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PERCY W HARRIS M I R E VOL. VI. OCTOBER, 1928. No. 24. EIkLDE!Ehi©n $E'

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CONTENT

- Page rag Editor's Chat . 359 Radioramophonic3 ... .. 393 .. 361 Within This Year At Olympia .. ., the Vacuum. . 399 .1 A " Stedipórer" Development .. 371 Why Not Read Morse .. .. 403 Make Your choice at the Wireless Baird's Television Apparatn .. 401 372 Exhibition ...... Happenings at Savoy lull .. 411

The "Radiano" Wiriug SIstem.. .. 376 - Comments From Coastruar 415

.. .. . - 377 The "Radiano" Four What's New - . 419 Building the "Radiano" Four .. 381 in Light& Vein .. 423

387 . Telephotography and Televisioa .. Queer Queries - .. 427 The Super-Regenerator on Shore Waves 389 Our News Bulletin ...... 428 i AI- nr 1L ____t. iIJIir tIIIIIijff -t L- 11111 illIIiiuuuiuuiiui 4 lIplIlIllIll d IlIlIllIllíli 'IlIjillIll IiIIiiìIIÍIII I ijilliN 0011 111111 L i I

Advance Details for 1928-1929. Fil - .6sstLifss. S'lt. .(1ssarlej fasta'- ype r.'.ti' I'ott AnISO. Valls 41,sssrr t"flttor Most valves of the present Marconi range will remain standard, but owing to certain developments the General Purpoll Valves characteristics have been - improved as shown in the table DEL 210 10,0 - 0.1 10.) - 12.000 15 10)1 on right:- sOL 210 *0 0.1 135 01)80 .I toic DEL 410 4.0 0,1 170 0l05) 11 10/0 I)El., 4110, 0.0 0.1 170 7,570 15 10/6 ) New Types of MARCONI VALVES I High - Which will be introduced during next Season. Resistance Capacity Coupling and Frequency Amplitying and Reetiiyin Valves Type Description Imia Mag. Price DEH 210 11.0 0.1 120 70,000 77 10/0 ¿ j' DER 410 4.0 0,1 100 66,600 30 10/6 P.403 3v. Super Power-Valve 4.0 0.00 1044 ClIC 4, 10/-' LS' 511 0.17-5.27 0.54 4410 2*000 105 25/. 180 1,600 7,s' P.3A Os'. Ser1'oweeVslre 6.0 0.22 15/. DER 610 (iO 5,1 130 60,460) '40 10/6 440 0,27 '0 0,-100 6.0 170 054 pos:, 15/. 11E OB 5-0 , (0.13 34,070 12/0

General l'sOPoSo Os. Foweg Amp1ifyin Valves 1.00 04,000 10 Volve 6,0 0.1 10/6 0,13 130 0,000 00.08 AC. 1)ireetl Heated DEP 017 2.0 7 17/a DEP 2441 0.0 0.1 1113 . 0,700 4 15/- Cathode uve for 130 - .5,000 DEI' 410 4,0 . 0.1 7,5 12/6 OI Reo, (Isp. Coupling 1 4,0.1-0,00 0.54 300 '5,5100 - r, 75!- 30 1.8 or . 0.6 0,0 150 0.5,060 15/- -(4)0 HF...' 130 SA - 4,55--7i,53 '044 75O 25/. AC. HL.0ß 1)ireeLy Heated 11E 5 5.6 Oso 13.0 7005 7' 12/6 Cathode Volve. IA 541 (020 170 4400 :1,5 '15/. 17 I)E - General Pssrpoee -. 0.6 04 73. 17.000 1 15/. 6.0 130 7000 .- 8 r' P0,0 AC, DIreet1, fleatesi TIEl' (110 0.1 12/0 Cathode aire fo,- Grid VSIV2 51.0 creensi - 0.8 0.6 150 6,000 11/6 si )3'3 1,0 (OilS Ills) 17(003.3 110) liT/a 0.0.8 AC. Direetly Heated I I j Cathode Valve stilli

Ses'eenesl Grist - - 0.0 0.8 10.4 .100,000 lilO 217. indi:ectly Heate'J Cathode Valv7s iv. 0,215 Sereessest Grist KL I 11.7 8,0 150 0.730 7.) I 11/6 .. ' 0.17 ISO 44)0,000 150 22/6 Valve yo EH I 1.3 2,0 130 711,460) 4) 112/. PT PenIsole Valse .. 5.11 0.0.' 130 0.1,000 1.5 22/- THE MARCONIPHONE CO., LTD., 210-212, Tottenhain Coii't 1oad, WÂ rrca S

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: the Wonderful. . : ' . IíIi See

. . B.T.HØ Display 'n . j: .' STANDS 86 eIQi ,

-rh. On these stands you will find the greatest

. . gt4 aggregation oínewandintrestingapparatus . : . the Exhibition. There are new moving- - coil devices, including an R.K. Amplifier !I . . t'I1 ji'4"Hi vith or without loud speaker unit, Junior R.K. Loud Speakers, .R.K. Unit, R.K. II ra . Mains Unit, etc. 'i N d FIIfL ' Taere are new receivers o sped and peculiar merit, a gramophone pick-up and l ,& -. ri !f Lj amplifier, the new B.T.H. Cone Loud . . and, most important of all the corn- I Speaker, ;J Li iJI . j . . M pleterangeof Mazda Nickel Filament Valves. AI1ilII 'i! . ' 17

1 O :. 'i You must not,on any account, fail to vkit B.T.EI. Stands. : ., the I

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Octoh3r, 928 ziE W IRELESS 4ONSTRUCTOR

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V, -''"/' - Below are given the titles of the new apparatus. Make a point of seeing and asking about these wonderful ,instrume1ts.

1. Bijou Crystal Receiver. The Complete Range 2. Two Stage Receiver. óf MAZDA NICKEL 3. Three Stage Receiver. FILAMENT VALVES 4. Four Stage Receiver. 5. Five Stage De Luxe Receiver. ,1ax. Ampi. 6. Portable Receiver. TYPO 1°P- Sia Il.Tvoltt Factor (ohms) 7. Cone Loud Speaker. TWO VOLTS 8. R.K. MovingCoil Loud speaker Unit. ci'. zio 13 14,030 OEcO 9. Junior RK. Loud Speaker (A.C. & D.C. models). HF. 210 150 za 2S, 0.70 lO. Senior RK. Loud Speaker. RC. 210 150 40 so,coo 0.47 11. 5 m.a. HT. Battery Eliminator. L.F. 215 120 7 7,000 1.00 12. IO HT. Pattery Eliminator. ma. P. 227 120 4 2,) 1.40 13. RK. HT. Battery Eliminator (AC. & D.0 FOUR models). -VOLTS GP. 407 120 14 14. Pick-up Amplifier, Scratch Filter &Volume Control 14,000 1.00 H.F. 407 150 18 21,000 085 15. RK. Amplifier (without R.K. unit.) R.C. 407 155 40 i0'.000 0.4) 16. Pick-up and Tone Arm. L.F. 407 120 8 5,7(Y) 1.40 17. Constructor's Kit. - P. 415 120 5.5 2,9(1) 1.90 IS. Two Stage Unit, - SIX VOLTS' 19. Variable Condensers . 20. Flexible Aerial Unit. G.?. 607 120 14 12,500 1.10 HF. 607 150 21.- Trickle Charger. 20 20,00) 1.00 RC. 607 150 22. Two Stage Valve. 40 90.000 0.45 L.F. 607 120 9 5,300 1.70 23. Screen Grid Valve. - . .' P. 615 120 6 2,600 2.30 P_x. 650 2(3) 3.5 1,750 2.00

I 'J he p',eftx letterti,, ¿fat the pur.' oto of a t'al,',, and tho figureo J u-hal, ft//ow, the fi/avu-nt vo.',: and ampere:. For / example e-LP, zi; reptesent: a 2.z'o.'t low frequency mrlijyh valve ta/mg o i atotf -re.

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I : V k rhiiil;t't, ¡'lic, H &, &,J ._ _' v w 4 . \:" ANY manufacturers of the finest receiving.sets and eliminators . ' . 1% II ; use Electrad Resistance Contro's. Scores of radio engineers IVI and technicians specify them exclusively. Only controls of i. 2 perfected designs, proven performance and dependability could enjoy I' such universal endorsement. Electrad specializes in a full line of resistance controls foi all radio

' - purposes. Dealers everywhere sell them. I

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Truvolt A1Ï-Wire Resistances : The unique; air-cooled construction of Truvolts makes for unusual ;::: accuracy and permits the carrying of heavy current loads with a high

. . factor of safety. . Truvolt Variables simplify H.T. Eliminator construction by eliminating difficult calculation and making all adjustments easy. Twenty-two

.' ' stock types. 15/6 each. . . t . ,ç Truvolt Fixed resistors are adjustable to different set values by the , use of sliding clip taps-an exclusive Truvolt feature I Made in all .

' ¿ , resistance values and circuit ratings. . . ç desirable

' TRUVOLT Variable High Resistances ' ' t Royah:y ..' - Here is a Variable High Resistance that is entirely free from harmful ,, : . inductance and capacity effects. It is widely recomménded wherever a unit of this type is required in the circuit. Eleven types covering a range for every purpose. 8/- each. Potentiometers 9/- each.

: ' TONATROL . .' Perfect control of volume to adaptyour receptionto the occasion and individual taste is necessary for the full enjoyment of your radio. - Tonatrol Volume Controls at-e designed in types to meet the specific -' needs of all circuits-A.C. or conventional battery type. Furnished in standard types or with filament switch or power switch attached. 8,'- to i 5/6 each. : , ROYALTY AEXAflLE RESISTANCES T e

, , ' . ' Please send me descriptive folder on all Electrad products and

. put me on your mailing list for similar literature ' % ' , : ' ., , - I ...... D am particularly interested in '

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Address......

: Represented by The " j

ROTHERMEL CORPORATION, LTD., ,

24-26, Maddox Street, London, W.1. .

Pfon,, Mayjcj 0578-9. 4286. Tc!,'5,am- Ro1hcmcI," Wcsd0. London. i s - - - - - ' , ---

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r Radio's first Loudspeaker Iw . ::. --' 4 -still the finest \ - S'- r I - - - -=------The moving coil type of loud-speaker was created by Magnavox in f1 - Iú,, '9". It is the only type of speaker that has stood through every period of speaker development. Supreme in the beginning-supreme '«««P l;kd to-day. Protected and controlled by Magnavox exclusive patent& . t . i4/I There are nearly half-a-million Magnavox Dynamic Speakers now in Í,, - use 7 r_____

Realism- . - ; : ' ì ' You can hear the bowing of the strings of the double bass and the - Ø beats of the drum in their true tone-colour with a MAGNAVOX - MOVING COIL LOUD-SPEAKER UNIT.

- - ; There are no jarring resonances, no " s " sounds missing, and the - f , I violin does not sound like a flute. The unit is complete with input transfc.rmer, leads and field switch, ready for connecting right away to receiver or gramophone amplifier. R.4 ,

O . 1#'A4 Models for AC, or D.0 - '1; -- . .4, ,

. , I TYPE D.8o/x. For operation from AC. lighting mains, -ioo/izo Ø 1 .e/ volt, 50/60 cycle, A.0 ...... xx ix o 4 TYPE D.8o/2. For operation from A.C. lihting mains, 200/240 , e- volt, 50/60 cycle, A.0 ...... L" i' o . ' TYPE R.5. For operation from D.C. lighting mains, zoo 240 volt " . . D.0 ...... xo Io O . .

TYPE R.4. - For operation from 6-volt accumulator or Trièkle , ' - Charger. Consumption amp so o ;; ...... Ç \.. - ( TYPE M.7K. Balanced armature unit £3 2 6 . - . . flh , ...... n.m . z /, , )z New Belvedere Fire Screen Baffle ...... £4 O O /

r' ; . ,. ;;ç "THE GREAT VOICE" -"-.' I 7 4 V " The Great Voice " is a 32_page booklet, profusely illústrated and - . . p written entirely in your interests with a view to enabling you to ' . - . obtain those better results for which you have persistently longed. ; ' 9c, This tooklet tells you all about moving-coil speakers, baffles, power ,' - - . M amplifiers for AC. Or D.C. volume controls and gramophone pick-ups. / - , Send for your copy to-day. Price 6d., post free. , , ,

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1 and get

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k $f 'Melod F \ ¶ Mak«r" \\

kC0w 't: of invaluable and interesting information.' Eén if you don't oin a Cossor "Melo(ly Maker' you will find this (.ossor Pubhc.ition exceedingly useful for the information and instructions it contains can also be applied to any type of Receiver. lt is fully illustrated-il teIle you how to bring in those distant stations with case and certainity

- : -how to get greater volume-how to look after your - - accumulators and I)aileries- it is chock full of hinté and tipe that will enable you to improve your reception enormously. -

IRIS CO - - No matter whether you own a "Melody Maker" or not- .v4send for your copy to.day-i's frei.

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Published by the Amalgamated Press, Fleetway House, Farringdon Street, E.C.4. THE EDITOR'S CHAT lu which Mr. Percy W. Harris, M.I.R.E., discusses the prospects oF a record Wireless Exhibitkr attendance, and also the receivers which are described in this issue.

F I can read the signs correctly, If now the reader takes this issue circuit, with a second and third .11 the National Radio Exhibition with him to the Wireless Exhibition, choice if need be. at Olympia this year will draw he can pick a circuit to suit his general In this way he will carry home with record attendances, which will be needs and jot down in the spaces him not a confused idea of the fully justified by interest of the provided his opinion of the best exhibitin, but certain definite exhibits. Radio has now passed components for the particular pur- opinions on which are the best coni- beyond the scientific curiosity stage, pose. By carefully examining the ponent.s to make a good all-round set. freak receivers are becoming thingß various exhibits he can build up in It is not intended that he should the past and the ever-insistent his own mind what lie considers the necessarily build any one of these cemand for quality is being excel- best modern interpretation of that circuits, the idea being rather that h ntly met on every side. Simplicity o control, high quality of repro- dutiòn, and a pleasing appearance, together with reasonable cost, are the features which the public ask to be provided, and it will be most interesting to see how far the manufac- turera have progressed towards this ideal. A Helpful Feature Several new loud speakers arc to be shown, and at last the public itself will have an opportunity of judging the much boomed subject of television. A big all-round improvement in the quality of components for ..-"..- the home constructor will be found, and in many directions the enthusiast will find so- many good things that

he will be embarrassed in making il

a choice. - 2 \Tisjts to any exhibition without a definite aim are apt to result in confusions of ideas, so that with the object of providing not only a helpful guido but an interesting series of notes for consideration at home, we are publishing in this issue four large circuit diagramcof well-tested circuits, and on opposite pages the names of the components without any indica- I One of the experhnentut lan1s huving short-wave trunsìniltcis boari under going tion of iiakers, leaving three columns tefs at the t3'chvieh eaperimental station. The steel aast ts the only ¿ieriOl nscel, 1

for first, second and third choices. J no wires (icing employed. - 1 39 -

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PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE W1RELES CONSTRUCTOR October, 1928 P.S-I might mention that I hava not missed an issue of the CoN- STRUCTO since the first number, or Readers' Results of " Modern Wireless " since the To Amcrica audRach Again 5'-hiiproriug the Single- Volver- Elstree Six" and also have all The " Straiqhit-Liue '' Four. ; numbers of " Popular Wirelcss " for the past two and a half years.. To America and Back Again! "Improving the Single.Valver" The "Straight-Line" Four SIR,-It may be of interest to Sin,-In the February issue of you and readers of your valuable the CONSTRUCTOn, Mr. L. H. Thomas Suu,-Congratulations on this re- book, the WIRELESS CoNsmucvon, described a set under tue heading ceiver. I made this up, and hìave got to hear the results I am getting with of " Improving the Single-lTalver." wonderful results. Its purity and the " Short-Wave Three." I built Having a Collinson split-primary trans- volume on foreign stations is remark- the "Radiano Short-Wave Two," former lying idle, I hooked-up the able. I tuned-in fifteen stations and was so delighted with it that circuit, using two Orniond S.L.F.'s at full Ibud-speaker strength the I have converted i' into the "S.W.3." as specified, nd a Cosmos choke. The first evening, and on Sunday morning Up.to the present I have had 2 X A F, valve holders are not anti-microphonic, got three stations all at Daventry 2 X AD, K D K A (62 m. and 26 m.), but with the addition of a Formo strength. P C J J, two German expriineutal 5-1 shrouded transformer I get Milan came in as loud as 5 X X; stations on 43 m. and 39 in., Radio excellent loud-speaker results on every word was distinct.. (I under- LL, and Radio Vitus, all on loud London and 5 G B, fair from Dublin, stand Italian and French.) speaker about 70 British, 10 French, Stuttgart, Frankfurt, Hamburg, Tou- -Aerial, 100 ft. from receiver, top and 8 Belgian amateurs on 'phones. 'ouse, Langenberg, and numerous end 40 ft. high. Last night, however, provided the others on the 'phones, including There was a four weeks' wait to best treat I have had on short waves. Cardiff, Bournemouth, and Edinburgh. get the nècessary components and I heard 2 X A F re-broadcast 5 S W As I am a keen short-wavite, I Leadex wire unattainable, but I used (Chelnisford) for 20 minutes. made a six-pin former, using a 18-gauge lead-covered wire. Another Fading was quite absent o 32 in., Becol 3-in, former with three turns point :-Is it really necessary to bond but was fairly bad on 24 m. However, prim., four turns sec., and four turns all the lead covering and stop up any word of the announce- react. 0005 across sec. I heard every ; holes in boxes free or where the after received 5 S W, 2 A ments from the. Savoy Hotel I have X F, lead wires enter ? it had crossed the Atlantic in both 2XAD, sud KDKA on 60 m., In my opinion, this is the best set rections (covering about 6,600 miles). and also on 26 m. (approx.), 2 N M you have ever designed, - The American announcer seemed and 2 M E (Melbourne). Of course, and renders ob solete all neutialising -very pleased at the success of the ex- there aie many amateurs using Moie. schemes. . neriment. but he was not half so pleased The Australian station was heard as I was; for the strength of X A F last Sunday, but the others are regular Wishing you every success. was so great that his programme could fish. Last evening I had both stations of . Yours truly, be comfortably followed in the icxt K D K A and 2 X AD, the latter strong R. NOBILE. room with the connecting door closed, enough to be heard on the speaker. Swindon Thanking you for the many fine The detector valve was a Mullard - articles which have appeared in P.M.3, 54 volts H.T. I S. the CONSTRUCTOR, of which I have Wishing the CoNsTRucToR and P.S.-What about a short-wave beeh a constant reader since No. 1. Mr. Thomas continued success, screened-grid set l - ' - . I remain, yours faithfully, Yours truly, [* Not absolutely necessary ecept BERNARD E. GILLETT. - F. C. SMITH. when using a frame aerial.

Harborne, Birmingham. Tooting, S.W.17. - -EDIToR J

The "Radino" Four, which makes scheine, obviating the changing of its first appearance in this issue, THE EDITOR'S CHAT is coils, will be described by Mr. G. P. presented to the wireless public with Kelsey next month, while the short- -GOflhi7iUCd from page 39 full confidence that it will meet their wave enthusiast will find Mr. Thomas's requirements as a good all-round and promised article on the super-re- easily-built four-valver. The extreme generator on short waves a most t when he does decide to build a set he simplicity of building a" Radiano" set fascinating contribution. has been further improved by can consult his notes, which will the May we take this opportunity of introduction of remind him that so-and-so's variable the new "R&liano" asking readers who visit the Wireless wiring condenser looks extremely well on system, while the novel wave- Exhibition to let us have their change the front of the panel, while the small arrangement, using the views upon it, particularly regard- space occupied by the "this-and- standard plug-in coils, makes it ing which features appeal to them unnecessary that " model makes it particularly to lilt the lid, and adds most, what they think could be suitable in a compact design. Members very considerably to the flexibility improved in future exhibitions, of wireless societies will find that a of the receiver. and what they missed or felt very interesting evening can be disappointed in not seeing. A selec- spent in comparing their respective- Readers Views Requested tion from the correspondence will notes and, in fact, competitions can Another useful and very practical then be publisher in a future

easily be arranged on these lines, set with an automatic wave-change issue. -

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Ii i t' i t I ¿Ç!:!!!L I 1L1 TTh J r THIS YEAR AT LYMPIA - A sn,nhienry of Ihe nein enhibits fo be seen ut Ih IFiree.s. E.shibUion, eoIn,nnevsg Sepie,»br 22t.

Atalanta, LW. Stand No. 271. Beuing & Lee, Ltd. Stands Nos. 220 and Brandes, Ltd. Stand No. 118. Being specialists in small pre- 221. Matched-tone headphones, loud cision tools, screwdrivers, etc., this Here will b found in profusion speakers, three- and four-valve sets, firm will be showing several tools the indicating terminals which havé transformers, condensers. accuinu- and gadgets particularly designed for made this firm so famous. In order lators and high-tension batteries form wireless assembly and djustment. to meet the requirements of the latest the main exhibits on this stand. A A special line of box spanners and developments in radio, terminals are special hire-purchase scheme run by screwdrivers will be shown, and, in now made with new indications, such this firm enables any of the products addition, there is the "Atalanta" as ' Pick-up," " Field," " Mains +," to the value of five pounds or over " Mains -," etc. to be purchased out of income. Constructors who in the past have Early ne:-:t season the firm ;iil be coveted such terminals, but thought adding to the range. . them too high in price, will be delighted with the sweeping price British Ebonite Co., No. 38. reductions which have been made; Ltd. Stand the large 9d. terminals being now Here is a display of ebonite which will not only delight - °'JitLIER only Gd., the Gd. being reduced to the prospective COUPLING,1 4d., while those formerly issued at constructor, but would please any T 3d. are now 3d. only. goldarn nigger by the sheer black beauty of it Panels of all sizes and It IIItI IIIItlIItIIIItIIIlIIII lit UIt tillO Be sure to visit the

EI- VRE[SS CONSTRUCTOR

In« LflIOILlCr -- At.t#.d. - Urli. IS Jt(tfl$ Our Stands are Nos. 135 & 166, with detachable resistances. and technical expelts will be in attend- E E ance to talk over matters of radio E constructor's set of tools. This very E interest with our readers- E comprises two screw- handy outfit IItIlIIItllIlIlIlIItIIlIIltIIIlIlIlIIIlIIIIlIIIiIlIIlltlI!IliIIItiIlIli drivers, three box spanners for 2, 4, and 6 BA. nuts, one soldering iron George Bowerman, Ltd. Stand No. 213. and flux, one small hammer, three An amazingly efficient and cheap files, two pairs of pliers, scriber, and little cone unit is the chief attraction centre-punch. The complete set, on this stand, all built with parts together with the rack for mounting, which cannot possibly come loose as costs 12s. 6d. is often found with other types of cone unit, and this little accessory should A. Baker, Ltd. Stand No. 172. find a very ready sale. A companion The Larnph.gh "Epieyclic Visoi' " con- This firm is showing a variety of also will be found on the stand in the denser, which is made of alunti,iiu,n moving-coil speaker units, selling form of an All-British headphone, to will, specially shaped plates. from £3 lOs, upwards. Readers of be sold at 12s. 6d. per pair. Each the WIRELESS CONSTRUCTOR who are pair is guaranteed and is extremely shapes, good to loo1 at and guar- interested aìil are in search of good light to wear and comfortable, while anteed, are here in large variety. For quality should certainly pay a visit to the magiets are of the finest copper the man who makes his owñ coils this stand. steel. - there are the " Becol " low-loss n 3uI

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T This Year at Olympia-continued

formers-a large raugç of sizes, too markabiy low for a set of this kind, Other special Burne-Jones features It is interesting to note that No. 5 is and is £5 15s. Od. without valves, which will attract the eye of the the originai former which was in- batteries or royalties. In addition to music-lover are the new 1929 model corporated in the set which took thn these new lines, of course, the well- gramophone pick-up, the moving- gold medal at the Antwerp Exhibi- known Brownie crystal sets, etc., coil loud-speaker outfit, and the push- tion. Another Becol line of special will be seen. pull power amplifier. The pick-up is 4s. contact-former and can be used on any gramophone in merit the 6d. A. F. Bulgin & Co., Ltd. Stands Nos. 203 base, made in such a way that it is and 204. place of the usual sound-box. impossible to make a false connection, In addition to a large range of There are three models of the when onco the coils have been wound. push-pull switches, indicators, am- thoving-coil speaker outfit, at different prices, all incorporating the B.T.H. Brown Bros., Ltd. Stands Nos. 177 and 178. meters, mill iàmmeters, panel brackets, chokes, etc., a large number of new Rice-Kellogg unit. The push-pull Crystals, vilves, amplifiers, L.T. power amplifier will be of especial accumulators, H .T. accumulators, lines will be on view for the first time on the 22nd. interest to the man who is limited charging apparatus, coils, chokes, to about 1W volts H.T., and may condensers, resistance-coupling units, be employed with anything from a grid-bias batteries, I-1.T. batteries, crystal set to a gramophone pick-up. loud speakers, and all sorts of radio components are to be found on this The Camden Engineering Co., Ltd. Stand famous wholesalers' stand. A par- No. 152. ticularly comprehensive range of loud The Camden Engineering Co. are speakers will be shown, all types be- the makers of the well-known ing represented, including the new Centroici " wireless products, which I moving-coil types. include variable condensers, slow- motion dials, fixed resistors, and The ERCO 3-valve ,»ajns-diive rvccivev, Brownie Wireiess, Ltd. Stand No. 104. six-pin This a special (E.K. Cole, Ltd.) - coils. year The chief exhibit on this stand feature is being made of copper and will be the popular Brownie Domi- These include a junior pattern aluminiuni screning, so if Tou are nion Beceiver, being an all-wave wall jack, central zero charge and building a set embodying screening model, covering wave-lengths from discharge ammeter for panel-mount- boxes or sheets look out for Stand 200 to 2,000 metres and operated ing, a filament tester, a small signal 52. by a single selector switch, so that lamp, a baseboard-mounting on- The Cantophone Wireless Co., Ltd. Stami coil changing is completely obviated. and-off switch, a baseboard-mounting No. 253. and an The set is highly selective simple short-circuit switch, and an This stand contains an interesting automatic station log which works array of complete recQivers, including on the roller-blind principle. Of the Cantophone portable receiver, i these, the filament tester should be which is a two-valve set capable of a a most handy instrument, consisting y, ' range of 100 miles on 5G B without T as it does of a device for instantly finding out whether the filament of a valve is intact or not, by simply plugging the instrument into the valve holder. At the price of 2s.. Gd. this should have a ready sale. H Burne-Jones & Co., Ltd. Stand No. 96. All the " Magnum " products will be on view here, including the HF. chokes, wire-wound R.C. units, volume controls, fixed condensers, calibratèd A rheostats, wave-traps, etc., that have won their way into so many sets and hearts, No constructor will be able to reist this display, rich in exactly the kind of gadgets that he wants L illu . to use. !l'Iie Eili.a,an sereene4t grid two-voller, Of especial interest to WLRELESS A new IJ'csti,,gl.oiise neIal rectifier, (teJt, Ernd the PU. tilo G-Eolt poirer valve. capable of a D.C. output of i ampere. CONSTRUCTOR readers is the "Road- additional and secondary aerial ter- side " Four portable receiver, as de- an aerial or earth. There is also a - minal has been introduced so that an scribed in the May, 1928, issue of most interesting innovation in the extra degree of selectivity may be this journal. Entirely self-contained form of a combined gramophone and obtained by those who live very near and so simple a child can operate it, wireless receiver which tnkes the form to the coast a.nd are troub!ed by this receiver, including four valves, of a five-valve wireless set, with a Morse, or those who live very near must be considered a great bargain simple throw-over switch which en- to a main station. The price is reat £17. ables electrical reproduction of th - 3&2

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Ths Year at Qlyiñpia-continued

granlophone to be en6yed, the whole Clarke & Co. (Manchester), Ltd. Stand exhibits of the show. The Cliftophone outfit being operated from the elec- No. 161. Pelican four-valve transportable set Before referring to the niains units tric-light mains. The cabinet, which is also to be on show, price £22 lOs. Od.; which are a feature of this is of the stand variety, includes an special and this also is fitted with the display, mention must be made of electrical-operated gramophone as special type of cone loud speaker. those old, firm well as the wireless set and pick-up. favourites, the Atlas It perates direct from the electric- coils. Complete ranges of several light socket on altèrnating current, - OHe ej the "Dina- types are on show, including centre- and is au entirely new departure in la a »1 " receiveis. tapped eoils, "X" or double-tapped (SI«d2Iir.) type of set. - coils, and the new short-wave coil ls which covers a wave-length from Climax Radio Electric, Ltd. Stand No. 80. 15 to 100 metres. The Climax radio productions are Another very interesting feature mostly of the modest kind that do not of this stand is the insulating ma- call for a steep purse. Here will he terials, in such profusion that the found earths, low-loss insulators, uninitiated are apt to be staggered shock absorhrs, lightning arresters, by the insulating sheets, washers, folding frame aeriais, and similar plates, clothi, silks, papers, mouIdins, gadgets of endless utility to the

tubes, sleevès, and so forth, - listenet'. The remarkable interest in The di.play of mains uñit8 Ebòth f of reception from the mains is well AC. and D.C. mains) i so illustrated again at this stall, where No batteries or accumulators are hensive that, no matter what the the display includes H,T. units for required, the whole thing operating reader's requirements in the way of AO. or D.C., grid-bias units, trickle straight from the electric-light switch. current or voltage may be, he is sure chargers, Auto-Bat transformers, One or two loud speakers can be used potential dividers, and several chokes as desired, in addition to the loud of the special types required by the speaker provided in the cabinet, I arduous' conditions of moderii high- which lòud speaker is of the horn1es quality reception from the electric- p- type: Included also in the cabinet is light system. A new model of the a case for 42 records, while an auto- Climax portable receiver is also Ga. matic repeating device for the record show, and altogether this display is will make special appeal to those one to linger over. of of fond dance music. The price E. K. Cole, Ltd. Stands Nos. 48, 49, and 50. the complete outfit (in walnut) is 95 As specialists in this class of guineas. instrument, the E. K. Cole display 19 Celestion Radio Co., Ltd. Stands Nos. has always been a of of and 20. sort Mecca the " mains man." Every wireless Celestion loud speakers need no requirement of the man who has introduction to the wireless public. This D.4bilier Fille, ¿tul is filled wii! electric light laid on is catered for, many models, ranging in «u e«rfhiuug tei',uival. There are from powerful mains-drive receivers price from £5 lOs. to £25, all good! down to the components, such as listeners are aware of the to find his needs are catered for. Most wire-wound resistances, etc. for sensitivity, Especial interest attaches to some of Cèlestion reputation One entirely new component is it will be a surprise many the AC. models which incorporate but to an " isolating" transformer which to iow that in the large model shown the Westinghouse dry rectifier. on this stand the diaphragm diameter Messrs. Cliftophone & Records, Ltd. Stanû is no less than 24 inches! And the No. 176. -instrument is fitted with an ingenious The chief exhibit on this stand is compensating device to preserve its the new Cliftophone armature loud adjustment and mechanical rigidity speaker, which has been evolved I wider all conditions. after a number of years experimental The popularity of pick-ups for work, and which is claimed to have the gramophone is demonstrated on a number of advantages over other this stand, where the elestion Wood- instruments which have hitherto rofTc type of instrument is shown. been considered very good. It is of With a view to redqcing the wear the cone type, the cone beil)g of on records to an absolute minimum, special material and not reinforced. great attention has been paid in this Reinforcement is stated to be un- model to the factor of lighthess, and necessary as iio amount of power will special damping arrangements are distort the paper. Wonderful am- incorporated. Music lovers who have plification properties, owing to the a train to catch are warned that if peculiar shape. of the cone, are claimed for this 1Od speaker, and it should they visit the Celestion stand they example of orn«,,icnß«I Io4- cre !ibIo to miss it! certainly form one cf the interesting speokev design (MJ'.A. tVire1e). -

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This Year at Olympia-continued

completely disconnects the loud the constructor will no doubt find C. S. Dunham. Stand No. 257. speaker or 'phones from a st 'with a Stand 235 extremely instructive. Complete receivers area strong suit power supply unit in use, thus at this store, ranging from " Simpb- obviating all danger from shock when The Dionoid Battery Co., Ltd. Stand city " two- ot three-valve sets (which accidental breakage anywhere in the No. 245. are operated by turning one dial only) installation occurs. All sorts of interesting things are to three- and four-valve sets which Constructors whose bank balances to be seen on this stand, where the can, if so desired, be adapted to wor1 (both are a bit anmic will be interested display includes accumulators L.T. and U.T. types), a series of hydrometers, and other interesting gadgets. A useful 1s. Gd.. worth is to be obtained here in the form of a tube of corrosive cure, which consists of a special paste for covering terminals. As the makers state, there are more volts, lost by bad terminal. contact than _are generally recognised. The cörrosive cure protects the terminals from acid, and is sup-. plied in a handy tube, like toothpaste. t The composition itself is stated to be t of a good character, and its presence merely acts as a film on the terminais, The B.TJI. J1.C.C. mit comprises also valve holder. irnil ConhleHsePs and in no way impairs the conduc- sprnRg The One of the popular .Iiayanond can be had in a variety of resistance which sells for (i/Il (OOO ,nfd.). tivit.y of the accumulator. values. in the hire-pnrehizse scheme in- off the electriclight mains. Apart The Dubilier Condenser Co. (1925), LId, augurated by this firm. Full details Stands Nos. 102 and 103. from the complete set there is much of t.his are available upon application. Such a bewildering display of to interest the constructor, including condensers is to be seen here that we mains units of several types and the Thos. re La Rue & Co., Ltd. Stand Tuner, spécially 235G. shall have to "condense" our remarks Dunham All-Wave designed to simplify home construc- picture wireless as a sort upon the various types. Not long ago Those who tion. hobby will get a bit of the word " Dubilier" conjured up of a side-line For the purchaser who desires to an eye-opener at this stall, where there "fixed condensers" to the constructor, experiment in long-wave reception is a comprehensive display of the and very little else. But nowadays without going to the expense of a bakelite fireproof and plastic mould- this firm has branched out not only powerful long-wave set, the compre- inge used in varions branches of the into variable condensers as well, but hensive wave-length r?nge of from radio business. Modern multi-way into a comprehensive range of com- 150 to 2,000 metres (covered in even of manufacture have been ponents including ll.F; chokes, grid methods the simplest two- or sets) applied, and many thousands of leaks, RC. units, Toroid coils, filter three-valve will a strong appeal, particu- articles per week are turned out from units, and, finally, complete portable make larly as the expense and trouble of the hardened steel dies for various radio gramophones. interchangeable coils for different wireless purposes. All these will be on view at the wave-lengths is avoided altogether. Over sixty grades- of material are Dubilier stand, and amongst the vari- required, an although its chief able condensers there is sure to be J. Dyson & Co., Ltd. Stand No.1. great interest in the K.C. (0005 and appeal will be to manufacturers, - Complete sets, mains units, coils 0003 mfd.), and in the Midget vari- and condensers are amongst the able condenser, which is designed for exhibits here. The design of tIì - reaction control or for use when a 'I neutralising condenser of relatively large capacity is required. Designed - for panel-mounting and complete with a knob, this Midget has a capacity of 0001 or 0002 mfd., and is a bargain at 5s. 6d. In addition to all the products specially suited to the wireless con- fi structor, Dubilier's will be showing at -- their stand various types of condensers for high-power radio and amateur transmitting stations, so that the stand is attractive from a general interest of view The new Etiiswu,i L.F. trunsform e, point apart from its The Ebswan home Ch#urger wrnhs from with iato of 3-5-1. possibilities to the purchaser. A.C. mains imd costs £2 irs. Gd. - - 3G4

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- = his Year at Olyrnpia-contb2ued

niicrotune S.L.F. condenser is especi- will be interested in the Eelcx mois- One feature which will appeal to ally interesting. Consisting as it does ture-retaining earth, which can be the discriminating buyer and to the of two separate knobs and pointers examined by any visitor to this stand. technically-minded set builder who (one giving ordinary semi-circular knows exactly what he wants (and calibration, and the other slowly means to get it), is the marking of the moving 360 deg.), it is possible to new Ediswan valves. Not only the calibrate this condenser to extremely filament volts and current, but also fine limits. Valve holders, high- the impedance and the amplification tension batteries, L.T. accumulators, factor of each valve is etched oa 11w and accessories make this an extremely bulb! This is an excellent idea which interesting exhibit. . not only assists the purchaser all the time that the valve is in his pos- DX. Coils, Ltd. Stand No. 223. session, but also gives him a "good" A strong feature of the D.X: coils feeling about the reliability and the which will be on show at this stand is constancy of the range of valves so the fact that they are wound only" on marked. air," i.e. without a former. Standard Battery eliminators and chargers coils, centre-tapped coils, and "X" which pay for themselves in a few coils with two tappins are available This " 3Ialuh'n " II.T. unit is sold months are other features of this net- at 2s. Gd. for the various circuit requirements, r. to-be-missed exhibit. and the range includes the D.X. short- Edison-Bell, Ltd. Stand No. 129. wave coil for use on the higher fre- Messrs. Edison-Bell, Ltd., have The Electron Co., Ltd. Stand No. 42A. quencies at which the absence of a recently been busy upon the produc- Famous for their series of Six-Sixty solid former is particularly, appre- tion of new apparatus to be'released valves, The Electron Co., Ltd., are ciable. in the autumn, and a special feature showing a new range of screened-grid In addition this firm is marketing a of these new lines will be made at this and Pentode valves, the former för low-priced L.F. transformer, and it is stand, Severalnew conulete receiving 2 and 4 volts, taking 15 and 075 interesting to note that in this, too, sets are included, such as the " Com- filament amp., and the latter for the coils are air-wound, i.e. no former pact Three" (which carries a cone- 2 and 4 volts, tal-ing 30 and '15 is employed, and the coil is an all- type speaker in the lid), and the filament amp. There will also be on wire one. Not only the ordinary five-valve portable with only two view the well-known Six-Sixty loud- i to 1, 2 to 1, and 3 to i ratios are controls-tuning and reaction. In speaker paper and the Six-Sity this set a switch is fitted for changing cone speaker assembly and turntable. from the high to low wave-lengths, and Visitors should make a point of independent connections for outside visiting this stand, and especially of aerisi and earth and speaker are pro- inspecting the new screened-grid and yided for use if desired. Pentode valves, as these are sure to This firm is also showing an come well to the fore during the interesting electro-magnetic pick-up present radio season. specially adapted for use with the complete sets already referred to.

