November. " IRELESS Vol

FIODERN November. " IRELESS Vol. 2.No. 2. Edited by JOHN SCOTT-TAGGART, F.Inst.P., Member I.R.E. November, 1923.

SPECIAL ARTICLES ON HOW TO MAKE : Vol. II. A HIGHLY SENSITIVE THREE -VALVE SET. By Percy W. Harris. A CRYSTAL RECEIVER WITH WAVE -TRAP. By G. P. Kendall, B.Sc. A PORTABLE ST 100 RECEIVER. By John Scott -Taggart, F.Inst.P. A HETERODYNE WAVEMETER. By Alan L. M. Douglas. A SINGLE VALVE -NOTE MAGNIFIER. ACCESSORIES FOR PEANUT VALVES. No. FRAME AERIALS. LOUD SPEAKERS. CRYSTAL HOLDERS.

I FREE WITH THIS ISSUE-"JUNIOR WIRELESS." A 16 -PAGE MAGAZINE FOR BOYS. MODERN WIRELESS November, 1923

WECOVALVES . (PEA -NUT TYPE).

N 44215-A. L'TENT Nos. 17580 (1915) 180090 46641-1921). Dimensions :2i in. X e in. Price - - Z1 10 0 THE WECOVALVE. THE new wireless valve which is to revolutionise wireless reception.Only 21 inches high and inchesindiameter,this small size valve. can be used equally well either as adetector oramplifierandoperatesoffasingledrycell,noaccumulatorsbeingnecessary. The WECOVALVE is the most economical valve existent, requiring only 0.25 of an ampere at o.8 to I.'volts,anditslifeismorethantwicethatoftungstenandother dull -emitter valves. The WE hasaspecial Bayonet Cap which prevents the possibility of destruction through careless insertion in the valve socket. Operating Characteristics :- Filament Current 0.25 amps. Detector Plate Voltage 17 - 22 volts. Filament Voltage o.8 - i.1 volts. Amplifier Plate Voltage 22 - 45 volts. THE SOCKET. ThisWECOVALVE socket is arranged for four soldered connections and has contact points faced with a gold and silver alloy which ensureperfectcontact with the base of the valve. THE ADAPTOR. The WECOVALVE adaptor makes it possible to usethe Wecovalve in your existingsets. Designed tofitinto valve sockets which carry the ordinary four pin type valves, this adaptor enableseveryonetotakeadvantageof the great economy in current consumption which the use of the Wecovalve effects. No. 44090. No. 44092. Dimensions : 1 in. x t in. WRITE FOR BOOKLETS- Dimensions:1i in. Pricels.6d. W.E. Co../32/W. 528 & W.E. Co./32/W. 529. Price 3s. 6d. Western Electric Compang Limited. (Wholesale Only) Connaught House, Aldwych, London, W.C.2.Telephone : Central 7345 (9 lines). Branches : Glasgow,Leeds,Birmingham,Manchester, Newcastle,Cardiff,Southampton,Dublin.

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11. November, 1923 MODERN WIRELESS The LISSENIUM AGE- LISSEN parts anticipate to-morrow- To aid users in obtaining the highest possible efficiency we have seen to it that there is a LISSEN part for every purpose.LISSEN made throughout, every part places at the user's command a service and efficiency which will sustain the fine tradition of the LISSEN Factory.Up to the present more than thirty times as many LISSEN parts have been bought in 1923 as in 1922. Why ? Because it has been found worth while to fit LISSEN parts.If you build your set you have got to use it-if you fit one LISSEN part you can depend upon it- if you fit all LISSEN parts you can depend upon the set. WE EXPECT TO HEAR FROM YOU IF YOU ARE NOT SATISFIED. AMERICAN TELEPHONY ON THREE VALVES ONLY -but ALL LISSEN PARTS Several reports have come to hand recently of American Tele- phony being received on 3 Valves only-but usirg ALL LISSEN PARTS, 1 LISSEN REGENERATIVE REACTANCE for 1stage H.F., 1 DETECTOR and 1H.F. A standard circuit was used. Build with ALL LISSEN PARTS ! 1.SUCCESSFULLY USEDinthe reception ofAMERICAN TELEPHONY- LISSEN REGENERATIVE REACTANCE replacesaerial reaction-non- radiating-introduced into the anode circuit, it forms an unequalled G / 6 first stage radio frequency ! Cheaper,easier to handle than plug-in coils 1-0 2.Rapid tuning is possible with the LISSEN REACTANCE-addsQ/6 range,power and steps up signals li eta good audio -frequency transformer 'LP S. USERS SAY LISSENSTAT CONTROL is the " most beautiful control imagin- able,"and it is !The interposition of the elastically deformable metal discs-there lies the secret of that perfectly free movement of the whole resister column of the LISSENSTAT. This feature CANNOT BE DUPLICATED, FOR 7/6

IT IS PROTECTED BY DEFINITE PATENT CLAIMS ... 4.LISSEN VARIABLE GRID LEAK-for correctgrid potential-/ 6 continuously variableto 6 megohms.Positive stops' both ways ... 5.LIS -EN VARIABLE ANODE RESISTANCE-continuously variable 20,000 to 250,eoo ohms-for dual, super -regenerative circuits, etc.Positive stops o/6 both ways.Same size and appearance as LISSEN Variable Grid Leak '4.4 S.LISSEN Ti TRANSFORMER, anincompirab eTransformer. Us^it alwa3s ni-diatelylot hind the Detectcr Valve and L.r pule ',Aver 3U/-

7.LISSEN TUNER-sharp tuning on all wavelengths-convenient 02/6 and compact -150 to 4,000 metres ... a. LISSENAGON COILS-there are three extra numbers in the series, Nos. 3o, 4o and 6o.This makes all the difference in tuning over the lower wavelengths, and °bviates the use of excessive capacity.These coils are intermediate between 25 and 35, 35 and 50, and 5o and 75 ...Price, 30 coil,4/10,40,4/10,60,5/4 9.LISSEN MICA VARIABLE CONDENSER-low resistance,7 7/6 no losses, signal strength always great, .00l, .00025, and .0005... 10.LISSEN VERNIER ADJUSTER-adds vernier adjustment to any existing condenser-drill one hole dose enough to bevelled edge of condenser dialrgt/. so that depression of adjuster engages its rubber friction washer on dial11 Other LISSEN PARTS includeLISIENT3 TRANSFORMER. Anexcellent LISSEN PARISINCLUDE EVERYTHING light 1r,.nsform r.One of the. 12,:st made 18/8 LISSEN T2 TRANSFORMER ... 25/- you need to go behind your panel LISSEN FIXED CONDENSERS, .000ito .00092 /-,.001 to .0032'8, .004to .0063/ - LSS TN PARTS have done away with r lithe bother of fitting -they go together easily-THEY ARE THE LARGEST SELLING PARTS There are other Lissen Parts as well. LISSEN PARTS ARE SOLD EVERYWHERE-should any attempt be made to sell a substitute, send direct to factory. No postage charged DEALERSLISSEN --claim your liberal stocking discount-all Radio, Motor,LIMITED Electrical and Hardware Factors sellI issen Parts-or send direct 20-24, WOODGER RD., GOLDHAWK RD., SHEPHERD'S BUSH, LONDON, W.12 N.B.-Close to Goldhawk Road (Met.) Station, Shepherd's Bush (Central London) or Hammersmith Tube.'Buses II and 32.'Phone: 1072 Hammersmith. ------BUILD-WITH ALL LISSEN PARTS ! ------

A MODERN WIRELESS November, 1923

11111111111 ill11111111111. 11111111111 H.T.C. mai! TRANSFORMERS reduce distortion to the absolute minimum. 3 -ELECTRODE VARIABLE CONDENSER .

CAPACITY BRIDGE A Striking Testimonial LENGTH Zee to the HEIGHT Vis' The principal factor to the success of the H.T.C. Transformer is he feature (prov. pat.) which gives agreater mass of iron at a lower magnetisation than any transformeryet produced of its size. VARIABLE BRIDGE CONDENSER High magnetisation of the iron core is the direct cause of distortion.The H.T.C. Transformer operates on telephony equal to other makes costing twice its price.That this is said is conclusive to the efficiency of the maker's designthattheH.T.C. Transformer should give the maximum amplification 3-E.V.C. with distortion reduced to the absolute minimum.Therefore noInteraction. H.T.C. Transformers may be mounted side by side. They have been proved exceptionally efficient on the S.T.i oo.This, without doubt, is one of the most rigorous tests to which a transformer may be (3 -Electrode Variable Condenser) subject. WHAT ANOTHER SAYS : London, In retailing your transformer at 15/-, Iconsideryou make a free present of a 10/- note with each one. Yours very truly, T. F. M. THE GENERAL ELECTRIC COMPANY Let your next Transformer be an H.T.C. You'll want another, becausethey (The largest electrical organisation in the United Kingdom, are free from distortion. Price 15 '- whose Technical Research Laboratories and staff are second to none) have,after careful test and examination, under- H. T. C. taken the manufacture of the 3-E.V.C. (under licence from VALVE HOLDERS High resistance Autoveyors, Limited). and low capacity are determined bythe spacing of the valve Variable Bridge Condensers are now obtainable from all legs themselves. In the manufacture GENERAL ELECTRIC CO.'S Branches, Agencies of the H.T.C. valve - holder, allowanceis and Gecophone Service Depots throughout the made for the varying spacing of legs of the world. differenttypesof Type C for below panel mounting. valves. Price 1/6. No metallic parts used in construction are exposed, making it impossible Beyond the wide use of the 3-E.V.C. as -a rejector of all to short the H.T. across the filament. Illustrations show two methods of mounting the H.T.C. valve holder. unwanted sounds, its enormous popularity as a CAPACITY There are at present in production five types of the H.T.C. valve -holder, BRIDGE has encouraged the manufacturers to improve it, providing a special pattern for all practical purposes. both as regards worktnanship and material used, to the very highest degree of efficiency.This involves a slight increase in retail prices, which, on and after Octobert St, will be Type A for above .00t Panel Mounting, 47/6.Cabinet mounted, 55/-. panelmounting. - Price The 3-E.V.C. isobtainable fromallhigh-class wireless 2/. dealers, or direct from

Trade enquiries AUTOVEYORS are solicited. Radio Engineers and Contractors, H.T.C. ELECTRICAL CO. 84, VICTORIA ST., WESTMINSTER, S. W.1. 2 & 2a, BOUNDARIES ROAD, BALHAM, S.W.12 Telegrams: " Autoveyor," Sowest, London. TELEPHONE :Battersea 374. 11111111111111111111111111111111111111111111111111111111111111 iv November, 1923 MODERN WIRELESS

EVERYTHING iEMEN for theRAD.O CONSTRUCTOR LOUD SPEAKER. An instrumentofthehighestclass. -even to Explanatory Wiring Diagrams.Showing all the components required, and. their relative positions for wiring up, these diagrains are in booklet form and are obtainable from your dealer CLEAR PRICE, each at 1 /- each. RECEPTION, WoodhallPaxolinVariometer. 120 ohms. Constructed of Paxolin tubing (not cardboard) thea walls allow close NO £2 10 0 coupling.The bearings are accurate DISTORTION, 2,000 ohms. and robust. Wound to300-450 metres 'and attached to panel by £2 12 6 drilling one hole only. Complete with HANDSOME 4,000 ohms, Terminals (less knob and dial). APPEARANCE. List No. 15341. 6/9each £2 15 0

Valve Adapter.

Provided with $011101PAhell suitable clips for with which is amalgamated carrying the "Q," THOM SON & BROWN BROTHERS QX," V24.," and other special LIMITED.Wholesale only. valves which are not suitable for the Head offices and warehouses: --- ordinary type of holder. Permits the Great Eastern Street, London, E.G. 2. quickinterchange of valves. 118, George Street, Edinburgh, and Also manufacturers of Branches. List No. 17312. Price5/8 WIRELESS ACCESSORIES OF ALL KINDS. Descriktive pamphlet obtainable from your local wireless dealer TRADE ONLY SUPPLIED. Kindly order from your or stores. usual dealer. SIEMENS BROTHERS & CO., LIMITED, Woolwich, London, S.E. 18.

O WE ARE EXHIBITING AT THE ALL - WHOLLY BRITISH SYE BRITISH WIRELESS EXHIBITION, WHITE CITY, SHEPHERD'S BUSH, MANUFACTURE NOV. 8th to21st,Stand No. 108;9. TWO -VALVE LONG RANGE ------777( RECEIVING SET WithAnode Tuning andReaction P\ . This instrument will meet all the requirements of those desiring perfect reception of Broadcast music and speech, either from local or distant stations, when operated on a standard P.M.G. aerial. 'The first valve is a high -frequency amplifier, and the second a detector ;the anode circuits biing coupled with a " Sterling " Anode Reaction Unit.Aerial tuning is accomplished, with the " Sterling " Vario- meter provided ;and, anode tuning with the " Ster-

ling " variable air condenser. ' In highly finished Walnut Cabinet, complete with two -"R " Valves, one pair of ", Sterling " No. R 1238 ,Super Quality Head Telephones (2,0oo ohms) with cord and plug, high-tenSion dry battery, TOW -tension accumulator and connecting cords. PRICE £20 :0 :O B.B.C. Tariff, 17/8 extra net. Obtainable fromall.ElectricalDealersandStores.

..- STERLING TELEPHONE & ELECTRIC Co.,Ltd., i = Manufacturers. of Telephones and Radio Apparatus, eta. E = (WHOLESALE ONLY) E F. Telephone House, 210-212, TOTTENHAM COURT ROAD, LONDON, Wzl. = Telephone:Museum 4144 (7 lines). Telegrams:" anemia Wesdo. London." g.. BIRMINGHAM: CARDIFF: MANCHESTER: N EWCASTLE -0 N -TY NE : WORKS: . gi 150. l'dmnrid Street 10, Ps*h Place. 14. St. Peter's Square. 21, Mosley Street. - Dagenham, Essex.

V MODERN WIRELESS November, 1923 IE:= HULL 0 CALLERS' PRICES ONLY. Hours of Business: CALLERS' PRICES ONLY. Every Day, 9 a. m. to 7.45 p. m. VALVES. Sundays, Having purchased 500 Valves Buy Best Goods at Low Prices. 10.30 a.m. to 1 p.m. Terminals (complete with Nuts). COSSOR, EDISWAN and WILLARD ORA doz. 1/3 Telephone, W.O. Pillar ... doz. 1/- Small Pillar doz. -/9 Switch Arm, 12 Studs and Nuts ... the lot-/10 from a firm giving up business Small Vario meters 250/850 Larger Variometers, 250/650 I offer same while they last at IgranicVariometer,Ebonite, 350/450 15/ - 2 -Way Coil Holders, for Duolateral Coils 6/8, 4/6

12/6 each 3 -Way Coil Holders, for Duolateral Coils ...6/11, 5/11 No Pcst Crdeis. French R Valves I I I Phillips R Type... Stop Pins with ,hculder a a ld, doz. -/5 Fixed Condensers to .001 RAYMOND'S Fixed Condensers to .005 Fixed Condensers to .006 1/8Variometer on Ebonite Valve Pins doz. -/6 Complete 13/-, VARIABLE CONDENSERS Valve Sockets ...... doz. -/9 2 4, 5 B.A. Nuts ... 3 doz. -/6 Assembled complete with Aluminium Basket Coils ... Set of 6 2/- Spade Terminals.. ... doz. -/4 ends, ebonite bushes, knob, pointer and Vario Couplers, with Knob ...... 4/11 Glass Enclosed Whisker Detector 1/6 flat bush (including screws). High-class Whisker Detector (large), enclosed 2/8 Fine Perikon, 2 Crystals, enclosed... 3/- Small Fenkon,1Crystals ... 1/8 .001 7'- Bell Wire, D.C.C., I.C. so yds. -/6 Twin Flex...... asyds. 1/7, 4 yds. 74.Transformer L.F.,12/4 .00075 6/- Plug Coils, Ebonite ... 1/-, -/9 and 15/ - Extra Quality, Otto on base 1/-, 1/3 .0005 5/- Pillar Terminals, Nut and Washer, 2 B.A., Large... 2 for -/6 Switch Arms -/9, -/10, 1/ - '0003 4/6 Filament Resistances 1/8, 1/10, 2/-, 2/3 !panic Resistances ... 4/6 .0002 3,9 !gram Vernier EnclosedDetector 4 Cats Whiskers, one gold Perikon, 2 crystals, 3/ - .0001 3/3 Single Basket Coil Holders whiskers2/6 2Crystals Variable Grid Leaks ...... 1/5 Whisker, 2/6. Vernier 3/ - Bretwcod Variable Grid Leaks, guaranteed 3 yews...... 3/ - Fin Terminals, ,crew pattern 11/3 Spade Terminals, screw pattern doz. ... 2 for -/3 Shaw's Genuine Herizite ...... -'9. 1/ - IL 40.( C.C.C. WIRE (including Reels). irr S.W.G. s lb. lb. lb. Grid Leaks and Condensers, .0003 ... ,.. ...3,'-, 2,3,2/ - Valve Sockets, wish shcu dsr 18 2/9.. 1/6 Basket Coils, Duplex Waxless ...... 5 for 2/- 20 3/- 1/8 -/11 3 -Way Coil Holder, 22 3/3..1/10 1/- 100,000 ohm Resistance 5/6, 6/6, 7/6. 1/2 Variometer on Ebonite, ball rotor, wound, D.C.C. ...9/11 24 .. 3/8.. 2/- Accumulator, 6 v. 50 amp. in handsome wood case, strap 26 .. 4/6.. 2/6 1/4 28 4/9.. 2,'8 1/6 Also 30, 32, 34, 36 stocked. Accumulators, 6 v. 60 amp., best make ... 33/- D.C.C. Wound Tapped Coils ...... ::: :i/-, 1/6AMR Fixed Condensers from L.F. INTERVALVE TRANSFORMERS. Double Phone Cards ...... pair-/9) Wound Coils, 12 x 4, best quality ...... 2/6 -10d. 5-1 Radio Instruments, Ltd. .. (1) 25, - Wound Coils, 6 x 3, best quality ...... 1/9 5-1 Igranic (2) ..21/- Aerial Wire, 7'22, hard drawn (subject to stock) ...so° ft.2/1 D.P.S.T. Switches, special (3) 15/- 5-1 Forms .. S.P.D.T. Nickel on Ebonite ...... 2/3 5-1 Raymond .. 12/6 D.P.D.T. Nickel on Ebonite ... 2/9Knob and Dial (Ebonite) Goods to UK the 1,- given on items a, 2, 3. 2 B.A. Rod, T2 in...... ;.for -31 1/6, 2/ - Basket Coil Holders, for 3 Coils 6/8 HEADPHONES. Plug and Socket, brass...... pair -/4 Fixed Condensers .01 ... 1/6 Raymond Lightweight:Phones, 4,000 ohins Pocket Lamp Batteries (best): ...... ::: 6 for N. and K., medium size, coo° ohms Special Filament Resistance sery fine value Sigde, very fine value, 4,000ohms. Igranie Coils, 25 upwards in stock. D.P.D.T. Nickel Switches for panel mounting. 3/ - Siede, grand for Crystal Bets,'8,000 ohms..- 16/11 Special ! Brunet, best type, 4,000 ohms .. 16/6 Lcud Speaker Receiver, 5o laminations each pole, fine value 18/11 4 v. 40 a. Accumulator, callers cnly...... 16 '6 H. T. Batteries...... 60 v...9 '6, 36 v. 41 All previous lists cancelled. Ebonite ValveHolder Hand Turned 1/-, 1/3.

:111111111111111111111141IMIIIIIIIIIWz RIGHT OPPOSITE RIGHT OPPOSITE 5. ==_ D ALY'S M. RAYMOND DA LY'S Ei GALLERY LOOR GALLERY DOOR 2: 27, LISLE STREET. W.C.2 . IIIIIIIIIIIIIIIIIIIlllllllllllllllllllllll dllllllllllllllllllllllllllllllllllllllll OPEN EVERY DAY 9 a.m. to 7.45 p.m.SUNDAYS 10,30 a.m. to 1 p.m. 0 ®r vi November, 1923 MODERN WIRELESS y.®

TESTIMONIALS. POST ORDER PAGE. Bampton Grange, Penrith, Cumberland. August 24, 1923. ONLY GOODS ON THIS PAGE, AND AT PRICES MENTIONED, ARE SENT BY POST " I am writing to tell you of the marvellous results from one of your 'oeo3 condensers pur-IN STRICT ROTATION AND AT EARLIEST POSSIBLE MOMENT. OWING TO chased some time ago.The signals wereTHE TREMENDOUS DEMANDS ON OUR MAIL ORDER DEPT., ITISQUITE wonderfully increased in volume, clarity and tone since I coupled the condenser to my set. IMPOSSIBLE TO GUARANTEE RETURN DELIVERY. Please forward sue your new catalogne."- Sincerely yours, N. Eastley. POST FREE U K. only. "Falsities," Church Street, Highbridge. RAYMOND'S August 24, 1923. Accumulators,high-class make, 4V. 40a. Sir,-On Monday lastI purchased at your Very Large Terminals,2 B.A. Nut and Washer 6 for 2/6 establishment a 3 -way coil holder for 6s. 6d. Valve Holders, Turned Ebonite,and nuts, each1/63 for4/ - I am delighted' with the quality and finish ofVariable Valve Socketsand Nuts, Plain... doz. 1/3 the holder and should like to take the op- Valve Sockets, with Shoulder and Nuts ... doz. 1/6 portunity of stating that although I have Variable Grid Leak studied your adver.s, week by week I haveCondensers Variable Grid Leak, "13reiwood " guaranteed 3 years3,6 hitherto refrained from sending orders as I Valves, Cossor, Ediswan, Multard ... each15 6 thought the prices Must entail " cheap and Duplex Waxless Basket Coils Set of. 5 2'8 nasty" stuff, which is dear at any price. gasket Coils, 6 in set, up to 3,500 ohms ... set 2/6 Now, however, I have a very different opinion. POST FREE Ebonite Coil Plugs,very best.Each1/3. 6 for6/6 -Yours, W. Chant. Ebonite Coil Plugs on Stand.Each1 '6 . 6 for7/6 Ebonite 2 -Way Coil Holders on Stand... IV-, 6/6, 7/- U.K. only. Ebonite 3 -Way Coil Holders on Stand... 7/-, 7/6, 8'6 Grove Mills, Heckmondwike. Ebonite Basket Coil Holders and Plug 2/2 Kindly forward me your new list of best Screw Spade Terminals,6 for1/- ... doz. 1/6 goods in stock.I previously had one of your Screw Pin Terminals, 6 for1/- ... doz. 1/6 valuable condensers and found same mostCompletely Assmbled with aluminium Variometers andKnob,Wound D.C.C., small ...each 3/8 satisfactory.-W. Sykes. endplates, 2fixingscrews,knob, Variometers and Nile%Wound D.C.C., large ...each 4/6 pointer, flat b ,sh, and ebonite bushes Ebonite Variometers andKnob,Wound D.C.C., Ball Rotor ... each10/- 81, Walsgrave Road, Coventry. Edison Ben or Igranic each August 28, 1923. Bell Wire I.C. D.C.C., 20 g.,rro yds...... 8,11 Sir,-My parts duly to hand this morning .0017/6 Bell Wire, I.C. D.C.C., 20 g.,55 yds...... 31- for which I thank you.With regard to the Twin Flexfor Leads, 12 yds...... 2/3 condenser and filament resistance, I consider .000756/9 Grid Leaks,2 mg...... 1/3 these excellently finished and splendid value Double Phone Cords ...... pair 1/4 for money.You will in due course have .00056/6 Dubilier Fixed Condensers, up to d0e05 ...... 3'- further orders from me and will certainly Dubilier Fixed Condensers, .00r to .006 ... 3 6 recommend you to my wireless friends.- .00035/4 Dub,lier Grid Leaks each 3 - Yours faithfully, F. R. Smith. Dubilier Anode Resistances, roo,000 ohms 56 .00024/6 100,000 ohms, Resistance, good 2 6 Parkview, Cumbemauld, By Glasgow. D.P.D.T. Switches, Nickel, OR Ebonite;small... 3 6 September 6, 1923. .00014/. S.P.D.T. Switches,Nickel, on Ebonite,small 2 9 Dear Sirs,-I receivedyourgoods,in Switch Arms, 1: -St,1:1 Studs and Nuts ... lot fulfilment of my last order a few days ago, and Vernier 3/9 Grid Leak and Condensers 3 must express myselfasbeing thoroughly Vernier Resistance " Igranic " satisfied with them.Your condensers in par- Filament Resistances, " Raymond " ticular are shillings cheaper than anything Filament Resistances,5 ohms ...... 2/3, 2.'6, 2/9 obtainable here, considering the quality,which, HEADPHONES. Filament Resistances, 7ohms 3/-, 4/6, 5/- to saytheleast,issurprising.- Yours, P otentiometers Igranic,7 ohms -. 7/6 Sipde, L.F. Intervalve Transformers, " Radio Instruments" 25/- J. Henderson. 4,000 ohms 14/11 L.F. Intervalve Transformers, " Igranic " 21/- Sipde,8,000 ohms.'...17/11 L.F. Intervals, Transformers, " Edison Bell "(square)25/9 Youngwoods, Alverthorpe, Wakefield. Brunet,4,000 ohms 17/11 L.F. Intervals, Transformers, " Form " ...15/9 October 4, 1923. LF. Intervalve Transformers, " Raymond " .. ...13/6 Dear Sir,-Ibegtoacknowledge safeB.B.C.Premier, very fine value, tight in (Above represent the pick of Transformers.) receipt of 3 variable condensers, etc., and to sayweight, no spacing rings, 4,000 ohms, Terminals --Phone, W.0, Pillar, Fancy ... doz. 1/9 Iconsider them remarkably good value.full of music, complete with headband When wanting furtheraccessoriesIshall All complete with nut and washer. certainly write you again- and recommendand cords your goodstowirelessfriends.- Yours 17/11 pair. truly, H. R. Haigh. The Simplex Broadcast Crystal Set. LOUD SPEAKER RECEIVER. THE MOST EFFICIENT, SIMPLE AND INEXPENSIVE rip, Coventry Road, Birmingham. 50 Laminations in each pole, with cord CRYSTAL SET MADE. RANGE, 200-600 METRES. WILL September 29, 1923. complete ... 18/11 RECEIVE ALL BROADCASTING STATIONS WITHIN Dear Sir,-I receivedyour goodsthis A RADIUS OF 40 MILES, USING TELEPHONES OF morning. Thanks exceedingly for your prompt AVERAGE SENSITIVITY, WITH A STANDARD P.M.G. attention.I am delighted withthe con-LOUD SPEAKER (Ampliondunr.), AERIAL. VERY FINE TUNING OBTAINABLE USING denser, it far exceeded my expectations and 54 /-. BASKET COILS OF VERY LOW SELF CAPACITY. in my estimation is much better than many(Subject to manufacturers' delivery). EVERY SET SOLD HAS BEEN TESTED ANDIS of the condensers now. on the marketat GUARANTEED. SIMPLE, CHEAPAND EFFSf,YENT, rrys. 6d.You may be sure thatIshall recommend you to all my friends and I hopeNAND K,Lightinweight, 12/6 per set. to place further orders with you in the course 4.coo ohms, pair ... 13/9 of a rest or am, yoursfaithfully, I.MacQueen. ALL PREVIOUS LISTS CANCELLED. Rightis reserved to return cash.

Dinittimmilintllininiuntim ,, ..,,,,,.,,, , i: RIGHT OPPOSITE M. Fi RIGHT OPPOSITE E, DA LY'S RAYMONDDA LY'S GALLERY DAR 27, LISLE STREET, W.C.2 E. GALLERY DOOR g. E11=11211=1 vii MODERN WIRELESS November, 1923

Comfreivfs Page Editorial ... 59 Regular Programmes 60 The Coast Dweller's Crystal Set... 61 By G. P. KENDALL, B.Sc. In Passing ... 64 The Transatlantic Receiver...... 66 Editor : By PERCY W. HARRIS, Assistant Editor. Scientific Adviser: What to Do with Two Valves 72 Prof. G. W. 0. Howe, JOHN SCOTT-TAGGART, ... F.Inst.P. By JOHN SCOTT-TAGGART, F.DISI.P. D.Sc., M.I.E.E. The All -British Wireless Exhibition ... 75 Advisory Editors : Joint Assistant Editors : A Note Magnifier for the All -Concert Receiver... 80 By PERCY W. HARRIS, Assistant Editor. Prof. R. WIIIDDINGTON, PERCY W. HARRIS. M.A., D.Sc. E. REDPATH. Rhythmic Beat Time Signals ... 83 By A. HUGHES BARLOW. Prof. C. L. FORTESCUE The Licence Question-A Settlement at Last ... 85 MA., M.I.E.E. Staff Editors : The Official Statement Issued by the Postmaster -General 86 E. H. CHAPMAN, If Advertisement Managers: How to Make a Portable ST100 Receiver 88 M.A., D.Sc. By JOHN SCOTT-TAGGART, F.Inst.P. SCHEFF PUBLICITY A. D. COWPER, M.SC. ORGANISATION, LTD., G. P. KENDALL, B.Sc. The Construction of a Heterodyne Wave -meter 91 5-5, Pall Mall, London, By ALAN L. M. DOUGLAS. R. W. HALLOWS, M.A. S.W.T. Single Layer Inductance Coils 99 S. G. RATTER. Tel 244o. A Reunion... 100

New Books... 102 Ia From a Reader 103 Some Causes of Weak Reception ... 105 By R. W. HALLOWS, M.A. Practical Notes ... 109 Tested by Ourselves 113 Above and Below the Broadcast Wave -lengths ... 114 Radio Society of Ireland... 117

For Crystal Users ... 118 eft JUNIOR WIRELESS. MODERN. WIRELESS ReccliniVreseiC41 All correspondence relating PUBLISHERS OF WIRELESS WEEKLY Nothing contained herein tocontributionsistobe istobe regarded as per- addressed to the Editor of D EV E R EUX COURT. mission or encouragement " Modern Wireless." to infringeany patent ST RAND.W.C.2 rights.

viii November, 1923 MODERN WIRELESS

AT long last the air has cleared and the ST zoo, containing all the batteries in a case home constructor knows exactly where with the receiveritself ;while distributed he is with regard to the law and his throughout the book are numerous construc- duties to his fellow -countrymen.Whilst the tional notes, hints and tips which will help to Postmaster -General's compromise-foritis simplify the work of the true home constructor. truly a compromise-has by no means satisfied We would like once more to draw attention everyone, at least it places broadcasting on a to the fact that the circuits and apparatus far more sensible basis than heretofore.It is described inthis magazine areessentially only fitting that our first number under the practical. The descriptions of sets are written new system should be a special constructor's and the drawings and photographs made from number, and we feel sure that readers will be apparatuswhich hasbeen carefully con- more than satisfied with the fare we have to structed from materials and with tools readily place before them.For the benefit of those available to every experimenter, and where new listeners who are situated in the Bourne- special problems have been met with in the mouth and Aberdeen areas and within crystal construction of the sets these are elucidated. receiving range of Newcastle, we are describing Only inthis way can the home constructor be a special crystal set with which has been truly served. incorporated a wave -trap to give the necessary Now that the constructor's licence has been selectivityintheseparts.Listenerstoo definitely settled, may we enter a plea for the frequently complain that they are unable better standardisation of radii) parts ?At the satisfactorily to hear the broadcast concerts present time much difficulty is experienced from owing to " jamming " from ships, and the set the fact that so many parts are different in in question should go far to remove the troubles ways which prevent the constructor substi- of the seaboard listener.For the more ex- tuting one for another.Take, for example, perienced experimenter we have the remarkable the plug-in type of intervalve transformer. and highly sensitive three -valve receiver to What is more natural than that an experimenter which the name " Transatlantic " has been should desire to compare the relative merits given ;for the man who wishes to get further of various makes of transformer ;yet, although strengdi with his set so as to operate a loud - all these transformers are mounted on stan- 'speaker we have the Single -Valve Magnifier dard valve bases, there is no standardisation described on another page.The experimenter whatever in the manner of connecting the with leanings towards accurate measurement primary and secondary windings to the pins. in his work is catered for by the provision of an For this reason only certain makes can be article describing how to make a heterodyne used unless the wiring is -changed each time wavemeter ;the man who wishes to carry his the change of transformer is made-quite an set about with him isgiven the. portable impracticableproceedinginmost cases.

59 MODERN WIRELESS November, 1923

hearagreatdealof the activities of the when trying out new circuits itis essential National Association of Radio Manufacturers, that we should be able to rely upon insulation. popularly known as the N.A.R.M. Surely The sale of inferior ebonite, while it may bring they candosomethingtowardsproper quick profit to the dealer, does an immense standardisation of parts without the necessity amount of harm to the trade, for the inex- of manufacturers losing their individuality in perienced constructor will often blame a first- the process. quality component for faults which, did he but One more point :it is high time that ebonite know it, arise from ebonite used to carry this was properly graded for sale.At present one part. A suggestion was made some weeks buys a sheet of a black substance the insulating ago in Wireless Weekly that ebonite should be qualities of which must be taken on trust.In sold plainly marked on one side with the comparatively few cases do we know who is%maker's name and an indication of its quality. the actual manufacturer, and not one ex- We believe that at least one firm is taking steps perimenter in a thousand isin a position to issue such ebonite, and otherfirms will properly totestthe insulating and other doubtless follow suit. properties of his ebonite panel.Particularly THE EDITOR. 000DOODE000000001100000000000000000000000100000000000000000000000=00C01 0 0 0 0 El REGULAR PROGRAMMES FROM BRITISH ANDo o Ci FRENCH BROADCASTING STATIONS oo o o o (Times in Greenwich Mean Time.) a o c000moopoomonomoomoopoomoom000Docoom0000m000moopoom000000nooDo GREAT BRITAIN. PARIS, RADIOLA. (1780 metres.)

Station. Call Wave- Weekdays (daily). Sign. length. Times. 11.30 a.m.Information (Cotton Exchange, Cardiff 5 WA353 3.3oto,4.3op.m. Havre, Liverpool, Alexandria). ... 363(except London) and London 2 LO 11.40 a.m.Concert. 2 ZY 3705.0,p.m.to10.3o Manchester... p.m. London (day 4.o p.m.Commercial information. Bournemouth6 BM385transmission)11.3o 4.10 p.m.Financial information. Newcastle...5N0400a.m. to 12.30 p.m. 4.2o p.m.Concert. ...5 SC Sundays. Glasgow 415 7.45 p.m.News. B rmingham5 IT 4208.3o to 10.30 p.m. London also 3.0 p.m. 8.o p.m.till 9.0 p.m.Concert. Aberdeen...6 BD 495to 5.o p.m. Thursday, 8.45 p.m. till 9.3o p.m. Dancing Note. -Thesewave -lengths may be altered concert. shortly. Sundays. FRANCE. 1.o p.m. till 2.o p.m.Concert. PARIS,EIFFEL TOWER. (FL,2,600 metres.) 7.45 p.m.News. Weekdays (daily). 8.o p.m.till 8.45 p.m.Concert. 6.4 a.m.Meteorological forecast. 8.45 p.m. till 9.3o p.m. Dancing conceit. 11.15 a.m.Meteor. forecast and time giving. PARIS.SCHOOL OF POST AND TELEGRAPHS. 2.0 p.m.Financial bulletin. (450 metres.) 5.10 p.m.Concert. 6.2o p.m.Meteor. forecast. Tuesday and Thursday. 1.15 p.m.Meteor. forecast. 7.30 p.m.Concert. Sundays. And very frequent radiophone transmissicns 5.10 p.m.Concert. of plays (comic operas). 6.2o p.m.Meteor. forecast. LYONS. YN, 3,100 metres. Other concerts specially announced from 9.45 a.m.Concert (gramophone). time to time. 2.35 p.m.Financial news.

6o November, 1923. MODERN _WIRELESS

00000000000000000000000000000000000000000000000000000= - = f!DE.10000=00000000000 O 0 0 ID O THE COAST -DWELLER'S CRYSTAL SET O 0 nO By G. P. KENDALL, B.Sc., Staff Editor. o O 0 0 Residents in the Bournemouth, Aberdeen, Newcastle and Cardiff areas are frequently tioubled with ship0 0 0 D jamming.This set will enable them to eliminate such interference. 0 Li 0 000000000000000000000000000000oommom000qopow0000morinnrinGanommoz,-E- ED

TH conditions of reception inmeritofnoveltyandinterest. Percy W. Harris in MODERN WIRE- and around the new broad-Moreover, there remains much toLESS. A trap unit is incorporated casting areas' of Aberdeenbe learned of their possibilities,which can be used as either a series and Bournemouth seem to be such and a great deal of most interest-absorber or a parallel shunt, and a as call for the adoption of someing experimental work can be doneswitching arrangement is provided special method of interference re- upon them with the aid of veryfor cutting out the trap circuit duction. In both districtsdiffi- simple apparatus. when it is not required, this last culty occurs in broadcast reception The receiver which is about tobeing desirable in view of the fact at times as a result of the inevitablebe described represents afairlythat the inclusion of the trap in interference by " spark" stations working on 300, 450 or boo metres, since the stations in question may often be very close to the receiving station and use a good deal of power. The elimination of such interference may be attempted by two chief methods, namely, by usinganultra -selectivecircuit, such as a loose -coupled tuner, or by incorporating some formof rejector or filter circuit in the receiver as a more or less separate uni t. An inductively coupled tuner is, of course, capable of reducing interference to a great extent, but it Fig. 1.-A planview of the finished set. complicates the operation of the receiver, and does not seem tosuccessful attempt to apply the circuit usually produces a reduc- appeal to the average constructor. wave -trapprinciple to a simpletion ofsignal strength-only a The devices now known as " wave -crystalsetofthesingle -circuit slight one ifthe wave -trapis traps,"on the other hand, aretype.No claims are made that it properly arranged, but nevertheless capable of producing a more com-is new in principle, but it seems to to be considered. pleteeliminationoftheinter-be the firstpractical set to be The trap circuit consists of a ference, enable the controls of the.designed and built for the express coilandcondensercapableof receivertoremainofafairlypurpose of using the eliminating covering the broadcast wave -band simplenature,andpossessthecircuits recently described by Mr. and extending upwards to -boo metres.Wound directly upon this coil are six turns of wire, which serve to couple itto the aerial circuit by connecting them either in series or parallel with the main tuning unit.In series we have the form of trap kno%yn as " type B," " type C " being the parallel connection. In type B the trap circuit is tuned to the wave -length of the interfering signals, and acts as an absorber, allowing the signals of the desired station (to which it is not tuned) to pass it by un- absorbed. This type seems to require a fairly considerable difference between the desired and undesired wave -lengths to function efficiently, but, given that, it gives very satisfactory elimination with ig,2.-A view showing the internal artangonent of the receiver. little loss of signal strengths 61 MODERN WIRELESS November, 1923 Type C, on the other hand, will separatesignalswhosewave- lengthsare verycloseto each other, but is prone to produce a more noticeable reduction in the strength of the desired signal.It is consequently a matter for experiment to determine which of these two types is more suitable in a given set of conditions, and accordingly the wiring diagrams show how either type can be connected upinthereceiverillustrated. Both types should certainly be tried.The circuit of the set when using type B and type C is shown in Figs. 3 and 5. The construction of the receiver Fig. 3.-The circuit when type B wave -trap is used. is a fairly simple matter, all the partsbeing mounted upon anthe telephoneSused,and itis presenceofthismetallicobject ebonite panel measuring 41 in. bypossible that some makes require aright inside the field ofthe coil to in.and in.thick. Thecondenser for the best results. would haVe harmful effects, but crystal receiver proper consists of The knob and dial on the rightcareful experiments with and with- a variometer of any good makeare thoseof the variablecon- out the rod failed to show that it and a crystal detector, these partsdenser in the trap circuit, whichhad the slightest effect upon either being clearly shown in the photo- should have a capacity of 0.0003 the strengthof signalsor the graphs.Immediately in front ofThe coils constituting the wave -efficiency of the wave -trap as such, the crystaldetectorisa smalltrapare wound uponapieceandthereforethisverysimple switch, whose function is to cut ofebonitetube 2f in.india-method of attachment was adopted. the wave -trap out of circuit whenmeterand 4 in.long,attached The wave -trap winding consists not wanted, as shown in the cir-to the panel in a manner which isof No. 28 double -cotton covered cuit and wiring diagrams. Anymade fairly clear by the photo-wire, 75 turns being the number suitable small switch can be used,graph of the underside of the set.adopted. The actual number of but the miniature type illustratedA piece of 2 B.A. brass rod isturns adopted appears to have a is recommended. Its connections in attached to the panel either byconsiderable effect upon the be- the type C wave -trap should beinserting it in a tapped hole or byhaviour of the trap, and it is here carefully noted and copied. using two nuts, one above and onethat much further experimenting At the left of the panel are the below the panel.This passes upis needed.The number quoted is aerial and earth terminals, and onthe axis of the ebonite tube, andone foundtobesuccessfulin the right are those for the tele-an ebonite cross -piece measuringpractice, but it is probable that phones. Theselatterare,not 31 by i byin. is slipped on tootherratiosof inductanceto shunted by a telephone condenser, the projecting end, and a nut iscapacity would be found by a since I have failed to observe anyscrewed down after it, thus causingpatient experimenter which would improvement in results when usingit to clamp the tube firmly againstgive even better results. Deter- one in this or any other crystal -the panel. minations of thissort,however, set.This probably depends upon It might be expected that theare somewhat laborious to make,

Fig. 4.-The wiring for type B wave -trap. 6z November, 1923 MODERN WIRELESS sinceeachexperimentinvolves winding a new coil, tappings being out of the question on account of thepeculiar dead-endeffects which they introduce into circuits of this sort. The coil coupling this to the aerial circuit consists of six turns of %.1 No. 20 gauge double cotton -covered wire, wound directly on top of the firstcoil,inthecentre. This winding can be seen in the photographs, and its connections will be made clear by the wiring diagrams, in which it is marked " primary." (The coil of 75 turns is marked " secondary " in these diagrams.) Fig. 5.-The circuit for type C trap. The ends of the 75 -turn coil were secured by passing them through desired signals and acts (apparently) aidofwhichever ofthe wTr'ng holes inthe ebonite tube, -andasarejector to them, causingdiagrams is chosen, and should be those of the 6 -turn winding bythem to pass through the receiver.done with tinned -copper wire of means of tape loops, whose endsUndesired signals, however, passNo. i8 or No. 20 gauge, all joints are passed under the turns andthrough it fairly freely, since theybeing carefully soldered. Since the pulled tight in the usual way. are of a different wave -length and wiringisextremely simple and The choice of the above -men-are thereby shunted past the re-all connections are well separated tioned sizes for the wire was theceiver proper without affecting it.from each other, it is quite un- result of a certain amount of ex-.For thisreason,ofcourse,thenecessary to sleeve them in systo- periment, and seems to providesetting of the condenser to elimi- flex. It was done in the case of something like the correct amountnate a given signal will be differentthe receiver illustrated simply and of damping in the wave -trap coil.with the type B and type C circuits. solely to make the wiring plainly This choice had to be somewhat ofWith type B, it must be set to tunevisible in the photograph, which a compromise, however, since thethe trap circuit to the wave -lengthend can always be achieved by the coil had to be designed as to func-of the undesired signal, and will,use of white systoflex. tion with reasonable efficiency asrequire slight alteration for elimi-. The actual dimensional lay -out either type B or type C trap.fisting different 600 -metre stations,of the panel is not 'given in con- Actually, a fair amount of damp-while with type C it is required tonection with this set, because. the ing is desirable in type B, whereastune the trap to the wave -lengthexact positions of the holes must, type C works best with low damp-of the desired signals, so that allbe dependent hpon the make of ing. The reason for this will beothers will be by-passed. Withthe components, and it was not understood whenitisremem- type C, then, the condehser once.desired to specify that the latter bered that type B is tuned to the set will not "require readjustment, -should be of any particular brand. wave -length of the undesired signalwhatever the wave -length of theSo long as the general arrange. and works by absorbing it, whereas interfering signals. ment indicated "in the illustrations type C acts upon a different prin- The wiring ofthe set can be ispreserved, satisfactoryresults. ciple ;this last iStuned to thefollowed out quite easily with theare assured.

Fig. 6.-The wiring of the set for type C trap.

63 MODERN WIRELESS November, 1923

, 7...!! ,.: 4,4.,,4111 aSsirv.

"..."11.

The New Bootlegging duties of valves, a horrid awaken-career would, I think, be a short WIRELESS men acrosstheing awaits the purchaser.Beingone in this country, for we wireless Herring Pond are suffer- made of inferior stuff their filamentsfolk are a hasty lot, having much ingsorely,Isee,from eat current at prodigious rates, onlyto try our tempers. bootlegging.By thisIdo notto snuff out after a few hours of mean that they are being deprivedwork.Then Habakkuk P. Blinks, All that Glitters of the sustenance that is needed or Zerubbabel K. Hertzheimer, or It happened not long ago that during the long nightly vigils whenwhatever the luckless buyer's namethe Bliggstreets, our local nouveaux they listen in eagerly for signalsmay be,shootsglancesoffire riches, installed in their palatial from distant quarters of the globe.through his horn -rimmed specs.,home the most wondrous of wireless No, the trouble is not here.It is tearstuftsfromtheluxuriantsets.It lived in a gorgeous mar- something far more serious.Thegrowth upon his head, and screamsquetry cabinet " embellished " with bootlegging of spots of comfortaloud in a terrible voice :" Boot-all kinds of amazing twiddly bits in having become so profitable that itlegged again, b'gosh I " wood, brass, ivory, and, if one is to now stands at the head of American believe Mrs. Bliggstreet, solid gold. national industries it is not surpris- This Freedom The cabinet was in fact a kind of ing that the fertile brains of Uncle America may be the land'of thecross on a small scale between a Sam's children should have led them free, but if this be freedom thenGothic cathedral, a Japanese temple to branch out in other directions inthank all the powers that we knowand a Turkish mosque.Within their pursuit of the nimble dollar.it not.Fancy what it would bewas a marvellous array of valves. The latest field for the bootlegger's, like if on going to buy an. Ora you Its owners averred that it was that isto say the law -dodger's,had to " moisten the Anger and seethe most expensive set that money activity is in the manufacture andwhether the white trade mark im- couldbuy.Inthisthey were

sale of spurious valves: pressed upon the glass would rubprobably right, but they omitted " BewaretheBootlegRadio off."Pictureyouranguishif, to mention also that it was .one of Tube " screams a big headline inwithout warning, shops of the baserthe worst.Never have I heard one of their papers, and the en-sort were flooded with dud valvessuch excruciating sounds as those suing article goes on to show howlooking for all the world like thebelched forth by the loud speaker extensive are the activities of the genuinearticle.Wouldlifebe cunninglyincorporatedintoits newest type of criminal.It ap-worth living if you had done in economy.You may -have heard pears that in the City of Newark,thirty bob on a peanut that atewhat thoroughly bad transformers New Jersey, alone there exist illicitabout an ampere of current ? can do on an ill -designed set ;you factories that are turning out no If you are the man I take you tomay know probably how vile music less than 3,50o counterfeit " toobs " be you would straightway conveymay sound when brought in by a day, whilst another 2,000 a daythe thing back to the criminal whooscillating valves ;you may have are produced in New York.The sold it to you ;you would beatsampled many of the horrors of bootlegged articles are perfect imi-him about the head with yourdistortedreception. Butthese tations of U.V.201A's, " pea-stoutest walking stick, then youthingsareas nought compared nuts " and a host of well-knownwould make him swallow it-thewiththe ghastly noises poured valves ;perfect, that is, to the eye,'valve not the stick-whilst tellingforth by the three hundred guinea but when they are installed uponhim exactly what you thought ofDulcivox when Mr. Bliggstreet has thesetto perform the properJim. The valvebootlegger'scleared its decks for action. November, 1923 MODERN WIRELESS

How the Party Went Off where languid young demonstrators allbroadcastingstations. His " I like plenty of noise, m'lad,"who ought to know better spendproud words do not take you in ; he says, cheerily, and he gets it.their time in making the sets underyou know that you are listening to Speakers all seem to have swallowed theirchargeproduce. enormousone of the most amusing forms of potatoes of the largest size, singersvolumes of dreadful noise, insteadwireless swank. Heprobably crack on every other note, orches-of in adjusting them so that theycould not distinguish with cer- tras appear to consist of playersare really worth listening to. tainty between God Save the King who have omitted to tune their in- and Yes, We Have No Bananas if struments, the piano resembles a On the Best Authority his musical ear were put to the test. hamstrung banjo,the violin an Yearsagothecharmingin- It is not fine programmes that his amorous Thoinas Pussy's serenadehabitants of Southern France had asoul craves for; he wants you to

to his lady love. terrible reputation for drawing thesay to yourself, " Now here is a It was unfortunate, perhaps, thatlong bow as no other men couldman with a set that is really worth the Bliggstreets should have chosen draw it.This, however, was en-calling a set." to turn on this atrocity on thetirely unjust, as the author of a Inyourwirelessyouth you night when they had a large party famousworkhasabundantlyprobably took him athisface in order to lionise Signor Strom-proved ;he has shown that it is value,butasyou growmore bonelli (ne John Gupp), the violinist, merely the result of the cheeryseasoned and gain experienCe of the whose playing was the rage of the effectof the bright sunshine oflittle ways ofradiomaniacs you musical world.The maestro lis-those parts.which makes them viewread him like an open book.And tened with horror in his eyes andeverything through slightly am-the funny thing is that he knows all sagging jaw to itsfirst raucousplifying spectacles.Here is a storythe time that you don't believe a notes ;then he turned a mute gazethat comes from Tarascon and may, single word of what he is saying. upon his hostess, .as who shouldtherefore, be accepted as absolutely The " Oh, I never think of using say :" What the blank,blank, true. that station "'attitude is, however, blank isthat instrument of tor- An ancient farmer went to thean excellent one to impress be- ture ? "" Oh,don't you thinkvillage telephone one morning toginners who are getting a little thiswirelessisjustsplendid," give an order to the stores in theuppish.Have you not found it gushes Mrs. Bliggstreet" there'sbig town.On his return he gat so ?Ihave.Be sure,though, nothing like it for making a partyhim to his pigstyes whilst Madamethat they are beginners. go off ! "" It's making this partyhis wife was busy in the garden. go off, anyhow," screamed the soul - High above their heads, so high Insults stricken man of music, who fled that it was a mere unnoticed speck, incontinently fromthe room, sailed an aeroplane.Filled with The quarrel that I havewith seized the first hat he saw in thethe cheerfulness that the southernmany wireless books is that they hall and strode out into the nightsun inspires, and unmindful of theare written by supermen to whom weeping the salt tears of a brokenfact that he carried cargo, the piloteven the most abstruse things are man. proceeded to loop the loop fromas plain as the proverbial paint. Abominations sheer high spirits.Out fell a par-Having conducted you through the firststagesof an argument by Quite seriously, why are so manycel which landed with a resoundingmeans of a bewildering mass of people content with sets that arethud just at the old lady's feet.figures intersperSed with cryptic anything but a pleasure to listen to ? " Say, then,Jean," she shrilled, signs they finish you off by saying: A good set is a joy for ever, bring-" the boots that thou didst order" It will thus be obvious (note the ing in speech and music withoutare arrived already by wireless " ! insult of that obvious) that this a sign of roughness or distortion ; The Radioswankist resolvesitselfintothesimple but a bad set that is being forced, (anotherinsult)formula made to produce the largest possible I always rather love the man volume of sound without any re-who professes to have a soul above v/cos 23 /9 tan 4 oc - gard to purity or smoothness, is thethe " tripe served out by the local moon's age kind of thing that I would like tobroadcasting station," and seeks see yoked like the Ancient Mariner's his amusements from others fartherin seconds; or something of that albatross to the neck of my worstafield, at home, or even on the,kind. foe, with its phones locked about hisContinent.You know the kind of Then you fling the book into the ears,its filaments glowing theirman I mean.Whenever you askfire and resolve that spillikin4 is a brightest and crackliest, and itshim how things are going he is atfar more elevating pastime than high tension voltage gingered up great pains to explain that having wireless.Yes, ours is a thorny path almosttoburstingpoint.Noa musical soul he cannot standand we are, indeed noble fellows viler thing exists. the programmes,butto follow it as we do. Yet you may see it and hear it always makes use of those of atits worst in many a saleroomthe latter being the most remote of THE LISTENER -IN. VISIT THE " RADIO PRESS " STAND AT THE ALL -BRITISH WIRELESS EXHIBITION

63 II OD_ERN WIRELESS November, 1923 0C100000=000001300000000130001;10000131200000000000000000000000000000000:9 0 THE " TRANSATLANTIC "RECEIVER H oD Two Stages of Tuned High -Frequency 0 By PERCY W. HARRIS, Assistant Editor. o B With this remarkable receiver no outdoor aerial, earth, indoor aerialor frame is 0 required to receive broadcasting up to eight or tin miles from n broadcasting station. oo With an outdoor aerial it brings in all the broadcasting stations without resort to critical D reaction.It is admirably suited to listening for. Transatlantic telephony, and- on a 013 Ducon or indoor aerial it will often bring in all British stations with ease. 8 OCIDOODOODOCIDODOODOODOCIOCCEIDOODEIDOMOODOODOEICIODOCIECODOCIDOODOODOODOODOEll

THE value of high -frequencybe added to existing sets. Un- cabinetcontainingtwofurther amplification in a wirelessfortunately, it is exceedingly diffi-'valves as note magnifiers. The receivercannotbetoo cult to design good high -frequency,set will then "be a five -valve set strongly emphasised. amplifiers, for there' are so many with two H. F. detector and two For long distance reception, we problems connected withthe-note magnifiers. I am calling it seed some arrangement of valve orefficient working ofthese devices the " Transatlantic receiver " be- valves which will magnify the in- that few multi -stage high -frequency cause itwillsuit those readers ooming currents to a point whenamplifiers are ever brought to awho are anxious to listen during they will pass the detecter valve.state of perfection. the coming winter to the concerts broadcast from the United States. The handling of th,is set, as will be explained later, is a little different from the ordinary receivers, but the degree of amplification obtainable on weak signals is surprising. It is, of course, possible to receive allthe broadcasting stationsin thiscountryquiteeasily,and, indeed, they have all been received with this set on a " Ducon." On an outdoor aerial the reception of British broadcasting is decidedly improved-good quality speech and music coining through from all the stations without that recourse to the last ounce of reaction to bring them in. For this reason distant music and speech is far purer and less distorted than is possible with any ,receiver containing only one stage of high -frequency amplification. Let us describe the set in detail. It contains a socket for a plug-in aerialcoil,threeterminalsar- ranged with a strap between two of them, so that the tuning condenser can be placed either in seriesorinparallelwiththe inductance, a .0005 variable condenser for tuning the receiver, two The complete instrument with valves and transformers in place. plug-intransformersaccurately tuned with a .00025 IX variable Once they are sufficiently. magnified; The present receiver is an attemptcondenser and three valves of the we can add low -frequency stages orto obtain efficiency in high.frequency low capacity type.The whole note magnifying valves, and obtainamplification without theusual ofthe apparatus iscarried on any. degreeofstrength we cancomplication ofadjustment.Itan ebonitepanel12 inches by reasonably require. - That many consists, as the photograph shows, of 8 inches, which can be supported amateurs realise the necessity ofa cabinet containing the tuner andin any kind ofcabinetdesired. high -frequency stages for long dis- three valves ;the first two actingI have placed mine in a sloping tance reception is shown by theas high -frequencyamplifiersand front cabinet whichIhappened number of requests we receive tothe last as a detector. In nextto have on hand and which suits describe how furtherstages-of month's MODERN WIRELESS I pro- this- verywell. Thereis,of high -frequency magnification canposetodescribeacompanioncourse, no reason why the panel

66 November, 1923 MODERN WIRELESS plate voltage than in the present set, it ako makes an exceedingly good high -frequency amplifier. Thesevalves, unfortunately, are much more expensive than the ordinary four -pin type.Mullard's, however,makealow -capacity valve with a similar mounting, but slightly larger, known as the " Ora B" which costs only x5s. 6d. The spacing of the clips. for these however, requires to be slightly greater. Thus by careful wiring and the use of low capacity valves and sockets, the coupling between stages is reduced to the lowest possible figure. In passing it' may be stated that the " neutrodyne " receiver is designed with neutralising devices to stop this tendency toself -oscillation, but it is not a very easy instrumentforthe beginner to make, and will not be dealt with here. The tuningdifficultyIhave overcome by using a special form of condenserfortuningthe two high -frequency stages. This consists of two variable condensers on the same shaft, the two con- densersbeingveryaccurately matched so as to have the same capacity and all adjustments from zero to Maximum. The one used was made by the Marconi Scientific Instrument Co., and the two con- The set with valves, coil transformers removed to show construction. densers have a capacity of .00025 each-quite a nice valve for tuning should not form the top of a box inhigh -frequencystages. The in the manner used in so many commercial sets. In designing the set with two stages of h gh-frequency, I knew I should be " up against " the old problem of self -oscillation, and I naturally took steps to reduce the tendency to this self -oscillation to the lowest possible point. The layout of the parts is such that the wiring is the shortest possible, and thecouplingbetween gridand platecircuitsarisingfrqmthe closeness ofthe valve pins and leads, in the usual four -pin valves and sockets, is avoided by using the type of valve shown.In these instead of the leads from the filament, grid and plate being brought through the base of the valve, they are taken through the ends and sides well apart from one another, and the clips between which these valvesaremountedalsowell spaced.The two first valves used forhigh -frequencyamplification are V 24's,while the detecting 'he wiring is very simple and short, so as to avoid unwanted valve is a QX, this latter being interaction. The two Igranic resistances are joined by a speciallydesignedfordetection, soldered wire on the frames, and not on the usual terminals. although when used with a higher This keeps the wire clear of the condenser vanes.

