-)("1 TAB

EDITOR: BERNARD .E.JONES

PAM&RADIO

TECHNICAL EDITOR: ...f.H.REYN ER P fAicwes)A.M./.E.E.

N94 JAI Y.1928ONE Sill LUNG

MORE ABOUT THE CHUMMY FOUR !

ask

j Wireless Magazine, Juty, 1928.,,..AMATEUR SET- CONSTRUCTOR'S

FULL-SIZE BLUEPRINTSPhotographic contact prints from the draughtmen's original designs, which act as drill-ing templates, layout guides and simplified 'tiring diagrams, are available of all setsdescribed in the " Wireless Magazine" and of most sets described in "Amateur Wireless "

CRYSTAL 27 SAll these 6d. each, post free.

For the R.C. EnthusiastFonotrol Set ..Hi -lo Set ..Two -programme Set ..Half-hour SetCentre -tap Set ..Alternative -programme. SetSuper Setlapped -coil Set ..

- WI` 113WM14.WM.r8WM25WM28WM5oAW 39AW 64AW 95

. WM47 WM54 WM66 AW 2AW 27 AW 46

. AW 65 AW 71 AW 78 AWro3TWO -VALVE SETS

wm20wm23

WM3oWM37WM44WM56WM62

. WM69WM76 AW 5

. AW 6 AW rr AW 21AW 28AW 34 AW 42

. AW 51AW 53AW 55

. AW 57 A W59AWOLAW 66

AW 74AW 77AW 83AW 90AW 91AW 92AW 99AWro9

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

One-valver for a Frame Aerial ..Long-range Hartley ..Reflexed One for the Loud -speakerAll -wave ReinartzHartley D.X.Reinartz Plug-in OneConstant -coupledEconomy One ..Loud -speaker. Special ..Ultra -sensitive Hartley One

All these ls. each, post free.Loftin -White 2 (D, Trans) Price is. 3d.,

with copy of "IV .M " .One -dial 2 (D, 'Frans)Girdle Two (D, 'trans) Price IS. 3d.,

with copy of "W.M." . . . .Mains -fed z (D, LF)British Broadcast z (D, Trans) ..Two -programme 2 (D, Trans)Q -coil 2 (D, Trans)Crusader (D, Trans)Flat -dweller's 2 (HF, D)KLi z-valver (D, Trans)One -control z (D, Trans) ..Wide -world Short-wave (D, Trans)Reinartz 2 (D, Trans) ..Empire Short-wave ..Next Step z (D, Trans) ..Centre -tap 2 (D, Trans)..Three -option z (D, Trans) ..Rover 2 (HF, D)General-purpose 2 (D, Trans)All -wave (D, Choke) .Yule (D Trans)30/- 2 (1), Trans)Economical 2 (D, RC) ..Britain's Favourite (D, Trans) Price 7d.,

with copy of "A.W.." ..Home -and -Abroad z (D, Trans)Two -wave (D, Trans) ..Ultra -selective Hartley (D, Trans)Oceanic Short-wave (D, Trans)Trapped Reinartz (D, Trans) .."Q" z (D, Trans)Long Distance Two (HF.D.)

A blueprint of any one set describedin the current issue of the "WirelessMagazine" can be obtained for half-price up to the date indicated on thecoupon (which is always to be foundon page iii of the cover) if this is sentwhen application is made. Theseblueprints are marked with an asterisk('p) in the above list and are printed inbold type. An extension of time will bemade in the case of overseas readers.

THREE -VALVE SETSAll these is. each post free.

Continental (HF, D, RC)Wave -catcher (HF, D, 'Frans) WM19Screened -grid (HF, D, RC) .. WM21Five -guinea 3 (HF, D, 'Frans) .. WM29Mains Three-valver (D, 2LF) WM34Dominions Shorevvaver (D, 2 'I'rans) WM39Tuned -anode from the Mains (HE, D, LF) WM43Screened -grid Short -waver (HF, D, 'Frans) WM5Metropolitan (13,2 LF) WM48Everyday (0, 2 Trans) . WM52Music Charmer (D, RC, Trans) WM6oBritannia (D, RC?t'rans) WM67Home and Gardeh 3 (D, 2 RC) .. WM78*Signal Three (HF, D, Trans) , WM84M. C.3 Star (HF, D, Trans) AW 16Split -primary (HF, D, Trans) .. AW 24Lighthouse 3 (D, 2 Trans) AW 29Modem Tuned -anode (HE', D, 'I'rans) AW 35Tetrode 3 (HF, 13, 'Frans) ..

All -from -the -Mains (D, 21,F)' AW 41Alternative -programme 3 (D, Trans) AW 38

Special (D,Economy 3 (D, 2RC) AW 48Short-wave (D, RC, Trans) .. AW 5oEther -searcher (D, RC, Trans) AW 52Standard (D, 2 Trans) AW 56Hartley D.X. (0, RC, 'Frans) .. AW 63Britain's Favourite (D, RC, Trans) Price

7d., with copy of "A.W." AW 72Broadcast 3 (D, RC, Trans) .. AW 76Selectus 3 (HF, D, Trans)

AWwW 8184

Q -coil 3 (D, RC, Trans)Clarion 3 (0, 2 Trans) AW 88Miniature Hartley Three AVViorSummer-time'Three (HF, D, Trans) AWro6Three -valve Mains Receiver (HF, D, Trans)

AWrio

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

Revelation (HF, D, RC, Trans) .. WM24.Simplicity (HF, D, z Trans) .. WM41Astral (HF, D, z RC) .. .. WM53Trapped 3-4 (D, 2RC Par illeled) WM61Station -finder (HF, D, 2120) WM68Gramo-Radio 4 (D, RC, z 'Frans Push-

pull) WM7oQ -coil 4 (HF, D, Trans, RC) ..*All -from -the -Mains Four (HF, D,

WM7 i

LF).. .. WM86Screened grid 4 (HF, D, 2RC,) .. WM77All-purpose 4 (HF, D, RC, Trans) .. AW 43Tuned -anode 3-4 (HF, D, z 'Frans) .. AW 4.9C.T.4 (HF, D, RC, Trans) AW 58Special 4 (HF, D, 2LF) " AW 70I.H.C. 4 (2E1F, D, Trans) AW 87"Q" 4 (HF, D, RC) .. AW 98

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

1927 Five (zHF, D, 2 Trans) .. WM 6Two-volter's 2 (Trans -Parallel Power) . WMiExhibition 5 (zHF, D, RC, Trans) .. W V133Phoenix (211F, D, 2LF) \\'\1421928 Five (zHF, D, 2 Trans) .. NI46All -the -world 5 (zHF, D, 214C) .. WM63Cataract 5 (HF, D, RC, Push-pull) .. WM79Individual 5 (zHF, D, 2 'Frans) AW 25School 5 (HF, D, 2RC) AW 85

SIX -VALVE SETS1 s. 6d. each, post free.

Nomad (zHF, D, RC, Push -Pull Trans) WM31Short-wave Super -6 (Super -het, Trans) AW 67Long -wave Adaptor .. AVV67a

SEVEN -VALVE SETSis. 6d. post free.

Simpladyne (Super -het) . . WM22

Springtime 2 (D, Trans) . . WMCountryside 4 (HF, D, 2 Trans) , . WM i7Handy 3 (D, 2 'Frans). WM27Sunshine 5 (zHF, D, z Trans) .. WM74Chummy 4 (HF, D, RC, Tr ,ns) . WM60*Sidecar Portable (2 HF, D, RC,

Trans) ..Motorists 4 (HF, D, 2 Trans) .. AW 14 1/0M.C. 3 (HF, D, Trans) AW 22 I/-Holiday 3 (D, z Trans) AW 32 " I/ -Easter 7 (Super -het, RC, Trans) .. AW 89 1/6Table Grand 4 (HF, D, 2RC) AW 93 116Attache Portable z (HF, D) AW 9,1 /-Companion 5 (zHF, D, RC, Trans) AW too 1/6Daventry Portable (D, Trans) .. AW 105 r/-Daventry Loud -speaker Portable

(aHF, D, RC, Trans) AW 107 1/6

PORTABLE SETS Price,Peat Free

1;'6

/6r/6

WM83 1/6

AMPLIFIERSAll the e Is. each, post free

Two -valve D.C. Mains AmplifierRange Extender (HF Unit) ..True -tone Amplifier (3 valves) .Grarno-radio Amplifier (2 v.) ..One -valve D.X. Unit ..Utility (RC, Trans)Screened -grid HF Unit ..One -valve LE Unit ..Add-on HF Unit ..Super -power Push-pull ..Hook on Short -waver ..Purity Amplifier ..

MISCELLANEOUS

WM16W M38W M47W M 72AW 37AW 68AW 75AW.79AW 82AM' 86A W ro4AWroti

Volume -control Unit .. WM4oA.C. Mains Eliminator .. WM41Cone Loud -speaker WM55A.C. Adapter for "Simpler Wire-

less" Sets WM57Moving -coil Loud -speaker .. WM38D.C. Mains Eliminator .. WA 139Wavetrap . . . . .\1'\I tValve Tester and Paralleling Unit W \ IPortable Cone Loud -speaker W1173Permanent -magnet Moving -toil

Loudspeaker . VVNI 7 :"Junior" Moving -coil Loudspeaker W1A Si*Universal Short-wave Adaptor WM82Heterodyne Wavemeter AW 7Rectifying Unit for " SimplerWire-less" Sets.. .. .. :\WH.T. from A.C. Mains .. AW 73`AW" Moving -coil Loud -speaker AW 97H.T. Eliminator for A.C. (too v.

output) .. .. to?.

-/6

Send a postal order (not stamps)TO

WirelessMagazine

Blueprint Dept., 58 61Fetter Lane - E.C.40000000000

li

Wireless Magazine, duty, 1928

Volume VIINo. 42 Wireless Magazine

" The Best Shillingsworth in Radio"

CONTENTS

July, 1928Price 1/.

