYE POLYMETEDISWAN COSSOR T.C.C. r1UBIIIERSIX -SIXTY COLVERN LOTUS W .B.CYLDON' 'XeMICHAEL PHILIPS MULLARDand all standard components, valves, etc. Ever -Ready.

Siemens, Exide Batteries.

BRITAIN'SFAVOURITETHREE (De luxe)Ormond Log .0005, 6'.;.00025, 5/6; 7 -ohm panelRheo 2;6; 3 BenjaminV.H., 4,'6; FormodenserType "J," 2 - ; .0003 andseries clip, 2i-; 2-meg.Leak, 1;-; Tunewell Allpurpose H.F. Choke, 5/9;R.C.C. Unit Dubilier, 7/-;50,000 ohm wire wound,5/6; 2-mfd. Mansbridge,3/6; L.F. TransformerR.I. Varley, 15/-; (addbalance any other), Push-pull Switch, 1/3, completewith Panel Brackets, In-dicator, G.B. Clips, 6 -pinBase, Connecting Wire,Thin Flex, 7 EngravedTerminals. EBONITEPanel 16 x 8. and 16 x 9Baseboard, 2 41n. Dials.The above lot ... s/LCash with order. .Tunewell Dual Coll 6 -pin,7/9 Lewcos Short Wave,20/45 or 40,90, 7/6.

VALVESMullard, B.T.H., Marconi,Edison, Osram, Cosmos,Cossor, Six -Sixty, Det.H.F., L.F., R.C., 10/6 each.Power 12 6, S. Power 151-,S.G. 2216, Pentode 25'-.,

CLEARTRONScreen Grid, 2 volt, 12;6.Usual Types, 41-; Power,

Post 6d. (3 post free).

TRIOTRONH.F., Det., R.C., 5/2 each ;Power, 6/9. 2-v. or 4-v.


DARIO RADIO -MICRO2-v. or 4-v. G.P. 5/6Super Power .. .. 7/6Super H.F., 2-v. or 4-v. 7/6


ORMOND8.51. Drum Diai , 5/-; Rheostata,6,15, 30 ohm, 21-; Midget .0001 max.,9/-; Log .0005 sad 4 in. Dial, 6/-;Log. .0003 and 4 in. Dial, 5/9.S.L.F. No. 3 same pree. We alwaysstock all ORMOND PARTS.

TRIOTRON UNIT4 - Pole Balanced With Cabinet as

6 ORArmature/ shown above and12"7Adjustable 1 Cane 27/6 r,t.

Q COILSLEWCOSQA 15/-

QSP, QAR, QSG,QAM, 21/- each.

LOTUSQA 15/-QSP 21/-

QM3 STAR 15/ -Complete with Switch.

COLVERN DUAL COILS, ALL CIRCUITS.

WEARITEDual Wave Toner 15/-. H.F.Choke 6,6. S.W. Choke 4,6.2 -way Switch 6,'-. 3 -way Switch7,-. Loading Coil 7,6. TitanCoil Unit 15 -.

Dubilier N.C. Condensers, FrictionControl, .0005 and .0003, each 12,-.Thumb Control, ditto, 15,6. TelsenRadio Grand L.P.. 12:6. TelsenAce L.F., 8,6. Brown HA. Speaker,£3,3,0. Amplion A.0.2., 21,-.ld.PA. Popular Plague Speaker,29,6. Ormond Turn -table for Port-ables,C-. Halpin All -wave Tuner,15,6. British General Tuner, 18/8.Wates 3 in 1 Test Meter, 816.Lotus Condensers, .0005, 619; .0003,5,6. Colvern Master 3 Star DuaCoil, 17 6.

TUNEWELLDUAL RANGE COILSClarion Aerial, 10:8. Clarion An-ode.10 0. Lissen Three, each 10/6.Cossor Three, each 10 6. All 5.0.Circuit Coils 21, -.pair, 200,2,000.Massive H.F. Choke, 5 9. HillardDual Coil, 7,9, P.M. 151. Six -pin Bases. 2,-.

Copper and Aluminium Screens, allsizes, or made to order, P.W.Screening Boxes, 12,8. P.W. Load-ing Coils, 7.6. Rothe Wave Selec-tor, 12.6. Tunewell Dual 3 Star,7,9. Combinel Wave Q 3 Star,12:6. Scott's All -wave Tuner, 13DX Set 4 short wave, 7,6. DX L.P.Standard Ratio, 8,'-. Weilo L.P.Power, 11;6. Weilo Standard, 8/6.

LATEST SQUIRE 97RIGID ALUMINIUM CRADLE, FLOATING CONE.CLAMPING BOARD ASSEMBLED AND SPARE /5/6CONE KIT FOR .Our model 97 is supplied assembled complete with duplex woven floatingcone, °tamping hoard AND a Kit of Parts for making kraf t cone.Diameter of cone 911n.OR COMPLETE WITH HANDSOME 15 in. The lotCABINET and BLUE SPOT UNIT 66K - Poet free

(Genuine Ideal Adjustable) (U.K.)

C.O.D

Goods despatched Cash on Delivery(pay po4tmanc)haatrsglieghtly increased

CLARION THREEKIT OF PARTS ('A.W." 9-3-29)

I Polar .0005, No. 3, at 5/9. .0001 Reaction 4/-.Dual range C.T. Coils, with Reaction (Tunewell),

Anode,10/6; Aerial, 10/0. 3 Lotus or Fenno V.H, at 1/3.Formodenser, "J," 2/-. Dubilier 1 mfd., 2/6. .01 Fixed.T.C.C., 1/9. 3-meg. Lissen or Edison Bell, 1/.. S.G. H.F.Choke, Peto - Scott, 5/.. H.F. Choke, Lissen, 5/6.L,F. Transformer, LI. d, Varley, 15/, Ebonite Strips.14x7 Ebonite Panel. Semen, II Engraved Terminals.Push-pull Switch, Flex, Plugs, 16-g. Wire, 2 S.M- Dials.

The Lot 70/- Post Free.0002 Fixed and Series Clip I/6 extra.

VALVES 2v.S.C. D 10/5. P 12,13.

(Mallard or Sin -Sixty)CLEARTRON

S.C., 2v. 12/6C.T.15, L.F. or H.F. . . 4/-

0/- over (U.K.), pass. train. C.T.15 x Power .. 6/ -ALL PREVIOUS OFFERS CANCELLED.

CATALOGUE -(144 pp.) Illus rated. V- Credited 10/- Order(er Free with 101- Order).

TYPE POLISHED CABINET120v., 2v. 45.

£4 . 17. 6Carriage 4/- up to 200 miles,

A.W. SPECIAL COUPON (64)FOR EVERY 30/- you spend retailYOU CAN buy ONE of the following for

3d. each extra (on this Coupon)H.F. Choke, Silk Loud -Speaker Cord, 9 -volt GridBias, Pair Panel Brackets, .0001 Reaction, 2 mfd.Mansbridge, 100 ft. Insulated Aerial, 4- or 5 -wayBattery Leads, 30 ft. Coloured Connecting Wire.S.M. Dial, 12 yds. Lead-in, Fuse and Holder, 12Nickel Terminals, 60X Coil, Permanent Detector,Battery Switch, .0003 and 2-meg. Leak, 6 -pin Coilbase, 12 yds. Twin Flex. 100ft. Indoor Aerial,..............

mateur WtreIT

" AN ALL -MAINS TWO "(Continued from page 55o)

3-megohm grid leak (Dubilier, T.C.C.S.P. type, Mullard, Graham-Farish).

.000z-microfarad fixed condenser (T.C.C.,Dubilier, Mullard, Graham-Farish).

Five 2-microfarad fixed condensers(Lissen, Ferranti, Dubilier, T.C.C., Mul-lard).

vo-ohm baseboard -mounting potentio-meter (Lissen, Igranic).

High -frequency choke (Lewcos, R.I. andVarley, Wearite, Burndept).

Low -frequency transformer (Cossor,Mullard, Lissen, Ferranti, R.I. & Varley,British General).

20,000 -ohm resistance (Graham-Farish,

EASY TERMSWe specialise in the supply of all good qualityRadio Apparatus on deferred terms. All well-known kits of parts now supplied from stock.

LOWEST TERMS.CASH ORDERS are dispatched POST FREE

and in most cases by return.Send List of requirements to

LONDON RADIO SUPPLY co.11 OAT LANE, NOBLE ST., LONDON, E.C.2

'Phons,: NATIONAL 1977

TheIL

Super Long Range5 Valve PORTABLE

Is the World's Greatest EntertainerBa'ance can be paid on easy monthly instal- YOURS FORmenus graded to suit your pocket. Everydesc ipt.on of Wireless Sets. Accessories, Lout 1 0/Speakers, Accumulators, etc., on the easiestterms. Also Gramophoncs. Records, etc.

Illustrated lists free. ' DOWN

v oF-Id WALLINGTONWIRELESS STORES SURREY.

gCOMPLETEThoemfpamoeus 'LUTONIA

Complete with Cmpone"n3tsV*ils(diting Long and Short Wave Tuner,inc all

assembled ready for wiring in handsome OakCabinet, suin. x 7in. with special oval panel.

LUTONIA RADIO SUPPLIES, 1, Wades Place,Mile End, E.1. Phone: East 454z

THE 31-GUI1IA FINISHING TOUCH for your ARCADIAN PORTABLE

CABINETS for this MODELBeautifully hand french -polished with all wooden parts completeMahogany Finish , 25/- CarriageSolid Oak . 30/- and PackingSolid Mahogany . 35/.. 31- extraPersonal guarantee of satisfaction, or filmy returned.

F. W. RAMSEY,63Shaftesbury St.. LONDON. N.1. Clerk 7139

E THE LITTLE CELLS THAT SATISFY- Layton Primary H.T. Battery, PI Porous Pot Cells, ig SI & S2 Sac Cetla. All compkete for assenSIY-

Ie!. !?-181.3°471.P1 elc ..59.. 1-SI ed. ... 3/- ... 5/3 ... 12/..

"Easeful" Filler : I -pint 1/..; Pint 1/6. Post 34 extra= Send lid stamp for booklet giving full particulars to-

THE LEYTON BATTERY Co.- 305 CHURCH ROAD LEYTON

576

R.I. & Vaxley, Lissen, lilullard, Dubilier).Mains power transformer (Marconiphone

model M).Smoothing choke (British General, R.I.

and Varley, Ferranti, Igranic.)Small panel brackets (Magnum, Camco).Grid -bias battery clips (Bulgin).Connecting wire (Glazite).Flex and adaptor (G.E.C.).Red and black wander plug (Clix).One yard of thin flex (Lewcoflex).With the blueprint as a drilling guide

and layout template, those who havetackled set construction before will bequite capable4of making the first steps inbuilding up this "two." Novices should,however, be guided solely by the construc-tional instructions which will be given innext week's issue, and which will dealfully with small snags which might arise.

A point which will be of great interestto London listeners is that this all -from -the -mains " two" will be exhibited in theSomerset Street windows of Messrs. Sel-fridge, Ltd.-

It is always a help to be able to see aset actually in the " flesh " before buildingit- up. Intending constructors within easydistance of Messrs. Selfridge's premiseswould be very well advised to take a glanceat the set in the Somerset Street' windowsbefore making it up themselves.

The Practical Electricians' PocketBook-This handy reference book has beenissued for thirty years, but the 1929 editionhas been entirely revised. Measuringinstruments, power -station plant, boilers,switchgear, illumination, wiring, pyrometry,armature construction and repair, dynamos,transformers, overhead transmission, sys-tems, and electric furnaces are just a few ofthe section headings. A 'valuable sectionfor the wireless amateur is a tabular list ofcentral stations throughout the UnitedKingdom and Ireland, giving details of thesupply voltages and the systems used. It ispublished by "Electricity," 93 Long Acre,London, W.C.2, price 25. 6d. nett (2s. rod.postage paid); and contains 596 pages withmany illustrations.

"Amateur Wireless and Radiovision." PriceThreepence. Published on Thursdays and bear-ing the date of Saturday immediately following.Post free to any part of the world : 3 months,4s. 6d. 6 months, Os. 9d.; 12 months, 17s. 6d.Postal Orders, Post Office Orders, or Chequesshould be made payable to " Bernard JonesPublications, Ltd.'General Correspondence is to be brief andwritten on one side of the paper only. Allsketches and drawings to be on separate sheets.Contributions are always welcome, will bepromptly considered, and if used will be paid for.Queries should be addressed to the Editor, andthe conditions printed at the head of " OurInformation Bureau" should be closely observed.Communications should be addressed, accord-ing to their nature, to The Editor, The Adver-tisement Manager, or the Publisher, "AmateurWireless," 58-61 Fetter Lane, London, E.C.4.

APRIL 13, 1929



bona fides of advertisers in this publication, they haveintroduced a system of deposit which it is recommendedshould be adopted by readers when dealing with personswith whom they are unacquainted. It is here explained.

Intending purchasers should forward to the Publishersthe amount of the purchase money of the article advertised.This will be acknowledged to both the Depositor and theVendor, whose names and addresses must necessarily begiven. The deposit is retained until advice is received ofthe completion of the purchase, or of the article havingbeen returned to and accepted by the Vendor. In additionto the amount of the Deposit, a Fee of 6d. for sums of £1and under, and 1s. for amounts in excess of £1, to coverpostage, etc., must be remitted at the same time. In casesof persons not resident within the United Kingdom, doubletees are charged.

The amount of the Deposit and Fee must be remitted byPostal Order or Registered Letter (Cheques cannot beaccepted), addressed to"AMATEUR WIRELESS," ADVERTISEMENT DEPARTMENT, -

58/61, FEiisR LANE, LONDON. E.C.4.'EARN MONEY AT HOME. You can earn money at nom,.,,, i noteer spare time writing Show Cards for us. No canvassing. We train Y.,

boat by our new simple method and furnish the Outfit free. WeImply, both men and women with steady work at home, no matter

s here you live, and pay you cash for all work completed each week,under our legal guarantee. Full particulars and Booklet free. Writs+.t enee or call. Show Card Service. Hitchin.

WIRELESS OPERATING APPOINTMENTS: fees payable after qua. ify-ing Ifor boarding students.) Morse classes. Wire.ess School, ManorGardens, Holloway, N.7.

BUSINESS FOR SALE. Wireless Business, Bournemouth, well estab-lished, exceedingly low rent, and very good prisitiou, £500 includingstock. Write "P" Smith's, Square, Bournemouth.LINEN SPEAKER. Drilled Bolt, Tapped and Screwed Extension to fitBlue Spot. No Soldering, 2/6. Bramhall, 53 Branton St., Birmingham.ENGINEERS-IMPORTANT homy,. Owing to the unprecedentedgrowth of this Institute, brought about by the -Success of our students,we have been compelled to take much larger premises in Oxford Street.If you wish for something more than a "bread and butter" lob, you oweit to yourself to investigate our Service. Our handbook "ENGINEERINGOPPORTUNITIES" has pointed the way to better things to over 15,000of your fellows. It contains details of A.M.I.Mech.E., A.M.I.C.E.,A.M.I.E.E., A.M.I.A.E., City & Guilds, G.P.O. Exams., and describesover 60 home study Courses in all branches of Electrical, Mechanical,and Motor Engineering. In a brilliant article, Professor A. M. Lowshows clearly the chances you are missing. The book and our advice arequite free. We guarantee "NO PASS-NO FEE." Don't delay, send apostcard-now. (State Branch or Exam.). We promise that it will be aminute of your time well spent. British Institute of Engineering Techno-logy, 109 Shakespeare House, 29-31 Oxford Street. London. W.I.

" TONE SUPERB"Assembled Baffled Floating Cone Chassis

The "Tone Superb" 16 -inch frettedfront 6 -ply barEed floating conechassis, repi °duces music and speechamazingly natural. Capable of enor-mous volume if required. Totalabsence of chatter or metallic noise,which is common in metal framechassis. Can be fitted into a frameforming a cabinet in a few moments,making a speaker, equal to any expen-sive model. Is in itself an attractivepiece oHumiture, supplied complete.Beautifully french polished, in richdark Oak or Mahogany. Any unit canhe fitted in 5 minutes. All holes areaccurately drilled, and bolts supplied.If stplied with Blue Spot milt fitted,25s. extra, _Triotron, 17s. 6d. extra,Hegra, 21s, extra.If above chassis supplied complete inattractive, hand -polished 17 -in. Oakcabinet to match, price 27s. 6d.Ditto in' Mahogany, 5s. extra. Priceof Chassis only, as illustrated, 21s.

Illustration of Chassis, Send lid. stamp for further detailed in -with both sides removed formation and convincing proof of theshowing method Of unit capabilities of the "TONE SUPERB"

mounting Chassis and other interesting components

WARRICK RADIO, 16 Berther Rd., Hornchurch,EssesTel., Hornehurch, 230. "

REPAIRSAny make of L.F. Transformer, Loud -speakeror Headphones repaired and dispatchsd within48 HOURS-TWELVE MONTHS' GUARANTEE

itlt earls repair. 4/- Post Free.Terms to Trade

TRANSFORMER REPAIR CO."Service" Dept.

214 High Street, Colliers Wood, London S.W.19

t&e13 RitdiOF S //IIt; 0

E BE/7 IN THE WE/T)10 tistt slant, LEICESTER SQUARE. tomMel.w.C.11.

almal orr,e Zit.we Z. %Ant forOPEN TILL. 711.4.4.WRITE FOR OEM GATALOGY1POSTAGE 66 Wit 10 CATI1RS

1

Lftau ateur Wirelesi

COUPONAvailable until Saturday,

APRIL 20th, 1929

APRIL 13,Ill maturWreI

smith ONAND LISTEN!t - ed Tone and Quality Of Ree eitteaf

LEWCOS " Coils willGive

vivisprovmoos

CENTRETAPPEDCOILS(Pat. No. 271334).

All Lewcos Medium -wave coils have a

range of 235/550metres and can thusbe used for anystation in G r ea tBritain.

QAS COILFOR

"MULLARDMASTER 3°."

Wavelmgt h range235550 in.,ta es.

BINOCULARCOILS

(Pat. No. 211373). CHOXE

117011,,'Lleprolit

B.F. .TRANSFORMERFORTOUCHSTONEANDLODESTONERECEIVERS

RADIO PRODUCTS REGD.

Obtainable from Stock of all Radio Dealers.The LONDON ELECTRIC WIRE COMPANY AND SMITHS LIMITED,CHURCH ROAD, LEYTON, E.10. Phone : Walthamslow 2531. Grams : Lewcos, Phone, London

Trade Counter and Cable Sales. 7 Playhouse Yard, Golden Lane, E.C.4LEWCOS RADIOPRODUCTS FORFETTER RECEPTION.

Pit*Kitire.010212P2&KoKeniPlal5gir402102/412KgSKAP211412kW.Iti&S02*&.****Cit4P2P2tArAnKolreAl

AT THE PRICE1 hese ere the actual words of a user.

,t Weilo Trandormtrs are 1CO% sound. Can herelied upon as a really excellent job. Annzin !purity of maximum amplification. Guaranteed 2yecrs. Why pay high prices-specify Weilo !Adt for details of our Push -Pull Trandormrt.11 b -Model 10, Ratios 1-1,3-1,1-1,5-1,25-1

8 6 A 3-1, -I-1, 5-1Wriff for interesting Catalogue of N.S.F.

nS Wei,o-Conobonent, to-S. LEWIS & CO., LTD. (13.-..pf. A.W.),39 Victoria Street,

PANELS FOR ALL CIRCUITS

Registered

The original BECOL LowLos; Former, made insizes 1" up to 4" outsidediameter in lengths up to36 in. The former that re-mains rigid when wound.

LOOK FORTRADEMARK

Trade Mark

Have you seen the newBECOL Pinless Formerand Base, which is abso-lutely foolproof ? If not

send for particulars.

DO NOT BE PUT OFF WITH AN IMITATION.Write for copy -of BECOL Handbook on Wireless Circuits. Full data of

windings and ifluhtraticns. Price 4c1. Post Free.Sole Makers:

THE BRITISH EBONITE CO., LTD., HANWELL, LONDON, W.7


V. /EARCOMPOAIS

W. James "Special 3 " Coils 25/- pairW. James "Binowave" Coils 25/- 9 9

ARCAD/AN PORTABLECoilsScreen ..H. F. Chokes ..Battery Switch, G22 (with terminals)Valve Holder, LAS5Grid Leak ClipsCoil Formers (unwound)

each 10,'69'66;'6

2/6-/6

pair 7'6

Dual Range Tuner, W.G.2, asused in FERRANTI Circuits 15'.

ALL FROM THE MAINS TWODual Range Tuner, W.G.2 pair 15:-H.F.. Choke . . . . 6,16

H.T. Choke ,, 21/ -Valve Holder, anti-microphonic, LAS5 each 2,6

WRIGHT & WEAIRE, Ltd,740, HIGH ROAD, TOTTENHAM, N./7.

Telephones; Tottenham 3847 and 3848

M. V. 25-r3.2.

entatturWiretzsi

MA

ce C?".

i *(4 , t.7: + e e" aye

teiree 0,,, s ee ' .,> t:, ce - I (." C, tis4 '') itZt.. °V :q5, (4.00 °I17", 9 -....,.., , 17i 0,...,

v4c. c°.; ',6cfr'e ' 'iC17 ' '/./..4i 'O x44..".- io 4 .. ' ("o -

,7 `.1' e, . ,... i'.e,P e ---,, (-, ,...ey4",''.. . :-

.? '

ati4,11'r <$ '?,

'',o ..-.....

4'./.44 1---

444115

P-9? -`?.,A .1i.4',:).:1_,C : ..tp ,...`Vq 7 v . a°_

;- t..014-eb *ks

115,e001.. ./6,,,0St& ''l '"14:. .Aect

6

Riv APRIL 13, 1929

TESTED once

TESTED twice

TESTED 3 times

Not only are all components ofMarconi Valves tested at everystage of manufacture, but beforethey can get Into the purple boxbearing the name Marconi thecompleted valves have to pass thefollowing triple test.

The " qualifying" or Factorytest.The "passing out" or Stocktest.The." third degree" or He7.d- _ .

quarters test.Marconi. Valves are consistentlygood because (hey are triple tested.

Write for Marconi Value Cats-lo ue IV-. 520 gitiing particularsand character:s is cures of alltypes, mention'ns AMATEUR

WIRELZSS."

TRIPLE TESTED

The Marconiphone Co., Ltd., 210-212. Tottenham Court Road, London, W.1--Showrooms: Marconi House, Strand, W.C.2

Printed in Enkland: l'ublished by Bernard Jones Publications, Ltd., 58/61 Fetter Lane, London,Sole Agents for South Africa: CENTRAL News ADEACY, Lt :TIED. Sole Agents fur Australasia: GORDO:4 A Gorcn, LIMITED. Saturday, Apri! 13 t9-21

AMATEUR WIRELESS, APRIL 20 W)

TWO SETS: "E5-5-0 PORTABLE" 86 "STABILITY 4"

Every aThursdau0

Vol. XIV. No. 358

OmakurWird,s1

CENTRETAPPED

COIL

SUPERCOIL

H.F.CHOKE

QCOIL.

I-EwccPRODfir--S

RAD -

LETTER-FORRule-118N,

APRIL 20. 1929

he hasts of

ect receptionNA/SITE

VOS ONE OS OSE,M

11LESEISSIRUCTIVE

ILEA

O' 1VVETSR.34

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CentreTappR.3s lligh 'Frequency

Cholce.

(X) Coils.

R.36Six -Pin Coils.

StandardR.3sQ Coils.

R.3/ BinocularCoils.Coils.

R.38 Dual ScreenedCils.

R.39NV av etr

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Fixed Potentiometer.

It.47QSG" 1-1.V.

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R4°R.4.3 SuperSix -pin Cods.

R.Asa Sheet illustratingrange of Levccos

Radio

RAS Dual Range Coils unscreened.Grid Valves.

Products.

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H.F. TRANSFORMER

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/Don't Forget to Say That You Saw it in "A.W."

APRIL 20, 1929

Vtt0NEARLY

50%THE reason for this astonishing reduction is

that by concentrating on one type only, wefeel that we are able to give the public the

finest Horn Loud Speaker in the World at avery reasonable price.This speaker has the original world-famous H.1Base mounted on a polished mahogany pedestaland is fitted with a "Q" shaped horn, finishedin black or brown enamel. The height of theinstrument is 20".Experts acknowledge that a horn type loud speaker giveslouder signals with less valves. They state also that itgives better long distance reception, than can be obtainedwith the cone. Therefore, owners who have only utilisedthe cone can now purchase the very best horn type loudspeaker for £3. 3. Od. Ask your dealer to show anddemonstrate this wonderful speaker to you. It is preciselythe same speaker which has helped so much to build upthe reputation of S. G. Brown, Ltd.

Advt. S. G. Brown, Ltd. Western Ave., 71. Acton, London. 1V

577

Don't Forget to Say That You Saw it in ."A. W."

e=taw WireiT

MI 8350

1

CI:tatter Wtrell!,

Ever Ready " STANDARD"Series. W. 16-66 volt.12s. 6d, 01 X 31 X 3/, for6 milliampere emission.These batteries represent the fines0value for money based on cost perhour of service for low powerreceiving sets.

Ever Ready " HIGH CA-PACITY " Series. W. 34-66volt. 22s. r4f X 51 X 3, for10-16 milliampere emission.These batteries represent the finestvalue for money for high powerreceiving sets.

" SUPER r " Super Capacity45 volt. 21s. 4a x St x 8, for16 milliamperes and over.

These batteries will give reliable serviceon any high power set known,

578 APRIL 20, 199

DOES YOUR SET CONSUMEFOR satisfactory and economical service you

must use H.T. Batteries of correct capacity.The following table is a useful guide to the

battery you should install:

The " WINNER " Series. Winner 66.Is. 6d. 91 x 3 x 21, for 6 milliampereemission.

These batteries are good value for money, and at thestated emission satisfactory service is guaranteed.

EVER REAfg 7RX XX

T fam-cor;

11tRit',Otk.V,RtI

1 -"ItAt)... .., 1 1,-,I RAT -1-A . to,Stytt

-.s, .. Aip

A" 7TREAD e4

The " POPULAR " Series.Popular 2-66 volt. 9s. 6d.91 x 3 I x 3. Small Capacity,for 6 milliampere emission.In brown metal containers.Suitable for the usual two -valve sets.Power Capacity, for ro-16milliampere emission. Popu-lar Power 64. 14s. 6d

X5 X3.These units have large capacitycells and will give economical ser-vice with power valves requiringheavy emission of current.

EVER READYSUM?. I

The Ever Ready Company providesa suitable and reliable Battery ofany voltage for every set. EverReady Batteries are convenient,trouble free, give purity of tone,and are the handiest form of H.T.supply.

O e4*

R BRITAIN'SBEST BATTERIES

Advt. of The Ever Ready Co. (G.B.), Ltd., Hercules Place, N.7.

Advertisers Appreciate Mention of !`A.W." with Your Order

0 ten i7)ten c2)c,a

§ APRIL 20, 1929 No. 358. Vol. XIV NCN

5 5

5 5

5

ub 5 5

S

S

.

5 5

6.5 The Leading Radio5§ Technical Editor : J. H. REYNER, B.Sc., A.M.I.E.E. Research Consultant : W. JAMES Assistant Editor: H. CORBISHLEY E

Weekly for the Constructor, Listener and Experimenter=---- Editor : BERNARD E. JONES

Controversial Politics I-and Politics byElstree Rivals Savoy Hill- Fultograph

Controversial Politics !-Theseries of political broadcasts organ-ised by the B.B.C. is certainlyhaving its effect. Following thefirst political speech a prominentdaily paper came out with a glaringposter "An Amazing Broadcast."Well, the B.B.C. won't need anyoutside defence. We've asked forthese controversial speeches, and inthe opinion of AMATEUR WIRELESS,it is far better to have them, and tohave daily papers fighting over theeffects on the following day, ratherthan to have continued with thedull incontroversial stuff that wasput out before the rule was changed.Controversy keeps the papers alive,and the same medicine is good forthe microphone.

-and Politics by Wire-More-over, the microphone isn't having themonopoly of politics. Great strides arebeing made in the land -line relays ofpolitical speeches, as was described recentlyin AMATEUR WIRELESS. Baldwin andNeville Chamberlain have, on severaloccasions, addressed audiences in other hallsby land -line and loud -speakers (withwireless -type amplifiers), but in no case hasthe number of unseen audiences exceeded

Wire-People's Palace " Pops "--and Weather-KDKA Television

formidable rivals to anything thatthe B.B.C. has done in this respect,and although those now being con-structed are only temporary, one is7o ft. long, 4o ft. wide and 25 ft.high. Two more giant rooms, whichwill be as big as anything in Holly-wood, will be started in a month orso. The talking -film engineers areadopting the flannel draping whichthe B.B.C. people appear largely tohave dropped.

The Operas-The opening nightof the opera season is April 22, andon that occasion Act I of .DerRosenkavalier is to be given from theRoyal Opera House, Covent Garden,

A new use for radio ! This armoured car, designed for therough roads of. India, has a complete transmitter and,

receiver. It is here seen being tested in London.

people have said, to be regretted that thelocality of the hall is against the possibilityof having the same kind of "gate" as wouldobtain were the concerts held elsewhere :but for the " mike, " environment must takesecond place, and acoustics come first !Incidentally, La.ndon ROnald seems to beputting in some very hard work, which iswell justified by results.

Elstree Rivals Savoy Hill-They arenine. But now we have Lloyd George's going great guns at Elstree's "talkie"speech to no fewer than twenty-eight studios. The studios themselves arecentres, the land -line arrangements Ocatencatice7icence7a.a.e,ne:aacencat.encete7,13necessitating about 3,000 miles of §route wire. Apparently the bigpolitical leaders pin faith to theloud -speaker, and they have notbeen loth to take advantage of themicrophone.

People's Palace " Pops "- 5The B.B.C.'s series of orchestral -5concerts from the People's Palace §in the East Erid of London seems to

going. very well. An AMATEURWIRELESS representative, who was ic.Y

at the Palace .during a recent Nbroadcast, found the arrangements §very similar to those employed on §previous occasions, and there is nodoubt but that the hall is quite goodacoustically. It is, as so many

PRINCIPAL CONTENTS

Current Topics .. Captain West Leaves the B.B.C.The £5 5s. Portable .. *Economy With Fibre. Needles ..

Page579580581582

Sources of H.T. Supply 583In My Wireless Den .. 584On Your Wavelength .. 587The Subtleties of Volume Control 589For the Newcomer .. 590Without Fear or Favour 591The " Stability Four 592"A.W." Tests of Apparatus 596An All -mains " Two ' 598Wireless Control of Models 600

5

to 2L0 and 5XX. It is a fact worthnoticing 'that arrangements havebeen made whereby during theseason, listener's to 5GB will also be

given the opportunity of hearing excerptsfrom the operas. Wagner's romanticopera, The Flying Dutchman, is beingproduced in the Savoy Hill studios onApril 24, the cast including many " stars,"but it will be heard from 2L0 only.

Fultograph and Weather-The secretwas disclosed in these columns recentlythat Fultograph apparatus has been triedout in high circles, namely, at `the RoyalAirship Works 'at Cardington. A weatherchart was recently prepared and trans-

mitted via Fultograph to the RoyalMeteorological Society at South

§ Kensington, and following this ageneral inference and weather fore-cast was also sent. We have seenboth the chart and the printed re-port, and both are excellent. As iswell known, the "straight line" testis most severe on wireless picture -machines of the Fultograph type,and there are plenty of such testsin weather charts !

KDKA Television-Here's a tip,"listen" for KDKA's televisionbroadcasts on 63 metres, betweenro and II G.M.T., on Mondays,Wednesdays and Fridays: speech on25 metres; 6o -hole disc; turning

5

§5

left to right, at 1,200 r.p.m.

(I mutest Wtrele-!5 580 APRIL 20, 1929

Capt. A. G. D. West

THE B.B.C. has been suffering heavylosses lately, particularly on its engin-

eering " front." The advent of talking filmshas attracted many engineers and severalof the leading " programme " people, in-cluding R. E. Jeffrey, the producer, to therather more prosperous parish of Elstree(Herts), which is England's Hollywood(Cal.). The latest important move is thatof Captain A. G. D. West, the B.B.C.research chief, who has just resigned inorder to take up an important position onthe technical side of the H.M.V. Gramo-phone Company.

Captain West will be chiefly rememberedby listeners in connection with the manystartling " stunts " he carried out in theearly years of broadcasting, such as thefirst American broadcast relay, the trans-missions from aeroplanes, railway trains,divers' helmets and the like, but most of hiswork has been carried out " behind themicrophone." I met Captain West whenthe original B.B.C. Development Depart-.ment was formed at the end of r923, thefirst year of British broadcasting. He hadcome to the B.B.C. after having been aWrangler with distinction in the mathem-atical tripos at Cambridge and achievint1st class honours at the London Universityin his stride. He also worked with SirErnest Rutherford and Professor Apple-ton at the Cavendish Laboratory for a year.Captain West served in all three servicesduring the war, but was concerned particu-larly with radio work in the R.A.F. Whenpeace "broke out," he went to Cambridge.

The. Development DepartmentWhen the B.B.C. first commenced broad-

casting, the stations were actually operatedby the radio manufacturers who haderected them. Birmingham, for instance,was maintained by the Western ElectricCompany, and London and Newcastle bythe Marconi Company. Broadcasting offi-cially commenced in November, 1922, butthe actual B.B.C. engineering staff number-ed only about half -a -dozen for many months.

CAPT. A. G. D. WESTLEAVES THE B.B.C.

Research Chief Turns Over to Radio Gramophone and TalkiesIn about the middle of 1923, the engineer-ing organization began to get into shapeand take over the operation of stations fromthe manufacturers. There came the neces-sity for an experimental section and CaptainWest was called in to investigate certainproblems and form his own DevelopmentDepartment. At the end of 5923, his"flying squad" was formed and I had thehonour of being appointed his assistant.I am now appointing myself his " Boswell"!

The First RelayOne of the first problems of Captain

West's department was the design of a"wireless link," to be used for relayingAmerican broadcasting. In those days, thereception of a weak station on a too -metrewavelength was no easy matter, screen -grid valves, neutrodynes and low -loss coilsnot- being general at that time. Never-theless, a receiver which included six H.F.valves, transformer coupled, was success-fully used, the stability being maintainedby careful design and the use of low -capacity sausage -shaped valves. Itseems a great pity that this type ofvalve, with its obvious advantages,should be abandoned in favour ofthe type of valve and holder thathas now become standard.

I well remember the days-andnights-we spent in a cold little hutat Biggin Hill Aerodrome, playingabout with this elaborate trans-atlantic receiver. Unfortunately,the signals of the distant KDKAdid not become steady or stronguntil the London station had closeddown and a relay was impossible.However, on the last day of 1923,half -an -hour's relay of KDKAwas carried out and we heaved asigh of relief and went home !

StuntsAfter the first relay came any

amount of stunts, and Captain Westkept J. A. Murray and myself busyin all kinds of awkward places,from aeroplane cockpits to the top ofBig Ben tower. Transmissions had to berelayed by wireless from the Old Vic. toSavoy Hill owing to the unsatisfactoryland -line, and a short-wave transmitterwas erected on the roof of a public housenext door to the theatre. The impulses froma microphone in the footlights were radiatedfrom this aerial and picked up on a super-heterodyne at Savoy Hill.

Another more straight -forward stuntwas the picking -up of the song of the night-ingale. This particular effort was especially

interesting in that it was indirectly the"cause" of all the fading and dissolvingtechnique of modern radio plays.

It was found necessary to set a numberof microphones in the woods at Oxted, andswitch on the particular microphone whichwas nearest to the singing nightingale.Clicks and noisy changeovers from onemicrophone to another could not be per-niitted, and the duplication of microphoneamplifiers meant the transport of muchadditional gear to the spot. Thereupon, the'fade or dissolve from one microphoneanother was evolved and successfully usedfor the first time at Oxted.

ResearchThe constant expansion of the engineering

side of the B.B.C. made it necessary for asub -division to be made in the experimentaldesign and research work carried on by theDevelopment Department. Captain Westwas appointed chief of a new section,'Research, and I (his faithful Boswell !)

Capt. West engaged in research work for the B.B.C.

followed him. Studio acoustics, reverbera-tion of auditoriums, measurements ofmicrophone, amplifier and loud -speakerefficiencies now formed the programme ofthe department

One of the first inventions of Captain Westafter taking up the question of acoustics,was the practical supply of an artificialecho on transmissions from highly dampedsmall rooms. It seems a pity that theB.B.C. are to lose the services of suchan experienced and enterprising researchworker as Captain West.

APRIL 20, 1929 58i maw Wire ,

THE 5050 PORTABLE

THAT when the fine weather comes theout-of-doors call may be stronger than

the attraction to the radio bench is almosta foregone conclusion, except in the case ofvery hardened "hams." Portable sets haveilong passed the experimental and labora-tory -stages, and nowadays they are notconfined to the expensive class.

Light and. CompactIn this new portable the AMATEUR WIRE-

f.ESS Technical Staff has set out on a newtrack which is bound to have many fol-

The Circuit of the £5.5.0 Portable

;lowers. This set is a simple, straightforwardtwo-valver, of just the type to which allamateurs are accustomed for indoor broad-cast, reception, and it is contained in aicabinet which is not hampered with loud -

Speaker or frame aerial.This means that in quite a small carrying

case there is the maximum possible batteryspace; you have not to make a special loud-speaker unless you feel so inclined, andyou have not to bother about winding aframe aerial.

It is intended that this receiver shouldbe used with an existing loud -speaker, thussaving the cost and time of making up aspecial instrument for use exclusively withthe portable set; and, moreover, that ashort improvised aerial should be slung upwherever convenient, for this will in

Weight and size are two important considerations in portable receiverdesign. In this Instrument both have been kept within reasonablelimits by the use of an external aerial and separate loud- speaker

many cases give a greater pick-upthan a midget frame aerial, and doesnot entail the same complications,either in itself or in the receiverwhich follows it.

The receiver has beendesigned as a two-valver,and no H.F. stage has beenincorporated, so -that initialcost is as low as possible.Indeed, many amateurs willhave at hand most of thenecessary parts for the construc-tion of this portable "two."

Even if all the parts have to be purchased,then the receiver is still an economicalproposition, because it may save the costof a portable gramophone. This, with asuitable stock of records, might cost doublethe price of the radio "portable," and stillwould not be capable of giving entertain-ment of endless variety.

As the circuit is a two-valver, there is nodifficulty of operation to contend with,and this point will be appreciated by allwho, when out of doors, have no timethemselves to meddle about with trickycontrols, nor would they hand over an un-manageable set to inexperienced friends.

Nowadays the operation of a two-valveris within the capabilities of everyone, justas everyone can change the needles andput a new record on a gramophone, and soit is just the thing for picnic and similaroccasions at a reasonable distance from astation.

The following parts will be required forthis receiver, that is assuming that youhave to purchase all new parts and havenot several of the components at hand.Potential constructors, however, who areattempting to cut the initial cost of thisreceiver should be guided by the type ofcomponents mentioned in the followinglist, and if those actually specified are notavailable the most approximate equiva-lents. should be used.

List of ComponentsEbonite or bakelite panel, i4 in. by 7 in.

(Becol, Raymond, Peto Scott, Radion,Paxolin).

Baseboard, 123,(1 in. by 4% in. (Clarion,Camco, Pickett).

.0005-mfd. variable condenser(Polar, No. 3, Lissen, Burndept, J .B.,Ormond, Burton).

.000r - mfd. reaction condenser(Bulgin, Lissen, Peto Scott, Ormond,Burton, J.B., Polar):

Two push-pull switches (Lissen,Peto Scott, Wearite).

Two valve holders (Lotus, Wearite,Lissen, W.B. Burton).

.000r-mfd. fixed condenser, and .0002-mfd. fixed condenser (Lissen, , Dubilier,T.C.C., Mullard, Graham-Farish).

Grid -leak holder (Lissen, Dubilier,Graham-Farish).

3-megohm grid leak (Lissen, Dubilier,Graham-Farish, Mullard).

High -frequency choke (Igranic, Burn-dept).

Low -frequency transformer (Philips, Mul-lard, Cossor, Ferranti).

Special dual -range coil (Peto Scott).Connecting wire (Glazite).Four terminals, marked Aerial, Earth,

L.S.-F, L.S.- (Belling -Lee, Eelex, Igranic).Three red and three black wander plugs

(Clix).Two spade terminals (Clix).