67 MODERN WIRELESS November, 1923

Fallonpeoplehavealsojustvalves, and in 'let when designingis shown immediately below the placedasimilarcondenseron a receiver with reaction,Ifre-plug-in coil.As Iestimated in the market, which will suit thsquently connect the grid of the high -designingtheset,only a very receiverquitewell. This con-frequency valve to the positiveslight positive bias is requisite to denser would of course do to tuneleads and make up for the lossescheck the self -oscillation, and as two tuned anode coils, but whenso introduced by reaction.In thethe slider of the potentiometer is we use tuned anode amplificationpresent case Idecided to use aconnected to the grids of the two it is necessary to have grid leakspotentiometer for the accurate ad-h.f. valvei, we can adjust matters and intervalve condensers, whichjustment of just the positive vol-very nicely. Reaction, then,is add slightly to the complication oftage required. adjusted on the potentiometer and, the wiring.The transformer coup- Theprincipleupon which aas we shall explain later, on the ling makes the wiring extremelypotentiometer operates in such afilament resistances. short and simple-naturally one ofset does not seem to be clearly A word now regarding the ar- the points I was aiming to achieve.understood by all readers.If werangement of terminals on the left- The observant reader -will haveconnect the grid of a valve to thehand side of the instrument. I noticed by this time that therepositive lead of the battery, therewas anxious to avoid all switches are no terminals or seeming pro -will be a positive bias on the gridin this set, for wherever we intro -

A "close-up" of the back of the panel, showing the double condenser. visionfor reaction in this set.depending upon the voltage of theduce switches we must have com- In designing this receiver I aimedlow-tension battery. If we con-plicationofwiring. Forthis that inshort wave work therenect it to the negative lead, there reasonIhope readers will not should be no necessity for them.will be zero voltage on the grid.write to me, and ask for a new I hoped in the design so to arrangeIf now we connectacrossthediagram with switches to cut in or the parts that the receiver couldpositive and negative leads from out the stages of amplification used. be kept just off the point of self -the accumulator a high resistanceIf we were tointroduce such oscillation so that the maximumof several hundred ohms, arrangedswitches into the present set, we reaction should be usable at will,so that a slider can run along thecould not possibly have the sim- and expected that if I took all thetarns, when the slider is pushed overplicity of wiring and consequent precautions enumerated and con-to the negative side, we shall havereduction of the tendency to self - nected the grids of the first twoas before zero voltage, and when oscillation.The wiring, too, would valves to the negative lead of theto the positive side, the positive" unbalance "the two high -fre- battery, the set would just oscillatevoltage mentioned. Between thesequency' stages, and it would prob- when the two stages were tuned totwo points we can set the sliderably not be so easy to tune two one another.This proved to beso asto give a very accuratestages on the one condenser. the case, the oscillation not beingadjustment of grid voltage any- IbelieveIwas thefirstto very violent.Now we can checkwhere between zero and the maxi-introduce the three terminal method self -oscillation by putting a smallmum. Such a potentiometer isfor obtaining series, and parallel positive bias upon the grids of theconnectel in this set, and its knobconnectionoftheaerialtuning

68 November, 1923 MODERN WIRELESS

F AERIAL COIL A H.T+ 0-P0 OLP

110 0.5.

E2 LT+

()A POTENTIOMETER

O TEL

TEL+

H.P.TUNING Il.F.RHEOSTAT CONDENSER DETECTOR RHEOSTAT AERIAL TUNING CONDENSER.

Arrangement of terminals, etc.

condenser. It is a very simple 2setsof valve sockets for held is quite suitable here, the arrangement, the wiring for which plugging - in the trans- leak being left in the clips). isscarcely longer than for the formers(Istrongly advise; I fixed condenser .002 µF. ordinary fixedparallelor series youtousethe separate' Ifixed condenser .oi pY or

arrangement.The two upper ter- legshereandnotthe larger (in the particular re- minals are connected by a strap ; ebonite -cased sockets usually ceiver described I used the the aerial being always connected supplied, as we want to get Dubilier type 577 which is to the top terminal. ' If now we the minimum capacity be- very convenient for panel keep the strap closed and connect tween the legs, and we shall mounting,butaMans - the earth to the bottom terminal, get this by drilling the panel bridge up to i tiF would be the condenser will be in parallel to take four separate sockets just as suitable if you can with the aerial tuning inductance. in each case.There is then find room for -it). If we open the Strap and connect a minimum of ebonite be- quantity of No. 18 bare - the earth to the middle terminal, tween the legs). tinned copper wire for wir- then the condenser will be in series. fixed condenser, 0.0003 IX, ing up. How to Build the Set and grid leak 2 megohms pair of plug-in transformers. (theDubiliertypewith Note.-The plug-in transformers To build the set we shall need clips in which the leak is must be matched. It is useless ua- the following components :- I ebonite panel, 12 inches by 8 by 1 inch thick. 9 terminals. i socket for plug-in coils. variable condenser, 0.0905 ei kiF capacity. double condenser, the two parts being each of .002 or .00025 µF capacity. i potentiometer. 2 filament resistances (it is not necessary to have three, as the two high-frequencyvalves can be controlled from a common resistance). 3setsofclipsfortubular Full-size drilling diagram for the valve clips for V 24 and valves. QX valves. Ora Bvalveswill requireslightlydifferent . i potentiometer. spacing.

69 MODERN WIRELESS November, 1923 less they are both of exactly the Laying Out the Panel cardboard of the exact size of the same dimensions.For this reason . Before youactuallypurchasepanel you will require, and mark they should both be of the sameyour panel, obtain all the otherout the holes for the various com- manufacture.Those shown werecomponents and lay them out onponents.You will probably want made by Messrs. McMichael, Ltd.,a sheet of paper to see whetherto make severalchanges before and have a range stated to be fromyou will be able to arrange themyou arequitesatisfied. When 30o to 600 metres, when a .0003all in the space given.Potentio-you have your dummy, the panel p.F condenser is connected acrossmeters vary considerably in shapecan be marked out and drilled. the primary.Actually in my re-andsize. ThatusedintheIt is, of course, possible to make ceiver owing to shortness of wiringpresent set was made by the Mar-up this receiver on a wooden panel, and low capacity of the valves, theconi Scientific Instrument Co. Theas in my other instruments de- range with a .00025 µF condenserIgranic people make an excellentscribed in MODERN WIRELESS, but is from about 25o metres up topotentiometerofpracticallytheowing to the fact that the low nearly 600 metres. There are a samesizeastheirwell-known capacity valves used require some number of different makes of plug-filamentresistances,whicharespace on the panel, not much is in transformers on the market,used in this set.Any good makesaved by using wood.Owing to -

H.T+ A

H.T.- El

0.0003 - LT+ j 2meq -Y Li - more 1

1 0.00025 (Top& dollen) TEL 0 0.0005 ,uF TEL+ 0

Practical wiring diagram.Note particularly the leads which go to bottom and top fixed plates of the double condenser, many of them being very excellent of potentiometer will do, and Ithe fact that the panel is com- devices. It is, however, necessarysimply mention the matter so thatparatively small and therefore not to make sure when purchasing,care may be taken in laying outparticularly dear,I Would advise that the connections of the pinsthe panel that the parts fit in theyou to use an ebonite panel in this are either as in my receiver, or ifspace allotted. instrument. they are different, then the con- Istronglyadvisereadersto AlthoughIso frequently em- nections of the instrument must beadhere as close as possible to thephasise the necessity of removing altered accordingly. It is one ofdetailed layout shown in the illus-the surface skin from ebonite be- the advantages of the present in-tration on this page and to thefore 'mounting parts, I still 'find a strument that as plug-in Coils arewiring diagram.Some makes ofnumber of readers ignore this pre- used we can cover any wavelengthvariable condenser have very largecaution. range we require by plugging -inend plates, and in some cases it When all the parts are in place, different coils and transformers. may be necessary slightly to ex-take a smooth file and rub the tips Noterevalves.-Altriciughas tend the panel in order to includeof all screws, etc., which have to mentioned two V 24 and QX arethe aerial tuning condenser. be soldered. Having done this used, the set will work quite well take afinebrush and remove with three V 24's.This point is Wiring Up every particle of brass filing from mentioned as the V 24 is a slightly Before drilling your panel I ad-the set.Then place the minutest cheaper valve than the QX, vise you to make a dummy ontouch of flux on the' points of all

70 November, :923 MODERN WIRELESS screws to be soldered,avoiding (I) have your points well tinnedwhich give you the best results. like the plague the use of an ex-beforehand with a small bead ofWhen accuratelytunedtothe cess of this material.In th's setsolder on the end ; (2) make sure thatnearest station turn your potentio- more than any other I have de-the ends of your wires are quitemeter knob from one end position scribed, it is essential to preserveclean and also nicely tinned ;(3) to the other.At one end the the insulation at the highest pos-be sure that your soldering ironsignals will be much stronger than sible pitch of perfection, and if youis very hot and perfectly clean atat the other.The end at which use much soldering flux, the hotthe end.You will soon succumbthey are weakest is the positive iron will tend to make it sputterto the fascination of wiring up inend, and you will aim to work as all over the place, and give con-this way, and the results obtainednear as possible to the opposite end. ducting film which is the last thingare electrically more efficient than We now come to the peculiar you want.Use a hot clean solder- by any other method. For thisprocedure with such a receiver ing iron, wiping it frequenty withreason stiff wire connections arewhich may confuse you at first. an old piece of cloth to remove thebeing more and more introducedDim the filament slightly Until the scum. Carefully tin the head ofinto commercial sets. signal strength starts to go off ;it every screw, and if the soldering is possible now that the speech and iron is hot enough, the solder on Operating the Set music will be distorted due to self - the head of the screw will run When the set is fully wired up, oscillation. Turn thepotentio- together as a little bead.If youturn the rheostats in the " off "meter §lowly from itsnegative .have not yet made up a set usingposition, place the valves in posi-position towards the positive until stiff wiring for connections, you maytion, plug-in the transformer andthe distortion ceases. If you are imagine the work is very difficult.connect up the batteries. You acquainted with self -oscillation you You will find it, however, quite easywill need a six -volt accumulatorwill recognise the symptoms. When if you follow the instructions given below. Thestiffwiringadds aoo 1.0P/1 greatly to the appearance of the 02 P set, and incidentally is economical 0.00025 7 as you avoid the expense of buying /P TS T5 insulating tubing.A further advantage is that it enables you to 2 /.0.0003 space the leads to the best possible advantagetopreventtheun- o72 wantedinteraction. towhichI op have referred. With thewiringdiagramin front of you (as usual a full size wiring diagram as a blue print is Po re.9 obtainable from Radio Press, Ltd., priceis.6d., post free), take a straight piece of wire and cut it The theoretical diagram. and bend it to join the first two connections(itdoes not matterfor these valves as they work atyou are used to these controls try which connection you make firstsomething over 5volts on thefor a different station.By this so long as they are all properly filament. Fifty volts highten-time you will know whicIr way to done in the end).Now take thesion will be quite enough as theseturn the condenser towards the hot soldering iron, dip it in thevalves are not designed for verystation you want,for you will solder and hold it successively to hightension. Highresistanceknow the wavelength of that to the two ends of the piece of wirephones will, of course, be needed.which you have been listening. you have cut.See that the endsFor the reception of British broad- If,for example, you have been are nicely tinned with a thin film.casting, plug-in a 25 or 35 Igranic,listening to London and wish to Having tinned the two ends, holdAtlas, Gambrell A, a No. 2 or aturn to Birmingham, you will need one end of the wire in place on itsNo. 3 Burndept concert coil or anyto 'advance the condensers towards particular screw, and place theother make of coil suitable for thethe maximum to hear it. You soldering iron at the point of con-particularwavelengthband. Iwill not need to make a very great tact. when if the temperature isalso find the "Magnum " tappedadvance with the high -frequency right you will find that the soldercoil quite good in this instrument. tuning condensers, and first of all bead on the end of the terminal First ofall connect your con-you may gather the impression And the solder film on the end of denserinparallel. Now turnthat the set is not at all selective. your wire will run together neatlyyour valve to almost the brightestGradually turn the condensers and in a well -finished joint; the other end positionofthe, filamentresis-adjust the filament resistance con- can now be done in the sama way. tances ;put your potentiometertrolling the high -frequency valve If you find difficulty in bendingtooneendofitsrun,and (you will find this very critical) ; toallthe shapes, you can cutset. your variable condensers atand a point will be reached when shorterleadsandsolderotherabout half way. Turn the twoyou will suddenly pick up the lengths on afterwards.This some -variable condensers until you pickstation for which you are searching t mes makes it easier in joining up.up the nearest station (this will bein great volume in the telephones. Successfulwiringup withthisan easy matter), and then note theFinal adjustment will be on the wire is dependent on three things :position on the two condensers (Continued on p. 87.)

71 MODERN WIRELESS November, 1923 D00000000000000000000000000000000000000000000000000000000000000000 ODD 0 WHAT TO DO WITH TWO VALVES By John Scott -Taggart, F.Inst.P., Editor.

Someadvice to those who wish to receive signals with two valves. DO0000000000000000000000000000000000000000000000010000000000000000000 IAM not infrequently asked whatcircuits using crystal detectors andthose who have already used a circuitIwould recommendthose in which a three -electrodecrystal detectoris the simple one for two -valve reception.My valve is used as a detector.Theshown in Fig.x. In this circuit answer would vary according to thecrystal, if of a good type, will be L1representsthevariablein- requirementsoftheindividualfound a very useful detector, andductance which may, say, be of questioner. Does he wish to carryit operates very well in conjunctionthe slider type and consist of a out long-distance reception usingwith valves. 34 in.diameter tube wound for headphones, or is he desirous of Probably the bestcircuitfor 5 in. with No. 24 enamelled copper working aloud -speaker ?What kind ofapparatusisavailable ? Has he a good quality intervalve transformer ?Ishisexperience and adjusting ability sufficient to justify the recommending of some circuit which requires a little more than ordinary ability to make it function to the best advantage ? All these questions require answering before a really satisfactory reply can be given.I propose in the following article to deal with several two -valvecircuits which may be thoroughly recommended, and to give some details of values of different components. Ipropose todeal both with Fig. 1.-Probably the best circuit for those who have already used a crystal detector.

Fig. 2.-Figure z shown pictorially.

72 November, 1923 MODERN WIRELESS wire.Instead of the inductance L1, an inductance shunted by a V, variable condenser may be employed.If it is not desired to use the plug-in type of coil, the in- ductanceL1mightconsistof 6o turns of No. 26 gauge double cotton covered wire wound on a VI cardboard tube 31 in. in diame .er. Tappings may be taken at every ten turns and the used portion of theinductanceshuntedbya variable condenser of0.0005 µF capacity. Preferably, a o.00x µF condenser, in series with a fixed condenser of0.001 µF, should be connected across L1 as explained inlastmonth'sarticleentitled Fig. 3.-A circuitwith high frequency amplification. " From Crystal to Valve."The object of the two condensers is so that the fixed one may be cut outmany cases, may be omitted withoutobtained with the higher voltage if with the result that the variableany disadvantage.The secondarythe incoming signals are compara- condenser has now a capacity ofT, is connected across the grid andtively strong.This circuit is only o.00r µF, whereas the combinationnegative terminal of the filamentsuitable when good, clear signals has, an effective maximum capacity'accumulator B1: Inthe anodeareobtainedwiththecrystal of 0.0005 µF. circuit of the first valve we havedetector alone. Across L1 we have the crystalthe primary T, ofthe step-up Fig. 2 shows the Fig. z circuit detector D, preferably of the cats -intervalve transformer T, T4.Inarranged,using components. whisker type, and the primary T1the anode circuitof the second It will not be long before the of the intervalve transformer T1 T2*valve we have the loud -speaker LS. beginner will want to try a circuit A fixed condenser C of 0.002 µFThe high-tension battery B2 mayusing high -frequency amplification, capacity ispreferably connectedhave a value of from 6o volts upand in this he is wise.The first acrossT1. Thiscondenser,into 12o volts, louder results beingcircuit which I would recommend

Fig. 4.-How to connect up the components in Fig. 3.

73 MODERN WIRELESS November, 1923 the beginner to try is shown in Fig.3. It will be seen that the variable inductanceLI,shunted by the condensers C, and C,, is in the grid circuit of the first valve which actsasa high -frequency C4 amplifier.In the anode circuit of C3 tit's valve we have the variable C6 inductance 1,2, shunted by the condensers C, and C4.Across the tuned anode circuit, as it is called, B2 we have the crystal detector D and the primary T, of the step-up intervalve transformer T1 T2.The R3 secondary Ty is connected across the grid of the second valve and the negative terminal of the filament accumulator Bi.The telephones, B or loud -speaker, are included in the anode circuit of the second valve. The beginner will be well advised Fig. 5.-The well:known ST34 circuit. to keepthe inductance L, well away from the inductance L, when The inductance LI may consist and loth turns. The coil is wound first experimenting with this cir- ofa31 in.tube wound with on a 3 in. tube which may slide in cuit.It is important to tune bothNo. 26 gauge double cotton covered and out of L1. the gridcircuit and the anode wire.Tappings may be taken at The next circuit which I would circuit accurately by means of thetheloth,loth,3oth,4oth and advise the beginner to construct variableinductancesand the5oth turns. The inductance 1,2 is shown in Fig. 5 and is commonly variable condenser. Correct tuningmay consist of a similar coil omit- known as the ST 34. is more or less a knack, but thereingtheloth turn tapping and The first valve acts as a high - should be no difficulty in tun'ng a providing a total of 7o turns, tapped frequency amplifier, the amplified simple circuit of this nature. at the loth, 3oth, 4oth, 5oth, both (Continued on page 104.)

Fig. 6.-ST34 circuit shown pictorially.

74 November, 1923 MODERN WIRELESS

DOOODEIODOODOMMODE1000001200000131:10000001:1000000000000DOMMODOME10000000000000 D D 0 0o r] THE ALL -BRITISH WIRELESS EXHIBITION 0 a o oO Interesting Exhibits at the"White City" o o 0 DOMODODODDDOODCIDDODOODOODODODOODODOODOODOODOOODOMODOODOODOODOOODOODOODODDO

AFORTHCOMING attrac- Ball, T. C. Igranic Electric Co., Ltd. tion,appealing particu- Coomes, J. A., Ltd. Jones, Sydney, & Co. larlytowirelessenthu- Canadian Brandes, Ltd. Marcohi's Wireless Telegraph Co., siasts, and of more than ordinary Chloride Electric Storage Co., Ltd. Ltd. interest to the public generally, is Cossor Valve Co., Ltd. McMichael, Ltd. the All -British Wireless Exhibition Chambers, L. J., & Co. Metropolitan -Vickers Co., Ltd. and Convention, to be held at the Climax Patents, Ltd. Mullard Radio Valve Co., Ltd. White City, Shepherd's Bush, W., Cassell & Co., Ltd. Marconi Scientific Instrument Co., from November 8 to November 21. Dubilier Condenser Co., Ltd. Ltd. - This Wireless Exhibition is being Davenport Wireless, Ltd. McClelland, J., & Co., Ltd. organisedinconjunctionwith Day, Bertram, & Co., Ltd. MacDonald, J., & Co. the National Association of Radio Diamond Wireless, Ltd. Marshall, Percival & Co. Manufacturers.Theactivepar- Edison Swan Electric Co., Ltd. National Wireless and Elec. Co., ticipation of this powerful associa- Ltd. tion will ensure presentation- on an, Odhams Press Ltd. adequate scale of all that is most Pye, W. G., & Co. up-to-date in wireless progress. Peto Scott Co., Ltd. Amateurs and experimenters will Preen, A., & Co. find alltheir requirements fully Peronet, Ltd. cateredfor,while the needs of Radio Communication Co. those who have yet to make their Radio Instruments, Ltd. first acquaintance with wireless are Rogers, Foster & Howell, Ltd. by no means being neglected. Apart Rawlplug Co., Ltd. from the actual exhibits, comprising Radio Press, Ltd. almost every conceivable form of Radio Supplies, Ltd. wireless apparatus, there will be a Radiax, Ltd. series of lectures and demonstra- Sterling Telephone Co., Ltd. tions, the latter by special arrange7 Siemens Bros. & Co., Ltd. ment with the British Broadcasting Sglidite Mfg. Co., Ltd: - Co., Ltd.Full advantage is be.ng Telephone Mfg. Co., Ltd. taken of the ideal facilities of the Trader Publishing Co., Ltd. White City to provide for the corn. Vanstone, W., Ltd. fort and convenience of visitors on Western Electric Co., Ltd.- an elaborate scale.The Exhibi- Wireless Press, Ltd. tion organisers are Bertram "Day Wilton Wireless, Ltd. --- SOME OF THE EXTHHITS. & Co., Ltd., 9 and I°, Charing A n interesting two -valve receiver Cross, London, S.W. 1. exhibited by Messrs. British Thomson - MESSRS. AUCKLAND'S WIRELESS, At, the time of writing, the follow Houston Co., Ltd. LTD., are showing a complete range ing firms have arranged to exhibit, of every component part 'required but many others have probably Ever -Ready, Co., Ltd. by the amateur for transmitting come in at a late hour :- Eagle Engineering Co., Ltd. - and receiving.Complete sets ,of Ashley Wireless Telegraph Co. Economic Car Light, Ltd. parts ready for assembling, suitable Auckland's Wireless, Ltd. Fuller'sUnitedElectricWorks, for amateurs who hold a construc- Abbey Industries, Ltd. Ltd. tor's licence.Complete broadcast Autoveyors, Ltd. Falk, Stadehnann & Co., Ltd. receiving apparatus ranging from Auto Sundries, Ltd. Fallon Condenser Co., Ltd. crystal and crystal -valve combina- Amalgamated Press, Ltd. General Electrie Co:, Ltd. tion3.Sets of single -valve, 2 -valve British Thomson -Houston Co., Ltd. General Radio Co., Ltd. and 3 -valve receivers. British L. M. Ericsson Mfg. Co., Graham, A., &. Co. MESSRS. AUTOVEYORS, LTD., have Ltd. Gamage, A..W., Ltd. arranged to exhibit, amongst other Burndept, Ltd. Great Motor Ballot. items, the follow;ng Brown, S. G., Ltd. Hart AccumulatorCo.,6.td. Clix Burns, J., Ltd. Henderson; W. J., ec . The Electro-linkwith 559 uses. Bowyer -Lowe Co., Ltd. Hestavox, Ltd. This consists of a combined plug Beldam Tyre Co., Ltd. Hough, J, E., Ltd. and socket which provides an instan- British Ebonite Co., Ltd. Hart Collins, Ltd. taneous contact suitable for any Brown Bros., Ltd. Harwell, Ltd. point of electrical connection.

75 MODERN WIRELESS November, 1923 also having the advantage of beingin a box composed of four panels quickly removable from the stirrup. ofB.T.H.insulating compound A special feature which is worthy of standing on a polished walnut base note is a lever adjustment whichand capped with a cover of the prevents the ear -cap from swivellingsame material.Its dimensions are too far round. approximately f o in. x 7i in. x 7 in. Another line will be their new Type B4 valves are used, and component parts. Each small com-when inusethefilamentsare ponent part is specially packed in avisible through inspection windows small carton, together with a small providedinthecover. These pamphlet of instructions on thevalves have been specially designed working of the component, and eachfor power amplification, and repro- componentwillalsocarrytheduction is free from all valve noises. Company's guarantee. The valve has unique characteristics in that the current consumption is very low, only 0.25 amp. at 6 volts being required.This represents about one -sixthofthe currentconsumptionof other makesof power. amplifying valves. Two switches are provided :oneapull-out switch for switching the The Clix link shown by Messrs. amplifier " on " or " off," Autoveyors, Ltd. the other being a rotary switch controlling the in- Variable Bridge Condenser tensity ofreproduction. (3-E.V.C.) By means of this switch For panel -mountingorcabinet - the volume of sound can mounted. be so regulated as to be This comprises threesections, suitable for all conditions. each consisting of a tier of rotary A varietyofloud- or semi -rotary parallel plates of speakers will also be ex- one-third disc area.Whilst prohibited by this firm,of vidingallthe essentialsofthe which we may mention ordinary 2 -electrode condenser, it the following has the ell -important addition of FORM CI.-This loud- the coupling of the third electrode, speakerisencasedin which may be employedwith polished aluminium and marked advantage in special appli- is provided withan cations. enamelled horn.The air - Filtron Variable Grid Leak and Potentio- meter. This device has proved very An Ever -Ready battery for dull enzith-rs. usefulinradiocircuitswhich THE BOWYER LOWE CO., LTD., necessitate a variable high ohmicwill. exhibit their crystal and valve resistance of precision. receivers, component parts, wave - meter, wave -trap, audibility meter, Filtron Combination and many other interesting devices A combined variable grid leakfor the experimenter.In particular and variable grid condenser. their new line of components for The main features of MESSRS.wood panel mounting will attract ASHLEY WIRELESS TELEPHONE Co., attention. LTD., exhibit this year will be their THE BRITISH THOMSON-HOUSTON Claritone "Loud -speakerandCOMPANY, -LTD., are arranging to new " Claritone " Headgear. show a complete line of receivers, Not only has the design been care-of which one is illustrated on the fully executed so that it will beprevious page. Theyarealso extremelycomfortabletowear,showing a large amplifier for loud- having forits main featureas speaker work. regards designthe new hygienic This amplifierisdesignedfor headband, but also the ear -piecesuse with loud -speakers when a are moulded ebonite, the pole -piecescomparativelylargevolumeof being moulded solidly into the ear-sound is required. pieces themselves, each ear -piece The working parts are enclosed An attractive "Cosmos" set.

,76 November, I9_:3 MODERN WIRELESS gap adjusting screw is mounted on -The range ofsets includes aand the casing, which measures the top of the receiver case. crystal set at1 is. od., crystal and13 in. x 7in. x 7 in., is covered in FORM Cz.-This instrument isvalve set, Note Magnifiers and the" Levant "leatherette.Thefit- provided with a " swan neck " horn, new" DW3 "Regenerative Re-tings are well finished and heavily which can b3 fitted either with aaction Set.This consists of H.F.nickel -plated, and a neat carrying wooden or a metal flare.The air - valve, detector, with tuned anodehandle is provided. gap screw is out of sight, but is verycoupling and reaction, together with Withinthecabineta sound readily accessible. one L.F. valve. conduit of entirely new design is FORM C3.-This is designed for Three anode coils replacethearranged.In form and construc- use with the tone arm of a gramo-ordinary tapped anode, controlledtion the conduit is the result of phone,usinganadapter.The by one spec; al anti -capacity switch. seriesof experiments conducted sound -box can readily be replacedThe reaction coil operates on thewith the single purpose of obtaining by this model, and excellent resultsparticular anodecoilincircuit.maximum amplification and added obtained. Aerial tuning iscarried out bytonal quality within the smallest means ofa Lissentunerwithpossible limits of space.From the FORM D.-This instrument is ofvariable air condenser, whilst thereceiver unit to the trumpet mouth the electro-dynamic type, which isanode circuits are tuned by a .00tthe development is gradual and in provided with a permanent magneticvariable air condenser with vernierthe course of the length of the fieldgenerated by a battery of cobalt steel magnets.Thus theplate with separate control. conduit a special grade of rubber. necessity for afield -exciting accumulator is avoided. To operate this loud -speaker the large two - valve amplifier is necessary. The output terminalsof the amplifierareconnectedtothe primary winding of a telephone transformer house efwithin a circular base of moulded insulating compound.Upon this base is mounted themagnetic structure. The secondary winding of the transformer is connected to a moving coil which floatsfreelyinthe permanent magnetic field.By this means any variation of current in thecoil causes a corresponding movement which is transmitted to aspeciallyselecteddiaphragm rigidly attached to the coil. THE BRITISH L. M. ERICSSON MANUFACTURING CO.,LTD.,are showing a line of receiving apparatus, their well-known headphones and their loud -speaker. MESSRS. S. G. BROWN, LTD., are exhibiting their loud -speaker and telephoneheadpiecesinseveral A new Gecophone set. patterns. a metal alloy, and, finally, wood THE COSSOR VALVE COMPANY'S The panel is handsomely mounted standwillundoubtedlyattract in an enclosed cabinet of Jacobean are employed. much attention, as they are showing design, whilst all terminals are at The receiver unit is the latest for the first time the new Cossor the rear of the panel. Amplion construction wherein dia- THE EVER -READY COMPANY phragmic resonance is avoided by dull emitter valve, for which many (GREAT BRITAIN), LTD., will exhibit the method in which the diaphragm advantages are claimed. all kinds and sizes of dry cells and is retained in position. Adjustment G. DAVENPORT (WIRELESS), LTD. accumulators,particularlytheir is effected in the usual Amplion -The exhibit of this Company will " Hercules " types of dry batteries manner by turning a knurled nut at comprise a complete range of com- for dull emitters.They will exhibit the rear of the receiver casing. ponents and sets. the convenience and efficiency of Telescoping to only isin. for Special attention will be centred these on their stand. stowage, each limb of the metal on a new headphone, BBC stamped; Oneofthemostinteresting tripod extends to 3 ft. 4 in., but it of exceptionally light construction, exhibits on the stand of MESSRS. is not necessary to open to the full with adjustable headband. ALFRED GRAHAM & CO. Will be length unlessdesired. Alterna- It is claimed that reception is the portable Amplion loud- tively, the portable Amplion may both true and undistorted with this speaker. be placed on a table or other avail- headphone, which will be marketed In appearance the instrumentable support, and the tripod re through the trade at 17s .6d. per pair. resembles a high-class box -cameramains where it is. MODERN WIRELESS November, 1923

seriesof receivershavewithsingle -valveand 2 -valve been put up as broadcast" Crystal -Set Amplifiers," specially components for the homedesigned to fit into the Crystal Set. constructorto assemble.They will also show a compre- These cover the same rangehensive assortment of Radio as the experimental sets.accessories, components and parts. They provide the same The special circuit now employed series of combinations asin the improved " Cosmos " Radio- othersets,viz., M.H. I,phone valve sets gives remarkable M.H.2, etc.Supplied withresults*, the performance obtained each ofthese setsis awith two valves being fully equal to diagram and descriptivethat hitherto obtained with three. matter showing how they The " Cosmos " valve sets are are to be assembled. designed on a " unit " principle. M.H. Accessories and The " Cosmos " Radiophone 2 -valve The McMichael M.H.B.R. 3 exhibited at the Components. set consists of a 2 -valve tuner unit, White City. The complete range ofwith the necessary batteries and the accessories and corn - telephones ;theadditionofa Messrs. Graham are also showing their latest models of " Amplion," which are now fitted with improved mechanism and wooden horns in place of the metal trumpets heretofore used on most models. MESSRS. L. MCMICHAEI., LTD., specialise tin" M.H." wireless receiving sets, which are all entirely British -made and of a high standard of manufacture and performance. Their stand (No. 83) at the All - BritishWirelessExhibitionwill contain a selection of some of the more importantoftheirM.H. products,andcanroughlybe divided into experimental receiving setsandunitsfortheexperi- menter;broadcast sets for the broadcast listener -in ; home assembly sets for the home constructor ;M.H. components for the home constructor ;components andaccessoriesfortheexperi- menter and constructor, and general accessories for all purposes. Home Assembly Sets. In order to provide for the home constructor the whole of the M.H.

"Cosmos" Radiobrix for the experimenter.

ponents will be displayed, giving 2 -valvenote -amplifier unitcon- some idea of the finish and designverts this into a 4 -valve set.Each which characterise M.H. products. unit is connected up to the next The chief features of the exhibitby a single plug, which cannot be of METROPOLITAN -VICKERS ELEC- inserted wrongly, so that connect- TRICAL CO.,LTD.,will be theiring up issimplicityitself.The latest improved types of 2 -valveunitsarearrangedtofitinto and 4 -valve sets with dual ampli-handsome cabinets of various de- fication circuits, and the "Cosmos " signs,or they may be used by Radiobrix.They will also be ex-themselves.Thus one may start hibiting a new 6 -valve set withwith a comparatively inexpensive frame aerial, and in addition theform of valve set, to which one The Radio Instruments wave -trap. f Cosmos "RadiophoneCrystalmay afterwards add if desired, and

78 November, 1923 MODERN WIRELESS so build up by degrees an elaborate Complete receivingsetsof 2,receiving set may be constructed set. 3 and 4 valves covering rangesin a short space of time, embody- The " Cosmos " Radiobrix com-from 300 to 3,400 metres.These ing any type or make of apparatus prises a comprehensive range of sets are mounted in various designs, without undue mechanical process. units, by various combinations ofincludingtheSimple Sloping - A further exhibit is the "Polar" which the Radio experimenter orCabinet,atabletype with aEconcmyPeanut-Valve and amateur can build up any type ofhinged lid covering valves,etc.,Equipment. -This has already been receiving set, and by connecting upand a very well designed pedestal-placed on the market.Its out- the standard Radiobrix in varioustypewithself-containedloud standing feature is extreme ways an immensevariety of circuitsspeaker. economy' in. space and also extreme can be tested and used. A 2 -valve power amplifierof economy in maintenance costs.

The 6 -valve . set comprises moderate cost and of very high The_ ".Polar.'.'specialised acces- threehigh -frequencyamplifying efficiency. sories form another feature of the valves,acarborundumcrystal Two low -frequency trans-exhibits and comprise :- detector, and three low -frequencyformers which have been designed The" Polar " Condenser ;the amplifying valyes.The high -fre- to give a uniform amplification over "Polar " Cam Vernier Coil -holder ; quencyvario-transformers are the whole range of music frequen-the" Polar "Fuseand Fuse - coupled together, so that simul- cies.One is particularly efficientholder ; the " Polar " Dynaphone ; taneous tuning of all three inter -on weak signals ; this should be used- theHolderstat ;the" Polar ". valve circuits iseffected by theafterthe detectorvalve.TheBattery Tester and many others. movement of a single knob.Non - other is for subsequent stages and RADIO INSTRUMENTS, LTD., have radiating adjustable reaction arranged to exhibit the follow. coupling is also fitted.Very ing :- fine tuning is thus obtained, and maximum efficiency over The Lyrian Series thewholerangeofwave- These comprise cabinet re- lengths,withthe simplest ceivers having 4 valves with possible adjustment. The self-contained loud -speaker and crystaldetector . isscrewed high-tensionbattery. The uptight, and thereisno loud -speaker can be supplied need to search for a sensitive separately if desired. spot ;it is adjusted by means The models are shown in of a potentiometer, and once satin -wood, silver birch, ma- this is set itwill remain for hogany, antiqueoakand weeks without needing further Radioinstruments combined variable various other stylesto suit adjustment;This type of , reaction and anode reactance. customer's taste. detector gives extremely perfect rectification without distortion.power amplification and is suitable Standard Valve Sets -The low -frequency amplifying for the loudest loud -speaker work. Thesearemadeinvarious circuitsarespeciallydesigned MESSRS. PETO SCOTT CO., Lm., are types, namely, 1, 2, 3, 4, 5 and 7 togivethe clearest and purestshowing their well-known receivers, valves. possible reproduction. and a new set of components for All models are now fitted with a THE NATIONAL WIRELESS AND wood mounting, which enable thesloping hinged lid arranged so that ELECTRIC CO. are showing theirexperimenterstodispensewiththe instrument can be closed with " Gnat "crystalreceiverandexpensive ebonite sheets. the valves and battery leads, etc., various valve receivers; as well RADIO COMMUNICATION CO., LTD. in position.This renders the in- as numerous component parts andare showing :- strument dustproof and will be a accessories. The 1924 Model "Polar " 7 -valvegreat boon to users. MESSRS. D. G. PYE AND Co.,cabinet setfittedwithremote The outstanding feature of all of Cambridge, are showing :- control.This is the very latestR.I. receivers is their wide range Patent tuning coils of the plug-form of their well-known 7 -valveof wave -length, all sets from two in typeof extremely lowself - set, but in this case it has beenvalves upwards being suitable for capacityandof veryrobustfitted into a cabinet, which cana range of wave -lengths of frcm character. be had in either of the periodSoo to 4,000 metres, bringing in all Tuning coil holders for 2 and 3styles - Chippendalemahogany,the British and Continental tele- coils fitted with vernier adjust-Adam mahogany, Jacobean oak.phony. -No pIug-in coils are used, ments giving very fine adjustmentThe remote control enables one tothe change from one wave -length of reaction. control the set from an armchairto another being effected by a well - Variable plate condensers of thewithout approaching it. made tapping switch.These are best quality, with fine adjusting Other set exhibits are the 4 andclaimed to be the only broadcasting plate. 7 valve sloping panel and bookcaseinstruments on the Market _with Patentanti -capacityswitchessets, with which the publicare this wide range of wave -length. for panel mounting suitable foralready familiar. All instruments from two to five high or low frequency and which The next item in importance isvalvesarefittedwithvariable incorporate a good rubbing con-the " Polar " Bloc system.Thisintervalve reaction and one H.F tact. is a cleverlydesignedand ab-tuned anode, LP., stages following A system of unit valve panelssolutely unique system of set con-according to the number of valves. from which anefficientmulti -struction (somewhat on the linesThe 7 -valve sets are fitted with three valve set can be built up. of Meccano), by which a complete (Continued on page 103.)

79 MODERN WIRELESS November, 1923 DOODDODELIODEDOODOEDOOD3C1=a10[1=10n1=0=EDEDEIC=0:10E0171EcnconnOLLED D 0 D 0 D CI ID 0 A NOTE MAGNIFIER D 17 D 0 0 0 O FOR THE ALL -CONCERT RECEIVER 0 D 0 0 0 By PERCY W HARRIS Assistant Editor ID Many requests have been received for a design of a note -magnifying panel to add to the " All -Concert" EI Receiver described in the September issue. The set described here has been specially made for the purpose9

and will convert the " All -Concert" Receiver into an efficient four -valve set. D 0 0 1=0:00DDOODIDOMMIDEDEELDEDGEODEDELOMEDODIDOODEDEIMODDEEDDOOODEIDEIDED001:1

SO manylettershave beenbe clear from an examination of valve socket. received from readers whothephotographs- anddiagrams. 10 terminals. have successfully constructed The following are the components filament resistance. the " All -Concert " Receiver, askingrequired : intervalvetransformerof for a suitable note magaifier good reliable make. to add to it, thatI have now z Mansbridge condenser produced one to match the of .3µF up to rp.F. set. It is designed to stand A suitable panel either alongsidethe" All -Con- of ebonite or wood. cert " Receiver, the con- If you use a wooden nection being as shown in panel, it will be necessary Fig. 6.It will be noticed to provide yourself with thatseparateterminals 'ebonite flanges and bushes are provided for the high- for the terminals and with tension supply to the note the flange type of valve magnifier, so that if very socket or else four separate high magnification is re- valvesocketsmounted quired(usingapower on a piece of ebonite which valve),ahightensicn can be placed over a hole voltageof the requisite in the panel. The filament figure can be applied with- resistance can be mounted out upsetting the working straight on to the wood of the preceding valves. of the panel.In the par- The same low-tension ticularinstrumentdes- battery isused in b oth cribed I used the bushes sets, the terminals b::ing and special wooden panel - bridged as shown. Addi- mountingvalvesockets tional terminals are also supplied by the Bowyer - provided for grid cells, so Lowe Co.These have a that we can, if necessary, very neat appearance and place a negative bias upon are a part 'of a new line the grid of the note mag- of components which en- nifier valve when using a able one to dispense en- high voltage on the plate. tirelywiththeusual This is sometimes neces- ebonite panel. sary to avoid distortion. The various parts can he However, in the majority fastened to the panel quite ofcasesit will not be simply, but there may be a necessary to use these ter- littledifficultywith the minals and they are then Mansbridge condenserif bridged by a wire or a it is not fitted with flanges strip ofmetal.Ifthe formounting,Ifthere same voltage is used on are no special means of the note magnifier as on mounting it may be neces- the previousvalves, we sary tocuttwo small can use the same high- pieces of brass toform tension battery for both right-anglebrackets and sets,leadsbeingtaken to solder them to the sides from the battery tothe of the condenser after the two sets of terminals. black paint has been re- The construction of the moved.These right-angle magnifier does not call for _brackets should have holes any special skill and will Fig. 1.-The complete unit. drilledin them so' that

8o November, 1923 MODERN WIRELESS

The operationofthisset is simplicity itself, as all one needs to do is to connect it up tothe All -Concert Receiver and switch on the filament. Any good make of valve will do, and if very high magnification isrequiredI would suggest the 11,-e of one of those valvesdesignedforusein p-.)wer amplifiers. When these are used a much higher plate voltagewill be required, eecessitatinga geedrobust intervalve transformer. Unless the makerrecommendshis transformer for use in a power amplifier I cannot advlse you to use a power valve, for these latter are useless without high plate voltage and a high plate voltage will burn out many ofthe transformers on the market.Make sure then,if you intend using power valves, Fig. 2.-One view of the underside of panels showing stiff wiring. that your transformer is suitable. Power valves will require wood screwscanbeusedfor a special grid battery for which securing the condenser to the panel. I recommend the ordinary type A Dubilier type 577 condenser of of high-tension battery tapped for .or I.LFis suitable for use in this at each 3 volts.This should be particular set and has provision connectedacrosstheterminals made for panel mounting, but it marked "grid cells " and varia- is much more expensive than the tions of grid potential should be Mansbridge type. tried until you get the best results. Wiring up is carried out with Of course, this amplifying unit No. 18 bare tinned copper, either can be connected to any other _round or square section.Full de- receiver.The only point to bear tails of how to carry out this wiring in mind when using it is that it with thick wire are given in my Fig. 3.-The circuit diagram. is essential for both magnifier and article in this issue dealing with the construction of the " Trans- atlantic " receiver, so I need not ge into further details here. Operating the Set This panel, when connected up to the All -Concert Receiver, _con- verts it into an excellent all-round four -valve set..-Icannot recom-_ mend the addition of a further note magnifying stage,as three note magnifiers together are never saEs factory,introducing,evenwith the best transformers, a certain amount of distortion 'which isilia-_ pleasant.Furthermore, three note magnifiers magnify everyslight disturbance and atmospheric noise intoamostdistressingcrash. Also, if signals are so weak that they require three stages of note rnagni fication to make them audible then they will' be unsuitablefor the operation 'ofa loud -speaker.If further amplification isrequired it should be by means of high- Fig. 4.-Another view of the underside, showing the Mansbridge condenser frequency and not of low -frequency. across the H.T. terminals. MODERN WIRELESS November, 1923

L.T.-I-@ @HT+ ©yr-

GRID CELLS

IN O TEL TEL

Fig. 5.-Arrangement of terminals. receiver to have their high-tension batteries connected the same way, ix., the high-tension negative must ba .connected to the low-tension p^sitive.Furthermore, it is essential that the all -filament resistances shall be placed in the negative leads of. the valves and not in the positives.. These two points are standard inall modernwireless receivers. The wiring diagram. Note carefully. the+ I:P., 0.P., I.S. and O.S. connections. Theii positions may diffir with different transformers, but 1,'u, wires must always be connected as shown. H. T+ HT- L.T+ L.T. - FROM A READER. TEL. To the Editor, with one stage of low frequency, TEL, MODERN WIRELESS. I receive Eiffel Tower on a loud- speaker (Brown Junior High Re- SIR, --Allow me to congratulatesistance) sufficently.loud to he com- you on the deSign of the " Threefortably audible: Fig. 6.-How to jointhesetto the Valve All -Concert Receiver " de= On the 21st September, between "All -Concert"receiver. The same scribed inthis. month's MODERN 1.43 to 2.36 a.m. I picked up WGY accumulator is used for both sets and, WIRELESS (September)..Ihave-General Electric Co.,Schenec- if desired, the same H.T. battery.Grid been using this circuit for sometady, New York.The music was cells are only inserted when very high considerable time, and still find itperfect and the speech quite clear. voltages are applied to the plates. the best all-iound broadcastre- The. other artistes could be heard ceiver.I use a .00i µF. variableclapping in the studio.They were condenser instead of .0003, in series - announcing a 30o dollar competition parallelarrangementwiththe NOTICE.Blue Prints of for a Radio drania play.(Aerial A.T.I.All B.B.C. stations come intvvin 43 ft. long on 40 ft. mast.) the all -concertreceiver with good strength.Eiffel Tower, _ I am, etc., are still obtainable.Price Radiola, Paris and Butch concerts 1/6 post free. withfairstrength.When only STANLEY F. BRIGHT?. using 2 valves (H.F. and detector) London, N.W.

