Design for a "Quality" Receiver

IS UE'S DESIGN FOR A "QUALITY" RECEIVER

Vol. LITI. No. 12

www.americanradiohistory.com Advertisements írc1cS% World December, 1947

The Research Engineer knows

that the best speaker for any

set is one that offers complete

reliability plus true tonal

fidelity. After exhaustive tests

his advice is always the same

-fit Rola and relax !

BRITISH ROLA LTD 8 UPPER GROSVENOR STREET LONDON W.1

www.americanradiohistory.com December, 1947 Wireless World Advertisements r

The 50 -range Model 7 Universal AvoMeter, the pioneer of the comprehensive range of " Avo " Precision Instruments, is the world's most widely used combination electrical testing instrument. Fully descriptive pamphlet available from the Sole Proprietors and Manufacturers :- THE AUTOMATIC COIL WINDER & ELECTRICAL EQUIPMENT CO., LTD.

- - ICTORIAi404/9 W I N D E R H O J S E D O U G L A S S T R E E T L O N D O N S W T'ELEPHONE. V

www.americanradiohistory.com 2 Advertisements Wireless World December, 19¢7

MARCONI 1Vlastery of 1Vleasirrement is displayed in its unique range of Communications Test Gear

FOR IMMEDIATE DELIVERY .

IMPEDANCE COMPARISON BRIDGE TYPE TF 202E

The instrument is a self- contained A.C. mains Brief Specification: operated bridge for the rapid comparison of Operating Frequency - 10 kc /s; similar capacitors, inductors or resistors and Range - - - L 250p11-1H ; comprises a 10 kc/s oscillator, a bridge network C 20ppF -lµF; and a visual balance- indicating system. It is R 20 ohms-1M ohm ; precision -made to give lasting. reliable service Accuracy - ± 0.2% MARCONI INSTRUMENTS LTD ST. ALBANS, HERTFORDSHIRE Phone: St Albans 6161 5

Office : 30 Northern ALBION STREET, HULL. Hull 16144 Western Office : 10 PORTVIEW ROAD, MONMOUTH, BRISTOL. Avonmouth 438 Southern Office: IC9 EATON SQUARE, LONDON, 5."ß.1 Sloane 8615

VITREOUS RESISTORS FOR EVERY PURPOSE BY PAINTON e CO LTD KII'GSTHORPE NORTHAMPTON

www.americanradiohistory.com December, 1947 Wireless World Advertisements 3

A Spire fitting never leaves go!

To tell the truth there's a bit of artist's licence about our illustration. But it is certainly a fact that if you use Spire for your assembly fixings, they have as much hope of coming adrift as the early worm has of escaping the bird. Much less in fact. For the slim Spire fixing depends, not on weight of metal but on a unique double- spring locking action. Spire fixings are easier and quicker to assemble, hold tighter when

they're on ; and yet they are quite easy to dismantle even after long periods. Sounds a big claim ? We're quite ready to prove it.

* A BETTER way of fixing 1 (Read.)N _- ';- A Spire Fix - the simplest, quickest, firmest and most tolerant form of light assembly. The illustration shows our Spire Fix No. FR337 suitable for use with 1" diameter studs. THAT'S Fixed THAT!

SIMMONDS AEROCESSORIES LIMITED TREFOREST GLAMORGAN

www.americanradiohistory.com 4 Advertisements rYirelrsc 'onId I)e1-euticr, T947

xx x4rk. A new departure 2)114-ete.:644:6n, in OSCILLOSCOPE DESIGN

The L.A.L. UNIT OSCILLOSCOPE presents an . entirely original approach to problems confronting the research engineer and industrial user. Constructed on the Unit principle, we can supply apparatus for every need from D.C. to radio frequencies. Built-in multiple plugs and sockets with mechanical couplers instantaneously complete all electrical circuits and secure a number of Units into a rigid assembly without the use of tools.

We suggest the following representative Units for general investigation.

Type 15. C.R.T. unit 6" tube and self- contained shift supplies.

Type 84. Time Base ; 5- 200,000 cps. with sweep

expansion ; automatic synchronizing ; push -pull

deflection ; single or triggered sweep.

Type 84Y. Amplifier ; gain 25 (cathode follower

input) or 600 ; response level I db 10- IOO,000cps.,

useful at 0.5 Mc. ; push -pull deflection. Also available :- D.C. amplifiers, medium and high gain. Extra low The following area Distributors MIDLANDS frequency time base. Circular or spiral heptode for U.I.C. Silvered Mica and Gothic Electrical Supplies Limited, time base. Voltage calibrator. Ceramic Capacitors, have now 23 -25, Constitution Hill, been appointed to he re- Birmingham 19. quirements of Retailers, Whole- salers and Service Engineers. Fully described in our illustrated leaflets ; EAST ANGLIA Flinders be by of post. NORTHERN IRELAND (Wholesale) Limited, your copies will sent return Eirco Services Limited, 14 -20, St. Peter's Street, Ipswich. 19, Ormeau Avenue, Belfast. LONDON YORKSHIRE & SCOTLAND L.E.S. Distributors Limited, A. C. Farnell Limited, 15 -16, Alfred Place, IS, Park Place, Leeds. Tottenham Court Road, W.C.I. IAL UODUe11bi'cu/e LANCASHIRE & N. CHESHIRE SOUTHERN ENGLAND Hardman & Company Limited, Robshaw Brothers, LYDIATE ASH LABORATORIES The Baum, Yorkshire Street, 10, The Square, Rochdale. Bournemouth. UNITED INSULATOR CO. LTD LYDIATE ASH NR. BROMSGROVE WORCS. Oakcroft Road, Tolworth, Surbiton, Surrey Telephone : Elmbridge 5241 Telegrams : Colonel, Surbiton

www.americanradiohistory.com December, 1947 Wireless World Advertisements 5

DERN MASTERS OF REPRODUCTION

PRESSURE TYPE DRIVING UNITS

EXPONENTIAL HORNS

WAFER SPEAKERS AUDITORIUM LOUD SPEAKERS HERE are speakers that go higher and speakers that go lower : other speakers 50% shallower and 40% lighter; a pickup which can repro- duce up to 20,000 c.p.s. ; another pickup giving moving -coil quality with I volt output; public address speakers for all occasions - designed and made by men with eighteen years' practical experience.

CABINET LOUD SPEAKERS

Write for full technical details -a postcard will do TRU lar O N TRUVOX ENGINEERING CO. LTD., TRUVOX HOUSE, EXHIBITION GROUNDS, WEMBLEY, MIDDLESEX

www.americanradiohistory.com h Adz crhsenacnts Wirele ++ World December, 1947

VIBRATORS FOR RELIABLE REPLACEMENTS Tes ted 104.

ego a'e4i

?-$.4 6-0 e /op C / Entirely British in design and C

construction, and fully approved for O0 th iL Government Service equipment,W.E.Vibrators are ready for all your replacements. They are fitted as standard components by leading radio manufacturers.

WIMBLEDON ENGINEERING C 0 . LTD. GARTH ROAD LOWER MORDEN SURREY TELEPHONE : DERWENT 4814, 5010.

117 Mr 41, 1/1WP11% C.R.C.2

YOUR CHOICE for QUALITY Manufacturers of high quality Broad- cast Receivers and Radiograms designed for Home and the Export Market. The Export Models have fully tropicalised components, achieving unsurpassed short -wave CHAIRSIDE MODEL A450

performance. The housing of this Receiver is unique in that it is contained in a bevelled plate -glass mirror cabinet, fitted to a wrought iron frame- Special dials supplied for any country work finished in Cream enamel. It embodies all the latest technical developments for easy handling, range and clarity of reception, and provides not a PRICES AND FULL PARTICULARS ON REQUEST only first -class radio but an attractive piece of furniture which can replace a Chairside Table and will harmonise with any surroundings.

SYMPHONY MODEL A920 This new Receiver embodies the very latest technique in construction. The cabinet is richly veneered in Walnut with a cross banding of Macassar Ebony. Clearly readable edge -lit dial with an 8 in. traverse magic eye and 2 -gear control. Instant, unerring selection of the required frequency range. Automatic volume control and an I.F. trap are incorporated in the circuit. Sockets are provided for gramophone pick -up and extension speaker.

ALLANDER INDUSTRIES LTD. ALLANDER 48, Avenue St. Bridgeton, Glasgow, Scotland.

www.americanradiohistory.com December, 1947 Wi World Advertisements 7 METALLISED CERAMICS Two new S.P. metallised bushes one at either end of the range

For full information and prices please write 0: STEATITE & PORCELAIN PRODUCTS LTD. STOURPORT -ON- SEVERN, WORCS. Telephone: Stourport Ill. Telegrams: Steatain, Stourport.

SP.42

www.americanradiohistory.com 8 Advertisements Wireless World December, 1947 The "Connoisseur" is proved by trade tests Exhaustive trade tests have substantiated our claims for the "CONNOISSEUR" pick -up. Below we give the response curve to which every "CONNOISSEUR" pick -up is individually tested. Supplies are very limited but we invite trade enquiries to our distributors who will endeavour to meet your requirements.

RESPONSE CURVE (OIIIIO/, Sear PICK -UP

1000

A.F. ATTENUATOR, TYPE I 3 5 8 Frequency Range, zero to 20Kc /s. Input Impedance,

600 ohms. Attenuation, 0 -110 dB in steps of I dB, FREQUENCY ry + I% nominal voltage ratio. LOWER CURVE DIRECT MOM PICK - UP TOP CURVE TRANSFORMER RESISTIVE LOAD SOR 00011 COUPLED I.R ON SEC OF TRANSFORMER Internal Termination of 600 ohms at option. 1. Every " Connoisseur " pick -up is hand Dissipation, 2 tested and passed to ± 2DB of above watts. response curve. 2. Our new type damping material working in gap direct on to armature does not affect bass resonance point. 3. The required downward pressure is 1.1/3 ozs. which has been ac'Eieved without counter -balancing or springs. * DIODE VOLTMETER, 4. Being a constant velocity device Bass compensation is required in the amp- TYPE 281 lifier and alternation of high fre- 0.1 -150 volts, 50 quencies to suit individual recordings. c /s. to 250 Mc /s. 5. Output direct from pickup .1 volt. ± 2% of F.S.D. Stable zero setting. Alternative With transformer coupled .5 volt. model having additional d.c. voltage ranges available.

" . ..R f' :. / ._' w 00, :' .. S F,it,l4 , ..,I.,R., NOR,TOR;L!. llE * HIGH DISSIPATION RESISTANCE BOX, TYPE 1752 0-I meg. in 5 decades. 6 watts per resistor, 60 watts per decade, except last decade which is 20 watts. Accuracy ± 5 °á. Voltage limit 1,000 volts. PRICES ON APPLICATION Apply to :- Albion Electric Stores, 125, Albion Street, d Leeds 1, or to LABORATORIES LTD. Lawton Brothers (Sales) Ltd., Henry Square, )ueiíi Ashton- -Lyne. under BOREHAM WOOD, HERTS Made by : A. R. SUGDEN AND CO. TELEPHONE. ELSTREE 1 177 (ENGINEERS) LTD., BRIGHOUSE, YORKS.

www.americanradiohistory.com llCre'rrtlee'r, le!-E, rel"S Norld I rl, v'rfie'me'nls

---fa1ifi e r designers

output. Triode of Tetrode) or (or beam the popularity pentode h sensitivity for hg ode) hasKT61, grown' are the demand beam type With Pentode (or articular outputoutp dwher P sensitivity an to se themmaximum withw M output where larg terrone widely used - a largercomoining high therefore Type KT6b in re fable reqrequired. unsurpassed along is rids - is and aligned g power with large umtrating triode output sensitivity at maxim uang. ce, performance hie impedance, life ho edemand ofquality,its lower as those because es For referrare heated the anditnotponly directly wide demand, wiring ase in for pX4 and 0X25 suitable of the also eminently to KT66 characteristics cathode. tetrio e giving volt indirect) a triode, with PX25, but

Il r'7'erV case.

CATHOnE RAY TußE`>

The Genera! tlectric Co., Ltd , Matnet House, Kingsway, W.C.I.

www.americanradiohistory.com . tyIr iu Advertisements Wireless World Llecertehrr H. T. REGT F ERS for broadcast receivers A range of rectifiers is now available which will meet manufacturers' general requirements for broadcast radio receivers. These units are very much smaller in bulk and weight, have a high efficiency and good regulation.

Overall dimensions Output Max. input Type Volts Volts mA Length Width Height 14A118 600 120 275 4- 2; 2f 14A79 400 120 210 3{ 21 24 14A79 400 75 210 3, 24 21 14A59 300 75 170 214 2f21 4A79* 245 120 250 31 2 2- 14A46* 270 60 250 2a 211 21 15846* 270 30 250 11b 11 1¡ 5D28í 120 20 108 119, 25/32

* For AC /DC receivers. t For battery eliminators. Write for full details to Dept. W.W., WESTINGHOUSE BRAKE & SIGNAL CO. LTD., 82 York Way, King's Cross, London, N. wfsTIl

(RADIO IN EVERY ROOM

with these NEW & BETTER EXTENSION SPEAKERS Are you enjoying the pleasure and convenience of having your radio instantly available in any room? These moderately priced Stentorian extension speakers, acoustic- with their handsome SENIOR MODEL ally designed wooden cabinets, Type SC with Universal Transtormer £5.15.6 SX minus , £5.2.6 give such superb quality of JUNIOR MODEL reproduction that you will be with Universal Transformer £5.0.0 Type J £4.10.6 amazed at the difference a , JX minus makes to your CADET MODEL Stentorian Type O. with Universal Transformer £4.10.0 receiver. CX minus £4.0.0 Other Cabinet models available from 3916 Ask your dealer for a demonstration.