The Edison-Swan Electric Co., Ltd. Stand No. 43. The 1929 Ediswan R.C. Threesome will cause a great many people p. to break the Tenth Commandment at The Boweriiau cone loud-speal«'r unit. this stand. In its new and up-to-date form thIs famous receiver embodies available, but this firm is also pro- several improvements, one sure-to- ducing a special 25 to i transformer be-popular innovation being the new for use where the output of a set is which has the windings to a moving-coil loud speaker. A-type unit, for both long and short waves J. J. Eastiek, Ltd. Stands Nos. 218 and 219. mounted upon it. With this unit the s Here will be semi the full range of set can be switched over in a second Eelex productions, including the popu- to either the long or the short wave- lar Eelex terminals and the safety lengths by means of a simple push- switch made by this firm, which pull switch.

combines a lead-in tube, switch and - Represented here, too, will be all .: ; lightning arrester. Standardised plugs the large family of Ediswan valves. and sockets are other features, and The whole range of these has been those who are overhauling their sets entirely revised to conform to the for the winter and who ntemp1ate most iodern standards and several OflC o! the ìuu.y IFesti,.ghouse ejththits- 1enewing their earth arrangements important additions have been made. 12%i 365

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This Year at Olympia-continued

Falk, Stadelmann & Co. Stand No. 127. In addition there a're chokes for 25 miles and 5 G B at loo miles on Efescaphone " complete receiving smoothing purposes, and for use in the loud speaker. The price, including sets in great profusion will be on show choke filter circuits ; then there are royalties, is eighteen guineas. here, including the now popular the wire-wound anode-feed resistances The "Advance" five-valve trans- Cromwell," " Wolfe," " Wel- (the anode-feed system was developed portable receiver is similar in appear- lington," and" Kitchener" sets that by the Ferranti Company) and many ance to the three-valve but tunes to vere introduced to the publie at last other interesting lines, including a the long waves also, and its price is year's show. In addition, there are loud speaker, a permanent LT. twenty-five pounds. The "Advance" some promising new lines, including trickle charger, radio meters (don't five-valve set employs a screened two sceened" Fours " and a screened miss these !) and permanent metal valve, the wave-length range (in this Three." The latter is priced at rectifiers. - case from 250 to 550 metres £13 lOs. (receiver only). and from 1,000 to 2,000) is Ñsily Several new HT. battery elimin- altered by means of a switch. The ators are being added to the Efesca set is.of the one-dial tuning variety, Tange, and in addition there are r - and the price, inclüding royalties, is shown some very attractive com- thirty guineas. ponents, including tuners, and an GametI, Whiteley & Co., Ltd. Stand No.115. coupling unit for use with I RC. The "Lotus" components on view general-purpose valves. at this stand will include thany The " Godwin " Concert G'and receiver, famous old favourites. In addition Ferranti Ltd. Stands Nos. 84 and 85 incmprn oflag The '' MicroS line con- to those Lotus lines which were so The astonishingly varied display of denser dials, and »tode bq Messrs. J. Ds;son & CO. successful a few years ago-such as apparatus at this stand will be an the Lotus two-way coil holder, the eye-opener to those who have always One interesting point about the vulve holder, and the great variety of associated the name Ferranti with display is well worthy of Ferranti jacks, switches, and gadgets for which transformers. Transformers there are, note. This famous firm, known all the this firm is famous-a number of new o.f course, in plenty, including the world over as manufacturers of lines are being exhibited for the first famous A.F.3, A.F.4 and the super transformers and electrical equipment, time this year. . type A.F.5. has decided not to manufacture any À very interesting line of push-pull transformers and other componens transfoamers will cause push-pull en- for supplying to constructors to enable thusiasts to push and pull their way them to build eliminators giving through the ¿rowds to inspect these, output t'oUages higher 1/ian 250. Fer- but apart from transformers the ranti's feel that the practice of using Ferranti people are catering exten- voltages of tIme order of 400 or 500 is sively for other wireless needs. Their dangerous and may lead to serious condensers, for instance, types Cl accidents. and C2, have a low internal resistance The careful constructor will there- and extremely high insulation resist- fore feel absolutely safe with this ance. The test voltages for these firm's products. condensers are 500 A.C. and 200 D.C. One thing that IF'erranti's point out respectively. which is not generally realised is that in an eliminator using valves and providing voltages of about "400," there may be transformers with about Mess,s. Porividge & Mee have brought 1,000 volts across them! So this out the above lIT.(ins. sujply unii for ul.C. decision, by such a famous firm as Ferranti, Ltd., should be carefully Included in these new lines are the .J considered by everyone who is con- Lotus portable set and the Lotus p templating utilising the, mains. A trans-portable 8et, but of special Ij interest will be the three new Lotus 'u - visit to the Ferriinti display will provide convincing proof of the components specially designed for thoroughness with which these and the modern set. These are the new the associated problems of radio Lotus logarithmic condenser, the reception have been investigated and Lotus vernier dial and a new series of catered for. tuned coils. Apart. from all these attractions i L G. Forster. Stand No. 3. there is one other feature which will 'H- Complete receivers are the attrac- specially interest the man who has tion here, several models of three- and his set installed but fails to get the five-valve sets being on display. The maximum enjoyment from it on Advance" three-valve portable has account of the fact that the programme 1'he E,neka "OrIhodgne Five" attache a wave-length range of from 250 to is only available in one room of the ease »aodeI- ea'tremey t::I - 750 metres and will bring in 2 L O at house. He should make a special

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T is Year at Olympia-continued

point of enquiring about the Lotus screen ed-grid valves, battery elimin- MeMì7zring instruments are now Remote Control. Several varieties of ators, battery switches and sundry becoming recognised as essential this arc on view, all impIe to instal components and accessories, are to pieces of wireless apparatus, and it is and easy to use, by means of which be found on this stand, the portable extremely satisfactory to find that the set can be switched on or off as receivers being obtainable in various not only is this demand being catered you wish by the mere insertion or designs and finishes. In addition a for so extensively, but that the latest withdrawal of the loud-speaker plug complete range of A.C. and D.C. development is a tendency not only

I in any room. A great stunt for the battery eliminators, all conforming to towards greater accuracy but also to lazy or luxurious! the lEE. regulations, are offered to a reduction in prices. the public. The Jewel Pen Co., Ltd. Stand No: 261. Hobday Bros., Ltd. Stands Nos. 173 and 174rn The crystal-detector user will nd This exhibit coustitutes quite an this a particularly interesting stand, i exhibition in itself, for Hobday for here will be shown a popular form Bros. (one of the foremost factors in of permanent detector which has done the wireless industry) will be showing much to oust the cat's-whisker from - i a comprehensive range of all the popularity. A reduction in price of latest developments in radio, includ- this detector is a particularly good :J! L sign of the times. Lectro-Linx, Ltd. Stand No. 23g. c?H The constructor who believes in good contact, first, second and all the time, will be particularly in- il pop.Iar giaiiiophoue pieh-ep is t!e " U'oodroffe,'' Uus(,-ated here. terested in the range of Clix - specialities. Pin terminals, spade rhe Halcyon Wireless Co., Ltd. Stands terminals, plugs, parallel sockets, and Nos. 16, 17 and 18. r all sorts of gadgets and "doo- The aim of this company is to hickeys" are shown, all carefully achieve a degree of wireless refinement k - designed with the idea of giving really which buyers of high-class sets have good contact in any type of set- a. right to expect, and they claim that crystal or valve. the 1923-29 model which is shown on At this stand the Home Constructor this stand is the hast expression of will be in danger of forgetting the modern technique in wireless tele- "Home," and will only remember the phony. The five-valve portable dc "Constructor" part of his hobby luxe model and a special de luxe lightweight model form the chief exhibits, E. J. Leer (Trix), Ltd. Stands Nos. 255 The noueZ und effZcunt IZipoult Iateie,l- and 256. each receiver containing five valves «cf ion vaiia&Ie condenser. and being capable of surprising Some very ingenious insulators are ing a special show of portable sets by results. A full-size Celestion type amongst the many components on the leading manufacturers. loud speaker is provided in each .set, show at this stand, and the man who Although this is primarily a trade provision is ma for the use of and show, the very compactness and com- telephones or an alternative loud prehensiveness of the exhibit will speaker if required. The weight of render it attractive to the ordinary t.he lightweight model is 31 lb. and visitor and purchaser. YA that of the heavier de luxe model Eoenewhat greater. The price of each Houghton-Bulcher, Ltdt Stands Nos. 136 is the same, namely, thirty-five and 137. guineas, and they cán be obtained This well-known firm is a wholesale either cash down or on the hire- house, but the ordinary listener will purchase system.. find on the stand an interesting summary of the leading lines of the Hart Bros. Electrical Manufacturing Co., :tLC. Ltd. Stand No. 215. various popular radio productions Another "gadget" stand, which and successes. no man who has on his mind a set to No. 273. A. H. Hunt, Ltd. Stand I i build will be able to pass without a This firm is making a speciality of '-t' strliggle. The main features are the a very extensive and complete range .i: Harbros "Easyfix" flex battery of electrical measuring instruments / cords, loud-speaker leads and instru- (already famed), and there are several ment wires. additions in calibrations and models W. J. Henderson & Co., Ltd. Stand No. 258. which are sure to be popular, the low- receivers of and One o! the many thousands of fixed eon- Portable the four- priced double-scale voltmeters being densers placed on the morhet - by The Live y a Ive varieties, employii. g particiil ny attractive. Telegt upu Co.idense Co. j 367

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- I Ins T ear - at. uiympia-continuea

is nervous of lightningshould not fail suitable for use on all wave-lengths L. McMichael, Ltd. Stand No. 128. to see the lightning arresters which from 20 to 2,250 metres, Among the many lines for which form a feature of the display. this firm is noted, several new features will make their appearance, notably Lithanoce Co., Ltd. Stand No. 226. the McMichael gramophone pick-up, Three diflerent patterns of unspill- which is made on a new principle able accumulators are on' show and giving greatly improved reproduction. will be of especial interest to those Sensitivity is extremely high,, and The Licen contemplating the building of port- nelr may be varied to suit individual able or trans-portable sets. u' i i' e - te o i, t, d taste. In addition is the 1929 ,.'esishu,ee foi W. & T. Lock, Ltd. Stands Nos. 229 and 230. screened portable, which represents an t'e,'fkyil or ¡,ori- A full range of cabinets suitable for outstanding ach-ievement in its appli- moving-coil speakers is an interesting 7OfltaJ nio..ttfing. cation of advanced design permitted feature of this display. by recent strides made by th val ve manufacturers. The "McMichacl The London Electric Wire Co. & Smiths Screened Threé" is a mains-driven Ltd. Stand No. 110. set which gives remarkably good Lewcos coils and Glazite wire have quality. The whole set is easily ÌI long been on the market, and this connected to the mains in the 'samc winter these two useful commodities way as an electric iron or fan can are to be joined by a special Lewcos be plugged in. HF. choke. It has a minimum self capacity of only 21 micro-microfarads, The Mainten Mfg. Co., Ltd. Stand No. 206, and its natural wave-length is far This last-developing firm of battery above that of the longest waye-length London Metal Warehouses, Ltd. Stand eliminator manufacturers is bringing used by any broadcasting station, No. 79. out a series of new lines encased in being somewhere in the ñeighbour- Aluminium aerial wire is a novelty metal, whereas the former eliminators hood of 5,400 metres. The choke is at this stand. have been cased in wood. All these : WHERE THEY ALL ARE

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-This Year at O1ymia-cotinued .-- -

-bbth for P.0: dnd A.C.-ar guar- is useful for the ordinary wave- (Four volts are necessry for the. anteed to be capable of working any lengths as well as for the short waves. filarnen supply voltage.) The ci rciiit average set.... Another interesting Marconiphone of this three-valve set is extremely' departure is the " Popular " trans- interesting, as it comprises a .scteeiied: Mareniphone Company, Ltd. Stands Nos. former having a ratio of 4 toi and grid valve H.P., a special P.M. t .5e, 80, 61, 68, 69, 70, 2? and.233. retailing at 12s. 6(1. detector, and a Pentone in the lúst- The eight stands which have been stage. All Luìe coils in the set ar booked bi.' th' . Marconihone Co., brought into operation by means of' Ltd., are bf such extraordinary interest a switch, which also controls the LT. that it isimpossibe to refer in detail supply. Provision is a]s,o inade to th varibus exhibits. No matter whereby the set can eailyj?e çiyrtd. what your radio reuireinents may be for AU. work should occasion arise.- òi will e sure to find something of The new Philips' inter-vlve traiìs- especial ihthest here, whether your former will be well in evideiie,luik' iieeds arc in the nature of single coin- this firm will bepleaséd todemonstrate ponents, units, transformers, valves any particular model of reeier.9r or acessorie in general, or the more loud speaker upon reuest, and for . amhitiOus field of complete receivers. 'lije Eieo "itll-Po,rea unii, 31o1c1 CIA, titis pirpose iiie mide a point of Many of these are too well known to foi D.C. purins. taking extensive sh'owroöin.' at .Wet.. need introduction, but the new Keiìsington alp The Mie Wireless Co. Stand o. 9. Gards, ostop,pQse. coniphone ortahle reccivór which the exhibition, for .tlmej purpose, of, This company markets the Zama will, bc ou show is of particular demonstrating any éL their components, two of which will be 'dts. interest. if onl' br it.s small Finally, mention should f tite shown, itamely, the Zampa moving- Iède cons.uniption, this being of the order of new loud 51)caker rccehtly. placed on. coil loud speaker and the Zampa 7to 9milliamps only. Fór this a tito market, in -. ínodel tuner. several walnut cabinet is adopted . as. being which will form a .pr6rninentfeatut more suitable for home use than of the exhibit. Tjii j one .of the. E. Paroussi. Stand No. 272. leather, and it is an open seet that latest additions to Philips' radio. Radio products par cxcel1emce of the macers have been delighted with products and is well, worth careful., the PAR-EX brand will be shown the range of rëceptio of this ilistru: examination. ., ment which lias proved to be quite here in great variety, and will prove . r.. .. Portable Utilities Co., L11. Stand No. 144.' remarkable. of special interest to the man who Eureka will edhith the eontrué-' Another interesting set is the uses or intends to use a screened valve.' tor as ho looks at this stañd. Marconiphone short-wave receiver, The Parex screened-valve holder, by Not only are there main.4 trans-' Model 34, the originaI model of which tli wy, is now made to fit not only tue ordinary screened-grid valve, but foriners, chokes, etc., but there. ir-a. vas taken on :a voya:ge to Singapore particularly leasing line of Eureka as a test. E'en under these arduous 'aiio the new Mullard SG. valvé. complete sets, including several new. conditions it succeeded iii receiving Users of screened-stage receivers, models. A Eureka" Orthodyne Four," 5 5 and the American whether of the kind employing W, PC J J, for, instance, brings in practically short-wáers regularly. .. Stàndad screened-grid or ordinary valves, will very.-one of the well-known European plug-in also can be used imfth be specially attracted, too, by tité display of screens of. all broâdcasting statioii, s weil as some. iiistrumeiit, witji, adaptor, so thatit extensive 'types, to suit different circuits and of the Americans. : receivers. The Eureka " Orthodyno Threi' " is by no means to be sneezed at, lar no - Partridge & Mee. Stand No. 147. (Continued on'pie 43G.) This firm, which makes a speciality of high-grade wireless and electrical apparatus, manufactures all types of I transformers, chokes and eliminators. Amongst them will be found twenty- five different types of transformers, also chokes, output transformers and rectifying apparatus.

-, lì Philips Lamps, Ltd. Stands. Nos. 94 and 122. u .Tt\, This well-known firm will exhibit iii:', a complete range of mains units and I battery. chargers, together. with a -. series of np-to-date receivers. As an example of these, the three-valve The "Tudor" C.L.H.j 4-volt 40-e.u. DO. model, type 2582, can be operated u to.c-lensionbatlerD;. The glass containers from D.C. direct from the mains ctable the condition of the plates and the . One of the most popo1«.- of loud sn,a:. I acid level fo lie seen with ease, through a .higlr-tenson ebminator. -the Celestion.

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NAME ADDR?.SS STAND NO. N.MR ADDRESS STAND NO - L - J Amalgamated Press, Ltd. Fleetway House. Farringdon Street. Hart Accumulator Co., Ltd. Marabgate Lane, Stratford, E.15 95 E.Ç.4 135 & 166 Hart Collins. Ltd..... 38a., Besaborough Street, S.W.1 .. Atalanta, Ltd 1.3, Brixton Rossi, S.W.I) .. 271 - Hart Bros. Electrical Mfg. Autouatic Coil Winder & Winder House, Rochester Bow, Co., Ltd 4, Queensway, Ponders End, Middx 215 Elec. Equipment co., Ltd S.W.1 ...... 150 & 131 Henderson & Co., Ltd., Axuel Time Switches, WI 45e, The Mall, Ealing, W.5 263 W, J 351. Fulham Road, S.W:10 258 Hobday Bros., Ltd... 21-27, Great Eastern Street, E.C.2 173 & 17 Baird Television Develop- Honghton-Butchcr ((It.

ment Co.. Ltd 133, Long Acre, W.0 2 ...... 11, 13, 14 Britain), Ltd... .. 8g-89, High Ilolborn W.0 136 & 13 Bakeilte. Ltd. SS. Victoria Street., S.W.1 160 Runt, Ltd., A. H HAIL Works, Tunsall Road, East Beaver Electrical Co., The 5.Great Chapel Street, Oxford Street.. Croydon 273 2 Bedford Electrical & Itadlo Igranic Electric Co., Ltd. 147. Queen Victoria Street, E.C.4, Company ...... 22, Campbell Rad, Bedford 35 and Bedford ...... 53, 54 & 7 BeUing & Lee, Ltd...... Q,ieensway Works, Ponders End, hufe & Sons, Liai. Dorset House, Tudor Street, E.C.4 145,148

Benjamin Electric, Ltd. . . Brantwood Works, Tariff Road, Incorporated RadiO SOCity

...... Tottenham. N i71 of Gt. Britain. 53, VictoriA Street, S SV.1 . . . 227 - Bowerman, Ltd., George 10 & 12, Ludgtte liJil, E.C.4 !t3 Bowyer-Lowe Co., Ltd., . J.R. Wirele Co G & S. Rosebery Avenue, ECl . 228 The Ru10 \Vorks, Letcbwnrth, Ilerts . 51 Jack.on Brni. . . . 8, Poland-Street, \V.1 105

Brandei. Ltd. Cray Works, Sideu Kent 118 Jewel Pen Co., Lt4 21, ßreat Sut,ton Street, E.C.1 . 261. flrittsh Ebonite Co., Ltd Nightingale Road, Haureit, W:7 . Junit Mfg. Co., Ltel Naper Rouse, 24-27 High Holborn, 93 .- :Brftish General Mfg. Co. w e. Ltd Broeklcy WTork, Urncklei S.E.4 10 British Radio Corporation, Elm Grove Road, *'eybndge, Lamltigh, Ltd., S. A Kings Road, Tyseley, Binninglaim 81 Jr 106 Ltd Surrey 141 Langham Radio 06, Regent Street, Wi 55 & 7 British Thomson-Houston . Leetro L!nx, Ltd 254. Vamhall Brídge Road, S.W.1 236 Co., Ltd., The Crown llanee, Adwycli, W.C.2 . S6 lOi Lever (Trie) Ltd., E. J 8-9, Cerkenwell Green. E.C.L . 255 & 256

Brown, Ltd., S. G Western Avenue, North Aeton, V.3 155 156 Lis.en, Ltd Friars Lane, Richmond, Surrey . 71, 72, 57 Brownie Wireless Co. of Nelson Street Works, Mornmgtou ' & 55

GB., Ltd., The Cresent., N.\V 101 Lithnode Co., Ltd. . 190, Queen's Road, Thittersea SW 226 Ilulgin & Co., A. F 9-11, Curstor Street, Chancery 1.ock, W. & T., Ltd St. Peter's Works, Bath 229 & 210 Lane, W.0 203 & 204 London Electric \Vire Co., 7 P'ayhouse Yard, Golden Lane. fluliphone, Ltd ...... 35, Iolywel Lane, Great Eastern Smiths, Ltd., The . .0 110

Street, E.C. . . 42 Burndept Wireless, Ltd Eastuor Hotise, Blaekhekt.h, S.E.3 112 & 113 London Metal Warehouses, HIll Street, Poeoek Street, JiIaek flume-Jones & Co., Ltd 288 t 2O0Borough High St... S.E.1 06 Ltd friars Road, S.E.1 70 Burton, C. F. str II Progrees Works, Bernard Street, LondonRadioMfg.Co.,Ltd Station Rou1, Merton Abbey, SW 209 & 210 WalaLl 184 & 155 ,

1,MichI, Ltd., L. . Wexham Road, Slough 128 Carhorundum Co. Ltd. . Traltoril Park, Manche!ter 130 Carrington \ug (o Ltd Cuneo V orkq '3audertead Itoad Manten 141g (.o 1L pt] Rve 206 107 . Mareoniihone Co., Ltd 210, Tottenhain Cours Road, W.1 59, 60. 61, Cateshys, Ltd ... . . 6'4-t To.'n?i?m itoaä, wi 25 cttrt 69, 0. Cantoptione Wireless Co. Remo house, 310. Regent St., W.1 253 . ,

Celestion Radio Co 20-31 ifigli Street, I4anipton Wick, . . ii 1elhuish, 8, Great Sntthn Street, 1i.C.1 . . K ' t TI es - 19 & 0 Metro \ ck Supplies i 32 & 41 Clilonile ricetrical Storage &cnue \% C Ltd Charing Cro Road W C 21tesy Mc Wireless Co ...... White. Place, Co., Ltd and Clifton Junction, Manchester 33. 40 & 241 Horse Market Street, & Co. (M/e.), Ltd Atlas Works, Eastnoi Street, Old ii Mollard Radio Vtiva Co., Ñghingil 88, 89, 90, Climax Itadio Electric. Ltd. Qulil Vo'rks, Quill IA L'utney, Ltd Lane, Baiham, S.W.12 97, 98, 99, i - S.W.15 8f) . Cole, 1.td., 1f. H Ekco Work,,, London Boati, Leigh- & Odhams Press, Ltd... 93, Long Acre W.0 183 " Colllneirns Precision Serew Provast' Works, Macdonald ni.°&ttd , . :: ' 01 Cossor Ltd., A. C eossoi Iliglihitry Grove, i'L5 163 ''? Parousi, 1f 10, Fentherstone B(dgs, High Rol- DX. Coils, Ltd '!42 Hlngsland Road, ILS 223 boni, W.0 272 9 Partridge & Mee, Ltd 1., Belvoir Street, Leieeater 147 ISa rite j d . IS. e LeeS - Peto ,t. Ifndford so Grosvenor Gardens S V i 67 I t. De Ittie C I I Co., Tho 30 Shernhall St Waithinistow E il 235 Peto-Scott Ltd 77, City Road, E.C.1 142 & 143 Philip' Lamps Ltd 14., Charing Cross Road \V C 91 & 122 Dew & f' A J 33 4 Rathb w t isi t. 18° - UtilitIes Co Dibben iSons William St Mary s Road South tinpton Portable Ltd Eureka House Fisher Street., WC 144 Pyo & Lo., W. (. Dionoid Battery co., Ltd., Victoria Works, l'rinee of \Veies' Gianta Works, Montague Road, The Road, Darniill, Sheffield 245 tilL I ge ...... Co. Ducon Works, Victoria Itoad,North 9? 102 & 103 Rj.& Varley, Ltd... 101, 1flngsway, W.0 56, 73 & 222 Co. Dunham, C. S .... . Elm Works. Elm Park, Brixton 257 (927 Bennett Street, Chiswick W.! .. 6 s flyson J 5 Goiittn St red Iiridford and Redfern Rubber Works Ltd Hyde. nr. Manclieeter 123 -. Co ei i ...... ian Street' E o ' 1 ...... - Bees Mace Mf g. Co., Ltd. 39n. Wellieck Street. W.1 268 Ripaults, Ltd . 1, King's Road, St. Paneras, N.W.i 24 Eagle Engineering Co., Ltd. Eagle Works, Warwick .. . Easlick & Sons, J. J. .. Eelcx house. Bunhuili Row, ROi 2i8 & 219 Edison Beil LIL Pdus,ni Bell V orts Gleng iii Road '7i s PP i y c o k St t W i 12 Peckkani, S.L.15 Selectqrs Ltd Der Stt W 1 23 & Co., Ltd. dlxton Housse, Westminster, S.W.1 164 & 165 LtIOfl Stañdard Wet Battery Oo. 184-8. Avenue, 7 3 Q Victoria Street K c. Sl,aftesburv WC. Electramouic Co Ltd Ber (,rrdens Park Street South Stapleton 3ldgs Lorriniore wart, SE 'ree"? 211 unnre cc rie o .....cray quare Stevens & Co. (1914), Ltd., * Mtg. w i ii s w i ' 83 & 131 F.nler,rise Co .. 83.87, Merton Road, Swig 217 & 238 I vor- e, y Staon , ea.: i.d1 '.: BiÌrral \r'ks, Bromsgroe Street, o . ( .), - 1.td Hercules Place, Holloway, N.7 44A . aun r i s Electron Co., Ltd 122, Charing Cross Road; WC. 4h Co n d coser o Wales Farm Rd., Forth Acton, W. 121 Treileborg Etoutte Works, Falk, Stadeinsann & Co., Ltd Union Place, Welk Street. W 224 Ltd ...... - 83, Farringelon Road, E.C.1 127 Tudor Accumulator Co. 2, Nortolk Street. W.C.2 , . 24g Fellows Rig. Co., 1.td Cumberland Avenue, Park Royal Turner & Co 54, Station Rood, Nil 234 36, 37, 04 & 68 Vanrlervell & Co., Ltd., Ferranti, Ltd Hollinwood, 1.anes. and Bush C. A Worple Way, Aeton, V.3 lii House. Strand, W.0 84 & 85 Formo Co., The Crown Works, Cricklewood, N W.2 140 Watmol Wireless Co, Ltd Imperial Works, High Street, Edgware, Middlesex 157 Gambrell Radio, Ltd. Merton Road Southfie!d, S.W.IS '27 & 108 Westinghouse Brake & Garnett, Vhiteley & Co Lotus Works, Broadgreen Road, Saxby Signal Ca., Ltd. 82, York Road, King's Croas, N.j 78 Ltd Liverpool ...... 115 Whiteley, Bonohain & Co., . - General Electric Co., Ltd Magnet Houst, Kingsway. W.C.2 28, 29, 46, Ltd Nottingham Road, Manslield, Notts 121) 47 & 225 Wliittingham SmIth & Co 110. Kew Green, Rese, Surrey 4 Goodmans 27, Farringdon Street., RC... 269A Wilkins ,t Wright Utility Works, Holyluead Road, Graham& Co.. R. P 45, Cambridge Road, Kingston-on- Birmingham ...... 252 Thames 212 Wireless Retailers' Asso- Graham Amplion 25-26, Ltd. Savile Row Regent St., \V.1 80 & '31 elation of Gt. Britain 70. Finsbnry Pavement, E.C.2 . 259

17, Masons - Gruham-Farish Ìig. Co Hill, 1ronsley, Kent 119 Wright k Weak's, Ltd. 740, High Road, Tottenham, N. , 2M & 252

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A "CTIflIDAU1t'D" nIV1I ADM1k1T

i r1fl rn1linul&

1rHE enormous interest aroused by make-up of the Tobe-Deutschmann cost of running the unit even with he iL the Harris " Stedipower " L.T. 3,600-mfd. condenser used in the seven-valve super-heterodyne is negli- Unit in our August issue "Stedipower" LT. Unit has beeiì gible-.say, a shilling a month at the continues unabated, and I have slightly improved. In the condenser outide for quite heavy use. received numerous letters not only already illustrated in this journal We should also like to take this from all parts of the ITnited Kingdom, soldering lugs are used for the three opportunity of poiliting out that when but from France and Germany and connections, but in the latest model it is desired to eiiergise the 6-volt Holland, congratulating the WIRE- flexible wires are already connected to winding of a moving-coil speaker from LESS CoNSTRucToR UPOfl being the the condenser lugs, thus obviating the the AC. mains there is no need to first journal to publish a design which necessity of soldering and increasing build a complete "Stedipower" L.T. enables any of its sets to be worked still further the simplicity of con- Unit. All that is necessary is to use direct from the AO. mains. Deli- struction. - - the transformer and the dry rectifier, veries of the special high-capacity as the inductance of the field winding condensers, transformers, chokes and No Soldering will give all the choking effect neces- rectifying units are now in full swing, It is now possible to construct the sary for smoothing. In our own and there is no reason whatever why unit entirely without solderiDg, and laboratory we use a transformer and any reader should not now be able to the new " Radiano " wiring system a WTestinghouse dry rectifier straight obtain supplies for making this fasci- described in this issue can be used on to the field winding, and the result nating and useful piece of apparatus perfectly satifactoriIy for it. This is quite satisfactory. within a day or two of placing the is a big boon and will, we are sure, order with his dealer. be f tihly appreciated by our readers. A D.C. Model? We have also drranged with the While there is a very slight hum, A New Rectifier - Westinghouse Brake and Saxby Signal it can only be heard by placing We are very pleased to be able to Co., Ltd., to supply their dry rectifier. the 'ear quite close to the speaker announce that the Westinghouse for the "Stedipower" unit fitted with during quiet .periods, and even Brake and Saxby Signal Co., Ltd., flexible wires, clearly marked. t h e weakest reproduction c o in- makers of the Westinghouse dry We should like to repeat, although pleteiv effaces what hum remains. A rectifying unit, are now producing a it has already been clearly stated in good combination for this purpose is special Westinghouse dry rectifier the Pye transforme,r reviewed ou specifically designed to fill the need another page, and the W cstinghouse of the Harris" Stedipower " LT. Unit. unit. In the 'Westinghouse series the of i!. This will be available to readers o 114-2-2 is recommended, with either the WIRELESS CONSTRUCTOR at an 'a Radio-Instrumeñts or Pye trans- attractive price by the time this issue former designed for this unit. appears on the bookstall. As the The "Stedipower" L.T. Unit can electrical characteristics of the West- not be used with D.C. mains. Experi- inghouse dry rectifier are not quite the ments are now being conducted in the same as those of the Kuprox, slightly laboratory for the purpose of evolving different transformer windings are the "Stedipower" D.C. Unit for LT. necessary, so we have arranged with supply, and as soon as satisfactory Messrs. Radio-Instruments, Ltd., to and reliable results are obtained the supply at the same price as the trans- design vihlbe published. former already marketed for the Kuprox one designed to fit the /(UP..OX UNIT L.T., Not H.T. Westinghouse unit. The "Stedipower" AeØD/F/CA 7/ON FO.9 ZC C. Another question which has been LT. Unit can thus now be made up .5..Crc'oz vr/o COWD.$'RJ asked is whether the Tobe-Deutsch- with either the Westinghouse or the The fhoreticut circuit of the " Stedi- mann 3,600-mfd. condenser can be pOurer '' Unit. Kuprox units. When ordering trans- used in H..T. mains unit. The answer íorrners and chokes for the "Stedi- the first article, that the" Stedipower" is emphatically no, as this condenser power" LT. Unit the reader should LT. Unit is designed to work only is designed only for low voltages, and particularly specify whether they are from alternating current mains, and would break down and be ruined with to be used with Westinghouse or the when made up according to the article such use. Used at the voltages which Kuprox dry rectifier. will give an L.T. output up to i amp. are applied to it in the Harris at 2, 4, or 6 volts-or, indeed, at any "Stedipower" LT. Unit, the con- Improved Condènsers voltage from 2 to 6. The output is denser is thoroughly reliable, but it is We are interested to find that, perfectly hum-free and indistinguish- not intended -to be used at voltages íJthough the price has not been in- able from the pure direct- current above those produced in the unit creased in any way, the mechanical available from an accumulator: The described. -

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ERE are four practical circuits r. with a list of parts for each. j If you were making them up Mi into receivers, which parts would you .. "r use ? Are you sure that you are up .to date in your knowledge of the best parts? Would your choice be the same as that of your friends ? C2 Take this copy of the WIRELESS 3C CONSTRUCTOR with you to the Wire- less Exhibition at O1yìpia. - Go I round the stands, and when you see a component that makes a special appeal to you, make anote of it as c/. your first or second choice. Then R2I when you go away you will have accumulated sorne very valuable notes which will be a great help in the coming winter when you are building sets. Members of wireless societies should nake a point of. comparing their ists with one another. The particular ircuits chosen are merely taken as epreseutative" frameworks" includ- n all of the parts most generally A Good One-Valve Reinartz Circait. sed.

/ O .1- ,'2 -

V2. 1.5. - - 1 C. Tr C2 fi R2H JI!IR4J CI - r .C.B L _1-JL,TI

I ('7 An Economical Two-Valver. JW/TCN y

i. 372

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One-Vàlve Circuit Parts

Type of Component First Choice Second Choice I J Cabinet Panel brackets

I No.60"X"c)jl(L1) ..

i No. 250 "X " cil (L1) .

i No. 35 or 50 coil (L2) . I No. loo or 150 coil (Le) 2 Board-mounting coil sockets

. 1 Variable condenser, OOO5 mid., and dial (C1) ...... i Variable condenser, Q003 mid., and dial (C3)...... I Fixed condenser and grid-leak clips, 0003 mid. (C2) ...... i Grid leak, 2 megohms (R1) I Fixed resistor (optional)to suit valve (R2)..

» i Valve holder . i Radio-frequency choke (L3) Terminal strip and terminals i Fixed condenser, i mid. (C4) i On-and-off switch i Pair headphones (T.) ...... Accumulator High-tension battery L-'-- ».

Two-Valve Circuit Parts

I -

Type of Component First Choice Second Choice

Cabinet ...... Panel ...... - .: Panel brackets ...... 1 No.60 "X" coil (L1) I No. 250 " X " coil (L1) i No. 50 coil (L) ...... -.1 1 No. 150 coil (L0)

1 Two-coil holder (variable coupling) (H.) . . 1 Variable condenser, 0005 mid. (C1) .... I Fixed condenser, 0003, and clips for leak (C2) 1 Grid leak, 2 megohms (H1) ...... 2 Fixed resistors (optional) (R2, R3) 2 Valve holder5 (V1, V) ...... i Fixed condenser, 0005 mfd. (C3)

F i Low-frequency transformer (Tr.) . i On-and-off switch (Sw.) strip and terminals Terminal ...... 2 Fixed condensers, i mid. (C4; C) . .

Accumulator ...... Ç battery ...... Grid-bias battery ¿ Loud speaker I

373.

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TIlE WIRELESS CONSTRUCTOR - - October, 1928

Make Your Choice at

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- ..i _____ A High-Grade Three-Valve "Distance-Getter."

5CREEH ÑP OIL CErR 7 0003 - C5, r7Rc. ____ - Rc. UNIT (:) f ':°°°' i k' - 5w2 r c V,

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Tue Circuit oI the Faioes "Concert" Four. V L*

a74.

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Three-Valve Circuit Parts

. Type of Component S First Choice Second Choice

Cabinet -

Panel -

Panel brackets ...... S - . - S

i Six-pin aerial coil for each wave-band - - S

(L1,L2) - -

: i Spilt-primary transformer for each wava- - - L5) band (L3, L1, ...... i S S S

.2 Six-pin bases . 2 Variable cndensers, 3003 mid. (C2, C2) i Variable condenser, 30Q3 mid. (C3) i Neutralisng condenser (C5) - r

3 Valve holders (V1, .V2, V3) . . -. . .

3 Fixed resistors (optional) R1, R R4) -- .- I i Fixed condenser, O003 mid. (C1) i Grid-leak holder ...... i 2-megohm gÑd leak (R2) - . ,1 i Rad jo-frequency choke (L6) i Low-frequency transformer (Tr.) :1 On-and-off switch (Sw.) .. .. 3 Mansbridge type ondensers, i mid. - - (Ce, C7, Cl ...... : i Terminal strip and terminals . Accumulator High-tension battery

Grid-bias battery ...... Loud speaker ...... Four-Valve Circuit Parts

Type of Component First Choice - Second Choice Cabinet Panel ...... -j Panel brackets ...... 2 Variable condensers, 3005 mid. (C1, C2) . 2 Vernier dials

i Reaction condenser, 3001 mid. (C5) . 1 No.60 "X" coil (L1) 1 No.250"X"coil(L1) ...... 1 No. 60 centre-tapped coil (L2) i No. 250 centre-tapped coil (L2) ...... 2 Board-mounting coil holders 1 Double-pole, double-throw lever switch (Sw2) ...... 2 Push-pull on-and-off switches ...... 1 Aluminium or copper screen, 8% in.x 6 iii. 1 Terminal strip

4 Valve holders ......

4 Fixed resistors (optional) .... -

i Neutralising condenser (C6) - - - .IJÇ3 2 Fixed condensers, mid. (C3, C7) .. 1 Fixed condenser, 0001 (C4)

1 Fixed condenser, 0i mid. (C9) ......

1 Grid leak, 2 megohms, with holder (R3) .. 1 Grid leak, megohm, with holder (R4) --- 1 Radio-frequency choke (L3) 1 Resistance-capacity-coupllng unit

1 Good-low-frequency transformer . ,-., 1 Mansbridge type condenser, 2 mid. (C8) 0 Accumulator - Ñigh-tension battery Grid-bias battery

O O - O Loud speaker t r

37 -

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THE-\VIRELESS CONSÌRUáTOR - October, 1928 THE NEW "RADIANO" WIRING SYSTEM

- By PERCY W. HARRIS, M.I.R.E:

Il - Poceed from one point to another of wires to templates, all laboriously according to the wiring chart, making made loops in exactly correct posi- the- leads buìg enough to Pass- round -tiouis, and many of the difficulties any obstacle, but short enough to - which accompahy sonic of the systems prevent them being too loose and whiclì have been put forward. for "floppy." - - wiring sets withoût soldering. - True, theappearanco of the set wired Check Your Wiring .in this manner is not so neat as with

- I - As you make each coñnection, stiff wire, but the electrical efficiency mark it off with a coloured chalk on .will not be found, to suffer, and the - the wiring diagram so that you can whole of the " Radiano " Four can be sci' which leads still remain to be wired up in this u-ay in an evening. 1 done. By making the leads in this Additional diagrams are given to way one avoith. all careful bending show just how to join the leads to - the switch points, and an examination of the photographs will also aid in the wiring. - -- - The first staqe of the proceedings. The Screening Box

- ¡N this year's"Radiano" set, instead With regard to those components which arc I of using flexible leads terminat- ing in pinch-on tags, we have mounted on the base- adopted a method which gives board within the box, still better electrical contact and a good deal of this prevents any lead coming adrift once 'wiring eau be done it lias been secured in position. before this inner base- Take, first of all, a reel of flexible board is placed in rubber-covered wire, place the receiver, position. - It is a good plan where itli all components, - Iéads go out of the box '!' positioui in front - of you, and havoon to allow more than the length actually required, your left the wiring r and to make the loop For your first i1bo,c ; The eire twisted only at the ends where (lila ,eedy fØy looping. they join the compo- colin ection-say that 1 from the aerial ter- Below: Twisting the nents in the box making loop to ,n(,t.e it fi,-u, (I$«L the other loop after. minal to the fixed (left) condiser-mue the finished job. holding the flexible wire between the two points. Now add two - inclies or so to this length and eut off the wire from the

bare each end br about an iiìch all(l a quarter, twist the lead between the fingers, as shown, bend round the barecF end so as to grip a loop with the fingers, give the loop a single twist, and then twist it still farther by inserting a thin1jcneil, a small piece of wood, or anyrounci object, so I as to make a tight and perfectly round loop of a size which will just go over the terminal. A finished ioop is shown in one of the photographs. Complete the process atthe other end, and you have a lead with two loops, each of which will fit over the terminal shank and can be secured in position with the greatest cf

ease, nmking a firm and sound joint. - 376

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FOUL?.. I .T.heiADIAN- ______

. ...P[1CY: . t:.

1 f I

L. . H HAflRIS' M' I' R»E - - Following the suecess of the Reti-tono" Three lije de- using . . . sign of a foto-volver the - speeicti "Radiano" set - - -. wiring scheine provides a that goes a step farther in , t.ensitivity and cjficiency. [HE great success of the "Radiano" original model, and thus keel) his set sound in its theoretical design, but .11 Three, which shows no sign of right up to date as far as component that it should be of a type that will diminishing, has brought an parts are concerned. be likely to remain standard for a insistent demand for a four-valve set considerable period after publication, with one stage of high-frequency pre- just as has.the ",Ra1iano" Three. In ceding the detector, and possessing the TWELVE STAR FEATURES OF! planning the "Radiano" Four in the saine features of simplicity in construc- THE "RADIANO" FOUR. laboratory the following features were so do the No coils to change. set down as desirable if not essential tion which had much to with high-frequency stage. Screened-arid 1., circuit, not dependent ... popularity and success of the original Panèl switch changes instatitane- A sound ," Radiano" Three. It would, of course, ously to long waves. upon any trickiness for its operation have been simple to have published a Standard plug-in coils used. -. : - and enabling a wide range of com- Perfect volume control. ponents to be used so that the four-valve design soon after the Six degrees of selectivity at choice. three, meeIy preceding the detector No soldered connections. reder need not be tied down to any valve in the original set vitli a stage Newwiring system...... one make. . of high-frequency, but Will' take single- or doubk.ended L' neutralised screened-rid valves. while this would doubtless have satis- Works perfectly on 2-volt valves. High Efficiency , fled many readers, the good name of Output filter incorporated. Low cost of construction. 2. High selectivity (preferably vari- - the óriginal "Rádianò" Three was a able) to modern - valued possessiom to b'e carefully suit conditions. guarded, and we had no desire to 3. No coil cliaiiging, so that the i. It was my desire that the "Radiano" reader' could switch from th médium ' atáh the word "Radiano" to a Mur which was not in itself as dis- Four should not oilv be noel and to the long wave-band without évn distinct in its make-np, as. well as lifting the lid bf the cabinet. - tinctive and as intéresting as the original three.

Unique Wiring * Th unique wiring system used in the" Radiano" Three, wherein flexible rubber-covered wire is adoed, il enables the possessor of a " Radiano" 7 1 i set to change any one component for :

an iiproved model without upsetting - the rest of the receiver. Thus with the arrival of a new vari- i.. able condenser of improved design, a better low-frequency transformer, an improved valve holder, or any other component which the expeii- menter desires tp incorporate in his ii: receiver, it is but the work of a few moments to substitute it for the A gene'. al vicie of the n,v" R.isuiictno" Four, showing the valves an4 coils in position. 377.

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The "Radiano" Four-continued

4. First-class toue quality. 12. A handsome appearance .and a be well to deal with the points one by 4, 5. High efficiency, not only on low cost of construction. one, as well as with the reasons which 6-volt valves, but on. 2-volt, for the In the list of desirable character- led -to the particular scheme finally benefit of those who find thc 2-volt istics given above no mention is made decided upon. Point No. 1-the selec- valves suit them best. of solderless connections, simplicity of tion of a sound circuit with no tricki- 6. High efficiency in the high- construction and ease of operation, ness in its operation and a wide range frequency stage, preferably by the use as these are considered fundamental of component&-led us naturally to of a screened-grid yalve. "Radiano " points which would have the circuit with one high-frequency to he rncorporated in any case. valve, a and low- 7. Smooth and adequate volume detector two Looking over this will be seen control so that there should he no dis- list it frequency stages. a 01 1iat may tortion m the reception of the local t presents nuflul)er station even when fully timed in. be cònsidered formidable problems. No Neutralising Many experiments were made and The use of a screened-grid valve as S. The incorporation of an output many schemes in turn rejected. The filter for the most satisfactory opera- the high-frequency magnifier meant sueroser final design of the receiver did not that there would be no trouble in tion of valves when begin to take shape until the niidde required. neutralising-one of the points which of this year, when each of the twelve had given a good deal of trouble in points had carefully been considered Handsome Appearance the past to the inexperienced wireless in relation to the others. Now, as the set user. 9. The u.se of reasonably priced of result much labour and numerous Point Ño. - 2, relating to high standard components with no special or careful tests, the "Radiano" Four is selectivity, i very important., par- expensive hand-wound orhigh-riced presented to the public iiith every ticularly as the use of a screened-grid commercial coils. confidence that it will be a receiver valve in the normal tvne of circuit. 10. The utilisation of as many ex- not only of unequalled all-round per- as recommended by he makers of isting parts as possible for the benefit formance, but of a type which is very these valves, generally furnishes a of those who were desirous of making badly needed and which is detined to set which is far from being selective. the set without spending tOo múiïch prove exóeedingly popular among all In the "Radiano" Four, six degrees of on new parts. O classes of users. selectivity are obtainable on either 11. Satisfactory operation entirely So many matters of interest arose wave-band, so that wherever the from the mains wherè necéssry.. during the eperiments that it may listeier may be situated he will have a variety of stations available without interference freni one another. The particular degree of selectivity is - decided upon when the set is first

_.. - put into operation, and no further alteration is necessary. / - The Switching Scheme Point No. 3 was one of the most

¡ difficult of all to settle. It should be I remembered that whatever switching i- scheme is chosen, it had to be one in which every connection could be by means of a terminal and not - . ' a soldering lug, while, as we desired to keep the efficiency as high as -. possible throughout, the use of long L - ,.'. O leads in the high-frequency portion of .' .,. the circuit vas debarred.

- The scheme ultimately decided

O upon i quite novel, very simpUm and highly efficient. It consists in

- . using two double-pole, double-throw

- switches of the " push-pull " variety,. two pairs of standard plug-in coils and two pairs of standard baseboard-mounting coil sockets. The first pair of coils are the w eli-known - "X" variety, and the second pair the - . equally well-known centre-tapped - coils. Not only are these available A photo of he se,eening-bor bu.seboaid showiig how tI,e..,ecw,d swjth is mounted everywhere in several makes, hut a end the fitting of the extension ioi,utIe poi. ' large number of rea1ers will have - 378

t -H

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The" Radiano" Fôur---continued

them already in their possession, to 580 metres is covered, while when gave excellent quality. Normally, particularly those who have been in the switches are pulled out we run of course, on a good make of dry the habit of building the sets de- from 900 to 2,400 or more (using a battery in good condition there scribed from time to time in the 0005-mfd. condenser in each case). would have been no howl without WIRELESS CONSTRUCTOR.' Thus on the long wave-band. we can the filter, but as all dr batteries listen to the aeroplañes and aircraft ultiniately deteriorate the incorpora- Easily Arranged stations if we so desire, while th tion of the filter was decided upon not - In the aerial Circuit the earth and Eiffel Tower station can justbe heard only for other advantages; but be- I filament connection is nermanentiv atthenpperlimitof the receiver's range. cause of this tendency to reduce made to both coils, thedouh1e-pole Point No. 4, regarding firt-class battery coupling and therefore to double-throw switch changing over quality, is obtained by the selection maintain the quality at a high stan- he tap on one coil to the tap on the of a high-grade resistance-capacity- dard. .other, and th grid connections of coupling unit, a good tiansforiner and the valve from one coil to the other. an output choke, which, incidentally, Two-Volt Valves- In the anode circuit of the high- I find has an important bearing on The point regarding high efficiency frequency valve a similar D.P.D.T. quality, as by using an output choke with 6-volt as well as 2-volt valves switch changes over the connections battery coupling troubles are largely is of no little importance to readers which go to the two ends of the coil, eliminated. This was tested by using who live in country districts where the centre-tap connection on both coils being permanently in position and .joined to H.T. positive. The circuit used is somewhat similar to that adopted in the highly popular "Concert" (WIRELuSS CON- STRUCTOR ENvELOPE No. 2, is. 6cl.), anode timing and reaction on the tuned-anode coil being obtainable with only one coil. I.. The switches used require only very slight modification before fitting I. 1 into this set. It is merely necessary to unscrew the insulated knob operat-. ing the switch, ud to screw in its place an ordinary 2 B.A. brass ter-

minal. The threaded plunger of the J switch passes only half-way into the terminal, leaving the other half of the terminal open. Switch Extension Pieces Into this a. short length of biss rod is screwed, añd the insulating i knob which has already been removed from the switch plunger is screwed in place at the end of this rod. This is clearly shown in the photographs, andas such threaded rod is available - I at almost every wireless dealer, the constructor can cut the necessary length himself in a few moments, or the complete switch with the length of rod can be obtained from a number of dealers. Another v1 of tite basebow,diehieh fits into the screeninp box anl upon which the By the use of these extension pieces anode sacitch, cito he, anoclé coils, detector valve, etc., are mounted. it is possible to place the switches close to the coils and to operate them a; very old.ánd high-resistance dry there Is difficulty in getting the ac- from the front of the set. There are battery for the suil of the receiver, cumulator charged and where the is of - two switch knobs, one by each tuning using direct loud-speaker, coupling. .. weight of the accumulator itself dial, and thus they are in the most In such circumstances the set gave importance. Statistics collected from convenient position for operation. an audio-frequency howl, but by the the various valve makers show that The tuning range is particularly large; introduction of the output filter there are far more 2-volt valve3 for when the switches are pushed in scheme as shown, the howl was im- in use thafl of any other voltage, and the band of wave-lengths from 200 mediately silenced and the receiver therefore it was important that the

V 79 . .

