leto WIRELESS WEEKL - World Radio History

Winans% incorporating' Wireless

Pio;leto WIRELESS WEEKL

Weekly,' OCTOBER 2. 1920

111E1110,0

INCORPORATING

LONG RANGE ONTWO DIALS

By STANLEY G. RATTEE, M.LR.E.

THROUGH THREE COUNTIESWITH A SUPERHETERODYNE

By JOHN UNDERDOWN

WIR.ELESS. October 2, 1928.

Every -reader and each of hisfriends should try to be thefortunate winner of one ofthese wonderful prizes. Fulldetails of the conditions ofentry \vill be published ill

the issue of WIRELEss datedOctober 9th, on sale Tuesdaynext.

The Elstree " Solodyne " -

the first prize --is the famousFive -Valve Receiver on Which110 fewer than fifty stationswere received on the loud-speaker On one dial.

Euy your copy of WIRELESSearly.

In addition, this issue willcontain many interestingarticles :

Mystery ArticleBy a well-known Radio Personality.

Atmospherics and their Pre-vention.

By Captain H. J. Round, MI.E.E.

Secrets of Modern Radio Effi-ciency (Part IV)

By J. H. Reyner, B.Sc. (Hons.),A.C.G.I., D.I.C., A.M.I.E.E.

What the New WavelengthsMean to You

By G. P. Kendall, B.Sc.

YOA MAY WINTHIS WONDERFUL FIRST PRIZE

A COMPLETE

ELSTREESOLODYNE

SECOND PRIZE "EST:A COMPLETEREFLEX " RECEIVER

THIRD PRIZE: A COMPLETE" RAZOR-SHARP " WAVEMETER

TH I'. Mystery Number of WIRELEss, on sale October 5th, willgive every reader the wonderful opportunity of winning an

equally wonderful receiver The Elstree" Solodyne."So great was the enthusiasm shown for this receiver at the recentFxhibition held at Olympia that we have every reason to believethis issue will have record sales.Copies of ti Mystery Number may be difficult to obtain excepton the day of publication. You may avoid any disappointmentby giving your'Newwent instructions to -day to deliver yourcopy on the morning c fpublication day.

'REISSINCORPORATING

WIRELESS WEEKLObtainable from all Newsagents, Bookstalls, and Booksellers, or direct from the Publishers,Radio Press, I td., Blizh House, Strand, London, W.C.2. Subscription Rates, 13'- per

annum throughout the world.

oit die

October 2, 1926. WIRELESS. 221

S P. 18RED SPCT.A real two - voltpower valveDesigned speciallyfor low frequencyamplification.Should always beused in last stage foroperating loudsneaker. It is alsosuitable as a detectorFil. Volts: 1'6.Amps.: '3.

PRICE 141-

S.P. 18GREEN SPOT.A high amp'ificationvalve having a mod-erate impedance.Designed as a highfrequency amplifierand as a detector.Also suitable for re-sistance, choks andtransformercoupling(.'xcept last stage,where an S.P. 18Red should alw.rysbe used).Fil. Volts: 1'6.Amps.: '3.

PRICE 141-

S P. 18BLUE SFOT.Extra high ampli-fication valve. De-skned for resistancecapacity, choke andearly stages of trans-former coupling. Ex-cellent as a detectoror tuned anode H.F.amplifier.Fil. Volts: 1.6.Amps.: '09.

PRICE 141-

earn,woirk

EAM WORK counts in Radio too.Unless valves work together har-moniously reception will never be

at its best. That is why BENJAMINValves should be used in every stage.They have been designed as a teamwhich, working together, will give resultsfar surpassing those that can be obtainedwith any other valves, in any other way.

Anode and filament are very closetogether, and therefore the electronstraverse a very short path. This in-creases amplification. A speciallydesigned filament consumes less current.Tone is improved. Ask your dealer orwrite for descriptive leaflet giving curves.

BELN7Asktil NSHORT'PATH

RADIO VALVESTHE BENJAMIN ELECTRIC LTD,Brantwood Works, Tottenham, N. 17.

D.E. 55.A very economicalgeneral purposevalve. For nighfrequency, detectorand low frequency(except last stage,when the S.P. 55 Redshould always beused.)Fil. Volts: 5.5.Amps.: '09.

PRICE 1816

S.P. 55BLUE SPOT.Extra high amn'i-ficaticn valve. De-signed for res(stancecapacity, choke andearly stage trans-former coupling.Also excellent as arectifier or high fre-quency ainplier.Fil. Volts: 5'5.Amps.: '09.

PRICE 1816

S.P. 55RED SPOT.Super power valvespecially designed asa last stage poweramplifier. Will givegreat power wit1:outdistortion. Also suit-able for detector orH.F. amplifier.Fil. Volts: 5'5.Amps.: '25.

PRICE 22/6

R V3

222 WIRELESS, October 2, 1926.

IN EN NM M WM III Mml

mis Nis s is N N min U N is IGRANIC CONDENSERS FOR ALL CIRCUITS

IGRANIC DUAL CONDENSER.

IGRANIC-PACENTSTRAIGHT LINE FREQUENCY

CONDENSER.

IGRANIC MICRO CONDENSERand

BASE MOUNTING BRACKET.

IGRANIC FIXED CONDENSERWITH IGRANIC FIXED GRIDLEAK AND MOUNTING BASE.

Look through your copies of the leading radio journals--notice the number of receivers in which Igraniccondensers have been used with such outstandingsuccess. Profit by the example of experts and useIgranic condensers in all your receivers.

am

IGRANIC DUAL CONDENSERS. Extremelylow losses, accurate square law characteristic, positiveconnection to moving plates, combined ball and frictionthrust bearings, stout brass plates and highest classworkmanship throughout. The two halves are matched.Dual pattern ... .0003 mfd. 22/6 .0005 mfd. 27/ -

Single pattern .00015 mfd. 17/-.0003 mfd. 18/6

.0005 mfd. 21/6.001 mfd. 25/ -

IGRANIC.PACENT STRAIGHT LINE FRE-QUENCY CONDENSERS. Straight line frequencytuning, extremely low losses, brass plates, negligibleminimum capacity, smooth action.Price ... . .00035 mfd. 14/6 .0005 mfd. 18/6

IGRANIC-PACENT TRIPLE GANG CON.DENSERS. Built up from three Igranic-Pacent .0005mfd. condensers. The sections are thoroughly insulated.Flexible couplings between sections. Price £3 10s.

IGRANIC MICRO CONDENSERS. Miniaturecondensers with brass plates of conventional shape.Adequate spacing between moving plates and controlknob eliminates hand capacity effects. Moulded coverprotects plates. Baseboard or panel mounting. (Singlehole fixing.)

Price ... 5/6 Baseboard Bracket 6d,

IGRANIC FIXED CONDENSERS. Plates ofbrass, dielectric of finest Ruby Mica, accurate andconstant capacity. Can be mounted in many differentways or supported on the wiring of a receiver.

c .001 mfd., .002 mfd. 1/6 each.Prices ... .003 mfd., .006 mfd. 2/. each.

Mounting Base ... 9d.

SEND FOR IGRANIC CATALOGUE No. S31.

IGRANIC ELECTRIC C. LT.D149, QUEEN VICTORIA STREET, LONDON.

Works : BEDFORD.

WS NM Il Il EN Ell Mil Il M Mil NM SIM lifft MI III M mm NM ME M OM EN MN MN ME M Il MN NM OM Er


INCORPORATING

Published by

RADIO PRESS, LTD.,Bush House, Strand, London, W.C.2.All communications concerning contribu-tions should be addressed to the Editorand must be accompanied by a stampedaddressed envelope if tile return of MSS.

is desired.Nothine contained herein is to be regardedas encouragement or permission to infringe

any patent rights.

THIS WEEK'S NOTESNext Year?

NOW that we are safely out of thethroes of the Exhibition, we are

all beginning to wonder what nextyear's show will have to offer. Whenwe look back for a year the changesthat have taken place seem startlingenough, although very few things seemto have changed f undamentally. Thevariable condenser still uses plates,although the shape is dif-ferent. I should not besurprised if smile of theforthcoming alterations aremuch more radical. Theremay not be such a thing as avariable condenser nextyear!

More IndicatorsI HEAR that it is very

likely now that " lumin-ous indicators " will be in-stalled in European broad-casting stations when the

-- new Geneva scheme comesinto force. These have beenin use in America in theexperimental stage for sometime. They consist of de-vices which cause a smallNeon tube to light imme-diately the wavelength of thestation varies in the slightestdegree. More red lights forthe studio !

AND NEWSshall take the forests of scaffold -polesas a matter of course, just, as we didin the case of the overhead standardsfor supporting the tramway cables.

The Latest in TelevisionALTHOUGH television is as yet

hardly more than an interestingexperiment, the experts are already onthe track of further possible develop -

winners, by the way, were valves andcoils and coil -holders, each occupyingprominent places on twenty-five stands,condensers and slow-motion dialshaving twenty to their credit.

HamburgNUMBERS of crystal users on the

East Coast are receiving Ham-burg regularly, and one or two reportscome from London; to the same effect.

Hamburg certainly does" deliver the goods nowa-

Some of the portable receiving and transmitting equip-ment used in the recent army manoeuvres in Hampshire

in which 10,000 troops took part.

Aerials and AppearancesI S it possible to have a street with

sixty houses equipped with, say,forty-five aerials in such a manner thatthe view from the back gardens is notimpaired? Everyone will agree thatthe best erected aerial is hardly anornament to the garden, and, with theincreasing number of them going up,it is becoming quite a problem to pre-vent suburban residences from lookinglike dockyards. I suppose in time we

meats. The first is tl It of colour.Germany is, I hear, hard on the track.

H.T. ErminatorsAPP A RENTLY the H.T. battery

eliminator has a great futurebefore it. At the Exhibition I wasrather interested to note that theywere on show at no fewer thantwenty-two stands, whereas H.T. andL.T. batteries themselves were only tobe seen on twenty-four stands. The

days, and Frankfurt is apowerful runner-up. Boththese stations are now usingten kilowatts.

No Escape !I RECENTLY had the-I opportunity to go on afairly long tour round thenorthern part of England,and, hardened as I am toradio, I must confess that Iwas astonished to find thatalmost every inn at which westopped or pulled up wasequipped with wireless and aloud -speaker. It's absolutelyimpossible to get away fromit !

Another New StationTHE new broadcasting

station shortly to beopened in Sao Paulo isclaimed to be " the mostpowerful and up-to-date

broadcasting station in the world."We look forward to hearing it speakfor itself.

An OverhaulTRE Gazette de Prague says that

since the equipment of thebroadcasting station at Poznan doesnot correspond with the recent pro-gress made in the industry, it is imme-diately being reconstructed on up -to -

(Continued on next page.)

224 WIRELESS. October 2, 1926.

The latest use of radio in the U.S.A. is for the trans-mission of weather maps. The maps, which are in-tended for ships at sea, are received on a cylindrical

drum similar to the one seen above.

date lines. \Vhen finished, it will besnore powerful than the Konigswuster-hausen station.

In Sweden'THE listeners in Sweden now

number nearly a quarter of amillion, representing about 35 licencesto every thousand inhabitants.

Short Waves ?I WONDER whether the B.B.0 will-11 ever radiate a short-wave pro-gramme similar to those sent out byKDKA and. WGY? The chief advan-tagei of such a programme would bethat foreign and colonial listenerscould he reasonably sure of receivingit with little or no interference fromatmospherics. From a friend of mineliving in India I recently heard thatseveral of the B.B.C. stations would bequite worth listening to were it not forthe latter source of interference.

The Southport ExhibitionSOFTHPORT Wireless Exhibition,

11.7 which will be organised by theSouthport Radio Society, is to be heldon October 28, 29 and 30.

For the Business ManGermany the home and foreignI Market news and quotations are

broadcast, picked up at fixed receivingstations and telephoned to catch ex-press trains, thus enabling travellersto obtain the latest news in theshortest possible time. When will ourrailways follow suit?

Oh !IHEAR on the highest authority

R that the following little incidentis absolutely true. After a little groupof rather eccentric literary celebritieshad broadcast, the 'phone rang, and avoice said, " Hullo, is that the B.B.C.?This is Colney Hatch speaking. Willyou .put the s in a taxi or shallwe send the ambulance along forthem? " I shall refrain (as usual)from comment.

ReTY,%%fggVERE8)63)3@4),9S6ERe6IMMVSTOEM3

THIS WEEK'S NOTES AND NEWS 0(Continued)

-',5eG,o,&8.,,,.,29A-')Z'*,W5'1*q.D'f3"et?ZCW3t6'g(83(894?349

Interesting TalksI SHOULD not be at

all surprised if wehear Mr. Alan Cob-ham from 21.0 afterhe returns from hisAustralian fligh t.Two or three topicaltalks of real interestwill, it is hoped, begiven every week infuture.

The generators at the Hamburg broad-casting station are rated to give 2,000

volts each.

An Interesting PossibilityI T is possible that

during the comingwinter the B.B.C. willgive us programmesselected by well-knownpublic men, who willbecome temporary" programme direc-tors." We look for-ward with curiosity tovarious possibilities inthis direction.Postmark PublicityI HEAR that the

Rugby radio ser-vice is to be one ofthe early victims ofthe " postmark pub-licity " campaign be-ing organised by theP.M.G. I hopeanother is inscribedwith the words " stoposcillating and payyour licence fee!

q3(830

Summer Time Ending

WITH the change over into" G.M.T." once more, we shall

have longer evenings, and the radiosets will have an hour's extra_ use eachday in many cases. The manufacturersare looking forward to the ending of" Summer Time " for this reason.Reception of distant stations shouldbe distinctly better at, say, 8 p.m.than it is at present.

Be Up -to -Date !HE Times recently issued an

appeal to radio enthusiasts touse up-to-date apparatus, and not tolet their results suffer simply for thesake of " using up old parts. " Fewp.eople," says the writer, " wouldthink nowadays of using a motor -car20 years old . . . . The wireless re-ceiver of to -day is an enormous ad-vance upon that of even two yearsago; its superiority is, in fact, on apar with that of the 1926 car over the

horseless carriage ' of 25 years ago."It is certainly true that very little canbe done to improve the results ob-tained from really ancient, out-of-date sets, short of substituting thenecessary new components and modern-ising the circuit.

No Women AnnouncersWE are, apparently, not to follow

the examples of Rome and SanSebastian, and -have women announcersat the B.B.C. stations. The B.B.C.consider that " women are tempera-mentally less suitable than men, andthat the heavy physical strain imposedon the announcer is greater than couldbe borne by the average woman."

CALL SIGN.

A view of part of the transmitting hall at the Nauenstation. Note the large banks of condensers in the

foreground.


HE ambition of thepresent-day home con-structor would seemto be largely in thedirection of receivingthose stations whichare hardest to get.

The more distant the station, the betterand the nearer the wavelength of thatstation to that used by the local trans-mitter the greater the joy, but ambi-tion does not stop here-on the con-trary, the desired station must be re-ceived clear of the local transmission,and no interference must beexperienced.

The Reason Why-

This ambition has probably comeabout as a result of the fact that re-ceivers which were built some timeago will not generally give the degreeof selectivity, and human nature issuch that we want most that which wecannot get, or that which is not easyto procure.

For safety in long-distance receptionit is usually better to employ two ormore high -frequency stages, but indoing so the question arises as to thedifficulty of operation, for if, for thesake of illustration, two H.F. stagesare used, these are generally tuned,making, therefore, three variable con-densers to handle, namely,the first grid circuit and thetwo high -frequency coup-lings.

To many, especially tothose who have hitherto onlyused a single -valve set, theoperation of three variablecondensers appears at firstsight somewhat difficult, tiedit is to those of the manyreaders of WIRELESS towhom the receiver to bedescribed *ill make specialappeal, as an intermediatestep to a more elaborateinstrument.