82 Nov. rnber, 1923 MODERN WIRELESS

DOOOD0000000000000000000OODOODODECOODOODOODOD00000000000000000O000000000ODO D D BEAT TIME -SIGNALS D 0 RHYTHMIC0. o o By A. HUGHES BARLOW , of Fleet Road Central School, Hampstead. o 0 D 0 Many readers have asked.for a popular explanation of the strange "dot time" signals 0 D O from the Eiffel- Tower.This article 'makes the method quite clear. D 0000moomoom0000m000000p00000000=0000000000000000000000Ooom000000000D o0

you remember thefirsttime you back to its starting -point.The True Solar D°receivedthe Eiffel . Towertime Day- varies in length as the year proceeds, its signals ?What a gloriouslY exciting greatest value being about 3o seconds more experience it was !And even now that the than .the Mean day, and its least value being glamour has worn off by familiarity, there is a some 21 secs. less than the normal 24 hours. fascination about thoe dots -and dashes that, The Mean .Solar Day is merely the average of quite outshines that of 2L0's " 56-57-58-59- 365 of these slightly varying solar days. DONG." The astronomer, however; needs an in- Your next thrill was. probably the reception variable time measure, corresponding to some of Nauen's time signals on 3, roo metres. If you invariableastronomicalfact,andthishe have a good crystal, and a good ear, you can finds in the Sidereal Day, which is the time get Nauen without valves ;but a valve with taken by the earth in making a complete reaction will give them more comfortably.. rotation on itsaxis.The Sidereal Day is At five minutes before Greenwich noon you 3 min. 56.55 secs. less than the Mean Solar listen -in, and hear first a succession of V's, Day that ordinary mortals keep ;and, being then " POZ, MGZ " followed by the well- itself divided into 24 equal parts called sidereal known International Time Signals.. hours, which again are divided into sidereal Allthisisquite simple, and has 'been minutes and seconds, itis obvious that all described many times ;but what about those these divisions are slightly shorter than the mysterioustick -tick -ticks that we hearat corresponding divisions of the ordinary day. aboutten o'clock inthe morning ? Do Also, it will be easily understood that the you receive them with a complete under- discrepancy between Sidereal Time and Mean standing of their import ?Or is their use Time gets greater day. by day until .a whole still confined to the deceiving of our guile. - period of 24 hours separates them-and then, lessfriendsinto the beliefthat they are of course, -they are together again.This, occurs actually hearing the tick of the clock at Paris once ayear, near the commencement of Observatory ? spring. Now, as the writer combines a passion for Now, it is the astronomer's sidereal clock that wireless experimenting with a love for astron- is corrected by the so-called " Scientific Time omy-having probed the starry depths for Signals " sent out by the .Eiffel Tower twice a many years with " home -constructed " tele- day, viz., at ro a.m. and io p.m.' G.M.T., and scopes-perhaps you will forgive him if he so their practical value to the ordinary listener - airs a bit of his knowledge about other sorts of in is nil.Still, he can get real pleasure in time than the ordinary, " mean," everyday " taking "thesignals andinqualifying variety. himself to give a satisfactory demonstration Greenwich Mean Timeis,asits 'name and explanation of them to his friends. suggests, an average time, so arranged that a Letustakeanactualexample :--On good, steady -going clock or watch need not be Sunday, October 7, the writer tuned -into disturbed in the regular carrying out of its 2,60o metres a few minutes before ten a.m. duties. by the dining -room clock At about two True Solar Time -is sometimes faster, some-. minutestoten, F.L. began by givinga times slower than the average or Mean Time, preliminary course of signals consisting of and depends on the actual time taken by the 59 dots, followed by the sign - - . - six sun to travel (apparently, of course) from the times repeated, " F.L." twice, and -. .. - meridian of Greenwich, round the world, and twice. By thistimealltheobservatory, MODERN WIRELESS November, 1923 listeners -in were, no doubt, ready for the test. the absolutely correct time is II 00 09 74 (the which began at a few seconds after the hour. time of the first dot) plus in of the whole time Dot, dot, dot went the F.L. transmitting of the sending of the dots (which-by simple clock, beating neither solar seconds nor sidereal subtraction-he knows to be 4 min. 53.23 secs.), seconds, but a slightly shorter one - .98 of a of this being 2 min. 38.87 secs., the true sidereal second, to be exact-so that the series sidereal time of the 163rd dot must have been of 300 dots (and spaces) took about 4 minutes II 02 48 61, and so the astronomer's clock is 53 seconds in transmission.To make the shown to be .39 of a second slow.As, by this counting of the dots rather easier there were method, the clock can be corrected to the near- pauses in place of 113 60th, 120th, 18oth and est hundredth of a second, the greatest possible - 240th dots.All this was duly noted. error still remainirgis .005 or 2Aof a second, Now if the astronomer knew the exact time and thisis near enough for allordinary of the transmission of these dots, he could astronomical purposes. proceed at once to correct his clock by them If you have patiently followed me so far, by noting which dots synchronised with the you may now be wondering how you can tell ticks of his own clock's pendulum.But, as a whether your reception is correct, as you have matter of fact, not even the F.L. operator no means-so you think-of knowing approxi- himself knows the exact times until he makes a mately the Sidereal Time at 10 a.m. G.M.T. calculation based on the observed synchronis- This need not trouble you long. .For a shilling ing of certain of the dots with the swinging of you can get Zadkiel's Almanack from any the pendulum of the Paris Observatory clock, newsagent, and in it you will find the Sidereal which has itself been corrected by obServations Time at Mean Noon for every day in the year. of the meridian transits of the stars.So we Subtract 2 hrs. o min. 20 secs. from this, and must needs wait about thirty-five minutes for you get the Sidereal Time at ro a.m. G.M.T. the announcement of the times of sending the In order; however, that no one need omit this first and last of the 300 dots. obserVation for want of data, I append the At 11.35 the writer took up his receivers ten o'clock Sidereal Times for every day in again and noticed that F.L. was engaged on November.: his daily " U.R.S.I." announcement ;and at 11.36 the long two -minute dash was given, hrs. mins. secs. hrs. mins. secs. (this is the " cue " for the astronomer, as the Nov.i.. 12 38 40 16.. 13 37 48 Sidereal Time announcement immediately fol- 2... 12 42 36 17..13 41 45 lows it).The writer then read :" Observ- 3.. 12 46 33 r8.. 13 45 41

4 53 29 19 13 49 38 atoire de Paris," - ...... " Temps 5.. 12 54 26 20.. 13 53 34 Sideral " ... - 6.. 12 58 23 21.. 13 57 31 1100 09 74 ....11 05 02 97 - . ... - -. . e2 19 22.. TA. OI 27 his meant that the first dot was transmitted 7 13 at i1 hrs. oo mins. 09.74 secs., and the last at 8 .. 13 c6 16 23.. 14 05 24 II hrs. 05 mins. 02.97 sees., both in Sidereal 9 .. 13 10 -12 24.. 14 09 21 Time. 10.. 13 14 09 25.. 14 t3 17 I may say here that the Sidereal. Time at II.. 13 18 05. 26.. 14 17 14 ro a.m. G.M.T. on this date (Oct. 7), as cal- 12... 13 22 02 27.. 14 21 10 culated from the almanac, was II hrs. oo mins. 13 .. 13 25 58 28.. 1.4 25 07 29 03 o6 secs., so that the first dot was sent about 14 13 29 55 29.. 14 15..1.3 33 3o .. 14 33 00 3 secs. after the hour, and the last 4 mins. 52. 53.23 secs. later. SPECIAL NOTE. Now, the method adopted by the astronomer. On listening -in at 10.40 on Oct. 14, the writer was to cheek his Sidereal clock is this :He watches interested to receive the following transmission from the pendif um of the clock as it ticks out the F.L.: " Notez.-Partir du 15 Octobre inclusles sidereal seconds, and at the same time he silences seront remplaces par des traits dans les Emissions de signaux rythmes."(Note that on and counts the dots from F.L. until one of them after Oct. 15, the " silences " will be replaced by exactly synchronises with the tick of the dashes in the emission of the rhythmic signals.) pendulum.Supposeatthis moment that This has ben verified by sub3equent observations. his clock says it hr. 02 min. 49 secs., and that The dashes are, more striking than the " silences " the FL dot was number 163.He knows that they replace ; and they occupy the time of two beats.

84- November, 1923 MODERN WIRELESS

DEEEDOODEEDOEIDOCEDEIECIDECIOMODEIDOODECEIDOODOCIEOCIDOMOODED=IDODOOMEICKIODECI 1 HE LICENCE QUESTION : A SETTLEMENT 0OCI ri 2 .AT LAST. 0 2 0 jE3EIDDEIMIDEOMECEIDOOODE_EIDEDDEDDECIODECOODE3i0E11100=0=DEIDEEEICIDOMIEEDLIO

EVERY wireless enthusiast you raise and the best means ofpersonwhoappliesin future willbedelightedthata meeting it,and a further com-foranExperimentalReceiving settlement has been arrivedmunication will be sent to you asLicence will be asked to sign adoclara- at with regard to the broadcasting soon as a decision is reached.-Iton that he will not use his set for the problem and the position of theam, Sir, your obedient servant, reception of broadcast programmes home constructor. We give below (Signed) S. W. PHILLIP. except for experimental purposes. the official statements issued by the For the Secretary. In accordance with the present G.P.O., which make most of the decision, however, provision will be points quite clear.However, on made on the new application forms perusing the report it is apparent POINTS TO NOTE. for this declaration to be dispensed that several matters of considerable with, if the applicant prefers instead importance were left undecided and Existing experimental receiving to pay a fee of 15s. a year in place in particular the position of the licences are notto be interfered of the normal fee of los.He will experimenter in relation to broad- with in any way. Existing experimental transmitting then be entitled to receive broadcast casting seemed very peculiar.It licences also will not be interfered programmes for entertainment was strange to us that holders of with in any way, and new licences purposes. experimental receiving licences of this type will be issued upon Experimental Receiving Licences issued after October4. would be compliance with the usual con- will, of course, only be issued to prohibited from listening to the ditions and upon payment of the bona -fide experimenters.-I am, Sir, broadcasttransmissionsforthe existing lee of 20s. per annum. your obedient servant, purpose of entertainment, and our Owners of unlicensed receiving apparatusofanytypewillbe (Signed) J. F. BROWN, companion journal, Wireless Weekly, required to take out before Octo- accord.nglywrotetothePost ber 31 a special interim licence at a We have come to the conclusion Office authorities pointing out that fee of 15s. that,ingeneral,asatisfactory the new regulations operated un- Those who desire to construct settlementofthebroadcasting fairly aga nst the holder of a new their own receiving apparatus, but problem has been arrived at, and experimental licence inasmuch as are not qualified for an experi- considerthatthePostmaster - he is prohibited from enjoying even mental licence, can obtain a con- General and the British Broad- a Sunday afternoon concert, unless structor's licence (fee15s.) upon casting Co. are to be congratulated. aconstructor'slicence(r5s.)is application at any head or branch Naturally,thereremainafew Post Office in the Kingdom.Both obtained in addition to his experi- theinterimandconstructor's minor points to be disposed of, but mental licence (los.). licences will remain in force until these are chiefly in reference to Wireless Weekly suggested that the end of 1924.Under the terms matters which affect the B.B.C. future applicants for experimental oftheselicences,foreign -made and its individual members rather licences should, upon payment of components may not knowingly be than users of wireless apparatus. an additional sum of 5s., be exempt used in the construction of appa- The response to the appeal to from signing thedeclaration ratus. experimenters and users of wireless regardinglistening -intobroad- Experimental receivinglicences apparatus to put themselves right casting. (fee 10s.) will continue to be issued, in regard to the law has been very but,inadditionto the present They also mentioned that they condition, applicants will be gratifying, and although in some had communicated with the British required to sign a declaration to quarters the idea that the so-called Broadcasting Co. in this matter, the effect that they will not use the " pirates " would act honourably and . understoodthatsuch an broadcast programmes except for was scouted, the most optimistic arrangement as suggested above experimental purposes. person could not have wished for a wouldbeperfectlysatisfactory Thisdeclarationcanbedis- betterresponse.This shows,as from their point of view. pensed with by a further payment we have always believed, that the Byreturn, Wireless Weekly of 5s.Provision for this is made home constructor and new experi- received the following reply on the application form. menter was as anxious to con- General Post Office, tribute his quota to the expenses of London, E.C. x. And on October 16 the followingbroadcastingasthe mostcon- October 5, 1923.further letter:- scientious purchaser of a B.B.C. SIR,-I am directed by the Post- SIR,--With further reference tolicence.Up to the time of writing master -Generaltoacknowledgeyour letter of the 4th inst., I amthis note some half a million wire- receipt of your letter of the 4th inst.,directed to inform you that the Post-less licences have been issued, of and to thank you for the suggestionmaster -General has decided to adoptwhich quite a half have been the contained therein. your suggestion concerning the con-special interim licences to people The Postmaster -General has com-ditions attached to new Experi-who had not previously taken out municated with the British Broad-mental Receiving Licences. a licence but were using a set at casting Co. concerning the point Asrecentlyannounced,anythe time the report was published

85 MODERN WIRELESS November, 1923

DOODOODOMOODOODOGOOD00000000000000000000000000000000000000MOODOMODOOMMO0 O 0 o

0 THE OFFICIAL STATEMENT ISSUED BY 0 0 THE POSTMASTER -GENERAL .0 O . 0 El WOla3MODOODDE1001:00000000000MODOCIECOMMOMEICIDOODOODOMEIMOODOEIMMODO0000 N giving instructions for thelicence,"topersons who makeapparatus from abroad, the issue of the Report of thetheir own sets or assemble themPostmaster -General has accepted 'Broadcasting Committee, thefrom ready-made parts, but whothis condition. Postniaster-General desires to ex-do not desire to carry on experi- There are,however, probably press publicly-as he has alreadyments.These receiving sets were 200,000 persons already in possession (lane privately-his warmestbeing used contrary to the terms ofof unlicased receiving apparatus, thanks to the Committee for thethe agreement.Large numbers ofand, as the Committee point out, great care which they have givensuch persons had applied to thethese persons are paying nothing to the consideration of the novelPost Office for licences, and prob-towards the cost of the programme, and difficult questions referred toably many others, realising that nobecause in the past there has been them by his predecessor. licence was in existence appropriatenolicenceapplicabletothem. The Report makes the followingtotheircase,have been usingA special interim licence will be main recommendations : their apparatus without . makingissued at a fee of 15s., covering That a Broadcasting Boardapplication. their present apparatus, whether should be established by Statute. The continuance of the presentmade or purchased and wherever That the, broadcasting servicesituation would be bad forallmade or purchased, which will be should. not be operated by aparties,theBroadcasting Co. granted to them provided that Government Department,and because it is losing a revenue uponthey apply for licences before Octo- that the existing service of thewhich it has counted, and the Post ber 15.* No charge will be made British Broadcasting Co. shouldOffice because, as the Departmentfor past user, and no proceedings be continued and extended forentrusted with the administrationwill be taken in respect of past two. years upon modified terms.of the law regarding the licensing user if the licence is taken out That one form of licence at aof wireless apparatus, it is unablebefore October 15.* fee of los. a year (of which theto enforce the contemplated restric- Constructors' and interim licences Broadcasting Co. should receivetion. as above will be placed on sale 7s.6d.and the Government In these circumstances a com-atallhead andbranchpost 2s.6d.) should be issued andpromise has had to be sought.Inoffices and certain sub -offices on placed on sale at Post Offices. order to recognise the company'sand from October 4.Applicants Thatnoprotectionshouldrights under its agreement and atfor such licences, as well as for be given to the British manu-the same time to meet the viewsthe existing B.B.C. licence,will facturers by. the licence. of the Committee as far as imme-be required to fill up and sign a Sir Laming Worthington -Evansdiately practicable, the Postmaster -simple form. Copiesofthese finds that it is not possible for theGeneral has agreed with the Broad-application forms may be obtained scheme recommended by the Com-casting Co. that a constructor'snot only at head and branch offices, mittee to be brought fully into licenceshould be issuedfor abut atall sub -officesat which operation immediately. As thelimited period at an annual feemoney orders are issued. Committee themselves point out,of 15s. (as compared with the fee This system of licensing will be ithas been necessary to have oflos.charged for the B.B.C.continued for an interim period regard to the existing agreementlicence).The additional5s.forexpiring on December 31,1924, with the British Broadcasting Co., the constructor's licence is justifiedafter which it will be possible for which does not expire until Decem-because otherwise the constructorsthe single form of licence recom- ber 31, 1924. Under this agree-would be obtaining the benefit ofmended by the Committee to be ment,andinaccordance withthe Broadcasting Co.'s programmeintroduced, without any condition the statements made in the Housewithout making a proportionateas to the marking or origin of the of Commons at the time, the manu-contribution to the expense. licensed apparatus, if it should be facturers are entitled to protection, The company have agreed tothen thought desirable. and nolicenceswere intendedthis arrangement on condition that Out of the fees of 15s. for the to be granted to any persons notthe licensee gives an undertakingconstructor's licence and los. for using sets marked " B.B.C." andthat, in constructing his apparatus,the B.B.C. licences, the company manufactured by members 'of thehe will not knowingly use parts will,ifthe House of Commons company. manufactured elsewhere than inagrees, receive I2S. 6d. and 7s. 6d. The immediate causeoftheGreat Britain or Northern Ireland.respectively,insteadof5s.per appointment of the Committee wasInallthecircumstances,andlicence which they receive under thedeadlock which had arisenespecially having regard to the un-the existing scheme. between the Post Office and theemployment which at present exists The Postmaster -General is not company in regard to the proposedand which would be accentuatedsatisfied that, even with the in - introduction of another form of by the importation of any consider- *EDITORIAL NOTE.-This date was licence,viz.,a" constructor's ablescaleofwirelessreceivinglater extended to October 31.

86 November, 1923 MODERN WIRELESS creased contribution from licencefactory service and are willing toselves right as regards the law, and fees, the revenue of the Companyerect additional stations where theat the same time to contribute their will, for some time to come, bePostmaster -General may considerquota towards the cost of a service sufficient to provide adequate pro-them necessary, he will not licensewhich is affording them so much grammes without a substantial con-anyotherbroadcastingserviceenjoyment. tribution in the form of royaltiesduring the interim period up to Copies of the Broadcasting Com- on the sale of sets by the manu-December 31, 1924. mittee's Report may be purchased facturers who form the Company. After that date,ifthe Post-through any bookseller or directly Hence he has stipulated for themaster -General should consider itfrom H.M.StationeryOfficeat continued payment of such a con-desirable that additional stationsthe following addresses :Imperial tribution, but on a reduced scale.should be established in any townHouse, Kingsway, London, W.C.2, The reduction will be approximatelyor district where the company'sand 28, Ab.ngdon Street, London, 5o per cent., except in the caseservice is not adequate, and if the ; York Street, Manchester ; ofcrystalreceivingsets,where -company arenotprepared to St. Andrew's Crescent, Cardiff ; it will be considerably more.Thisprovide such stations, the Post-and 12o, George Street, Edinburgh. reductionshouldenableacutmaster -General reserves the rightIts price is 9d., or, if ordered by to be made in the cost of, receivingnot only to license other organisa-post, id. extra for postage. sets.The proportion of the licencetions to do so, but also to give them G.P.O.,October,1923. fees receivable by the Companyan appropriate share of the revenue will,after December31,1924,arising from new receiving licences be placed on a sliding scale basedinthe district in question.He on the number of licences on thealso reserves the right to license one hand and the cost of Main-other services (without regard to (Continued from page 71.) taining an adequate broadcastinggeographical area) without with-.tuning condenser, filament resist. service on the other hand.Anydrawing from the company anyance and potentiometer.You will surplusprofitaccruingtothepart of the licence fees to whichnot find the detector filament re- company over and above 71 perthey may be entitled.In eithersistance at all critical, and once cent. on its capital and a necessarycase, he reserves the right to allotthe best position has been found reserve for depreciation,etc.,ofsuitable wave -lengths to the newfor this, it can be left there.If plant and machinery will be sur-organisation, whiletaking allyou have difficulty in making the rendered to the Post Office;inreasonable steps to avoid creatingset oscillate, try the condenser in. other words, the profitsof theinterference with the company'sseries. company are limited to 71 per cent.services. The first night I tested this set The existing experimental The Postmaster -General proposesonBritishbroadcasting I-suc- licence, at an annual fee of ios.,at an early date to appoint an ceededinlisteningtoGlasgow will continue to be issued from theAdvisory Board, as recommendedand Newcastle without the slightest General Post Office to persons whoby the Committee, to assist himinterference from London, although are able to satisfy. the Postmaster-.in all important questions relatingthis latter station is only six miles General that they desire the licenceto broadcasting. He has noted withfrom me.Manchester came in far for bona fideexperimental pur-pleasuretheCommittee'scom-betterthanIhad ever heard poses, and are qualified to conductmendation of the present broad-before with only slight interference experiments,and whosignacastingservice ;and hetrustsfrom London.Cardiff could only declaration to the effect that theythat the service will give increasingbe heard properly when London will not use the broadcast pro-satisfaction under the new condi-was not working,although,of grammes except for experimentaltions, and that a great impetuscourse, a - trap circuit connected purpose. will be given to the sale of British -with this.receivercompletely Each new licence(asdistinctmade receiving apparatus. eliminates this jamming. from renewed licences) will cover In the enforcement of the new With the set on the table and a period of twelve months fromschemeoflicensing,much willthe high and low-tension batteries the first day of the month of issue.depend upon the willing co-opera-connected and a 50 -coil plugged Renewed licences will cover twelvetionof the public.So long asinto its socket, it is quite good months from the date of expirationthere has been no licence to fit theenough for telephonic reception up of the old licence. caseofthe many thousands ofto io miles from a broadcasting The basis of membership of the" listeners " who are using home-station without any aerial or earth BroadcastingCompanywillbemade apparatus,itwould havewhatever.I have read an amateur extended so as to include dealers,been unreasonable forthe Postat 13 miles in this way.However, with suitable representation on theOffice to attempt to enforce theeven on an outdooraerialthe boardofdirectors for the newlaw with any strictness ;but nowvolume is never great enough to membership if it becomes at allthat such a licence isavailable,work a loud -speaker satisfactorily, substantial ;and the deposit ofthere will no longer be any excuseeven from a local station, as there 5o now required from membersfor the use of receiving apparatusis no note magnification to give will be abolished. The licence'without licence.The Postmaster -volume. In next month's issue I heldby the company willbeGeneralbelieves,however,thatshall describe a companion cabinet prolonged, on suitable conditions, tothe " listening " public will requirewith two note -magnifying valves the end of 1926, as recommendedno pressure in this respect.He isso as to work a loud -speaker, also by the Committee. confident that they will be not onlya few modifications for obtaining If the company supply a satis-willing, but anxious, to put them -reaction on long waves.

87 MODERN WIRELESS November, 1923

DOODDOOODODOODODOODOODOODOCIDOODOODDOMODOCIOODOCCODODODOOODOOODOODDOOD0 D 0 HOW TO MAKE A PORTABLE ST.100 0 oO 0 O 0 O RECEIVER o o D 0 By JOHN SCOTT-TAGGART, F.Inst.P. El O 0 This article deals with a portable two -valve receiver which may be used with either a frame aerial or 0 oO o o an outdoor aerial, and which will give loud -speaker results on even small aerials up to 20 miles from o oD a broadcasting station. 0 DOOODOODOODOODOODOODEDOODOODEDOODOOODOODDOODODOODOODDODOOODDOODOOD000

IN response to many requests,nectedacrossthe terminals T,etc.These connections were found I am giving below thede- and T7, the high-tension batteryto be suitable with the transformer scription ofan ST. ioore- across the terminals T5 and T,,employed in the set, but if the com- ceiver wh_ch has given excellentand the six -volt accumulator acrosspleted instrument tends to buzz results -and which presents a neatthe terminals Ts and T4. at low frequencies, the constructor appearance.The set is illustrated In Fig.2, T12, T10, T T21 isis advised to try reversing the leads in Fig. I. a step-up intervalve transformer,to one of the primary windings. It will be seen that the panel,T12 and T1, being the primary and In Fig. 2, various- points in the underwriicharemountedtheT, and T11 being the secondary.circuit are numbered ; for example, various components, is fixed into a box provided with a deep lid, on the top of which is secured a leatherstrap.Two hooksare provided to close the lid which on the other side is hinged. The circuit used is the ST. ioo, wh ch is conta ned, with various modifications and alternatives, in my second book of valve circuits entitled" More PracticalValve Circuits."*The circuit has been modified somewhat inorder to provide for the alternative use of the aerial condenser C1 in series orparallel with theaerialin- ductance L1.Also, terminals are provided for the use of a loop instead of an aerial.These various terminals are shown as A1, Al, B, C and E in Fig: 2.In: Fig. 2, two terminals T, and T1 -are- pro- videdinnthe two grid circuits. A battery of from 3 volts to some- times9 volts may be connected across the terminals T2 and T1, - T2 being next to the negative terminal and T1 to the positive terminal of the battery.To start with, however, the terminals T1 - Fig. i.-The complete instrument in case. and Ta should be short-circuited ; likewise, the author recommends' Likewise, T14, T15, T13, T2, T,,, T23.These different points that the aerial should be connectedis a similar intervalve transformer.correspond to the wiring diagram, on to the terminal Al so as to useThe condenser C, is a fixed con-Fig. 6, so that anybody studying the variablecondenser Ca in seriesdenser of o.00i IX capacity.Theth-s latter figure will be able to see with theaerialinductanceL1, - fixed condenser C Wh_ch is con-at a glance where the various points the terminal A, should have noth=nected acrossthe terminals T5, comeenthecircuitdiagram, ing connected to it, while. B and CT,, has a value of o.o02 tLF ;theFig. 2. should short-circintecl; the" resistance R, is a roo,000 ohms Fig. 3 shows a closer view of the earth lead is -taken to 'the' terminalfixed resistance ; 'the trahsformers, panel itself.It will be seen that E.The loud -speaker L S is con-it will be noted, are marked on Fig.at the back of the panel we have 2 in such a way as to indicatefour terminals which correspond * Published on November 7 by Radio Press, which is the " in " secondary andto A1, A,, B, C and E in Fig. 2 Limited.Price 3s. Ed., cloth bound. out " secondary (I S and 0 S),and Fig. 6.At the right of the

88 November, 1923 MODERN WIRELESS

TI8 the various terminals belong to. Tz6 OP IP J. 6 The terminals T and T are 7-27 L2 Th5 TI'QQQQ the I S and 0 S terminals of one T25' 73 T7 9T5 of the transformers.The terminals Ci 97-17 CTOO} T and T, which, of course, are A2 0 T28T20 T.30 rins 105Tis /- 17/ /5 R2 on the other side of the transformer, L1 are the 0 P and I P terminals Ti Tz.9 respectively.Similarly,theter- T3 minals T. and T11 are the I S and IP O S terminals of the other trans- TI2 former,while T and T are To TT2 T7 the 0 P and I P terminals on the other sideof that transformer. OP OS Tzi R., of course, is the roo,coo ohm o TI resistance mounted between two clips.T23 and T have nothing to do with the two Polar condensers, but are the screws which go to the Fig. 2.-The circuit diagram numbered to correspond with the wiring diagram. terminals of the crystal detector. The two little vertical rectangles, panel we have four terminals, thethe wiring is done with thick bareT and T aretheterminal top two go to the high-tension copperwire,preferablytinned.lugs of the Polar condenser.The battery, while the lower two goNo. 16 gauge wire will do, or No. r4. similar connections, T and T to the filament accumulator.TheAll the connections are soldered.are the terminal lugs of the other two terminals in frcnt correspondIf this method of wiring is found tooPolar condenser.The holes, T19 difficult, there is no reason whyand T20 pass the wire connections tothe terminals T1 and T. in going to the moving coil holder Fig. 2and 6 ;these terminals properlyinsulatedcopperwire are usually shorted, but a gridshould not be employed.Itis which containsthe coil in the battery may be connected acrossto be noted that two fixed con-anode circuit of thefirst valve themifdesired.The two ter-densersareused ;acondenser (L2).The holes, T arid T minals cn the left of the panel of - o.00r ttF capacity is connectedsimilarly communicate with the have connected td them the leadsacross the terminals of the second-fixedcoil holder which contains frcm the loud -speaker.The crystal ary of the right-hand transformer,the aerial coil L1. detector will be seen in the middleand that a fixedcondenser of It is to be noted, with regard to background.Itisofthe -cat-0.002 tiF capacityis connectedthese connections, that NA hen opera- whisker type enclosed in a glassacross the two terminals cn theting the set, the two coils should at tube. Two Polar condensers areright to which the loud -speaker isfirst be kept well apart ; that is to shown onthepanel;eachof connected. say, at right angles to each other. these condensers has a maximum Fig.6istheactualwiring As the moving coilisbrought capacity of o.000. µT.. Other typesdiagram.The Figure will requirecloser to the fixed coil, reaction ofcondenserscould,ofcourse, close,attentionto see whatshould be introduced, and an in - be equally :well employed: In the frontofthe panel is a two -coil holder;the left-handholderis fixed,while the nght-hand one may be moved through an angle of about 90 degrees by means of the long. extension handle consisting of, a piece of- brass -red with aii ebonite knob at. the end. Pg. -4 is a plan of the, pane!; show ng how the differentcorn-, per:Li:zits are arranged.It will be noted that in the, left-hand coiner we have thefilamentrheostat wh ch controls the filament current to both valves.. F g. 5 is a back view of the panel .how ng how_ the transformers and condensers,etc.,aremounted'. be seen that a special ledge is provided for mounting the two intervalve transformers. This ledgeispreferablyapieceof ebonite supported by two other pieces Of ebonite screwed to the panel.Itwill be noted that Fig. 3.-A "Close-up" of the pane*.

89 MODERN WIRELESS November, 1923 crease of signal strength noted as the two variable condensers are readjusted.If the signal strength does not increase,itis a clear indication that reverse reaction is bringobtained.Owingtothe largenumberofplug-incoils which are now being employed, it may be found necessary to reverse the connections to one of the coils to get the reaction effect.This reversal of connections is best done on the moving coil.In the case of most coils, it is a vary simple matter to undo one or two screws, and without undoing the connection reverse the coil itself on its holder; screw up again and use the coil as before, preferably marking it with the letter R to indicate that its coil has been reversed from the normal. Thealternativeisto reversetheleads going to T17 CD * and T. ® ® As in Fig. 6 itis not possible to show the condenser C4 very clearly, a special remark will be notedabovethe, terminalT7. This is to the effect that there isa condenser C4of 0.002 µF Kg. 4. -Panel plan, condenser connected across the terminals T7 aed T. The box, into which the panel ismounted,isdimensionedas shown in Fig. 7.The ebonite panel Measures 9 ins. by 8 ins., and is secured by four terminals let into the wooden vertical partition shown in Fig. 7.The other dimensions 'of the bax are clearly indicated in. Fig. 7.'The compartment on the leftcontains a zoovolts high- tension battery, as the set is in - t ended to operate with too volts. A special high-tension battery of zoo volts and of suitable size has been specially designed by Messrs. A. H. Hunt,Limited,Tunstall Road, Croydon.The two compartments on the right side of the box are intended to hold the coils, etc., and to provide a compartment ich. the filament accurnulator. The size of the accumulator will depend upon whether dull emitter valves of ordinary valves are employed. An ordinary dry battery, suitable for dull emitter valves, might be placed in one of the compartments, or, if preferred, a dry battery could be connected in each of the com partments. Those readers who prefer to mount the panel in an ordinary box Without any compartments may, of course, do so. Fig. 5.-A photograph of the rear of the panel. Continued on page 98.

90 November, r923 MODERN WIRELESS

DDEDEDDEEDD000000000000=00000000000000000000G0000000000000000000000=000

pi THE CONSTRUCTION OF A HETERODYNE

WAVE -METER

Covering a Wave -length Range of from 300-4,500 Metres

The following article describes how a simple and reliable generator of local oscillations for use in heterodyne reception of continuous waves and for other purposes may readily be made.

By ALAN L. M. DOUGLAS. ODOM MEJOIDOODOODOOODOD=DOMMECOMEOCODOOMOODE=0000000000000000000E000 ALOCAL oscillationgenera- device), it will be apparent that therenectionswill be observed from toremployingathree - are only two adjustments to be madeFig. 4. It will be seen that a electrode valve isofthefor the production of continuousvalve of the V 24 pattern is used in greatest value to the experimenterwaves of any frequency betweenthe oscillator, and the low capacity when receiving continuous waves, the range limits of the instrument.existing between the fitting and especiallyinthe longer wave-This feature greatly increases thealso in the valve itself makes this lengths where the loss in efficiency usefulness of the heterodyne, andpatternparticularlysuitablefor due to the employment ofself - isduetotheintroductionof use intheshorter wave -lengths heterodyning receivers is very con-separate reactioncoilsinto thewhere the frequency is abnormally siderable.Inaddition,thein- various oscillatory circuits instead high.The reader is therefore ad- tensity of the oscillations is readilyof adjusting the coupling of thevised to adopt this make of valve, controlled, and any desired degree grid coil.This function is carriedasitis also a very consistent ofcouplingwiththereceivingout by means of the rotary switchoscillation generator and most re- amplifier may be obtained.Again, seen in the centre of the panel inliable.The filament circuit, it will if suitably connected and accuratelyFig.3, and the scheme of con -be observed,isarranged to in- made, the device may be corporate a small rheostat calibrated against stan- (referred to later on) with dard waves and subse-. the intention of allowing quently employed as a - the valve to work at about wave -meter. Finally 5.4 volts from a 6 -volt there are many experi- battery, at which point it mental purposes for appears to work best. A which the oscillator may variable rheostat might be be used in conjunction used,butthisentirely with an ordinary reaction upsets the working of the circuit in order to produce instrument, and it would great selectivity, or under not be suitable for cali- certain circumstances an bration. increase insignal Let us now see what strength. materials are required for Theinstrumentde- the actual construction of tailed in this articleis the oscillator before we remarkablysimplein proceed any further.In adjustment andopera- the first place an ebonite tion, and, owing to the panel 8 in. by 61 in. by nature of the inductances, lin. thick will be required, may be relied upon to which might be finished to remain constant in opera- suit.In the author's case tionatalltimes- this panel was obtained providedthebattery with the edges already cut heating the filament does and rounded off,which not discharge itself too saved a certain amount far. of initial and more or less Before examining the unpleasant work. Such constructional datalet panels may be obtained usobserve the general from several supply design and arrangement houses, and in thispar- of the instrument. Frcm ticular size are of great the photographs, Figs. r usefor any component and 2 (which show front partsofreceiving am- and rear views of the Fig. r.-Front view of oscillator. plifiers, etc.

91 MODERN WIRELESS Novemoer, 1923

Having' Obtained the panel to Turning now to Fig.5, whichtherefore be turned out to about the dimensions already given, there showstheconstructionofthe in., and a separator, to ensure will also be required :- ebonite blocks carrying the neces-correct coupling between the grid 4 oz. No. 40 swg.d.s.c. coppersary coils,itwill be seen thatand anode coils, consisting of a disc wire. circles have to be turned out ofof 4 -in.ebonite sheet1 in.dia. }lb. x8 swg. bare tinned -copper the slabs to accommodate the coils. (with a r -in. centre hole, through wire and 3 yards systoflex tubingIn order to ensure these latterwhich, of course, the former passes), for connecting up. fitting well, and as the depth ofshould be made.While the coils, variable 'condenser havingawinding may vary somewhat inetc., for the first range are therefore capacity of 0.0012 PF, whichindividual cases, it will be best tonewly made, we can assemble the should preferably have an airmake the coils first and turn thecomplete oscillatory circuit for this dielectric in order that the mini-holes in the ebonite later.Therange in the following manner. mum capacity may be small. various coils are all wound withThe slab, having the hole turned in r small fixed condenser of 0.0005 tiFthe No. 40 swg. d.s.c. wire in theits centre, is laid on the bench on capacity. form of basket coils on ar in.a sheet of glass and one 75 -turn 2 yards ofNo. 23swg.d.s.c. ebonite former, which should bebasket coil placed in it, the leads Eureka wire. being brought out.The 9 contact studs and nuts, separator is then inserted etc. and pressed down in the A 2 -inch ebonite knob and firstcoil. The former spindle, knob, etc. isplacedthroughthe About 6 in. of fin. by 116- in. separator and thefirst springy phosphor -bronze coil and the second coil strip. put into position on the 2feetofNo.4B.A. former untilitisalso screwed brass rod and lying within the slab of nuts. ebonite.The leads from 4 in. by 4 in. by .002 in. these are brought out and copper foil.V.24 valve alittleparaffin -waxis clips and nuts, etc. poured into each coil so 3ebonitecoilformers, astohold theentire which will be detailed, assembly firmly in posi- and forwhich about tion. The first range slab 31 in. by 12 in. by 4 in. is now complete. ebonitesheetwillbe The coils for the second oscillatingsystemcan required. now be prepared if de- About 12square inches sired,andtheanode of, 4 in. ebonite sheet. coilfor this group may 6 B.A. by 4 in. screws and consistof15o turns of nuts, 6 terminals. the same wire x in. of # in. ebonite rod. aspreviously V.24 Valve. usedonthe This completes the list same size forof component parts, from mer :this will which it will be seen that occupy just nothing very formidable under a 2 -in. is required, with the pos- hole in the slab, sibleexceptionofthe sothatthe variableaircondenser. recess may be This should be purchasedFig. 2.-View of instrument, showing grid and anode coils separated, andturned out to readymade,asitis ebonite spacing washers. thisdiameter. vital thatthecapacity Fig. 6 will shouldremainconstant.Itis, cut up into 34 -in.sections.The make clear the appearance of the however, possible to construct quitefirst coil should have 75 turns ofslabs and the method of turning a satisfactory device oneself, if duethe 40 d.s.c. wire, which will deter- the cover disc for the last coil, care is taken, but attention mightmine the diameter of the hole to whilstthephotograph,Fig.4, be drawn to the necessity for having be turned in the first block for thisshows at the bottom right-hand reallyrigidendplates. These coil.At the same time anothercorner two of the separator discs. should be atleastfir,. thick.coil of 75 turns may be made, as Another ofthese latterdiscs 2 B.A. brass rod should also bethese constitutethe anode andmay, now conveniently be turned usedforthe side supports,asgrid coils for the first or lowestup, so as to space the second grid greater rigidity is thereby assured.range of the oscillator.The wave-coil from the anode coil, and the Several excellent condensers having length range of this set of coils isgrid coil itself, consisting of 6o turns metal end plates are now on the from 300 to 76o metres. of the No. 4o d.s.c. wire, placed in market, and can be recommended ; The overall diameter of this coilposition. The leadsfrom these they may be obtained from adver- willprobably beapproximatelycoils should be brought out at the tisers in this journal. 1i in.The hole in the slab shouldtopand bottomoftheslabs

92 November, 1923 MODERN WIRELESS respectively, and are to be well separated. Wax can be used to fill up the interstices of . the coil and make the whole second range slab complete as before. At this point itwill be, convenient to note that the screen which is fitted over the first range coils may be made.This consists of a plate of thin copper sheet of the same area asthe slab and having four holes punched through itscorners,so asto anchor it firmly in the guide supports for the coils, and is necessary to prevent the proximity of the large coils minimising the production of oscillations in the lower range.It is cut from sheet copper and electrically connectedtothe junction between theH.T. - and the' L.T. -F,as shown inthe circuit diagram.Care must be taken to see that none of the fine wire leads from the coils are in danger of short- circuiting on this plate, and grooves should be fitted along the surface of the ebonite where these wires pass out. Connections to the range slabs are made by means of small 8 B.A. cheese -headed brass screws attached Fig. 4.-Layout of underside of panel and wiring scheme

to the underside of the small range disc, and which can be clearly seen 6%. in the figures. A row of screws along the top connects the anode coilsincircuit, and asimilar row at the foot connects the grid 00 coils ;the common wire being that 18.A Holes attached to the linked screws in 3 each case.The constructionof the highest range coils may now be undertaken, and the hole for this will require to be 2I in. diameter in its slab.The anode coil consists of 30o turns of the No. 40 d.s.c. 0 wire in the I -in. former, with the 8x4 separator as before, and the grid coil 14o turns of the same wire on the same sizeofformer.The cover -plateshowninFig.5, which protects this last slab, may be made and attached if desired, the leads from the coils having been brought out and the slab filled with wax as in the previous cases.This completes the construction of the coils,anditonlyremainsto examine their method of mounting. Th's is carried out, as will be seen from the figures, by means of r- B.A. screwed brass rod attached Fig. 3.-Layout of top of pane. -in the rear of the panel and passing through four holes in the corner of slabs.No special instructions

93 13 MODERN WIRELESS November, 1923

ably be -rigid.-The methodof attachment can be seen- from the photograph, and it is of importance that the valve should be so fitted in order thatthe anode -gridcon- nections on the various circuits may be short. Thevariableaircondenser already referred to may be affixed to the panel as shown, and in this case again the terminal or other connections should be placed so that they are near to the switch. A condenser having rigid plates and a perfect contact with the Fig. 5.-Ebonile coil holders and details of switch arms. rotatingspindle should be used in order that inaccuracies may not are necessary here, as the rods arenecting up it is so far immaterialarise. screwed into tapped holes in thewhich arm is which, as long as the The L.T. and H.T: terminals can, panel and the slabs held in place proper sequence of studs is adhered of course,- be of any desired type, by means ofnuts and washersto. and the telephone contacts (which suitably disposed on the rods. This switch is mounted in theare normally short-circuited) 'might The next item to which atten-centre of the panel in any manner tion should be directed is the con-convenient to the reader, as it is a struction of the range switch which purely mechanical job and may be can be seen in the photograph,constructedinvarious ways at Fig.r,andalso indetailin will. Fig. 6.This has, as will be seen, The next item will be the fila- three arms which make contactment rheostat, which isa very simultaneou-sly with three differentsimple job.It is of such a nature setsofcontactstuds.Oneof that the valve burns at a fixed these arms controls the anode coils,temperature all the time, provided one the grid coils, and the third thethat a six -volt accumulator reason- capacity introduced by rotation ofably charged is used.The resist- the condenser knob.This is lessance is 1.4 ohm, and this made relatively on the shorter range thanfrom 2 yd. of No. 23swg. d.s.c. on the other two.The construc-Eureka or otherresistance wire tional details are clear- from thewound on a short length of x in. figures, it being merely necessarydiameter ebonite rod and affixed to say that care must be taken,,to the underside ofthepanel, should the knob. selected for this beneaththerangeslabs.Two switch have a metal bush, that6 B.A. by Fin. brass screws inserted only one of the three arms be. infrom the front of the panel serve to Fig. 6.-Assembly of coils and contact with this.Connection tohold this in position. switch. the other two is made by means The clips for holding the valve in offlexiblerubber -coveredwire position may be made, if desired, soldered to the contact arms andfrom the same material used forbe either terminals or, better still, brought through appropriate holesthe arms of the rotary switch, butan appropriate plug connection. in the front of the panel.In con - at least one contact should prefer- This completes the description of the oscillator, a final word in connection with the wiring being necessary.Should oscillations not be produced on one of the ranges, 'the connections to the grid coil of VALVE - the range in question should be . reversed ;this may be effected by G means of the screws connections - already referred to.It -may save trouble ifit is remembered that when wiring up the coils,if the H.T. direction of winding of each pair is the same, then if the connection to the grid is taken from the inner end of the first coil, the connection LLT. to the anode -will come from the outer end of the second coil. Fig. 7showsthe theoretical Fig. 7.-TheOretical circuit diagram. wiring scheme.

94 November, 1923 MODERN WIRELESS

Broadcastlraveleny,as

Ultra Long Waves may become a " blind spot " to so approaches more nearly the sur- ITislikelythatweshall short waves during the hours of face of the earth.Even the middle hear a good deal in the neardaylight, but be able to pick up layer may at times become ionised. future. ofthe use ofultra - long ones.By night these effects The longer the wave the more longwavesforwirelesstrans- willnotbequiteso marked,sharply will it be reflected back to missions, particularly those overthough,otherconditionsbeing earth by the ionised layers, and, great distances.Very short waves, equal, the long waves will still give conversely, the shorter itisthe ,of which we spoke some time agorather more powerful signals. more will it tend to dissipate its inthesenotes, have the great energy in the conducting or semi- advantagethattheycanbe How Short Waves Dissipate conducting portions of the atmos- focusedby meansof suitable Energy phere.The advantageofusing parabolicreflectors into a beam This is due chiefly to the con-great wave -lengths for stations that or pencil and so directed in adition of the upper atmosphere. must be able to rely upon covering saaight line..As we saw, veryThrough a medium which isa huge distances at any time during successful tests have been madeperfectdielectricwirelessofall thetwenty-fourhoursisnow with waves ranging from ri tokinds pass without loss of energy, apparent. 15 metres, the Wave -lengths near directing properties AudibleFre- of the transmitter quencies beingsuch thatV The highest wave- signalscould not length now i n be pickedup by commercial use is stations half a mile 'ocooloom that of Bordeaux, off a straight line (0000) which transmits joining transmitter MA /NS on 23,450 metres ; andreceiver. but it is likely that Against this, how- before long we shall ever, must be set see stations using the fact that, speak- oo,000oreven ing generally, a very NW A. 300,000 metres. shortwave -length Al/A At 23,450 the fre- means a very short quency is12,793, range ;the writer whichapproaches believesthatioo the upper limit of miles is the greatest audibility. At distance over which ioo,000 metres it such transmis- Fig. 1.-A typical aerodrome transmitting st would be 3,000 and sionshavebeen at300,000 only attempted up to date.Even waves but if the medium loses its dielectric L000.Either of these last is well of far greater length, that is toqualities and becomes more andwithin the compass of the human say those which lie between 18omore of a conductor there will be ear.In fact, a frequency of r,000 and 1,50o metres, are very much considerable losses by absorption as is only a little above the average affected by a whole host of varyingwaves travel through it.Further, for broadcast transmissions ;low factors.Their range is enormously in such conditions short waves will frequencytransformers intended increased at night time, they are dissipate a much greater proportion for receiving telephony are usually much affected by the dampness or oftheirenergy thanwilllong designed for an average frequency dryness of the soil over which they ones. By night only the outerof 75o cycles a second. travel and they are very liableportionof theatmosphereis The useofultra -longwave- to be deflected by ranges of hills,ionised, but during the hours oflengths, then, opens up the way especially in the daytime.Thus adaylighttheionisedconductingto entirely new fields in wireless. receiving station situated in a valleylayer rapidly increases in depth andExperiments already made in this

95 MODERN WIRELESS November, 1923

country and in France have shown Thechiefhomestations, indelivers Lso milliamperes at raoo that extremely good results areaddition to these three, are nowto 2,000 volts. obtainable.It may well be thatManchester, Guernsey and Ren- the adoption of wave -lengths fromfrew, so that wherever one's station Aeroplane.Sets four to twelve times the length ofmay be there is always a wide The original R.A.F. aeroplane any now in use will go far to solvechoice of home transmissions attransmitting set is seen in Fig. 2, the pressing problem of the over- differentranges.Beyondthese and the Marconi commercial 'plane crowding of the ether. there are the stations at Le Bourget, set in Fig. 3.The latter is now in St. Inglevert and at Rotterdam, universal use on British passenger Atmospherics and Long Waves all of which are to be heard at 'planes.It is known as the A.D.2 There can be no doubt that it frequentintervalstransmittingand consists of a modulator and an will result in longer ranges for given weatherreportsorascertainingoscillator, with choke control. The power and that it will render longfrom pilots the position of theirvalvesareof a specialaircraft distancewireless transmissions 'planes. pattern, rated at 6o watts. A - wind - much more reliable than they are at driven generator supplies 600 volts present.One difficulty, however, " Ground " Transmitters to the anodes.The ranges of this will probably arise, and that is the Croydon, perhaps the best knowntransmitter are :Continuous Wave question of preventing interferenceof all aerodrome- stations, has an zoo miles, Tonic Train 13o, and from atmospherics.Anyone whoimposing aerial of the twin four -Telephony Ioo. hasexperimented with a very'wire cage type 250 .feet in length, In favourable circumstances the large tuning inductance, one withsuspended between lattice girdertelephonic range given above is. a value of the order of 2,5oo micro- masts 13o feet high.The trans-considerablyexceeded ;recently henrie, when atmospherics were mitter is Marconi built, and follows a 'plane was in direct verbal com- at all bad will have found thatthe lines of Fig, x, which shows amunication with Croydon from the certain of them come in not astypical aerodrome transmitting in-time of leaving the aerodrome until scraping or tearing noises, but as stallation.At Croydon the oscilla-it was over Le Bourget. Croydon, loud musical notes. however, usesa This would seem verypowerful to show that as we receiver with four approach xoo,000 stages of high -fre- metres we are quencyamplifica- comingnearthe tion. wave -length of at 'Plane Ranges any rate some at- The amateur mospherics. As al usingtwo H.P. their strength is in- _N.stagesmayfeel finitelygreater quite satisfied with than that ofany hissetifitwill transmission, very bring in aeroplane serious interference 0 H. WA telephony at from might be expected 25 to3omiles. if their tuning W thiscombi-, approximated to . nation the Writer that ofreceived Fig.2.-The original R.A.F. aeroplanetransmitting set. has,onseveral signals. occasions heard - torisduplicated, two 500 -wattpilots stating that they were just Aerodrome Stations valveSbeingusedinparallel. leaving or arriving at the French Most wireless men can rememberThe input is i4 kilowatts.The coast, the point given being about the time when broadcasting did nothigh tension supply isobtained8o miles from his -aerial. - Ent these exist and when the experimenterby means of a transformer from the receptionstookplace onparti- who was working in the daytimemains,the stepped up voltagecularly favourable days when the on telephonic_reception was almost being 7,000. -This is rectified by- a- -- signal- strengthofall distant entirely dependent upon the airpair of valves, as seen in the diaw-stations was above the normal. stations.The Eiffel Tower coulding.This rotary transformer is one - To pick up 'plane -transmissions usually be relied upon for some-of -the blots on Croydon's otherwisedemands qu ck and accurate tun- thing during the afternoon, and atfairescutcheon,forevery ex- ing ;qu' ckbecausethe-pilot's nighttherewere the - amateurs. -perimenter knows its loud hum,replies or queries are usually very F.L., however, had then, as now,which can be heard the moment short,and accuratesincethese a wave=length of 2,600 metres andtheswitch is thrown over. comparatively feeble transmissions was,therefore, outside the scope Croydon's ground to air telephonicallow little or no margin of error. of short wave work, whilst the range is Zoo miles. Ifyoursetistunedcarefully arhateurs, then working on r,000 The other stations are fitted with to Croydon's wave -length it will not metres, wererarebirdsbefore the Service(R.A.F.) Transmitterusually be necessary to touch either nightfall.:ItwasonCroydon, type - 56,though ih some casesA.T.C. or C.C.C. in order to catch Lympne andPulhamthat wemodifications'h-avebeenmade. a message -from a 'plane, to which relied -chiefly, and to -day they areThis transmitter uses the E- 9B he is speaking:It is best to work as useful asever,for they are250 -watt valve, and is rated atwith the coupling between A.T.I. - always to be found at work during I kilowatt.The anode supply isand C.C.L. or the reaction coupling. flying hours. obtained from a generator whichTiny variations in these, the latter

96 November, 1923 MODERN WIRELESS especially, generally suffice to en-capacity such as that used is very The Aerial at Fault able one to obtain the necessarygreat.The result is that reception Sometimes it is not the set but sharpness of tuning. is very poor, and that the set fallsthe aerial that is at fault. Amateurs in oscillation at the slightest pro-are occasionally fired with the idea Reaching the Short Wave -lengths vocation. of erecting a very large aerial whose Many people find it very difficult A moment's thought will show roofconsistsof many parallel indeed to get down to 18o or eventhat when the condenser is in serieswires.Though excellent for long 200 metres with sets that are notthe old rule about using the biggestwave reception, such a contrivance built specially for short wave work ; inductance and thesmallestwill not give good service on the in fact, quite a number of experi- capacity does not apply.It holds shorter wave -lengths. The capacity menters complain that they cannotgood only when the condenser isof a standard amateur aerial con- tune in the amateurs at all success-in parallel.When it is in series itsisting of twin wires 6o feet long, fully now that they are workingis a sound rule not to letitsseparated by six foot spreaders and on the very short wave -lengths.capac ty be reduced below suspended 3o feet above the ground The 'cause of the trouble may lie 00025 µF.Hence, if its maximumis about .0003 µF.Every added at several points in the set.When, capacity is.00i µF the pointerwire increases the capacity and for instance, high frequency trans- should not be turned below 45therefore the natural wave -length formers are fitted, these are seldom degrees ; if .0005 µF, then 90 degrees of the aerial.You can load an so wound that they will tune down should be the lowest limit. aerial up to many times its natural efficiently to below 25o 'metres or wave -length, but any attempt tc thereabouts.Itwillbefound Unsuitable Wiring receive short waves with an aeriai better to substitute the tuned plate The wiring of the set,again, of large capacity will result either method of coupling, using as anodemay be so carried out as to makein no signals being heard at all, 01 inductance coils of in their coming in the smallest possi- with verypool b1e self capacity. strength. Again, four -pin Aen al insulation valvesseatedin is another particu- moulded ebonite larly important holdersmake point to notice in matters difficult connection w i t 11 owing to the fairly short wave recep- large capacities ex- tion.Most of the istingnot only losses thattake withinthevalve place in the receiv- but alsobetween ing aerial are due to the sockets, wh ch currents passing by are separated by capacitythrough an excellent dielec- the insulators. The tric. The combned h gherthefre- capacities in a fou r - quency the more pin valve mounted WA. easily will currents inthis way may 0H escape ;hence on amount to as much E short waves itis as .00006 µF, which Fig. 3.-The Marconi Commercial' Plane set. naturaaly essential isquitesufficient to reduce insulator to make it very capacitytoits hard to reach theshort waves. it quite unsuited to work at verysmallest possible limit. high frequencies.On the longer LAMBDA. The Series Condenser waves a certain amount of capacity0000000000000000000000 A point frequently overlookedbetween plate and grid leads may not giverise to appreciableill D A USEFUL DEVICE is that the aerial tuning inductance 00 may be much too large, making it effects ;but once we descend to0000000000000000000000 necessary to turn the pointer of thethe short waves the presence of any The Bay -Brooke Co.,Ltd.,of series mounted variable condensersuch capacity is felt at once.ItHarborne, Birmingham, send us a almost to zero.One occasionallyputs up the natural wave -length ofspecimen of their valve templates. comes across a friend who complains thecircuits,makingitsome- This consists of a square of glazed bitterly about the feebleness of atimes impossible to tune belowcloth having printed on itthe particular station's transmissions.certainfairly highlimitssatis-correct spacing of the valve pins He has done everything that hefactorily,anditincreases very andthepencilscrew,together ought to have done, he explains,markedlythetendency toself with two circles.The outer circle placed the condenser in series and oscillation. is the average diameter of an R obeyed all other rules. Examination To make the set efficient on shortvalve and the inner circle is the generallyshowsthatthecon- wavesre -wireit,eschewingin- average diameter of an Ora, Edi- denser to bring in this station mustsulated leads and using stiff bareswanA.R.,Dutch,Cossoror be set at something under io degrees. wire.Keep all wires as short asXaudion valve. The back of the This means that the aerial is practic-you possibly can, separate theMtemplate is covered with a special ally cut out, for even at high fre-well and see that no two run adhesive composition which readily quencies the reactance of a tinyparallel and close together. adheres to ebonite.