Receiver ArrangementA blueprint is available for this set, which

can be obtained, price is. post free, fromAMATEUR WIRELESS, 58-61 Fetter Lane,London, E.C.4. An examination of thisblueprint, or of the small reproductiongiven herewith, clearly shows the layoutof the receiver and the general idea of thecontaining cabinet. These features will bea great advantage to constructors who, in aset of this type, should get a clear idea of thegeneral arrangement of the componentsbefore starting to make up the receiver.

So far as the receiver portion itself isconcerned, this is constructed somewhat ina conventional manner, with a small base-board at right angles to the panel. Thisarrangement is eminently suitable for this


This pictureshows t We -rear of the

receiver

Cingite" 582

ECONOMY WITH FIBRE NEEDLESHow To Make a Simple Culler

APRIL 20, 1929

AUSEFUL little device for cutting fibreneedles may easily be made from a

piece of wood and an old Gilette razor blade.The fibre needle is much better than theordinary steel needle, especially for gramo-radio purposes; but ofcourse, when these are useda cutter is needed if economyis to be studied so that theneedles 5an be re -cut. Asa rule, a needle can be cutand re -set as many as fourtimes. The important thingto see to is that the cuttingangle is correct.

First, take a block ofwood, r in. by r in. by

in., and take a cut outof this at an angle of 45degrees, as shown in thedrawing. Also make a saw -cut as indicated, and a bev-elled edge at an angle of6o degrees with a V cut forthe needle to sit in. Theaccuracy of this last detailis important, but the workis quite easy to do if careis taken. The razor bladeis pivoted in the sawcut aridheld by means of a screw and

nut. A small link pinned over the' bevelledneedle rest will allow the needle to beinserted in the groove and held in positionfor cutting. The razor is then just drawndown and a perfect cut is made at the

GILLETTE RAZOR BLADE

WOOD BLOCK'V1?Ye*X laig x%3'

A pictorial diagram showing the construction of the cutter

correct angle. The wood used for the blockshould be preferably hard and a piece ofoak or mahogany will do for the purpose.

A small handle should be attached to therazor blade to make the gadget easy to'

handle. The -blade may beremoved at any time for re-setting or replacing with anew blade. It will be foundthat with this device the cutwill be perfectly sharp andthere will be no burred edgesat any point of the needle.For the rest of the details thedrawing is quite easy tofollow and self-explanatory.

Owing to the fact thatwith this cutter an extremelyfine cut may be made, itwill bo possible to make amaximum number of cutsbefore the needle is finishedwith. As this cutter trimsthe needle at the correctangle, it is also importantthat when the needle is used,it should be set in the pick-up at the correct playingangle and this should bb at6o degrees to the surface ofthe record.

" THE £5 : 5 : 0 P ORTAB LE " (Continued from preceding page)

particular set and, above all, having theadvantage of conventionality, it can bemade up without any additional difficultiesby those who are accustomed to makingordinary receivers. Moreover, the arrange-ment of the receiver components in thisway allows of ample battery space in thecabinet.

The tuning of the set is carried out withthe aid of the special portable coil whichhas been developed for *use in receivers ofthis type, and which will be a standardfeature in AMATEUR WIRELESS portables.It was, you may remember, used in theArcadian Portable, described in AMATEURWIRELESS, Nos. 354 and 355. This coil has

13411the advantage of cover-

PANELing both the mediumwAvEcHANcire RirA

and the long wave.SWITCH bands, by an externalL.

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switch on the panel,and an incorporatedreaction coil givessmooth control of

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DETECTOR VALVE

HT -LT+ Li-

The Wiring Diagram. Blueprint available, price 1/ -

oscillation on bothbands. It has beendesigned by theAMATEUR WIRELESSTechnical Staff for thejob in hand. Apartfrom being very efficientand convenient in useit is compact.

With the aid of theblueprint which canbe used to show thedrilling centres, thepanel can be drilledand the terminals, two

switches and two variable condensersmounted thereon. All the parts can bemounted on the baseboard and there is noneed to leave the positioning of any to alater stage in order that the wiring can be.more easily carried out.

Rigid insulated wire is advisable formaking the point-to-point connections,because in a )Sortable set, which is apt tobe subject to bumps and jolts, connectingwires in the inside of the set are apt totouch. This might cause short circuits werebare wire used for connections, and, ofcourse, the extrThouble entailed by thebaring of the ends of covered wire whenconnecting up is very small.

In our next issue some further construc-tional particulars, including the details ofthe case together with operating notesand a test report, will be given.

Readers in the London district who con-template making up this set are advised tosee it for themselves where it is displayedin the Somerset Street windows of Messrs.'Selfridge & Co., Ltd.

In future, except in the case of imminentperil, ships at sea are not to use the SOSsignal; in circumstances in which help isrequired, but no immediate rescue is askedfor, the letters XXX are tote transmitted.

APRIL 20. 1929

SOURCE,

mateur Wiretes5,

UPPLY

I. THE DRY EATTERY

iTN this series of short articles I am going11. to sum up briefly the points for and'against the four commonly -used methods ofhigh-tension supply-the dry battery, thewet Leclanche battery, the accumulator,and the battery eliminator. Not only thebeginner who contemplates installing avalve set, but also the old hand who maythink of making a change in his H.T.supply system, may find them of use, sincethey embody the results of long practicalexperience and of extensive laboratorytests.

Satisfaction with Dry BatteriesOne meets many people who swear at,

!rather than by, the dry high-tension!battery. I am going to be so bold as to say!pat I have never yet come across a case ofunsatisfactory results with this type ofbattery in which the user had not himself to

Some typical dry H.T. batteries

blame for his trouble, or was not moredeserving of the hard words uttered thanwas the component that moved him towrath. Though I touch wood as I write it, Imake extensive use of dry H.T.B's, and in:the last five years I have not had one singleinstance of trouble traceable to a faulty!battery or of failure On the part of a batteryito give long and faithful service. The whole!secret of success with the dry -cell high-itension battery'. may be summed up inseven words : " it must be up to its load.

;Modern ConditionsAt one time of day when we all used,

because there was nothing else, the bright -emitter general-purpose valve, we thoughtiin plate volts and gave no heed at all to theplate circuit milliamperes. This was quitenatural since the plate -filament resistanceof the valves was high; about one milli -

By R. W. HALLOWS

ampere per valve throughout the set was anormal high-tension load. This being so,a high-tension battery made of tiny cellssufficed for any ordinary set and makersnaturally put on the market numbers ofbatteries of a capacity which, though small,was quite sufficient for all ordinary needs.These batteries were made up of the samecells that were used for flashlamp refills,cells measuring on the average % in. indiameter by 2 yi in. in height. Five or sixyiars ago no other kind of dry -cell H.T.B.was generally obtainable.

Batteries with cells of the size mentionedthus became the standard components andthe pity of it is, that though valves havealtered enormously, many people still failto realize that any other kind of batteryexists.

With the exception of the R.C. valve allmodern triodes have a much lower plate -

filament resistance than theoriginal G.P. valves. Of thetetrodes, the screen -grid valveuses about four times as muchplate current as these earlybright emitters and the space -charge grid valve may require agreat deal more. A single pen-;tode passes normally about asmuch plate current as from four-teen to twenty old G.P. valves.

The Question of SizeNow the dry Leclanche cell in its most

up-to-date form is a very efficient piece ofelectrical apparatus; but it has naturally itslimitations. Just as a little boiler candeliver only a moderate quantity of steamthough the pressure may be quite high, sothe small dry cell can supply but a modestamount of current if it is to do itself justice.

The dry cell is in some respects very like aboiler. The fuel in its case is zinc instead ofcoal One of the most important charac-teristics of this kind of cell is that when it isplaced under load, the internal resistancerises, with a resulting fall in the terminalvoltage.

The standard cell of the dimensionsalready mentioned cannot possibly ,supplyeconomically more than 5 milliamperes ofcurrent for about three hours out of thetwenty-four. Ask it to do more than thisand you are courting trouble from two

different sources. First of all its life will beshort and, secondly, during an eveningtreception, a big fall in the voltage will takeplace. Short life means naturally frequentrenewals and therefore undue expense. Aheavy drop in voltage means "end -of -the -evening" distortion due to the fact that theplates of the valves, and particularly theoutput valve, in the set are starved, whilstthe grid bias remains almost unchanged.

If -you double the load upon a dry cell,you do much more than halve its life. '

Fit the Battery to the SetThe sound rule is always to make the

battery fit the receiving set with which it isused. If it does so the voltage drop duringan evening's run is small and the life of -thebattery is long. If it does not . . well,perhaps now you zee what I meant when Isaid that the man who found dry -cellH .T.B.'s troublesome had him=elf to blame.

Whatever you do, ascertain as soon asspossible the load put on the H.T.B. by yourset. Should you not possess a milliammeter,buy one or borrow one. When the loadexceeds five milliamperes, but is less thaneight, a double capacity battery maysuffice, though a treble will be a betterinvestment. A treble capacity battery canundertake loads between the latter figureand about 12 milliamperes; above this thelargest capacity H.T.B. made is by far themost economical investment.

But the use of undersized dry batteriesis not the only source of high-tensionsupply troubles. There are many whoplump for the cheapest article offered,irrespective of quality. To them I wouldsay that our country is regarded byforeigners as the happy hunting ground ofthe dumper. Batteries made on theContinent and of a quality so appalling thatthey could find no market elsewhere, areexported to us --and they sell like theproverbial hot cakes.

If you want freedom from trouble withdry H.T. batteries do not be above taking aword of advice from one who has tested outthe majority of the patterns now on themarket.

Buy batteries that are big enough ; buythose turned out by first-rate makers andyou will have little cause to quarrel with thedry -cell battery for high-tension supply.

=blur Wren 584 APRIL 20, 1929


and

Theoretical-Screen -grid Voltage

THE manufacturers of shielded valvesrecommend that when the anode vol-

tage applied to the valve is I20, the shieldvoltage shall be 6o or 86 volts according tothe type. I have found, however: thatbecause there are differences as betweenone valve and another, arid between circuits,it is quite desirable when the best possibleresults are sought for to regulate the screenvoltage. The recommended voltage maybe used to commence with, but the effectof increasing or reducing it should alwaysbe tried.

" Quiet" DetectorsValves having a high magnification

factor are often used for detection withthe result that a bad contact in the valve, ora slight defect in its design, may give riseto microphonic noises or howling. It istherefore quite essential to employ a"quiet" valve for detection, as any dis-turbances which originate here are greatlymagnified by the low -frequency amplifier.In portable receivers in particular, greatcare has to be taken to select suitablespecimens.

The non -rigid valve holders are notalways sufficient to prevent a shock beingtransmitted to the valve and additionalmeans have sometimes to be employedbefore satisfactory results can be obtained,A rubber band which fits tightly over thebulb is a help in minimising a certain typeof hoWling, but sometimes it is necessaryto surround more than one of the valveswith cotton wool. However, I have nodoubt the time will arrive when the manu-facturers will be able to guarantee that allvalves will be quiet in operation.

A Strange WhistleA few days ago I was trying a receiver

which was supplied with high-tensioncurrent from a mains unit. This unit wasbuilt into the receiver, with the result that acertain amount of coupling might havebeen expected. It appeared from my, tests,however, that there was no couplingbetween the transformer and chokes of theeliminator, and the transformer and outputchoke of the set.

What I did find, however, was a form ofcapacity coupling. This produced a ratherhigh-pitched whistle. It was not very loud,

but still, it &uld be heard during silentperiods in transmissions. Various thingswere tried, but it was not until the detectorvalve itself .was covered with tin foil andearthed that the noise disappeared. Thecoating of the inner glass wall of the bulbof modern gettered valves is responsiblefor peculiar effects at times, but earthed tinfoil can often be relied upon for shielding.

H.F. Troubles-

One of the reasons, I find, for instabilityoccurring in sets having a stage of H.F.

A stable H.F. circuit

amplification is poor filtering of high -frequency currents. The best practice isto provide an anode filter circuit, whichmay comprise a resistance and by-passcondenser or some other form of filterwhich will limit the amount of H.F.current flowing through the H.T, circuits.

In this connection I can recommend thecircuit shown above. Here the anode cur-rent for the high -frequency amplifying valve(which in this instance is of the screen -gridtype), has to pass through a high -frequencychoke and the tuned -anode circuit Lc isjoined between the anode of the valve andits filament.

A fixed condenser is, of course, employedin series with the tuned circuit in order toprevent the anode coil from short circuitingthe H.T. This circuit has a number ofadvantages in addition to the one already

Let Amateur Wireless "solve -your problems.


mentioned. Anode bend rectification maybe employed with ease and this method isshown in the diagram.

Winding a FrameWhen constructing an ordinary tuning

coil or high -frequency transformer oneemploys wire of such a gauge that the bestresults will be obtained. Sometimes theobject is to produce a coil having thelowest possible losses, or perhaps, to buildthe most effective coil of a certain bulk.

A frame aerial is really only a tuning'coil of relatively large dimensions. As a'rule, the sizes are fixed by other considera-,tions, such as the space occupied b'y the'receiver proper, its batteries and loud-speaker. It is, therefore, necessary for thedesigner so to arrange the windings of theframe aerial that the best advantage willbe taken of the amount of room available.But here a difficulty often crops up.

The wire employed must be sufficiently'strong and well insulated for the purpose.This may prevent one from usirirg the bestgauge of wire as determined by electricalefficiency, but fortunately, the amateur isable to obtain quite good results on frames'of normal sip by using a stranded wire.]This wire may be purchased in lengths ofroo feet and may be recommended for the';medium wavelength winding of a frame Iaerial.

Radio in the GardenThose who cannot afford a portable

receiver to take into the garden duringperiods of fine weathef should not overlookthe fact that even lengthy extension leadsfitted to the loud -speaker will be satis-factory provided an output transformer orfilter circuit is used. These two partsprevent the flow of the high-tension currentthrough the extension leads and loud-speaker and, therefore, remove the chief,difficulty.

It is not advisable to employ a twistedpair of flexible wires unless they are rela-tively short as the capacity may have theeffect of lowering the tone of the repro-duction. I have heard people remark thata good deal of power must be lost because,of the resistance of lengthy extension leads,but as a matter of fact, the losses arenegligible when the loud -speaker is of theusual high resistance type.

APRIL 20, 1929 585 inateur Wtre-LT

INTERLOCKEDELECTRODESMAKECossor ScreenedGrid Valve-

SHOCK - PROOF !10 Here you seethe double lengthof Cossor filamentfamed for its colos-sal emission. Notethe seonite bridgeholding it rigidlyin position.

3. Note the enor-mous strength andrigidity of thescreen, See howit is built on fourstout supports andcapped by a metalbridge - piece anchored to seoniteinsulator.

2. Around thetwo stout grid sup-ports is wound thefirst grid, electric-ally welded attwenty -fire points.

4. Finally, cb-serve the construc-tion of the anode.Actually tworectangular nickelplatesa re used andfor greater rigidityeach is diagonallyribbed.

Only Cossor ScreenedGrid Valves have inter-locked Electrodes

TechnicalData.

Coes., 220 S.G. (2volts,.2 amps.) and 410 S.G.(4 volts, 1 ampere MacAnode Volta 150, Impedance 200,000, Amplifi-cation Factor 200, GridBias 1.5 volts at max -

Price <each> 22/6anode Volts.

A. C. Cossor Ltd.. High bury Grove, London, N.S.

These illustrations show why the Cossor ScreenedGrid Valve is the most robust-the most depend-able-and the most uniform Screened Grid Valvemade in Great Britain. This wonderful newsystem of interlocked construction is to be foundonly in the Cossor Screened Grid Valve.

NOISE - PROOF INoises are generally clue to loose elements in avalve. In the Cossor Screened Grid Valve theelements are interlocked. Every joint is scientifi-cally welded to ensure long life and completerigidity. Even under the heaviest shock individualmovement is impossible.

BREAK -PROOF IEven the hardest blow cannot disturlIpthe perfectalignment of the Electrodes which are rigidlybraced at top and bottom. As a result, everyCossor Screened Grid Valve retains its charac-teristics throughout its abnormally long life.For any Screened Grid Receiv er choose Cossor.Accept no substitute-for there is no adequatesubstitute for the Cossor system of Interlockedconstruction.

CossorScreened GridTHE ONLY SCREENED GRID VALVEWITH INTERLOCKED CONSTRUCTION


(imam WireIR.si 586

PORTABLESHOW TO CHOOSE, BUY

Over ioo portable sets, with details 5

of circuits, wavelength ranges, dimen-sions, weights and prices are describedin the illustrated supplement of theMay Number of "Wireless Magazine."Special articles include " How to GetBest Results from a Portable," bythe Assistant Editor, " Designing aPortable," by W. James. " THEWAYFARER," a portable designedby J. H. Reyner, illustrated below,

5

5

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5

5

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55

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ite'RP4 20. 1929

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BUILD & OPERATE

Some of the other features are :-Howwill Broadcasting Affect the GeneralElection ? by B.B.C. Officials -WhatAre Alternating Currents ? Amp andProfessor Megohm Discuss someFundamentals-Russia's Revolution-ary Radio, by J. Godchaux Abrahams-THE TWINFLEX, a modern reflextwo-valver without crystal detector-GRAMO-RADIO SECTION-THEAT-HOME THREE, a completeinstallation for i r etc. etc.

WIRELESS MAGAZINEFOR MAY. ON SALE ON APRIL 24TH. [-

ORDER YOURS NOW !

APRIL 20, 1929

The Portable SetTHE bright weather of the last few

days has brought out all the portablesets-and the dull programmes have sentthem in again I Many listeners have setforth in their cars and on their boats downthe river with portable sets to carry musicwherever they go, so to speak.

Of course, the great demand is for dancemusic. Who has bean down theThames, for instance, without hearingdozens of gramophones blaring out " SonnyBoy" or its equivalent? Personally, Iregard this type of music on the river asanything but an attraction, and am pro-bably in the minority when I hope thatthe B.B.C. will not add to the jazz plugging.On the other hand, light orchestral music,trios, and military band broadcasts wouldbe very acceptable, and would probablyreplace the noises created by some of thewheezy gramophones. If the cost of ex-tended daytime programmes of this typeproved too great, then broadcasts ofselected records would be a good alterna-tive. One of the most enjoyable symphonyconcerts I have ever heard was picked upone summer evening at the end of a littlepier on Coniston Lake. My pipe, my rod,and my portable set seemed to be in har-mony with the beautiful surroundings,and the dramatic power of Brahms ,wasenhanced by the grandeur of the moun-tains. Now, if it had been jazz . . .

Talking FilmsThe " talkies " seem to be booming in

London, at any rate. The great technicalbattle of the "gauges" is coming to an end,the sound -on -strip film systems beatingthe synchronised gramophone record andother types of sound recordings. Photo-graphic recording and reproduction ofsound has been brought to a high state of .efficiency, and the quality of this type ofrecording now surpasses that of the disc.The weakest link of the chain is still theloudaspeaker. But, apart from technical

Bad BusinessPlease don't think that I'm a jazz hater!

I simply hold the humble opinion that jazzthti -

is more in place in the drawing -room, withe carpet pulled back, than in the beauful surroundings of the open country, river,

ofofillhe

and lake. Possibly I am hopelessly outdate, and that the present discontentthe portable radio set manufacturers _weventually force the B.B.C. to flood tcountryside with " Sonny Boy" at twenty -

inill

minute intervals, as is happeningAmerica. Let us hope that the B.B.C. wcompromise by broadcasting daytime con-certs of light orchestral music and as few

veballads as possible. " The Floral Dance,""Cherry Ripe," and similar songs habeen "plugged" far too often.

KI241...Getaikete .04.,0%.00....mt,000ftoftio

considerations, the battle was almost wonon broken records, and cases of the wrongrecords being sent with the right film !Then again, the " cutting " and editing oftalking pictures made on disc systems wasalmost impossible.

B.B.C. LossesOne hears almost daily news of B.B.C.

people going over to the "talkies." CaptainA. G. D. West, the head of the B.B.C.Research Department, has not gone by thesame route, but instead has joined the,H.M.V. Gramophone Company. CaptainWest will be remembered by listeners inconnection with the first American broad-casting relays, the nightingale, and allkinds of "stunt" broadcasts, from aero-plane concerts to talks from the FlyingScotsman footplate and the murky depthsof the Thames. His work, however, hasbeen mostly very much " behind themicrophone," many problems of which hehas effectively solved. Captain West willbe in charge of the electrical side of theH.M.V. Company's activities, which are tobe greatly extended in the near future.

Synchronism and IsochronismI see that the recent renewed interest in

television has given rise to flirt* argu-ments on the question of synchronism.Judging from a demonstration that I hadthe" opportunity of witnessing the otherday, this problem appears to have beensolved in an ingenious and effective mannerin the Baird system. From conversationsI have had and articles I have read, how-ever, I find that it, is not so much thedetails of working that call for comment asthe effects produced when perfect syn-chronism is absent. A word on this matterwould therefore appear to be seasonable.

Where people often stumble is in con-fusing synchronism and isochronism. Wecan have two mechanisms in isochronismand yet not in synchronism, and there is adistinction which should always be bornein mind, especially where television is con-cerned. If two machines are running inisochronism it means that they are run-ning at identical speeds, but are out ofstep. An accurate clock in the BritishIsles is in isochronism with anotheraccurate clock in the U.S.A., but obviouslythey register different times at the sameinstant, and hence are not in synchronism.To achieve synchronism, speed and phasemust be identical; that is, the clocksshould register the same time at the sameinstant.

What to RememberIn a photo -telegraphy system, absence

of ,synchronism evidences itself as a dia-mond -shaped picture for consistent aboveor below normal running, or in a wavy

effect if a mixture of the two. Coming totelevision, we find that the effects of phaserelationship are frequently misunderstood.If the speeds of the transmitter andreceiver scanning discs are identical, butthere is a phase difference, it will be foundthat actual definition is unaltered. Thereis no blurring of the image on the screen,but merely a displacement. It then onlybecomes necessary to "frame" the picturecorrectly on the screen. The effect can besaid to resemble what happens on a cine-matograph screen when a picture appearsshowing a scene with the head of an actorat the bottom of the screen and his feet

at the top.Lack of isochronism will evidence itself

as a distorted or blurred image, but notalways lack of synchronism. If we bear inmind that we can have isochronism with-out synchronism, but never synchronismwithout isochronism, then there will notbe any difficulty in comprehending the truestate of affairs. To achieve the best tele-vision results the synchronising methodsemployed should be practically automaticin action, and the simplicity of Mr. Baird'sarrangement contributes in a large measureto its success. The use of a separatechannel for communicating a synchronisingcurrent adds to the complication of working.and by dispensing with this the Britishinventor has made a big step in the right

direction.

Radio JerksAn American doctor, I see, has just been

telling the world that the early morningphysical exercises-the daily dozen, theycall them over there-broadcast by wire-less stations are far from being as health -giving as many people imagine. He doesnot believe in the rude awakening thatensues when an alarm clock, set to rousethe sleeper in time for his morning exercises,goes off with its horrid explosion of soundin the early hours. Here I cordially agreewith him, for I must confess that in the oldproverb I have always been more struckby the folly of the early worm than by theluck of the early bird. The doctor goes onto say that radio jerks so far from makingthe United States a nation of athletes, bidfair to turn our horn -rimmed cousins intoa race of nervous wrecks. We haven't yethad the early morning daily dozen overhere, and personally I don't very muchmind whether we have them or not, solong as they don't bring in a law makingparticipation in the revels compulsory.

Valve RumoursA non -wireless paper contained an

announcement the other day that we mightexpect in the not far distant future high -frequency amplifying valves with amplifica-tion factors in the region of I,000 to 2,000.

A matter Wink!, 588 APRIL 20, 1929

t0s0 On Your Wavelength ! (continued)

I have heard similar rumours from timeto time, and I am far too old a bird to saythat anything is impossible in wireless.Still, somehow, I don't see such valvesreaching the practical stage, at any rate,until a great many more ether waves haveflowed round our aerials. It is one thing tomake a valve with a huge mag. factor andquite another to be able to get out of it theamplification that in theory it ought tobe able to give. You can quite easily rig up,for instance, two B.F. stages in cascade,each provided with a triode with an ampli-fication of 2o. But you will not get out ofthe two anything like an overall magnifica-tion of 20 by 20 or 400, neutralise younever so wisely. So also with the screen -grid valve. It gives a wonderful degree ofamplification, but it does not quite live inpractice up to its theoretical magnificationfactor.

An ObstacleThere are several very serious obstacles

in the way of the practical use of hugeH.F. amplification. Perhaps the mostimportant of these is that, when receptionconditions are such that with a moderatedegree of amplification one would call thempractically ideal, there is always in realitya great deal of parasitic and other forms ofinterference in the background, thoughwe may hear nothing of them. Increase themagnification and up they come. There is,in fact, much the same difference betweenthe broadcast band tested by a normalset and by one with huge amplification asthere is between a drop of water seen firstwith the naked eye and then under themicroscope. Another point not alwaysrealised is that the - rectifying valve isdistinctly limited as regards the amplitudeof the oscillations with which it can deal.We have long been told that the grid -leak -and -condenser rectifier "packs up" underthe influence of big grid swings, and wehave been led to believe that the anode -bend rectifier could deal with almost any-thing that you like to apply to it. This,however, is not so, for even with a singleH.F. stage the local station at mediumrange may overload an anode -bend rectifieron occasion.

We Still Need ItFor years now in these columns I have

been begging makers to turnout a specialiseddetector valve. There are one or two on themarket to -day, and very good they are, sofar as they go. It is still, though, an exceed-ingly difficult feat, as any who haveexperimented in the matter know only toowell, to obtain anything like perfect andundistorted rectification of strong signals.The valve that I have in mind would bespecially designed for the anode -bendsystem. Its amplification factor would bequite low, for it is rectification: and notamplification, that we want primarily fromthe detector valve. It must, though, have a

pronounced lower bend and a very longstraight portion in its characteristic, sothat no distortion may be produced whenthe local station is modulating deeply andis producing some pretty pronounced peaks.The screen -grid valve now gives me high -frequency amplification satisfying all mywants; with either the pentode or the low -impedance output valve and proper L.F.circuits, first-rate audio -frequency amplifi-cation is obtainable. Once our rectificationis as good as our H.F. and L.F. magnifica-tion, there will be little to grumble about inwireless reception.

Can You Spot It ?Now, then, you fault-finding experts,

here is a little problem for you. The set is athree-valver with a screen -grid valvecoupled by the parallel -feed method to ananode -bend rectifier which is followed byresistance coupling and a low -impedanceoutput valve. On the Monday night when Iwent to bed it was working perfectly;on the Tuesday afternoon when I pushedthe loud -speaker plug into the jack nothingbut large chunks of silence issued from thespout of the instrument. The batteries wereright up, all the valves were in good order,and there were no disconnections anywherein the wiring inside or outside the set.What is that you say? Oh, no, the aerialwas not earthed.

A Simple MatterI wonder just how long that fault would

have' taken most beginners and not a fewold hands. to spot. Though he hates toblow his own trumpet, your "Thermion"tracked it down in about a minute. For-ward the milliainmeter ! Connect it into thecommon H.T. negative lead. Remove allthe H.T. wander plugs 'except those con-nected to Vr. Current is shown to bepassing. Try the same experiment withV3. Again the juice is there. But what ofV2, the detector? The insertion of itswander -plug all by itself produces never aquiver of the milliammeter needle. Anothervalve is substituted; the result is the same.When this kind of thing happens the firstthing to look at is always the filamentcircuit. Here there is no rheostat or fixedresistor and the wires running to the fila-ment terminals are obviously as they shouldbe. Just to make sure, try an old bright -emitter valve (a most useful possessionfor testing purposes, since it lights up soobviously) or a flash -lamp tester in theholder. There is no answering gleam.Since the wires are as they should be, theholder must be at fault. Examination dis-closes a break in one of the spring connec-tions between the valve socket and thefilament negative terminal.

A Short-wave ImprovementThe short waves have been considerably

below par all through the winter, for only

on occasional nights has anything likefirst-rate reception of distant stations been'possible. We seldom had, anything like thebig signal strength that we used to associatewith short-wave transmissions a year ormore ago, and fading was almost invariablya great nuisance. At the present momentthere are signs of a very distinct improve-ment in short-wave reception. The day-light stations PLE and PLF '(formerly ANEand ANH) at Bandoeng, in Java, can bepicked up almost whenever they are work-ing, and after dark quite a number ofAmericans are coming through extra-ordinarily well. If your short-wave set hasbeen laid up now is the time to bring it out.

Still At ItThough there is undoubtedly much less

of the oscillation nuisance than there usedto be, Ham -Handed Henry and OscillatingOswald still' show us at times what theycan do if they try. But- the worst person ofall is he who oscillates good and plentyright through some particularly interestingprogramme from the local station. One ofthis fraternity absolutely spoilt a fineconcert for me and hundreds of others afew nights ago, and I can't really think thathe enjoyed it very much himself. There isno excuse nowadays either for the squealeror for the squeaking set. If your apparatusbegins to misbehave itself, as sets will attimes, refusing to function without howls,for heaven's sake don't begin a long seriesof experiments, using the local station'swavelength, during the evening programme.If you really feel that you must locate thetrouble without delay let me counsel youto go down to the bottom of the broadcastband and to make your adjustments withthe help of one of the powerful transmis-

sions that you will find down there.

A Spring CleanF9r years now Mrs. " Thermion" has

been urging me to turn out the shelves ofthe several cupboards which are devotedto my wireless bits and pieces. For yearshave been promising to do so, and for yearsjunk has been steadily accumulating.Fired with sudden energy the other day, Iundertook the task. I really did. We wire-less folk are a curious race. We find itdifficult to give or throw anything away.There is always a feeling that if we do so itwill be just the very bit or piece that weshall want when we tackle the next radiojob. And so our shelves harbour an increas-ing stock of components that grow steadilymore and more out of date. We shall neveruse --the things; then, why not get rid oftheni. You will find, as I find, that there areany number of youngsters whose enthusiasmoutruns their purses to whom you can giveyour unwanted stuff with the certaintythat it will be thoroughly appreciated andput to useful purposes. TH E

V

Fig. 2. With choke coupling the chokemay be tapped

APRIL 20, 1929

THE maximum amount of output to beobtained from a receiver is funda-

mentally determined by the arrangementof the last stage in the set. By the last stageis meant the valve or valves,its power supply, and let usnot forget, the loud -speaker withits filter circuit or transformer.

It does not matter how Manyamplifying valves are includedin the receiver-one can only fullyload the last stage. Thus, the setmay comprise a detector valvein addition to the last stage; inthis instance probably only thelocal station and perhaps 5XX or5GB will be heard at the maximumpossible strength. I am assuming,of course, that the receiver isused at a place not too far fromthe local station in order thatthe last stage may be fullyloaded.

The addition of a further low -frequencyamplifying stage, or of a high -frequencystage, cannot possibly alter the amount ofthe volume to be obtained from this stationwithout distortion. These additional valvesmagnify the weaker signals, however,with the result that more distant stationsmay be heard at the full strength. Thepoint I particularly wish to bring out isthis : that when the same type of outputvalve, output circuit, loud -speaker and powersupply are used, the maximum amountof volume to be obtained without distortionis identical, regardless of whether the setincludes low -frequency or high -frequencymagnification. The only difference inperformance will be in the number of

589

ubtlefies ofume Control

stations to be heard at the full strength.All this is rather obvious, but yet the

listener with a three -valve set does occa-sionally expect to obtain more volume from,

Fig. 1. Volume control for resistance coupling

Fig. 3. Tn this case adjustable resistancesare placed at ross the transformer

say, the local station, than another listenerhaving only a two -valve receiver. He may,of course, appear to obtain greater volumebecause he has a reserve of power, but if hedoes, and the two output circuits areidentical, it must be accompanied by dis-tortion as the result of overloading.

More power Output without distortioncan only be obtained by increasing the

+ high-tension and grid bias, or by fitting aTau: larger output valve or a combination of

valves for parallel or push-pull working.But in many instances the high-tensionhas to be obtained from a dry battery andthen the size of the output valve is auto -

matically limited provided a reasonablelife is expected from the battery. Therefore,when it is remembered that an ordinarypower valve may easily be fully loaded1. la+ when it is used in a two -valve

receiver for the reception of thelocal station, it is obvious thata volume control must be em-ployed to limit the input to thelast stage of a receiver havingmore than two valves.

There are many methods forcontrolling volume. I have dis-cussed de -tuning and the effects ofvarying the amount of reaction

Iv:- when a condenser control is usedin previous articles. The othermethods depend upon the arrange-ment of the valves and thecouplings employed.

Any control must obviously beso connected that it affects thestrength of the signal applied to

the grid of the last valve. A variable re-sistance or other device connected to theloud -speaker itself may be used to cutdown the volume, but it certainly cannotbe recommended, as there is no controlover the input to the valve which maytherefore be greatly overloaded.

The best position for a volume controldepends upon the type of receiver. Whenthe set includes a detector and two low -frequency stages the control is best con-nected to the inter -valve coupling betweenthe detector and first low -frequency stage.There are several satisfactory schemes.Thus, when a resistance -coupling is em-ployed, as in Fig. r, the anode resistance or


tr:

ernattnr WIrelez,

Fig. 4. Here use is made of a ged-biastransformer -secondary tapping

590 APRIL 20, 1929emaim. Wtrete5

111

111 For the Newcomer to Wireless :- AN you tell me why it is that though valley. You know, for instance, that my

CRobinson and I use exactly the own set is pretty good, though my aerialffi same kind of receiving sets he receives is down in the valley. You remember the111 many foreign stations at much greater night that.' took it up to Smith's house

strength than I do, whilst some of the on the hill?hi -more distant ones that he gets simply Rather. You were astonished at the

do not come in at all on my set ? improvement in its performance.That is one of the queerest problems I was. In fact I found that I was what

in wireless. We know that reception is I should call half a valve better. I meanaffected by local conditions though there that when I substituted a triode for ais still considerable uncertainty about screen -grid H.F. valve the set did justthe actual causes of the differences in as well in Smith's house as it usuallyrange and signal strength that are found does in mine.in various localities. Then if your house is on low-lying

Can you tell me something about them? ground I suppose it is best to have asOne thing does seem pretty certain. high an aerial as possible?

In- the great majority of cases we find In theory, yes, but don't forget thatthat greater all round signal strength is a very high aerial is an excellent collectorobtained from an aerial at or near the not only of signals that you do want, buttop of a hill than from one in a neigh- also of atmospherics and other parasiticbouring valley. noises as well as of spark signals. One

Why is that? has to compromise, as in so many otherII i It is probably due to the fact that the wireless matters.

aerial down below is to some extent What other causes are there of differentscreened by the hills on either side of the behaviour in different houses?

111

111

LOCALCONDITIONS

One of the commonest, though it isnot always realised, depends upon thenature of the soil.

How do you mean ?If clay happens to come very near the

surface, almost any kind of earth con-nection will give reasonably good results.Suppose, however, that there is a thicklayer of chalk or gravel, even a large earthplate well buried may prove inefficient.Not everyone knows how important itis to get down to the clay subsoil.

I have heard that underground veinsmay affect reception.

It has been proved that they certainlycan and that even large systems of buriedwaterpipes and so on may have anadverse effect. It is quite possible thatmetallic veins may be responsible forsome of the blind or partially blind spotsthat occur. Sheffield presented theB.B.C. with a very difficult problem,possibly owing ito the big slag heaps inthe locality which contain large quan-tities of metal.

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" THE SUBTLETIES OF VOLUME CONTROL " (Continued from preceding page)the grid leak may be tapped. The twoarrangements are indicated in the figure,at A and B respectively. (H.T. filter circuitsare omitted for simplicity) and it shouldbe noted that the whole of the anoderesistance, or grid leak, is included in thecircuit.

The quality of the reproduction is notchanged by either of these schemes, andthere is little to choose between them froman electrical point of view, but it is probablyeasier in practice to arrange a potentiometertype grid leak.

When a choke -coupled stage is used be-tween the detector and first low -frequencyvalve the choking coil may be tapped, or

An impression of Arnold Eagle, the conductorof Shepherds Bush Pavilion Orchestra

the grid leak as before. A tapped choke isindicated in Fig. 2, and it should be notedthat the whole of the choke is included inthe anode current.

Transformer ControlSometimes a transformer is employed to

couple the detector valve with the first low -frequency valve. An adjustable resistanceconnected across the primary winding as inFig. 3 may then be used with every satis-faction. A suitable resistance would havethe maximum value of about roo,000 ohms.Alternatively, an adjustable high -resistancewith the maximum value of about 500,000ohms may be connected across the second-ary winding, but it is better to employ aresistance joined across the primary. Thisresistance will carry a certain amount ofcurrent and should, therefore, be of suitableconstruction.

A further scheme is indicated in Fig. 4Here the secondary winning of the trans-former is tapped and a switch is employedto connect the grid bias to one of the tap-pings. I do not recommend this scheme,because a special transformer must beused and further, its frequcncy characteris-tics will change with the amount of thesecondary included in the circuit. Probablythe best arrangement when a resistance -coupled stage is used is that which includesa potentiometer type of grid leak. A suitablecomponent is not very expensive and occu-pies only a little space. It is sometimesnecessary to take particular care with thewiring or hand -capacity effects may givetrouble. Thus, for example, when the sliding

contact is connected to the grid and thespindle is of metal, a howl may be pro-duced if the fingers touch the spindle. Thegrid -connecting wire should, therefore, beas short as possible and a knob of generoussize be employed.

The methods described above are themore important ones suitable for employ-ment in sets of the detector and one or twolow -frequency type. When a high -frequencystage is used other methods of controlmay be advisable.

WOS, Jefferson City, Missouri, is said tobe the only state-owned radio station ittAmerica.

\D51.2.4.4 A

Julian Rose, the famous HebrewComedian-a caricature

APRIL 23, 1929

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591

A Weekly Programme Criticism by SychIWAS interested in the appeal on behalf

of the Aylesbury After -Care Associa-tion which was made by Lady Ampthill.I wrote about this subject of Borstal twoor more years ago, and I remember, whenmy book came out, that it was suggestedthat my sketches on the convict of to -day'would be of interest to listeners.

However, I was told that the subjectwas " too morbid " I But, as in so manyother instances, there has been a changeof mind.

The Salvation Army Service from theCongress Hall, Clapton, was a rather dif-ferent affair from those services I used tohear in East London thirty years ago.But the "congregational song" was thesame : " Just as I am, without one plea."Very nicely rendered, too.

How extraordinarily popular is JackHylton with his band. The relay from theLondon Palladium, however, showedclearly that visual audiences have more ofthe game than listeners.

Jack in the limelight, with full effects,'gets over well when you see him. I heardand saw him do the "Babette" numberquite effectively, but he cannot reallysing for "nuts," and the uninitiated listenermay well have wondered what all the fusswas about. No doubt, television will cometo Jack's aid.

And, by the way, half an hour of dancemusic in the middle of an ordinary pro-gramme-by Jack Payne (or by anybodyelse, for that matter)-does not amusethose of us who don't dance, and whoconsequently feel a certain sameness aboutthese hotch-potches. After hours, cer-tainity; but not on Saturday nights between7.36 and 8 o'clock, when the majority ofordinary listeners want a little variety inthe programme.

- .Now, what could be more popular than

the People's Palace concert by the B.B.C.Symphony Orchestra, well conducted bySir Landon Ronald and Percy Pitt ? From" William Tell" to "Les Preludes" theprogramme was full o' plums. And withMegan Thomas as vocalist and Pouishnoffas the pianist-what more do you want 1

I heard 'em all a -laughing at our Mabel

as I came through the door. Wonchow she keeps up her form.

The first of de Courville's " Gay Spgave us many laughs and fair entement, and a good many sketches, bis bound to compare it with Chariot's

Chariot was quite good ; but then,perhaps de Courville has somethingup his sleeve.

Thanks are due to "Gay Spagiving us the opportunity of hImito. Here is real talent. His birdtions were excellent. Let's have mhim and his family of farmyard habitues.

Fred Duprez was most -emphatically notat his best. As a solo turn Duprez is quitegood. In the revue he did not have enoughto do, and when we did hear him he soundedrestrained and totally unlike his usual self.

"Harold "-my tame lowbrow-has alot to write this week about our friend SirWalford. He writes :-

"Sir Walford Davies, in his talk at 9.15last Tuesday night (an unearthly hour fora music lesson) said that a friend of hisrecently had asked exactly what he (SirWalford) was aiming at in his talks. Iagree with the friend. A talk on musicaltechnique is totally out of place in the lateevening. If itwere given inthe afternoon,so that schoolchildren couldlisten andderive benefittherefrom, itwould be muchbetter."

As a matterof fact, SirWalford is onin the after-noon. Indeed,he appears tobe goingstrong.

A correspon-dent who signshimself " TenYears a Motor -

Reader," writing from a seaside resort,that my criticism of certain wirelesscomedians is unfair.