Iii the first place, thoughtwo H.F. stages are used, thereare only two controls, the secondH.F. stage being aperiodic. Itmay be thought at first that thereceiver would be improved bytuning this stage, and though thiscould of course be done with certain

CI

LONG RANGE ONTWO DIALS

By STANLEY G. RATTEE, M.I.R.E.With the advent of the dark evenings, DX recep-tion is much more easily accomplished. Thereceiver described in this article is capable ofbringing in quite a number of distant stations, andis specially designed to serve as an introductionto long-range work for those constructors whoseprevious experience has been limited to crystal and

one -valve sets.

modifications in design, the simplicitywith which the Set can be worked inits present form would be lost to someextent.

Some ResultsTo give some indication of the,

merits of the set as -illustrated,

TO ANODE

TO awo /6 CI 2

THESE TERMINALSJOINED TOGETHER-

Fig. 1.-This sketch of the special coilbase is intended to assist the process

of wiring.

or VI

ro/1.7."+

Bournemouth can be received clear ofLondon, in the Crystal Palace dis-trict (S.E. London), while a number ofthe foreign stations working on wave -

24.

C

14-

.3$*

6'4"

Radio -Belgique, and one or two others'whose identity has not 'been revealedduring hours of listening.

The CircuitThe circuit used in the receiver is

shown in the theoretical diagram,from which it will be seen that thefirst high -frequency valve is neu-tralised. The aerial coil L, and thegrid coil L2 are both of the plug-intype, the latter being a centre -tappedspecimen, tuned by the variable con-denser C,. The high -frequency trans-former L2 L, is a commercially made" fieldless " unit, while the variablecondenser Ca tunes the secondarywinding. This latter winding is madein two coils, the ends of which arebrought out to four connecting pins,numbered 3, 4, 5 and 6. The termi-nals 4 and 5 are joined together bymeans of a piece of wire, and termi-nals 3 and 6 are connected to L.T.negative and the grid of the secondvalve respectively.

The fixed condenser C, is best madeof one of the clip -in variety, forshould it be found that the receivertends to burst into self -oscillation inspite of the first valve being satisfac-torily neutralised, a reduction in thevalue of C, will bring about the de-

sired effect of stabilising the

Fig. 2.-Only eleven holes are required in the panel,the positions of which are shown in this dimensioned

diagram.lengths near to that used by Bourne-mouth can also be received withoutinterference. Other stations whichhave been received without difficultyare Newcastle, Birmingham, Glasgow,Daventry, Union -Radio, Madrid,Elberfeld, Rome; Radio -Toulouse,

set.If instability is experi-

enced' at all it will be found"to occur at a definite settingof the variable condensers,even though the first valiebe perfectly stable; andthough this position may befairly wide, a careful choicein the value of the C, con-denser will bring aboutcomplete stability over thewhole tuning range.

A RefinementAcross the windings of

the aperiodic transformerL, is still another fixed con-

denser, C, ; and though this isnot absolutely essential it will gener-ally be found that it gives ar. increasein signal strength when the variablecondensers are adjusted near to their



Long Range on Two Dials-continued

WIRING IN 37 RUC T ON S

Join L.T. + to H.T. - and thenceto " grid " socket of H.F. transformerholder and to F + contacts of V1, V2,and VI.

Join L.T. - to one side of Switch S.Join other side of S to one side of Ri,

and to terminal 3 of L4, one side of RI,one side of 113, moving plates of C2and right hand " filament " socket ofH.F. transformer holder respectively.Join same side of 111, also to flex lead(L2 tap).

Join aerial terminal to one side of

Join earth terminal to other side ofLi.

Join one side of L2 to fixed platesClof and to G of Vl.Join other side of L2 to top contact

of C3, and thence to remaining side ofCl.

Join other side of C3 to A of V1, andthence to terminal 1 of L3.

Join terminals 4 and 5 of L4 together.

minimum and maximumsettings, especially if the sig-nals are at all weak.

As to components requiredfor building a receiver tothese specifications, theseare given separately; andthough ether suitable makesmay be found in theadvertisement pages, it is stronglyadvised that no departure be madefrom the values given, otherwisesome difficulty may arise as tostability, wavelength range or othercircumstances. The value of the con-denser Cr should, as given above, befound by experiment in the event ofinstability, but the other values shouldnot be departed from.

Easily BuiltThe construc-

tional work in-volved in buildingthe receiver willbe found to beof the simplest.The componentsshould be laidout upon thepanel as near tot h e positionsgiven in the wir-ing diagram asthe componentschosen will per-mit, while beforeactually screwingthem down thecoils and valves should be mounted toensure that sufficient clearance is beingallowed, not forgettino' that long -wave.coils may sometimes be used. Thewiring of the receiver is again asimple matter, and it is recommended

ISP LINE OE qASEBOARD.

BOTTOM EDIE Or FAl;C

R2

+HT- +Lr- sThe written instructions accompanying this diagramcan be used to eradicate any difficulties which may arise

when the connections are being made.

that all the internal connections withthe exception of that to the centretapping on the coil L, be soldered.The arrangement of the componentsand the space between them rendersthe use of a soldering iron an easymatter, in that in no circumstancewill the constructor find his positioncramped.or otherwise difficult of access.The components to the back of the

Fig. 3.-The condenser shown variable at C3 is the neutralibaseboard, that is, those near to thepanel, should be wired up first, fol-lowed by connecting up those uponthe panel, when the remainder willbe found to be quite straight-forward.

WIRING 1NSTR T.JC1 ION3

Join terminal 6 of L4 to 0 of VI andto remaining side of C2.

Join A of V2 to one side of H.F.choke and thence to one side of C4.

Join other side of H.F. choke toH.T. + and thence to terminal 2 ofL3. Same side of H.F. choke also totelephone + terminal.

Join remaining side of Cl to one sideof C5 and thence to remaining " fila-ment" socket of H.F. transformerholder.

Join other side of CS to " plate "socket of H.F. transformer holder andto one side of CO and R4 (the two latterare combined and have commonterminals).

Join other side of C6 and R4 to G ofV3.

Join A of V3 to remaining telephoneterminal.

Join remaining sides of RI, RI, andR3 to F - contacts of V1, VI and V3respectively.

First TestsWith the wiring complete

and checked against the dia-gram, turn all the filamentrheostats to their off posi-tion; turn the on and offswitch to its " off " posi-tion, insert the H.F. trans-

formers in their respective sockets,and with a No. 25 coil for L,insert a No. 60 or " B " centre -tappedcoil in L, and connect the flexiblelead.

Insert the valves in their socketsafter having connected the 'phones,batteries, aerial and earth to theirrespective terminals; whereupon turnon the switch and adjust the filament

rheostats so thatthe valves areburning at a suit -a b 1 e brilliance,and tune in thelocal station bymeans of thevariable con -

3 densers to itsloudest volume.

With this doneturn the first fila-ment rheostat sothat the firstvalve is ex-tinguished, when,if the local sta-tion is still

sing condenser. audible, turn theneutralising con-

denser either one way or the otheruntil signals are no longer audible.Now light the first valve once more,and again tune to the local sta mn,when signals should be loud and freefrom distortion


A Simply -Controlled Three -Valve Receiver

SearchingSlowly turn the two con-

denser dials so as to keep thecircuits L2, C, and L C2 intune, when it will not be longbefore a distant station isfound, the local stationhaving disappeared after thefirst few degrees were passedthrough.

As the unit -scale readingof the condensers isapproached, it may be found,though not necessarily, thatthe receiver has a tendencyto oscillate, and should thisbe the case do not upset theneutralising adjustment, butexperiment with the value ofthe condenser C4. In thereceiver, as illustrated, thecondenser used is a .0002,this being found to be a safevalue, though .0001 would be

This photograph will convey a clear impression of thecompleted receiver with coils and valves in position.

tried in this receiver, andwith an H. T . voltageranging between 60 and90 volts, all gave satis-factory results. Valves speci-ally designed for high -fre-quency work should be usedfor preference, thoughgeneral-purpose types willalso give satisfaction shouldthe constructor alreadypossess some of this type.

For Loud -Speaker WorkThe receiver has now been

in use for some considerabletime in conjunction with the" Wireless" TransformerAmplifier, the combinationbeing used as a loud -speakeroutfit. Using telephonesalone, however, distant re-ception is a comparativelyeasy accomplishment, f o rthough the tuning is sharp,

Trolite panel, 14 in. by 7 in. by 3/16thin. (F. A. Hughes & Co., Ltd.)

Cabinet, and baseboard measuring9 in. by 14 in. by in. (Camco. )

Two Right Angle Brackets. (Burne.Jones & Co., Ltd.)

Two coil holders, baseboard mounting.(Burne-Jones & Co., Ltd.)

One " Fieldless " coil, 300-f00 metres,and six socket base. (Lissen Ltd. )

One Neutralising Condenser. (L.McMichael, Ltd.)

Two .0005 Variable Condensers,"Popular" type. (Bowyer -Lowe Co., Ltd.)

WHAT YOU WILL NEEDOne Radio Frequency Choke. (Beard &

Fitch, Ltd.)One .0002 Clip -in Condenser and base.

(L. McMichael, Ltd. )Three shock -absorbing valve holders.

(Benjamin Electric, Ltd. )One Baseboard mounting valve holder,

ordinary type. (Radi-Arc Electrical Co.,Ltd.)

One " Aperiodic " H.F. transformer,300-600 metres. ( Burne,-jones & Co., Ltd.)

One .0001 fixed condenser. (DubilierCondenser Co., Ltd.

One.0003 grid condenser and 2 megohmleak. (Watmel Wireless Co., Ltd.)

Three baseboard mounting 35 ohmrheostats. Lissen Ltd.)

One On and Cff switch. (RothermelRadio Corporation, Ltd.)

Four terminals, " aerial," " earth,"" phones -- " and " phones --." (J. J.Eastick & Sons.)

One terminal strip and four terminals.(Burne-Jones & Co., Ltd.)

Quantity of No. 16 " Clazite " con-necting wire.

Packet Radio Press panel transfers.Short length of rubber covered flexible

wire.

safer still with possibly- someslight loss in signal strength.

It will be found that theoperation of the variablecondensers calls for somecare, as the tuning of thereceiver is quite sharp, par-ticularly when the aerial coilL, is made smaller than a No.25, as suggested above.

Long WavesShould the constructor

desire to receive the long -wave stations, as for in-stance, Daventry and Radio -Paris, then the coil L1 shouldbe changed for a No. 75 or100, and L, for a No. 250centre -tapped s p e c i m e n.The " fieldless " coil andthe aperiodic transformershould also be changed forsimilar components, but oflong -wave design.

The operation of the receiver uponthese longer wavelengths is preciselythe same as on the shorter band, and

When wiring up the receiver, reference to thiswill be helpful.

no difficulty will be experienced inthis direction.

As to valves, various specimens of2-, 4- and 6 -volt valves have been

slowly turning the condenserdials together, " brings in "stations well and clearlywithout that doubtfulpleasure of operating areceiver to the limit ofstability, as is the case withmany smaller sets.

It is not suggested that thereceiver is the very best thatone can do with three valves,but it certainly does presenta means whereby long-dis-tance work may be indulgedin without very much prac-tice in this art of tuning.

It must be rememberedthat the receiver was notdesigned for loud -speakerwork, and even though whenused near to a B.B.C. sta-tion it is doubtful whetheranything approaching loud-speaker signals would beobtained. Should it be de-sired to receive signals on a

loud -speaker, then the addition of asingle stage of transformer -coupledlow -frequency magnification will givethe desired results.

view


0 far we have discussedroughly the numberof tuned circuitsnecessary in order toobtain good qualitywith good selectivity,and secondly t h e

general methods by which the tunedcircuits required are associated withthe high -frequency amplifying valvesin a receiver.

Stability TroublesApart from the general principle,

however, there are certain other diffi-culties which have to be overcome.One of the main causes of troublewhich was experienced when tuningcircuits in general began to increasein efficiency was the fact that the cir-cuits were not satisfactorily undercontrol. As they came into tune, sothey burst into oscillation, and thisoscillation could only be checked eitherby mistuning, or by introducingadditional damping into the circuit,either of which courses was retrogradeand therefore unsatisfactory.

The CauseAs is by now well known, the reason

for this oscillation is that a reactioneffect is produced by currents whichflow inside the valve through thecapacity between the anode and thegrid. In the circumstances whichusually apply in a high -frequencyamplifier this reaction effect is suffi-cient in quantity, and in the rightdirection, to produce continuousoscillation.

The success of a modern receiver isvery largely due to the fact thatmethods are adopted to counteractthe effect of this capacity feed -back.If we could eliminate the feed -backitself, then we should solve the pro-blem, but so far this has not beendone ,to any extent. Reports havebeen published, however, of speciallyconstructed valves having shieldedgrids in which neutralising as weknow it to -day is unnecessary, andthere will probably be considerabledevelopment in the future along somesuch lines.

Principal RemediesIn the present-day circuits, how-

ever, the ordinary three -electrode

IIIDEECIEDDEEEEEMEEDEDEEICEE=000:1ESEDMOLLEDIDEOMO

SECRETS OF STABILITY 0

IN MODERN RECEIVERSBy J. H. REYNER, 0

B.Sc. (Hons.), A.C.C.I., D.I.C., A.M.I.E.E. OO

IlltDEMMEEDEMLEEEE=C37.:=MMEEEMOMEEDEETEIE111

This, the third of a series of articles by Mr. Reyner, dealswith the subject of neutralising and explains the remarkableway in which it has been developed during the last few months.

valve is employed, and the effect ofthe valve capacity is overcome byspecial devices external to the valve.These devices , are of two principaltypes, which were disdussed togetherwith the whole question of neutralis-ing in an article appearing in WIRE-LESS, Vol. 5, No. 1. Briefly the twomethods are :-

(a) The voltages on the anode of thevalve in question are fed through asmall neutralising condenser to somepoint on or associated with the gridcircuit, such that counter -reaction

NC

(a) (b)Fig. 1.- Two skeleton neutralisedcircuits in which centre -tapped coils

are employed.

effects are produced in opposition tothose produced by the valve itself.

(b) A point is chosen on or asso-ciated with the anode circuit of thevalve at which the voltages producedare opposite and usually approxi-mately equal to those at the anodeitself. These voltages are fed througha small neutralising condenser backto the grid of the valve, so that againcounter -reaction is produced. Byutilising an arrangement of this sortthe counter -reaction effect can beadjusted to be equal and opposite tothe positive feed -back through thevalve over the whole range of wave-length of the receiver.

Greater EfficiencyI do not propose to elaborate this

question in any greater detail be-cause it has already been discussed atsome length in recent issues of

WIRELESS and most people are by nowaware of the general principle under-lying neutralising in a high -frequencycircuit. It may be of interest toremark in passing that a neutralisedcircuit gives essentially considerablygreater efficiency than a circuit whichis not stabilised in this manner.Apart from the use of devices whichactually overcome the feed -back in thevalie (e.g., the use of special valves),the only other means at our disposalin order to check oscillations are theintroduction of damping in the cir-cuit, or the reduction of the ampli-fication of the valve itself .(by dim-ming the filament or by some similararrangement).

It must be obvious in such casesthat we are not obtaining the maxi-mum output from the valve. Themore efficient we make the tuningcircuit associated with the valve, themore readily does it oscillate. If wecheck its oscillation by reintroducingresistance or by cutting down theamplification of the valve we obviouslyare simply wasting time in endeavour-ing to make the tuning circuitefficient. If on the other hand we

.definitely counteract in some mannerthe tendency to oscillate we can thentake full advantage of the extraselectivity and greater amplificationafforded by the use of efficient tuningcircuits.