97 MODERN WIRELESS November, 1923

BA:CK C B A2 AI

FIXED CONOEN5R C4 0-00211F

T71 0

//I

L 21 FRONT

Fig. 6.-The actual wiring diagram.

Continued from page 9o. A complete blue print, containing both a full sized wiring diagram, similar to Fig. 6, and also a full sized panel layout, as in Fig. 4, onlylarger,isobtainable from Radio Press, Limited,Es_wereux Court, Strand, W.C.2, for the sum of is. 6d., each.These blue prints are produced purely for the convenience of those of our readers who desire them.

5 READ Wireless Weekly for Latest Wireless News. Fig. 7.-The box dimensions.

93 November, 1923 MODERN WIRELESS

001:101:10000OOMMOMMOMEIEMOODOCIOCIODOCIDOMOMOODOCIODOLIUDOEMODOODOOMODOODOO

ElOD O 0 SINGLE -LAYER INDUCTANCE COILS 8 O 0 D SUITABLE FOR RADIO FREQUENCY STANDARDS* o oa° 00001:00171MOMMOODOOMMOOMMECOODOEICIMODOMMOOMMOODOMMOIDOCIOMMOOMOO EDITORIAL NoTE.-The following article, which is a reprint of a publication issued by the Bureau of Standards of Washington, will be found to be exceedingly useful to all who desire to obtain accuracy in their radio frequency measurements.If the coils described are wound exactly as indicated and used with variable condensers, the value of which is accurately known, the experimenter will be able to construct a calibrated wavemeter with great ease. WING tothe increasedinterestin The several coils have been designed and radio -frequencymeasurements,this grouped so that the coil rings for the coils in paper has been, prepared, giving rather groups II, III and IV are cut from the waste detailed instructions for the construction of from the rings in group V.The coil in group I. a series of single -layer inductance coils suitable (one coil only) is small and is therefore grouped for radio -frequency standards.Coils of this by itself to avoid design difficulties. type have many uses in the laboratory where No definite specifications for size and kind a fixed inductor of a known inductance and of wire can be given.It is probable that after having a small radio -frequency resistance is the complete series of coils have been made, desired.This type of coil in conjunction with either in sheet or moulded materials, sufficient a high-grade variable air condenser such as measurements can be made to determine these the Bureau of Standards type forms a very factors.It is possible to use various kinds of dependable and accurate wavemeter. solid conductor such as bare copper, tinned or This series of inductors, seventeen in number, nickelled bare copper, enamelled copper, single have been designed to cover the approximate or double cotton -covered copper, single or double inductance range of 8 to 5,000 microhenries. silk -covered copper.All other factors being the Beginning with the smaller coil, each succes- same, when solid copper wire is used, the bare sive coil has approximately 1.5 times the induct- wire would -be preferable.This isbecause ance of the previous coil.The following table (i) such wire does not add another dielectric gives the approximate values of inductance of in the field of the coil, and (2) cotton, silk each of the coils in the several groups : or other such fibres may contain a percentage Coil Inductance of moisture which will further add to the dis- designation L tributed capacity of thecoil.When bare number. Group. microhenries. wire is used it would seem preferable, from 1 I.... 8.o the standpoint of appearance and also because 2 ... II.... 12.0 of certain electrical and mechanical advan- 3 ... II.... 17.9 tages, to use either tinned or nickelled wire. 4 II.... 26.7 The uncoated wire will become discoloured 5 ... II.... 40- and form an oxide coat which is not a good

6 ...III. .. 59.8 dielectric. Furthermore, the tinned or nickelled

7 O se III. 89.4 wire is more easily soldered.If silk or cotton - 8 ...III...... 134. covered wire is used, it is probable that the

9 ...III. ... 200. silk would be preferable, but for general use 10 ...... IV...... 299. it cannot be definitely stated that the advan- II . IV...... 447. tage gained would be sufficient to demand its ' 12 . ... IV...... 669. use.The use of solid enamelled wire may add 13 ... IV. .moo. to the appearance of the finished coil, and for 14 V. ..1495. thecoils having sufficientlylarge winding 15 V. . .2235. pitch the electricalcharacteristics may for i6 V... 3342. practical purposes be comparable to those of 17 V. . .5000. cotton or silk -covered wire. * Preparedby J.I..Preston, Physicist, and High -frequency (" litzendraht ") cable can M. S. Strock, Assistant Physicist. also be used.Itis understood that high_

99 MODERN WIRELESS November, 1923 frequency cable employs two types of dielectrics (insulation) in itself. The individual strands areofsmall diameter wire, enamel -covered, and theas- sembled cable is given a single or double serving of silk. This outer covering isessential to protect the fine wire and the enamel insulation underneath. If high -frequency cable is used, itisvery important thatit pass certain requirements. Two importantrequirementsare, thateach individualstrand should be continuous throughout the entire length of the cable and each strand should be insulated from every other strand throughout the entire length. As to the size of the wire, it would seen that, for mechanical reasons, the wire should notbe much larger than No. 18* (B. & S.).This limitation permits of the use of high -frequencycableas large as 48 strands of No. 38t wire.

* Approx. No. 19 S.W.G. ig.1.Details of the coil formers.Dimensions are given in the Approx. No. 40 S.W.G. table on the next page. 000D001000100000000000D0D0range of from the shortest wavesO 00000000000000000000000 D 0 O 0now in use up to just over 4,000 D Practical Hints on 0El metres witha.00i I.LFvariable D 0 condenser.In Figs.1 and 2 allEl A REUNION 1=1 Using the Tables D dimensionsaregiven and con- 0El structionaldetailsfurnishedto 0 100000000000=0000000000enable the experimenter to buildO 00000000000000000DOODEO IT will be noticed that the in-up his coils to the best advantage. Arrangements have been made for ductance of the coils is givenThe small tables in Fig. 2 may need a little explaining.The columnthe Annual Reunion Dinner for in microhenries.To calculate past and present officersofthe the wave -length with these coils itmarked SYM means symbol and is only necessary to use the simplerefers to the symbols used in theW /T School and Squadron, Royal formula (wave -length in metres) figures. Column 2 marked REQAir Force, to take place in London, A= 1.885,/Lx C means the number required.Thus onDecember 5. Itisto be in the first table where under REQ 8regretted that it will not be possible /L in microhenries and is given this indicates that in making kC in microfarads the coil you will require eight ribs.to issue direct invitations this year Every wireless club should have S.milarly two brace rods are required. to all ex -officers interested, owing an accurately calibrated variableThe columns marked withtheto the fact that certain records, condenserof good make, agan3tletters A to K refer, of course, tocontaining lists of addresses, have wh.ch the membersshouldbe the various letters in the diagram. been mislaid.The Secretary will able to calibrate their own vari-To give one further example, alsotherefore be glad if those concerned able condensers. If the reader istaken from thefirsttable,the will regard this announcement as a able to calibrate a variable con-radius of the coil marked B in thepersonal invitation. Applications denser, then with the aid of thesediagram and in the table is 5.12 beten coils and the data there given, he willcentimetres. When the purpose fortickets(whichwill be able to determine wave -lengths ofthesetablesisgraspedthe shillings, inclusive) should be made accurately. reader will find it very easy to useto the Secretary, Reunion Dinner, These coils cover a wave -length them. P. W. H. Wireless School, R.A.F.,Winchester. 100 7 SoLor_R WIRE. PIN FRAMEWORK FOR GROUP I . PITCH DIMENSIONS IN CENTIMETERS. NEAL 10-32 BRASSWIRE 1,Tat,R51,coil_ DESCRIPTION 28 Ril LEG -RIGHT NO 1- 6248.71A ? 512 4.01 C 492 06 crn.; N MBERCF052.05 TURNS 22 0.95 8. 40. I. F 0 0.48 H 0.43 2.23 ° BRASS SCREW 543 2.2 LEOBRACE.END -LEFT BRACL ROO 7.75 1.27 2.22.2225.12 4.01 492 0.55 Z.050.48 Z. 0.95 0.48 0.48 POSITION OF HOLE -AMEWORA. FOR GROUP U DIMENSIONS IN CENTIMETERS.. COIL NO "PITCH 08; I-UW*48 a 8.71 A-SYM. 7.75 IN OPPOSITE. RING . . A-SYN.?, 9.91 8.95 14 2 11.71 ., 10.75 5LDT FOR SYN REA DESCRIPTION 5 . . I 14 2, 581 I 5, 8.5$ K RIB NO. t 2 I 2 RING 8.32 705A 578 B 45' 0.64- 0.55 525' DF..F'0 H J 453 2 22 LEA-La -RIGHT LF_ST 8 R2. BRACE ROD LNG. BRACE !ale 8.31532705518525i2.54 705 1.27 5.78 095 57Z 1:35$ 0.48 2292.54495'046 P.4.7'GIVEN.r. 0.48 ABOVE 048255 255 625' 625'1270.04518(L.772222540.9 FRAMEWORK FOR GROUP El. A -SYN.DIMENSIONS 2. 1251 A-SYM I CENTIMETERS 11.55 coiLN0.9,piTcH Q.6:TuRris 15 8 0 2.2IS 2,2,15.31 12.11 15.11 5 14111.714.3 II 1 3YM RFQ DESCRIPTION B . 04 A B 28 2,, F H K II T 212 RIB2 RING LEG -RIGHT 12.012.0 10.4110.41064318 883 1.55 30.0.64 0.95 1.95 0.95805" 8.83 8.38 2,77 3.185.18 0.95 0.48 0.48 3.18 J 805" FRAMEWORK - INSULATING MATERIAL THROUGHOUT 4 2 5END 2 BRACE. BRACE ROD 2. LEG -LEFT 1743.18 315 I 59 095 0.48 1.27 GIVEN ABOVE 838 277 495 1 FRAMEWORK FOR GROUP 1St DIMENSIONS IN CENTIME -Taff 14.15 A LE COIL 810.10:PITCH 04:TURNS 28 1312 1 0.2.040,4 485037 A-SYM. 2 15.11 2.2, 23.11 18.711291 A-SYM. 5. 5.11955..6. 2i.15 1775 rr -TD T 3Th. 2 RFO. C65C2 RIBRING RIPTKIN 15.8614.27124815.6 A 853 328 338 495 0.48 0.48311514270.64B I165 C 18 55930' 0.64 0.95 0.93F G H 76 Ca.j. 76' ---t--T Ti 3 2 LOG-RI1 GHT 2 ENDLEG -LEFTBRA CL )586)4272245 iza 3.189 53 328 318 05 041_ 048 318 3.18 1.59 095 0.48 76' T 029 cm A A FRAMEWORK45 FOR GROUP V 2 BR CE OD a a !?-7 GIVEN ABOVE DIMENSIONS IN CENTIMETERS,o is NO.1 . 15 .., 420.2020.41TLIRNS 65 -. 1148666 A-SYM. 2. 2.2, 251120.1116.1123.91 A -3Y11. 5. . 5,5. 24.7527.9519.1515.15 SYM.RE4D7.7_42 I 16 RIB2 RING i ON 2024 J8.35 1643 225'054 464 3.81 C 1.91 0.55 1.450.95F G61 J FIG 2 .- WORKING DIMENSIONSOF FOR INDUCTANCE PARTS COIL FRAMEWORKS. 3 2 BRACELEG -RIGHT-LEFT ROD END BRACE. 2.0.242024 1833 18.35 1643 16 1254 43 11.94 3.96 3.96 4". GIVEN ABOVE311 7=r16 381 1.915,95 0483.81381 0950.95 048 0.48 0.48046 382381 sY 1110DERN-WIRELESS - Novemb-er, 1923

D ODOODODOODOODOODOODDODOODOODOODOMOODDOODOODO ODOMMED=MODOODO OODOODOD DE D 0 8 08 00° NEW BOOKS. 0 E 1

0° Valuable Additions to the Wireless Library. 912 0 0 0 O DOODDEIME10 0 D DIJODODEID D El 0 DODEI=DDLLIDDLIDMDLIDOM=DODOODOODOODDDODOODOODOOM THE autumn publishing seasonvalve Reinartz receiver of original -provided with a very full index, so of Radio Press opens .thisdesign, incorporating a stage ofthat any required piece of informa- month with the appearance high -frequencyamplification ' in tion may be readily found. of a group of new books of greatsucha way thattheoriginal interest to all types of wirelessvirtues of the Reinartz circuit arePictorial Wireless Circuits. By enthusiasts.Detailed announce- preserved. Oswald J. Rankin. ments regardingtheirdateof Every set has been constructed The ideal book for the beginner publication appear elsewherein by the author hiniself and exhaus-who finds it difficult to wire up a this magazine, and it will be seentively tested,and therefore theset from a circuit diagram. Each that they appeal toallclasses. reader may feel confident that eachcomponent is represented pictori- Readers will be interested to learnoneisathoroughlypracticalally and the actual wiring is shown, something of their principal con-design.The earlier designs haveso that no technical knowledge is tents, arid we give on this page abeen amplified and several addi-required to assemble a set. A general outline of the scope of eachtions suggested by the experiencevariety of gocd standard valve bock. of readers have been made. and crystal circuits are given, each Radio Valves and How to UseMore Practical Wireless Circuits.accompanied by useful notes and Them. By John Scott -Taggart, By John Scott- Taggart, F.Inst.P.thevaluesofthecomponents, F.Inst.P. Another book on the generalbesides a miscellaneous section of This volume constitutes a com- linesoftheperennially -useful switching arrangements, etc., and plete course in the theory and" Practical wireless valve circuits."a useful data section. operation of the thermionic valve,Besides a great variety of standardWirelessSetsfor Home Con- commencing with such elementarycircuits of allsorts, the volume , structors.By E. Redpath.. considerations of its working ascontains all the latest developments Mr. Redpath is well' known to will enable the absolute beginnerin super -regenerative, super -hetero-the wireless public as a writer of to tackle the subject easily anddyneandreflexcircuits, in- sound and practical constructional leading right on to the theory ofcluding ST75, ST 76,' STioo, andarticles, and as this book contains a such recent developments as the,a numb :r of original, and hitherto collection of his most successful sets, Flewelling circuit. The text of theunpublished circuits.Each circuittOgether with previbusly unpub- book takes the form of questionis accompanied by a short descrip-lished descriptions of severalnew and answer, the questions havingtion and some useful notes on itssets of original type, it should meet been carefully fram-ed to bring up working. Correct values of all thewith a, ready welcome. The original the difficulties which perplex begin- components ineachcircuitare constructional articles have been ner and advanced experimentergiven. enlarged to include explanations alike in such a way as to settle the 500Wireless Questions Answered.of the theory and operation of the problem once and for all in the By E. Redpath and G. P. Ken-sets, and much useful and interest- mind of the reader. A special dall, B.Sc. ing matter has been added. feature of the book is the plentiful One of the first things that the Full instructions are given for use of, pictorial diagrams, whichbeginner in wireless discovers ismaking a variety of sets, both have been specially drawn to showthat there is an amazing differencecrystal and valve, the latter includ- the relation between a theoreticalbetween understanding the generaling examples employing from one circuit, diagram and the actualprinciplesas expoundedinanto font valves. wiring of the corresponding receiv- elementary text -book and possessing Home -built Wireless Components. ing set. the really practical and detailed This book constitutes a veritable Twelve Tested Wireless Sets andknowledge. required to construct encyclopediaforthe man who How to Build Them. By Percyand operate wireless sets success-makes his own c.c..mponents.It W. Harris. fully. " 500 Wireless Questionscontains detailed instructions for Probably one of the most popularAnswered " has been compiled forthe construction of every type of writers of constructional articles,the express purpose of -bridging thecomponentpart by, thebest Mr. Harrishasdescribedin gap and solving all the problemsmethods, and has whole ,sections MODERN WIRELESS and Wireless which confront the beginner whendealing 'with such things as valve Weeklya large number of ex-he turns to the practical side ofpanels, variable grid leaks, frame tremely practical and useful receiv- wireless,explaining the" why aerials,coils and coil -holders, ingsets,andcertainofthese of many things which even theresistances,variablecondensers, designs are brought together for the moreexperienced experimenterswitches, crystal detectors, poten- first time in this book, a togetheroften does not understand. tiometers, and fixedcondensers, with information and description The volume is broken up intoand is unusually fully illustrated. not previously published. A newsections covering all the principalAn invaluable book in the work- bet of special interest is a three -branches of the science andis shop.

102 November, 1923 MODERN WIRELESS (Continued from page 79.) a special drilling template is pro- FROM A READER. stages of H.F., the standard H.F. vided. DEAR SIRS,-I have recently put transformers being used for in- RADIO SUPPLIES, LTD., are show- up the " All Concert "setde- tervalvecoupling,followedbying a special line ofbroadcastscri bed in the September number of 3 L.F. intervalve transformers. apparatus:apparatus for the use MODERN. WIRELESS, but instead of of experimenters, and componentsa box I used a panel, 0.5 micro - Components to suit constructors' licences whichfarad between H.T., and 3 megohms The components comprise high -have just been issued.They havegridleak. and low -frequencytransformers,also a speciallinein low - fre- The results are excellent.Last anode reactances, condensers (bathquency transformers, telephones,night' I got Radiola on the loud- fixed and variable), series parall.eland their well-koownElectronitespeaker and Elfel Tower also 'on switches, the famous L.F. trans-crystal.They are alsoshowingprevious night. Using- head- formers,rheostats,coil - holders, high-tension batteries of superiorphones, Ihave had most Con- crystal detectors, the new patentquality. tinental stations.I have not had R.I. eliminator for cutting out in- THE STERLING TELEPHONE AND many EngLsh stations, asI am terference, and various switches,ELECTRIC CO., LTD., are showingtoo near 2L0, and have not as yet etc., used by experimenters. their well-known line of receivers, had a chance of work; ng it between The most interesting of all theincluding the combined Valve -and3.3o and 4.3o. My aer.al is about components are the new improvedCrystal Receiving Set,two -valve 5o feet high and a twin of about H.F. and variable intervalve re-long-range receiver and four -valve35 feet long lead-in about 20 feet. action units specially designed forlong-range instrument.They areValves, 2 Ediswan (A.R.), r Mullard panel mounting ;these are self-also exhibiting their RadiO unitOra as detector. contained, with switches, and cansystem, Baby,Standard and One day, when I can find the be fittedto any experimenter'sMagnavox loud -speakers, and aenergy, I intend to have a shot at panel in a few niinutes by using thevariety of component parts for theAmerica.. scale of the component as a drillingexperimenter, including their new Many thanks for the excellent template.Inthecaseofthevariable air condensers (square andcircuit.Yours faithfully, M.R.C.S. variable intervalvereaction unitlow). Upper Norwood, S.E. IN A FRENCH HIGH -POWER STATION.

The giant aerial tuning inductances at the St. Assise station, near Paris.This station cdmmunicates direct with America.

.103 MODERN WIRELESS November 1023

(Continued from page 74.) osellations appearing in the tuned anodecircuitconsistingofthe inductance L2 shunted by the two condensers Cs andC4, C, being LS thevariable condenser. The bottom of the circuit L2,C3, C isconnectedthroughthegrid condenser Cs to the grid of the secondvalve,a gridleak R3 of abouttwo megohmsresistance S being connected in the position shown. In the anode circuit .of the Bp second valve .is the reaction coil L. which is variably coupled to I the inductance L2, and in this anode circuit we also have the" telephone i T shunted by a fixed condenser C, of o.002 µF capacity. . It is important to see that the coil L. introduces reaction into the Fig. 7.-The ST75 circuit, circuit L2, C3, Ca, and not reverse reaction.It is therefore importantL2 in Fig. 3. The reaction coilprove of assistance to those who to try reversing the leads to L3L3 in Fig.5 may consist of 5oare not yet familiar with the use of to see which way round gives theturns of No. 26 gauge double cottoncircuits. best results.The inductance L1 covered wire wound on a 3f in. tube, We now come to the ST 75 circuit may consist of the same number ofslipping over the inductance L2. which appears to enjoy considerable turns, etc., as the inductance L1 Fig. 6 shows how the differentpopularity: Thiscircuitisa in Fig. 3, while L2 may consist ofcomponents are wired up. This development of the ST 34 shown the same number of turns, etc., asmethod of illustrating them should (Continued on page 1170

.Fig: 8.-The above circuit shown in photographic loin.

104 November, 1923 MODERN WIRELESS ODOMMODOMOMEEEMODOE0000000O0000000==0000000:100000000000CD0000000 0 D U 0 SOME CAUSES OF POOR RECEPTION ri D 0 O D By R. W. HALLOWS, M.A., Staff Editor. r0 0 0 O Are your signals mysteriously weak ? Vis article may help to solve your reception CI O 0 O problems very rapidly. 0 O 0 DOODDOOD0000000000000=0000000000000=00 000000000000000000000000000= 0

HERE isprobably no wirelessen - ing sets are giving good results, nothing can be thusiast who has not had experience done with that in use in a certain house.In at one time or. another of weakness in this case there is something in the building reception, whose cause was most difficult to itself-an iron frame, an iron staircase, or even trace, if, indeed, it did not baffle all attempts a complicated system of water or heatirg pipes at finding a lolution.The most curious cases that is providirg a screen sufficient to deflect are those in which the lack of strength is per- impulses.I came across an instance of this manent. A set known to work perfectly under some months ago when I was on a visit to the normal conditionsisinstalled ina- certain West Country. locality, and straightway it refuses to produce The set was a Burndept four-valver in perfect more than a fraction of the volume of scund condition, but even when a Brown's micro - that should be heard in its telephones or loud- phone amplifier relay was added it could not be speaker. made to work a loud speaker.The only If no fault is to be found with aerial, earth or broadcasting station that was audible at all was batteries, the only conclusion that one can come Birmirgharn, whose transmissions came in very to is that this weakly. All particular local- kindsofex- ity is a blind or pedientswere partly blind tried, butresults spot. Such didnotimprove. places are quite AE Eventua 1 ly numerous.Poor- SeAAre PARCHED SO/L someone had ness of reception 56 the inspiration in themis PERFECTLY CONDUCTING SURFACE of, rigging up a some - frame aerial, caused Fig. 1.- Zenneck's calculation of the effect of surface losses uQOWtherange of times bythe a given transmitting station. and a consider- presenceof large able increase in masses of semi -metallic substance such as the signal strength was at once obtained.The set slag heaps that are to be found round Sheffield is. now used with an indoor aerial suspended -a notorious blind spot-and other towns. round _the cornice of the room.Its .signal where iron and steel are worked.Or it may be strength and range are both excellent, but

that the soil is of such a porous character that - whenever the outside aerial is tried, the same it becomes rapidly dry and parched for some poor results are obtained.I cannot explain distance below the surface.Over dry soil why this should be, but anyone who is similarly wireless waves travel extremely badly.It has circumstanced may find that his difficulties been calculated (Fig. 1) that a transmitting are solved by the adoption of an indoor aerial, station whose range over a perfectly conducting for I have known several other cases of the surface would be 1,000 miles, may not be able same kind in which it has given much better to cover more than one -twentieth of that results than the normal outdoor aerial. distance over arid areas, and these figures If signal strength varies considerably from accord well with observed facts. time to time the cause for a falling off is fre- A blind spot can always be identified by corn- quently to be found in neighbouring aerials paring the performances of other receiving whose owners allow them to oscillate.The sets in the same neighbourhood.If all of oscillations may not be sufficiently powerful to those in one particular area are affected, the give rise to audible squeals or howls, but if the cause must lie in local conditions.Sometimes, sets from which they emanate are rather flatly however, it will occur that, though neighbour- - tuned, they may cause either a slight increase

105 MODERN WIRELESS November, 1923 or a slight decrease in the signal strength of The aerial shown is rather too low.The other receivers according to the phase difference cure here is to suspend the house end from a between the locally radiated waves and those chimney -stack and to raise the other until it is of the transmitting station.It isfor this on the same level or a little higher.The tree reason, I believe, that we sometimes hear of should be trimmed if possible. amazing feats of reception with crystal sets But even if height is obtained, and screening done away with, the aerial may still prove unsatisfactory.Fig. 3 shows athoroughlybadarrangement, which contains a surprising number of faults.In the first place the free end is the lower of the two.This is undesirable. Now look at the down lead.Its branches, instead of coming from the very ends of the suspended wires, are txed to points at some distance from the insulators. This turns what was intended to be Fig. 2.An aerial screened at both ends. an inverted L aerial into one of the in certain conditions they are aided by the T type,witharmsof unequal length. radiation from other aerials.It also accounts When reception is in progress, the portion for the prevalence of one kind of fading in ABD will be tuned to one wavelength and districts which have a large wireless population. the portion CBD to another, for each has The causes of trouble mentioned so far are its ownnaturalwavelengthwhich is such as are beyond the control of the victim. varied by the tuning inductance and the con- We now come to those with which he can deal. denser.With a down -lead affixed in this way It may not always be easy to find them, but tuning cannot be sharp and signal strength will once they have been tracked down, something suffer.Yet it is one of the most usual of faults can be doneto improve matters.These in aerial ,dcs,gn, as you may easily see by divide themselves into two classes : those due noticing next time you are travelling through to faults in the appliances which bring in a town by train, tram or 'bus, how often it oscillations for the receiving set to deal with, occurs in those that are visible as you pass that is, the aerial, the earth, and their respec- along. tive leads ; and those due to defects in some Notice, too, that the down -lead shown in the part of the set itself. drawing is long and slack.If any wind is One of the commonest causes of poor recep- blowing it will swaynow against the building, tion is to be found in the aerial so slung that it now away from it, producing changes in signal is screened at both ends.Fig. 2 gives a strength due to the varying capacity to earth. typical example of this.The free end of this The earth lead is too long, and it rests upon the aerial is blanketed by the tree, its other end ' surface of the ground for some distance before by the building itself.With an aerial of this it goes down to make contact with the plate. kind, reception may be fairly good in winter -time, but in summer it will fall off markedly.The reason is that in winter the tree is dry and leafless, whilst in summer it is not only full of sap, but is also covered with a mass ofjuicy leaves.If the tree happens to lie in line between the free end of the aerial and a broad casting station which is some distance away, the chances are that that station's transmissions will not come in at all during the summer months. Fig. 3.How many faults can you find in this aerial ?

106 November, 1923 MODERN WIRELESS This lead should be as short as possible, and it valves that require the full voltage output of should be insulated from the ground, being your accumulator.This applies especially to supported, if necessary, on a short pole until ORA valves and others of this type worked it is actually over the plate, otherwise a con- from a 4 -volt accumulator. siderable resistance may be set up which will The high-tension battery may suffer badly materially affect reception and may give rise at the hands of its bridging condenser.The to self -oscillation of the most puzzling kind. paper dielectric condensers generally used for Our " fearful example " among aerials is the purpose are usually good enough, but some- provided with only one insulator at either end times they develop a small leak, and if the of each wire, which is not enough.If insulators battery is left with its plugs in place when the are of good quality, leakage in the receiving set is out of use, it will run down rapidly.No aerial does not occur as a rule across their one would think of suspecting a new or nearly surfaces unless these become covered with a new H.T. battery ;yet it, or rather its con- conducting coat of soot and dust.But condenser, may be the source of the trouble. These siderable leakage may take place by capacity. condensers should be tested from time to time in the following simple way.Switch on both batteries, then switch off first the L.T and then the H.T.Wait a few moments and switch on the L.T. battery again.There C should be a loud click in the 'phones due to the Fig. 4.-How leakage occurs by capacity C in an insulator. discharge of the condenser.With a really good condenser the click should be heard even if the Fig. 4 shows an insulator of the shell type in set has been switched off for a considerable which the aerial wire is separated from the time.If it is not there on switching on after, supporting wire or rope by a thickness of por- say, 3o seconds, the condenser should be celain.There is capacity between the two, discarded. which we may represent by the little condenser shown at C, through the porcelain dielectric. Are the wiring connections beneath your Now, if we place condensers in series, their panels all that they should be ?Are they total capacity is reduced, for it is calculated soldered, or merely made with nuts ?If they are of the latter kind a falling off in signal by the formula : 1+ I + A single insu- strength that cannot be otherwise explained is ....1 N.-,3. probably due to one of them that has worked lator may by its capacity offer a fairly free path or jarred loose.To make quite sure of your to earth for oscillating currents ; but when we connections, solder them all ;but take care add others in series the capacity is so greatly when you do so, for there is a pitfall here that . reduced that even they cannot pass to any may give trouble.If too much resinous flux appreciable extent.To be on the safe side it is used it will " spit " when the soldering iron is best to have two insulators at each end of touches it, and a good deal will be deposited hoth wires and one at the junction between on the ebonite.Examine a panel when solder- supporting wire and bridle.An aerial with a ing operationsarefinished and you will smaller number of insulators may work quite 'probably find a thin film of the flux lying be- well, but results will be improved if attention tween terminals or valve legs.Some experi- is paid to this point. ments made the other day with a megger were Both lead-in and earth lead should be of enlightening.Clean ebonite showed a resist- stout cabled wire so as to offer the smallest ance of hundreds of megohms, but when two resistance.The tubes through which they are points were taken between which there lay a brought into the house must be stout and made thin coating of the flux, the resistance was of material with good insulating qualities such found to have fallen to less than one megohm. as ebonite, porcelain or glass.If these tubes Between one pair of valve legs it was actually are not good, leakages will occur through the as low as boo ohms.When, therefore, you do woodwork of the window frame, especially in soldering jobs, be careful to clean the panels wet or damp weather. Turning now to the set itself, we are faced well afterwards with petrol. with a whole host of possible causes of poor For the same reason panels should never be signal strength.Let us take the batteries first marked out with a lead pencil, for the linen. of all.Be careful of long leads if you are using that it makes provide high resistance leaks 107 MODERN WIRELESS November, 1923 and may result in very poor performances type of tuning inductance, which may be when the set is finished. responsible at times for poor performances.If Many -of us are very fond of switches. It is so the inductance is badly made, or if it has been convenient to be able to throw a valve in or in use for a long time, the slider may fit rather out of action by the mere touch of a knob, or loosely on the square or triangular rod upon 'to change from one circuit to another without which it travels.If this is so it can be twisted the bother of undoing a single connection. slightly from side to side.On examining .the -But switches,especially on 'the H.F.side inductance carefully you will probably find of the set, are a delusion and a snare, for they that it is possible for the spring point to make may lead to endless, trouble.There must either good or bad contact with the turns of always beacertain amount of capacity wire according as the slider is turned a little between the parts of even the best designed of upon the rod.One's natural tendency in them, and additional capacity among the H.F. moving the slider along is to twist it a little, components is exactly what we do not want. hence when the set is in use, contact with the But their worst fault is that their contacts are point may be very bad.The best way of often not sufficiently good, and what an effect tightening up the slider is to drill and tap a a poor contact can have in a grid or plate 3 B.A. bole through it and to fit a screw as circuit will be fully realised by any who have had experience of leads that looked all right, but were the tiniest bit loose.Be sparing, then, of your switches, 'and keep the blades and the contacts of those that you must use bright and clean. Valves themselves can provide perplexing problems.The prongs of the ordinary type Fig, 5,-How to remedy a loose slider, should be opened out with a penknife, as everyone knows, to make them fit tightly into their shown in Fig. 6.The screw can be used to take sockets ; but even this will not suffice if the up any play, and to fix the slider in position pins are greasy or dirty.It is a good thing to with a firm contact once the correct tuning give them a shine up at intervals with a piece of adjustmenth as been found. worn *emery cloth ;the resulting increase of The crystal itself must be kept perfectly free sound in the receivers will sometimes be an from grease or dust.An occasional rub over agreeablesurprise.Itisparticularly im- With a small tooth brush dipped in spirits of portant that the plate and grid contact caps of wine-not methylated spirits, which contains " test tube " valves, like the V 24 or the impurities that will form a coating when the Mullard S 5,should be kept bright.The alcohol evaporates, or petrol, which is unsatis- spring clips do not make a very powerful con- factory for the same reason-will keep it in tact with them in any case, and if they are dull condition,The contact point of the " cat or dirty there may be a big falling off in signal whisker " should be kept smooth and rounded strength.The clips that hold the gridleak, by being touched every now and then with a and the caps of the leak itself, should receive fine file. the same attention. There are countless other possible causes of These are some of the chief causes of poor poor signal strength, but to mention all would signals in the valve set.All that has been said need more space than that allotted to one short about connections and about fixed condensers article.The wholesecretof having an applies equally to the crystal receiver, and efficient wireless set is to pay constant attention there are one or two special points about it that to little points of detail, for it is causes that must be noticed. might seem trifling that often rob us of the The first concerns the single or double slide volume of sound which should be ours to hear.

108 November, 1923 MODERN WIRELESS

1 rQcficQl

0000000001500C.IL100C0E110000000000000000000000000000 0 0 0 A RHEOSTAT FOR "PEANUT "0 0 AND OTHER DULL EMITTERS. D0 00000D0000D0D0000DD0000000000000DDDD000000000DD D THE special rheostat about topillars so that they are perfectly be described will be of par-in line. ticularinteresttothose The former is a 2 -in, length of who wish to work the latest typeebonite rod jE in. in diameter.If of " Peanut " low -temperaturea screw -cutting lathe is available Fig. 2.-Showing the pillars. valves off a 6 -volt accumulator.it is best to put a very shallow It can be used either in addition to,thread upon it to take the wireto prevent the screwed rod from or as a substitute for the existingwindings.This, however,is notshifting in the former when the rheostat, and as it enables minuteabsolutely necessary. Through rheostat is in use. adjustments of current and poten-the long axis of the former a z B.A. The former may now be mounted tial to be made, it will be foundhole is drilled and tapped, everyas seen in the drawing and a knob extremely handy also for use withprecaution b inn taken to see thatfixed to the longer eud of the rod, soft valves of the " high tempera-this is true.A 6f -in. length ofFig. 2 shows the details of the ture " type, whose filament poten-2 B.A. screwed rod is then inserted contact pillar and the arm which it tial is extremely critical. as shown in Fig. sso that 21 in.supports.The pillar is of ebonite or brass and has the same dimensions as those used for supporting the brass rod.The arm is a springy piece of phosphor bronze I in. long and *in. wide at the end fixed to the pillar.At the other end it is tapered off to about f in. in width and is curved as shown in the drawing in order that its action may be smooth.The adjusting screw(X,Fig.2)allowsthe pressure of the arm upon the windings to be regulated so that a good Fig. 1. --The finished resistance. contact is always obtained. Screws to take the leads from the low- The base consists of a piece ofprotrude at one end and 28 in. attension battery are provided in the ebonite 4 in. thick, measuring 5 in.the other in order to provide apillar B and in the contact pillar. by 2 4 in.On this are mounted thehold for the knob. The rheostat described has a two brass pillars A and B (Fig. I), Upon- the former are wound 70resistance of a little over 30 ohms. by means of 4 B.A. screws driventurns of No. 3o Eureka resistanceThe carrying capacity of the wire upwards from below.The pillarswire spaced with thread, which isused is .59 ampere.The rheostat are r f in. in height,in. wide andafterwards removed. The wind-canthereforebeemployedto I in. thick.In these 2 B.A. holesings must he as tight and as evenregulate a pairofanyof are drilled and tapped, their centresas possible.One end is anchoredthe following valves :Wecovalve, being I in. from the bottoms of theby being passed through a fine A.R.D.E., D.E.V., D.E.Q. and L.F. pillars. The threads should be anhole drilled in the ebonite ;theOra A.It must not be used with easy fit for 2 B.A. studding.Careother is clamped between the endmore than one D.E.R. or L.F. must be taken to make the holesof the former and the nut D.Ora B or C ;otherwise it may be absolutely true and to mount theThis nut, together with C, servesburnt out. R. W. H.

109 MODERN WIRELESS November, 1923

ODOODOMOODOODEMDCGD00000000000000000000000001:00 0 El El 0 A HOLDER FOR " PEANUT 10 ID El D VALVES D DE10000000000000000000000000000000DOD00000D0000000IDD THE little" Peanut " valvesso that connections may be made now on the marketde- or unmade in a moment. mand aspecialtype of Fig. shows the appearance holder since they are made withof the finished holder, which con- caps of the. American type.Theresists of a short length of ebonite are no pins but simply four smalltube fixed into an upper plate A. contact points, and the valve fitsThen it is mounted on the lower into its holder in much the sameplate B by means of 4 B.A. screws. On the lower plate are four terminals from which run metal stripsFig. 4.-Underside of " B " in Fig. I. that serve to form the contacts. The tube (Fig. 2) has an insidehowever, be deep enough to allow diameter of4 in.and outsideroom for the contact points to move. diameter of 4 in. It is 4 in. long. The contact stripsare,made of An L-shaped slot for the retainingphosphor bronze or brass.They pin is cut as shown in the figure. are 4 in. wide, tapering to rather less This slot should, however, not bethan -A. in. at their free ends.The cut until the tube has been mounted points of the contacts rest on the circumference of a circle slightly Fig. 1.-A peanut holder. on Plate A, for the end of the foot "of the inverted L mustless than I in. in diameter. These should be bent a little upwards so way as an ordinary electric bulb, that they may press firmly against except that the bayonet grip is the leading -out lugs of the valve. securedbyasinglepin.The R. W. H. usual American holders are of no use, for this little valve is barely 000000000000DOODODOMD inch in diameter at the cap. Both 0 holder and adapters have been VALVE -LEG o° placed on the market in this country o° and very good they are. Ho SWI ICHES The holder has, however, two drawbacks from the point of view 0000000000000000000000HD of the experimenter who makes bench " hook-ups " :in the first VALVE pins and sockets are place It is too small to stand quite being used more and more safely by itself, being only xi inches in wirelessapparatusfor in. diameter ;secondly, it is not switching purposes, especially by adapted for the rapid making of experimenters who like to be able connections, which is essential withFig. 3.-Underside of " A " in Fig. i.quickly to try out new circuits experimental work.The contacts without making alterations under come exactly over the nearest edgethe panels of their sets.If the con- of the strip connected to the gridnections to the various components terminal. are terminated in valve sockets, The tube should preferably beand a number of short flexible con- threaded for 4 in. and screwed intonections made with a valve pin plateA.If,however,there- attached to each end, it is surprising sources of the workshop do nothow quickly a new circuit can be permit the doing of this, plate Aset up.The contacts are very can be made circular in shape and reliable, as they are kept clean by the tube fixed in place by means of therubbing actionof inserting a couple of 4 B.A. screws driven in from the edge.These screws must Pod Fig. 2.-The ebonite socket. be arranged so as not to foul those which fix this plate to plate B and of the holder are small metal lugs alsosecurethecontactstrips. to which leads must be soldered. Fig. 3 shows the lay -out of plate A, The design described below has that of plate B being given in Fig. 4. the advantage of being considerably The 4 in. diameter hole shown in larger and therefore much steadier ; Fig. 4 need not be made right it is also provided with 4 terminalsthrough theebonite ;itmust, Fig. 1.-The connecting link. II0 November, 1923 MODERN WIRELESS

Another pur- poseto which thisform of switch may be put isto connect a fixed condenser in series or parallel with a variable one.The fixed condenserwill reduce the mini- mumcapacity of the variable when connected C. inseries,and increase the Fig. 2.-.Aerial switching. maximvm when in parallel. Thus a smaller con-Fig. 4.-.Anotheraerialarrangement, the pins.Switches constructed in densercanbe used which will this way take up very little spacenot require so deep acaseas The two arrangements described on the panel, and they have the wouldbe necessaryifa singleabove may be combined by using advantage over theusual studadjustable capacity were employedeight sockets joined up as in Fig. 4. form of switch that the sockets can to cover the same range of wave-The method of plugging in the be spaced well apart, while brasslength, and finer tuning will belinks will be the same as already dust is not likely to collect on the explained ; Fig.4 surface of the ebonite and reduce gives as an example the insulation.In many cases it is the two condensers possible so to arrange the circuits inseries with each that fixed links can be used to make other but in parallel the connections, thus doing away with the tuning coil. with flexible wires, which are better A thirduse for avoided. A few examples this type of switch pin switches of this kind may be is in connection with of interest. variometers. The The first is a useful series -parallel two coilsof these switch which only occupiejs about instruments,stator one square inchofthepanel. A 8. C. androtor,are The sockets should be arranged in Fig. 3.-Capacityswitching. usually connected in the form of a square and spaced series, but if they are about in.apart,thedrilling joinedinparallel, being done accurately, so that theobtained when the two conden-the wave -length is reduced.The links about to be described may besers are in series. Fig. 3 illustratesv a ri ation covered by a given interchangeable.These links (seethis arrangement, "A" showinginstrument can thus be very much Fig. i) consist of a small piece ofthe condensers in parallel and "B"increased by means ofa series - I in, ebonite shaped as shown,in series, while in "C" the variableparallel switch. and drilled and tapped to take condenser alone is connected. Three Care must be exercised in con- two valve pins which are screwedranges are in this way available. necting up the switch that it is as into it, the connection between the pins being a strip of copper foil clamped under two nuts on the pins. The method of wiring is given in Fig.2,which also illustrates, by means of dotted lines, where links may be plugged in to obtain the various connections.In "A " the aerial is connected direct to earth and the tuning coil and condenser disconnected, protecting theset from static discharges when not in use, while "B" and "C" show the tuning condenser in parallel and series respectivelywith thein- ductance.It will be noticed that two links are needed when the condenser is in parallel, but only one when it is in series. Fig. 5.-Reversingthesenseof the reaction coil.

III MODERN WIRELESS November, 1923

in Fig. 5 so that the same directionto be able to reverse the directionterminal.If preferred the hole in of movement of the dial or pointerof current through the coil, andthe brass strip may be elongated will give increase or decrease ofthis can be done by inserting the$0 that the top crystal may be moved to make contact with any part of the lower crystal.The top crystal cup is held by a terminal and spring washer sothatits position may be slightly altered without slackeningtheterminal which holds the brass strip in its place.Tile upper nut is used to apply the contact pressure between the crystals.Suitable combinations are: Top Crystal: --Galena, zincite, metal points. Lower Crystals : - Tellurium, graphite ;bornite,calcapyrite, tellurium ;ironpyritesand silicon.

Fig. 6. -Variometer switching.

wave -length whichever way thereversing switch between the anode coils are connected.Diagram "A"of the valve and the reaction coil. Fig.5 shows the windingsinThe arrows show how the current series, while "B " indicates the'may be reversed by plugging the links plugged in to join them inlinks vertically or horizontally. parallel. Many more examples 'of the use Fig. 2.-The finished detector. The same arrangement of valve -of this system of changing con- Metal points will be found to be legs arranged in the form of anections rapidly might be given,more stable in the form of short square can also be made to serve but these examples will be sufficientneedle than wire spirals. A pair as areversingswitch.Fig.6 to show thatit has importantof these detectors with a switch explains one use in connection withadvantages over the use of thewould be admirably suitable for a wireless apparatus.When a re-usual form of switches. dual circuit with crystal detection. action coil is used, it is convenient G. H. L. S. C. H. E1000000000000000000000 E000000000000=DEEDOCIDOODDOODOOODODOOEIDED0000 0 0 19 A PANEL HINT 9 D 0

0 0 utillIELIECODODECIODOODOODO hi AN EASILY MADE CRYSTAL 0 CI Itmayinterestreadersto O 0 know how Iget over the high DETECTOR 0cost of ebomte, using a material o owhich is much cheaper and works 9 000000000000C1D0000000000000DO00000D0000000000Dquite well.The necessary materials are, one baking tin (size depends ACRYSTAL detector which is lengthI f in.as radius and theon size of panel required), enough rigid, neat and easily adjust-centre of the hole just marked asparaffin wax (miner's lamp wax or able, being especially suitablecentre, draw an arc, and upon it candles)tocoverabout in. for the double crystal type of detec-mark the centres of the three (orin the tin, and enough in. ply- tor, can be constructed from a doubleother number decided upon) holes wood (five-ply, preferably) to make terminal such as those advertisedfor the lower crystal cups, and thenthepanels. Toproceed,cut in this journal at various times.drill the four holes to suit the andsandpaperthepanel to Take atrip of brass 3 in. long, components.Insert the three cups, size.Next, melt the wax in the Ay in. wide, and A in. thick, andconnect them together, and fromtin until it just begins to smoke, drill three holes init as shownthem take a lead, whilst anotherimmerse the wood and let it cook, in Fig. 1.It is then bent round aleadistaken fromthe double keepingitimmersed ;turnit pieceof rod of in.diameter, occasionally.Cook itfor about sothat the light -handholeis .1 twenty minutes altogether.Drain directly above the centralhole. 54; ononecorner,andscrapeif Now take the ebonite upon whicjh fret* necessary.Ordinary wood is very the detector is to be mounted and a liable to warp unless frequently mark the hole for the centre of the turned. doubleterminal. Thentaking Fig.'.-The strip. L. S. Wir.soisr.

112 November, 1923 MODERN WIRELESS

SPECIAL NOTE .-All apparatus described in this section has been tested by our expert, and readers can therefore rely fully on the opinions given.