" Over the Easter holidays I had occa-sion to see a certain wireless turn and,remembering your criticism of it in thepast, settled down with a certain amountof scepticism. However, I found theirantics-rather than their wit-extremelyfunny. May I add that you cannot reallydo a turn of this description full justiceunless you see it."

I myself have made this reservationwhen criticising comedians. However, mycorrespondent finishes up on a note ofhope : "When we get television perhapsthis difficulty will be overcome 1"

A NEW "TALKIE" STUDIO. One of England's largest "talkie" studios has beenbuilt at Elstree. The photograph shows the interior of the sound -recording cabinet

.,,,,..0/HAVE often been asked whether it is

possible to produce a receiver similarto the old "M.C." receiver, utilising

"Q" coils. The "M.C." receivers whichwere popular about two years ago havemany adherents even in these days ofscreen -grid valves and other modernpractices, and the view which is expressedis that if these receivers can be broughtup to date by the use of dual -range tuningarrangements such as are provided by the"Q" coil, they would then be quite up topreient-day standards.

The matter has 'accordingly been put tothe test in the Furzehill laboratories and Ifound that it was possible to obtain goodresults using standard types of "Q" coil.The results were slightly below the oldstandard, this being due principally to the

`,fact that for best results somewhat criticalvalues of magnetic and electric couplingmust be used in the high -frequency trans-former. This would have necessitated thedesign of a special "Q " coil for the purposeand I felt that this would be undesirable.Since I could obtain quite good resultswithout any difficulty on the standardQSP coil, I felt that this would be the moresatisfactory solution.

The Loftin -White PrincipleThe Loftin -White 'principle embodied in

the M.C. receivers and in the ,presentversion consists in the use of a combinedmagnetic and capacity coupling in thehigh -frequency transformer, This is donefor the following reasons.

An ordinary transformer having a mag-netic coupling operates mere efficiently

592 593

STABILITY FOUA Loftin -White Receiver Embodying "Q" Coils. By J. H. REYNER, B.Sc., A.M.I.E.E.

towards the bottom end of the tuningrange where the voltage induced fromprimary to secondary is greater by reasonof the higher frequency of the current. Inconsequence, we obtain a transference ofenergy which decreases as the wavelengthincreases somewhat as indicated in Fig. x(p. 594). If, however, we arrange a capacitytapping in the circuit we can obtain thereverse state of affairs, for the voltagedeveloped across the condenser increasesas the frequency is reduced, this beingexactly the opposite to the voltage developedacross an inductance or transferred acrossa mutual inductance such as is constitutedby the primary and secondary of a high -frequency transformer.

Constant ReactionThe effect of a capacity coupling there-

fore, is to transfer energy in 'increasingquantities as the wavelength is increased,giving an arrangement similar to thatshown by the dotted line in Fig. 1. If thetwo effects can be balanced accurately wecan obtain a transfer of energy over thewhole scale.

This in itself may not be a particularlyimportant matter. Its advantage inpractice is that we can put in a smallreaction control which is adjusted to givean operating point relatively near to theoscillation point, so that the receiver is ina state of liveliness, and this control thendoes not require to be altered in tuningfrom one station to another. The original"M.C." Three and "M.C." Four possessedthis property to quite a marked extentand it was possible to tune in one station

after another by merely rotating two dialswithout any reaction control. A furthersomewhat important aspect of the questionhowever, arises from the methods adoptedto stabilise the receiver.

Oscillations in a high -frequency amplifier

IMO000

grid circuit, in which case a reaction effectis obtained, or it may be in such a directionas to oppose the grid circuit in which caseadditional damping is introduced.

This condition of affairs is exactly thesame to the reversal of the. direction of

1-1A: CH014-6-

.00/0

ODD/ n " i I

-1i I

G

IiiI I

Fig. 3.

1 2AN

L

The Circuit Diagram

occur because of the feedback which istransferred through the internal capacityof the valve. This feedback depends, to alarge extent, upon the nature of the anodecircuit. It will be quite clear, withoutgoing into detail, that energy transfen-edback in this manner may be such as tocoincide with the energy alfeady in the

--4Dia-r06.8+

ea -2-01.1-

reaction in in a simple reaction circuit, and inpractice we can actually obtain either of thetwo conditions or any condition inter-mediate between them. It is thus possibleto obtain a point at which the feedbackneither helps nor opposes the grid circuit,but has no effect whatever.

Which of the three poSsible conditions

s

These three photographs show practically all the constructional features of this fine receiver

0

occurs depends upon the anode circuit.Wiliere the anode circuit is inductive, thatis to say, possesses in general the character-istics of a simple coil, the energy feedbackis positive and self -oscillation or a tendencythereto will result. If the anode circuit isresistive, the feedback has no effect what-ever while if it is capacitative, the feedbackis negative and damping is introducedinstead of any tendency to oscillation. Itmay not be quite clear how the anodecircuit can pass through these variousstates, but we can consider a simple tunedcircuit.

StabilityIf we vary the frequency of the current,

then at low frequencies the effect of thecondenser is small and most of the currentflows through the inductance, giving us apredominantly inductive anode circuit.When the frequency is tuned to resonancewith the circuit, both the coil and condenserhave equal effects and tend to balance eachother out leaving us solely with the resist-ance of the circuit. The circuit is thuspurely inductive or nearly so, while at thehigher frequencies the current prefers toflow mainly through the condenser and thecircuit becomes predominantly capacitative.Thus, with an ordinary circuit like this, atthe tuning point and above it, the circuit isstable while on the other side thecircuit tends to be unstable and mayactually burst into oscillation.

It may be thought that it shouldbe possible to weaken the coupling tosuch an extent that the circuit neveractually bursts into oscillation. This

matter Wirek5

13g

is quite feasible, but the energy transfer atthe other end of the scale would then be sosmall that the receiver would be hopelesslyinsensitive. . . .

With an ordinary arrangement, the circuitis most lively at the bottom end of thetuning scale and if we so arrange thecoupling that there is no tendency to self -oscillation at this point, reception at thetop of the scale would be very poor indeed,and an enormous quantity of reactionwould have to be applied. It is here thatthe constant -coupling system is of use forif we can arrange the constant energytransfer over the whole scale and further-more arrange the coupling to be such thatno oscillation occurs then we have not onlya stable receiver, but one which is uniformlysensitive throughout the wavelength scale.

The basic circuit by which this is accom-plished is shown in Fig, 2 (p. 594.) H.T. tothe H.F. valve is obtained through an H.F.choke. The high -frequency currents arepassed through a fixed condenser on to theprimary of the transformer which iscoupled to the secondary in the ordinarymanner. The primary current, however,

An end view of the " Stability Four "

having passed through the primary windingdoes not go straight to earth, but is causedto pass through a fixed condenser whichalso forms part of the secondary circuit.Voltages are induced in the secondary,therefore, from two causes.

Eirstly, there is the magnetic inductionbetween the primary and the secondarywindings, while secondly, the primarycurrent in passing through the couplingcondenser C sets up voltages which areautomatically introduced into the second-ary circuit. We thus have voltages intro-duced from both magnetic and capacitycoupling and as we have seen, these canbe so balanced that we can so arrangematters that the two effects balance andgive us a nearly constant coupling.1 ...1

ematturWirelgO 594 APRIL 20, 1929

Old Tenants and New LodgersJOTTINGS FROM MY LOG

EVEN in the broadcasting world, leasesexpire and are renewed or granted to

new owners. Such is the case of Mont-pellier (France) which,' after having limpedalong for some months, suddenly gave upthe ghost and blossomed out afresh as aunit of the P.T.T. provincial broadcastingsystem. That it has not yet got into itsfull stride is demonstrated by the fact thatits transmissions have not yet been placedon a regular basis, and it has not yet beendefinitely included in the Ecole Superieurenet. You can, however, pick it up now andagain in the region of 253 metres, but itswavelength is wobbly, for at times youwill find it above Rennes, at others belowPTT Toulouse.

These three stations are difficult toidentify individually as they devote themajor part of the day to relaying the Parisbroadcast, and seldom work on their own.Lack of funds prevents their claiming theirindependence from the mother station orof giving any display of local initiative.Owing to its numerous provincial parasites,to -day PTT Paris is unable to put out aconcise call. If you are lucky to tune in at

By JAY COOTEthe moment the Paris station opens itstransmission you will hear a rapid volleyin French which, unless you are a linguist,may prove a puzzle, The Paris announcerrattles off the following in double quicktime : "lei les stations radiotelephoniquesdu reseau de l'Etat de PEcole Superieure desPastes et Teldgraphes de Paris et les Posiesde radiodiffusion de la Tour Eiffel, Lille,Rennes, Toulouse, Limoges, Lyons, Bor-deaux, Grenoble et Marseilles," after which,I take it, he falls back breathless in hisarm -chair I

Eiffel Tower InterferenceTalking of Paris reminds me that the

Eiffel Tower has again been experiencingtrouble, as shoals of protests have reachedthe authorities in regard to thq, interfer-ence caused by its transmissions. La Tourfor some time has been anxious to reduceits wavelength to r,47o metres in ordergive itself more elbow -room, and thus freeitself from its immediate neighbours. Atfirst sight, the choice of wavelength wouldappear to be an unfavourable one, in viewof its close proximity to that on which the

Le Bourget Aerodrome operates, but inpractice it has been .found that the twotransmissions are clear of each other. Toalleviate further the trouble experiencedby Paris fans, the authorities have decidedto curtail. the Eiffel Tower broadcasts inthe ear future, The station will be silentfrom midday to 2 p.m., from 5 to 7 p.m.,and the evening concert will terminate at8.40 P.m.

Listeners to WGY (Schenectady) andto KDKA (East Pittsburg) or to theirrespective short-wave stations may begiven the opportunity of hearing messagesexchanged with the Byrd Antarctic Expe-dition. These U.S.A. stations broadcaston alternate Saturday nights, KDKA at6 p.m. and WGY at 5 p.m. G.M.T. As it isthought that the general public may beinterested in these communications, KDKA(East Pittsburg) has made arrangementsto rebroadcast the replies from members ofthe Byrd Expedition.' KDKA operateson 306 metres and its short-wave relays on24.5, 26, 63, and 65 metres; WGY on 38031.4, and 21.96 metres.

" THE STABILITY FOUR" (Continued from preceding page)

The value of the phasing condenser cris so adjusted as to make the whole anodecircuit just capacitative so that the circuitis completely stable throughout the wholerange. The smaller this condenser is made,the more stable does the arrangement

.fMill101.

figleNITICCOUP' 1/4V

"IC.-C6V/PL/he

..07PRC/TYC01/191//0

FREQUENCY

Fig. 1. If the magnetic and capacity couplingsare equal a level curve is obtained

become, but it also loses efficiency; ifdesired a pre-set condenser may be employedhi place of the fixed condenser used. Acondenser having a value of .00r has beenused in the actual receiver, but the valueof this is a matter for experiment.

This briefly is the underlying principleutilised in the present receiver, the fullcircuit -of which is shown on the precedingpages (Fig. 3).

Components RequiredThe following is a 4ist of components

required to build the set :Ebonite or bakelite panel, 18 in. by 7 in.

(Raymond, Becol, Ebonart, Paxolin).Two ebonite strips, 2 in. by 2 in., and

strip 8 in. by _g in. (Raymond, Becol,Ebonart, Paxolin).

Cabinet, 18 in. by 7 in., with ro in.baseboard (Miscellaneous Trading, Clarion,Cameo, Pickett).

Two .0005-microfarad variable condensers(Burton, Lissen, Ormond, Utility, J.B.,Polar, Igranic).

.000 r-rnicrofarad reaction condenser(Dubilier, Burton, Lissen, Ormond, Utility,J.B., Polar, Igranic).

Four valve holders (Lotus, Benjamin,Lissen, Burton, W.B., Wearite).

Q.A.A. coil (Lewcos, Lotus, Wearite,Stone).

Q.S.P. coil (Lewcos, Lotus, Wearite,Stone).

Filament switch (Lissen, Benjamin, Trix,Wearite).

Two .002, one .000r and one .0003 -micro -farad fixed condensers (Lissen, Dubilier,T.C.C., Mullard, Graham-Farish).

Two high -frequency chokes (Wearite,Lissen, Lewcos, Dubilier, R.I. & Varley).

One 2-megohm and one .25-megohmgrid leak (Dubilier, Lissen, T.C.C., Graham -Parish).

Two grid -leak holders (Lissen, Dubilier,Graham-Farish).

Resistance -capacity coupling unit (Gra-ham-Farish, type z, R.I. & Varley, Mullard,Dubilier, Lissen).

roo,000-dlim resistance with holder(Graham-Farish, R.I. & Varley, Mullard,Lissen, Dubilier).

2-microfarad fixed condenser (T.C.C.,Lissen, Dubilier, Ferranti, Mullard).

Low -frequency transformer (Lissen,

Fig. 2. A practical Constant -coupled Circuit

R.I. & Varley, Ferranti, Mullard, Phillips).Eleven terminals marked Aerial, Earth,

L.T.+, L.T.-, H.T.-, H.T. G.B.+,G.B.-r, G.B.-2,. L.S.-I-, L.S.- (Eelex,Igranic, Belling -Lee, Burton).

Connecting wire (Glazite).1% -volt cell (Siemens G.T., Lissen, Ever

Ready).Next week full constructional details will

be given together with a reduced repro-duction of the blueprint of the layout. Inthe meantime readers who desire to have acopy of the full-size blueprint may obtainthis from the offices of AMATEUR WIRE-LESS 58-61 Fetter Lane, London, E.C.4,price is. 6d,

APRIL 20, 1929 595 0 mate= Wtretzzsl

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ESPOT66A Unit21,6

0 matterVirelesi 596 APRIL 20, 1929

41.11M1=111111MIIMINIMIN,

"A W "Conducted by our

The TeKaDe Trickle ChargerWE have recently tested a very interest-

ing metal trickle charger known as theTeKaDe; this is made in Germany and ismarketed in this country by Dr. Nesper(Ltd., Colindale Avenue, Hendon. Someidea of its compactness may be gaugedfrom the fact that its overall dimensionsare as follows : 53/4 in. by 3 in. by 21y4 in.high. The secondary voltage is applied toa special form of metal rectifier with whichwe have not previously had experience.This comprises a series of sheets of thinfoil in contact with a treated metal plate.The rectifier is provided with large coolingfins in order to work at a low temperature.TV output is taken to three terminals soarranged that either 4- Or 2 -volt accumula-tors may be charged.

We found that the charging was approxi-mately .5 amp. at both 4 and 2 volts. If a6 -volt accumulator is charged on thy 4 -volttap, the current falls to .26 amp., Theefficiency is approximately 18 per cent., butwhen it is considered that the mainsconsumption is only 12 watts or approxi-mately one -fifth of the power taken by anordinary electric light lamp, the unit maybe termed economical. Although during

TeKaDe Trickle Charger

our tests, the unit was made to charge fora number of hours on end, the rectifier andtransformer remained noticeably cool. Thisinstrument can be recommended to readers.

A Simple Battery FillerMANY readers must have experienced

the difficulty of filling small Leclanchecells with solution; this process, in fact,may occupy a considerable tithe owing tothe care needed to prevent spilling theelectrolyte.

We have received a very useful deviceknown as the Easeful filler, made by, theLeyton Battery Co., of Walthamstow,London, E. This article consists of alarge bottle, fitted with a large -diameter

TESTS OF APPARATUSTechnical Editor, I. H. REYNER. B.Sc. (Hons.). A.M.I.E.E.

cork into which two tubes are fitted. Oneof these bends over in the form of a spout,whilst the other acts as a valve control. Touse the device the glass container is filledwith the electrolyte and placing a fingeron the top of the valve tube, the container

Easeful Battery Filler

is inclined until the spout rests above thecells to be filled; then by removing thefinger from the valve the liquid pours outand can be stopped at a moment's notice byreplacing the finger.

Although primarily designed for fillingLeclanche cells, this article has other useswhich will suggest themsplves to readers.All those who are troubled with this difficultyshould obtain one of these fillers.

Ready Radio H.F. ChokeALTHOUGH many well -designed general

purpose H.F. chokes will operateefficiently on the ultra -short wavelengthsbelow zoo metres, it is often consideredadvisable for maximum results on thesewavelengths to utilise a separate chokehaving a lower natural inductance and,more important still, a lower self -Capacity.Provided the inductance exceeds a givenvalue, the efficiency of the choke on theultra -short wavelengths depends almostwholly on the self -capacity.

We have recently tested a short-wavechoke, manufactured by the Ready RadioSupply Co., of 159, Borough High Street,S.E.

We found that the inductance value was17,000 mics., which in practice is sufficientto give adequate choking. This was con-firmed by a test made over a wavelengthrange extending from below 15 metres upto roo metres. The first peali occurredjust below ioo metres, indicating that thecomponent was ceasing to function at thiswavelength.

This little component should appeal toreaders.

Squire Large Cone UnitAGREAT deal of technical...matter has

been written on the correct sizes forcone and moving -coil loud-spealters. Someassert, particularly in the case of a movingcoil loud -speaker, that a small -diametercone is preferable, while others say that ifthe cone material can be made sufficientlyrigid, the larger varieties will give the betterresults.

We have recently completed a test on aSquire aluminium cradle frame fitted with awoven cone having a diameter of 16 inches.

Surrounding the aluminium frame is asmall wooden baffle designed to be used inconjunction with a larger baffle, the recom-mended size being some 3 _ft. by 2 ft. by2 ft. 6 in. We tested the assembly with therecommended units, and found that thesecould easilybe fitted, the design of the chassishaving been well thought out. With theparticular cone supplied the "speech wasinclined to be slightly muffled, but therewas no doubt that the reproduction hadboth life and body. The sensitivity was upto standard.

The manufaqurers also provide specialpaper for building up this type of diaphragmto go with the cradle frame; one may

Squire Large Cone Unit

therefore try the effect of various types ofpaper. The maker is Frederick Squire, 24Leswin Road, N.16.

Knight's Floating Cone Unit.-Lastweek, on page 562, we gave a test reporton a most satisfactory floating -cone unitmanufactured by Messrs. Knight & Co., of6 Chapel Street, London, E.C.2. It is to beregretted that the address was incorrectlygiven in the report. The correct address isthat above, and was correctly stated inMessrs. Knight's advertisement on page574 of the same issue.

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RUPERT COLLINS SERVICE

Citnakitr Wire 598 APRIL 20, 1929

AFEATURE about this set which willappeal to constructors is that without

sacrificing neatness of layout, or complicat-ing the construction in any way, the mainssection is kept quite distinct frorm thereceiver section, although both are mountedon the baseboard. A list of componentswas given last week to serve as a guide tothose who' re making up this set. Althoughthe cost of this set may appear to be re-latively higher than an ordinary two-valvei,it should be born in mind that there are no'batteries to purchase.The Mains Section

The mains portion comprises, primarily,atransformercarryinga number of tappings,a rectifier valve, a smoothing choke and therequisite number of large capacity smooth-ing condensers. As explained last weekthe tappings on the transformer (onewinding of which, of course, is connecteddirectly across the mains) provide fullvoltage H.T. to the rectifying elements ofthe valve, a supply of alternating currentL.T. to the filament of the rectifier valveand, finally, 2.5 -amps at .8 -volts for thefilaments of the receiving valves. If youcare to glance at the theoretical circuitdiagram the whole arrangement will bemade quite clear.

Now, so far as construction is concerneda blueprint will be found a great asset tothis particular instance and, of course, asusual, one is obtainable for this set fromAMATEUR WIRELESS, 58-61 Fetter Lane,London, E.C.4. The price is r/- post free.The Layout

The first use to which it can be put is as adrilling template for the panel. The panel,of course, carries simply the aerial tuningcondenser (on the right looking from thefront) the aerial tuner and, below, fourterminals for aerial, earth, and loud-speaker respectively. All these parts canbe mounted, but the panel should not, atthis stage, be attached to the baseboard.In this set it will, indeed, be found much

Last week a technical description was given of the workingarrangements of the All -Mains Two, a simple transformer -coupled two -valuer obtaining both H.T. and L.T. fromA.C. mains. Here are some concluding constructional

notes and hints on operation

more convenient to screwin place and wire up mostof the baseboard partsbefore the panel com-ponents are added. Nodifficulty should_ be ex-perienced in completingthe baseboard assemblyproviding the blueprint isused as a guide both for

positioning and wiring up the components.Assembling the Components

A brief explanation of the layout, whichmay at first seem rather complicated, maybe helpful. Between the aerial coil andcondenser is situated the .0002-microfaradfixed reaction condenser and the 2 -micro farads condenser in series with the earthlead. These components are placed sideby side.

Then, in a row, looking from the frontend of the baseboard we have the detectorvalve (with the grid condenser and leak infront of it), the H.F. choke in the detectorplate circuit, the L.F. transformer and,finally, the L.F. valve.

At the back of these is a second groupof components, also almost in a line. Theseare, from, left to right, the potentiometer(to the moving arm of which is taken thelower end of the 3-megohm grid leak) andat the back of it one of the 2-microfaradsmoothing condensers. Next are two 2-microfarad fixed condensers in parallel,forming a 4-microfarad bank. In front ofthese is a 20,00o -ohm fixed resistancewhich forms one part of the anti -motor -boating unit. The 2-microfarad fixed -con-denser which forms the second part is justat the back of the L.F. transformer.

At the back of this group of components,from left to right, are placed the smoothingchoke, rectifier valve, power transformerand grid -bias battery.

Wiring up should be carried out withrigid insulated wire, such as Glazite in orderto prevent the possibility of short-circuits.When the wiring is complete carefullycheck it over in conjunction with the blue-print and, if you feel capable of doing so,with the theoretical circuit diagram.

OperationSo far as operation is concerned the

receiver can be treated very much asthough it were a straight -forward detectorand one L.F. set, deriving H.T. and L.T.from batteries and accumulators respective-

. .

ly. There is no switching to be done, for inorder to bring the receiver into operationit is necessary simply to insert the mainsplug into a light point. The anti -motor -boating unit should effectively preventthe possibility of L.F. instability.

On the receiver side a point which willbe noted is that the tuner is provided withtwo tappings, namely AI and Az and aflex lead can be taken to either one or theother, according to the degree of selectivityrequired. The tapping Ai gives the greaternumber of turns in the aerial coupling.The changing from the short to the longwaves and vice versa is obtained simply bypushing and pulling the centre knob of the

Simply insertthe mainsplug into a

light point

tuner. The larger rotating knob, of course,is the reaction control.

Valves to UseSo far as valves are concerned the

Marconi or Osram directly -heated valvesare those for which the receiver has beenparticularly designed. The H.L. .8 valveshould be used as a detector and the P .8 asan L.F. valve.

Owing to a printing error, it was, insome copies of AMATEUR WIRELESSNo. 356, not made clear that the price of.4 and .5-microfarad Dubilier paper di-electric fixed condensers is 2S. 6d., asstated in the advertisement of Messrs.Dubilier on cover iii of that issue.

APRIL 20, 1929 599 mateur it

WE' `ITCOAiPOIV-AnS

W. James "Special 3" Coils .. 25'^ pearW. James "Binowave" Coils 25;"

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each

Dual Range Tuner, W.G.2, asused in FERRANTI Circuits 15/-

10/69/66/61/-2/6-/67/6

ALL FROM THE MAINS TWODual Range Tuner, W.G.2 pair 15/-H.F. Choke .. 6/6H.T. Choke .. 21/-Valve Holder, anti-microphonic, LAS5 each 2;6

WRIGHT & WEAIRE, Ltd.740, HIGH ROAD, TOTTENHAM, NM.

Telephones; Tottenham 3847 and 3848

---

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The days are lengthening andyou will be spending more andmore time outdoors. Add toYour enjoyment whether on theriver, in the country, or athome in the garden, by havinga portable instrument. Why

not build your own wirelessportable set? We can supplycabinets from 30/-, and com-plete kits of parts for construct-ing any type of set. We canalso supply immediately any ofthe well-known wireless orgramophone portables including:

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Ask for leaflet onimproved methods.

simplifies all solderingSOLDERINGSET, complete

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HELLESENDRY BATTERIES

PRICESStandard Capacity

" Wiray " 9 -volt GridBias Type ... 2/-

Wirin " 00 -voltType ... 10/6

" Wirup " 99 -volt H.T.Type ... 18/.

" Wisol " 108 -volt H.T.Type ... 20/ -Treble Capacity.

" Kolin " 00 -volt H.T.Type ... 19/-

" Kolup " 99 -volt H.T.Typo ... 32/1

SOME GOING !I saw a 99 -volt Hellesen H.T.Battery the other day thathad accidentally been left onshort circuit.So great was the energygiven off that the sealingcompound had melted awayand the battery was twistedand contorted.The irrepressible Ridley onseeing it remarked that ithad evidently waxed hot, butI couldn't help wondering ifthere was any other make ofbattery which would havewithstood the strain as thisHellesen did and still show27 volts on open circuitafterwards.

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4

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mateur Wtrcl P is 600

THE WIRELESS CONTROL OF MODELSPART TWO -THE RECEIVING GEAR (Concluded)

By MAJOR RAYMOND PHILLIPS

APRIL 20, 1929

PTHE pneumatic arrangement of the"dashpot " simply consists of small bel-

lows similar to those made for piano players.Any dealer in piano player componentswill supply the bellows. The latter shouldbe mounted as shown in Fig. 3 (No. 357). Ahole drilled in the top of the wooden partof the bellows, and fitted with a wooden

towtocts e,99o949mz`h cal/WIleveysfityy

Terminals connectedwith OWnei/coilv

°petaled /one/m.411/c60ashpolOeme

L

CZ4j ;-7.jged/1\ \/

t fr. if gee/kere/01dh894vmoaee

Ta/701/>g,aeUe

Fig. 5. Details of selector base

plug, is useful for adjusting the admissionof air to the bellows, as a small slot can becut at the side of the plug, and enlarged asdesired. The object of the bellows is toretard the upward movement of the arma-ture of the electro-magnet, and so closefor a period a circuit connected with theselector electro-magnet. This is necessary,otherwise there would be a risk of theselector not functioning correctly.

nERigt7 TERmpyms7

WHERERORCII/I

OSNTGI/

NR//Y SW/101

°TERM/M PN

Fig. 8. Details of receiver case

The construction of the special selectorshould not present any serious difficulties.When commencing the construction it willbe necessary to cut a brass plate 5 in. longby z in. wide by -1 in. thick as shown inFig. 4 to form a base for mounting thevarious components. The brass plateshould he mounted upon a wooden base,and four terminals fitted to the base, andwired up to the selector electro-magnet,and contacts respectively as shown inFig. 5.

The magnet of the selector (Fig. 6) shouldbe f y4 in. long with a soft iron core % in.in diameter. The latter should be drilledto allow a soft iron rod 11 in. diameter topass freely through the centre of the core.At one end of the round rod there shouldbe secured a soft iron armature in. by

1 in. The electro-magnet should be woundwith No. 25 -gauge enamelled copper wire.

The Selector MechanismThe mechanism of the selector is quite

simple. It consists of a brass contact lever3 in. long by 1/2 in. wide by -116- in. thick,tapered at one end to which is secured apiece of .005 in. hard brass sheet to forma rubbing contact with two other contactsmounted on the wooden base. An actuatinglever r % in. long by 1/4 in. wide made ofbrass sheet in. thick is loosely securedto one end of the round soft iron rod whichpasses through the core of the electro-magnet. It will be observed on reference toFig. 6 that the soft iron rod is bent at right -angles at one end and passes through a, slotcut in the brass plate, forming a base forthe components of the selector. One end ofthe actuating lever is V-shaped to engagewith a double V -cut in the contact lever.A small spiral spring made of No. 28 -gaugehard steel wire iszecured to the other endof the actuating lever, and the brass plate.It will be apparent that when the electro-magnet of the selector is energised, theactuating lever will engage with the contactlever causing the latter to move in eitherdirection, thus opening or closing a circuitconnected with the two contacts mountedon the wooden base. The whole arrange-ment is clearly shown in Fig. 7.

The CaseThe remaining parts for the receiver

comprise a case and the coherer.It is advisable to construct a case to

accommodate a sheet of glass at each side,as it is well to be able to watch the mechan-ism in operation:

The size of the case should be r8 in.long by 14 in. wide by 14 in: deep, and itshould be fitted with a removable par-tition (see Fig. 8). The upper half shouldcontain the coherer, decoherer, relay, and31/2 -volt dry battery, the latter an ordinarypocket -lamp battery.

The lower portion of the case shouldcontain the magnetically operated pneu-matic dashpot device, and the specialselector. Four holes should be drilled in thetop of the, case to accommodate four largeterminals ; the latter being arranged tohold two aluminium rods 1/4 in. diameter by4 ft. long to form an aerial. The top of thecase should have a hinged lid.

Two holes should next be drilled in eachend of the case to accommodate four ter-minals for connecting .to an accumulator,or other source of electrical energy and(in the case of a model electric railway) tothe "conductor," and "outer" rails -of amodel railway.

Two 5 -amp. switches are fitted at eachend of the case. These are for insertion inthe coherer and main circuits respectively.

The remaining components, consisting ofa brass pedestal and brass spring contactfor a vertical type of coherer, can be made.

For a pedestal it is only necessary to

Fig. 7. The selector magnet with contacts

1

t§1

Fig. 6. The selector electro-magnet

solder a piece of round brass rod 3/4 in.long by % in. diameter in the centre of abrass disc r % in. diameter by in. thick.

When the soldering is completed it willbe necessary to drill a hole 3,132 in. diameterdown the centre of the pedestal to admit thesupport or shank of the coherer. Anotherhole should be drilled and screw threadedtransversely through the shank of thepedestal so that a No. 6B.A. screw, % in.

Fig. 9. Method of mounting coherer

long, can be inserted to hold the shank ofthe coherer. Three / in. holes should thenbe drilled in the base of the pedestal forthe purpose of securing it to the partitionin the case containing the components.A brass spring contact 31/2 in. long by 1/2 in.wide should next be made by cutting thesize required from a piece of No. 28 -gaugehard brass sheet. The whole arrangementis shown by Fig. 9.

All components are now ready for assemb-ling. It will be well to commence by secur-ing the coherer pedestal, arid spring con-tact in position on the wooden partition ofthe case by the brass wood screws alreadydescribed. When this is done the coherershould be placed in position, and thedecoherer, or tapping device (i.e. electric

(Cot:chided at foot of page 602)

APRIL 20, 1929 601 0mo/es( WireiT

r.....s.........solv..00mm.s........"...os.m......sa....e............1...s.........o....61,TO HOME CONSTRUCTORS! I

i Build the Peerless " Resonic 2"Anyone -.can build this set in 6() 'minutes. No drilling. No soldering. All

radioWires cut and bent. JUST ASSEMBLE and then immediately enjoy theentertainment. which is of splendid tone and comes in at good loudspeaker ivolume. Circuit allows use of standard valve (I H.F. & I Power). Blueprint

..and easily followed Dia-

:i

igram of Connections in-

ieluded with every set.

! Cabinet and full Kit i

isupplied in Garton.

i

13.15.0 1Obtainable from i

i all dealers, o: iTHE BEDFORD ELEC. iTRICAL & RADIO CO., !

IRegd. No. 456002 LTD., 22 Campbell Rd., i

BEDFORD. !..

CLARION CABINETSAre manufactured in the cabinet-making centre of London, byexperts in woodwork. We canquote you for any size or type ofreceiver or loud -speaker cabinetin solid oak or mahogany

CLARION RADIO FURNITUREPhone: Mansford Street, London, E.2Bishopsgate 6371

411110M1.0411.1.000.2.0............0001.10.1111,0404M.0042.100.1.1,C.11101M011110.

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The Shielded Four -elec-trode Valve.

Loud -speaker Crystal Sets.Wireless -controlled Mechan-

ism for Amateurs.The Wireless Man's Work-

shop. Book.THE BOOK OF THE NEUTRODYNE, by J. H. Reyner, B.Sc.

(Hons.), A.M.I.E.E. Price 1/6 net, or post free for 1;'9

The Practical " Super -het "Book.

Perfect Broadcast Reception.The Short-wave Handbook.The Practical Wireless Data

Of all Newsagents and Booksellers or by post, 3d.extra, from Cassell E3 Co., La Belle Sauvage,E.C.I.

THE

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BRITISHComponents Throughout

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HERE IS THEOAK WIRELESS CABINET

YOU ARE LOOKING FORDo not put a fine piece ofwork into a fourth -rate box

Install a " LAN GM ORE "

These

No. 1.

No. 2.

No. 3.

No. 4.

and be proud of your set.cabinets are made in thefollowing sizes :-Panel, 16 in. x 7 in.Cabinet, 2 ft. 6 in. high,

ft. 8 in, wide, 12 in. Nos. & 2

Panel, 18 in. x 7 in. 27/6deep.

Cabinet, 2 ft. 6 in. high, Each1 ft. to in. wide, 12 in.deep.

Panel, at in. X 7 in.Cabinet, 2 ft. 6 in. high,

ft. t in. wide, 12 in.deep.Panel, 18 in. X 8 in.Cabinet, 3 ft. high, t ft.loin, wide, lz in, deep,

Nos. 3 & 4

32/6Each

All the above with Battery Shelf, enclosed backand sides, and double doors in front of same,

10/- extra.PACKED and SENT CARRIAGE PAID to ANY ADDRESS in GREAT BRITAINAll are fitted with hinged top, heavy baseboard, etc., and a tray underneath givesaccommodation for batteries. London made. Highly finished in Jacobean style.

Please note this price does not include Panel.Other sizes and styles, prices on application. Trade enquiries invited.

THE MISCELLANEOUS TRADING CO. LTD.'Phone: Hol. 4894. 143 High Holborn, London, W.C.1

8/' RetailRatio 3 to I

aarHere is the famous D.X. Transformerwhich is setting a standard in value formoney and is already known whereverradio is heard of. A really first-classpiece of workmanship, conscientiouslymade in accordance with modern scienti-fic principles at a price that places itwithin reach of all.Write to us for leaflets and particulars ofthis transformer and give one a trial.You cannot fail to be delighted.Ask for particulars of our new circuit, the

D.X.3.

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Famous FORMO COMPONENTS as used in thisSet and in all Notable Published Circuits

"1928" LOGCONDENSER 5/-'0005 '00035 '00025

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25/- 0005 61. 00035'00025 '00015 10/6 each

THE FORMO CO., CROWN WORKS, CRICKLEWOOD LANE, LONDON, N W 2

Don't Forget to Say That Yon Saw it in "A.W."

FORMO-DENSOR 2/-ln four variable capacities

VALVE HOLDER 1/3

602 APRIL 20, 1929

0111111111112/11/0 01\11111illizie

/4/MilligISO" /*///01111111100

RULES.-Please write distinctly and keep to the point. We reply promptly by post. Please give all necessary details. Ask onequestion at a time to ensure a prompt reply, and please put sketches, layouts, diagrams, etc., on separate sheets containing your nameand address. See announcement below. Address Queries-AstaTuua WIRELESS Information Bureau,38/6r Fetter Lane, London, E.C.4

S

Loose Material in Valves.Q.-I have some cheap foreign valves which,

although still functioning quite well, havedeveloped a rattle inside when shaken. I havetraced the cause to a small deposit inside thebulb and this appears to be a strip of metal.Am I likely to do any damage. if I continue touse these valves ?-J. B. (Wandsworth).

A.-The strip inside the bulb is not a partof the electrodes but is a small piece of magne-sium which did not become used up in theexhausting process. Originally this magnesiumwas attached to one of the valve electrodes,but has become dislodged and has fallen off.Do not shake the valve more than you canhelp as this loose piece of magnesium maytouch two electrodes at once and so cause a" short." Should you take the valve out ofthe set at any time see that the piece of magne-sium is at the bottom of the bulb beforereplacing the valve in use.-C. L.Home-made Sets

Q.-I have a four -valve home -constructed setwhich I now wish to sell in order that the cashso obtained can be expended for the building of afive -valve set. I know that a royalty is payablein respect to patents and I have no wish to evadethe payment of this, but I do not know to whomI should address a letter for guidance in this

matter. Can you assist me in this respect ?-W. A.(Cardiff).

A.-You should address a letter to Marconi's

°0 0



A Fee of One Shilling (postal orderor postage stamps) must accompanyeach question and also a stampedaddressed envelope and the couponwhich will be found on the last page.Rough sketches and circuit diagramscan be provided, but it will be neces-sary to charge a special fee (which willbe quoted upon request) for detaillayouts and designs.

g.tMAA, AZAAM, MAIMnWireless Telegraph Co., Ltd., Marconi House,Strand, London, W.C.2, and state in yourletter that you have a four -valve home -built

set which you wish to sell. Further, requestinformation regarding what royalty fee isrequired and any other details which willfacilitate your selling the set.-L. C.Poor Earth.

Q.-I find that when I disconnect my earthwire from my receiver I get much louder signalsand better results than with the earth wire con-nected. Can you account for this and suggesthow I may get the better results with the earthlead connected. Without the earth lead the setis very prone to oscillation when tuning.-G. D,(Sevenoaks).

A.-Your experience points to the earth leadhaving a high -resistance. You should try tofind a better earth connection and in thisrespect we should suggest a shept of copperabout 2 ft. square sunk at least 4 ft. below thesurface of the ground. Several lengths ofinsulated copper cable should be soldered tothe earth plate and all of them should be takendirect to the earth terminal of the set. Be sureto use copper wire for the earth leads and alsofor the aerial, as this ensures a reasonablylow -resistance and therefore good results.Using a smaller aerial tuning coil or reversingthe connections to the reaction coil may alsoimprove matters.-C. L.

" THE WIRELESS CONTROL OF MODELS " (Continued from page 6o3)

bell movement) should be so mounted thatwhen it functions its hammer strikes thecoherer.

The relay should be mounted eitherat the side or behind the decoheringdevice.

In the lower portion -of the casethe magnetically -operated pneumaticdashpot device and selector shouldbe mounted alongside of each other.Everything will now be ready forwiring.

Ordinary electric light twin flexis excellent for the wiring. A wiringdiagram is shown by Fig. io.

When the wiring is completed itwill be necessary first to test out thewhole apparatus electrically.

The 4 -volt accumulator whichsupplies electric current for operatingthe various mechanisms should befully charged and the dry battery ingood condition. Being assured ofthese important matters, the switchinserted in the coherer circuit beingclosed, the selector should functioninstantly each time two of the aerialterminals are short circuited.

The apparatus is now ready for awireless test. Should the apparatusfail to function, it will generally be found,:that either there are insufficient filings in

the coherer, or else there is a loose con-nection somewhere in the wiring.

COHERER WITHPEDESTAL

/7ERIgL

ORSHPOTVEIICE

(BELLOWS/WSW,

SELECTORELECTROAgo/YET

RR/1Y

4V IICCUM.1"ORCO/Y/YECTIO/YS FROM

4 VOLT

OTHER SOURCE Or 17CCUAto

EL EC TRICNL E./VERO 1'1

AERIAL

COHERERCIRCUITBATTERY

SWITCH

IRE/AYCONTACTS

SWITCH

SELECTOR9CONTRCIS

lilt

MODEL

Fig. 10. The circuit arrangements of the Receiving Gear

Assuming everything is in order, and thetransmitter described in previous articles

is ready for use, it will be well to carry outthe first wireless test by tapping the morse

key in the transmitter, when thereceiving apparatus should instantlyfunction. When this is done, and ifeverything is satisfactory the micro-phone fitted to the transmitter canbe tested by speaking the word"stop" in a loud voice near thediaphragm. The receiver shouldthen instantly function the same aswhen tested in the ordinary way.It will be found that best resultsare obtained when the aerial rodsare opposite and parallel to oneanother.

If it is desired to control a modelelectric train, the locomotive ofwhich is fitted with a " sequencereversing mechanism, it is onlynecessary to connect the remainingtwo terminals of the receiver withthe " conductor " and "outer " railsof a model railway, and close theswitch (secured to the receiver) in-serted in the main circuit, when someextremely interesting effects can beproduced by shouting the words"ahead," "stop," and "back," insequence into the microphone of,the transmitter.

(CoxcLusioN)

V V \°A)/ VV / 7

APRIL 20, 1929

12(9°DIOGR(IA/1-43

®April 8 the north regional studioswere removed to Broadcasting House,

Manchester, which comprise, in additionto the necessary offices, a concert hall, twostoreys high, with a gallery foi an audienceof about eighty people. In the same build-ing accommodation has been found for adramatic and sound -effects Studio and thenecessary echo -room.

Listeners should not miss the vaudevilleprogramme to be broadcast by 2L0 and5XX on April 27, for during the entertain-ment they will hear the Albert SandlerTrio, Ronald Frankau, Claud Hulbert andEnid Trevor, Deslys and Clark, and ClaraEvelyn, the musical -comedy star.

