40.4**-- selpik sop.oar 04 TFy teTh, es"fez s r\to1 MONTHLY 40 %* tit 141.04 lob 4ff-11%cl(MIN tortoirtN eroPOforviterioN" orarNter1/4", ei411\ Nklogp to%%01 44- IhOt 10# %141.°Iles Slid f Vol. III. JANUARY. 1927 No 3 baw . 6*. SPECIAL DOUBLE NUMBER PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor WIRELESS1041100in* CONSTRUCTOR January, 1927 O -1,11,14o4v sto WRITE NOW for your copy of the. complete N.P.L. Report giving irrefutable proof of the value and merits of Mullard P.M. Valves with the wonderful P.M. Filament. Full valve guide and instructions to secure better results from your radio. An opportunity that should not be missed by any radio valve user. 1. .99ts- The ciT4 Mullard Wireless cpX3V Service Co., Ltd. Milliard House. Denmark St. 1C\-5 London, W.C.2 rC Please send me a copy of you, N.P.L. I Mullard AVA Brochure and Valve Guide giving me full par - THEMASTER. VALVE titulars why valves with the wonderful P.M. Filament will improve my radio receiver. THE RADIO VALVE WITH A PUBLISHED I m NATIONAL PHYSICAL LABORATORY TES Add ess ADVT. 1HE MULLARD WIRELESS SERVICECO., LTD., MULLARD HOUSE, DENMARX STREET,LOND:N,W.C.2 ii PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR IRELE' S ONSTRUCTOR, CONTENTS A Selective Three .. 183 Listen to America Direct ByJ.H.REYNER,B.Sc. (Hons.), A.M.I.E.E. By A. V. D.HORT.B.A. How Wireless Components are Made. Sets That You Can Build .. .. 241 No. 2 189 Things Every Operator Should Kncw ..243 By CaptainJACK FROST,M.I.R.E. By G. P.KENDALL,B.Sc. How to Make Your Own Screened Coils191 How to Use a Wavemeter 247 All Round Europe with Plug-in Coils ..193 By J. H.REYNER,B.SC.(Hops), By C. P.ALLINSON,A.M.I.R.E. Choose Your Own Circuit .. ..252 Mr. Gumplethorpe's Christmas Party201 ByBRIAN ST. CLAIR, Making Use of Your Supply Mains..207 Operating the "All -British Six'..' Workshop Hints .. 257 The " Economical Two " Further Notes on the "Night Hawk" 263 By W. Q.KAY. Some Solutionsto Your Superhet Are You Satisfied With Your Set? 223 Puzzles 265 By L. H.THOMAS By JOHN HNDERDOWN. Loud -Speaker and Receiver in One 226 An Experimenter's Base -Board 273 The Radio Play of the Future.. 233 By H.BRAMFORD. ByMADGE TITHERADGE. Apparatus Tested.. 280 On the inside-the business side-as well as on the outside of the panel, fit " Utility " Components.This is the " Utility " Micro - Dial that isusually fitted by thepeople who" know."The " UtilityMicro -Dial begins where other dials finish.The best adjustment with n ordinary dial is the preliminary movement of the " Utility," in which slow motion mechanism gives the finest possible tuning after the dial has provided coarse adjustment. Unlimited movement. No backlashCan be fitted to all makes of Condensers. Insist upon " Utility" Micro -Dial ; No -Capacity Change -Over Switch; Low Loss Condenser Jack and Plug; Push Pull Switch-All good dealers stock them. COMPONENT./ "Utility " Condenser. Price .0005 IV - WILKINS &WRIGHTLT! Price .0003 14/ - when fitted with KENYON ST. BIRMINGHAM this Micro -Dial. 611:11111M111111 osa A In replying to advertisers, please mention THE WIRELESS CONSTRUCTOR., 181, PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 A t> v 4.V.AYA,VAVAVAVAVACreWiNre7Gat)(I° 6 ev47 The Truth About the Tests. vs Not only do S.T. valves represent the highest le el of Ith, vale design and manufacture to -day, but whenever .41'.* or wherever you get an S.T. you know that that AT particular -valve has been app oved by John Scott- z1,1 Taggart, F.inst.P., A.M.I.E.E. V, 1> You take your package home, knowingithas ,..4 actvally been in his own hands, and it is almost as if P., Scott. aggart himself wereaanding. by you, con- 44 fidently waiting for your set to spring Into new life as you put his p c. ed valves into your set.if it so rids g., D too good to be true, read the following Stat itory ,.....1 Declaration made before a Commissions for Oaths : V, .14 STATUTORYDECLARATION. , I, JOHN SLOTT-TAGGART, ca 2, Melbourne Place, in IQ! I;0' the County of London, do solemnly and sincerely declare V.V., 4 that: , .14 (x)I am the Managing and TechnicalDirectorof 17,, S.T.Limited and am responsible for the maintenance :.c1 of the high standard of S.T. valves. VA (2)The test department is under my immediate control, ,VI and every S.T. valve is given a number of tests li& which include a factory test, a laboratory test, in 3 N which a minimum of nine electrical measurements V > are taken with precision meters, a test in a receiver p on broadcasting, and a final laboratory test identical PI, Ct to the previous one in which the same nine or more .1? .