T. C. B. Filament Resistance. this later pattern are all that one-was found to be correct ;in re- We have received from T.C. could desire ;it can confidentlysistance -capacity high -frequency Ball a later and improved pattern be recommended to those who arecoupling, with 120 volts H.T. and of the type of filament resistance tired of the trashy type of com-R valves, it was free from the un- p-saviously submitted for test, and ponents now flooding the market,pleasant wheezing and crackling which had already produced aand who will appreciate a thor-noises often associated with anode favourable impression by its com- oughly sound and reliable fitting resistances ;and on thelonger pactness and smoothness of action. which will outlast half a dozen ofwaves gave excellent amplification, This resistance occupies less than the ordinary cheap type. the Paris Radibla concert on 1,78o a square inch on the panel, and a metres being readily pickedup d.pth of about two inches.The with two valves and this intervalve stout brass frame requires but two coupling, as well as a world of long - small holes for fixing below the wave Morse. As stabilising resistance in the panel. A neat knob actuates a mum spindle with a quick -thread screw, S.T. io9 circuit, the value appeared which moves a spring sliding con- to be a little high, as whistling: tact the length of a solenoid -form threatened, especially when a small ofresistanceinthree complete series condenser was used in the turns, giving a very fine and smooth aerialcircuit.For this purpose, adjustment. Positivestopsare the resistances of thisseriesof provided at each end of travel, of. rather lower value would be preferable. ' course ;and there is a definite off The T.C.B. Resistance. position. Convenient terminal screws are fitted in this improved An Anode Resistance Dynaphones. form.The insulation was good We have received from Messrs. Messrs. RadioCominun:cation on test ;the resistance of the coilDubilier Condenser Co. (r9zr ), Ltd.,Co., Ltd., have provided an oppor- tested about 5 ohms, and it carrieda sample of -the type of anode re-tunity oftestingtheir" Dyna- the current for an R valve withoutsistances which they make withphones," a telephone set in which heating up noticeably. from 20,000 to eoo,000 ohms re-itisclaimedboththeusual On extendedtrialinactualsistance. These are substantialdirectmagneticaction' onthe receptionofbroadcasting,and units,inappearancesuggestingdiaphragm isobtained,aridalso also in laborious and critical experi-enlarged editions of the well-knownan electro-dyriamic effect, by the mental work, the velvety smooth-grid -leak resistances made by thisinduction of currents directly in the ness of action and complete silencefirm ; with brass caps, and mounted diaphragm, and thereactionof inoperationwerenoticeable : between clips on an ebonite stripthese in a permanent magnetic criticaladjustmentofdetectorabout 4. in. by r in., with two handy fill.Great clearness of reproduc- valve and critical control of oscil-terminals, the whole being sub-tionisclaimed,asaresult, lation became easy with this longstantiallyconstructedandwell and the possibility of using a much screw action and the absence offinished. larger, and more robust, winding. back -lash. On practical trial of the 100,000 Theresistanceofthe windings The workmanship and finish ofohm resistance submitted, the value is4,000 ohms ;averylarge

113 MODERN WIRELESS Nirvember; 1923 audio - frequency impedance is inmanycasesthisnon-linear On practical test of the sample, quoted by the makers. characteristiccanbeextremely it was found to work with the The phones are unusually light valuable :e.g., by simply slippingusual radio -constructor's small and small ;and comfortable on the scale back (provision for whichtoolsquitewell,beinginfact the head.They are neatly finished,operation is made in the instru-similar to very hard fibre.As with and a good length of cord is pro-ment) the same condenser can befibre, care had to be taken to keep vided. Incrystalandvalveused as a " vernier " or fine-tuning the tools sharp ;and drilling had reception the tone was clear, andcondenser of low maximum andto be done with a light cut ;if there was no noticeable distortionextremely low minimum capacity.force was used, the drill tended to A low ohmic loss is also claimed forjam,It could be tapped, filed, the condenser, the conductors beingetc. ;and a pleasing mat finish 001a massive and the path of flow short.' could be got with fine emery -paper, 000.9 On test, the insulator was foundit preferred to the polished surface excellent ;on most careful com-(free from the treacherouspro- 0007 parativetrialwithastandardperties of new ebonite surfaces) on .0007 air -dielectric condenser, no sensible thematerial as supplied. A .0000 difference in signal -strength on the3/l6ths in.panel seemed to be broadcast wave could be detectedmechanicallystrongenoughto 00L4 when used alternately with thereplace thicker ebonite, and gave 0004 same inductance, etc.The cali-no trouble from splitting out at bration was checked, and showedthe back when drilled.The edges .000.9 the extremely low minimum of couldbefinishedattractively. 0002 .00004 IX; and maximum closeElectrically,theinsulationwas unexceptionable. .0001 to the nominal value of .00r Thematerial The condenser was silent in use, stood up to the severe testof 0 /0 20 .70 40 ,70 00 .70 BO .90 100and easy to adjust.The work-soldering close up to the panel Calibration curve of the Connecticut manship and general appearancewithout unpleasant results. condenser. were good, the condenser being mounted in a composition. case An Interesting Voltmeter. even if signals were not very loudabout 3 in. diam. and 2 in. high ; We have been afforded recently in comparison with the ordinarywith a knob, and engraved scalean opportunityofinspecting type. Theyrepresentanin- reading to too ;substantial stops ; examples of the Moullin low -reading teresting experiment in one line ofand terminals mounted on an ex- A.C.voltmeter,and of viewing attack on that appalling inefficiencytension of the base in the " port-the processes of assembling and factorofthepresenttypeof able type submitted. bmch tests of the instruments, by telephone, where less than one per. Messrs. The Cambridge and Paul cent.of the electrical energy is Condensite Celoron Panel. Instrument Co., Ltd. usefully. employed. A sample of the " Condensite This voltmeter depends for its Celoron " panel material, an alter-action on the rectifying properties A Variable Condenser. native to the customary eboniteof a triode valve, and therefore An interesting type of variable (whichitcloselyresemblesin hasminimalelectricalcapacity condenser isthat submitted forsuperficial appearance), has beenand. power -absorption, and is in- test by Messrs. R. A. Rothermel,sent for inspection and practicaldependent of frequency. Itis Ltd. :the" Connecticut "con- test by the Diamond Fibre Co. In an mideintwoforms:type A denser.This is a very compactinteresting booklet accompanyingemploys the curvature of the anode form, with only two plates, and athe sample there was a great dealcurrent grid potential characteris- mixed dielectric of air and mica,of information as to the varioustic ;no separate H.T. battery is theadjustmentofitscapacitygradesofthismaterialmanu-needed, andthescalereads beingeffectedby alteringthefacturedfor most varying pur-directly(on. aunipivot micro - relative distance of the metal plateposes, and useful information asammeter) from. 0 to1.5volts ; by a screw and nut action. to machining operations and finish-type B uses a grid -condenser and The effect of this, with the high ing.The Gradero,'forradio leak, with separate H.T. battery of dielectric constant of the thin micaequipment, it is claimed, can be about 70 volts ; the scale reads from plate coming into play principally sawn,drilled,tapped, turned or oto iovolts(onaunipivot when the plates are brought ex- milled ;but cannot be moulded milleammeter). tremely close, is to give a peculiarwhen once cured.It is described In both instrument zero -adjust- typeofcalibration -curve. The asbeingessentiallyvulcanised ments on the pointers compensate latter shows an extremely smallfibre impregnated with a phenol -for slight variations in the bat- minimum capadity, and slow in-formaldehyde condensation product teries ;as only 3.6 volts are used crease with angular rotation of theand hardened by heating.It ison the valve -filaments, and the screw spindle, at first :then, asmade in sheets and rods up to 3 in. valves are aged before calibration, the air -gap is reduced, and thethick ;and tubes up to 6 in. diam.their effective life will be long ; mica begins to fill a larger fractionCertain methods of machining giveand the makers will, we under- of it, and finally predominate, an best results, and are given in detail,stand, undertake the replacement extremely rapid rise in capacity toas mentioned.Very sharp tools,and recalibration at a moderate a high maximum (relative to thefrequently changed,. appear to becharge. bulk of the instrument).Actually, the main requisite. The particular advantage of the

114 November, 1923 MODERN WIRELES-S

B type is that an A.C. superim- type,withagglomerateblocks - is low, too low in fact for any but the posed on a D.C. can readily bearound carbon positive plates ; and pea-fiut type of dull-einitter valVe, measured. Many other applica-a very large box -shaped zinc nega-two will run a tWe-valve set with tions are suggested :e.g., as high - tive plate comes very close to theEnglish dull emitters for a very frequency ammeter, by measuring positive, giving an exceedingly low long period, We haVe no hesitation the P.D. across a known capacityinternal resistance. The Makersin'strongly recommending these or inductance ;conversely, measur-claim that manganese is not used gaint cellS for use in remote country ing small inductances by passing afor depolariser. The eledtrolytedistricts and the like where the known H.F. current through themappears to be a familiar andin - efiarging of nccumulators is an even and measuring the P.D. across the noxious powdered substance, readilyMore harassing problem than it is terminals ;measurement of signalmade up and safe to carry in stock.16 the sutUrbanite. j ' E.M.F.s in radio receivers and atThe zincs can be renewed at a- cost different stages in amplifiers, etc.that compares favourably with -that The Darimont Cell: An actual measurement was wit-of a couple of trips to the garage Messrs. Darimont Electric Bat. nessed at the works :the P.D.with an ordinary accumulator forteries,Ltd., have submitted fox across the secondary of two very recharging. test a couple of their Type Tr5 loosely coupled inductances being The cell is in a neat black com-primary cells,of nominal 73-75 measureddirectlywiththe Aposition container, about 64 in. by ampere -hoursavailablecapacity, type, at a frequency of about 168 in. by ro in. ; and is quite lightwhich are suitable, it is suggested, cycles,and thevariation withwhen uncharged.Terminals andfor use to replace acumulators for degree of coupling readily followed. supplyingtheL.T.currentto Other examples of measurements of valves.These are of the two -fluid this type are some made recently type, with zinc and carbon poles ; by Mr. M. H. Lawes on the P.D. the electrolytes being, respectively across tuning inductances on a a viscous emulsion with sodium P.M.G. aerialin London,of a chloride as main constituent, as type invaluable as a guide to pro- excitant ;whilst a solution mainly gress in real experimental work : of ferric chloride is used as depo- e.g.,on 2 LO's carrier -wave a P.D. lariser. A porous pot is used ; and of 1.9 volts was found across a it is claimed that a semi -permeable basket -coilcorrespondingtoa membrane is formed by precipita- little over No. 40 of plug-in types, tion in the pores of the pot, thus with parallel condenser ;4.2 volts preventing diffusion and mixing across one corresponding to about of the electrolytes. 8o turns with seriescondenser, The cells are in glass containers, undamped ;but sinking to1.3 about 6 in. square by gin. high ; volts and only .95 volts respec- and a terminal and connecting tively when perikon crystal was strap are provided. When spent, placed across them-thus giving the old electrolyte is to be poured realdataonthelong -debated out, and fresh material together " series versus parallel condenser " with new zincs substituted. controversy.Similarly with loose - On a practical test -run, taking coupled primary and secondary thecurrentequivalent approxi- coils, the voltmeter gave 1.6 volts mately to thatrequired by a optimum (when coupled at / to 3 greedy R valve, about 3-4 ampere ; inch centres) with primary tuned the two cells gave 1.7 volts available by parallel condenser ;1.5 volts E.M.F. at the start ;after 24 optimum at 3 -inch centres. with The AD. Primary Cell. hour's continuous run-afairly equal -Sized coils, the first tuned by severe test compared with ordinary series condenser.With these in-connecting straps are provided.Ifintermittent use-the E.M.F. had struments a great deal of light canpreferred the electrolyte is suppliedfallen to 1.4 ;and after 48 hours be thrown on such very practicalready made up in a can ; but it was (corresponding to abont36 ampere - problems. a very easy matter to dissolve the hours,or, say, a month's casual In finish and workmanship thepowder and set up the cell, whichlistening for an hour Of se every instruments are beyond criticism ; gave over 20 amperes on actual testevening on one. valve) to i.2 volts they are beautiful examples of thein short-circuit shortly after filling ; nearly. On open circuit the E.M.F. British instrument -maker's art. and about 1.4 volts on practicalat the end of the run was 2.5 volts A.D.C. test over a considerable period with approximately, or 1.8 volts when a dull -emitter valve.There wasgiving the current corresponding A Large Primary Cell, the " A.D." absolutely no sign either of polari-to one dull -emitter valve. On Messrs. Le Carbone have sub-sation or of noise. We can see noshort circuit the two cells .gave mitted for test an interesting typereason why this cell should giveamperes at the end.tensiderable of giant wet cell, Type B.I.C., forany more trouble in use than anfrothing was noticeable,aswell making up primary batteries forordinary wet bell -battery ; and theas marked electric endosmosis into supplying filament current under -renewal of spent zincs and electro-the porous pot,at the conclusion circumstances where the (alwayslyte would be the simplest possibleof the test run ; some mixing of troublesome) accumulator isnotjob, and not at all costly. While, ofelectrolytes had evidently occurred available.This is of the Leclanchecourse, the E.M.F. of a single cellas well. MODERN WIRELESS November, 1923

These results confirm the elabo- denser ;and a swinging reaction -noisy C.W. Morse all along the rate tests made with similar cells,coil' controlled by a small knobhigher ranges, some stations being mainly at lower and intermittent,coaxial with the wave -length con-audible over the house with 'phones discharge -rates, by _the National, trol. This is arranged for mounting alone.There was no doubt as to Physical Laboratory ;the internalbehind the panel in an elegant andtheeffectivenessoftheanode resistance of the cells, which isexceedingly convenient way by thereactance coupling, though careful quite appreciable, also coming outprovision of a small false panel, on use of reaction was necessary to tune about the same. Evidently, whilstwhich the instrument is assembled ; out 2 LO and some noisy English quite suitable for operating oneand of four small brass columns bystations of medium wave -length, ortwodull -emitter valves forwhich the whole is fixed in the rear even in the top range. considerable periods (one cell, forof the receiver panel by four small For those experimenters who find example, beingadequateforascrews. interest in long -wave Morse this peanut type of dull emitter), the On practical test on a two -valveunit, which has the same high finish limited available voltage (on ac-receiver in London, with R valvesas the unit already mentioned, will countofthesensibleinternaland about 7o volts H.T. represent-provide a compact and convenient resistance) would make the L.T.ing approximately standard prac-intervalve coupling unit. equipment for a multi -valve re-tice, on a fairly good suburban The other unit of this series was ceiver using ordinary valves father aerial, comfortableloud-speak:ngalso tested and found satisfactory. was obtained on local broadcasting ; . . Birmingham, the Ecole SuperieureA Moderate Priced 2 -Valve B.B.C. (Paris),Newcastle and Glasgow Receiver. came in well on the phones, and Messrs. Bowyer -Lowe have re- easily readable-, Glasgow in par-centlytackledtheproblemof ticular being very good, loud anddesigning and marketing a two - steady, whilSt 2 LO was going ; valvebroadcastreceiverwhich Bournemouth at surprising strengthwill meet the wants, and suit the and intelligible even whilst Londonpurse of the man of moderate

was on, with critical reaction-notmeans. The .result is an interest- a common feat with commercialing little set which has been sub- types of apparatus. The ships camemitted to us for practical trial. in in a loud chorus ;Aberdeen's This" utility "instrumentis good -night was clear, though fa'nt ; neatly cased in a polished hard- and amongst thelonger waveswoodbox,withebonitepanel Eiffel shouted finely on two valves,forming the lid ;is well -finished, withinnumerableother Morse and the components are of re- stations. liablemake. An on -and -off switch is fitted, but no filament Tapped Anode Reactance. resistance ; and accommodation is provided for leading coils of the From Messrs. Radio Instruments, plug-in variety. Ltd., comes also a semi-aperiodic An extremely simple resistance - tapped reactance unit, with the capacity -coupledcircuitisused, same type of panel -mounting byrectification being performed by a means of a small false panel, and crystal,which is ina movable three small brass columns, a whitefittingplugging into the panel. engraved scale appearing on theThe well-known Bowyer -Lowe front of the receiver panel and alsovariometer incorporated in the set providing a drilling template. Thistunes from about 340 to 66o meters covers from 15o to no less thanon a P.M.G. aerial, and is the sole 20,000metres wave -length withcontrol. 12 tappings ; having a total resist- The Darimoht Cell. ance of over 600 ohms it comes On practical trial on local trans- under the semi-aperiodic class, andmissions,clearsignals were ob- cumbersome. For use with one orno tuning condenser is needed totained,at "pleasant strength for twoEnglish dull emittersthere bridge between the tappings, thetwo or more pairs of phones, in an are decided possibilitiesfor this tuning being flat enough to dispenseouter suburb. A littletrouble interesting type of primary cell. with it.This, of course, greatlywas experienced with the particu- simplifies the tuning of a circuit, aslar crystal supplied with the set, Anode Reactance with Variableif capacity reaction is used from thebut when replaced by another of Reaction. second valve anode to the first grid,the same make (which has already Messrs. Radio Instruments, Ltd.,as.in the tests carried out with thisbeen noticed in the columns of the have submitted for test a unit, suit-instrument, there are only the two Radio Press) a good spot was easily able for panel mounting by thecontrols necessary, A.T.C. and re-found. amateur constructor, comprising aaction. In the tests it was found to In all, the receiver is a neat, tapped reactance coil covering acover amply the range claimed :ingenious, and good-looking little range from 200 to 4,000 metres London came in strongly on the twoinstrument, in which pains have wave -length with 5 tappings whenvalves towards the lower limit ; andbeen taken to give good value for used with a .0002 p.F variable con-a regular boilermakers' chorus ofmoney.

116 November, 1923 MODERN WIRELESS

(Continued front page 104.) formerT, the secondary T2000000000110E0=00000E00 in Fig. 5, and it is possible, by theis included in the aerial circuit and correct use of an intervalve trans-impresses low -frequency potentials RADIO PRESS former, T, T2,to increase - the -on the gridofthefirstvalve. INFORMATION signal strength some four or fiveThis valve proceedsto amplify H DEPARTMENT times.It will be seen from Fig. 7 thelow -frequencycurrents,the that the loud -speaker, shunted bymagnified currents then flowing.D000000000000000000000M a condenser Co of o:oo2 /.:F capacity, through the loud -speaker LS. Owing to a tremendous increase in the or more, is connected in the anode -ThevalueSof - the - different number of queries, and the policy of the circuit of the first valve next toinductancecoilsaresimilarto Radio Press to given expert advice and not connection with merely " paper circuits," it has been found the anode. The second valye actsthOse given in necessary to enlarge our staff dealing with asthedetector,and thelow - Fig:5. - - such matters.The slight delay in answering frequency currents, which pass in Fig.8 shows,pictorially, how letters will shortly cease.In view of the the anode Circuitof the secondthedifferentcomponentparts, expense incurred we are reluctantly com- valve, flow through the primarYT, .indicated by'letters in Fig.7, may pelled to increase our charge for replies to of the stepTup intervalve trans be wiredup.. 2s. 6d., according to the rules below. If readers will comply with -the conditions laid down they may be assured of more 000000D000E0000,000000000010D.Or-inEMEDEDEEMEDE0000O0 prompt attention. All queries are replied to by post, and .8 - THE RADIO SOCIETY OF therefore the following regulations must be . 0 O complied with :- - IRELAND (1) A postal order to the value of 2s. 6d. for each question must be en- 000000000D0G0E00000000000000E=0000000000=0000000 closed, together with the coupon. GENERAL meeting of the Professor J: J. Dowling, National from the current issueanda ARadio Association of IrelandUniversity, dealt in detail with the stamped addressed envelope. -development of wireless for broad- (2) Not more than three questions will was held in the Municipal. be answered at once. Technical Institute, Kevin Street,casting weather forecasts, and men- (3) Complete designs. for sets and com- Dublin,onOctober16, 1923, tioned the efficient system in opera- plicatedwiringdiagramsare Professor W. J. Lyons presiding.tionintheeasternstatesof outside the scope of the depart- There was a large attendance, in-America, due to wireless. ment and cannot be supplied. cluding representatives of the old Professor Lyons, in summing up, (4) Queries should be -addressedto Dublin Wireless Club, of business he was satisfiedwith the Information Department, Radio interests, of the Universities; andmeeting, and hoped the Dublin Press,Ltd.,DevereuxCourt, the communications branch of theWireless Club would discuss the Strand, London, W.C.2, marking matter, bearing in mind that they the envelope " Query." National Army and the Post Office 00000000000000000000M00 engineering staff. all had common interests. 0 The chairman spoke of the large Itwas announcedthatthe 0 hadre- APPRECIATION number trained in wireless at theAssociation'ssecretary 0 Municipal Technical Institute, butceived a letter frcm thesecre-0 0 the slump in shipping had giventary to the G.P.O. approving the000000000000000000000000 no outlet and others qualified forAssociation, and that its co-opera- DEAR SIRS,-I am pleased to in- certificates were unabletogettion in securing the observance ofform you of the results I have ob- an examination.With these mentheregulationsbyholdersoftained using the ST.Ioo circuit de- originated the idea of an Associa-licences would be welcomed, and scribed in MODERN WIRELESS, No. 6. tion, but not as an Association ofwould be glad to seek the viewUsing I Mullard Ora and r "R" Professional Wireless telegraphistsof the Radio Association on anyValve, Hertzite detector, Igranc and not as catering for enthusiasticquestions that might arise.The L.F. transformers, aerial condenser amateurs.They had to considerExecutive Report gave the follow-in series, Nos. 75 and zoo Igranic all interests, especially in view ofing as having agreed to becomehoneycomb coils, 117 volts, H.T. the development of broadcasting.vice-presidents :-W. D. Morgan,shunted by r mfd. condenser. The The Government had also to deter-Esq., B.A. ;J.J. Dowling, Esq.,following are some, of the stations mine whether a man who got the M.A.,NationalUniversity ;G. Ihave received :- Postmaster -General's certificate Marshall Harris,Esq., M.I.E.E., 2L0,5IT,5WA, 5NO,5SC, here would have the same rank asGeneral Manager, Dublin United 2BD (Aberdeen Testing), School of the man who gottheBritishTramway Co. ; Professo'r W. Thrift, Posts and Telegraphs, Paris, Croy- Postmaster -Gene: -al's certificate. T.C.D., Trinity College, Dublin ;don (GED), 2B0 (Writhe), and The Goverment would also needT. Hempenstall, Esq. ;Professordozens of amateurs including 2WX advice on the question of broad-Hackett, M.A., Ph.D., College of(BrIerly Hill, Staffordshire, which casting.Mr. E. Hancock, presi- Science,Dublin ;ProfessorT.is 98 miles from here).The follow- dent, Institute of Electrical En- Dillon,M.A.,D.Sc.,Universitying stations are heard on the loud gineers,spoke of home manufac- College, Galway.The formationspeaker 5IT,and 5SC. ture and protection for apparatusof a programme was left to theGlasgow can be heard in a 15 -ft. madeinIreland.Mr.Bridle,Executive Committee. square room loud and clear, almost secretary of the Dublin Wireless H. HODGENS, Hon. Sec. as loud as London. Club,agreedthattherewas Radio Dept., Yours faithfully, room for only one association in Municipal Technical Institute, W. E. Goss. Ireland; Kevin Street, Dublin. Gt. Berkhamsted.

I17 MODERN WIRELESS sly ovenwer, 1923 D0000000010000000000000DE10000000000000000E0000000000000000000000=000 9

a 0 FOR . CRYSTAL USERS. 0 El 0

a El El Hints and Suggestions on Mounting and Using. 0

0000000000000000=0000D00000170110110000000000001100100111D00000E10000000Drnmpti WE are glad to see that manufacturersmanufaurers It is surprising that with such a good demand in increasing numbers are placing for crystal receivers there should be such crystals on the market ready mounted a lack of originality in design, especially in in suitable cups.Seeing that the majority of regard tothedetectoritself.More than

, crystals are used by beginners, who cannot be go per cent. of the crystal receivers placed on expected always to realise the importance of the market are fitted, with a very crude form ,such matters as not overheating the Wood's of adjustment for the cat -whisker point, and metal when mounting, avoiding touching the in nine cases out -of ten the cat -whisker itself surface of the crystal with warm fingers, and ismuch toothick.We have frequently other important points, ready mounted crystals advised the use of a gold cat -whisker, and at should go far towards making good reception present a large number of such wires are on.the more general. market, but unfortunately in the majority of cases we find that the percentage of gold is extremely low and 'that the wire consists Facility of interchange will bring about in mainly of copper.Such alloys, while slightly turn greater curiosity on the part of the user better than ordinary copper, are by no means as to the relative merits of the various crystals. free from tendency to oxidise.Silver cat - We must remember that the requirements of whiskers are often sold, and are probably all listeners are not the same, for the man who superior to those in which there is a tiny per- liyes in the shadow of a broadcasting station centage of gold.Silver whiskers have the can well sacrifice a little sensitiveness in his advantage of greater springiness than the crystal in return for added.reliability..On gold.When the latter is of a good quality, it the other hand, the man living, say, 25 to is frequently extremely soft and easily pushed 3o miles from the station will need to get a out of place. or bent into an awkward shape, very fine adjustment on his crystal if the set which makes the setting of the crystal difficult. is to give any results worth speaking of, and for this reason he would be, bound to seek everywhere for sensitivity even at the sacrifice A point of interest in the design of a crystal of constancy of adjustment.For the " close- receiver which is frequently overlooked is the up " man carborundum with a suitably applied necessity of connecting the slider and its rod potential is almost ideal, the contact between to the earth and not to the aerial.If the the carborundum and the metal plate being so slider is connected to the aerial, every time we firm that even considerable vibration of a adjust it and bring our hand against the rod table will not put it off adjustment.It is signals will be shunted to earth through our sometimes argued that the necessity of apply- body.If, on the other hand, the slider is ing a separate potential to the carborundum earthed, we shall not alter the tuning by crystal is a good reason for avoiding it, but now touching the rod.As long as the wire itself that excellent potentiometers are obtainable and the aerial terminals are well insulated in every dealer's shop at a reasonable figure, from the framework, there is no need whatever and, as flashlight dry cells are so cheap, there to insnlate the rod from the base, as in any is no real reason for avoiding its use in situa- case itis connected to earth.The crystal tions where it will serve such a good purpose. itself should always be connected between Any wireless book dealing with crystal receivers the aerial terminal and the telephones, not, as will explain the use of a potentiometer and we sometimes see in beginner's sets, between how to connect it up. the telephones and the earth terminals, November, 1923 JUNIOR W I R E L E S S-Supplement to Modern Wireless

O A yi For Boijs of allairs i 1

Edited by Perci9 W.Harris

Vol. 1.No. 3. NOVEMBER. Published Monthly. THE EDITOR'S CHAIR WHEN the members of thewho has contributed much to wire-in America and C. S. Franklin in British Broadcasting Co.less and who is known to everyEngland. We hear a great deal in met together recently toreader as the inventor of the famousthese days about the use and abuse consider the new regulations regard- " Armstrong super," was scarcelyof reaction, so I have arranged to ing licence, a suggestion was mademore than a schoolboy when hispublishthismonth anarticle that a special schoolboys' licencefirst great discovery of regenerationdescribing in simple language just might be issued to be granted by what reactionis.To show you theschoolmasterto suitable i'_111110111111111111111111111111111111111111111111111111111111111111E the practical application of reaction applicants.I do not know whether in a way which cannot cause inter- therewouldbeanyparticular ference to your neighbours, we also advantage in this, as it is very .easy Contents. publish a complete and detailed for any boy to go to the nearest description of how to make a two - post -office and obtain a construc- Page valve receiver utilising reaction in tor's licence, and I have no doubt Editor's Chair - 33 the best way. With this I am sure that thousands of my readers have Junior Wireless Reaction Set 34 F,1 you will get wonderful results ;it done so since the publication of our By G. P. KENDALL, B.SC. is a set which is just about as last issue. Boringlarga Holes - - 37 -E efficient as is possible to get it, and Nov is the time to start a school on a good aerial, when conditions radioclub,if you haven't one = Tha School Rad!o C:ub - - 38 t:are normal, you should be able to :.=-- already.On another pageDr. A Set in a Matchbox - - 39 hear several, if not all, of the broad- Chapman, who has had much = A Folding Frame Aerial - 41 R. castingstations.The two -valve experience with such clubs,tells note magnifier, described in the = Reaction: a sample explanation 43 you just how to proceed.There E first issue Of JUNIOR WIRELESS, are many advantages in a school Wireless Cabinet Work - - 48 E. - when added to this receiver will radio club, not the least of which is By R. W. HALLOWS, M.A. make a splendid set with loud - the great benefit which comes to speaking strength. every member by the interchange Ti1111111111111111111111111111111111111111111111111111111111111110. A good wireless set is always ofideasandexperiments. Wewas published.Marconihimselfworth a goodcabinet.Bought cannot go far in amateur wirelesshad not come of age when hecabinets are generally expensive without experimenting, and it mustinvented wireless telegraphy ;soitems, and most boys will want to not be forgotten that it is by noage does not count for everything,make their own.In this number means always the highly traineddoes it ? we publish an articleby Mr. R. W. experts who make great inventions ; The principle of regeneration-orHallows, M.A., which will tell you many have been produced by thoseas we call it on this side of thehow to make your wireless wood- who only recently started to studywater, " reaction "-was describedwork to the best advantage. thesubject. Major Armstrong,about the same time by Armstrong THE EDITOR.

33 J U N I 0 R W I R E L E S S.-Supplement to Modern Wireless. November, 1923 DOODODODEDDOODOCIE=DOEDDOODOOMEDE100000OODEJDOOOODOOOODEICIDOODOCCODOODOO O 0 D Li THE " JUNIOR WIRELESS " REACTION SET D O A simple non -radiating set for the beginner. a o° oo El D O By G. P. KENDALL, B.Sc., Staff Editor. 0 O 0 O We can recommend this set as highly efficient in spite of its sim- 0 O plicity.ft should receive all British broadcasting on a good aerial. 0 0O 0- 000000000000000DOODOODOOODOODOODDE3DOODODOODOODOODEDD0000000000000000D0 IF reaction is to be used so asinthecircuitdiagram,which coils, because your aerial may be notto annoy one'sneigh-automaticallyconsists of two of unusual dimensions. bours, andyetto get the basket coils, one of which is fastened The plate circuit is tuned by full benefit of it oneself, it must beto the base board and the other anotherbasketcoil,L,, and a confined to one ofthecircuitsto a wooden arm which is pivoted variable condenser C1.The coil which are not connected or coupledat the end so that it can be movedhas eighty turns of No. 22 double to the aerial, and one of the mostover the lower coil.Variations of cotton -coveredwireanditis practical ways of doing so is thattuning can therefore be done byfastened to the base -board with shown in the circuit.This i s knownmoving the arm.These two coilsstring as before. _ as circuit S.T.34 and was originatedwith their wooden strip can be seen .The variable condenser should by the Editor of MODERN WIRELESS. on the left of the photograph ofhave a capacity of .0003 µF, and Itconsistsof one valve actingthe set. the method of mounting it will be described later.The reaction coil is a basket having fifty turns of No. 28 double cotton -covered wire, fastened to the right-hand wooden arm in the way already explained. Materials Required The set is a very cheap one to construct, besides being very easily made, as the following list will show. The total cost should not exceed 3os., the one shown in the photographs having cost rather less. base -board, 9 by 15 in. 2 wooden arms, 8 by ti by in. 2 filament resistances. 2 flange -typevalvesockets. 7 terminals.

variable condenser of .0003 µF.This should be of the type having more or less square ebonite top and bottom plates, for reasons Notice tee simple variometer onthe left.it is made from basket coils.The which will become apparent condenser tunes the anode coil,and reaction is obtained by moving the right- later. hand strip. grid condenser of good make, capacity .0003 µF. as a high -frequency amplifier with The coils are fastened to the grid leak, also of good make, a tuned plate circuit, across whichbase and to the arm respectively 2 megohms. isconnected the detector valveby drilling holes in the wood and I-lb. No. 22 d.c.c. wire. (V2 in the diagram) through thetying - each coil tightly in place oz. No. 28 d.c.c. wire. (C2). Re-withstring.Eachcoilconsists usual grid - condenser telephone condenser of actionisobtained by providingof 4o turns of No. 22 S.W.G. double .002 µF. capacity. a " reaction coil " L4 in the platecotton covered wire, and they are Systoflex and tinned copper circuit of the detector valve whichjoined in series, that is, the end of wire for connections. isarranged to couple with theone is joined to the beginning of tuned anode coil Le, the couplingthe other, as shown in the diagram Base -board being varied to- produce the re-of variometer connections.They Thebase -boardIusedwas quired effects. should be joined so that the current bought ready-made for 4s., and is flows the same way round in eachmade of well dried and varnished Tinting Arrangements for most sizes of aerials, but if youmahogany which has proved to be The aerial circuit is tuned byfind a difficulty in tuning in witha very good insulator, no ebonite means of a very simple form ofthe set when finished try reversingbeing used anywhere.Ifyou variometer represented by L2, L2,the two connections to one of thesemake it for yourself remember to

34 November, 1923 JUNIOR W I R E L E S S.-Supplement to Modern Wireless put two crosswise pieces at the ends basket type, with the exceptionterminal, that on the right is the to lift it off the table to leave room that where inbasket windingearth, and the one in the centre for the wiring,etc., underneath. the wire is looped alternately overisa common terminalfor the Suitabledimensionsforthese and under the spokes of the spider, negatives of both high' and low pieces are i in. square by gin. long, in double basket winding itis tension batteries.Immediately to and they can be fastened to the taken under two and over twothe right of this is the H.T. positive, board with glue or a few, screws. spokes.The result is a strongerand on the left is the L.T. positive. and more compact coil. Notice that the connection shown AERIAL TERMINAL After winding the coils should bedotted in the circuit diagram is not soaked in diluted shellac varnishmade inside the set at all, but is EARTH TERMINAL (thin it down with about half itsto be done with a piece of wire volume of methylated spirit), driedbetween the earth terminal and one eAsmer and well baked in front of the fireof the battery terminals.This is co/LS (allow them to dry for half an hourto enable the user to connect the How the variometer coils are joined. before baking).They can then beearthto either the positive or bound with insulating tape andnegatiye of the accumulator, since Ishould strongly advise youmounted in the way I have ex-it is interesting to try which gives not to take any risks with the in- plained. the best results with various ad- sulation of your base -board, but The two wooden arms carryingjustments ofthe reaction.In to separately insulate each terminal the moving coils are mounted so asgeneral it is best to connect this by proceeding asfollows :Drill to turn upon a point near theirwire to the positive, partly because the holes for the terminal shanksends by means of two pieces ofthat seems the most efficient for a little large, insert the terminal 2B.A. screwed brass rod.These long distance work, but chiefly and pour very hot melted paraffin are passed through holes in thebecause it reduces the risk of any wax round each before screwing base-'3oards andthearms, theoscillationsin the platecircuit down thenuts.The wax will getting back into the aerial circuit. soak into the wood and render it and being radiated to the annoy- damp-proof and prevent leakage ance of everyone around.I should in damp weather. A still better be interested to hear from those method would be to fit the terminals who make t.p this set which con- with the ebonite bushes now sold nection they find the best, either by various firms. for producing loud signals from, a - Since the terminals have to be near -by station or for picking up a attached directly to the base the How to secure the arms. far distant one. latter should not be thicker than The two terminals at the front Ith in.',and would be better if latter being heldattherightare for the phones, and the tele- only,18,- in. height by means of nuts and a pairphone condenser is screwed to the of spring washers, as shown in theunderside of the board beneath Filament Resistances diagram. them, as is shown in the wiring It must be noted that the fila- diagram. ment resistances are to be of the Arrangement of Terminals pattern which can be mounted on Of the terminals arranged at the Mounting the Grid Leak the top of the board, such as those back of the board, that on the left The method of mounting the illustrated in the photograph. These (in the photograph) is the aerialgrid leak isfairly plain in the are of Igranic make and seem very convenient for sets laid out on boards,althoughcheaperones would serve quite well. Mounting the Variable Condenser Thereasonforspecifyinga variable condenser having square top and bottom plates will now be seen.The condenser is mounted upon the board by placing it upon edge and passing two wires over the ebonite top plate and down through two holes in the board. If these wires are twisted up tight the condenser will be held firmly in position. Winding the Coils The coils are all wound upon the double basket principle, and seem efficient in use, since the results given by the set are certainly very good.The methodofwinding is similar to that of the ordinary A view of the set from the rear.

35 JUNIOR W I R E L E S S.-Supplement to Modern Wireless. November, 1923 photograph.One end of it is held All joints should be soldered,the arrangement of the terminals. by one of the clips of the Dubilier ofcourse,and careshould beAlso make sure that the batteries grid condenser, while the other istaken to see that every connection areproperlyconnected before held by a grid leak clip (sold byis really good and sound. A pointplacing the valves in their holders. most dealers in accessories) screwed to be noted is that the wires shown All this being done, put the tothe base -board without anydotted in the diagram run on thephones on, turn the valves up until special insulation, since this end issurface of the board. they are fairly bright, and proceed at the potential of the filament anddoesnot require isolation. The position of the grid condenser \l /x (betweenthevalvesockets)is worth noting, and should be followed carefully, since it enables the grid connection wires to be kept very short. -II Wiring The wiring will be quite easily C2 followed out from the diagram showing the underside of the board, and pains should be taken to copy it exactly.It should be done with No. zo tinned copper wire, with the exception of the connections to the moving coils, which require The theoretical diagram. short pieces of flex.All the wires should be sleeved inSystofiex, Operating the Set to tune in as follows :First bring withthepossibleexceptionof When the set is finished andthe reaction coil over the tuned thoseofthefilamentcircuit, ready to be tested, connect up anode coil gradually, at the same Which only require to be coveredaerial, earth, batteries and phones, timevaryingthetuningcon- where they cross and might touchand remember to add the connection denser,until theset begins to others. A few pence can be savedshown dotted in the circuit diagram oscillate.Test for oscillation by in this way. and mentioned in connection with touching the set of plates of the

1 io L I r *-7 I I S=IC LEAA"--.44 l`c* R/ ilc--- - 'w / ...,-- . - 1 - 1, '"!-,---.-,.. L / BLE CONZ,EATE.7.4.- t.;:,,_. . /. ,,,,...... s ---,' 1-,,T..- _ 1 ' IL Ir t- 1-4- St- IL/ I v. --- I / i ,-/- _ 4J 1 I fr( 1 1 I . i-4---I -- I I - COND329 ,EI J , ,/ -T-f------PHONES

Practical wiring diagram.

36 November, 1923 JUNIOR W I R E L ES S.-Supplement to Modern Wir.dess variable condenser which are con- Almost any valves may be usedthrough a right angle.As the dri!1 nected to the plate of the firstin this set, such as Mullard Ora,is intended for ebonite there is no valve ; when the set is oscillatingEdiswan A.R., any type of Rneed to harden the cutter, so it a strong click will be heard eachvalve, or A.R.D.E. if dull emittersshouldbelefttocoolslowly. time these plates are touched.Ifarepreferred.About6ovolts When cold the cutter may be cut the set will not oscillate, reverseH.T. will give good results withto size and formed.The cutting the connections of the reaction coil.any of the foregoing valves. edge should be leftabout I in. Next, keep the set oscillating and long.(Itwillthen be possible search for carrier waves by turning to cut ebonite up to about I in. the condenser slowly and moving Results Obtained thick.)The shank should not be the left-hand upper coil quickly Remarkably good results haveleft longer than about 2 in. long. backwards and forwards across thebeen given by the set shown in theThe formation of the cutting edge lower (fixed) one. When a carrierphotograph, apparently as a resultwill best be understood by reference wave has been picked up tune toof a happy choice of coil valuesto the diagram, care being taken the " silent point " (that means theand the shortness of the importantto see that the actual cutting edge place midway between the squeals) wires.At my address in Northoccurs on a diameter.The set and gradually weaken the reactionLondon I can hear both Glasgowscrew should be of steel or iron (not untilself -oscillationstops, .re - and Birmingham'faintly but clearly Adjusting the condenser as you do on a Ducon aenal (i.e., when using so.The speech and music willthe lighting mains as an aerial) 4:=1 - then be heard clearly.It maywith very careful and critical ad- CUT A WA Y assist you to know that the broad-justment of tuning and reaction, so casting stations will come in atthat with an outside aerial most points between zero and 5o onof the B.B.C. stations should be the condenser scale. heard in almost any situation.As a Should you experience any diffi-result of the thick wire used for the culty in getting the signals pro-coils tuning is sharp and Glasgow perly tuned in on the aerial circuit,can be heard with only very slight remember about reversing the con-interference from London ata nections of one of the aerial coils. distance of five miles from 2L0. It may interest you later to try With the addition of the note the effect of connecting a smallmagnifier described inthefirst fixed condenser of about .00031.1.F number of JUNIOR WIRELESS very 6:5° between the aerial and the aerial good loud -speaker signals should be terminal of the set, since this some-obtained up to distances of about CZ/777N6 EDGE times improves results considerably. fifty miles. Fig. i.-How to make the drill. 000000C00000000C0000000000CE0000000000=0=000000 0 brass, as it is too brittle) and the 0 0head should be less than in. 0 AN ADJUSTABLE DRILL 0 diameter. 0 The drill may be used in either C FOR LARGE HOLES a..large, hand drill or a carpenter's A brace,. orfor preference a drilling 0000000000000000017100000000ommoomonnopoommomo Machine.The. pressure should be . just, sufficient to -produce a thin

MOST amateurconstructorssize from I in.toabout 3 in.shaving but no more: - - at some time oi other havediameter, cleanly and accuratelyi To use. thedrill,first drill . a wanted to drill a large hole It is quite simple to construct and;f in.: hole with a standard size in ebonite and have been at a lossunlike a twist -drill, does not need twist -drill; then, insert the_ drill .or tofindasuitabledrill.Twistaccurate grinding to make a true boring -bar- .(having,, previously set drills ofover in.arerather -hole. the cutter to the repured radius) costly, 'and, as is well known, do' The:main body of the drill con-and. drill half -way through. Re- riotleave- a' truly circular hole.sists of a piece of silver steel aboutverse the panel and cut through For holes up to, Say, -11 in. diameter6 in.or. 8in.long andIin. from therreverse.side. _If the brace which do not need to be an exact 'diameter.Besurethatitis has been kept. vertical the hole size,in- ordiriary wood -worker's+ in.. (o.25o in.)diameter,and'produced_will be found to be quite centre -bit may often be made to'not a few thousandths of an inch one:clean without any ragged edges serve the purpose. There are tithes, -way or the other.Drill a * in. or mark where the first cut finished. how ever, when it become's necessary hole * in.from one endfor It cannot be emphasised- how to drill a large. hole, for which thethe cutter.At the -same end drill -useful a stock of various, sizes of cost of a twist drill would be out ofa 4 B.A. clearance _ hole up the silVersteelcanbe.Itisnot the question and of such a sizecentre Of the rod until it meets theexpensive, about a shilling a pound; that a centre -bitcould not becross hole.This hole, which is forand is most useful fcir making odd obtained.In .such cases the drillthe set screw; must now be tappedsized taps and drills. . It is quite to be described will be found to4 B.A.To make the cutter, take a'easy to forge and harden and with " fill the bill." piece of * in. diameter silver steel,a little skill -quite a number of use- Thisdrill,or more correctlyheat one end to a bright cherryfultools may be made from a boring -bar, will bore holes of anyred in the fire, and bend one endfew lengths of silver steel.

37 JUNIOR W I R E L E S S.-Supplement to Modern Wireless. November, 1923

DOODOCOODCOODDOODOODOODOODOODOODOODODODOODOODDOMEDEDEDDOODEDDEO=DEDLOODDO0 0 0 THE SCHOOL RADIO CLUB 0 0 0 By E. H. CHAPMAN, M.A. (Comb.), D.Sc. (Lond.). G ri El D Every school should have its Wireless Club.This article will tell you how to start it. MOODDCOODDOODDDOODOODOODDOODEDDOODODODOODOOD0===MODDEDODOODODOODODED

THERE is always a fascina-the prime movers . in starting theof copper wireisrequired, but tionaboutforming andclub will, by force of personality,take no, notice of. him.Let him running a school radio club. stand above the others.He is the wag. For one thing, there will crop up aone to be made leader.As to the Other matters to discuss and number of those delightfulsur- title of this wireless club leader,decide on at this meeting are (i.) 9Hprises which make school life sothere is no better plan than to callrules of -the club, (ii..) subscription, enjoyable.You find, for example, him captain.All the other schooland (iii.) programme for the term. that Jones of the lower fourth,clubs have a captain, and by usingWith regard to the rules of the whose record for school work is suchthe same title for the chief officerclub, the best advice to follow is a poor one, can use his fingers withof the radio club you will be givingto keep the rules as few 'and' 'as alltheskillof an experiencedthat club some, at least, of thesimple as possible.Circumstances mechanic when it comes to buildingdignity and standing of the othervary so much from one school to the school wireless set.You may school clubs. another that one '-cannot say much afso find that Smith, who has never Let us suppose that our threeabout the subscription except to once opened his mouth when thestalwart wireless enthusiasts aresuggest' that it be as small as school debating society has beennamed Brown, White and Green.possible, since there' are s6 many debating on the usual subjects,Let us also suppose that White,calls on a Schoolboy's purse these can speak, most intelligently on aby reason of his personality, is the days.The drawing up of a pro- matter of scientific interest. obvious choice for captain._Thengramme for the term is an engaging For the formation of a schoolone of the other two, BrOwn say, and interesting task for the captain, radio club two things are necessary : shouldclearlybe madevice - vice -captainandthehonorary enthusiasm and capital.Of thecaptain and Green should be madesecretary.Herearesuggestions former essential, enthusiasm, therehonorary secretary. for the programme of a school radio cannot be too much. With regard to . .A most important point is toclub which meets weekly : thesecondessential,however,enlist the sympathies of the head- although itis impossible to 'laymaster and to ask him to becorne r. Lecture on capacity.Experi- down any hard and fast rules, onethe president of the club.Inter-mentalillustrations. Questions thing is certain, the usefulness of aviews 'withaheadmasterareand answers. school radio club may be. just asoften strikingly painful, but White, 2. The construction of a simple easily spoiled by too much capitalBrown and Green have nothing to -_crystal set. .Open discussion. at the beginning as by too little.fear when they approach the head --- 3._ Experiments with a simple It is far and away better to startmaster on behalfof the schooltransmitter and receiver. a club in a small way than toradioclub. A headmaster, likes 4. Lecture on inductance.Ex- begin in a big and ambitious man-'to see his boys busy and, above all,perimental illustrations.Questions ner. Clubs which at the com-he likesto see them take theand answers. mencement have fewmembersinitiative.Nextthere is-the -- 5. The construction of a one - and very little apparatus, generallymatter of vice-presidents.If therevalve set.Open discussion. succeed, but clubs which start withshould happen to be any other 6. Experiments on aerials, "outmany members and much ap-master who is interested in wirelessdoor, indoor and frame. paratus have a curious knack ofhe should be persuaded to act as a 7. Lecture on primary and second. fizzling out suddenly.The greatvice-president also. ary batteries.Experimental illus- thing to remember isthat it is Having now a complete list oftrations.Questions and answers. comparatively easy to arouse en-officers of the radio club, a notice 8. The constructionof a low thusiasm over a new thing, while it isshould be put up calling a meetingfrequencyamplifier.Opendis- a difficult matter to retain interestof all those interested in wireless.cussion. and enthusiasm when the newnessThis notice should be signed by the 9. Experimentswithportable has worn off. honorar' secretary pro tern. aerials and portable sets, with a At the outset a school radio Let us suppose that those in-view to the construction of a set club will depend for its. being onterested have met together andfor the next school camp. A.! two or three, not more, stalwartthat one of the vice-presidents from There is scope for a great deal wirelessenthusiasts.Therewillthe chair has explained that aof careful thought in the drawing be many more boys who are in-radiO club is to be formed.The up of a programme for a school terested, but the initial work alwaysfirst formal business will be theradio club.It must not be for- dependsonthetwo orthreeelection of the proposed officers.gotten that the school scientific stalwarts.First of all the radioThere should be no opposition.apparatusis a great asset.Far club requires a leader.In mostThe school wag may propose amore experimental work can be cases it is pretty Obvious who thatred-haired fellow for captain ondone by a school radio club than leader should be.One or other ofthe grounds that a plentiful supplyby other radio clubs.

33 November, 1923 J U N I 0 R W I R E rE S S.-Supplement to Modern Wireless 8000000000000000DODOOEOODOOD000000000000000000DOOODEDOLILJU01:100000000000 O 0 O 0 O D 0 A RECEIVING SET ON A MATCHBOX 0 D D D By W. ERIC BARNES. 0 O D Matchbox sets are not new, but this instrument is efficient as well as small. D O Fi O . D0000000000000000000000000000000000000000000000000000000000000000000000

THE small crystal set describ:dthread the last turn through thethe sliding contact is a piece ofin. hereunder was constructed loop, and make fast by gently pull-diameter brass rcd, turned or filed of quite elementary piecesing one or both of the ends of theat one end (F g. 5), to drive into the of material, and the reprcducticnribbon, which project through theebonitebase,anddrilledand by the reader will be found awinding,until the final turnis slotted at the other to receive the moderately simple molter. firmly held. Four inches or so ofsliding contact rcd.A piece of The windings,onthevario-free end of wire should be left forx /i 6 in. diameter brass wire with meter principle, were designed toconnecting up later.The windingsa glass bead firmly fastened to one approximate a wave -length of 35oshould be, given a coat of shellacend will serve as a contact rod, to to 38a metres, in order to receivevarnish and allowed to set firmly which a spiral consistingof threeor the broadcast concerts frcm thebefore further handling. four turns of fine brass or cc pper wire London station 2 LO. Thebaseformountingthe (to act as a cat -whisker contact) The various aerials to which thisterminals and crystal, etc., can bewill be. later fitted and soldered to set has been connected have beencut fromin. sheet ebonite (a goodthe opposite end when mounted fifteen to twenty miles distant fromquality worn-out gramophonein the post. A connecting strip 2 LO, and the reception has proved record will make a fairly service-frcm the post to the condenser is very satisfactory, being very clearable substitute), size 2 in. by xi in., cut frcm strip brass rft in. by kin. and distinct, and the set readilydrilled and counter -sunk as shownby .020 in., drilled and bentas in accommodates Fig. 6. three or four pairsof 'phones The 'phone withoutuncom- condenser, Fig. 3, fortablediminu- consists of eight tionin signal pieces of copper strength. foil x s in. by fin., The special and ninepieces interestofthe of .003 in.thick constructionlies mica x in. by f in., in the former assembledalter- carrying the_ two nately in the windings,which usual manner, consists of an allowing I in.to ordinary match- fold over on the box withits top to form con- sliding tray. The nections. A little outer winding shellac varnish is comprises 55 smeared over the turns of No. 24 plates during D.C.C. wire, and assembly, taking is wound on the care that the outsideo fthe varnish does not box, and the This matehbox receiver is tuned by pulling theinteriorin and out. spread to the inner winding of outeredges, forty turns of the same size wirein Fig. r.To fasten the base towhich form the connections, the is wound on a block of wood, thethe wound box a pair ofbrasscondenser being ultimately clamped size of which when wound shouldclips will be required.These canbetween two stout metal plates and fit snugly inside the tray. be cut from medium hard stripslightly warmed in an oven for Toanchortheendsofthebrass k in. byin., about .02 in.aboutone hour and afterwards windings," babyribbon"I in.thick, bent as shown in Fig. 2. allowedtocoolbefore removal wide will prove effective, and is The crystal holder is a smallfrom the clamp. employed by folding,say,3 in.spacing washer, as used in variable With four 6 B.A. by fin. counter- back on itself, thus forming a loopcondensers, and is sawn throughsunk brass screws, four hexagon in. long..During the process ofwith a fret -saw or filed with a finenuts to suit, and two 4 B.A. brass winding the coil, and before the lastslotting file as shown in Ft. 3, andwashers,theass(mblycanbe eight to ten turns are put on, placesoldered to a strip of .ozo in. brassproceeded with.Mcunt the con- the loop in position to approximate * in. by 1 in., and drilled for thedenser between the two terminal the finish of the last turn, wind theterminal screw, the assembly show-holes drilled in base, fit a screw to rest of the turns over the ribbon, ing as in Fig. 4.The post carryingeach hole, and a washer over the

39 JUNIOR W I R E L E S S.-Supplement to Modern Wireless November, 1923

As AssE/181. AD

frt QCRYSTAL /"

64 44 fOkOIN4 Jot. DE RED FoLDEC ovER Ti 674 0 Iu /7111 CoPPflk Y160114 DIM 16 MICA

'---r-i I _Lr- x --, 41 COMPLETE DENSE0.

FIG 2 O FIG 3

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T.NEC ay 5,,o,,c TRAY FIG 6

FIG.4, Full constructional details are given in the above illustrations. screw so that it clips the contacts ofthe tray, andtothe corre-Before permanently joining up.and of the condenser, and thread on asponding inner faces of the outer' fixing, make a rough test in order nut.Thepostandconnectingcase, so that each pair of stripsto determine that the correct work- strip, Figs. 5 and 6, can now beforms contact at every position thating relationship or sense of the two fitted.The shouldered portion ofthe sliding tray can assume.Need- coils has been made. Two the post is passed through the holeless to add, these strips must beremedial tests will suffice to put in the strip, and just entered in thewell cleaned or a poor contact will mattersright. hole provided in the base.Next,result.Further, in order to accom- (a) Reversetrayandre -test, gently drive the post into the basemodatetheextra.040 in.,i.e., and /or until the shoulder rests firmly onthe thickness of the four strips, (b) Reverse junction X -Y to X -Z. the strip.Push in the contact rodchoose a box in which the tray is The aerial terminal is the screw and solder the " cat -whisker " ina loose fit sideways.The writercarrying the crystal holder and the position. found that a Bryant and May boxbeginning of theoutercoil.A The crystal holder is fitted towas the most suitable and thefurther hexagon nut, or better, a the base with a screw and nutstrongest of the many varietiessmall milled -edge nut, will permit through the top left-hand corner available. To complete the connectionto theaerial. The hole(viewing base with 'phoneassembly, the base is given a coatearth terminal is mounted to the condenser nearest you), the begin-of shellac on its underside, also thetray, and formed by a piece of ning of the outer coil being sub-face of the coil upon which it will 6 B.A.screwedbrassrod I in. sequently joined to this screw. rest, together with the plain ends long,screwedintothe wooden The coil connections can be madeof the clips, Fig. 2, and while theblock inside the tray, and made quite simply by connecting twoshellac isstill wet push in thefirm by shellac smeared on the short lengths of flex between thelonger ends of the clips between threadsbeforescrewingin.If outer fixed winding and the innerthe coil and box, and with the basethe outer end of the screw is held sliding coil, or a neater job can bein position, set the clips so that thein a small flame for a few moments made by mounting strips of .010 in. bent, or hook, end firmly clampsthe shellac will set hard.Connect by f in.brass (acting as wipingthe base.Leave to set. theouterorfreeendofthe contacts), Fig. 7, and fastened to Join up the windings and theinner coil to this point by a nut, the two longer sides of the outsiderest of the circuit as in Fig. 8. (Continued bottom of next page.)