On the occasion of the Newspaper PressFund Dinner, to be held at the MayfairHotel on April 23, the London station willrelay the Prime Minister's speech propos-ing the toast of " Journalism." On thisevening Sir James Barrie's manuscript ofhis short play The Twelve Pound Looh isto be auctioned, by Sir Herbert Morgan,and the sale will be included in the broad-cast.

On May i Billy Mayerl will pay a returnvisit to the Savoy Hill studio to giveanother illustrated talk on the playing ofdance accompaniments.

A Mad Mummer's Bright Dream, byCharles Brewer, with Tommy Handley inthe part of Mummer, should prove a livelyentertainment on April 23; he will beassisted by a strong cast.

The Eternal Waltz, a musical burlesqueby Leo Fall, is down for broadcast from2L0 and 5XX on May 3; the book is byR. E. Jeffrey.

In a Festival of Music and Drama to begiven at Canterbury Cathedral during theweek August 19 to 24 the B.B.C. will pro-vide the orchestra, of which the conductoris to be Dr. Adrian Boult. Apart fromchoral, orchestral, and 'chamber concerts,the dramatic side of the festival will in-clude Everyman, acted outside the Cathe-dral, and Marlowe's Dr. Faustus, presentedby the Norwich Players from the Madder -market Theatre.

It is expected that within the next fewweeks experiments in broadcast televisionon the Baird system will be made throughthe Konigswusterhausen transmitter. Inthe meantime Berlin (Witzleben) is testingthe Mihaly Telehor apparatus for the trans-mission of cine films, on a frequency of9,000 kilocycles.

According to a Vienna wireless journal,a transmission from Rosenhuegel waspicked up at Chicago, Illinois, U.S.A., onFebruary 26 last. The Affierican fan statesthat he was using a 14 -valve receiver 1

603

Although attempts were made by severalEuropean transmitters, Vienna was theonly short-wave station able to secure two -Way communication with the Zeppelinairship on its recent flight across SouthernEurope. Messages from Dr. Eckener, itscommander, were received on i,o2o.metres.

Announcements are now made fromPC J (Hilversum) in the Dutch, German,French, Spanish, and Portuguese lan-guages.

Arrangements have been made for theregular relay by the Italian broadcastingstations, of performances from the- ScalaOpera House, at Milan; the Royal Theatre,Turin; the Carlo Felice, Genoa; the, SanCarlo Theatre, 'Naples; and the RoyalOpera House, at Rome.

Since the opening of the Turin andGenoa* broadcasting stations the numberof registered licences in Italy has attained6o,000; it is computed, however, that thereexist in the country nearly one, million:pirates, and drastic steps are to be takento induce these illicit owners to legalisetheir status as wireless listeners.

The new short-wave transmitter to beerected at Rome will possess a power ofsome 12 kilowatts in the aerial. It hasbeen decided to adopt two wavelengths,namely, 25 metres for transmissions des-tined to the Italian colonies in Africa and8o metres for Europe. The 50 -kilowatthigh -power broadcasting station to beinstalled in the capital will be supplied bythe Radio Corporation of America towardsthe end of the_coming summer.

It is proposed that a Scottish Councilfor Schodl Broadcasting should be set up,consisting of twenty-fi'o members repre-senting the various bodies dealing witheducation in Scotland.

The musically inclined of Messrs. Har-land & Wolff's employees are provingthemselves capable of providing a Belfastwireless programme from their own re-sources. The Queen's Island Military Bandis the only flat -pitch military band, in thecountry, and is already well known onthe ether, while the Male Voice Choir hasgained distinction at many contests.

In view of the dissatisfaction of Edin-burgh listeners regarding the quality oftransmissions, the B.B.C. point out thatthere is a system of lines available on az4 -hour basis between Glasgow, Dundee,and Edinburgh. Hence, if the trans-missions of 5XX as received at Edinburghare unsatisfactory, due to fading, inter-ference or other causes, the London pro-gramme can be taken from the relayingreceiver at Dundee or Glasgow, or a localprogramme substituted.

More than 500,000 letters were receivedfrom protesting listenerS when the FederalRadio Commission ordered a reduction inthe broadcasting time of station WGY atSchenectady.

mateur

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TO PERFECT RADIO

In addition to their own extensive range,PETO SCOTT offer YOU Every KnownRadio Receiver or Component-all on

EASY TERMSThe following list is merely representative, andwe ask you to fill in the coupon below or send us

a list of your requirements.THE FIVE GUINEA PORTABLE, described in this

issue. Send only 10!-, balance in easy payments.COSSOR MELODY MAKER Send only 10/-, balance

in 11 monthly instalments of 14/7.MULLARD MASTER THREE STAR. Send only 10/.,

balance in 11 monthly payments of 15/3.

LEADING MAKES OF H.T. ELIMINATORS from417 down. Balance in 11 monthly payments of 4/7.

ARCADIAN PORTABLE. Kit of parts (see "A.W."March 30), Send only 201-, balance in easy payments.

EXIDE 120 -VOLT H.T. ACCUMULATOR 2,500 rotahours, with crates. Send only 6/11, balance in 11monthly payments of 6/11.

"A.W." ALL MAINS TWO. Kit of parts. Send only15/-, balance in easy instalments.

Build your own set the Easy Way NOW!Our Catalogue contains an leading makes of Re-ceivers, Accessories, Kita of Components for theHome Constructor.

Mail Confirm in unsealed enyeloke under Id. shrink.

PETO SCOTT ElkPlease send me your big Illustrated Lists

NAME

ADDRESS

A.W. 20 411=111mil OIM 101 Imam Nom= e OMNI

Free Demonstntions sad Advice by QualiSei Engineers atcar Shops :-


4, MANCHESTER STREET, LIVERPOOL.33, WHTIELOW RDAN

CHESTER.,CHORLTON.CUM.HARDY,

M

44 TONE- SUPERB "Baffled Floating Cone

Employing a 16 -in. Bafflewith our famous 10 -in.impregnated kraft cone.Completely asserr bled coneof correct angle, suspendedwith extra supple skin.The reproduction of theBess without sacrifice ofthe Treble, is reallyamazing.Supplied as illustratedwith pamphlet showingmethod of unit mounting.

PRICE 5/6, post 9d.

Write for further details.

WARRICK RADIO16 BERTHER ROAD, HORNCHURCH, ESSEX

CABINETS for ALL "A.W." CIRCUITSThat set you've constructed it's worthy, of a first-classcabinet isn't it? Yes! Well then let me have particulars,(panel and baseboard size) and we will house your set in awell made hand french -polished cabinet, at a price well Withinyour reach, under a guarantee of satisfaction or money back.Baseboards 9d. per square foot cut while you wait.

For promptness, courtesy and satisfaction deal with:-F. W. RAMSEY, 63 Shaftesbury S:., London, N.I. Clerk 7139

OUR BLUEPRINT SERVICEConstructors of receivers described inthis Journal should make full use ofour Blueprint Service and avoid all risk

of failure.164111.11101.010,1111116.

From Our Own Correspondent

1VIR. DAY asked the Prime Ministerwhether, in view of the increasing

public interest in broadcasting, consulta-tions had taken place this year with theleaders of the opposition parties of theHouse with a view to broadcasting the forth-coming Budget speech.

Mr. Baldwin said he had no reason tothink, since the question was last raised,that there was any change in the generalfeeling of the House that the broadcastingof its proceedings was undesirable.

Sir W. Mitchell -Thomson informed Mr.Day that the -present number of wirelessreceiving licences issued free to blind per-sons under the Wireless Telegraphy (BlindPersons Facilities) Act, 1926, was 14,372,representing a remission of licence revenueof £7,186 a year.

TRADE NOTES

SUBSTANTIAL reductions have recentlybeen made in the price of Cyldon con-

densers, and a folder giving details and thelatest prices may be obtained from SydneyS. Bird & Sons, Cyldon Works, SarnesfieldRoad, Enfield Town, Middlesex.

Price reductions have been made in con-nection with Siemens H.T. batteries forportable sets, we are informed by SiemensBros. & Co., Ltd., of Woolwich. The priceof the 126 -volt battery, type 1075 has-beenreduced from 3os. to 25s. and that of theo8 -volt type 1077 battery from 25s. to

2 1 s. 6d. It should also be noted by construc-tors of portables that the length of thewell-known 6o -volt popular type batteryhas been increased from inches to 9inches.

Garnett Whiteley & Co., Ltd., makersof Lotus sets and components, inform usthat they have now taken offices at 125High Holborn, London, W.C.r. The Lon-don representative of the firm is Mr.W. J. Holland.

The Mullard Wireless Service Co., Ltd.,of Mullard House, Denmark Street, London,W.C.2, have issued .a number of leaflets forinsertion in readers' Mullard catalogues.These leaflets, replacing the leaflets VR47,54 and 55, and VT17, which should bedestroyed, deal with the PM6, PMIHF,PM256 and DO/4o valves respectively.Two new leaflets have also been issuedgiving details of the DFA9 and DO/2ovalves.

A- constructor's chart for building up theFerranti type No. 5 A.C. H.T. supply unit(giving an output up to 200 volts and loomilliamps as required), has been issued byFerranti Ltd., Hollinwood, Lancashire.


5/9 each.

DUAL ILMULL AR

COD SandBritain'sFavour-ite ThreeDual Coils7/9 and 10/6

TWO - PINCOILS

all types Illustration of our Cossor Circuit Dual

from 1/6 Herten Coil,and susliztgoiltxt. mounting

APRIL 20, 1929

"POPULAR" TRANSFORMERWhen planning your new set ensure perfectamplification by including a Brownie 'Popular.Transformer as recommended by AMATEURWIRELESS for use in a number of their specialcircuits. The core iron and the windings, whichare the very finest obtainable, are assembled in thefamous Brownie Factory; while all the delicateparts are protected by an attractive mouldedBakelite casing which seals the whole transformeragainst any atmospheric interference. Send P.C.to Dept. 23 at address below for free booklet.

Wireless without Worry."

BROWNIE WIRELESS CO. (G. B.) LTD.Nelson St. Works, Mornington Crescent,

LONDON, N.W .1


and CHOKESCLARION THREELI SS EN THREECOSSOR THREE

and all other

SCREEN -GRIDCIRCUIT COILSat 21/- per pairRange 20012000 metres

for Panel Mount-ing, Valve HolderBase, or 6 - pinBase Mounting.

TURNER & CO. fINISZTIO:NRDi

APRIL 20, 1929 605 ematturWireiT

I) ROADCAST TELEPHONY(Broadcasting stations classified by country and in order of wavelengths)

Hilo- Station and Power Kilo- Station and Power Kilo- Station and PowerMetres cycles Call Sign (Kw.) Metres cycles Call Sign (Kw.) Metres cycles Call Sign (KW.)

GREAT BRITAIN 291.3 1,030 Radio Lyons -. 1.5276 2,c8o TurinITALY25.5311,752 Chelmsford 302 999 Bordeaux (PTT) 0.5... 7.0333 1.5goo Naples (Napoli)

- (58W) 15.0 204775 Genoa293.9 x,230 Newcastle (5NO) 1.0 305 387 9.0

258.4 r,i6z Leeds (2LS) ... 0.1:1 322 443.8 676 Rome (Roma).- 3.027(1.3 1,109 Sheffield (6LE) 0.13 336 89a

353 849 ta2 56;85Bolzanolan 0.3

7.0288.5 1,040 Bournemouth(61351) 1.0 370 817

JUGO-SLAVIA382.2 7.55288.5 1,040 Bradford (2LS) 0.13400 749 308.3 973 Zagreb (Agram) 1.25288.5 ',no Edinburgh 452 664 Belgrade ,,,..... 4.0414 724, (2EH) 00.2 7 3/5 Ljubljana 5.0288.6 1,040 *Hull (6KH) 0.2

288.5 1,040 *Dundee (2DE) 0.13 928 701 LATVIA288.5 7,040 *Liverpool (6LV) 0.13 430 697 523 367 Riga 2.0

*Stoke-on-Trent204.1 /Aso551') 0.13 448

2,0f, 0 1500ITIrovAnNo IA

15.0294.1 2,020 *Swansea (5 X) 0.13302.6 gg.t.7 Belfast (2BE) 1.0311 964 Aberdeen (2BD) 1.0323 928 Cardiff (5WA)... 1.0358 838 London (2L0)... 2.0978 793 Manchester

(2ZY) 1.0996 757 Plymouth (SPY) 0.13401 748.3 Glasgow (6SC) 1.0482 62a Daventry Ex.

(5GB) 25.01,504 zga 1Daventry

(5XX) 25.0 Relay stations. (Relays 2L0.

AUSTRIA248 2,209 Linz 0.6277.8 1,090 Salzburg (under

construction) 0.5254.2 847 Gras 0.5456 694 Klagenfurt 0.5456 094 )nnsbruck 03620 577 Vienna 20.0


Brussels 0.5275 7,090 Ghent 0.6280 1,070 Liege 0.5312 gto Anonl 0.25512. .85 Brussels 10.0

CZECHO-SLOVAKIA265 7,128 Kosice 2.0278 x,080 Feriby (testing) 12.0299.3.7,000 Br'tislava 4.0343 873 Prague (Praha) 6.0432.3 694 Braila (Brno) 2.4

DENMARK883 Copenhagen

(Kjobenhavn) 1.0s 6o Kalundborg . 7.5

ESTHONIA408 735 Reval (Tallinn) 1.3

FINLAND374 £00 lielsingfors

(Helsinki) 0 81,542 199 Lahti 20.0

FRANCE80.75 9,755 Agen 0>25200 1,500 Fecamp 0.3211.3 7,420 Dealers 0.1238 x,a6o Bordeaux (Radio

Sud-Ouest) 2.0245 1,254 Lille (PTT) 0.8252.1 1,190 Juan-les-Pins 0,4253 2,185 Montpellier 0,25254 r,s8o Rennes (PTT) : 1.0255 1,175 Toulouse (PTT) 1.0208 1,118 Strasbourg 0:3274 7,592 Limoges (PTT) 0.5

4731,4701,755

982 Marseilles (PTT) 0.598s Agen 0.3930 Vitus (Paris) 2.0

Petit Parisien 0.5Algiers (PTT) 2.0Radio LL, Paris 1.0Toulouse (Radio) 9.0Mont de Marna 0.4Radio Maroc

(Rabat) 2.0Grenoble (PTT) 1.5Radio Flandre

Lille 0.25(68 Paris (Ecole

Sup., PTT) 0.7635.1 Lyons (PTT) 5.0203 Eiffel Tower 8.0271 Radio Paris 8.0

GERMANY219' 1,370 Flensburg 1.5go 7,250 N kitbag 4.0250 1,200 Kiel 0.7250 7,200 Cassel 0.7263.2 1,740 Cologne 4.0267.8 1,120 Muenster 1.5273.1 1,09.5.8 Kaiserslautern 1.5280.4 1,070 Kilnigsberg 4.0284 1,056.7 Berlin (E) 0.7284 1,056.7 Stettin 0.7284 7,056.7 Magdeburg 0.7817.5 945 Dresden 0.7a320 937 Breslau 4.0326.4 grg Gleiwitz 6.0929 910 Bremen 0.75801.0 Le' 4.0874.1 8o2 Stuttgart991.6 766 Hamburg 4.0423 Frankfurt 4.0455.9 654 Danzig 0.75456 651 Aachen 0.75462.2 649 Langenberg 25.0476 63o Berlin 4.0537 559 Munich 4.0566 530 Augsburg 0.5566 530 Hanover 0.7577 5so Freiburg 0.7

1,050 r8a Zeesen 20.01,650 38a Norddeich 10.0


1.280334.2 Radio Luxembourg 0.25


(PCJ) 25.038.8 Kootwijk

(PCL) 32.0(Wed. 12.40 G.M.T.)

825.6 813 Huizen (until5.40 p.m.) 5.0

1,075 279.2 Hilverstun(ANRO) 5.0

1,f 32 262 Huizen (after5.40 p.m. and on

Sundays) 5.01,082 ifs Scheveningen.

haven 5.0


t ICELAND833.3 goo Reykjavik 1.0

IRISH FREE STATE222.2 1,311 Cork (5CK) ... 1.5411 732 Dublin(2RN) 1.5

,240NOREIrkAanY242 z

1,010 Notoddea1.0

32 ,,69

38057Bergenraeiesui

drknsrad1.0.0.7

6931.01.01.5

608 350 Maniac 0.71.0

314 953 Cracow1.5V76, 5 78:20 1Piattnowitz

1.5

956 658 Wilno10.0

1,395 2/5 Warsaw 10.01.5



ROUMANIA805 757 Bucharest 4.0

RUSSIA825 363.5 Moscow (PTT) 25.0925 323 Hemel ....1 2.5

1,000 300 Leningrad 20.01,442 208 Moscow 30.01,6a5 178 Kharkov 15.0

SPAIN314 956 Oviedo (EA J19) 0.5350 855 Barcelona(EA J1) 3.5370 8or Seville (EAJ5) 0.5400 750 Radio Espalia 1.0405 744 San Sebastian

427 '703 Madrid (0Jj78)) (81436 658 Salamanca

(EAJ22) 0.55

SWEDEN261 1,750 H firby 10.0265 1,230 Trollhattau 0.4333 goo Falun 0.5346.8 865 Goteborg 0.0437 686 Stockholm 1.5645.5 55o Sundsvall 1.0770 390 Ostersund 2.0

1,200 25o Boden 2.01,942 223 Motala 30.0

SWITZERLAND408 739 Berne 1.0489.4 613 Zurich 0.0680 44r Lausanne 0.0760 395 Geneva 0.5

1,010 297 Basle 0.25


Parts for " Britain's Fal7ouriteThree." -In the advertisement of Messrs.H.' & 13. Radio, Ltd., which appeared inour issue of 6, the price for the kit ofcomponents for " Britain's Favourite Threede Luxe" does not ,iticlude the dual -wavecoil. If this coil is required the total costis increased by los. 6d. The number ofthe Blueprint of this famous set, bythe way, was 'not very clearly printed insome copies. Readers wishing to order itshould note that the number is A.W. 179.

Seventeen stations are now licensed fortelevision in America, They will broadcaston three short wavebands, ranging from2,000 kilocycles to 2,95o kilocycles.

1.11)/ecoot_ct

"GRAWOR"Comes to your aid !

THE " SECTORPHONE "LOUD - SPEAKER CHASSISembodying the famous" Grawor " Double MagnetUnit and an entirely new andPatented design of diaphragmhas set a new standard inreproduction.Every independent test has provedthese statements.The " Grawor" Unit fitted has apowerful double Magnetic System.

Balanced armaturemovement. PerfectReed adjustment.Carries full loadswithout a vestige ofdistortion.SECTORPHONE'Chassis with" GRAWOR " Unitmounted ready forimmediate u s e.Size,12 V2in. square(see illustration).

Price. With Double Magnet Unit 53/ -With Single Magnet Unit 48/ -

Obtainable front all Dealers, or direct.

HENRY JOSEPH,11 Red Lion Square, London, W.C.1Sole Agent and Licensee for Great Britain

VISIT THE

WIRELESSEXHIBITION

(April 15 to May 8)

YORK HOUSESouthampton Row, London, W.C.1

(Corner of Theobalds Road)

DEMONSTRATION OF ALL SETSHIRE-PURCHASE ARRANGED

A HIGH-CLASS SHOW OF ALL THELATEST SETS

"A.W." Solves Your Wireless Problems

o

it RECEIVER atirrQ

UP TO DATE! te.\Fit a Bulgin Multi Coil and Electrostatic Condenser asillustrated. The alteration can be effected in half an hour. aiii14If you will forward to us the diagram of your present con-nections, we shall be pleased to show you the new wiring. ' PRICE 5/6 EACH

SEND FOR OUR FREE 56 PAGE CATALOGUE & WIRELESS MANUALA. F. MAIN & CO., 9-10-11 CURSITOR ST., CHANCERY LANE, LONDON, E.C.4

RADIOPRODUCTS

ernakar Wtrete 606 APRIL 20, 1929

441

ELECTRADIXBARGAINS

GRAMOPHONE MOTORS. Electric A.C. or D.C.Powerful full size Panatrope model with vertical doublesuspension slung electric motor with silent reductiondrive to 12 in. Turntable. Aluminium frame, overalldimensicns 111 in. long x 61 in. wide x 81 in. high.Total weight 8 lbs. 8 ozs. Identical type used by leadingGramophone Companies for big halls. Motor wound 100volts for use on any mains voltage with series lamp orfixed resistance. Takes 20 watts only. This B.T.H.Electric Gramophone Motor is a very efficient and reliableinstrument, which is capable of playing two hundred 12 -in.records at the cost of one unit of electricity. With a lampor small resistance, the motor can be operated on anysupply circuit from 50/250 volts D.C., or 100/250 -volts25/60 cycle A.C. The Motor is silent in operation, andthe speed perfectly constant. Every precaution has beentaken to minimise wear and vibration. List Price, £6 6s.Sale price, 45/., and guaranteed O.K.

CHOKES. Special offer of 30 Henry large output couplingor smoothing Chokes by the Marconiphone Co., Capt.Round's design. It is a really good choke for a load of100 to 160 milliamps it is still a long way from saturation:The only choke, at a popular price, which can be used forsmoothing, where series connected filaments are used.As an Output Filter Choke it can be used equally wellafter a super -power valve, or several power valves inparallel. Listed, 27/6. Sale price, 7/6.

TRANSFORMERS. B.T.H. latest design Intervalve andvarious special ratios, 10/. each. B.T.H. POWER Modelfor 220 volt, 50 cycle A.C. mains. With centre tap L.T.for two rectifier valve supply. centre tap L.T. for Amplifierfilaments and centre tap H.T. for Anode supply. List65/-. Sale 25/. only.

MOVING COIL LOUD SPEAKER PARTS.Genuine B.T.H. Rice -Kellogg CONES fitted 11 in.Moving Coil and flexible floating leather edge with flangefor fixing to baffle board. Slightly soiled only 7/6 each.A few only Marconiphone centre -suspension CONESwith brass rod to fit on magnet and with 1 in. MovingCoil at apex. 10/. each.

ELECTRO-MAGNET POTS. Marconiphone 6 -voltMagnet Pots. Brand new, takes amp. Just the thingfor your home-made M.G. speaker. Takes I in. MovingCoil. 20/. each.

3.VALVE POWER AMPLIFIERS. For working directoff mains supply A.C. Fitted B.T.H. Power Transformerfor 2 -valve Rectifier. Resistance and Transformer coupledwith Choke output. Cost £30. Sale price, £4 5s. each.D.C. mains model, 65/.. 3 -Valve receivers, 27/6.

WESTON MICRO GRID -BIAS METERS. One shouldbe on every wireless set. Sensitive Moving -coil, flushPanel Model 375 with 21 in. dial; indicates 30 -millionthsof an ampere per Division for use in Grid Bias circuits foradjustment to zero G.B. current. Excellent as Milli -voltmeter, Bridge Galvo, Micro -ammeter or HeterodyneWavemeter Indicator as needle in centre zero. Thesefiatne357.e.ters are Listed 65/.. but are offered during Sale

WIRE. There is such a terrific variety of insulated wire of allgauges, copper and resistance wire that it would take apage tolist it. We must therefore ask customers to kindlyspecify the sizes that interest them and we shall be pleasedto quote. Principal items are wire for winding short waveinductance coils 22 -gauge copper cotton -covered overenamel. This is specified in the Service to prevent losses,List, 2/.16.; Sale price, 1/3 per lb. i oz. reels silk -covered28 -gauge wire, 4d. Fine 5-36 silk -covered wire, 12 yards,9d. Heavy twin flex V.I.R. 35-40, 2J6 per dozen yards.Twin red and black flex, 12 yards, 1/6. Single enamelledand cotton -covered insulated wire for phone extension,100 yards, 10d. Twin bell wire, 2 colours, 3/- per 100 yards.Single 1-044 Insulated V.I.R. Cable. 5/6 per 100 yard coil.

PHONE CORDS. Single, 6d. Double head, 10d. Brownsindestructible double headphone cords, 1/.. Loud-speaker long twin cords, 8d.

April Edition of our Surplus Bargains fn Radio and reerriealGoods ready. Send stamped addressed envelope for large sale

list. SAVES RADIO USERS POUNDS.

ELECTRADIX RADIOS218 Upper Thames St., London, E.C.4Blackfriara Station, Underground Railway. City 0191.

V7VVYTTYYVVYYYTYVVVYVVVYYMV

Solved !You will find all those little pro-blems that crop up when you areexperimenting solved in the

Letts' Amateur Wireless1929 NOtebook Diary

Post free, in two bindings, 1/9 and 2/9AALAAAAA



The " Home and Abroad Two "SIR,-I am sending an appreciation of

the "Home and Abroad Two." I havejust finished it and get such good results,having had KDKA within about an hourof wiring up the set,-R. (Battersea).

" Britain's FavoUrite Three "SIR,-Having waited a week to see the

details of the 1929 "Favourite," I,

hasten to congratulate you on a fine set.I have been using the 1928 "Favourite"since its publication and welcome the no -coil -changing idea .-T. (Tipton).

5XX ProgrammesSIR,-Your correspondent ".British Six"

(Penzance) says he imagines I have anumber of stations at my disposal. Suchis not the case. I have a two -valve setAnd,except at lunch-time, I use only one y41veand headphones.

My set is tuned to 5XX, and I rarelytry to receive any other station. The onlytimes I have heard foreign transmissionshave been relays from Daventry from thesets of friends a few times.

All I can say about foreign programmesis that what I have heard of them-exceptfor the relays-I can very well do without.I don't like the whole of the British pro-grammes, but some of the things I dislikeare enjoyed by others, and the many appre-ciations I have heard have been made bylisteners who, like myself, listen to 5XXand 5GB programmes.

-A. M. H. (Coventry).

Sunday BroadcastingcIR,-I am an interested reader of

"Thermion's" columns which appearin AMATEUR WIRELESS, and usually I amin agreement with suggestions he makesfrom time to time regarding broadcasting.

But there is one point on which, I think,a certain amount of unintentional unfair-ness appears; that is, the extension ofbroadcasting hours on Sunday.

The unfairness lies in the lack of con-sideration (to my mind) for the amateurtransmitter, who would, in that event, losethe only remaining time of freedom left tohim for daylight research. I think you willagree that we are entitled to a certainamount of -Aught, as we pay considerablymore for our licences.

If all B.C.L.'s were technicians andcapable of building and operating highlyefficient receivers, then everything wouldbe O.K., but, as it is, there are still crowdsof crystal sets about, and with these-well, in my own case, I cannot key evena 5 -watt transmitter without wiping outmy neighbours on either side, who are

both using crystal sets purchased about1923.

I would like to have "Thermion's" viewson this, but I think you will realise thatwe are not unreasonable in pleading for theretention of the little time we do have onSundays.-G2AX (London, N.).

Publid BroadcastsSIR, It has been suggested that broad-

casting theatres should be opened. Ithink perhaps the following experiencemay be of interest. I have. control of apublic hall in the centre of Portsmouth andapplied to the magistrates for permissionto hold concerts on Sunday nights. Thiswas refused, but I was allowed to repro-duce the B.B.C. programme between the'hours of 8 and to p.m. The result was acomplete failure.

On the first Sunday about 270 attended.The service came from St. Martin -in -the -Fields and was followed by a good concert.The set employed was quite a good one.By the end of the evening I formed theopinion that, whatever might be the suit-ability of the programme for home recep-tion, it was perfectly hopeless for publicreception. There are nearly always longintervals between the items, which wouldhardly be, noticed if one is reading a book,but which are very noticeable in a publichall. The charitable appeal, news andweather report are all exceedingly dull.

That my opinion was shared by theaudience is proved by the fact that on thesecond Sunday only about half the numberturned up, and on the third and lastSunday the audience had dwindled to 40.Of course, if I had had the freedom toreproduce any programme I liked, theresult might have been different, but I donot think that any public broadcasts arelikely to be very popular Until the broad-casting authorities realise that people wantwireless for amusement-not for educationnor religion-and also realise that it isdesirable to shorten breaks between items.

-F. P. (Sbuthsea).

Our Best Comedian ?SIR, -I notice with regret in your issue

dated March 3o that Mr. Moseley con-siders Leonard Henry our first comedian.I had 10 re -read the paragraph to makesure that my eyes did not deceive me, andI consider it a great insult to TommyHandley. Had Mr. Moseley heard hischoice of comedians last week and againthis week, I feel sure that he would havealtered his opinion. --N. S. (Leicester)

We much regret that in the advertise-ment of Messrs. Partridge & Mee, whichappeared in our issue of March 3o, theblock of the Heavy Duty choke appearedupside down. If readers will refer to thearticle in the same issue on "How toObtain H.T. Supply from the Mains" theywill see the correct way of mounting thischoke.

APRIL 20, 1929

BLUEPRINTSIndex Sitters " A.W." refer to "to " Wireless Magazine " sets.

el'17Mf 7:Magazine "001

:n1o Amateur containing ds-rriptions of all these sets can be obtabitedat Is. 3d. and 4.1. respectively, post free.Amateur Wireless" sets and " W.M."

girl

CRYSTA1929 Crystal Receiver

ONE-VALVBeginners' One-valverReinartz One .

Post Free

L SET (6d.). Aw165

E SETS (1s. each)

Aw 140wmi27

TWO -VALVE SETS (Is. each)East to West Short-wave Two (D. Trans.)Beginner's Two (D, Trans)Auto Two (D, Trans) ...All -Mains Two (D, Trans) ..Key -to -the -Ether Two (D, Tram)Meteor Two (D, Tram) .. Clipper Two (D. Trans)Twinflex (Reflex)

AW159/XVIII 71AW174AW18oWM1o7W114114WMI35

.. WM138

THREE -VALVE SETS (ts. each)MI -wave Mains Three (HF, D, Trans, Rectifier) AWt 44All-purpose Short-wave Three (ll, RC, Trans) AW147Screen -grid Q Coil Three (HF, D, Trans) AWt5oAll-BritagiThree (HF, D, Trans) AW158Bantam Three (D, RC, Trans) AW t 6oHartley Dual -range Three (ll, RC, Tram) AW166Listener's 'three (HF, D, Trans) price 4d. free

with copy of "AW" AVI/169The Binowave Three (D, RC, Trans) AW172Clarion Three (SG, D, Trans) AW1751929 Favourite Three (D, RC, Trans) AW 179Everyday (D, z Trans) WM521All -wave Screen -grid Three (HE, D, Trans.) WMItoStandard Coil Three (HF. D, 'Frans) WAI117

WMtt3WM120

.. WM t23WNIx24

. WM 29.. WM 13 t.. WM136

Festival Three (D, 2LE-dual Imp.) ..Wide -world Short -waver (SG, D, Frans)New Year Three (SG, D, Pentode) ..The Q3 (D, RC, Trans)Lodestone Three (HF, D, Trans) ..Simple Screen Three (HF, D, Trans) ..Dynamic Three (SG, D, Trans) ..At Home Three (D.2RC) . WM141

FOUR -VALVE SETS (1s. 6d. each)Overseas Short -waver (HF, D, 2Trans)The Ranger( SG, 0, RC, Trans) ..Broadcast Picture Four (HF, D, 211C) .

Orchestra Four (D. RC, Push-pull) ..All Europe Four (2 HF. D, Trans) ..Stability Four (H.F, D, RC, 'Trans)

AW133AWI43AW 63AW 67AW173AWx 82

"Q "-coil 4 (HF,D, RC,Trans).. WM7tFive -pounder Four (HF, D, RC, Trans) .. WM9tTouchstone (HF, D, RC, Trans) WM1o9Reyner's Furzehill Four (SG, D, zTrans) WM112Economy Screen -grid Four (SG, ll, RC, Trans) WM ti3Binowave Foul (SG, D, RC, Trans) 'WM [ 19Standard -coil Four (HF, D, 2 RC) WM122Dominions Four (2SG, D, Trans) .. WM134The Drum Major (HF, 13, RC, 'Frans) .. WM t37

FIVE -VALVE SETS (1s. 6d. each)" Q " Gang -control Five (2HF, ll, aTrans) AWOLEmpire Five (a SG, D, RC, Trans) .. WM95Fidelity Five (HF, D, 2 RC) WM13o

SIX -VALVE SETS (1s. 6d. each)Short-wave Super -6 (Super -het, Trans).. AW 67Eagle Six (3 HF, D, RC, 'Frans) WITho6

AMPLIFIERS (ts. each)Screened -grid HF Amplifier . " A.W." Gramophone Amplifier (3RC)Searcher Unit (11E1 .. . ..Gramo-radio Amplifier (2v) (Trans.)Signal Booster (HF Unit) .

Auditrol Amplifier

AW138AVV162

.. AW176WM7aWMi28W/Mr32

MISCELLANEOUS (ts. each)H.T. Eliminator for A.C. (zoo v. output) ,. AWio2L.T. and H.T. Mains Unit (D.C.) .. AW123Listener's Speaker, price 4d. tree with copy of

"AW" . AW170Arcadian Linen -diaphragm Loud -speaker (Full-

DT.tnit (We)1: . AWynA

AW s78Universal Short-wave Adaptor .. WM32Buzzer Wavemeter (ed.) .. WM121H.T. Unit for A.C. Mains ..Lodestone Loud -speaker .. WM t26James H.T. Unit for D.C. Mains WMt 33Short-wave Adaptor for Dominions Five WA114o

PORTABLE SETSHouse Portable (SG, D, RC, Trans) .. AW163 116Arcadian Portable (SG, 13, 2 'Trans) with

linen -diaphragm loud -speaker (half -scale) AWt 72 1/6£5.5.0 Portable (D.Trans.) AWISiChummy 4 (with modifications for LS

and HT) -. W M801 1;6Wayfarer Portable (Super -set) WM139 1;6

Send, preferably, a Postal Order (stamps over sixpencein value unacceptable) to Blueprint Service

AMATEUR WIRELESS 55-61 FETTER LANEFETTER

LANE

607 ((maim- PAT

C. 0. D where possible. SendOrders sent by return

order PAY POSTMAN

GENUINE IDEAL BLUE SPOTAdjustable Power 66K (101)4 -pole Balanced ArmatureComplete with Cord /-HANDSOME OAK POLISHED

PEAKER CABINETS 13 x 13 x 6

1 2 / 1 1 r,o3"

Cannot guarantee exactpattern of front panel,but all good designs.

TUNEWELLDUAL RANGE COILSClarion Aerial, 10 6. Clarion An-ode, 10 6. Lissen Three, each 10 6.

Cassor Three, each 10 8. All S.G.Circuit Coils 21,- pair, 200 2,000.Massive H.F. Choke, 5,9. MallardDual Coil, 7,9, P.M. 10AL Six -

pin Bases, 2,-.

Copper and Aluminium Screens, allsizes, or made to order, P.W.Screening Boxes, 12 6. P.W. Load-ing Coils, 7 6. Bailie Wave Selec-tor, 12 6. Tunewell Dual 3 Star,79. Combined Wave Q 3 Star.12 8. Scott's All -wave Tuner, 13/6.DX Set 4 short wave, 7,6. DX L.F.Standard Ratio. Weilo L.P.Power, 118. Weilo Standard, 8;6.Dubilier K.C. Condensers, FrictionControl, .0005 and .0003. each 12,l-.

Thumb Control, ditto, 15 6. TelsenRadio Grand L.F., 12,6. TelsenAce L.F., 8.6. Brown H.Q. Speaker,23,3,0, Amplion A.0.2., 21:-.M.P.A. Popular Plaque Speaker,2918L Ormond Turn -table for Port-ables, 6:-. Bulgin All -wave Toner.15,8. British General Tuner, 18 h.Wateg 3 in 1 Test Meter, 8,6.

Lotus Condensers, .0005, 6 9; .0003.

5 6. Colvern Muter 3 Star DualColl, 17 6.

W EA RITEDual Wave Tuner 15;-. H.F.Choke B.B. S.W. Choke 4;6.2 -way Switch B'-. 3 -way Switch7,'-. Loading Coil 7,6. TitanCoil Unit 15 -.

BLUE nSPOT da 5/-66K Shown above.

OR CABINET

BLUESPOT

12" CONEThe Lot Carr. Pd.

Aluminium Cradle withFitted Floating Cone 9"Takes all Bal. ArmatureUnits. Post Free 7/11

LEWCOSLewcosC.A.C.5,10,6;C.A.C.2012 6; C.S P.5, 1016; C.S.P.20,12,6; P4 to 14, 3/- each; PI6 to22,4". each. Touchstone Coils,311/. pair. C.T. Coils, 316, 5/3.Q Coils Q.A.,15/-; Q.S.P., 21 -;Q.A R , 21/. ; Q.A.A., 15,-;Q.S.G.. 21!-. All Incas Products.

LOTUS Q COILSQA, 15 - ; QSP 21-,MASTER 3 STAR 15 '-ALL LOTUS PARTS.

T RI °TRIM4 Pole Balanced

17/6ArmatureAdjustable Unit

ILLUSTRATED


Come to LEICESTER SQUARE TUBE.This address is at the back of Daly'sTheatre Phones Gerrard 4637 and 2821

HOURS OF EVERY DAY 9 to 8SATRDAY to 9BUSINESS SUN.U

9MORN. II to 1

DON'T FORGET OURWHOLESALE DEPT ALL LINES

. STOC KED.HOURS OF BUSINESS AS ABOVE.

WE STOCKWHOLESALE & RETAILBulgin, Ferranti, Ekco,Amplion, Celistion, Igranic,Lissen, M.P.A., Ediswan,Cossor, Colvern,Cyldon, 117e1li.lael,Watmel,Lewcos, Polar, Climax, Or-mond, J.B., Pye, Polymet,T.C.C., Dubilier, Lotus,W.B.,Philips, Mallard and all stan-dard COM pon en ts , al yes , le.

TRIOT RONU.S., Det., R.C., 5,2 each ;Power, 6/9. 2-v. or 4-v.

Post 6d. 13 post free).

DARIO MR A DC IR 0O-I2 -v. or 4-v. C.P. .. 5/6Super Power .. 7/6Super H.F., 2-v. or 4-v. 7/6


LISSEN PARTSALWAYS TN STOCK.

VALVESMallard, B.T.H., Marconi,Edison, Osram, Cosmos,Cossor, Six -Sixty, Dee.H.F., L.F., R.C., 10,6 each.Power 12/6, S. Power 15/-,S.G. 22/6, Pentode 25,'-.B.T.H.Tone-arm with Pick-up complete - - 451-D.X. Auto -Track Tone -arm

10/-Watmel Tone -arm - 7,6Goodman Cone ChassisAssembly 16,6Squire 97 do. 15/6Blue Spot do, - 12/6R.1.-Varley Pick-up - 03/-

CLEARTRONVALVES

Power or R.C. - 6/-L.F.,H.F. or Det. 4/ -Screen Grid. 2v. 12,6

POST 6e1. (3 Post Free).

A.W. FOUR VALVER " A.W.,"9

April 20th.192

SET OF PARTS -2 Ormond .0005 at Reaction .0001 atV-. 4 Sprung Valve Holders at 1)3. Q.A.A. Lewcos,Q.S.P., 21/-. Two .002, one each .0001 and .0003 fixed, 57-.H.F. Choke Wearite, 6/6. Ditto Watmel, 5f- (add balanceany other). 2 meg., 1/-. .25 meg.,1/-. 2 G.L.K. Holders,

R.C.C. Unit Lissen, 4/-. i00,00 ohm res. with holder,5/6. 2 M.F.D. Dubilier, 3/6. Lissen L.F., 8/6, completewith L.T. switch. 2 Strips. Handsome panel 18x7. 51.1 Engraved Terminals. Connecting Wire. Base-board.18x10. CARRIAGE PM)) U.K.CLARION THREE KIT OF PARTS

("A.W." 93-292 Punt .0(105, No. 3, at 5/9. .0001 Reaction 4,'..2 Dual range 4.7.T. (Tunewell), Anode, 10/0; Aerial,10/8. 3 Sprung V.H. at 1/3. Formoden,ser, "J," 2/-. Dub-ilier 1 mid., 2/8. .01 Fixed, T.O.C., 1/9. 3-meg. 1/-. 8,0ILK Choke, Peto - Scott, 5/.. 11.F. Choke, Lissen, 516.L.F. Transformer, 11.1. & Varley, 15/s. Ebonite Strips.140 Ebonite Panel. Screen, 8/x6. 8 Engraved Terminals.Push-pull Switch, Flex, Plugs, 10-9. Wire, 2 S.M. Dials.The Lot 70/- I I c -T FREE

.0002 Fixed and Series Clio I 6 extra.VALVESfor CLARIONS.C. 2.216. D 10/6. P 12/i.