SlenloiianSET THE FINEST EXTRA SPEAKER FOR ANY MANSFIELD, NOTTS. WHITELEY ELECTRICAL RADIO CO. LTD.,

www.americanradiohistory.com December, 1947 Wireless World 1 dvert:sements iI

Because only with a solder wire having more than one core of flux can you be sure that the flux is always present. The 3 cores of Ersin Multicore Solder are filled with Ersin -the extra active non -corrosive flux. Only Ersin Multicore Solder can guarantee you freedom from dry joints, elimination of waste, rapid melting and speedy soldering. Write for technical information and free samples to Multicore Solders Ltd., Mellier House, Albemarle Street, London, W.1 or phone REGent 1411 (P.B.X. 4 lines).

www.americanradiohistory.com ' Lleceml7er, 1947 12 Advertisements N'irPlrsc World

We believe that the only way to build a receiver is to begin at the beginning with a sound circuit design -a design that's been tested and re- tested -a design that will stand up to the most critical examination. From this design a prototype is constructed in which every component receives the some rigorous testing. We leave the experts to pass judgment on the resulting Sobell receivers. We are confident that for ease of control and absolute fidelity of reproduction these models will be found to have no equals -that, in fact, you will pronounce them to be technically outstanding'.

Roll top gives easy access to gramophone turntable. The receiver is a 5 -valve super -het. operating from 200 /250 volts, 40 /100 cycles per second A.C. supply. Wave range : 16 -5o metres; 193 -577 metres; 800 -z, 140 metres.

SO BELL MODEL 717 7 -VA LV E RECEIVER

Built with a push -pull output stage giving 8 watts 'undistorted output. Incorporates a to loudspeaker. Covers long, medium and two short wave ranges. Voltages as for 516 T.G.

RADIO THE S. S. WHITE COMPANY BRITANNIA WORKS

ST. PANCRAS WA" - CAMDE" 11OWN LONDON N.W.I. WESDO, PHONE, LONDON Cable Address : WHICODENT&

Telephone : EUSTON 4758 -4759

TWO YEARS' FREE ALL -IN SERVICE IN THE HOME Notiert Sharp It ewers mvt. of Sobell Industries Ltd., Langley Park, near Slough, Bucks.

www.americanradiohistory.com December, 2947 Wireless World Advertisements 13 PREMIER RADIO COMPANY MORRIS & CO. (RADIO) LTD. ALL POST ORDERS to 167 LOWER CLAPTON RD., LONDON, E.S. 'Phone : Amherst 4723. ALL CALLERS to 169 FLEET STREET, LONDON, E.C.4. 'Phone : Central 2833. Terms of Business : Cash with order or C.O.D. over £1. Send 212d stamp for new Nov. 1947 list. RADIOGRAM CABINETS MIDGET RADIO KITS PREMIER PEDESTAL PLAYING DESKS

MIDGET RADIO HIT. Build your o. a midget radio. A complete cet of paris, including valves. loudspeaker and instructions. In fact, everything except cabinet, necessary to build 4.valve Medium and long Wave T.R.F. radio operating on 200 -250 v- mains, A/C or D /C. Valve line -up, 6117, 6J7, 25A6, 25Y5. Wavelength, covered 200.557 and 700- 2,000. Size 10 x 6 x 61n. Com- pletely drilled chassis. Price, including tax, £7 7s. 6d. SUPERHET MIDGET RADIO KIT. A complete kit Dignified appearance and good workmanship. Size parts for a 5 -valve superhet, Covers 16.50 and 200 -557 311in. high, 181in. deep, 33in. wide. French polished, metres, AC /DC 200.250 v. 6K8, 6117, 6Q7 2510, 251(5. veneered walnut. Price £26. Also available complete Size, 10 x 6 x Sin. Completely drilled chassis. Price with electric motor, auto stop and magnetic pick -up. including tax, £8 5s. A well made mahogany finished pedestal cabinet, Mining a quality electric con £34 5s. Od. An attractive brown takelite cabinet, 1,a gramophone motor and pick -up Illustrated in upper compartment and Ditto with Rothermel Crystal Fick-up, £36 2s. ld., or above, can be supplied for either kit at a cost of 25/ -. record space In lower. with S record -mixer changer, Height, 30in. Width loin Depth, 15ín. Price £18 £45 7s. 6d. MAINS TRANSF, RMER6. All input, 230 v. 50 e- 18s. SUPER OUTPUT TRANSFORMERS. By means of n Type 30, output 30 v. 4 a., 20,- ; Type 31, output 40 v. 2 -VALVE SHORT -WAVE BATTERY HIT. A series parallel arrangement wherein the maximum 3 a. complete and 104 v. 13 a, (auto -wound), 21/- ; Type 32. kit of parta for a 2 -valve receiver, coveting 15.600 wluding is used for each ratio extremely high efficiency 700 +700 metre:. 160 m /A, 1,000 v. 30 m/A (half wave), 4 v, 1 a. including valves, coils, drilled chassie, H.T and Is obtained. Any valve single or pushpull may be matched 4 r. 3.5 a -, L.T. der 40/- ; Type 33, 32, 34, 36, 38 v. at, 2 a.. 15! -. batteries to last approximately ti to 12 months. A pit, to any voice Coll (2 to 30 ohms) type Mo. 15.15 watts, 30/ -. of GOVERNMENT double headphones and full Instructions- Price GOVERNMENT SURPLUS OFFERS 8URPLUS'OPFERS An can be £3 10s. extra coli supplied covering 600 -1; )UU TEST UNIT AP58874 consists of a Test Unit for a U.H.F. R.A.F.1155 Receivers. Complete with valves, £12 101 metres at 4/ -. 'r.S., incorporates a 230 v. 50 a. Power Pack, with a to callers. Packing and carriage, 301- extra. 230 c smor thed output of 240 v. up to 50 m/A and 6.3 V. 2 a., A/C pow erpack for same, 50/- SUPERHET TUNING PACKS. Completely wired an,, 2 KF50, 1 EC52, 1 EA50, 1 6Z4G, 1 aligned. 13.40, 40 -120, 190 -570 metres. Y63 Magic Eye, and METAL RECTIFIERS. R.F. stage. a large quantity of Condensers, Resistors and Tuning 465 k /c. ; 9 connections only. Complete Output Volta Current with 3 -ganc Gear. Contained in an attractive steel cause. Size Type Price condenser, calibrated, engraved Perspex dial, and Stitt 101 x 0 x 81. Price 45/ -. Carriage and packing, 5/-. 600 40 m 'a. H,M', 5,- drive. Lita wound polystyrene insulation, permeability TEST UNIT TYPE 78 consists of a special purpose Oscillo. 280 40 m'a. H,W. or V.D. 5/- tuned I.F.'s. 7 t -e.. bandwidth. Price complete scope that requires only rewiring and the addition of a 32.3 65 co/a. H.W. or V.D. 5/- £3 17e. 6d. few condensers and resistors to convert into a standard 31, . 75 m /a. Oscilloscope, input 230 v. 50 c. A 33in. C.R. tube and Bridge 1/6 SHORT -WAVE CONDENSERS. High -grade ceramic . 1 amp. insulation, super midget 1 SU220A, 1 EB34, 1 5Z4, 3 SP41, 2 EA50, are included. 16 Bridge 12/6 type, single gangs available in 48 10, 20, 50, 75 (75 pf. Controls are "Brightnees," "Velocity," "X Shift," . 11 amp. Bridge 25/- has double spindle for ganging). Price 2/6. 2-GANO in 4 8, 0.6, 27.1, "Y Shift," Forms Amplifier, "In /out." "Orlihrate," 16 .. .. 5 amps. Bridge 30'- 50. 75 p.f. Price 5 / -. "sn;ot! TX." Price £8 Carriage 8e. Od. and packing, 16 .. Sumps. Bndge 37,6 PREMIER MAINS TRANSFORMERS. 20/-, 4 .. .. 1 amp. H.W. All primaries are tipped for 200 -230 RELAY UNIT Type 9, consists of a 24 v. operated relay 5;- -250 v. mvdnc 40 -1110 cycle'. AU primaries are screened. All LT8 or unit incorporating 3 KT33C valves, a telephone line TEST SET Type 87. A specialised signal Generator centre tapped. (uniseiector) switch with 6 poles 26 contacts, 5 Y.O. Type Unit covering 150.300 Me /s. Input, 230 v. 60 c. type relays, 2 high -speed relaye and a quantity of other Contains a completely smoothed power pack output List No. Output, Prit,, material. Contained in an attractive 250 v. 100 m /A., 6.3 v. 4-6 a., 1 R1.18. 8 1 relay rack type VR65, 574. SP.250A. 250-0-250 v. 60 Ma, 8.3 v. 2-3 a...3 v. 2 a. 25 - metal 19 x 9 x 91 Contained In superb case deep. Price £4 5s. Od., or without standard Sig. Gen. ste.1 case, size SP.250B. 250-0-250 v. 60 m/a. 4 v. 1-2 a., 4 v. valves 308. Carriage and packing 5e, 23 x 10 x 10, Price £4 10s. Od., carriage and packing 3-5 a. 10s 25; SIGNAL GENERATOR Type 88 consists of a battery- SP.300A. 300-0-300 v. 60 m;a. 6.3 v, 2-3 a., 5 v driven Generator, with two separate units for approx. 2 a. 25- 1 metre and 5 metre operation. Includes two CV6 ALL-WAVE SUPERHET HIT. A complete kit of parts SP.300B. 300-0-300 v. 60 m/a. 4 v. 2-3 a., 4 v. ,VR135) "Horned" triodes and 1 diode- A large to build a 6 -valve short (16.50) medium and long wave 35 a., 4 v. 1-2 a. 25 quantity of U.H.F. tuning gear. Contained in a teak set. Including valves, drilled chassie, OP trans 3/16 ohms SP.301A, 300-0-300 v. 120 m'a. 5 v. 2-3 a., 6.3 v. case size 18 x 8 x S. Price 30e. and full instructions. Incorporates Wearite iron -cored 3-4 a. 28'- OUTPUT TESTER Type 9 connoto of a unit incorporating coil unit, 5 watts pushpnil output. Valve line up. OKB. SP.301B. 300-0-300 c. 120 m 4 v. 2.3 a-, 4 v 't separate diode detectors and a 3-valve amplifier, each 11K7, 6Q7, 6.77. two 25.0. Operates on A/C or D,'C 2-3 a,, 4 v. 3-5 a. diode with its separate U.H.F. tuning system. A 2011.250 v. The Ideal radiogram chassis. Book yours SP.350A. 350-0=350 v. 100 m a. 5 v, 2.3 a., 8.3 v. retractable 18m. aerial is fitted and three VRI30 (Hí23) for delivery December 1. Price £10 10s. Od., without 2-3 a. 29- valves, 3 Dl diodes and a large quantity of U.H.F. speaker. SP.350B. 350-0.350 v. 100 m:.. 4 v. 2-3 a., 4 v. a-, tuning gear is included. Contained in a teak ease size GRAMOPHONE AMPLIFIER KIT. A complete kif 2.3 4 v. 3-5 a. 29 - loo S x d. Price 30e., or minus three HL23 valves, 15e. of panto to construct a good quality mains -driven SP.351 350.0.350 v-, 150 m/a, 4 v. 1-2 a., 4 v METERS. A huge purchase of 21 -watt gramophone amplifier. 2.3 a., 4 v. 3-6 a. military surplus meters May be used with miy SP.351A. 36 - allows ns to offer the following bargains. Best makes pick -up. Complete with circuit, £3 5s. 350-0-550 v. 150 Ma. 4 v. 2-3 a., 4 v Bakelite cases, prices are approx. I original cost. 3-8 a., 4 v, 1-2 a.. 4 v. 1-sa, 39- OSCILLOGRAPH POWER UNIT v SP,383 350-0-350 v. .150 Range Ext. Basic KITS. Input 230 m'a. 5 v. 2-3 a , Fitting Type Price Include transformer, metal 6.3 v. D1am, Movement rectifiers, voltage doubling 2-3 a., 6.3 v. 2-3 a. 36 - 300 v. ;33' hand smoothing condensers. SP.375A. 375-0-375 v. 250 mitt. 6.3 v. 2-3 S M/a Flush M.1.A'C 12.6 Type 409, a 500 M/A 3' Prol. output 900 v. 28'" 6,3 v. 3-5 a.. 5 v. 2-3 a. 46, - - M IS C 126 Type 410, output 1,800 v. 251 - SP.375B. 375-0-375 10 v. ' It M/A Kush 34/C D C 7/6 Y. 250 mia. 4 v. 2-3 a.., 4 v 23 A ' Flush Thermo BABY ALARM KIT. Consists of a complete kit of parts 2.3 a., 4 v. 3-8 a. 46'- - 7/8 for a mains -driven S P.425A. 425.0-425 v 200 4.A 21" - Port H. Wire 7/6 amplifier, microphone and Midget m;a. 8.3 v. 2.3 a 20A 2' 26 M/A Flush M,C D/O speaker, to enable Hound of baby's breathing or crying 6.3 v. 3-5 a., 5 v. 2-3 a. 47 7/6 to be heard SP.425B. 425-0-423 v. 40A 2" 121 M/A Flush M/C D/C 7/6 in any room. Complete with circuit, 55/ -. 200 m/a. 4 v. 2.5 a., 4 v 25A 31" 5 M/A Flush M/C D/C ALUMINIUM CHASSIS. Substantially 2-3 a., 4 v. 346 a. 7/6 made of bright 8P.501 500-0-500 150 25A W 25 M/A Prof. M/C D/C ... 7/6 aluminium. with 'our aides. v. m/a. 4 v, 2-3 a., 4 v, M/A 2" /A 2-3 a., 4 v. 2-3 a., 4 v, 3.5 a. i 1M Flush M /CD /C 7/6 17 x 31 x tin. x x 47/- 150 M/A 33' 150 .. 41 93 41 21n. SP.501A. 500-0-500 v. 150 m/a, 5 v. 2-3 a,, M/A Flush M/C D/C ... 10x8x211n. .. 7/- 12 9x23in. 200 M/A 31" 200 M/A Flush M/C D/C .. 7/9 6.3 v. 2-3 a 6.3 v. 2-3 a 50/- 1$ /6 14x9x211n. .. 8/3 16x8x231n. SP.503 500-0-500 v. i MA 31" 1 M/A Flush M/C D/C 250 m/a. 5 v. 2-3 a 1EEE222 99 20 x e x 211n. .. 10.13 22x10 x23in. 6.3 .. 13'6 v. 2.3 a., 6.3 P. S-5 a 65 -