40 November, 1923. JUNIOR W I R E L E S S.-Supplement to Modern Wireless DOODOODMOODDOOD0000000000000000000000000000L00000 D 0 THE CONSTRUCTION OF A id NOVEL FOLDING FRAME rd

AERIAL

n En-ocoommoomoomooDooLoompoommomoommommo Fig. 3.-Details of spacing tube. THE use of a frame aerial forframe aerial which was designedbrass rodsisgoverned by the receiving circuitshas notwith the object of obtaining a com-number of turns used on the aerial. progressedasrapidlyas pact and portable frame which could For example,toreceivethe might have been expected, con-be brought into use at a moment'sBritish Broadcasting with this 3 ft. sidering the many advantages thisnotice, and when notrequired frame,tenturnsarenecessary form of aerial has over the outdoorcould be packed away in a veryusing a .0003 1.4F max. condenser. type.It is probably due to thesmall space.The construction isTherefore, ten insulating bobbins fact that the energy received in thesimple and the cost negligible. will be required on each brass rod, average frame aerial is so small It is not important to follow theif standard porcela n bobb_n in- that it requires a circuit employingdimensions given, as no doubt thesulators as supplied by the General asensitivevalvedetectorandexperimenter will have his ownElectric Co. are used, the turns will various stages of amplicatioti forideas as to the most suitab:e size be 4 inch apart, and with two 2 -inch satisfactory long-distance reception. forhisparticularrequirements, end distance piece, which can be However,itisnotgenerally but itisgenerally agreed thatmade up with eight extra porcelain appreciated that excellent resultswithin certain limits a large framebobbins or two 2 -in.lengths of canbe obtained with framewith few turns is the best com-ebonite tube (Fig. 3) the length of aerial using a simple circuit such asbination for short-wave reception,each brass rod will then be 12 in., the S.T.ioo for the reception ofand more turns on a smaller framewhich allows for lock nuts to fasten for long -wave reception. the frame together.It is impor- On reference to Figs. x and 2 ittant to use a wing nut at one of the will be seen that the principle ofjoints for locking the frame when the frame isbased on a trellisin position. formation, and indeed there is very It will also be seen from Fig. x little description necessary to ex-that, for the sake of rigidity, two plain the construction. cross pieces of wood are fixed to the The wood used for a three-foot legs of the frame. square frame isIf in. wide by In conclusion, it should be borne f in. thick. in mind that when considering the Four pieces are cut measuringdesign of a frame aerial the wire 3 ft. r4 in.long, and four piecesused should have a low resistance. 6 ft. f in. long. A suitable gauge is 22 to i6 S.W.G., Inthefourshorterlengths and the tuning condenser should /tit in.clearance holes aredrilled have a maximum capacity of about exactly f in. from each end, that.00r ILF at most. P. J. B. is to say 3 ft. apart. In each of the longer lengths one (Continued from previous page.) /3- in. clearanceholeisdrilledalsoaflexibleconnectionlong fin.from the end and anotherenough to allow full movement to -A- clearance hole is drilled exactly the slide and joined at the other 3 ft. from this. end to the left-hand 'phone terminal. The assembly is simple. If strips as in Fig. 7 are used, make Fig.-1.-The frame open. Two frames are actually formed,one connection under this nut, the eachhaving two ofthe6ft.flex not being required. local broadcasting stations if theI in. lengths of wood and two of The crystal used was hertzite, distance is not too great.Fromthe3ft. in.lengths. A and is retained in the holder by the experimenter's point of viewglance at Fig. i will make it clearspringing the slot with a screw- there are many possibilities in thehow these are connected together.driver whilst inserting the crystal, development of frame aerialre-Four 2 B.A. screwed brass rodsanduponreleasethecrystal ception, and it must be agreed thatare used on which areplaced becomesfirmlygrippedinthe a great advancement will be madesmall porcelain or ebonite bobbinholder. in the progress of wireless from ainsulators. The length of these Improvementswillnaturally popular point of view when a sub- suggest themselves to the reader stitute can be found for the un- and may be readily incorporated, sightly outdoor aerial which will the foregoing merely illustrating a give results reasonably approaching rough - and - ready arrangement those obtained with the standard which, however, has proved exceed- Post Office aerial. ingly efficient. Used in conjunction Itisthewriter'sobjectto with two valves and a loud -speaker, describe a novel form of folding Fig, 2.-Closed for packing away. full -toned reception was obtained.

1 JUNIOR W I R E L E S S.-Supplement to Modern Wireless November, 1923

001700000000D0000000000DODOODDOOD0000000000000

oATRIPLE MOVEMENT COIL Id HOLDER. 0000000000000000000000000000000000000000000000 AN excellent basket coil holder,is drilled through the centre to make having atriple adjustinga tight fit on the in. rod.On movementfortuning inthe bottom edge a hole is drilled purposes, may be made as shown inand tapped to receive a short length Fig. 1.It is particularly easy toof 2 B.A., to which a bushed knob is manipulate, isin no way a cum-fixed. A hole is then drilled on bersome article, and is a greateachsideedge and tappedto improvement un the existing typesreceive two terminals which take which only have the one or twothe connections from the coil.A movements. groove is made to receive the coil The base is made up of* in.support which is made of*in. mahogany, 9 in. by 3 in., and isebonite * in. by 2 a in.The support drilled in the manner shown in theis placed in the groove and fixed details in Fig.2.A rectangularwith one screw.The hole in the portion is cut out each ,end of thesupport is drilled to clear a 6 B.A. base to make a rigid fit for the twoscrew which holds the coils by supports.The six holes are drilledmeans of a nut.The moving coil Fig 2.-A new basket coil -holder. in the positions shown to receiveholdersare made in a similarto receive the coil support, which six terminals.Two side supportsmanner with a fewexceptions. is the same as that used for the are next required which are madeThe ebonite squareblocks,thefixed coil with the exception of the length, which is22. in. When a pair of these are assembled they are .28 A. CLEARANCE 2.63A attached to the ebonite block by meansofthe two terminals, a spring washer being placed between the terminals and the side pieces. 334" The three holders are then placed on the * in. rod, which is fixed into base supports and tightened up each end by means of two nuts.It will be seen that the coil holders may /OA STANDARDS be adjusted by means of a sliding BASE 2 movement along the rod, or by a ...5.L/DE ROO lieC?::!EARANC 46" radial movement to the left and /OFF '43 " 3/' right, or by a further radial move- jii.o mentbackwardsand forwards. TER /NAL S 3/ Connectionsare made from the -v.144'6 terminals on the coil-holderS to I" 45' the corresponding terminals on the R./1' ON Aieon base. 17//NOES H. B. 4 OPP .T/XED COIL HOLDER Mov/No Co& HOLDERS EIDDECEEEEEEEEDEEDODODEDO 8 0 /ace oF, 0 0 0 o o o Fig. 2. _How to make the parts of the holder. o Do not miss 0 0 0 from a in. wood r in. by 3* in. Theterminals, and the knobs are made hole is drilled to clear a 2 B.A. rod.asbefore,butthesupportis Radio Press Stand E 0 These supports are forced into theslightly different.Four side -pieceso o slotsin the base and fixed withare made of ebonite. oDa t the o in. by I in.o o o one screw each.The slide rod isby /in., and two holes are drilledo o made from some in. round brass,in each.One hole is to receive a 0o All British Wireless 9 9in. long, tapped forin. eachsmall fixing screw and the other is0 0 end to a 2 B.A. thread. Nextto clear the terminal screw.Pe-0 0 0 Exhibition. 9 thecoil -holdersaremade. Totween each pair of these side pieces0 0 make the fixed one, a block ofis fixed a wooden block a in. square0 0 ebonite is cut r in. square. A hole by r in., which is grooved as before U D0OODDEDOOD0D000000DOEDOEI

42 November, 1923 JUNIOR W I R E L E S S.-Supplement to Modern Wireless DODOODDEDO000001710=01701710=0DOMODDODOOD=1:10 That New Set Why waste panel space? RD REACTION: A Simple Explanation EH0 0 By G. P. KENDALL, B.Sc., Staff Editor. THE 0 9 9 Misuse of reaction is the cause of the howls you sometimes hear when 9 T. C. B. Resistances listening to broadcasting. D (Regd. No. 9057.) 9 0 occupy less than one square in. of the DDIODOODDOODEIDOODOODDEDDODODDOODDOODEIDEIECEIMOOD panel.Silent, compact, with full on stop and off switch-the perfect resistance at last. IN many ways the wireless valveheated by a current from an accu- 6 ohm Filament R'stance Price 41 - Dull Emitter Resistance 41- (or " toob " our Americanmulator ; the grid, consisting of a 300 ohm Resistance It SI' friends call it) is a good andwire spiral or gauze surrounding the Of all Agents or from faithful servant, but a shockinglyfilament; and then outsidethis T. C. BALL, bad master, and in no respect is itagain is the plate (also called the 39,Windsor Road, Ealing, W.S. more so than in the matter ofanode), which is generally a metal See them at stand 23a at the White City. reaction.If we understand it andtube or hood enclosing the other know how to use it properly, re-parts. When the filament is heated, MAKE YOUR OWN HIGH action is one of the most usefula stream of electrons passes through EFFICIENCY TUNING COILS. the grid to the plate, and the action See page so October'Modtrfra properties of the valve, and will DOUBLE SPIDER FORMER, STAGGERED enable us to do wonderful thingsof the grid is to enable us to con- Makes Sell -supporting coils up to 3,000 metres. with. simple sets,. but if we let ittrol the stream in such a way that Accuratelyspaced. Brass body. Toledo Steel, screwed, removable prongs. become uncontrollable, and if wewe can amplify any given signals. Complete, Carriage Paid, 7s. ed. do not understand its ways, it will If small fluctuations of voltage, LIVINGSTON,497, Hessle Rd.,HULL. Coilholders complete with strap, not merely spoil our own reception,such as incoming signals produce, plugs, etc., ls. 9d. but it will convert our set into aare applied to the grid, relatively miniature transmitter and radiatelarge variations result in the volume enough energy to interfere withof the stream of electrons passing 1/6 D-X-ITE 1/6 everyone in the neighbourhood. through it, and, hence, the same Finest Crystal Manufactured. It is most important that everysignals are reproduced on a larger Speaks for itself. boy who means to play the wirelessscale in the plate circuit. A fuller Obtained only from game decently and according to theexplanation of the action of the J. E. JONES & Co., rulesshouldclearlyunderstandvalve was given in the first issue 33,Stormont Rd., Lavender Hill, about this part of the possibilitiesof Junior Wireless. LONDON, S.W.11. ofreaction.Only by gaining a The fundamentalprincipleof good knowledge of it will he be ablereaction is really very simple, when "CATSEYE" CRYSTAL DETECTOR to feel sure that he is not causingonce we have grasped the idea of Ever -set and ready. Smallest, annoyance to his neighbours, and,there being more energy flowing Loudest, Latest. Complete with moreover,suchknowledgewillin the plate circuit of the valve holder 1 ffit post free. remove all temptation to run thethan in its grid circuit.This being A.F'.A.i.L., 37, Red Lion Street, risk of causing annoyance, becauseso, we can see that, if we can feed LONDON, W.C. 2. Agents Wanted it will show him how to use reactiona little of the energy in the plate in safe ways. circuit back again to the grid in Before we try to see what reactionsuch a way as to increase that which is and what it does we must firstis already present, this increase will remind ourselves of the workingbe amplified and will appear as a principle of the valve, and here Istill greater increase in the currents am going to advise all new handsflowing in the plate circuit. LOOK! at wireless to get some simple book, The total result is greatly to aug- How attractive such as " Wireless Valves Simplyment the energy available in the Explained,"bytheEditorof plate circuit, as we shall see if we these little MODERN WIRELESS (Which can betake a numerical example.Sup- " ads." are on obtained from the Radio Press atpose that signals containing one thePagesof Devereux Court, Strand, W.C. 2). unit of energy are flowing in the The reason for my recommendinggrid circuit, and assume that the you to do so, of course, is simplyvalve magnifies them ten times ; JUNIOR WIRELESS that although I will give here justthere will therefore be ten units the elementary idea of how a valveof energy in the currents flowing works, so that you may understandin the plate circuit.Now suppose reaction, everyone ought to knowthat one unit is fed back into the more about valves than that if theygrid circuit and is added to the are to be used properly. one unit already there, what will BOOK! Inside a valve, as you may seehappen ?Since the valve is sup- for yourself,are three principalposed to magnify ten times what- yours for the parts(hence the name " three -ever signal energy is present in the electrode valve "), these being thegrid circuit, we shall now have December Number filament, which is usually a finetwenty units of energy in the plate straightwirecapableofbeingcircuit, from which must be sub -

43 JUNIORW I R E L E S S.-Supplement to Modern Wifeless November, 1923 tracted the one unit which is beingrest ;if there were no friction in 6aNET continuously fed back to boost upits bearings and the air offered no Daily lExprree the currents on the grid side.Thus,resistance to its passage it would we now have nineteen units ofcontinue to swing indefinitely and WIRELESS energy in the plate circuit wherewould never come to rest. Similarly, FOR ALL previously we only had ten, showingin a wireless circuit if there were that we have nearly doubled ourno energy lo.3ses there would be signal strength. no. damping, and oscillations once Thesefigures,ofcourse,arestarted would never die out. Now, quite, imaginary, and must not beif we kept giving the pendulum taken as representing exactly whata gentle tap at the end of each happens, but they do illustrate theswing we could make it keep on principle of reaction as being basedswinging for a much longer period upon the idea of feeding energybefore coming to. rest, and if the back into the grid circuit to be re -taps were strong enough it would amplified. be possible to keep it swinging Now let us try to get a somewhatindefinitely. This, ofcourse, clearer and more exact idea of thewould happen when the amount of way reaction helps to boost up theenergy supplied to the pendulum signals in the grid circuit.It willby the series of taps equalled the be rememberedthat when weenergy expendedinovercoming Every beginner speak of signal currents in the gridthe friction in its bearings and the circuit we mean oscillating currentsair resistance. needs this Book. of high frequency which are pro- We shall see that very similar duced by the passing wireless waves.,things take _ place in a wireless THIS is the most famous littleNoW, ordinary circuits possess whatcircuit, since the damping of such book ever written on Wire-is called " damping," which meansa circuit is very much like the fric- less-thousands upon thousandsthat when the passing waves ceasetion and air -resistance losses in the have been sold since it was first pendulum case, and acts similarly Published alittleover twelve to energise them the oscillations months ago. gradually die down and cease, orin causing the oscillations to die It is safe to say that no other are" damped out."This is be-out gradually.Just as in the case book has beenthe means ofcause there are various causes ofof the swinging pendulum we can explaining the mysteries of Wire- loss in every circuit, chiefly amongprolongthedying -downprocess less to so many people.Old orwhich is the resistance of the tuningby supplying energy to compensate young, all need this little book coil. for that which is lost, so in an oscil- when taking up Wireless, because This damping out of the oscilla-latory circuit we can feed in energy ittreats the subject sofully.tions may be very well illustratedand wipe out the effects of damping. The author --John Scott -Taggart, F.Inst.P., is a recognised Wire-by the analogy of a pendulum set If we use reaction to feed energy lessauthority,and hehas swinging and gradually coming toback into the grid circuit of a valve certainly succeeded in presenting UNCLES AND AUNTS. asomewhatdifficulttechnical subject in a most readable and bright manner. Contents-- - - - How toTell what Stationis 1, Working-How Wireless Signals areactuallysent-Lightand WirelessWaves Compared-. I Meaning of Wavelength --How Wireless Wave's are Set lip and Detected-How Wireless Stations work at' the same time without interferingwitheach other- I Ddes Weather affect' WireleSs ? -Waves from a Wireless Tele- phoneStation= -General 'Notes Different Kindsof Waves - Received-How, a Wireless _ ReceiverDetects. Waves-The Aerial-The Earth Connection- ' How a Wireless Set is Tuned to a Certain Wavelength-Tbe Vari- able -Coralenser=TheCrystal Detector-The Complete Wireless Receiving Circuit - Special I Toning Arrangements-How a Valve Works.

From allBooksellers, or lid. post free direct: - RADIO PRESS, LTD., DEVEREUR COURT, Here are the Uncles and Aunts' from me London" station.Reading from the STRAND, W C. 2 left:-Uncles Arthur, Rex, Jeff;AuhtsVivian,Sophie,Phyllis, and Radio Press Wireless Library No.1. (standing behind) Uncle Caracta,cus.

44 November, 1923 JUNIOR W I R E L E S S.-Supplement to Modern Wireless we can so adjust matters that theproduce howls and whistles in the oscillations produced by passingreceivers of everyone within many' waves are prolonged and die awaymiles who may happen to be listen- gradually, or we can feed back aing to the same station. Moreover, axamp larger amount, so that once osclIla-the speech heard in the oscillating tions are started they are main-receiver will be more or less dis- The highest grade Interval'', Transformer. Laminated tained indefinitely.This latter con-torted and spoiled, although a little core, well Insulated windings,tested to500 volts. dition is called " self -oscillation,"louder than when the reaction is Vary silent in action and freefromalldistortion. and occurs when the energy fedproperly adjusted. Fully guaranteed. 18/0 back balances that lost in over- To make proper use of reaction PETO-SCOTT CO., LTD., Bead °Peet coming resistance, and so on. when receiving telephony it should 64, High HolboTh W.C.1. Branch s; To all intents and purposes thisbe adjusted so that the circuit is 99. High Holborn, W.C.1. process is equivalent to reducingalmost oscillating, but not quite. 3, Wellington Street, W.C.2 the damping of the circuit, and itBring the coils gradually together, 4. Manchester St. Liverpool is most beneficial in increasing thenoticing how the " signals " get sharpness of the tuning of the cir-louder as you do so, until the point cuit, since it is well known thatis reached at which the set beginsLF.Transfornter the lower the damping the sharperto oscillate, and then separate the the tuning, and this holds good upcoils a little so that it stops and No. 2A, 1213 and 75 'Buses pass the Door. to the point at which self -oscillationthespeechor musicisheard WE HAVE NO HALF MILLI° commences, when the damping isloudly and clearly. SATISFIED CUSTOMERS. BU1 To be able WE HAVE NO DISSATISFIED said to be reduced to zero. to do this accurately and easily YESONES. WE STOCK EVERY CONCEIVABLE The actual method of producingyou must know how to find out PART, NUT OR SCREW FOR WIRELESS. reactionisquite simple ;itis when the set is oscillating, which ALL usually done by including in theis a little difficult if you happen to LISSEN, WILTONIA, plate circuit of the valve a coilbe very close to a broadcasting EDISON-BELL, and FORM PRODUCTS, AND ALSO which is arranged to act inductivelystation. The surest way to find out Give You Extra Good PostalServioe. upon the tuning coil in the gridistokeep touching theaerial WRITE OR CALL FOR LIST. tDOZ. ASSORTED NUTS,SCREWS, circuit, either by placing the twoterminal with your finger, which CLIPS, ETC., coils in a two -coil holder or bywill cause clicks in the phones when Given Free arranging one to slide within thethe set is oscillating ;but usually WITH EVERY ORDER OR OVER. other.Coils so placed are said toit is quite obvious when the set BELL WIRELE'S CO. be inductively coupled, since cur-beginstooscillate, because the SELL GREEN, LOWER SYDENHAM, rents flowingin one coilcausespeech becomes distorted and vary- similar currents to flow in the ing and the tuning makes loud whist- other by the familiar process ofling and howling noises. TheseA Ma'vellousWire'essPatent electro-magnetic induction. Hence,latterdisappear whentheset WILLESFORD'S MULTI - this arrangement isoften calledis tuned exactly to the wave -length POINTED CAT'S -WHISKER Makes Crys al Set as loud and better toned reactioncoupling. A setusingof the broadcasting station,- and than va've set.No trouble finding points. this kind of reaction is describedare not heard at all when the re- Atall retai ers V-.or by po.o.P.O. 12/ - Buy i ng Agents anted elsewhere in Junior Wireless. ceiver is only a few miles from the WILLESFORD'S, 20/1, Buektn _ham Street, So far we have only consideredtransmitter,and,therefore, you &I and, London, W C 2. the beneficial properties of 'reaction,must not conclude .that your set which are undoubtedly great ; manyis not oscillating ifyou do notLONDON RADIO COLLEGE, LTD. people regard it as being at leasthear any howls or whistles. Stafford House, as good as an extra high -frequency It is quite clear that when such82/83, HIGH STREET, BRENTFORD. valve. 'We must not forget, how-a receiver is being adjusted there ever, that reaction wrongly usedare bound to be moments when it Students trained for the may be a curse instead of a blessing,oscillates and becomes 'apublic Marine Wireless Service not only to the user but to all hisnuisance.It is permitted, however, & Appointments obtained. neighbours aswell.Itisquiteto use reaction upon any circuitwhichApply far full particulars Dept, M. easy to see how -this may be ifis not coupled in anyway to the we rememberthatreactionisaerial, and consequently we can capable of producing continuousobtain all the benefits of reaction oscillations in the grid circuit of ain a legal manner if we usea valve.If that grid circuit is con-" tuned anode" circuit with reac- nected to an aerial,- it is obvioustion coupled tothe anode .coil. that oscillations will flow in theThis arrangement is a fairly safe 2 in. x 2 in. aerial, and the whole becornes aone to use, since if oscillations are

miniaturetransmitterradiating' generated they are more or less rather weak continuous waves. confined to the tuned anode circuit This radiation, of course, takesand do not get into the aerial £3 place upon whatever wave -lengthcircuit to be radiated. The reaction the user of the set isreceiving,set illustrated elsewhere in Junior' per insertion. and, hence, if he is trying to receiveWireless shouldbestudiedin broadcasting, theradiationwillthis connection, since it employs be right on top of the waves fromthe permitted formofreaction the broadcasting station and willcoupling.

45 J U N I 0 1?W IR E L E S S.-Supplement to Modern Wireless. November, 1923

0000000000000000000000E0=DOODEMODEDO0000000 O 0 El D What is MAKING YOUR OWN CI 0 0 WIRELESS CABINETS 0 O 0 Reaction ? O By R. W. HALLOWS, M.A. 0 O 0 O In this article instructions are given for building neat and D O 0 THE whistling sound of an O efficient cabinets for any wireless set. D 0 oscillating setisfamiliar 000000=0000000000000D0D00000000=00000DEIDOOD0 to you-perhaps you have even suffered from your neighbour's NEITHER great skill nor anadded pleasure of knowing that for set.But do you really under- extensive outfit of tools areits good appearance your set owes , necessary for carrying out nothing to other people's efforts. stand what Reaction is ?There thevariouswoodworking jobs The first thing to decide is the has been plenty of articles about thatcropupwhenwireless wood that you are going to use. ReactioninalltheWireless apparatusis under construc- Bought cabinets and other wooden Magazines, but practically none tion. The mainthing, aswe components are usually made of shall see, is to be accurate in themahogany,anexpensivewood of them ever go so far as topreliminary marking out ;'thenvery difficult to work in on account explainitstrue meaning and how it is caused. In" Wireless Valves Simply Explained," however, the author takes great pains to clear up this and all other technical difficulties which are so often glossed over, Buy a copy to-day-you'll enjoy reading it. " Wireless Valves Simply Explained"

By JOHN SCOTT-TAGGART, F.Inst.P. (Editorof Modern Wireless and Wireless Weekly.) Contents- - The Theory of the Thermionic Valve. The 3 -Electrode Valve and its Applications. Cascade Valve Amplifiers. Principles of Reaction Amplifi- cation and Self -oscillation. How to make joints in wireless cabinets. The bottom picture shows how to Reaction Reception of Wireless fit ebonite strips for terminals. Signals. ContinuousWave Receiving Circuits. use the tools carefully and not in aof its hardness.But mahogany Valve Transmitters. hasty slapdash fashion.By makingis by no means the only wood suit- WirelessTelephone Transmitters I Using Valves. your own cabinets,baseboards, able for the purpose.Walnut is Broadcast Receivers. coil mountings and so on you' can cheaper, easier to work and capable save a good deal of money, for all of taking a beautiful finish.Even of these things are expensive to buy well -seasoned deal has much to ready made." Shop finish "isrecommend it, for it is very cheap certainly very beautiful, but byand it looks quite well when its making use of the simple methodssurface has been carefully smoothed From all Booksellers, or 218 post free direct: and varnished. RADIO PRESS,LTD., to be described 'you can turn out DEVEREUX COURT, STRAND, W.C.2. really good-looking articles that do The best wood of all for the Radio Press Wireless Library, No. 10. the set credit, and you have theamateur is probably oak, which

46 November, 1923 JUNIOR W I R E L E S S.-Supplement to Modern Wireless. fulfils The mitred joint is excellent for all requirements and looks - 11401.11.1411 quite as well as mahogany when itvery shallowcabinetssuchas 8.1 (410) THE CONSTRUCTION has been finished up.For cabinetsthose used for containing small of the wood should be from 1 toinchfixed condensers, grid -leaksand WIRELESS RECEIVING thick when planed down accordingso on, but it is not easy to make APPARATUS to their size ;for single layer in-up a cabinet four inches deep in PAULO PPM ductance mountings 1 inch thick,this way. and for baseboards from 1 inch to The plaindovetail (as shown inch. in the secondpicture) is better. There is only one case where oakThe dovetail proper is strong and is not quite a suitable wood, andlooks well ;itisfirstratefor that is when you are making aboxes such asthe accumulator crate to hold your accumulator.crate that have to carry heavy a For this teak should be employed,weights. It is, however, not very PREzT. well treated with the beeswax com-easy to make neatly without some .111111.1.0.0111, WSJ pound that is used for polishingexperience of wood working.The floors.Dilute sulphuric acid has asimplest of all joints is that made very rapid and destructive actionby " halving in" which is shown upon softer woods, but beeswaxedin the fourth illustration.It is teak is practically immune fromneat, easy to make and strong. We Save Money its attacks.Hence if any of the willthereforeselectitfor the acid from thebatteriesshould cabinet in hand. happen to splash on to the crate, We will use I inch wood through- you need have no fear of the con-out. We shall, therefore, requirethisway sequences so long as this wood istwo pieces 6 by 4 inches for the It is not difficultto make the used. ends and two91 by 4 for the Here is an easy way of finishingsides.If we were dovetailing, the majority of the components for up oak which givesit mediumsides would be the full so inches your Wireless Set if you can only brown colour with a pleasant semi -inlength,but halving inlops get the right information. polished surface :-Rub the wood3 /16 inchoffeitherend.The down with fine glass paper untilfifth and sixth illustrationswill The book " The Construction of you have made it as smooth as youmake this plain.For the bottom WirelessReceivingApparatus," can,thenapplylinseed oil-awe need a piece 61 by sot in order should be particularly useful to good deal of it-and allow it to soakto allow for a bevelled edge pro- any enthusiast who possesses a in.A cabinet so treated has quitejecting inch all round. few simple tools and who can a good appearance and it can be The first step is to plane down used as soon as it is dry; but thethe long edges of the plank from follow out elementary instruc- processisnot complete.After which ends and sides are cut until tions.With a little care, your some days you will find that thethey are absolutely straight and home-made apparatus should grain of the wood, has risen, makingparallel. We then mark itout work almost as well as bought inequalities in the surface. Rub itwith the help of the set square and components, and will leave you down again and repeat the dressing cut it with a stiff-backed saw. Next of oil.A third smoothing off andwe rule a line } inch from each money to spend in other direc- oiling may be needed after two or endof the short pieces and a tions. three weeks.-Once 'the wood hassecond right across the end 3/16 settled down and dried thoroughlyinch from what isgoing to beYou can makeall it may be polished with a littlethe inner surface.The piece of beeswax and turpentine. wood lying between these lines istheseComponents Now let us suppose we are.goingremoved with the saw, and any to tackle the making of an oakroughness is smoothed down withat home cabinet 6 inches by so and 4 inchesa small chisel. deepfor housing acrystalset We can now put the ends and Anode and Grid Resistances. or a valve panel.We must firstsides of the box together roughly Filament Rheostats. of all settle what kind of jointsby means of one fine brass screw Potentiometers. we are goingto make at theat each corner. When driving small Crystal Detectors. corners. The first fourfigures brass screws into oak or other hard L.F. Transformers. show some of the various jointswood always make the holes big H.F. Transformers. that may be used.In the firstenough, otherwise the screws are Basket Coils, illustrationisseenthemitredliable to break as they are forced in. Slab Coils. The heads of the screws should be Solenoid Coils. joint, which is the same as that Duolateral Coils. of countersunk either with a counter - usedat the corners picture H.T. Batteries. frames.In order to be able tosinker or by making a few careful make 'it you must have a mitreturns with ainch twist drill at Condensers. board, thatisa saw guide tothe top of each hole. Bevel off . From allBooksellers,or1 /8post free enable the ends to be cut at an Now for the bottom. direct .angle of exactly 45 degrees, andthe edges with a plane, then using RADIO PRESS, LTD., a shooting board by means ofthe set square mark a pencil line DEVERETJR COURT, STRAND, W.C.2 which they are planed up true.1 inch inside each edge. Three - RadioPressWirelessLibraryNo.8.

47 JUNIORW I R E L E S S. --Supplement to Modern Wireless. November, 1923 sixteenths of an inch inside thesefor a piece of ebonite measuring io lines drill four holes in each of the by 6 inches a cabinet made of 111adto3PreasStries Illy 3. long sides and three in the short. inch wood would have to be These holes should allow the screws"ref by 6f outside.If the panel is that you are using to pass through to lie flush, cut out two battens them easily, and they should bemeasuring ro inches in length by countersunk on the lower side. / inch thick by I inch wide and fix Place the frame of the cabinet onthem by screws to the inside of the bottom so that its edges resteach long Side the thicknesS of the on the pencilled lines.Then pierceebonite below the top.The panel How to make holes in one side by passing acan then be screwed down to them. your own bradawlthroughthOsealready The panel, may however, be made

1 Broadcast Receiver drilled in the bottom. Drive *crewsof oak, which is a great saving in John Scott Togo ert FinOP upwards from below.The otherexpense.Ifthisisdone, valve Edda. of Modern Mre/ess side and the two ends are fixed inholdersordetectorsmustbe Es 1/6 the same way, the set square beingmounted on small blocks of ebonite 4t,E4.` used as well as the pencilled linesand terminals on long strips of the to see that the corners form exactsame insulating material. A way right angles.The halved jointsof making an oak panel with may be securely fixed by drivingebonite insetsis" shown in the two additional screws into each. seventh picture.The position to The ebonite panel may be mounted be occupied by the ebonite having Splendid Broad-directly ontothe topof thebeen carefully marked out with cabinet, but a neater job is madepencil and set square, the wood castSetsmadeif it is let in to lie flush.If thisis removed with a fretsaw.Small is done the cabinet's inside measure- battens are then screwed on to the without specialments must be the same as theunderside at each end of the slot dimensionsofthepanel.Thus and the ebonite is secured to thesa. skill. EnEEDDEDEDEDED=E00±00000DEEDEEDED0000000000 TT is not often easy to condense 0° [F] -I- into a singleconstructional Article all the details necessary CATALOGUES RECEIVED q for a complete beginner to build ou P1 up a Broadcast Receiver. NEW SETS AND COMPONENTS 0 Naturally the space in a Magazine D° 8 like MODERN WIRELESS iS rather ODECOOLIODDOODOODODOODOODOODOECIODODODOODOODODDEI limited.Therefore,if you are Messrs. Peto-Scott Co., Ltd., send FromtheSterlingTelephone looking for a first-class book on us their new catalogue of wirelessand Electric Co., Ltd., we have how to build good Crystal Sets,components-a well produced list receivedleafletsdescribingtheir you cannot do better than getcontaining prices and illustrationscrystalreceivingsetwith low - this one." How to make yourof all kinds of wireless apparatusfrequency amplification, a simple own Broadcast Receiver " is written from completely finished sets downcrystal receiving set with a semi- by John Scott -Taggart, F.Inst.P.to the smallest accessories in theautomaticcrystaldetector,and (Editorof- MODERN WIRELESS way of screws.In this cataloguetheirvariable air condensers and Wireless Weekly).It dealswill be found many items which (squarelaw)with and without with the whole subject from A to the experimenter needs and whichvernier. These latter instruments Z, and if you are at all handyhe does not quite know where toare.ofparticularinterestto buy.Cabinetsforwirelesssetsthosewhoaremaking. -wave - with your fingers, you can easily and accumulator boxes are twometers, for the wave -length curve build up an excellent Reqeiver at examples of what we mean. with these condensers is a straight small cost. From the Bowyer -Lowe Co., of line. Remember you do not need toLetchworth, wehavereceived We havereceivedfromthe know a single thing about RadioseveralleafletsdescribingtheirMetropolitan Vickers Electrical Co., -it's all in the book, and you cancrystalreceiver,Mark1, theLtd., a highly artistic showcard of learn it in a few hours. Bowyer -Lowe " Ne Plus Ultra " (atheirCosmosradiophones. It two -valve and crystal receiver), and contains a large picture in colours the Bowyer -Lowe wave trap, typeentitled" Ethereal Danceand Get a copyC, the circuit which was describedSong," depicting nymphs dancing by Mr. Percy W. Harris in Wire- rounda tree with Pan playing 1 /6 TO -DAY. lessWeekly and MODERN WIRE-his pipes in the branches. Be- LESS. They also send an interest-low, on a dark background, are From all Booksellers, or 1 /1; post free. inglittlebooklet entitled" Theshown two Cosmos radiophones, RADIO PRESS,LTD., Charm ofWireless," containingone an. elaborate cabinet instru- DEVEREUX COURT, STRAND, W.C. 2. popular descriptions of their variousment and the other a small crystal Radio Press Wireless Library,No. 3. receivers and component parts. set.

43 November, 1923 MODERN WIRELESS mut&

" R" Type Valve. Length, including cap, rio m /m. A general purposes valve which will perform all the diverse functions of the Thermionic Valve. If you use a Valve Receiving Set you will do well PRICE 15/- EACH. to realise that the efficiency of your outfit is largely

dependent upon your choice of Valves. Its the D.E.R." Type Valve that counts. Valve. You will positively ensure the best reception of Length, including cap, 115 mim. vocal and musical items by using MAXAgehlm The special feature of this valve is that the filament which are made-and made to last-with the same current and voltage,i.e., the working filament watt- scrupulous care that has always characterised the age, isvery small, being in some cases less than ONE QUARTER of that manufacturing operations of the famous OSRAM required by ordinary valves havingsimilar operating Factory. characteristics.The filament runs ata dull red temperature, thus ensuring a very long life, as well as You use OSRAM Lamps at home,use the Valves freedom from crackling,etc. with the "OSRAM MADE" reputation ! PRICE 27 /6 EACH.. BUY BRITISH GOODS ONLY.

We are exhibiting at the N. A.R.M. ARCONIkIfALVES Exhibition, White City, November 8-u. (MADE AT HEOSRA--kLAMP WORKS)

(Wholesale only) Sold by leading Electrical Contractors, Wireless Dealers and Stores. The General Electric Co., Ltd., Magnet House, Kingsway, London, W.C.2.

ix MODERN TV IRELT SS November, 1923 Published November 8th.

In 2 9 9 ? ? 7 7 ? ? ? 7 ? 7 ? ? fl 0- 500

111111111111111111 Wireless Questions 111111111 ;1111111

Cs- Answered N. By E. REDPATH and G. P. KENDALL, B.Sc.

? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?

Questions An expert at your elbow ! about: THIS Book is going to be one of the most Aerials. usiqul and popular Radio Books ever Frame Aerials. published.No matter how much or how Earths. littleyou know, . therewill oftenariselittle difficulties and queries which need explanation. Waves. Instead of having to wade through pages of Wave -Lengths. text -book matter to obtain the information you Tuning Coils. need, all that you have to do is to refer to 500 Tuning Condensers. Wireless Questions Answered and in a moment Valves. you hava the information accurately and con-

cisely. - Reaction. If you are in difficulties with the Set you are Primary Batteries. building-if the Set you are using is not working Secondary Batteries. to your complete satisfaction, it is probably due to Crystal Sets. your lack of knowledge of some fundamental Amplifiers. Wireless principle.Get the facts from this real " Wireless Encyclopaedia"; it will save its cost Grid Leaks and Condensers. to you time and again. Loud -speakers. Wire. Published by Range (transmittingand RADIO PRESS LTD., From allBooksellers receiving.) Devereux Court, STRAND, and Newsagents or Interference. W.C.2. 2/8 post free. 2/6 Morse Signals. Sounds and Signals heard Telephone Receivers. abio puss *fits On. 15.

inillilluminiiii11111111111111111111;11i:1111111111111111111111111110111111111111111111111111111111111111' 111111:1111 November, 1923 MODERN WIRELESS

cYlteClteivt THE " MULLARD WECOVALVE."

Mr. " ORA " welcomes the baby " Mullard Wecovalve

r to the family. Like most emithivitiumiumfimium fathers he looks to his son to uphold the traditions of the house and, indeed, to go one better. The baby " Mullard Weco- valve " shows every evidence of living up to these expectations.It consumes very little current, lasts twice as long as other valves, and needs no accumulators. If you are buying or making a newset, Wecovalveswill II

save you money as they cut i:4(0,1111,41 41114'. /I" i1111011111 out accumulators. r: Ifyouhaveavalveset, muLLARDWECOVALVE will payfor 30 /. Wecovalves SOCKETS 1 /6 themselves in a few weeks. 4 -PIN ADAPTORS . . 3/6 FILAMENT RESISTANCE In anycasewritetothe FOR WECOVALVES . 3/11 manufacturers orask yoar We are exhibiting at the dealerforList M.W.r. It N. A .R.IvI. Exhibition, tellsyouallaboutthis White City, Nov. 8-21. wonderful new valve. Stand 90. Full Manufacturing Licence wider British Patents, Nos. 17580, 123126, 1800go.

Advt. of The Mallard Radio Valve Co., Ltd., Balhanz, S. W.12. ullardxi MODERN WIRELESS November, 1923 TINGEY SUPERFIVE CABINET RECEIVER -1 The last word in Perfect Reproduction, Selectivity, and Strength of Signals. Enclosed in Lock -up Oak Cabinets, complete with High Tension Battery of 120 Volts. Composed of Two High Frequency, one H.F. Rect., and two L.F. Power Valves. By means of two simple Wander pings any combinationor number of valves may be employed. Each set is supplied with a set of Coils covering the wavelengths of British Broad- Price, as illustrated, including Special casting Stations.Other sets of Coils may Valves and High Tension Battery....£56 5.0 be supplied at extra charge. ASK FOR SUPERFIVE PAMPHLET. We manufacture Valve Sets1, 2, 3, 4 and 5 Valves, also an excellent Crystal Set. Send for our new Components LIST --free on request. Few Agencies still open. Offices and Showrooms :- Open 8 to 7, Saturdays 8 to 1. 92, Queen St., Hammersmith, London, W16. TINGEY WIRELESS LTD. 'Phone : 'Grams : Hammersmith 1916. " Tingoidar, London." Chismick Agents:The Askew Motor Works, Ltd., 72, High Road, W.4.

ddimmasommaismar

RADIO PRESS SAVE MONEY! Wireless Library CHARGE No. 3 your Filament Batteries at HOME with ELLA Converters. vi to make These little machines are I your 041" noiseless in running, re- BroadcasLileceivoNor quire no attention, and 't SAVE their cost in a few .(Mae.rn Wirele+s months. Price £5-12-6 If required can be fitted withregulatingresist- ance and pole indicator - ammeter. PR ICE : As illustration, BC 15 0 A Crystal Set is Resistance and Ammeter mounted readytofit L.T. terminals of exist- always useful ing Converters. PRICE 51 2 G. When your accumulator runs down, your H.T. Send for " ELLA" Wire. Battery develops noises right in the middle of less Accessories List. a Concert, you would give anything for means of carrying on. VALVES fromstock. Marconi-Osram,Mullard, Why not prepare for such a contingency now Ediswan, Cossor, etc. by getting this book and building one of the Also New PEANUT. For D.C. Circuits ONLY. Front all Booksellers, three Crystal receivers described in it ? Output 5 amps., 9 volts. TRADE SUPPLIED. or rs. 71d. post free. You will be surprised how efficient they are- yet how simply they can be constructed, with- --- o.m. p.m rm I Radio Press Ltd., out the necessity for special tools, and from the LIONEL ROBINSON & CO., Devereux Court, most elementary materials. Written by John Scott -Taggart, F. Inst (Dept. M.W.), 3,Staple Inn, London, W.C.1. Strand, W.C.2 Editor of this Magazine.

See Advt. page xxix.

xii NOVeillber, 1923 MODERN WIRELESS falOWs LoversofMusic. Wherever you live, stay at home in comfort and enjoy all the best concerts brought to your music room by the Fellows Super Two Set.

A 2 -Valve Set of superior quality mounted In a highly finished case,that will receive any Entis.h or Continental telephony even though the nearestBroadcasting Station is working. PRICE : COMPLETE WITHH.T. BATTERY -

ACCUMULATOR, too ft. 7/22 STRANDED COPPER WIRE, 2 INSULATORS, I pr. 4,000 ohms HEAD PliONES. £9 plus B.B.C. Tax, 17/6, Marconi Tax, 21 5s., and 2 valves. A new 2 -valve amplifier mounted in cabinet uniform with super 2 set £5 10s.,plus B.B.0tax,1 0 ,-and Ph arc.,ni Tax 21 5s., plus 2 valves. FELLOWS MAGNETO Co., Ltd., LONDON, N.W.10 Telephone: Telegrams : Willesden 1560-x. "Quint/rig," Phone, London.

FT1 Erg

Use your electric light wires as an aerial in perfect safety. Plug a " Ducon " into any lampholder or wall socket, connect it to your wireless receiver and you will receive the broadcasting perfectly.USE A " DUCON "and you don't need an aerial. " Ducons " are perfectly safe-each one is tested to 2,50ovolts ;they consume nocurrentand do not affect the electric light in any way.They constitute an ideal filament in cases where an outside aerial is not possible. The RAC POSTAGE, 6d. is obtainable from leading wireless dealers,electrical contractors and stores,ordirect from the makers. Dealers not yet stocking are invited to write for Trade Terms. OVER 50,000 IN USE. The Dubilier Condenser Co. (1921) Ltd. (Dept. D) anon Works, Goldhawk Road, Shepherd's Bush, W.12 'Phone- 'Grams- Hammersmith 1084. Hivoltcon, Phone, London. MODERN WIRELESS November, 1923 GREAT RADIO SENSATION

NO OUTSIDE AERIAL. NO EARTH. PORTABLE AS A GRAM OPHONE. COSTS LIT1 LE. GETS ALL STATIONS ON ITS FOLDING FRAME AERIAL.

The Set for the Broadcaster, Constructor and Experimenter. AWIRELESS SET that doesn't wanta water -pipe and doesn't want youtogo on to the roof to put up an aerial in the garden you may not have. A wireless set that ii self-contained and as portable as a small gramophone. A wireless set that cuts all the nuisan:e out of wireless and gives you all the pleasures. Its efficiency gives you all the broadcasting stations. Its selectivity cuts out those you don't want. Its simplicity gives you ease of Operation. Its one valve gives you economy. Its design enables you to construct and experiment. It's British made of British materials by skilled British workmen. Its workmanship makes it a pleasure to have in the home. It is called the cLIMA)c hof N OVALVE Pv/ And now look at the Fr7ce THE CLIMAX MONOVALVE, WITH CLIMAX COLLAPSIBLE FRAME AERIAL, If used with BBC licence, BBC Tax 11 I- extra. Accessories required :-Head Telephones, Valve and Batteries. Approx. cost, $4, according to choice. This advertisement will be seen by thousands. If you want early delivery, place your order now, either direct or with your usual dealer. CLIMAX PATENTS Ltd., 182, CHURCH ST., KENSINGTON, LONDON, W.8. Telephone : Park 2023. Wireless Exhibition, White City, Stand 25, November 8-2r. (E.P.S.i.)

xiv November, 1923 MODERN WIRELESS

" IGRANIC" RADIODEVICES GIVEENTIRESATISFACTION

-.....,,.,.. a ..4

FILAMENT RHEOSTAT IGRANIC HONEYCOMB COILS (Patent No. 195933.) (De Forest Patent 141344.) A splendid instrument for filament control under These world famous coils are renowned for their GIMBOLDER TUNING STAND allconditions.Novel method of construction high efficiency, low self 'capacity, small absorption (Patent applied for.) ensures smooth and silent operation.Designed factor and minimum high -frequency -resistance. This coil holder has been designed and for individual valve control.Adjustable contact No dead-end losses.Each turn surrounded by producedforaccommodatinggimbal mounted honeycomb coils, which enable fingers.Permits of resistance valuesfrom zero to air pocket.Made in two types, plug and gimbal extremely fine settings to be obtained. four ohms by fine variation.Supplied in tw° Wavelengths approximatelytooto In addition to the angular relation of the mounted. types, plain and vernier. 25,000 metres.The only coils that uphold their coils being varied, they can also be rotated about their own axis, thus giving extremely claims for negligible losses.Prices vary with sizes. fine and critical adjustment when used on Prices : Plain, 4/8 Vernier. 2,-. selective and regenerativecircuits.

t) ,ifV'' Inspect Our Devices at our 0, ,,,,I .1,4 .p.,4 STAND No. 43 a All British Wireless c Exhibition , _____

White City, November 8 to 21 tIN

INTERVALVE TRANSFORMERS BATTERY POTENTIOMETERS (Patent applied for.) (PatentNo. 20503.) An Igranic Potentiometer is a necessity where one or more Designed for the distortionless reproduction o f speech and music.The steel shroud effectively tages of high frequency amplification is used.Stabilises grid shields from external interference.Recent improvements in design render it the and eliminates noises and self oscillation.Resistance 300 ohms. finest amplifying transformer Current consumption negligible.Nickelled finish, complete fixing screws, knob and pointer.Price 7/-. Priem : Decoded, 21/- Open. 29/-.

, - - ,______-----<= T7'. - -'-' - __,-

r, ----- \),, ---.,,

._-,--,- .., '''------,------_-, TYPE H VARIOMETER TYPE SR VARIOMETER TYPE H R VARIOCOUPLER Recommended for use in the aerial circuit of Designed for secondaryand tunedanode Statorand rotor of hard moulded insulation, crystal and valve sets.:Wavelength range circuits. 'Wavelengths150toboometres and windings impregnated solid.Tappings approximately 150 -boo metres, with P.M.G. on primary enable fine tuning to be obtained, standardaerie.Statorandrotorbest approximately.Similar to Type " H ", but thus eliminating condenser.Coupling con quality mouldings, windings self-supporting with larger winding,1\ ,knilded insulation and tinuonsly variable over wide range.Price, and impregnated solid.Price,with knob, CID and fixing bracket, t5/-. windingsimpregnatedsolid. Price18/-. with knob, dial and fixingbrackets, 19/- ALL HIGH -CLASS DEALERS STOCK THEM :-: :-: :-- :-: WRITE FOR LISTSZ109.

Manchester -30, Cross Street - Cardiff-Western Mail Chambers 7RA..- Birmingham -73/4,Exchange Buildings 7 Bradford -18, Woodview Terrace, Manningham GlasgoW-5o, Wellington Street IGILINIC 'Newcastle -9o, Pilgrim Street - E i E CTRIC C 0.. Ltzi 149, QueenVictoria Street, Works: LONDON. :viNDINV ElstowRoad,BEDFORD.

NV MODERN W R E -L ESS November, 1923

WONDER SOUNDS WHAT IT IS e SOLID

At presentaMystery -will later be History! diT Something more permanent than a LUXOR interest here. No `1"- mouldering in musty museums for the contents of this box-to be shown to the' Wireless world on November -8; at the N.A.R.14I. Exhibition, White City, 411. "Polar Blok" is going to place perfect wireless sets within the hands of everybody who can hold a screwdriver, and is going to give those, amateurs with an experimental turn of mind their ideal conception of elastic set -building. forget the Stand Number, rir, and don't miss seeing the 41Don't-0 most practical, simple, neat and economical scheme ever presented to the Wireless Public. POLAR BLOW N.A.R.M. EX ITION, STAND No. 111WHITE CIT Y, NOV.8 to21. RADIO COMMUNICATION Co., Ld., Telephone : Telegrams : CENTRAL 843o 34 /35, NORFOLK STREET, RADIOCOMCO-ESTRA ND, (3 lines ). LONDON, W.C.2. LONDON. _ Fleet Ad. Co. ovember, ,1923 MODERN WIRELESS EQUIPMENT FOR 111.1111111..1111r.4XPERIMENTERS ansawasa 1

s sa a WELCOME NEWS

PRELIMINARY SAFETY

NO matterwhattype -For the Experimenter II

111 " of circuit you intend IIusing in your receiving set, TOTALLY NEW EQUIPMENT FOR SET -BUILDERS, M yourresultsarewholly II IIdependent upon the quality FOR ..some time past much of our time has a been concentrated on the production of a of your preliminary corn- a complete series of' component parts with ,,he IIponent purchases. Modern II 'help - of Which' the assembly of the latest Visit III Radio experience andre- III receivers, embodying the ideas set forth in II search is embodied inall. II " Wireless Weekly" and "Modern Wireless," IN can be male with the minimum of time, and Stand WEBBER PRO- Niath-the certainty of first-class results. DUCTIONS. They ill The designs of these components are entirely ensure preliminary safety in new, and constitute further examples of the IIoutlay, and are supremely a efficiency and robustnessof Bowyer -Lowe 6 W5.1 III productions. IN neat, compact and economical. Equipped with a selectiOn of these compo- . The WEBBER COMPLETE SAFETY VALVE PANEL 0 nents,the experimenterwillbeableto Wireless W53 is illustrated.This panel is fitted with a POLARII assemble a receiver of pleasing appearance III FUSE to protect the valve and an Igranic Rheostat to .in an extremely short time, -while the expense II give smooth control.The Rheostat terminal is clearly MI incurredin changing from one circuitto II another is trilling. Exhibition . marked to enable positive and negative lead changes m An illustrated descriptive pamphlet is now MI during experiment. ready and a copy will be sent on application. II Send a. postcard now, WhiteCity, II Size complete 4 in. by 4 in. Supplies of the components can be obtained from any wireless dealer or, in case of diffi- ...... Pric,,e 11.601/,66 NI! IIWith ordinary rheostat... culty, we shall he pleased to supply direct. Nov. 8-21 MI With vernier .10 ii5 Approved by the Radio Communication Co., Ltd., and;

a on view at 35, Norfolk Street, W.C. 2. The BOWYER-LOWE Co., Ltd., CO Manufacturers of Wireless Instruments,

Write for descriptive list, post free. RadioWks., Commerce Avenue, Letchworth, Herts.

aN. V. WEBBER & Co., Radio Engineers, Wholesale Distrit,stors : II El Walton House, Walton -on -Thames, Surrey. LTD MILLIGAN WIRELUS, Ltd., 23-25, Renfrew St, GLASGOW H. WADSWORTH eiLLERS & Ca., Standard Buildims. Leads 11 ARKS2 il alliMIESINIMilliNESIESIIIIIIMININSIMESE11111111111111111111111M

WINTER NIGHTS AND FIRESIDE COMFORT reach perfection if you possess the " DESKOPHONE " Its purity of tone is a constant delight.INSTAL ONE NOW " THE DESKONIONE " TWO -VALVE SET (P.O. No. 2020). Tuner. HighFrequency Amplifier and Detector, complete. withHeadphones. H.T. Battery, Aerial, Lead-in Wire, and Insulat rs.