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I'HE \VIRELESS CONSTRUCTOR October, 1928

The "Radiano" Four-continued

"Radiano "Four should be thoroughly voltage applied to the detector valve. It is always the policy of the uccessful on 2-volt vals es. In the "Radiano "Four this is done by WIRELESS CoNsTRUcToR to design, Fortunately we now have excel- means of a variable, resistance eón- as far as possible, efficient receivers lent screened-grid valves of the 2- trolling the filament of the screened- utilising (very frequently in a new volt variety made by.Marconi, Osranì, grid valve, and when this valve is manner) parts already available, Mullard, Cossor and Ediswan, while eitinguished, as can be done with the and, if possible, obtainable frm_ 2-volt output valves of high volume control, no signals whatever several makers. Take, for example, quality, coming almost into the get through unless a very powerful the low-frequency transformer. super-power class, are also now avail- station is very close to the set, when a Great Britain is particularly fortunate able. All the tests with the "Radiano" slight whisper can be heard. in having a number of makers who 1?our have been carried out with 2- tnri1 out really high-grade instru volt valves throughout, and the 'The Output Filter ments, and while .onè particular maké rcuIts given in this article ar those Point 8, namely, the use of an out- must be chosen when the set is de'- obtainable with such valves. put filter, has also been explained signed, since all makes cannot be incor- above, but here it should be said porated in one receiver, the choice of High Efficiency that not only has the output filter the, particular instrument illustrated Obviously improved results are the advantage of reducing battery must not be taken as meaning that obtainable with the 6-volt varieties, coupling troubles to a large extent, but this is the only one for the purpos&. and those who have such valves and also by removing the loud speaker from Unless it is specifically stated other accumulators available are strongly the path of the direct current flowing wise, any other equally high-grade recommendéd to use them, but the in the pate of the valvé it enables a components can be substituted for readers who are limited to -volt higher efficiency to be obtained with those shown. valves may rest assured therefore super-powef valves, while protecting that the receiver is thoough1y effi- the loud-speaker wirldingB froth heavy All Mains Operation cient on such valves and will give.them currents, which would otherwise pass In point No. 10, reference is made full satisfaction. through it. The choke and condenser to the uso of existing parts. A large Point No.6, regarding high efficiency method is used here in preference to number of experimenters when build- in the high-frequency stage, is really a the transformer. ing a new receiver like to utilise as matter of set design, and by the use Point No. 9, relating to the use of many parts as possible from an older of a screened-grid valve this has un- standard components with no special set. In the "Radiano Four this can questionably been obtained. or expensive coils, is of most import- be done very efiectively, and many Tite volumecontrol point, No. 7, ance in the design of a really popular readers will find they have practically all the parts on hand. Point No. 11-that the set must be capable of operating entirely from the mains when desired-is completely solved so far as AC. mains are concerned by the " Stedipower "L.T. and H.T. uníts which have already been 44» 4, F described in our pages. Incidentally it should be pointed out that the "Stedipower" H.T. Unit is one of the few that it is convenient to use with scÑened-grid valves, for one can get not only a definite and smooth adjustment of high-tension voltage on the tapping for the screen

grids but can also see on the voltmeter exactly what voltage one is obtaining. * The operation of this set from D.C. mains is possible so far as H.T. is concerned, for there is a number of D.C. high-tension units now avail,. able. A D.C. "Steclipower" I he iterioi of the ct-eoncoa(e1 from ge.cial view-is somewhat i.miUds, looking, ¿(mie (o ¡he mnethomi of meiliug, but this is no real drawback, the simple operation of On the LT. side no "Stedipower the sel ô,,d ils e1reme cge of construction being vely valuable features. unit for D.C. is yet ready, but laboratory experiments are being conducted lias already been partially explained receiver. Every designer worthy of with snch a design, and we hope to above, and here it may be said that the name can work out a set which publish some re.ults soon. Finally, all experts are agreed that the only will have many advantages provided point No. 12-a handsome appearance really stisfactorv form, of volume that special parts are built for it and combined with low cost has, we think, control is one which reduces the oniy these parts used. been satisfactorily effected. L 380

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ßJA 44 a.pj# ßJ4 4 4 Va ViV4 Va Vß V4a V4 V4 VA VA VA VA VA VA VAAAV4 A V4A VAAL4AVA4 A -VV'aV 'W' '- , 1 BUILDING THE "RADIANO" FOUR The phenomenal success anti popularity of tite" Radiano" system of wiring, as illustrated by the famous" Radiano " Three, published bist year, has prompted the originator of tite scheme, Mr. Percy Harris, to go.one better, which hie undoubtedly u,s done in the design of titis masterpiece of sets-Tue " Rad jano " Four. -

By PERCY W. HARRIS, M.I.R.E. 4ç * ._ * tja ja n ja n ja n n ja n ' n n ja n n n.ja ja ja ja j4 n n nja n n ja ja n n ja jja ja n ja n n n ja n n n ja-ja n n n n a n n n n ja ja ¿a ¿4 a& a, a a a ç o ,? o o o o o o o a o ,flr o te te j

U1LDING the " Radiano" Four is bad plan to secure the two bthckets to indicate where the box hole is to .JL.) an easy matter. The wiring to the baseboard with screws tern- be drilled.

method described on another iorarily. - Now remove the box and drill a

page is so simple and such a wide Do not yet mount any of the- large-hole in it, using the scratched - range of components is now avail- components On the panel itself, but circle as the centre. A i-in. drill able that it has not been thought take the standard screening box and will suit quite well. You will 'find necessary to publish a full-size tem- bring it up against the back surface the drilling easier if you stañd the plate of the actual wires, as these box with the surface to be drilled can be cut as one goes along by a very upwards and pack the- inside 'itli TWO-HOUR TEST REPORT. simple method of measurement which pieces of wood so that you are will b described a little later. mci- Speciál Note.-All stations below Vpressing on a block of wood under- were received on 2-volt valves through- to dentally it may be mentioned that out. In no case was strength of 'neath the copper when, drilling. This the "Radiano" wiring system using reception below that which is fully will avoid bending the box. Several adequate for comfortable reception in rubber-covered wire possesses the V firms will supply the boxes withthé a good-sized living-room, and in following great advantages. - many oases the volume control had: holes cut if necessary. 1. Careful bending of wires and to be used to reduce strength to a lo6ps o exact shape and size is en- comfortable figure. All reception The Switch Support V V tirely obviated. within two hours. The only other VW!1l' be 2. The change from one' make of hole it NORMAL WAVE-BAND. V necessary for you to drill, and which component to another does not necessi- - Reading on is not already provided in the standard tate cutting and making new leads, and Nameof Station second dial. of a set Stettin 21 screening box, is the small hole to while the internal appeara.nce...... V Bremen ..... 33 take the, lead which goes from the '.' is V wired system V under the Radiano" Cologne V VV 35 V plate of the screened-grid valve 'into

not so pleasing as one wired itli stiff V Belfast ...... 41 the box. This is drilled an inch from wire, "handsome is aandsome *Bourflemouth 43 Barcelona the top of the left side of the box

who are V does," and those readers ...... V

'London . 54 more skilled in set building will fina it V and in the middle of that side. Unión Radi'o (Madrid) 57 The screening box is provided with set with 58 very, simple to wire i.p this V V Stuttgart ...... V Toulouse 60 - a removable interior basêboai'd, and stiff wire if they so desire. - ...... :. VV.VVV..VVV. 61 VV -you 3. There is no need for gréat Hamburg .with -this-in'position should take Frankfurt 68 a strip of ebonite 1 in. wide and V accuracy of leads...... - . in the length . -Rome. ., 7t _V V in. long, and hold vertically with : 'Langenbeg .: 75 it 79 its, lower -end pressed against the Easy. to . Build Daventry Exp.: ...... i Budapest . 89 interior basebnard and its front V V VV! While the constructioñal work is V :- V siirface- against the' inside of the V very -simple, it is advisable to follow - LOÑG WAVE-BAÑD. V V copper box against the large hole E Hilversum - V 26 -. E V V the liner laid down in this rticle V Kalundborg 32 whicEy'oúhavealindy rilled for the all of ...... V fit V in order that the parts may 40 switch plunger. Arrange this strip accurately, no matter what make is V Motala 46-' V.: SO that the large holà comes on its .. used. V - - .. 62 71 centre' line, and then scratch through The first step is to lay out the panel "Radio Paris ...... V 74 the hole in the box with a scriber or E Angora : .... and to drill the holes for the com- .- ...... 77 Huizen. V other sharp instrument to indicate ponents shown as mounted thereon. Readings for.flrst dial will be very the position of the hole in the strip similar, but will yary according to The two holes for the plungers of the which will take the switch itself. wave-change switches should be only which of the six degrees of selectivity is chosen, and the aerial V.' used. slightly larger than the rods themselves Stations marked with a star, are re- The Extension Rod in order that the panel itself may form ceivable in broad daylight' in London a bearing. area. When this is marked remove the Next stand the panel' vertically strip and drill it with a -in. hole against the front edge of the base- of the front panel' so that the hole for the double-pole double-throw board and mark out the positions for in the panel for the second variable push-pull switch. A similar pro- the two panel brackets. Drill the condenser comes in the middle of the cedure for marking the position of the holes for these and mount the front of the box. Holding the box hole for the switch for the aerial brackets on the panel. You can now firmly in position against the panel connections should be adopted, but stand the panel vertically against take a sharp instrument and scratch in this case the ebonite strip will be the front edge of the baseboard through the second switch-hole a 1 in. wide and 3 in. long. -The ready for the next step. It is not a circle on the front of the box, so as exact length of these two strips does

381 .

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- Building the "Radiano, Four-continued

not matter provided you get the copper box, seeing that both holes Unscrew the knob of the aerial level on the panel. Next cut two I switch and screw in its place a brass switch holes in the right places. are i Remember that the distance from thin strips of wood about iii. or terminal so that the thread on the the bottom of the strip to the centre in. thick, and approximately 14 in. switch plunger will only go half-way the two ebonite into the terminal. A 2 BA. terminal of the switch hole will be diflerent by 2 in., and fasten Si in the two cases, owing to the fact strips which are to carry the switches is needed, as a 2 B.A. thread is cut

1IMt fir- f

3 ., - i T' T

Ge#LIJ. -I U ''I (WqV-CH.QÑGE LT 5W/TCN/NG -L O,WfrED) F,G.L

that in the case of the aerial switching vertically against the front edges of òn the plunger of the switch. Now the bottom edge of the ebonite strip these, and screw them into position, take a piece of brass rod 4 in. long eones against the main baseboard, as shown, on the inner baseboard of and threaded 2 B.A. for a short dis-

whereas with the switch inside the the copper box and the main base- tance at each end. - opper box the distance will be board respectively. The correct posi- Brass rod threaded B.A. for its shortened by the thickness of the tions on the baseboards are ascer- whole length can be obtained quite

inner baseboard plus that of the tained as follow. - easily from any wireless dealer, and

LIST OF COMPONENTS. NOTE.-Except in the case of the i Terminal strip with 5 terminals, IMullard). R.L-Varley, Lissen, radio-frequency hoke (see article), 5 in.. X 1} in. Dubilier. and the special switches, any other i Terminal strip with 7 terminals, i Grid leak and holder, 250,000 ohms high-grade components can be sub- 7 in. x 1% in. (Not necessary if Mullard R.C. unit stituted for those used and named. 4 Valve holders (Lotus). Benjamin, is used. See article). Names in brackets are those ifius- Magnum, W. B., Formo, Igranic, i Low-frequency transformer (Philips trated. Marconiphone, B.T.H., etc. or any of the many high-grade Cabinet with 10-in, baseboard (Art- ' Board-mounting coil holders (Mas- makes flow available). craft). Bond, Raymond, Camco, num, Lotus, etc.). i Low-frequency output choke (Igranic Caxton, etc. 2 Fixed condensers, 'O01 mf d F., Marconi, Ferranti, R.I.-Varley). Ebonite panel, 21 in. X 7 in. (Resiston, (T.C.C.). Lissen, Dubiier, Igranic, i Standard screening box, "M.W." decorated corners). Ebonart, Becol, Milliard, Atlas, Magnum, etc. pattern (Peto-Scott). Magnum, etc. - Camden, Paroussi. 1 Fixed condenser, '0003 mId. (T.C.C.). 2 Vernier dials (Indigraph). Lissen, 2 Pieces of wood, 1 in. X 2 in. X in. S (See above.) 1 etc. . Fixed condenser, '0003 3 4 B.A. metal screws (cheesehead) 2 Variable condensers, '0005 mfd. i mid., with s.p. terminals (T.C.C.). (See above.) and nuts. (Lissen). About 25 yards rubber-covered, flexible I Reaction conlenser, '0001 or '00015 i Grid leak, 2 megohms (Dubilier). wire (Lewcos). Ward & Goldstone. mfd. (Peto-Scott, Cyidon, Bowyer- Llssen Mollard, Igranic, etc. (Note.-This will aUow ample supply

i Lowe, etc. Formodenser, 00003 mid. max. for battery leads, etc.) - i On-and-off switch (Benjamin, Lotus, (Note.-Do not mistake this for i "X '- coil, No. 60. Lissen, Igrani; etc.). 0003 mid. pattern.) i "X" coil, No. 250. i 30-ohm panel-mounting rheostat 2 i-mfd. fixed condensers (Dubiier). i Centre-tapped coil, No. 60. I - (Lissen). Igranic, Peerless, etc. T.C.C., Lissen, Mullard, Ferranti, i Centre-tapped coil, No. 250. 2 Double-pole double-throw push-pull Hydra, etc. i Screened-grid valve (Cossor, Ed1 switches; with terminals (Lotus). i 2-mîd. ditto. swan, Marconi, Osram, Mullard,

2 Brass rQds, threaded 2 B.A., 4 ¡. i Radio-frequency choke (RJ.-Var- Six-Sixty). - i. long. ley). Magnum, Climax, see note in i B.C. type valve. L i 2 Panel brackets (Magnum). Peto- article. i H.F. type valve.

- Scott, Camco. - - i Resistance-capacity-coupling unit i Power or super-power valve. -

382

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October, 1928 THE WIRELESS CONSTRUCTOR

Building the "Radiano" Four-rcontinued

this will do quite well for the purpose. from the copper box, being careful used has four terminals, so that the Next, screw the knob which you have not to move the copper box from its two windings inside can be used in removed from the switch tightly on position. The box itself should now series or in parallel, the parallel one end, and then insert the rod from be screwed to the baseboard. arrangement being used in the present the front of the panel through the Depressions should be made on the set. Other makes of low-frequency aerial switch hole, and screw it into underside of the- inner baseboard to chokes or output filters have only the front of the brass terminal, which allow for the heads of the screws two terminals. The wiring up of you have fixed on the plunger of the whieh holdthe copper box to the main this set is simplicity itheif. switch itself. A little adjustment baseboard, otherwise these screw- will baseboard will screw both rod into the terminal heads lift the inner -_ '-HT' and terminal on to the switch quite above the position it should properly occupy.

Further Construction - The varions components can now be mounted on the panel and on the baseboard. There are no other critical positions, hut you should follow as closely- as possible the positions shown in the drawings and photographs. The Mullard resistance-capacity-coupling unit shown has incorporated in it a high-frequency stopping device, aiid if you use any L1 firmly. Push the switch in, and by other make it is advisable to put a ñG.3. i j moving the switch assembly about on grid-leak holder with a .-megohm -- the panel you will find the position grid leak on the right of the copper in which the small baseboard carrying box (looking from the Iront) near The first valve should be a four-pin the switch supports can be secured. to the grid termina-1 of the first note- screened-grid valve of the 2-volt Screw the small wooden baseboard magnifying valve. variety, the detector a 2-volt RC. - down to the main wooden baseboard This -megohrn leak shou'd be valve, the first note-magnifying stage with two small wood screws, and you joined in series between the grid a 2-volt HF. type, and the output can remove the rod from the switch terminal of the R.C.C. unit and the either a 2-volt power valve or the - until such time as you Mill per- grid of the first note-magnifying newer 2-volt super-power valve. In manently mount the panel in position. valve. The Igranic output choke the screened-grid valves excellent Mounting the Switches To ascertain the position of the switch inside the copper box, place the copper. box in position on the baseboard so that its back comes

about - in. from the back edge, and a line drawn from the second condenser holè to the back of the baseboard runs in the middle of the copper box. The photographs and diagrams will make this clear. Place the removable baseboard inside the copper box, take another piece of threaded tod, of the same dimensions as before, screw the knob of the switch ou one end and pans it as before through the panel, and in this case through the large hole in the copper box. Push the switch plunger in and screw the knob into a brass terminal which has been fitted to the plunger of the switch, and adjust for position as before. This second switch assembly can now be screwed to the inner baseboard of the copper box in the correct I The s.eiteh and miado circuit baseboard, eh ich fits into the screenin(J bor insist be carela-lb; hti4 out as shown. position. Remove the rod, pull it

out and remove the inner baseboard - 383

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T WIRELESS CONSTRUCTOR - October, 1928

Building the "Ra diano ". Four-continued

results have been obtained in this you use. This tapping only supplies for the particular output valv you set with the Cossor, Ediswan, Six-Sixty the screened-grid voltage. H.T. use for 120 volts. and Mullard screened-grid valves. . positive 2 should have 120 volts. As there is no neutralisatiot to be HT. positive i should have the Three volts grid bias ill do for carried out, onecair operate the set - value given by the makers for the G.B.I, and G.B.2 should have the directly it is finished. Remember screening grid according to the valve grid bias recommended by the makers that when the switches are ptilled

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Building the' " Rdiano' Foúr-éontwed

i. out you will be on the long wave- as either tap can be used wifli i high enough use the 0001 condenser band, and when they are in you are any of the condenser instead of 0003 mid. J arrangements, j the on wave-band. The the shorter wave- six degrees of selectivity aíe I For your first test you should set

length ranges are approximately 200 obtainable. I the reaction ondenser at zero and J - the Formo baseboard condenser about 2r two turns off maximum. Turn thé 44 2 J volume control (which is really the filament resistance on the high- frequency valve) to the full on position. You will not find that the twò dials will tune exactly the same, as .64 CT/ON the influence of the copper screening ON-O,, box will slightly alter the tuning of 3' T: the coils inside that box.

L I t f i 1H Vólume Control P.4NL, ¿Ardor There is, however, only a few degrees difference, and on some read to 580 on the shorter band and frjifl 'As a sart, connect the lead from ings they will come approximately J00 to 2,4OQon the longer bánd. the aerial terminal to the 0003-mft. the same. Typical readings are cöndenscr and the lead whi'eh goes given in the test report, and the Selectivity Variations from the end of this condenser to the readings on your own set should be Sidegiees of selectivity are obtain- higher tapping on each" X "coil. This very much the same. able by taking the lead which goes will give you an excellent degree of If a station comes in too loud you from the aerial terminal either to the selectivity for general work, and if will find the volume control will give 0001-mfd., the '0003-mM. condenser, you carry out your preliminary tests you perfect control of strength with- or onto the output side of these tw in this way you will probably find out in any way altering the tuning condenser which is conneôted thatthe selectivity will be quite good or the quality. In fact, the quality through the switch to the tap on the enòugh for your purpose. If you want will be improved on using this when a "X " coil. Similarly, you have a choice it higher, first of all changé the tap- station is' nearby, as it will cure any of two tappings on. each ' X" coil, and, pings of the "X" coils, and if this is not distortion due. to overloading your

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4 ,eie,a1 vww of the ' fludiano '' Four, showing the sereened-grùt vulve -in position und the other eulves and cuits «Eso reaiig for worh. 'The lid of the screening bo bus been veglio ved to show the cwnpon eut-s inside. 35

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Building the " Radiano '' Four-continued

valves. Reaction will only occa- as there will be nothing in this par- strength of signals received from sionally be used to stTengthen signals ticular' socket when the double-ended Angora, Turkey, on the long waves. and slightly to sharpen tuning, but valve is used. This was so loud that the volume you will get a very large number of No other changes of any kind are control had to be used to reduce stations without any recourse to necessary, so that the set is equally distortion. this. - utilisable with the single, or double- For those who desire to use the

eded screened-grid . valve. The ordinary type of H.F. va've and not High Sensitivity test, report does not indicate, all-the .the screened grid, a special articlç If you wish to use this set with tations. which have 'been received will be provided next month., A 6-volt valves and the double-ended on this set, but only those received number of further useful notes, on type of screened-grid valve, the only in a 'relatively short period on one this set will also'be given in, thenext niteration necessary will be to take evening. Extremely.high sensitivity issue. ' a flexible lead from the HT. positive i is obtainable on both short and long terminal to a spring clip, and clip waves, and irsing 'the' outside aerial this on tie screening-grid, pin, which at Wimbledon, 5 X X, Radio-Paris JTHE "RADIANO":' will now go on top of the valve. and Hilversum all need the' voluthe Another clip should be attached to control in daylight to ' prevent THREE -the plate lead. You need not trouble overioauing tne vaives. * to remove the existing connection One of the most astonishing experi-

- which goes to what is normally the ences with the set when it was first SIR,-Ha.ving built the " Radiano" plate terminal on the valve holder, put on test was the x'enìarkable Three a few weeks ago, I thought I would let you know some of the results obtained from same. London coils, I have tuned in - With fifteen,statións on loud speaker. AU German stations1 Radio Toulouse, and a Spanish station come in exceptionally loud, but iire subject to fading. (I use flat coils on cardboard formers, instead of those stated in book, and find these give greater volume on foreign stations, though not quite so selective.) - Have had splendid results on short waves, down to 15 metres. Stations ! received are as follow: With coils statel in book: K D K A (very loud), Nauen (testing), Radio LL (loud speaker). I' . Melbourne Received ç4Y - With Tgranic coils (No 2), aerial, 4 turns, and (No. 4) reaction, 9 turns, No. 2 tapped ofT at 3 turns, with -.

small flat coil for choke, and vâriahie - grid leak set practically at zero, I get 930 2 X A F, on condenser, at -full Ioud-sieaker strength. 3 L O, Mel- ., - - _í bourne, comes in at 72.5°, with 2 N M, Caterham, at 920, and I can oscillate down to 70°. * - ( By placing a small neutralising condenser in series with aerial and ..- - shorting three turns of reaction, I get 5 S W on loud speaker at 42.5°. ! By furt-her shorting another turn on (-. 'p reaction, I can oscillate down to zero. Valves used are three ,Cossor general-

purpose, 2 volts. -

. .:- - - Yours faithfully, The L.F. end of She set. Note l,oiC cas.; the ,cirinp s to connect j.p. No SYDNEY W. H. sojderin; is required, the Semis just being taken front point to point «s required. en 386

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revohe,sotheptme 'il be :ece ed T E LE P HO TO G RA P experimnts pro.re successful ad adequate receiving instruments a re placed upon the market at reasonable cost, listeners will be able to receive in their own homes news photographs, I maps, diagrams, dressmaking sketches, picture puzzles, crossword puzzles, and a multitude of other things:

- The Fultograph It is possible that a good mny readers, on listening-in to 2 L O a.n r 5 X X after midnight during the past few weeks, have heard peculiar sounds, something like clicks and whistles, etc., and have wondered about them. They have been due to the experimental picture transmissions which _- L______have been made by the B.B.C. The B.B.C., of course, will not at the Siwli wc sOon have .Tcn'plioto broadcasts, or Television 7nogr«mnies ? This question is discussed -by moment say exactly what picture system it is going to adopt. Probably OUR SPECIAL CORRESPONDENT L the best known is that of the Fultograph, which is the invention flrHE B.B.C. recently stated tMt of lata in the Press. it l's till evident of Captain Otho Fulton, an English- i - iL it hoped to begin an ex- that quite a number of people are man who lias for some time lived perirnental service of pictur çonfused as to the, real meaning of abroad in Vienna, and whose system transmission early in the autumn. picture transmission and television. is the only one in regular use by a This announcement caused a con- It may be quite simply. expressed broadcasting station, i.e., that of siderable amount of interest, inasmuch thus: that pictùre transmision is Vienna. as only a few weeks ago the B.B.C. that of still pictures, the process There is a coñsidetable doubt. as stated that it had definitely decided taking sevral minutes, while tele- to whether the average listener is not to experiment (in the public vision is the transmission and re- anxious to include in his daily pro- sense) with television or telephoto- ception of moving pictures instan- gramme the reception of still pictures. graphy. taneously. Telephotography is, of course; very But it seems that the engineers In picture transmission a still distinct' from television, but it is of the B.B.C. have had cause to picture is transmitted ffom a station quite likely that many people will change their minds, and there is and received on a revolving cylinder, imagine that in due course tele- no doubt that the progress which has been made in the transmission of still pictures has, during the last twelve months, been very remarkable. An Experimental Service - Nevertheless, listeners should not .; : 1) count definitely on a regular picture out e.vpe'rneuts ia

service transmitted from the B.B:C. S0000lC - tt(«CISlOfl iii'; - " stations. It is quite likely that lubovatuvy .ii Long .-tr,S;-. some sort of experimental service will he inaugurated in the autumn, but it all depends, of course, how successful the transmissions are, and whether the public responds in the matter of patronising the service by the purchase of the necessary picture-receiving apparatus. In any case, the B.B.C. still seems disinclined somewhat similarth the early gramo- pliotograpy an be ' speeded up" to say definitely that their service phone cylindei.. This cylinder is so that regula .lnoving pictures can will be a regular feature. covered with a sheêt of snsitised be received in the home. But the The B.B.C. has quite rightly paper, and on it a fairly hcurate principIe of still-picture transmision pointed out that there is a very great black-and-white icture can be snt and moving-picture transmission are difference between picture trans- in a few minutes. Listeners possessing -verydiffrent, and it should not be mission nd television. Despite uch receivers will be ible the anticipàtd ht the B.B.C.'s in- the tremendous amount of publicity- picture gradually coming out at augural telephotography experiments which has been given to both subjects the receiving end and, as the cylindr are a prelude to a television service. 387

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Telephotography and Television -continüed -

It has been definitely stated by the say, the head arid shoulders of a The author of the "Times ' articlé B.B.C. that it will have nothing persoTa from one place to another, the sums up by saying that, "so far s to do with known systems of tele- system is exceedingly complicated one can judge from the technicái vision because, in the opinion of the and, although built up on sound information available, it would appear B.B.C. experts, television is still engineering principles, leaves the that the image obtained from a home in the experimental stage and, con- originators of the scheme very much, set would b& an exceedinglv coarse sequently, not suitable for public in doubt as to whether it would offer and horribly distorted affair, and service at the nioment. That it will a hopeful system for broadcasting would dnly be seen at intervals when be some day nobody doubts.; but because of the zery great expense exactS syichronism had been ob- it would be as well to get the idea it would be necessary to incur. tained. The service area would be clearl in one's head that television As the author of the article points small, and the wave-length channels : is not for us at tue preseiit. out in the ".Times," to receive tele- required very wide." vision by the American Telegraph and This latter point is interesting Some Press Correspondence Telephone Company's method would because it is obvious that severe con- - Regarding television, it lias been require apparatus costing hundreds gestion in the ether would be caused. interesting to note that the " Times" of pounds and, most probably, a staff lias recently been publishing some of skilled engineers to work the set. No Licence Necessary? correspondence on that much-debated Consequently, in his opinion-and in A discussion has arisen out of the question. Mi'. A. A. Campbell Swin- the opinion of all those who have proposed television service for October ton, FRS., has contributed two letters taken the trouble technically to study which may lead to very interesting to that paper, which have, in them- the various systems of television-a developments. An announcement re- selves, constituted an act of public home set on these lines is quite out of cently appeared in the" Daily Mail service, inasmuch as they have the question. stating that in an interview with the considerably cleared up many mis- secretary of the company which pro- apprehensions in connection with Severe Ether Congestion poses to start the television service in television. Although Mr. Campbell Why. therefore, asks the author of October, a " Daily Mail" reporter

Swintons theories were criticised the " Times " article, are there pro- was informed that no licence had been -- - by Dr. Robinson, Mr. Campbell posais both in j\merica and this applied for from the Post Office because the company had been informed - on high legal authority that television, being a new development, did not come within the scope of the Acts - -- governing the use of wire]essin this country. - -: - That view is, òf course, a matter of 4 7 legal opinion; but it is interesting - - td remember that not so longago a -.

Wireless amateur refused tO pay.his - - liceìce fee on the grounds that listening-in with a modern receiving apparatus was nöt an öffence because he did not purchase a licence. That

amateur, of course, as our readers . - will remember, took his case to Court :

and lost it - The Wireless Telegraph Acts - Ci,,t. O. Paillon (right) with sorno of his «pparall.s by ,a.00ns of which 8till-piCtiicS can The original Wireless Telegraph be bao«tic«tt. (Nofc tiiot these mc "still "piel ,res-not nioriiag "telcrision.") Ac of 1904 prohibits the establishment of any wireless telegraph station Swinton, in reply, very neatly and country to sell home sets and to and the installation or working of any very conclusively made it quite deaf inaugurate a broadcasting service ? apparatus for wireless telegraphy. that Dr. Robinson's arguments did Although no full details of the In 1904, öf course, broadcast receptioñ not hold water. system to be used in Great Britain had not been contemplated, and, in for the television service promised for the amateur test case above referred Expensive Apparatus October have so far been published, to, a doubt arose when the B.B.C. In tlìe " Times " for August 8th, it is fairly clear that in order to make system became established as to an article also appeared following the receiving set simple in construc- whether this original Act of 1904 upon Mr. Campbell Swinton's corre- tion, all the safeguards that the sufficiently coveied the use of broad- spondence, in which it was pointed American Telegraph and Telephone cast receivers. out that although the American Company found necessary for the This point was' settled by the Telegraph and Telephone Conipany reproduction of detail and the thain passing of the Wireless Telegraphy were able to transmit a very tenance of exact synchronism are (Explanation) Act in 1925, in which faithful picturo by television of, likely to be sacrificed. -. (Contimu&L oa paje 44). 388

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j S Reçenerator / I Wàves II

S point for receiving signals. S CW. The terms below md 'bove 'ire - somewhat, misleading, but S express the meaning in a crude sort of way. t should be made clear at the aIIIIIIUlIÌ!IUhIIIIIIIIHhIlI!IItIflhtHhÌUIUhtI;IlIlIIIIIHI I outset that tue set described in A remarkably .qen.citire reeeirei' E Most Sensitive this article is intended rather E on which the il,ncricu,i stations E The point to be brought out is this as a novelty or the opeuing for a = can be received "almost as loud E E as they can in the usu(IL way with E -that although the yery " thres- fresh line of experiment by the = a detector ami lico stages of L.F." E hold " of oscillation is the most short-wave enthusiast than as a sensitive condition in which it is first set " for the man who has not, By L. H. THOMAS possible to operate a receiver, we never do it. This is for the simple reason lu iiiiiiiiw ìIlIItt IIIH ill 1111111 Dli lili lID 111111W I flHlUhlU i. that it is impossible. to make a set COMPONENTS USED stay at this point. The average i Panel 12 in. x 8 in. x in. (Any worrying to those who are not already eceiver has quite a smooth control good branded materia». used thhandling a short-wave set of of reaction, as we say, but at the same I Cabinet for above size, with loose some description or other. time there is always a very definite baseboard 9 in. deep. (Artcraft, Bond, Cameo, Caxton, Makerimport, It is mainly a telephony receiver, point at which it ceases to be a non. Pickett, Raymond, etc.). although Morse may he received oscillating set and becomes one of the i 00025 variable condenser (Marconi- quite satisfactorily. The point is oscillating variety. This is not to be phone in set. Any good make). I "Volume-Control "Carostat (Louis bizman). NB.. ¿3 &L4 AR HFvo.k-E3 COUPLO TOE7WE. i On-off switch (Benjamin, Lissen, 4 Lotus, Igranic; etc.). HT-W i Baseboard-mounting rheostat Lissen or similar tipe). NFC » L416 FD. 2 H.F. chokes (Burne-Jones. See text). ï H.F. choke (Metro-Vick or other standard make. Igranic, RL- .0003 - . C2 . . Varley, etc.) I

I - - - . . - I 2 Valve holders (Redfern or other II . standard make). 2 Baseboard-mounting coil söckets Cij /IT (Lotus or. other good make). L, 0003, 2 0005, and i 001 lixed eon- 6OOOOJ( _j densers (Clarke, Dubilier, Igranic, :. . L-'-' Lissen, Mullard, T.C.C., etc.). - i -5-meohm and i 60,000-ohm grid leak (Ediawan).

- i Baseboard - mounting ne'itralising - F/G./

condenser (Igranic or other good i . 7/IEORE7/CAL CIRCO/i: - make). X337 i Two-terminal and i seven-terminal strip. that the benefits of the set show up confused with i 1-mid. Mansbridge type condenser "phoppy" reaction. (Diibilier, Ferranti, Hydra, Ltssen, more on telephony than on anything It is always the case. Mullard, T.C.C., etc.). else. Tinned copper wire, wood srews bolts, Many readers will doubtless know Super-Regeneration etc. by now the principle of super- If the set is used in the non- regeneration. A few words concerning oscillating state and we increase the as yet, descended lower in the wave- its advantages as applied to short- reaction control (whether this is a length scale than the lower of the wave reception *ill not, however, be variable condenser or a swinging broadctsting stations. out of place. coil is immaterial) there is just the The ordinary regenerative, short- merest fraction of a second during- Quite Different wave receiver, i.e. the standard de- which the valve is extraordinarily Although there is nothing freakish tector with reaction, possibly followed sensitive; but it is only a fraction of about the circuit employed or the by bne or two stages of L..F., can be a second, andis gone before we know operation of the set, it is quite worked in two ways. It is either it is there. different in its le1ormance from the operating just below the oscillation Now, if we slacken off the reaction general run of short-wavers, and is point for the purpose of receiving control again, we i encounter another- therefore liable to prove rather telephony, or just aba-re the oscillation - fraction of a second during which the

- 389

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The Super-Regenerator on Short Waves-continued, -

valve is super-sensitive, and then we have passed the point and the set is" below "oscillation point again.

I remember reading in ai American --"---.. I paper a long time ago a short " popu- --'. _ 3- lar" article on super-regeneration in which the writer was talking about this super-sensitive point which is not attainable in any ordinary set, and he remarked that if one had the patience and the, skill to keep jerking the reaction coxitrol across the oscillation point, so as to be continually

1 encountering this spot we have been t . talking about, he would have produced all the advantages of super- regeneration. Bui be would have to I - d it at the rate of something hike 10,000 times per second t An Ingenious Scheme This gives one a very clear general Fio 3. F,WN7' ÔF PANEL. yogi idea of the principles involved. A super.regenerative receiver embodies some device which keeps it, to all valver, which is controlled by what Ït will be seei from the circuit diagram intents and purposes, " standing on we may term a "10,000-cycle modu- that the short-wave detector circuit the threshold " of oscillation, by lator," which is another valve oscil- is absolútely straight with thQ excep- -causing it to stop oscillating and to lating on a very long wave-length, tion that the grid leak, instead of start again at a tremendously high corresponding to a frequency of 10,000 being taken down to the filament circuit, is taken t&the grid circuit of the long-wave oscillator, thus allow- ing some of the energy of this latter valve to be fed to the detector. Thus we are doing the necessary P control of the detector by throwing its grid bias backwards and forwards at a sufficiently high rate to draw it in and out of oscillation extremely rapidly. This is a more practical method than a hand- or motor-driven reaction coil revolving at the rate of

10,000 times per second! - The frequency at which this modulator operates affects the sensitivity of the set. The lower the frequency, within limits, the greater is the tb sensitivity, for if we make it too high the super-regenerative action does not develop at all, or, rather, is cut off L : before we realise that it is there. Telephony Specially Good Tiais plaoto gaves u vicar of part of tue If, however, we attempt to use a buck of the set to- frequency lower than 10,000 cycles it qellaer with a iie,e oj becomes audible (many persons i tue fvoaat paiael. l'oaa atril can seo haut hic receiver is a just hear a note of 12,000 cycles or s inapte, sfra ightfor.ewd so as a very Jìigh-pithed seseam), assembly. - .- and we have to arrange all manner of filter circuits and the like to cut frequency. This is probably the very cycles (which gives us 30,000 metres), out the undesired musical note. simplest way in which to express a so coupled to the detector as to cause Fortunately, for short-wave work rather complicated principle. it to stop oscillating and restart 10,000 cycles is quite low enough to In the receiver described here we 10,000 times per second. be perfectly satisfactory and we do ha'e an ordinary .'9:»yP .g1e: To come down to practical details, not meet this trouble. If it.is audible 390

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The Super-Regenerator on Short Wavés-continaed

it is sufficiently high and subdued valve in this case is only to oscillate in this case is a neutralising condenser, not to be at all worrying. Probably hard! So great is the sensitivity which is nearly alwaysworked in the the actual frequency is somewhat òf the circuit that it makes hardly all out" position. above 10,000 in this act. any difference to the- average signal The grid condenser has a value of With the short-wave detector work- if one removes the aerial altogether 0003, the fixed reaction condenser-is iig under the conditions we have and even earths it! 001. and the grid leak (which, it must arranged now, it never really oscil- The detector ircuit, then, is quite be remembered, does not operate in the ordinary way) is of 60,000 ohms. - 1 Modulator Arrangements Turning now to the 10,000-cycle mochilator arrangements, it was most O v - -I happily found that two H.F. chokes could he arranged as the necessary j coils for producing the long-wave

- T1r4 k! i - HY. cIaoles oscillations. One of the more usual boltedlogetlicbopeb.: ways isto use a 1,500- anda 1,250- - J - - turn coil, but these large coils are J fl -i j coupling. Tiwynuthe bulky as well as expensive and the a neat ae,nbly and j «re Jar more neat component produced by bolting f poet Uu,n tiie large two 11F. chokes together is a positive k joy to the eye! Magnum chokes were re general Ice re- used, and are supported from the :- eeivers. W baseboard by a smaji bracket. As a

- \ matter of fact, the bracket is supplied ii - with the " Clarostat," which is re-

o ferredto later, in case one should / -- -* want to mount it on the baseboard, ______I - - buj as it has been placed on the panel

- - - the bracket was used for mountin

- the "double choke"t

lates persistently at all, with the standard, parallel feed being ein- Choke Connections result that we do not. obtain the usual ployed for the high-tension supply, Note carefully the qonnections to beat-notes with C.W. signals and which is conveyed to the anode via a the two chokes, as shown in the back- carrier-waves. When the carrier- high-frequency choke. The aerial is of-panel diagram. It should be wave is modulated with speech or coupled to the grid circuit through a remembered that th& plate and grid music, however, the advantages of very small capacity -indeed, which of the 'calve are conieeted to "oppo3ite the system show up to the full. For the benefit of the Morse enthusiast it may be stated that there are ii ...- fi few OW. signals which have such a smooth carrier-wave that they may Tile ternünals are, fso,a left fo ,iqst not be read quite comfortably on this 'phones, 1I.T.+1.FI.T. set.. Any little ripple or noise in the ±2,H.T.-. LT.-. LT. a,ad, on the C.W. makes them quite easy to copy, 4-, ,,,(,U st sip, Ernt

and even the few "dead pure" ones und ilertat. - may be read by their clicks, so sensitive is the receiver! Low-Loss Unnecessary Turning to the finished receiver, it will be noticed that the short-wave --- 'i.,. detector has been kept to the right- II hand side of the baseboard (looking at one of the rear views), and I he modulator valve has been kept separate as far aS possible: Plug-in coils on ordinary bases have been used for the detector. Low- loss óoils and condensers are not so -desirable as in the ordinary oscillating réceiver, since the purpose of the 39'

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______WIR IN G D IA GRAM. F :..: : .. .. cI i .: '.. 14Ç»4 L Sj

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.n . . '. .R . O, 0003 2 e [p: .t :J __ o _ I C4 - TL4/ 'I1

LÍ I PHONE: +tHT+2 H T- LT +: £ A

392 -

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Odob, 1928 - THE WIRELESS CONSTRUCTOR

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"The Condenser is one which can be thoroughly recommended." Mr. Percy W. Harri, "Wireless Constructor," September.

: -'i CONDENSER I OR years Lissen have made almost every radio part except an air-spaced variable condensèr. r Many have wondered why Lissen have so long delayed making a variable condenser of ( tU - that type. The answer is that Lissen had decided

- ('s. to make only a really low loss condenser which should be without tne laults so commonly met with in most cordensers and at a price which should be in keeping with the Lissen tradition for fine value. It has taken years for Lissen to .1 make a condenser which at last satisfies every Lissen requirement. But now Lissen has produced a / - condenser which for fine and facile tuning, or ,- f low loss, for universal use, is surely without a riyal. i J

/ You can use it as a standard condenser ¡ in any circuit. í T ¡ You can gang it-two or- lhree of them T together. F .' You can use a drum control for it instead of a dial. .!, You can mount -it on o pànel ond it has '0001 mid. capacity - - 5/9 feet for bse-bord mounting, too. '0002 ,, ,,- - - 5/9

0003 ,, ,, - - - You are now able to get a high-grade condenser, offering you - which is so '00035 ,, ,, 6/3 - advantages you can get in no othercondenscr, at a price - - low that users who dcsirc to improve their tuning in existing acts i '0005 ,, ,, - - 6/6 can actually afford to replace their present condensers with this new Lissen. Certainly old condensers will never pay to patch up now that this new Lissen is available. One bole fixing, of course. i

And you get- exactly -thé full:

- rated capacity ¡n every condenser

You can get the new Lissen Variable Condenser from most radio dealers. II you heve any difficulty, order on a postcard stating capacity required, and condenser wifl be - sent COD. by return of post. Kindly give dealer's name and address if possible.

i 26-30, FRIARS LANE, RICHMOND, SURREY

LISSEN LIMITED, (Mancigng Director : Thomas N. CoIe.)

393

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KTEWSaII11eLOIiiSS(and! V ,èl___ I A ' Two new compon t ents-two new sets ' - being introduced by 1 : _ )J Lotus' ir There is a new Variable -. Condenser and Vernier Dial .1 both typical Lotus quality '\ V ::: !i . The condenser is mid-line and logarithmic It is made J '. w i t h chemically cleaned brass vanes andend _____ 'r c* ¿tes V II and ball bearings PRICES 1 t , - fhe Lotus Vernier Dial is a New Lotus Variable Co, slov motion dial with denser .- ¿ _V _ machine geared movement 000s 519 V_ 1 VVV__V .. - giving a ratio of 14 to I A 0003 5/6 ' V

. closely-marked satin alu- 00025 . . . . 5/3 V i minium dial reading o i8o , to rear fits flat 00015 j against panel and a nickel- NewLotusVernier i . . V rfittedplated cursor is rotated Dial 4/9 , t L ,V

L by small knob the e L iound ç dial / V- The famous Lotus Remote The New I

l21V Controls, Buoyancy Valve . L O T U S VV: Remote Controi Rei%Y Holders Coil Holders ' .. Jacks Portable and '- i Switches and Plugs are also Ç>V , / Transportable r on view. V I Sets The new Lotus sets are . , the latest vireiess tri- VV L - tjsingthcnew ': :' i ivi o. . s- IuiIard Sceenod and A' . valves. cir- Pentofle the ; is a ootnbination of V t..::2: . / V latest wireless discoveries :V: \ JcuitV 1rnriririrt : , V:V :.:-: - ';J fiveVvalve ; . V of results :. vaivz'ider Transportabie modelsin Coj$IloMtr4L1S

41 /j rARNETT, WHITELE & CO., LIMIT)D, V' V j LOTUS WORKS BROADGREEN ROAD LIVERPOOL

Lotus Coil Holder. i.