(Mallard or Six -Sixty)

CATALOGUE(144 pages). 1/- refunded on

first 10'. order.

QUO TATIONSFOR SETS OF PARTSOVER 25/. IN VALUE(where possible)

LATEST SQUIRE 97RIGID ALUMINIUM CRADLE, FLOATING CONE.CLAMPING BOARD ASSEMBLED AND SPARE 15/6CONE KIT FOR ..

Ultra Short Wave Co:Isfor Cossor New MelodyWarr) and p. PAIR

Coltone / /(Post 61.)

ECKO UNITSFor use with S.G. Valves,A.C. with Valve and

Royalty - 78/681,12 87/6

D.C. 3F12 S.G. - 39/6ALL ECHO EASY TERMS

CLEARTRONS.C., 2v. .. 12 6C.T.15, L.F. or H.F... 4C.T.I5 x Power . 6'.B. FAV. 3 (DE LUXE)SET OF PARTS, 63 .

See issue April 13th forLIST OF PARTS.

Tunewell Dual Coil 6 -pin,7/9 ; Lewcos Short Wave,20/45 or 40/90, 7/6 extra.

O R M O N DS.M. Drum Dial, 5/-; Itheost ats.6,15,30 ohm, 2/-; Midget.00014/..: Log .0005 and 4 in. Dial, #31-;Log. .0903 and 4 in. Dial, 5/9.B.L.F. No. 3 same price. We alwaysclock all ORMOND PARTS.

OSRAM MUSIC MAGNETKit of Parts and Valves,

53 : 12 :6.Booklet Free.

LEADING HOUSE for

KITS OF PARTS

1,000 Mile RANGE on Tour 1927 COSSORLIST OF PARTS FOR CONVERSION

SCREEN ASSEMBLY -2 EX T R AS- Cossor S.G.Valve type 220 - - 2216Pair of Ilighwave Coils

12/6 PAIR'2 Cossor Pattern S.M. Dials

- 61- PAIRPOST EXTRA.

Coil Holders, McMichael Bin-ocular Choke, Peto-Scott.0001. Peerless Rheostat,Dubilier 1 M.F.D., InsulatedWire, 2 Coils for 200/ on/BOO metres. Post Free zrPI

A.W. SPECIAL COUPON (64)FOR EVERY 30/- you spend retailYOU CAN buy ONE of the following for

3d. each extra (on this Coupon)H.F. Choke, Silk Loud -Speaker Cord, 9 -volt GridBias, Pair Panel Brackets, .0001 Reaction, 2 mfd.Mansbridge, 100 ft. Insulated Aerial, 4- or 5 -wayBattery Leads, 30 ft, Coloured Connecting Wire.S.M. Dial, 12 yds. Lead-in, Fuse and Holder, 12Nickel Terminals, 60X Coil, Permanent Detector,

:Battery Switch, .0003 and 2-meg. Leak, 6 -pin Coil!base. 12 yds. Twin Flex. 100 It. Indoor Aerial.


Ocr model 97 i s supplied assembled complete with duplex woven Coatingone, clamping beard AND a Kit of Parts for making Matt cone.

Diameter of cone St In.OR COMPLETE WITH HANDSOME OAK ThelotCABINET and BLUE SPOT UNIT 66K (U.K.)

poet tree

(Genuine Ideal Adjustable)

entattur Whate)


LONDON AND DAVENTRY

April 22 Covent Garden opera.23 St. George's Day programme.

,, 24 The Flying Dutchman, an opera by RichardWagner.

25 St. Joan, by George Bernard Shaw, Part 1.26 St. Joan, by George Bernard Shaw, Part 2.

DAVENTRY EXPERIMENTAL 5GB

April 21 An orchestral programme.,, 22 The Flying Dutchman, an opera by Richard

Wagner.25 B.B.C. orchestral concert, relayed from the

People's Palace.26 Covent Garden opera.

CARDIFF

April 27 A popular request programme.

MANCHESTERApril 26 A programme of musical comedy memories.

ABERDEENApril 22 A variety programme.

BELFASTThe Dragon's Bride, a musical comedy en

casserole, by Mabel Constanduros.April ZZ

An attempt is being made to provideGreece with a broadcasting system; amonopoly is to be offered to a concession-naire for a period of twenty years, at theend of which the transmitters would passinto the hands of the State. The schemecalls for the erection \of a high -powerstation at Athens.

Radio Paris has been equipped with aFultograph picture transmitter' and broad-casts are experimentally carried out dailyat 6.15 p.m. G.M.T.

BURY YOUR CONTACT TROUBLESWITH THIS CLIX SPADE.

Patented.

CLIR Spade Terminals are obtainableeither nickel or lead -plated. The latter,for use with accumulators, often lessresistance to the flow of L.F. current,and is not easily affected by acid.The patented method of wiring theseterminals ensures a positive grip, perfectcontact and no risks of shorts. Red orBlack insulators.

Chosen for theSignal Booster"

" Dynamic Three""Drum Major"

in the " Wireless Magazine."

2d. Write for the Clix Catalogue.

LECTRO LINX LTD.,EACH 254 Vauxhall Bridge Road, 5.W.1

WIRELESS CABINETSMAKE YOUR OWN

Send stamp for Free catalogue and pricelist.

WOODWORK, 199 HIGH ROAD, LEE,LONDON, S.E.13.

608

WITH THE AIR MAILTO INDIA !

Wireless Communication en routeWIRELESS is playing a vital part inthe organisation of the new air snail

service to India, inaugurated on the morn-ing of Saturday, March 3o, when G-EBLF(the Imperial Airways liner City of Glasbow)left Croydon outward bound for Paris andBasle, carrying the mails on the first stageof their seven days' journey. '

As full particulars had appeared in thePress regarding the itinerary of this air-liner, its time of departure, and the arrange-ments made for wireless communicationen route, a good many wireless enthusiastsdoubtless followed the progress of theflight by radio.

Those who are able to read morse mayhave picked up the inter -aerodrome messagein C.W. on 1,40o metres from GFK, theCroydon air -port "route service" station,informing the Continental aerodromes thatthe huge twenty -seater Argosy machinehad duly departed with its passengers,baggage, and mail.

Even listeners who are unacquaintedwith the language of dots and dashes couldfollow the subsequent conversations inradio -telephony on 90o metres betweenthe pilot of Imperial LF and the operatorsat Croydon and the Continental aerodromestations. W. 0.

The series <4 for bee -keepersbroadcast from the Scottish stations lastyear proved so successful that a furtherand more elaborate series has been ar-ranged for 1929 in collaboration with theScottish Bee -keepers' Association. Thetalks will be given fortnightly on Thursdayevenings.

"Amateur Wireless and Radiovision." PriceThreepence. Published on Thursdays and bear-ing the date of Saturday immediately following.Post free to any part of the world : 3 months,4s. 6d.; 6 months, 8s. 9d.; 12 months, 17s. 6d.Postal Orders, Post Office Orders, or Chequesshould be made payable to " Bernard JonesPublications, Ltd."General Correspondence is to be brief andwritten on one side of the paper only. Allsketches and drawings to be on separate sheets.Contributions are always welcome, will bepromptly considered, and if used will be paid for.Queries should be addressed to the Editor, andthe conditions printed at the head of " OurInformation Bureau" should be closely observed.Communications should be addressed, accord-ing to their nature, to The Editor, The Adver-tisement Manager, or the Publisher, "AmateurWireless," 58-61 Fetter Lane, London, E.C.4.

APRIL 20, 1929



bona fides of advertisers Li this publication, they haveintroduced a system of deposit which it is recommendedshould be adopted by readers when dealing with personswith whom they are unacquainted. It is here explained.

Intending purchasers should forward to the Publishersthe amount of the purchase money of the article adverlised.This will be acknowledged to both the Depositor anti theVendor, whose names and addresses must necessarily begiven. The deposit ,s retained until advice is received ofthe completion of the purchase, or of the article hearingbeen returned to and accepted by the Vendor. In additionto the amount of the Deposit, a Fee of 6d. for sums of Etand under, and is. for amounts in excess of it, to coverpostage, etc., must be remitted at the same time. In ,rasesof persons not resident within the United kingdom, doublefees are charged.

The amount of the Deposit and Fee must be remitted byPostal Order or Registered Letter (Cheques canner beaccepted), addressed to"AMATEUR WIRELESS," ADVERTISEMENT DEPARTMENT.

58/61, FEUER LANE, LONDON, P C.4.

PATENTS,-Trade Marks, Advice Handbook free.-D. T. Kin;,Patent Agent, 146 Queen Victoria Street, London.

EARN MONEY AT HOME. You an earn money at home in wholecr spare time writing Show Cards for us. No canvassing. We train youby post by our new simple method and furnIsh"the Outfit free. Weropply both men and women with steady work at lrome,.no matterwhere you live, and pay you cash for all work completed each week,under our legal guarantee. Full particulars and Booklet tree. Writeat once or call. Show Card Service, Hitchin.

WIRELESS OPERATING APPOINTMENTS: fees payable after qualify.ing (for boarding students.) Morse classes. Wire:ess School, ManorGardens, Holloway, N.7.

SATISFACTIONand Quick Service

We give you BOTH!Our large Stocks and extensive neap include Sets andAccessories of every description, and which enables usto give almost immediate delivary of anyth'ng you mayrequire for Cash or on the EASIEST DEFERREDTERMS. Send us a list of your requirements and letus quote you by retu-n. Lists Free,

Gramophones and Records on Easy Payment Terms

,WIRELISS STORESWALLINGTON . 'SURREY

WET H.T. BATTERIESSoles all H.T. troubles

SELF -CHARGING, SILENT, ECONOMICALJARS (waxed) Ss" x 11" sj. .. 1/3 dos.Zuns, New Type. 101. dos. SACS 1/2 dos,tia mole do, (15 volts), complete with bandsand electrolyte 4/1, post 9d., Sample unit.64. illustrated booklet tree. Bargain list free.AMPLIFIERS, 30/. 3VALVE SET, f5.A. TAYLOR, 57 Studley Rd.,

Stockwell, London.

50/- as shown

LOEWE RAM4 Fountayne Rd.,Tottenham, N.15

WARRICK RADIO, ARTISTIC FRETTED FRONTS,for Loud -speaker, Gramophone, or Portable !cabinets.Many designs. Sizes: is in. to 24 in. Prices : 1 /6 to 5/6Special sizes for " Lion" chassis, and " Linen " speakers.

Rend for Illustrated List. Trade invited.WARRICK RADIO, 16 BE'RTHER RD., HORNOHURCH, ESSEX.

SUPPLY UNITSHIGH TENSION

For Multi -Valve ReceiversGuaranteed silent; No valves:No expensive replacements;

Components from

47/6 Guaranteed

7 DAYS' FREE TRIAL AGAINST CASH.THE TULSEVIERE MANFG, CO., Dalton Street, West Norwood, S.E.27.

FOR A.C. MAINS ,-_r,-/LOW TENSION

Incorporating Westinghouse MetalRectifier.

2, 4 or 6 volts at i an amp:No renewals. No attention

Complete Coils Irons

47/6'Phone: Streatham 6731:

mateurCOUPON

Available until Saturday,

APRIL 27th, 1929

APittl.! 20, 19214

DUBILIER VARIABLESFOR INVARIABLE

EFFICIENCY

K.C. CONDENSERWith knob, dialand slow-motion 12/

device, 60'00D3 or 0005

Without knob, dialor slow-motion

device,00D3 or .0005

K.C. DRUM CONTROLCONDENSERS

With Drum Control and slow-motion device, 00fl3 or 0005

Triple K.C., each condenser.0003 or .0005

Triple K.C. Combination of0003 and 0005

15/6

38/3

40/ -

MIDGETCONDENSER

A small variable condenserfor panel mounting

00005,0001 or .0002 5/6Dubilier

for Selectivity !

"TOREADORSCREEN -GRID FOUR."

This set Incorporates the latestdevelopments in Receiver design-full constructional details free on

request.

DUBILIERCONDENSERS

IIf unobtainable from yourdealer, write direct to usgiving his 'name and address.

doe IL /4...

3)9 4,C7.0.1 WWI

Advt. of Dubilier Condenser Co.,(1925) Ltd., Ducon Works, Victoria

Road, N. Acton, London, W.3f023

Ill

MINME11111aUSIMMITMENNINMEIMM

Your set will do allthat the designerclaims for it if you useLotus Components.Every Lotus unit youuse is a sturdy, ac-curate link towardsperfection. The bestbakelite, the bestmetals and the bestBritish workmanshipgo into all LotusComponents a n devery one is severelytested before it comesto you.When you buy yourcomponents ask forLotus Componentsand ensure your set'ssuccess.

From all Radio Dealers.

WWI RenaotControls,from 351.

WI 2 row.,

Lobs VarianCondensers,

from 51.

'0441ID0000NEKSIUES.efi

011.1111111111:1111,11111:11:1;tiii'llIthlli=r"-

GARNETT, WHITELEY. & Co., Ltd., LIVERPOOLAmmommiammmors


lv APRIL 1.0, 1929

THE STANDARDFOR COMPARISON

The highest tribute thatcould possibly be paid toour wire -wound AnodeResistances, and yet onethat is literally true.Practically every researchlaboratory in the UnitedKingdom uses R.I. andVarley Anode ResistancesL -they can rely on these

. world-famous products-they know that they arepractically dead accuratein every instance.Behind these real " stan-dar& " of comparison is

,the story of the Bi-duplgxwinding. As far back as1896, it first came intobeing; each year has seenfurther improvements,until to -day this per-fected science has placedin the hands of the wfrnot)lesspublic not onlyGreat Britain, but ofthe world one of thebig achievementsof radio science.

Wier

Section C of our Cata-logueLfree on application-gives full particulars ofour complete range oftlieie famous products.

. Prices, corn. lete- with- - Unitrersal Holder, from

5/6- to 17/6

Trie otily L.Fchoke

of its kind

The R.I. & VarleyChoke is the only one of

its kind. With numerousapplications it possesses

the same degree of real efficiency in each -case.Firstly, it is a really good choke, for eliminatorsmoothing circuits. On a load of -100 milliampsit is still a long way from saturation point infact, it is the, only choke, at a popular price, whichcan be used for smoothing where series con-nected filaments are used.As an Output Filter Choke it can be used equallywell affer_a single power valve, or after severalsuper -power valves in parallel. One has indeedonly ,to refer to the pages of any of the WirelessJournals of to -day to realise -the extent to whichthe R.I. & Varley L.F. Choke is being used by theTechnical Experts in this country.These Chokes have a huge iron circuit, adequateinductance, and Low Resistance.Write for Section E of ourCatdogue-free.on application

-for full particulars.28 14 Henries. 0-100 ma,

'10 ohms D.C. Resistance1 : 1 0

14/7 Henries, 0100 m,'a120 ohms D.C. Resistance,

1 1 :0Don't forget we make areonife;ful L.F. Low Ten-sion Choke. Mice

THE MARK OF BETTER RADIO,igsna!). Hotne,-103 hing-nray,Lcindori.

Printed in -England: Published by ilernardjones Publications, Ltd., 58/61 Fetter Lane, London, E.C.4Sole Agents for South Africa; CENTRAL NEM s AGENCY, LIMITED. Sole Agents for Australasia ; GonooN & GOTCII, LIMITED, Saturday, April so, 1,92g

AMATEUR WIRELESS, APRIL IT, 11/23

CUTTING OUT POWERFUL STATION AT 1 MILE

Saturday, April 27, 1929

CUTS OUT LONDONAT I ILE

SEEPACE

621

Registered at the G.P.O. so a Naospapst

saattur Wtrele:c)A FRIL 27, 1929

0450BREAKS

Because months of Fr tient research have beendevoted to their perfection, Mullard Pentoneand Screened Grid valves break all recordsfor ,super.efficient performance They havethe lowest current consumption combinedwith the highest efficiency of any valves oftheir type on the market.

We have never used the public as our researchdepartment. We wouldn't risk losing evenone of our friends to satisfy an experiment,certainly not after all the years we've beentogether, up and down every European broad-casting station.

You can take our word for it, MullardPentene and Screened Grid Vrlves are perfectto the last detail, modern to the minute.Otherwise they wouldn't be stamped withthe Mullard P.M. monogram.

Mullard.THE MASTER.- VALVE

Advert :-The Mullard Wireless Service Co., Ltd., Mullard House, Charing Cross Road, London, W.C.2..4 rks.


APRIL 27, 1929 609 matt= Wirelers5

BLUE SPOT 101

A speaker of unusual design,striking yet not obtrusive, theBlue Spot 101 takes its placeamong the world's leading loud-speakers. To say that the BlueSpot 101 speaker reproducesperfectly both speech and musicis to endorse the opinion of

thousands of satisfied owners.Ask your dealer to demonstratethe Blue Spot 101 to -day.It is driven by the Blue Spot66K unit which is also obtain-able for constructors as aseparate unit, price 25/-.

F. A. HUGHES & CO., LTD., 204-6 Great Portland Street, LONDON, W.iDistributors for Northern England, Scotland and North Wales: H. C. RAWSON (SHEFFIELD & LONDON) LTD.,

zoo LONDON ROAD, SHEFFIELD; 185 PRINCESS STREET, MANCHESTER.

You will Help Yourself and Help Us by Mentioning !`A.W." to Advertisers

(Luau,- Wu-eik. 610 APRIL 27, 1929

ONLYIn the Cossor Screened Grid Valve allthe inherent weaknesses of valve designhave been eliminated. By means of thewonderful new Cossor system of con-struction-illustrated here-each ele-ment is rigidly secured top and bottom.Even under the hardest blow individualmovement is impossible. The CossorScreened Grid Valve is

SHOCK -PROOFNoises in a valve are generally due toloose elements. In the Cossor ScreenedGrid Valve the elements cannot becomeloose because they are rigidly bracedtogether and because every joint isscientifically welded. The CossorScreened Grid Valve is

NOISE -PROOF !,Even the heaviest shock cannot disturbthe perfect alignment of the electrodesin the Cossor Screened Grid Valve. Itis the most robust and the most de-pendable Screened Grid Valve madein Great Britain. The Cossor ScreenedGrid Valve is

BREAK -PROOFFor any Screened Grid Receiver chooseCossor. Accept no substitute-for there isno adequate substitute for the Cossorsystem of Interlocked Construction.

TechnicalData.

Comer 220 S.G. (2volta,.2 amps.) and 410 S.G.(4 volts, 1 ...vms, MaxAnode Volta 150, Impe-dance 200,000, Amplifi-cation Factor 200, GridBias 1.5 volts at max -

Price (each>Volta. 22/6de

C. Cossor Ltd., Highbury Grove, Landon N.J.

CossorScreened GridValves--HAVE

INTERLOCKEDELECTRODES

Here you see thedouble length of Cossorfilament' famed for itscolossal emission. Notethe seonite bridge hold-ing it rigidly in position.

3. Note the enormousstrength and rigidity ofthe screen. -See how it isbuilt on four stout sup-ports and capped by ametal bridge -piece an-chored to seoniteinsulator.

2. 'Around the twostout grid supports iswound the first grid,electrically welded attwenty-five points.

4. Finally, observe theconstruction of the anode.Actually two rectangularnickel plates are usedand for greater rigidityeach is diagonally ribbed.

CossorScreened GridBRITAIN'S STRONGEST AND MOSTDEPENDABLE SCREENED GRID VALVE

8446

Advertisers Appreciate Mention of !`.4.W." with Your Order

Ell

55 -APRIL 27, 1929 No. 359. Vol. XIV

55

5 55 5

S ,5

Lift 5 5

an . '5 d 55 The Leading Radio Weekly for the Constructor, Listener and Experimenter 5

55 = Editor : BERNARD E. JONES = §

55 Technical Editor : J. H. REYNER, B.Sc., A.M.I.E.E. :: Research e...oiisultant: W. JAMES :: Assistant Editor: H. CORBISHLEYljtaticatatzzctacearc7).)c)catc7IcatIce%)cceir47.)catc7ecat7.0.atIt.ear.act,e7o.e:57)tc.acte73catar.:tc743

Television to Come-Portable Set Licences-Free Radio-A Gipsy Told Me !-A Popular Set-D.F. on Ships-How Much to Broadcast ?-Holidays at Home

Television to Come-As wasalways the case, and without greatjustification, television developmentsin this country have been shrouded'with mystery. Therefore at presentwe cannot give any definite details,but from a reliable source we learn'that negotiations are going onbetween Baird and the B.B.C., andit is hoped that actual broad-casts may be made in the very near.future. There is, of course, a certain'amount of technical ground work tobe covered, and quite a deal of the'difficulties which Baird has success-fully overcome have been describedfrom time to time in AMATEURWIRELESS.

A NOTABLE "O.B."-Major egrave before the microphoneon the occasion of his speech on arrival at Southampton. He

broadcast his impressions of "speeding."

Portable Set Licences-It is welcomenews, as announced recently, that theP.M.G. has sanctioned the use of one port-able set without additional licence by theowner of a permit for a set at a fixed address.The only snag is that when a set is usedaway -from the home address, the owner mustcarry the licence with him, and produce it ifnecessary. This somewhat savours ofmotorists' driving licences, which servevery little purpose, even for identification.Nevertheless this concession is well worthhaving and one can't expect officialdomto descend to practicality !

Free Radio-Some good work is goingahead in the provision of free,wireless sets in mining areas wheredistress is particularly acute. Thisis possible by means of co-operationbetween the B.B.C. and the CentralCouncil for Broadcast Adult Educa-tion. Altogether, free sets are beingsupplied in twelve localities inSouth Wales and about the samenumber in Durham and Northum-berland. Efforts are being made tointerest the local residents and it issuggested that they should formlistening groups for discussion.

A Gipsy Told Me!-There is alittle bit of romance attached toa new song which was included in arecent De Courville revue, GaySparks. This is one of the first

songs written by Mr. Jack Mosdell, a clerkin a Government office. He took up song -writing in his spare time on the adviceof a fortune teller who told him that hewould succeed in this direction, although hehad never before atterpted to write a song.

A Popular Set-Our Technical Depart-ment has received so many requests forinformation regarding the fitting of themost up-to-date improvements to thatpopular set "Britain's Favourite Two"that they are at present engaged on a newversion. The 1929 "Favourite" will bepublished in an early issue. Keep a lookout for it!

0,,,),,,,It,,,tatv.,,..it,,,te,1t.,t,,,,,,,,A.e,1w.,uplu,1,,,lo§ PRINCIPAL CONTENTS Page 5

§ Current Topics .. .. .. 611,

.§ Broadcast Artistesin- Picture 612 §

The " Stability Four " .. .. 613. §§ This Modern Music 1 615 §

616 cOn Your Wavelength 619§In My Wireless Den

§ Cutting Out 2L0 .. -621 N

§ How it Happened ! .. 622 §§ Without Fear or Favour .. .. .. 623 §

More About the " £5 5 0 Portable " .. 624 §"A.W." Tests of Apparatus - .. .. 626Radiograms .. .. .. .. .. 628

§ Some Recent Loud -speaker Developments ..' 630 N

§ Cabinet Making at Home .. .. .. 632 §§ Secrets of the Test Room .. .. .. 634 §§ Broadcast Telephony .. .. ... .. 638 §Clte9)Ge5Ite:"104t.e'ltelte9VG)tc:76telteVententelte7)WIte:71tGlte;11:1

D.P. on Ships-Radio direction -finding equipment is standard on somany ships that it is apt to be for-gotten, and its marvels overlooked.Yet here we have a report from themaster of a ship fitted with modernD.F. equipment and it is nothingbut a piean of praise. The particularapparatus employed incorporates avery small frame aerial in the chartroom,' and the master states thatevery passage would take longerwere he not aided by radio.

How Much to Broadcast?-The annual statement of theNational Broadcasting Co. (inAmerica) states that 9,000,000dollars was expended by that

company during 1928 for artistes' fees, wirenetwork and general overhead expenses.Conservative estimates place the weeklyrevenue of the N.B.C. from commercialaccounts at more than 200,000 dollars. Thissum does not include entertainment whichmust be supplied by the adVertiser.

Holidays at Home-The correspondentin a daily paper has found' a new reasonto grumble at B.B.C. talks 1 He says that arecent broadcast talk on the merits andbeauty of Switzerland as a holiday resortshould not have been given. We are doingour best to boost our own holiday resorts,"says this cm -respondent, ' and it stems some-

what short-sighted if not definitelyunfair to give talks on Continentalattractions." Well, that's as good areason to grouse as any

A New S.W. Tester-TheVienna short-wave transmitter car-ries out tests every Tuesday andThursday on a wavelength of 49.4metres; in the course of a week orten days this experimental pro-gramme will, be extended to Wed-nesdays and Saturdays. It hadbeen hoped to carry out a simul-taneous broadcast of the Viennaevening concerts with Rosenhuegeland the . new short-wave station,but its close proximity to thehigh -power transmitter is causingtrouble.

emate= Wirell!, 612 APRIL 27, 1929

LEFF POUISHNOFF.-This brilliantpianist has had an almost spectacular careersince his early appearances at Queen's Hall.ht his early broadcasts he was known as the" mystery pianist." He has just given

another series of recitals.

LBROADCAST ARTISTES IN PICTURE

VERA GILMAN.-A favourite and fre-quent broadcaster. This clever young actresswas heard on April 13 in the revue, " Hip-Hip-Hoo Radio." Both as singer and actress,she has scored in many popular productions.

CECIL BAUMER.-A famous pianistknown by his many appearances at the greatclassical concerts. Recently, following onmany earlier broadcasts, 1w gave a series of

recitals from 2L0.

MARY OGDEN.-A well-known Man-chester singer, famous in oratorio work. Shehas broadcast in Rossini's " Tell"

and many other musical programmes.

HELEN OGILVIE.-Frequently heard oflate from 21,0 and provincial stations,Miss Ogilvie is a member of the Carl RosaOpera Company and was heard in its firstbroadcast of " Faust." She possesses a wide

range of tone and a clear diction.

MAY BLYTHE.-One of the best knownof the B.N.O.C. stars, she has probablybroadcast more than any other singer. Herprincipal roles have been in " Hansel andGretel," " Cavalkria Rusticana," and

" Carmen."

EDWARD CLARK. The popular musicaldirector of Newcastle station, Mr. Clark hashad a wide Continental and Britishmusical experience. He seas closely connected

with a season of the Russian Ballet.

MAURICE YACOBSON.-A clever pian-ist and composer, and holder of the StanfordScholarship; his works include many songsand orchestral works. Best known are hissetting of Vaughan Williams Mass in B minor,

and the Beggar's Opera Fantasia.

i1.10IIMAUD COUPER.-One of the earliest ofall broadcast elocutionists, Miss Couper haswon fame in Scotland for her treatment ofreal Scottish humour. She is always a

favourite at London Scats gatherings.

APRIL 27, 1929 613 omattur Wux) v,

A Lof tin -WhiteReceiver Embodying

" Q" Coils THE aerial circuit is coupled by the

use of a "QAA" coil, this being the newform of "QA" coil having centre taparrangement so that the aerial can be con-nected to a tapping on the coil insteadof across the whole coil. By this means,both the wavelength range and the selec-tivity are somewhat improved over theolder form of "QA" type. Any reader,however, who possesses a " QA"coil can utilise it in this positionif he wishes, in which circum-stances the aerial is connected,through its pre-set condenser,to terminal No. i instead ofterminal No. 4.

In the anode circuit we havethe H.F. choke and a phasingcondenser, whence the currentsare led through to a primarywinding of a "QSP" transfor-mer. A .CO2 fixed condenser, isinserted as a coupling condenserin series with the .0005 tuningcondenser. The value of thiscoupling condenser determinesthe t xtent of the capacitycoupling. In the present instancethis value was chosen becausewith the value of magnetic coupling givenby the "QSP" coil the reaction demandwas approximately constant. Reaction isobtained by capacity control, the windingbetween terminals 2 and 6 being utilisedas is usual in the case of -the "QSP" coil.

Following the detector, there is a resist-ance -coupled stage while the final stage is

Last week the principle upon whichthis receiver, which provides constantreaction effects, operates was describ-ed. In the article below an explana-tion of the circuit is given, togetherwith the necessary information for theconstruction of the actual set as shown

by the photographs.

This is a reproduction of the

OYI. H. REY N ER,

B.Sc.,

To obviate this, a stopper circuit hasbeen connected in the detector lead consis-ting of a ioo,000-ohm resistance with a2-microfarad condenser shunting it to earth.

The circuit is thus generally of a straight-forward character, the principal advantagesin use being (first) the circuit does notrequire any neutralising, while at the sametime it gives a good measure of high -

frequency amplification, enablingoll.r. distant stations to be obtained

with greater ease and local sta-tions to be cut out by means ofthese two tunes, and (second) auniform transfer of energy overthe whole scale so that thereaction adjustment is tolerablyconstant. This constancy hasbeen arranged to apply princi-pally to the short-wave band andit will very probably be foundthat the reaction adjustment isnot so good on the long waves.This, however, is again due to,the use of a standard "Q" coil,for, as has already been pointedout, it was not considered advis-

circuit diagram shown last week

transformer -coupled, a Lissen Super trans-former being used in this instance. Despiteits relatively low price, this instrument hasa really super performance, and, in fact,the principal difficulty I had with its usewas that it was rather too good and gaveme trouble due to battery feedback whenthe arrangement was used on an eliminator.

Two picturesof the rear

of the"Stability Four."

Other photo-graphs appearedin last week's

issue

able to produce a special coil forthis, particular purpose.

Both the "QAA" and "QSP" coils arestandard items and can readily be obtainedfrom any dealers. It has been found in cer-tain instances that the reaction control isnot as constant as is desirable, in which caseslight variations of the value of the .002coupling condenser may be tried. Thiscondenser must not be reduced seriously

=imomm.mom614 APRIL 27, 1929

REACTIDNI CONDENSER000/ mid

2

" THE STABILITY FOUR " (Continued from preceding page)

or the tuning range of the circuit will beaffected. It may be increased if necessarywithout serious effect, the larger the con-denser, the less being the capacity coupling.

Batteries and ValvesThe receiver should be connected up to

the batteries in the customary way, thevoltages being as follows : Either two, four,or six volts may be used for the L.T.,depending upon the valves in use, while avoltage of roo to 120 is satisfactory for theH.T., there being only one H.T. tap. Gridbias should suit the valves in use, but formost purposes, a bias of 3 volts on the firstL.F. and 9 volts on the second L.F. willprove satisfactory.

The valves to use are not critical. AnH.F. valve of the ordinary medium resis-tance type (20,000 to 30,000 ohms) gives thebest results in the H.F. stage. The detectotshould be a resistance -coupled valvehaving an A.C. resistance of the order of4.0,000 to 80,000 ohms. An L.F. valveshould be used in the first L.F. stage,following which we may place a power orsuper -power valve in the last stage. The

selectivity, rendering the tuning of thecircuit sharper. The actual current con-sumption of the particular model describedwas only 7 milliamps with a ioo-voltbattery using the following valves :

H.F. B.T.H. HF2roDet. . Mullard PM r A1st L.F. Osram HL2r02nd L.F.... B.T.H. P227

TuningThe method of tuning is to set the right-

hand dial approximately to the positionrequired; increase the reaction settingslightly until the receiver is just oscillatingor just about to oscillate. Then, onrotating the left-hand dial, the point atwhich the receiver is in tune will at once beobserved as the signal strength and mushwill come up at one particular point. Thereaction control may then be slacked offslightly and the station tuned in in thenormal manner.' On the long waves inparticular it will be found that there is verylittle "pull" between the circuits. Thismeans that if the detector circuit is allowedto oscillate by increasing the reaction

control, then as theH.F. dial is movedthrough the tuningpoint, the note of.the oscillation only

raLUEPRINT IN.A.W 182

LTSWITCH

NE TUN/NDCONDENSER

000.5

0-

PANEL OW"

5'AERIAL TUN/NC

CONDENSER000.5.41

Tama

G8-2 CD- HT, HT- LT LT,

The Wiring Diagram. Blueprint available, price

makers will recommend suitable grid -biasvoltages and these should be followed, butin general about 3 volts on the first stageand 9 on the second, unles's a super -powervalve is used, in which case the last valveshould have 12 to 15 volts bias.

It will have been observed that a gridbias of r 1/2 volts is included in the H.F.stage. This not only reduces the currenttaken from the H.T. battery which mightotherwise be somewhat high for the H.F.valve, but it also materially increases the

BASEBOARD

varies very slightly,indicating thatthere is very littlecoupling betweenthe circuits.

On the shor t -wave position,somewhat m o r epull will be found;the H.F. circuitmakes quite anappreciable differ-ence to the noteand for this reasona little more caremust be taken inthe tuning. Thetuning operation,however, will ingeneral be foundvery simple be-cause there is noneutralising adjust -

1/6. ment and thereceiver once con-

structed is _ready for operation withoutpreliminary adjustment of any sort. Slow-motion dials, incidentally, will be found avery valuable aid in tuning if it is desiredto search for distant stations. For ordinarypurposes, plain dials are satisfactory.

An additional feature which may beadded with advantage is the connection of a.000r fixed condenser from the anode of thedetector valve to L.T.-. The diagram onthis page indicates just where this may beconnected in the circuit. The effect of this

is to increase the signal strength slightlyand to make the reaction control smoother.Test Results

On test, I found the receiver behavedwell. Although the reaction control was

/./</..W.W/././

0

-000/ Enid- ........ .....

Diagram showing connection of fixed condenserfrom anode of detector to L.T. negative

not quite constant, it was sufficiently so toenable me to tune in a number of stationswithout any alteration to the reactioncontrol. This, of course, was after dark.The selectivity is of a fair order, it beingpossible to tune the local station out with-out much difficulty. This selectivity isassisted by the grid bias on the H.F. valveand also by the use of the "QAA" coil. Ifextreme selectivity is required, the H.F.valve in the first stage should be replacedwith an R.C. valve.

There are now so many stations operatingthat it is a fairly easy matter to tune in anumber of foreign programmes at goodloud -speaker strength. Instead of giving atest report of the total number of stationsreceived on the set, therefore, I have simplychosen a few stations which were receivedsufficiently well to be at good loud -speakerstrength during daylight. The test wasactually made on a Sunday afternoori and

TEST REPORTWave- Dial

LONG WAVES- length readingRadio Paris 000 1,750 165Daventry 4.0 1,562.5 150Eiffel Tower 10 1,470 142,Kalundborg 1,155 103Hilversum 1,073 92

SHORT WAVES-Daventry Junior... 482 165Langenberg 462 16oLondon ... 359 120Huizen 337 115Cologne ... 269 70

the wavelengths and dial settings given willserve as an indication of the approximatetuning position at which various stationsmay he expected. The dial readings areonly given for the H.F. dial, the aerial dialbeing similar, but the actual setting varyingwith different aerials. It should particu-larly be noted that this test report onlyapplies when condensers of the same type asthose used in the original set are employed.The receiver will work with other types ofcondensers, but the stations will not tunein at the same dial readings.

APRIL 27, 1929 615 =dear WtreLT

.4 or- ow. III I .1141iiiiiith.AI 1 ' I 1.1 ,..11 I 741111111\, 111111114, r am -

00D evening, listeners all-especially\--/ invalids !" says Sir Walford Davies

at the commencement of his musicallectures, and one million non -Musicallisteners promptly switch off their sets. Iknow that this happens, because I was atone time exceedingly unmusical and regu-larly committed this sacrilege. That is tosay, I played no musical instrument andwas incapable of absorbing any music

"I had to listen .. ."

except that of the order of " In a MonasteryGarden " and " Yes, We have no Bananas."So you see that when such an ignorantperson as myself ventures to express anyopinions on music, they will be from thepoint of view of the "man in the street,".and will be unbiased by a musical educa-tion. Sir Walford Davies has always hadthree " bees in his bonnet "-Bach, Brahms,and Beethoven ; I don't suppose he has everlistened to a dance band sympathetically.In fact, it was probably his unsympatheticreferences to jazz which turned us awayfrom listening to his lectures.

The ClassicsAbout four years ago, I probably had the

same reaction to. classical music as many ofyou have now. That is to say, symphonyand chamber music concerts came out of myloud -speaker and went in one ear and cameout of the other ! Bach indicated a moaningnoise, Brahms raised hopes of a Hungariandance and Beethoven sometimes remindedme of something I had heard at the cinema.That was all. And then-alas !-I wasforced to listen to all these dull classicalfogies' music and, worse still, to the noisesinvented by composers who were still livingand had not yet died in poverty ! I had, as

API'O

?HY!'

a matter of fact, to carry out a series ofreception quality tests of 2LO's trans-missions over a period of months. I had tolisten.

Spoon-feeding the ClassicsNight after night I listened to music of all

kinds, classical-ancient and modern, jazzand military band, hearing the same piecesplayed time and time again and gradually

becoming aware of the existenceof those particular classics whichcome in the "hackneyed " category.I began to find that the less familiarmusic, which required some effortof the brain, gave me much morepleasure than such compositions asRachmaninoff's " Prelude," thatcheery musical description of a manbeing buried alive. The recurringthemes in symplienies began tointerest me, and I realized , thedramatic power of, for instapce,Tchaikovsky's Fourth Symphonyand the charm of Elgar's veryEnglish music. For a time, EdwardGerman was a " best seller," so far

as I was concerned. Stravinsky, Scriabin,and Bartok were, of course, merely un-pleasant noises, and there " didn't seem tobe anything " in Hoist.

The AftermathThe result of this course of forced musical

culture left me in mid-air. Atleast, that is what I thought atthe time, for I still obtaineda great deal of pleasure fromlistening to jazz music, especi-ally when it was composed bya new man named Gershwin.It is this " middle " stage ofmusical appreciation whichhas been reached by themajority of radio listeners,who are, in spite of themselves,far more musical than that pool.unfortunate " man in thestreet." The appreciation ofgood music is much the same asthe appreciation of good food. There is,first, the bread -and -cheese and beer stage;secondly, the lemon sole and Chablistaste; and- lastly, the gourmet's judgmentof good caviar and bad champagne. Itwould seem impossible for the gourmet,with his very sophisticated palate, to be

Chinese

able to digest the bread, cheese, and beerwithout shuddering. And yet, in theparallel case of music, it is being donenightly by way of the loud -speaker.

The ModernsThe tendency of modern composers is to

treat melody as quite a secondary con-sideration to tempo and phrasing. (Musicallisteners will probably have given me up indisgust, so it hardly matters if I don't usethe correct technical terms.) That is whyit is so difficult to listen to at first. Genera-tions of melody makers have drugged ourmusical senses to anything which is the leastbit out of the ordinary. Chinese musicdoesn't mean a thing to us, and yet, to thegood people who regularly listen to it, it isprobably as dramatic as Tchaikovsky or assentimental as Ketelby. It is, indeed, a. -difficult matter to get out of the musical

"rut, but if one really tries a new musicaldiet in carefully graduated doses, a newmusical pleasure will be discov&ed.-

Ultra Molern- It is the caviar -and -champagne stage that

seems to upset most of us. Bartok, Con-stant Lambert, Schoneberg, and the laterStravinsky works seem to be as colourlessand potent as vodka. I can't say that Iunderstand or fully appreciate these com-posers, particularly Bartok. But I amwilling to try to understand Bartok, and

music is probably as dramatic as Tchaikovskyor as sentimental as Ketelby

I am quite sure that a great deal of pleasureand musical mind -broadening will be theresult of such an effort, even if it beunsuccessful. Constant Lambert's "RioGrande," with its curious drum breaks andsyncopated piano, interested me as much as

(Concluded in third col. of next page)

0nm/ear Wirdeo 616 APRIL 27, 1929

WIWeekly Tips,Constructional

and

Theoretical-Loud -speaker PositionA RECEIVER is generally installed in a

corner of a room or in some positionwhere it is conveniently placed as regardsthe aerial and earth. Very often I find theloud -speaker is put by the side of thereceiver, or even on top of it, regardless ofthe fact that the quality of the reproduc-tion is dependent to no small extent uponthe position of the, loud -speaker withreference to the furnishings of the room.

This is a point that is often overlooked.It is surprising how the quality may changeas the loud -speaker is moved about theroom, and a position can geneially befound which is convenient and where thebest all-round xesults are obtained. By theway, have you listened to a loud -speaker inthe bathroom? If not, do so, and thenlisten outside the bathroom with the dooropen, and then partly open, noticing thechanges in the quality

Anchoring L.F. TransformersMany makes of inter -valve transformer

are provided with a terminal or other con-nection that is joined or fastened to the:metal case of the instrument. It is providedin order that the user may convenientlyconnect the case to earth or an equivalentpoint, such as the negative side of the low-tension battery, as it is found that low -frequency howling and instability mayoften be prevented by this means.