Centre -tapped CircuitsNow, one of the principal types of

neutralised circuit which has beendeveloped is that employing a centre -tapped tuning circuit. For example,the skeleton circuit shown in Fig. 1 (a)gives an idea of the main principle.Instead of connecting the whole tunedcircuit across the grid and filament,one end is connected to the grid, butthe filament is taken to the centrepoint on the coil. The other end ofthe coil is then taken through aneutralising condenser to the anodecircuit. By this means the capacityfeed -back of the valve itself isneutralised by the feed -back throughthe neutralising condenser, which isapplied to a point exactly opposite inpotential to the grid and therefore acounter -reaction effect is produced.

(Continued on page 233.)


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SECRETS OF STABILITY IN MODERN RECEIVERS-(continued).

A similar arrangement can, ofcourse, be obtained by employing atuned circuit in the anode of thevalve, as shown in Fig. 1(b), neutralis-ing in this case being carried out by thesecond of the two methods previouslyoutlined. The neutralising condenseris connected to a point at an oppositepotential to the anode and the energyobtained from this point is applieddirect to the grid.

" Parasitic " TroublesThe principal difficulty with this

type of circuit lies in the fact that

Fig. 2.- In this example the p imarywinding is not tuned, but is coupled to

a tuned secondary.

where two such circuits are used thereis a danger of the production of" parasitic " oscillations. The coilsthemselves possess a certain self -capa-city and it will readily be seen thatone-half of the coil is virtually in thegrid circuit, while the other half is inthe anode circuit. Each half of thecoil tends to oscillate at its own naturalfrequency, that is, the frequency towhich the half -coil tunes with its ownself -capacity. This natural frequencyis very high, usually about ten timesas great as that being received, so thatthese parasitic oscillations correspondto a wavelength of the order of 30 to 60metres.

The SymptomsAt these high frequencies the im-

pedance of the neutralising condenseris very small, so that its effct is negli-gible. The circuits therefore wouldtend to oscillate at this frequency,quite irrespective of the normal fre-quency to which they would tune withthe condenser C,. These oscillationsmanifest themselves by the fact thatthe receiver suddenly goes " dead "with a loud click, and nothing what-ever can be received. If the grids ofthe valves are touched with the finger,the usual click denoting oscillation isobtained, but no heterodyne whistleswith the carriers of the ordinarybroadcast stations are obtained, indi-cating that the oscillation is at atotally different frequency.

How They Were DiscoveredThese parasitic oscillations were dis-

covered by various people more or less

simultaneously. I believe the first dis-covery was due to Capt. Round, ofthe Marconi CO., who happened to beexperimenting with some high -fre-quency circuits in Cornwall, near tothe famous Poldhu station, at whichthe Marconi Co. were at the time ex-perimenting with the short-wave trans-mission and reception. The engineerin charge of 'the latter experiments,Mr. C. S. Franklin, explained in con-versation with Capt. Round that hewas receiving extraordinary jammingon his short-wave reception, and hecould not trace it in any way. Thiswent on for some time, when it wassuddenly established that the short-wave jamming only occurred when ex-periments were being done with thehigh -frequency amplifiers tuned to thenormal broadcasting wave, and as theresult of investigations the presence ofthese hitherto unsuspected parasiticoscillations was determined.

Various other experimenters, notablyMr. Pound, of Messrs. McMichael,observed and traced the effect, whilethe WIRELESS Laboratories at Elstree,which had been investigating theproblem of high -frequency amplifica-tion for some months, also inde-pendently observed, traced, and over-came the trouble.

RemediesElstree's interest in the matter was

that of obtaining superlative circuitsfor the amateur experimenter and con-structor, and the results of these re-searches have been seen in the recentElstree circuits. The " RemarkableFive -Valve " receiver was one of thefirst circuits published which included

Fig. 3.- The primary winding properis represented at XZ, ZY being a

neutralising winding.

an anti -parasitic device, and subse-quently a still better arrangement,more widely applicable to a large bandof wavelengths, was obtained in the" Elstree Six " circuit.

In the latter case, as is well known,the trouble is overcome by taking thecentre tapping to the tuned circuit atthe middle point of a twin condenserinstead of on the coil itself, and thiseffectively overcame the difficulty whilepermitting the coil to be changed forone covering another wavelength band,without alteration to the circuit.


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Secrets of Stabilityin Modern Receivers

(Continued from page 233.)

Following the " Elstree Six " wehave the " Mewflex " and the " Dista-flex," published in Modern Wirelessand The * Wireless Constructor, andthe " Elstreflex Two," which is beingdescribed in WIRELESS at the presenttime, all of which are developments ofthis split -condenser principle. Mr.Harris's " Night Hawk," which com-bines extreme efficiency with compara-tively low cost, utilises a modifiedversion of this same principle.

Another MethodAnother method of overcoming the

difficulty consists in the use of auxiliarywindings, apart from the tuned wind-ings, for producing the requiredneutralising voltages. Various methodsof adopting this principle have been

could not obtain satisfactory resultswith more than one stage of this typeunless the two portions of the primary -winding were very closely coupled. Thisled to the development of the type oftransformer which was utilised in the" Magic Five " receiver, and in the" Solodyne," in which the two halvesof the primary winding are wound oneover the other. The circuit thenbecomes as shown in Fig. 3, in whichthere are really three windings-thetuned secondary, the primary proper,which is the winding X Z, and theneutralising winding, which is thewinding Z Y.

This circuit has several advantages,one being that the full voltage of thetuned circuit is utilised, and not onlyhalf, as is the case with the circuits

This chair, whichwas exhibited atthe Olympia Exhi-bition by Messrs.Alphian Wireless,Ltd., contains acomplete wirelessreceiving set. Theframe is wound inthe back of the

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utilised from time to time, but theprincipal disadvantage is that theneutralising settings do not hold goodover the whole .of the tuning range.

There is one exception to this, andthat is the case where a split -primarywinding is adopted. A skeleton circuitof this type is shown in Fig. 2. Thiswill be seen to be somewhat similar toFig. 1 (b), save that the primary wind-ing is not tuned, but is only coupledto a tuned secondary. It will be im-mediately obvious that if satisfactoryresults are to be obtained, the primarywinding must be so tightly coupled tothe secondary that it behaves to allintents and purposes as if- it weretuned. Then the potentials at thepoints X and Y are substantially equaland opposite, and will remain sothroughout the whole tuning range,which is the condition required forsatisfactory neutralisation,

DifficultiesEven so, however, I found that I

shown in Fig. 1. Moreover, it is veryeasy to neutralise, and can satisfac-torily be used without any trouble fromparasitic oscillations.

Design ProblemsThis is by no means the whole of the

story. There are many little pointswhich' differentiate between a gooddesign and an indifferent one. Tworeceivers both having. what isapparently the same circuit, maybehave in different manners, one beingmuch more easy to control and tohandle than the other. There is alsoanother factor which enters consider-ably into the efficiency of a multi -stagehigh -frequency amplifier, and that isthe problem of interaction and directpickup. I shall deal in my next articlewith one particular point in designwhich makes for ease of control, thequestion of capacity coupling betweenprimary and secondary, and finally thequestion of screening in high -frequencyamplifiers.

01,-(..vcyt 2, 1926, WIRELESS. 235

FIRST IN ENGLANDRADIO PRESS TRIUMPH

IN BOTH MULTI -VALVE CLASSES ININTERNATIONAL COMPETITION IN NEW YORK

THREE INTERNATIONALPRIZES

A specially interesting feature of thegreat annual Radio World's Fair at NewMadison Square Garden, New York, wasthe international competition for home.constructed sets of all types. The prin.cipal class, and the only one in whichRadio Press readers entered, was themulti.valve (3 or more valves) category.

Entries were invited from all over theglobe, and many sets were sent in byBritish amateurs, a truly internationalcontest of set -builders resulting. Theawards were made on a basis of " work=manship, appearance, volume, distance,selectivity and tone," a body of leadingAmerican experts, headed by Dr. AlfredGoldsmith, being the judges.

Every set sent was tested by indepen.dent engineers, a very thorough investiga=tion into the powers of each instrumenttaking place.

There was a special competition in eachclass for entrants under the age of sixteen,and this proved an eagerly.seized oppor=tunity for the keen juniors of a numberof countries.

The result has proved to be a triumphfor Radio Press readers, and also forRadio Press designs. The third prize inthe multi -valve class in the senior compe-tition was won by a six -valve set using the" Elstree " circuit, entered by Mr. H. E.Hassall, of 40, Norfolk Street, Strand,London, while in the junior equivalent

competition a " Mewflex " receive'(described in " Modern Wireless "),entered by a thirteen.year-old British cont.petitor, J. A. E. Black, of Mill HillSchool, won the second prize. This setalso won a special cup for general fineworkmanship.

These Radio Press readers head the listof the British multi --valve entrants inthe international competition-anothertriumph for Elstree, whose circuit andcomplete design were respectively used.

CORRESPONDENCE

" Cut Him Out "SIR,-It may be of interest to you to

hear of the success I have had with thewave -trap desio-ned by Mr. Kendall, andpublished in the issue of NVIRELE-; datedAugust 14, 1926.

I have made several traps, but havemet with little or no success, so you mayimagine that I was reluctant to make thisone. However, I made it, and when Itell you that I am only 700 yards fromthe Aberdeen aerial, and that -I can tunein Newcastle, Manchester, Birmingham,Bournemouth, and several other stationswithout the least interference from Aber-deen, I tisink you will agree that thatin itself speaks volumes for the practical-ness of the trap, and more than fulfils theclaims made for it.-Yours faithfully,

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WORKING YOUR" ELSTREFLEX TWO"

Some helpful operating instructions for the Radio Press "Star"receiver which was described in detail in our last issue.

N important point ingetting the best re-

, sults from the" Elstreflex " receiverconcerns the type ofvalve employed, and,as already explained

last week, these should both be of thelow impedance, type. It must beremembered that the second valveshould naturally be regarded as apower amplifier, while the. first has tocarry both the high_ and the low -frequency currents, and it is thereforeimportant that here also one shoulduse a type with a long,straight portion uponthe useful part of itscharacteristic.

Grid BiasWhat is required,

then, is a valve of whatis commonly called thepower type in eachsocket, with a correctlyadjusted amount of gridbias upon each. Thegrid bias upon thesecond valve can beadjusted, straight awayto the value given bythe makers of the valve,probably about 6 or 9volts, with something inthe neighbourhood of 100

a tendency to rectify,signals will be heardfrom the local stationeven when the crystaldetector is disconnected,or when its two partsare separated by lifting the knob. Theaim should be to find some value ofgrid bias in the neighbourhood of 44;to 6 volts which makes the signals asweak as possible when the crystaldetector is not functioning.

NeutralisingAssuming a correct adjustment of

neutralising condenser which preventsself -oscillation, although some slightsigns of distortion may be noticed asthe adjustment of the neutralising con-denser is brought nearer to the set-tings which permit the receiver tooscillate.

The " Elstreflex Two" Receiver.

volts upon the anode, while thatupon the first valve is best adjustedexperimentally.

A useful guide as to the correctadjustment of the first valve may befound in the fact that if this valve has

The arrangement of components at the rear of thelatest Elstree " Star " set.

grid bias and high tension, the latterbeing in the neighbourhood of 100 or120 volts upon the second valve, andperhaps a little less upon the firstvalve, say, 90 volts, the final adjust-ment of y the neutralising condenser

should be per-formed. It willmostly be foundthat with vales ofthe recommendedtype the receiverwill oscillate freelyat some readings oft h e neutralisingcondenser, and theaim should be tofind such a readingthat the set doesnot oscillate at anycombination o freadings on thetuning condenserdials. For thelocal station it willbe found that goodresults are obtainedat practically anysetting of the

Be Careful !For the reception of

distant stations, how-ever, a more delicate

adjustment of theneutralising condenserwill be needed for thebest results, and here itwill be found that thereis an appreciable differ-ence between the fully -neutralised conditionand that in which the setis only just nicely re-moved from the oscilla-tion point. Considerablecare is necessary inmaking this adjustment,however. for it must beremembered that if theset is allowed to oscillate

it will radiate and cause interference.Searching

When searching for distant stationswith the receiver adjusted to its mostsensitive condition, it will be foundthat tuning is particularly sharp, andsome practice may be needed toacquire the necessary skill in mani-pulating the two dials at the requiredrate of travel. The knack of keepingthe two circuits in tune with eachother as searching proceeds will soonbe acquired, however, and it will befound that the sound of liveliness willserve as adequate guide.

Further ResultsThe qualities of the " Elstreflex

Two " as a local receiver were indi-cated last week, and some resultsobtained in a long-distance, test maybe of interest. Both Bournemouthand Birmingham gave loud -speakerresults, as also did Hamburg, Frank-furt and Berne (the latter on oneevening only). Telephone signalswere obtained from a number of sta-tions, of which Glasgow, NewcastleBelfast and Brussels were identified.,

October 2, 19264 WIRELESS. 237

SHORT-WAVE NOTESAND NEWS

Liu

UROPEAN work still seems tobe the order of the day,although the Americanstations are coming throughquite well in the early

mornings. None of the United Statesstations now seem to give calls in-tended exclusively for the Britishamateurs, as they often used to do.In fact, with the exception of a merehandful of stations still using it, theold familiar call " CQ gu " isnever heard on the air at all.

German ActivitiesSeveral of the German amateurs are

now apparently working with crystalcontrol, judging from the beautifulnotes one hears from them. In thematter of call -signs, however, they arerapidly becoming as bad as the Frenchtransmitters. Three of them, 4MCA,4MFL and 4YAE, are particularly badmouthfuls. It is probably just as wellthat they are adopting call -signs ofthis kind, though, as their others wereoften apt to clash with those ofBelgian stations.

Low -Power TestsThe T. and R. Section of the

R.S.G.B. is organising a series of tests,to be held in November, with a view togiving the low -power man a realchance to show what he is made of.All stations using powers higher thanabout 10 watts are to be asked toremain silent, and steps are beingtaken to minimise the amount of Con-tinental interference, which will, inci-dentally, cause the greatest amount oftrouble. Wonderful things may beanticipated, seeing what has been doneby the owners of microscopic powersin the past.

The ConventionThe recent Convention held by the

T. and R. Section was a great success,and will undoubtedly be repeated infuture years. A gathering of thisdescription does more towards pro-moting the " true ham spirit " amongthe members than anything else coulddo. The Editor of the Bulletin pre-dicted that before long it would be" very similar to QST, but twice asbig! " Perhaps when the membershipis equal to that of the A.R.R.L. thisdream will come true !

More CommercialsStill more commercial stations are

invading the 30-50 metre wave -band.One evening the writer counted nofewer than 38 of them, all workingwithin this band. There seems littledoubt that the amateurs will eventu-ally be " crowded out " altogetherfrom this band which they themselveshelped to develop.

(Contiwned on page 243.)

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From 54 15 0Write to -day for descrip-tive pamphlet and sugges-tions for adapting yourreceiver or panel in ourStandard Cabinets.

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238 WIRELESS. October 2, t926.

(717e

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October 2, 11926, WIRELESS. 239

N thinking, things care-fully over I have cometo the conclusion thatnext time I attendthe Wireless Exhibi-tion I shall go bymyself and not with

the Little Puddleton Wireless Club.It is not that I am unsociable, markyou; it is not that any snobbish feel-ing makes me dislike to be seen incompany with fellows like Gubbsworthyand Bumpleby Brown. It is simplythat whenever the club does anythingin a body they always seem to get intomischief, despite all my best effortsto keep them out of it. Believe meor not, if they are a handful in theold home town they are a positivenightmare when they go in a drove tosuch a place as Olympia.

How It BeganTrouble started directly we entered

the building, for Professor Goop, whowas in a cheerful frame of mind, in-sisted upon demonstrating what onepossessed of that Kruschen feeling cando, by leaping over the turnstiles.There was hardly sufficientlanding space within for onedisplaying his fine freeaction ; the result was thathis leap brought him to theedge of the first step, andthat on the rebound helanded slap in the middle ofa stand covered with loud-speakers. Four commis-sionaires pounced upon himat once, and fearing thatour old friend was about tobe roughly handled I gavethe order to charge. Theclub stormed the turnstilesin a body, effecting a neatrescue. I need hardly saythat we were all promptly ejected.