PAGE PAGE PAGE

The Chummy Four Makes With L.F. Amplification .. 510 The Gramo-Radio Vol-Friends ! . . . . 483 Under My Aerial. Halyard's ume Control . . , . 534

New Valves with Five Elec- chat on the Month's Topics 513 A Romance of the Future.trodes . 486 Lamentation ! Verse .. . . 515 Verse . . . . .. 535

What Are Other Stations Like? 487 Decorating Your Loud- An Outline of GramophoneThe All -from -the -mains speaker Baffle ! 516 Developments . . . . 536

Four. Works direct from Slow and Sure ! 517 Pick-ups Are not Always toD.C. or A.C. Mains 488 " Wander " Plugs .. 517 Blame .. . .. 538

Mixing Battery Juice . . 491 A Ceremony of Induction. A Turning Music into Volts . . 538The Problems of Miss Priscilla Radio Story. 518 Use a Moving -Coil Loud-

Playne-Smythe . . 492 Through Fire and Water ! 521 speaker for the Best Re-Just Pushing the Button ! 494 Is My Aerial a Lightning Con- sults . . 538A Folding Frame Aerial 495 ductor? By A. Si Hunter . 522Roadside Adventures ! 496 A Combined Loud -speaker Some B.B.C. Autumn Pro-The Sidecar Portable. Fits and Bookcase 523 gramme Revelations. .. 539

Any Standard Machine 497 Make Your Own Photo- H.T. Eliminator Voltages .. 540Is Your Crystal as Good as a electric Cell 524 Half Hours with the Profes-

Valve? 502 Are My Mains A.C. or D.C.? 524 sor : A Chat about ShortCan You Read a Circuit Dia- The Signal Three. A Good Waves . . . . . . 541

gram? 503 General-purpose Receiver 525 What is the Resistance ofIs Short-wave Work Beyond A Lesson in Neatness 527 Your Battery? .. .. 543

the Ordinary Listener? .. 504 Charging Your Accumulator If the Aerial Neutralises .. 543Do You Give Modern Music at Home .. 528 Broadcast Music of the Month 544

a Chance? Special article Continental Notes. .. 529 Capt. Round Takes a Bus-by Sir Dan Godfrey . . 505 The World's Broadcasting .. 530 man's Holiday .. .. 548

Radio and Our Special Senses 506 A Crystal Set as a Trans-How to Choose a Moving - mitter .. 556

coil Loud -speaker. By D. Gramo-Radio Section : Australian Call -signs .. 556Sisson Relph .. 507 Introduction .. 531 Sets Which Are " Gay " .. 557

The Wrecker of Ohms ! Three Gramo-Radio Sets A Reader's Opinion of theDrawing by Glossop . . 509 to Choose From . . 532 1928 Five.. 557

The Universal Short -Wave Test Records for Gramo- Reference Sheets 558Adaptor. For Any Set Radio . . 533 Odd Jottings .. 560

Published by BERNARD ,ONES PUBLICATIONS, LTD., publishers of "Wireless Magazine" and "Amateur Wireless." Editor : Bernard E. Yones.Technical Editor : Y. H. Reyner. B.Sc. (Hons.), A.M.I.E.E. Editorial and Advertisement Offices : 0161 Fetter Lane, London. E.C.4. Telet hmeCity 3733, 3734. Telegrams : "Beejapee, Fleet, London." Published about the 25th day of the month and bears the date of the month hIlmming.Subscription : Great Brttain and Abroad, 155. 6d. a year, post free (Canada only, 13s. 6d.). Contributions are invited and will be promptly considered.

What is Happening in the Radio WorldTHIS year's portables are real quality receivers. No earlierportable can compare in range, volume, and quality with

this year's-either manufactured or home -constructed. We havenever heard finer sets than J. H. Reyner's Sunshine Five and theChummy Four, and in this, the July issue, we have a furtherarticle on the second of them ; its success was instantaneous.

Still another new portable is introduced by us this month-a special set for the sidecar-and we believe it to be the firstportable particularly adapted to be carried by the motor -cyclist.It employs a frame aerial specially arranged for folding into smallcompass.

J. F. Johnston's All -from -the -mains Four will interestreaders who have tried out the earlier sets working on his remark-ably simple system of using current direct from the mains.

One of this month's sets that will please the broadcastlistener anxious to do a little short-wave work is the UniversalShort-wave Adaptor, so designed that it can be used inconnection with almost any existing set.

The Gramo-Radio Section makes its second appearancethis month, and is specially interesting because of Capt. Barnett'sarticle on Test Records. "An Outline of Gramophone

Registered at the General Post Office for

Development" will be read, too, with considerable interest.No sooner do we reach the summer than we think of the

autumn and winter. It is a very open secret that the valvemanufacturers contemplate some striking developments and thatthese will mostly be ready for the big Wireless Exhibition to beheld for one week at Olympia from Saturday, September 22.We are able in this issue to give a description with illustrationsof one of the coming season's novelties.

An article in this issue," Is My Aerial a Lightning Conduc-tor ? " is written by a member of our staff who has had theopportunity of enquiring personally into the conditions of someof the accidents that have recently occurred, and will reassureany nervous readers.

By the way, our friend Capt. Round (who writes forWIRELESS MAGAZINE and Amateur Wireless exclusively)has beencruising the Mediterraneanwith two receiving sets and youwill read, under his own title" A Busman's Holiday," ofsome of his experiences andconclusions.

Transmission by Canadian Magazine Post

481

Wireless Magazine, uly 1928]

You have heard him from Eastbourne. You have heard himfrom London. You heard him last on Sunday, the 27th. Andfeasts of feasts, you are going to hear him regularly for some time to come.You will hear him make wonderful melody and harmony on the strings ofhis famous violin. Yon will hear his music as he would like you to hear it ifyou use a Lissen New Process Battery in your set. For there comes from thisbattery such fine power that your loud -speaker utterance keeps clear and loudall the time, natural and true. All the light and shade of fine music con-ceived by a master mind and played by a master's hand is there for you toenjoy it you use the Lissen New Process Battery. The fine current of thisbattery is due to the new process and new chemical comtinat on which isknown and used only by Lissen, and you can got it in no other battery.Ask fora Lissen New Process Battery at any one of 10,000 radio dealers. IfYou value fine radio reproduction ask for it in a way that shows you intendto take no other.

60 volt. (reads 66)100 volt (reads 108) 12/1160 volt Super Power 13/69 volt Grid Bias4i volt Pocket Battery (4/6 doz.) 5d.

LISSEN LTD., Friars Lane, Richmond, Surrey. Managing Director: Thomas. N. Cole.482

Wireless Magazine. July 1928

Although details of it were published only a month ago, the Chummy Four is ".going greatguns." This set is the first portable to use a screened -grid high -frequency valve and theresults it gives are really astonishing. In one evening thirty-one stations were received onthe loud-speaker-and that in South London where conditions are none too good!

%Churnings*

RIGHT from the day of publication of theprevious issue of the WIRELESS MAGAZINE,

in which full constructional details for makingit were given, the Chummy Four has made friendswith everybody who has read about it. Duringthe past few weeks the original WIRELESS MAGA-ZINE set, which, it will be remembered, was thefirst portable set to make use of a screened -gridvalve, has been demonstrated to a number of well-known people in the wireless trade and all of themwithout exception have expressed keen interestin the design.

Although it weighs 3o lb. when all thebatteries are in position, the Chummy Fouris not cumbersome; for it is so well balancedand the case is so narrow that it swingsfreely by the side of the legs. It is undoubtedlythe ideal receiver for those who want goodradio reception with the minimum amountof trouble.

Although the design of the Chummy Four isvery compact and the space available has been usedto the best advantage, there is no difficulty at allabout the construction and those who work froma full-size blueprint will be able to put the receivertogether in a few hours.

In his original test of the Chummy Four,Mr. J. Godchaux Abrahams received andidentified on the loud -speaker no less thantwenty-one stations and in an independenttest a member of the WIRELESS MAGAZINEStaff achieved the reception of thirty-onestations, although all of these were notidentified.

We shallbe delighted to have from WIRELESSMAGAZINE readers detailed reports of theresults they obtain from this receiver:

des nods/The Best Portable Set Yet Produced:Makes Use of a Screened -grid ValveDesigned, Built and Tested by the" Wireless Magazine " Technical Staff

H.F.CHOKE

ANODEREACTION CONDENSER

CONDENSER \

BLOCKINGCONDENSERS

L.F.TRANSFORMER -

ANODECONDENSER"'E.- GRID LEAKS

POWER VALVE'

L.F. VALVE'

DETECTOR

VALVE

60 -VOLT H.T.-BATTERY

ANODE COIL

SCREENINGBOX

HE COUPLINGCONDENSER FRAME

CONDENSER

H.F.VALVERHEOSTAT

H. F. VALVEHOLDER

TWO 9 -VOLTG.B.BATTERIES

CONELOUD -SPEAKER

TWO 2 -VOLT ACCUMULATORSIN PARALLEL (C.A4

The arrangement of all the parts in the Chummy Four is clear from thisphotograph. It consists of a high -frequency amplifier , a detector, aresistance -coupled low -frequency amplifier and a transformer -coupled

amplifier

60 -VOLT H.T.BATTERY

ANODE -TUNING CONDENSER

EF LFAFROM TRAM'

FRAM: TUMNO,COIN 0 E 5FIL

RAME AERIAL

LOUD -SPEAKER

ADJUSTMENTThis photograph clearly shows the various controls of the Chummy Four

REACTIONCONDENSER

483

ON -OFF SWITCH

Wireless Magazine, ly 19281

Trying out the ChummyFour after a car journey.Vibration does not

affect it

Some Advice to theConstructor

IN these pages are reproduced forI the benefit of those who missed itlast month a number of photographswhich make clear the special characterof the design of the Chummy Four,the first portable set to make use ofthe screened -grid valve. Only repre-sentative photographs are includedand for full constructional diagrams,the reader is referred to pages 399to 406 of the June issue of theWIRELESS MAGAZINE.

Normally, the complete set of parts

The Chummy Four (continued)valve to be utilised. Not only does the

full-size blueprint indi-cate the exact positionsof all the components,but it also acts as avery clear wiring dia-gram, all the points tobe wired together beingindicated by smallletters, the alphabeticalsequence of which coin-cides with the simplest

distance tests, and the addition ofextra terminals and a switch so thatthe high-tension supply can beobtained from an eliminator or othersource of supply, if desired, when theset is used indoors.

Although it is possible to gettwenty-five to thirty stations on theloud -speaker the number could, ofcourse, be very greatly increasedwith headphone reception and thismodification is being made at therequest of a large number of listeners.