The question therefore arises as towhether all transformers should be pro-vided with a metal case that may beearthed. Numbers of them are not, buthave a moulded cover. Their manufac-turers have evidently decided that it is notessential to provide a metal cover whichmay be earthed, and practical experienceindicates that stability, and freedom fromhowling, are not dependent upon theemployment of this form of cover when onlyone transformer is included in a receiver.When two or more are used, the metalcover may be an advantage, but I havefound that no general rule can be made.Everything depends upon the arrangementof the set or amplifier, the amount of theamplification, the types of valves employed,and other factors. I have even foundinstances where the best results were to beobtained by no' connecting an earthing wireto the case of the transformer;

Improving SelectivityI am often asked how the selectivity of a

receiver may be improved without muchtrouble or expense, and I always reply thatthis can be done by connecting a fixed con-denser in the aerial circuit. This fixedcondenser should be joined between theaerial and the coil included in the aerialcircuit (Fig. i).

A good value to try is .000! microfarad.The inclusion of a fixed condenser- of thiscapacity in the aerial circuit may reducethe signal strength by a small amount.This will probably not matter so far as thelocal station and Daventry are concerned,but may be serious when receiving the moredistant stations. It is, therefore, advisableto -have two aerial terminals, one of which

fien:Q/ Stied/ye.6.Candoyset

Fig. I. An arrangement by means ofwhich the degree of selectivity is very

easily controllable

is joined directly to the coil and the otherthrough a fixed condenser.

A Mains PointReceivers which are supplied with their

filament and high-tension current throughsuitable apparatus from alternating -currentmains are very common in America andwill no doubt in time be popular in thiscountry. They have the great advantagethat when once they are satisfactorilyinstalled maintenance is negligible.

Occasionally a new valve has to be fitted,however, and according to my experiencethis should be carefully effected. I havefound that a hum may be heard from theloud -speaker when the grid pin of the valveis a relatively loose fit in the holder. It is,therefore, wise to open each of the pins inorder that all contacts shall be good ones.

NEXT WEEK:A SHORT-WAVE ADAPTOR

ENWJAMES


The grid circuit of a mains -operated valveis very liable to collect small alternatingvoltages which, being magnified by thereceiver, will be heard as hum.

Arranging the EarthA question which is very often asked is

what is the best size of earth wire to employ?Sometimes I find a relatively thin connect-ing wire is used between the receiver and theearth connection and on other occasions Ihave noted that a thick wire or a conductorsuch as 7/20 is used. Personally, I employ astranded cable in order that the actualresistance of the earth circuit shall be aslow as possible.

A covered conductor is considered ratherbetter than a bare one and it should, ofcourse, be treated as an extension of theaerial. Do not fasten it to walls and do notlead it into the house too close to theaerial wire. As I have before mentioned;I generally prefer to use a buried earthplate rather than a water pipe for the actual

,4 THIS MODERN MUSIC",(Continued from preceding page)

Gershwin's " Rhapsody in Blue," thejazz classic. Stravinsky's "Soldier's Tale"is really a fantastic ballet and did notbroadcast well; nevertheless, having someidea of the grotesque dancing and figuresthat "went with" the music, I obtainedquite a lot of entertainment and not a littleamusement. You should bear this in mindwhen listening to ballet music in particular.Stravinsky's " Firebird " is relatively easy,as is his " Petroushka,' the compositionin which he successfully imitates a streetorgan by clever orchestration.

SympathyThe object of my article is to show that a

non-musical person can obtain a great dealof enjoyment and pleasure from the moreadvanced classical and modern music, andfrom the advanced and specially orches-trated jazz, if he will only listen sympa-thetically. You can take it from me thatthere is something in it, even if it only takesus out of the quagmire of sugared melodyinto which we have been sinking. I muststop. There's a barrel organ outsideplaying "Sonny Boy " I

APRIL 27, 1929 617 ematxx.wwdeJ

0BANISH

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in. Carriage, London, 2/-; Mid-lands, 31-; elsewhere, 4/-. Weight,34 ib. Two masts for 40;-.

The "Super"Mast

42Feet high. Insections of

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PAINTING.Any protective coating applied before dispatch gets sodamaged by the Carriers that it is essential to paint theMast before erection. All P.R. Masts are sent out oxide -finished ready for painting. One coat of P.R. Colloidcovering applied-a 10 minutes' job-to all parts of theMast when ready to erect sets dead bard in an hour andprotects it against all weathers.

PRICE OF ACCESSORIES.P.R. Colloid Covering sufficient for a Mast-with brush,2/6. Halyard Log Line-Ryland's patent rot -proof;For 26-f t. Mast, 1;6. 344 t., 42-f t., 2/6. Per 100 f t., 3/-.Note.-Double length supplied to make lowering of Aerialeasy.

A HIGHLY EFFICIENT AERIAL.P.R. Aerial is made of 14-28 High Conductivity PureCopper Enamelled Wire-each strand insulated from itsneighbour to give the highest signal strength obtainable.100 It., 4/3; 50 ft., 2/3.

THE TWO BESTTHINGS EVEROFFERED TO YOUAnd both are British made to the hilt. Both are sent youon the money -back -if -not -satisfied principle.We don't want you to keep anything you buy from us-asyou can easily understand it PAYS US BETTER for you toreturn the goods than harbour spleen. We want you to besatisfied and give us the CHEAPEST ADVERTISEMENT-tell your friends we play the game.We have sold more goods through people telling each other they WERESATISFIED than by all the advertisements we have paid hundreds for.You have seen our advertisements fordoubted mail order houses - yetreason it out-could e keep onspending hundreds in advertisingunless we had THE GOODS ? ? ?We still, and always will, stickto our guns. Try one-norisk-if not fully satisfiedthat it equals yourfavourite at any price,your money will berefunded by return.You are the solejudge.

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LIST OF DULL EMITTERSFil. Imp. Amp.

Type Volts Amp. Ohm; Fat

PR 2PR 3PR 4PR 9PR10

222

3.5-43.5-4

PR11 3.5-4PR17 5-6PR18 5-8PR19 5-6

PR20 2PR40 4PIM 6

.095

.095.095.063.063.063

.1

.1

.15

.15.1

28,00015,000

120,00018,00010,00028,00018,0009,500

£0,000

138

32148.7

4017

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UARANT All valves dispatched under guaranteeWMoney Back m Full if not satisfied within

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Tell us your set-we will send correct 'Valves. MatchedValves extra. All orders executed by ream of post.

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inatta4 Wags., 618 PR1L 27, 1929

.0.404.0440.44<44.4.40.000.4.0.0tA sketchof 2L0 The May "Wireless Magaiine"

Meets All Your PortableNeeds !

Lo you know thatto get the best results fa portable the edge of theframe aerial must be pointingin the direction of the broadcasting station? Many otherpractical points of this kind are discussed in the May" Wireless Magazine."

No matter how much you know about radio,

Whether you intend to build or buy, every-thing you want to know about the modernportable is dealt with in the May number ofthe " Wireless Magazine " which includes anextra 16 -page Suoplement, printed on specialpaper, giving details of more than 100portable receivers now on the market. TeUyour friends about this great number

you willalways find many articles in the " Wireless Magazine "- thatyou will understand and appreciate. Amongst its 45 featuresthis month there are articles to suit everybody's tastes- -adisclosure of Russian broadcasting activities, details for

building four fine sets, a radio detective story, hints fordecorating a linen -diaphragm loud -speaker, etc., etc. You can-not fail to find something of particular interest to yourself.

Note the attractiveappearance of the At-home

Three, which has self-containedbatteries. It costs less than £6.

By using the Special Coupon to be found inevery issue of the " Wireless Magazine " you canget for half - price a full - size constructional

blueprint of any set !

THREE SPECIAL- PORTABLE

ARTICLES.GETTING T H EBEST FROM AMODERN PORT-

ABLE. ByD. Sisson Reiph

(Assistant Editor).

THE WAYFARER.A Five -valve Port-able Super -het des-

cribed byJ. H. Reyner, B.Sc.,

A.M.I.E.E.(Technical Editor).

HOW I SHOULDDESIGN A FORT -

ABLE. ByW. JAMES

Research Consultant

Here you seeJ. H. Reyner'sWayfarer-A port-able five -valve Super -het which weighs only 271b.

OTHER CONTENTS OF THIS ISSUEValves to Use in Your SetWavelengths of the Euro-

pean StationsIn Tune with the Trade !Do Your Pets Like Radio ?How Will Broadcasting

Affect the General Elec-tion? By B.B.C. Officials

What Are Alternating Cur-rents? Amp and ProfessorMegohm Discuss SomeFundamentals

Leaves from A Listener'sLog. By Jay Coote

Curing Threshold HowlThe Twinflex. A Modern

Reflex Two-valver with-out Crystal Detector

Japan Has the Most Power-ful Station

The Inevitable Radio-inthe U.S.A.

A Countryman's DiaryHow the Law Acts When

Your Aerial Collapses !Speeding News by Air-

and Radio, Too !

The Dominions Four.Converting It to A Short-wave Super -het

Under My Aerial. Hal-yard's Chat on theMonth's Topics

Is Your Turntable True?Speed Traps for RecordsNoisy Electric DrivesBuilding Your Own

GramophoneThe Best Dance Records.

By H. T. BarnettPlanning your Aerial. By

E. H. Chapman, M.A.The Music Listener. By

C. Whitaker -WilsonThe Horse -power of A

KilowattBroadcast Music of the

Month. By StudiusNovelties and New_Appa-

ratus TestedReaction-A Mixed Busi-

ness !Reference Sheets. Compiled

by J. H. Reyner, B.Sc.00.00Get Your Copy of 66 Wireless Magazine" To-day-Price 1/-094440

APRIL 27, 1929 619 urWirete

ejave.6.4.e/f / dosia...000,00%0000+011%

The RegionalAFTER taking a look at the new

regional station at Brookman's Park,not yet completed, I feel justified in ven-turing the opinion that this station will bethe "last word" in broadcast transmitter'design. Machines, switchboards, and quitea lot of apparatus are already in the build-ings, and the actual transmitting gear willsoon be assembled. The whole outfit willbe entirely self-contained, current beinggenerated by dynamos driven by oilengines, and oil being supplied to theengines from a huge gasometer -like tank.There is a studio in the building which willbe used for tests and emergencies.

Disguised!For some reason or other the B.B.C.

haven't been encouraging callers at the13raokrnan's Park station, and the " Pressare, for the moment, strictly not adMitted.Therefore, in order to find out the positionof things for your especial benefit, I reallyhad to assume :the disguise I have oftenreferred to in my lighter paragraphs.. No,I'm not joking this time !. I did assume adisguise, and I did succeed in passing the" guards " and having a good look insidethe mysterious building. I won't say whatthe " disguise " was, because the B.B.C.may read this paragraph-and I may wantto use it another time !

Tice B.B.C. RushAs I have said before, quite a number of

B.B.C. people, particularly from the en-gineering side, have turned over to talkingpicture activities. The successful negotia-tion of half a dozen contracts has put thespark to the gunpowder with a vengeance.Rumours 'of huge salaries to be earnedelsewhere have had effect. The productionmanager of one film -producing firm hastold me that he has had between thirtyand forty applicationslor jobs from B.B.C.engineers as the result of a small announce-ment in the Press that his firm contem-plated entering the " talkie" field. By theway, I didn't tell you that all the trtpeople say " talker " now-" talkie " is arelic of a past age.

The chief sound engineers of half a dozenproduction units already formed havebeen taken from one B.B.C. experimentalsection alone. The meetings of the "soundsection" of the Society of Motion PictureEngineers will be like a reunion of B.B.C.people, now become hated rivals !

L.P. TroublesFunny-isn't it --how often in wireless

we cast aside some circuit or componentonly to re -discover it later on and to returnto it full of enthusiasm. Low -frequency

circuits are a very good case in point. It'as proved to us conclusively by expertsthat transformers did, must, and alwayswould distort. We hurled our transformerson 'to the rubbish heap in order tofit R. C. couplers. Then super -expertsshowed that R.C. had a little way ofsuppressing certain frequencies. Meantime,transformer designers were busy, and beforelong they produced components guaranteedto deal faithfully with any sand from theroar of a lion to the squeak of 'a bat. Thetransformer came into favour again, butwe all nodded wisely and said that whereyou had two L.F. stages only one of ,themmust be transformer coupled:' Arid wetold each other just why' this was so.There certainly was distortion if two trans-formers were used, but very few havereally understood why it came about.Actually transformers, if of first-ratequality, were blameless; the nasty noiseswere due to something quite different.

Back CouplingsWhen a common source of H.T. is used

we provide the valves of the receiving setwith a very simple way of metaphoricallyputting their thumbs to their noses andlaughing at us. In saying "common," bythe way, I am referring to the fact thatthey all shared it, though matters are madevery much worse if it is also common inthe cheap and nasty sense. The resistanceof this H.T. source is at the root of thetrouble, for it serves to link up valve withvalve' in a way not contemplated by thedesigners of sets. The result is that we -getan undesirable feed back or reaction effectwhich may have most unpleasant results. -

Theory and PracticeThe detector valve may be quite a

nuisance in this way. In theory its platecircuit contains only D.C. and audio -fre-quency oscillations. In practice a certainamount of radio -frequency oscillationsgenerally manage to find their way through.With the kind help of a common ' H.T.source we may find the firstnote-magnifyingvalve oscillating quite happily at radio -frequency. In this case there is no howling,but reception is very woolly and the loud-speaker emits a distinct plock whenever thefinger touches or leaves the grid terminal ofthe valve holder. Then note-mag. numberone may become back -coupled to note-mag.number two to such an extent that audio -frequency oscillation occurs, and we geteither a howl or that disgusting successionof pops which is known as motor -boating.

The RemedyYou can sometimes cure L.F. howling

or rnotor-bOating by the simple process

of wiring a fixed -resistance with a value ofabout a quarter of a megohm between thegrid of each low -frequency valve and itsnormal connection. This is a cure of a kind,but it does not strike at the root of thetrouble, and the best way really is to pre-vent, rather than to cure. Your set may bequite blameless when the batteries are new,supposinglthat it works from a dry H.T.B.,but as time- goes on quality becomessteadily worse and worse. You put thedistortion down probably to the fact thatthe plate voltage is declining, whereas it is

, due not so much to that as to the risingresistance of the common H.T.B. which mayreach astonishingly high figures. I haveknown a 44 -cell battery, which still showedover 4.0 volts on a good meter, develop aresistance of nearly 5,000 ohms --quiteenough to cause all kinds of L.F. worries.You can end your L.F. troubles and improvethe quality of almost any ret by simplyfitting de -coupling circuits consisting of asuitable series resistance with a path toearth, via a fixed condenser, for oscillations.The effect is to keep oscillating currentsclean out of the source of H.T. supply andthus to prevent undesirable couplings.

Short-wave NewsI mentioned recently that short-wave

conditions were showing a very markedimprovement. At the time of writing theyare about as good as they have been fortwelve months or more. On any afternoonwhen he is working you can be pretty sursof picking up PLE from Bandeong inJava, whilst W2XG, the American end ofthe transatlantic telephone service, is to beheafd very powerfully .on a wavelength thatvaries from time to time. I have had beauti-Ing reception lately from W2XAD, the19.56 metre relay of WGY, as well as fromW2 X0, which transmits the same station'sprogrammes on 21.96 metres, KDKA isnearly always to be picked up by way ofW8 XK on 25.24 metres, and NV2XAF which-relays KDKA on 31.46 metres, is excellentunless interfered with by a miserable C.W.signal that for some unexplained reasonappears to have adopted the same wave-length. The Nairobi station, 7LO, is easilypicked up, as a rule, on 31 metres. Thereare several good transmissions from theContinent, the best of which are DOberitz(AFK) and Madrid (EAR' ro).

A Good CombinationFor short-wave work just now I am using

a grid -leak -and -condenser detector, fol-lowed by a pentode valve, with transformercoupling between the two. This I find anexceedingly good combination, for it givesone splendid signal strength, with none ofthe noisy background that one is apt to get

emattur WirdT 620 APRIL 27, 1929

4 On Your Wavelength ! (continued) is even with the most carefully designed two -stage note -magnifier. This combinationgives me really good loud -speaker receptionof a number of American stations on anyfavourable evening, and it is delightfullyeasy to work with, since there is only onetuning control and a reaction condenser.This short-wave set has also a larger set ofcoils, which enables it to be used for recep-tion of the kcal station.

The Portable LicenceThe concession made by the Postmaster -

General to portable -set owners will be verymuch appreciated, except possibly by thosewho have already taken out a second licenceand cannot get their money back ! The newregulation is that, provided that youalready have a licence for a stationary setat home, you need not take out another forthe portable, but if you are using the latteraway from home you must carry the licencewith you and produce it when requested todo so by duly authorised officials. Picnicparties, therefore, may receive visits, sincethe local lists obviously won't show thenames of motorists who have come fromsome little distance. The best tip, by theway, is not to carry the licence in yourpocket, but to gum it inside the case of theportable. It will then always be at handwhen asked for, instead of having been left'in the pocket of one's other coat.

- A Television Society LectureAlthough it is of recent birth, I was

made to realise the other evening that theTelevision,Society is a very live one. I paida visit to the Engineers' Club and listenedto a paper by Mr. J. Cameron Rennieentitled, "Some Notes on Exploring."Lord Angus Kennedy was in the chair; andprior to the lecture proper an informal dis-cussion took place, and it was a delight.tosee the earnestness with which membersparticipated.

In introducing his topic, Mr. Rennieformulated some rather novel lines ofthought, and compared and contrasted thefive human senses-feeling, tasting, smell-ing, hearing, and seeing-in their relation-ship to exploration. The first three are verylimited in their scope; but, since the lasttwo depended up -On wave motion g high

frequencies for their action, it was sug-gested that possibly in some hitherto

..u.nreyealed fashion, feeling, tasting, andsmelling may be governed by wavelengthsat a frequency bordering on. zero ! In con-nection with the human eye; if has to beeducated to perform its natural function- inan efficient manner, Nit when we turn tothe television eye, namely, - the photci-electric cell, it does not lend itself to such aprocess. It cannot take in -a whole scene,but has to be Made to explore it spot byspot at a rapid speed. This is where the

exploring or scanning disc comes into being,since it enables a spot of light to traversethe object being televised and thus permitthe cell to convert the varying -light inten-sities into electrical pulsations.

Exploring or Scanning?The lecturer lodged a plea for the use of

the word "exploring" as against "scan-ning" where television is concerned, attri-buting the latter word to American origin.It is surprising how the term which is firstapplied to describe a new process shows atendency to retrain, and since scanning wasused initially it is now adopted fairlyextensively. A Chambers's Dictionaryseems to offer little solution to the differ-ence _etween the two terms, for scan isgiven' to examine carefully, to scrutinise,"and explore is given " to search for the pur-pose of discovery, to examine thoroughly."We are so often apt to use the word scanin the relation of a quick glance that it issmall wonder that it has been applied totelevision, for obviously the object beingtransmitted is disintegrated by the spot-light at a rapid rate. On the other hand,whereas a quick glance by a person is sureto miss detail, our television eye will not failin this respect; so perhaps the palm shouldbe awarded to " exploring." Official tele-vision terminology will, no doubt; settlethis question in the near future.

Have You Ever Thought of It?Has it ever occurred to you how aston-

ishingly cheap is the wire of which we useso many yards in making those sets whichfor some queer reason are called wireless?For coil making one buys a pound reel of,say, No. 26 double-cottOn-covered wire forabout four shillings. That reel containssome three hundred yards of 'wire, drawnwith astonishing exactness to a standarddiameter 'and covered with two layers ofcotton insulation. To make a 6o -turn .coilon a 3 -inch former we need roughly15 yards of wire, or one -twentieth of apound, of which the cost is rather overtwopence.' Even of the very 'fine wire,which must be queer stuff to - handle in-the making, one gets an almost miraculousamount for one's money. When you buyNo. 36 .41:c:c. at gs. 6d. a pound you obtainwell oVerla, mile, whilst No". 45, which sellsat about 22S. 6d.' "enamelled or 16s.double silk covered, runs out to eight miles-to the pound.

ADAPT YOUR SETTO THE SHORT WAVES

WITH THE UNIQUEADAPTOR TO BE

DESCRIBED NEXT WEEK

For Cone UsersThe cone type of loud -speaker is del

servedly very popular, for if it is given afair chance by the use of the right kind of,valves in the right kind of receiving set it'provides reproduction of wonderful quality)Cones, however, do repay a little attentionsnow and then. On this point I speak with!experience, for I have an old friend nowt'that by the exercise of a little care I havekept in every bit as good condition aswhen it was first acquired. First of all,don't forget that permanent magnets arenot really permanent. They tend in courseof time to lose a certain amount of theiroriginal strength. When this happens theinstrument may become overloaded witha volume considerably smaller than itcould originally handle with ease. Re -magnetising costs only a shilling or two,1and it is well worth while to have it done)periodically.

Another TroubleHere is another point that may be found

useful. One of my cones, whose magnetwas known to be in first-rate condition,began -to " zizz" when certain notes were,being reproduced at fair strength. I knew'that no overloading was taking placeiwithin the receiving set, so that obviouslysomething was wrong with the loud -speaker,itself. On. examining the mechanism,found that several small screws had worked!a little loose; probably owing to the con-stant vibration to which they are sub -1jected. When these had been tightened'up all signs of the trouble di',appeared.1

Wireless PlaysI am :glad to see that a good deal more

attention is being paid nowadays to the'choice of plays that are really suitable forbroadcasting. Heaps of modern dramatiC,works don't fit in a bit, mainly becausethey rely so much upon stage effects,'which, of course, one cannot have-exceptthe " noises off " part of them-from theloud -speaker. Shakespeare has alwaysbeen a favourite with wireless folk, andthough they haven't realised it, the reasonis largely that Shakespeare had to writefora stage which had little or nothing in,the way of effects. In his day, at the oldGlobe Theatre, the scenery consisted attimes of a blackboard upon which was!chalked up, "This is the sea shore ofBohemia" or something of that kind)Shakespeare relies, then, mainly upon hisdialogue, and that is why his plays broad-:cast so well. One or two -excellent modernplaywrights are engaged, I` heat', on playswritten particularly .for broadcasting, andvery special attention will be paid to, theirtproduction. I. am sure that all listenerswill look forward with the greatest interest'to hearing the results. THERMION.

APRIL 27, 1929 621 mateurWLr

CUTTING OUT 2L0 INSQUARE

ER

IT is always gratifying to.I. hear of readers' successwith our sets. Corres-pondence of this natureforms, of course, quite aconsiderable portion ofthe daily post bag, andwe always prefer letters which laud theirpraise in plain facts hnd, preferably, give astation log, rather than those which talk invague terms of wonderful reception and,after all, are rather empty pmans of praise.

The AMATEUR WIRELESS Technical Stafflikes to have reception reports, whethergood, bad, or indifferent, because this is oneway in which a census can be taken ofreaders' opinions and popular demandssupplied. Therefore if you have built an

AMATEUR WIRELESS set,do not hesitate to writeto AMATEUR WIRELESSabout it.

The "Clarion Screen -grid Three" is a case inpoint. This was designed,given a thorough testing,End described in AMATEUR

This photo-graph shows the

main constructionalfeatures of the " Clarion "

TIMTHEIT SUCCESSWITHe7ire,_

%Id\ #4

WIRELESS, Nos. 352 and 353. As it wasfelt that this was an average -man set andsomewhat out of the ordinary on accountof the good performance it could put up,and yet at the same time be simple tobuild and operate, we diverged somewhatfrom our usual course and placed the set inthe hands of an enthusiastic AMATEURWIRELESS reader, living in the Londonarea. This test report was published inAMATEUR WIRELESS, No. 353, and it isnecessary only to repeat that this indepen-dent tester succeeded in receiving thirty-one stations at full loud -speaker strength !

Wonderful ResultsAs is always the case, the results obtained

with any super -performance set receivesceptical reception on the part of a few

amateurs who still cling toold-fashioned receivers andideas, and never take thetrouble to modernise eitherand realise what amazingresults can be obtainedwith the aid of present-dayconstructional facilities.

The "Clarion Three" hasmet with a most enthusiasticreception from ordinarylisteners and from wirelessdealers. Quite a large

proportion of the reportsreceived regarding the" Clarion Three" havebeen from dealers whohave sold kits and partsfor making up the"Clarion" to AMATEUR

WIRELESS readers. They, in their turn,have received appreciation from the pur-chasers on account of a good investmentfor a little money and have passed theappreciations on to us.

To take just one instance, Messrs. K.Raymond, of 27 and 28a Lisle Street,London, .W.C.2, have made a speciality ofthe "Clarion" largely on account of thefact that they have found this to be one ofthe very few sets that get distant stationswhile London is working ! And this at adistance of one mile from 2L0 !

In consequence, the "Clarion" is beingused largely as a demonstration receiver,and every day during programme time

woe

000025AIFO

rf

The circu

The Clarion Three was tested at the London workshops of Messrs. Raymond, within a mile of theLondon aerial and in an area wherein 5GB and 5XX are only faintly received on most sets, owing toshielding of the aerial. Although the aerial wire is about 6o feet from the ground, the proximity ofneighbouring roofs gives it an effective electrical height of only a few feet,

With the Clarion attached to the business end of the aerial however, conditions were found to be en-tirely different. Both the long and the short-wave Daventry's came in at good loud -speaker strengthand quite free from any kind of interference, Greatly to the surprise of the operators, Radio Pariswas also received on the loud -speaker without any interference and with excellent strength against abackground of silence. The test was mode early in the evening when not many foreigners were onthe air. On the short waves it was notable that Langenberg was received well enough to provide acomplete evening's programme had this been so desi.-ed.

as

'Da

OLI'

as- as°it of the "Clarion Three "

there is a large crowdgathered round the LisleStreet Depot judging the' Clarion " for themselves.

Recently, at the requestof Messrs. Raymond, somemembers of the TechnicalStaff tested the set while(Continued at foot of next page)

lh: interest that the " Clarion Three " has continued to arouse is evident from these photographs taken outside a well-known London wirelessdealer's a few days ago

622 APRIL 27, 1929

HOW IT HAPPENEDIN recounting an experience which befell

me quite recently I. do so to warnothers of what might happen should theydo the self -same thing as I did.

It all happenedlike this. I was con-ducting some experi-ments with a newscreen - grid valveportable and as Idid not want thetrouble of discon-necting the entireset of connectionsto t h e batteriesa n d withdrawingmy valves eachtime I tried anexperiment, r merely switched off the valvefilaments and took very good care to see thatno straggling wire from the H.T. supplyside of the set came into contact with thepositive L.T. feed wire.

The circuit I was testing was that shownby Fig. r. From this it will be seen thatwhen the filament switch was broken nocurrent could pass from the H.T. circuit

or L.T. circuit through the receiver.Nevertheless with the H.T. battery con-

nections in place and the valves in positionin the set I was unfortunate enough to blow

up four perfectly good valves.-0/201K+ A reference to Fig. I will

601Na+ make things quite clear. I was

H. Z-.1

-ON.'+2

POs/,,On,AOR FUSE

TO z.7.--

si7-4---c:No o L.1: -P

Figs. 3 and 4.

NT -

L.1:+

Fig. 1 (left). Thecircuit with whichtests were being

made

Fig, 2 (right). Thepath of the H.T.current is shown by

the arrows

HT

c-6-°(,---77-/Rif PO/NT

SW/70/IT

}

t This story of the loss of fourperfectly good valves may

e serve as a warning to youwith the copper screen and point marked a.

The result was disastrous for although theL.T. switch was " broken " the valves blew.

A glance at Fig. 2 will make clear thecomplete path for the H.T. current throughthe valve filaments. Many alternativeconnections for the battery system sugges-

N.E ejLt

.4

incifORT.ORCEI/TSTOPRar 1

\I0 C' I

1010 I

I

I

I

COMMON-

-

011+

it

How such an accident can be prevented is shown by these diagrams

experimenting with the 2-mfd. condenserbetween a and b to find its best position incircuit. It had already been connectedbetween points marked a and b and I wastrying it between points marked a and c.This position did not seem so satisfactoryas position a and b and in trying to dis-connect and wire up again to this positionone end of the wire came in contact

HZ.

ted themselves as ameans of avoiding arecurrence of thetrouble, but the oneI finally settled upenis shown by Fig. 3,

Even so, I nowtake the precautionof disconnecting theH.T. leads fro mthe batteries andalso pulling out thevalves from theirholders. Once bitten,

twice shy, is a motto I shall remember forsome months to come. A few alternativesystems of battery connections are shownby Fig. 4.

A final word of advice to owners of,screen -grid valve sets. Fit a` safety fuse:between the negative H.T. wanderplug of

the battery and the negative H.T. terminalor wire on the set. ADSUM.

" CUTTING OUT 2L0 INLEICESTER SQUARE "(Continued from preceding page)

London was working, and succeeded inobtaining stations quite free from inter-ference.

Another reason why the "Clarion" ispopular is because it necessitates the veryminimum of components for the maximumin the way of results. As a matter of interestit is perhaps opportune to give the com-ponents list.

As with all AMATEUR WIRELESS sets, ablueprint has been prepared to assist con-structors of the "Clarion Three," and thiscan be obtained, price Is., post free, fromthe 'Blueprint Department of AMATEURWIRELESS, 58-61 Fetter .Lane, London,E .C.4.

It will be remembered that when the"Clarion Three " was first, published,Messrs. Selfridge & Co., of Oxford Street,London, W.1, thought so highly of it, that

"Clarion Three" ComponentsEbonite panel, in. by 7 in., and two strips, one

6 in. by 2 in. and one z in. by z in. (Becol,. Raymond,Ebonaet, Radion).

Baseboard, 14 in. by 9 in. and cabinet (Pickett).Two .0003-microfarad variable condensers (Polar No. 3,

Formo, J.B., Burndept, Lissen, Burton)..000i-microfarad reaction condenser (Burton, J.B.,

Lissen, Polar, Ormond).Two dual -range centre -tapped coils, one aerial coil and

one anode coil with reaction (Tunewell).Push-pull filament switch (Bulgin, Lissen, Trix,

Wearite).Three valve holders (Lotus, Lissen, W.B., Benjamin,

Burton, Formo).Pre-set series aerial condenser (Formodenser Type J.,

Igranic).1-microfarad fixed condenser (Lissen, Dubilier,

Mullard)..ox-microfarad fixed condenser (Dubilier, type 61o,

Lissen, T.C.C., Mullard)..000z-microfarad fixed condenser (Dubilier, Lissen,

T.C.C., Mullard).3-megohm grid leak (Lissen, Dubilier, T.C.C., Mullard).,Screen -grid H.F. choke (Peto-Scott).H.F. choke (Lissen, R.I. & Varley, Polar, Trix, Wearite,

Burndept).L.F. transformer (RI. & Varley,. Ferranti, Lissen,

Philips, Igranic, Marconiphone, British General). '

Screen, 81 in. by 6 in. (Parex, Peto-Scott)Eight terminals marked, Aerial, Earth, L.T.A- ,

H.T.+ H.T.+z,L.S.+ , L.S.- (Belling -Lee, Eelex,Igranic, Raymond)

One yard thin flex (Lewcoflex).One red and one black wander plug (Clix).Quantity of No. 16 gauge bare connecting wire (LewcoS).Two slow-motion dials (Brownie).

they authorised us to inform readers thatthey themselves would have pleasure insending a blueprint, gratis and post free, toevery reader making application. Weunderstand that Messrs. Selfridge still havea limited number of blueprints available,and readers may obtain one by addressinga post card to the Radio Department,mentioning AMATEUR WIRELESS, or bymaking a personal call.

So far as the operation of the completeset is concerned, there is nothing at all toworry about in this. The panel carries anon -off switch, which controls the filamentsof all valves, two tuning condensers, the'dials of which can be set practically in stepand a midget reaction condenser, which, inmost cases, is used simply as a volumecontrol. Simplicity itself !

Let "Amateur Wireless"solve your problems

APRIL 27, 1929 623 =lair Wtretess

WITHOMUSIC

(11111111111111111111111 11[11111111111111

A Weekly Programme Criticism by Sydney A. Moseley

HAVE you been to the People's Palaceconcerts. You should go. The best

and cheapest concerts in the country.Every listener should make it a point togo to an occasional B.B.C. outside trans -Mission. Besides being a change, you hearquite a lot.

So far as the Mile End concerts are con-cerned, here are a few points : Percy Pitt

Dora Maughan-a caricature

and his ear. What's wrong with it ? Any-way, a habit not to be encouraged-if it isnot too late. Apparently he felt the fullestconfidence in the violas, for he had hisback'to them most of the time. Refresh-ment arrangements too stupid for words.Can't the B.B.C. see to this? You have toline up and buy tickets, estimating theamount you propose to spend !

The idea of bringing Miriam Licettedown for one song only is difficult to under-stand-particularly since there are noencores. I suggest that notice of therebeing no encores in either half should beclearly stated in the programme.

Walter Widdop had a good reception.He is a real broadcasting artiste, since helets us know what he is singing about.How do you think both these popularartistes look in the flesh Go and see !

Was Segrave's talk really impromptu ?Sounded much too good for it. What awonderful thing it is to get into intimate

touch with these men of the moment.What memories our grandparents wouldhave had of Pitt, General Gordon, Dickens,etc.

Let us remain conscious of this wonderof ours which was denied our forebears.

+

Regimental marches with brief descrip-tions by Walter Wood, quite interesting,but I didn't much care for the GlasgowSingers.

The correspondent who asks the Editorto interest me in the Sunday programmesmust be a new reader. (He is none the lesswelcome because of that 1) If not, he hassurely overlooked my repeated criticismof the very thing he wishes me to criticise.However, we shall persevere with our taskof reforming the seventh -day programmes.Let us not have to depend on Continentalprogrammes 1

I was not able to hear the second "GaySpades," but everybody has been tellingme that it was splendid. "One of the mostentertaining hours I've heard yet" is oneemphatic opinion. Charlot appears to havescored a bull's-eye this time.

"Memories of Leslie Stuart" was stagedsuperbly by the Birmingham station. Itwas a treat to hear again such undyingtunes as "Dolly Daydream" and "Lily ofLaguna" -and played and sung so well.

Couldn't you imagine how the middle-aged folk were enraptured ? Couldn't youhear them saying : "Ah ! You can't beatthe good old songs. This modern-(sniff !)-jazz can't be compared with them." Ofcourse, that irredeemable friend "Harold"has his point of view. He says :-

"All those slow, mournful songs about'fair lilies' give me the creeps': What thepublic needs is good solid rhythmic peppysyncopation-and then some-"

Need I say he belongs to the moderns

Foden's Motor Works possess a versatilebrass band. They do not confine them-selves to the usual overtures and selections,but reach out to other musical fields.Ronald Whitehead, who was the vocalistin a recent programme, has a bass voice ofdepth and purity. Did you hear him sing"Drinking" ?

Charlot's Charity Hour was welcome,although it consisted merely of are -hashof old numbers, some of which have beenplayed so often that we know them insideout.

I still hear good accounts of VernonBartlett's talks. His is a difficult job in allconscience, and that he has been able tomake good up to now is all to his credit.

I wonder if any listeners are intriguedby the personalities of those who deliverthe lessons on Sunday afternoons. Thespeakers remain anonymous, but I havegood reason to believe that many well-known men are very willingly brought infor this purpose. One is an ex -PrimeMinister.

Not long ago I remarked in thesecolumns on the unsuitability of Philip

W. H. Berry as Lissenden sees him

Brown's Dance Band which often accom-panies variety from 5GB. According torecent correspondence on this matter, mypoint of view was shared. However, mylatest correspondent asks me to revise myopinion because " they are showing markedimprovement these days. In fact, theirstandard is now so good that they remindone of a certain snappy little combinationwhich used to broadcast from the Savoy."

mateur Wpb 624 625 =tear Wis.elt5

11

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THE appeal of the portable is in nosense an inexplicable one. It is, infact, simply an extension of the

enthusiasm which every true lover ofwireless discovers when he has the oppor-tunity to take hisreceiver cut of doors.

The " L'5 : 5 : o Portable," the receiversection of which was described last week,is an ingenious little receiver which, apartfrom its attraction on account of the lowinitial cost, fills a definite niche which, webelieve, has not yet been covered in port-able receiver design ; that is to say, althoughit is a portable and can be used out of doorswith equal facility to that provided by aset incorporating a frame aerial, it can beused as a transportable or even as a some-time indoor set, on account of the fact thatan outdoor aerial is employed.

Small SizeA convenient feature is the smallness of

the dimensions of the containing case.This can easily be constructed from 1/2 -inch

NZlitrita ri1/4.VVIZMMOMWAYANAViir ANZVaTS$1Y ESIWIZAValartiCle

MORE ABO.14son

`4;AYAVV.?PiaNS-4492altIPAM.WerAWM.W.64"NWACTAWIMiz NseICANg... AM= AtSVVPIAONV Zr.h VartrA -. SIVeiri SWIM aN.' AI) ON 1/4. 47.X.,%;

T THE 5:5:0 PORTABLE 1UMAKING THE CABINET : AERIAL EFFICIENCY : VALVES AND TUNING

1..ms,wood. The overall dimensions are 13% in.by 13%2 in. by 4% in. One of the largersides of the cabinet is a lid by means ofwhich access can be gained to the back ofthe receiver and the battery compartment.On the other side of the cabinet is thereceiver panel which, of course, as men-tioned last week, is r31/2 in. by 6 in. Theinternal dimensions of the battery compart-ment are, roughly, 121/2 in. by 7 in. Thisallows of the fitting of an H.T. battery,amply able to stand up to the job of supply-ing anode juice for the detector and powervalves, and also the provision of an ade-quate accumulator and a grid -bias battery.

The baseboard on which the main com-ponents of the receiver are mounted forms

a shelf which is mounted on smallwooden ledges at each side of thereceiver cabinet. The baseboardhas the dimensions 12 Y8 in. by 4% in.and this, with the panel, slideseasily into the cabinet and formsa complete tinit.

Advantage of Separate AerialFor the reasons enumerated last

week, neither frame aerial nor specialloud -speaker is incorporated in thecabinet. If any further argumentbe needed it remains; only to bepointed out that the addition of aloud -speaker considerably increasesthe cost of a portable receiver, andas most enthusiasts have loud-speakers of their own in use in con-junction with a home set, the con-struction of a special - instrumentfor the job is not always necessary.

Of course, for those who want tomake the '! : 5 : o Portable " asomewhat more ambitious receiver,many types of loud -speaker can bemodified to suit the dimensions ofthe present portable. A loud-speaker of the type which is eminently

suited for the " L5 : 5 : o Portable" re-ceiver is the linen -diaphragm loud -speakerdescribed in AMATEUR WIRELESS, No. 355.A blueprint is available for this unitand by slight modification of the dimen-sions of the cabinet a linen -diaphragmloud -speaker could easily be added. Mostlisteners, how-

Wrod onever, who make cornersup the "5:5:oPortable"will preferto use it inconjunctionwith some im-promptu formof aerial slungup just wherev-er convenient.

Really t h eaerial difficultyis very oftenlargely exagger-ated when dis-cussing theworking of out-of-doors wire-less. Of course

AMBER FEET 1-1/NCE

'this diagram shows all the

it is not to be expected that a two-valverwill be worked on the fringe of what theB.B.C. calls the service area of any mainstation. To get the best from any two-valver, portable or otherwise, and even withthe best of outdoor aerials, it should beworked generously within the allotted range.

More particu-larly is this thecase with port-ables from whichfair volume isexpected evenperhaps at theexpense of spar -tan purity.

A SuitableAerial

For the aerialit is safe tocarry a smallreel of about3o ft. or 4o ft.

r=ed of wire, pre-ferably insula-ted. Bare wire,with insulators,

POSIT/ON (FRAN&AND BASEEVARD

METHOD OFSECUR/NODOOR

BAITER,'SPACE

,o/Pftvd

HOLE

necessary details of the case

This is a plan view of the actual receiver portion of the " £5 : 5 : 0 Portable "

0.0 0 .0 00 0

is rather more troublesome to erectin a hurry, whereas insulated wire can beslung about almost.anywhere required.Bare wire is, however, perhaps better forthe earth lead as there are many occasions(such as when working a portable on theriver and so on) when a direct earth caneasily be made.

Batteries and ValvesBatteries and valves are always an

important point in a portable because tosome extent there must be a compromisebetween valves capable of dealing fullyand adequately with the job in hand andthe batteries which can be carried to supplytheir requirements; of course, the twolimits in this respect are size and weight.

An accompanying table gives a selectionof suitable two -volt valves and most usersof this portable will prefer to use two-volters if for no other reason than that atwo -volt accumulator is, of necessity,smaller, capacity for capacity, than a six -volt accumulator.