I managed to get back again quitequickly. As I was walking rathersadly down the street a stout man infront of me removed a tall hat in orderto mop his bald head. Quick aslightning I borrowed the hat, givinghim in exchange the trilby that hadstood me in good stead for the pastten years. Before he realised whathad happened to him I had disappearedinto the main entrance, where Isimply went to the turnstile labelled" Officials," said "Afternoon, George,"to the man in charge, and passedin unquestioned. I have always felt

The Little Puddleton WirelessClub's visit to the Radio Exhibitionended rather suddenly. " WirelessWayfarer " has now decided tovisit similar shows in the future

on his own !

that a countenance stamped indeliblywith marks of breeding and brains willcarry one almost anywhere.

They Trickle BackI was at the Mullard stand, where

I had almost succeeded in convincingthe chappie in charge that it wouldbe a fine stroke of business for him tosend me down a dozen P.M.'s withhis compliments when I heard a sud-den uproar coming from the directionof the cigarette stall in the corner.It appeared that Poddleby had triedto sneak in through the staff entrancedisguised as a " Nippy " and wasbeing pushed out with enthusiasm.The only member who was really suc-cessful in getting in without paying

end, though Bumpleby-Brown nevergot any further than the annexe, andtold people when he got home , thatthere was not a. thing to see at theExhibition. By skilful manoeuvring Imanaged to separate Professor Goopfrom the rest, so that he and I mightmake a select tour together; I alwaysthink that it is better for the brainymembers of the club to go off on theirown and for the others to do likewise.Then at the next meeting you havetwo quite different sets of impressions,which produce a really interestingdiscussion.

The Professor is PopularProfessor Goop won every heart

amongst the demonstrators by thehelpful attitude that he adopted. Hisidea was that the demonstrator peoplewere very much overworked, and thathe would be doing them a really goodturn if he' helped to entertain thewaiting throngs round their stands andto display the good qual'':ies of theexhibits. At one condenser stand hewas sublime. " If you will allow me,"he said to the demonstrator, " I think

that I can do you a reallygood turn." He thenstarted to tell the crowd allabout variable condensers." For the best results," heremarked, " it is essentialto have brass vanes; thisinstrument (and here he 4

seized one from the stand)has, as you will perceive,aluminium vanes. It ismost important, too, thatthere should be no end -playin the spindle, If you cando like this (and here hepulled the knob out abouta foot and pushed it backagain) the thing is simply

no good at all. The slow -Motiongearing should contain no back-lash; you will observe that Ican move this dial four degreesin either directibn without anythinghappening to the plates. It is mostimportant that there -should be a posi-tive. . . . " He got no further, forat this point the demonstrator awokefrom his stupor and swatted himrather neatly over the ear with anearth tube. Good Samaritans areseldom appreciated properly.

CoilsWe moved on to a stand where there

That Kruschen feeling 11

again was Gubbsworthy, who told thefellows at the door that he was theWicked Uncle. One look at him con-vinced them that he was right, andthey let him go in without a question.

The Unlucky GeneralThey refused utterly to believe the

General's tale that he was doing thetopical talk ; they told him that hewas not likely to be wanted-theGeneral was, no doubt, a little workedup, and it was certainly a hot day-unless the B.B.C. thought of puttingon a tropical talk. However, they alldribbled back again somehow in the

240 WIRELESS. October 2, 1920.,

Jottings by the Way-continuedwere heaps and heaps of coils. I muchregret the lack of compactness in thesemodern inductances you could gettwo or three of the old type into yourpockets without their making a notice-able bulge, but I had not borrowedmore than one of these new-fangledthings before the fellow at the standobserved that it would spoil the hangof my coat and deftly retrieved it." I see," said the Professor, " thatyou have a Unimic and a Dimic ' why,I ask you, not a Trimic and a Quad-rimic ? And why should you stopthere? Let us have a Quinquimic oreven a Undevigintimic? " The demon-strator looked frightened. " But,"continued the Professor, "I have some-thing here in my pocket that puts allthese in the shade."

He fumbled for a moment and pro-duced a bath bun. " No, no," hesaid, trying again. Having broughtout in turn his spare collar (he hadonly come to London for a week, andwas therefore travellinglight), a piece of Chatter -ton's compound, two files, arubber hot water bottle, thereturn half of his ticket, astick of solder, and a tin offluxite without a lid, he atlast lighted upon the objectof his search. " Here it is,"he said with a beamingsmile. He drew out one ofhis famous Slimic coils woundupon a natural starfishformer. A sea atmosphereis apparently out of placeat Olympia, for the thronground the stand, acting likeone man, grasped his nosewith the forefinger andthumb of the right hand, and fledincontinently.

The "X" CircuitWe visited next the display of the

new " Z " circuit, in which the Pro-fessor was enormously interested. Heinsisted upon showing the crowdexactly why it would not work and ontelling them something of his new" X " circuit, which completely solvesthe problem of interference by radia-tion. The " X " circuit is, of course,exceedingly hush-hush at the presenttime so that I can hardly give" youdetails of it. The main idea, however,is to use an aerial earthed at bothends and to get your dance music froma gramophone fitted with a numberof electric -lamp bulbs and providedwith a panel studded with knobs.

Worse and WorseThe Professor endeared himself par-

ticularly with the transformer makersby proving conclusively to them andthe crowds round their stands that re-sistance -capacity amplification alonecould give undistorted reproduction.When we got to -the( people who makeresistance -capacity units he demon-

strated to them and the general publicat large that their exhibits would beas right as rain if only they were notall wrong. We passed on to the valvestands. At the first of these the Pro-fessor showed that unbreakable valveswere quite breakable by cracking onelike a nut beneath his heel. At thenext he got the demonstrator so tiedinto knots by talking about Eccleslumped volts that the crowd cheeredhim to the echo.

UnfortunateThinking that we 'had perhaps

better retire to the Gallery for a littleuntil things had become calmer downbelow, I took him upstairs, where wejoined the queue that was defilingbefore the plate -glass window of thestudio. As soon as we reached thewindow I realised at once that thingswere going to happen, for there beforethe microphone, topical talking likeanything, was his rival, Professor

that some member of the club was in-volved in a fragas, I made my waythere like a flash of lightning, brush-ing aside the crowd (with the utmostcourtesy and a pair of .sharp elbows)as I moved.

The trouble, I found, was beingcaused by the General, who had pur-chased an enormous loud -speaker witha swan -necked horn which he wascarrying about in his arms. It isnaturally somewhat difficult to movein a crowded hall with such an encum-brance, and if you'll believe me, thecrowd had refused to make allowancesfor the General's little difficulties.When on turning suddenly to the lefthe had winded a man on his right, thefellow had grown quite nasty as soonas he was able to speak. Hearing hisremarks, the General had swung roundto the right, removing the hat of some-body on his left.

Being the most courteous of men,the General naturally turned to apolo-

gise, and in doing sodelivered yet another blow tohim whom he had firstsmitten, Turning now thisway, now that, to say howsorry he was, the Generalhad knocked out about adozen people who were stand-ing behind, building a kindof rampart of fallen bodies.

The EndHearing a roar, the other

members were convergingfrom .different points as fastas they could, leaving a trailof prostrate forms in theirwake. Just as I got there,prepared to explain the

whole thing, a large hand grippedme .by the scruff of the neck,and I observed similar hands beinglaid upon other Little Puddletonscruffs. In about two ticks we wereout in the street again, and though weprotested that it was the rest of the,crowd and not us that ought to beejected, they would not listen to a wordthat we said. If they must hold wire-less exhibitions, I do not see why they

,should not provide shock -absorbers onthe pavement outside.

WiR.ELESS WAYFARER.

4' ' Afternoon, George . . ."

Blimp. The way in which ProfessorGoop leaped from the queue, brushedaside attendants, thrust open the doorof the studio and burst in is beyondany feeble descriptive words of mine.Stupefied, I watched the whole scenethrough the window. I saw him stealup behind Professor Blimp andadminister a box on the ears that musthave produced in countless thousandsof homes an atmospheric which causedaerials to be earthed instanter. In asecond Professor Goop was talkinghard into the microphone, telling theworld, as he afterwards informed me,that all that they had just heard wastripe of the first water. In two secondsa bevy of uncles had descended uponProfessor Goop and handed him overto stout commissionaires, who rushedhim downstairs, through the hall, andout through the exit door.

More TroubleFeeling a little relieved, I made my

way down again, proceeding to makea quiet tour of the more interestingstands all alone. I had not done morethan three of them when I heard soundsof strife coming from near the middleof the Hall. Guessing in a moment

0 0QRA's Found

G-5IW: Intern:i t ional StandardElectric Corporation, ConnaughtHouse, Aldwych.

G-6TP : Lord Egerton of Tatton,,Tatton Park, Knutsford.

G-2ABL : N. Doble, Jr., 1, Pick-wick Road, Dulwich Village, S.E.21.

SAD: Swedish Naval FloatingStation at Stockholm.

BZ-1BH: M. Godafredo Damm,Rua da Quintanda, N.137, Rio deJaneiro.

D-7ZG: H. T. Petersen, " Fribo,"Ostergade, Norresundby, Denmark.


TRANSFORMERTHE NEW LISSENthe transformer for the Elstreflex

Mr. Scott Taggart says : " The only point of the circuit (the Elstre-- - `--er7"- --'----- --- c---,-- 2,-,Ilex) which is at all critical is that the transformer used in the reflex ,-- ') ------ c'F-''.. -----. --'`,stage should have a low secondary self -capacity." -..._.- .----=,---- ---, ----..

- -

----......._....._,

The New Lissen Transformer was_...,

chosen above all others for this stage.Mr. Scott Taggart says : " The whole problem (of parasitic oscilla-tion) can be avoided if the transformer specified is used."-THATREFERRED TO THE NEW LISSEN.

Use New Lissen forit

the all stages-tooIII

Not only the reflex stage, but for the second stage-for all circuits and valves you are likely to use you willnot get a better transformer than the new LISSEN.Two or three of these splendid transformers can be usedtogether, if desired.By cutting out all wholesale profits, due to our newdirect to dealer distribution policy, in addition to our Ibig production programme, this new Lissen transformer ---

,

..6,

1 -

is available to you at an unprecedented price. You I/ 'ti,ungwould never pay a high price for any transformer if -,-,0

"-

you knew the remarkable tone purity and power of this - -

" 4 all_new I issen. ,,,------7

77177111,1111,Compare it against 11,1,1,11

--7P111 l' ill

any.DEALERS AT A LOSS For Elstreflex building you will also want a .002

LISSEN FIXED CONDENSER-the condenser whichAsked to name the price at which they thought they delivers all its stored -up energy-the LISSEN WIREcould sell this new Lissen Transformer, many of the- RHEOSTAT. Lissen one -hole fixing, of course, pricetrade buyers who visited our Stand at Olympia named 2/6 (previously 4/-), and the LISSEN VALVEa figure close to Li. Many named 25/-, and many evenmore than that.

HOLDER, base board mounting, price 1/- (previouslyx/8).

THE GOOD LOOKS OF THIS NEW Another Lissen milestoneLISSEN ARE MORE THAN CONFIRMED The new Lissen (Mansbridge type) Condenser (inBY ITS PROVED PERFORMANCE moulded case, which does away with all risk of con-

denser short circuit, on to its outer case)-is another

Tested by a Trade Paper improvement to radio parts. Prices no higher than forthe ordinary tin -cased type.

Reviewing its performance, this trade paper says : " Itis infinitely better than the average transformer aroundthis price. . . . Its strength was only slightly below our PRICES :standard transformer which is 4:I."-NO TRANS- a mfd. .. .. .. .. .. .. 4/8FORMER HOWEVER HIGH THE PRICE CAN a .. .. .. .. .. 3/10BE MORE 'THAN " INFINITELY BETTER."

.5 o 3/4You can rely that the standard transformer againstwhich the new Lissen was tested was an EXPENSIVE .. .. .. 3/-TRANSFORMER.AND THE NEW LISSEN WAS STATED TO BE . .. .. .. .. .. ..x 2/6NEARLY AS .GOOD FOR POWER. Nothing was saidabout purity, and we know that for purity and power

.or .o9 m

this new Lissen transformer is not excelled by the verybest YOU Your Lissen dealer will show you every Lissen part youtransformer made-YETCAN BUY IT FOR .. .. want, and you can build with-you'll find him friendly

and anxious to help you. If any difficulty, however,Guaranteed for I2 months. send remittance direct to factory, .and the goods will be

sent by return. Post free, but please mention your dealer'sTURNS RATIO 3 : x RESISTANCE RATIO 4 : x name and address.Test it for seven days-if you are not satisfied take itback to your dealer's, or send it back to us.

LISSEN, LTD., 18-22, Friars Lane, Richmond, Surrey.Managing Director : 1'. No COLE.

" Give us a better transformer "-and Lissen have responded with a lower price too !1.77


What are thevirtues ofa reallygood telephone?

c.-1 First it must be sensitive. Distantsignals must come in clear and dis-tinct to do justice to any ordinarily

ca efficient receiver.

2it must, for broadcast especially,possess a good trine, clear and freefrom muffling or " tinniness."It must, in additlo to being efficient,

3 be comfortably capable of being wornfor long listening -in periods withoutany feeling of cramp or discomfort.

ERICSSON Super -Sensitive Telephonesmeasure up to all these re-

quirements and to -day set the standard in telephoneefficiency. Wonderfully sensitive, possessing a beautifultone and very comfortable to wear.

In three resistances -120, 2,000 & 4,000 ohms.ALL ONE PRICE

20/-Write to -day for literature, treating on ourvalve sets, components, loudspeakers, etc.

ERICSSON TELEPHONES LT2.67/73, Kingsway, London, W.C.2.

SUPER -SENSITIVETELEPHONES

Prar .. 0,

The New CombinationLotus Grid Leak

and Buoyancy

Valve Holder,coo, -.,,c-4 E4''Se..,,,doc

ter' -111111, ii,.

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OW 'it

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4P :!

I4111a4 . :I VHI/

Pro. Pat, : ' . ------_-..20339

Pat.256833 The Grid Leak is not dis-

cernible, being totallyenclosed in BakeliteValve Bolder Base.

Yet AnotherLOTUS Triumph

in Component DesignLike all other LOTUS Components,the new Combination Grid Leak andValve Holder is guaranteed efficientin construction and design. Iteliminates unnecessary wiring andsoldering, and makes for economy in

cost and space.

Ordinary Terminal Valve Combination Grid LeakHolder, 2s. ed. and terminal Valve Holder,

Without terminals, 2s. 2d. 3s. 9d,

]All Anti-Microphonic

'®)

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Combination

GRID LEAK BUOYANCYANI3 VALVE HOLDER

Anti-MicrophonicFrom all Radio Dealers. Write for List.

Garnett, Whiteley & Co., Ltd.Lotus Works, Broadgreen Road, Liverpool.

Makers of the famous Vernier Coil Holders.

Octoner 2, 1926. WIRELESS. 243

SHORT-WAVE NOTESAND NEWS

(Continued from page 237)

Perhaps the " Beam " stations willnot be quite so bad as some of theflatly -tuned variety that we hearnowadays.

SMXAThe call -sign " SMXA "

future be used as a kind of" CQ," and will denote " Allamateur transmitters."

will, inSwedishSwedish

Transmission in MalayaTransmitting licences are now being

issued in the Federated Malay States.One of the first has been issued to Mr.Chas. Randall, Amber Rubber Estate,Johore, with the Call -sign JM-3AB.JM is the Official Intermediate, signi-fying Johore, Malaya.