394

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The Super-Regenerator on Short Waves-continued

corners," whatever make of choke is to be working on short -waves try than is obtainable from a detector employed, assuming, of course, that to set the detector roughly to his and one L.F. stage, and are, in fact, both chokes are wound in the sama wave-length, and you should have no almost as loud as they are in the direction. trouble in finding him. usual way with a detector and two Note also that the lead from the Careful adjustment of the variable stages. free end of the detector's 60,000-ohm resistance should, show a point at grid leak is not taken directly on to which the telephony is much clearer Absence of Background the grid of the modulator valve but and more free from "'background " In addition to this, there is an to the other side of its own grid than at any other. almost complete absence of back-

condenser and leak, i.e. to the top The right sizes of ccii must, pf ground and mushy noises when the - of the grid coil." course, be inserted in the detector- set s correctly adjusted (the principal The grid condenser on the moda- coil sockets or the set probably will adjustment for this purpose being Jator has a value of 0003, and the not operate at al]. For the 40-metre the Clarostat). You should also try g±id leak is of 5 megohm. A 0005 band two 9-turn coils, or a 6-turn the effect of adjusting the ncutralising coupling condenser is also connected as secondary and a 9-turn as reaction, condenser in series with the aerial, across the two extremes of the coils, will he suitable. For the 20- and since tQo ,ligh -a degree of aerial i.e. from the anode to the grid end f the grid coil. - Reaction Control it is desirable to have a reac- tionSince control on the detector which will not affect the wave-length, this lvx been arranged by means of a 9rrìable high-resistance in the anode circuit, across which a by-pass con- dnser of I mid. is connected. Operation is very simple indeed once one has succeeded in making t4ie few original adjustments, which are also perfectly straightforward. b 1' - A small power valve should be 1 inserted in the modulator socket (V2), r and for the detector almost any general-purpose valve will prove efficient. Regarding H.T. voltages, about '-S- 90 volts on the modulator and 60 0h ii the detector gave best results with - the actual set, hut other valves and - oltages may be used with success,

I aiid should, if possible and conve- il nient be tried. I .1 switched on set the vari- -'¿Havingable resistance at a high value, and il decrease it slowly until a hiss is heard .4 view of the set whi('S .sliouhl prove invaluable to you duilag the ,nounVnj the components, anti whiph, ,zed in conjunction titii the wiring diagram ou the in the 'phones. Decreasing it farther precious paye, should greatly facilitate tite wiring. stil,l below this will probably result in a shrill squeal, and if this occurs 3O-rnetr bands a 4-turn secondary coupling will produe aT laige amount it should be re-set to the position and a 6-turn reaction coil will be of background; which can easily be that gives the gentle hiss. This needed. - cut down without-noticeably affecting adjustment should not be at all 2 X A D, of course, operates on signals simply by reducing the critical, and should hardly vary at all 2196 metres, and 2 X A F oñ 3277 coupling. with wave-length. metres. If neither of them is on, the There shoul4 irever be any hetero- set can be tested out on 5.S W on dyning or howling when the set is Pecüliar Effect 24 metres, who is, by the way, not as being operated. If there is it probably - Now rotate the main tuning control strong as 2 X A D in most parts of means that. the variable resistance slowly, when many stations will be this country, and therefore makes has been reduced to too low a .i,alue, heard. The general effect will not be quite a good test in spite of his in . which case' it should, of bourse,

at all what you expect, most of. the proximity. Numerous amateurs may be increased again.

C.W. stations merely alteiing the also be heard during the evenings It should be mentioned that the - volume of the " hiss." If this first and week-ends. "Clarostat" has a left-hand thread, test is carried out at a time of day The American stations are received so that the adjustment will be the when a telephony station is likely on this set at rather greater strength oppOsite to what one is used to. 395

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4 nionihty article for the yaniohone S - enthu.iast. r ..... Fecd-baeI-Speed Regutat ion-A Ne -

Reco,d Wem. L ByA JOHNSON RANDALL - _____ L

1í is stípr in hc)w much troable a slight JL Is éaiçi running the loud- va.riátión -. sjicker leads too close to the between leadsfr?m the setto the pick-up. the vol- . - There iatèiiIehcy to place. the tages of

lodsjke i&i the gramophone difierent . ifrnÇtable dud thc two sets of 'leads Ft eri s- a'àpf to become intertwined. Thüs nains will alter the speed. There- often cause distórtion aid. general w have the amplified Iow-frequuícy fore, each turntable shouldbe adjusted fedùpne ' n'the art f the - mpu1ses in the output circuit bf to suit th mains ithi whiôh it i to borne constructor. . -. the anlifier being fed back to tite be used. We have received 'oneo the new first EF. valve via the pick-lip leads, While oit this subject of L.F. But:ndejt pick-ups for test.:. It is and ih this wa low-frequency oscilla- oscillation the old bughear of " motor- an extremely eiImad oionent tiod is frequently set up. The yrnp- boating" mtist not be forgotten. functioning on th elecnàgnetic tnre violent howling or chronic This form of L.F. trouble has been pritéip1e, the pem&ñiuit thgiet being distórtion without howling. When very. difficult to overcome, but I othplcteiy proteted by a- ñèat b1ae tr6ubIe. of this kind is experienced am glad to see that there is a number moulding of insulati,ngin'tterial it is advisable to see whether these of anode-feed units and resistanes t*o sets of iriug arc well separated iyhich are being placed on the ma'ket - A Well-Mad"Deikê k 1. . -bèfoe looking elsewhere for the fault. 'with tite bbject of obviating troubles The two terminals .to which are a of this nature. These anode-feed lds..re A Second Possibility attached the ick:iip also rèsistances are very useful bòcaue mounted onth&case:: TItis is particularly the case when it is possible to employ one H.T.: The device can be obtained com- the thiìplifìer is pàrt óf a broadcast voltage throughout, applying the plete. with volume control,; ánd this -. receivei, and functions quite atia- maximum to tite last valve (or valves, is recommended to those. who have factdrjjy for the reception of the ho means of strength '. ordimuy adio programmes, bursting incorporated in the set. into violent oscillation directly the On test th ick-up -gave Lyer good piek;iip is ligged in. results, and there. yas a marked O# course, this is not the ônly absence of chatter., The bass tomes possibility. out very well, ,provided a uitable - In th majority of cases, when tite tq, amplifier and loud speaker. are used, pick-up is plugged in an additiunal and there is no noticiable loss of " ?/í L.F. valve is brought into operation I . the higher frequencies; (uually the detector which is arranged The price of,thepick.up is 20s., to work as an L.F. stage) and there and it can be well recommended. consequently a slightly increased r 'is V. tendency to self-oscillation, and if Record Wea . the remaining'stagcs are not quite I receie quite nutiTher of queries up to tite mark the amplifier may' concerning record wear, and I am " spill over " and hol. afraid that I can only -inform my Electrical Turntables juerists that some pick-uris do tend -. - T.. -. to produce fairly rapid' wear. There Thse who ltve pufchased Cloe- = is still a lot to be learnt about the tric'al' turntables ma5 be' having a Burutlept " I1eci'ieul Srnf,Id-bwe " design of gramophone, pick-ups, and spot of b:other .ovr the ped'reui- described in tlis article. - in some cases makers, in their eager- tion. There is on mOst of these ness to ensure, high-quality repro- turntables a sinai! adjuster and this if there are two in parallel) and duction, seem, to havé overlooked ,can be set to give any repiircd sjeed. cutting it down with the feed resist- the important qùestion of wear on .he revolutions per minute - can ances to suit the remaining stages. the record. be determined as described in last This is another step in the right We hope to be in a osition to pub- month's article. It must be remem- direction towards the simplifying of lish details of some' eperiments on bered that these turntables cannot set design and the prevention of this question, and also that of balanc- be pre-set owing to the fact that those annoying troubles which so ing the tone árrn, in the near futuro. 396

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October, 1928 - - - THE WIRELESS CONSTRUCTOR

- ;

7:»: -" . vi;'- ir""' '\ --

ì - ," - \ ' \\

i \ ' ?r k\ ' \ - \ - I . \ t\: EVERYDAY ¿:..--'' PUBLIC ./ 'Y;

; : II : GIVE :Lt US ¡f

1 EVIDENCE u

: THAT RCGD L

: I, BRITAiN'S ßEST ßAFTERIES:

L GIVE THE PUREST ç SWEETEST TONE &

: fi LONGESt - SERVICE i: AT CO ST LJP LTEAST

::, - --. vo 3':

'j . . . . L From all Wireless Stores, Elec- - .;J - ticianS etc. Complete Battery L , - : :- - post free from - ; : ' Catalogue 3 ' t - , - THE EVER READY CO. (Gt --- 4 . - Ltd., Hercules Place, ' , - . : g Britain), Holloway N 7 , I We are exhibiting at the RADIO EXHIBITION Olympia - e . - representative wilt be r Sept 22 29 Stand No 44a Our to be of assistance to you ç \_ :;--- pleased .

;-_. - 397

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THE WIRELESS CONSTRUCTOR Octber, 1928

Make good results. a: cértainty by using BURNDEPT Compoúent

IRELESS experts throughout the country have taken this advice-because they know that - 01 !NtII%C IAL. , EURNDEPT is a name that stands for absolute reliability and excellent results. Amateurs, too, swelI i. \ the army of BURNDEPT users-and if you are going to build a set, you will do well to follow their exampI. i I' See the BURNDEPT 4atcst range of componeits I. and Radio on 112-113 / - sets Stands at the RADIO k' EXHIBITION, September 22-29.

VARIABLE

I CONDENSERS - - give increased signal strengih, and absolute freedom from hand- capacity. Their special features are the insulated spindle and SCREENED metal earth shield, which mean improved results and eas:er GRID VALVE HOLDER manipulation. With this holder, the valve can only be inserted "Square Law. its proper pesition. Adjustable to varying sizes - of same type of %alve, and provided with terminals ETHO VERNIER.. 00007 or 00o1 mfds. Price 13/8. and soldering tags. Price, complete with drilling template 4'-. DIAL Log Laa'.' Gives easier tuning, fine tuning 0003 mfds. Price 15/-. 0005 being a simple matter because mfds. Price 15,6. of the i8-I ratio. Noiseless- Calibrated Scales. gearless, and free from backlash. 550-3,000 metres (for Log Law With Etholog and card scales. type). Price 1,'6. s Price 6,'-.

t ff1 Jill THE NEW H.F; CHOKE

I JJ 1J Has high inductance (5o,000 mhys.). Suitable for (ongest- wave-lengths and with, extremely low

. capacity of 000007 mfds. Ideal for shortest wave- lengths. Price, 3,6.

V . Latest Catalorue 1 - . - FIXED RESISTORS rRLE on request Made in all values from to 50 ohms. Cheaper than rheostats. Ensure constant filament current. Obviate danger of burning out valves by applying excess L.T. current. Price 1/6 each,

. .

Offices. . - BLACKHEATH LONDON, S.E3 London Showrooms 15 BEDFORD STREET, STRAND. W.C.2

T.w. .W8

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HI VJ TH t

IFhut ice cnn expect fo see In the vulve tine «t óly;npiu. Neu; vvc

- und ,wiv prices. : -

By KEITH D. ROGERS.

NEVER before in the history of iniportant-prices will be dow by a have faded away while other new ones radio has there been such a useful amount. have come into prominence, but on tremendous number of valves Visitors at the show will find the whole you will find the saine of all types and sizes on show under valves of every description and makes turned out with their usual one roof. This year's exhibition at type. HF. valves for neutralised reliability but greatly reinforced by Olympia will surpass anything that circuits, screened-grid H.F, valves, fresh types added to their ranks, and has been done either in this country or resistance-coupling L.F. valves, ordin- in many cases redesigned from base to America, and especially as regards ary L.F. valves, power valves, super- top. exhibits of the thermionic receiving power valves, a complete series in the Among the redesigned valves must valve. be mentioned some of the 2-volt During the last two years or so we screened-grid valves which were first have not been exactly " hard up" for put upon the market with the three- This is the neu, valves, although we may possibly have type of Cossor pin mounting at one end and the lacked some really big super-power screened-grid two-pin mounting at the other, 11F. valve, which valves, especially in the 2-volt classes, among other designed to be used in horizontal but now this is being remedied and ,m,kes is aailabße holders. Except for the S.625, these we can safely say that we have valves for ra,iouq vol- have been scrapped and redesigned to toges. Note the for every requirement and to suit every difference in de- produce a valve suitäble for plugging poket. sign between fl,i into the ordinary valve holder, hut This year at Olympia things have valve and that with the extra connection at the top,' of a ' year ago gone further than ever, and we shall shown in the head- so that we have the Muhlard, Cossor, see types of " tubes " which will make iiç, of this article. Six-Sixty,Ediswan,Marconi and Osram T li e horizontal it even more difficult to make up one's type of screened- screened-grid valves all arranged for one will use for any grid ralee is now mind which 7A 4eh'4 ta6 the four-pin base carrying the grid, particular purpose. being replaced bp; the screened grid and two , the Upright 4-pin the filaments und cap type such with the plate comirg out at the top t as is shown here. Many More Valves The horizontal of the valve to a special terminal. It will be worth the while of any Marconi & Osrant SM2S will be still WIRELESS CONSTRUCTOR visitor, to available and is Wonderfully Efficient Olympia to spend some considerable not bei.ìg tahen These valves ' are wonderfully time round the valve stalls and to oJJ the ,nurket. efficient, and I would very strongly study as well as he can the various advise all my readers who have not types and characteristics of the valves yet tested the possibilities of the on show. He will find that he can get ordinary battery LT. type, then the screened-grid H.F. valve to do so anything from an ordinary dull- whole range again for A.C., to run without delay. emitter detector of quite a cheap order direct off the A.C. mains, and finally A special range of AC. valves to the large super-power valve which we must not forget that valve which will be making its appearance, also can be used for very low-power has recently come into prominence, known as type Pcrint 8, taking 8 transmission, and which is employed the five-electrode valve known as the amp. and 8 filament volt. This by a great number of people for public Pentode. range is absolutely complete in that I- address systems and for working Certain changes in the lists of it has an ordinary H.F., a screened- moving-coil loud speakers at really valve manufacturers have been made grid H.F., L.F. and power valve. füll .kolume And what is most since the last show,some members The obly thing that might be said to

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Withi the Vacuum-continued

be lacking is the real super-power Now, finally, in regards to the world of valves, and all readers, not valve, for the lowest impedance of this exhibition, I must emphasise the only valve-set owners, should go to range is a little higher than perhaps neèessity for a careful survey of the Olympia, if possible more than once, one. might wish for sorné output valves on show, due attention being and really study things-it will be well purposes. given to their characteristics and worth their while. New super - power valves of 015 consideration of the newer classes and 025 filament current types from which may mean a great deVI to set * *** ** * ** * ***** * BT-H and Marconi and Osram, and design in the near future. 4h' with low impedances of 2,700 ohms USING CHEAP VALVES will be making their appearance, Fresh Set Designs * ** * * * * * *** *** *** and these constitute a really definite Already there are, and will be shown advance in the design of lw-imped- at Olymia, a number of receiiers ou SIR,-I have constructed the " Ra- ance output valves having a low the market specially designed for diano" Three, and have built it in filament consumption. Pentode valves, a large quantity of my spare time, and T can honestly say that I cannot find enough ap- Pentode Valves sets having three-valve circuith for use with a screened-grid H.F., a dtector preciation for it as I have no tröuble Messrs. Ediswan will be putting on and theii a Pentode as L.F. whatever in manipulating it. T have the market several new valves, includ- The screened-grid H.F. valve has got cheap valves in it, but I am ing some specially designed output come to stay, the Pentode also cannot going to purchase three good valves. valves, while the same firm, together be ignored, while the special AC. T have got quite a good number of with most of the other firms, will be valves and the new super-power stations on it. I have constructed marketing the five-electrode Pentode, valves promise to still further advance different sets at difierent times, but being specially designed for output the progress made in quality reception. I can assure you that I do not think circuits, and upon which I have Altogether, this vears " show that there is any other to come upto it. journal. commented before in this dcmonstiates real advance in the E.7. M. A. SHADRAKE. Regarding that previous comment on the Pentode, I should like to say here that tests are still being carried - - - out with the valve and that so far I cannot give any further details and can neithèr criticise nor commend it until it has been given a really points of view. 'S..... a, thorough from all - test - Readers will appreciate that it is a - not sufficient to take a valve and plug it into a set, listen to results, check .9 jt.s filament current and its anode - current, and then pass an opinion. Ei' The valve may work very well, or it - H - à-. - not work at all, but in any case may - it is not fair to the valve.

Thorough Test Essential 1f a valve is to be thoroughly tested, especially anew valve which is really 1» the only one of its type upon the market, it has to be taken very care- with fully, its characteristics taken . ('-L. i extreme care, and then the valve must .i. -- - be subjected to al) sorts of tests in various types of efreuits, in an endeavour to find the best circuit to I suit the valve, so that it may be given every opportunity of providing its

maxi mum efficiency and the best I, - quality of reproduction. Thus in the case of an output vaIv it is essential that it be placed in an output circuit where the impedance Ç .. J . II t of the valve and that of the output circuit are properly suited, having a 'u. I-. - proper ratio -to each other, before one Senatore M«rco,ii and Mr. G. I. 1h,thieu (icho i.s shown above) liare recently deneloped OPflUltipleX s,pitent of ,sidio commnnicalion ii.sinq short waves. Mu-sic has been seni can judee whether the valve is a bcood - from Montreal i,smru; the saine beam aerials a.q those ihm on,1h which t,vo sm,nidtaneous

or not. - one - Morse tClé jjmnph mersa ges n'ere being sent, and sees es'iellemflly received at ilridgmt'ater. - - -

400 -

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, .. T'.

i ... :1: #7p, ,f

'4 st.::t:

140 000 sIMPEDANCE

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- Make a point of inspecting the range of new Ediswan Low Temperature Valves at Olympia, Stand 43, Main Hall. - - - - -: ------i---I- 401

______': ------______

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a t.

: f t }tor n the Success T

I 0f thj5 year's Radio Exhibition' 4 o! the new DUBILIER COMPQ ITENTSH

- See them and the öther new Duhilier Products

DUBILIER FILTER UNITS at.- DUBILIER Made in four types 2 8/6. MIDGET CONDENSER 47/6, 72/6, 14 Made in two capacities .0001 or .0002, STANDS complete with Knob 102/103 ,-. r-t' DUBILIER K.C. CONDENSER Knob, Dial or Slow. Without DUBILIER motion device H.F. CHOKE Finely moulded case protects - .0003 or .0005, flUBILIEP. CONI3ENSERS £. windings and givesit neat appearance. 4 /'6

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L .

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(I 18 j

À i

1 N*EL9_

- (

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'you will note' tÑat both trans- iuhIuhIIItIIIItIlIHIIcIIIIIlIIIIflhIHuuIItHIItIItIIuhIIIIIlIIIIIII' th learner with ä cramped, clumsy Ji mission and reception have E Ire you »Iissing half the interest E. style for life. The arm of the key E of your .shrnt-,rare set P, Why not E been mentioned at intervals E learn to reati Morse by the special E should be of a good leñgth, not less in the preceding lines, and it should E easy ,nethotls describeti in this and E than four inches, ánd it should be E tite precediny article which ap- E perhaps be explained that whether or E peared last month. E pivoted at a point about one third of not you will need to learn to send as its Iength.from one end and not at well as to receive will depend largely By G. P. KENDALL, B.Sc. the end. Further, the tension of the upon whether you can get a friend to iiiiiiiiiuiiiiiiiiiuiiu,itiiiuiitiiiiiiiiiiiiuiiiiiuii,iiiiiiiiiii spring should be easily adjustable. help you in your you can task. If some sort of practice outfit, and this find a friend who is willing to either may take the form of one of the Get a Good Buzzer learn the alphabet 01. already knows it complete signalling sets made up in The buzzer should preferably be of so much to good, because you will the boxes, which are sold by various the variety giving a high musical note, then get on much more rapidly. firms, or it may consist of a couple of since signals of this sort are much Besides, you will find the whole dry cells, a buzzer, and a Morse key less fatiguing to read than those business very much more interesting if arranged upon a table. produced by instruments which merely two or more of you can join forces The key should be of goòd quality, give a harsh buzzing sound. A good and have regular Morse practice as and it is well worth while to spend high-note buzzer may' èost about often as possible. ten shillings or so upon one, for a bad 5s. 6d., or, alternatively, one may be key in the early stages may saddle improvised by cutting off the Avoid Too Much Sending J hanmer There is little doubt that the best method of practising is by means of a Morse key and a buzzer, but to use this method successfully, either to memorise the alphabet in the first place, or for practising reading and sending, it is absolutely essential to have an assistant. The practice obtained by a solitary learner from the Morse key is oniy beneficial ,up to a point, for as soon as he has memorised the alphabet it becomes actually harmful to go on practising sending interminably. When he omes to learn to read, it will be all the harder for him, in that he has already acquireda one-sided facilityin sending. The aim should always be to develop i the learner's skill at reading and send- if a ing equally with, anything, slight . _- preponderance of reading (of. course, - it is obviously being assumed that it is as well to make a proper job of it while you are about it, and learn both tó send and to receive). Fo,i will ,,of be able to reach the speeds of trans,nission und reception accomplished by the a,itoni alio system employed ut t he Be,,,» stations, but with prnctice you, should The first essential, of course, is I be able to read the nuess«yes of nuuny of the l,antl-operated con,n,ercud stations.

li. . 403

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- Why. Not Read Morse ?-contfriued

of an old electric bell and judiciously speed should he such that the The unlucky man who, finds it is scung a siliall piece of felt or cotton reader has just time to recognise quite impossible to locate a fellow wool between the armature and the about four ut of five of the letters -enthusiast to help him can, unfor- pole-pieces. - bent, and is kept distinctly on the tunately, make but little use o the The set may be aasembled Upon a stretch to keep up, since this is the Isuzzer metho1. It will perhaps he a- table and the parts wired up in series. way to acquire speed in recétion little helpful to him to fix np a buzzer The key, by the way, should be firnìly very little good is done by practise at and key in the manner which has screwed or clamped down. a speçd which enables the Jea raer to been described and practise forming At the outset it is well to spend a recognise every lettei. the varions letters so that he can be little time obtaining command over It is a great advantage if a good assured that he has thoroughly

the key, and learning hìow to form the telegraphist can be obtained to do the memorised the whole alphabet ; but letters with precision and accuracy. sending, but quite useful Practice beyond that he cannot go, since, as First note that the proper way to can be obtained from the sending' of has been explained, to obtain a great hold the key is with the first two a novice, if he will take the greatest deal of practice at sending and none fingers on top of the knob and the of pains to form his letters correctly at receiving is worse than useless. - thumb at the side, tHen set to work and observe the proper spaces, equal to learn to handle it easily and to one (lash between letters and two For the Solitary Learner certainly. dashes between words. A further Probably the simplest solution öf point of considerable importance the diflculty of the solitary learner Remember Your Timing concerns the type of rnatte,cho,sen for illbc foûnd in a set of special graìo- Practise forming single dots and 'phovc reco'rd sold' b the H.M.V. dashes at first, trying to estimate Oòmpa.y, wliich in -themselves, ,coi- their correct lengths (remember that. :ct,jtuta.cÔ1ête êourse of instruc- tión in Morse r'ciding. If you possess a dash is three times as long as a dot), -, then practise the letters I and M, -i gramoph6ne', here is 'hat the writer followed by S and O, and then H. woild suggest. First lení the corn- Form the. letters very slowly, and take pIetè' iilpbabét in thi iainer which great pains to observe the most hs beén explained, an&'then uñi to accurate spaces between the dots and the grathohone records' ánd proceed dashes'that you can;' speed will come to run through them in the correct later, and accuracy is the first order and try to become letter pei- essential. When these letters can 'feet. Just a yord of warning, how- 1e sent easily, and without hesitation, i:. eier. Do not use these records over ahd over again until you have notti- - take letters- containing both dots and dashes, starting with A, the simplest, ally mernorised their contents, since in so doing von are hound to fall.intô - and so proceed - until the whole alphabet has been niastered the ven' bad habit of coiìstantl' Next, practice can be obtained in guessing the next nord intead of reading; let one of the learners send honestly reading it. This is a great very slowly, and the other try to handicap, -and will cornpletel ruin recognise the letters as they are sent yont cliaices of becoming a good I ' and write them down for checking reader. It is ahsolutely essential; later. It may be necessary at first if ou are ever to become really to send one letter at a time, and then proficient, to read without guessing wait for the reader to name it. If Listening fo a loud speaher fron, a sel ]etter by letter, as the message cöiiès tuned to a ton g-ivave eoìH merciai station through and write it down quite with this procedure is adopted, sender and is excellent practice for the student of reader should exchange duties about Morse. ¡n this photograph the listener's out thinking-whether it makes ense cha ir has been occupied by the toj, who or not, at any rate in the èar1 tae every five minutes, to equalise the seems to be very interested. practice which they obtain and to of your practice. prevent fatigue on the part of either. practice transmission. Precautions The Last Stage should be taken right frohi the start With the aid of one or other of tlì Acquiring Speed to prevent the learner from falling various methods which we have con When the letters can he recogiised into the pernicious habit of trying to sidered, the reader will be able tq fairly easily the sender may start to guess what is coming when he is learn to recognise the Morse characters send passages of twenty or thirty reading. Useful remedies are the when they conie in slowly, and after words at a slow ràte, without stopping lise of a foreign language, or the a while to write down correctly com- for the reader to name them, the latter simple expedient of sending each plete messages in Morse, and when he being expected to write them down and word backwards. can do this with reasonable accuracy mark the omission of any which he A final word of ad ice : never he can take the next step in his train has not time to recognise by a dot on either send or read for more than ten ing as an amateur operator. Thip is to his paper. At the close of tbe minutes at a time in the early stages, derive his practice from the receiving transmission the letters written down for longer periods produce undue set itself, and the messages which he should be checked, in order that the fatigue and lead to sloppy sending can-pick up therewith, and it is then reader may note his mistakes. The nd inaccurate reading. tC0tiflV44 4Q4

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i A New Transformer / by Igranic. >'«T; .7 / /77'

-. '_1 i-.- / / H .\ HIS JI / ,,,/ new Igranic Transformerupsets ¡ - all former ideas of value. Ihe discovery of a super-efficient new iron circuit has enabled the Igranic

I- engineers to designa transformer of less. - I than one half the weight and size of other - \ \ transformers that approach its performance and, consequently, with a much - . i' \ lower price. The new iron circuit in the Igranic L.F.

. Transformer, Type J, has the effect of

- giving a high primary inductance with a \ . / / small winding, the interwinding capacity \ . //. .' --. .. being therefore reduced to the minimum cnsistent with maximum coupling. The .

. \ / ... result is that the amplification ofall notes f . t ,.' - . between ioo and 9,000 cycles is practically / / constant, the low notes being rproduced . RANIC with all their natural mellowness and the / ...... high note: with complete freedom from L. F. 'FR.ANSFORPVIER

f . . For complete particulars of this , - wonderful, new transformer write V. e , - WE ARE EXHIBITINGAT . . . -- for List No. J.662. A free copy of

- - V - "Selected Circuits," by H. J.

' V Ratios - Barton Chapple, B.Sc., will also ... be sent you. 3:1 and 6: 1 - - .. -. V--, ..- ' .

V V cIGTRm

I ' w- 149, QUEEN VICTORIA STREET,' LONDON, E.CA.

Stands 53, 54 & 75 Works: Bedford. While at Olympia Come and hear Igranic apparatut Branches demonstrated at I 28. West Kensington Gardens MANCHESTER, NEWCASTLE, BIRMINGHAM, LEED, GLASGOW, BRISTOL, CARDIFF (adjoining Olympia) -

- 405 '

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ing- sc,. - d You GOOD NEWS! Wonderful ne.vs! - need not bother any more with expensive short-lived ) -- , batteries if you install a Clarke's ' ATLAS" Battery

NO VALVES TO BURN OUT.S. NO LIQUIDS. NO RENEWALS. Just flick the switch and u'll know - - the good news is contained in the words:- - -, - 4

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I BATTERY E L M IN ATOR 5555 Price -

£3 - 5 - o -i: j There's a Model to suit your pocket, and every instrument carries the "Atlas "- guarantee. Send now L I -. for a copy of the new Eliminator Brochure No. 32 to , T H. CLARKE & CO. (M/cr.), LTD., them t : Atlas Works, Old Trafford, d j MANCHESTER. Exhib'd, O1jnp, - : Septentber 22-29' :sTANDNo.161: -

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Baird's.

Television

- RECENT DEVELOPMENTS.

By Our Pateit Expert.

TELEVISION system capable of plate or film is responsive to variations such a cell is placed iii' eries with a £T transmitting moving scenes of light and shade in such a way that s'uitable battery the value of the through the ether on ali fours after certain chemical treatment the current flowing through the' circuit as with the present broadcast sevice is complete picture is reproduced in a whole fluctuates acc'oi-dingly, just fornì: as a a "consummation devoutly to be permanent I the current lough microphone wished for " by all good radio enthu- The photo-electric, cell used for flùctuates in' accordance with the siasts. Judging by recent reports in varying pressure of sound-waves. the Daily Press, the prospects of such - Z/CN7-SEMSY7/ VE The continually-changing current flCELL - .. a service are daily increasing. d .,COUN7EPSNAFt from the photo-electric cell is first It has, in fact, been definitely state4 - amplified, and is then transmitted that a televisor set capable of receiving either directly over a connecting wire, moving-picture effects will be demon- / s, or as a modulation upon a radiated strated at the forthcoming Radio . carrierwave, to the receiving station. Exhibition, and is to be sold to the 0 - Here it is detected, if necessary, ampli- 0--.O J/ OßJEc general public at a price in the neigh- fied, and then fed to a sensitive glow- bourhood of £30. .' lamp, so that the illumination of the latter changes instantaneously with O1,o Little Information the variatiófis of the incoming signal Meantime,' vers' little technical in- current: formation has been given regarding the ways 'and means by which the i Complicited Problem latest moving-picture results hive So far the whole process is very ben secured. The gcieal thery similar to that used in ordinary tele- underlying the original ajpiratusas phony, if one imagines the microphone used by Mr. Baird has certainly -been to be replaced by a photo-electric publishEd, but details of more recent cell, and the incident sound waves by advances are not generally available: a ray of light of fluctuating intensity. It must be borne in mind that the The outstanding difference, hovever, principle underlying all televisioi between telephony and television lies

systems consists in throwing an image - hi this fact. In telephony there is no of the scene to be transmitted upon A niet hod of epIo2ing j,at eut ed b1 need to arrange the received signals M2. - a selenium or photo-electric cell, cap- Bqird. in any definite spatial relation. One able of responding quntitativeIy to television is sensitive to light in some- note simply follows the next in a light of varying intensity. 'In this thing of the same manner, except that sequence of time. In harmony several way, the gradations of light and shade it reacts by altering its e1ectri resist- notes may he superposed, but the produce 'electric currents of corre- alice continuously with changes in the trained ear is able to detect aiíd ap- ponding value. I» photography, for mteiisity (i.e. light and shade) of the preciate them simultaneously in time. instauice, the sensitised surface of the ray thrown upon it. If, therefore, In television, on the other hand, it

A . C' A . 2 - CELL ¶iï=/

F,c.2. ooríc LeVER o END V/EWOPD/..t J An ingenious ,,ietliod of speeding up the passage of the light rag across the seleniuui oeil. 407

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Baird's Television Apparatus-còntinued

is necessary to send the scene in ton Buildings, London, WC., at a what may be described as an optical separate small sections or areas one cost of one shilling each. lever for increasing the speed at which after the other, so that the forehead, the ray of light can be made to move - I Paient No. 253,957, granted to JI,. across eyes, itose, and mouth, for instance, J L. Baird. the optically-ìensitive cell. To groups of do this he a series of arc transmitted as separate .The disc D shown in Fig. i is pro- mouxs rotating discs shown in signal elements, one following the vided with a number of spirally A-E, as Fig. 2, in such a way of other at an enormously rapid rate. arranged lenses, and is rapidly rotated that the image the - signal object O (shown as a grotesque doll's At the receiving station each in front of the object to be televised head) projected is impulse is separately received and (shown as adut-outcros.), sothateach by the first disc A the "explored" by the second disc B. must be separately projected from lens sweeps »out a parallel track across glow-lamp so.ajto reaçh the viewing the òbjèct' and projects a correspond- As the lenses of the second disé cross the image in direc- screen (a) ifi Tits proper Ìôsitiofl in ing beam of light on to a light- the opposite tion to the movement of disc A, space (so that the forehead, nose, and sònsjtive cell. the mouth are not blurred into one unrc the eflective speed of exploration is cognisable mass) anti (b) so rapidly Shadow Effects - R46ó that the whole picture is repeated no If the source of light illuminating less than twelve to sixteentirne er the .ohject comes from behind, each second, as, othewise thé kihemato lenswilrrecive a'ray of light that is graphic effect of aìiiniation is lot. diminished periodically by the outliné The First, Systeii,:: óf 'th« object. In othe words, the shaaöofflfeo1iject will be thrown In the igiiàl str ú4ddiy 1ir. npon thè pptical cell in consecutive Baird thì jìcture t ,th& tMnsthitiig btinds or gmnta. - station is ciit'up.ór "'eiphìFed 'iiitó If, on the other hand, t he source of suitable signal eleriînts by a rapiIly light ilIum iiig.the cell lies on the rotating disc, providéd it1ï a scTie same 'side òf th "cross" as the ex- of spiralI riangedlehésor .hç1s loring .dic, then the latter will only PEO UCEO - L /CMT TQ4NSM/ 77fR whilst at th ieeeiiñg :-d tiê ,e' pick uj refleted. light and not the ¿in attempt to reduce tue tiqht needed to eeived signals ar seihlèdïn thei direct. ry By íbig reflected light it ittnrninnte the object to be televised. becomes possible to transmit details determined by the relative motion, so on the surface of.the" cross " instead that if the two shafts X, Y are rota- of a mere silhouette, though, of course, ting at the se rate the speed will be L\ the intensity,of each' ray of light doubled., considerably diminished. The image passing through the disc As the rays of light reach the sensi- B is in turn scanned by the disc O,' tive cell, fluctuating currents are set with a corresponding gain in relativ'e: -up in the- circuit P, and these are motion, and so the speed is doubled subsequently amplified by a valve V, at each stage, as the image is projectd

ready for transmission to the distant in turn from óne disc to another, - F/o-J station. moving from left to right. S TEREO6COP/C In order to obtain a finer sub- AA'O COLOUQED TEL L V/$/ON. division of the objects to be televised Loss of Light the shaft S supporting the rotating As in this arrangement the lenses D, lens disc may be moved to and fro at áre mounted on each disc in a perfect 00 right angles to its length by means of circle, and not spirally, it is necessary 000 C a frame F, which is rocked about-a to introduce a traversing movement second shaft S against spring action across the sensitive cell at the last- b an eccéntric cam or disc C mounted stage. This can be done either by in- on an upper countershaft as shown. troducing an oscillating or rotating mirror between the last disc E and The- Neit Devêloprnent the sensiti'ie cell, or by displacing the g467 Patent No. 26564Ò, 'jranied to Mr. suiportin shaft of- an extra disc F so The ssbjeet ei Patent No. 24t,J5J. J. L. Baird: th its leses move across the optical proper order by a similar disc driven - One obvious criticism to be urged axis 0M in a direction at right angles at the same speed as the one used for against the use of any purely mechani- to those of the discs D or E. transmission. cal exploring device, such as a rotating In spite of the highly ingenious Bearing in mind these fundamental disc with spiral lenses, is that the character of this arrangement, it points, it may now be of interest to necessary speed to ensure a close- would appear that a considerable loss give a short description of some of the grained and clear-cut reproduction of of light intensity must occur at each television patents granted to Mr. J. L. the transmitted scene cannot be point where the image projected by Baird and to Television, Ltd. Copies obtained, owing to pirely mechanical one discis traversed by the lens of the of the printed patent specification consideratiòns. next following disc. In other words, can be obtained by those interested Mr. Baird therefore proposes to although the speed at which the ray

from the Patent Qffice, 25, Southa.mp- overome this objection by utilising (Continued on page 450.) -

.,-. 4O8 - '- --..--.. -

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'.The "ORMOND" I CABINET LÖuDSPEAKR. '1HE new "Ormoñd" I Loudspeaker açhieves - I?IL an almost perfect .faith- fulness of reproduction that gives the speaker ör vocalist a personality, that brings the listener into sympathy with the artist. 1t reproduces those over- tones by which each instrument attains, its individual characteristic tone. :. - 's No adjustments to be made, the setting being obtained in a most effective manner, ensuring the excellency of reproduction no matter how litth or how great the volume. The "Ormond" Loudspeaker is particularly suited to sets using high values of high- tensiôn supply, with "Super-power" as the Loudspeaker Valve. We would recommend that the mäximum values of high-tension voltage be used as given by the valve manufacturers. I. Hear the "Ormond" Loudspçaker demonstrated,' compare reproduction on the upper register as well as the lower tones, with any other 'Loudspeaker whàtever

'its price. ' - ' . . ,

Test it for volume as well as for purity and you must concude it 'is the greatest -

achievement in Loudspeaker construction. , - Models

I- Mahogany ;C44O I' and Oak Ristc,d T,u

THE ORMOND ENGINEERING ÇOMPANY, LTD., 199-205, PENTONVILLE ROAD, K1NG CROSS, LONDON, ,N.1. 9344-56 Telephone: Clerkenwell - Telegrams: Ormondengi. Kineross,', H Factories: - - WHISKIN STREET AND HARDWICK STREET, CLERKEN WELL, E.C.z Continental Agents: - Messrs. Pettigrew & Merriman, Ltd., "Phonos House," z and 4, Bucknall Street, New Oxford Street, W.C.i

409

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JITI4A

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METAL RECTIFIER Î

TYFEA.3 -

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ONVIEWON S S -

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No.781 5 AT THE H RADIOINATIONAL I EXHIBITION I______I ____1 ______

- This rectifier unit has- been designed for use in a low- tension battery eliminator, such as the Harris " Stedipower," using chokes and electrolytic condensers. Its output is

'1 ampere at 9 volts, and its price is .

.- :

23/6 _5 L WESTINGHOUSE RECTIFIER UNITS ARE CONSTRUCTED THROUGHOUT OF RIGIDLY FIXED METAL. THERE ARE NO WEARING OR MOVING PARTS, NOR VALVES OR - ELECTROLYTE REQUIRING PERIODiCAL RENEWAL.

When ordering your type A.3 Rectifier, ask your dealer for- particulars of other types of Westinghouse Metal. Rectifiers, for use in trickle chargers, H.T. battery eliminators and chargers, etc. -

- MANUFACTÌED ENTIRELY IN EÑGLAND BY - - THE WESTINGHOUSE BRAKE. & SAXBY SIGNAL CO., LTD., 82, YORK ROAD,KING'S CROSS, LONDON, N.!.'

410

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i 1928 October, - THE WIRELESS - COÑSTRUCTOR i I-

r. C. - ,.DPENINGS . SAVOY F11LI L By OUR SPECIAL COMMISSIONER

Changes of November Ist. sudden outburst of interest when the paration for the reassembling ofthe P.M.G. brought down his estimates. House in November. - changes in relay stations, ex: 1rHE The Liberals were inclined to ñiake a .1l clusively announced for the partv issue of the criticisms of the The "Listeners' Committee." first time in August WIRELESS programmes, but on second thoughts Now that the Wireless League ha 'CONSTRUCTOR, will take effect on preferred to begin by " flying a few so contracted its activities as almost November 1 st Ten relay stations kites." to be as quiescent as the Radi? will be put oxi -one exclusive national The extremely bitter and mostly ill- Association and the Wireless Associa- wave (2885 metres, I believe), will be informed criticism put up by indi- tion, it will be of interest to see what a central drive in controlled by vidual Liberal members did not augur becomes of Captain Ian Frazer's London, will radiate the same and well for the effectiveness of a regular Advisory Committee which has been programme except tor rare items party campaign on the same lines. meetingmonthly for nearly two years will be given in Regional groups. that Nevertheless a " Broadcasting Vigi- at Savoy Hill. This change should greatly extend the lance Committee" did emerge from This was originally meant to meet value of the service in such industrial that debate. This consists of about time recommendation of Lord Craw- Sheffield and Brad- centres as Leeds, twenty members, all Liberals except ford's Committee that the B.B.C. are about iord,wherepresentconditions three, the minority being Conser- should rely more upon competent and as bad as they could be with the steady vatives. - Labour stands aloof because ieprescntative advisory committees. station hetero- increase in foreign it sees the move developing, into a But gradually its whole basis of reprc- failure of dyning and the lamentable demand for the "dis-establishing" of sentation has been undermined. waves." the "international common the B.B.C. asa state concern. It would be a pity if the committee News Bulletins One strange feature of the pro- simply lapsed. Its members have now ceedings of this nucleus Parliamentary acquired valuable knowledge of the I gather there is a good deal of coinmittée is that it meets in secret working of the B.B.C.-lnìowledge heart-searching at Savoy lull about and pledges its nenìbers to avoid which enables them to put. up con- future of news bulletins. the the any Press discussion. There would structive criticism and suggestions The arrangement with the Agencies appear to be some " COUp " in pre: which really count. Itis understood comes up for annual reconsideration in November. During the past TOURING TALKERS twelve months the B.B.C. has ex- panded the scope of its bulletins by adding to the service of information secured from Government depart- ments. This was all very well so long as it gave interesting or useful iiifor- mation; but during recent months there has been a marked tendency to include departmental propaganda a.nd altogether too much ' ballast" of the official and semi-official brand. The reformers at Savoy Hill are all -'f for taking over the collection of news I and organising a proper service for / 'f., listeners. If I were asked what V1/ would happen I would say that the present arrangement will prevail for another two years, but after that tinie the B.B.C. will be forced by its public to collect its own news and to put it out at all times of the day and night. New Situation in Parliament I have frequently called attention to the apathy and ignorance of Par- liament on all matters connected with broadcasting. Towards the end o IIer is the latest broadcastiní, t'an in nse ft contains all the «rnpliJies I . necessavi for outside broadcasts while ou top is a pial/ovni fioni tcIHch events 'ast session, however, there was a «,. I and thaia- descriptions (wowlcast in moderate comfort,

i; - - 411 : - -

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B.B.C. and specially designed for HAPPENINGS. AT SAVOY reception when the Regional scheme «RADIANO» THREE HiLL has been, installed. This scheme' had i its birth in the fertile brain of Mr. SAILS ROUND THE -co?uInuea W. H. Lynas, when he was still WORLD! ManagingDirector of Messrs. Graham that the Governors are really trying Amplion,.Ltd. I imagine Mr. Lynas to do away with this Committee. If has stuck to his idea, and I should not so, their move should be promptly be surprised to see him shortly launch Sxn,-It may interest you to know côuntered by Captain Fraser and a new scheme of his own. the results I have obtained with the Lieutenant-Colonel Moore-Brabazon The decision to try out the new "Ra'diano" Three. I have bein from their seats in the House of Corn- statioñs a single wave-length trans- using this set on board a ship forthe. past ten months, and it has given mon if necessary. - mitters in the first instance will give him ample time to get his new enter- every satisfaction. I can say that, B.B.C. nd thé Trade prise under weigh if he is really con- for power and quality, it is the finest Relations between the B.B.C. and tenrnlatin it. tjre-valver I havetried, and I ha-ve the wireless trade appear -to be êstab- tried a few. - -- lished on a firm foudation of amity Admiral Carpendale's Future I made two alterations from the and mutual help, after an unneces- When the last rumours of Sir John original. I use a 0003 coñdèiiser sarily long period of suspicion Reith's mòements 'sere current, it in place of the 0005, and aperiodic

and recrimination. . - was accetcd that his successor at aerial coupling, as I find these best The Trade Committee on Broad- Savoy Hill would conic frm òutside for short-wave work. casting under Mr. Mclnstry,of Metro- the Corporation as a patronage ap- Mycoils for short-wave are: aerial Vicks, is an active and conscientious pointinent to be made by Mr. J. C. C. 4 turns, secondary 6 turns, and body. It stirs up the B.B.C. and Davidson. But nOw the situation reaction 9 turns, home-made to fit

keeps it to its pledges ; at the has c.haìged a good deal. Admiral Igranic Universal holders. I think thatthìe set is all you claim for it, O5 BOARD . THI "ELÈTTRA" r. - and in the "Radiano" Three I have T an efficient receiver that can tune from 15 metres upwards. Several B:B.C. and continental stations were received 150 miles west of- Ireland, Daventry in the. Mediter- ranean, Bombay.at 600 miles, Cape Town was receivd on two successive nights in South Atlantic at 1,400 miles, W G Y and K D K A were

- heard in South Cuba at 1,600 miles. All these stations were heard dear and undistorted on the loud speaker. Morse Sim1y Floats In " The set is not quite so stable on short-wave telephony, but the Morso simply floats in. However, with

r careful tuning I was able to obtain - -0 the following stations 2 X A F was rccei'cd in South Atlantic at 6,000 ., niiles, and K D K A at 4,000 miles. Chelmsford was received on three successive evenings at Cienfuego3, Cuba; the last hour's dance music, Titis is « section of the magnificent «ppa ratu on board Senatore Marconi's yacht, Big-Ben, and the announcer's voice 'E1ettia." Sonto important experiments have recently been curried out ou the vessel coming through at sufficient strength in connection with tite '' fleam." to be heard and enjoyed by some of same time defending it against Carpendale, second- in-command and the ship's company at six feet from

unfair criticism and accusations. I disciplinary chief of the B.B.C., has the loud speaker. - am told that Captain Gambier Parry come to the fore rapidly during the I may add that all tuning was done deserves very well of the B.B.C. for past twelve months. on the loud speaker, as my 'phones his share in the new spirit of co-opera- His remarkable auccess as Chairnian had broken down. I am construct- tion with the trade. Messrs. Strachan of the International Radio Union has ing another "Radiano" for my and Moodie have been the happy marked him out as possessing quali- home in Edinburgh; and next voyagii ambassadors on the other side. ties of more pre-eminence than was mean to build your" Radiano" short- formerly supposed by discerning waver, as the efficiency of this set - That Mass-Production students of broadcasting. Moreover, was demonstrated to me by an en- Regional Set it is an open secret that the whole of thusiastic constructor in Singapore. Very little has been heard lately of Sir John Reith's great influence will be Yours truly, the scheme for a cheap mass-pro- directed in securing the succession of D. R. M. duction valve set approved by the I his devoted ássistat. - - - London. (ch. Engï.).