www.americanradiohistory.com December, 1947 14 Advertisements Wireless World

The UNIVERSAL TAYLOR j N TAYLORMETER

90 RANGES Sensitivity 20,000 ohms per volt A.C. and D.C.

MODEL 85A

Resistance readings from 0.1 ohm to 20 megohms in three Model 400 Meter with 4in. scale and Improved Taylor ranges with self-contained batteries. robust movement. inductance overload protection. Capacity readings from .0002 to 100 mfd. and Automatic Meter Henries, with Adaptor. Volt readings from .001 volt D.C. and 0.1 volt A.C. up to readings from 0.2 to 1,000 5,000 volts D.C. and A.C. Buzzer for continuity tests. 10 amperes readings from I micro- ampere to 5 Current Size 1011 in. x 71 in. x i! in. Weight lbs. D.C. and A.C. PRICE Av ailable Immediate Delivery . Hire Purchase Terms £19.19. 0 includ ing Multirange Instruments, Signal Generators, Valve Testers. also manufacture a complete range of Radio Test Equipment We Measuring Bridges, and Ohmmeters ; also Moving Coil Instru- Output Meters, Insulation Testers, Circuit Analysers, Oscilloscopes, A.C. meets with scale lengths from 2in. to Sin. write for technical brochure to Please LTD., 419.424 MONTROSE AVENUE, TAYLOR ELECTRICAL INSTRUMENTS, SrLmOsUGHL,NB,SL000. Telephone : SLOUGH 21331 -M. R. SUPPLIES Ltd from New and perfect material, Sully and fairly described, for immediate delivery FOR THE 8.ock. A.l prices Nett. THERM)STATIC SWITCHES. Accurate Air Ministry pattn. Switch capacity 1.5 amp. Switch on at 32 deg. F. and off at 59 deg. F., therefore right for frost protection RADIO SERVICEMAN in garages. works, laboratories, greenhouses, etc. Operating temperature can be adjusted. 416 each, 45/- doe. COUNTERS. Counting up to 9999, operating from 6/24 v. ELECTRO- MAGNETIC and window, D.C. (or mains voltage A.C.). We offer only brand new ones with case DEALER AND OWNER at 718 each. INSTRUMENT RECTIFIERS (Full -wave) 1 m.a. orb m.a., either 5!-. The man who enrols for a I.C.S. TRANSMITTING COILS, eels of four coils for the B2 Mk. III Transmitter, 10/6 per et. Radio Course learns radiothoroughly, BLOWERS. Fine new offer of G.E.O. machines, operating from CENTRIFUGAL overall 8lin. Very When he 6/12 v. D.C. or 12/15 v. A.C. Intake Olin., outlet 1lin., height completely, practically. blast. Continuously rated to B.S.B. 170 /1939, 57/6. Also a powerful auction and overall, earns his Diploma, he will KNOW few left of the smaller model, 12 v. A.C. /D.C., outlet fin. eq., height 51n. STEP -DOWN MAINS TRANSFORMERS to suit these Blowers : Prim. 200/220 are not content merely to 35/ -. 11 15 v. 2 amps. radio. We v. Sec. 8 and 15 v. 4 amps. for larger size), 38/6. Sec. 7 and at /240 v. 6 teach the principles of radio, we want for smaller). 22/6. Also same prim., sec. 22 v. 2 amps., 21 : -. Sec. b. 12, 17 Sec. 7, 8, 15 v. 12 amps., 77/6 (des. p.t. 26). how to app'y amps. 52:6. v. Secs..450l0 to show our students TRANSFORMERS for amplifiers , etc. Prim.,200 /220 /240 /450 PJWER p.t. 2/ -). Also every -day y. 150 ma., 6.3 v. 5 a.. 6.3 v. 2 a., 5 v. S a., weight 13 lbs.. 49/8 (des. that training in practical, 120/150 m.c., 4 v. 4 a., (ex Govt. new) Prim. 200/240 v. In 10 v. taps., sec. b00/0/500 them 1 brackets with p. and s. terminal radio service work. We train O.T., 4 v. 4 a. C.T., 4 v. 3.5 a. C.T. and 10 v. a., in (des. 2/d. panels, r6 with handle and top drop -flap to be successful. L JUDBPEAKER CABINETS, well -made portable type domestic or P.A. use. 17ín. square by 6Lin. to the I.C.S. AdvIsory Dent. %toeing your compartment for leads, etc., ideal for Write deep. Opening ER die. 27/6 ade es Is f ee. RTRRB. the newyVibrator type,fully smoothed and filtered for all requirements. Our D.C./A.C. 4 lbs.), wave -lengths. 2001240 v. D.C. to 200/240 v. 50 c. 100watte (weight £9. 22 lbs.), £14. NOTE: -Fr television we recommend the 75 200 -watt (weight Converters. Input You may use this coupon. cycle model, same price. Very special offer of Admiralty Rotary but capable of heavier 100 /110 v. D.C., Output 230 v. 60 c. Rated at 200 -watts CORRESPONDENCE SCHOOL Ltd. duty. Fully enclosed in housing 19in. long by lllbe. high by 91n. dia. Weight approx. INTERNATIONAL 100 lbs., £9/101- (des. etc., 10 / -). LON.ON, W.C.2 best portable insulation test Instruments 38, INTERNATIONAL BUILDINGS, KINGSWAY, EVERSHED WEE- MEOGERS." The DEPT. v. reading 0/20 megohms and inf. with pocket and log in the subject marked X. from atock. Pressure 500 Please explain fully about your instruction books, £12i7í6. spring-reserve instruments Radio Engineering Radio Service Engineering VENNER TIME SWITCHES (Process Timers). Precision Complete Elementary Radio automatically rewound every 8 hours from mains but will run 72 hours on one wind. and Sales (or two) minutes. In weatherproof Radio Service Pulsing : Four -second closed circuit every one Examinations 9in. by 61n. by 4tn. £5. And the following Radio :- housing, P.M. MiCoil pressure Radio Engineers RA. SPEAKERS. Brand new reelected horn type with 10.watt British Institution of imp. Flare 121n. long and 141n. dla. On swivel mount with pillar. Operators unit, 15 -ohms these and all P.A. P.M.G. Certificates for Wireless Ideal for mobile use, £711216 ides. 5! -). STEEL TRIPODS for and Guilds Telecommunications ext. to 121t.,rigid under all conditions, the beet type made, 66/ (des. 3 /6). City R.A.F. speakers, and Power Pack. Wireless Operators and Wireless Mechanics, 8H_BT -WAVE RECEIVERS. The excellent B2 Mk. III Receiver any A.C. mains and 6 -volt. Range 3.1 to 16.5 me /s (18 to 100 metres). are coached till successful. Operation Pack 4in. by Mn. by I.C.S. students for Examination Superbet with B.F.O. Receiver : 411n. sq. by Olin. Power waterproof steel transit case, £7/17/6 (deg. Age ...... Hain. With ail leads, phones, etc., in Name. p.t. 6 / -). (Please include sufficient for packing and despatch.) Address, New Oxford Street, London, W.C.1 'Cs M. R . SUPPLIES Ltd., 68, Telephone MUSeum 2958

www.americanradiohistory.com lkcerrtbif, 1947 R'ircicss IiVorid Advertisements

more than 30 years, radio and electrical designers FORhave found and engineers in all parts of the world their most exacting requirements met by the unrivalled Dubilier ranges of capacitors and resistors, renowned for their constancy and complete reliability under the most arduous operating conditions. These capacitors and resistors, so important in Radio, Radar and Television equipment, are being continuously developed and extended in order to conceivable application. provide for every Dubilier capacitors and resistors owe their unvarying quality, technical excellence and high degree of stability to the close control which is maintained thoughout all stages of their manufacture. Full technical data and prices supplied upon request. UBILIE CONDENSER CO. (10251 LTD. DUEILIER CONDENSER CO. (1925) LTD., DUCON WORKS, VICTORIA ROAD, Telephone : Acorn 2241 (5 NORTH ACTON, W.3 lines) Telegrams Hivoltcoe, Phone, London Cables : H:voltcon, London Marconi International Code DÍ2A

www.americanradiohistory.com Dec r nibs r, /947 1V .l tl'i.t'rltst'Int'ut Wirclli%P World FOR RADIO, TELECOMMUNICATION AND GENERAL ELECTRICAL WORK ROSIN huhN erspeed CORED PORTABLE PATTERN SPECIAL / SOLDER INSTRUMENTS Outstanding Characteristics of "SUPERSPEED SPECIAL" ROSIN CORED SOLDER I. Chemically activated metals, maintaining perfect rosin core ensures high electrical conductivity. degree of " wetting." 5. Reduces to a minimum the solder required per joint 2. Increased fluidity acceler- and cuts down waste. ates production. 6. Residue is non- corrosive, 3. Allows more moderate solidifies to a semi- trans- soldering iron bit tempera- parent film of high electrical tures, and minimises the risk insulation value, is non - of physical damage and altera- hygroscopic and unaffectei tion to the electrical values under tropical conditions. com- of small pre -calibrated 7. The heating of the ponents such as Capacitors, activated rosin core does etc. Resistors, Coil windings, not cause any deleterious for 4. Ensures complete fume deposits, or unpleasant SUSTAINED mechanical bonding of joint odour. ACCURACY AIR MINISTRY APPROVED GOOD and reels, works Type PC Moving Coil. Supplied in a wide range of Gauges and Alloys on lib. 71b. - DAMPING application. PR - Rectifier, Moving Coil. coils, or as required. Prices on Iron. PI - Moving ROBUST Sole Manufacturers :- CONSTRUCTION West H. J. Enthoven & Sons Ltd., 230 Thornton Road, MODERN Croydon, Surrey. THOrnton Heath 2462. Enthoven Phone London Each type is available APPEARANCE in single or multi -range versions, and either an Industrial Model with SYLMAR RADIO LTD. of First Grade Accuracy or a Precision Model with are now distributors Sub -Standard Accuracy can be supplied. The move- T.R.E.L. PRODUCTS, (Tolworth Radio & Electrics Ltd.) against extraneous mag- m. ment is carefully shielded SUPER HET TUNING UNIT. 16-50, 200 -550, 1,000 -2,000 Consisting of 2 -gang Condenser, Silver Screen Dial, printed in blue, Drive, Price. netic fields. The case is of cast alloy with all black IFs., Coils, etc. Completely wired and aligned on Broadcast signals. with circuit, ES 5s. Od. Obtainable through Retailers. finish, carrying handle and resilient rubber feet. VIBRATOR PACKS. 12 volt Input, 210v. 70 mA. out- Wired for 610 put consisting of Input Smoothing, n; 1K7 valves. Vibrator, Transformer, Rectifier. PRICE LIST specials to and two 20 mfd. Conch., etc. order. (SECTION Cl UPON REQUEST. Size 8lin. x 3 ?.in. x41in. Limited quantity only, 3216. NOW IN PRODUCTION. The inexpensiveT.R.F. Battery Receiver, retailing at £717;6. Plus Tax C1 /15 -. ALSO S Valve AC; DC Med. and Long Wave Midget, in Handsome Bakelite Cabinet. Latest Super - het. circuit. Excellent performance and superb quality. E10 ¡10, -, Plus Tax £2/6/8. 3 -Wave Coil Packs. Complete with trimmers and wavechange Type PD - GET OUR QUOTATION for all switch, 30j -. and Long Dynamomet ar your requirements. T.R.F. Coils, Medium wave. Complete with circuit, Wattmeter. Retailer's Enquiries welcomed. 6'6 pair. Superhet Coils. 3 Aer. and 3 Osc. Set of 6, 12, -. Phone : PROspect 6651. Sin. P.M. Loudspeakers, 17/6. mfd. 6d., 10 Ex -Govt. Surplus. Condensers 0.1 mfd. 6d., 0.01 450 v. 2,9, 25 mfd. 25 v. 1/9, 50 mfd. 12 v. 1/9. Valveholders, mid. 2/6 doz. MEASURING INSTRUMENTS (PULLIN) LTD Octal 6d., Mazda type 4d. Resistances, all values to Dept. 1, Electrin Works, Address all enquiries LTD. 17 RiCHMOND,HSURNREYOAD Winchester Street, Acton, London, W.3. Telephone: Acorn 4651 -4 SYLMAR RADIO

www.americanradiohistory.com December, 7947 ircless World Advertisements 17

,1 11: 11 ONDON CENTRA RADIO STORES Special Offer of Ex-Govt. Receivers, etc. 10-VALVE COMMUNICATION FRACTIONAL H.P. A.C. MOTORS Type R1147A RECEIVER -Type R1155 Converted from ex -Govt. Generators 7 -VALVE U.H.F. RECEIVER Range approx. 200 megacycles l,'rn =h type 220- (with 4 Acorn valves) 770 v. 50 cycles approx. 5,000 r.p.m. Overall diem. 10 x 41n.