One Evening's "Bag"Wove -length inmetres Station236.2 Stettin241.9 Nuremberg25o Muenster.279 Lille 59283 Cologne 62297 Hanover319 Dublin i3Si322.6 Breslau 85337 Copenhagan.. 00340 *Frenchman (Petit

Parisien ?L. 92 65 55

Dial Dial Rear -No t No. 2 tion

36 15 4043 19 38

23 4050425042

3240465762 4965 55

by Mr. J. G. AbrahamsmelWenayte-

Dial Dial Rem.-Station No. i No. 2 Lion

364 London (2L0) tot 7t NoR.337695 Stuttgart..104 76 40389 Toulouse. 112 85 36

107 81 36

396 Hamburg.rt.

114 :1 59428 Frankfurt. 123 54468 Langenberg(5G..B)

142 118 20138 112 58

459315.7 Dmauvneinctryh

150 124 66549.3 Milan 155 130 30555.6 Buda-Pesth t6o us 6o

(Tested on April 29, 1928.) *This station could not be identified; for thirty minutes itbroadcast election results, but gave no call I

How the parts are arranged in the Chummy Four

costs approximately 415, but thisprice may be reduced by the use ofalternative parts as specified in thelist of components required, which isagain reproduced on the oppositepage. There is, of course, no altern-ative for the screened -grid high -frequency valve, which is a Cossor,as this is at present the only z -volttype on the market and there is noroom in the cabinet for a 6 -voltaccumulator, which would be neces-sary were any other screened -grid

sequence of wiring up.These blueprints, which

are 1/6 post free (theycannot now be obtainedunder the half-price cou-pon scheme), are avail-able from the BlueprintDepartment, WIRELESSMAGAZINE, 58/61 FetterLane, E.C.4. When send-ing for a blueprint enclosea postal order for 1/6 andsimply ask for No.W.M.8o ;your copy will then besent by return of post.

In the nextissue we shalldescribe a num-ber of interestingmodifications

which constructors can maketo their receivers should theyso desire. It should beclearly understood, however,that these modifications arenot essential and in no wayaffect the reproduction. Thepoints that will be explainedare the inclusion of terminalsfor the use of an externalaerial and earth for experi-mental work, the inclusion ofa headphone jack for long -

484

Further CommentsBy J. GODCHAUX

ABRAHAMS

FOR the past fortnight, by hookand by crook, I have held on to

the Chummy Four. In a weakmoment the Editor of WIRELESSMAGAZINE allowed me to take itaway from his den, "for a furthertest," I suggested. Since thatmoment IT (the set, not the Editor,of course 1) has been my constantcompanion.

A welcome addition to the tea party-the Chummy Four quickly makes

friends

Wireless Magazine. uly, 1928

Amazing Success of the First Screened -grid PortableWhen I tested out the Chummy

Four last month I dwelt more on thequestion of selectivity and ability toreach out than on the quality andtone of its reproduction. Now, at myleisure, I have tuned into the differentstations I had picked up previouslyand logged, have checked the con-denser readings carefully, and haveheld each individual transmission fora reasonable period. I have listenedto concerts, not merely listened -in ;there is a wide difference between thetwo terms.

I selected four stations, namely,Copenhagen, Stuttgart, Hamburg,and Milan ; they were taken at ran-dom from my log, but were those Ican receive almost nightly on a seven -valve super -het. The Chummy Fourcaptured and held them for me, andif the volume was not quite equal tothat obtained with the larger receiver,the portable scored one advantage:it brought in less mush and, if any-thing, the tone was purer and clearer.

Cutting Out the "Local"From the roof of my house I can

see the 2L0 aerial; I doubt whetherit is much more thanyet the moving of the vernier dialssome two or three degrees will cutout the London transmission. In mycase the reception of the local con-cert through an ordinary three- orfour -valve receiver proves too power-ful for my loud -speaker.

Not so with the Chummy Four, asto control volume it is only necessaryto dim the filament of the screened -grid high -frequency valve by meansof the rheostat knob. There is noneed to detune or to turn the frameaerial away from the station, both of

LEADS TO FRAME~-AERIAL INSIDE LID

Receiver unit of the Chummy Four photographed from topof panel. Note the bracket for the grid -bias batteries

COMPONENTS REQUIRED FOR THE CHUMMY FOUR1-Ebonite panel, 16 in. by 8 in.

(Resiston, Becol; or Raymond).1-Metal screening box with lid

(Magnum or Formo).2-.0005-microfarad variable con-

densers (Formo 1928 Log).2-Vernier dials (McMichael).1-.0002-microfarad variable con-

denser with small dial (Cyldon).1 -7 -ohm panel rheostat (Lissen,

Igranic, or Peerless).1-Screened-grid valve -holder (Burn -

dept).2-2-microfarad fixed condensers

(Lissen, Dubilier, or T.C.C.).1-Anode coil as specification (Burne-

Jones).1-High-frequency choke (Omnora,

Wearite, or Igranic).1-Low-frequency transformer, ratio

4 to 1 (Mullard).3-Anti-microphonic valve holders

(Redferns).1-On-off switch (Bulgin Midget,

Lotus, or Lissen).1-Pair small panel brackets (Mag-

num, Camco, or Bulgin).2-2-megohm grid leaks with clips

(Loewe).1-.005-microfarad fixed condenser

with clips (Loewe).1-.0003-microfarad fixed condenser

with clips (Loewe).1-.25-megohm grid leak with clips

(Loewe).1-Ebonite strip, 2} in. by 11 in.

(Resiston, Becol, or ReadyRadio).

2-Ebonite washers, f in. bore and1 in. thick (Ready Radio).

6-Lengths 'Glazite.3-yards thin rubber -covered flex

(Lewcos).2 -60 -volt high-tension batteries

(Lissen).2 -9 -volt grid -bias batteries (Lissen).2 -2 -volt accumulators (C.A.V. type

2NS9, with jellied acid).1-Loud-speaker unit (Goodman

doubt -acting).1-Piece gold -finished cone paper

(Goodman).1-Piece rubber sheet, 1 ft. square

(any sixpenny stores).10-Wander plugs, 6 red and 4 black

(Igranic).10-Indicating tabs for flexible wire,

marked : two H.T.±, oneH.T.-, two G.B.+, one G.B. - ,one L.T.+, one L.T.-, oneL.S.+, one L.S. - (Bulgin).

1-Cabinet with baseboard, batterybrackets, loud -speaker, front andback (Ready Radio).

2-Ozs. No. 28 -gauge d.s.e. wire forframe aerial (Lewcos).

8-Ebonite strips, 11 in. by 1 in.(Ready Radio).

12-6B.A. 1 in. round -head screwswith nuts (Bulgin or ReadyRadio).

36-f in. No. 3 brass wood screws(Bulgin or Ready Radio).

2-14 in. brass wood screws (Bulginor Ready Radio).

3-Dial indicators (Bulgin).1-Station log, small (Bulgin).

which processes invariably spoil theclarity of the reproduction.

The actual tuning of the receiveris mere child's play; just log thestations received. As soon as youhave done this, unless the transmit-ters should change their wavelengths,you may find them again and againwithout any further trouble. A frameaerial possesses one great advantage,the condenser readings cannot vary.

An easily -constructed wireless setwhich will give you a selection ofsome twenty-five to thirty stations

485

at any favourable time of the day ornight is an excellent investment.

On My Conscience!Whether the Editor ever gets this

receiver back again is a moot point;it must entirely rely on my conscience.But I have never felt so tempted tobreak the eighth commandment !

Failing this alternative, I shall becompelled to build the Chummy Fourmyself-whatever happens, I musthave one.

J. GODCHAUX ABRAHAMS.

View of back of Chummy Four receiver. The lid ofthe metal screening box has been removed

NVirelessMagAzine. Juty, 1928

NewValvesWith live Bedrocks!Similar inappearanceto any three -electrodevalve, theextra con-nection re-quired by thePentone isbrought outto an extraterminal onthe base. Thevalve fitsthe standardfour -pinholder anddoes notnecessitateany circuitalterations.

IN every receiver intendedfor really good loud-

speaker reproduction it isnecessary at present to in-corporate at least two stages,and in many cases threestages, of low -frequency amp-lification.

Two Valves OnlyThe advent of an entirely

new type of power valve withfive electrodes will make itpossible, however, in the verynear future to work a loud-speaker at full volume from

A new era in receiver design is heralded by the announce-.ment of a special type of five -electrode power valve (itgives equivalent results to two ordinary valves), whichthe " Wireless Magazine " is able here to give special

advance details for the benefit of readers.results in both the Chummy Fourand the Sunshine Five portables.

Known as the Pentone, because itcontains five electrodes, the new valvecontains normal filament and anodebetween which are placed three grids.That nearest the filament is the ordin-ary operating or control grid suchas employed in the ordinary three -electrode valve, while the nextgrid (that is, the central electrode)has applied to it the same highvoltage as fed to the anode. Thethird grid (nearest the anode) isconnected internally to the filament.

This combination produces a valve

structional difficulties about the useof Pentone valves, and readers canrest assured that as soon as theybecome available the WIRELESSMAGAZINE will lose no time in pub-lishing details of a receiver that willmake the best possible use of them.

Two- and Four-Volters OnlyAt first only two -volt and four -

volt Pentones will be produced andthese will be known as the MullardPM22 and PM24 respectively. Weare able to give here, for the benefitOf WIRELESS MAGAZINE readers, thefirst details of the new valves :-

"W" FILAMENT

-ANODE.

OUTER GRIDJOINED TOFILAMENT

Arrangementof electrodes.

INNER CONTROLGRID

M DOLE GRIDCARRYING1-1iGn POTENTIAL

a simple receiver consistingof a good detector and only one ofthe new power valves.

Hitherto no details of these valveshave been published, but in thesepages the WIRELESS MAGAZINE isable to give its readers some mostinteresting advance informationconcerning them. It must be clearlyunderstood, though, that the valveswill not be on the market for someweeks to come.

A Mullard DevelopmentIn the meantime everybody will be

glad to know something of this latestdevelopment, which is due to researchwork carried out during the past fewmonths by the Mullard WirelessService Co., Ltd., whose new Perma-core transformer has given such fine

with remarkable characteristics andconstitutes one of the most revolu-tionary developments of recentmonths. It is no exaggeration to saythat these new valves will, in a veryshort time, revolutionise receiverdesign. (Readers will remember -that Capt. Round foreshadowed thisdevelopment in his article, " NeedWe Improve the Valve? " whichappeared on page 218 of the Aprilissue of the WIRELESS MAGAZINE.)

Moreover a point that will particu-larly appeal to the home -constructoris that the new valve can be used inthe standard four -pin holder, theconnection to the auxiliary grid whichcarries a high potential being broughtout to a terminal at one side of theebonite base.

There will, therefore, be no con -

486

Mullard PM22Filament voltage, 2 volts.Filament current, .3 ampere.Maximum anode voltage, 15o

volts.Auxiliary grid voltage, same

as anode.Anode impedance, 62,50o

ohms.Amplification factor, 8z.Mutual conductance, 1.3 milli-

amperes per volt.(The impedance, amplifica-

tion factor and mutual con-ductance quoted are thcs3measured at roo anode volts,zero volts on control grid,and roo volts on auxiliarygrid.).,.

How elaborateis the construc-tion of thePentone can bejudged from thisspecial " Wire-less Magazine"photograph.Thevalve has givenexcellent resultsin our labora-tories. The pricewill be 22s. 6d.