412 S

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have whole of The J.B. policy is, and always bas been, to provide discriminating 'During the summer J.l3. experts devoted the their use really nembers of the Radio public with precision condensers of unsurpassed time to the design of new precision instruments for wiLls excellence and efficiency, modern rereivers. The complete J.B. range of cone1'sserS now meets every Radio This policy has earned for them a reputation of which they are requirement. justly proud, and which s enjoyed by ver', few manufacturers in the write in to-day for our new illustrated catalogue and watch Ilse Radio world. lt has been Said on many occasions that the addition editorial announcements of our new lines-and always insist on of J.B. precision condensers to a Receiver automatically doUbles the the real Precision Cotdensers. number of stations tuncd in. Brief description of new condensers illustrated: A.-J.S. VERNIER DRUM DIAL. Fitted with new and unique devices, and superseding the old and unsetisfaclory thumb-Control models - of other makes. B.-ATTRACTIVE PANEL PLATE supplied with Ve,nier Drum Dial. Neat and artisbcally designed. C.-NEW iB. MIDGET CONDENSER. The smallest and best yet designed. Supplied complets with neat pointer knob. '0005 '0004 n.fd. '000025 sn/U. I'eices : 00O in/U. 5/9 ; 'noue seId. 516 00055 saId. 4/9 mId. 4/6 4/- 9 D.-NEW J. B. SLOW MOTION S.L.F. and Log. Models. .00035 niJl.-S.L.F. ,efd. (Log.) 00025 in/a. 000i5 mid. 15f-; Prices: OoO5flfd. i 6/6 ; 15/6 .0003 15/6 15/- ; STAN ì. i 05- OLY1VIPLA

POL ST. S' - - 8 OXPO 4.Ol'i0Ot W.I L Geemo 74

413

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i- -- TIlE LOP1G VVIE%V

J Take the long view-a set which . does not give perfect reproduction ( i - - need not be all wrong. Examined -

- - stage by stage-a better component I fitted here, another there, will with I

u V V'. V _____ . each improvement bring you nearer I the goal of perfection. Constructors -

. who have fitted the Mullard."Per- .

- - -. , V - . macore" Transformèr in their re-

. .i - V ceivers have discovered what won- V

I derful tone . and volume can be V obtained with this transformer. It .

V . ' V is generally admitted, too, that the Mullard P.M. Valve improves any

' V. - ' V 'Th Now the new Mullard Pure Music -

V ' V - stiliV V ' - Speaker marks a nearer ap-

V ' V ' I V proach to perfection. Its wonderful

V ' . sensitivity, its life-like reproduction . - Mullard and the tone control switch, by . r V e fl c re which the pitch can be raised or Trans j ormer. V __VV . lowered and shrillness removed, all - V 25 - V contribute to your greater enjoy- I ment. Take an early opportunity V\ V 9Q' -. A of hearing it. , - g V Oi - 1.-O... .'«4.\ . O S The Mullard P M Speaker, O' S V V . Model ' C,' suitable for - - I hanging or standing 90 PRICE 53x6 V

V 14m:. - - ullard

Mullard P.M. Filament. MA S TER RADIO

414

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COMMENTS - I f - '1 f FROM CONSTRUCTORS

88 Staticns n One - W. ,g Cu1Ing (at IThtcntp; \iI,l Tappu,g

I I ¡tU) ndept lin etes Ltd -Powei Output Det ices-The" Roadside Fou, -

- of our readers in this district who On one idäI night thfrty-eight would be interested in it, as you see, station. were logged; or shall I say the only extra cost over that of the heard, as thy wére ñot all identified. Cutting-out Daventry ordinary crystal set is that of the Before I clòsè may I repeat a re- Siu,-Having been a reader of the extra condenser. quest you have heard before? WIRELESS CONSTRUCTOR for some Wishing you and the WIRELESS "When shall we havé the 'Radiano' ? time, I thought you might perhaps be - CONSTRUCTOR every possible success. Four " [In thiisue !--Editor.} -. I remain, ous truly, interested in the enclosed circuit. I remain, - As you are no doubt aware, most Yours faithfully, - A. E. HERMAN. people in this locality find it diffiult ARTHUR W. BETTS. IRedcliffe, Bristol.

- .LU[LJWI1J1JWJ1. Tapping a Hole 38 Stations in One Night Sin,-In a recent issue of your OOTU,?f Sir,-Just another letter in praise valuable paper you gave a hint how of the " Radiano "Three, which I made to tap a hole straight. up as soon as it was published in your There is another way, much used -' by engineers magazine. The following is a list of in marine work, where stations received: aQcurate hand tapping has to be clone on occasions. It is as follows: 761&wvs SpDT_.,. 2L0 (quiet). First a nut is ruñ up the tap to be 2cOCC SWITCH 'Daventry (5 X X) (strong). used, then the tap is inserted into the 'Daventry (5 G B) (skong). PHONES *CardiI (strong). -. \1-{PPsO) Oslo (strong). Bournernouth (strong).

- T Hamhurg (strong). 'Dublin (stronz, but fading at M. IJelts' selective cysIui circuit. times). to separate 5 X X from 5 G B on Belfast (strong, but fading at the ordinary crystal set, owing to the times). poxiniity to Daventry. Cork (strong, but fading at times). Of course, the simplest way is to Radio Paris (strong). NUT/N, TRio a 0001-rnfd. fixed condenser Toulóuse (strong). insert SECTION in series itIi the aerial, but as this Graz (quiet). results iii a loss of signal strength aid Frankfurt (strong). does not always cut out 5 G B, the 'Langenberg (strong). using of a wave-trap is much to be 'Berlin (strong). preferred. lt wás with this idea in BarceIona (strong). *1- mind that I made a set, of which thé Copenhagen (strong). enclosed is the circuit. Stuttga (strong). As you will see, the main idea of Glasgow (faint). To BE 2PPEO Aberdeen (faint). the set is the using of the same 31aiinq cure the hole is tapped dead true coil for the two stations, in the one Manchester (faint). is aceómplislwd by Mr. G'iiffon n this case as th inductance coil for 5 G B, Also amateur stations. Also several Pitan ser. and in the other as the wave-trap coil other foreign stations which have not hole to he tapped, and the nut run when receiving 5 X X. been identifièd. down the tap to contact with thejob. I think the idea is quite original, (Time stations marked with a can It is then quite easy to see that the and I have tried the set on several be tuned in practically nightly.) tap is being driven straight-the different aerials in the district and ALso I niight mention I do not use nut is, of course, held stationary. found it highly successful. phones; neither have I any centre- Perhaps the sketch will show what I If you could find space to publish tapped coils, these results being mean. The method is also good for the circuit I am sure there are several obtained with ordinary coils. small, accurate work. This tip may 45

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Comments from Constructors-continued -

be old to you, but perhaps some of Power Output Devices speaker. On the other hand, with your readers may be able to tap Sia,-The following difficulty has these two valves in parallel, using a traight holes with it. repeatedly been brought to our notice choke filter or output transformer, Yours faithfully, - and wo therefore write to drav your the results may be quite satisfactory, W F. GRAFTON. -- attention to it with a view, if possible, and immediately the push-pull system. Kenton, Middsx. to your mentioning it suitably in your is regarded definitely inferior. columns. The fact of the matter is, of coursé, - Burndept Wireless, Limited Experimenters and others when that with the valves in parallel their SIR,-The recent appointment by Changing. over rçm a single output effective impedance is approximately the Court of a Reôeiver and Manager valve to narahlel valves, or to push- 1,400 ohms, which is just about right does not mean that the business is to pull, fr&juently tend to ovrlook with a speaker of the resistance close down, and any reports to the the fact that the conditions governing mentioned, whereas when the valves coiìtrary are entirely unfounded. the output obtained arc changed are in push-pull their impedances are in The Receiver and Maiiager is con- quite seriously, and this, . unless al- series and amount to about 5,500 tinning iio only the sales side of the lowed for, may result,in an inferior ohms, so that the ratio of the output business but also the manufacturing performance when changing over transformer is quite unsuitable. sides of the latest types of Receiving from the parallel-valve rhethod to An Important Point Setts and Components. Adequate the push-pull arrangement, *hereas In this case, an output transformer stocks of all lines are already held and the latter with properly designed having a ratio equal to the square root production will continue. Research components should give, if anything, of the effective valve impedance and development are being main- a superior performance: - divided by the speaker impedance, tained, and the Receiver has every : An example of what we bave in namely, a 2/1 output transformer, intention of preserving the interests of mind will make this clear. should be used, and to deal with all Bnind'ept customers. In a particular case. the output cases of this -kind we have laid oûr-

:: selves out to supply transformers of special ratios such as this where necessary. At the saine time, we would point - out that when using the push-pull systcm the same grid bias should be employed as when either of the push-pull valves is used singly. Thth is àn important j)oint, as biasing the valve to a limit of the straig1t portion of their characteristics usually introduces distortion. Yours faithfully,

- FERRANTI, LIMITED. Holhinwood, Lancashife.

- The "Roadside" Fu .. -s Sin,-Permit me to report that th

. - i, - results obtained from the "Roadside" Four are excellent, and this portable is highly recommnded to your readers. .There is, however a great disa- pointment to the user to find that the portable set is actually of very little tise for the purpose it is intended for, and it is hoped that you will use your u -. best endeavours to persuade the It.'hy is it liait we i,ea;d s,,eli « lot about ,u,,sic fvouuz the air and yet this type of B.B.C. that they are ignoring the buo«dcust set «eec, ,uuahes its appcaeanee at uñy radio ehlbition? By riyhts we requirements of the portable-set user should expect to see Mi. There,niu «ud his " ,,,iisleuI box'' «t Olympia this »,onIh. by delaying their afternoon pro- In the hope of bringing the above valves employed are two L.S.5A grammes until 4 p.m. upon most facts to the notice of all interested, valves, uand the. moving coil has an days, and providing very unsuitable perhaps you will kindly give 'sorne impedancó of-about 1,300 ohms. items in their programmes at this prominence to this notification in your These valves, arc connected in time. Surely light musical items of next issue. push-pull with a 1/1 output au entertaining character are the Yours faithfully, - transformer and the result is very most suitable for summer-time trans: Foi the Receiv'er and Manager, unsatisfactory in that it may be missions, and theie 'should be early Burndept Wireless Limited, found that the output valves will be in the afternoon.

- H. SLATER, seriously overloaded without obtain- Yours faithfully, Sales Manager. ing a satisfactory response from the Huddersfiéld. S. T. 416

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October, 1928 ThÉ WIRELESÉ CONiUTOR

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: . V V »íffA: I. - V . \k14- . - ..4J. i L . The constructiona1 details of Philips Seven ' I Cornered Loud Speaker will interest you " because they are very unusual in such a

VV V : .- V . ,- -. -:: '- :VV . V low-priced instrurnent. V

- The electro magnetic movement is of the balanced armature type and is fitted with a cone of ample surface area, which retains rigidity under all conditions Con 4 V iV VV .1 : V V V sequently Philips' Loud Speaker responds - to an unusually wide range of frequencies e and maintains a very natural tone .

V ViV.VV. V

' . V is also a switch controlling a special There V ' VV V' V V ' ' device which enables you to obtain asuit V able impedance '

I As you see, Philips Seven Cornered Loud Speaker is something pew in value a first ,- class instrument which sets a new low

. V Call in at your dealers . . . price standard . V I V VV V . will be a I V and ask to hear one, it pleasere V V V . . . V : . V zq V

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Adul. Philips Lamps, Ltd., Radio Department, Philips House, i, Chaving Cross Rozd, Loadak', WC. 2.

417

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BOWY! 1%-L AMNOUNOE -\

(Ç AÌWi6iof EPÒCR ,. 7;ÑG

-, SETSAND : "OYDITY i. CO1IPONENT$ L

"LOG MAJOR." O - . .. LONG RANGE H.F.

. CHOKE. -

A new sie logarithmic full .-ìH' - condenser with cast steel spindle - . on cone t,ype ball 3' diamster .'. . Operates over whole wave- piece, bearings. One pig-tail. ¡ -' length range from 7 tO 4,000 o. Length - .-,, ,. i - - -- metres without flat spots. Self - List Behind capacity of the order of 5 or 6 uuF.

No. Mfd. Panel. O List No. 337. 7/- 330. .00025 29!16 12/- - - -

33L. .0003 2r 12/6 O

332. .00035 3 13f- , - . - ,-,, -._ .- - ,13/6 O 333. EndPare3xIL.00013' THE SCREENED VOX POPUL! THREE. "The Set of the Year." This Screened Three marks the biggest advance in set design and construction since the industry began. The "WHITELINE" VALVE quality of its reproduction is amazing and its selectivity is no less HOLDER. wonderful, utilising a screened grid I-1F. valve and a 5 electrode Pentode for the amplifying stage. List No. 339. Set in dark polished oak, beautifully finished, cosiplete with grid bias and three special / / Marconi Royalty. valves tested and snatched to set. I / - 37/6

A miniature of tise " Log Major" with spindle 3/16" [1 diameter.. Length List ' Behind No Mid. Panel. 334. .0003 2V 7/6 .004 An instrument "rneclanically 335. 37/16" 8/6 t 336. .005 4 9/6 and electrically perfect." Large Supplied with ebonite dielectric initial amplitude to shock, but for portable sees. quick and smooth danping. Length List No. 282. 1/9 List Behind No. Mid. Panel. 338. .0005 12" II,- Mode Zn any size for set ,nakers ELFIN CONDENSER. THE PENTOVOX TWO. A Two Station L.S. Set. The Pentovox will be one of sets on the market-no colt VARIABLE RESISTOR the most popular sets of the chanm, easy and simple control coming season. It is a two valve by slow motion dial. receiver using the new Pentode List No. 329. Set valve and, despite its luxur'j in dark polished oak. £ 5 kr equipment and outstanding per- Two Special Valves. LI/I 5/ formance, is one of the cheapest . Marconi Royalty. 25f- ii. Bowyer-Lowe are introducing a Screened Vox Populi Four, a nets The smallest logárithmic con Short Wave Receiver and a Cone Loud Speaker. Full descriptive details denser made. A precision can be had on request. instru- in ment especially suited forS sets For baseboard mounting where space is at a premium. two ranges, o- - ohms and List No. Mid. o-3o ohms. Resistance wire is wound on non-shrinking former 311. .0001 .. 5/9 3i2..00015.. 6/- with bakelite base. 313.0002.. 6/3 List No. 289. 0-5 ohn,s. 3fr 3i4...03025 .. 6/6 Bo4i3iÑvc' List No. 290. 0-30 ohms. 3/ Jr. Â SiTS.(O 'ONENTSLO1IDS' iLc BOWYER-LOWE CO., LTD., RADIO WORKS, LETCHWORTH, HERTS. )

,. S-

418 -

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Ferranti Wire-Wound bakelite bases with clips and terminals show that the losses düe to the Resistances are provided for these resistances, so presence of solid dielectric have been that the convenience of rapid inter- reduced to a very low figure, thus USEFUL addition to the Ferranti changeability is obtained. n'iaking. the holder efficient ou very .LT1 range of ireless components is short-wave work. -. the line of wire-wound resist- JItIIHjIHtluImhtIuflIuuIIIIuhIHIliuIIIIUIIHHhIIIIUiIIIIIlI ances now available for use in mains A MONTHLY REVIEW OF The Philips L.F. Transformer units, in high-tension leads (in con- TESTED APPARATUS. At one time very small transformers junetkn with fixed condensers) as a NOTE: AU apparatus reviewed were almost invariably very poor means of motor boating," E iii this section each month has E stopping" E been tested in the Editor's private E transformers, as thesmall sizegenerally and as resistances for reducing the E laboratory, under his own personal indicated insufficient iron in the core voltage applied to a valve so that one E supervision. E and insufficient wire on the bobbins. voltage of battery can be used through- IItIIIUIIflhtIIttIIIIUIflhIlIIIIIIIIIIUIIlIIIIIlIIIIIIIIIIIII(IIIIII but with the introduction of the newer out a receiver. A wide range of values Magnum Valve Holder irons. such as " Permalloy," it is now is available from 2,000ohms to 100,000 possible to obtain time effects we ohms, the current-carrying capacity The Magnum valve holder illus- .requirc with a very much fmaller I of the 2,0(30 ohms being 60 milliamps trated herewith has several interesting qtíantity of iron. The Philjps' trans- and that of the 100,000 ohms 5 muli- features. - It is of the sprung formers are a good example of the amps respectively, the current-carry- variety, the central sprung portion application of Permalloy in. modem ing capacity falling off, naturally, as carrying the valve sockets being low-frequency transformer design. the value of the resistance rises. ingeniously constructed so as to re- Although the transformer itself is Used for the purposes for which they move a much as possible of the olid small in physical dimensions, the are designed, these resistances are dielectric from between the sockets. performance is excellent over the most useful. Measurements show that whole musical range, and can be re- the values are marked with a satis- commended for use in any type of set. factory degree of accuracy. No Its small size and light weight attempt is apparently made to wind make it particularly suitable for these resistances in non-inductive portable receivers, and thus it is no form, although they are sectionìsed. longer neces.sary to sacrifice quality Measurements showed that the 3,000- of reproduction in order to obtain ohm resistance had an actual value light weight. The make-up of the of 3,220 ohms and an inductance of instrument itself is very convenient, 4,200 microhenries. The actual make- substantial termimials and soldering up of these resistances is in the con- lugs being provided. The base is of ventional cartridge form generally moulded bakelite and underneath associated with w i re-wound resistances ..- I.

Low-loss ernzsfrnc(im, is a special fe,luie of lisis MagnHni t,1rc ¡,ot,(er. This is effected by the provision of a , central hole and cutting away a good deal of the solid material between the sockets themselves, asshown in the illustration. Four termináis are pthvided at the A Ferranti wire-wOHn1t rc8istaHCe. corners of the square, and as these A iiw L.F. t;«usfornler due to Philips Lamps, Ltd. used for resistance-capacity-coupling. terminals do not- project the space It is not intended that this Ferranti occupied by the holder is extremely there is a convenient diagram of resistance should, be used for R.C. small, which, of course, is a distinct cpnnectioìis. - . - oupIiiìg, and the Ferránti resistances advantage in portable sets. The Tue ratio is 3 to I, and like most high must not be considered as being inter- method of springing is quite sound and quality modern transformers, the type changeable with the other types. good contact is established with the of valve generally called ' high Substantial and well-made moulded valve pins. High-frequency tests frequency" works- epl1ently in 49

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- What's New-continued

front of it. The makers have adopted Daventrv range should certainly con- The Lisseñ Super Transformer the practical method of marking sider this model when making a The new Lissen Super Transformer, G for grid, P for plate, Positive for new choice. illustrated herewith, is a welcome ad- H.T., and -O for grid bias. dition to the line of first-rate British It is rather peculiar to find a low-frequency transformers. Careful European manufacturer adopting the tests in the laboratory revealed that American " O" for grid bias. How- the reproduction with tliisinstrument ever, this method is far superior to is of very high quality, the low notes the IP., OP., IS., and OS., which being faithfully reproduced as well sorne transformer makers still persist » - as the high, reproduction being re- in using, though it means nothing to muarkably uniform over the whole . ;_ most modern users and is only a source range. A detailed examination of the of confusion. instrument itself shows that a very The "Leweos" H.F. Choke substantial iron core is used, the secondary being wound with two The latest addition to the line of bobbins, one inside and one outside high-frequency now available chokes the primary bobbin. to home constructors is the" Lewcos," Each bobbin is further subdivided manufactured by The London Electric so as to obtain a very low distributed Wire Co. In appearance following the capacity. A ratio of 4 to i is used and conventional lines with a slotted a fixed condenser of O003 mfd. is former and sectionised winding, the placed across the primary terminals choke on test showed a remarkably inside the casina. which is of moulded exteiiclea range or uselwness, its The Pyc I«itsfor nier for Westinghouse bakelite. TIii super transformer tatural period coming lar higher than rectifiers. should not be confused with the is usual with such devices. maker's popular 8s. 6d. model. The Our laboratory tests showed that A Transformer for the Westing. latter, while excellent value for the in a normal circuit it can be used up house Dry Rectifier to wave-lengths well above 4,000 The increasing use of the Westing- metres arid dowii to 50 or lower. We house dry rectifier has created a demand for a transformer which will function satisfactorily with this useful device. 1lessrs. Pye's, of Cambridge, who have a well-deserved reputation for transformers, are now producing, at the reasonable price of 15s. a useful transformer tapped on its mains side for 200 to 220 and 230 to 250 volts L AC., while on the output side a voltage of 85 is obtainable for use with the \Testinghouse dry rectifier, types R4-2-1 and R4-2-2. One of these transformers and a Westinghouse R4-2-2 unit make au admirable i combination for providing the field current for moving-coil loud speakers p of the low voltage variety, as no special smoothing circuit is required; the choking effect of the field windings usually providing all that is necessary. This is the Lissen super transformer. The transformer under review is up to the high standard associated with money, is not comparable with the Messrs. Py&s prolucts and should new model in performance over the The ne.v " Leicos " II.F. choke. pIO\ e extremely useful for a variety whole frequency range. of purposes. In our opinion the advantages understand from the makers that this iiiuiIIIIIIIIIIIIIIIIlIIIiIItIIIiIIiIiIIIIIIIIIIlIII1IlItII)IIIIIIIlli gained by using a high-grade low- ehoke has been brought. out in response frequency transformer in a receiver to a demand for aciioke which will be LATEST in practically all cases outweigh the really effective around the Daventry EXHIBITION NEWS difference in cost between the two and Radio-Paris range, as many of See "Popular \Vireless" for all types. Considering the performance the existing models cease their choking the latst news from Olympia. obtained, the price of the new super actiouwell belowthe2,000-metretnark. ON SALE THURSDAYS tansformer at 19s. is remarkably low, Readers who have had trouble with PRICE 3(1. and we congratulate the makers in their radio-frequency chokes on the producing such a fine component. 420

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&TAND 42a - I I OLYMPIA

- The Electron Co., Lid, 122-124, Charing Cross Road, Londcn, W.C.2.

-421'

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HF. CHOKE CURVES

I, - Showing thQ pefoiwutiice offJiLewcosHFChob4 '

VV V contpad WaIL oI-Jiai inahcs.

± _ _

WA rA VA 5QQ 750 0O0 1250 1500 1750 ¿000 -()

WAVE LENGTH METRES - i

9!_ - PRICE EACH For maximum efficiency from your set on all wave- bands from 20-2,000 metres-use the "LEWCOS" Minimum self-capacity i 62 H.F. Choke. Wireless enthusiasts will welcome the micro - microfarads (N. P. L. test). design of this new choke because it cuts down H.F. Natural Wave-length 5,200 leakage to a minimum. The terminals are arranged I metres (tested with Tt4oullin one at the top and the other at the base of the ciil Voltmeter). - to eliminate the risk of additional self-capacity in The shaded portion of the diagram indicates the danger wiring a receiver. one wherein self-oscillation is liable lo occur in a receiver. The diagram shows the percentage choking effect of It will he noticed that 1/je LEWCOS H.F. ChoIce curve the LEWCOS H.F. Choke on all wave-lengths from is well above 1/je danger zone 20 to 2,250 metres, as compared with three other throughout the whole range of wavelengths, whereas Wit/i the popular makes A, B, and C. -' - other three maltes the opposite is 1/ic cose. Obtainablè through any good Radin dealer.

LFA CO (REGD.) HIGH FREQUENCY CHOFE

V The London Electric Wire Company. and Smiths Limited

Church Rd., V V Leyton, London, E.1O Phone: Walthamstow 2531 Te1erarns: "Lewcos, Phone, London."

422 -

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___

.,1c;: :'-.- J:::>l..ø -.. IL yJ"er ' (JJLrCI.- . LO

- --

1k AFu as I respect and admire Super-what's-its-name, the first recti- what I said, for after concussion of iVI Professor Goop, who has been fication process is done by passing the brain one's memory is apt to be a justly described as "one of the them between rubber-faced rollers little faulty, and concussion is liable greatest intellects of all time" (what- operating on the ordinary super- to supervene when a fellow swats cvçr that may mean), I do not think manglodync principle. They are then you over the head with a case-opener. after mature consideration that I stepped-up to umpteen thousand I was not in thó least offended with am going motoring with him again. metres, after which they arc re-recti- the professor when I had recovered, Once smitten, twice fly, as the old fied and then, following a considerable for, after all, thd very fact that one proverb has it. amount of further mucking about, they can have concussioh proves conclu- are passed on to the low-frequency sively that one .hasarbrain, a matter Goop's Quaint Habit side of the apparatus which delivers over which I had hd quite a heated

I do not really mind his quaint them to the loud speaker. argument withGosbthton Crump only lial)it of driving at full speed in Owing to this remarkable invention, the week before: . reverse oñ arterial roads in dry weather it is possible to-day to make a seven- iii order to keep the dust out of his teen-valve set that is quite as efficient A Practical Demonst*ation eyes; my timbers remained un- as. the four-valver of yesteryear. Shortly al tér thy discharje from shivered and my iron nerves un- The super-whatyoumaycallit has to hospital, the pfepr inistcd upon shattered (though I can hardly say be heard to be believed. Those who mc taking at iIi what he was pleased have practical experidnc of it abso- to call a practical demonstratioir. lutely rave about it. In fact, asylums "We will tune in Aberdeen here," he throughout the country are now said, "and you shall iìot the quality. practically full tp the doors with We will then get into my car and we people who have tiied the circuit will drive northwards taking the and simply can't stop raving. set with us. At suitable intervals we Durng our conversation the pro-; will tune in the Scottish station, and r fessor told me that he had just made I guarantee that you will agree that up a set operating upon this principle the quality originally was every bit " One simply wnits o(ltsI(le King's ,oss or Euston." whose perfection was such that the as fine as that which we chah obtain distant station came in every whit as when we are within buta mile or so the same of my gent's natty suiting) well as the local. of our destination. How, by the way, when a burst front tyre sustained t does one get to Abudeen? ninety miles an hour landed him, Getting the "Granite" City his car and his passenger in the "Take Aberdeen-" he said. - gorsiest patch of one of our gorse- Impossible," I replied sadly. covered commons, in order to point With Aberdeen it is a case of put out the beauties of which he had añd take; you put and they take. removed both hands from the steering- In that braw city every other shop is wheel. These little things are all in a dry-cleaner's establishment. They the day's work, and one takes them are enabled to pay enormous dividends as they come. It is more serious simply through the business they do &Ç Il/bere ?" Rto,fled the pio! essoi. matters that have stifled at birth my in cleaning poppies and roses for use " Il/are! " I insisted. desire to go motoring with Professor on future occasions." - Coop. "Tut, tut," grunted the pro- If," I rTeturned, " one is an Our last-at leait, I hope that it fessor. " What I meant was that Aberdonian one goes to the docks and is the last-trip together came about Aberdeenprovided a notable example. selects a ship round which no sea- as the result of an evening that I You Will hear 2 B D as well here in my gulls are hovering. Being thus assured had spent with him. In the course of house as you would at a point but of its port of registry one stows away it he told mc souiething of the beauties a mile or two from the centre oLwhat on board- and probably pays one's of a new receiving st that he had just I believe is known as the Igranic expenses for the next three months by designed. This works on the familiar City." writing lurid articles on ' How I super-something principle, whose "Granite," I corrected, but the Caused the S.O.S. to be Sent Out, By name is so well-known that for the professor shushed me into silence A Stowaway.' Of course, if one is moment I have forgotten it. and went on with his theme.. liable to seasickness oe simply waits Impulses brought in by the aerial I told him that I did not believe outside Euston or King's Cross until take the form, of course, of waves, nd a word of it. I mean, of course, I was some Celtic visitor to the Metropolis these have to be rectified or flattened quite polite about it. I did not put drops his return half.". out by means ofa detetor. In the it just like that. forget exactly " I meant," snarled the professor,

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I I -

In Lighter. Vein---contirniecl ...

what road does one take, for I, of some zip about it. That I suppose is in for crry-go-ronds suggsting course, invariably thotor from place why ho has a Baby Forcedin body on that they -should hàvé the corners to place ? his 90 h.p. Spaghetti chassis. properly banked. I told him that there was practi- "What's our next point ? " he We had a littl.c.trouble just notli cally one-way traffic to the South on queried when the countryside had of Berwick owing to a slight .puntire all roads leading over the border, but flashed past for a few minutes. sustaihed by contact with a harrow he refused to listn to my words. "Hitchin," I shouted. that somebody had caielessly left Aftr consult.thg..maps. hd things we So am I," called the professor; lyilig about. It wâsn-k actiiàlly on found that. th Great North Road was scratching a leg; "but do be careful of the róad, for the- professor, -who. is junt ththiiig. '. your aitehes. These mosquitoes-" always one for the great olien spaces, A blur of houses and things'oöcirred was tying a'shbrt'ôut' acrOss :côuntx. "Wiiere?" "Why, Ware!" and we were once more upon the open À " Litt ',Ó'visiht,' Where do we make for first from road. . Still, I do think th farmes ought here ? " que'rid :the professor. You know," remarked the pro- Wac,' I aid. fessor suddenly, " I think the tr'oublc to be 'a little ni'ore careful .a,bd,t the "Two. quious don't make an with most short-wave nthusiasts is way in which they leave their tools answer," eri&the 'professor. " I said that they can't 'niako :fine enough about the place. Luckily it was no a where? " adjustments. If you give just a'tin tyrethat ivas pun'ctured. - The pro- Au&I_,iLUWre," qouth I. turn (he did so to 'the stéering wheel Where ? " stormed the professor. and, we: n:arowly. mi&ed a hàystackj Ware," I insisted. Seeing him you can tune in 2 X A'F.to perfeotion. reaching för the.poker and reinember But if;you o 'lik' tl,tis (and. here ing that I had.,alreadydeinonst,ated ho gave the thing ì yank) yoiì'simply thaJ posss3d a brain, I hastily don't know where you aie." - iiointed to the piace upon the map: A'Rapid Rolation Wo nine to-morrow," - wilir start at We shot down a turning to the left said the proLessor. and before I had ëined breath The j,roJ'csso,' tcas truing « short cut Ack or2pi.p_enima ? " I inquired. «cross country. '" enough to point out that we were off àm not fond of acks; in fact, if I I the track we found ourselves in Bristol: fessor failed to see a stout beam' fixed may so piìt_itr, they give inc the pip. It uvas there that we'struck one'of 'across the gateway between two fields the world, is Inçan,j.din't think those 'merry-go-round affairs, whi'cli and the car stopped rather suddenly, aired before midday. All prperly acid so much to the hilarity of modern with the result that he sailed through with t.li& lark is this talk ab9ut rising motoring. Being somcwhât unused to the air and brought up sittiñg upon real!yrather rot. Larcs fini it such a this form of traffic-c6ntrol, the pro- the implement in question. ,With the go streiiious giine that they have to fessor, once he had becun to rotate. help of the jack I was 'sOon able to fouud himself coiupltly unable to prise hiii off it and we resumed our get out of the rina. Like a straw journey, though for some reason the caught np in a whirlpool we circled professor elected to drive staiiding ¿p. madly round and round. " And now," said the professor, At one time a 60 h.p. Moonshine was when we had left the border well he- ahead of us, but in the seventeenth la hind jis, "the time has come to give we left it absolutely standing still. I you a convincing demonstation. We have often wondered since whether it will get out the set and tunó in Aher- Knotlin7j my ncclJie fis ICC spcd mistook that lamp standard for the' deen. Ile o1)encd the lid of the glory- w'inniimg post, or whether the driver hole thing at the back of the car and to bed just when decent people are was a little disconcerted by the skilful begai to rummage about. "I am getting up. Give me nightingales way in which the professor edged him afraid," he remarked, glancing ûp every time. . - lap by lap nearer the pavement. At resently, " that by a little oversight The pinfessor, however, was ada- length the. professor announced that I have left the set at home. Jump in mant. 'An early morning start, he he was feeling giddy and that the only and we will go back to fetch it." said, was essential. I promised with cure was to go round the other way. I suggested that he should go back some nuisgivings to be ut the rendez- alone whilst I remained behind.' I vous at the appointed hour, but I A Little Trouble! promised that I would have a tern- quite forgot that Wilfred, iuy alarm 11e performed a masterly gear porary aerial erected by the time that clock,1 hros m own feelings and change from top to reverse, and after he returned. The professor shot off nvariabl goes off about six hours half a dozen more laps saw a way in a huff and a cloud of dust. When he late. Asamttcf of fact, though, we ppen. We shot down a turning, had gone I set out for tue nearest did get imder way by midday, but I brushing motor-buses and things railway station. had to púli on my opks and complete aside, and after a merry little turn What's the next train for the the knotting of my ieckfie as we sped rounçi Wales found ourselves back on South ? " I asked the booking clerk. northward s. the Great North Road in simply no There's one in half an hour;" ho The professor's taste in cars is a time at all. The Professor has sinèe replied, " but it's only a slow." !ittic queer. He likes something with written to all local authorities who o "Thank heaven for that! "1 cried. 424

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October, 28 THE WIFELESS CONSTRUCÏOR

- -- FIRST ANNOUNCEMENT OF J(,,' (J 1929 MODELS,.

- - M ( I D M t I' le iew ornpiete iange in ivetai annet ¿iT "Eleco," the pioneers andforemost As primarily "EKCO" con- and 'jj inventors manufacturers of sumption from thc mains is ' ' Marns-Pqwcr Isadio Devices in Great Bi-itain, have pleasure in announcing pract:cally negligible- For Effi- - - '- their Braun New Range of Models for ciency-Ekconomise!" 1929, and that all "MEGO" Models MODEL A,C,s,F.ro tIOIJlLD.C.,Ii.io of the 2 and upwards valueof too 1T The " ' FECO ' MAINS- are obtainable on easy payments through your local deatci-, DRIVE Receiver is oiie pf - the outsthnding ach ioveinciits of - JAll models are contained in vcry - - - attractive metal cabinets of ari the new season and is easily the ,4 artistic cryst-illiric dati biown fanisli soundest the simplest md th_ ,ffl ,_- ham Ing the appcar--mncc of quilrty ir Y most erononmical rccerm er )et leather, Jhe metal case increase pro d uce d '-a' J,J ' " efficiency b)' its "shielding" proper- [JI .-. tiesandchminatesanvdangeroi fine ¿iJ Wirte now br the new tiles - and all terminals and leads hram'ily insu- J trtod " ERCO" Booklet post )ated,ensurrrigabsolutcaletyconforming - A ,) D EL - D C - F60 to the latest ILL, recommendations, tice, g' u1,, full details I ItICKLC CHARGER

: .1! COMPLETE PRICE A C iuoluveValv Ill f D A C :thhb0 -- Tappings 6 I 1TJI'pC Volttge 13 - 1I 'i' £3 Output 6 - Curent 90 Or 120 9 . r . o " 60 £1 - Model - ______18 6 - MILLIAMPS sets, or those Valve £4 I 3 valve 10 and:2O ------0 '- For I to more than 60 £2 10 H IF.lO not 6 requiring _-_i;;----_- £5 8 mullamos 60 ,, --Valve 6 2F.1O ,, £2 18 - 120 15 6 - £6

. . 3FA.20 20 MILLIAMPS - 12O'1XeI1 , used those- 30 Westinghouse 1VA.20, sets, or 60 ,, Metal 5 valve 20 - For I to more than 120 " - not Rectifier reautring 2 6 -:- - - £7 SF8.20 milliamps - - -- 6 - £3 12 - -- O fixed - - - - '13 6 - £7 - 120 - - - fixed 6 - 18 - 'Power" ' £3 - * var. ._, ' 4F.60 O-120 Valve - - fixed it2 6 60 MILLIAMPS- 120 - £8 - " fixed or those O - 10 valve sets 60 "Power O For I to more than var. £5 IV.60 'flot O-120 requiring 'lO O nillilamps ii'xe - £15 " fixed 0 - " Power £7 15 2V.60 U-3U var. Valve - ,, O-120 - ' - lived -.-,-----.-'-.- n 120 MILLtAMP 200 vn I) 'J

super-Power - Fv.120 j power. 12 6 -- fixed - £2 UN1T. var. 100 H.T. O-120 to 25. :4 -POWER"inilliamps. fLR us 60 to fl amo. C.IA LT un A.C. Westinghouse 6 5 troia Metal Rectifier 12 volt accumulators -Il LECliARGER.2, 4 or O O Charges ,, amo continuously £5 T.500 Mains at ______Valve - UNITS. 21 D.C. Units. RECTIFIER attaching to For 6omiij 15s.Od. For mains 119 Gns' in use. R.20 on A.C. IVaIVO unit Is For use a power supply o from set where RECEIVER. or 'Phones Ii 3-VALVE Loud-Speaker MAINS-DRIVE tor isolatIng VISIT TRANSFORMER, ISOLATING - -STI4NDSISS44T/1 NA TIONAL RADIO EXHIBITION, OL YMPIA J EJOLEJI Dept. M,. "EKCO" WORKS, LONDON RD., LEIGH-ON-SEA.

- J . 49 - X --1

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Ir .10 ;.;j

AT NEW. .REDUÇED PRICES ! : SUPER GENERAL POWER PURPOSE VALVES and FOR R.C.C. LOUD-SPEAKER UFRtO RECEPTION VALVES. 2 and 4 2and 4 VOLTS VOLTS

E 1V1ITTI F1V1ITT

We claim that with the latest Dario Valves thé greatest volume and selectivity can be obtained with the greatest ecOnomy of filament current, as the G.P. 2 and 4 volts consume only O5 amps. and the Super Power 4 and 2 volts 1 amp. and 18 amp, respectively. DARIO VALVES DARK EMITTER RADIO MICRO Can be obtained at the new prices from all high-class radio dealers all over the British Isles. If unobtainable locally write to us mentioning name and address of usual dealer. IMPEX. ELECTRICAL LTD. II 538, High Road, Leytonstone, Londoñ, E.11 Telephoie: Wanstead. 2722. I DEALERS' Enqufries are welcome and will be ätteñdd to promptly. -- - 426

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I should say that thére is no'dóubt that this is exactly what had happened V in this case, though it is certainly ot at all a cothmon fault nowadays. Some years ago, however, when valve

filaments were so fragile that one was V afraid to look at them, it was quite a common habit to carefully tap the V

VV valve when the set " packed up," in the hope- of restoring the fractured filament, or of unsticking the filamept

from the grid. Fortunately, the u

modern valve very seldom gets trouble -

of this kind, but our Hampstead - friend's experience is Van interesting

one as a good instance of perseverance -

rewarded. V - -

More Trö'uble! - - V

Some typical faults and remedies reviewed. . - -. - - Old-timers and those who are By P. R BIRD. I skilled at the radio game will not need to be told much about that old trouble reaction overlap. But as 1T' OLLOWIXO my recent remarks tap. No results. But directly the JL this is the time of the year when a I.- upon the queer things that can old one was tapped in 2L O came good many newcomers to wireless are Imppei if contacts are bad, I again. On placing another alve in I 4 glad of hints about regulating reaction, recei\' ed a letter from a rcadér of the the bld one's position the set worked I think I ought to tell you about the WIRELESS CONSTRUCTOR who lives at as of old. I found out the truth about dreadful trouble of an Essex reader. West End Lane, Hampstead, N.W., a week later. Six closely written pages lie sent, London. He instances a case which, dealing in detail with way his although unusual, might llave hap- Cause of the Trouble the set was misbehaving itself, and to pened to anybody, and I think that I Wiat had happened was that when judge the blots and the cannot do better than to put it into I was at business a friend had soldered by under- lining in his he not his own words. a lead in place for inc. Ill order to letter could haye been more worried and distressed if After saying some very nice things the accumulator had- blown up, about the WIRELESS CONSTRUCTOR, caught the set on fire, and brought the he coñtinues as follows : "My set is THE TECHNICAL QUERIES mast down smack right- upon the a two-valver-Det.-L.F.--and some DEPARTMENT tend erest spot in the vicinity. And the time ago I liad the misfortune to Are yoti in trouble with youriet? whole trouble was nothing more blow a valve, and therefore replaced nor Have you any 1notty little B.adio problems less than overlap it with a new one. But on nutting requiring eolution? Tho WIRELESS COESTRUCTOR Technical i this in position, much to my attonish' Queries Depart ment has been thoroughly

I reorganiseci and is now in a position to give Reaction Overlap -. . the meut set would not work at all au unrivalled service. Flic aim of the do- I tested the L.T., HT., transformer, partment is to furnish really helpful advice For the beieflt of those who do no in connection with any radIo problem, etc-all O.K. theoretical or practical. recognise the name, I must explain Full details, including the revised and, in overlap is a trouble ill geiting cases, considerably reduced scale of eharqos, that fhe Magic Knock can be obtained direct from the Technical good reaction results. If, for instance, Queries Department, WIRELESS CoN- It then dawned upon me that I sTRucTon, Fleetway House, Fairingdon QU have a condenser-controlled re- Street, London, E.C.4. action, you should be able to increase may have placed the valve in wrongly, A postcard will do : on receIpt of this all the necessary literature will be sent to ydu free : - the reaction effects slowly and but this did not appear to be the case. aud post frco, immediately. This applica- I again switched on the set., and in tion will place you under no obligation steadily; starting at a minimum whatever. Every reader of the W'IIIELNsS :' should be no reaction doing so I happened to knock on one CowsrarcrOa should have these details by there effect at him. form is i - valves. An application included all, and then, as the condenser is ofthe (Not the new one, the which will enable you to ask your questions, old one.) Suddenly 2 L O came in I so that we can deal with them expeditiously slowly increased, the feedback should of and with the minimum delay. Having : - be slowly increased also, until one with a roar, but my joy vas short- this form you sull know exactly what at lived. About five seconds afterwards information we require to hau'c before us in point on the scale the set should I order to solve your problems. all was silent again. I again gave the gently and almost imperceptibly go valve a tap and it came through again, into oscillation. but again it vanished. Then I tried do this he had removed the valve and Further increase should increase pushing the valve down farther in the quite innocently remarked to me that the oscillation until at " maximum socket, hut it was already down as he had lIad great difficulty in moving setting the set can be made to oscillate faf as it would go. Next, I began to one of them, nnd when it did come violently. The point is. that you should slip in and of oscillatior. suspect the valve holder, when out it came out with a jerk and hit the out examination showed that this was top of the cabinet: I take it that one aIitöst imperceptibly as the reaätio,u control is moved in and out. O.K. . Apparently the only thing end of the filament had temporarily that remained was the valve itself. come unstuck as a result of that blow Now this reader down on the farm To make definitely sure I reversed and the tapping of the valve relaccd in Essex, like many another g9od man,

the valves and gave the new one a it." - (Continued on pzge 452.) _ I -..- -.,.