ScreeningAlthough amateur transmitters in

London have much to put up with inthe way of interference by powerstations, trains, trams, etc., they arevery little troubled by the type ofscreening that is to be found in severalparts of England, notably the Northand West, in the form of high rangesof hills several miles long. Someargue that screening of this type isnot serious when we are concernedwith short-wave work, and quote theHeaviside layer theory. The behaviourof low -power transmissions is alwayssomewhat eccentric in districts of thisnature. The chief feature, however,always seems to be that long distancesmay be covered with ease, whereaslocal transmissions are very difficult topick up. Is this a word in favour ofthe Heaviside layer?

Favourable LocationsThose transmitters who live near the

sea always appear to be fortunatelyplaced as far as reception is concerned.The 'writer is not thinking of interfer-ence from spark stations, since thisnever does cause much trouble on theshort waves. One does not even knowthat the short waves travel betterover water than land, but the factremains that reception is generallymuch better. Can any reader offer anexplanation?

QRA's FoundP-1AW : Mario Neves, Largo do

Directorio 4, Lisbon, Portugal.GLYK: M. -Y. " Adventuress," c/o

Col. Millard, Royal Thames YachtSquadron, Knightsbridge, London.

XII-2RV: J. V. Candido, 584, E.26th Street, Brooklyn, N.Y., U.S.A.

Z-3AJ: Post Office, Rangiora, NewZealand.

Z-3AD: R. G. F. Blake, Blaketown,Greymouth, N.Z.

Z-3AG: W. H. Claxton, 165, Dean'sAvenue, Christchurch, N.Z.

Has your H.T. Battery ever been stale when youbought it ?

Have you ever thought it did not last as long as itshould have done ?

This is a risk you need not run. Insist on a LissenNew Process battery. These, thanks to our new direct -to -dealer distribution policy (which also cuts out allwholesale profits), are actually on sale in the Londonarea within three days of being made in our Richmondfactory.

Every battery therefore is brimful of new energy whenyou buy it, and our secret new process causes them toretain this energy for an unusually long time and alsoyields far clearer loud -speaker reproduction.

Ask for it at your dealer's, or if any difficulty senddirect. No postage charged, but mention dealer's name.

Price Wouldhave been 53/ -but for our new

policy.

. .Quality tells in rheostatic devicesUse a Lissen 35 Ohm Rheostat for the Elstreflex.

- Let your wire rheostat or potentiometer be a4,ift and shortcircuitpleasantlyMLISSEN-thentcoaet wires cannotmovesannots

firmlytasany

/ 1

ti,,.......,

-the heat resisting former cannot soften-thereare accessible terminals-and the combined knoband pointer will fit flush with the neat photo-, engraved dial when mounted. Lastly note the

'. I irresistible appeal of the new prices, made possibleefil 1,!Jo by our big production programme and our new

Idirect -to -dealer distribution policy, which cuts

'=!5 ..,..-,- -out all wholesale profits.'1

II

, . .. 'fili

Compare a LISSEN with any high-priced rheostat-remember that LISSEN rheostats have them-selves been high priced-then think of the new

------.4 F LISSEN prices, and you will make a quickdecision to buy a LISSEN.

tio0 7 Ohms .. Previously 4/- NOW 2/6. AI 35 1, 4/- NOW 2/6

....... ::. Dual .. 6/- NOW 4/6... ...-

Potentiometer, 400 ohms 4/6 NOW 2/6Important to the trade t Orders for all LISSEN parts must now be sent to factoryand not to usual wholesale dealers. Apply for particulars of new trading policy ifnot already advised. Every dealer in his own interest should be registered with us.

LISSEN LIMITED, 18-22, Friars Lane, Richmond, Surrey.Managing Director : T. N. COLE.

1, 76

244 WIRELESS. October 2, T926.

Through Three Counties witha Portable Superheterodyne

By JOHN UNDERDOWNAn account of the reception conditions experienced in thecourse of a " wireless holiday " taken by the designer ofthe receiver described in this journal under the title

"Simplifying the Superheterodyne."

N the front cover ofthis issue a photo-graph of a portablereceiver in use in theopen country will beseen. The set actuallyis the 5 -valve super-

heterodyne, consisting of a modifiedTropadyne combined oscillator -detec-tor, two intermediates, a seconddetector and one transformer -couplednote magnifier, which I described inthe issues of this journal forAugust 28 and September 4.

In the latter of these two articles itwas indicated that further resultsobtained with the receiver would bepublished and here it is proposed togive particulars of the set's capabili-ties as evidenced during tests carriedout on a 600 -mile run. The tour,which extended over one week to-wards the end of August, started andfinished in London. The course takenwas through Tonbridge, Guildford,Basingistoke, Andover and Amesburyto Wincanton, and thence south toDorchester, Lulworth, Bournemouth,through the New Forest to Winches-ter, Petersfield, Midhurst andStorrington to Shoreham,Hove and Brighton, andback through Tonbridge toLondon.

Unfailing ServiceThroughout the run,

although circumstances, suchas late arrival At a stoppingplace and difficulty in findingaccommodation, preventedmore than three or fourthorough tests being carriedout, in no position where itwas tried, usually during aroadside stop for ref resh-mentA, did the set fail togive at least one station atsatisfactory loud - speakerstrength.

Battery ArrangementsThe photograph in the

heading shows the receiver inuse near Midhurst in Hamp-shire, where during an after-noon stop both London and Bourne-mouth were heard at satisfactorystrength upon the loud -speaker.From this picture it may beobserved that an accumulator wascarried to provide the L.T. supply,actually a 6 -volt 30 -ampere -hourbattery. This arrangement permitsof the set being used within doors

during the evening,which is impossibleif the car battery isemployed. This lat-ter battery wastried from time totime and provedperfectly satisfac-tory, excepting forthe above limita-tion. The H.T.supply was a 108 -volt Hellesen bat-tery, of smallcell type, which,although not really to be recom-mended on account of the some-what heavy current taken by fivevalves; proved perfectly satisfactorythroughout the week and is stillfunctioning well, but now upon a2 -valve set only.

The FrameThe frame aerial was the " Suc-

cess " portable type, this componentpacking away in a comparativelysmall space; a feature of considerableimportance where space is limited.

The receiver used on the tour was described in" Wireless," Volume 5, No. 2.

over roads, which in some cases werelittle better than cart tracks, thewhole outfit came through without asingle mishap to a valve or a con-nection coming loose.

Valve ProtectionThe valves were not removed from

the holders during the whole time,and the method of preventing themfrom jumping, out of the anti -vibra-tory sockets may be of interest. Thecases in which the valves werereceived were employed to hold them

in position, the lids of thecases being removed. Tissuepaper was wrapped roundthe valves so that the casescould be placed over themand arranged at such aheight that the lid of thecase just held the whole fairlyfirmly. Thanks to thismethod of carrying, althougha spare valve was taken, itwas not .required.

The valves used were of6 -volt type, an Electron SS.6serving for the combinedoscillator -detector, two D.E.8H.F.'s as the intermediateamplifiers, a D.F.A.4 as thesecond detector and a B.4 asthe note magnifier.

The First TestStarting from Town in the

early evening of Saturday,August 21, the first stop wasmade at Tonbridge, where itwas decided to spend the

week -end. The set was rigged up ina house actually in the town itself,which is somewhat low lying and sur-rounded by hills, the position beinglocated at approximately half a, mileon the south side of the River Med-way. It was dusk when the receiverwas ready, but before 10,30 p.m. nine


Mr. J. Eccleston, who recently broadcast a talk from2L0 on the subject of " A Day in a Signalman's Life."

On the score of portability a smallloud -speaker had to be chosen and an" Ultra " hornless type, which readilypacked into a small attache case, to-gether with the H.T. battery, wasused throughout.

The set, frame aerial and batterieswere accommodated in the back of thecar; and despite the severe jolting


S.S. 2A., H.F. and L.F.D.E., rS volts, 1 amp.,H.F., L.F. and Detector

S.S. 10.14/.

D.E., 2 volts, 5 amp.,Power Amplifier .. 18/6

S.S. 7.D.E., 3-7 volts, I amp.,Power Amplifier .. 18/6

S.S.8.D.E., 3-4 volts, 1 amp.,General Purpose .. 14/.These prices do not apply in

the Irish Free State.

Duo - triantularSuspension

affordsCOMPLETEPROTECTION

to theFILAMENT

ORTHY of the wonderfulSix -Sixty filament itself'!

6 Our new D'uo-Triangularsystem of suspensionaffords complete protec-

tion to the filament, safeguardingit even when subjected to theroughest handling, and enabling itto function with the highest degree ofefficiency.In this new construction, the filamentis supported at each corner of bothtriangles, with the result that theunsupported length is relativelysmall. This unique method of sus-pension eliminates all possibilityof sag, and renders it unnecessaryeither to assemble the filament intension, or introduce springs or othermaterials for maintaining it in posi-tion. Accidental knocks which woulddisplace or fracture the filament inany ordinary valve have no effect,firstly, because the relative positionsof filament, grid, and anode are fixed,and secondly, as the filament is notin tension, all possibility of fractureis practically eliminated.And remember, the Six -Sixty filamentis no ordinary filament. Its currentconsumption is barely .1 amp., andwhen operating at the rated voltage,there is absolutely no sign of " glow" ;in fact, there are no valves on themarket to -day that can boast of alonger life,because there are no valvesthat operate at a lower temperature.The new Six -Sixty Point OneValves are suitable for operation inall stages of a receiver, whether theL.T. supply be 2, 4, or 6 volts.After exacting and exhaustive testsMessrs. A. J. Stevens (1914) Ltd., havedecided to standardise SIX -SIXTYValves in their famous " Symphony"

Range of Receivers.Descriptive Leaflet S.S.9-26, giving full par-ticulars of complete range, on application.

vv

SIX -SIXTY VALVESBenet' by Six Times Sixty'

The Electron Co., Ltd., Triumph Howe, 189, Regent Street, London, W.I. 4A

OUBI LI ERWIRE WOUNDRESISTANCE

100,000 CI

The Dubilierwire -woundresistanceNo new Dubilier Product is placed on themarket until it has undergone prolongedtests under working conditions.

In this manner you can always be assured ofthe perfect reliability of any product bearingthe Dubilier name.

The new Dubilier Wire Wound AnodeResistances will be found to be ideal forresistance capacity circuits.

Self induction and self capacity effects arevirtually non-existent, and the resistancevalues remain constant throughout allvariations of climatic conditions.

20, 30, 40, 50, 60, 70, 80, 90 and 100 thousand ohms. 5!- each.

200 thousand ohms .. . .. 8/- each.HOLDERS (as shown, extra) 1/6 each.

Specify Dubilier.

0 RCISTE RE D

NJ ILl

TRADE, MARK

DUBIL/ ERCONDENSER CO(1925)LTD

ADVT. OF THE DURILIER CONDENSER co. (1925) LTD.. DUCON WORKS,

VICTORIA ROAD. N. ACTON, LONDON, w.3. Tel. Chiswick 2241-2-3.E.P.S. 4110

246 WIRELESS.

THROUGH THREECOUNTIES WITH A PORT-ABLE SUPERHETERODYNE


stations had been heard upon the loud-speaker. The first tuned in was thelocal station, 2L0, about 35 miles dis-tant, volume being too great for com-fort in a room of average size. Ham-burg also gave really good loud-speaker strength, and was, in fact,much better than most of the Britishstations, both here and in other posi-tions in which the set was used.Frankfurt also came in quite well, asdid Newcastle, Madrid, Belfast, EcoleSuperieure, Dublin, and several un-identified transmissions.

On Sunday little was done with thereceiver excepting to listen, upon thehills to the south of the town, to theafternoon transmission from 2L0,which came in at good strength, theset being used at approximately onemile from the nearest aerial, so thatthere was no question of any pick-uptaking place.

Reception Near GuildfordThe run taken on Monday was a

comparatively short cross-country oneto Ewhurst, near Guildford, the dis-tance from London being approxi-mately 30 miles. Here again a goodopportunity of trying the set presented

itself, and again London and our oldfriend Hamburg were heard first atsimilar strength to that obtained onthe first stop. Oslo, Breslau, Berlin,Glasgow, and several other stations

One of the new receivers which wasexhibited at the Radio Exhibition, the

Rotola Baby Grand Model.

were heard rangingin volume from goodto fair loud -speaker strength.

A Poor LocalityOn Tuesday it was somewhat' late

before the stop for the night was made

October z, r926.

at Mere, a small town in Wiltshireabout 20 miles west of Salisbury.Mere itself nestles under a very steephill, upon which a castle was oncesituated, this hill coming roughly be-t8een the hotel at which I stayedand Cardiff, about 50 miles away;35 to 40 miles to the south-westBournemouth is located, and this sta-tion was first tuned in, and was, infact, the only station which gavereally satisfactory loud -speakerstrength, to be heard all over a, verylarge room, whilst Cardiff made only apoor second. Five or six other trans-missions were heard, at weak loud-speaker strength only, none being defi-nitely recognised by their call sign.2110, which had been so strong on theprevious evening, was heard faintly,and was only identified by the con-denser dial settings.

LulworthContinuing on Wednesday morning,

the course taken was through Win -canton, Yeovil, and Dorchester to Lul-worth Cove, the first halt for recep-tion being made upon the hills abovethis latter place. Here in full day-light the Bournemouth transmissionwas received at good loud -speakerstrength. Having listened to this sta-tion for. some time, the journey wascontinued. Here the roads taken wereperfectly execrable, in some cases littlebetter than cart tracks, and we wentseriously astray, so that our arrival


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The vernier movementcomprises three setsof enclosed precision

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Side plates, coil blocks,and knobs in artistic bake-lite mouldings. All metalparts heavily nickel plated.Made for left as well as righthand.

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October 2, 1926.

Time TellsUSE " HART " Wireless

Accumulators in prefer-ence to dry batteries-always.

You will quickly note thedifference, and the longeryou use them the greaterwill be your appreciation oftheir undoubted merits.

There are models for all lowand high tension wirelesscircuits.

THE BATTERY OF QUALITY

If you are not already using -

" HART " BATTER IES -

write to -day for full list toDept. W.3.

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Ebonart has high insulatingproperties and a leak -freesurface. It's highly polishedsurface, never touched by metalfoil, has a sheen like satin, inblack or mahogany. Fine S.B.matt is also available.

The homogeneous structureof Ebonart ensures accurate.cutting and drilling, with easeof manipulation.

Ebonart, in the 21 stan-dardised panel sizes, is sold inattractive cartons which protectits beautiful surface.

REDFERNrs RUBBER WORKS 1.0,Hyde. - Cheshire

Send for Folder 262A0

IAN

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248 WIRELESS. October z, x926.

Aerinl-

SAFETY SWITCHThe Eelex safety switch, the latest develop-ment in Safety First devices, enables theoperator to earth the aerial outside the house.By pushing the knob the set is at onceconnected to the aerial. A pull instantlydisconnects the set from the aerial system,automatically earthing the aerial.

The spark gap providesample means of by-passing any electricaldischarge which mayoccur while the set isin operation.

Sunk Socketto take T14plug to Aerialof Set.

eg--4

r TubePRICE

5/6Write for full particulars to

118, BUNHILL ROW, E.C.

NEWS IN ADVERTISEMENTS

Messrs. Ericsson Telephones, Ltd.,request readers to send for their litera-ture on the Ericsson valve sets, com-ponents, loud -speakers, and tele-phones.

* *

The Dubilier wire -wound resistanceis now available.

* * *Two new cone speakers-the Table -

cone and the Ellipticon-feature inthe advertisements of Messrs. Brandes,Ltd., in addition to the new Brandesetreceiving sets.

* * *

Messrs. Igranic Electric Co., Ltd.,are offering to send their catalogueNo. S31 upon request.