Wii-elessMagazine, July 1928

Mullard PM24Filament voltage, 4 volts.Filament current, .15 ampere. 'Maximum anode voltage, 15o volts.Auxiliary grid voltage, same as anode.Anode impedance; 28,600 ohms.Amplification factor, 62.Mutual conductance, 2.3 milliamperes

per volt.(The impedance, amplification faC-

tor and - mutualconductancequoted are thosemeasured underthe same con-ditions as for thePM22.)

The remarkablenature of the newvalves is evidentfrom these partic-ulars. Particularnote should bemade of the enor-mous amplifica-tion factor ofthese valves, forthat of a standardthree -electrodepower valve is inthe neighbour-hood of 3 to 5.The high imped-ance is no draw-back because ofthe large anode -current outputthat is available-as much as 33 mil-liamperes at zerogrid volts in therase of the PMz4,with 125 voltson the anode and auxiliary grid.

It will be evident that with itshigh amplification and large anodecurrent one Pentone will give resultsequal to those at present obtainedfrom an ordinary two -valve amplifiercomprising a medium -impedance andlow -impedance power valve, but

there will be a great saving of filamentcurrent and one intervalve couplingwill be obviated. This will, of course,greatly simplify receiver design andis a point that will at .once make astrong appeal to the home -construc-tor, who wants the best possiblereproduction with the least amount

a slope of only 1.3 milliamperes pervolt the four-volter has a slope of2.3 milliamperes per volt, whichmeans, of course, that it, is a verymuch more efficient amplifier.Moreover " the filament current re-quired by the four -volt valve is onlyhalf that needed by two -volt type.

This is to introduce Mr. S. R. Mallard, Managing Director of thp MullardService Co., Ltd., to " Wireless Magazine" readers

of trouble in building and operating.The case for developing four -volt

valves rather than abolishing them(the latter course has been stronglyadvocated in some quarters) is wellemphasised by these PM22 and FM24characteristics. It will be notedthat while the two -volt valve has

Not for SaleThese advance

particulars willundoubtedly cre-ate great interestin amateur radiocircles every-where, but onceagain the WIRE-LESS MAGAZINEwishes to pointout that these areadvance detailsand that thevalves themselvesare not yet avail-able. As soon asthey are on themarket full oper-ating particularswill be publishedin these pages andreaders can restassured that theTechnical Staff issparing no painsin preparing togive the amateur,when the timecomes, the bestinformation on

how to use Pentones to the greatestadvantage.

We have had an opportunity oftesting the new valves and knowfrom personal experience that theyare really good. For the rest, readersmust possess themselves with pati-ence for a few weeks I

Wireless

ALISTENER in this countryusually receives a mild shock

when he goes abroad for the firsttime and hears Berlin, for ex-ample, within a mile of the capitalitself.

Reception Noticeably DifferentHe finds that reception is noticeably

different. The station doesn't seemthe same Berlin as that to which helistened on his set at home. For onething, the local reception is muchlouder, unless he has a super set.Arid for another, he is hearing it forthe first time as the station is meantto be heard, namely, locally.

What Are OtherStations Like?

This is not meant to be a slighton Merlin, but it must be rememberedthat every station (except 5SW)caters for listeners within its normalzone. London does not cater forGerman listeners, so conversely, itseems strange to a British listenerto hear Berlin without any distancedistortion or fading.

Programmes? That is a differentmatter. There are not manyregular listeners to Continental andother centres who would willingly

487

exchange our B.B.C. programmes forthose of the French, German, orAmerican broadcasters.

All these do, occasionally, broadcastsome item of outstanding merit, andit may, on that particular occasion,be better than anything being "puton the air," by the B.B.C. But thesetimes are rare.

Without wishing to take over therole of publicity man to the Corpora-tion, I may say that I think mostof us prefer the consistent good -quality B.B.C. matter to the periodicspurts of stations in many otherscountries.

QUEUE.

Wireless Magazine. Ju ly, 1928

ALL-FROMTIRAINSfOOR

The rectifying unit on the right is added for A.C. working

THERE are still quite a lot ofexperimenters to whom no

trouble is too great to be undertakenin the cause of wireless. Such peopletake a keen delight in tinkering with,caring for, and generally lookingafter, their wireless gear, and wouldnot take much interest in a set whichnever required any attention.

But the very great majority of thepeople who use wireless nowadays doso simply and solely for the sake of theprogrammes they are thereby enabledto enjoy. The ideal set for this greatclass of people would be one whichcould be entirely forgotten until themoment it was required for use-aset which required no other attentionthan the touching of a switch to startit and stop it when required.

Battery TroublesNow, it is perfectly obvious that no

receiver which depends for its currentsupply on any kind of batteries caneven approach this ideal, as if such aset is to be always available for use,one has constantly to keep in mindthe state of the batteries and whenthey require renewing or replacing.

A great step towards achievingreal trouble -free wireless is takenwhen all the necessary current isderived from the lighting mains, thus

Can be Operated Direct fromDirect - current or Alternating -

current Electric Mains

Described by J. F. JOHNSTON

Built by the "W.M." TechnicalStaff

eliminating batteries altogether. Onecan then at least be sure of a steady,continuous and never -failing supply.

To work entirely from the mains inthis way is now no novelty, but untilrecently the only way to do so wasto use " battery eliminators " and anordinary receiver. That is to say, tonse a set designed -to be worked frombatteries, but to replace these latterwith piecesof appar-atus whichcould beconnectedto the mainsand which wouldsupply to theset current ofthe same natureas that prev-iously suppliedby the orthodox batteries.

The introduction of the "SimplerWireless" system inaugurated a neworder of things. A " Simpler Wire-less" set is a mains set in itself, anddoes not require either batteries orbattery eliminators.

Several " Simpler Wireless " setshave already been described inthe WIRELESS MAGAZINE, but theone with which this article isconcerned is the first four-valver

to be dealt with in this periodical.Those 'readers who have studied

the articles dealing with previouF."Simpler Wireless" sets will find thecircuit diagram familiar-to newreaders the circuit will, no doubt,appear rather strange at first.

The set is intended to work fromD.C. electric -lighting mains, having avoltage of from zoo to 240 or, with

Plan view of the All -from -the -mains Four

the attachment of the rectifying unit,here described, from A.C. mains ofa similar voltage. The filaments ofall the valves are connected in serieswith each other and with a numberof resistances. All the valves usedare of the .r -ampere type and theresistance of the series circuit (whichis connected across the mains, or theoutput of the rectifier) is varied untila milliammeter shows that the correctcurrent is passing.

Constant Voltage DropAs the current is .I ampere,

there will obviously be a volt-age drop of one volt acrossevery ten ohms resistance.Looking at the circuit, it will beseen that, according to this, thefilament of the second valve isfive volts positive with respectto the filament of the first valve,while there is a difference of asmuch as 4o volts between thefilaments of the second andthird valves, and also between

Imo0003

EME.GOMMS

Circuit of the All -from -the -mains Four fordirect -current mains

488

g MFD

10 L.S. 0-1maiM ED.

Wireless Magazine. July, 1928

those of the third and fourth valves.The first valve is, of course, an H.F.

amplifier, and is neutralised. There isnothing at all out of the ordinaryabout this stage. The second valve isan anode -bend rectifier, and can begiven a negative bias of anything upto five volts by altering the point atwhich the return grid lead joins the50 -ohm resistance.

"Direct " Valve CouplingsThe coupling

between thesecond and thirdvalves is of the"direct" type,peculiar to the"Simpler Wire-less" system.The anode of thesecond valve isdirectly con-nected to thegrid of the thirdvalve, and thismakes possibleeven greaterpurity thancould be ob-tained byresistance -capacity coup-ling, on accountof the absence ofa coupling con-denser or gridleak. Directcoupling is alsoused betweenthe last twovalves, so thatpractically per-fect amplifica-tion may bedepended uponfrom the L.F.side, providedthat the correctcomponents andvalves are used,and that the set

is correctly adjusted.As regards safety,

which is a matter ofsome considerationwhen dealingwith themains, it maybe pointedout that thetwo high -voltage con-densers, one The All -from -the -mains Four

DRILL TO TEMPLATESUPPLIED BY

I MR TO SOIT

4k,

MILLIAMMETEROSLO

.114-

51' 1. 5" ,

(113/214 Yell 16

26'

Panel layout of the All -from -the -mains Four

T8'

U4

This layout and wiring diagram can be obtained as a full-size blueprint for half-price-that is 9d. post free-if the coupon on page iii of the cover is used before

July 31. Ask for No. W.M.86

0.0005

0

111]

loud -speaker,thus effectuallyinsulating it.

When build-ing this set, thecomponentsspecified mustbe used, if theset is to operatesatisfactorily."Simpler Wire-less" sets havemany peculiari-ties and may bequite upset ifunsuitable com-ponents are used.

This is a veryeasy andstraightforwardset to build, andmay safely beattempted evenby those whohave never builta set before.The four term -

01.) inals, two vari-able condensers,two potentio-meters, and themilli ammeterare mounted onthe panel, andrest of the com-ponents arefixed on the base-board. The

neutralising condenser, however, isfirst screwed to a small block of woodwhich, in turn, is screwed to thebaseboard. This is done to get thespindle of the neutralising condenserparallel to the baseboard. A clear-ance hole is drilled in the panel,through which the spindle of theneutralising condenser passes.

How to Wire UpIn wiring up, first connect all the

points marked a, then all the pointsmarked b, and so on.

A 'point to notice is that nothingThe All -from -the -

mains Four

in series with theaerial and theother withthe earthlead, ensurethat neither

the aerialnor theearth wirewill be

"live," while thefilter circuit, by means of

which the loud -speaker is connectedto the plate circuit of the last valve,has a condenser on each side of the

489

Wireless Magazine. uly, 1928

The All -from -the -mains Four (Continued)The All -from -the -mains Four

on the front of the panel is "live"when the set is connected up to themains. The aerial, earth, and loud-speaker terminals are, as alreadyexplained, insulated by fixed con-densers, while even the grub -screwswhich secure the dials of the variablecondensers to their spindles are not" live " as the spindles of the Burn -dept condensers are made of aninsulating material.

Results to be ExpectedThe performance of the set, as far

as range and volume go, will be verysimilar to that of any good four-valver with one H.F. and two L.F.stages. There is nothing about theH.F. stage to make it any more orless efficient than the H.F. stage ofany other set.

As regards the L.F. side, theamplification will be about the sameas that given by one transformer -coupled stage, plus one resistance -capacity coupled stage, but thequality will, if everything is correctlyadjusted, be better than that obtain-

able even when usingtwo R.C.-coupledstages. This finereproduction is, of

course, due entirelyto the direct

coupling of theL.F. valves.