l ln. spindle ex tends lin- both ende. Post 5,'6 ester- tf

A new delivery! RADAR VIEWING UNITS These sets are equal to new, need only a power pack for Consisting of bin. diameter Electrostatic C.R. Tube, 7 Immediate use (see " W.W.," July, 1946). Free. muse valves Including four EF50, potentiometers, resistance, 7.5 me 's. or 1,500 kc /s., complete with 10 valves, including and other associated components. In metal cabinet magic eye. Enclosed in strong metal box. Each receiver 10 x 8 x 7¢in. aerial nested. Bargain price (plus ear, and pkg. 7/6) 3i JJ A Real Opportunity! Complete with Power Peak aes Loudspeake -, for Beautifully constructed and Otted with micro -condenser A.C. mains 20C -2t Ov. Type Demolition Mk. 1. drive. Valve types: two EF36, one EBC33, three 954, (Carr. and pkg. 10/6 extra) £20 ne 955. In black metal rase. 8 e 7 x bin. Set Drf 7 a Ex -ARMY TEST SET -NEW complete with vol,,,', Carr. ro.1 3L

POLARISED RELAYS Ex- R.A.F. CAMERA MOTORS Dimensions 3' x 2' x1i 12v and 24v. 115 ohms + 115 ohms. bin. x 3in, 6/_ 8/6 Model *AN /APA -1. Ex- U.S.A. AMERICAN AIRCRAFT 2 -VALVE BATTERY AMPLIFIERS RADAR UNIT Type A1134

For circuit continuity and general tenting. In hardwood tarrying cane. Carriage paid £3,10.0

RUBBER COVERED 5 -WAY CABLE Heavy duty. 7/6 dot. yards. U.P.Y. output. Complete with 2-volt valves. lo ctreng wood transit case 101 x 8 x 71n, New bargain 25 /. 115v. 006 apeles. 'ompleoe with Cathode offer. Carr. and pkg. 2/6 extra. lia. Ray Tube, ! 11 valves, Power pack, etc. In black crackle metal PULSE MODULATOR AND MIXER caer. Brand new tad boxed. With full 14.10.0 W6331 instructions. Carr. paid aie ELECTRO MAGNETIC COUNTERS ExO.P.O., every one perfect, electro-magnetic, 500 ohm Super Quality Heavy TWIN coil, counting to 9,999, operated from 25v.-50r. 5 C Duty - 11.C., many industrial and domestic applications {! ELEMENT SLIDING RESISTANCES 5.4 ohm at 20 amp. 47/6 12 ohm at 10 amp. 39.'6 VISUAL UNITS 70 ohm at 5 amp. 35 - Singla.Elemeat 14 ohm at 5 amp. 13 6 TELEPHONE LINE or UNIQEtECTOR SWITCHES 4- or 6 -bank, 21 constants. Have various applications including automatic trifling, circuit selection, etc. Operates on 2$S0v. With 4in. Cathode Ray Tube. two t.F50 and two VR54 Valves: two 6J5, three V11106, one VRib, one 0334, and valves, potentiometers, etc. Complete on Aft /6 Rectifier 5E4. Transformers, resistances, eon- 4 -bank 28/8 chassis 15 x 51 x Sin. Cart, and pkg. o,/- extra. {! dessero, eta. Carr. and pkg. 5/. extra 40/ 0 -hank 30/- Please Note: All carriage charges relate to the British Isles only We do not issue lists or catalogues

LONDON CENTRAL RADIO STORES, 23, LISLE ST. (GERrard 2969) LONDON, W.C.2 Closed Thursday 1 p.m. Open all 'ay Saturiay and weekdays 9 a.m. -6 p.m.

www.americanradiohistory.com i8 Advertisements Wireless World December, 1947 THE "BIG" SELLERS AT RADIOLYMPIA THE "Q -MAX " ALL -DRY THE NEW " Q -MAX 4 VALVE SHORT WAVE CHASSIS CUTTER RECEIVER

Coverage : 11-350 Metres. 12 GNS. (P.T. L2. 17.5) Excluding Coils, Speaker & Battery

SPECIAL XMAS OFFERS MUIRHEAD 50 -1 S.M. Drives 17;'6 CERAMIC SWITCHES

'POLYMAX' 3b, 5w, I p. 15;'6 The JONES 8 -way Plug CUTS METAL EASILY AND CLEANLY and Socket IO - Unbreak- (Button Base) 10/3 with Key 3-Pin FLUSH MOUNTING ab:e Plug and Socket 5 - 1t 10/3 do. I ;' Insulator 5" CER. FORMER 5,- 1t,.t 1,., 12,'6 (Key -) 01 /1000v 1/6 (Postage 6d. extra). Stand -offs METALPACK 1/350v I;6 N.B. -The same key Fits Ii ", 1}" and I §" 4° 6d., MICROPACK IOmf,125v 216 Caralopu 6d. Post Free. I" 9d., 25mf /25v 2 ¡' 2mf /350v 2/9 It" I -. 4mf /200v 2/9 4" METALMITE 0021I000v 1'6 Spreaders -Imf 150v MIDGET I,'- 25, HIGH HOLBORN, 1 3. ALL.BRAND NEW LONDON, W.C.I (Onp. Chancery Lane). Tel. HOL.horn 6231.

A FINE QUALITY GRAMOPHONE RECORD REPRODUCER

Features unique Ardente Con- trast Expansion restoring original dynamic range without distortion. Illuminated dial shows readings of contrast expansion, volume, separate tone controls at a glance. Walnut console cabinet houses 250 records, r has auto -change, sapphire pointed P.U. ,` NEW TYPES FOR Labyrinth Loudspeaker reproduces very wide range MIDGET RECEIVERS THE SCIENTIFIC with utmost of frequencies fidelity. HEARING AIDS VALVE METEOROLOGICAL Details, demonstration, trade terms from INSTRUMENTS BRITISH MADE ETC.

4R EDNTE ACOUSTIC LABORATORIES [Tp Greenhill Crescent, Phone HARROW GUILDFORD, SURREY. GUILDFORD 3278. HIVAC LIMITED Harrow on the HiII.Middx. 0895 Landon heaueh : 308 oatoed Sheet, W.1 ltaytair 7917

www.americanradiohistory.com lI°ce+tLru, 1..)47 Wireless n'orld A d'2!U'q-;Cir.2lb/s ) 9

the $rter -Comm for whit, tFe pJblic has been waiting, EFL; marvel in niniattre provide! for

complete comnunicatior between all points i e. any cam unit can communicate wi_F any other unit

at wil .

provides for two way calling and communication between master unit and are or all of :he sub stat,ons and also ncorparates the navel featu of a desk radio .vhich can be relayed to het sub-stations.

Frovei to b? well n acvanae of any sin lar 3 equ preen:. Provides all facilities for'' Staff Lcca- tion Musk for the Workers" ' Time Signar," etc.

Firms with suitable sales, installation, and rnaintiance facilities, are invited to write for details of our agency scheme, enquiries from overseas markets especially welcomed. Radle SOUND EQUIPMEN S BEARWOOD ROAD, SMETHWICK, STAFFS. Phone BEArwood 2575/6

www.americanradiohistory.com iv/7 20 Advertisements WireIes% World rruiltrr,

Measuring,

a condenser in /'11e('ll1 lr

COMPONENT BRIDGE B101 in situ, 5 pfd. to 500 mfd. - - in eight ranges To examine this cathode bypass condenser 5 ohms to 500 Megohms - in eight ranges the Power Factor control is used to balance out the 0 I Hy. to 5,000 Hys. - in four ranges parallel resistance and the main scale will then give an Leakage 0 to I.5 m /a. Q : 0 to 30. Precision Comparator. Price 26 Gns. accurate measurement of capacity - one of the many unusual facilities provided by this flexible instrument. Wayne Kerr WAYNE KERR LABORATORIES LIMITED, NEW MALDEN SURREY PHONE: MALDEN 2202

"You're CERTAIN to get it at ARTHURS SMALL GEARED * VALVES : We have probably the largest MOTOR UNITS stock of valves in the Country. Let as know your requirements. AVOMETERS. NOW IN STOCK. AVOMETER, Model 7 E19 IO 0 AVOMETER, Model 40 E17 IO 0 VALVE TESTER (Complete) L16 IO 0 TEST BRIDGE Ell 0 0 AVOMINOR, Universal Model E8 IO O AVOMINOR, D.C. Model E4 4 0 SIGNAL GENERATORS, A.0 E13 0 0 The Drayton "R.Q." is a 25-watt motor unit NOW IN geared to a final shaft, to which may be fitted for TAYLORS' METERS. SOCK. eccentrics, arms or cranks, gears, links or Operating Valves, for actuating valves or dampers, move- C.O.D. pulbys Dampers or Rheostats, All orders sent STAGE EQUIPMENT Terms ments, switchgear or other devices. or cash with order. Cinema Projectors, by return ofPost PROJECTOR LAMPS or reversing, with or without Unidirectional Rotating Screens, self -switching, for xoo /r to or 2oo /25o volts A.C. Radio Dealers. Illuminated Signs, London's Oldest Leading an auxiliary two- Both types are fitted with Small Working Models, way switch actuated by movement of the final shaft, for operating auxiliary gear such Geneva Movements for as fan motors, pumps, interlocking devices, Drum -type Switches, etc. Rocking Baths, Work EST. 1919 FINAL SHAFT SPEEDS Movement, Soldering Reversing Max 600 R.P.M 27 min. per rev. and Welding Fixluret, e 80 min, rev. LTO. Unidirectional Max 280 R.P.OL per Continuous Turning. ARTHUR GRAY. 60 lbs. max. vROPS. TORQUE: Reversing . .. in. Feed of Light Strip Unidirectional .. .. 87 in. lbs. max. Under Process. Gray House, 150, Charing Cross Rd., Dur Only Address: Send for List 302 -x /N London, W.C.2 TEMPIe Bar 5833'4. RADIO ENGINEERS. Drayton Regulator & Instrument Co., Ltd., West Drayton, Mdx. ELECTRICAL, TELEVISION &

www.americanradiohistory.com 1)crcutlurr, tya¡ iraIrti N orld .1 dcerltsemenls 2 1 CANADA

World Market Place

in 1948

Attend the CANADIAN INTERNATIONAL TRADE FAIR

Toronto, May 31 June 12, 1948 Follow the trade offerings of the world. Visit Canada in 1948. At the Canadian International Trade Fair, sponsored and directed by the Canadian Government, you will find the goods of many nations -hundreds of industries-on display. You can meet manufacturers, exporters, importers -buyers and sellers. You will get new ideas, find new products, make valuable contacts. Plan NOW to attend the Canadian International Trade Fair in 1948 -or to send a representative. Full details, including information on transportation and k accommodation, are available from - LONDON: R. P. Bower, Commercial Secretary, Office of the High Commissioner for Canada, Canada House, Trafalgar Square, S.W.x. LIVERPOOL : M. y. Vechsler, Canadian Government Trade Commissioner, Martins Bank Building, Water Street. GLASGOW: G. F. G. Hughes, Acting Canadian Government Trade Commissioner, zoo St. Vincent Street.

DEPARTMENT OF TRADE AND COMMERCE

OTTAWA v',,; CANADA

www.americanradiohistory.com 22 Adver'tisetf2elfts Wireless World December. 1947

IRAN SF0 RE RS Litz wound. Adjusted by High Permeability Iron Dust Cores. High L/C ratio. High Q. Frequency 460/465 Kcs. Side or end tuning. Size l ; x1 x 31 ins. long. Also available in miniature size.

LABORATORY

The " Aristocrat TESTED Planned for the connoisseur requiring a high quality cab :net suitable for a quality receiver. H. C. ATKINS Laboratories, 32, Cumberland Road, Kew. As good as pre -war and embodying all that is Richmond 2410 best in British craftsmanship and design. For AK tuz export or for those holding or who can obtain timber permits. Private enquiries are invited and those interested will have their names entered on our lists. If in doubt we shall be pleased to render every assistance and advise where possible. Dimensions: Length, 40 in., Height, 32 in., Depth, 171 in. Capacity approx. 12 cu. fc. Weight, I cwt. approx. Concealed castors. Sloping baffle. Slag wool and felt lining. Felt lined lid. Ample accommodation for large receiver and amplifier and heavy duty speaker. Interview by appointment only. Details and Prices ready November 1st, 1947 LOCKWOOD & CO. LOWLANDS ROAD, HARROW, MIDDX. Telephone : BYRon 3704

Model 'Q' Resistors produced by the cracked car- AUTOMATIC bon process remain stable to ± t% of COIL WINDING initial value. *Tolerance ± r% MACHINES A well designed and substantially built machine, for ±2% ±5% coils up to 6f " diameter to 6 long, also, a similar machine up to 6f diameter to 14' long. } H.P. Motor drive L o w temperature with hand -drive handle supplied. Specification of the coefficient. Model 'Q' illustrated and lists of the other machines on application. ETA TOOL CO (LEICESTE,2) LTD.