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**************************W*************** broadcasting the same programme. -

- - Captain Eckersley has pointed out that if two stations, exactly syn- :*OUR NEWS BULLETI chronjsed, broadcast the same pro- 4 gramme, each will give a satisfactory Some of the More Interesting. Happenings - local service in a specified area Out- side this area the two stations would - in the Radio World. this Month. * probably create what is known as a '******************************** ******** ' mush" area, where quality of reception would be bad; but a third Call-Signs For Planes Although there are about twice as station, on another wave-length, would AO call-signs have now been many European broadcasting stations serve this ' mush" area. .iL'.. fixed for aircraft by the Berne as - there are available wave-lengths, Committee, and it has been and many stations have to share a Wide Areas Covered decided that each aeroplane is to have common wavß-lengt h, interference be- The main benefits of the plan are a call of fue letters, the first repre- tween stations is not so chronic as it that two wave-lengths would be senting the nationality-U, in the case was a year or so ago.. enough to broadcást one programme of the United Kingdom. The other Still, there is room for improve- over a very wide area. four letters are the registration mark ment; awl it is likely that in the This new plan, if adopted, would of the aeroplane. So if an aeroplane near future the Union Internationale probably mean the end of the inter- bears on its wings the letters GEYOR, de Radiophonie will give its sanction national common wave, i.e. a wave that also will be its call for radio to what is considered to be a good shared by different stations broad- purposes. The second letter usually is plan for miuimising interference be- casting different programmes; and what may be termed the sub-nation- tween broadcasting stations. countries now using only one wave ality letter, English aeroplanes using would have extra ones at their disposal. the letter E. "Syiichronised "Transmissions Although the above plan has not General calls hìave also been fixed. Captain Eckersley, the chief engineer yet been officially adopted, it is For example, the general call for all of the British Broadcasting Corpora- reasonable to forecast that, in the French aeroplanes is FOZ. The tion, eems to favour this new plan, near future, it will he tried out- general call for all vessels of the Royal states the "Daily Telegraph," which, possibly with modifications, but essen- Air Force is GEZAA. briefly, turns on the question of single tially as outlined above. Most aeroplanes operate on waves wave-length working-that is, the The B.B.OE's transatlantic broad- froni 600 to 1,550 metres, with 900 sharing of one wave between several casti ng scheme is, technically, not new, metres äs a standby wave. stations exactly synchronised and (Continueil on page 430.)

. -.- .

MAGNUM HARRIS "STEDIPOWER" UNITS Construct the

H.F. . (CHOKES " RADIANO" FOUR as described in this ¡ssue by Mr. Percy W. Harris Lud. Oak Cabinet, with banebonrd ,...... _, 1 16 0 Rcuisi,on Ornamental Panel. 2i z 7 10 9 '-Ì1ttI1. Indigraph finis 15 an - Recognised the moot efficient of their typon. Made ...... 0 r 2 Lianen Variable Condensers. ru two rangea, . 0005 mid 13 0 - Cyidon Reaction STANDARD. 50 to 3,000 metres. PrIes 716. j Coosdenner. '000k mid '7 6 Fioul biow 10 metres - On'and-Off Switch ...... 1 6 . STT1 OP to loo J L.T. 'and H.T. from A.C. MAINS. Linsen Panel Rliostot. 30 olinto 2 6 Lotus Push-Pull D.P.C.O. - Sivitolien. with 'Flle ' extension Stedipower" The "Stoalipower" rods, knobo, and mountings , 11 0 - MAGNUM r' / L.T. Unit. HT. Unit. Magnum Panni Br'acketu ...... 2 6 f Terminal Strip, wIlli 7 indicating terminais 4 6 / . Beady wir-ed rind tented. Ready wired and tCsted, Terminai Slrlp, wlih 5 indicating VOLUME I COH1° . Suitable for 2. 4, or fi' a vaine. terminata 3 0 and including 13.5 Magnum Vibro Valve Holders ...... 8 0 .fi. voit vaiven. the totsi Osiput 50 ItA. Two 4 CONTROL Magnum Coli Hoidero ...... 6 0 couoaaanptlon of which ontrnuotiiy variable 2 i two Magnum Fixed Condennero, '0001 mid 3 Su p ¡rI ed in . does t'nt exceed i iii- and one fixed tapping io 0 i Magnum Fixed Condenser 0003 mId i Resistance vallico- J POI_e, provided, O j, F.C.C. Fixed Oond.. SJp type. 2 asd 2 . '0003 mid 4 £9 lOs. Od. £13 Os. Od. Formodenser, '0003 Itype BI ...... 2 0 Dubilior Fixed Condennero, 1 . ntfd.,.,.,, 5 0 -. . Royalty extra. . Dubilier Fixed Condenser, 2 mId 3 6 Price . - flubilior Grid 2 ...... Ti you wish to build lire00 tirito yonrself, we vilyply ihn Leak. meg ...... 2 6 7/6 d complete kilo of components. including Cabineto, 05 oliswo Magnum R,F. Choke ...... 7 6 Mollard R.C.O. Unit ...... ' 17 6 LT. Unit, complete kit of Paris .... £8 1 7s. Od. i Fuligo' LP. 'rransformnr ...... 1 5 0 'Offer Igranic L,F. Choke, type F Special ' N.T. Unit, complete kit of parto ...... 1h O Magnum Copper Screening Box, with all boleo suitably drilled ...... 12 o SYards Flex ...... 40 . Lisaen 'naI Receivers X Çoil, No. 60 ., ...... 6 4 Linsen X Coli. No, 250 ...... 9 9 Lianen Centre-Tapped Coli. No. 60 ...... _, 6 4 g Linnen Ceniro-Tapped COil, No. 250 ,,.,., 9 9 - ynoCOnlflkflg Sundry Screws ...... i BUILMEJONES .3

Three . . . are avail. S.... C O LTD., . - able:- 1929 screened these purtecan be MAG N U -. H O U S E l'Ça M - Magnsrn 1929 Purity TELPH ONE: HOP 6257-8 nea onswi- Ifoyaltios estra .,. £2 10 0 Make n point of cecino tuna" Colin. An entirely ¿shiblko Set of 4 m'd 288,BOROUGW HIGH ST. talve for above ...... £2160 Yev sesuon's catalogue Universal . Set at., our . COThpents supplied tpr all pets and apparatus and listS cmb oñ receipt Stand No. 96, Olympia ' described sa this Issue. of 19d, stamp. Radio Exhibition. $ ß O N S E I ¡' ) - ' / .' - s'. '- t_c_ " 55 -z-. - - 428

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. -. . - - . '-A'- - .: -

NEW IDEAi. .- -.--

I "Two Stage". .. -: L.F. Unit One stage RESISTANCE and One stage TRANSFORMER - ANEW. in sealed Bakelite moulding

r, VALVE DELIGHTFULLY CLEAR HOLDER "BE LUXE" Mode' Lo Condenser - REPRODUCTION AND ANTI-MICROPHONIC - - - - in - SOCLE VOLUME - SHOCK ABSORBING \ \\\\\\. . CONCEALED Terminals very con- 1111111 -::. ' ERAKI II , veniently arranged, PIGTAIL \ \ / f making the corn- \\\\\\\ 30 ponents extremely / simple to wire. Q'( FL? -: crtt i&uininii - wEIGrrr 43'u cts

- --2"-. - This Condenser ha an Capqcjly - - - s i ingenious NOISELESS '0005 Price i i 3 - "PIGTAIL" incorporated 00035 iu' I in a manner unobtainable '00025 i" including of mou!di_,,, BAKELITE throughout. in any other Condenser. '000l5 f BASE PLATE. - j Practically DUSTPROOF. Price- .6i - eac :- The springing is such that even rough The" Pigtail "passes through a centre //I 2Ç\ usage will not affect its liveliness. boring practically the full length of the spindle, and is The "float-" is reeessed- on -top, thus securely fastened to the making, easier the manipulation of end bearing, which is integral with the :1. valve when- plugging into holder. Rotor Terminal. The means employed completely overcome , the noises As will be seen from illustration, associated with the generally used («..J\ ) Terminals- are provided well as clock spring and similar loose external soldering tags. devices. ' -

-o\ TWO STAGE ' Vc j,ì Send for Full Catalogue and FREE COPY of <»\ / LF.UNIT \ BOOKLET-" L.F. AMPLIFICATION." SHORT WÄVE A postcàrd will do. I L DE LUXE 00015 CONDENSER

- -OUTFIT ANEW FROM HIGH TO LOW WAVE WITH. PRICE VV U- OUT CHANGE OF !Ç : i 1 0'G

RANGEA very neat and (Wthout. Dial) dent Aerial Coupler with G pins in standard poition, this can be j The Condenser is the De (Relnartz) with any standard P... used Luxe Model DB. type, 6-pin base. maximum capacity 000 15, PRICE - The change over from for Short Wave work. The Ebonite Tube is 4 in. 1 0/6 long x in. diameter, in. switch on panel. - - Brass insert at Dial end, Base2/- 42 drilled, tapped, and the necessary screws fitted.

ROWN N.W.2 1 Visit STAND 140, OLYMPIA, Sept. 22-29 WORKS, CRICKLEWOOD LANE, Telephone: Hampieod 1787

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able for the microphone, and the dined the aid of the B.B.C., had at OUR NEWS BULLETIN dramatic productions' director of the last accepted the friendly business will for -conlinued from puqje 428 B.B.C. keep a sharp look-out overtures of Savoy Hill. novel turns during a Continental Up to a point negotiations went holiday. While in Germany and well, and it seemed that Sir Thomas but it has not yet been put into France he will visit cabarets, theatres Beecharn's dream of permanent opera. official use in this country. and music-halls in the hope of finding and a permanent first-class symphony The scheme consists of trans- some fresh " turn" for the many orchestra would become a reality. But, mitting the same programme from an variety lovers among listeners. It is not perhaps unexpectedly, differences American station on five different hoped that in return British artists have arisen. The B.B.C. has strong wave-lengths-all between 16 and 50 will be heard from foreign stations. views about business, and when it metres-at once. At Keston five spends money it wants to have a receiving sets will he at work-with IMPORTANT NOTICE. say as to how and where and when it shall be other words, the aid of n aerial which can be The Wireless Constructor " Radiano " spent. In pointed in any direction at will.and Three Envelope which, following a it likes control. on heavy demand, was for a time " out-of Sir Thomas will-not tolerate (]iCta- the thery is that what is missed print," has been reprinted. It is now one wave-length and one receiving obtainable, price 1/6, at ail newsagents tion on matters concerning the artistic aet will be picked up on atiotlier. and bookstalis, or post free 1/9 from sidè of his work. In that respect he Wireless Constructor Envelopes," insists on liberty. - All the signals received, will be Amalgamated Press Ltd., Bear Alley, unfettered combined at Keston, and in that Farringdon Street, London, E.C.4. A slight hitch consequently arose, strengthened form nassed on to British but listeners will now be glad to hear listeners. The ida of receiving at Talks will be warmly discussed when that the trouble ha been cleared five different points is not, of course; next the B.B.C. Governors meet. away and Sir Thomas is again friendly with B.B.C. new, but-no one has yet sent out the Some of the Goverñors are . against the same programme on five transmitters, the present talks' policy, and sonic are each witji a different wave-length. for it, and it is anticipated that the Music Cliques at Savoy Hill Captain Eckersley favours the scheine, arguments will be lively when the There are disquieting rumours in and it is hoped that before the end of Governors "get together." musical circles that the music depart- the year it will have been put. into nient at Savoy Hill has fallen under practice and have proved satisfactory. The Imperial Opera League the control of two or three little It was reported in " Popular Wire- exclusive and faddist cliques, who are A Search for Talent less" and the "Daily Telegraph" making it almost impossible for new For some time the B.B.C. has been recently that the Imperial Opera talent to get a hearing. The very looking for new variety artists suit- League, which had for some time de- (Ctinued.h sage 432.)

r ii i i --- IIO r umbia--.-

al reductions In the prices Ler Columbia batteries s. High (Triple) Copacil', (No. 4780) 20/- s. High (Triple) Capocity (No. 4767) 1/6 s. Veriicil High (Triple) Copaciiu (No. 4772) 10/6 its.-. Power Grid (No. 4766) 9/- s. High Copocil,, Grid (No.4771) 2/- -The 100% Battery for - Valve Receivers-Columbia rbllt" - - 25/- for our recenllij published re, " Why Radio is belier will, Power ' -Free. J. R. MORRIS erial House, Kingsway, London, W.C.2. i: J. T. Carlwrighl. 3, Cadogan Sire.et. Gla,gow.

430

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IS H . HEARING THAT ALMOST SEEING

FROM 29'6 UPWARDS - I

'I SPEAKERS ARE i

- INCOMPARABLE AT THE PRICE "How lifelike! ' 'What volume! What delicacy of tone I" "I never - knew loud-speakers had reached such - ' perfection!" These are but a few ,,. f ' .,'' - of the often voluntary exclamations k //$' passed by delighted listeners on '' -- hearing M.P.A. instruments for the ' -

first time. And no wonder f every

I model is a miracle of its kind. Hear z THE POPULAR PLAQUE - one at your local dealers. If not in MOVING COIL SPEAKERS You search the World over without finding I- This is the cone speaker which has caused an up- stock, he can get you one by return. could heaval in the wireless world. Never before has better reproduction than that of the famous anything like its value been offered. And . . . le M.P.A. Moving Coil Speakers, at whatever price has recently been fitted with a new and improved you were prepared to pay. The result of years of centre adjusting movement. Such volume, auch painstaking research, they bear striking teso- delicacy, such clarity of reproduction you would mony to the skill of M.P.A. Wireless engineers. only expect from a model costing five times as Here, indeed, is "Hearing that is almostseeing I" Exquisitely clear! Wonderfully lifelike I All much. Hear it I See it I Both its performance j and appearance will make you desire it. Its models in beautifully polished mahogany, either amazing price, in either dark mahogany or oak, mains driven or for use with accumulator, or with trickle charger. 15 29/6. - accumulator combined Costs id a week or less to operate. Prices loto 15 guineas. S-.,

5 .5-, THE DE LUXE MOÒEL ¶? I -z Two inches larger than the Popular Model, the de Luxe Plaque has a " matched Impedance" sa -S--.. fret, fitted with the new patented M.P.A. ' - - - Iogarithmatic cone, and has a wood base. Finished in eithe r dark mahogany or oak, it not only gives astonishingly excellent results, but is unobtrusively handsome in appearance and 5-- - will harmonise with any decorative scheme. ...:- - - Price - - - r - 47/s DUAL INDUCTANCE I i MAHOGANY TABLE SEE ME SELF-ENERGISING I CABINET SPEAKER A T T H E MOVING COIL SPEAKER - Another amazing example of M.P.A. quality and A Model which ¡s miles ahead of anything of its I kind. It places moving coil reproduction within I value! This Model is ntted with a centre adjust- R I all. Catches the moat elusive A D O the reach of - ing movement, and the renowned M.P.A. fi I Patented Logarithmatic Cone. It covers an cadencies of the humanvoice or instrument, and exceptionally wide range of frequencies and in EXHIBITION is startlingly lifelike. Fitted with a vastly ini- I exclusive to M.P.A. . performance is in every way up to the high proved type of movement Speakers, no energising is required from either I standard set by this House. The Cabinet is in - ST A N D S Cabinet is in I handsomely polished mahogany with "matched main or accumulator. The - impedance fretattractivelydesignedbothsides. beautifully polished mahogany fretted both I sides. In every way an instrument of which I - - - Price guineas guineas. - anyone would be proud. Price 5 - I LTD., TEL.GERRARD 02, CONDUIT ST., - *M.A,WiRELES5 LONDON, WI. 0844* 1

- j 43

PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor .THE \Viu.ss CONSTRUCTOR - - - October, 1 9

- I the problem of television. "Within a to the fluctuations of the current OUR NEWS BULLETIN I foreseeable time," says the "Vossische I from the transmitter. Zcitirng," which gives the fullest The old Karolus apparatus to uiinei1 from píg 4O i. account of h apparatus, "we shall which it is fitted, operated by the have iiì the_-house, alongside the falling of a thin light ray in spiral lines radio receiver, the telephotogiaphic on a rotating drum, whence it was existence of such rumoirs is reason apparatus, so that it will he possible reflected onto a photo-cell which trans- for an investigation, which should be :to tranímit siniultaneously the scene formed light energy into a fluctuating made to cover auditions and hó and music ofañ opera." electrical current. whole system, of searching for new An expert in telephotography, who At the B.A. Meeting material. witnesed the working of the Karolus Papers on Broadcasting will be device when it was running far short read British Association Sunday Programmes of full power and transmitting'lper at the meeting, Sir William Bragg and Undaunted by their reverse of last second only eight pictures of eight and part. spring, the Freethinkers are launchiíig thousand light points each, stated that Sir Oliver Lodge are to take There will also be demonstrations of another attack on the Sunday pro- lie received "absolutely tite illusion television and noctovision by Mr. J. L. grammes» again asking for sonic of movement, though, indeed, some- Baird, a genuine entertainment, alternative to what angulr and jerky, as in the caso the inventor; meteorological by Meteor- the religious services. Every time of a slowly running film." The pictures exhibition arranged the ological a musical these attacks aro made they seem to were " clear and recognisable, the Office; display illustrating of music gain a little in strength, with the face of each separate actor being easy the development result that there is each time just a to identify." in the schools, by Mr. Hugh S. little more " give " at avo Hill. That, continues the report, was Roberton, conductor of the Orpheus But they will have to return twice with eight pictures per second, and it Choir; and an exhibition of industrial and other films. Sir more before they get what they want. is claimed that the apparatns has instructional John Reith will not read his paper Why don't they try Parliament, iiow been improved to a point at which away in which is now ready and anxious to it can transmit twelve. Its cheapest at the meeting as he will be exp1ot the difficulties of the B.B.C. ? will " Karolus - constituent be the cll," which, atthe same time, is its essential Another Regional Station Television Solved ? novelty. This relay, I - , . electric light from It is reported that a site has been '

a . I The " Times " recently published which, it is asserted, the element of -provisionally chosen for the erection ' I report from Berlin to the effect that inertia hasbeencompletelyeliminatcd, of the next high-power twin-wave . Professor Karolus, the physicist, of is filled with nitro-benzol, and varies regional B.B.C. station near Glasgow, LeipzigUnivcrsity, hasactuallysolved its penetrabflity for light according (Consinued on pg 434.) : ' .

-. a ' _*, ç .A ' ç------Ç -. , 4 ' =_1=_- -

F H In Spain and o; the Toreadors) The ".11rOwn" has a large the .1l3tOVU"LoudSpeaker I - following S1%2í. in the land where is recognised and appreci. . 11p't.' ...... u . "manana" istherule. Good atedbythesermitiveSpanish I r . music k fittingly ear. II / ¡ . appre. All over the world the . - . dated where life is care free ßrOWn" gives pleasure . and easy. That is why the to discrlminatin listeners . . .,. faultless reproductton of -it i so very frue i

- They listen to the 1J l'fI It C) ti

- Adpi. 5. G. Brown. L*d.. Wenem Awnoc. North Acton. London. W. 3 4)3

432

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L, The Onlij Weston standards 1 of Accuracij 'L. H.j Weèk. are sufficient

iVeek ( L. K:,

'Bàdio

Model 506 Pin Jack Voltmeier with High Range Stand, measures High and Low Enthusiasts Tension Voltages. TheWeston free booklet'Radio Control" explàins the uses of this and other Weston Radio Instruments. Write for your copy. Price ' ' 2.1O,O -.

.006S A.e

: (W50N

Mnlcl 544 lttllAmmeter should he SIcs.lel 506 Panel Voltmeter, ensure piacr,l n the HT. circuit of the l,erfllaflent 4rctr'cy With a 111gb v,,ise to ensure correct 011erut.lOn thtexnai resistance 0f 155 oltn,s. per antI check diutortion. l'anel yolit. tony make ¡ructirally ,,o lati M&uutlng t.Yj4e. on the batteries. Neat and corn rA ° -. . - pact...... , Prices . - . -. Prices o -r £1.15.O £2.15.O £l.i5.O-2.15.O

t.-

u ..o,---iji A

Motto! 46) in tranne eircuit bout,ic.Ron2e troubles. Matie In sarl. - D.. VoItrnetr I a ou rang with different - neeeeary portable testi'sg aeetiitiea. SIm'lar hatru. At Olympia this year meut for you will seethebest - - in Modern Radio WEST 'N SIANDARD ThE WORLD OVER.

- Pioneers since 1888

Ornised III,çt,irer$' y Th &idio Ma,, 4jsoja:i,.,, -: WESTON ELECTRICAL INSTRUMENT CO. LTD. - - 1. GT. SAFFRON HILL. LONDON, E.C.1. -_ r

PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor TH WIRELESS CONSTRUCTOR October,. 1928e - .. wirelessly have. been macle from This synchroniser controls the OUR NEWS BULLETIN time to time, but it is pleasing to pendulum of a standard "Pu1-Sy- learn that at Leicester, automatic Etic" Time Transmitter. - -co,thnu&1 Jrorn page 432 wireless synchronisation has been in The last dot impulse, in addition to continuous operation for the Past effecting -synchronisation, automati- eighteen months at the residerce of cally switches off the valves with the and that if, as is anticipated, the plans Mr. Alfred E. Ball, F.B.H.I. result that their period of lighting Postmaster- are quickly passed by the Mr. Ball has app'ied his invntion i less than half a minute per day, General, work will be started. on to the well-known "Pul-Syn-Efic" and the non-sulphating D.F.G. type the new station very shortly. System of Electric Clocks of Gent of accumulator employed only needs The first regional statjon is already and Co., Ltd. recharging once per annum. in course of construction at Brook- The automatic control employs the man's Park, near Potter's Bar, and well-known Daventry six-dot time will probably be operating by next signal, the last dot of which indicates - '- Buy Britain's April. Plans for the other regional Greenwich time, and the special E - Leading Radio Weekly stations have been ready for some apparatus above mentioned utilises time, but have not been put into this last dot. "POPULAR WIRELESS" E

operation because of the delay in - -. The paer that marie obtaining permission from the Post- The Lait Dot - . E master-General. A small aerial is permanently tuned- WIRELESS POPULAR in for Daventry, and a :fotirvaIve - - On Sale Everywhere. receiving set, are installed for the sole Price 3d. Every Thursday. purpose of effecting synchronisation, THE WIRELESS and this set is daily switched in SYNCHRONISER automatically by one of the impulse Au electrical switch automatically clocks some seconds befofé the 10.30 eerths the aerial at all times, except' n.m. time signal. The special appara- for the brief period the valves are lit, 1tv1a since the. advent- of wireleas tus is designed to receive the six-dot and switches off the valves automati- .iLa telegraphy we have been wireless impulses, but to utilise the cally at 10.31 if the time signal fails. hearing the question "Why last dot only for the operation of a The time control has been highly: not make use of- -wireless wivc for synchronising device khown as the successful, and the results excecdingl

- the automatic synchronisation of our See-Saw Synchroniser, which has useful, as Greenwich time has always

clocks ? " - - been designed by Gent and Co., Ltd., been given by the eight clocks '.itbi Various suggestions as to the and is in use for land-line synchronisa- one second plus or minus, without any, means of effecting the desired object tion. attentión whatever. vd&&* :!e4W for your WIRELESS SET or GRAMOPHONE LOUD SPEAKER with the . a WRITE OR CALL C4ROSTAT

- FOROVR - VARY THE VOLUME TO THE OCcASION - OUU ur so,, as your rancy a,cfazcs: A "ClarOstat" enabics you to apply Loud or Soit 1928-1929 F Pedals to your Speaker. S01t when desired just asa fuit irtslanl!y - background": volume available when a particular item becomes the centre .01 CATALOGVE r interest, or for dancing. 11 you are reproducing Gramophone records you can dictate exactly the volume that pleases you, suiting the volume to th style ot the ______record -. VOLUME CONTROL. TONE CONTROL, just - published containing I J particulars and - and 57 other uses. ,,RO - details of all the latest lines exhibited J 4 Tone Control can also be arranged, lowering and mellowing the quality of your high-pitched Spahrr at the Wireless Exhibition. 70 pages of VOLUME until it reproduces rich, deep flotes equal to the most CONTROL expensive instruments. Wireless and Gramophone accessories CLAROSTAT All "ClarOstats" are beautifully made, are mioro- are in every use- (One hole fising; metric in adjustment, and are guaranteed noiseless that day by all experi- bracket for Case- in operation. board mountLug also menters, constructors, and amateurs. Included free) Also available: Standard "ClarOstat " (20 WattS) and PO\VFR" Clarcstat" (40 Watts), for Elimini- Send 6d. to cover cost of postage for your - copy- 816 tors Send for t-page pamphlet, free, On how to FREE to callers. build the most powerful and silent AC. HT. Jtliminator yet designed. Ask for pamphlet It always "Pais to go to Day's" for all wireless - TABLE TYPE "POWER. accessories and parts. CLAROSTAT 2928 1 Place it by your tide when Price I U /6 -- dining, reading, resting in Post free. STAND 248 bed, etc.,etc.,thtls providing ree I

' Gallery, Wireless Exhibition, Sept. 22-29. distant control. Cords have e - 'Ow generous length.

At all good Dealers: ljtc,uie - WILL DAY. LTD.. FREE from (ThBestntheWe,t) t CLAUDE LYONS LIMITED I 19, Lisle Street, Leicester Sqùar.i, WI.. ' I -'Phone: Regent 0921 and 0922. 'Gearnn: Titles Westrand London." 76, Old Hall Str ee t, Liverpool

I L

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.11

If you have alternating currentSu pply in your home you can

DISPENSE WITH H.T. BATTERIES. and build an Eliminator wÏth Ferranti components.

DIAGRAM :- ..

- .,-- -

's . 's,.

L LJ

This Eliminator is suitablé for a Receiver comprising H.F. Detector and two L.F. stages, but is not suitable for a set employing a screened-grid valve.

JIRED :-- PARTS REQ . PRICE. ..

- i Double Pole Switch - - - - '- - approx." LO 5. 0

2 Fuses, i amp. - - - - - . - ,, .0 2 6 I Ferranti Mains TransÇormer, type P.1 -. - - . - - - 1 15 0 - i Wesunghouse Metal RectIfier, type 4-55-,l ------4 4 0 . - I Choke, type B.2 - . - . - - . - - -. I I O .. - I , typeB.3 - ' - . - -.. - 0 14 0 6 Anode Feed Resistances @ 5/:. -. - - . - - - i lo o 9 Condensers, 2 mfd. each, type C.l @5/6 - - -. - 2 9 6 Baseboard, terminals, wire, etc. - - - - approx. 0 6 0

8 Prices of Resistances vary between 51- and bl-. each, according to value in ohms.

An eliminator built to this specification is free from hum and motor-boating, and when used on a 230 volts AC. supply will give a maximum output of 160 volts, 60 milliamps. lt should be noted that the anode feed resistances and by-pass condensers necessary in a Receiver to overcome interaction and motor-boating form a part of this Eliminatorand need not be incorporated in the set. This in reality makes the Eliminator cheaper than it appears to be. If further information is required, such as the values of the resistances, this will be furnished on application, stating the valves used and the mains voltage. Please write to us if you have any difficulty. Descriptive List will be sent on request.

Visit our Stands Nos. 84 & 85 at the Radio Exhibition, Olympia. FERRANTI LTD.,' HOLLINWOOD, :LANCASHIRE

435 -

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-. ' Ortnd" thodel five- alvo set, ernploymg a very Another very iníerestjng peciality of this large loud speaker. Various forms of double-cone enterprising firm will be a panel wjtb dual finish, .speakers, etc., also are on view. that is to say, ahighly po!isl mahogany finish THIS YEAR AT OLYMPIA ou one side o lt. and a highly polished black finish -continsied f,oas page 309 Reeent Radio Supply Co. Stand No. 62. on the other. Can you beat it? TitIs stand svili be of interest to the man with Ltd. Stands Nos. 56, 73 and electric light in the house, various models (for R.L-Varley, 222. high- Have you sects Anti-MeSo - direct current and alternating current) of This is not a female relative who has lost herself kà than thirty stations have been logged without tension and low-tension battery eliminators being at the Exhibition, is the name of a component ariil or earth on this receiver, and a large number but of alternative programmes specially designed for the series-resistance-con- arc always available denser method -of preventing L.F. reaction. os' at loud-speaker strength. "motor-boatIng," from whence it gets its name.- both the performance and finish are extremely The JU.-Varley stands are full of good ideas of high, an&it is interesting to note that the screen- this kind, and only a few of tite ontstnnm.ting grid valve figures in both these succeful sets. components can be reviewed in the brief space at MentIon must also be made of the popular Ortho- nur dispoed. Mention must be made of the new cyclic condenser whIch is now a firm favourite aperiodic tuner covering two bands of wave-lengths 'with the public. Both the above-mentioned sets by means of a simple change-over switch. It is are extremely light in weight and are entirely fitted with a slow-motion dis! for react-ion self-contained, other valuable features being eomrol, th whole adaptable for one- the switch-over from short to long waves and the thing being control fiole-fixIng. - - - vohime that with the two dlaL makes R.C.C. enthusiasts should make sure of seeing each lnstrumen extremely sImple to control. the RL RC. couplers which are fitted willi wire- wound resistances, ansI carefully balanced, the W. G. Pye & Co., Ltd. Stands Nos. 87 and 100. Visitors are sure of condenser Incorporated being tested up to 1 500 a goodly array nf really volts. --N.P.L curves of these. -couplers show first-class components on these stands, all kinds iiniforib amplification over whole range of being exhibited. Notable amongst will be the these audible freeiuenclea, fromm 23 to 10,000 cycles, a gearcil condensers, special heavy-duty chokes for proud. ciutpnt circuits, output transformers, low-frequency fact of which R.i.-Varley aro justly-very chokes of all sises, push-pull In addition to titisee there are the new Anti-Mobo transformers, gr,I RC. Couplers which in order to obviate the leaks, valve holders, power transformers, HT. : '«H pøsibillt y of "motor-boating" incorporate the transformers and trickle-charger transformers. As to above. Another is well-known, this Is Anti-Mobo device referred firm famous for it trans- notable component is the RI. 11.1'. choke, the formera, and an exceptionally góod selection will be found on thesc stand In interesting moving-cuff lernt spealecr inductance of which is 60,000 mic-ro-Imenrics, the product (Par b-id ge et, Mee). effective choking range Claimed for this bring - frani 30 to OQO metres without a break or a Radi-Arc Electrical Co., LtiL Stand No. 0. spot. Lts of parle for supersonic sets, for 'blind suitable all on view. All titeas instriunents conform in every Tise multi-ratio transformers will wave-lengths from ten to fanions RI. three thousand metres, detail with the regulations issued by the Institute be on view, together with new models, and timore are ou view hcrc. With sets built front these parts of-Electrical Engineers. excellent loud-speaker is a complete range of Westinghouse rectifier reception from a nùmber of- eliminator units for H.T.,and L.T.and also for HT.. stations can be obtained in - daylight on a small Ripault, Ltd. Stand Ne. 24. LT. anti GB. The ncw L.F. clìok& is another frame aerial, and Bournemouth, London, Cardiff, One good exhibit here is t-lie well-known ItIpaull Nottingham. etc., can be sperlahly interesting exhibit, anti for the uranio. brought in without any lateral-action variable condenser. Tite ingenious phono limera is a new 1t.l.-Varlcy lick-imp. difficulty. In addition to the supersonic units, construction of this component gave t (estant cuan several Other Interesting lines lrnpimoved Altogether this i..-in extraordinarily interesting will be on view, popularity, but it is now available in show, should ori no account be missed. including battery eliminators, the Liberty gramo- form. which phone pick-up, and a complete Liberty gramophone Apart from the iml)rovcments in the actual A. W. Stapleton. Stami No. 211. amplifier. construation, another enormous advantage from The Loristat, Loriometer and Loriodnptor wilt the constructor's point of view is the fact that hic be on View at this stand the latter being an adaptor .'Reea-ltIaee MIg. Co., Ltd. StanI Mo, 268. price of this component lias now been cons,lerably for plugging Into the lamp-holder, which enabte. Complete receivers iii large variety are reduced, and two models of dials' are available for tIte tiser to charge his accumulator while getting displayed here, including one very interesting it, one retailing at 2e. 3d., and a slow-motion type his light. It is especially thtended for ehargin Pentodo three.valve receiver, in port4lble form, which is priced at 4e. Od. 1bonitc of all hinds- H.T. accumulators, since it can only be employed with double-cone loud speaher.' Another interest tubes, rods, sheets and panels-is also a strong on D.C. mains. Ing set is the "Baby Five," and there is also a feature of this display. (Continued on poye 430) ,C.S. 'SpIendid between Sept. / P. ..models , To EVERYONE who, ist & 22nd inclusive, buys a - n ow w i 1h i n i,a!ts SeIf-RegcnertWe - the,,reach'of all' rREE - 11.1. Dry Batte'y That fine" De Luxe" model or" Standard" model which, alter 'II (The Battery (hat gives 50%. Longer Life) bearing, you have always longed to possees, is now obtainabl. at an undreamt of price-buy now and enhance your eVenings S . we will send Free, and Post Free, a with better Slid more enjoyable reception. RIPAULTS 9-VOLT. GRID BIAS BATTERY To the sender of the first coupon opened ¡n our mail each morning 7îe ' from Sept. 3rd to 24th inclusive we will also present Free, and Post Free, a ÖQLWQ . 'Standard modal model RIPAULTS 99-VOLT. STANDARD ¡J "SELF-REGENERATIVE liT. )RY AT1ERY We know that our Batteries are the most efficient ever made and we want you also to prove to your own satisfaction that they not only give o% Longer Get one on thway home and surprise the Life but enormously inctease the quality of the reception ot your receiver. syife-tiiey all love a peu bargain. - HOW TOSECURE YOUR BATTERY Buy one of the " Ripaults" Batterica listed hIow, fill in the Coupon amad Foal it together with your Daler's receipt, to reach us not later than first 'L' post Monday, September 24th, 1928. t QrPbean STANDARD CAPACITY ...... 60 volt, lOIS 99 iolt. 16/6 ALIL (Chocolate Label) DOUBLE CAPACITY 45 voit. 11/6 60 uolt. 15/6 90 vOlt. 22/6 (Blue Label) arethe best possible value on the rnarketto.day for' their really fine artistic finish and the purity and TREBLE CAPACITY' £(5 vOlt, 15/- 60 s'oit., 19x6 90 vOlt. 29,'6

i volume of their tonal quality. All who hear them Orange Labol) are amazed at theirlow price and high performance - QUADRUPLE CAPACITY 45 voIt. 186 60 uolt. 23/6 90 colt. 36/6 i Prices: " De Luxe "model, 50/- "Standard" (Blaçk Label) 'Phone model, 40/- ; "Gem" model, 30/- '?jmbLQdon _ Your local dealer will de,nonsirafe. 4Ö58. i FlU. IN THIS COUPO f hereby certily that I purchased on the data LONDON RADIO MFG. CO., LTD. i shown the " Ripaults" Self-Regenerative HT. Dry Battery as covered i Local Dealer Head Office and lVorks by the enclosed receipt from my Station Road, Meton Abbey. London, S.W.1) NAME ......

ADDRESS ...... Come and see thee models and the i Write in BLOCI lettera anti POST to:- ORPHEAN 3-VALVE PORTABLE at RIPAULTS LTD., 1, linq's Road, London, N.W.i OLYMPIA. STANDS Nos. 209 & 210 RIPAULTS SELF-REQNERATIVE J1.T. DRY BATTERIES (Gallery) 18-17. 436

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S I

Iç 1 InFroducinef H 66K'..:., i

RANGE-. . . . ,. . . . I. .... the. Adjustable VOLUME-" . SELECTIVITY 4 oi unit

CONTROL Again and again constructors-have told us :-" That's a jolly good unit of yours-but why don't you make an adjustable one? " So we put the idea up to the works and the works goì busy-and here wearé. Ra&o Exhibition The new 66K is just the well-knosn 66A made still better. lt is designed oh the same ?inciple-a jour-pole magnet unit giving a straight-line movement to the driving spindle, over a very wide range of audio frequencies. The current preserves an evenly ba!anced ÓLYMPIA, 1928 flow that úives such exceptional quality to the 'interpretation of

- speéch and music.

The new adjustor kafure enables the butterfly longue to be kept exactly and conatantlj ositionedbetwen the poles of' the magnet. This unit, incorporated in all the latest Blue Spot models, baa VISIT. had repealed commendation under test. lt is supp!ied comp!ete to with dust-prooF cover and two padded washera receive - STAND No. .9! cone. The price is the old price - - -. - . - - The original four-polearmature unit without the adusting movement is preferred by somè constructors, and is now to examine the new Colvern obtainable at a specially redtíced price - - - Dual-Range Coil. i Complete instructtons are ppled for building cone speakers-both floating edge and free-edge type - around the four-ole unit. Provided the speaker is built to these specifications and the set is not forced or overloaded, we claim that reception will be virtually as good as il the listener were actually sitting in the COLVERN transmitting studio. ACCURATE SPACE WOUND ' 1IDEAL4PO DJU5TABLE ARMATURE UNU! coiLs A F. A. Hughes & Co., Limited, 204/6, Great Portland Street, London, W.1.

Colvern Ltd.,; Mawney's Road DISTRIBUTORS FOR NORTHERN ENGLAND. SCOTLAND AND NORTH WALES: Romford EEE ii. C. Rawson (.SIocffiehl and London), Ltd., 100. London R05d, S!icff:th!j l8, Princess Street,. Iilanchester. 437

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though one of the best-knowa suppliers of storage be on view at this stami, Besi4 the well-known batteries for the heavier branches of electrical C.A.Y. products, there will be several new additions THIS OLYMPIA eiiginecring. A very comprehensive range of amongst these being the massed pibte LT: YEAR AT high-tension batteries will he shown here, of any accumulator, type AIIM. required of -CfJfltin4Le4 paqe 43l gapacity and voltage. Special unspillable This type celi is recommended for low rates from types of low-tension cells of slow discharge will of discharge, and special plates are introduced also be on show, and an entirely new type of enabling it to be used for comparatively long low-tension battery, primarily intended for periods between recharges without injuring the Sylvex, LU. Stand No. 175. filaments of six-volt power valves, and also for plabis. In addition to the Sylverex and Reactojie types supplying current for the field excitation of coil- Titis battery is supplied in a dry-charged I of crystal and the Syiverex permanent detector driven speakers. con(iitìon, amad only requires filling with diluted and cone washers which this finn ha for a long sulptCiric acid to be ready for immediate use. I lino had on the market, a new accessory in the Although originally produced at 5s., the price blm of the Syiverex cone materiel, macic of has already been reduced to 4s. fil., and the battery I genuine pertinax and retailed at is. Od. per is not only reliable In operation, bitt will lust for envelope, will be on show. This material is far macny years. tronger and is claimed to be far better than any of the matcrials for eones now on tIte market, Watmel Wireless Co. StaatS No. 157. md is also claimed to respond to every vibration. In addItion to the various Watmel components 'L'hose readers who aro contemplating building which no doubt will be known to most. renders, their own cone loud speaker should therefore this unu is showing a complete range of radio pay a visit to this stand. receivers, incbuing a muslims receiver which is suitable for the home, dance hail club, etc. The Telegraph Condenser Co.. Ltd. Stani No. 121. This instrument costs less titan a fartiming nfl hour All kinds of fixed condensers for receiving sets to rim from time mains, and there are no batteries wilt be found at the stan1 of this welt-known firm, or other accessories. Of particular interest among which, in accordance with its practice of the last tut components Is the new double-range tuner. twenty-three years, continues to confine its I energies solely to the production of fixed con- Western Wireless Co. Stand No. 262. ' clensers. All types are available in paper and As this is not a manufacturing liria1 the Western nitra dielectric, in capacities from .flQ up to Wireless Co.'s efforts at the exhibition will be revend hundred mfd., and at vnriôds voltages. strictly retail. Leading makes of various sets An Interesting new exhibit is the flat nalca and components will be shown, either for cash type condenser with the recently introduced or for hire-purchase. - fixing arrangement which gives one the alternative of mounting time condenser either upright or The Westinghouse Brake & Saxby Signal- Co., Lb'.. fiat as rwiuired. This, by the way, is a great con- Stand No. 78. venietice 1- and 2-mfd. Ail types of battery chargers and metal rectifiers with condensers. The new vußve-hohfca- orni screen eo,n- Apart from the standard lines for the construetor for radio purposes will be shown 'on this stand, several special Unes will be shown, such as adjust- binai ion los- all t qpes of scs-eened valves. and also special rectifiers designed for the Harris able condensers as supplied to the various cable (Peto-Scott, Ltd.) "Stedipowcr" L.T. Unit. All readers of the companies, etc., and transmitting condensers as WIIIELRSs CONSTRUCTOR should make a point of supplied to the B.B.C. and the rost Office, Of Many unusual features 'are incorporated in titis seeing titis new component which has. been exceptional interest wifl be the new electrolytic battery which is sure to Create great interest. specialty brought out in answer to the response condenser as used in time recently developed Time Tudor Accmmnmmmlator Co. may be newcomers for such n unit. All sorts of voltmeters HCrris fltedibowcr LT. Unit.," samples of which to Olympia, but they ar certainly okt hands at and other instruments suitable for radio purposes will be on view. the battery game. will also be seen on time Westinghouse stand. Trelleborg Ebonite Co., Ltd. Stand No. 224. Turner & Co. Stand No. 234 Wilkins & Wright, LIII. Stand No. 152. Turned anti machined componente and necee- An interesting collection of components will be Most of the Utíllty" components will need no tories, manufactured troia Trelleborg's ebonite, found on stall 234, including a nou-dèad-end Introduction to readers a large proportion ot and including panels, formers, bobbins, switches, tuner six-pin coils, bases, etc, who,n have used the 'Utility switches or the lead-in tubes, will he Been in nsioit . logarithmic condensers, dials, etc., which are absud. . C. A. Vanitervell & Co., Ltd. StanI No. 114. amongst the popular products of this firm. Vandervell's have embarked with great enter- Several new lines aro being released et th The Tudor Accumulator Co., Ltd. Stand No. 249. prIse into the making of many radio componente exhibition, the chief of these being a new anti- This firm ¡s a comparatively newcomer to radio, and accessories, anti all their leading lines will (Continued on page 440.)

Positive Cóntrol AT - of H.F. and L.F. To secure that refinement in quality and selectivity you must have a perfect means of controlling both the High and Low Frequency sides of your receivet. The Gambrell Neutroverria and. Voluvernia will each give you positive control with a smoothness and graduation that results ici a marked increase in selectivity, quality and volume of reproduction. The GAMBRELL NEUTROVERNI.& This excellent component can be used as either a Capacity Reaction Control, Balancing Condenser, or - Neu tralising Condenser. Price 5/6.