One cen-tre -tapped

and two plain coils arerequired for each waveband. On theordinary broadcast band a No. 6ocentre -tapped coil in the aerial socketand two No. 75 untapped coils inthe other two socketswere found to be thebest combination, al-though for some aerials

may be better touse a No. 75 centre -tapped coil in the firstposition. 5XX waswell received using aNo. zoo centre -tappedcoil in the aerial socketand two No. 200'Sin the other sockets.Here, again, it maysometimes be better touse a No. 25o centre -tapped coil instead ofNo. 200 in the aerialcircuit.

The valves to beused in a " SimplerWireless" set need, ofcourse, very carefulchoice. In the presentset an H.F. valve will be required ineach of the first two positions, an R.C.valve in the third stage and a power

COMPONENTS REQUIRED for the ALL -FROM -THE -MAINS FOUR

r-Ebonite panel, z6 in. by 8 in. (Becol,Radion, or Raymond).

2-.coos-microfarad variable condenserswith vernier dials (Bumdept orGecophone).

1-2-megohm grid leak with holder(Graham-Farish, Mullard, or Lissen).

1 -50 -ohm panel potentiometer (Faradexor Igranic).

i-Neutralising condenser, panel mounting(Bulgin or Peto-Scott).

I-Milliammeter, reading 0-300 (Sifam).1 -4.00 -ohm rheostat ' or potentiometer

(Faradex).4-Terminals, insulated type, marked :

Aerial, Earth, L.S.± , L.S.- (Belling -Lee).

3-Single-coil holders (Lotus, Lissen, orMagnum).

2-.0oo3-microfarad fixed condensers,tested to 2,000 volts (Dubilier type577)

4-Anti-microphonic valve -holders (Benja-min, Lotus, or W.B.).

z-Low-frequency chokes (Watmel, Lissen,or Faradex).

4 -400 -ohm baseboard resistances (Faradex).t-4-microfarad fixed condenser, 750 -volts

test (Hydra, Faradex, or Dubilier).i-8-microfarad fixed condenser, 750 -volts

test (Hydra, Faradex, or Dubilier).2-1-microfarad fixed condensers (Dubilier,

Lissen, or Hydra).1--Double-wound low -frequency choke

(Faradex).I-Safety mains plug and socket (Bulgin).1-Cabinet with 8 in. baseboard (Artcraft).

A.C. RECTIFYING UNITr-" Simpler Wireless " rectifier (Faradex).3-8-microfarad fixed condensers, 70o -volt

test (Faradex, Dubilier, or Hydra).1-Batten-type lamp holder (Bulgin).i-Safety mains plug (Bulgin).1-Baseboard, la in. by gin. (Artcraft).

490

Mt"

BASEBOARD

OUTPUTTO

RECEIVER

valve or, preferably, a super -powervalve, in the last stage. As all thevalves must, of course, take afilament current of .1 ampere, thelast position is the most difficult oneto fill. However, the Cossor StentorSix is ideally suitable for the laststage of a " Simpler Wireless " set, asnot only is it a .1 -ampere valve, but itis also a super -power valve and avery good one at that.

As a Cossor Stentor Six is undoubt-edly the best valve available for thelast stage, the rest of the set has beendesigned to take other Cossor valves

UUAt. MAIRS

nPUT

BLUEPEOBT El,WM87

MARIS

SAFETYLAMP

This layout and wiring diagram of the improved rectifyingunit can be obtained as a full-size blueprint for half-price --that is 6d. post free-if the coupon on page iii of

the cover is used by July 31. Ask for No. W.M.87

and the combination recommendedis two Cossor 4 -volt H.F. valves ineach of the first two positions, aCossor 4 -volt R.C. valve in the thirdposition, and a Cossor Stentor Six inthe last stage. The equivalent z -voltCossor valves may be used in any ofthe first three positions, but the6 -volt valves do not seem to suit theset so well.

Other Makes of ValvesOther makes of valves may be

used in the first three stages, but,as there is no other .1 -ampere super-power valve available, it is stronglyrecommended that only the StentorSix be used in the last stage. If anR.C. valve other than a Cossor is usedin the third stage, it may be necessaryto use a different value of anoderesistance in the plate circuit of thethird valve.

Wireless Magazine. July. 1928

All L.T., H.T. and G.B. Direct from the MainsThe operation of the set needs little

explanation except, perhaps, to saythat it is intended that reaction shouldbe controlled by means of theneutralising condenser. When search-ing for a distant station, besides thetwo variable condensers and theneutralising condenser, the 50 -ohmpotentiometer controlling the gridpotential of the anode -bend rectifiershould also be adjusted. During ourtests, carried out to miles fromLondon, besides the local station and5GB, Langenberg, Stuttgart andFrankfurt were received at very greatstrength without changing coils.Several other stations were, of course,also received at fairly good strength,but no other wasquite so loud asthose mentioned.

The set itself, c,as has already Ebeen stated, issuitable for D.C.mains havingvoltages of from200 to 240, the40o -ohm variableresistance having

months back, butboth the cells and theelectrodes are muchlonger thanbefore and, infact, therectifier con-tains justtwice thequantity ofelectrolyte usedpreviously.

The rectifier has been re -designedso as to make it more suitable forprolonged spells of hard work. Theelectrolyte in the original model usedto evaporate rather quickly if theset was used for several hours each

day, and trouble

Circuit of the improvedrectifying unit

sufficient variation to compensate forthe different voltages. The set is alsoquite suitable for use on A.C. mainsof any frequency and having voltagesbetween zoo and 240, providing thatthe rectifier unit now to be describedis interposed between the set and themains.

Improved Rectifying UnitThe rectifying unit is a very simple

affair, requiring only a very fewcomponents, which are mounted on abaseboard measuring 12 in. by 9 in.,and the few simple connections areclearly shown in the wiring diagramThe improved Faradex rectifier issimilar to the one used in the " Simp-ler Wireless " rectifying unit describedin the WIRELESS MAGAZINE a few

Simplifiedrectifying

unit

urr

A.C.

from overheatingoccurred whenusers omitted tokeep up the elect-rolyte level bythe addition ofdistilled water.The new modelwill be found tokeep very cool,even when used

for several hours on end.It is necessary to use a lamp as a

resistance in the rectifying unit andthis is, of course, inserted in the bat-ten -type lamp -socket. The correctlamp to use will depend upon thevoltage of the A.C. supply. In anycase a i to -volt lamp should be used,but the wattage should be 4o whenthe mains have a voltage of zoo to220, while a 3o -watt lamp should beused for 23o or 240 volt mains._ncreasing the wattage of the r to -volt lamp will increase the currentthrough the set, which should not, ofcourse, be allowed to exceed f oomilliamps.

It is hardly necessary to say thatthe rectifier unit should be placed ina position where the various " live "parts are not likely to be accidentallytouched. It should not, however, beplaced in a tightly -closed box, as therectifier can only be expected to keepcool if the small amount of heatgenerated is able to radiate away.

There will be, of course, a rightand a wrong way of attaching theset to the rectifier, just as there willbe when plugging the set into D.C.mains. It will not matter muchwhich way round the rectifying

491

Another viewof the set

unit is plugged into A.C. mains,though even here it will be worthwhile to try both ways, as there maybe a slight background in the loud-speaker with the plug one way roundand not when the plug is reversed.

A No -trouble OutfitFrom the foregoing description it

will be seen that the use of the All -from -the -Mains Four run difect fromD.C. lighting mains or through theimproved rectifying unit from A.C.mains provides a no -trouble radiooutfit that can be maintained at avery low cost.

Mixing Battery JuiceTHE following rule -of -thumb pro-

portions may prove of use whenit is required to mix accumulator acid.Final checking should always be madewith an hydrometer. By volume,one part of water to one of acid(s.g. 1.842) gives a solution havinga specific gravity of 1.42. One part ofacid to three of water gives an acidwith an S.G. value of 1.2f , and one ofacid to four of water a solution of1.17 S.G. value.

By weight, one part of acid to twoof water gives a resultant of 1.18.

K. B.

Another view ofthe rectifying unit

Wireless Magazine. July. 1928

MISS PRISCILLA PLAYNE-SMYTHE WANTS TO KNOW

Stewcombe Manor,Little Bodley.Near Hurdham.

15th May, 1928.To the Editor WIRELESS MAGAZINEDEAR SIR,

I really feel I must tell you, as nodoubt so very many have donealready, how completely I appreciateyour splendid paper, which is aperfect boon to those of us who livein such secluded places as this. Mynephew, Tom-a promising lad-built me the uncanniest wireless setlast winter, and, thanks to it andto your valuable periodical, I amnever at a loss for the most nourishingentertainment nowadays, be it lec-tures or even music, in severallanguages.

In my spare time, I have beenstudying my receiver, also from thescientific point of view, with the helpof your technical articles, and Ialready understand quite a great dealabout " impediments " (or is itimpedencies?), potential -meters andso on.

But there are two things upon

VrOnifflfMISS PriSC

/8%VnegillYgeBy HUGH R SEELEY

which I am stillnot quite clear.Do you thinkyou could helpme? Now, whatis a Kw? I pre-sume it is aforeign word, be-cause althoughwe have all triedhere, we cannotpronounce it.Some stationsappear to possessfour of them,and others, lessfavoured-or is

it due to lack of funds ?-only seemto have a part of one. Is this fair?

From the exhaustive World'sBroadcasting list which you publishevery month I can see quite clearly,the waves used by each station andsome of them my set is able to cap-ture quite well, even though theirfrequencies are not always so verymany. But when it comes to the littlewee waves which I presume are muchlighter and easier to send out, theresults are not so good, although yourtable shows them to be ever so muchmore frequent !

Does it not seem to you that thereverse should be absolutely the case,and that if Gavle (in Sweden, Ibelieve) takes the trouble to usewaves as profusely as 1,47o times, myset should apprehend them moreeasily than those of Daventry, whichonly sends 187 of them. Yet, try as Iwill, I cannot get a murmur fromGavle which should reach me nearlyeight times more clearly (187 into1,470) I

Mr. Candlemas, our organist, sug-gests most cleverly that perhaps the" frequencies " refer to the numberof programmes broadcast, but yousee, of course, that this only makes

492

things worse, for it would mean thatGavle not only uses eight times morewaves than Daventry, but alsobroadcasts eight times more often.Dear Mr. Editor, this makes themystery more perplexing still !

I have come to the conclusionthat there may still be some smallabstruse aspect of wireless which Ihave failed to master and if youcould clear up my difficulty in yournext issue, in just a few illuminatingwords, I should be ever so deeplyindebted to you.