11 uyn mmeom resistor 16; METCALF STREET, LEICESTER. WELWYN ELECTRICAL LABORATORIES LTD. 'Phone -S386. eWelwyn Garden City, Herts. Telephone : Welwyn Garden 38168

www.americanradiohistory.com December, 1947 Wireless World Advertisements 23

at- adtge+

A Superb Instrument for the Perfect Reproduction of Gramophone Records

Here at last is an instrument which will * The Microgram attracted much interest and favourable give you the perfect record reproduction comment from both the trade of Which you have and public, when exïlbited at dreamed ... the full Radiolympla recently. beauty of the quiet passages . . .' the excitement of the finale ... the vigour of the bass ... the trill of the soprano. And the Collare Microgram is completely self contained . . . completely portable. Just plug in ... and hear your records as they were meant to be heard. Ask to hear the Microgram at your usual dealer's ... or write to address below for Illustrated Brochure.

The " De Luxe " Model illustrated is Complete with 6I inch Speaker, and lightweight Crystal Pick-up, neatly fitted into a handsome imitation lizard -skin case.

maa PRICES : De Luxe Model £19 19 0 e ia um Plus Purchase Tax £4 8 8 Standard Model £16 16 0 U ree&pticeQtaffier&me, Plus Purchase Tax £8 14 8 Trade Enquiries to :-

COLLARD LTD., RIPPLE WORKS, BY -PASS RD., BARKING, ESSEX Ripplewayn3333

www.americanradiohistory.com 24 .9ctvertrsement Wireless World Decemberr, ty¢;

ALL -POWER Constant Voltage Power Supplies

MODEL 1108 -S Type No, 19 Type No. 22 One of our low- priced industrial units. LET ELECTRONIC STABILIZATION SOLVE YOUR POWER SUPPLY PROBLEMS

ALL -POWER TRANSFORMERS LTD. 8a Gladstone Rd., Wimbledon, S.W.19 SYDNEY S. BIRD /did, Telephone: LIBerty 3303 AD. ENFIELD. é R CAMBRIDGE EapacARTERIAL tyfJnDX.

2. 5 and IO Metre 24 ea e .0eAt CONVERTERS AND RECEIVERS Great Reduction of Prices

Due to a fortunate purchase we are now able to offer the type 25 and 27 RADIO HEART Converters and the RI 147 A and B Receivers at considerably reduced prices. FOR AMATEUR, TRADE OR SMALL MANUFACTURER

Details of these are : AS 5 VALVE QUALITY SUPER HET RECEIVER OR AS R.F. TUNING UNIT WITH TYPE 25 CONVERTER 30 -45 m /cs. 3 -6 volt SP4I's, HF, Mixer, Osc., 7 m /cs. I.F. Output. 5 Pre -set Frequencies. Easily converted to tuneable 10 metre Converter by replacing ceramic switch O R with 3 ganging type 15 pf. Condensers. PRICE 20í- QUALITY AMPLIFIER KIT TYPE 27 CONVERTER 60-80 turcs. EF54 HF., EF54 Mixer ; EC52 Osc. 7 m/cs. I.F. Output. These Converters are tuneable and fitted with Sin. (attractive Cabinets available) 5/M Dial. Can be converted for use on 58.5 60 mc!s or 144 mc's. Ham bands. PRICE 30/-

R1147 A and B Receiver. App. 150 mc's. Model "A" 954 Mixer, 955 Osc., 2- 954I.F's. (25 me /s.) EBC33 2nd Det. and B.F.O., 2 EF36's Audio stages. Model " B " EF54 Mixer, EC52Osc. 2 EF50 I.F's. Audio stages as Model " A " Needs alteration after 2nd Det. for satis- W extraor,i:rir... factory results. Just the job for the new 144 me /s band. PRICE 451-

Packing and postage 2;6 extra on type 25 and 27 Converters. 5,'- on RI 147 A or B.

NOTE : A circuit diagram is supplied with each type 27 Converter, and R1147 Receiver. Let us send you details :- So/e Manufacturers:- RADIOMART MORGAN,OSBORN E&CO. LTD 48, HOLLOWAY HEAD, BIRMINGHAM, I. Warlingham SURREYupPe2560n9ham

www.americanradiohistory.com December, 19.17 %%Tireless 14'orld Adverttisements 25 e mi % hame P4- -,

" NOTHING LIKE IT ! I . J , 4att boo() how

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www.americanradiohistory.com Wireless World Radio and Electronics Proprietors: Branch Offices: 37th YEAR OF PUBLICATION ILIFFE & SONS LTD. COVENTRY : 8 -10. Corporation Street. Managing Editor: 1947 T.'b phone: Coventry 5211,. HUGH S. POCOCK, DECEMBER Telegrams : M.I.E.E. Autoear, Coveutrv." MONTHLY COMMENTARY 453 Editor: BIRMINGHAM : JUBILEE. By P. P. Eckersley 454 H. F. SMITH BROADCASTING King Edward House. NEW POLICE RADIO 457 New Street, 2. Editorial, Advertising W. T. Telephone: DEFLECTOR COIL EFFICIENCY. By lines). and Publishing Offices: 460 Midland 7195 (7 Cocking Telegrams : DORSET HOUSE, IGNITION INTERFERENCE- 2. By W. Nethercot 463 " Autopress, Birmingham." STAMFORD STREET, UNBIASED.. By " Free Grid " 467 MANCHESTER : LONDON, S.E.I. SIDEBANDS AGAIN. By " Cathode Ray " 468 260, Deansgate, 3. "fcicphnnc: By S. A. Knight Telephone : Waterloo 3333 (50 QUALITY SUPERHETERODYNE. 472 Blackfriars 4452 (4 hues). Telegrams : WORLD OF WIRELESS ...... 477 Telegrams : " Ethatcorld, Sediol, London.' " Ilitfe, Manchester." TELEVISION RECEIVER CONSTRUCTION io . . 481 A GLASGOW : NEW " ALL -STAGE " VALVE . . 483 26a, Renfield Street, C.2. PUBLISHED CATHODE -RAY TUBE DATA 484 Telephone : Central 4857. MONTHLY SHORT -WAVE CONDITIONS. By T. W. Bennington 485 Telegrams: "Iliffe, Glasgow." Price: 1/6 ADDITIVE AND MULTIPLICATIVE MIXING. By A 486 J. W. Whitehead .. As many of the circuits and (Publication date 26th apparatus described in these of preceding month) LETTERS TO THE EDITOR 487 pages are covered by patents, readers are advised, before RANDOM RADIATIONS. By " Diallist " . . 490 Subscription Kate: making use of them, to satisfy themselves that they would Home and A broad NEW BOOKS . . 492 sol- per annuvr. lot be infringing patents.

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VALVES AND THEIR APPLICATIONS

By M. G. SCROGGIE, B.Sc., M.I.E.E.

No. 12: Mullard V.N.F. Power -Amplifier Double -Tetrode QV07 -40

THE great advantage of a tetrode for r.f. by -pass. So in the QV07 -40 there is an internal amplification is the internal screening, by -pass of 65 pF, arranged so that the inductance which renders neutralizing almost (if not is 'negligible. At 200 Mc /s its impedance is quite) unnecessary. The effectiveness of the about 1211, and even less at the valve's maximum screening is largely lost, however, if the screen rated frequency, 250 Mc /s. grid is not tied down to a constant potential. If the valve is used at comparatively low For example, is if there an impedance in series frequencies this internal by -pass is likely to be with the screen, and no by -pass capacitor, its insufficient, and the usual external capacitor potential is free to vary, and it can do little to should be used. A little attention may be prevent r.f. potentials at the anode from needed at frequencies of the order of 100 -150 affecting the control grid.. Mc /s to ensure that the inductance of the screen At moderate radio frequencies a by -pass connection, internal and external, does not tune capacitor effectively ties the screen grid to earth the internal by -pass as a rejector circuit. or cathode. But at v.h.f. the internal connection to the screen has an appreciable inductance. Some Q V07 -40 Data: Even with careful valve design it is of the order Heaters : 1.125 A at 12.6 V (series) of 0.015pH, which at 200 Mc /s is an impedance or 2.25 A at 6.3 V (parallel) of about 20i2. The only way to reduce it by Max. Anode Voltage : 750 doing anything outside the valve is by tuning it Max. Screen Voltage : 225 to resonance as an acceptor circuit. The Max. Anode Dissipation : 40 W disadvantage then is that the by -pass is effective Output at 200 Mc /s : 70 -80 W only at the one spot frequency, and there is nothing to prevent instability at other frequencies. One of the merits of push -pull is that any variation of the screen potentials is in opposite phase, so that if the screens are connected together they help to keep one another steady. This object, of course, is defeated if the connection between them has a substantial This is the twelfth of a series _written by M. G. impedance ; but if the two valves are in one Scroggie, B.Sc., M.I.E.E., the well-known Consulting envelope the inductance of these leads can be Radio Engineer. Reprints for schools and technical colleges may be obtained free of charge from the kept very small. That is what is done in the address below. Technical Data Sheets on the QV07 -40. Q V07-40 and other valves are also available. Still, it is not wise to trust entirely to balanced THE MULLARD WIRELESS SERVICE CO. LTD., anti -phase for the screening, and as we have TECHNICAL PUBLICATI ONS DEPARTMENT, seen there are difficulties about the external CENTURY HOUSE, SHAFTESBURY AVE., W.C.2

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Vol. LIII. No. 12 DECEMBER, 1947 Price ls. 6d.

MONTHLY COMMENTARY The "Elevated Electrode" IN referring to the 5oth anniversary of the only a fortnight before. This controversy seems to foundation of the Marconi Company, we said have been general in the English technical press of (June issue) that Marconi's first great technical the time ; and it was probably provoked by an contribution was the addition of an elevated aerial editorial statement in the Electrical Review of to Hertz' oscillator. We had believed that Marconi's October 8th, 1897, which read:- aerial priority was now beyond dispute. " But we think there can be no doubt that In this belief we were wrong. Our statement has Marconi is the true and first inventor of the been questioned, and in particular it has been elevated electrodes on the receiver and transmitter, claimed that the Russian physicist Popov was the and this detail appears to have contributed more true originator, not only of wireless telegraphy but to extend the possible distance of telegraphy by also of the aerial, with which we are here concerned. electric waves than anything that has been dis- On this question we published (September issue) ex- covered." tracts from an article by the Marchese Solari, one That statement brought forward counter -claims of Marconi's earliest living associates, who also con- by or on behalf of Minchin, Tesla and Edison -but tributes a letter to the present issue. These com- not Popov. Those claims were apparently not re- munications, though lending support to our conten- garded as entirely valid even at the time ; now, with tions, do not constitute documentary proof, and so the accumulated knowledge of 5o years, we realize we have delved into the half- forgotten literature of that the " elevated electrodes " devised by these the dawn of wireless. Here are the results. early workers and used in the manner they described Exactly 5o years ago (November 26th, 1897) Popov could not have contributed much to progress. wrote a letter to The Electrician, which was pub- Pioneer the issue of December loth. He gave a A True lished in Popov's early work. On the translated précis of a paper of his that had appeared We do not belittle years ago we agreed that, subject in Journal of the Russian Physical and Chemical contrary, some the the Russian documentation, he is Society for January, 1896. In it was described the to verification of as the originator of the idea of using use of a coherer for recording atmospheric electric to be regarded Hertzian waves for communication. Popov's pub- ; a lightning conductor was connected disturbances Marconi's first patent, but of the coherer and the other was earthed. lished work pre -dated to one side originated anything-in- expressed hopes that his apparatus there is no record that he The author electrodes " on transmitter and eventually be applied to signalling at great cluding " elevated would turned Hertz' oscillator and Branly's distances and went on to describe his use of a receiver -which a practical means of communication. modified coherer for detecting electromagnetic waves coherer into was essentially modest ; such phrases as up to 5 km. Aerials for either trans- Popov at distances work," and " repeating some of O. mitting or receiving were not mentioned here or " my little . . which comes after the précis. This Lodge's experiments with the coherer ." in the specific claim that bear witness Marconi's receiver was a reproduction occur in his letter to The Electrician claim was that were he alive to -day, he " lightning recorder." to that, and suggest that, of Popov's have been a party to the exaggerated It seems highly significant that Popov made no would hardly aerial. His letter showed, by referring claims made on his behalf. claims to the have deplored as much as we number of November 12th, that he was a He would probably to a back article (containing, incidentally. reader of The Electrician, and so he may be assumed do an intemperate reference to Wireless World) published to have known of the controversy on the origin of a slighting in the U.S.S.R. journal Culture and Life. the aerial that had ended in the pages of that journal recently

www.americanradiohistory.com 454 Wireless World December, r9 ¡.j Looking Backwards -and Forwards