(41 measurements ,are taken by a different technical gi Al.? assistant. (3)Only those valves which pass all four independent N WA tests are sold, and after I have satisfied myself that ...4 a valve is within this specification, it is packed in a I> carton bearing a certificate containing a white space < ,._v4 on which I sign my initials. I> D (4) No single valve has been issued by S.T. Limited ...41 which has not passed the required tests, and every ,t V, carton bears my initials which, without exception, s .,,, have been affixed with my own hand and pen. 9, And I make this solemn declaration conscientiously _all Q',4 believing the same to be true and by virtue ofthe tt Provisions of the Statutory Declarations Act of 1835. 5 P", SI r04%/SCO'l V, ...1" , 11c!, 4 Declared at so, Norfolk Street, Strand, S :4 in the County of London, this 19th'day , ,Z.I of November, 1926, before me, ,,,C1 VA P, Litl )i.a.19C. L.det ) fi-nztj L'I' V, V ',..1 A Commissioner for Oaths. 4 TYPES AND PRICES. I> 1:),4 2 VOLT. 41 Co I> S.T. 21(H.F.) . 0.1 amp. .. ......141. ..,,, S.T. 22 (L.F. and 0.1 amp. .. 141. 4 li:* 4_ S.T. 23 (Power). 0.15 amp...........18/6 4 11 ST. 41 (H.F. and DVIT.0.1 amp...14/- t>, Q S.T. 42 (Power) ..0.I amp. .. 18/6 ,9 1:11. S.T. 43 (Super Power)0.25 amp... 22/6 V' 6 VOLT. 4 S.T. 61 (H.F. and Det.) 0.1 amp...18/6 trt. S.T. 62 (Power) ..0.1 amp... -16/6 S.T. 63 (Super Power) .0.25 amp... 22/6 0' 182 In replying to advertisers, please mention THE WIRELESS CONSTRUCTOR. PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR Published by The Amalgamated Press (1922), Ltd., The Fleetway House, Farringdon Street, E.C.4. A SELECTIVE THREE By J. H. REYNER B.Sc. (Hons.), A.M.I.E.E. Here is the set to build for this Christmas!The construction is simple, the coils you can make up yourself, the set is easy_ to operate and you can expect excellent results from its up-to-date circuit and design. THERE are many readers nowadays apart from the copper screening cases increaseinefficiency over the usual who wish to avail themselves of which are now so familiar. arrangement, with the result that a the latest developments in high - very selectivereceiver is obtained. - frequency amplification, but who Home -Made Transformers The circuit used for the receiver in preferifpossible to make up their In the present set a more or less questionisa standard split -primary own high -frequency transformers. standard circuit has been utilised, but arrangement. An ordinary auto - Recent improvements have been con- special home -constructed transformers coupledaerialcircuitis utilisedto fined principallytothe production have been made for the benefit of apply the signals to the grid of the and standardisation of various types those readers who prefer actually to first high -frequency valve.The anode of plug-in high -frequency transformers constructtheir own apparatus.At circuit of this valve istransformer - made to fit a standard 6 -pin base, so the same time, by winding thecoils coupled to the grid of the detector that they may be used either inside or specially,itispossible to obtain an valve, the secondary of the tranformer 183 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 A Selective Three-continued being tuned. The primary is wound in neutralisethereceivercorrectlyin two sections, one being the primary the manner described later, when no BUILD THIS SET WITH: proper and the other the neutralising danger from this trouble will arise. One ebonite panel, 21 in. by 7 in. by section. Aerial Coil Winding One suitable cabinet, with baseboard, A Popular Arrangement The first operation in the construc- Siin. deep.(Peto-Scott Co., Ltd) A straightforward transformer - tion of the receiver is the making up Two .0005 and one .00025 "lateral of the high -frequency transformer and action " variable condensers. (Ripaults.) coupled note -magnifier is included for Two 3i in. and one 2i in. diameter ribbed ebonite formers, each 3 in. long. (Redferns.) TEST REPORT Three valve holders.(Lotus.) Three fixed resistors, to suit valves The following stations were received, all on the loud -speaker, using used.(Peto-Scott Co., Ltd.) an aerial about 60 ft.