* * *

List H. and L.T. 11, issued byMessrs. The Radio Service Co., willprove interesting to readers within a12 -mile radius of Charing Cross.,

* * *

Messrs. Hart Accumulator Co., Ltd.,will send a complete list of their accu-mulators on application to Dept. W.3.

* *

Two booklets regarding Columbiadry batteries can be obtained freeupon request.

THROUGH THREECOUNTIES WITH A PORT-ABLE SUPERHETERODYNE


in Bournemouth in the evening wasvery late, and only after considerabledifficulty were we able to find accom-modation for the night. This was atlast secured in a private house, andthe set was connected up in time tohear the last few minutes of theBournemouth station's programme. Itwas too late, however, to spend muchtime searching for other stations inearnest, but one or two ContinentalsWere heard.

A Wayside StopLeaving Bournemouth in the early

morning the journey was resumedthrough the New Forest and Winches-ter to Midhurst, where in the middleof the afternoon a roadside halt wasmade, both Bournemouth and Londonbeing tuned in at moderate loud-speaker strength. After leaving Mid-hurst no opportunity of trying the setoccurred until we arrived back at Ton -bridge on the Saturday evening and

NEXT WEEKFurther details of thenew Loewe valve andthe receiver in which

it is used.

again rigged up the equipment, thistime in an ideal situation above thehills overlooking Tunbridge Wells. Thestations previously logged in the townof Tonbridge itself were again heard,this time at considerably improvedstrength, the directional effects of theframe aerial being much more notice-able than was the case in the townitself, where most stations seemed tocome in from approximately the samedirection.

ConclusionReviewing reception throughout the

week, the set behaved very much aswas expected, in no position failingto give at least one station at reallysatisfactory loud -speaker strength, forwhich purpose it was originally de-signed. It adequately proved that itwas capable of standing up to veryrough treatment, and is a very satis-factory receiver for the motorist who,vishes for a set which can be usedanywhere with very little trouble. Thewhole trip confirmed the writer'sbelief that a good five -valve super willgive dependable loud -speaker resultsfrom at least one station in practicallyany locality.

DON'TFIDDLE INTHE DARK!Ask for a DECKOREVI"DIALITE"and illuminate your dials. Anecessity for every set. Can be easilyfitted and connected to L.T. accu-

mulator supply.HIGHLY NICKEL -PLATED.

PRICE 2/6 EACH.Bulk extra.

New Catalogues Now Ready.OBTAINABLE PROM ALL DEALERS OR

SULGIN go_ eoccoasivonTEL HOLBORN 2Z72 CWSSGLSV LANE EC 4. won, CHISWICK

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Ttrabiledne*thedAS C000 AS NEW!!(Except Weoo, S.P.'s and lowcapacity types.) Minimum D.E.Current 0.16 amps when repaired.

ALL BRIGHT & DULL EMITTERSListed at less than 10/..

Minimum charge - - I /-NALCOLTD. Dept. W., TabooGrove.Wimbledon. r

2 VALVE AMPLIFIER, 35/1 -Valve Amplifier, 20/-, as new; Valves, D.E. .06,

each ; smart Headphones, 8/6 pair ; new 4 -VoltAccumulator, celluloid ease, 18/-; new 60 -Volt H.T.Battery, guaranteed, 7/-; 2 -Valve All -Station Set,

H. Approval willingly.R. Taylor, 57, Studley Rd., Stockwell, London.

GLASS JARS AND ZINCSFOR WET H.T. BATTERIESParticulars and Samples -3d. stamps.

Paper Diaphragm Type Speaker Parte.SPENCER'S STORES, LTD.,

4/5, Mason's Avenue, Coleman St., Lothbury,E.C.2. (Near Bank.)

CRITERION COILSHUGE REDUCTION IN PRICES.

23-1/3, 30-1/8, 35-14, 40-1/6, 50-1/6,75-1/8, 100-1/9, 125-2/, 150-2/, 176-2/3.

200-2/8, 230-2/6, 300-2/9, 400-3/3, 500-4/..Criterion Coils are not of Basket, Honeycomb or Duo -Lateral formation. They are Laterally wound Coils,with an air.space between each layer.TRADE SUPPLIED. SATISFACTION GUARANTEED.

RUNDLE & CO.,2, Kingley Street, Regent Street, London, W.1


1114.4P -4.4 -404 -*---4.4-4,-+ --÷-*-4-4-4.-4-4-4o-4---4.-4-4--4--N--4-4.-0-4----44----O--4.-to-e4---+----4.-4-4,--4-4---+-÷4-+-G4,+-4 4-4-4.4.4.4-4.4.4-4.-4........

The Pye portable receiver, which isdesigned to receive Daventry on the

loud -speaker.

r-0 define a receiver as

portable is apt to con-vey the wrong impres-sion that with sum-mer over the appara-tus is of little useuntil next year.

After a lengthy visit' to the recentRadio Ex sibition, during which I wasable to ,see and hear many of thelatest portable receivers, it wouldseem that in the majority of cases theaim has been to produce a " drawing -room portable " which can be used atany time. Such a receiver containseverything necessary for loud -speakeroperation, including a frame aerialand loud -speaker, and it should be pro-duced in such a manner as to be ofpleasing appearance.

This, of course, is what has beenneeded for a long while by flat dwellersand people in the similar unfortunateposition of being unable to erect anaerial of any kind.

Some Olympia ModelsIt was thought that the information

resulting from the visit would formthe text of an interesting article,although it should be understood thatthe limitations of space will not allowof a detailed description of all modelsexhibited.

The first stall at which I stoppedto make inquiries was that of Messrs.W. G. Pye, on which was shown a verycompact five -valve receiver for the re-ception of Daventry only. The cir-cuit consists of two H.F. valves, adetector, and two L.P. valves, a switchbeing incorporated to cut out the lastamplifier, also to switch the instru-ment off. Visible at the front of thecabinet (which is of walnut) is anAmplion Radiolux loud -speaker, whilethe frame is internal at the rear. Thisreceiver, the control of which is sim-plicity itself, is designed only for thereception of 5XX on the loud -speaker,and the makers claim that this is pos-,sible anywhere in the British Isles.

The Vogue of PortabilityBY OUR SPECIAL REPRESENTATIVE

A review of some of the latest portable receivers which were shown atthe recent National Rael7o Exhibition.

A Three -valve SuperI was now moved on, more by the

crowd than anything else, until I cameto another stall, upon which a port-able receiver was shown, this time atthe stand of the British Thomson -Houston Co., Ltd., upon which I tookrefuge to learn a little about theirmodel. It is described as a three -valve superheterodyne receiver, and isentirely self-contained, no externalaerial or batteries being required. Theloud -speaker to go with this instru-ment is contained, with a two -valveamplifier, in a separate cabinet. Thereceiver proper is claimed to give loudresults within a radius of 30-40 milesfrom main B.B.O. stations and 100miles from the high -power station. A

A four -valve receiver for long or shortwaves manufactured by Messrs. Hart

Collins.

novel feature of the set is a small com-pass which is mounted on the top ofthe case to facilitate determination ofthe best direction for the reception ofa desired station.

A Good RangeUpon the " Alphian Wireless "

stand a very complete range of port-ables was on view. The two -valvemodel of this make includes everythingneedful for operation with the excep-tion of the loud -speaker, althougheven this can be built in if desired.The complete broadcast range from150 to 3,000 metres is covered bymeans of a simple switch for high orlow wavelengths and the usual tuningcondensers. This model is designedto operate a loud -speaker at any dis-tance up to 15 miles from a mainstation. A very useful feature is theincorporation of a filament voltmeterby means of which the correct amountof resistance to suit each valve can beascertained. The batteries are claimedto last five months without attention.

The Igranic Model" Can I show you anything, sir? "

to which I replied that I was interestedin portable 'receivers, was productiveof useful information regarding theIgranic model shown on Stand 72. Aseven -valve superheterodyne circuitforms the basis of this receiver. Thecircuit consists of a neutralised H.F.valve, a separate oscillator and firstdetector valve, two intermediate fre-quency stages, the second detector, anda power amplifier. A wavelengthrange of 250-1,800 metres is obtainedby using interchangeable oscillatorcoils, and there are practically onlythree tuning controls. This receiver,strange as it may sound, has an all -metal panel, and the intermediate fre-quency stages are screened. The re-ceiver proper does not includebatteries, loud -speaker, or frameaerial, although a pair of telephonesare ingeniously fitted in the lid. Aseparate carrying case which matchesthat of the receiver contains the neces-sary batteries, and connection iseffected between the two units bymeans of multiple flex cable having aplug and socket at the receiver end.The frame aerial for use with thereceiver is also sold separately, and acarrying case can be supplied.

In Two PartsOn the stand of Messrs. Autoveyors,

Ltd., was exhibited a portable receiverknown as the " 7 -valve ultra -sonic."This new model, which is encased ina handsome oak carrying cabinet, has


The " Celestion Radiofour," a four -valve receiver which employs no L.F.transformers or chokes and no reaction.

250 WIRELESS. October 2, r926.

Why buy them for youtNeutrodyne or Superhet ?

Use British MadeRADION 5.25 5/.Power Valve

They are supplied in bothAmerican and British bases.Specially designed for these

circuits on the Imes of the bestAmerican. Satisfaction abso-lutely guaranteed. Every valveis practically identical. Can be

supplted in matched sets.Fil. 5.5 max. .25 amps.Impedance 8.000 ohms.Amplification 7.2.

British Base 525B. American Base525C. Guarantee in every.::::11...000box.

se-Obtainable from

BARKERS, BENETFINKS, GAMAGES,W HITELEYS,

and most other untied dealers.

If any difficulty write the sole manufacturers :

RADIONS LTD., Bollington, Macclesfield, England,List Free on request.

WIRELESS MASTS60ft. Complete fittZ:. ORDERATONCEsrh 261-

35tt. IATS'algt,'33tatET:li tgaldb,tr= 21/-

H.T. ACCUMULATORS60 Volts. ---Price 32/6

DO YOU REALISE that light weight and lowcost may be linked up to high efficiencyThe inexpensive 6o volt -3 amp hour ELITE-High Tension Accumulator which actually costsunder a id. to recharge will do all that the moreexpensive types will do and are never done.Therefore look before you leap at ourDescriptive Folders, which will be forwardedper return on application.

Type 02. Semi Oil Submerged.

60 volts ruatiraet ttis 32/6 10 ;roll:lip:if.Obtainable only from-

ACCUMULATORS ELITE,32, KING CROSS STREET, HALIFAX.

Tele. :1304. Trade Supplied. Telegrams : Elite, Halifax.London Distributor:

CECIL POHLMAN, 77, Great Portland Street, London, W.1.

VALVES !Radio Micro Power 3v .1 amp., 10/9; do. 3v .3 atop.,9/6 ; do. D.E. 3v .06 amp., 7/.. Fama D.E. 4v .06amp., 5/9. Fama Power 4v .2 amp. 8/6 ; do. D.E.2v .2 stop., M.R., D.E. 3v .06 amp., 5/6. Polo60 -volt Batteries, 3 -volt Tappings Guaranteed 7/6.

Trade Enquiries Invited. Write for Lists-

W. SEGAL, IlsnotErLIDOVVE:

LIVE TRAVELLERS WANTED, calling uponWireless Dealers in the following districts :

South Midlands, Eastern Counties, North & SouthWales, Lancashire & Cheshire. Exceptional oppor-tunity for good men. Liberal commission, goodselling novelties. Apply by letter to Box No. A.47,WIRELESS, Bush House, Strand, London, W.C.2.

The Vogue of Portability(Continued from previous page)

a total weight of 14 lbs., and thedimensions are 161- in. by 7 in. by9 in. The weight given does not in-clude that of the batteries and loud-speaker, which are incorporated in anoak cabinet exactly similar, but quiteapart from the receiver box.

A Station LogThe Curtis portable superheterodyne

8, which I had an opportunity ofviewing on Stand 159, is sold com-plete with self-contained loud -speaker,aerial, valves and high and low-ten-sion batteries. This is the product ofMessrs. Peter Curtis, Ltd., and witheach instrument sold a log is suppliedgiving the tuning condenser settingsfor all prine;pal European broadcast-ing stations. A master switch is pro-vided to cut off or switch on the entirecurrent supply.

The Neutron ExhibitEmploying a modified Silver -Mar-

shall circuit,the Neutronportablemodel, whichcan be sup-plied as a six -or seven -valvereceiver, i svery compact.The receiveris containedin a carryingcabinet 51 in.x 15 in, x131 in., andthe totalweight, whichincludes a n81 -volt H.T,battery, anunspill ablea c c umulatoi,and also aloud - speaker,is given asonly 24. lbs.The loud-speaker, aBrown, has a.specially d e -signed woodenhorn, theopening to which is situated at oneside of the cabinet. A tapped frameaerial, which can be used on high orlow wavelengths, is fixed inside thedoor. Access to the inside of the re-ceiver for the purpose of adjusting theloud -speaker, etc., is effected at theback of the cabinet, which is in realitya large door.

A Handsome ModelAn inquiry at the General Electric

Co.'s stand elicited the informationthat a new portable supersonic set

The " Rolls" portavalve model exhibiDistributors. The

speaker are b

ble, a handsome three-ted by Messrs. Detexframe aerial and loud -alit into the lid.

had just been placed on the market.The complete equipment, comprisinga seven -valve set, loud -speaker, H.T.and L.T. batteries, and frame aerial,is housed in one cabinet, quite ahandsome looking affair measuring21 in. x 15 in. x 9 in. Two wave-length ranges are obtainable with thisinstrument, the first 230-645 metresand the second 725-2,800 metres. Aswitch is employed for changing therange of wavelength, and when this isin the central position it breaks thebattery circuits. The panel layout ofthe present instrument is very sym-metrical, and strength of signals canbe regulated by means of a volumecontrol.

The M.P.A. " Self-containedFour "

The only model I saw in the showwith an expanding frame aerial wasthat exhibited by Messrs. M.P.A. and

known as the" Self - con-tained Four."The novelmanner i nwhich theframe ex-pands isclaimed to bea specialfeature of thisportable re-ceiver. The

' loud - speakerbuilt uponthe cone prin-ciple, and em-ploying a"Brown"base, occupiesthe lower halfof the cabinet.Possessing avery simplelayout, t h epanel issituated abovethe large dia-phragm. Only26 lbs. is theall -in weightof the M.P.A.

model. For covering, dark blue or redmorocco leatherette has been used tosuit individual requirements.

The " Radiofour "The " Celestion Radiofour " exhi-

bited on the stand of the Celestion_Radio Co. has some points worthy ofnote. It is a four -valve receiver whichemploys no L.F. transformers orchokes and no reaction is introduced.Daventry or the local station can be



/-,BURNDEPT of ip.fiTYPE 750 LOUD SPEAKERS.

FRCM NOTES BY FRANK PHILLIPS, KLEE., CHIEF ENGINEER.QOME months ago I made up my mind that the so called "high--/ resistance," (2,000 ohm) Loud Speakers were no longer suitablefor modern valve sets, because all such sets use a low impedancedull -emitter power valve for the last stage, and the 2,000 ohm LoudSpeaker was designed for the obsolete bright " R " valve . . . itstands to reason that what was right for one cannot be right for theother. Accordingly, I decided that all 1926-27 models of BurndeptLoud Speakers should be of 75o ohms resistance, and I want to explainwhy they give better results than those of higher resistance. (Thedetailed explanation is contained in Mr. Phillips' report sent free onrequest.)

. . . I desire to give you my assurance that with any receiving set using a modernpower valve in the last stage, Type 75o Loud Speakers will give better, purer andlouder reproduction than is obtainable from 2,000 ohm Loud Speakers, and further,Type 75o can be substituted for 2,000 ohm without any change in wiring, as bothgo straight in the plate circuit of the last valve, no transformer being required.Send for a complete copy of Mr. Phillips' notes and for full particulars of

Burndept "Ethovox" and "Etho-Cone" Loud Speakers.