back from a technical the reproduction, I should doubt ings in the service we offered. Ì vantage -point over the if I hear OOKING any frequency higher set down the points of a policy broadcasting scene makes than 3,500 c /s, and I know that which seemed to me to be sound the far -away look very close ; the orchestral reproductions are and which I had determined, were view is clear because not obscured muzzy and confused. I am sure I to be allowed to remain in the by any remarkable event. Per- that I got at least as much Corporation, to put into practice. haps the 25- year -old emergence of pleasure, apart from the physical These were (i) that the listener broadcasting shows some mazy discomfort, from a crystal and wherever he lived in Great detail, not so clear as the rest telephones, circa 1923. I dare say Britain should be given the oppor- on the whole, how- tunity to hear ever, the more it B.B.C. programmes changes the more it without extraneous is the same thing. interference ; (z ) T h e programmes that the conditions have shown a tre- Broadcasti ng of transmissi on mendous improve- should be such that ment; the senior the reproduc- people must have tion should read my be a book and Jubilee faithful cop y of adopted some of its the original sounds ; suggestions ! How- (3) that the condi- ever, the muttons By P. P. ECKERSLEY, M.l.E.E. tions of transmission here are technical (Formerly chie Engineer, B.B.C.) should permit the and it is this tech- cost of the receiver nical aspect that to be within the is so singularly flat and un- behind the obscuring screen of means of the lower wage. earner ; dramatic. annoyances which mar my (4) that there should be a suffi- I listen to broadcasting on an pleasure .I can detect a better cient number of channels of pro- ordinary set belonging to a friend. acoustical environment in the gramme distribution to allow the This was bought just as the ordin- studios. But I do ask, without diffusion of as many different pro- ary non -technical person buys trying to be funny, what remark- grammes as there were different any household appliance, a able difference is there between programmes to diffuse. vacuum cleaner, sewing machine the reproductions of programmes The Regional Scheme initiated or electric fire. . , I can get " a given to the public now and those the policy : high -power senders large number of stations ; I get given twenty years ago? gave to a majority that strong the Home, Light and Third pro- As chief engineer of the B.B.C. field essential to overcome inter- grammes. The first two are in the middle 'twenties I was ference and there were two pro- reasonably free from background, conscious of manifold shortcom- grammes to choose between. The the last is annoyingly accom- field strength was enough to per- panied by sounds made by the OLD AND NEW. -The original Brookmans Park masts for London mit the use of simple, and there- electric lift. I can also hear regional station, fore cheap, receivers. of with, on the ghosts other programmes be- right, the recently erected Soo -ft The adoption of the policy of hind the highbrow elegancies of mast radiator are shown in the using high -power senders by Con- the distinguished Third. As to title illustration. tinental broadcasting authorities

www.americanradiohistory.com December, ry¢j ms-!ed 455 was (and is) one which has made given by a miserly employer to pursued we still want more chan- of it impossible to carry out the his workmen : " If it were any nels for the sake quality. policy in full. The too -small fre- worse we couldn't 'a -drunk it ; if Some argue that the ordinary quency separation between car- it were any better we shouldn't listener does not like high -fidelity riers causes sidebands to overlap a-got it." reproduction. What is in fact and- receivers are perforce de- What does the future hold? true is that he does not like the signed with a narrow bandwidth What tools do we possess which harsh and glittering top that is, of reception. High -fidelity repro- could fashion a more exciting at present, an almost universal duction becomes impossible. The structure than we have to -day? concomitant of wide -band repro- obsolescent method of distribut- The primary requirement is duction. Given a constant ser- ing programmes by modulating more channels of distribution. vice, encouraging true high fidel- medium waves, with the conse- This technical provision would ity, the rather difficult problems quent lack of enough channels, give to the listener a wider choice of top reproduction would, in time, be solved, and their solution would be welcomed by all. There are two main methods available to give us more channels : short -wave radio and car - rier-on -wire networks. I am not concerned which of the two methods is adopted, but I do most devoutly hope that some day soon we shall get at least an experimental service, somehow, somewhere. On the short -wave side we have the new, exciting and revolution- ary method of frequency modulation. There was once a doubt as to whether the extravagantly wide sidebands essential to F.M. would not be a relative disadvantage of the system. In other words, more A.M. senders than F.M. senders might give a more efficient national service. H. L.

B.B.C. PROGRESS : 1922 -1947 In striking contrast are these photographs of the original Writtle, Chelmsford, transmitter, 2MT, which operated from February 1922 to January 1923, and the modulated amplifier tank of the B.B.C.'s most powerful station at Ottringham, near Hull. completely nullifies any possibility of giving the listener a wide range of choice between different and clearly heard programmes. The efforts I made, after leav- ing the B.B.C., to develop a scheme of wire broadcasting were attempts to pursue the policy of giving the public a high -fidelity multi -programme service. The attempts were in part frustrated, but the relay services have gained a wide measure of support, in spite of every obstacle, put in their of programmes. I know the Kirke has investigated and shows chiefly bureaucratic, far as distribution is con- way. But broadcasting remains necessity for this is doubted by that, so be- cerned, F.M. is the better system. much as it has always been -a the pundits ; it was doubted fore the Third programme was There is still, however, this public service satisfying a public more opportunity boïn and given such a wide wel- doubt : the F.M. receiver is which is refused an than the A.M. type. to be better satisfied. One re- come. Even if the pusillanimous complex is Has this factor, throwing a members the story of the beer policy of denial of quantity

www.americanradiohistory.com 456 q'ireless World Decerraber, 1947 Broadcasting Jubilee - sion. Early sound broadcasting greater burden on the public, was a mediocre business. OUR COVER illustration been taken into account? To my way of thinking, tele- 1 happen to believe that wire vision should be developed as is this month devoted to an broadcasting method is the bet- much by the cinema people as by unusual view of the B.B.C.'s ter. Wire broadcasting receivers are the B.B.C. Some of the reasons cheap and efficient, the channels are obvious -competition for ser- most powerful station at numerous, and no ether channels, vice, widened experience and so Ottringham, near Hull. It so essential for mobile services, forth-but one seems to be para- consists of four 200 -k W are used. The argument that wire mount. Apparently some of the broadcasting cuts off the listener imperfections of the images re- transmitters, for operating from foreign -station listening is produced in the home to -day in the long- or medium - equally applicable to short -wave could be rubbed out by using a wave bands, which can be radio broadcasting. It was al- larger number of lines. On the coupled to an output ways a stupid argument ; if " the other hand, the use of higher and give of people " watch " the Govern- higher frequency carrier waves, 800 kW. The old 2L0 transmitter had a power 1927. -This cartoon appeared in Wireless ofIkW! World in June, 1927, when the Dutch station, PCJJ, having started short- wider than by flogging the imper- wave overseas fect system essential at the broadcasting some moment as a public service. months prior to the There is an introduction of Em- easy and delightful pire broadcasting by pastime in exaggerating the vir- the B.B.C., emula- tues of the good old days ; what I ted the Dutch com- think makes anecdotage neglig- mander Admiral ible is the existence of some bet- Tromp. ter new ones. One therefore ends this brief looking- backwards look- ment" then no one need be cut essential to increased lines, would ing- forwards with the specific off If dictatôrship comes, be sure cause distortion because of reflec- hope that something may soon be that radio will be cut off what- tions. This is a problem that done to give listeners a wider ever its technique. Quite likely could be solved, given a consider- choice between faithfully repro- the dictator would install a wire able expenditure, at any given duced programmes than they get broadcasting system and confis- reception location; i.e., at any to-day. Monopoly can never be cate all radio sets! particular cinema theatre. Ergo, justified ; at least it might be ad- As to the network, probably the cinema reproductions could be mired for its courage and enthu- in the long run the telephone better and the experience gained siasm. wires are the most suitable. It is said, moreover, by competent x °,; - authorities that it would be possible to distribute television programmes via subscribers' lines. I am as certain as I can be that the electric mains would be quite unsuitable for use in diffusing television programmes. Which leads to question about the future of television. I have little doubt that eventually the greater part of broadcasting will contain sound and vision images. The operative word here is " eventually." To- day television is a technical marvel and a cultural horror. In its reportorial aspects it is useful to those who must know the latest at the earliest, to those who like to join in events, to sports enthusiasts maybe ; but in its creative exhibitions it has hardly passed PIONEERS. this group of embryonic -In of pioneers of the Writtle days are (seated, the standards the second from left) Sir Noel Ashbridge, now B.B.C. Deputy Director General, cinema. This does not blame (standing, second and third from left) H. L. Kirke, head of B.B.C. Research anyone ; inevitably a new art has Dept., and R. T. B. Wynn, B.B.C. Assistant Chief Engineer. P. P. Eckersley to find its new forms of expres- the author of this article is seated in the centre. [Coureesy, "London Cal Ong."]

www.americanradiohistory.com December, 1947 Wireless World 457 Police Radio Two -station Diversity System with Radio -link Control

Two steel towers reliability, since there are fewer support the Lever - pieces of equipment to develop stock Green aerials. defects. On the distant The block diagram of the in- one is a 6- element the arrangement on stallation shows array beamed of the equipment at the three Hatfield for recep- : Hatfield, Lever - tion on the link fre- main centres quency and a verstock Green and Barkway. tical half -wave aer- The to -watt transmitter at ial for reception Hatfield operates on a frequency from the patrol cars. of the order of 150 Mc /s and feeds The near tower a half -wave horizontal aerial at sup Forts similar the top of a too -ft steel tower. aerials for trans- This is the link over which the mitting. switching signals are sent for starting up the two too -W trans- the experiments other at Leverstock Green, in the mitters and for conveying OME of the early outgoing speech signals which made by the Home Office south -west corner. Both these stations are controlled modulate these transmitters. S radio branch which finally unattended Barkway system of and operated by radio links from Leverstock Green and produced a workable on two carrier frequencies V.H.F. diversity transmission for the county police headquarters at operate telephonic communication with Hatfield. already been In one of the earlier experi- police cars have trans- described in Wireless World.' mental installations the of the equipment mitter at the headquarters Descriptions an in- used in these tests2 or developed station was used to control services of this termediate transmitter located at especially for transmitting kind3.4.: have already been pub- one of the main lished. sites. This transmitter, possible to give details of about 3o watts output. It is now supplied of the latest installation planned controlled and for the Hertfordshire county modulation to the other police. This is thought to be the two stations in the chain. first large -scale scheme of its kind In the case of the Hert- employing diversity transmission fordshire scheme the head- with amplitude modulation. quarters transmitter itself The scheme employs two too- performs these functions. watt V.H.F. transmitters one This not only reduces the located at Barkway in the north- amount of equipment east corner of the county, and the needed ; it also simplifies the installation and, inci- Multi-carrier Communication Sys- dentally, makes for greater tem, Wireless World, February, 1946, pp. 59-61. V.H.F. Communication Equip- The equipment rack inside ment, Wireless World, June, the Leverstock Green station, 1946, pp. 18o -181. building. The three racks Mobile V.H.F. Gear, Wireless contain the zoo -watt and to- World. November, 1946, p. 368. watt transmitters, link and Miniature V.H.F. Transmitter - service receivers, modulation Receiver, Wireless World, July, amplifiers and power supplies. for replace- 1947, p. 269. Spare equipment Mobile Radio -telephone, Wireless ment in the event of a defect World. October, 1947, p. 357. s also included.

www.americanradiohistory.com 458 Wireless World December. 1947 New Police Radio - miles to the radio path to of the order of 8o Mc /s, the fre- Leverstock Green, thereby quency separation being about bringing the modulation ro kc /s. This is considerably at this station in phase closer than the experimental sys- with that of Barkway. tems already described for in Likewise a delay of the those multi- carrier installations same amount is inserted in the carrier separation was zo kc /s the incoming signal path and since three stations were used at Leverstock Green. the bandwidth of the operational signal receivers, mobile and fixed, was roo The aerial system at Hatfield kc /s. With the frequency Police Headquarters consists spacing reduced to ro kc /s and of two 6- element horizontal only two stations the receiver's receiving arrays beamed on bandwith can be brought down to Leverstock Green and Bark- 4o kc / s. In order to prevent aud- way respecti ,ely and a hori- ible heterodyne of the two car- zontal halt -wave dipole for riers the upper audio response is transmission. restricted to just below 5 kc /s. This provides good speech qual- Despite these delay networks zontally polarized. The other two ity ; indeed, this curtailment was some phase difference is bound to are vertical half -wave dipoles and certainly not suspected during exist as the patrol car will not al- are used for transmitting to and the demonstration run at which ways be the same disgtance from receiving from the patrol cars. time these details were not both stations. Extensive use has At Leverstock Green the aerials known. shown, however, that such phase are supported on two 2o -ft steel It will be seen that a 5o -µsec difference that may occur under towers, but at Barkway an exist. delay network is inserted between normal conditions does not intro- ing tower 24oft high has been the link receiver and the main duce noticeable distortion. used. transmitter at Leverstock Green, Four aerials are used at each Details of the receivers and but not at Barkway. There is a main transmitting site, those at transmitters fitted in the patrol difference of ro miles in the dis- Leverstock Green consisting of cars have appeared on previous 50/1SEC DELAY occasions, so it will suffice here LEVERSTOCK GREEN to say that the radiated power is about ro watts at a frequency of the order of roo Mc /s. A vertical roof aerial is used and the receiver is a superheterodyne. Both trans- c. . \5á .\DBJ HATF/EL D \ \, 80. R°/s \ROSM - °/s . \ ---.. BARKWAY \. \ -\.\.