Yours very truly,(Miss) PRISCILLA PLAYNE-SMYTHE.

P.S.-When using the fifth studand wave No. 133, last evening onthe "long" with the round wirestouching each other, I heard what Itook to be a woman's voice singing amelody similar to Boys and Girls ComeOut to Play. Where would this be?I do not see this mentioned in anyprogrammes.

P.S.S.-Mr. Candlemas, who waswith me at the time, assures me thatit was a Saxophone; he is so clever atmusic. He was positive it was one ofthe old London street cries : Buy, Buy,Blackbirds ! It is so interesting.Could you enlighten me?

MISS PRISCILLA PLAYNE-SMYTHE STILL WANTS TO

KNOWStewcombe Manor,

Little Bodley,Near Hurdham.

19th May, 1928.DEAR SIR,

I do think it was so considerate ofyou to have replied to my last letterby post and to have dismissed mydifficulties at once instead of leavingme floundering until your next issue.

In a general sense, more or less, Iquite follow all you were good enough

to write me, but when I try to applyyour advice practically, I am afraidI am not nearly so successful. Mr.Pringle, of our local garage, whoregularly rejuvenates my battery,has pointed out most helpfully that myset has valves for both high and lowfrequencies-it is the set my nephewbuilt last winter, and it is a mosthandsome one-and that I should usethem " according, " but I find thatif I turn on exclusively the highfrequency valve for the little tinywaves or the low frequency one forthe long waves, I simply do not getany of them at all !

When I use all the valves at once(which seems so wasteful, for mysitting -room is quite a small one), Istill only get two stations clearly, ofwhich one is London and the other isnot. Now and again I hear fuzzyechoes from other places, but hardlythink they can be from the Continent,because the only words I couldrecognise were spoken by a man whowanted to be told how he lookedwhen he was asleep !

I can assure you that I switched offthe set at once as I felt sure that thiswas a private communication. I donot know whether I ought to tellyou this as I believe my licenceforbids it.

Now I realise, of course, that therecan be no stations like our Britishones, but one should make it a dutyto hear foreign ones also, don't youthink? You see, although one maynot understand what they say, it isonly equitable to hear both sides ofthe question, is it not?

I have been pondering a greatdeal on the scientific aspect of wire-less and it has occurred to me that Imay have stumbled upon the reasonwhy I and so many of your corres-spondents do not get quite all theresults of which these magicalmachines are capable.

Does it not depend upon theposition of the set, I mean itsdistance from the sender? To put itstill more concretely, I should explainthat if my house is, say, 160,400metres from Daventry, then Daven-try's wave of r,6o4 metres wouldbound or ricochet one hundred timesbefore it reaches me, after havingbeen released, and the end of thewave-surely its very clearest andmost perfect point-would just touchmy receiver.

Wireless Magazine. uly. 1928

But if, on the other hand, my setwere half or any other fraction of awavelength nearer to, or further from,Daventry, then, of course, it wouldmerely catch the last incompletebound on the hop, as it were, and theresults would be quite otherwise.

I do hope you will agree with methat this may be the right explanationand that neither my knowledge ormanagement of my set are at fault.If I am right-and I sincerely do notsee how I can be otherwise-then itwill merely be a question of findingout the exact distance from anystation to my house, dividing this bythe wavelength and, if there is"nothing over" I must get perfectlyclear results, must I not?

Do please excuse the length of thisletter, but I find the more esoteric sideof the wireless so entirely engrossing,don't you ?

Yours very truly,(MISS) PRISCILLA PLAYNE-SMYTHE.

P.S.-Mr. Candlemas, our organist,tells me that the man who askedsomebody to tell him how he lookedwhen he had retired for the night,was singing a new dance tune. Ihad not noticed it. I think I musthave caught an American wave,because his accent was not at allEnglish. Could you say whether itwas a New York station ? I shouldso like to know?

P.S.S.-Please reply, as it woulddelight my nephew Tom so much,he made the set, you know.

MISS PRISCILLA PLAYNE-SMYTHE MAKES A

DISCOVERYStewcombe Manor,

Little Bodley,Near Hurdham.

31st May, 1928.DEAR MR. EDITOR,

I feel I cannot await your reply tomy last letter before informing youthat the wireless book you advisedme to read has proved such a dis-appointment. I began to read it in amost hopeful and unprejudiced spirit,but I find its peculiar misuse ofordinary English words makes italmost unintelligible. How does oneoscillate without moving; if " fre-quencies " do not mean oftennesses,what are they, and, finally, does nota grid always leak?

Also this writer takes such anutterly materialistic attitude towardshis subject, leaving out of accountaltogether, the finer, more quintessen-tial aspect, that he leaves me with afeeling of being besmirched. To me,wireless is something transcendentand infinitely precious in its subtleappeal and it does seem such a pityto reduce it to the grosser terms ofmechanics and commerce. -

The writer comes to his subjectwith a perpetually leaking grid in onehand and a soldering bit in the other,and, to me, his attitude is franklytantamount to sacrilege.

Neither is it necessary at all to gointo these crude anatomical details.On the contrary, even quite simplefolk, like myself, can contributesomething, even though we do notswathe ourselves in the debasedtechnical patois which seems to meto be merely a cloak for ignorance.

It is quite a personal little matter,but I could mention-since it is forthe benefit for real, reverent scientificresearch-a small discovery which Imade only the other day with theassistance of Mr. Bonecraft, ourlocal veterinary surgeon, and a mostcharming man, who had called quiteprofessionally, because of some mostalarming symptoms which I hadobserved in one of my cats.

We were partaking of tea afterthe consultation, when he asked me todemonstrate my set (a most hand-some one, built by my nephew lastwinter), as he has one of his own inthe village and he would like tocompare results.

Almost quite immediately, I wasable to attune myself to the wavefrom London and we enjoyed theprogramme for several minutes,though it still consisted of an impas-sioned appeal by some most feverishperson to be told how he looks whilstasleep. In trying to focus anotherwave, I must have moved one of thesmall rings on the lid, for a loudkeening sound proceeded from thebox, only ceasing when I removedone of the wires which convey theinfluence from the electrical battery.

When I re -tied the wire, the wail-oh, such a sad one !-was stillthere and Mr. Bonecraft, who is notonly charming and a widower, butmost accomplished, at once sug-gested that this must be oscillation

Do Not Miss Capt. Round's Article on Page 548493

Wireless Magazine, July, 1928

The Problems of Miss Priscilla Playne-Smythe (Continued)

(but nothing was moving) and heshowed me just how to banish it.

I had observed this phenomenonmany, many, times before, but hadalways thought that at last I hadcaptured a stray wave from someopera house, and, not being veryversed in this modern music, I hadmerely disconnected my set afterwaiting for the end of the act, whichnever seemed to come.

Mr. Bonecraft proceeded to explainthat when my receiver made thisnoise I was, in fact, a little broad-casting station on my own, and hehad often wondered who it could bethat had the enterprise to broadcastat Hurdham. Then a great ideaflashed across my mind; an idea, Iventure to say which could only haveillumined a brain uncluttered withleaking grids and ironmongery.

At once I saw that if I could senda wave, however unmelodious, thenanyone could receive it and listen toit, and if this was so and since Mr.Bonecraft also owns a set (thoughmost unlike mine, he assures me),then all I need do to call him, ifPussy needs him again, is to broad-cast an appeal to him to come tosee her.

He seemed to think the suggestion alittle unprofessional at first, but I soonpersuaded him that I was only actua-ted by a sense of strict duty, andwe agreed upon a simple little code.

All I had to do was to disconnectthe wire and to stroke the left-handtop button with its end, whilsttaking care that the two little ringson the lid were sufficiently close

Kel Keech

together. An experiment made onthe spot resulted in a most encourag-ing succession of ear -piercing squeaks.

So, in future, three low moansand a short squeal were to serve to

inform Mr. Bonecraft (at -any timewhen he might be listening) that hislittle patient was not quite so well,whilst, on the other hand, shouldMr. Bonecraft feel anxious andrequire news, then he was to oscillatesharply twice, to which I shouldreply by one or two shrieks as thecase might be, to indicate an improve-ment or otherwise.

It was almost providential that wehad made this arrangement for thatvery evening pussy was worse, or atleast she appeared so to me, and itwas a great boon to secure Mr. Bone -craft's invaluable advice within afew minutes of my call to him.Unfortunately the complaint wouldappear to be a most complicated one.Since our first experiment we haveextended our little code considerably,but this development of our researchwork can hardly be expected, ofcourse, to interest you!

I have written you at some length,because I am confident that you willlike to know to what useful ends,wireless can be applied, even (orshould I say especially?) by un-bigoted minds.

If the technique of our methods isstill not quite clear to you and youwould like more explicit details oreven a demonstration, I shall indeedbe most happy to supply them.

Yours most truly,(Miss) PRISCILLA PLAYNE-SMYTHE.

Just Pushing the Button !WHEN you come to think of it,

quite a number of the morerecent radio inventions have comeabout simply because most peopleare naturally lazy.

The present vogue of " just pushingthe button," in order to switch ona set has come about because listenerswould sooner push one buttonthan operate an L.T. switch, anH.T. switch, and an aerial -earth

switch.There is yet another " push -the -

button " craze, which has morereason for its existence, namely,the pushing of a selector button foreach station. Push button A, andLondon comes in ; button B brings inDaventry; c, Berlin, and so on.

This is really quite a naturaldevelopment, because for the"uninitiated" tuning -in is still atricky business, and pushing a but-ton is much to be preferred to opera-ting tuning controls.

Without wishing to assume therole of prophet, I think that push -the -button sets of this kind will becomeincreasingly popular, despite thefact that they must be " pre-set " bysomeone experienced in tuning.

There are two ways of solving thepush -the -button -to -tune problem, onemechanical and the other electrical.The simple act of pushing the" Daventry " button, say, may setin action some ingenious clockworkmechanism which will put the dials

494

to the correct position. That is themechanical solution.

Alternatively, the buttons for eachstation may be so connected thattouching one of the controls directlyalters a condenser value and bringsa common circuit into correct tunefor the station it is desired to receive.That is the electrical method, and isreally the simpler of the two.

A simple method of receiving eitherstation A or station B, alternatively,is to have two distinct tuningcircuits, and a D.P.C.O. switch tobring either circuit into action.Several D.P.C.O. switches of the push-button or pull -button type aremarketed.

AERO.

Wireless Magazine. July, 1928

A FOLDING FRAMEAERIALALTHOUGH it is intended specially for use with the

Sidecar Portable, described on page .07 of thisissue, the folding frame aerial illustrated on this page isequally suitable for use with any other receiver if themethod of connecting it to the set is slightly modified.