LOW FREQUENCY AMPLIFIER, built to the same design, can be added to greatly increase the volume of sound. PRICE, £4: 12 :6. Royalty Paid. Valve only extra. Send for particulars of our new 4 Valve Model 'Phone: HOLBORN 2368 PRICE £28 COMPLETEr--PRICE£12: 17 : 6 COMPLETE

I ACCESSORIES, : 17 : 6. i all PRICEWITHOUT £9 Royalties and accessories : : 6 Extra. Valves Extra. included. Royalties £2 2 The HOLBORN RADIO Co., Ltd., 26'7,lildfilotiolif§tiONDOlq:WZT. MODERN WIRELESS November, 1923 .1 RadioValves E how to use the By ohn Scott-Taggar F.Inst.P.

JUST acompletecourseof PUBLISHED ! instruction on the Valve

make real progress in Wireless oyou must be able to understand the principles of the Radio Valve. The importance of this cannot be em- Can you answer phasised too strongly. While there are several Books on the these questions fully ? Valve by the same author, none of them What is meant by Reactance - covers quite the same field as "Radio capacity coupling ? Valves and how to use them." Whichismoreselective- " Tuned Anode "or" Reac- This Book- is rather more elementary tance capacity " for H.F. use ? in its appeal and should be extremely What is Reaction ? useful to those who are beginning to take What is meant by " Dual a more serious interest in Wireless. Amplification " ? How is self-oscillatic n caused ? Its explanations are most lucid and What is an aperiodic trans- graphically illustrated by a very large former and its advantages ? number of diagrams.It is a Book which, although dealing with a difficult subject, is most fascinating and intriguing in its appeal. A Book which ought, in fact, to 2/6 be on every wireless enthusiast's book- fromallBooksellers, or 2./8post freedirectfrom shelf. publishers, RADIO . PRESS, LTD., It is written from the point of view of Devereux Court, Strand, W.C. 2. the man who is going to use valves. 1allotressZeriezi10. 12. November, 1923 MODERN WIRELESS The Two -valveset that will give YOU satisfaction-

THE NEW V.S.1 TWO-VALVE COSMOS RADIOPHONES aregiving highlysatisfactory13 roadcast and The kolian Co., Ltd., "Eolian Hall, 531-137, New Bond Street. Telegraphy reception in all partg of the British LONDON, IV. t. 3/1o/23. Isles, as is shown by the few extracts given from Gentlemen, the numerous testimonials we are receiving. We reallymust expressour appreciation of the remarkable 2 -valve wireless set you are supplying to us, and which we understandis your standard model, These sets are now fitted with :- approved by the Postmaster -General. Exhaustive tests hem: been made, and in whatever (I) A dual amplification circuit whereby results part of the country they' have been carried out, every station, including Paris (45o metres), has come in with are obtained with two valves fully equal to equal volume. Thus, Glasgow at 40o miles comes in with the same those hitherto obtained with three. volume as London (26 miles).The setis sufficiently critical to make tuning -in a pleasure, and the only difficult piece of tuning we fcunt was when our chief (2) A highlyefficient non -radiating reaction engineer, Mr. M. R: Howard, tuned in the Buffalo (N.Y., U.S.A.) transmission on Sunday morning last circuit. on the same a -valve imelrument.This transmission was received clearly at Chesham, Bucks, and almost every The results are :- item was heard, not imaginatively, but as a concrete fact, and no higher tribute could be paid to your remarkable circuits. UNEQUALLED RANGE, Yours faithfully, THEiEOLIANCO., LTD. ENORMOUS AMPLIFICATION, (Signed) MAURICE R. HOWARD. PERFECT REPRODUCTION, and the sets are designed for simple operation, so THE Mirk Cl Ettic:emy. that these results can be obtained by the beginner who has no wireless knowledge or skill. WE AR E " Cosmos " Radiophones are sold through the trade, but we extend a hearty invitation to all SHOWING Showroom in your AT THE who contemplate the purchase of a set to pay a visit of inspection to our WIRELESS You will not be pressed to buy, but you will have the opportunity of hearing " Cosmos" district. EXHIBITIONi reception and of seeing the whole range of " Cosmos " components and the very latest develop- AND C.ONVENTION ment, " RADIOBRIX." WHITE CITYtt ovattONOV.21s_t

LONDON : EDINBURGH : 232-233, High Holborn, W.C. I. ik Kr itOPOLI TAW 127, George Street. BIRMINGHAM : MANCHESTER : Daimler House, 33-34, Paradise St. 14, Long Mitigate. MPITleketS NEWCASTLE -ON -TYNE : BRISTOL : Cosmos House, 7, Saville Row. 43, Park Street. ELECTRICAL CO.. LTD SHEFFIELD : CARDIFF : R Howard Gallery, Chapel Walk, Metrovick House, Custom House St. Head Office &Works: TRAFFORD PARK, MANCHESTER 13-5 Fargate.

xix MODERN WIRELESS November, 1923 Scientific Instrument TT. 0 .BUSS, Maker, 77, CLERKENWELL ROAD, LONDON, E.C.1. Established 1850. Exhibition !twarbs-London 1862.Sydney 1879.Melbourne 1880. HEADPHONES Terminals. "EBONITE" Genuine French Telephones,14/11 Postage tree.Any size cut. most sensitive obtainable, 4,000 ohms with cords s. d. £s.d. (Double Receivers)....post free t, nom 111111.1411[ 8XxX1 I2X1OXI -76 4X4Xt .. z 3 /7x8x1 -8 9 7g6gii .. 2 8 French "Brunet" Headphones en x6 Xi a8xrElx1 - 159 39 27X5gi .. 5 3 36x18xf a 76 4,000 ohms1 7/6 POSTAGE 9d. Post free. VALVES. Dull, Emitter 27/6 Instrument Wires Cossor, Pink Top 15/- British Made Copper Wires Marconi " R " a.v., 45/60 ..15 Prices per lb. Ediswan 15 /- Other sizes in stock. A charge of 3d. Cossor, P.2 .. 15 No, 4 extra is made for reeling off in small Mullard Ora ..1 5/- quantities.Postage extra. best type yds.ohms. French " R," 10/6 Nw2 S.W.G. perper S.C.C. D.C.C. S.S.C. D.S.C. CONDENSERS. Assemb ed Completeter Enmld. Cabinet Mounting. No. 3 lb.;ca., Complete Sets ofParts. II yds. Approx. No. 3 Terminals,2 B.A., with nut and washer,2/- Approx. No. doz.By post,2/6. 22 140 39 2/9 3/-4/- 6/- 2/7 Capacity of Price. Capacity Price. 24 230 63 3/- 3/6 4/6 8/- 2/8 Microf'ds. No. 2 Terminals, War Office Pattern,with nut and Microf'ds.Plates. washer,1/3doz.Post, 1;"9. 26 34o 95 3/7 4/1 5/- 8/- 3/2 No.4 Terminals, Telephone,with nut and washer,1/3 28 53o 140 4/4 4/8 8/- 9/- 3/6 .001 67 7/8 .001 fik 3o 716 200 5/- 6/6 7/-10/-3/10 .0005 5,11 doz.By post,1/9. .00075 43 6/9 No. 1 Terminals,with nut and washer, 1.'- doz.By 32 950 262 6/- 7/3 8/-12/8 4/2 .0005 .. 29 5/8 .0003 5/ 2 36z 7/- 8/39/-13/6 4/4 .0002 4/6 post,1/8 34 2,300 .0003 x9 4/6 (large), 36 2,000 53o 8/810,'-12/-15/6 4/8 .0002 13 3/6 .000r 4/- Ttrminah aerial and earth, complete with 2 nuts and 2 washers (a B.A.), 2 for8d. Bypost, .coor 7 3/ - 1/-. FIXED CONDENSERS,.0003,.0005,.002,.003, WirelessCrystals 10d.and1/-each..004,1/6each. Post, 3.71. VARIABLE GRID LEAK, 6,-each. " Hertzite " 1 /- Carborundum 64. GRID LEAK AND CONDENSER, .0003, 2/6each. Zincite 9d. Molybdenite 6d. roo,000 ohmsResistance,2/3each.Postage Silicon 6d. Pyrites 6d. on above, 3d. each, Bornite 64. Galena 6d. WIRELESS PARTS Copper Pyrites 6d. Graphite 64. AND ACCESSORIES. Wood's Metal6d. Tellurium 1 /- Aerial Wire,7/22 bare copper, stranded.Price per Post free. ion ft.,2/6and 2/4.By Post,3/6. Aluminium Vanes, rdoz.,5d. By Post,8d. Basket Coils,7 in. set,3/-set.By Post,3/4. Intervalve Transformers Brass Washers,2, 3, 4 Or 5 B.A. , dozen2d. Size 3 x 3 x / i.Ebonite Top and Bottom. Nuts,2 B.A... .. dozenIfd. ,,Nuts,3, 4 or 5 B.A.dozen2d. Ratio 5 to 1 Rod(screwed)- Post free 1 5/ aA., in I2-111. lengths ..each3d. 3 B.A., in 12-1n. lengths each3d. H.F. Variable Transformer,5 Tappings, 4 B.A., in 12 -in. lengths ..each20. 14/6.Post 6d. extra. ContactStuds,in. by t in., complete with nut and H.F. Transformers, Plug-in Type, from washer,511.doz. Copper Foil Sheets,uniform thickness, t2 in. bysill. 4/6.Post 4d. extra. 3d. each. Crystal Detectors on Ebonite, 1/8each. Crystal Detector,cup enclosed with glass cover, dust Celluloid Accumulators proof, 3/6.By Post,4/-. Ebonite Dials,with engraved scale o -18o, 1/- each. BEST BRITISH MAKE. By post, 1/6. Amp. hrs.Amp. hrs. Engraved Ivorine Scales,o-lito round ends. 4d. ea. Volts.continuous, ignition. Price.Post. Filament Resistance, 1/6, 2/6each.By Post, 1/10 Oldham 6 20 40 28/-21- and2.10. PO 6 3o 8o 35/-3/- Inductance Coils Wound Enamel Wire,12 by 4,3/-. 6o By post,5/-. VARIOM ETERS. VI, 6 40 45/-3/- 11 Insulating skewing, ed.yd. By post4/-doz. yds. Bushed Bearings, Ebonite Dialo -loo.. Relax 4 20 Insulators, Egg,4 tor110., 2/6per doz.ny post, and Knobs.Metal Parts Plated.Wave- M A L. 4 20 3/6 doz. length 34o to 56o metres. 2 Insulators, Reel, 11d.each.By post,6d.doz.. extra. 20 4440: . 11087 // --- 111%/ -: Intervalve Transformers (lowfrequency), tested and Possessing high insulating properties, H.T.Batteries, 3o volt, 5;6 (by post, 1/3 guaranteed 5-1, 14/- each.By post, 15/-. and the finish of the instrument through- extra). Knobs,with brass nut (z B.A.),3d.each.By post, 31d. out is excellent. H.T. Batteries, 6o volt, 9/6 (by post, LargeSpacer Washers,3 doz.,9d. By post,1/-. Adequate provision is made for mount- 1/3 extra). Lead -14 Tubes,ebonite with brass terminals, 9 ing on a panel, and the dial is neatly and By post,1/4.12 in.,1/4.By post, 1/8. clearly engraved. Sliderand Plunger, 4d.Ny post,6d. Inductance Tithes Slider Knob, Plungerand 03 in. rod,8d.the set. A variable condenser of .0005 micro - Cardboard. Cannot be sent by post. farad capacity in series of parallel for Small Spacer Washers6 doz.1/-By post,1/4, I2 X 21, 4d. Post 214. I2 X 31, 6d. Post 44, Switch Arms,with polished knob, bushed 2 B.A. nut, the short and longer wavelengths re- /2 x 3, 5d. Post 34-d. 12x 4,ed.Post, Sid. laminated blade. spring coil washer, nuts and bush, spectively. 1/- and1/6each.By post,1;'3and1/9. Tin Foil,free from :cad.Sheets, 57 in. by II in., Mahogany Boxes 4d.each. Polished, Post. Valve Legs,with nuts and washers,1d.each, 9d, doz.; Marvellous A ValveHoldersebonite, complete with nuts, 1/-. 41 X 41 X 31 in...... 2/93d. Valve Pins, split,7d.doz. 41X 41-x 5 in...... 3/36d. Price q's.6d. 61x 6-1- x 4 in...... 4 /61 /- TRADE SU l- PLIED. 13x 6x 4in...... 7/-1/ - Terms on Apolication. Post 6d. extra. Any size to order.

X November, 1923 MODERN WIRELESS

In4t4144ftritiAl avve4te ateRedwee/ted

The New Ultra IV. Mark II. All Purpose Receiver.

A-4 The New Ethophone V. Broadcast Receiver. ALL Ethophones are primarily designed for Broadcast THE Burndept Ultra IV. Mark II. is the last word in reception,andthedesigncallsforthehighest Wireless Receivers.It is a 4 -valve set with ono valve efficiency combinedwithsimplicityofcontrol, amplifying at Radio Frequency, and a detector, followed and can bo used successfully by any member of the family. by two stages of note magnification. No Radio Frequency Tho tuner and receiver is incorporated, the valves and transformers are used, but the design.- allows for steady and high -voltage batteries are encloged out of harm's way, but regular High Frequency amplification on all wave -lengths aro instantly accessible, the whole thing forming a com- from 150 to 25,000 metres. plete unit. A new feature of importance has been incorporated with The new Ethophono V. Mark II. is a tuner, receiver and the original design, the last stage of Audio Frequency is power amplifier combined, while the price 'is only that of now a power stage, using a power value, and gives a much a receiver of premier quality.The last valve is a power greater volume of sound, morse or speech, music and song, stage, which allows an enormous volume absolutely undis- without in any way impairing tho 'hitherto unequalled torted, whether it be speech, music or song, the tone pro- quality of reproduction so closely associated with the duced is sweet and mellow over the whole range of the earlier models. On the other hand, there is a decided im- musical scale. provement, and, critics will be surprised at the full faithful There aro many people who arc dubious about the purity mellow reproduction, and the complete absence of the cf tone obtainable from a Loud Speaker. We would like feeling that the strength was being forced. them to call at any of our showrooms, and to demonstrate Each valve is separately switched and is controlled by a to them, when we feel confident that what they hear would separate Rheostat, two important points in experimental bo in the nature of a revelation to thein.The most conser- receiver design. vative musical critic could find no cause for complaint. The price remains the same. To obtain these results, we would use the Ethovox Loud No. 104 S in sloping cabinet, £35, to which must be added Speaker. Broadcast Tariff, £1 5s. Od. TheEthophonoV. Mark II., when used on a moderately The best all-roundtuner for use with the Ultra IV. good aerial, and with a 'little practice in handling will Mark II. is the Burndept Mark III. designed for selective bring the programme of all the British broadcast stations double -circuit tuning, and provided with a Tune -standby to your home, most of them on a Loud Speaker. Further, switch and a long handle Vernier Condenser for fine ' there are very few places where French and other continental adjustment. concerts cannot also be heard on a Loud Speaker. No. 123 S.-Price £9 10s. (in sloping cabinet). Regularly we hear from Custotnors that they have received American broadcast on -this instrument, but this we cannot Performance. guarantee. With the Ultra IV. Mark II. a reasonably good aerial, Tho Ethophono V. was taken into the Arctic by the usual locality and intelligent handling, all British Broadcast Morton College Arctic Expedition and the members were Programmes and the French and other continental concerts able at times to listen to British broadcasted concerts. should be heard-most of them on a Loud Speaker. Reports No. 508.-Ethophone V. Mark II. complete with of American Broadcast reception on -loud opeakers aro valves and High Voltage Battery not uncommon, but this we cannot guarantee.London 237 10 0 Broadcasting is hoard with this instrument in places as far PTroiewe whichmust be added Broadcast apart as Christiania, Rome and Madrid.It is well worth Tariff ...... I 50 your consideration. Our new catalogue, consisting of 88 fully illustrated pages, will be received from the printers on November 1st.We are All -British Wireless Exhibition.To be held at the White confident that this will be thefinest descriptive wireless City from November 8th -21st, under the auspices of the catalogue yet produced in this country. Everybody interested National Association of Radio Manufacturers. Our Stands in wireless should have It on his bookshelf for reference. No. are 75 and 112. Write to us for a copy. A Written Guaranteeissent out withall Burndept Apparatus. BURNDEPT LTD., Head Office : Aldine House, Bedford Street, Strand, W.C.2. 'Phone: Gerrard 7794 Branches :LEEDS, NEWCASTLE, CARDIFF, NORTHAMPTON. 'Grams :" Burndept, Westrand, London." LBURNDEPT

xxi MODERN WIRELESS Novtrnber, 1923

1001111100400000000. 000000

Dependable Books -your greatest aid Choose your Books fi om this List : T0 attempttounderstandWireless Price. is r. Wireless for All 6d. without the aid of good books, By JOHN SCO I I-TAGGART, F.Inst.P. 2.Simplified Wireless.. 1/ - both foolish and shortsighted. True, ByJOHN SCOTT-TAGGART, F.Inst.P. 3. Howto Mate Your Broadcast Re- you can make a certain amount of progress egvar 1/6 By JOHN SCOTT-TAGGART, F.Inst.P. by your own endeavours-just as you Can 4. How to Erect Your Wireless Aerial .. 1/- learn to swim without the assistance of an -ByMITTELL, A.M.I.E.F,. 5,The Construction ofWireless Re- instructor-but ineach case progressis ceiving Apparatus 1/6 Br P. D. TVERS. much mote rapid and pleasant if you have 6.The Construction of Crystal Receivers1/6 By ALAN L. M. DOUGLAS. a helping hand to guide you. 7.How to Make a " Unit " Wireless Receiver . . 2/6 By E. REDPATII. The list of books given here comprises a 8.Pictorial Wireless Circuits By OSWALD J. RANKIN. complete library, dealing with every phase 9.Wireless Valves Simply Explained 2/6 By Joinv SCOTT-TAGGART, F. Inst.P. of Wireless.Each book is written in a so.Practical WirelessValve Circuits ..2/6 By JonN SCOTT-TAGGART, F.Inst.P. masterly fashion by an authority. The II.Wireless Licences and How to Obtain Them 1/ - fact that Radio Press, Ltd., are publishers ByE. REDPATII. exclusively of Wireless Books is a guarantee 12.Radio Valves and How to Use them..2/6 By JOHN SCOTT-TAGGART, F.Inst.P. of their accuracy and dependability. 13.500 Wireless Questions Answered.. 2/6 By G. P. KENDALL and E. REDEATH. 14.12 Tested Wireless Sets 2/6 These books can be obtained fromall By P. W. HARRIS. 15.More Practical Wireless Circuits.. 3/11 booksellers or direct from publishers (postage ,f °TIN SCOTT-TAGGART, F.Inst.P. In.Home Built Wireless Components 2/6 2d. per volume extra). 17.Wireless Sets for Home Construction2/6 By E. RFC/PATH. Elementary Text -book on Wireless RADIO PRESS, LTD. Vacuum Tubes .. 10/ - Devereux Court, Strand, W.C.2. ByJOHN SLOTT-TAGG RT, F.II1SC P. (post free) adioTres5 Strirq. il

Gilbert Ad. X Xn A'ovem,79er, 1923 MODERN WIRELESS

WIRELESS ACCESSORIES. FOR morethan 50 years we have been manufacturing Electric Apparatus, a period of experience that guarantees consistently high quality in our Wireless Accessories. There can be no better assurance of reliability than the name Silvertown."

SILVERTOWN TELEPHONE HEADPIECES, The " Stalloy " diaphragms are matched., as t,secure a balanceoftoneandquality. Light and comfortable, highly sensitive, easily adju.ted,firstclass SILVERTOWN INTERVALVE TRANS- workmanship a n d FORMERS. finish. Resistance t20, Testedi,000 voltsbetween winding, and 2,500, 00, 8,000and 2,000 voltsbetweenwindingand frame. oo at in. high by 31 in. wide by al in. deep overall. Weighs r lb. 3t oz. Price 21/- each.

SILVERTOWN SILVERTOWNVARIABLE CONDENSERS (for panel mounting). CRYSTAL HOLDERS. "FEATHERWEIGHT " Capacities o.000i , n.oco2, o.0o5, and o.oit mfd. Mounted onebonitebase 3in. by z in. INSULATOR. Moving vanes are shaped to give low minimum wishglasstoprotectcrystals from dust. capacity.These condensers are fitted with a A feature of this crystal holder is that it con Weight oz. stop to allow of a movement of 18o degrees be easilytaken to pieces and set up again. Length 5 in. only. each,Pries 7/6,8 /., 11/6 & 15/. Price 4/6 each. Price 2/. each.

Small in diameter, small SILVERTOWN " EVER - area for service leakage. DRY "INSULATOR. Cup in centre keeps a Weight al oz. portion of the insulator Length yin. dry in wet weather. Price 3/. each. Ends are made of Duralumin, to reduce weight. Electrical efficiency is superior to that of a number of porcelain insulators in series. The " capacity" effect of Silvertown Insulators is very small. EBONITE CONDENSER. DIALS AND 'KNOBS. In one piece, graduated in white o-roo or These arethe hestandmosteffective SILVERTOWN POTENTIOMETERS o-t8o, highly finished. Complete with fixing insulators ever devised. (tarpanelmounting). screw. Dial approximately3 in. diameter. On rectangular ebonite former, complete Pricecomplete,1 /3each. Dialsonly with knob and pointer. Former mounted on cast brassframe.Resistanceapproxi- 10d. each. mately 400 ohms.Price 7/6 each. Silvertown Accessories are obtainableofall dealers. When buying Wireless Accessories specify Silvertown and be sure of having the best. MAKERS-The SilvertownCompany, 106, CannonStreet,London, E.C.4. MODERN WIRELESS November, 1923 On SaleShortly. TRADE deo MARK

llllllllllllllllll H1111111111 llllll GRAFTON ELECTRIC REMEMBER TO REMEMBER CATALOGUE to s nd for OUR 100 -PAGE CATALOGUE A message to IT IS STILL THE LARGEST YET PUBLISHED AND CONTAINS THOUSANDS OF USEFUL ACCES:.ORIEs REQUIRED BY THE AMA- TEUR. PRICES AR-. REDUCED TO TtiE themanwho VERY LOW t ST. CONSISTENT WITH BEST WORKMANSHIP. SPECIAL DEPARTMENT TO DEAL WITH MAIL ORDERS. Post 3d. Free. hasneverbuilt .1311111=1111111' /st 0111I1C11 aReceiving Set. TOTTENHAM COURT ROAD, VV.L. FOR the man who has read Books 'Phones : REGENT 609. EAST HAM 172. WIMBLEDON 2393. and Articles* on how to build Receiving Sets and whostill THE I.RM, 3 VALVE feels that he does not possess the requisite amount of skill to build a SET. really good one, we have a new idea. A highlyefficientreceiver We are shortly publishing a series with one stage of H.F. (tuned anode) amplification, and one of Portfolios, each one dealing with stage note magnification. This setwillreceiveall one Receiving Setin a very com- British and Continental prehensive manner. The Portfolio broadcasting.Loud -speaker resultshave actuallybeen will contain a Booklet describing the obtained at over 350 mi. es range. Set, how it is made and operated and Panel to inches square only. illustrated with actual photographs PRICE,completely assembled, withB.B.C.and Marconi to show every stage of construction Licences paid,£9 9s. Best qualitycomponents togetherwithfullsizeworking for this set or any circuit drawings. supplied to constructors and experimenters at lowest possible prices.Technical ad- No effort has been spared to make vice free. these instructions clear and lucid and THE I.R.M. WAVE TRAP. With On-. trap attached to any set, a station half any man can commence building his a mile away can be completely cut cut.tree15s.ed. SEND FOR ILLUSTRATED PAMPHLETS. Set with every confidence that he will The Wonderful " N.S." Accumulatormay be charged inone hour.Will achieve complete success. not sulphate _under any circumstances.Can be charged and discharged at any rate without damage. May be left idle and uncharged for an indefinite period without deteriorating.Betterandcheaper than any other accumulator on the market. PRICES :- 4 volt, 30 A.H. actual,£1 2E.Carriage, 2S.3d. volt, 30 A.H. actual,£1 10s.Carriage, 2s. 9d. Envelope No. 1. WE SUPPLY EVERYTHING WIRELESS. SEND US YOUR INQUIRIES. Ready Nou. 7th. Containinginstruction Booklet, INTERNATIONAL RADIO full-size working drawings, com- MANUFACTURERS, Ltd., plete list of all components, etc., for building up a 2 -Valve Reflex 16, Palace House, Receiveremployingthewell- 128, Shaftesbury Avenue, W.1 known S.T. too Circuit. Designed2/6 and at39,StationRd., Manor Park,E. 12. by John Scott -Taggart, F.Inst.P.

AMATEUR CONSTRUCTORS! Envelope No. 2. We Supply Everything. ALL BRITISH. Tapp d inductances are tar in advance of any other tuning. Ready providing the tappings are correctly arranged. Our tuning Nov. 21,1: inductances at eWOUIld 011specially Intim glutted 35in. tubes ContaininginstructionBooklet with 26 s.w.n. dl ubin cotton -covered e pper wire in the following ratio10 sections of 10 turns each, and 10 sections full size working drawings, com- of 1 turn each. This winding will tune flora 200 to 1,000 plete list of all components, for metres. Price 3/-. building. up a 4 -Valve Receiver Ebonite panels for the tapped inductances, Tin. by 6 in. by embodying a large number of en- 3/16 in., trilled for 2 sets of 11 ash tirely new features. Designed by contact studs and terminals, corn- 2/6 Percy W. Harris (assistant editor yl to with 22 studs, 2 switch arms, 2 ph tne, earth and aerial .errni- Mcdern Wireless). no 1s,assembled as shown, and blue print of connections. Price 1/ - Polished Mahogany sloping front t'abi tat for above panel, Price6/- The C. tit and P inel make a mos efficient tuner for Crystal or Valve Cut out your Local Station with our new REJECTOR. The REJtsC OH is fiAed into a polished mahogany cab ne We gas antes you can cut out yo r local station and receive others, providing cur set has the necessarj large. Price 19/6 RADIO PRESS LTD. BOYS P. H. BOYS & CO Electricalss Wireless andEngineers, 187,G RD., LO VDON, E.0 1 Devereux Court - STRAND, W.C.2. 'PhoneClerkenavell 4454. xxiv November, 1923. MODERN WIRELESS t6e LIFE BATTERY.

,texlareet

terminals.

Extra space above top of 4 Volt- 6 Vol t- plates. oldpriceaerd,oriceold pricenewprice Wood separa- C23J-417-4- 27/- -c5-1711-- 4016 tors prevent frothing. CZ4.41-9fr" 32/-- -6074' 48 /- Large mud ez5446-7hg- 37/- 55/6 space prevents 7 short circuits. eZo-Jet=42/--Fe?"63 i-- Each cell a separate unit.

Exibe Batteries Do Not Froth on Charge. Stand No. 7. W RELESS EXHIBITION Ask for New Price List giving Reductions In All Types. WHITE CITY.

Obtainable from all Dealers and Garages, 40:14kinbo ELECTRICM, STORAGE and -- A- COMPANY LIMITED. 350 Service Agents

HEAD OFFICE & WORKS: CLIFTON JUNCTION, NR. MANCHESTER. LONDON :219-229, Shaftesbury Avenue, W.C.2. Use Chloride

BATTERIES BIRMINGHAM :57-58, Dale End. Batteries for House Lighting. SERVICE STATION MANCHESTER: 1, Bridge Street.

XXV MODERN WIRELESS November, 1923 RADIONS Ltd., Beg to announce that in consequence oftheirever-increasingbusinessin Repairing Wireless Valves

they have now taken extensive works, and equipped them with the most modern plant.This plant is operated by a highly -skilled staff, and they are now in a position to give the utmost satisfaction,combined with PROMPT DELIVERY. Write forPrices and Particulars.

111111111111111111,111111111111, 1, RADIONS Ltd., LORD STREET, Telegrams: "Radions, Bollington." BOLLINGTON, nr. MACCLESFIELD. Making yourown Efficiency Inductances Double Plug or Plug and Socket. set? Ifsoyoushoulduseonlycomponentsof proved efficiencyandreliability. Our components are not built to a price, but to a definite quality standard.The coils illustrated here are an example of the scientific design of our apparatus.All the turns in the coil are spaced and all the coils for any wavelength are the same size.Those with the fewest turns for the lowest wavelengths consequently have the greatest spacing-an important feature. A list of coils,coil -holders, condensers, transformers, rheostats,, etc., will be sent on request, and all our apparatus may be inspected at our London Office.

Gambrell Bros., Ltd. 76, Victoria Street, S.W.1. Phone :Victoria 9938. Works : Merton Road, Southfields, S.W.18. Phone : Putney 2100. xxvi November, 1923 MODERN WIRELESS

useCossorValves and cut out the Banjoaccompaniment ! yOU may have heard noises like the twang- The most exacting tests have failed to show ing of banjo strings when you have been any signs of movement of the Cossor Grid, using a Loud Speaker.Perhaps you have no matter what the workingconditionsare. been unable to account for these sounds, and That isthe secret ofitsremarkable freedom have imagined them to be faults in transmission. from microphonic noises. It is probably nothing of the kind !These noises are' termed microphonic noises and may be A spiral Grid, on the other hand, is much more actually produced by the valves in your set. delicate and pronetotransmittheslightest vibration of the set.Such movements are so Now, owing toitsunique construction,the imperceptible as to be almost unnoticeable in Cossor Valveissingularlyfree from micro- the ordinary way, but Radio picks them up phonic noises.Let us explain why. and,magnifying them,spoilsthepurityof The Grid of the Cossor is hood -shaped and your reception. wound on a stout Grid Band.The When next you buy valves, make up your mind to cut out the banjo accompaniment and choose securely laced and anchored TYPES : wiring is Pl. For Detector and Co sor Valves-their greateramplification Low Frequency usesi_ factor,freedom from distortion,andhigher in no less than three distinct povtions P2(with red top).For to every turn.The result is a grid High Frequency use each efficiencyforlong-distanceworkwillmaka From all Dealers. you regret thatyou hadnot bought them which is particularly robust and rigid. sooner. COSSOR VALVE Co.,Ltd.-HIGHBURY GROVE, LONDON, N 5. Gilbert kd. xxvii MODERN WIRELESS November, 1923

OVER HALF A MILLION SATISFIED CUSTOMERS WIRELESS !WIRELESS !WIRELESS !and EVERYTHING forit. PIONEERS OF Great Britain's Largest DON'T PAY MORE! CHEAP PRICES. exclusiveWireless Stores NOTE. -We are exclusively WIRELESS - NOT DABBLERS ! Quality, Quantityand ConsistencyourMotto. See our six -window display of popular bargains. We otter for the first timethenew "FELLOWS " Special Offer -STERLING New Lightweight Headphones, 4,000 ohms.A masterpiece of workmanship. Lightweight Headphones.Stamped B.B.C., A guaranteewitheverypair.Honestly worth30/--. Per pair 1816 4,000 ohms. ... Our Price 19/3 ELKAY LIGHTWEIGHT BRUNET Phones. The N. & K. 'Phones. The Headphones.4,000 ohms12/9 genuine article 13/11 genuine article. Our Price12/9 EDISWAN Valves ..12/3 Bankrupt Stock and of Limited MULLARD "ORA" Valves 12/3 COSSOR Valves ..12,3 Guaranteed all New. EDISWAN DULL EMITTER. MARCONI "R" Valves 12/3 Quantity. Our Price...... 25/9

DUTCH VALVES 6/11 BELL WIRE,tinned copper, 12 yards 6d. VARIABLE CONDENSERSof highquality. nut and washereachId.,per doz.10d. With Aluminium Top and Bottom plates. PHILLIPS DUTCH VALVES 7/11VALVE LEGS, Complete with knob and dial, guaranteed L.F.TRANSFORMERS,Ratio 5 to1. All VALVE PINS,nut and washereach 16., per doz.9d. accurate: - guaranteed (postage, 1/-) each11/3PLUNGER SPRINGS,complete each 1d. Vernier 3/- CRYSTAL DETECTORS 1/9, 1/3and 10(d.SLIDER ROD,brass, 13 in. long, I, in. square, .0002 4/8 CRYSTAL DETECTORS, enclosed in glass drilled each 33d. .0003 5/6 case 2/6, 2/3, 1/8 .0005 6/- SLIDER KNOB each 2d. .00075 7/- AERIAL WIRE,7122, guaranteed hard -drawn SWITCHES ON EBONITE,S.P.S.T. (quality the .001 6/ - copper, too ft. (postage, 1/-) 1/1011 best) each 1/6SUPER QUALITY 2 -WAY COIL HOLDER 5/3 CONDENSER VANES,fixed or moving, per SWITCHES ON EBONITE,S.P.D.T. (quality the REAL EBONITE 3 -WAY COIL HOLDER 7/9 doz. 31d. best) each1/11O.B.A. NUTS per doz. 4d. DETECTORARMS,Ball Joints, Ebonite Handle REAL GOLD CAT'S WHISKERS,each2d.,per SWITCHES ON EBONITE,D.P.D.T. (quality doz. 1/5 and Whisker Holder 31(1. the best) each 2/9WOOD SCREW TERMINALS each 1 Id. EILVER CAT'S WHISKERS,eachtd.,per doz. 7d. CONDENSER SPINDLES,all sizes in stock, SHELLAC per bot.104.and6d. CONDENSER SCALES, 0 to18o each31d. from each 1',d.AERIAL PULLEYS each 100.,848,6d.and41d. IVORINE LABEL SET,12differenttitles, the set 61d. SCREWED ROD,2 B.A., 12 in. long each 3d. TINFOIL large sheet 4d. COPPER FOIL,6 in. wide per ft. 5d. BASKET COILS,set of 6, up to 3,000 metres ... 2/4 IP 4 I3.A., 12 in. long each2(d.GRIDLEAKS, 21 and 2 meg each 101d. SLEEVING,3 yds. assorted colours, for 111d. RUBBER -INSULATED LEADING -IN FLEX(Twin), various colours per yard 2d. NUTS, 2 B.A. per doz.2(d. WIRE per yd. lid,CONNECTING WIRE,tinned copper, 20 gauge INSULATORS,white reel, 2 -in., eachtd.,per doz. 11d. 3 yards 2d. NUTS, 4, 5, 6and8 B.A. per doz. 2d. ENAMEL WIRE,in I, 1 and 1 lb. reels:- INSULATORS,white egg each2d.,per doz. 1/8 WASHERS, 4 B.A. per doz. 1c1. 22 24 26 28 per doz. 1(d.WOUND INDUCTION COILS(postage, 9d.) :- perlb. 2/4 2/8 3/2 3/8 CONTACT STUDS,with nuts and washers, per 52 X 4 9 x 4 8 X 21: G x 3 6 X 2 Note. -Bobbins,2d.each extra. doz. 4d. 2/5 2'3 1,11 1/8 1/5 POTENTIOMETERS,guaranteed up toSoo TERMINALS,with nut and washers,each1d., 11d.TAPPED INDUCTANCE COILS,zo tappings, ohms, superior make, compact size 7/3 and2d. wound to 1,600 metres each 2,/8CRYSTAL DETECTOR,glass enclosed, fitted on EBONITE KNOBS, 2 B.A. each2d.and3d. 4 x 2 ebonite panel with terminals for aerial, SPACING WASHERS,large per doz. 2(d.VARIOMETER8 (Tube type), complete with earth and 'phones, already wired and beauti- small per doz. 11d. knob . 3/11 and2/11 fully finished 4/9 CRYSTAL CUPS,2 screw, eachtd.4 screw, each 2d. DOUBLE 'PHONE CORDS,full length 111d,VALVE HOLDERS each101d.and1/3 FIXED CONDENSERS,all capacities each10 -id. H ERTZITE,Genuine Large Piece 9!.d.BATTERIES,H.T., dry: - EBONITE,cut to any size by machinery while 30 volts, including Wander Plugs ...... 5/9 you wait per lb. 3/6TALITE,Genuine Large Piece ' 6o volts, including Wander Plugs 9/6 TELEPHONE TERMINALS,nuts and washer, PERMANITE,Genuine LargePiece ...... d. AMALGO-PLASTIC METAL,for fixing crystals eachlid.,per doz.1/3ZINCITE,Genuine Large Piece 9a, No Wood's metal necessary 6d. W.O. TERMINALS,nuts and washers, each2d., BORNITE,Genuine Large 6d.GOLD SEAL PLASTIC METAL,for fixing par doz. 1/7MIXED CRYSTALS(6 kinds) gel. crystals 6d. PANEL BUSHES,drilled each 11 per doz. 1/3CARBORUNDUM 51d. IVORINE NAME -PLATES,all readings, each- TOP CONDENSERbushes each 1d., per doz.9d.ZINCITE and BORNITE,both in box 1/ - Id.,per doz.9d. BOTTOM CONDENSERbushes eachld.,per doz.7d.COIL PLUGS,real ebonite 5/3, and91d. EARTH CLIPS,Copper, adjustable each 5!,(1. SWITCH ARMS,4 laminations, ebonite knob, H.F. PLUG TYPE TRANSFORMER :- RADIONETTE CRYSTAL SET,complete complete with panel, bush, nuts and spring 1 350 to 450 metres 3/9 stamped B.B.C. and including one pair 4,000 washer 81d. 2 250 IC 700 4/- ohms 'phones,roo ft.7/22aerial wire,4 STOPS,with nuts per doe. 6d. 3 450 to 1200 2, ...... 4/3 insulators,lead-intube,6yardslead-in FILAMENT RESISTANCES,smoothaction, 4 900 to 20 0 5/6 insulated wire and adjustable earthclip. marvellous value 1/9 5 1600 to 3200 4/9 Ready to listen -in.Honestly worth 3 gns..-36/6 With engraved dials 2/6 6 22oo to 5600 , 5/-RADIONETTE ONE -VALVE L.F. AMPLIFIER FILAMENT COMPLETE CIRCLE RESISTANCE EBONITE CONDENSER KNOB AND DIAL 1/6 for above 34'8 SCALES, 0 to300 each 6d. FILAMENT RESISTANCE DIALS 8-1d. CABINETS,all shapes and sizes in stock. IMPORTANT NOTICE.In;g1t7encrgusdettitinsrictroionandatincrease intheearliestpossiemome;oliothecrod;oikayLorner. OurMailgrderhsrstwewish toinrormourcustomrs that alt post orders

Make no mistake when- you call on us. " ELKAY" WIRELESS CO., SEE THAT I 225 & 227, B1SHOPSGATE, LONDON, E.C.2. YOU ARE I AT Open Saturday all day. To the Trade -New Trade Counter now open. Wholesale, Bishopsgate2313. Please remit ample postage.We open Sundays, 11-2.30 mirNote ourTelephoneNos.- ELKAY'S I SPECIAL TERMS 10 RADIO CLUBS.Retail, Central 8544. SAVEMONEY BY STUDYING OUR ADVERTISEMENTS. For alterations of prices see our weekly Advertisements in " Wireless Weekly," " Popular Wireless," and "Amateur Wireless." NOVellIbel, 1923 MODERN WIRELESS TRADE MARK U.NI 111

E V E IZ- RE, TfitsDAY WIRELESS DRY BATTERIES & ACCUMULATORS

BRITISH MADE OVER 20years'experience and research, the finest materials, expert supervision, andcarefultestingatallstagesof manufacture are the reasons for the superiority of " Ever -Ready " Wireless Batteries. The consistent high standard ofquality has established for "Ever -Ready" products a reputation for absolute reliability which is jealously main- tained. The " Ever -Ready " Series embraceall types of Batteries for every wireless purpose. A new and complete list of standard sizes will be sent on request to :-

Service D.X, Dept. "gaieue/o Wideao The EVER -READY Coy. Great Britain, Ltd - eveL,- Hercules Place, Holloway, London, N.7. $l-dia471. /ocaiyadtfeatiney.

ELLA" BATTERY CHARGERS. TO THE WIRELESSPUBLIC REPUTATION-You must have seen, heard, or tried the They workfrom a Lamp -holder. famous French S.I.D.P.E. Head Phone -100,000 net sale CHARGE and -still going strong.The PremierTelephone andIN ireless your Co., Ltd., were the pioneers of this master production. Filament Battery EXPERIENCE -Now-as a result of 20 years' telephone ex- AT HOME. perience-we wish to introduce another masterpiece, Illustration shows the "ELLA" The Premier Phone. Each Phone isstamped BatteryCharger for useon alter- Premier (PTC). nating currentcircuits.It is supplied complete with Pole -Indica- GUARANTEE-Ask your Wireless Dealer for the PREMIER tingAmmeter,Adaptorand PHONE. Don't accept imitations.Write direct for a Flexiblefor Lampholder con- sample, 17/6 post free.Every Phone guaranteed perfect. nection and spring clips with wires for coupling to Battery. SPECIFICATION-Light in weight. Highly efficient. 4,000 Pries : ohms resistance.Beautifully finished aluminium, with £6 6s.,carr. paid U.K. insulated connections. Stalloy Diaphragms, no Spacing Highor Low voltage. State Frequency when ordering. Rings, easy fitting, Your Electricity Meter shows comfortable riding Ear- both voltage and frequency. pieces, and Cords of the Delivery early November. ALL PHONES best finish. Also " ELLA "Battery GUARANTEED Charger for D.C. Circuits. Complete with Switch- "They're Pal el 17/6 board, etc. A11 British. post free. See MODERN WIRELESS, Stamped B.B.C. October.. And the S.I.D.P.E. Pries, 56 15s., carr paid. Phone at 15 /- subject. In returnable box, S.I.D.P.E. loud -speaking FOR A.C.CIRCUITS ONLY. 4s.extra. Receivers,50lamina- Output3j10 amps, 68 volts. Deliveryfrom Stock. tions eachPolePiece, Send for ELLA Wireless List. TRADE SUPPLIED. 21/- subject. rratle:Orc,t,Itiows,rrt apptication, LION EL ROBINSON & CO. PREMIER TELEPHONE and WIRELESS Co.,Ltd., (Dept. M.W.), 3, Staple Inn, London, W.C.1. 62, OXFORD STREET, W.1. See also Advt. Page xii. Tel. No. : 17.

1 MODERN WIRELESS November, 1923

UTILITY ENDORSED BY THE EDITOR OF "WIRELESS WEEKLY."

The Sequelto "Wireless forAll"

OUR HIGH GRADE RUBBER COVERED TELEPHONE AFTERyourWireless CABLE GIVES WONDERFUL RESULTS AS AN AERIAL friend has read "Wire- INDOORS AND OUT. less for All," get him WirelessMasts and a copy of this Book. Insulators Abolished. He will be deeply interested The simplicity in erec- in the practical explanation tion is beyondthe dreams of all wireless asto how a WirelessSet enthusiasts, as the trou- receives and will appreciate blesome insulators are the elementaryinstructions absolutely unnecessary. Suspend this wire where for building anefficient you will, lead in, and Crystal Set from the simplest your result is there. of materials. It is a simple matter to make a portable aerial from this wire or to run a lead-in from the house to the garden, whether it is Simplified a few yards or half a mile. Ideal for telephone work all over the world. READ THIS CONVINCING Wireless UNSOLICITED TESTIMONIAL. By JOHN SCOTT-TAGGART ;a, Alverstone Rd., Waddiscombe, AERIAL and Sept,, 1923, F.Inst.P. The Manager, New London Electron Works. Dear Sir,-I am pleased to inform you that (Editor of WirelessWeekly) the wire arrived safely yesterday, for which many thanks 1/8 Post Free direct I should like to mention thatI have taken Content - my ordinary aerial down, and erected one wi 100 feet. your thin wire, and with 89 feet I obtain results Post Paid anywhere Some General Remarks regarding much better in every way than I had before. Wireless-TheTelephone Re- Yours faithfully-(Signed)GEO. FURMINCER. ceiver --Transformers-- Air -core Sold by all Book- andIron -coreTransformers- Supplied in 3 Thicknesses on origual drums. Special terms to the Trade Step-np and Step-down Trans- sellers and pub- formers - Inductances - Con- lished by Class 0kinumiles (Thin for light work). 15/.1Per densers-Frequency and Wave- drum, length-The Aerial Circuit of a RADIO 1,1,111: (Medium for most jobs). Wireless Receiver-The Use of a Class 1 35/-Carriage Variable Condenser when Tuning forward. PRESS Imurni(Thickest for heavier work). -The Crystal Detector-A Re- Class 2 le 70/- ceiver Using aVariable Con- LTD., Orders for 6 miles assorted (if required), carriage paid. denser-Loose-coupledCircuits Smaller Quantities of Class 1 (medium) sent carriage pa.d. -Notes ontheErectionof Aerials --Frame Aerials-Loud Deveieux Ho feet,1/8 500 feet,6/3 1,000 feet,10/3 Speakers-How to Make a Simple Court, (Sufficient for the finest AERIAL.) Carriage Paid, BroadcastReceiver-Operation of the Receiver-The Variable Strand, W.C,2 Inductances-Some simple forms Ideal for all Training Purposes in the Garden, of Crystal Detector-The Tele- Fruit Trees, Peas, Beans, etc. phoneCondenser-The Com- plete Arrangement of the Appara- NEW LONDON ELECTRON WORKS,LTD., tus-Operation of the Circuit. 99, Regent's Dock, Limehouse, E.14. Telephone :East 1821. Telegrams :" Stannum, Step, London."

XXX November, 1923 MODERN WIRELESS

Hello! Hello! Hello! C.Q.-"ATLAS" COILS callingI

(.,),1 Wavelength in metro, with.001Variable Price. "ATLAS" Patent Plug-in Coils ". Condenser in shunt. 8.cl. Min. Max. 25 120 0 Tune in Telephony Trium- 375 5 35 175 515 5 0 phantly on b5o 5 2 Long or Short Waves. 40 180 78o 5 2 Adjustment Simplicity itself. 50 230 6 Superiority unsurpassed. 65 280 1000 5 75 325 1120 5 6 100 410 152o 7 0 Capacity reduced to a mini- 15o 66o 230o 7 10 mum. 200 85o 3100 88 Optimum Wavelength 25o 128o 415o 9 0 Range. Induction- Maximum ob- 300 155o 4940 9 5 tainable. SPECIAL FEATURES : 400 2045 638o 10 3 Leave nothing to be desired. Wound in true concentric circles, thus obvi- 5002980 8900 10 6 ating sharp bends.Result :fine tuning. 600400o 12100 II 0 Signal Strength increased. Air -spaced between layers and turns. 750 4970 1500o II 10 Users say : 10006100 20000 12 8 12507000 22000 140 " Absolutely the best." 1500 8200 2600o 150 Enquiries solicited for all Radio Components. Discounts for Quantities. CATALOGUE ON REQUEST. Trade Terms on Application.

Our Worksare replete withModern Machinery and our Staff is expert in all matters Radio. ONLY HIGH-CLASS GOODS SUPPLIED, AND ALL INSTRUMENTS TESTED AND PASSEDPRIOR TOLEAVING OUR WORKS. H. CLARKE & CO. (Manchester) Ltd., Radio Engineers, ATLAS WORKS, OLD TRAFFORD, MANCHESTER. TE r rphone Nos: 683 and 793 Trafford Park,, grams) "PIRTOID, Manchester/" MODERN WIRELESS November, 1923 a WITHIN 24 HOURS ! You'll need GUARANTEED GOODS, DELIVERY BY RETURN - IF UNSATISFACTORY MONEY RETURNED IN FULL. Diaryanyway, Aluminium Vanes, 5d. doz.Aerial Pulleys, 6d.Anti -Capacity Handles, 6d. Cats Whiskers -Gold, 2d.; Silver, 1d. ;Spearpoint, ld. Packet of 4, 6d. Coils, Basket. Setof 6, 2/-. Waxless, 2/4. 4/vt. Batteries (British) 6d. each. sowhy not have CoilHolders, solid ebonite, z -way, 3/6 ;3 -way, 4/6.Sockets, 7id. each. Condenser and Grid -leaks, 2/6.Grid -leaks, all megs., 1/- and 1/6. Condensers, Fixed. -To .00x, 9d.; To .005, 1/-; To .01, 2/-; To .r, 3/6: Ditto., Variable -.00r, 8/-;.0005, 5/11 ;.0003, 5/2;.000z, 4/8; .000i, 4/-.With ebonite or aluminium end plates, .o88 spacers. aWireless one? Condenser Dials, o.18o, lid. ; with knob, 1/4 and 1/9.Bushes-T,p, ld.; Bottom, ld. Ditto End Plates, 1/6 pair, drilled and tapped.Solid ebonite. Contact Studs, 4d. doz.Stops, 2 a Id.Connecting Wire, tinned copper, your appointments -to 3 yds. 2d. FOR Crystals.Every make stocked.Zincite, 9d. ;Bornite, 6d.;Talite, 1/-; chronicle your doings -for the Hertzite, 1/-; Galena, Silicon, Carborun dum, 3d. ;Copper Pyrites, 6d. thousandand one things Gold Seal r lactic Mita for fixir g Crystals, 6d. box. intimately connected with your life, Crystal Cups, 4 -screw, lid.Detector Glasses, 4id. each.Boners, 2/6. Crystal Detectors.Plain brass, 1/3 ;Nickel, 1/6 ;Dustproof, 1/9, 2/6 ; you need a Diary. Plug-in Type, 3/6 ;Perikon, 2/6, 3/6 (with Zincite and Bornitc). a Crystal Detector Parts, in envelope, 10id.Nickel, 1/-. 'Thisyear,purChase Wireless Earth Clips, adjustable, 6d.Ebonite, 3/6 lb., any size.Fil. Resist. Dial, 9d. Diary and get some useful information Filament Resistances, 1/6, 2/-, 3/-; with dial, 2/6; porcelain base, 4/6. without extra cost. Foil.Copper, 3d. foot.Tin, 4d.Formers, 12 by 2, 3d. ;12 by 4, 4d.; 12by 5, 5d. These two 12abio Press Diaries are Headphones.Continents], 12/9 ;British, 18/6 ; Very Best, 22/6.N. & K., both extremely neat and well -produced 12/9. Insulated Hooks, lid.Tape, 6d. roll. Insulators -Egg, lid. ;Reel, Id. : littleBooks.Theydo everything Shell, 2d.Frame Aerials, detachable, 19,6. that a Diary should do -they are Jack and Plug,1/6. Lightning Arresters,2/6 each. Spade Terminals, ld. each. convenient in size and shape -do not Knobs, finest, 4d. and 2d.Lead-in Tubes, rz in., 11d. ;9 in., 10d. ;6 in., 9d. Loud -Speaker Aluminium Trumpets, 6;'9 each.Screwed Rod, 12 in. 2 B.A., bulgethepoqket-strongly bound 3d. ;4 B.A., 21d. to give a whole year's service, and Mica, .002, 2d. sheet.Nuts, 2 B.A., 2id.; 4/5/6/8 BA., 2d. doz. ; D.B.A., more besides,ifneeded.Just the 4d. doz. Scales, Ivorine, o.itio, 3d.Set Name Tabs; 6d.Bell Wire, 12 yds. 6d. Diary,infact,tosuitthemost Slider Rods, 31d. Plunger, 2d. B. st Ebonite, 6d. Wound Varie-couplers, 6/6. critical. Spacers, large, so. doz. ;small, lid. doz.Spring Washers, 3d. doz. Sleeving, all colours, 3 yds., 2 MM., 11d.Shellac, 8d. bottle. The Handbook and Diary contains Switches, lacquered brass on ebonite,S.P.S.T., 1/-;S.P.D.T., 1/6; data of a more technical nature than I).P.D.T., that in the Popular Diary, Switch Arms, 1st quality, 8d.Screws, all B.A.'s-Toin., 5d. ;To x in., 9d. doz. Transformers, H.F. Plug, 1, 250/600, 3/9;2, 350/700, 4/-; 3, 500/900, 4/3 ;4, Soo/1,35o, 5/6; 5, 1,500/3,200, 4/9 ;6, 1,2005,600,5/-. READY Transformers, approx. 5 tor,L.F., 11/9 and 15/-;allguaranteed. RadioPressHandbook " Powquip," 13/6 ;best nickel, 14/6.Bobbins, 1/6. H.F. Formers, 2/-. NOV. 15th, Terminals, W.O., 2d. ;telephone, 10.; pillar, 2d.; wood screw, lid. Telephone Cords, 10id. Tablets (Earth,Aerial, etc.), Id. each. Flex (twin) and Diaryfor 1924. 2d.al. Vanometers, double wound, 2/11 ;Ebonite mounted, US. Formers, 6d. Size 54 in. by 34 in., solidly bound pair.Wound Coils, 12 by 4, 2/5; 6 by 3, 1/8; 9 by 3, 2'3. Valve Holders, finest ebonite, 1/3; moulded, 9d. (all with nut and washer). in grained leather cloth, fitted with Valve Legs, Id. each.Valve Pins, ld. each.Voltmeters, 6/6, 7/6. pencil.Diary portion shows a whole Wander Plugs, 3d. each. Washers, all B.A.'s, 1d. doz.Wood's Metal, 3d. week at an opening.Large number EVERY ACCESSORY ON THE MARKET STOCKED. of pages of technical data, including Largest Stocks in British isles. several pagesofelectricalformula Imperative.Kindly send ample postage ;balance always refunded. which will -prove invaluable to the SEND FOR FREE LIST. Trade supplied at separate trade counter. serious worker. RADIO STOCKS, Ltd. On sale at all Booksellers, Museum 4213. (Mail Order, " Radio House."), 87 /89, NEWMAN ST., OXFORD ST., LONDON, W. Post free 2/8.2/6 Between Oxford Circus and Tort' nham Court Rood, And at 44a, Cranbourn St., Leicester. Square, W. Radio Press Popular Wireless Diary for 1924. JUST OUT !