MOB /LE

L£VERSTOCK HATFLEL CREEN - . - L44 '707-*

04 HIGH- POWER TRANSMITTER y

LOW -POWER TRANSMITTER Block schematic diagram of the Hert- fordshire county police radio instal- BARKWAY lation giving the actual frequencies in RECEIVER use when the service was inaugurated. tances of these stations from Hat- two six- element Yagi arrays, one mitter and receiver are crystal field, Leverstock Green being the for the incoming and one for the controlled. nearer of the tAvo. The So -usec outgoing link signals. These are A point of interest of the Hert- delay is equivalent to adding ro beamed on Hatfield and are hori- fordshire scheme is that the six

www.americanradiohistory.com December, 1947 itreles% World divisional police headquarters in Hatfield in the same way as the BOOKS RECEIVED the county are also included in patrol cars, small to -watt trans- the radio chain. These stations mitters being employed. Television Explained. -By W. E. use re- Miller. The various parts of a tele- the same transmitting and The actual frequencies at pre- vision set are simply explained and the ceiving frequencies as the patrol sent employed are marked on the hook provides an introduction to cars, and can therefore receive all block schematic diagram of the television which is suited to those outgoing messages, but they can- installation, but it is understood acquainted with ordinary wireless equipment. Covering the receiver not receive from or transmit to that these will be amended stage -by- stage, it deals with aerials, the cars. They have communica- shortly as some are outside the R.F., I.F. and V.F. amplification, sync tion by two-way radio -telephone hands agreed on recently at At- separation, time bases for electrostatic with the main headquarters in lantic City. and electromagnetic tubes, cathode -ray tubes and power supplies. Pp. 5o, with 56 illustrations. Riffe and Sons, Ltd., Dorset House, Stamford Street, London, S.E.1. Price 3s 6d. School Broadcasting in Britain. -By Richard Palmer Claimed to be the first considerable contribution on the subject of school broadcasting to be Rotating Dual Aerial System published in this country, this book describes the growth and scope of the system introduced by the B.B.C. in Electric Drive and Remote Indicators 1924. 144 pages. British Broadcasting Corporation, London, \V.! Price qs od. here is a remotely by .Reference Data for Radio Engineers. SHOWN con- tooter an electric motor and -Second editions of two manuals with trolled dual beam -aerial system reduction gearing. this title have been received from the which has been erected by C. G. Clamped to the driving shaft is associated companies Standard Tele- Allen at his ama- phones & Cables teur station, G81G (London) a n d in Bromley, Kent. Federal Tele- It is mounted on phone & Radio a wooden tower 30 Corp. (New York). There is feet high and con- .t marked simi- sists of a three- larity between It array for them, but in the 20 t t Ares and a S.T.C. publica. simï t one above tim the material for c metres. has been Angli- C , i- cized. The books spacing were originally uset lit both aerial- ompiled for the ant . t lis has re- use of the staffs sut ced in a very of the respective 1 o w impedance- companies. The about 6 ohms -at scope of the the centre of the S.T.C. book, radiator. which was first In order to bring made available this up to match a 5o -ohm coaxial feeder a folded radiator is used. It consists of a ;1-in diameter tube with a rA -in tube in parallel. The feeder is The two -band aerial joined into the centre of the thinner array for to and 20 tube. met:es erected on The dimensions of the 20 -metre a 3o ft tower with array are: -reflector 36ft, radiator its electric driving 35ft and director 32ft. The reflec- mechanism shown tor is 'oft behind the radiator and in the insert. the director 7ft in front. The boom carrying the elements, which are insulated from it, is '7 ft long and to the public in 1942, can be gathered a rotary switch with 18 equally - 2 -in diameter. Reflector and direc- from some of the chapter headings: ITV-in diameter and the spaced contact studs. In the trans- Engineer- tor are circle map of General Engineering Tables; whole is made of duralumin " B " mitting room is a great- ing and Material Data; Audio and tubing and it weighs the w9rld on a circular metal plate, Radio Design in General; Rectifiers, thin -walled a 36o- compass scale 281b complete. with degree Valves and Amplifiers; R.F. Transmis- Supported 7ft above the 20 -metre round the circumference and in sion Lines; Radio Propagation and of it scaled down which 18 radial slots are cut. Be- Aerials; Noise and Noise Measurement; . array is a replica a Non -Sinusoidal Waveforms, Mathemati- -size for io metres and using hind each slot, in a reflector, is to half small lamp connected to the corre- cal Formulte; Tables and General in- diameter tubes. : smaller sponding stud on the mast switch. formation. British 175 pages, Standard The whole head is carried in ball Telephones & Cables, Connaught House, bearings and is driven through a As the aerial rotates the lamps Aldwych, London, W.C.2. Price 5s. vertical shaft from the base of the light up . The American edition costs $2.

www.americanradiohistory.com } 0o Wireless World December. 1947

HEN considering the problems associated with w the electromagnetic deflection of a cathode -ray beam Deflector Coil it is useful to have available information about the energy the paper the magnetic field is stored in the field is H2v /8ar ergs. and power needed in the ideal perpendicular to this plane over The volume v = ado24l4 and so case. It is useful because the ideal the area bounded by lo and do, energy = 1.425 X to -8 x power requirement is one which the cross - section being circular d -e- sin2 ergs .. (2) can never be reached and it of diameter do. If the total angle EHT z serves as a measure of the efficiency of deflection from one extreme to If at the end of every scan this of a practical system and so the other is ¢, the maximum energy is dissipated during the indicates the possibility of im- angle from the undeflected position fly -back in a resistance it must be provement. is ¢/2 and the beam is shown in supplied f times a second where In a recent articles. *, Schlesinger this position. f is the scanning frequency. Con- has given equa- The path of the sequently, the power supplied is. beam through the tions for the P = 1.425 x 10 -16 X energy in the mag- field follows an netic field and for arc ABC of radius EHT f sin2 2 watts (3) the power needed Losses in r and the path of to provide that the beam outside If the field H in the volume y energy once every the field is tan- were produced by a current I in scanning cycle. Television gential to the arc a coil L, and if it were the only Similar equations at the boundary. field produced by the coil, the are developed be- By inspection energy in the field would be low and extended Scanning L CDE = 0/2 = j

www.americanradiohistory.com December, 1947 %1'01Id 461

By one -half of the total. The power needed is proportional to the W. T. COCKING, square of the field ; therefore -Lfficiency M.I.E.E. the loss in the ends of the coils increases the power needed about 5 cm in length. If EHT = 6 kV values to be unchanged the 4 times. the formulae give the following efficiency is 10.7 per cent. Instead These two factors make the values :- of the input power being 2.175 W input 4 x 1.6i = 6.4 times the H = 33.2 oersteds ; it must be 20.3 W. ideal, or 14 W. P = 2.175 watts ; It is instructive to examine the There is a loss in the resistance Energy = 2.16 x Io -4 joules ; reasons for this low efficiency. of the coils which amounts to I = 0.222 ampere ; In the first place, the effective some 2.7 per cent of the total, or assuming an inductance of 8.9 mH diameter of the magnetic field 0.56 watt. All this brings the and f = 10.125 kc /s. is necessarily larger than the power up to 17.56 watts and Now in any practical circiiit the diameter of the tube neck. Allow- leaves 2.74 .watts so far un- current .IL through the deflector ing some clearance between the accounted. coil needed to produce a given inside of the coils and the tube This represents the loss of deflection d at a given final anode the mean diameter of the assembly field external to the coils. If no voltage EHT is easily measured, can rarely be much less than 4.5 outer iron ring were used, one- as are also the inductance LL and cm. Taking this as the real half of the field produced by the the resistance RL of the coil. diameter of the field, the power sides would be wasted and a Following the, same reasoning as is increased by (4.5/3.55)2 = 1.61 further increase . of four times in before, if the energy in the times. the power would be needed ! The magnetic field is dissipated in To obtain a uniform field the usual outer iron ring provides a resistance during the fly -back, the ends of the coils are usually bent path of low reluctance for the power supplied to produce the external flux and o field is : by so doing it 2 increases the in- PL =2I LL X log ternal flux. These various is loss in resistance and there a the sources of loss of are shown in the IL2RL P,. = /12 4)h Table as per- Therefore' the total power is 2 PT = 2 LLf X, IOg {I + RL /(6 X log LLf)} .. (9) the units being watts, amperes, kc /s, S2, henrys, kV. It has been shown2 that, in these units, IL EHT (Io) - 80.4 where k2 is a factor related to the deflection -coil efficiency which is easily determined in any practical case by measuring IL and d, the deflection on the screen, for lo any convenient value of EHT. In terms of k2, then,n Fig. r (a). The deflecting { field is assumed to be uni- PT = 7.78 k22d2LLJ BHT X form across the neck of the (b! {I + RL /(6 x ro3 LLf) }.. (II) C.R. tube and to exist for the distance lo along of practical it. (b). The field is uniform over the area iodo The efficiency the the paper. The beam coil relative to the ideal and perpendicular to deflector follows an arc ABC of radius r through the field.. is thus centages of the total power so b it is easy to see their relative do sine that P 2 importance. It should, of course, 1.83 (12) that this break- rl = = RL/(6 IogLLf be understood k22lodo2LL{I -!- x )} down into components of loss is In one practical case with LL = away from the neck of the tube only approximate. The useful 8.9 and RL = 15 Q, the factor and so the field from the ends deflecting power is accurately mH, power k2 was r.o8. Assuming the other contributes little or nothing to the calculable and the input useful field. The wire on the ends can be measured, so that the " Television $.H.T. Supply," by W. T. is about one -half the total wire in total loss is known accurately. Cocking, Wireless World, June 1947, Vol. 53, field is also about The resistance loss can be corn. p. 207. the coils and the

www.americanradiohistory.com 462 Wireless World December, r9L7

Deflector Coil Efficiency- same dimensions and for the same to one -quarter, the increase ' of puted quite well from the known deflection angle the power needed frame input would be no more current and D.C. resistance of is 50/10,125 = 0.00495 of that for than z W and the total saving the windings. The loss remaining the line scan ; that is, 0.0108 W would be as much as 8 W. is apportioned among the three instead of 2.175 W. One cannot go too far in this main causes largely by estimation However, the losses in the series way, of course, because the and any individual one may be resistance of the coils are much efficiencies of the valve and of considerably in error. more important. With the same the valve -to -coil coupling are What the breakdown does values as before, but taking f = often much lower at frame than reveal is that there is one major 0.05 kc /s (5o c /s), Equ. (1z) gives at line frequency. Nevertheless, source of loss -the end field n = 0.0166. The same deflector it may pay well to sacrifice frame of the coils -and a number of coil has an efficiency of 1.66 per coil efficiency if by so doing it is minor ones and that appreciable cent at frame frequency corn - possible to improve the line coil improvement in efficiency can be pared with 10.7 per cent at line. efficiency. made only by attending to this The difference occurs solely major loss. Only when this loss because the series resistance losses can be reduced to a figure com- are independent of frequency parable with the others will it whereas the " reactive losses " are CRYSTAL be profitable to spend much time greatly reduced at frame fre- in efforts to reduce them also. quency, and consequently form a SET: The main problem in deflector smaller proportion of the total. coil design is clearly to obtain a In practice, of course, the uniform field in the neck of the absolute magnitude of the power New Version tube without also producing .a needed, is more important than lot of waste field outside the tube. the efficiency, and in the frame It should be pointed out that scan the power is so small that This fountain -pen- even the low value of 1.66 per sized receiver, TABLE cent is not very important. It which was shown watts per cent means a power of about 0.65 W at Olympia by Useful deflecting as compared with 20 W for the B.T -H., employs a power 2.175 10.7 line scan. radar -type crystal Wasted power in ex- For mechanical reasons it is detector and has cess of mean dia- usually necessary to make the permeability meter of coils over tuning. tube neck dia- frame coils rather shorter than meter ... 1.325 6.53 the line, and this reduction of 1, Wasted power in makes it necessary to increase the ends of coils 13.5 66.5 input somewhat. However, the Wasted power in amplitude of scan needed is only Miniature coil resistance 0.56 2.77 8o per cent of that of the line Wasted power in and these two effects roughly Soldering Iron field external to cancel each other. coils 2.74 13.5 ALIGHTWEIGIII soldering iron Because the line scan requires a for fine work and instrument 20.3 100 much bigger power input than repairs has been introduced by the frame the efficiency of the Adcola Products, Alliance House, line coils is much more important Caxton Street, London, S.W.I. The expression for the efficiency of the frame. In long copper bit (hin dia.) is integral the than that with the heater element. of deflecting coil holds whether of is the spite the fact that the latter Despite its diminutive size it d- or not resistance damping is already by far the lower of the velops a surprising amount of heat used. Both expressions for the two, it would pay handsomely to in the copper hit. A usable tem- power, in the ideal and in the improve the line efficiency even perature was reached just over a practical cases, are based on the if it entailed a reduction of the minute after switching on and within assumption that the energy in the frame efficiency. -Thus, in the two minutes it was possible to solder field is dissipated in a resistance case considered, doubling the a No. 16 S.W.G. wire to a tag with during each fly -back. These ex- line efficiency would save to W ease. is approximately 25 pressions do not hold, therefore, input power to the coils. If this Consuthption watts ; supply voltages between 12 in cases where some of the energy improvement could be made only and 25o. Price is 22s 6d ; a replace- is utilized to provide part of the by reducing the frame efficiency ment element, which includes the next scan, but their ratio, which hit, costs 12s 6d. is the efficiency of the coils, does hold in all cases. Equation (1z) is, therefore the most useful one. Before concluding, it may be as well to consider very briefly conditions for the frame scan. In the ideal case, the power input required is proportional to frequency so that for a field of the Adcola lightweight soldering iron.

www.americanradiohistory.com ilccenaber, i947 Wireless World Advertisements 3r

IF YOU'RE SHORT OF 6F5 IS - SOLUTION IS TO gRIMARIZE/

TYPES 6F1 and ¡2F; are high -mu triodes for which the triode portions of the double -diode- triode types 6Q7GT and I2Q7GT form efficient substitutes. These valves are International Octals and call for very little alteration to the wiring. Any connections to pins 3 and y of the 6F5 socket will be for anchoring purposes only and these must be removed before Brimarizing.

CHANGE SOCKET CHANGE CONNECTIONS PERFORMANCE CHANGE REMARKS TYPE FROM TO FROM OLD TO NEW 6F5 SOCKET SOCKET I2F5 In certain sets IN PIN 3 REMOVE T/OCTAL pins 3 and 5 6Q7GT 4 PIN 3 SLIGHTLY of NO CHANGE the 6F5 may be 5 REMOVE LESS GAIN used as soldering tags. Any connections PIN 3 REMOVE INT /OCTAL SLIGHTLY to these tags I2Q7GT 4 PIN 3 must be re- NO CHANGE LESS GAIN 5 REMOVF moved before Brimariaing.

c, RATED CHARACTERISTICS cup 6F5 6Q7G /GT Heater Voltage 6.3 6.3 volts

Heater Current 0.3 0.3 amp.