-,...

III

.,---

, ..,..A,

1)1Val \

"A?

... L--,,.

BURNDEPTNo. 963. 1, /7.,/:::,!..z7 No. 966.f' i0" ETHOVOX " ., ETHOVOX "

(Type 750) with 4,e'," .0 ,"./;' z4 --- :".:444--- 4 / :. / 0 '7,,, %"" ----% ' A,/..d / /..///./ / / ....// ..m (Type 750) withMetal Horn ; for Mahogany Horn ;use direct in the Head Office & Factory : Blackheath, London, S.E.3. for use direct in

plate circuit. Telephone : Lee Green 2100. Telegrams : B arum -oil, Phone, London. the plate circuit.PRICE London Office & Showrooms: Bedford St., Strand, W.C. PRICE

£4 10 0 Telephone : Gerrard 9072. Telegrams : Burndept, Westrand, London. £5 5 0

AGENTS AND BRANCHES EVERYWHERE Rti I

Second and third prizes in AmericanAmateur competition won by users ofCopex Copper Coil Screensand Copex "0-C" Coils

In the recent American AmateurCompetition the 3rd Prize wasawarded to a set using C' IPEX" O -C " COILS AND COPPERSHIELDS. This was the highestaward given to any European entry.Also 2nd Prize awarded to the" Mew flex " (section for entrant:,under 16 years of age), usingCOPEX COPPER SHIELDSAND COPEX COILS.The principal advantages of COPEX" " coiLs over all otherscreened coils are :-I. Oscillation is rendered perfectly

under control.2. High Amplification. These fac-

tors are due to an improved andpatented method of construction.

Here are the prices of COPEX COILS.CO I EX COPPER ANDSCREEN and 6 -pin base 15/-

( Fnll dela Is of Copex Coils and Screens ICOPEX " O -C " Type Split

I appear g.`shtealtTeF:1(1,:rp;t1V-ty"I Secondary Transformer,

Li 2 50; 550 N. ... 10/6Patentees and Sole illanufacturers :

PETO-SC:ITT Co., Ltd., 77, City Road, E.C.1.Branches at 62, High Holborn, W.C.1, Walthamstow,

Plymouth and Liverpool.

Don't Experiment-Fit Copex!J'..5. 5943

SISPaew-

f 011110PO EnA co.

A MONUMENT IN THEMARCH OF PROGRESS.

The Formo Shrouded Transformeris the universal favourite.

1016Madein Ratios 1.1, 1-2, 1-3, 1-4and 1-5.1-3 and 1-5 for First and Second Stages.

SEND FOR CATALOGUE AND DESCRIPTIVELITERATURE OF COMPLETE FORMO RANGE.

THE FORM() COMPANY,CROWN WORKS, CRICKLEWCOD. N.W.2.

'Phone: Hemp. 1787.Mancheater: Mr. J. B. Levee, 23, Hartley Street.Levenehulme. 'Phone: Heaton Moor 975

See page 256 forFormo S.L.F. Condenser.

N NINHIMMEIMENNIMMMONIMMINNIMINIMMINNIMINNIMM NNNNNm mommoommoorimussmemmussammomessussiunums N

II Frelat the best Dull Emitter ill i : costs less, lasts longer. NIP

N INr.I There is not a better Valve made, yet it II m

ccsts only 4s. I'd. Next time you are 1 abuying valves, whether for experimental kg N

M

II 1 station work or better entertainment from a al

N eais ®N 1-1

home programmes, fit 1 relat and note iii improved results. If your Dealer cannot msupply send e.O. 4s. lid. (post free), or II m

E11 m

11 r request delivery C.O.D. and send td. in 111 611 i If 1 1 stamps. N .M m

m .3THE CONTINENTAL RADIO IMPORT CO., LTD.,

8, SPITAL SQUARE, LONDON, E.1

$

: NNI N 4/11,

. la "K" aType 1. III

NIilim mmeismnosm NummitssMNIMMINNIMMI MINHIMMONN

252 WIRELESS October 2, 1926.

NEXT WEEKGREAT "POPULARITY" COMPETITION

VALUABLE PRIZES WHICH ANYREADER MAY WIN

SPECIAL CONTENTS

Next week appears a special issue ofWIRELESS, which has been announcedas the " Mystery Number," anddetails can now be given of the great" Popularity " competition, which isa feature of the issue. A list of com-mon types of sets and their circuitswill be given, and readers will beinvited to arrange these in what theyconsider to be their order of popu-larity. The correct order, as revealedby the entries, will be determined bymeans of special adding machines, andthe winners of the first, second andthird prizes will be those competitorswho approach most closely to theorder thus discovered.

In addition to the three fine prizes

announced last week, there will beone hundred consolation prizes, eachconsisting of a valve, for the nexthundred competitors, so addinganother attraction to this alreadyfascinating competition.

A very special list of contents hasbeen prepared for this issue, the con-tributors including Captain H. J.Round, M.C., M.I.E.E., J. H.Reyner, B.Sc. (lions.), A.C.G.I.,D.I.C., A .M.I.E.E., a certain promi-nent radio personality whose identitywe will leave our readers to discoverin due course, G. P. Kendall, B.Sc.,and others well known to readers ofthis journal.

The complete prize -list for the com-petition is now as follows : -

FIRST PRIZE.An " Elstree Solodyne," the wonder-

ful one -knob five -valve set describedin Modern, Wireless.

SECOND PRIZE.An " Elstreflex Two " receiver.

THIRD PRIZE.A " Razorsharp " wavemeter, de-

signed by Mr. J. H. Reyner.Consolation Prizes : One hundred

valves.

In view of the probable greatdemand for next week's specialnumber of " Wireless " readersare recommended to order

early.Why not place a standing order

with your newsagent?

CATALOGUE RECEIVEDFrom Messrs. Pettigrew & Merriman,

Ltd., we have received a catalogue inwhich is described the " Newey 4 -PointCondenser," which possesses the charac-teristic feature of lateral motion and a360° calibration range. This cataloguecan be obtained direct from Messrs. Petti-grew & Merriman (1925), Ltd., 2 and 4,Bucknall Street, New Oxford Street,London, W.1.

TABLE 1 TABLE 2

CoilCoil Inductance in Self -capacityin micro-

microfaradsCoil

Parallel capacityin micro-

microfaradsWave -lengths

in metresEffective resist -ante in ohms.

35 61 15 35 3oc 264 2.840 90 15 40 » 318 2.950 150 9 50 33 406 3.36o 200 13 Go ,., 472 4.475 295 12 75 » 573 5.3

no 540 II no » 774 6.6150 1,410 12 150 » 1,250 15.8200 2,220 17 200 » 1,580 19.7250 3,070 17 250 » 1,860 24.9300 4,800 14 300 » 2,320 28.2

Results of in-dependent H.F.tests made bythe N.P.L.

Here are the figures judge for yourself !The National Physical Laboratoryfigures fully bear out our claim thatthe LEWCOS Coil is the mostefficient produced. In the design ofradio inductances, the smaller the R/Lvalue for any circuit, the greater is theselectivity and the signal strength.This fact has predominated over allother considerations in producingLewcos Inductance Coils with the

result that we can publish without fearthe R/L values for LEWCOS Induc-tance Coils as obtained from the N.P.L.measurements together with the wavelength at which measurement was made.LEWCOS Coils make all the differencein reception. Ask your wireless dealerto demonstrate the Lewcos Coil onhis set. Descriptive leaflet gladly senton application.

Inductance

COILThe LONDON ELECTRIC WIRE COMPANY and SMITHS, LIMITED

Phone: Clerkenwell 1388 Playhouse Yard, Golden Lane, London, E.C.1 Telegrams: Electric, London

JUDD


THE VOGUE OFPORTABILITY

(Continued from, page 250)

rpeived on the " Celestion " loud-speaker fixed in the lid of the leathersuit case. One H.F., one detectorand two low -frequency amplifiers com-prise the circuit, and very faithfulreproduction is claimed to be afeature. Another special point is thatthe closing of the lid automaticallyoperates a switch to cut off thobatteries.

A Range of PortablesPossessing only one tuning control,

the four -valve model shown by Messrs.Hart Collins comprises one H.F., onedetector and two transformer -coupledlow -frequency valves. It is an all -inportable instrument of handsomeappearance, and reproduction iseffected by an Amplion loud -speakerbase and A .specially designed horn.From 300-500 and 900-2,000 metres arethe wavelength ranges covered by thisset, which is claimed to receive -mainB.B.C. stations on the loud -speakerup to 30 miles and 5XX up to 150miles. Although a frame is included,an outside aerial and earth can beused if desired.

In the GalleryThe gallery contained exhibits of

still more portable sets, and my nextvisit was to the stall of the Canto -phone Wireless Co., where I foundexhibited a very neat all -in three -valveset. One of the main features of thisreceiver is the special loud -speakerdiaphragm, which is the subject of .apatent. The only controls to operatethe set are three small knobs on thetop of the case.

The Rees -Mace RangeWhilst in the gallery I also i-al led at

the stall of the Rees -Mace Manufac-turing Co., Ltd., to see still anotherrange of portables. Here the arrayincluded a four -valve receiver of in-teresting design, having for the circuita tuned -anode H.F. valve, detectorand two transformer -coupled L.F.valves. The size of the instrument is14 in. x, 14 in. x 7 in., and it weighs30 lbs. High or low wavelengths,three or four valves, on or off position,are all carried out by switches; and itis quite easy to replace the frameincluded by an outside aerial.

Down Below AgainThere were, still many stands to be

visited on the ground floor ; for in-stance, on the Rotax stand a veryneat and entirely self-contained three -valve set was to be seen. Possessingall the useful features of a portable,this model also includes a horn ofspecial design which is composed ofimpregnated cloth. It is known by thename of the Rotola portable, and isoperative upon both short and long

(Continued on page 2561)

14-'19ICJ ETD C=71:1[7.= 0

DRY BATTERIES ARE SAFERTHINK of the perfect ease with which dry

batteries are handled - and especiallyCOLUMBIA. They are safe, clean and

convenient. They can be tucked away in a cabinetand no care need be given to acid and glass casings.COLUMBIA give better, longer and moreeconomic service, and dispense with the troubleand expense of frequent accumulator renewals.Use dry batteries for every radio need and alwaysCOLUMBIA.

The right batteryin the right placenaturally means agreat deal to yourreception. There-fore " How to getthe most out ofyour radio bat-teries" is a littlebook which willbe most useful toyou. It is packedfull of really prac-tical and interest-ing information.The se bookletsare sent free onrequest.

Send for " Howto get the mostout of your radiobatteries " a n d"Choosing' a n dusing the rightradio batteries."It is astonishingwhat will result inmarked economyin operation andimproved qualityof reception whenyou have a littledefinite know-ledge as to the cor-rect use of yourradio batteries.

Ask your Dealer for COLUMBIA High Tension Battery, No. 4780, 6o volts, aspecial size with large radio cells. Or COLUMBIA High Tension Battery, No.4770. 45 volts (extra heavy duty) for long service and economy. COLUMBIA' A " Dry Cell Batteries for Dull Emitter Valves will meet heavy current de-mands and give much longer service than other batteries. All COLUMBIABatteries are fitted with spring clip terminals to ensure quick and secureconnections.

ASK ANY GOOD DEALER FOR COLUMBIA.

J. R. MORRIS, 15-19, KINGSWAY, LONDON, W.C.2.Telegrams: Colcerprod, London. Telephone: Gerrard 3038.

Scottish Representative:JOHN T. CARTWRIGHT, 3, Cadogan Street, Glasgow.


WHEN first I heard that the newEuropean wavelengths were

being arranged on a frequency basis,thus assuring that stations areseparated by the narrowest ,.possiblemargin, I wondered what steps weregoing to be taken to ensure that noneof the stations " slipped " off itscorrect - wavelength. Now I heardefinitely that some of the stations., atleast, will use " luminous frequencyindicators." I do not know whetherthese will be of the same design asthose recently used in America, butthe latter consisted of quartz crystalresonators used in conjunction withNeon tubes. Three or four of thesewere placed upon a little stand;arranged so that their wavelengthswere separated by. a quarter of ametre or so. When the station isoperating on its correct wavelength acertain tube should be glowing. If,however, it moves up or down, one ofthe others will glow. Thus a stationwill have a visual indicator of itswavelength, as simple in operation asthose floats that indicate the S.G. ofyour accumulator acid.

* *

MY impressions of the Exhibitionwere, on the whkle, very favour-

able,' but I could not help noticing the-usual lack of qualified demonstrators.It has always been the ease since thefirst Exhibition of the kind, and isvery discouraging to thosevisitors who have a fairlyadvanced knowledge of thesubject. One salesman Iapproached during the recentshow had apparently not theslightest idea of the advan-tages of the S.L.F. con-denser; he bad not much ofa notion as to the differencebetween this and the S.L.C.type ! The only exceptionsseemed to be certain of thelarger firms, where one could,on occasion, obtain reallydetailed and interesting in-formation. When are our shows going to improve inthis direction?

IAM wondering whatfuture developments we

may expect to follow on theheels of the B.B.C.'s takingover of the Albert Hall for

their first great series of " Interna-tional Concerts." With the growth ofbroadcast entertainment there has, ofcourse, been an increasing tendency toremove the actual performance from

The microphone and part of the studioof station WOC, Davenport, Iowa. Theformer is mounted on a stand made ofrustic wood to obtain an artistic effect.

the studio and to hold it in somemuch larger place possessing acousticproperties more suitable for the broad-casting of a large orchestra or choir.The absence of echo in a studio,though very favourable for solos, isnot always pleasing when concerteditems are broadcast.

The. B.B.C. cannot, however, bealways hiring the Chenil Galleries,much less the Albert Hall, so that Iam very much inclined to think thatthere will, before long, be a large haltspecially devoted to broadcast works,to which the public will probably beadmitted. Optimists prophesy that a

.huge " radio theatre " will existbefore long, large enough to shelterthe entire staff and transmittingplant, with all the necessary apparatusfor the arrangement. of special broad-cast plays, and which, at the sametime, will also be adaptable for theperformance of operas and musicalplays of the ordinary description.

* *

I THOUGHT the recent broadcast ofGilbert and Sullivan was particu-

larly successful. _While the major partof the credit goes, of course, to theB.B.C., one must always realise thatthe fact that one has seen a play like" The Mikado" several times alwaysmakes for greater appreciation of thebroadcast performance. Mora l;More and still more of it!

The scene at the opening of the Belfast WirelessExhibition. The Lord Mayor, who performed theopening ceremony, is in the centre of the front row.

HY, I wonder, is it sucha favourite .claim for

c e r t a in makes of loud-speakers that all harmoniesa r e eliminated, therebyenabling the true purity oftone to be heard? Do themanufacturers not realiSethat it is solely the harmonicsand overtones that are re-sponsible for the fact that wecan distinguish the tone ofa violin from, say, an oboe?Without them all instru-ments would sound the same.Perhaps the loud -speakers inquestion make a piano soundlike a flute! Certainly thatcould be called " purity oftone," but it would hardlybe natural reproduction!

WAVE -TRAP.


W. 41 41 44.. 41 41 41... 44. 41

THE NEW LOEWE VALVEINTERESTING TESTS AT ELSTREE

THREE VALVES IN ONE

Readers will remember that a recentissue of WIRELESS contained a descrip-tion of a new German valve, and onthe evening of the 20th of September,at the Radio Press Laboratories, inthe presence of Mr. John Scott -Taggart. and members of the staff, theinventor, Dr. Loewe, demonstrated thecapabilities of a receiver employingtwo of these new valves.

Lack of space in this issue as weclose for press will not allow of adetailed description of all the appara-tus used in the tests, but a few wordsregarding the receiver prior todescribing the results obtained shouldprove of interest.