The GAMBRELL - VOLUVERNIA ,1- This control for the L.F. side enables one to obtain the exact -- volume required and eliminates all the distortion which results 11 ! - from the common practice of detuning. It graduates volume from, maximum volume tO a mere murmur. It is also exactly suited for use with Gramophone I WHITELEY-BONEHAM Amplifiers. Resistance o-x meohm Price 6,9.

- LOUD $Pt*IE.R Obtainable Jrom all Dea!rs. -il SEE OUR FULL RANGE ON STANDS-27 & 1)18 0E Uo,aeh!z, zam!a anfie,l. ot !!! GAMBRELL RADIO LTD. - ______"Buckingham House," Buekingham Street, Strand, W C

- 438

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[WIT I THE REACH OF ALL "i'mgoiñgtomake H 'IS rnoney V more - I am tired of workirg for a smell -

V V f'.7/////Ç1J/J/1/// salary-tired of the strain of endeavour-

- ing to keep up appearances-tired of s seeing me in 't - f, lfl - /f//////fr ffJ/,/ others beat the struggle //J/]fj of of - t / / for promotion-tired the fear un- / /,4J/ employment V VI MIItI\ ,; %3 l'va been blind fe some ways, but nose \ flJJJ ' V V / I sea denny that diligence, integrity, and

i '. V long service are not enough. To succeed V V - " one muet have a special vocational train- .. IV sog. The men who are going ahead of V V j V me have oniy ene advantage-they are f V V V V V trained, while I am not. That malice

V -- ,.,.' ' ' all the difference, but I am determined

V V ,i// to raise myself to their standard with-

r , out a day's d]ay. The International V 'I tenC: ,: helped of ta V Many a min, at last realising that tremendous handicap cf being nntra'lned; P,ov. . has thought along those lines and then become an I.CVS. student, greatly to bis Pa.'. . advantage and happiness.

V V V - I - V In every line of business mea and women are holding important positions and a receiving splendid salaries-because they because I.C.S. students. You, too, by studying at house in your own time, can quality lot the position you -.... . want in the work you like best-no matter what your age, your occupation, or your means. - Thousands of wireless enthusiasts have longed for a Moving Coil The LC.S. originated spare-time technical training by post 37 years ago, and is by Speaker, but-well, there war always the question of expense. Now, lar the largest institution ol its kini in the world. lt baa teacbing centree in eleven however, GOODMANS have made sugli remarkable strides in the countries and students in fifty. design and construction of Moving Coil Speakers that it coals little, as how help if anything more, to build your own Moving Cod Speaker than to Write to-day for full information to the I.C.S. can you purchase a good ordinary Loudspeaker. in yisur chosen vocation. There are 360 Standard courses, of which That wonderful quality of reproduction, that depth of tone in the bass the following are the most important groups notes, that almost uncanny realism is now within the reach of alL Wirelers Telegraphy (Elementary and Advanced) The GOODMAN CENTREX" Stand and Frame (shown above) Accounlancy Drsughlsmasiship Salesmanship. is the last word in Moving Coil Speaker De.ign-there's nothing Adveetising Engineering (all Scientific Management else like it on thc market. Write for particulars (free) of our Architecture branches) Showoard Writing complete range for 2-, 4- or 6-volt accumulators, or for D.C. Mains. Building French and Spanish Textiles Commercial Art General Education Window Dressing Commercial Training Professional Exams. Woodworking There is a spccial booklet for each iPa which will be .;00DA4AN seni free on request.. Tall us the one you would like io see. 27 FARRINCDON S1LONDON.E.C.4! International Correspondence Schools, Ltd. Teleptone City 4472. 172, International Buildings, Kingsway, London, W.C.2

THE ONLY BRJTISHVALVE WITH A WRITTEN GUARANTEE AS TO PERFORMANCE AND LIFE. NOW ONLY A T flTL11'D Q Q' A y lavourably with many well-known makes.' WH - 1 1 1IiJ C.O.D. Pion' FIL Imp. Aj . Tpe Volts Am of LV E S Po t 4d -- P . R. VA PR 2 095 2S,000 13 Dot. -" 2 r 6!9 Unsurpassed for va.: :g PunIr , &ìd equa of any, - 3 Valves for 10/- PR 8 3.5.4 '063 23.000 15 selecttvsty-the - / HF. ,._-' Post 6d. i bC opinion expressrd in hundreds o ,.....- PR 9 3.5.4 '063 18,000 14 Der.. ,__-' 4 Valves for 131- PRIO 3.5.4 063 10,000 8'7 L.F, letters from satshed users-the orxwols ,_,. 40 RC COO se seen at our offices. .-.-_' ...... ,,_.-" ..-' -Ali orders executed return o! post. .3 PRI? 5.6 1 18,000 17 Det. Tell us your set-we will send by -. correct Valves. I - PRI8 5.6 '1 9 500 9 L.F All valves dcpatcbd - i PRI9 5.6 '1 80:000 40 p,, Matched Valves 11- extra. - GUARANTEE. under guarantee of ______-- ,, . . Moncy Bock. -it, Full ,f not entisfied. All valves PR'O 2 '15 7000 -6 P .- . ._ . are carefully pocked and brealages replacad. Each PR4O 4 15 7'OOO Post4d 17-3. Paternoster Square, 8 1 5:000 :: ' VALVES

CASON 1929 COMPONENTS.

SIX PIN BASE. J ANTI-MICROPHONIC VALVE HOLR As shown. Size: 2 by 2". I Moulded throughout including I As shown. Hiehest g?'ade legs. Makes shorting im- mouldings througlout. Patent coil spring ;n cach kg. Circular possible. Recommended for I vibration motion guarasiteeing ai! circuits perfect vulve safety, Wth Price with terminals terminals and red - anode. Prick only 1 '6 ANTI-CAPACITY VALVE HOLDER. TOGGLE-SWITCH.

- - - - . - - Price - - bd. Price 9d CASON MOULDINGS, CHISWICK ROAD, LOWER EDMONTON, lONDON N.9

439

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nil In addition there are the new wirewound fixed type, for which this-firm la very well known, these condensers which are sure to create a good deal of cells showing at a glance whether the battery is THIS YEAR AT OLYMPIA interest. fully-charged, half-charged, or completely run down. - - - -.conhiùed frompage' 438 The LR. Wireless Company. Stand No. 228. TOO LATE FOR CLASSIFICATION. Following up their sloçan of Buy the coil wills the purple winding,-.. tisIs firm showing PIPA. Wireless, Ltd. Stands Nos. 21 and 22. are capacIty. a. thumb-controlled condesser; ali sorts '0f coils from lixcd coils for any circuit, siteh, The exhibits here will include the MP.A. chokes, coils, .r two thumb-controlled dials (One l)laLn and ono Etliatrope, the all-elcetric radio gramophone, uF, plug-in coils for the Cossor "Melody Maker," etc., etc. - I veruier), aluminium shielding boxes, and a coja- which is a il ret-class four-valve radio set, requiring bin&1 drum (ontrol with verilier dial. Tisis latter no aerial or earth, and a combined valve-amplified The Igranic Electric Co., Ltd. Stands Nos. 53, 54 has a twelve-to-one rat jo. 'Tises-e is also a " Mite" electrically-driven gramophone. and 75. condenser of tite type now so popular for incor- There is such a wealth of comproents to be poration In rather crowded sets, where there is Coilinson's Precision Screw Co. Stand No. 91. seen on these stands that it is impossible to give Only room for a mite to stand. pecial attention should be paid on this stand anything like an idea of their appearance. Ail to tito Colvern dual-range coil, which eoverd wave- sorts of apparatus will be exhibited, Irons chokes, Williams & Reif at, Ltd. Stand No. 265. bands from 250 to550 metres and 951) tO 2,100 fixed coil holders, variable condensers, valve On tliia stand the makers of tise Simplicon metres, Tisis new coil is in addition to tls sitany holders, pick-ups, transformers, potential dividers, radio products will be showing a complete range types of coils for which Colvern, Ltd., have been wander plugs, resisters, output chokes, short-wave of asid a long line of new accessories. components itinsosis for some tIme. - receivers and portable seta. n with - Among the latter special condenser ball- - Truly a bewildering array of sorno of the finest should bearing spindle and extremely rigid btiild apparatus to be found anywhere I be noted tisis condenser being available in the !' suai capacitIes asid being sold at a very low price. Tho9. De La Rue & Co., Ltd. Stand No. 235. For use with tisis condenser, or to be used in Mainly tise exhibit on this stand will be a corn- conjunction with other condensers of tuo same preiteissive display of Bakeilte, fireproof and make, a new vernier dial wiii make its,appcarance, plastie naosildinge. These are produced by a nasi tisis will be available in two, different gear tsso,irss imsititi-production method at the rate of ratios, namely, 100 to 1 nnd approximately sunny hisous,-tiids Iwr week,"and assi demonstration 200 to i for speeialsliort-wave reci'Ç'trs. Finally, O oi tite vast manufacturing capacity of this firm, a compact neutralising condenser and a drum- iatosmidissgs troni in. diameter up to 3 ft. 6 in; drive ordinary variable condenser, complete with 'K turc bciisg exhibited. - a front panel cover face, must be mentioned as Special attention should be drawis to tise range among the more interesting items on this stand. of24 types of mosslded low-tension battery boxes for accumulators of from 2 to 12 volts. Wright & Weaire, Ltd. Stand Nos. 251 and 252. The " Selector " Short-Wave-3 Set. Wilkins & Wright, Ltd. Stand No. 152. Standard "P.W." and 51W." loading new show on of The Falif, Sfadelmann & Co., Ltd. Stand No. 127. The lines on tite stand this well. coils, proved so extremely - which have successful All sorts of Efeseaphonc receiving known firm include n new anti-capacity switch, in many popular sets, 'trill be on show at this sets and vernier control condensers, aiuuulsiium shielding stand, and tite Wearite Company have also a Efca components 't'iil be shown on this stand, which is weil worth an inspection by all visitors boxes a!Ìd panels and combined drum control very attractive series of email components, one at with vernier dials, which have a ratio of 12 to 1. very ingenious item being the Wearlte Flux Gun. Olympia. An ordinary tin of flux will fill titis gun twelve The Rothermel Corpöration, Ltd. Runbaken Magneto Co. Stand No. 244. times, and one gunful of flux will snake 2,500 Owing to the faetthat the goods sold by titis A stew combined HT. and LT. model for AO. joints I Every drop of flux cnn be used up by titis firm are imported, they are excluded from ex- mains, which has no valve or complications new method, instead of fifty per cent of it being hibiting at the Radio Exhibition but readers asid which will deliver 50 to 350 suilliamps, 'tvilI applied to the fingers, the bench, tite componènts 1soulti note that they have arranged a special be on show, together with an assortment of nearby, and to wastage on stray matches, bits of demonstration and. show of their pro(iuèts at charges's, ET. units, and polarity finders. solder or wire. Fitted with a long, fine nozzle, the 24, Maddox Street, during of tite time tue Olympia Rook Bros., Ltd. Stands Nos. 76 Wearite flux gun really is a most Interesting and Show, and any readers of the VIRELESS- CON- and 77. e ingenious little gadget which can be sure of a big STRUCTOR will be welcomed at these showrooms. Many new lines, including a range of com- sale. - ponents specially designed for 'tise in battery Another speciality of this firm is a very com- Peto & Radiord. Stand No. 67. eliminators and mains sots, arc, to be seen here. prehensive list of copper screens, polislìed.,aad All sorts of accumulators of LT. and H.T. types. The more impos'tant of these mains components lacquered, made up for all sorts of popular sets, Ail accumulators will be of tIte patent indicating - (Catinsied on pio 442.) -

Keep plugging away with-- The man who experiments- cannot afford to be without "ELLIOTT" interchangeable connectors. Any desired terminal, spade, pin or plug, may be instantly fixed without disturbing the leads. The terminal is screwed right down on to the wire of the fies, giving direct contact, the ends :4: and frayed of the flex covering are tucked Snugly away out of sight. i Supplied in six colours, with or without PARALLEL flexible leads. Samplo trial set 01 four connector bodies and PLUGS elI,t assorted tortoleals Cor 1/S. obtainable lrnÌ all rrti,il svirriena deputo, or Incuso of These well designed difficulty direct fruta the manufacturers. - Parallel Plugs embody the The ELLIOTT (Patent) CONNECIOR '' - " Clix" patent Tesilint principle which ensures - PRiCE 2JD. EACH - r..1- quick yet sure contact vith - (Complef e Conecfop Body sud ose i-i . ,e; all valve sockets and the 2ersni,iof} ST ND -No.236 "Clix" Parallel Sockets. E. ELLIOTT, 126-128, Brearley Street, BIRMINGHAM OLYMPIA rs Looh out foi this Showcase. PRICE 2 EACH

This ParaPet P1u is one of the eight positive contact aids in ("WIRELESS-. ÇONSTRUCTOR THE "CLIX" SHOWCASE ON YOUR DEALER'S COUNTER / Advertiáement Rates The Showcasc includes - Single Insertion - - £60 O O CLIX PARALLEL PLUGS. 2d. CLIX PARALLEL per page and pro rata SOCKETS id. & lid. CLIX COIL PINS. . . 2d. 6 CONSECUTIVE Insertions CLIX PIN TERMINALS . 2d. 55 0 0 CLIX SPIRAL WANDER per page and pro rata -. CLIX LOX WANDER PLUG 2id. I PLUGS 2d. CLIX TERMINAL 12 CONSECUTIVE Insertions 50 0 0 CLIX SPADE TERMINALS 2d. BRACKETS ld. per page and pro rata Supplies and Illustrated Catalogues obtainable from all Deler. ONE INCH single col. (2h" wjde) 2 5 0 MinimumSpace,half-an-inch 1 2 6 IMPORTANT. Copy and Blocks must be in hand by 20th o! each LECTRO LINX LTD. mouth tor issue placed on sale 15th day o! the foflowing month. ALL. communication, respecting advertising musi be made io:- 254, Vauxhall Bridge Road, London, S.W,1. JOHN H. LILE Ltd., 4, Ludgate Circus, London, E.C.4

'Phone: CITY 7261; -

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: GPEA1L0 IN

H RE. PRICES T. of) JNG;LEEH TERM NALS

Last year, when Belling-Lee . patented terminais enjoyed . a by , popularity reached n 4% -'1 ot},er terminals, we were LAID obligèdtoextendourFactory 1W L % premises in order to meet 7 th overrhelming demand. cheap, untried condensers is like The result is that we have- buying eggs. You buy on trust. You can- I now increased our output by jUY1G fifty cent. iiot tell the quality of an egg by its outward per appearance. Neither can you judge a condeti. Increased efficiency and ' ser by looking at il. output, and the sacrificing of profit to turnover have en- 'fhat is why - you should insist ou seng -abled us-to effect-the fow- on the condenser you buy. Then you ing substantial reductions jn

- know that you arc using a coutlensei that has behind it a 22year-old reputation. You knaw L that it has passed rigorous factory tests. 1( is c" Type"B". Standard large - insulated guaranteed açcurale to a minute ehegrçe; - modcl (Polished black - bakelite).

rdilalde to a, point almost of infallibility. - - - 6d. each (formerly 9d.). P,...l..L! It will pay you to buy "T.C.C."-'ihe conden- --o T."M" scrs ial the green cases. - ¡oled. : 4d.each(formerly6d.) ? Specfid for the Type "R". Cheap competi., Cossor Melody Jtfaler' - live model wit/i ratatine name. & 3d. each (formerly 3!d. each).

Send to-day for our new Seasou-a's illuctrated Catalogue. -

STANDS 220 and 221 .í

-u AT OLYMPIA -i. i. s :1 T C C rBELLITLEE11 Adv Telegtaph Coiuezuer Co Ltd Jiaie4 Farn Rd N Acton Londo, W3 E R M I N A L S ji

Be!Iin & Loe, Ltd., Quoensway Works, Pondrs End, Middlese; L

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- s - Catesby, Ltd. Stand No. 25. i the electric light and requiring no batteries or Messrs. Catesby are showing the three-valve accumulators of any description. This viII - pedeat.-il type "A " receiver, and the -Catesby i prove a most fascinating stand, and certainly

THIS YEAR AT OLYMPIA coutmi mo(lel thrse-valve sereenedid trans- I should be visited by ll our readers. portable. Thia latter makes use of the new _-coninu4 from page 440 Multard screened-grid valve and the 5-electrode Wingrove & Rogera (Polar), Ltd. Stand No. 111. valve: In effect, the set is said to be equal to most-five-valve portable receivers, and is available Slow-motion condensers, Polar drum-controlled at the price of 25 to 28 guineas. condensers, all sorts of condensers in fact, will To round off their exhibits, Messrs. Catesby lorin a formidable array upon Stami No. 111. High-frequency chokes and other components form very interesting exhibits. Besides these, are slìowipg. all the latest loud speakers made by reputable makers. of the utmost interest will rank scarcely less in avery special-feature of the stand will be t-lic new importance, and will help to make a most simpler wireless" mains receiver, of which interesting al-ray of goods. - two models for A.C. or D.C. will be available. The Eagle Engineering Co. Stand No. 139. A large series of Clïakaphone components, such as battery operated sets, mains equipment and The British Radio Corporation, Ltd. Stand No. 141. A. J. Dew & Co. Stands Nos. 181 and 182. loud speakers, will be shown on this stand. In addition to the popular B.R.C. sets, which The exhibits embrace a representative range are already well known, among the new apparatus of radio receIving sets, accessories and com- The Benjamin Electric Co. Stand No. 171. will be found a three-valve mains receiver, using ponents. All latest designs of receiving sete W'ell noted for their excellent valve holder, this AC. mains, and employing the new type AC. including the portable, self-contained ami firm is Introducing a new valve holder which is valve, with a range of wave-lengths of 200 to maintenance models, by leading manufacturers, smaller in size but embodies all tite essential 2,000 metres and single-eontroltiinlng. Also a will be shown. features of tite standard type. A special new Portable set using screen valves will thkkc earthiing devlees soil a range of interesting its first appearance. In tills latter a gramónbone corsiponents are also to be seen here. amplifier is incorporated. Walker Bros. Stand No. 154. Many of the standard produCts of tisis firm 11111111111111111111111 Metro-Vick Supplies, Ltd.. Stands Nos. 32 and 41. - including a complete wange of horn type loud Perhaps the most prominent feature of this speakers, and special portable cabinets will be Be sure to visit the exhibit will be the amount of attention givento on slsow, while snsong the new lines the well- the mains-operated sets. lis addition to timo known popular model, the Varitone, and WIRELESS CONSTRUCTOR well-known Motro-Vick five-valve set three- assd the ordinary Waibro models, with loud speakers, four-valve resistance and resistance r.snsfornser- is cabinet form, will be shown. at OLYMPIA. coupled sets are being exhibited, asid these can either be obtained completely wired-up and StandsNos'135and166. tested, or the individual cousiponent parts essa be A. W. Stapleton. Stand No. 211. purchased, with full details for rtdng and A special D.C. charging adaptor, at the price Il llllhhhhhhhllhllllllhhllltllhlllllllhllllhhl 11111 lilI llhhhhhlhhlhlhhii assembling. - of 4s. Od., is one of the sualis things to be seen here, A considerable array of Cosmps AC. rectifying and high-resistance potentiometers for anode- C. A. Vandervehl & Co., Ltd. Stand No. 114. and ordinary valves will, of coure, take part. irs On tisis stand tlsere will be a full range of the wonderful display of sipprsratsts to he seen bend reetificatiorf, and- the' famous Loriostat high and low-tension, type resistances will also be on sisow. batteries suitable for and ois the Metro-Vick stand. - suitable for many other Iturioses. Tise batteries Otlser interesting components are tise new shown on this stand are so complete in all their skeleton 11CC. .deteetor units, nioulded anode 'types, designs, and sIzes, that it is impossible for resistances f guaranteed permanency, and the Standsd Wet BatterY Coi Stand No. 7. give a in tise small space at our disposal. us to list well-knowis A.N.1'. coil, Clsoke, etc. - The exhibits on show here mainly consist of %e can but say tisat all readers should visit this A special hospital set iii oak cabinet will be Standard Wet Batteries, fitted with tlic new stand, and they will find here items of the exhibited aisd tisis is siauilai' to the recent very wooden irnlbloek containers. Each container supremest interest., whether they use a one-valve suecessfuf installation made by lisis company for holds 3? colIs, giving a niaxinsum of 48 volts. set or go in for multi-valve receivers with moving- tIsé Lodge Moor Hospital at Sheffield. incidentally, Separate cell assembly can be supplied, the coil loud 8peakers. e%an)ples of Metro-Vick's new short-wave three- ii'ices being of a very popular order. valve receiver, with resistance-coupled L.F. \nother exhibit is a new instrument called the Ganibrell Radio, Ltd. Stands Nos. 27 and 108. stages, specially designed foi- the Dominions for the \Vatea Volt-Amp. Teat Meter." This bistro- Famous for their coils and tow loss components, reception of short-wave programmes, will be usent is worked ori an entirely new principle, this firm is branching still further intothe complete slsosr'n. -, gis-liig three readings on ono dial.-. Tise readings set world, and Is exhibiting a largo number of (Continued on page 444). rire Volts f) to Volts O to 6, Mull-amp. O to 30. mains receivers, suitable for working direct oft

"PAREX"1, PRODUCTS EXCELLENCE e4%frJ4si4 Valve Holders PAR :; fofl.SlesI "PAREX" SCREENS - 1jJ5CEÑBOx- FOR ALL CIRCUITS ( 'j -- WITH LID FOR THE - '' RADIANO' 4 as specified 12/6 »(NATIONAL RADIO EXHIBITION) -L All screens are made o! highly - - .CyJdon Condense'rs set the I I polIshed and mottled copper, and highe'»st standard of dísign and are UNTARNISHABLE. manufacture. Specified in leadiñg L » receivers, standardksed by leading. E. PAROIJSSI manufacturers. Ask to see our - 10, Fetherstone Building., - » -,», NEW MODELS. » LONDON, W.C.I. - BEBE CONDENSER' At OLYMPIA vhit Stand 272. 'Phone- Chancery 7O1O - . Cyldon "Bebe" Condensers were prinriTy designed (or use as reaction High-grade condensers-but the larger capacities - aie i.deal as tuning condensers where. QUEEN ANNE STYLE space is limited. FIGURED OAK CABINET Specified (or the "Radiano Four" and l'f Height 3 It. 3 ins. Depth I ft. 3 nv. - other leading circuits. For Panels up to,21 in,.X 7 ins. ' - Made iv 1ive capacities 0001 - 7/6 '00015 - 8j '0002- 8/6 00025 - 9,'6 '0003 - 11!- . - Packin Free. - Ccmpkte with 2-in, knob and dial. Carnage Paid. Prices of other sizes in prnportkn. Manufacturer of 0lt types at wireless cabivets and furniture of every de- ___ scription. GILBERT, SYDNEY S. BIRD & SONS, LTD. CABINET MAKER, Cyldon Worka, Enfield T,'wr., Middleax -. SWINDON. - Telephone : Enlield 2071-2. Telegram,: ' Capacity, Enfietmi." Estimates Free. E5td. 1866.

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Note these Special Features

I Easy two hole fixing \ \ 2 No friction joints \hatever 3 Improed bakehsed former Vibro1der is a better i - - nameforabettervalve- I rjI - _' 4 Re ersible diii to allow of holder The new Ben- I - upright or horizontal jamin Vibrolder will cJ! - mounting fit every type of British 5. Knobs fixed by means of four-pin vatve. It - ensures P.erfect. results i - - grub screw spindle. - j - on as the point of contact j between valve leg and valve socket is self- aligning. lt is truly anti-mscrophonic in JB GEÑERALI character, protecting the delicate filament from every trace of TUNING UNlT shock and vibration. - From all wireless dealers of repute, or dirent from BRITISE GENERAla MANUYP"TUBING C, LTD., ' Brockley Works, London, S.E.4. 1'6-. STAND 10 AT ThE RADIO ee the Vibrolder, the EXHIBITIONI improved Benjamin battery switch and the whole range of Benjamin corn-. -'--STAND. i 72- - ponents on OLYMPIA-SEPTEMBER 22-29. STAND.. 17 aÍ OLYMPIA

ii: Due to its great popular- I BAKER'S - ity the òriginal Benjamin anti-microphonic va1ve. LJ SELHURST. I. holder is retained. RADIO Price 2/- Moving Coil Loud Speakers - give the best possible results. Write for Illustrated Booklet :- BAKER'S SELHURST RADIO 42, Cherry Orchard Road, East Croydon. (Tclephone: Croydon 1618) .STAND i 72 CABINETS IFREJE PORTABLE CASES MOVING-cOIL AND \\;- CONE SPEAKER CABINETS VAVEENRS . A twenty-page catalogue showing our \\::; Send \\ BNJN - \\t: latest range of CABINETS. ,'1\ for a FREE copy. ELECTRIC -: ',Ulh" \\ OLYMPIA: Stand No. 107. t: \'\ \\\ Carrington Manufacturing Co., Ltd., LIMITED - \\ Cameo Works, Sanderstead Rd., South Croydon. Tel.: Cro5don 0623 (2 lines'. Brantwood Works - . rir - TOTrENHAM N 17 ìnnan ¶lllIll.CPSB$E:csI ASFIO

ti -

I - 443

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' THE WIRELESS CONSTRUCTOR - October, 1 928

THIS YEAR ATOLYMPIA kt' -.--continacd frmi paffe 442

. - .: ' EXTRA The Bowyer-Low Co., LW; Stani No. 51. Although at the tune of going to press no details of the Bosvyer-Lore exhibit had been received troia this well-known firm, there Is no doubt POWER' bitt that there will be lilenty of Interest (lispIaye(I in the goods shown at this stand. Bowyer-Lowc. :' - have the Iiapp knack of knowing what the radio ,' 'ALLUTHETIME iablic wants and consequently a gret many e satisfIed purchasers of tÌe past rill be interested PATENT STEEL In seeing the latest products of this famous Letch- . worth firm. Anyone in search of a good valve holder will he WIRÈLESSMAST; well advised to pay a visit to Stand ¿1, as it is all O!)Cft secret that the new Whiteline valve A High Aerial ¿s as good as another Valve, holder marketed b Boayer-Lowo Co,, Ltd., has already iiiade quite a big lilt. - -., DAMP PROOF! - HOT PROOF!! . Baird Television Development Co., Ltd. Stands . , NOs. 11.13 and 14. CALE PROOF!!! One of the big sensations of the Exhibition is (_e.__ Feet high. In sure to ientre round these stands, where the long- _uQ' 3 . sections of Ihn. looked-for Baird Combined Wireless Receivers Steel tube tapering will - and Televisor Mets be on view. 'The Coippaisy 'to s in, Carriage, hits announced that lt proposes as soon as liossible l.ondori 1/6; Mid- 15'- to commence broadcasting its own programmes ______Is ida, 26 ; else- for those of tise, publie who own tise new Baud where 3/6. Weight 24 lbs. Two dual sets, for wluiehs orders willhJertakeo at the masts for 28/6. Exhibition. Full particulars can be obtaiued at Stande 13 and 14. 34Feethigh.ectionsof shin.')Ifl41f ' Steel tube tapering I 6 British Thomson-Houston Co., Ltd. Stan.s NO3. to s In. Carriage London al-; 88 and 101. a_ of MIdlands 3f-; elsewhere 4/-. Although the many-sided radio uistcrests Weight 34 lbs. Two masts this world-fanions concerts 'trill be well represented for 40/-. at Olympia, in all probabitity the chief attraction ./) ! of tIse display will be tisé extraordinarily com- The "Super" Mast. prehensive array of valves. All kinds are available. Feet high. In In attiser the two-, fossi'-, or six-volt range you can 40 5 sections of 'IU have a B.T.H. vals-e specially designed for re- heavy Steel 6 - sistance-capacity coupling, for amplification, shin. HF. tube tapering to s in. A ,eab for "general-purpose" and detector, for low'- I , taegain. Carriage London frequency ami,litleation, or for power and loud- 216; Midlands 3/6' else- speaker operation. I where4?6. Weight'46 ba. In addition there are special valves, such as Two masts for 55/. the type RH. I, which is a half-wave rectifier, f - for supplying D.C. power from an AC. Buitree. are mado of - by step the world-famous (This valve was specially produced for use with >_ / British Steel in the RK. loud speaker.) o I P.R 9 ft. lengths, group of Ccicstion Loud- Another particularly interesting BTU. valve MASTS from s} in., - STEpspeakers has advanced through iii the special class is tise P.X.8.O. a s'ery efficient : I tapering to z I ' iM. and are supplied ivithi scientific development to a position of eoper-power valve, designed for the operation of s. No snoving'coil loud speakers. / cast - iron bed plate, unquestioned supremacy. greater At these staII(ls, also, still be shown the new . sIech ground pegs, stay human effort could have been made Mazda Steep Slope Iickel Fihainetit. Valves. This " rings, galvauiscd steel t perfect every detail of" Celestion slew series was Invented at Rugby, and com- ftexible svirg slays cut to - lengths, pulleys, construction than has been made. - prises a complete range of sixteen valves, covering every rcciulrement of the 2-, 4-. and 6-volt user. s i bolts and fullest erect- The lamous Cele.stion group consists The full details of the electrical characterIstics /// f f !.W \\l ing instructions. No of these 'valves are now available, and are cer' I 'i (Mi I 't-i further outlay acces- of four models, in oak or mahogany. thinly interesting. as shown above, with prices varyfng Some idea of tise wide variations covered by from the C. io in oak at £5- IO - O the different types can be gaitied from the fact Minimum Rad1u GUARANTEE. to the Ca4 in mahogany at that in thê 6-voltera the impedance of tiie power - 3 ft.'6 ns. Mònry refa,iefed £25. valve is only' 1,750 ohms, whilst that of tite RC. The easiest Mast to without questIon Why not hear a demo,,'sfraton with- valve Is 00,0110 ohms the respective amplification erect, if not satisfied, obli the new factors being S'S and 40. So be altre to askthe Anyone can put it up. Pay COD., out galion at Celestion BTU. people for the free booklet describing Waterproof Log Line, double length, aú' Mast Showrooms, one minute from Victoria these new nickel-filament -valves. 1/6; Mast 2f-; 42' Mast 2/6. - Station? Or ask your dealer to P.R. ColloidCoatin'g for protecting the Masts against.weather-seta in one hour. 2/6. Sollt- demonstrate. Celestion illustTated S. G. Brown. Stands Nos. 155 and 156. dent for one Mast. - literature giving Full particulars of The 1928-9 season sees several notable additions to tite list of productions çf Messrs. S. G. Brown, P.' 1. W1ATS all models - and of the Celestion- Ltd. of Aeton. Tite most interesting newcomer (Opposite Post Office Tube) Woodroffe Gramophone Pickup, is die "Cubist" moving-coil lodd speaker, a 17-3, PATERNOSTER SQ.. NE WOATE ST., LONDON,E.C4- price £4-4-O, sert free on request. magnificent example of its type. - -i - -_' ,..,, - Messrs. Browns also introduce a moving-coil Made icad, lice ace. unit which merits and will receive a great deal of miniature edition of tise attention. A popular . Make VISIT US AT STANDS Mascot" loud speaker is another interesting Innovation, to which the noose of" Duckling" has The DAILY SKETCH i Nos.19& 20 been given. Tisis model is beitg marketed at an extremely attractive price. - YOUR Picture Paper NATIONAL RADIO EXHIBITION The Brown L.F. transformer completes tlic - OLYMPIA ï new season's Introductions, and since it is tise outcome of many months of painstaking research it will doubtless prove s thoroughly eflicient instrument, fully living up to the great reputation 11th YEAR- 12,000 SUCCESSES .:. it will have to uphold in this new field for the activities of Messss. S. G. Browis. ENGINEERS! Tise way to rapid advancement to a well-paid Burudept Wireless, Ltd. Stands Noo. 112 and executive post in any branch of engineering is through 113. the wonderful home-study courses of The 'Tech. Up to the time of going to press no information - Write TO-NIGHT to find out Cr as to the special display arranged for at Olympia low The 'Tech can help YOU: has been forwarded to us, but we know that at Ltsci state your age and experience Tue Very Soul of rfJC tise Burndept stands there is a special attraction and mark your letter Confiden. in tise form of a new pick-up. As every owner of - tial Advice. (Moderate Fees- n gramophone ssow knows, the electrical pick-up - Easy InxlnlmeflIx). Write to Dept. L, is a device for plugging into the detector or first FREE BOOK. L.F. ampliller of a multi-valve set, enabling Erérylhiug about lO,oineerin THE CELESTION RADIO CO., gramophone music, speech, etc., to be reproduced how t,, become A.Ot.1.MechI'L. LONDON RD, KINGSTON-ON-THAMES. the loud peakcr (witls sin eno! nsous gain in AMi.EE,. etc.''-tItS greats. 'ía book ever publl,t,ed on Opportuai. Tel.: Kingston 5656 (4 lines). clarity, and, If required, in volume). There are ties for the practical engineer. several noteworthy features in tise Burndcpt Showrooms: pick-tsp, so a visit to these stands should not be The Technological Institute ol Great Britain, io, VICTORIA STREET, S.W.z omitteI, on tIns account alone. 200, TempIe Bar flouse, London, E.O.4.

- - - -. -. (Continued on = page 445.) _s__. 444

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THIS-YEAR AT OLYMPIA ._eoedinuedfrcrni page 444 - I4'V'J:. Liasen, Ltd. Stands Nos. 11, 72. 57 and 58. - Visitors to lost year's Exhibition will remember that the Liasen display was one of the most In- teresting and Informative staged in Olympia, and this year there is every prospect ota repetition of the success scOred twelve months ago, Many new lines will tempt the eye at once, but before attention is paid to these it l worth while pausing tu marvel at the success of the already establishe Liasen - lines-the LF. transformer, the new-process batteries, etc. Not only is there no sign of saturatioa being reached in the market.

foi the particular Liasen lines which lieve scored (1;;;;=':;2 such spectacular triumphs in the past, but as tI'be goes on there seems to be a still keener apprecia- tion of their merits. - ,

Amongst tite new tines sure to create a sensation u r,

are the new Liasen super-transfonner and the I L\ Lissenota graniophone. I J) i.. The new super-transformer rehtils at lOs., and I ri - t SI I representa value in high-priced transformers to a I

remarkable degree. The ratio is 3 to i, and the I . - . -. results are really "super"; In fact, the instomment I - should be heard to be believed. Country. and I - provincial listeners who are not able to get Umis I new transformer front their dealers wilt be inter- I estedlu the order-by-postcard scheute which I ensotes the instrument being sentC.O.fl. byretuni I a fl)! 4#1 s1rÉ' . .. - Othr Liasen innovations includé th gramo- pitone pick-up (by means of which the set can reproduce gramophone music upon the loud I

speaker), the new vernier dial, ami the already I popular Limean variable condenser which was I recently reviewed In the "What's New" columns I uf this journal. t'lnally, there is the Lissenola I gramophone, which, n view of the increasing liaison between radio aisel gramophone, will be of interest te practically every listener and con. etructor, lt's up to you to see that you get full value

fron the money you spend on valves. - Mollard Wireless Service Co., Ltd. Standa Nos. 88, 89, 90, 97, 98, 99, 133 and 267. - A few days ago a Cleartron user 'wróte to The fact that the Mollard products now requiie no less than ciaht stands in order to be adequately us to say that he had had three of these represented to the public at Olympia Is in itself a noteworthy tribute to the progressive policy of valves in regular use for over four years; ibis famous firm. But however wide the lncnrsions They had outlasted. three accumulators and into wireless by Mullards may become, and whatever product they turn their attention to in the -giveñ excellent reception all the time. future, there Is no doubt that they will always know leap to the listener's mind in connection fut and We're not surprised. We that Cleartrone are foremost with rahe.c. madé with skill and care on the finest machinery money Nullard P.M. valves, the Nullard P.M. fila. - The - can buy. Thousands of letters testify to their worth. meats, the Nullard system of msstcjmed electrodes -'-who has not heard of and experienced them! They are inexpensive because nowadays there ja no Not content with renewals or with repeating tise - good reason for valves to be dear. . - successes already scored, the Nullard organisation is continually on the look-out for sonietlslng new - - Have you discovered that yet? 1f not, buy your first and better in the valve line. This year there Is set of Two, and six types sure to he euomthouß interest In the screened-grin Cleartrons. four volt are valve, but In addition to this recent revolutionary mnde for every p*rpose n radio. Power types 6e., product there is now another claimant to public General-purpose types 4f.. interest In- the form of time "l'entoime." Full details of this, and of the wide range of valves for 1f your deáler cannot supply, order direct, or send the all ordinary purposes of reception, can be obtained coupon for illustrated brochure, and' give u your -s upon application at the stands. dealer's name. .The many other Mollard components repre- . . sent.ed at Olympia must flot be missed, and amongst these the" Permaeorc" LT. transformer is of especial Ijiterest.. This transformar has a silver winding, and combines big ainpifficat ion with small bulk In au extraordinary deee. The 9 ratio is3to i, and the price 25s. Oldhnm & Son. Ltd. Stands Nos 125 and 128. All kinds ot batteries for low-tenlon and high- tension isupply wili be founil st flic stands of this old-established and p)pular finn whose prouc- tions have long been firmly esisbllshed in the public favour. Those listeners who are thinking of "adding a valve' or of getting a bigger set should not fall to remember that extra valves mean incrc.ised consumption; and that they will not be running the filament and anode supplies economically unless the batteries chosen are able to stand up to the demands made upon them. The Oldliam range of bathries lias been de- - - signed to cover every requirement, and particulars R PO$TTHI$COUPO4- of the various lines will gladly be fun,ished upon application. CLEARTRON (1927), LTD., Sales -- Dept. 6, 21, Cumberland Street, Engineering Co., Ltd. Stands Nos. 138, Ormond - 162, 163. Birmingham. . Variable condenseN of every type, slow-motion / Please send me your new hrochure describing the characteristics direction of tnnln3 improvements and condenser of all types of Cleariron Valves. construction, will be found embodied in the coin- ponents displayed at these standi. Name ...... -

reto-Scott, Ltd. Stands Nos. 142 and 143 . / jÇ ...... Address j here will be found the Keystone components in great variety, including many new lines sure to be of interest to set-builders and listeners. Whilst J - (Conluwed o, page dt6.) .

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-. V THIS YEAR AT OLYMPIA'. EVERY: -continued from.page 445. \ THING FROM lt. would be difficult to y what is moSt likely to prove of special interest titis yeal, there is ito doubt that tite Keystone Midget condenser and tite THE Keystone tlrum diive will be amongst the favourite features of the display. The drum-drive fits all standard condensers, which can be mounted right ;' MAINS ot left of tite drive. A delightfully smooth slow- motion drive gives a reduction of P to 1.