Four- or six -volt valves can, ofcourse, be used and there may besome listeners who will prefei to doso in order that they may use thesame valves as are used in a homeset and possibly even the setaccumulator.

So far as valve types are con-cerned the detector should be ageneral-purpose valve with an im-pedance of about 20,000 ohms.Grid condenser and leak rectifi-cation is employed and the detectorstage is followed by an efficientmedium -ratio L.F. transformer.As is well known, these two factors havea primary bearing on the selection of avalve for a detector stage. The great pointabout the power valve is that it should beeconomical in filament consumption. Thispresents no great problem nowadays for

valves of the D.E.P. class, capable ofdealing with an adequate grid swing takeno more than .15 -amp. filament current.Larger valves, say of the DEP24o type, arereally hardly necessary in a portable set.

SUITABLE TWO -VOLT VALVESto use with

THE " £5 : 5 : 0 PORTABLE "

Mahe Detector L.F.

Cosmos . . . . SPI6/G SPI8/RR

CossoR . . . . 2I OHF 220P

EDISWAN . . . . HF2I0 PV2I5

MARCONI .. . . HL2 10 DEP2I5

MAZDA .. . . GP2I0 LF2 15

MULLARD .. . . PMI/IF PM2

OSRAM . . . . HL2I0 DEP2I5

SIX -SIXTY . . . . 2I0FIF 215P

A value of 120 -volts H.T. should begiven to the anodes of the valves, and, asmentioned, the battery compartment is

- quite capable ofcontaining.an ad-equate dry .bat-tery.. With mostpower valvesabout 71j2 to 9volts grid biaswill be necessary.

Thearrangement

of receiver andcase is quite simple

0

Ottawa Wirelefl 626 APRIL 27, 1929

"A.W." TESTS OF APPARATUSConducted by our Technical Editor, J. H. REYNER, B.Sc.(Hons.), A.M.1.E.E.

Handy Battery TagsSO soon as the construction of a set has

been completed, one is apt to makeconnections in a slipshod manner usingardinary copper wire bent round at the'ends to make connections with the accumu-ator. Perhaps the high-tension battery istreated with more respect by fitting some:form of wander plug'S.

Now, although this type of, connection tothe accumulator is all right for experimentalwork, the ends of the copper wire areUltimately liable to corrode and cause badcontacts or breaking of the wire altogether.It is preferable in the first place to fit propertags to the L.T. leads,

Some useful connectors have been sub-mitted by Messrs. Lectro Linx Ltd., 254Vauxhall Bridge Rd., S.W.r. These aremade in two forms, one being a spade tagwith the slot cut in the side and the other atag with a central hole, In order to guardagainst corrosion, these components maybe obtained with a lead coating on a brassfoundation in place of the normal nickelplating: This is a good feature and shouldaid in preventing corrosion.

, .

Jelectro Acid SolidifierSELDOM do eisen careful people manage

to handte, accumulators without spillingsome acid at one time or other. It may beonly a drop or two, but this is- quitesufficient to harm clothes or other articleswith which it comes in contact. Althoughunspillable accumulators are made, eventhese may not always be fool -proof. It was,therefore, with interest,that We tried a newliquid preparation known as- Jelectro,made by the Jelectro Laboratories, Edg-ware Road, London. This solution, whichmay be obtained in bottles, has merely tobe added to a quantity of acid in theproportion of three parts of acid to one ofJelectro and the solution will ultimatelysolidify to a jelly. It is important, in orderto ensure proper solidification, to see thatthe acid has a specific gravity of 125o.

It follows that in solidifying an accumu-lator, one should first pour the acid out intoa suitable container and adjust the specificgravity, by adding concentrated acid ordistilled water as required. Then havingtaken a careful measurement of the'quantity of acid available, add a third of theamount of Jelectro.

We carried out these instructions withthe acid of a small two -volt portableaccumulator and, after mixing the solutionthoroughly, poured it back into the'accumulator. It was then left overnight,and in the morning proved to have solidi -

lied in a most satisfactory manner. Noliquid whatsoever remained and it was,therefore, impossible to shake any of theelectrolyte out of the container.

The accumulator was then charged andplaced on a test discharge. The figuresindicated that it was behaving in a satis-

Microfuse Safety

factory manner, the jelly electrolyticapparently functioning as well as theliquid.

MicrofusesMOST readers have experienced the

misfortune of 'burning out a set ofvalves, yet such a calamity might have beenavoided by the use of suitable fuses. It is,indeed, safe to prophesy that at 'no verydistant date every receiver will be ade-quately fused. The reason this is not doneat the present time may be that fuses forradio use are not always obtainable.

We have just tested a device known asthe Micro -fuse, manufactured by Messrs.

Fuse

Airmax Dual -range Coil

Microfuses, Ltd., of 3 Finsbury' Square,E.C.2, This component is made in the fOrrnof a cartridge somewhat similar to a gridleak and fits in a special holder. The samplewhich we tested is rated to blow at a currentof between 15 and zo milliamps-a valuesufficiently low entirely to safeguard theslenderest of valve filaments. When testedin our laboratories, ,this sample actuallyblew approximately at 14 milliamps.

The construction of the component isinteresting for in order to obtain a very finemetal surface without tendency for thissurface to break due to insufficientmechanical strength, a fine glass rod iscoated with a metal deposit and this itselfforms the fuse. Such a device is quitefool -proof and fully protected by an outerglass casing.

Airmax Dual -range CoilDUAL -RANGE coils have enjoyed con-

siderable popularity during the pastseason and indeed it is likely that this willcontinue during the coming season. Usersof wireless apparatus feel naturally indis-posed to:change soils when tuning from onewavelength band to another; therefore anydevice which -overcomes the necessity forchanging is regarded in a favourable light.

One of the most popular of the circuitsutilising the dual -range coils has been the"Mullard Master Three Star, " and it is notsurprising therefore that in addition to thespecified coils, other manufacturers shoulddesign inductances for use with this. circuit.One of these inductances, an Airmax dual -range coil, designed specially for the"Master Three Star, " has been submittedfor test by Messrs. J. Dyson & Co., Ltd.,5-7 Goodwin Street, Bradford, Yorks.

In this coil, the grid and reaction windingsare placed in;, io slots on an hexagonalair -spaced former. The reaction windings,which occupy two of these slots, are placedin between the short- and long -wavewindings. The change -over from one wavelength range to another is accomplished bya push-pull switch, and this fitted on tothe panel by drilling one hole, forms asupport for the coil. The ends of the windingare taken out to six terminals numbered inthe standard manner for' the "MasterThree Star."

As in the standard circuit, the aerial is'led to the coil through a .000i fixed con-denser. We carried out a number of tests,using the coil in an actual "Master ThreeStar" circuit, and were quite favourablyimpressed with the performance, exceptthat the wavelength ranges do not appearto be quite correctly chosen. For example*with an average size outside aerial, therange of the low wavelengths extendedfrom 30o metres to 58o and on the highwavelengths from ',too metres up to3,300 metres approximately. In both casesthe minimum wavelengths are ratherhigher than usual. Used with a 3o ft.indoor aerial, the minimum short-waveposition gives 28o metres. and the long -waveposition 1,050 metres.

APRIL 27, 1929 627 emattur Wale!)

I'

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IGRANIC L.F. TRANSFORMER TYFE C.For pure and distortionless amplification over the widest rangeof audible frequencies this transformer is unequalled.See the remarkable straight-line curves publishedfrom data supplied by the National PhysicalLaboratory. Hear the difference it makesto any receiver, giving mellow, full bass,and clear high notes. It can befully relied on for long and Cillconstant use. Use it for

ci 17/6first or second L.F. ,.=... ,u stage or both. IGRANIC at>

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COUPLING UNITt-The best and simplest means of get

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1

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volume from weak signals and ideal quality when the input :,.

is greater. 11

Easily mounted and can be connected as a unit containing ' --only one fixed resistance.

Apply to your dealer or write direct to Dept. D. 118.

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YOU CAN NOWCHARGE YOUR ACCUMULATORS AT HOME

ORWORK YOUR WIRELESS SET

BYGAS, PETROL, ELECTRICITY, STEAM

orAnything that gives Heat will do it !

" THERMATTAIX **

converts heat into Electricity without the use of either valves,liquids or moving, deteriorating fragile parts.When the Gas or Petrol burners are lit, or a switch or steamturned on, according to type required, " THERMATTAIX "at once begins to generate a steady Electric Current, and will doso for ever, as long as there is Heat." THERMATTAIX " is everlasting and cannot wear out.The three types for immediate use supplied from stock are for the

Pat. No. 255822.

use with Gas, Petrol or Electricity. The sizes are for 6 volts,4 volts, or 2 volts, and the output a half dr one ampere.Some of those to whom we have supplied these types are : over zooGas Companies The Woolwich Army Experimental Department,the Dutch, Italian and French Armies, the R.A.F., and (withspecially built models) the British Railways, Doctors, Architectsof note, Colleges, Universities, Radio Clubs, and Big GameHunting Expeditions for use in Africa and India.

Prices are frcm £4 173. 6d. Wr:te at once and secureimmediate delivery.

Testimonials and Descriptive Leaflet Sent on Application. I06/6a, High St.,MATHESON to' KEMP, Ltd., Head Office & Works : SOUTHAMPTONLONDON OFFICE: 12, GROSVENOR GARDENS, S.W.1.

Don't Forget to Say That You Saw it in "A. W."

emaleurWtretes_ 628 APRIL 27, 1929

12(9IDIOGROWSON Tuesday, April 3o, the London

Zoological Society will celebrate itscentenary, and in honour of this birthdayanniversary a special broadcast will becarried out by the B.B.C. It has not yetbeen decided which particular cages the"mike" will visit, but listeners may expectto be switched over to the lions' den, thesea lions' enclosure, the haunts of thelaughing hyena, and possibly, amongstothers, the parrot house.

Ebe Novarini, who is only eighteen yearsof age, and a newcomer to the Birminghammicrophone, will give a violin recital fromDaventry 5GB on April 3o. Ebe Novariniobtained a scholarship at the Royal Con-servatorio of Music in Milan when onlyseven years of age, and has given recitalsbefore members of the Italian RoyalHouse.

Two plays, The Ghost of Jerry Bundler,by W. W. Jacobs and Charles Rock, andThe Boatswain's Mate, by W. W. Jacobsand H. C. Sargent, will be heard bylisteners to Daventry 5GB on May Ir.

The well-known pianist, Harriet Cohen,will give a recital at the B.B.C.'s People'sPalace concert to be broadcast on May 2.

The Daventry 5GB vaudeville pro-gramme on May 6 includes the following

artistes : Ronald ' Frankau (entertainer);The Gay Pair (light songs and duets),Victor Sheath (banjo), Angela Mande(character songs), and Philip Brown'sDominoes Dance Band.

. From 5GB on April 29 listeners willhear the 'band of the Chatham Division,Rokal Marines. The conductor is Lieut.P. S. G. O'Donnell, whose brother is theconductor of the Wireless Military Band.

Moonshine is the title Of a new "radioshow" by Charles Brewer,, of the Birming-ham staff of the B.B.C., which' will bebroadcast from 5GB on May ro. Sketchesby Edwin Lewis will also be given, andOther popular artistes who will take partin this programme are Vera Gilman,Edith James, Harry Sennett, Brian Victor,Alfred Butler, and Harry. Saxton; alsoJack Venables and Walter Randall at thepianos.

Another of the popular "old folks"programmes will be given from the. 5GBstudio on May r r. The soloist is WilliamBennett (bass). The Birmingham StudioChorus, conducted by Joseph Lewis, willalso take part in this broadcast.

Listeners to Newcastle on April 28 willhear the Newcastle -on -Tyne PhilharmonicOrchestra, conducted by Edgar L. Bainton.

The solo artistes will be Grace Angutt(soprano) and Evelyn Barrow (pianoforte).

Wales is at' present the only countrypossessing a separate Priory of the St.John Ambulance Association, and Cardiffwill broadcast a programme in honour ofthis Order on May 8, which will include

- four scenes illustrating its history andworktthioughout the centuries.

Adolphe Hallis (pianoforte) and KateWinter (soprano) will take part in theNational Orchestra of Wales SymphonyConcert to be broadcast from the AssemhlyRoom, City Hall, Cardiff on May 9 at7.45 to 9 p.m. The popular concert at thesame time on May ix will also be relayed.

On April 30 the Newcastle station Willendeavour to give listeners an impressionof the atmosphere of a village inn; theconversation, dancing, etc., and doings: inthe back parlour will be faithfully con-veyed through the microphone to'the earsof listeners.

All Northern stations on April 28 willbroadcast a service from the SheffieldCathedral; the address will be given bythe Vicar of Sheffield, Archdeacon J.Russell Darbyshire. A Russian programme, including gipsysongs sung by Marova, songs of the Ukraine,and Russian dances, is to be given fromBelfast on May 6. The Radio Singers -andthe station orchestra will also take part inthis concert.

Demand is made by listeners to theGlasgow station for a musical lunch-timeprogramnie, such as that transmitted byother stations between 12 noon and2 p.m. The present transmission of music-from rr a.m. till noon-is suitable onlyfor the unemployed, it is argued.

FLEX JUNIOR GETS STATIC-w

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NOW THERE'SAN ORCHESTRAI,:q. AY I NO.,vE NEVER -GOTA FOR.:.....GQ

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APRIL 27, 1929

HAVE you had your copyof this descriptive fold-

er and blueprint ? It tellsyou how to build the 1929Imperial 3-the latest andmost modern set you canwish for. It also tells youhow you can at very littleexpense convert sets of olddesign into up-to-date re-ceivers giving remarkablepurity stability and volumeDrop us a card to -day ifyour dealer cannot supply

THE famous %Vat melDouble Range Tuner

gives your set accuratecontrol over the tuning onall waves between 250-600metres, and at the push ofa switch, 1,000 - 2,00')metres. A beautifullymade and handsome look-ing instrument selling atthe remarkable 12price of .

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FREEAn booklet of these eat,heels with pa, titters also of planedfretwood, transfers, tared ntoulding,ornaments, etc., free on request.

The Simplest and Cheapest MethodEach parcel contains good quality Mahogany, supplied planed, cut true,and ready for making up into a useful and handsome cabinet. There is a

variety of sizes for popular sets, and an illustrated comtruction sheetsupplied with each. You can't go wrong.

No. 6. Panel 16 x 8 -Depth 8in. 8/ 6 No. 9. Pane114 / 7 -Depth Sin. 7 -No. 7 12 x 6 6in. 4/9 No.10. 21 x 7 9in.10, 6No. 8 9 x 6 6in. 3/ 9 No.11. 24 x 8 9in. 1 2/ -

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OME RECENT

tOUDASPEAKE DVELOPMENTS\\AvAlots.'

APRIL 27, 1929

Although the loud -speaker is now such an excellent instrument it is realised that there is stillpossibility of improvement, and constant attempts are being made therefore to effect this. Inthis article Morton Barr describes some lines of development which are receiving attention

APART from the valve, the loud -speakermay fairly be regarded as the most

ingenious appliance used in wireless recep-tion. It has, of course, a larger record ofdevelopment than the valve, tracing itsorigin back to the original earpiece receiverused some fifty years ago in the begin-ning of line telephony.

Compared with the first telephonereceiver, the modern "loud" speakerowes almost as much to the gramo-phone industry as it does to wireless.In fact, in a recent High Court actiondealing with patent rights in the conetype of speaker it was admitted thatthe first large -diaphragm or "hornless"reproducer was designed for use with agramophone.

The difference between the gramo-phone model, driven by a stylus froma record, and the modern loud -speaker asused for broadcast reception lies chiefly inthe power handled by the latter, the energy

power amplifierbeing so muchgreater thanthe drive givenby a stylusmoving over a

S/ record.The develop-

ment of instru-ments capableof dealing witha large volumeof sound bastaken placealong two dis-tinct paths.The firstmethod de-pends upon theuse of variousdesigns of hornto act as asound ampli-fier, whilst re-taining a corn-parati,vely,small dia-phragm. Thesecond reliedupon an in-creased size ofdiaphragmadapted to

radiate the sound directly to the air.The moving -coil type of instrument is a

comparatively modem develbpment, inpractice, though, the broad idea in itselfdates back for many years. The sameremark applies to the use of both reed -

TO D.0 SUPPLY

output from a modern

ELEVATION.

PLAN

Fig. 2, An attempt that hasbeen made to cover the wholerange of audible frequencies

FROM

Fig. 1. Diagram explanatory of the principle of theelectrostatic speaker

driven diaphragms and to the recentappearance of the electrostatic type ofspeaker.

In some respects, particularly as regardssimplicity of construction, the electrostatictype of speaker offers. many ,distinctadvantages. Its chief handicap has beenthe necessity for using a comparativelyhigh biasing voltage, though this dis-advantage disappears when a mains -supply unit is available.

Electrostatic SpeakersThe construction and operation of

a modern form of electrostatic loud-speaker is illustrated diagrammatic-ally in Fig. I. The sound -repro-ducing surface consists of a tightlystretched - metal membrane 3,1

mounted centrally between two per-forated plates P, PI.

The energising current derivedfrom a power amplifier is appliedacross the two outer plates as shown.In this type of instrument a steadybiasing potential is also applied tothe membrane. If this were not doneeach complete cycle of the appliedfrequency would vibrate the mem-brane twice--i.e., at the crest and troughof each wave-instead of once, and thusgive rise to a false frequency response.

However, by means of a biasing voltagefrom the D.C. supply the membrane Ni isconstantly kept at a positive voltage,which varies from a maximum to a mini-

mum per cycle, with respect to both plates,instead of becoming positive and negativealternately. In operation the outer platespull at the biased membrane successivelyin opposite directions, thus setting it intovibration at a frequency corresponding to

that of the output current from the set.Since the static loud -speaker is

SET voltage -operated, as distinct from, say,the moving -coil type of instrument, partof the biasing voltage can be providedby rectifying the speech frequency cur-rents as amplified by a pair of push-pull amplifiers. The additional voltageso produced is then combined with theordinary H.T. supply to the poweramplifiers. With this arrangement astatic speaker can be operated from ar2o-volt battery, or from ordinary D.C.mains where it is not possible to use

a step-up transformer.In the ordinary cone -type of speaker one

of the difficulties is to design a diaphragmthat will respond with equal efficiencythroughout the whole range of audible fre-quencies. In general a perfect response canonly be obtained either at the lower fre-quencies or at the higher, but not for both.

Fig. 3. This is a scheme for a multi -coneloud -speaker, again with the Idea of cover-

ing all frequencies

Fig. 2 illustrates one method which hasrecently been proposed to overcome thisdifficulty. It consists in using two separatecone diaphragms A B fed either in seriesor in parallel from the set and mounted

(Continued on next page)

APRIL 27, 1929 631

face to face so as partly to overlap, asshown clearly in the plan and elevation.

The spindle s of the cone A is secured toa partition wall w of three-ply wood, whichis resonant to the lower range of frequencies,and therefore imparts this quality to thecone. The cone B, on the other hand, issupported by a heavy rigid column c,firmly clamped to a fixed base plate. p, sothat it responds mainly to the higherrange of frequencies. The combinationtherefore covers the entire musical range.

The overlap of the two diaphragrxis cen-tralises the sound, and merges bothspeakers into one apparent output. Simul-taneous adjustment can be made from aingle knob K, the two spindles s, si being

connected by the chain gearing Shown at G

in the plan view.

A Multi -cone SpeakerFig. 3 illustrates another arrangement

which has recently been protected for over-coming the same difficulty. Here the solu-tion has been sought by utilising, in placeof one large diaphragm, a number of smallcones, symmetrically arranged around acommon driving movement,

It will be seen that no fewer than sevencones have been grouped together, eachcone being individually energised by itsown separate spindle from the magneticdrive M.

In connection with this arrangement it ispointed out that when a single large dia-phragm is used its effective vibrating areais dependent upon the particular frequencyto which it is responding at any moment.For instance, at high frequencies only alimited area near the centre of a large coneis actually in vibration.

Now by increasing the number of conesthe central portion of each cone is set intovibration by a high note. Actually thetotal area so affected is then larger than inthe case of a single large cone, so that alouder response is obtained.

For- the lower notes an increasingly largevibration area becomes necessary. In fact,a cone of four or five feet diameter isdesirable in theory though such a size ishardly practical for ordinary use onaccount of mechanical and other difficulties.

Where a large -sized cone is used thenatural resonance of the vibrating surfacecomes into play and tends to produce a:humming noise. But by substituting anumber of smaller -sized cones, mounted incombination, the natural or resonant periodof the system remains the same as that ofeach separate unit, so that the "drum.ruing" effect is no longer heard.

For Whitsuntide the Lille (France)Itailio Club has organised a two and a halfdays' visit to London and Daventry; it isexpected that a large number of Frenchradio fans from the northern districts ofFrance will take this opportunity to inspectthe B.B.C. high -power transmitter.

Conversion Chartsfor the 1927

CossorMelody Maker

This illustration shows the 1927 typeCossor Melody Maker after conver-sion. The original dials may be usedif desired though the latest patternCossor Slow Motion Dials are recom-mended.

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about the wonderful Cossor Con-version Kit which includes all theparts you need for making your 1927 Mel-ody Maker into a modern Screened GridReceiver. The chart shows how simplythis can be done-only two holes to drill, aslight re -arrangement of the wiring-that'sall. You can easily do it in an evening.A full size baseboard plan is included. Onthe back of the Chart you will find full in-structions for operating your convertedCossor Melody Maker-how to cut out thelocal broadcast and bring in station afterstation at full loud -speaker strength.Don't delay-post the coupon now foryour copy of the Cossor Conversion Chart.

CossorCONVERSION KIT

CONTENTS:One Colmar Screened Grid

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632 APRIL 27, 1929estates:. WirdT

CABINETMAKING

AT HOMEParts for Cabinet's are now obtainable ready forassembling and finishing. This article gives some

hints on the procedureBy ARTHUR YORKE

8 in. are obtainable from Messrs. Hobbies,of Dereham, Norfolk, and the only workrequired, apart from securing the base,sides, back, and small top strip together bymeans of glue and nails or screws,. is to ,hinge the lid to the back portion and roundoff the upper edges of the base and top inorder to give a good appearance to thefinished article. A small rubber foot maybe fastened near each corner of the under-side of the base if the cabinet is to stand ona polished surface.

Before staining and polishing, it will beadvisable for the sake of appearance to fillin the holes left above the heads of thenails or screws with putty or plastic wood,so that when staining and polishing is com-pleted the holes will not be noticeable.

Staining and polishing can be carried outin a very simple manner by utilising one ofthe Lightning polishing outfits obtainablefrom Messrs. Hobbies.

If the work is carefully done, the finished,cabinet will have the appearance of a pro-fessionally made article, and as timber offirst-class quality is provided, the life of thecabinet should at least equal that of theset itself.

Messrs. C. A. Osborn, of zr Essex Road,London, N. r, are supplying sets of machinedparts ready for making pedestal cabinets

with compartments forboth wireless set andbatteries or mains unit.

The accompanyingphotographs show theparti of one of thesecabinets, and also a

A Hobbies Cabinet builtfrom the parts shown

below

THE primary points to consider whendeciding on the details of a cabinet for

the housing of a wireleSs 'set are the'dimensions of the panel and baseboard. Ifthe receiver is already built, there will beno difficulty about this, but when -thecatinei is to be constructed before buildingthe §et it will be advisable to go thoroughlyinto the details of the proposed panel andbaseboard sizes before ordering the timberor set of parts for the cabinet.

In cases where the batteries or mainsunit are to be housed as well as the receiver,,the overall dimensions of! these accessoriesmust be obtained beforehand, so that there'will be no possibility of the cabinet beingfound too small after it is built.

The foregoing may seem obvious and notworth, mentioning, but it is very easy tomake a miscalculation in regard to theprincipal measurements of the woodworkand perhaps find the cabinet too smallafter many hours' labour and a substantialportion of one's pocket money have beenspent on its construction.

Parts AvailabteSets of wood parts for the building of

American -type cabinets to take panels 9 in.:by 6 in., rz in. by 6 in., r4 in. by 7 in.,16 in. by 8 in., 2r in. by 7 in., and 24 in. by

p

This is a partly assembledpedestal cabinet also made

from parts shown below

cabinet in course of construction, thisparticular example taking a panel 21 in. by8 in.; smaller sized panels may, however,easily be accommodated by fitting woodstrips at each side of the panel or byemploying a plywood vignette.

The Tools RequiredThe parts supplied by. Messrs. C. A.


Here are the parts for constructing the Hobbies and Osborn Cabinets as described in the text

APRIL 27, 1929 633 ((mutat, Wtretesj

TUNEWELLwith our DUAL RANGE COILS and CHOKES

CLARION THREESee this issue for the results obtained with our

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Contains a complete outfit for a receiving set with a2 -Electrode Valve giving marvellous results. Completewith circuit, drilled and engraved panel at £2 : 19 :6

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ASK YOUR DEALER

MAKE YOUR WIRELESS CABINET THE OSBORNWAY-MACHINED READY TO ASSEMBLE

No. 191. A JACOBEAN WIRELESS CABI-NET of very neat design, with panelleddoors and panelled ends, and a large spaceat the bottom for accumulators, 3 It. high,2 ft. wide, and 1 ft. 4 ins, deep. Openingat the front and the top to take a panel21 ins. x 7 ins. or 8 ins. A wooden frameis supplied tree should the site cf yourpanel be smaller.Machined ready toassemble, in Oak £ 1 1 5 0Assembled in Gals, _Ca noready to polish . olise Ge 7 6Assembled and .03 0polished in Oak air

CARRIAGE PAIDCall and see the actual article, "

52 -Page catalog:le seat Post free anreeei fit of 11. in stand's to Debt. B.

CHAS. A. OSBORN, The RegentWorks, Arlington Street, London, N.1.Open to 7-30 P.m. Saturdays, 4-30 p.m.And at 21, Essex Road, Islington, N.1.Open to 8 p.m. Saturdays, 9 p.m.

"AMATEUR WIRELESS" HANDBOOKS 2/6Of all Newsagents and Booksellers, or 2,9 post free front Cassell and Company, Limitel, La Belle Sauvage, London, E.C.4

The SHIELDED FOUR -ELECTRODE VALVE Theory &By Captain H. J. Round, M.G. PracticeCapt. Round is one of the greatest authorities in the world on radio science and practice. andhis book is a complete guide to the principles under which this latest and most remarkablevalve should be operated.

LOUD -SPEAKER CRYSTAL SETSHow to Make and Manage ThemProvides working instructions for building a number of highly efficient crystal sets; makin'gan attachment for simple connection to existing wireless set; and designs for crystal setsembodying the crystal loud -speaker system.

WIRELESS -CONTROLLED MECHANISMFor Amateurs. By Raymond PhillipsThis book is an illustrated practical guide to the making and using of short-range wirelesscontrol apparatus, and it has been written so simply that it can be understood by any enthusiastpossessing an elementary knowledge of wireless.

THE PRACTICAL " SUPER -HET " BOOKExplains what the Super -het is, what it does, how it works, and hew to build up a number ofsuper -het eels made of tested, British -made components.

PERFECT BROADCAST RECEPTIONBy Ernest H. Robinson (5YM)Explains how most. sets tall short of the ideal and hose to obtain perfect reception. Ie virtuallya popular exposition of the main problems of transinimion and reception. Very valuablealike to listeners and experhnenters.

THE SHORT-WAVE HANDBOOKBy Ernest H. Robinson (5YM)Describes in very simple language the wireless apparatus used in short-wave work, shows howto make it and how to use it, and explains the technical principles with which the beginnerwill need to become acquainted.

THE PRACTICAL WIRELESS DATA BOOKThe intelligent novice, and partionlarlY the home etinstrinhor and the keen wireless amateurwho is always rigging op different circuits and experimenting for progress, will find this DataBook extremely helpful.

THE WIRELESS MAN'S WORKSHOPBy R. W. Hallows, M.A.Written by a practical home constructor, this book-containing much useful wireless informa-tion-enlightens readers on the selection and right methods of using the tools and materialsused in constructing wireless sets.

eachnet

THE BOOK- OF THE NEUTRODYNE, Contents : Why Neutralising is necessary; Systems of Neutralising; Difficulties .Encountered in Neutralised Ciretrite;Hpw to obtain GooaBy J. H. Reyner,. B.Sc. (Hons.), A.M.I.E.E.: Selectivity Without Loss of qua its; Design of High -Frequency Transformers; Lay -out in Neutralised Receivers; Some :inhabit Circuits.

Price 1,6 net, or post free for 1/9


emaim- Wirdiasi 634 APRIL 27, 1929

One of the most important dutiesperformed by AIVIATEUR WIRELESSfor readers is that of advisingon the choice of components andapparatus. This is done byreporting upon new apparatus as

ONE of the fairest tests which can bemade on any piece of apparatus is

that of time. If the instrument gives therequired results and continues to do so inuse, then it is en -titled to be consideredsatisfactory.

The nature of the tests and the timeinvolved depends upon the apparatus inquestion. Some apparatus is such that it is

A photograph of the test bridge in use at thFurzehill Laboratories

possible to make a test of its suitabilityalmost immediately, while other apparatusrequires a more prolonged test and mayperhaps be required to be put into operationfor a certain length of time in order tosee how it behaves in practice. One of theobjects of the test room, however, is todevise methods of examining apparatuswhich will show up any defects as rapidlyas possible and will enable a fairly accurategauge of the quality of the particularapparatus to be determined without, thenecessity for a prolonged trial.

Many Different MethodsIt is not necessary or desirable to go.into

considerable detail, but there are caseswhere the general method employed is ofinterest to readers, while in certain othercases the actual form of the results may

require some explanation. A particularexample of this is the testing of high-tensionbatteries where we quote- a- milliampere -

hour figure based on the mean dischargerate. This has been the subject of a certainamount of confusion and the matter willbe dealt with more exhaustively in a futurearticle in this series. The present articledeals with one of the simplest forms oftest, that. of small condensers, whetherfixed or variable.

Condensers for radio purposes fall inthree classes. The first of these is thevery small capacity used for neutral-ising or some such adjustment whichinvolves the measurement of capac-ities of the order of r or z micro-microfarads at the minimum. Thesecond class comprises capacitiesused for tuning purposes and fixedcondensers used for a variety of pur-poses such as by-passing, blocking,coupling andAhe like. The thirdclass is the large -capacity condenser,fixed in value, which is used princi-pally for by-passing and for filteringand smoothing generally.

Each of these three types requirese its own particular method. The first

and second can both be measuredby similar methods, slightly greater pre-cautions having to be taken when measur-ing the very small capacities and for suchvalues, a bridge method is customarilyadopted.

The Wien BridgeThe arrangement is known as a Wien

bridge and is shown by the diagram: Thereare two fixed capacities CI and C2 whichare known as ratio arms, while the third andfourth arms of the bridge contain the un-known capacity and the standard calibratedvariable condenser respectively. Alternat-ing current is applied across two terminalsof the bridge and a pair of telephones isconnected across theother two. Withoutgoing into detail, it will be clear from thesymmetry of the figure that if the tworatio capacities are made equal, then apoint of balance will be obtained when thestandard capacity is equal to the unknowncapacity and all we have to do is to vary

it appears under the heading of"A.W. Tests of Apparatus." Thepresent series of articles is in-tended to illustrate some of themethods employed in testing themore usual types of components

the standard capacity until a balance pointis obtained. In this position_ no sound isheard in the telephones.

It is not always practicable to obtain therequired results with a 1: r ratio such asthis, but it is quite an easy matter to makeone of the ratio capacities greater than theother by a predetermined amount whenthe standard will be the same numberof times greater or less than the condenserunder test, and it is only necessary tomultiply by a simple factor in order tcobtain the required results.

Precautions RequiredThe arrangement is quite simple in

theory but in practice there are minordifficulties to be contended with in obtain-ing accurate results. In the first place, thewave form applied must be a pure sine waveas far as possible, although this is not soimpoftant in the case of the capacitybridge as in certain other bridges whichhave to be used in measurement work.Secondly, capacity effects to earth mustbe avoided or nullified as far as possible.

LEOSC/LLATORI

Circuit of Wien Bridge

The presence of the body introduces acapacity to earth, the disposition of theapparatus all affects the problem and ingeneral the layout of the bridge is usuallyfound to be most important. Where theapparatus is correctly arranged, the mini-mum is a true silent point and is very

(Continued on next page)

APRIL 27, 1929

sharply defined. Where the bridge is badlydesigned, the minimum is not definite andthe sound never actually dies away. It isnecessary to make a guess at the balancepoint by trying to estimate the point ofminimum sound and this is a much moredifficult operation than determining anactual silent point.

A further difficulty which is oftenencountered is that the quality of the notemay change as one passes through theminimum point and this renders ,the actualdetermination of the minimum difficultagain. This effect can be entirely obviatedby a correct arrangement of the componentsand some considerable time must usuallybe spent in experimenting with a bridgebefore it can be put into commission. Moreparticularly is this important where thevery small capacities have to be measuredaccurately-for here quite a small capacityto earth may introduce a large error.

Large Capacity MeasurementVery large capacities are measured by a

different form of bridge which will bediscussed in a future article. The photo-graph accompanying this article illustratesthe bridge in use at the Furzehill labora-tories. On the left can be seen the standardvariable condenser, while on the right at theback can be seen the ratio arms. A pair oftelephones is connected in position by meansof a plug and jack; a special pair of sensitivetelephones being used for this and severalother bridges. A condenser can actuallybe seen on test, while on the table just infront of the apparatus is a fixed standardmica condenser used for checking theaccuracy of it.

CABINET MAKING AT HOME "(Continued from page 632)

Osborn are rough machine finished, alljoints being shaped ready for cleaning upand fitting, while the surface of the timberexcepting the lid portion, is smooth planedr :ady for sand -papering. The lid of tie

BrRfsh made.BPrem. Pat.29144/29.

Turned up end pre.vents top twistingwhen screwing up.

ULLDOGE conomiseto H.T. Re-place faultycells easily.Tappingsevery 4hvolts. Gripslike a vice.G saran tee delectrical con-

tact.

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cabinet is supplied already sandpapered.Little difficulty should, therefore, be

encountered in glueing up and finishingthese cabinets-it is, in fact, quite interest-ing work-but it should be understoodthat to produce a well -finished article suchtools as a good plane, saw, and shootingblock are essential, in addition to the usualscrewdriver, hammer, etc.

METAL -PANEL MATTERSIt should be noted -that, owing to a

draughtsman's error, in the circuit given

V

A simple circuit for a metal panel

on page 552 (" A.W." No. 357) the H.T.was shown " Shorted " through the anodecoil to L.T. negative. The correct diagramis given herewith.

"Amateur Wireless and Radiovision." PriceThreepence. Published on Thursdays and bear-ing the date of Saturday immediately following.Post free to any part of the world : 3 months,4s. 6d.; 6 months, 8s. 9d.; 12 months, 17s. 6d.Postal Orders, Post Office Orders, or Chequesshould be made payable to " Bernard JonesPublications, Ltd.'General Correspondence is to be brief andwritten on one side of the paper only. Allsketches and drawings to be on separate sheets.Contributions are always welcome, will bepromptly considered, and if used will be paid for.Queries should be addressed to the Editor, andthe conditions printed at the head of ** OurInformation Bureau" should be closely observed.Communications should be addressed, accord-ing to their nature, to The Editor, The Adver-tisement Manager, or the Publisher, **AmateurWireless," 58-61 Fetter Lane, London, E.C.4.

etnaleurWtreig5

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TO PERFECT RADIO%Or

NNW

In addition to their own extensive range,PETO SCOTT offer YOU Every KnownRadio Receiver or Component-all on

EASY TERMSThe following list is merely representative. andwe ask you to fill in the coupon below or send us

a list of your requirements.THE FIVE GUINEA PORTABLE TWO. Complete

Kit of Components. (See last week's issue). Send only10/.., balance in easy payments.

CLARION THREE Kit of Components. Send only14;7, balance in easy payments.

COSSOR MELODY MAKER. Send only 10/., balancein 11 monthly instalments of 143.

MULLARD MASTER THREE STAR. Send only 10/.,balance in 11 monthly instalments of 15/3.

LEADING MAKES OF H.T. ELIMINATORS front4,7 down. Balance in 11 monthly insta'm -nts of 4/7.

EXIDE 120 -VOLT H.T. ACCUMULATORS, withcrates, Send on.y 6. 11, laalanre in 11 monthly instal-ments of 6/11.

CELESTION C.12 SPEAKER. Send only 13.4,balance in 11 monthly instalments of 13,4.

Build your own set the Easy Way NOW!Our Catalogue contains all leading makes of Re-ceivers, Accessories, Kits of Components for theHome Constructor.

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PRICE 61- Post 9d,Send a postcard for our illustrated list of Loud-

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WARRICK RADIO16 Berther Road, Hornchurch, Essex.

maitur Wirelesj 636 APRIL 27, 1929

DOMINION

BROWNIE are now producing 2,000Dominion Vernier Dials a day.

That is why it is possible to offer thishigh-grade dial at the wonderfulprice of 3/6.The mechanism is a special non -backlash design with a reductionratio which makes fine tuning easywithout becoming tedious.Obtainable from all wireless dealersin beautifully finished plain black orlovely grained mahogany bakelite.

ihir,LSON sr. W./1(1%S LO DON. N.W.

CLARION THREEStill a tremendous success. We can still supplythis wonderful THREE H. & B. KIT at £4 4s. Od.Including wire, screws, baseboard and best qualityebonite panel and strips ready £4 - 4 - 0drilled. Cash priceOr 15/- down and 5 monthly payments of 15'-.See our advertisement in A.W. No. 353, March 16th.CLARION THREE CVS3 KIT.-Complete kitas C1 3, but including Cabinet, 120 -volt Ever -Readybattery, Oldham, Exile accumulator and Amplionspeaker A.R.9. Cash price eio 5 6Or 251- down and 12 payments

of 16/3.TUNEWELLS CLARION DUAL RANGE

COILS 2I/- pair.DUAL RANGE COILS for the ARCADIANPORTABLE and the 5 GNS. 2 VALVE

PORTABLE 10/6 each.

TWO VALVEPORTABLE

Take it with you this week -end. Build this handyPORTABLE (described in this issue). The H. B.KIT contains all the BEST parts, includingMULLARD or PHILLIPS TRANSFORMER ;also our special DUAL RANGE COIL, bestquality ebonite ready drilled (conterdts fist sent onrequest). Complete kit of partsandat/.Or 14/- down 4 monthly payments vo

of 14/-. Cabinet in Oak £1 extra.COMPLETE KIT : Cabinet, 2 MULLARDVALVES, EVER -READY PORTABLE BAT-TERIES and EXIDE non -spillable .c.c 42_9ACCUMULATOR. Price

Or 20/8 and 10 monthly payments of 10/4.MARCONI CONE SPEAKER f, 1 - 19 - 6as .recommended by A.W. Price

Or 8/9 down and 4 monthly payments of 8/9.

GRADUAL PAYMENTSThe very best terms possible on all wireless apparatus(Speakers,Kits, Valves, H.T. Units, Wet Batteries,etc.) State your requirements and -we will quote youby rcturn. Immediate delivery. Carriage paid on all

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Telephone : Ger. 2834



A Good Valve CombinationSIR,-My own experience is similar to

that of Thermion," page 555. I usea screen -grid, an R.C. detector, and apentode.

I get far more volume than I need, andI find a volume control at the H.F. end anabsolute necessity. It is also necessary touse an anti -motor -boating arrangementand an H.F. stopper in the R.C. couplingunit. I use about 8o volts on the auxiliarygrid of the pentode and 20 volts negativegrid bias. The set is quite small, and I saveH.T. considerably. W. J. F. (Redruth).

Exponential HornsSIR, May I endorse the points raised in

the article " About Exponential Horns"in No. 356 and amplify them by statingthat a solution of the domestic loud -speakerof the future may be found in a re-entrantexponential horn used in conjunction witha miniature moving coil unit. Such a loud-speaker, only requiring a moderate powerinput both to the field and moving coil,would give realistic reproduction of goodvolume. Having had an opportunity ofhearing a direct comparison made betweena Schlenper loud -speaker (moving -coil typewith a large diaphragm of stretched dura-lumin) and a Western Electric Co. 555Wloud -speaker (moving -coil type with anexponential horn), I was greatly impressedby the increased output given by thelatter for equal power input.

It is doubtful whether the full benefit ofthe exponential horn can be utilised withthe average moving -iron type of unit.