A Simple ReceiverBuilt on the upright panel system,

the receiver has a strong superficialresemblance to those of British manu-facture. On the panel are three maindials and one small knob and one ortwo switches. Lifting up the lid atthe top of the receiver revealed what

appeared to be an amazing thing, 'forapart from the valves and theirholders there was nothing else to heseen inside with the exception of threevariable condensers and one or twoconnections. The components ' com-pleting the receiver were a two-waycoil holder on each side of the cabinet.A glance at the circuit revealed thatthe first valve (which was really twovalves resistance -coupled in one bulb)amplified at H.F.- by means of the well-known T.A.T. systeth, The secondvalve (in. reality three valves in onevacuum) consisted of the detector andtwo resistance -coupled note magnifiers,the great feature 'being; of course, thatall the auxiliary apparatus, namely,resistances and condensers, were con-tained inside the valve.

Some ResultsAnd now for the results obtained.

Using one of the valves only (thedetector and two resistance -coupledamplifiers), London was received at

Elstree at full' loud -speaker strength,the quality of reproduction- beingexcellent. It is interesting to notethat no reaction was used in the loud-speaker reception of 2LO.

Using Two ValvesThe other -rah c was now switched

into circuit (the two H.F. amplifiers),and in the course of the tests ten sta-tions, including main British andContinental, were tuned -in on theloud -speaker.

There can he little doubt that thereceiver was very sensitive, althoughthere is room for improvement in the

matter of selectivity. Next week'sissue will contain further details ofthese interesting tests, with photo-graphs of the receiver and -the circuit.

NEW CALL -SIGNS ALLOTTED

G-5HL : H. B. Elliott, 11, Kensing-ton Gardens, Brighton (for BrightonElectric Supply Co.).

G-5RD: A. R. Gardner, " Ash-leigh," Abbots Road, Abbots Langley,Watford (ex 2BAV).

G-6AP : A. C. Porter, 1A, ManorRoad, Brockley, S.E.4 (ex 2BOC).

G-6DG : S. E. Dowding, 6, ChampionRoad, Upminster, Essex.

G-6LM : R. A. Hiscocks, " Sylvan- dale," Malmesbury Road, Chippen.ham, Wilts.

G -6Y : E. Whaley, 50, ClementsonRoad, Sheffield.

#1 SAXON CUIDETO WIRELESS 14'This book enables any beginner to construct Wireless Sets which areunequalled in price, quality or efficiency, and the cost is only one.fccrth the price charged for a reads -made instrument not half a,

good. The exact cost of each set is clearly stated.

FULL INSTRUCTIONS WITH CLEAR WIRING DIAGRAMSarc gives for making Super Efficient Crystal yeti, Dual AmplificationReceivers, Single Valve Sets, One and Two Valve Amplifiers ; Two,Three and Four -Valve Tuned Anode All -Wave Receivers, and the

Very Latest Type of Five -Valve Resistance Capacity Receiver.NO SOLDERING, NO SPECIAL TOOLSNO KNOWLEDGE REQUIRED.The chapter on testing wireless components is 1/2 POSTalone worth the price charged. 176 PAGES. U FREE

1

SPECIAL OFFER,This book will be sent on approval on receipt of your promise to

return seine post paid or to remit 1'3 within seven days.SAXON RADIO CO. (Dept. 32), SOUTH SHORE, BLACKPOOL

Frani all dealers or direct.

3T9"PEERLESS"Dual Rheostat

TWO WINDINGSSpecially made for either dull or brightemitter valves, One winding has resist-ance of 6 ohms nod continues on toa go ohm strip winding. Resistancewire wound on hard fibre strip undergreat teasion and immune from damage.One hole fixing, terminals convenientlyplaced. Contact arm has smooth, silkyaction. All metal parts nickel plated.Complete with ebonite combined n n

Knob and Dial SiV

THE BEDFORD ELECTRICAL & RADIO CO., LTD.22, Campbell Road, Bedford:

HIGH AND LOW TENSIONACCUMULATORS FOR HIRE

WHY be worried with the bother and expense of accumu-lators or uncertain dry batteries when we will keep youcontinuously supplied with fully charge' Rotax L.T. orH.T. ACCUMULATORS for far less than you spend onbatteries at present ?Regular and punctual deliveries to any address within 12 miles ofCharing Cress weekly or fortnightly as desired. Special reducedrates for those with one or more accumulators of their own.Our service --the largest and most complete of its kind in England-improves reception, saves you money, disappointment and trouble.

Write for price list " H. & L.T.11."OUR RADIO DOCTOR IS ALWAYS AT YOUR SERVICE FOR

REPAIRS, OVERHAULS OR RECONSTRUCTION.

THE RADIO SERVICE CO., 105, Torriano Avenue, London, N.W.5.Telephone: North 06231415.

SAVE 25°Y0Get your COIL PLUGS for5/6 per doz. (4/6 gross lots).Made of best tested materials through-out, these Plugs offer the advantages ofnickel -plated side plate contacts, havin,2patent lip. Send 6d. to cover postage

upon sample dozen orders.

CECIL RIDLEY358,37 DUNDAS MEWSMIDDLESBROUGH


soleLtd.,

Famous

Rollo

Imp ®m ComponentsIllustrated Catalogue free on application.

Distributors Pettigrew & Merriman (1925),PHON OS HOUSE, 2 & 4, Bucknall Street,

New Oxford Street, London, W.C.I.Telephone : Gerrard 4248-49.

LISSENOLA & BROWN "A " USERS.Get the wonderful 14 -inch

CINCINNATI CONE, 11/6Complete with bronze base and support, ready tohave Brown teed phone screwed on making it intocomplete cone speaker, post I /6. Attachment forLissenola, 2/6 fully guaranteed.J. W. MILLER, 68, Farringdon Street, E.C.4.Sole British Distributor. Phone, Central 1950.

SOLDERING SUPERSEDED

SIMPLE: EASILYAPPLIED. EFFECTIYE: MEAT: ENSURE BETTER'RESULTS.O

iti?:11Pti Alt/

1.11044.41M!

ere rem JOINTS m'ERISCROV FOR EVERY CONTACT

Prices from 1/- per dos. Send for List.ECRISCROS COMPANY, 50. GRAY'S INN ROAD. LONDON, W.0 1

Build Your Own LOUDSPEAKERWITH A LISSENOLA OR BROWN Aand our COMPONENTS. You can construct yourself ahandsome PAPER DIAPHRAGM type, or CONE typeLOUDSPEAKER in half an hour for less than it wouldcost you for the ordinary cheap horn type Loudspeaker.You will obtain VOLUME, CLARITY, and unsurpassedtonal quality. Prices, particulars and Diagramsfor stamp. TRADE Inquiries invited. Tell your dealerGood man's, 27, Farrirgdon St., E.C.4

(Tel. : City 4472.)Also obtrOnabie from Spencer's Stores,4-5,Mason'sAre,E.C.2

THE VOGUE OFPORTABILITY


wavelengths. As is the case with mostother models, the frame is incorporatedin the lid and provision is made forthe use of external aerial and earth.

Superheterodyne PopularityThere can be little doubt that

superheterodyne portables aro in themajority, and on the stand of theRadi-arc Electrical Co., Ltd., I cameacross another one, the " Liberty "seven -valve model. The standard setproduced by this company is complete,with the exception of the loud -speaker,but if desired one can be included foran extra charge. TO quote themakers' claims for this instrument," It will receive all main British andContinental stations between 250 and3,000 metres."

For MotoristsDesigned chiefly for motorists, the

next model that I inspected, also asuperheterodyne, was exhibited on thestand of the Pete -Scott Co., Ltd.Contained in a strong leather case, itcan be had as a seven- or eight -valvemodel. A filament voltmeter, whichby simple switching can be used fortesting the voltage across each valve,is mounted on the panel of the finishedreceiver.

T IUMPHCUSHION

ANTI-MIOROPHON ICVALVE - HOLDERTEST

this new holder :gaisitsitifioalongside any otherand youwill agreewith ex-perts inpronouncing it best.

NO METAL SPRINGS.VIBRATIONS QUICKLY DAMPEDAsk your Dealer for tree list of TRIUMPHGUARANTEED COMPONENTS AND SETS,

or send P.C. mentioninv Wireless to .A. H. CLACHSON, Ltd.,White Hart Works, London, 8.22

.2+ P.APO

fp,RefNo

V190Price9,0

w I RELESS. - Capable, trustworthy men" with spare time who wish to substantiallyincrease income required where we are notfully represented. Applicants must havepractical knowledge of installation of Set andAerial, be a householder or live with parents,and be able to give references; state age andexperience. Address : Dept. 38, GENERALRADIO COMPANY, LIMITED, Radio House,Regent Street, London, W.I.

WET H.T. BATTERIESBritish made round or square Leclanche Glass Jars,25 x 15 a 15, for wet H.T. Units. Waxed, 1/3 doe. ;plain, 1/ -doe. Carriage and packing extra. 'Phones and

Loud Speakers reconditioned, 4/6 & 5/ -.-The H.R.P. CO.1, Cottrill Road, nr. Hackney Downs Station, London, E.S.

5/-SECURES

51- down &12 monthlypayments offive shillings

" BULLPHONE NIGHTINGALE"

LOUD SPEAKERCLEARTONE

($3

GREATVOLUME

POST your deposit of 5/. now and getby return the famous " BullphoneNightingale Loud Speaker.

Individually tested and guaranteed to besuperior to any other Loud Speaker regardlessof price, for finish, purity and strength oftone and value. Cash price 60/-, post freeI_ nited Kingdom.Specification. Height 21 ins., Bell Mouth14 ins., nickel arm and stand. Black crystalbell head, as photo. Also de luxe model,mahogany finish hell same size. 65/- cash or1C/- deposit. List free.

Wo BULLEN 38, HOLYWELL LANE,

(Dept. ivi.) LONDON E.C. 2.

11111111111J1111111iIII11111111111111111

f011110..reuttOPtUlaco,..

ULTRA LOW LOSSStraight Line Frequency Condenser.

Cone bearings. Braced Vanes. PositiveCollector. A real precision job.

Condenser only--'0003 pY, 'C005 ... 91-,

Condenser with plain dial.Standard 1' dia. Shaft 1016

Send for Catalogue and DescriptiveLiterature of Complete Forms Range.

THE FORMO COMPANY,CROWN WORTS, CRICIELEWOOD, N.W.2.

Harnp. 1787.Manchester: Mr. J. B. Levee, 23, Hartley Street.

Leyenehultne. 'Phone Heaton Moor, 475.See page 251 for Forma

Transiormer.

1--.s111111111111111111

All communications rega:-cling advertisementsshould be addressed to :

The Advertisement Manager,"W 1 RE L E S S,"

Bush House, Strand, London, W.C.2 Telephone:City 9911.

."' WIRELESS." CO U PO N. Vol. V. No. 7.

QUESTIONS AND ANSWERS.Th:s coupon must be accompanied by a P.O. for 2/6 for each question,and a stamped addressed envelope when sending queries to the

Radio Press information Dept. for a postal reply.

WIRELESS. ifi

The Editor of MODERN WIRELESS "J. H. REVIVER, B.Sc. (lions.), A.C.G.I., D.I.C.,

A.M.I.E.E.

The Contents for the October issue will include:HOW TO BUILD AN EIGHT -VALVE

SCREENED -COIL SUPERHETERODYNEBy G. P. KENDALL, B.Sc.

MODERN DESIGN IN SIMPLE SETSBy J. H. REYNER, B.Sc. (Hons.), A.C.G.I.,

DJ C., A.M.I.E.E.AN H.T. CHARGING UNIT FOR HOME USE

By the Staff of the Elstree Laboratories.MORE ABOUT THE ELSTREE " SOLODYNE "FURTHER HINTS ON THE " MEWFLEX "REPRODUCING THE LOW TONES

By CAPT. H. J. ROUND, M.I.E. E.

MWIRELES SObtainable from all Newsagents, Booksellers or Bookstalls, or directfrom the Publishers, Radio Press, Ltd., Bush House, Strand, London,W.C.2. Subscription Rates r5/- per annum (03,6 per annum Canadaand Newfoundland). Lesser periods pro rata

FRE cevia

r/teAwonderful FREE GIFT BOOKLET, " THE RAPID

STATION GUIDE " will be presented with every copyof the October issue of MODERN WIRELESi, on sale

at all Newsagents, Bookstalls and Booksellers on Friday.The wavelength redistribution of European stations, whichcomes into operation on October Oh, will make this pre-sentation booklet extremely useful to every listener.The first of the Big Four .published by Radio Press Ltd.,MODERN WIRELESS provides radio enthusiasts withdetails of new developments, original set designs, and tech-nical information of outstanding interest.Be wise and buy your copy to -day. In two or three days' time youmay have difficulty in obtaining a copy.

1 /-MONTHLY

alvm the ?wade?" heeactize"i"---

iv WIRELESS.4 ,;

Octo,ber 2, 1926..,

Below the P

NEW REDUCED PRICESFor 4 -volt accumulator or 3 dry cellsTHE P.M.3 (General Purpose)

0'1 amp. 14/-T17F, P.151.1 (Power) 0'1 amp. 18;6

For 6 -volt accumulator or 4 dry cellsTHE P.M.5 (General Purpose)

0'1 amp. 18/6THE P.111.8 (Power) 0/1 amp. 18/6

For 2-voll accumulatorTHE P.M.1 H.P. 01 amp. 14: -THE P.M.I 0'1 amp. 14i -THE P.M.2 (Power) 0'15 amp. 18,6

nese prices do not applyin Irish Free State.

Britishmade in aBritishFactory

4 DVT. THE MULLARD WIRELESS SERVICE

The pyrometercan recordtobetween 700°Cand a,zoo.c.

rometer scale

THE LOW OPERATING TEMPERATUREOF THE WONDERFUL P.M. FILAMENT

The pyrometer can no longer claim to record theoperating temperatures of all valve filaments

The wonderful P.M. Filament has a working tem-perature that is as low as 180 degrees below thepyrometer scale.'No sign of glow can be discerned from this uniquefilament with its striking economy of heat.You will appreciate the greatly increased valve lifethat can be secured with this P.M. Filament.Nothing is sacrificed.With the P.M. Filament you receive up to 51 timesthe emission of an ordinary filament.The current consumption (only one -tenth ampere)makes your accumulator charges last seven timesas long.In addition, the P.M. Filament is so tough and well -supported that itcannot be broken except by the very roughest handling.

For continuous satisfaction give your receiver valves with the wonderful .P.M. Filament and make your radio better, stronger and 85% moreeconomical.

ASK YOUR RADIO DEALER FOR P.M. VALVES

MullardTHE MASTEUR. VALVE

CO., LTD., MULLARD HOUSE. DENMARK STREET. LONDON, W.C.2

Published by RADIO PRESS, LIMITED, Bush House, Strand, London, W.C.2, on Tuesday of each week, and printed for them by TuE AVENUE PRESS(L. Upcott Gill & Son, Ltd.), 55-57, Drury Lane, London, W.C.2. Address for Subscriptions and Editorial Communications :-Bush House, Strand,London, W.C.2. Address for Advertisements :--Advertisement Manager, WIRELESS, Bush House, Strand, London, W.C.2 'Phone: City 991.1. Regis-tered as a newspaper and for transmission by Canadian Magazine Post. Subscription rates U.K. and abroad :-13s. per annum. 6s. 6d. for sixmonths, post free. Sole Agents for Australasia :-GORDON GOTCH (Australasia), LTD. POP South Africa :-CENTRAL NEWS AGENCY, LTD. AMR/UR 0Agents :-INnnuivriONAL NEWS CO., New York. Canadian Agents :-THE AMERICAN NEWS CO., LTD., also IMPERIAL NEWS CO., LTD.

leto WIRELESS WEEKL - World Radio History

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Transcript of leto WIRELESS WEEKL - World Radio History