Size2 in.by 4i in.Strongly bound in pluviusin with roundedcorners. One complete week shown at each TheGRAMAPHIX opening.: Wireless pages include information oncallsigns,circuit LOUD SPEAKER diagrams, Morse Code, electtical data, This is a most efficient device, to full instructions for building a com- which the ordinary headphones plete Receiving Set, etc., etc. are clipped and the Gramaphix mounted on the tone -arm of a On sale at all Booksellers gramophone. Post free 1/41/ Str,,ight or Curved Horns In leather, with pcncil supplied to fit Gramaphix Post free 118-1/6 Straight ...6/6Wireless List Curved ...... 12/6`I' sent post Gramaphix...... 10/6 free. [Postage 9d. extra.; Published in conjunction with RICHARD MELHUISH, Ltd., ElectricalEngineersand Wire'ess Experts, CHAS. LETTS & Co. 5o, 51 & 84, FETTER LANE, LONDON, E.C.4. Estd. 1828. November, 1923 MODERN WIRELESS

THE PRECISION J. B.VARIABLE CIINDENSERS A lot depends BRITISH MANUFACTURE. SCIENTIFICALLYDESIGNED BY EXPERTS. uponyourBaitey ONE HOLE ONLY FOR FIXING TO PANEL. LARGE METAL -TO -METAL Make sure it's a Fuller " Block "-the battery BEARINGS. that is built for wireless and which has proved by comparative test to be the best for anv set. Owing to the ACCURATE CLOSE SPACING, these Instru- Here are a few of the reasons why :Double the ments take up much less room outbut compared with an ordinary plate type in Panel. battery of the same rating, it holds its charge COMPLETELY even when inactive for months and there is ASSEMBLED never any risk of accidental shorting or fire. WITH KNOB& DIAL Get one to -day, a twelve months' guarantee goes with it. '001 816 PACKING 00075 and 8 /- POSTAGE '0005 7I- Extra. 6 -VOLT LET. 0003 5 j9 Ebonite containers, leather handles. '0002 5/- One only9d. Two I /- S. d. VERNIER4/-Three I /3 B. W. X. 6 /24 1 9 3 B. W. X. 6/45 20 0 These Condensers are being used by leading makers of sets, who 86 after severe test for best results have given their preference to the B. W. X. 6 /60 2 which isYOUR GUIDE TO REAL SATISFACTION. B. W. X. 6,90 ... 3 8 9 I hey are unconditionally guaranteed to be scientifically B. W. X.6;120 ... 4 7 6 correct,JB.mechanicallyperfect,and built for unusual durability. Obtainable through your Dealer or direct from the Manufacturers: 30 -VOLT H.T. JACKSON BROS., imp) ',wed 400,1case,outside terminals, FIRST sliding lid. FLOOR 8, POLAND ST., OXFORD ST., s.d. 'Phone: Gerrard6187. LONDON, W.1. H. T. ... 110 0 Works: LEW1SH AK, S.E.'Pito : Lee Green 1225 Trade Inquiries I auted Stocked by all our Service Agents.Additional Agents required in towns not yet covered.Over zoofully equipped Illireless Battery Service Agents throughout the country ready to give you advice and charge batteries. Demand FORMO Products OBTAINABLE FROM ALL RELIABLETRADERS. A NEW "FORMO" LINE.

Plug-in . Detectorwith-----(ItNQ) Idealfor S.T.100 and the 0 -.7 other Circuits and General t9 Experimental Work. Will F 0 R M 0 -. 1-- v work onallStandard JOINT. -2-..., , ,,, Circuits recent Trans- Fr:ce tr...... ______-'former Coupled and Freak Circuits. 4 /-. FOR THE TOTAL Illustrated List B.22 ELIMINATION OF onapplication. DISTORTION. 1 111 /-1 YOU ARE CORDIALLY INVITED TO VISIT OUR STAND AT THE ALL-3RITISH WIRELESS EXHIBITION, NOV. It., to 21st. DO NOT BUY SWISS OR GERMAN NUTS, TERMINALS, SCREWS, ETC. WE MAKE AND SUPPLY BETTER GOODS AT LOWER PRICES.

THE FAMOUS 5 "" To meet all reouirements apt it is now supplied in the FORMO ,,_-... following windings. TRANSFORMER .-7---- A. Ratio... 1-2 B.illaattiioo is,through sheer merit, the if, - 0 ..:: 11:31 most widely used. It is not rD. Ratio... 1-5 sold by frantic advertising. 0' D. is supplied as standard Owing to stringent test, winding. breakdown under ail li We advise D.forrst ordinaryworkingcon- Stage, B. for end Stage. diticnsis impossible. 0.CT)i Fuller's United Electric Works L.. i One Price, 18,' - ShroudedType. WOODLAND WORKS.CHADWELL HEATH, E. THE FORMO OPEN TYPETRANSFORMERIS THE FINEST GENERAL London Depot : Telegrams : elephone : 58, HIGH ST., W.C.2. PURPOSE INSTRUMENT OBTAINABLEAT 15/-. THE FORMO RHEOSTAT LFORD1200 " FULLER. IS NOT EQUALLED AT 2 6. Make Use of the Formo Service. (6 lines). (Adjacentto nham CHADWELL The FORM()COMPANY, Rd. Stn.). GERRTotteARD50Ct.70. HEATH." Office and Works :32, CRICKLEWOODLANE, N.W. 2.'Phone : Hamp.1787. MODERN WIRELESS November, 1923

By the Author of : Elementary Text -book on Wireless Vacuum Tubes. Wireless Valvessimply explained. Practical Winless Valve Circuits. Wireless for All. Simplified Wireless. How to make your own Broadcast Receixer, site., etc. More Practical Wireless Circuits By JOHN SCOTT-TAGGART, F.Inst.P. Edifor of "Modern Wireless .cnd "Wireless Weekly " The " MAXONE " ' Superlative All -BritishHeadphone.Sold with a guarantee of satisfaction. the All parts replaceable. 22 /6 each. ONE of the first - and still If you want the very best out of yetir set-that extra finer tuning, and purer standard-Books onValve Cir- reproduction insist on " Maxone "guaranteed components. See how they sell ! A smile of satisfaction on every customer's face. cuits "Practical Wireless Valve Keenest prices to factors and the Trade. Don't miss our. stand-No. 28-at the Wireless Exhibition.Special demon- Circuits " has been so appreciated by strations of the famous Claralfat 3 -valve receiver. Gives the best results in your many thousands ofkeenWireless drawing -room or picnicking or on 'the river.Special portable types.Send for folder and Press reports on its wonderful performances. experimenters throughout the country, J. MACDONALD & CO., Wireless Manufacturers, that theauthor has been encouraged 2, High Street, Camden Town, London,N.W.1. to bring out a second Book of Circuits. 'Phone: North 4386. 'Crams :" Fraochan, Norwest, London." This is an entirely new work and contains thefullestdetailsof the well- known S.T. roo, also the S.T. 75, r-, 2-, CliniligiMil.....11.1111.111.1111.11.111. and 3 -Valve dual amplifications circuits, WIRELESS For theArmstrongSuper, theimproved B.B.0. DRY B.B.C. Flewelling, etc., etc. BATTERIES Sets In addition there area number of original Circuits by the Author whin No. 1 W. To connect in Series insert straight Ter- have not yet been made public, and Standard Pocket minalinSpiralof whicharelikely to arouse quiteas Lamp Size -4l volt next battery.Bend much interest among enthsiasts as did withpatentspiral spiral and thus ensure wireterminalsand permanent electrical the S.T. roo. plug sockets to take connectionwithout Wander Plugs. soldering. This is not a book for casual reading, Note :- rdoz..34 onewhicheveryexperimenter volts. but shouldhave in his reference library. Used units replaced BRITISH MADE. easily. Its utility is very much increased _by thefactthatallworkingvalves. Patent applied for are given. Connect as illustrated. This Book contains all valves of com- PRICE CARRIAGE PAID, 7/- PER DOZEN, WITH PLUG. ponents up to S.T. 15o together with all Standard Sizes : the valves for the circuits in "Practic d No. 2 W. Slab,16} volts, 3 -volt tappings, Sire approx. 9 x 1 x 3ins...... , , . ...Price3/- each Wireless Valve Circuits," No. 4 W. Slab, 36 volts.3 -volt tappings.Size approx. 10 x a x 3 ins. No. 5 W. Block. 60 volts. 3 -volt tappings. Size approx. Sold tyallBooksellers, 3 /8. ,., Or Seri, past free, 0} x 3} x Si ins. 12/- Prices include Wander Plug.Carriage Paid. Published by 11 anufactured by Telephone: Watford 617 RADIO PRESS, LTD. Devereux Court, 316 Strand, W.C.2 The BRITISH BATTERY C°L.TD. *Rabic)Vreos Zerio11o.13. CLARENDON RD., WATFORD, HERTS. November, 1923 MODERN -WIRELESS

The 3 Stages comprise sufficient equipment for most experiments WASTE NOT WANTNOT with 3 ValveCircuits,both " Straight " and " Dual." THE SCIENTIFIC SUPPLY STORES'component Stage 1. parts for " above -board " assembly, as advocated Single Valve Reflex by MODERN WIRELESs and WIRELESS WEE KLY. .Single Valve, Expn.Panel£0 8 6 Eminently suitablefor 3 & 4. '2 Variometers at 13/- 1 10 0 experimentingwith.the 6. L.F. Transformer...... 0 13 6 modern.reflex circuits. 9. Crystal Detector ... . 0 2 6 Assemblyis progressive ro. Stabilising Resist- and no part is wasted, all ance, Variable ... 0 3 6 being useable insuccessive 3 Fixed Condensers, .00r, stages. .002, .0003, at r/- 03 0 49 Stage 2,1 Valve Reflex Base board, rz in. by r8 in, 0 (E.G., St. roo). - £3 5 9 Additional to Stage r 3. avalve Panel£38 6 Stage 15) rL.F. Trans- 3 Valve, E. G., St. moo and former ... 013 6 All components for Stage III, £1 20 as illustrated,£6 9 0 SCIENTIFIC SUPPLY STORES, 1:6,Newington Causeway, S.E.I. TelePlionc: 1101) 4177.

Turnock's Specialities TAKE a little trouble with your Aerial K7 /4000 ohms. Headphones, retail at 14/6. and you will be amply repaid by the (A line of special value.) vastly superior results you will get. Besides, a poorly erected Aerial is often XPI8 Grasshopper Crystal Set, retail at 21/- a menace-it might collapse and cause serious damage.Better put up a good one while you are on the job. of Get a copy of this Book and read how A proprietary article easily a good one may be erected. attractive appearance. Cry- Radio Press, Ltd stal is operated by a special Devereux Ct.,Strand, W.C.2.

non - oxidizing Magnet, From all Radio Press giving perfect adjustment Booksellers Wireless and News- Library agents, or No. 4. non-microphonic.Ithas 1/14 Post paralleltuningarrange- Free, ment.Its popularity has assureditsuccess. A Crystal Set of finality.

Turnock's Telephone Works, How to erect you r 41, High Street, Aston, BIRMINGHAM.

WirelessBy B. Mittel A.M.I.E.E.Aerial ADVERTISEMENT RATES " WIRELESS WEEKLY." ORDIAARY POSITIONS. NEXT MATTER (In columns only). 13 insertions consecutive- £15 per page and pro rata. 13 insertions consecutive -£20 per page and p.-ci rata. 6 - £15 plus 5% per page and pro rata. -£20 plus 5% per page and pro rata. 1 to 5 -£15 plus 10% per page and pro rata, 1 to 5 -£20 plus 104/o per page and pro rata. SCHEFF PUBLICITY ORGANISATION, LTD. (Advertisement Managers, Wireless Weekly and Modern Wireless), 125, PALL MALL, LONDON, S.VV.1. 'Phone-Regent 2440'2 lines.

X_NX V MODERN WIRELESS November, 1921 JUST PUBLISHED The Construction of Crystal Receivers By Alan L. M. Douglas

\...

OW of oi "ifteConstruction Ctystalieceivers 13 Gceptioneneral INioadcast -andtheCrystal 'Re

T4:7=1;cvetV Receiverstillgives the purest speech

IN spite of the very marked advance in the design and construction of Valves, there

is no shadow of a doubt that the Crystal still gives the purest speech. CONTENTS. Many remarkablelong-distancereception The Crystal Detector-its tests have been recently carried out, and would Development and De- sign. show that the Crystal Receiver is far from being CrystalReceptionCir- superseded. cuits. Inductances for Crystal Even if you already possess a Valve Receiver, Work.(Singlelayer solenoid,honeycomb, it will be to your advantage to get this new Book basket,slab,inductively coupled, etc.). and build one of the super -crystal Sets described Condensers fixed and in it.Beides enabling you to make interesting Variable. Fullcon- structionaldetails. comparative tests, you will have a very useful Telephone Headgear-including transformers receiver as a stand-by in case your Valve Set and loud -speakers. should fail you at a critical moment. How to make a Crystal ReceiverforBritish Broadcasting.(Wave- length range, 550 -boo metres.) Published by How to make falong Range Receiver. RADIO PRESS, LTD., (Wave -length, 300- 3,000 metres). Deveretix Court, The " Mark III."Short- wave Government' STrtAND, W.C.2, Tuner, and useful eon.- versiOnsandmodi- 1/6 fications. Soldby allBooksellersand Newsagents, or r/8 post free direct. Aerial and EarthCir- cuits-their faults and remedies.

_ Appendix containing instructions for making three extremely simple and practical. sets. Itabinpuss*triesOrr. G. xxxvi November, 1923 MODERN WIRELESS 411..1,,o1M \ AnAlillfl....1WMI4*./M ALAIEI.A.,A.I1Nb..A.A0M...:AMM,.a../,AM....g4IN.....a0..AL olveSegrPRON

WIRELESS RECEIVING SETS IT'S AS SIMPLE AS ABC to install and operate " EFESCAPHONE " Wireless Receiving Sets. -Printed instructions are enclosed with all sets, valve or crystal. The " Nelson " Model de luxe illustrated is a superb valve set. The wavelength range is exceptionally wide-from 150 to 4,003 metres-enabling the user to pick up not only British Broad- casting Stations, butParis, The Hague, and ships' signal s The two -valve set has a telephony range of approximately 125 miles with headphones, and the three valveset a range of zso miles with headphones or 75 mileswith a loud speaker. Finally, the appearance of " Efescaphone " Sets is all that could be desired. The layout is neat and compact ;the cabinet work distinctive.In the set illustrated the instrument panel is enclosed, when not in use, by a neat roll shutter, and the headphones accommodated in a cupboard in the base. All connecting wires are out of the way at the back of the cabinet. Ask your wireless dealer for particulars or write for Illustrated Catalogue of this and less expensive sets and name of local agent. (Model de Luxe) Wholesaleonry- FALK, STADELMANN & CO., LTD. Reduced prices complete with everything except valves. EFESCA ELECTRICAL WORKS, No. R. 90002. Two -valve set £22 No. R. 90003.Three -valve set ...£26 83, 85, 87, Farringdon Road, London, E.C.1 Plea BBC tariff extra. And at Gln,ttnw. Man^he5ter and Rirrnin,tharn.

The Tungar (for use on Alternating Current only) will enable you to charge your wireless battery at home, without trouble and at negligible cost.It has no moving or vibrating parts, and requires no attention.Install a Tungar and avoid the risk of your battery running down when you are entertaining guests. Full particulars from your nearest dealer or from- The British Thomson Houston Co., Ltd. 77, Upper Thames St., E.C. Branches inall large towns. Tuna r FOR CHARGING BATTERIES ON ?/, 4 ALTERNATING CURRENT. SUPPLY 7/ ,/ 184311 MODERN WIRELESS November, 1923 -GRIFFIN'S JUST OUT ! 80, NEWINGTON CAUSEWAY Hop 18o6. (Corner of Lancaster St.), Elephant & Castle, London, S.E.1. AGENTS for all the LEADING Manufacturers. " Polar" STOCKISTS. Genuine Radio Experts. SPECIALISTS IN PARTS FOR. ALL C RCUtTS Including "S.T.ano and " P. W." Combination. SPECIALS. -but I don't "GRIFFIN"- Medgeteg L.F. Train! or mars, Ratio 4I to 1,...22/6 We aaine they have no equal. Acknowledged to be the finest on, the rket. No. 2 "G RI FPNONES," 4,001 ohms. Adj. PolsPieces_ Sent "on appro."Beautiful Finish 131S Small ll).P.n.T. Switches for panel mounting, nickel plated 3 /- understand CALL AT OUR SHOWROOMS AND INSPECT THE LARGEST RANGE OF COMPONENTS IN SOUTH LONDON. AdvLe New Catalogu e free on abhliention. Also trade list. Circuit diagrams saRt RAMO WHEN awireless enthusiast decides to build his own Set, III 41131MMEMEMp. his first job is to study the orom I 111KMLARAKEEMEr necessary wiring diagram. And that *mu ousat is where quite a numb 2r meet their luous$ Waterloo. iiiiir(410)1 Those of us who can read circuit diagrams as easily. as ,we can our morning paper are aptito show but littlesympathyfortheextreme .961 Fyn eye elergke novice making his first flounders into Wireless. To the EXPERIMENTER. Radio Press, however, appreciate To the CONSTRUCTOR. that the correct reading of circuit diagrams is the first essential to the To those purchasing COMPLETE SETS. successful building of a Set, and are publishing an entirely new Book which We are,Radio. Engineers of fang and wide completely cuts out this difficulty. experience. able to, advise you with confidence and without prejudice. Every circuit diagram in "Pict rial Wireless Ci.ctrits " Why not call at our lounge showroom, - is shown pictorially- where we have reputable apparatus and thatistosay, the parts from terminals to a 1K.W. ship set. Pictorial actual components used are drawn instead You willfind that we can Wireless of conventional signs help you-call to -day fora far them.Thus there demonstration or write to us. will be no excuse, for Circuits example, for any enthusiast not know- GENERAL WIRELESS, LTD., ing the correct position Gee'. 8460. by for his filament rheo- 21a, GARRICK STREET, W.0.2. OSWALD J. RANKIN stat. Near Leicester Square Tube. Altogether over ryo circuitsare shown, From 1 /71 ranging fromsimple all CrystalReceivers Book- post to s oilers 1/6 fr e more elaborate Multi - JUST ONE valve Sets. EL -BE UTILITY If difficulty in reading Circuit dia- For others see " MODERN WIRELESS " October, 1923. grams hashithertopreventedyou " EL -BE MODERN " TUNER from buildingorimprovingyour SetL-get a copy of this Book to -day. It will be eighteenpence well spent/ Beautifully finished on 12 months' Polished Stand. guarantee. Published by RADIO PRESS, LTD: Gives you finest rossible tuning. Devereux Court, Strand, \V.C.2 ASK YOUR DEALER FOR IT. LEIGH BR )S. 37, Si Imou h St., Kings Cross, London, W.C.1. Tel: Museu 4547. Rabin Puss rits x vii]

November, 1923 MODERN WIRELESS NO MORE H -T BATTERY TROUBLE CLICKS and crackles in your phones or THE "M -L" loud - speaker generally indicatethat one or more of the small cells of your H.T. ANODE Battery has become run down or polarised. CONVERTER The " M -L " Anode Converter obviates the use of H.T. Batteries.It will give you smooth, noiseess reception, and can be relied upon to function always.Worked from the ordinary 6 -volt accumulator of your set, its consumption is only 1.15 amperes.The low-tension battery imput is regulated by a rheostat, giving corn-; plete control of the anode potential. For power amplifier work where the life of the ordinary H.T. Battery is very limited it is ideal. The " M -L " Anode THE " M -L " TWIN COIL Converter is supplied for the following standard voltage ranges. TRANSFORMER. Special machines can be made toorder. will give you clearer, stronger signals and greater range from Type " A,"6- 70 volts.. For generalrecep- your set. High Primary Induc- tion. tance. Very Low Self Capacity. Type " B,"6-120 volts 1 For two -stage power Entireabsenceof distortion. Primary to Secondary Ratio 1-4. Type " C," 12-300 volts J amplification: AUser writes: All types can give up to 15 milliamps. con- "it isthe best trans - PR: CE tinuously without overheating.Write for pr_ces former I have tried so far,andI have had and full particulars. considerableexperience since1917. I am de- CARR. PAM. We invite Traders to write us for terms.' lighted with the results Ready for I am now getting, thanks Mounting. THE M -L MAGNETO SYND., LTD., to you." WIRELESS DEPT,, COVENTRY.

The Mark of High Efficiency. ROW LEY& LOUIS 12, The Broadway,Muswell H111, N.10. Telephone :Hornsey 668. AN ANNOUNCEMENT COIL HOLDERS Aluminium and Ebonite. Anti - OF IMPORTANCE ) capacity handles.Highly finished TO WIRELESS ENTHUSIASTS and of excellent value. 3 -way 8/6. 2 -way 6,8 'ASTRA' CONPONEN rs Headphones: Reel and Egg Insulators ... each 00//22 A veritable revolution in components for Receiving Sets Genuine Brunets, 4,000 ohms 16/6 Insulated Hooks each of every description is portended by the introduction of N. uc K., best finish, very loud 14/11 Spade Terminals, threaded, each 10. ASTRA " COMPONENTS. French D.L., 4,000 ohms 11/6 BushedEbonite Knobs; best,each0/3 In every case a sound engineering production ; in every Lead-in Tubes, any length, per in.0/1 instance a unique component of unique properties, and Aerial Wire,7/22copper, coo ft.2/2 BestEbonite, only in sheets, in every detail a reliable but inexpensive job. Lead-in Wire per yd.2d.and 3d. x /8 in., 3/16 in., fin.,... per lb.4/6 For instance :-- Silk -covered Twin Flex...per yd.0/3 Systoflex, best per yd. 0/6 Switch Arms, complete, best only0/9 Systoflex, cheap per yd. 0/3 The 'ASTRA' Vernier Condenser Filament resistances, best only...2/- Best quality Coil Holders, 2 -way 6/6 can be added to any existing condenser, giving Fixed 1/- Best euality Coil Holders, 3 -way6/6 micrometer adjustment.Can also be used Best Condenser Dials 2/- Knife Switches for panel mounting 0/8 for panel mounting as a separate instrument. Basket Coils, 250-5,000 metres, Engraved Rheostat Dials...each0/4 Ebonite, with anti -capacity handle ;only set of 7 3/- Crystal Cups, with 4 screws, each0/2 one connection necessary. 7/6, Post Free. Ebonite Valve Holders,best C.A.V. Accumulator, 6 volt, 6o The 'ASTRA' Dual Switch quality 0/9 amp., in case with switch, fuses a super -tuning device which can be used to Valve Sockets per doz.0/9 etc S1 19 0 tune in any circuit, on crystal or valve, with- Valve Pins per doz.0/9 Special R type Dutch Valve, out condenser, and enables user to handle Brunet L.F. Transformers 14/- guaranteed best quality 8/6 High -class Guranteed L.F All types of valves at cut prices. high-trequency circuits over a range of zoo Transformer 9/6 to3,000 metres. withoutcondenser.Fine Instrument Wires. tuning, no dead-end effects, micrometer ad- H.F. Transformers, any wave justment, anti -capacity handles, ebonite and length 3/6 Prices per lb. rum. brass. 10,6, Post Free. Crystal Detectors, in glass 1/6 No. D.C.C.D.S.C. elled Shaw's Genuine Hertzite, large 0/8 18 2/6 3/9 2/3 WATCH for further announcements of other " ASTRA Herbo Cat's Whisker improves 20 2/6 3/9 2/3 components, but in the meantime WRITE US about results on any crystal set 0/6 22 2/8 3/11 2/6 your wants, and we will add your name to our mailing Phone Cords, best per set1/3 24 3/4 4/4 2/6 list for advice of everything we market. Condenser Plates per pairlid. 26 4/- 4/11 3/- Contact Studs per doz.0/4 28 4/6 5/10 3/4 GeorgeManufacturing Co. Small Spacers.... per doz.na. 30 5/4 6/10 3/9 Nelson Chambers, High Street, Birmingham. Large Spacers per doz.0/3 32 7/2 7/10 3/11 Tele. : Central 5778. Tele. : AcTSNA, Birmingham. Brass Bushes eachlid. 34 8/- 8/10 4/4 2 a"d 4 B.A. Threaded Rod, per ft. 0 3 36 8/6 11/6 4/8 ShellInsulators, large... each0/6 All sizes in stock. Shall Insulators, small each0/3 rd. extra for reeling underxlb. All goods sent off same day as ordered. Enclose sufficient for postage, extra postage will be returned.

XXXIX

MODERN WIRELESS November, 1923 FRENCH THOMSON-HOUSTON PHONES The Headphone with the Two Years' Guarantee All GENUINE French Thomson -Houston Headphones are now Guaran- teed against Defective Workmanship for 2 years. A guarantee is given with each Headphone sold. What more do you want ?-This speaks for itself. If your local Dealer cannot supply you send direct to us. DELIVERY AT ONCE FROM LONDON STOCK. Revised List post free.

LIST No. SPECIFICATION. TOTAL PRICE POSTAGE. RESISTANCE Polished aluminium detachablereceivers. 250 Double horn headbands, fullyadjustable. 4,000 6d. Long flexible cords. Beautifully finished and 19/- perfect workmanshipthroughout. Un- doubtedly the very best value for money obtainable. 210 As above, but fitted with double imitation 4,000 6d. tortoiseshell headbands.Particularly suit- 22/- able for ladies. The French Thomson -Houston Phone. 212 As No. 250 but wound to a total resistance of 8,000 6d. 8,000 ohms. 24/- READ THIS.-Have you a Crystal Set? If so you cannot afford to be without one of our " Eccentro " Detectors. A real novelty in Detectors (vide " Amateur Wireless ").It is Semi -automatic Dust -proof, Shock- proof and a temper saver.IT NEVER FAILS. NOTE.-This is not the " Hit and Miss " Type, it is a real piece of Mechanism and something to give entire satisfaction. Our price 8/- Post free. TRADE SUPPLIED AT RIGHT PRICES. FOR W. JOANESPHONES 42, Jenner Rd., Stoke Newington, London, N.16 [Phone :Dalston 4741. Telegrams :" Creneva, Stoke, London."

To getthe BestResults fromyourS.T.100 and " All -Concert," you mustuse MAGNUM TAPPED COILS, designed especially for use with all experimental circuits. R.E.C. No. 1 Coil, 180-1,000 metres 15/6 (BRITISH) No. 2 Coil, 600-2,600 metres 17/6 Post free Cash with Order. The Pleasure and Romance of Wireless is unbounded when " Listening " on a Set of your own construction, but- WirelessApparatus MAGNUM COMPONENTS ARE ESSENTIAL. MAGNUM COMPONENTSfor the Greatly Reduced Prices TRANSATLANTIC RECEIVER as described in this issue. £ s.d. Rotary Filament Resistance 046 Dubilier H.T. Condenser... 07 6 R E.C. Telephones Dubilier Grid Leak and Con- denser ...... 050 Dubilier Fixed Condenser .002030 R.E.C. CrystalSets VariableCondenser.0005, with scale and knob ... 080 R.E.C. Amplifiers 1111771104Nmais Du al Condenser .00025 ...1 17 6 Potentiometer ...... 09 6 Patent H.F. Transformer... each04 6 R.E.C. Valve Sets applied for Terminals (lacquered) 002 Valve Clips...... per set 0 1 0 Valve Legs...... each 00 1 V 24 Valves...... 1 4 0 SPECIAL EXHIBITION. Q.X. Valves 1 4 0 Magnum No. 1 Aerial Coil ...... 0 15 6 Call at our Showrooms and see for yourself Ebonite, i in. thick ...... per lb. 040 MAGNUM COMPONENTS for " ALL -CONCERT " NOTE theremarkable value weareoffering. MAGNIFIER. Magnum Transformer ...... 0 Filament Resistance, with scale ...... 02 6 Terminals. (lacquered) ...... each 002 Valve Legs, mounted on Ebonite ...... 0 1 2 THE RADIO EQUIPMENT CO.LTD., Ebonite Bushes and Discs ...... each 002 Cali with order.Carriage Paid on Orders for 82 or over. Officesand Showrooms : Bank Chambers, 329, HIGH HOLBiRN, LONDON W.C.1 BURNS -JONES & Co., Ltd., RMad ouEngin ne s , Telephone: Telegrams: MONTFORD PLACE, KENNINGTON ROAD, LONDON, S.E. 11. Holborn raag. " Exportation, Holb, London.'-' 'Phone :Hop 6257.

xl November, 1923 MODERN WIRELESS Build this Splendid 1 -Valve Reflex Set -British throughout, conformstoall the P.M.G.'s Regulations. Constructor'sLicencewillnow 1UEenable new you to build any Set, provided-. 1. That you use British components. 2.That the Set does not cause interference. You cannot do better than build this splendid one -Valve Reflex Set, which will enable you to pick up every B.B.C. station at any time. You can add a Peto-Scott Amplifier when you wish to use a Loud Speaker. Remember this Set gives you the equivalent of practically three Valves at the cost of only one.Send for a set of parts to -day and start building it up. Complete Set of Parts Ebonite Panel, in.; thick, engraved, drilled,. and tapped.Polished Cabinet to fit. VariableI Condenser.00x assembled ;ditto.0002I (in parts for assemb-I Something New ! ling) ;one MAX -AMP I Transformer ; Rheo- stat, two Utility; Self -recuperative Batteries switches, Series -par- g Our latestintroduction-interestingtestsin allelSwitch,Crystal; our own workshops have proved that these new Detector, two Coil Batteries will outlast at least three of the large Holders, Valve Sockets, Dry Batteries usually recommended for use with allterminals, screws,; Dull -Emitter Valves. insulating sleevine,&c.,; Each battery gives1.5 andfull volts per cell and continuous output of .5 amps instructions, for a period of 4 /5 hours. Last for months without10/6 inclusive of all royaltiesi any attention-a boon to country dwellers, as four in series can be used with the ordinary type each. ---£4 12 6 of Valve. Head Office 5 64, HIGHHOLBORN, w.c.1 Branches : 99, High Holborn, W.C. r.3, Wellington St., Strand, W.C. 2; Peto-Scott Co., Ltd., Cardiff :94, Queen St. Liverpool :4, Manchester St. BUY SCHEFFPUBLICITYORGANISATION and 125, PALL MALL, LONDON, S.W.1 -== BUILD =- are Advertisement Managers for your sets from MODERN WIRELESS BROWN'S of Manchester A few good lines to be going on with. WIRELESS WEEKLY SingleEarpieces(completewithCord)2,000 ohms6/- r; n 4,000 ohms7 /- Particulars on application of RATES DOUBLE Headphones(Frenchmake) 4,000 ohms 16/ - for both publications. (French Thomson -Houston imitation TortoiseshellBands) 'Phone: Regent 2440 (Two Lines).

4,000 ohms 22/.. g11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111

(Sterling Type, R 126o) 4,000 ohms 25 It ( I, R 5238) 4,000 ohms42 /_

(Brown's Featherweight) 4,000 ohms 25 /_ 0 T - " D " Type) 4,000 ohms 52 /- RECRPTION ON Loop 'TURRET' Crystal Detectors (on Ebonite Base) 2/- Colfirob'an Pt (Enclosed) .. .. - 216 Pine Masts

(Perikon) . ,, .. 4/9 il Howto fix an Variometers, Panel Mounting .. 9/- &7/6each T efficient 100 -ft. " Sterling Type" Aerial in a 30 -ft. 11 .. 21/ - garden. All IGRANIC Components Stocked. 100 -ft. Aerial with Insulators, Slings,etc.,7/9 ACCUMULATORS. All sizes in stock. We also charge and EJECTIO,N-ONCAPACITY AERIAL repair same.Everything for the wireless enthusiast. too *LOOP sac RECEPTION I II 1:3. a%'13let/ei.17 Call and see us to discuss your wireless problems.Send P.C. for 9 iP 36 -ft. - 79/6 list.Postage free on orders of 301- and over in U.K. I k:* 42 -ft. Telescopic -"Th ''---' 41 .15rk _ 891 6 BROWN & CO., ,i=zAt____.------i 56 -ft. do. 96 18 8 Electrical a d Radio Engineers, 13 ft. Roof 17, Newton St., Piccadilly; & 4a, Withy Grove, Masts, :8/6 Manchester. 13 -ft. Poles, 5/9 'Phone : City 6912 and Cent. 5443. SIMPSON & BLYTHE, 8-9, Sherwood St., Piccadilly, W.I.2651'0117X ,:',.,1 xli MODERN TVIR.ELESS November, 1923 Published Nov.8th. Twelve tested Wireless Sets

Mr. Harris's latest and best constructional Book.. By P. W. Harris Assistant Editor of "Modern Wireless."

Shows you how to build all these AnewBook by the ReceivingSets : master designer of i.A 2 /6 Crystal Set. 2.A Crystal Set on a home -built Sets New Principle. 3. A. single Valve Mag- PROBABLY no writer of Books and Articles nifier. dealing with the constructionalside of 4.A 2 -Valve Magnifier. Wireless is more popular than Percy W. 5.A Simple2 -Valve Harris. Receiver. 6.A 2 -Valve Cabinet The reasons for this may be two -fold.Firstly Set. that he takes extraordinary pains to make every 7. An" OldFolks ". detail clear and intelligible to even the veriest Receiver. novice, and secondly, that the Inst . einents he 8.A 3 -Valve " All describes, although refreshingly original in design, Concert "Receiver. give extraordinarily gocd results. 9.A " Transatlantic " No purchaser of this Book need be afraid that Receiver. so.A 3 -Valve Reinartz he does not possess sufficient skillto build a Set. Wireless Receiving Set or that elaborate tools xi.An S.T. roe Set for are necessary.If he has sufficient patience to the beginner. follow clear diagrams and explanations, and if he 12. Wavetraps in can use a small saw, a file and a drill, then success various forms. is assured:

Published by RADIO PRESS LTD., 2 FromallBook- De vereux Court, STRAND, W.C.2, sellers and News- agentsor as.3d. post free. abio puss *airs 00. 14. November, 1923 MODERN WIRELESS

Regd. Manufacture of Broadcasting Apparatus. omolnimmoidour SET, W:RELESS ?tie o/ Patentel. Constructional THE pioneer work of the Marconi Company in con- Receiving Set. nection with wireless telegraphy and telephony is well-known, and as the result of many. years of British Made. research work and considerable expenditure, the Company PHENOMENAL RESULTS! controls numerous patents relating to the manfuacture WillreceiveSignalsand or use of wireless telegraph and telephone apparatus. Broadcasting Entertainments as loudly and clearly as most The Company is prepared to grant a licence for the use expensive Crystal Sets. of its patents in connection with the manufacture of Can easily be constructed in broadcasting apparatus to any member of the British a few minutes. Broadcasting Company, Limited. No Tools or Technical Know- ledge required. A large number of firms (including the principalmanu- Complete Set of Parts, in- facturers)are already so licensed and pay royalty for the cluding "Sonyte"Crystal, use of these patents, and all apparatus manufactured packedinattractivebox, under licence is so marked. with illustrated diagram of Any person or firms manufacturing or offering for sale Instructions, valveapparatus embodyingpatentscontrolledby 5/5.Post3d. We also supply the Set ready Marconi's Wireless Telegraph Company, Ltd., without its constructed.Price, including permission render themselves liable to legal proceedings B.B.C. Fee,7/6.Post3d. for infringement. The " Claristal " Aerial Set, comprising : zoo ft.Aerial Whilst hoping that it will not be forced to take legal Wire, 6 Insulators, Leading - proceedings the Marconi Company wishes to give notice in Tube, and 3 yds. Insulated of its intention to protect its own interests and those of Wire,3/6.Post13d. its licensees, and in case of infringero.nt the Company Double Head Receivers, British Made, 4,000 ohms, will be reluctantly compelled to take such steps as may 17/6,post free. be necessary to defend its patent rights. Single Head Receivers, 2,000 ohms,9.-6,post free. The UNIVERSAL Complete withCords and Marconi's Wireless Telegraphic Co., Ltd., ELECTRIC SUPPLY Co., Ltd. stamped B.B.C. 4 BROVI N STREET, Fully Illustrated Radio I Marconi House, Strand, London, W.C.2. MANCHESTER. Catalogue postfree oil l request. l ESTABLISHED 1892. Box No. G.P.O. 519

"DUANODE" CONDENSER " As good asthe best', Realisingthediffi- cultyoftuninga circuit in which two stages of tuned anode H.F.Amplification isused,we have designed the " DUA- NODE " Condenser, as illustrated.This Condenser consists ofTWO matched Condensers operated by one knob.Thus by using matched To allExperimenters COILS it is possible to tune BOTH circuits perfectly with the ideal tool for all-round utility, one operation only. wide scope and genuine worth is the The two sets of fixed

Vanes arecarefully insulated one from the other, and the moving Vanes connected electrically ;the DRUMMOND 4 -in. Universal Lathe - spindle can thus be connected to H.T. PositiVe.This condenser can also be used for other purposes. Besides all turning andsct"ew-cutting,this lathe, with its circular The two halves (each of .0002 mfd.) can be used in series or.1, parallel, giving capacities of .000r, 0002 and .0004. Price , theslotted bed, sliding saddle with slotted face, and and For "FALLON " COMPONENTS seeour advertisements in " Wireless World," swivelling -topslide, enables thousands ofmilling,drilling, " Amateur Wireless " and " Popidar Wireless " every week.. - boring and facing jobs to be performed speedily and g 9 we are Exhibiting at the All -British Wireless Exhibition (Stand No. 11), White accurately. Ourlists give full details.Price only City,Nov. 8th -21st. REPUTATION.-Yourcomponent is not a " FALLON " unless thename " FALLON " appears on same. DRUMMOND BROS. LTD. MUM Our motto isQUALITY FIRST, andevery article carriesocr money back- guarantee. AllBRITISHManufacture.Prompt Delivery. Post this Coupon - Cash with order.Please include postage on each article. ------THE COIL ENSER P:OPLE, Please send me listNa...... FALLON of 4 -in. lathe, with 230a, Hermitage Road, London, N. 4. details of deferred 'Phone : Tottenham 1932. payment system. Address Londion Agents :-Vanstones, Ltd., 61, Chandos Street, London. W.C.2 Sole Trade Distributors:-Messrs. G. W. I., Ltd., Shanklin Road, Crouch End, (Send in unsealed London, N.8,to whom all Trade Enquiries should be sent. envelopefor (td.) FALLON00VDENSER MANUFAOTURING CO., L

X.111 MODERN WIRELESS November, 1923

A cheerful A fire-

a cosychair and frIRIMPRIMMINIMA

,74 Iplum lllllllllll maim Iii,lida "the finest weekly Radio Magazine ever produced." WITH a very wide rangeof Wire- lesspublicationsnowbeing issued, you may be interested to ask, " What sort of a Magazine is Wire- less Weekly, and who buys it ? Radio Press, Ltd.-its publishers-are PwWici actuated by much the same motives as the builders of a superfine car, who Crli"ier jr1 persistently, and often in the face of V I I 41 Rill great difficulties, refusetoproduce AMP, t anything but the best. Their aim isto publish a Weekly Magazine worthy of the best type of Wireless experimenter.They realise that although Radio may not be an Published every Wednesday, and intellectualpursuit,ithas always sold by all attracted, and is still attracting, some Newsagents. of the keenest brains in the country. To -day the fascination of wireless is EDITORIAL STAFF. complete.Fromthebigbusiness Editor. man to the butcher's boy-all are JOHN SCOTT-TAGGART, F.Inst.P. imbued with the keenest desire to Assistant Editors. know more of its mysteries. E. REDPATH. P. W. HARRIS. frankly, Wireless Weekly is Scientific Adviser. Quite PROF. G. W. 0. HOWE, D.Sc., M.I.E.E. intended to appeal to those able to Advisory Editors. appreciate a really first-class weekly PROF. R. WHIDDINGTON, MA., D.Sc. publication-to those with a sense of PROP. C. L. FORTESCUE, M.A., M.I.E.E. discriminationand proportion-and Staff Editors. as such it carries a great amount of E. H. CHAPMAN, M.A., D.Sc.G. P. KENDALL, B.Sc.. prestige and importance. "and more than A. D. COWPER, M.Sc. R. W. HALLOWS, M.A. worth it 1" S. G. RATTER. If you desire to he kept up-to-date and to obtain a worth -while opinion on the Radio problems of the day, then see to RADIO PRESS, LTD., DEVEREUX COURT, STRAND, W.C. it that you are a regular reader. aaModern

sliv November, 1923 MODERN WIRELESS

Constructional Articlesreally up-to-the-minute!

The development of the reflex Circuit as far as its popularity among amateurs is concerned dates from the announcement of the very successful S.T. 100 Circuit. The fullest details of this Circuit, together with constructional Articles oil how to build up different types of Sets incorporating its principles, have been given in Wireless Week! y. Obviously a weekly Radio paper-if its editorial staffis live-always has the advantage over a monthly magazine in the matter of speedy information on new ideas.The aim and purpose of Wireless Weekly- has always been to present to its readers the fullest details of every development in Wireless as quickly as possible. The new Flevelling Circuit is a typical example.Here -is a super -sensitive one - valve Receiver-almost absurdinits extremesimplicity-yethundredsof reader have builtit up and are getting extraordinary resUlts from it. Mr. Flewelling wrote his article expressly for the benefit of readersofVI irelcss Weekly. The Magazine Remember this point, too : the Editorial 5you'llliketo Staff of Wireless Weekly are Wireless tell your friends Experimenters to a man, and with such you read. experts" asIotIn Scott -Taggart, F.Inst.P., E. Rapath, and Percy Harris writing exclusively for Radio Press publications, you cannot afford to miss the results of their contributions to the science of Radio. Wireless"

Gilbert.1d. MODERN WIRELESS November, 1923 Index to Advertisers PAGE PAGE A.P.A.I.L. .. Junior Wireless43 Formo Co. Mallard Radi 1 Valve Co. Ltd. Auto veyors Ltd. iv Fuller's United Elec. Works, Ltd. (Facing matter) .. .. xi Ball (T.C.) .. Junior Wireless43 Gambrell Bros., Ltd. . New London Electron Works.. xxx Bell Wireless Co.,Junior Wireless45 General Electric Co., Ltd. (Facing Peto-Scott Ca., Ltd. (The) Bowyer -Lowe Co. xli and Junior Wireless 45 xvii matter) Boys (P.IL) & Co., Ltd. .. xxiv General Wireless Ltd.. Premier Telephone Co... .. xxix British Battery Co., Ltd. (The)xxxiv George Mfg. Co... Radio Communication Co., Ltd. xvi British Thomson -Houston Co., Ltd. xxxvii Grafton Electric Co. Radio Equipment Co. .. .. xl Brown Bros. . Radio Instruments, Ltd. .. Cover iv .. Griffin's Brown & Co. .. xli Radions, Ltd... .. xxvi Burndept, Ltd. .. . xxi Holborn Radio Co. xvii Radio Stocks, Ltd. .. xxxii Burne-Jones,.. Ltd. xr H.T.C. Electrical Co. - iv Raymond (M.).. .. vi,vii Buss (T.0.) .. . xx Igranie Electric Co., Ltd. xv Robinson, Lionel & Co. xii, xxix Chloride Elee. Storage Co. xxv International Radio Mfrs. xxiv Rowley & Louis .. .. xxxix .. Scientific Supply Stores' Clarke (H.) & Co. (Manchester), Ltd. xxxi Jackson Bros... xxxiii .. xxxv Climax Patents Ltd. (Facing matter) xiv Joanes, W. .. xl Siemens Bros. & Co., Ltd. .. v Cossor Valve Co. .. xxvii - Silvertown Co...... xxiii Jones, J. B. Junior Wireless 43 Simpson & Blythe .. xli Dixon (Leslie) & Co... xlvi Laker (John & James) Co. .. xlvi Slider (G. W.)...... xlvi Drummond Bros. .. .. xliii Leigh Bros. .. xxxviii Dubilier Condenser Co. (1921), Ltd. Sterling Telephone and Electric Lissen Co. Co., Ltd...... v (Facing matter) . xiii Livingston J. ..Junior Wireless43 Tingey Wireless; Ltd. (Facing Elkay Wireless Co. .. .. xxviii London Radio College, Junior Wireless 45 matter) xii Ever Ready Co. (Gt. Brit.), Ltd.xxix MacDonald. J., & Co... xxxiv Turnock's Telephone Works.. xxxv Falk, Stadehnann & Co., Ltd. xxxvii Marconi Wireless Telegraph Co., Ltd. xliii Universal Electric Co., Ltd... xliii Fallon Condenser Co... xliii Melhuish (Rd.).. xxxii Webber, N. V...... xvii Fellows Magneto Co., Ltd. (Facing Metropolitan -Vickers Elee. Co. Ltd. -xix Western Electric Co., Ltd. .. Utter ii

matter) xiii M. L. Magneto Syndicate .. xxxix NVIllesford ..Junior Wireless45

WALKERS' WIRELESS EDINBURGH. Hold the largest variety of wireless appara- Geo. Wilkinson, WirelessSpecialist, 152, Spensers (Scotland), Ltd., 119, George St.. tus in the North.Send for particulars. Church Street, Preston (onoositeMiller Edinburgh.Agents for Burndept. Ltd. 31. Westgate Road. Newcastle -on -Tyne. Arcade).Supplies and Service.

For perfect tuning use the G. W. SLIDER. -LAKER" STEEL " EIFFEL'TOWER " MASTS. You cannot tune a coil induct- (Trade Mark) Reg. Des. 694837. ance correctly without it.Made MASTS. Tinhaeds:sec- W I L K I N S O N.Lonsdale Road, in nickel ed brass. All first -etas. dealersstoatit,ora sample tional steel masts are Write for Lists. Kilburn, N.W.6. will be sent to your deer for built for Service. The your inspection.A_sk to see If steel tubing is of large Price 1/- or postfree1 3.From diameter (ainches) 1,3!'r &James Laker, t, Rom ford Rd... London. 6.7 having a big margin Are of reservestrength. POST PA ID WIRELESS MATERIALS. "Laker"Mastsare Brown'sType A New Ex Govt. 120 ohm. WIRELESS INVENTORS. easily assembled and Headphones, 25s.60 volt H.T. Battery 6s. Advice Handbook on Patents and Trade erected ;they present Complete Price List Free.-J. H. TAYLOR Marks. Consultationsfree.-B.T. King, a handsome appear - & Co., Macaulay Street, Hudtiersfleld. Regd. Patent Agent, 146a, Queen Victoria an= whensetup. St., E. C.4. Phone: Central 682.38 yrs. refs. Prices,withacces- sories painted green, readyfurerection. SCMERS-c.T. EDINBURGH. 2511, 35i-; 30ft. 42V-; 35ft. A. A. TURNEY, Mid",te !irythorn, Streete, Wm. Sinclair, 60-64, Thistle St" Edinburgh, 62.6;90ft. 63 -. 95ft. 78, - Eomer.et.Wireless Engineer, 1912-19,_3. All component parts in stock atlowes-t, JOHN JAMES LAKER, Engineers, -Exp-rience toilets !Portable Set visits prices. 457. Roma° d Road. London, E. anywhere on request.

=.,.11,,,,,,,,,m,.._, USE THIS C(.'UPON = F. in writing to advertisers in "Modern Wireless." = COUPON = CUT HERE Questions and Answers ;9 ...... =E. In future this coupon must be accompanied with2/6P.O. ..F In connection with your announcement in MODERN g:- " MODERN WIRELESS" November, 1923.E: WIRELESS, please supply me with : 41111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111110

Enclosed please find remittance of EL t CTRADIX RADIOMETERS. (Leave blank it not au order) Wavemeters rom to 102000 metres. From £2 10 0. New Ex. W.D- If an open envelope is used in applying for catalogues a half- Milliameters for Fine Tuning 17/6 to 35t-. penny stamp will cover postage. Voltmeters, Panel and Portable, a volts to 2,50o volts, 5/- to £5. Recorders.Wireless Morse Inkers make long wave reception interesting.£6100. Name Motor Alternators.Wonderful 43o machines for £3.Ex. Aircraft. Potentiometers. Army 350 ohm 3/6. For details see " Wireless World" or our 3d. Catalogue. Address We have many thousand pounds' worth of the pick of Government Wireless gear displayed at our London Showrooms at 9,Colonial Avanue, Minories (near Aldgate Station), LESLIE DIXON & CO. Ave. 41 . Date xlvi