Siemens Bros. & Co., Ltd. Stand Nos. 164 and 165 HT. UNIT TRANSFORMERS. Siemens Brothers k Co., Ltd., Wooiwlch, have Centre tapped. quite exceptional experience extending over a volts ma, volti amps. perlai of fiity years in the manufacture of bat- 200 20 4 0.8 12/6 teiles of nil kinds, and titere Is no doubt that 400 20 4 1.6 17/6 as ist knowlecite and experience count just much 440 -30 3.5 I 20f- battery manufacttuc as they do in every other 500 50 S 2 28/- walk of life. 750 60 5 2. 40/.. Inspite of ail that has been said and written, lt 800 120 8.. 3 55/- would seem that the dry battery continues to be 1000 120 8 - 3 60/- the nìost nonular anti convenient form of HT. supply. particuIarI', perhaps, in the hands of L.TTRANSFORMERS for Power Valves,. those who are not technical enthusiasts. The Metal Rectifiers. A.C. etc. WRITE FOR Siemens display inCludes Valves,

HT. btterie: Small capacity5 standard volta amps. - volts ampa' -tpc small capacity popular type : large 6 3 1216 8.5 0.8 10f. TH!S 5 3 12/6 83 1.6 1216 capncity,-power type : extra-large capacity, super-radio battery hIgh-capacity batteries 7.5 - 3 ' 12/6 - 30 2 17/6 - for portable sets. - - 4 5 12/6 50 2 22/6 FREE BOOKLET Grid- bias batteries. 4 3 8/4 250 160 ms. 17/6 Special batteries for overseas. and learn all about the rystaee accumulators. H.T. and L.T. FILTER CHOKES. J.T. dry cells and batteries. 50 henrys 25 ma. 12/6 25 henrys I amp. 12/6 Radio testing instruments. 30 ,, 50 mn. 1216 50 , 100 ma. 20f- EELEX gnomes of eflici- In conclusion, the fact that Siemens Brothers' batteries are of British manufacture throughout Largest and most varied stacks In I.ondon of Elirnin ency and how by using is perhaps worth emphasising. olor and Clsacger corn ponenla and Meters. EELEX TREBLE- Delivery cx stock. Liais free. Above components suitable for Harris JhIhlliiiiiiiiilliiiiiiiiiiiiiiiitilhhIlIlIillIhhIhihliilIIllIlilhiilIIl,' DUTY TERMiNALS "Stedipower" Unit, -. you can make these 'YOU WANT. F. 'C. HEAYBERD & CO., accessories the centre of THE 8/9, Talbot Court, Eastcbeap, industry in your set. London, E.C.3. This interesting little BEST and BRIGHTEST! (One rni,sulejrorn Monssrnen! Underground Siaiion.) booklet also gives you full Radio Weekly. In other words, The Picture Paper with the MOSTNews particulars of other Eelex ITIS accessories that will save SUNDAY GRAPHIC:: you pounds. Every con- POPULAR WIRELESS I THAT WET HT. BATTERIES structor should write for e Sols-eallfl.'r.troable,. SELP-CHARGINO, SILENT,ECONOMICAL a copy-a postcard will YOU WANT JARS (waxed) 2)' 1) ii., 1)3 doz. Zinc, Now type, lid doe. SACS 1/2 doz. Hlllllllhllllllt!lUIIllIIllIll lllllllIlllIllllllll 111111 IllIllIllIll iii bring it to-morrow. Sample doz. (18 volts), complote with Ii bands sod electrolyte, 4/3, poet Od. Bad Terminal Connections r Sample Unit. 6d. ¡hue. bookli free, Gooilinans,, Stand No. 269A. Bargain list ires. are often the Cause of losses Goodnians are one of the firms that have - AMPLIFIERs. ¡II-. 2-VALVE SET. £4- and reception. come bd into the limelight vitls the advent of tise inbring- C. TAYLOR, 57. Studley Rd.. Saféguard yourself by using Coil loue! speaker, and niready this firm lias Stockwell. Lossdou. ncliicvecl remarkable popularity with its products. Fi-orn n standard set of Goodmnn parts it is quite a simple irnntter for tuo ordinary constructor RPAIS to make tip a moving-coil 10(1(1 speaker for himself, Any make of LP. Transformer, Loudspealiem which may give him the stil-prise of Isis life in the or Headphones repaired and despatched within matter of reproduction quality, il he lias hitherto 48 HOURS-TWELVE MONTHS'GUARANTEE TREBLE-DUTY been content with an oki-faslilonect typo of loud- with each repair. 4/- Post treo. speaker. Ternis lo Trade. A vec noteworthy feature Of the Goodman TER.M INAL.S display is tue self-centring device, which enables TRANSFORMER REPAIR CO., that exactitude of adjustment to be Obtained that Dept. 5f," the terminal with indicating gets the very best Out of this type Of loud speaker. 214. High Street, Colliers Wood, LOtiilon.S.W.19. top you can plug into. Graham Amplion, Ltd. Stands Nos. 30 and 31. The choice Of a loud speak-er is always n dIfficult matter. But if figures are any guide to the per- plexed purchaser lie will find a great attraction in .CW1RLeSS S eT the Graham Amplion boast that well over half-a. ,iiillion Ainplion loud speakers have been sold! OUR STANDARD On these two ptands there are types for every CABINETS purpose and es-cry pocket. The variety of hiapcs are DUSTPEOOF and house and styles alone Is simply astounding to the the whole apparatus. loue. . - Z uninitiated, ant! the success Of this firm In catering log no parte to be Inter. fered wIth, All you do i, for all styles of appearance is no doubt one of the - factors that moved their sales over the liait. AND TUNE- 'IN. the. g,nber22_29 UNLOCK million neark. Tite Junior Cone (A.C.2) which is Made on mass production -- t, i ...... priced at 37s. Od.. the handsome "Chippendale" line, hence the losv price, -. Pres4nlon le made to take - . Mahogany Cabinet (A.C.9) (retailing at £7 Os. Od.) 30e or any one of the extensive range of modela in panel from 16 to wIde, - ..-:- . between give you tIse reproduction iJarriage paid and packed <: will faithful Ires England and Wales ...... of Amplion loue! speakers. expected the Thouland, supplied with From £4 15 0. J. J. EASTICK & SONS lull satislaction. Wrutefo-day for deacrlp. Hart Accumulator Co., Ltd. Stand No. 95. - MAKERIMPORT Co. yi EELEX HOUSE, The Hart Accumulator Co. is no newcomer to Dept. ut receiver or psnel in our radio, ncl this year, as in the past, its stand will York Street, bristle willi battery bargains. As the firm special- 9, LIVERPOOL. 118. BUNHILL ROW. LONDON, E.C.1 iseo in this particular branch of radio its whole

(Co,tinued on poc 447.) I WHEN REPL1NO TO ADVERTISEMENTS. 446

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-' A enwne THIS YEÀRAT OLYMPIA -

-conf iuued front page 44l - Spare-time_Business energies are concentrated upon the solution of i'_ those problems and difficulties that beset the ttcedia: PATENT-PROTECTED ARTICLES battery-user, and the various types of wireless accumulator evolved have all had their origin In CAN MAKE AT HOME. some real radio need. No matter what class of YOU amperage s required, the liart accumulators are ready to supply It, so those intent upon the choice of a battery should not fail to visit Stand No. 95. Good Profits Jackson Bros. Stand No. 105. The "J.B." policy is to provide dIscriminating Guaranteed! members 01 the radio public with precision condensers of unsurpassed quality and efficiency. IF you are interested in any way in Wireless, During the summer tuuis firm's experts have here is a wonderfully interesting way of devoted the whole of their time to the design of 7..FROM. money in your new instruments for use with really modern and making spare time. Sun- up-to-date receivers. Consequently, there are ply write for particulars, and by return you several new J.B. lines of really outstanding will be given full details how to make at interest, including a rernier drum drive and an I -. TO -DAY home a most marvellously improved article attractive panel plate for use with this. Another very interesting line is the new J.B. which reduces the upkeep costs of all valve Midget condenser, which is supplied complete with sets, gives splendidly neat pointer knob sat the following prices : Ç- This is news indeed! The - efficient service, con- nsfd., 5e. Od.; 0002 mId., 5. Od .; 00015 infd., tains no harmful in- 4s. tIti; 0001 mfd., 4e. Od. (Larger capacities arc world-famous W.B. available if required.) - gredients whatever, In addition there are the new J.B. slow-motion Anti-phonic valve is S.L.F. anti log models, attractively priced ami as andwhich in en- holder, specified by - thusiastic giving every evidence of the excellent design and \ demand scrupulous workmanship for wl)iclt this firm is \ ali the leading designers all over the country. justly framed. - of the day, is reduced in NO" PLANT " NEEDED Junit Mf g. Co., LIII. Stand No. 93. price to Kitchen Table or Tolling, rejoicing, soldering-onward through -The 1,6 life goes the home constructor. And the fact that Complete with - &ny Small Out-building many of his soldering troubles have been reduced in the past will always of terminals Can Be Your " Factory." redound to the credit the Junit Ml_g. Co., who are again showing a very VS without terminais. attractive range of gadgets for set-builders. - ______Thu The work is fascinat- Junit wire and soldering-iron will not need intro- Why ing. You can put in duction to many of our readers, but the newcomer are W.B. valve just as many or just as to radio who is not yet ises1iiaiist.ed with their holders chosen time after la your npare time w&nted few hours' work per advantages will certainly be well advised to give time Why not turn it tO time for good account ond change week as you desire. this stand special attention. the premier the whole of your future The children can help. circuits? Because they life for nometbhig better There is no mess, no S; A. Lamplugh, Ltd. - Stands No. 81 and 106. and bigger? smell, nothing disagree- do definitely exclude able whatever, nor is Although we have not received (sill dotails of. there any inconvenient on the display to be given at Olympia by tuis well- microphonic noises. demand space. A sparc known firm of wireless manufacturers, we under- room, an outhouse, or even your kitchen table, Can again be used as your " factory "-a factory without stand that they will be featuring the many Sprung on specially machinery or plant or electric current. The few popular Lamplugh peoduets which In tuo peat have shaped W.B. - tools needed proved so acceptable to the radio public. Ita springs, simple you are shown how to make will be yourself, or buy for addition there several improvements to hoI- a accorsi with tise latest advances lu radio technique, Anti-phonic valve shilling or two. - such as the ,opicyclic visor variable condenser, ders ensure really pure which is Illustrated upon another page In tisis Easily Sold. Output section of the VIIRELESS Coysmtic'rost. reception. -

Each articic you Carrington Min. Co., Ltd. Stand No. 107. make is protected by Cabinets, more cabinets, and stili more cabinets, Royal Letters Patent, form the order of tIse day here. All the popular COME AND SEE US AT so that your rights / designs are on show, as weil as a number of new cannot be infringed. / designs, worked out in a delightful variety of OLYMPIA - STAND 120. The market is im- styles ansi prices. Tise Cameo cabinets arc too mense, and only a :?/ weil known to need much recommendation, but strictly limited number it may fairly he said that tIsis year tille popular 1- are allowed to manu- __ finn have fairly surpassed themselves In antici' facture, thus giving Why not snake money this pating and fulfilling the needs of the wireless con- you a huge field for eoy. fa.orinating way? a,. structor, wlieher iii the direction of small and sales at a very big us,mber that proOto are guoranteed. and that the coinpssct receivers or in the onoro ambitio,ss Il eid w.--. .8 profit. The articles you coupon below bring, you of insulti-valve sets which nusaquierade sss handsome can produce without FULL partioulare PRIE.I pieces of modern furniture. any mechanical skill or talent are manifestly superior in quality and value Chloride Electrical Storage Co., Ltd. Stands Nos. if for money to anything on the market, and you 83, 40 and 241. have the least ctifticulty in disposing of your output to friends, private owners of wireless sets, wireless If you lusse beesa under tise ImpressIon that Ilse or electrical dealers in your district, arrangements will polusolarity of nualuis units lias knocked tise bsuttrry be made to take it off your hands, thus guaranteeIng makers out, you shouid take a look at tise Chiloritic Co.'s stands, where there is ample evidence to Ito your profits - - what you could do with pounds extra còntrary. Batteries of -ail kinds, Irons suent-y Think of would any grid, to huge per week i Think of the delightful hobby you little fellows that bias can pursue instead of flndiisg time hang heavily on great batteries that appear to be of unlimited your hands! Think of the nest and most interesting capacity-all are here. - rango will Include the new series of Exide field opened to you as responsible " master man" I The do not delay i single moment in sending the patent unspillabie cells of spècial design with s -and new form of nnsplilable device. These cells have below I - - - coupon been designed to give maximum capacity in the Send this form now for full particulars. small space available in inodora portable sets, and at the sanie time ensure that the plates aro coin- pletely immersed in electrolyte in two positions viz., the carrying and operating positions. ANTI PHONIC "MAKEIMÓNEY-AT-HOMF»' Iii aAlditiofl to the above-mentioned batteries a T I complete new range of Exide trickle chargers ior AC. mains will be on exhibition for the first ÇOUPON time. VALVE HOLDER - A selection of loose plates, separators and othx To THE ENGLAND.RICHARDS CO., Ltd., I component parts will also be exhibited. I 97, King's Lynn, Nortolk WHITELEY, BONEHAM & CO., J - fiuti A. C. Cossor, Ltd. Stands Nos. 116, 117. 231 and I Sirs.-Piease send me at once, and FREIl, LIMiTED, an to how j can Make Money at llame in 280. I 2d. stampa for postage. no' aparo time. I enclose Cosser valves, of course; but if you think that Nottingham Road, Mansfield, Notts. is you already' know what that means It will pay you -I Priai your same asad address boliliq capiSci ¿lila J I lettera on a_plain sheet of paper ans! pis to have a good look at the tossor stands, lust I COtspOfltO it. tirs» huas penetrated f-f J to sec how lar this into the 5- Wlreleon Oonstructor.'' October. 1528. 5.--5.-.--- , - (CoatI inued ois page 448.) 447

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K. RAYMOND 27 & 28a LISLE ST., LONDON, W.C.2 to I PEERLESS I Come Leiceeter Square Tube. This address is at the back ot Dal V's Theatre. 'Phones: 4637 2821. Gerrard and science of val%e product/on. All tite oh! frieude are here, of course, but in addition there have been Master Switch .WEAREOPENI xr_ several interesting events in the Cosoor valve Valves, all 'atest stocked. I. ALL DAY SATURDAY I family. Tu-o newcomers are especially noteworthy DAY THURSDAY D. LP.. HF., P., 1018. screened grid and Pontode valves. ALL 1216 each; DUb. 15!-: -the.. the DAY EVERY DAY I Muilard P.M4.D.. 12e.. Melody Makers " will be sure to cluster round HoursALL : 9 the Cossor staisde like flies round a honey-pot, bitt a.m. to 8p.m. I EdsWafl. Csssor, MuIlard. - Sat. : 9 a.m, to O p.m. Marconi. Osrm. Si.sixtY. whet-her or no you have built this famous set yost : Screened Grid. 22)6. ought to try foi a copy of the booklet, ' How to Sunday morning 11-1. ¡ - get tite best from your Cossor Melody Maker" lt .'1 SEND CARD FOR PRICE LISTS. is fully illustrated, anti tells you how to bring in those distiint stations, how to get greater volume / . . - Orders despatched same day how to look after your batteries-in fact, it is foil 08 where possible. of Iduts and t/ps about that es-cr-engrossing pro- received t \. -ç- blemn of the improvement of radio reception. t t,-- -..- Send ORDER with .r_ i C. 0:0. \ j (U.K. ONLY.) tions añd pay Postman. Ever-Ready Co. (G.B.), Ltd. Stand No. 44A. e .e ne Orders for abroad or outside U.K.. addlUonal Car. I At the stand of the Ever-Ready Co. there is r'- and packing, lnsuraflcc. etc .. must be Included. I__nage I sut.e to be plenty of Interest-, tliougl; this lirio itas We stock Igranio. Climax Ever.Read.y, tiot-at the mosuclit of writing-advised us of ally Hellenen, Siemens, Formo. Fer'ranti, Wearite, new hues or departures froto their normal Istigo of Ormond, SB., Benlaiflin. Lotus. Mullard. jiroilticts for the radio enthusiast. In ally case, Peto.ScottDubilier, Linsen, LewCos. Utility. Magnum, the coiistriiction of primary batteries is a well- McMichael, Peerless, Burndept. Pye, Marconi. Cosmos. Carborundufli, RI.. twitted-down Industry, so that many purchasers StandNo.35, i;, Varley. Gambrell, Brown's. Sterling, Amplions would sooner rely tipOmi the products of a firm .s OlYmpia. -! -in fact. evetything it possible to stock. whirli they have found satisfactory in the past l - -. KITS for all CIRCUITS. titan volIttire (ato dcaiing with noveltIes. lu tite of parts past the wide range of Ever-Ready batteries for Ths switch is exactly sui;ed for the control LIST for keen quotation. all wireless I)iit'POSeS lias been tested by innumer- Make out 0E current where Butery Eliminators are Wireless W HAVE IT. able listeners, and the high reputation which this DON'T worry,iî it's finn lias woii will ensure that anything sltow;i used. Cuts oíl both Htgh and Low Ten- 11(1051 tItis stand is well worth tise attention of the sion and will carry a very high potential Ei OCTRON BRITISLI keen battery buyer. s s E N across condenser such as that passing when : Valve Holders. 1!' ; Pleed VALVES, 2,4 &6 volts. 1). Current is broken suddenly. Con.. 1J, 1/6 ; Lests. ; L.F., R.C., H.F., 5/-. The Fornio Co. Stand No. 140. Switcbes. 1/6, 2/0; Latest 2.way Power, 6/9. sere avili he found a host of good things for tite A Soundly-constructed British Swhch. Cam Vernier, 4/8; discriminating eoiiatrmmetor. Special memitiost nnint Itheostat,. 218: DII., PRICE (as Full Guarantee. be given to the stew Formo dual - inipedailce illustrated), 2/9. 1316; L.V . 16: Linsenola. Obtu/saM, from olJ Dealers. Transformera, 8'6 Coils. Chart FREE. device. This is a special two-stage LP. unit, ineor- 6Ox. 614; 25ó? 919: EBONITE cutwhile you wait pointing one stage ot resistance-impedance coupling, THE BEDFORD ELECTRICAL & 60-v H T., 7111: '100-v., atid. square inch. also Ile. followed by a singie stage of ordinary L.F. trans- 12111; Super 60.v. 13/6; RADIO CO., LTD., Ord Bias. 116; 4'S. bd. atid. Only the beot,upplled. former coupling. Titis unit is limit ti in tIIC form No cheap rubbish. of a neat cylinder, with appropriate terminals, and 22, Campbell Road, Bedford. ______bears a very cleat diagram of connections ai part "Dario" Valves ORMOND 91 the component, thus assisting in the wIring and LONDON: GLASGOW: (Genuine RadioMicro) No. 3 CONDENSERS. its tite understanding of the principie upon which 2i, Bartlett's BIdes., 1i3, Vincent St., Beet in the World. 0002S 5(6; 00035 5(9; tite (levic'e works. Holborn Circus, E.C.4. C.2. BI.VOLT 2.v. -05 5/6; 0005, '6/- (wIth 4.j Dial). Loud Speaker alve, Friøtion Geared, 0005 7/6; RC. -05 1-8. 5/6; 15/.; 0003, 14(6' 00025' - 'tIllllllIlIl(llllllIIllll(llllllllltlllllllllllIllllllllllllllllllllllllll.! 35 .05, 5/6; Loud 13/6. Straight Li,, Speaker ValVe, 7/6; Frequency Friction 3-5 RC. 07, 5/6. Post Geared, .0005, 201-; - -00035. 19/6; S.L.F.. 6d. each. - 0005, 12/.; 00035. 11f-. GOING TO BUILD A SET ? Log 0O05 13/.; -00035 M.W. an1 P.W. 12/6; .00d25 12/.. S.M Then you ought - to see the September Loading Coils, Dial, 5/., - E issueoE - . - MELODY MAKER £4COSSOR MODERN WIRELESS, : I O : O kit. As COSSOR Specification whch, in addition to the features, Leaflet free. (Watmel Choke Included) uual . of 2 Ormoond, 'OOO; 2 Do. S,M. Dial,; 6 TOC. contains full details ¿1w DubilierCondensers; 2 B.B. Clips; B.B. Rheostat; 3 Leaks; 3 Lotus V.H. ; Ferranti A.F.3; FOUR FINE SETS. 2 Switches' 1 Cossor Wound Coil; Terminals,. Glazite. Grid Bias, Watmel Choke. Now on Sale, Price 11-. HanhorneOakCabinet12/6. FREE with parts } There must be something unusual , Al,o Cabinet, at 11(11. li/lI. DrIlled High-grade 21 z 7 lIllIllIllIllIllI llllllllllllllllllllll III in this condenser to win-and hold at Polished Panel and Strip. I / and Mahogany Polished. y.\ 20,-. carriage ai.. Wood Screws. Carriage 1/-. the confidence of the most mm- j- COSSOR VALVES 2, 4, or 6-Volt for above. L.F. Another lieu Forino, product is a de luxe variable - portant Eliminator manu- :' o., R.C., or HF., 1Q16 each. Power, 12/6. condenser, which is fitted with a bearing at each / a style. of \ end, in very natty Another feature facturers, i-ici only in Britain, , - L.EWC.OS PRODUCTS tub product which is particularly pleasing is the / - CT. Collo. 40. 50, 60, 75, 3/6 each. 100, 150. 200. concealed pigtail which cifects comitact between : but the world over. 5/3 each. 0(azite bd. 10 ft. Lito Wire, 9/38. 4/- the moving pintes and tite ternìinai which makcs - \ 50 yda. 9/38 alI silk, 5(6 50 yds. Aleo In 20-yard tite connection to tite circuit. ydo. %Vlre. rvdo. Lflz. 2//42, lije 50 Frame Aerial CAPACITIES . 3/6 100 ft. flattery Leads. 'sway. 5(6: 5-way, 516; _\ 6-way, 7(6 ; 7-way. 8/6. All Binocular Coils. General Electric Co., Ltd. Stand Nos. 28, 29, 46, . , .- Irom 'I MF. upwards. Q Coils, 21/. Aerial, 151-. In stool. 47 and 225. - o \ All tite weil-knowit liEti producta will be Tcsied at 500 vol/s D.C., , PETO-SCOTT H.F. UNIT COMPONENTS represented at one or another of these stands, and a ' foscina(ing display they make. Probably - I 500 vol/s AC., and - r FOR COSSOR " MELODY MAKER." very ;_ upwards io 10,000 tite largest single attractIon will be tite Osram . 1 Ormond S.L.F. Variable Condenser -0005 I Aim extraordinarily comprehensive l-ange s - mids., 6/- ; 1 Ormofld Slow-Motion Dial, 5/.; valves. volts D.C. 10-ohm Rheostat, 216; 3. Screen Assembly of these sviti be on show, and besides the old \ drilled Sor valve-holder. 3/6; 1 Screened Grid favottrites there will be many new departurcs, Valve-holder. 3/. - 2 Socket Connectors, with Including the new Osram S.215 vaive. Titis is a fies and tags 6L - 1 TOC.. 1 mid.. 2/10; 1 .. SG. Choke, &f- ; i boil (Lite wound) for short new screened-grid vai-ce for 2-voit users, and it waves, 8/6; 3. Coil for long waves, 9/.; 3. Coil is very Interesting to recall that last year the Base, 1/9. Osram S.625 was tite pioncer of the screen-grId .'r:-: type of valve. C.O.D. (U.K.) post freè for 47'6 Those listeners svito posscss electric light froua °" ' FREE with above: Drilled panel and alternating current mnhuins will be specially inter- l .. R cited in tite new Osrain series foi AC. full details j . , - strips, 7 engraved terminals, baseboard, of which are now available and can be obtained . . ---\ I the stands. - - wire and screws. at Titis firm is also announcing the Osram " tode "-a wonderful new five-electrode power COSSOR Screened Grid VALVES, 22/6 valve which will ahortly be placed upon the market.. At the time of writing it is not certain that titis

Send your orders, wire, phone or write (plainly will be available for - display at tite Olympia please). Personal attention to your requirements. Exhibition, but it would be an awfttl pity to tuina LOUIS HOLZMAN, 34, Kingsway, London, W.C.2. it if it is, no tite only course for tite man svito Wattts C.O.D. U.K. ONLY. - to be bang up-to-date is to call at the G.E.C. RADIANO FOUR PARTS. SEND FOR QUOTATION. stands to make sure. - 448

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TELEPHOTOGRAPHY :n:. AND TELEVISION 5bi '9e,,, - -co-ntinved from pag& 388.

'i, - MILLIAMPE $ - i t it is stated that the original Act in- * chides "and shall be deemed always to have incrude thereception as well as the sending of messages." Television is, of course, another new development not contemplated when the Acts of 1904 and 1925 were passed, :but it is the opinion of legal J i authorities with whom we have discussed this matter that the sending An I ohmite anode resistance isn't of living or still pictures by wireless is covered by the definition in Sub- superstitious; it's only rated to u section .7 of the 1904 Act: "Any carry 10 milliamperes, and 13 is system of communication .. reputed to be unlucky, but if it i without the aid of any wire." burns out at this we will replace it, i Consequent'y, it follows that any but systematic of service television or no Ohmite has ever been burnt i . still-picture transmission must neces- citate, as a preliminary, a licence from 'outyet! the Postmaster-General; and, further,

it is a widely considered opinion that - . , That's ivhy ' any such service offered without a licence 'would be a breach of the experimental licence issued to any GRAHAM FARISM .. '1 experimenter, and also a breach of, the exclusive and monopolistic .112 ANODE -. licence already issued by the' Post- JILIflhIL RESISTANCES master-General to the B.B.C. Nevertheless, it is quite likely that aX. 2A4- _J/. legal argument may require a more detailed interpretation of the Act, and it is evident that there is already a school of legal opinion which be- I Y2MEG 2'3.H lieves that on a technical point radio television, or picture-transmission, as GRAHAM FARISH of BROMLEY, KENT a new development, stands outside the present wording of the Acts. But in the unlikely event of this contention being upheld in the Courts, there is : DON'T WAIT ASTONISHING no doubt that Parliament would Par the 'S&iiiteru: be asked to pass an amending Act to YOUR SETNOWIU BARGAINS in regularise the position. EVERYTHING WIRELESS. our ON U 'NEW CATALOGUE EASY PAYMENT TERMS 72 Pages, well illustrated end oller!ng the WHY NOT READ MORSE? : First Monthly Payment Secures Delivery. greatest choke obtainable in radio products. -.eonlinaed f,osn page 404 Call at our showrooms or send list of require- Get a copy. Post Free 4d. mente. Best monthly terms quoted by RETURN.0 P.D.P. Co. Ltd., Dept.C., ELECTRADIX RADIOS,' 121. Cheapside, E.C.2. Phone: City D846. 218, Upper Thames Street, London, E,C.4 that he begins to discover the real I interest of the thing. - The best method is to choose the slowest and clearest sounding- trans- mission you can find, and settle ----iED t down to try and pick out a few letters bere and there, writing them down - GUARANTEED EBONIÏE PANELS quickly and listening for others. When you have práctised suffi- MAHOGANY ciently to be able to copy correctly CUT TO GRAIN MATT slower of S A F E T Y FI R S T the the amateur trans- ANY SIZE OR BLACK missions which you hear, the new POLISHED interest which you will find in your short-wave receiver will amply repay E.C.1 you for all the seeming drudgery of PETO-SCOTT CO;, LTD 77, CITY ROAD, LONDON, L your practice days. - )552S - - 449

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BAIRD'S TELEVISION READY RADIO SUPPLY 00. 'APPARATUS 41, Newcomen Street, London Bridge, S.E.1 -conünued from FoUr 408 Telephone: Hop 6167. IMMEDIATE BESPATCH OF of light emerging from the optical ALL THE CORRECT PARTS lever system and impacting upon the as used in the sensitive cell is increased, the intensity of that ray, and therefore its power "RADIANO FOUR" to stimulate or energise the cell, 1 CabInet & Baseboard, 21' x 7'xlO' j 10 0 1 Ebonite Panel. 21' o 7 ...... 11 6 would appear to be proportionally 2 Indugraph Vernier Diala 15 0 2 LInsen Variable Condenoero -0005 13 0 weakened. * i Peto-Scott Reaction COud -0001 5 6 1 Benjamin On.&.OfT Switch 1 3 I Liasen P.M. Rheostat. 30 ohms 2 6 "Stere'oscopic" Pictures 2 Lotuo D.P.D.T. Switches, vIthi terminal, ...... B O Patent No. 266,564, granted lo Tele- 2 Brasa Rodo. 2BA, 4' long4 2 Magnum Panel Brackets 2 6 2 Terminal Strips, WILh 5 and 7 vision, Ltd., and Mr. J. L. Baird. tpr,nlnals ...... 2 6 4 Lotuo Vain, ¡Toldero and terminals 7 0 Here is a Panel In the case of kinematographic re- 4 Peto-Scott B.B. Coil Holders 6.0 2 TOO. Condensers. 0001 ...... 3 8 production from a series of film photo- i TOM. Oofldenoer, .0003 ...... 1 10 i TOC. Condenser, '0003. with SV. that will not split graphs, many attempts have been terInln4slo ------2 4 i Dubiller Grid Leak. 2 megohms ... 2 6

made to secure what is called the i Forniodoneer, -00003 max. Ref. A 2 6 - 2 Dubilier Condensers, i nild ...... 5 0 or break or crack stereoscopic effect. That is to say, i Dubilier Condenser, 2 mId ------3 6 i 11.1.-Varley Radio Frequency Chubs 9 6 instead of the moving picture being i Mollard ROC. tait ------17 6 i Philips' LV. Transformer 1 5 0 thrown upon the screen as a flat or j Igranle Output Choke, type F ... 16 0 i Peto-Scott Sereoniog Box -(MW.) 12 6 HAVE you ever wathed 25 Tardo Lewcos Rubber.eovored Flex 3 6 two-dimensional" reproduction, it 2 Seto Liosen Coils, med. and higli- the fracture run across appears to have as well. wane ------1122 depth i Set Onacor and Marconi Valses ... 2 16 0 the panel just as you think In one known system tlìis result Wood Blocko and Metal Screws ... O you've finished drilling? It's has been attained with a considerable £14 19 1 degree of success by throwing two Write, wire or 'phone (Hop 6767) your order. a common experience unless Any of the above parto can be supplied 000arateip. pictures on the screen simultaneously, Drilling free. The act can be supplad complete fur you choose. Resiston. an extra Charge at £6, Hoyalties paid. and providing the audience with INLAND: Ail orders POST FREE. spectacles of differently-coloured OVERSEAS consignments caretully packed and insured. Resiston Panels, like Radion, lenses, so that each picture is seen are made from nothing but.pure separately by each rye. The action of EVERYTHING WIRELESS tite human eye then automatically rubber. They are tough with- CPrDI L,.I&G) merges the two separate images into 'rIi W ir1mm øto' out being brittle. They can be will call and cure your set (London and Home one harmonious whole, in which the Counties). A oPecialist in quality reproduction. sawn with ease, they can be various objects stand out from one 2u, Woodville Grove, N.16. Sloane 1100. Clisoold 36$. drilled without fear of fracture, another in their natural perspective, and when tapped vill take a Mr. Baird has invented an arrange- good thread. ment whereby the same stereoscopic To All effect is said to be imparted to pictures s or scenes transmitted by television. Advertisers With Resiston, the home con His method is illustrated in Fig. 3, and PLEASE note that communica- structor runs little risk of ruin- consists in using two sensitive light tIOns concerning advert,s,ni in cells A and B placed slightly ing his panel. Its strength; its apart, WIRELESS CONSTRUCTOR each cell receiving separate light- perfect insulation, beauty of POPULAR' WIRELESS. surface and colour permanence impulses from the object O to be televised. MODERN WIRELESS are lastingly .assured. Th&Receiver must be made to Send for iew booklet. At the receiving end two light John H. Lue, Ltd. sources M and N are similarly dis- 4, Ludgate Circus, London, E.C.4. placed, and are respectively energised ('Phone: City 7261.) Please send nie, free, a copy of your new and NOT to th Editorial or PubIishin by the currents derived from the two Officeu. booklet, "Tue Panel Makes all 1/je Difference." cells A, B. The resulting variations in V.Con. Oct. light intensity are separately synthe- 1 i., of Qua1iIy ÑAME...... sized or reassembled, and are then f o viewed through an ordinary stereo- I every \ U rol L,.,.'r.,te' i .i-tIcUl.ir. irnri ADDRESS ...... scope. (;D1s.th, .c:n.I i.' ,.,r.ie,urr. V i. a.- r,,' lion., :i, Ijaskn-e 'troce. lit. LOna.,n.k. In order to keep each image separate Mare from the other a special rotating dise RAFT D is used in exploring the object O ARtC through a lens L. This disc has two series of spiral holes or lenses marked fl A'PR11kt4B(L5T VALUt.. -, S and S1. The spiral lenses S are 1h/ arranged so as to throw one series of Thi ARTCRAFI COMPANY ntiL ... 156,CH FURY ORCHARD RTROYDON 5685 lightrays on, say, the cell A, whilst the other lenses S1 feed the cell B. When replying to advertisers please be Americapi Hard Rubber Co., Ltd., 13a, Fore St., £C. (Continued on paqc 451.) sure to mentibu "Wireless ConstrucLor." - J 450

S- - s- S-SS--- -_s._ _&__ - . -- --- S -- -- _

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BAIRD'S TELEVISION APPARATUS -continued from page 450

The two imago beams may be pre- vented from creating mutual interference by providing a partition be- M: tween the two series of lenses, which

partition may. either be made rigid i with the exploring disc, or else it may THE. - be made to rotate relatively to the disc.. HALL T The reassembling disc D1 at the receiving end is also provided with MARK two separate series of spiral lenses in

order to project each completed pic- OF :1 , turo separately. KEYSTONE MIDGET By interposing a stationary orange- REACTION CONDENSER QUAL TY red screen between the exploring disc PRICE... 0®1 mid. ... 5f- and the light-sensitive cell A, and a 00005 mid. . . . 4,6 KEYSTONE ALUMINIUM stationary green-blue disc between ANGLE BRACKET the same disc and the cell B, Mr. Baird PRICE 2,'- per pair states that the object to be televised may be transmitted in natural colours, WRITE FOR LIST No. 25

similar coloured screens being pro- GIVING PARTICULARS ., - vided for the light sources M, N at OF FULL RANGE OF thé eceiving end. KEYSTONE COMPONENTS- qN Patent No. 266,591, granled to Mr. J. L. Baird. CU. L In the original experiments carried KEYSTONE PUSH.PULL PETO-SCO KEYSTONE HIGHLOW out by Mr. Baird, the light directed SWITCH 77, City Road, London, E.C.1 H.F. CHOKE upon the sitter's face was so powerful PRICE ...... 1;3 PRICE ...... 3,6 as to be almost intolerable after a C5,j 528 very short time. - In order to avoid this inconveni- ence, Mr. Baird At Once! proposes to reduce Get Your Copy 'i the brilliance of illumination by using ALL SPORTS FOOTBALL ANNUAL two light-sensitive cells of one, ALL. SPORTS instead gives all the latest infotmation about the and energising both cells simultane- League Teams. Contents include Laws ously with light-beams from the same of Football. Four Pages of Photographs. FOOTBALL object. The two series of light signals All English League Fixtures for ¿928-29. so produced are sent separately to the All last season's results. Full particulars receiving station and are there re- of New Players, etc. Everything to help ANNUAL 3d. combined into one picture. you with your Football Competitions. In order to keep each picture separate from the other in the process of transmission, a different inter- MODERNISE YOUR WIRELESS ruption frequency is used in each "RED DIAMOND" 2WAY The case. As shown in Fig. 4, an exploring "RADIOLA" COIL HOLDER disc D is used to traverse the BUREAU - - object O, and the resulting light rays Cotti,tgno niera than are then cut into two a Loud Spec her, up different i quickly transforms frequencies by means of a second disc, YOUR SE into '- e Stately Drawmt- No. R.D.32. TPAtE kAR D1, provided with an inner and outer Room Receiver Parallel seorking. Fine adjust- series of interrupting holes a, b. High est approval, ment. \Vorm driven. Coils con- RED DIAMOND There are twice as niany holes in Radio Prrs, iea.Iin, not tall. Easy movement. Perfect experts - and over ,', 6nlslo. Of all high-class / 3000deliáhtedclients the circle a as in the circle b, so that - 4 radio dealers or by in- f - light falling on the sensitive cell A FROM sured post, 4/6. ,each is iñterrupted at a frequency double £5.5.O R.D. 39.. Switch at which the rays falling on the 3 1,. hlh. Solid oak Pull-and-Push 'hat or mahoanny. Beauti- Robust construction. Definite cell B are interrupted. In this way fully polished D L11tc Model "on" and 'of! ' pOsitlOns. No ON APPROVAL every shaking. Perfect contacts. .each image-signal can be transmitted Sent in sizes (or set. Terminals for easy flttiug.Price Send for full particulars - FREE. separately from the others to the Lofe Afaees: distant station. There the two signals 'L' JEWEL PEN CO., LTD. aré sèparately rectified and the re- \ [f Radio Dept. 41, 21/2, Gt.Suton St., London, E.C.1 sultant currents fed in cpmbination W.C.WORKS, BEXLEYHEATH, KENT. to the illuminating g1ow-lamp. 451

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QUEER QUERIES -ijontinue4 from page 427

could not get his reaction to work like that at all. When the condenser was adjusted at zero there was no reaction, andadjusting it up to about half-way did not seem to make very A much difierence. But suddenly there MONEY OU SAVE . li came a point vhen there was asoit of I.T. SUPPLY plop.". -and the set started to oscillate violently. 1THT a:tr Whén turning the condenser slowly after dry battery back again the puzz1ing part of the and the over-present \ performance started. Itjstead of it bogey of. spoiled k, .'s programmes. Banish plopping óut as iV had plopped into \\\\ t hi s for ev er.l '°" osillatidn, it kept on oscillating even Instal the amazing though the reaction condenser ,vas Standard Wet H.T. turned several degrees back beyond Battery-the battery that recharges itself where the point it bgan to oscillate. overnight. Don't -' ÑoLT In this paticu1ar instance there delay. Send for free - were five degrees on tite reaction booklet describing.every dctil, for install- \ condeiìser iìich "ovèrlapped." As ing and maintaining this super - efficient e and money-saving battery. Mention Dept. our friend was trying hard to get G when replying to this advertisement. 1 distant stations and knew that SPECIAL OPPORTUNITY smooth reaction was essential to "?UNIBLOC CABINET" titis, you can understanI. his 96-Volt unit complete. Cash Price terrible trouble." £21S15, or 8f i doivn and 5 monthly par. :Pocket mente of8/i.Ço references. No deposit. 11 RA eiwrD$ CIeLS STOJJES. C1J(51S STttSJ5 N Curing "Overlap" o,i csi,o, ,/ejc,rei DOW u-oolwortlis are now stocking 6d. Units seo the nir%, STANDARD on every sr. zt! Quite a number of factois will cause - trouble of this kind. The first thing RADIO EXHIBITION. OLYMPIA to suspect where overlap is present (On right of main ¡ t,.iii, j'O. I , entrasen.- POCKET MODEL. is that - incorréct voltage is being applied by the L.T. or the HT. The Standard Wet Battery Co. RADIO METER (probably the latter). Another fre- )Wdt. HT. Battery Ca.) of Sifam Radio Meters He,-if Offices, Showrooms, and lVa,-eho,lse- sold is now '1$4-18B Shnftest'ury Avenue, buden, W.C.i approaching the quent cause of this trouble is a reaction Near THEnumberenormous figure of half a million. New Oxford Street end. lise_. absolute dead-beat movement. - coil which is too big, and if neither guaranteed accuracy and robust con- of these appear to make much struction of the Pocket Model Meter STJtN bave, from the first day of production, différence, thé source' of the trouble won the approval and confidence of Permanent . T. Supply. listeners every.whe. . may. be either, the grid leak or the This greatly increased production has grid condenser, or both. brought manufacturing economies in its - wake. This saving is being handed on Incorrect values of either leak or to the purchaser by a reduction iii price from 9 6.to 76. .._ Get -your_Sifam Meter condenser can give rise to these now, from wireless dealers everyinliere, symptoms, but generally the H.T. is price 7/6 ...... - W,i?e for interesting free leaflet " DetecIi,, wrong as well. In any given set, Distortion'...... from Dept. C. 'certain valves will be found to be SIFAM ELECTRICAL INSTRUMENTS Co., Ltd. prone to the trouble and others not, R0Thi,iïta so a change of valves, if is BUSH-HOUSEALDWYCH,litis, W.Ç.2. this Vlñß possible, may do the trick.

Dobiijer Condenser Co. (1925), Lt(I. 402 M. . AVireless l;d. . 41 - 446 MuUa relessSemeeojtd (merit 414 UIDEX TÖ Co Ltd ADVERTISERS England-Richards Co ...... 447 .Petq-Scott Co. Ltd ...... 449 451 Electron Co., Ltd ...... 421 P.D:P, Co.7 Ltd ...... '..44

Electradix Radios ...... 441) Pickett's Cablitet Works ...... : American liard T(nbber Co.. ltd. ' .... 4j Artthlt, The. (\ ...... 450 Ever-Ready Co. (Great Britain), Ltd 397 Philips Lamps, Ltd ..... 417 Advertisement Racs ...... 440 Ferranti, Ltd ...... 435 .PR. Masts . . .. 444 Company 'P.R.. .a1ves ...... 439 . Formo ...... 420 '.AItSpts 'Foòtball AnnuÌ : -. . r- .'-451 'lite ...... 433 Bediord Electrical.& Radio Co.. Ltd ...... 448 Gainbrell Radio, Ltd ...... 438 itadlo Exhibition. Wisiteley & Co., Ltd ...... 394 ltaymond, K ...... - ...... 448. BellinR,&Lee Ltd.. ' ...... 441 (larnett, Bird,SdncyS., k Sons, Ltd ...... 442 Gilbert (Cabinets) ...... 442 Ready. Radio Snppl Co ...... O Bond[V. C., k Sons ...... '450 Goodmans' ...... 439 JRipiiultP. Limited ...... 436 Graham Farishi ot Brointey ...... I. & 1l1lCy, Ltd ...... ('over iv r Boder-Lowe5Co., Ltd ...... 418 449 British-Thomson Co.:ttd. 354; 355 Henyberd, F. C., & Co ...... 446 Rotliermel Corpii.; Ltd ...... 356, 357 Bnrndept Wireless, Ltd ...... 398 Holzman, Louis ...... 448 Standard %Vet Battery ('o.. Tite ...... 452 Electrical Co.. Borne-Jones & Co., Ltd 428 Hughes, F. A., & co., Ltd 437 .Siíam Inst. Ltd ...... 45" f ...... Taylor. C ..... 446 BlackYAIeander ...... 450 - linpex Electrical, Ltd .. ' ... 426 ...... 'eelipo1ogictil Institute oí 61. BrtSin 444 Brown, S. G., Ltd 432 International Corr. Schools Ltd ...... 431) ...... Telegraph Co., .. Baker's Selhurst Radio ...... 443 Igranie Electric Co., Ltd ...... 405 Condenser Ltd ...... 441 Benjamin Electric Ltd 443 Jackson Bros 4j3 Transfonner Repair Co ...... 446 ...... Weston Elect. Inst. Co., Ltd 433 -1 British Gener,ci M?c. Co., ltd ...... 443 Jewel Pen Co., Ltd 451 ...... Westinghouse Brake & Saxby Signal Co., Ltd. 410 Carrington Manfg. Co., Ltd ...... 443 Lectro Linx, Ltd 410 ...... Whiteley, Boneham & Co., Ltd .... 438, 447 I Casson Monldings ...... 439 Lissen, Ltd ...... 393 . Celestion Itadio Co.. 441 London Eier. \V,reCo. & Smiths, Ltd 42 . Clarke, H., & ('o. (Mcr),The. Ltd ...... 400 London itadlo MIg. Co., Ltd ...... 430 -iI Cole, E. K.. ltd ...... 425 Lyons, Claude, Ltd ...... 434 All communications concerning advertising in j Cossor, A. C., Ltd ...... 358 Marconiphone Co., Ltd ...... 355 JJircless Oonstructor" must be made to j Colvern, Ltd ...... 437 Makerimpoit Co ...... 446 Join R. Lite, Ltd., 4, Ludgate Gircus, London, Cleartron, Ltd ...... 445 Motro.Viek Supplies. Ltd ...... Cover iii E.C.4. Telepiwne: City 7?GL Day, Will, Ltd ...... 434 Morris, J. lt ...... 433 ,Nf R

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OF ChARACTER - - Don't engage a Valve with. out a good character! Cosmos-Met-Vick Valves are each supplied with a written character that will bear the closest scrutiny. It tells of the Valve's ability to do the work for which it is designed, its conduct (on test) and its qualification for a situation in your set. You can have the fullest confidence that the (ji, characteristic curves oft a Cosmos-Met-Vick "Shortpath" Valve are closely in accord with the inherent character of the Valve. Here are some of the details of the two-volt family :- - -."-

S.P. S.P. SP. I s.P... 16/B 16/G FILAMENT VOLTS lOIR 18/RH BLUE GREEN 2 RED DOUBLE SPOT SPOT SPOT RED SPOT

0.09 0.09 FILAMENT CURRENT (amps) 0.09 0.3 35 16 AMPLIFICATION FACTOR 9 6.5 0.5 0.95 SLOPE (MA. PER VOLT) 0.9 1.4 70,000 17,000 IMPEDANCE (OHMS) 10,000 4,500

10/6 lO!6 PRICE lO 6 12 6

The Booklet 4117/3 (MS. 4667) gives the complete information showing why Cosmos-Met-Vick Va1ve . . AMPLIFICATION, i6/p j/ give HIGH PURE TONE, ?. - I NO DISTORTION!

. !7J ./ '-I Ask your dealer for a py j . - . ::-'-!-i i ..:: METRO-VICK SUPPLIES LTD. ¡ -.7 I (Proprietors Metropolitan Vickers Electrical Co Ltd.) :1 / '-I' ... t- 155, Charing Cross Road, - / ',j: LONDON, W.C.2. ¡g :.'' I

k.. .o - .. ------, -

Call andee / SS 4tF VII b 112 VALVE S

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THE WIRELESS CONSTRUCTOR October 1928 components p7 - adio Recep4j*'Pto

J / \ Every year brings us nearer . in wireless -. - 4...... ,...... PERFECTION /n: n. \ reception. This season the new j \ R.I. and Varley components are such-a J

\ marked improvement on existing f

i apparatus that they completely eclipse ¡ - - anything that has been achieved in the f n - - .

.-'::1 past. ¡ .-. --- - - n -- Behind all these new improvements f

i \ is the one big factor, QUALITY. I il i}ed I1-ii \ eptn I 4 D. ' LIs [ why R.I. and - . 41 ..- foreground-that's f / \ Varley products are so popular j ' - / to-day among every section of j r- ¿ f . the radio public. i Come and see- Stands 56 f , 1 n and at the National n: t . ìn 73 f

- n:: Radio Exhibition-you will f then be able to judge for J \ yourself the vast strides Ç 4 Si.' ¡ we have made during f e, the last year. - f

s .

.. /

- I -- ___%. Areriotho Tuner L - e:aAe br both medium Un.t and ong waves -i for both medium . / ?.:------and long waves.

L - .

n - - ANrI-MOrO

i.- ER. Xn RES$TANCE . - F n - - - CAPACITY -_-

- . COUPLER

- L- - nfl, MPca )r,lGN -

'- I - - '-'t 2__

H I Bi-Duplex *Mobo Resu- LS. Intervalve \ = f tance Capacity - - Transtomer .- Coupler 27/8. - f ,, / j.M!L) '' Tyne Z 25?- ( '- Y 25!- X 25/- L

C emp!?g?::n 1I' I derful new system of suspension - £3.3.O V THE MARK OF :BETTER RADIO Kingsway House, 103, Kingsway, London, W.C.z Telephone: Holborn 5303.

Printed and published on the 15th of each month by the Proprietors, The Amalgamated Press, Ltd., The Fleetway Rouse, Farringdoa St., Loi'Ion, &C.4.. Advertisement Offices only: Messrs. John E. Lue, Ltd., 4, Ludgate Circus, London, E.C.4. Registered for transmission by Canadian Magazine Post. Sutxzriptlon rates: Inland and Abroad, 8/6 per annum. Canada only, 7/6 per annum. Sole Agents for South Africa: Central News Agency, Ltd. Soie agents for Aust.rIia and New Zealand: Messrs. Gordon & Gotth, Ltd., and for Canada: Tise Imperial News Company (Canada), Ltd. - R/E

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