G. B. S. (West Ealing).

Linen -diaphragm Loud -speakersSIR,-It is surely unnecessary for F. S.

to confine tone -deafness to inhabitantsof these islands. -The jazz band originatedin America, and is quite popular on theContinent! The linen loud -speaker maynot be up to a first-class M.C. workedunder laboratory conditions; but howmany, outside laboratories and F.S.'shome, are? The linen speaker is probablyquite as good as the average -listener'soperative conditions can take advantageof. As F.S. himself says, the ordinary0-V-2 or I -V-2 cannot deal adequatelywith a moving -coil loud -speaker with120 volts H.T. Besides, even the M.C.has its disadvantages. It requires largeinput, its magnet system has to be energised(unless the relatively insensitive permanent -magnet type is used), and many M.C.instruments are sadly deficient in theupper register, while diaphragm resonanceand the weight of the coil produce abundantproblems for the designer.

The moving coil is unexcelled in its own

sphere, but it is not yet entirely suitablefor average operating conditions-mediumpower sets with medium voltages.

G. W. P. (Woking).

Sunday ProgrammesSIR,-Regarding the letter of your

correspondent C.S. (of my native townof Birkenhead) on- the subject of Sundayprogrammes, he says that he is " one ofthousands who don't want to listen toreligion at all." He must have an enormouscircle of acquaintances. I fancy that if wewere to demand details of these "thou-sands" he would be mightily hard pressedto name a dozen actual cases. I used tothink I knew hundreds .of people who likeda certain class of music. When I came tocount them I found they totalled five !

Since C.S. gets some three -and -a -quarterhours of " entertainment " on Sunday, itseems rather weak that he and his "thou-sands" cannot turn their sets off for three-quarters of an hour and have a little peaceand quiet. Three-quarters of an hour perweek, mark you ! On six nights per weekhe can have well-nigh any kind of " enter-tainment " he fancies.

Does C.S. realise that the mere fact ofSunday's existence is due to the religionwhich he seems to dislike? Had it notbeen for religion there would be no Sunday.

Surely C.S. must realise that those whoarrange programmes cannot suit everysingle listener, and since they know farbetter than he (or she), I think he shouldbow to the majority with better grace.

M. E. P. (Coventry).

The third annual Netherlands RadioExhibition will take place in the Schevenin-gen Kurhaus on May 26.

Easy lermsYOU CHOOSE YOURGOODSWE PAY FOR THEMImmediate delivery.No troublesome enquiries.

ALL ADVERTISED GOODSIN THIS PAPER SUPPLIED

Let us know your requirements; wewill quote you per return.

SEND FOR OURILLUSTRATED CATALOGUE

Giving details of all the latest RadioReceivers, components and accessories.

geb3 Mimeo ,aleg Co.,56 LUDGATE HILL, LONDON, E.C.4

'PHONE - CENTRAL 2716

APRIL 27, 1929 637

OV.11111111111111140/

INF/00111111111111100\'

t011\111111111111814.

' ////111111111111110

RULES .-Please write distinctly and keep to the point. We reply promptly by post. Please give all necessary details. Ask onequestion at a time to ensure a prompt reply, and please put sketches, layouts, diagrams, etc., on separate sheets containing your nameand address. See announcement below. Address Queries-Am/alma WIRELESS Information Bureau, 58/61 Fetter Lane, London, E.C.4

Troublesome Oscillation.Q.-I have built a four-valver using a screen -

grid H.F. stage, and experience difficulty ingetting rid of oscillation. The H.F. stage iscompletely screened and the coils are woundastatically. The wiring has been checked for goodspacing and all wires kept as short as possible.I have dAe everything I can think of to eliminatethe trouble, yet as soon as the aerial and H.F.circuits are in tune the set will persist in oscillating.Can you suggest a reason for this and method ofovercoming the difficulty? I would mention Ihave wound my own coils and I am sure these arequite efficent and cover the desired wavebands.-F. D. (Dover).

A.-It is more than possible that your coilsare too efficient for the receiver in question asit appears that your aerial circuit oscillatesfreely as soon as the anode circuit is broughtnear to its resonant tuning point. A way ofovercoming the difficulty is to use a finergauge of wire for either the aerial coil or theanode coil, or both, or failing this we wouldsuggest that you try the effect of connecting agrid leak of .25 megohms (250,000 ohms) acrossthe grid filament circuit of the H.F. screen -gridvalve. The latter is a cure, but rather a drasticone in that it is liable considerably to flatten

tuning. The best course to follow is to rewindyour coils'\vith thinner wire. Some experiment -



A Fee of One Shilling (postal ordero or 'postage stamps) must accompany

each question and also a stampedO addressed envelope and the coupon

which will be found on the last page.Rough sketches and circuit diagrams

° can be provided, but it will be neces-O sary to charge a special fee (which willO be quoted upon request) for detail

layouts and designs.

ing will be necessary in this direction to ensurethe very best results as the use of too fine a

mattur Wirete.D.

gauge will result in excessive damping.-A. L.

Portables and Screen -grid Valves.Q.-I have a portable set in which a screen -

grid H.F. valve is incorporated. Originally theset was designed for .use with a double -endedS.G. valve, but with the advent of the new single -ended valves a suitable ordinary type valveholder has been substituted. Since this change Inotice that the receiver is inclined to " hoot atthe slightest provocation and if allowed to con-tinue this hoot resolves itself into a roar. Canyou explain this and suggest a remedy?-D. K.(Brighton).

A.-If you have used an ordinary fixedvalve holder and not one of the anti -micro -phonic pr spring -type holders, then thisaccounts for your trouble. Screen -grid valvesare prone to microphonics as are mostvalves. In the case of the later single -endedS.G. valves, it seems nearly impossible to use asolid -type valve holder, especially in b portable.This latter statement is open to criticism, butit appears to cover the trouble in your case.We have tested quite a number of S.G. valvesin portables, and find that in most cases it:isvery advisable to use a spring -type valveholder -C. B.

BECIP NY 1540LL

N C C 207

maItur Wtreiv. 638 APRIL 27, 1929

YOU NEVER NEED BUY ANOTHER DRY H.T. BATTERYInstall the wonderful Standard Permanent Batteryand it will give you abundant H.T. that will LASTFOR YEARS. Hundreds of thousands of del ghtedlisteners use it. It recharges itself overnight, and inthe morning is full powered -as fresh as the dawn.Supplies a smooth non -sagging constant pressure ofcurrent that puts new tone in reception. Solve YOURH.T. problem once and for all. Install Standard.

AMAZING TRIBUTE TO STANDARD.Essex, 12-3-29

Running on an average of 3o hours per weekon an output of from xo-t 5 M/A, has given everysatisfaction, not been attended to in any way.

Was surprised, not to say delighted to find thatthe 1st tray registered 44v., the and 46v. and the3rd practically 48v. Thus showing a loss of only5% after over 7 months constant use.

I think this result is somewhat remarkable andshall have great pleasure in recommending yourbatteries with confidence to any of my friendswho are interested.

Signed, R. A. B.NRLOViv.SEND NOW FOR FREE BOOK THAT TELLSYOU ALL YOU WANT TO KNOW.

96 -volt Popular Model " Unibloc " Cabinet NOWwas 8'1 down, new 7'6 down and five monthly sin/payments of 7,6. Cash £2 3s. Id. Obtainablefrom Halford's Stores, Curry's Stores and all DOWNRadio dealers on cash or deferred terms. Also SuperCapacity No.3 Battery. 10;1 down, and five instalmentsof 10/1, for 3 valve sets and over. Any voltage batteryfrom volts upwards. Capacity up to 60 milliampswith new Na. 4 cell,

SAt SECLANSINa.

THE STANDARD WET BATTERY Co. (Dept. A.W.)184-138 SHAFTESBURY AVENUE, LONDON, W.C.21.1.............. MBAWIRELESS CABINETS

MAKE YOUR OWNSend stamp for Free catalogue and price

list.WOODWORK, 199 HIGH ROAD, LEE,

LONDON, S.E.13.

Build the "All Mains Two"Mains Transformers guaranteed one year 25, -

Chokes, double wound 16/64 Infd. Condenser 6/9 2 mfd. 4/-: tested 5oo volt A.C.We are specialists in Mains Equipment. Send us

your enquiries.Electrical and Radio Company

HATHERTON STREET, WALSALL.

OUR BLUEPRINT SERVICEConstructors of receivers described in this journalshould make full use of cur Blueprint Service and

avoid all risk of failure.

ROA IP CAST TELEPHONY(Broadcasting stations classified by country and in order of wavelengths)

Kilo- Station and PowerMetres cycles Call Sign 1Kw.)

GREAT BRITAIN26.5311,751 Chelmsford

(5SW) 15.0243.9 1,230 Newcastle (5NO) 1.0258.4 .7,762 'Leeds (2LS) 0.1:1270.3 2,209 'Sheffield (6LF) 0.13288.5 2,040 Bournemouth

(6BM) 1.0288.5 2,040 *Bradford (2LS) 0.13288.5 2,04o 'Edinburgh

(2EH) 0.35288.6 z,04o *Hull (6KH) 0.2288.5 1,o40 !Dundee (2DE) 0.13288.5 2,040 *Liverpool (6LV) 0.13288.5 1,040 'Stoke-on-Trent

(6ST) 0.13294.1. 1,020 'Swansea (5SX) 0.13302.6 991.1 Belfast (2BE) 1.0311 964 Aberdeen (2BD) 1.0323 928 Cardiff (SWA) 1.0858 F38 London (2L0) 2.0378 793 Manchester

(2ZY) 1.0396 757 'Plymouth (SPY) 0.13401 748.3 Glasgow (5SC) 1.0482 622 Daventry Ex.

(5GB) 25.01,566.5 29.2.5 fDaventry

(5XX) 25.0 Relay stations. 1 Relays 2L0.

AUSTRIA248 1,209 Linz 0.5277.8 1,060 Salzburg (under

construction) 0.5Graz 0.5

456 694 KlagenfurtInnsbruck 0.5

520 577 Vienna 20.0


Brussels 0.5275 1,090 Ghent 0.5289 2mo Liege 0.5812 910 Arlon .. 0.25612 L86 Brussels 10.0

354.2 847

456 t94

CZECHO-SLOVAKIA265 1,125 Kosice ... 2.0278 r,o8o Feriby (testing) 12.0299.3 2,000 Bratislava 4.0843 873 Prague (Praha) 5.0932.3 694 Brunn (Brno) , 2.4


(Kjobenhavn) 1.01,158 :60 Kalundborg 7.5

ESTHONIA408 735 Reval (Tallinn) 1.3

FINLAND371 too Helsingfors

(Helsinki) 081,502 49 Lahti 20.0

FRANCE30.752002.11.3230.8233

245252.1253254255268 274

9,755 Agen 0.251,500 Fecamp 0.31,420 Dealers 0.11,3or Radio Nimes 1.01,260 Bordeaux (Radio

Sud-Ouest) 2.02,224 Lille (PTT) 0.82,290 Juan-les-Pins 0.41,185 Montpellier 0.25z,18z Rennes (PTT) 1.07,175 Toulouse (PTT) 1.02,118 Strasbourg 0.32,c92 Limoges (PTT) 0.5

. Kilo- Station and PowerMetres cycles Call Sign (Kw.)

291.3 1,030 Radio Lyons ... 1.5302 999 Bordeaux (PTT) 0.5804 582 Marseilles (PTT) 0.5305 982 Agen 0.3322 93o Vitus (Paris) 2.0536 8'92 Petit Parisien 0.5353 S49 Algiers (PTT) 2.0370 8i1 Radio LL, Paris 1.0382.2 785 Toulouse (Radio) 9.0405 749 Mont de Marna 0.4411 724 Radio Maroc

(Rabat) 2.0428 ,or Grenoble (p.m 1.5430 69y Radio Flandre

Lille 0.25443 (68 Paris (Ecole

Sup., PTT) 0.7468.8 (40 Lyons (PTT) 5.0

1,470 203 Eiffel Tower 8.01,755 171 Radio Paris 8.0

GERMANY219 2,37o Flensburg 1.5240. 2,25* Ntimberg 4.0250 2,200 Kiel 0.7250 1,200 Cassel 0.7263.2 z,z4o Cologne 4.0267.8 1,120 Muenster 1.5273.1 7,098.8 Kaiserslautern 1.5280.4 z,o7o K Onigsberg284 1,056.7 Berlin (E) 0.7284 1,056.7 Stettin 0.7284 2,056.7 Magdeburg 0.7817.5 945 Dresden 0.75820 937 Breslau 4.0826.4 929 Gleiwitz 6.0

0.754.04.04.0

329 pro Bremen361.9 829 Leipzig374.1. 8o2 Stuttgart391.6 766 Hamburg423 712 Frankfurt455.9 654 Danzig 0.75456 651 Aachen 0.75462.2 649 Langenberg 25.0476 630 Berlin 4.0537 559 Munich 4.0666 530 Augsburg 0.5586 530 Hanover 0.7577 Sao Freiburg 0.7

1,653 281.4 Zeesen 20.01,650 282 Norddeich 10.0


1,280234.2 Radio Luxembourg

HOLLANI181.4 9,554 Eindhoven

(KJ) 25.088.8 - Kootwijk

(PCL) 32.0(Wed. 12.40 G.M.T.)

376.3 892.5 Huizen (until5.40 p.m.) 6.0

1,072.8 279.6 Hilversum(AN RO) 5.0

zez Huizen (after6.40 p.m. and on

Sundays ) 5.01,152 262 Scheveain,gen-

haven 6.0

1,152

0.25



IRISH FREE STATE222.2 z, (4 Cork (5CK) 1.5411 730 Dublin(2RN) 1.6

Kilo- Station andMetres cycles Call Sign

ITALY276 2,085 Turin

338373

Genoa(Napoli) 31..05

443.8 667586 131207.06(01toma) 3.0

504.2 595 Milan- 0.3

7.0

JUGO-SLAVIA308.3 973 Zagreb (Agram) 1.25450 :II

LjubljanaBelgr ade 4.0

582 5.0

523 567 Riga2.0LITHUANIA

2,0(.0- 35o Kovno 15.0

NORRiukWAanY242 1,240297 1,010 Notodden

1.0

365 820 Bergen0.7

.,. 1.0384 780 Fredriksstad 1.0456 657 Aalesund 1.0459 653 Porsgrund 1.0496 604 Oslo ... 1.5

563 350 Hamar1.0500 600 Troms6

POLAND

415.5

1.51.5

31 k 955 Cracow333 890 Posen

456 658 Will10107}722 Kattowitz1.5

1,401 214.1 Warsaw 10.0



Power(Kw.)

0.7

ROUMANIA757 Bucharest 4.0`

RUSSIA825 363.5 Moscow (PTT) 25.0925 323 Hornet 2.5

1,002.4 299.2 Leningrad 20.01,442 208 Moscow 30.01,605 178 Kharkov ' 15.0

SPAIN318 956 Oviedo (EA J191 0.5350 855 Barcelona(EA J1) 3.5370 Sox Seville (EA J5) 0.5400 95o Radio Espana 1.0401 748.1 San Sebastian

(EAJ8) 0.5427 103 Madrid (EAJ7) 8.0456 658., Salamanca

(EAJ22) 0.55

805

SWEDEN261 1,75o Horby 10.0265 .1,130 Trollhattan 0.4$33 goo Falun 0.5346.5 865 Goteborg 6.0437 686 Stockholm 1.5545.5 55o Sundsvall770 390 Ostersund 2.0

1,200 250 Roden 2.01,345 223 Motala 30.0

SWITZERLAND406 739 Berne 1.0489.4, 623 Zurich 0.6080, 441 Lausanne 0.6460 395 Geneva 0.5

1,010 297 Basle 0.25

TURKEY1,200 r5o Stamboul 6.01,810 103 Angora 5.0


LONDON AND DAVENTRY (5XX)April z8 A programme of oratorio.

29 Covent Garden opera.3o De Cour% ille'S Hour.

May 3 The Eternal Waltz, a musical burlesque :music by Leo Fall, book by R. E. Jeffrey.

DAVENTRY EXPERIMENTAL (5GB)April 30May I

234

April 3o

An Edward German programme.Plantation song, and negro spirituals.A vaudeville programme.Covent Garden opera.The Prisoner of Zenda.

MANCHESTERA programme by the band and pipers of the

Queen's Own Cameron Highlanders.

NEWCASTLEApril 3o Here's Tae Yo ! an evening in a village inn.May 4 North of England Musical Tournament,

relayed from the City

The Sheffield station is now transmittingon the national common wavelength of288.5 metres (1,o4o kilohertz), which isultimately to be adopted by practically allBritish relay stations.

That the hunt for wireless "pirates"still proceeds in Scotland is indicated bythe occasional cases which come beforethe courts. The latest offender to bebrought to justice was a Lossiemouthmaster baker, whose omission to take outa receiving licence cost him 13.

APRIL 27, 1929 639 (finalturWiretesj

SCREEN ASSEMBLY -2Coil Holders, McMichael Bin-ocular Choke, Peto-Scott.000L Peerless Rheostat,Dubilier .1 M.F.D., InsulatedWire, 2 Coils for 200/ OR/(100 metres. Post Free aliv/

ammosmima

The Original COSSOR MELODY MAKER

SPECIFIED COMPONENTS:2 Ormond .0005, 2 do. S.M. Dials, 6 T.C.C. Condensers, 2B.B. Clips, 1 B.B. Rheostat, 3 Dubilier Leaks, 3 LotusV.H., Ferranti A.F.3, 2 Switches, 9 named Terminals,Glazite, 9-v. Grid Bias, splendid D.S.C. wound Coil onPirite former, Drilled High-grade 21 x 7 Polished Paneland Strip, Wood Screws.ABOVE KIT OF PARTS £3 19Carri age 1/0.Handsome Oak Cabinet, 12,6 VALVESwith parts, Baseboard Free. Cossor Valves 2,4 or 6-v. forAlso Cabinets at 15 11, 18,11, above L.F ,D R C. or H F.,and Mahogany Polished, at 106 .each. Pow"er., 12;6 each.'

20"-. Carriage 2 '-

1,000 MILE RANGE onYOUR 1927 COSSOR

LIST OF PARTS FOR CONVERSIONE X TR AS- Cossor S.G.Valve type 220 - - 22/6Pair of High -wave Coils

12/6 PAIR2 Cossor Pattern S.M. Dials

6/- PAIRPOST EXTRA.

GENUINE IDEAL BLUE SPOTAdjustable Power 66K (101)

254 -pole Balanced ArmatureComplete with Cord . . . /-HANDSOME OAK POLISHEDSPEAKER CABINETS 13 X 13 X 6

12/11 PatBLUE /SPOT 25I66K (101)See above for specifications.

OR CABINET girlBLUESPOTjar.12" CONE

The Lot Carr. Pd.

ALUMINIUM

CRADLEWith fitted 10 in. Float-ing Cone and 12 in.Square Baffle Board.Takes all Bal. Armature

Units.

7f11Post 9(1. U.K.

WEI LO(N S.F.)

L.F. Transformer No. 10,11'8 ; No. 3, 8'6 ; Output 1-1,11.6 ; 2 mfd, 3, 6 ; .01, 1 9 ;

etc., etc.I RECOMMEND ABOVE

PERSONALLY.

LEADING HOUSE for

KITS OF PARTS

OSRAM MUSIC MAGNETKit of Parts and Valves,

£3 : 12 : 0.

Booklet Free.

Orders despatched same day as re -C0330 ceived where possible. Send ORDER

with instructions and pay Postman.C,OD. APPLIES TO UNITED KINGDOM ONLY.

LEVvCOSLeweos C.A.C.5,10/6;C.A.C.2012/6; C.S P.5, 10/6; C.S.P.20,12/6; P4 to 14, 3/- each; PI6 tc22,41- each. Touchstone Coil,.30'. pair. C.T. Coils, 3/6, 5'3.

-;Q.A.R., 21/-; Q.A.A., 15-;0.S.G..21/.. All lawns Products

KITS of parts tor all CIRCUITSMake out List for keen quotationDon't worry, if it's Wireless WE HAVE IT

ASTOUNDING OFFER IN3 -VALVE LOUD al

SPEAKER SETSReceives London5GB, 5XX, andmany Contin-ental Station;.

D. & 2 L.F.

No Coilsto ChangeAss emb' e dready for use.

SPECIFICATION Tax paid. Beautifully finishedcabinet with hinged lid, all

parts enclosed -3 British Dull Emitter Valves (1 Power).Latest Type Condenser, S.M. Dial, distant stations areeasily obtainable with standard aerial. High TensionBattery 100 volts. L.T. 2 volt Exide or Oldham. All AerialEquipment, Earth Switch and Wire. Tunes 259 to 2000metres. A REAL SET, at a price within anyone's reach.TRY ONE.

CONE or HORN TYPE SPEAKERWhichever you prefer.

5/-

The Complete £c la a NpaEckgTin.,

s vSet uim Carr. and

CLEARTRONVALVES

Power or R.C. - 6/-L.P., B.F. or Det. 4/ -Screen Grid. 2v. 12/6

POST 6d. (3 Post Free).

Ultra Short Wave Coilsfor Cossor New MelodyWard and N. /L. PAIR

Goltone (Post 6d.)

Ebonite cut while you wait atsquare inch, also inch

at 1. Only the best supplied.Drilled Panels for all cir-cuits.

LOTUS Q COILSQA, 15/- ; QSP 21 /-,MASTER 3 STAR 15/ -ALL LOTUS PARTS.

1

WEAR1TEDual Wave Tuner 15,-. B.F.Choke 66. S.W. Choke 4,6.2 -way Switch 6'-. 3 -way Switch7 -. Loading Coil 7;0. TitanCoil Unit 15'-.

LATEST SQUIRE 97RIGID ALUMINIUM CRADLE, FLOATING CONE.CLAMPING BOARD ASSEMBLED AND SPARE 15/6CONE KIT FOR ... ... ... ... ...Our model 97 i s emptied assembled complete with duplex woven floatingcone, clamping board AND a Kit of Parte for making kraft cone.Diameter of cone 91 in.OR COMPLETE WITH HANDSOME OAK The lotCABINET and BLUE SPOT UNIT 66K poet ree

(Genuine Ideal Adjustable) (U.K.)

ORMONDS.M. Drum Dia1,5/-; Rheostats, 6,15, 30 ohm, 21-; Midget0001 mar-4/-; Log .0005 and 4in. NM, 5/-;Log. .0003 and 415. Dial. 5/9.6.L.P. No. 3 same price. We always...Melt all ORMOND PARTS.

VALVESMallard, B.T.H., Marconi,Edison, Osram, Cosmos,Cossor, Six -Sixty, Det.H.F., L.F., R.C., 10,6 each.Power 12, 6, S. Power 15;'-,S.C. 22,6, Pentode 25--.

5 ValveSUITCASE

PORTABLES30$. down

10 payments 25$.

TRIOTRONB.F., Det., R.C., 5/2 eachPower, 6/9. 2-v. or 4-v.

Post 6d. i3 cost free).

DARIO RADIO -M I CRO

2-v. or 4-v. G.P. .. 5/6Super Power .. 7/6Super H.F., 2-v. or 4-v. 7/6


Copper and Aluminium Screens allsizes, or made to order. P.W.Screening Boxes, 126. P.W. Load -Mg Coils, 7/6. Harlie Wave Selec-

'tor 12;6. Tunewell Dual 3 Star,7.9. Combined Wave Q 3 Star.126. Scott's All -wave Tuner, 13,6.DX Set 4 short wave, 76. DX L.F.Standard Ratio, 81-. Weilo L.F.Power, 11[8. Weito Standard, 8/6.Dubilier H.C. Condensers, FrictionControl, .0005 and .0003, each 12/,Thumb Control, ditto, 156. TelseuRadio Grand L.F., 126. TelsenAce L.F., 8/8. Brown H.Q. Speaker,£36/0 Amplion A.0.2.. 21:-.M.P.A. Popular Plaque Speaker,296. Ormond Turn -table foe Port-ables, Bulgin All -wave Tuner,156. British General Tuner, 1810.Wale, 3 in 1 Test Meter, 8,6.Lotus Corriensers, .0005, 5/0; .0003.5/6. Colvern Master 3 Star DualColl. 17 it.


Come to LEICESTER SQUARE TUBEThis address is at the hack of DalS'sTheatre. Phones: Gerrard 4637 and 2821

B. FAV. 3(DE LUXE)

SET OF PARTS, 63/ -See issue April 13th lot

LIST OF PARTS.Tunewell Dual Coil 6 -pin7/9; Lewcos Short Wave20/45 or 40/90, 7j6 extra

SPECIALFOR EVERY 30/-

COUPON (64)you spend retail

YOU CAN buy ONE of the following for3d. each extra (on this Coupon)

H.F. Choke, Silk Loud -Speaker Cord, 9 -volt GridBias, Pair Panel Brackets, .0001 Reaction, 2 mfd.Mansbridge, 100 ft. Insulated Aerial, 4- or 5 -wayBattery Leads, 30 ft. Coloured Connecting Wire.S.M. Dial, 12 yds. Lead-in, Fuse and Holder, 12Nickel Terminals, 60X Coil, Permanent Detector,Battery Switch, .0003 and 2-meg. Leak, 6 -pin Coilbase, 12 yds. Twin Flex. 100ft. Indoor Aerial,.0005 Variable, Set of 12 Plugs and Sockets (red orblack), Set of 3 Coil Plugs with Terminals, WaveChange Switch, .01 Fixed Condenser.

WE ARE OPENALL DAY SATURDAYALL DAY THURSDAYALL DAY EVERYDAYHours 9 a.m. to 8p.mSat. 9 a.m. to 9 p.m.Sunday morning 11-1

QUOTATIONSfor

SETS OF PARTSSPECIAL PRICESon LISTS of 257- °VCALLERS or POST.

DON'T FORGET OURWHOLESALE DEPT ALL LINES

STOCKED.HOURS OF BUSINESS AS ABOVE.

The above photograph was taken 16th April to.

demonstrate the CLARION 3 to CUT OUT 2L0and obtain 5GB at full loud -speaker strength.

(Distance mile 2L0).

CLARION SCREENEDGRID 3

KIT OF PARTSAny other Condenser, H.F. Choke, or L.F. Transformer

supplied by adding balance.2 Polar .0005, No. 3, at 6/9. .0001 Reaction 4/-.2 Dual range C.T. Coils, with Reaction (Tnnewell), Anode,10/0; Aerial, 10/6. 3 Lotus or Forrno V.H. at 1/3. Formo-tenser, "J," 2/-. Dubilier 1 rufd., 2/6. .01 Fixed, T.C.C.,1/9. 3-meg. Lissen or Edison Ilell,1/-. S.G. H.F. Choke,Peto - Scott, 5/-. H.F. Choke, Lisien, 6/6. L.P. Trans-former, 11.1, Se Varley, 15/, Ebonite Strips.PRICE OF ABOVE KIT OF PARTS (INCLUDING THE

FOLLOWING:14x7 Ebonite Panel. Screen, E4.,x6. 8 Engraved Terminals.Push-pull Swatch, Flex, Plugs, 1G -g. Wire, 2 S.M. Dials.

£3 : 10 : 0Post Free U.K. .0002 and Strip omited, 1.6 extra.

Marconi S.C. Valve, USED IN ABOVE TEST on April 16th,price 22,6, and 2 Six -Sixty, 10;6 and 12;'6. Previous offers

cancelled.

TUNEWELLFOR CLARION

AERIAL . - 1 0 6ANODE - - 10/6Plash Pull, Panel Mounting.DUALRANGE

(As Illustrated)6 PIN - 7/9LISSEN 3 10/6 eachCOSSOR 3 1 0/6 each

TRADE SUPPLIED.ALL TUNEWELL PARTS.


enuiteurWtrelesi

ELECTRADIX BARGAINS

April Editionof our

Surplus Bargainsin

Radio & ElectricalGoods Ready.

Send stamped addressed envelope for bigSales List

ELECTRADIX RADIOS,218, Upper Thames St., E.C.4

(PAR EX)SCREENS COILS"THE ARCADIAN PORTABLE"

Copper Box as specified (5" x 5" x 5,") 9/6"ALL EUROPE." Copper Screen, each 4/6

"THE LISTENER'S THREE," Screen and Foil 4/6"THE CLARION THREE," The Screen as

specified 3/6COILS : Short Wave, each 5/6 Long Wave. each 6/5

From your Dealer or directj rowsE. PAROUSSI 10 Featherstone Buildings,

H i gh Holborn, W.C.IPhone : CHANCERY 7013

TheMIRACLESuper Long Range5 -Valve PORTABLEBalance payable by easy monthly instal- Yours forments, Every description of radio apparatuson Easy Terms. Also Gramophones and 1 0/"'Records. Illustrated Lists Free.MOWS WIRELESS STORES, Wallington, Surrey DOWN

TAYLEX WET H.T. BATTERIESbow Prices: Jars 1 /3. Saes 1/2, Zinca 101. Gamins so:.IS Volta complete with bands and electrcayte 4/1., po3t J1.Sample unit ed. Illus. booklet tree. Bargain li.t free.AMPLIFIE1P.3. 30 3 VALVC ALL -STATION SET £5.A. TAYLOR, 57 Studley Road, Stockwell. LONDON

EASY TERMSWe specialise in the supply of all good quality RadioApparatus on deferred terms. All well-known kits ofparts, components and sets, now supplied from stock.LOWEST TERMS. Send List of requirements to

LONDON RADIO SUPPLY CO.11, OAT LANE, NOBLE STREET, LONDON, E.C.2.

Phone: NAT IONA): 1977

A wireless telephone service betweenFrance and the Dutch East Indies wasformally inaugurated on April 13, whenM. Pasquier, the French Governor-Generalof Indo-China, talked with the DutchAmbassador in Paris. The new servicefunctioned perfectly, the voices of thespeakers being quite clear.

640

BLUEPRINTSConies of the " Wireless Magazine" andof " Amateur Wireless" containing des-criptions of all these sets can be obtainedat 1.s. 3d. and 4d. respectively, post free.

Index letters " A.W." refer to "Amateur Wireless " sets and " W.01."to " Wireless Magazine " sets.

All Post Free

CRYSTAL SET (6d.)i929 Crystal Receiver .. MVOs

ONE -VALVE SETS (1s. each)Beginners' One-valver AW 140

WM127Reinartz One ..

TWO -VALVE SETS (1s. each)East to West Short-wave Two (D. Trans.)Beginner's Two (D, Trans)Auto Two (D, Trans)All -Mains Two (I), Trans) ..Key -to -the -Ether Two (D, Trans)Meteor Two (D. Trans) ..Clipper Two (D, Trans) .

Twinflex (Reflex)

AW159ANVI7tAW174AWII3o

WM1o7.. WM114

WIs/1135..WIVII38

THREE -VALVE SETS (1s. each)All -wave Mains Three (LIE, D, Trans, Rectifier) AW144All-purpose Short-wave 'Three (I), RC, Trans) AW147Screen -grid Q Coil Three (HE, D, Trans) .. ANATI 50All -Britain 'Fhree (HF, D, Trans) AWt 58Bantam Three (D, RC, 'Frans) .. AW16oHartley Dual -range Three (13, RC, Trans) .. AW166Listener's 'three (HF, I), Tram.) price 4d. free

with -copy of "AW" AW t69The Binowave Three (D, RC, Trans) AW172Clarion Three (SG, D, Trans) AW1751929 Favourite Three (D, RC, Trans)

WAV M: 5:1 8479

Everyday (D, Trans) WAll -wave Screen -grid Three (HF, D Trans.) WMI to

WM tzo

M2WVM:234WMtz9

WIN,M14WWMi336:

Standard Coil 'Fliree (HF, 1), Trans) ...Festival Three (D, 2LE-dual Imp.) ..Wide -world Short -waver (SG, D, Trans)New Year Three (SG, D, Pentode)The Q3 (D, RC, Trans) Lodestone Three (HF, D, Trans) ..Simple Screen Three (HF. D, Trans) ..Dynamic Three (SG, D, Trans) ..At Home Three (D.zRC)

FOUR -VALVE SETS (13. 6d. each)Overseas Short -waver (HF, D, 2Trans) AWI33The Ranger( SG, D, RC, Trans) AW145Broadcast Picture Four (HF, D, 2 RC) AW163Orchestra Four (D. RC, Push-pull) .. AWL 67All Europe Four (2 HF. D. Trans) .. AWI 73Stability Four (H.F, D, RC, Trans) .. AW t82

Q -coil 4 (HF ,D, RC,Trans). WM71Five -pounder Four (HF, D, RC:Trans) WM9tTouchstone (HF, D RC, Trans) WM1o9Reyner's Furzehill Four (SG, D, 2Trans) WM112Economy Screen -grid Four (SG, D, RC, Trans) WM113Ifinowave Four (SG, D, RC, Trans) WM119Standard -coil Four (HF, D, 2 RC) .. WM 22Dominions Four (2SG, D, Trans) WM134The Drum Major (ULF, D, RC, Trans) .. WM137

FIVE -VALVE SETS (Is. 6d. each)" Q " Gang -control Five (al -IF, D, 2Trand AW16tEmpire Five (2 SG, D, RC, Trans) .. WM96Fidelity Five (HF, D, 2 RC) .. WM13o

SIX -VALVE SETS (Is. 6d. each)Short-wave Super -6 (Super -het, Trans) .. AW 67Eagle Six (3 HF, 1), RC, Trans) WM1 o6

AMPLIFIERS (1s. each)Screened -grid HF Amplifier

A.W." Gramophone Amplifier (3RC)Searcher Unit (HF)Gramo-radio Amplifier (2v) (Trans,'Signal Booster (HE Unit)Auditrol Amplifier

PORTABLE SETSHouse Portable (SG, D, RC, Trans) . AW t68 e/6Arcadian Portable (SG, D. z Trans) with

linen -diaphragm loud -speaker (half -scale) AW t 77 1/6£5.5.0 Portable (0. Trans.) AW18Chummy 4 (with modifications for LS

and HT) WM801 I/6Wayfarer Portable (Super -set) .. WM139

AW133AW162AW1 76

.. WM72.. WM x 28

WM132

1/6

Send, preferably, a Postal Order (stamps over sixpencein value unacceptable) to Blueprint Service

AMATEUR WIRELESS 58-61 FETTER LANELONDON E.C.4

APRIL 27, 1929

PREPAID ADVERTISEMENTS,Advertisements under this head are chargedTHREEPENCE PER WORD, minimum chargeTHREE SHILLINGS.


bona fides of advertisers in this publication, they haveintroduced a system of deposit which it is recommendedshould be adopted by readers when dealing with personswith whom they are unacquainted. It is here explained.

Intending purchasers should forward to the Publishersthe amount of the purchase money of the article advertised.This will be acknowledged to both the Depositor and theVendor, whose names and addresses must necessarily begiven. The deposit is retained until advice is received ofthe completion of the purchase, or of the article havingbeen returned to and accepted by the Vendor. In additionto the amount of the Deposit, a Fee of 6d. for sums of SIand under, and Is. for amounts in excess of LI, to coverpostage, etc., must be remitted at the same time. In casesof persons not resident within the United Kingdom, double.fees are charged.

The amount of the Deposit and Fee must be remitted byPostal Order or Registered Letter (Cheques cannot beaccepted), addressed to"AMATEUR WIRELESS," ADVERTISEMENT DEPARTMENT,

58/61, FETTER LANE, LONDON, E.C.4.

EARN MONEY AT HOME. You can earn money nt home in wholecr spare time writing Show Cards for us. No canvassing. We train yolk!I.y poet by our new simple method and furnish the Outfit free. WSimsely both men and women with steady work at home, no matter,a here you live, and pny you cash for all work completed each week, under our legal guarantee. Full particulars and Booklet free. WritsLt once or call. Show Card Service. Tlitchin.

WIRELESS OPERATING APPOINTMENTS: fees payable alter qualify-ing (for boarding students.) Morse classes. Wireless School, ManorGardens, Holloway, N.7.

ASSISTANT. Wireless Retail Shop. Mitchell's, 182 Rye Lane, B.E.I4

110 WEEKLY EASILY EARNED by selling Portable Wireless Bets,iGramophones, Records, etc. Illustrated Catalogue and particulars fromW.W., 1 Grosvenor Parade, Wallington.

Iturndeptradio receivers

REPAIRSAny make of L.F. Transformer, Loud -speakeror Headphones repaired and dispatched within48 HOURS-TWELVE MONTHS' GUARANTEElath each repair. 4/. Post Free.

Terms to TradeTRANSFORMER REPAIR CO.

"service" Dept.214 High Street. Colliers Wood, London S.W.19

(THE BEAT IN THE WE/T)19 LISLE STREET. MUSTER SOARS.. LONDON.W.C.R.Wr., Opt/ ProogoosoT

OPEN TILL 7 P.09.liotro9oustomm99.Posukctadrearouom

i

As.k444244,

STANDARD HIGH TENSION No. 16217 "Daimon " Battery 60 volts with Grid BiasNo. 16219 " Daimon " Battery 100 volts with Grid Bias

BATTERIES with GRID BIAS From all good dealersIssued by The Mandaw Company, Ltd., 945 Whitecross Street, London, E.C.r

7/3 each12/3 each

mateur Wirete, AvailableCOUPON

until Saturday,MAY 4th, 1929

APRIL 27, 1929 II! (i mutat:. WLretv.1

L

arn.A MIrr,7111r1111111111.11111111"11111111.1118111111111.1r111...1.11.11MIA!!!orlHirlwou'll'11111111!111111111111111111111111111[111111111111111111111111111111N1111111[111Wimp

DUBILIERFIXED

CONDENSERS

14

.1.LJ

Type 610

,

MAILSBRIDGE-

0-rONDEOSER

----

MICACONDENSERS

Type 610 and 620.00005 to .0009 - 2/6.00I to .006 - 3/-.007 to .009 - 3;6

Type B 775.01 - 4/- '.1 - 8/6

.5 - 37/6Intermediate Capacities at pro-

portionate prices.

Typo 620

PAPERDIELECTRIC

CONDENSER SAll capacities from

upwards..or to .t.125 and .2

and .3

eacheacheach

.4 and .5 - eacht.o each2.0 - each

Other prices onapplication.

2/-2/32/52/32/6

3/5

DUBILIER for DURABILITY"TOREADOR SCREEN -GRID FOUR"

This set incorporates the latest developments in Receiverdesign-full constructional, details free on request.

DIMMERCONDENSERS

If unobtainable from yourdect'er, write direct to usRipne his nome and address. , ,, sie L. tt Advt. of Dubilier Condenser Co.,

(3925) Ltd., Ducon Works, VictoriaRoad, N. Acton, Lo.tdon, W.3

tO230IF

Don't Forget to Say Ti at You Saw it in "A. ."

Lotus Componentswill make the best

of yourset

Lotus DualHare Coils,

15, - 6, 21,-.

Clear, untroubled re-ception, the capacityto do well all that thedesigner claims-theseare what you expectwhen you build a set,and what you get ifyou choose LotusComponents

For every Lotus unitis neat, strong andaccurate, car eful l ymade from the bestmaterials, tested andtried before comingto you.

Give your set everychance by using LotusComponents. Everydealer sells Lotus.

From all Radio lika!ers.

Lotus ValveHolder,

1;3

Rent,,,te

/.-7 30i.,.

otus VariableCondensers,Jam 5,-.

MooOMcoistsivils

GARNETT, WHITELEY & CO., LID., LIVERPOOL

ivAPRIL 27, 1.923

17/ 1-2_.:10.1711-4LOUDSPEAKE RS

Marconiphone Moving Coil Speaker. Master of the entiremusical range. Its unique method of double' cone suspen-sion places 'it far in advance of speakers of the same type.Prices from £ 1 0 -1 - . Units only, £6 -6 -0

Write, mentioning AMATEUR WIRELESS, for particularsof all Marconiphone Loud Speakers and Receiving Instruments

,. THE MARCONIPHONE CO. LTD:(Dept. P.)- 2m-212 Tmtenhain Court Road, London,'W.I.-

Showrooms : 210-212, Tottenham _Court Road, W.1, and Marconi House,Strand, W.C.2.

Listen to a MarconiphoneSpeaker ; as the room becomesflooded with notes of bewitchingpurity you lose all sense of yoursurroundings. You imagine your-self at the other end of themicrophone, in the great concerthall itself. Hearing becomesalmost seeing.

Marconiphone Cone Speaker-Model75. Gives ideal reproduction, sur-passing in every respect that ofother cone speakers. Its particularlypleasing design and finish make itsuitable for any room. Adjustmentis at the front, and the cone isprotected at the back. Price T.7 -

Printed in England': Published by Bernard Jones Publications, Ltd., 58/6t Fetter Lane, London, E.C4Sole Agents for South Africa; CENTRAL NEWS AGENCY, LIMII ED. Sole Agents for Australasia; GORDON & GOTCH, LIMITED. Saturday, April 27, tq.2)

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