Cost of Building only a Few ShillingsThe photographs reproduced here show clearly

into what a compact shape the aerial folds when it isdesired to carry it about and the design will undoubt-edly appeal to a very large number of WIRELESSMAGAZINE readers. Moreover the cost of this foldingframe aerial is very low and all the wood can be obtainedfor a shilling or so.

On the leftthe frame isseen foldedready for

carrying

Briefly the aerial consists of four arms, three ofwhich are pivoted at the centre, rigidity beinggiven to the whole device by two circular clampingdiscs as illustrated.

The bottom arm is fixed, while the two side armsfold downwards. The top arm is pivoted so that itfolds at right angles to the clamping discs, passingthrough a slot provided in one of them. When theaerial is erected this top bar is held in position bya wood locking bar, the position of which isclear from the sketch of the complete aerial.

For the Low WavesFor the medium -wavelength

band, that is approximately 25oto 600 metres, eight slots areprovided at each side of eacharm. This will be clear from oneof the detail diagrams. Beforestarting to wind the frame, tie thetwo side arms by means of string to

FOLDING THE FRAME AERIALTo fold theframe thewooden barthat locks thetop arm inpositionmust bereleased

It can be easily adap-ted for use with any

receiver by modi-fying the plug

and socketmount the top

arm (whichshould belocked inposition) sothat they donot slipdownwardswhen the

In use withSidecarPortable

PLUG STRIP

Designed and Builtby the " W.M."

Technical Staff

SLOT FORRIN0C0 FRAME

ARM

FIXED FRAME ARM

num These dia-grams showall the de-tails of con-struction

wire is being put on.Obtain a box of

Lewcos silk -coveredframe aerial wire (thisactually contains Tooft.) and begin windinginside at the bottom ofthe frame, first passingthe wire through ahole to anchor it asshown.

Wind one turn onthe front of the frame

...,6.+7.,..1 6,-rs 4i;APART EACH SIDE10i.1FRAME. NIM5 I

3.5111:1*. k-31: 1174LORDCOVER STR1

WITH SLOT1WIBIOUT

EBOH ITLSTRIP

1.-1114.-Itlip,

PdwUOp

1ZRnrwoas

ARMLOCIVI%

BAR

5q.4

I ARM 510P5 I

axi"Lom2,

and then wind another turn in the corresponding slots atthe back of the frame. When two turns have been thuswound, wind the third turn on the front again and thefourth on the back and so on until eight turns have beenplaced on both back and front of the frame.

For reception on the higher waveband, twenty-fiveslots spaced fin. apart instead of fin. apart should beprovided on each side of the arms. The winding canconsist of the same type of wire.

495

WON

Wireless Magazine. July, 192

Exhilarating speed on the road witha big Harley-Davidson combinationand afterwards the additional plea-sure of listening with the Sidecar

Portable !

Although the loud -speaker and batterycase includes a two -volt accumulator,with such a machine as the electrically -equipped Harley-Davidson it is possibleto run six -volt valves from the lighting

battery

I§IDECAP. PORTABLEFIN USE

7The receiver portion of the Sidecar Portable (describedin detail in the following pages) fits easily into the side-car and does not get in the way of the passenger's legs.The loud -speaker and battery case can be accom-

modated in the rear locker.

in the above photograph the Sidecar Portable is seenin use in the country, while on the right the frame aerialis being folded, and the loud -speaker and battery caseput into the rear locker. The construction of a specialframe aerial is described on the preceding page. Ontest the Sidecar Portable has given extraordinarily goodresults and it will be greatly appreciated by every side-

car enthusiast.

496

Wireless Magazine. July 1928

[demi 1.)aritibleCAN BE ACCOMMODATED INANY STANDARD MACHINE

A Special Five -valuer Designed,Built and Tested by the" Wireless Magazine" Technical

Staff

Comprises TwoAperiodic High -frequency Stages,Detector, Resist-ance -coupled Low -frequency Amplifierand Transformer -coupled Low -frequency Amplifier

OBVIOUSLY the design of a port-able set for the sidecar calls for

special consideration. The essentialsare that the case occupies only aconvenient position and that it can befixed so that it does not rattle aboutwhen the machine is on. the road.The WIRELESS MAGAZINE TechnicalStaff believes that it has solved theproblem in the design of the five-valver described and illustrated inthese pages.

For convenience the whole outfit iscomprised of three separateunits;which are arrang«1 asfollcws :

I. Frame Aer-ial.-This is asimple affair andcan be easily foldedwhen being trans-ported. (A rathermore elaboratefolding frame aer-ial is described inanother article inthis issue.) Nor-mally the frame iswound for recep-

be seen

" She shall have music wherever she goes"

tion on the lower broadcast band,but the receiver covers both bands.If it is desired to receive on the upperbroadcast band, a separate long -waveframe must be wound.

2. Five -valve Receiver.-Theshape of this receiver canfrom the photographs andthe position it occupies inthe sidecar is illustratedabove.

The overall di-mensions are so

On the left is the loud -speaker and battery case, while thereceiver and frame aerial are on the right

497

O

small that the case will not foul thepassenger's legs at all in the normalsidecar. The height to the top of themain tuning dial is 8 in. and the depth71/s in. The coupling for the twohigh -frequency valves is aperiodic(that is, untuned), and covers bothupper and lower broadcast wave-

bands. A single knob in the centreof the top panel controls the

condenser tuning the frameaerial. The other only con-

trols are a small reactioncondenser and an on -off

filament switch.3. Loud -speaker

and BatteryCase.-A separ-ate case which,

tion, either in the nose ofthe sidecar or in the locker

be carried in any posi-tion,

transit, can

usually provided at theback, contains the cone loud-speaker and low-tension, high-tension, and grid -bias batteries.A special cord provided with aplug fits a socket on the receiver

*Wireless Magazine. Ju ly, 1928

COMPONENTS REQUIRED1-Ebonite panel, 12 in. by 4 in.

(Raymond, Will Day, orBecol).

I-Neutralising condenser (Gam-brell or McMichael).

I-.0005-microfarad variable con-denser (Formo 1928 Log orPeerless).

1-Vernier dial (McMichael).i-On-off switch (Deckorem, Lissen,

or Lotus).1-Dual high -frequency coupling

unit (Polar).3-Anti-microphonic valve -holders

(Pye, Lotus, or W. & B.).1-.0003-microfarad fixed condenser

(Lissen, Dubilier, or Graham-Farish).

-.0005-microfarad fixed condenser(Li33en, Dubilier, or Graham-Farish).

1-Resistance-capacity couplingunit (Lissen, Trix, or Car-borundum).

I-.25-megohm grid leak (Lissen,Dubilier, or Ediswan).

I-2-megohm grid leak (Lissen,Dubilier, or Ediswan).

1 -400 -ohm potentiometer, base-board mounting (Lissen orIgranic).

-Low -frequency transformer, 4to 1 (Gecophone, Mullard, orIgranic).

1 -6 -way battery connector(Igranic).

2-Small plugs and sockets (LectroLinx).

1-Cabinet (Ready Radio).4 -2 -ft. lengths Glazite.2 yds. rubber -covered flex (Lewcos).

Loud -speaker and BatteryUait

1-Loud-speaker unit complete withcone and frame (Electron).

2 -6o -volt high-tension batteries(Ever -Ready, Winner or Lis-sen).

2 -9 -volt grid -bias batteries (Ever -Ready or Lissen).

r -2 -volt unspillable accumulator(C.A.V., type 2NSI3).

1-Cabinet with fretted front forloud -speaker (Ready Radio).Ramt qoM

unit and provides all thenecessary battery and loud -speakerconnections.

Useful for Other PurposesFrom the foregoing it will be appre-

ciated that although the SidecarPortable is specially intended for amotor -cycle combination, it can beused for other purposes if a three -unitoutfit is not objected to. (Other quiteself-contained portable receivers ofup-to-date design recently describedin the WIRELESS MAGAZINE are theSunshine Five-May-and theChummy Four-June--the latterbeing the first portable set toincorporate a screened -grid valve.)

The Sidecar Portable (Continued)

The circuit used for the SidecarPortable is similar to that employedin the Sunshine Five, except that thelow -frequency stages incorporate aresistance -capacity coupling and atransformer coupling in place of twotransformer couplings.

The Circuit ExplainedA glance at the circuit diagram will

make the arrangement clear. Theframe aerial is tuned by a .0005-microfarad condenser. The dottedline enclosing that part of the circuitcomprising the two high -frequencyamplifying valves indicates that theparts are made up as one completeunit, which must be bought as it isby the constructor. Values for therespective components cannot begiven in these pages, as the unit is aproprietary article manufactured bythe Polar people.

Leaky -grid rectification is employedfor the detectorvalve, further criti-cal control beingobtained by meansof a potentiometer,to the slider ofwhich one end ofthe grid leak is at-tachcd. The reac-tion condenserconsists of what isvirtually a " neu-tr a lis ing" con-denser.

The resistance -capacity couplingunit for the firstlow -frequencystage is another complete unit, butnote should be made of the fact that

This is thecircuit of theSidecar Port-

able

Gl

-I

am I/t I.0005

498

The controls at the top are the reactioncondenser, main tuning control, andon -off switch. Below are the socket forthe battery cord and the sockets for

the frame aerial

This case contains the cone loud-speaker, high-tension,low-tension and

grid -bias batteries

in the grid circuit of the first low -frequency valve is an extra .25-

megohm leak,which acts as an"H.F. stopper."The final trans -f ormer- coupledstage is arrangedin the ordinaryway.

The points onthe circuit dia-gram marked withfigures in dottedcircles are thosewhich are con-nected to thesocket for the plugattached to the six -way connecting

cord which is provided in the loud-speaker and battery case.

Wireless Magazine. duty, 1928

Extremely Compact Yet Highly EfficientAlthough the construction of the

receiver is very simple indeed and allthe essential particulars are repro-duced in these pages, a large numberof readers will prefer to work froma full-size blueprint. This can beobtained for half-price, that is, 9d.,post free, up to the end of July, if thecoupon on page iii of the cover is used.

Send for Blueprint No. W.M. 83!Ask for blueprint No. W.M.83, and

address your inquiry to BlueprintDept., WIRELESS MAGAZINE, 58/61Fetter Lane, E.C.4. Remittancesshould be made by postal order.

When constructing the set, what isreally the back should be treated asthe base and the part of the cabineton which the battery socket ismounted should be placed uppermost.

H F. COUPLINGUNIT

I sT. H.F.VALVE!OLDER

GRID -LEAKAND

CONDENSER

2 No. H.FVALVE

HOLDER

POTENTIOMETER

BY-PASSCONDENSER

BATTERYSOCKET

can be adjusted.A glance at the

plug on the bat-tery cord willshow that twoleads (blackand green)are broughtto a com-mon point.Disconnectthe greenwire andattach it tothe centreguidingsocket(which hasa solderingtag at-tached) ,

R.C.COUPLINGUNIT

DETECTOR VALVE '25-MEGOHMHOLDER GRID LEAK

TRANSFORMER

1ST L.F.VALVEHOLDER

2 ND. L.F. VALVEHOLDER

Another view of the Sidecar Portable, which clearly shows thedisposition of the components

There is no need here to refer indetail to the positions of the variousparts; they are comparatively few innumber and can easily be recognised,even by the novice, on the blueprintor the reduced reproduction includedin these pages.

Components Connected with FlexIt should be noted that the two

holders for the low -frequency valvesare placed so that the filament tag ofone overlaps the filament tag of theother and is soldered to it, thusobviating one lead. Note also thatthe panel components are connectedto the rest of the set with flexibleleads and that the panel should notbe screwed into position until aftera test has been carried out, sothat the grid -leak potentiometer

as possible,the wiring

Inside view of the Sidecar Portable.Note the special high -frequency coupling unit on the left

this makingthe lead for

4:I L.F. G . B . -(No. 6 onthe circuitdiagram).

When allthe com-ponentshave beenfirml yscrewed in-to position,wiring upcan be start-ed. Firstconnect to-gether withone wire, oras few wires

all those points ondiagram marked a;

then connect all those pointsmarked b; and so on through thealphabet to o.

Battery -cord ConnectionsExplained

As regards the battery cord, notethat point to (No. I on circuit dia-gram) goes to G.B. -2 ; n (No. 2) goesto negative of loud -speaker ; g (No. 3)goes to H.T.+ ; d (No. 4) goes toL.T.-, H.T.-, and G.B.+ ; o (No. 5)goes to L.T.± ; while h (No. 6, centrepoint) goes to G.B.-1.

tackle the construction of theframe aerial. This is very simple, andall the constructional details are indi-cated on the diagram. Ten turns ofthin rubber -covered flex should beprovided. A more elaborate frameaerial, also suitable for the SidecarPortable, is described elsewhere in

VALVES TO USE IN THE SIDECAR PORTABLE

Make.1st H.F. and

Detector. 2nd H.F. 1st L.P. 2nd L.F.

B21oH - B2 IOL B215PCossor ... ... 2IoRC 2 roLF 2 IOLF 22OP

Cosmos ... ... SPI8B - SPISR SPI8REEdiswan ... - DR2 GP2 PV2Marconi . . ... DEH210 HLzio DEL2xo DEP215

Mullard ... ... }MIA PMiHF PMILF PM252

Osram ... ... DEH2 xo FIL2io DEL2D3 DEP215

Six -Sixty ... SS2 1 oRC SS2IoHF SS2xoLF SS23oSP

499

Wireless Magazine. July 1928]

The Sidecar Portable (Continued)

NEUTRALISING CONDENSERUSED FOR 0EACTION CONTROL

ON -OFFSWITCH

.0005-MFD.VARIABLE CONDENSER

Arrangement of the components on the top panel of the SidecarPortable, which must be connected with flexible leads

this issue. For the upperband of wavelengths,thirty-five turns should beprovided.

There is little difficultyabout the assembly of thebattery and loud -speakerbox. The cone loud-speaker is bought asa complete unitmounted in a metalframe, and this canbe easily screwedinto position. Thetwo high-tension batteries are placedone on either side of the case, whilethe 2 -volt accumulator, which is sup-plied with jellied acid and is there-fore quite unspillable, is placed be-tween them. At the top of thecabinet are accommodated the twogrid -bias batteries and the six -waycord when the set is not in use. Thevarious connections are clearly indi-cated in one of the diagrams reproduced on this page.

At one side of the cabinetis provided a small slot,through which the batterycord can be drawn when required.When not needed, it can be pushedback into the cabinet without diffi-culty.

VALVE LEGFOR BATTERYPLUG SUPPORT

Suitable ValvesAs regards valves, these are the

same as required for the SunshineFive. Both the first high -frequencyamplifier and the detector can be ofthe high -impedance type, with animpedance of 6o,000 to 8o,000 ohms.The second high -frequency amplifiershould have a lower impedance, in theneighbourhood of 25,000 ohms. Thefirst low -frequency valve should havean impedance of the order of 15,000

ohms, whilethe final valveshould have aslow an imped-ance as is pos-sible takinginto accountfilament andanode consump-tions; anythingbelow 5, 000 ohmswill be suitable.

To carry outa preliminarytest of the Side -

CENTREONTACT

On the left is a view of the battery andloud -speaker case, while on the right is a

diagram of connections

4BLOT FORBATTERY

CORD

Details of the loud -speaker and battery case

car Portable, insert the necessaryvalves in their holders and plug in asuitable frame aerial (that is, onewound either for the lower or theupper broadcasting bands of wave-lengths). Next insert the plug on thecord from the loud -speaker and bat-tery case into the socket at the lower

500

part of the receiver and pull up theknob of the on -off switch (on theright of the main tuning dial lookingfrom the front of the receiver).

Adjusting the Reaction ControlNext adjust the reaction control

(on the left of the main tuning dial)until the slight rustling or hissingsound is heard from the loud -speakerwhich indicates that the set is on theverge of oscillation. Now turn themain tuning condenser until a stationis picked up, when the grid -leakpotentiometer mounted on the base

of the receiver shouldbe adjusted for maxi-mum sensitivity.

At this stage thevarious battery volt-ages can be read-justed if desired. The

120 V.

more grid bias that isapplied the lower willbe the high-tensioncurrent consumptionand therefore themore economical the

operation of the set.When the set is working satisfac-

torily (and it will do so without agreat deal of special adjustment), thetop panel can be screwed into position.When the receiver is actually beingcarried in the sidecar, it is recom-mended that two small wood blocksbe screwed to the floor to hold thecase against the seat so that it doesnot slip forward.

Great Scope for IngenuityAs the frame aerial is arranged it

is, of course, necessary to take the setout of the sidecar in order to carry

out reception.If this arrangement dces

not appeal to the con-structor, there is greatscope for ingenuity inmounting a frame -aerial

socket on some part of the sidecar, sothat a folding frame can be placed inposition and connected to the receiver

Top panel layout of the SidecarPortable

Wireless Magazine. July 192.1]

A Special Five-valveritself by means of two flexible leads.

With some sidecars, for example, itis possible to arrange a plug -and -jack

FILAMENTSwiTCK

L F.TFLMSEORSTEJ

powER

a

R.0UNIT

(LOUD -SPEAKER-

damage being done. Theother batteries are heldfirmly in position by means

e ULT+

d p. LT-

?.

MT 0

/ KT* KO To 100 V.

BLULPFUNT NsWM 83

SEACTSDNCONDENSER

)1

0000

G

FRAMEAERIAL

CONNECTS)

VALVFunIT

This layout and wiring diagram of the Sidecar Portable can beobtained for half-price, that is, 9d., post free, if the coupon on page

iii of the cover is used by July 31

mount on the sidecar, so that theframe can be swung in any positionwithout difficulty. We shall be inter-ested to hear from constructors ofthis set who invent any special aerialfitting for their own particularmachines.

Foolproof Battery UnitEspecial attention is drawn to the

fact that the loud -speaker and batterycase can be carried in any position,although it should not be subjectedto excessive vibration. The accumu-lator used is filled with jellied acidand can be placed at any angle with-out the slightest chance of any

TWO 9 -VOLTGRID -BIASBATTERIES

COMPLETE CONELOUD -SPEAKER

UNIT

TWO 60 -VOLTHIGH-TENSIONBATTER IES

2 -VOLTACCUMULATO

Arrangement of parts inthe loud -speaker and

battery case

of wooden battens and brackets as shown.It will be realised that this battery and loud-

speaker unit can be used in conjunction withany existingreceiver, ifthe latter isprovidedwith a soc-ket

3/e:

to takethe plugattached tothe six -way

i-r/cord. Alter-natively anordinarysix -waycord pro -vided with spadge tags and wander plugs can beutilised, without altering the connections shown.

Details of11t.

ifIF YOU WANT AREALLY GOODPORTABLE SETOF ORTHODOXDESIGN YOUWILL NOT BEABLE TO BEATTHE CHUMMYFOUR, DESCRIB-

ED IN THE PRE-VIOUS ISSUE

MMMMMMMMMM MMMMMMMMMM MI

501

-4- kraldLOOJE IfillYED 611/1.0

JO//YT Fog

0/J/WYTtl/Y6

IOTUR/Yi RUBBER

OWED FLEA'

//OYES FOR LEODetails of simple frame aerial which can be folded with-out difficulty. One frame is required for each wave-length band (thirty-five turns for the long waves). Amore elaborate type of frame is described on page 495.

Wireless Magazine. July, 19*

Curing Trouble& That Prevent the Crystal From Doing Its Best

IslourCrystalAsGoodAsnalve?VVHEN you listen to the broad-cast programmes on your

crystal set, do you just sit back in aneasy chair, with a smile of content-ment, whilst your headphones re-sound with signals that would docredit. to a one-valver ? Or do you,on the contrary, have to spend mostof the time fiddling with your detec-tor, engrossed in that exasperatingpastime of "searching for a sensi-tive spot" on the crystal?

What Can Be DoneIf the latter describes your experi-

ence of broadcast reception with acrystal receiver, just listen to this(unless, of course, it makes you feeltoo envious).

At the moment of writing, I canhear (faintly, but unmistakably) thesounds of music emitted from a pairof headphones lying on the table sixfeet away. They are connected toa simple crystal circuit tuned to2LO, which is five miles distant frommy aerial.

" Ah," you say, " then you havejust been adjusting the crystaldetector to a nicety."

Not a bit of it. My crystal detec-tor has not been touched at all forten days.

" Well, then," you retort triumph-antly, " you must be using an excep-tionally sensitive permanent detec-tor."

An Ordinary DetectorBut again, emphatically no ! The

detector in my set is just an ordinaryone, of the glass -enclosed type,containing a really sensitive crystal(one of the many good makes nowon the market), used in conjunctionwith a catwhisker made of finecopper wire.

This detector almost invariablyremains in good adjustment for .tweek or more at a stretch; it is unaf-fected by an ordinary amount ofvibration, and when at last it doesneed readjustment, a fresh sensitivespot can always be found in a matterof seconds. Nevertheless, there isnothing really exceptional about this;it merely does what any efficient

This Crystal Set ina nutshell is the workof an ingenious Ger-

man amateur

type of crystal detector can be madeto do.

The principal explanation of thosetroubles which give rise to the impres-