Anode Voltage 250 250 volts

Anode Current 0.9 1.1 mA 5 KEY KE Amp. Factor 100 70 6F5 6Q7GT I2F5 I2Q7GT Bias Resistor 3,000 3,000 ohms NOTE : The characteristics of types 12F5 and I2Q7GT are identical to those of types 6F5 and 6Q7G /GT respectively, except for the heater ratings, which are 12.6v., 0.15A.

a service offer BRIMARIZI NGdealers sets first-class tain PWMAII which fiers whose certain °ned round RADIO VALVES beendeli thane are now valves which

STANDARD TELEPHONES AND CABLES LIMITED, FOOTSCRAY, SIDCUP. KENT. 9 A SERVICE PLAN FOR THE SERVICE MAN

www.americanradiohistory.com 32 Advertisements Wireless World December, 1917 MWILSON. COIL UNITS IN KIT FORM SMALL BOX TYPE

6- WAVEBAND SUPERHET UNIT Small Box Type With R.F. Stage, 5-2,000 metres. Unit. Designed by F. H. Wilson and used during the PAST THREE YEARS in our Circuit No. 20. BRIEF SPECIFICATION Coil Screens in alum. 18 s.w.g. (Three sections R.F., H.F., and Osc.) Coils. These are dust iron -cored High "Q" with adjustable inductances sealed to suit the screening factor. Tuning Range from 5 to 2,000 metres with a gap between for the I.F. frequencies. A.V.C. is operative on all wave bands. A.V.C. and H.T., decoupling resistors and condensers are fitted to each section, the condensers being silver mica and non -inductive. The complete screening, short wiring, superb workmanship, together with the best obtainable components contribute to the magnificent performance achieved with this unit. Testimonials to this effect are being constantly received from distances as far as West Africa, Australia, America, and home users. The Switch is a two pole, six way, three bank, with Sporting Plates on both primary and secondary to short circuit coil windings not used. Two Aerial connections are provided, both screened, A.I for Broadcast reception, A.2. Di -pole for short waves, all variable trimmers and padders are of the ceramic type, fixed padders being silver mica. Measurements when assembled, 0 5" deep x 51" wide x 3" high. Price £57 10 All connecting leads are colour coded and full -size practical and theoretical blue prints are supplied FLAT TYFE 6- WAVEBAND SUPERHET UNIT With R.F. Stage. 5 -2,000 metres. Designed by F. H. Wilson and used in our UNIT SYSTEM OF CONSTRUCTION (No. 3 Unit) for over two years. The specification is the same as for the Small Box type. Measurements when assembled, lt C 10 51" deep 8.'," wide 3I" high. Price 7 7 0 SPECIAL NOTICE Look out for our new circuit with the following outstanding features : (I) Two R.F. Stages. (2) Double Superheterodyne, 2 I.F. Frequencies. (3) Super -regenerative I.F. Stage. (4) Variable Selectivity. (5) Noise Suppressor. (6) Push -Pull triode output. (7) Flat Type Unit 6 Wave bands as above unit but extra R.F. Stage. BLUE PRINTS CIRCUIT No. 20. 9 -VALVE SUPERHET, including magic eye 6 -VALVE SUPERHET CIRCUIT including magic eye and and rectifier. 6- Wavebands with R.F. stage. 12 watts push - rectifier. 3- Wavebands 16 -47m, 200 -540m. and 800-2,000m. The pull output with radiogram switch. R.F. and audio volume few Long Wave Stations now operating are well received, with high fidelity on the Medium band and the performance control. A.V.C. and negative feed -back. Full specification on Short Waves is as good as obtained on some purely short- on 2 Full -size application. practical and one theoretical blue wave receivers 2 Full -size practical and one theoretical prints with detailed price list of components, 5'- per set. blue prints with detailed price list of components, 3'6 per set. Demonstrations of the above receivers can be heard during business hours. 307, HIGH HOLBORN M. WILSON LTD HOLborn 4631 LONDON, W.C.1

www.americanradiohistory.com December, 1947 reiess rIQI 463 Ignition Interference

TTENTION to the design military equipment operates. The that optimum results are obtained and layout of the engine method has, however, serious dis- with such resistors suitably dis- ignition system, on the lines advantages; the capacitive load posed in the H.T. circuit. suggested in the first part of this on the system reduces the voltage It is impossible to generalize article, may often reduce the in- output and necessitates the use of about the degree of suppression to terference considerably, but such high -energy coils and magnetos ; be expected with a given combina- reduction will not in general give there is increased wear on the con- tion of resistors, as this varies with the degree of protection to radio tact points and the sparking plug the particular vehicle under test, services specified in the old or en- electrodes erode rapidly unless the frequency of measurement and visaged in the new British Stan- erosion resistors are fitted. These the way in which the resistors are dard Specification for automobile resistors, of the order of 1,000 fitted in the ignition circuit. How- interference. ohms, serve to limit the peak dis- ever, for the frequency band up Additional suppression is, there- charge current-and prevent arc- to zoo Mc / s and more particularly fore, necessary. The methods in around the television frequencies, common use are complete screen- the following statements hold. " ing, and resistors in the high -ten- Concentrated resistors, for opti- sion leads. High- frequency chokes 2.- Methods of mum efficiency, must be placed as in the leads will reduce the inter- close as possible to the source of ference and proprietary types Suppression the spark, i.e., at the actual plug were marketed at one time. If and distributor terminals. For they are used it is essential to in- equal values of resistance the dis- corporate a small capacitor be- By W. NETHERCOT, tributed type gives rather more tween earth and the point of M.A., B.Sc., F.Inst.P. suppression than does the concen- attachment of the lead to the trated one. The resistance of an choke. Tests made on proprie- (British Electrical and Allied individual concentrated resistor or tary types at frequencies up to Industries Research Association) a distributed resistance lead 5o Mc / s showed them to give should not usually be less than rather less suppression than does 5,000 ohms nor need be greater the average resistor. It is to be ing ; they do not contribute than 15,000 ohms. With some en- expected that they would have a materially to the suppression of gines in which the distance be- frequency characteristic and prob- interference. tween coil and the distributor is ably the suppression efficiency Insulation problems are more very short, it may not be possible falls off at the higher frequencies. acute due to the increased stress to employ a distributed resistance They are not used today because on the H.T. cables and termina- lead of more than 1,000 -2,000 they compare unfavourably with tions and moisture penetration ohms. resistors in size, cost and ease of into the harness has to be pre- The increase of suppression with fitting. vented. The equipment i . expen- increase of the total resistance be- Complete Screening. -In com- sive and inevitably the accessi- tween the H.T. terminal of the plete screening the coil or mag- bility is much reduced. These coil or magneto and the sparking neto is encased in a metal box to disadvantages have to be tolerated plug falls off as the value ap- which is attached, by a suitable in aircraft and for military and proaches 25,000 ohms. E.R.A. gland, the screened harness. This other purposes where radio recep- tests have shown that between consists of a flexible screened tion is of paramount importance, 25,00o and roo,000 ohms the in- cable leading to the distributor, but they rule o:-t the method for crease of suppression is never similarly encased in a metal box, general adoption on ordinary more than 6 db and often is quite and screened leads from the dis- vehicles. negligible. tributor to the sparking plugs. Resistor Suppression. -This is The maximum suppression The screened sparking plugs are the method which is employed in likely to be achieved by resistors joined to the high- tension leads by all cases where the highest degree i 40 -5o db, and at any frequency metallic glands completely enclos- of suppression is not required. It in the band 200 kc / s -ioo Mc is it ing the plug leads. The screened is simple and inexpensive, but is possible to obtain not less than cable is bonded at frequent inter- gives good suppression over much about zo db. vals to the engine. With coil Cif the frequency range. The re- The simplest arrangement for ignition the low- tension lead to sistors may be of the concentrated coil ignition and for magnetos with the battery is fed through a or the distributed type ; in the separate distributors is one resis- screened choke -capacitance filter. latter the centr: ! conductor of the tor (or resistive lead) between the Complete screening, if properly ignition cable has a resistance of coil and distributor. With this it designed, reduces the ignition in- 5,000 -55,000 ohms per foot. The is possible in some cases to reduce terference to a level which is too concentrated types are made in the interference at television fre- low to be measured, at least over values of 5,000, io,000 and 55,000 quencies to below the 50µV / m the frequency range in which most ohms, experience having shown level at Soft. It is usually ineffec-

www.americanradiohistory.com 464 Wireless World December, 1947

Ignition Interference - zo db is attainable for frequencies effective resistance at television tive above 8o Mc / s and may even up to too Mc/s. frequencies was approximately increase the interference level. The efficiency of distributed re- 15,000 ohms. Such resistors Tests made on about 4o differ sistors can be increased consider- might be of use in cases where ent vehicles showed that the ably by covering a short length of engine performance is affected by addition of a t5,000-ohm concen the lead at the plug end by a the ordinary resistors as they pre- trated resistor i.i the coil lead re- screen of metal foil to form a sent a low impedance to the low - duced the interference at 45 Mc / s small capacitor of about 2oµµ F, frequency components of the ig- by 3 to 23 db. This is a wide the foil being bonded to the nition spark and so have little range, and it means that the single cylinder block. This forms a net- effect on the energy dissipated. resistor would easily reduce the work giving a high attenuation It would be interesting to experi- interference from some vehicles to from the plug at high frequencies. ment with high permeability below 501.(V /m and on others it Up to to db extra suppression materials such as Mumetal. would have practically no effect. may be obtained in this way, but The suppression efficiency of re- On most of the vehicles the reduc- as the method creates problems sistors at frequencies higher than tion was between to and 15 db as of cable insulation and earth too Mc /s was investigated in the evidenced by tho mean value of termination it has so far been series of tests described on page 14 db. used only experimentally. 355 of the October issue and Further suppression is obtained The use of iron wire as a re- quantitative estimates for both by inserting resistors at the spark- sistance material for distributed concentrated and distributed ing plugs (essential for magnetos resistors appears to offer some types were obtained over the fre- with integral distributors) and at possibilities. Suppression of the quency range 40 -65o Mc / s. So the distributor end of the sparking order of 25 db has been obtained far as the author is aware, these plug leads. Alternatively dis- at television frequencies with are the only measurements which leads can tributed resistance plug 40 be used. In the above series of tests the effect of adding resist- N--N HORIZONTAL POLARISATION ance up to 15,000 ohms between . -- VERTICAL POLARISATION the distributor and sparking plugs was to increase the suppression by 50 anything up to zo db. A British military vehicles which \ were not carrying radio equipment were suppressed so that they did 20 Akil not cause interference to those í 111 that were. Concentrated resistors V w I NIP' I were used, 5,000 ohms at the coil 1 , V \L and sparking -plug terminals of the 10 II \ distributor and 15,000 ohms at V \i the sparking plugs. This is the combination of concentrated resistors which is likely to give opti 0 100 200 300 400 500 600 700 mum results, although often the plug resistance can be reduced to FREQUENCY IN McIs 5,000 ohms and those at the spark- Fig. I. Suppression efficiency of concentrated resistors on ing -plug terminals of the distribu- Vauxhall "14" car. tor omitted without noticeable loss in suppression efficiency. some cars fitted with distributed have been made over this fre- Table I shows the suppression resistors comprising lengths of quency range. achieved by such a combination 3o S.W.G. iron wire wound in a Concentrated resistors, 5,000 on two 1940 Vauxhall cars. single layer on a thin strip of in- ohms in the coil lead and 5,000 and 15,000 ohms at the distributor and sparking plugs re- TABLE 1 spectively were tested together with a distributed resistor harness Suppression in db for the " 14 " car. This con- Vehicle sisted of a coil lead of 1,800 ohms 30 35 40 45 50 80 100 Me/s and sparking plug leads varying between 2,70o and 5,000 ohms. Vauxhall 12 33 25 36 33 24 >16 21 Vauxhall 14 21 27 25 27 35 23 22 Figs. 1 and z show the respective efficiencies of the concentrated and distributed resistors between 40 and 65o Mc /s for the This shows that the degree of sulating material. The D.C. re- " 14 " car. Fig. 3 shows the con suppression varies with the fre- sistance of these particular sup - centrated resistor results for the quency but that a minimum of pressors was 70 ohms but thei? `1z." These curves are exceed-

www.americanradiohistory.com December, 194.7 Wireless World 465 ingly peaky, part of which may high frequencies are different and trouble is experienced with the re- be due to the difficulty of in some respects more serious than sistors themselves and electrical measurement. These cannot be those at television frequencies. failures are fairly rare. The disadvantages are that it is not very 4 easy to fit the plug type on some

1 I 1 1 I engines with jacketed plugs ; fur- el--k HORIZONTAL POLARISATION thermore the connections have a .--r VERTICAL POLARISATION tendency to work loose and short- .3 ing may occur due to the exposed I metal ends touching some part of the engine. With the coil lead type it is impossible to put them 20 i. x absolutely adjacent to the points r' \\Y ;" v of sparkover and so maximum f efficiency may not be obtained. In the event of general adop- 10 I \ + `\\ % tion of suppression for vehicles, iiV V either voluntarily by the motor manufacturers or as a result of 1 legislation, the manufacturer will 100 200 300 400 500 600 700 assume the responsibility of producing his vehicles suppressed to FREQUENCY IN Mcfs some specified level. If the suppression is obtained by resistors, Fig. z. Suppression ratios with distributed resistors on Vauxhall " r4 ". then it will be maintained only for as long as the resistors are not re- easily hap- relied on to an accuracy better Design of Resistor Suppressors. moved, which might db and as the suppression In commercial types of concen- pen when servicing or replacing than 5 faulty components of the ignition curves were obtained by sub- trated suppressors the resistor ele- tracting suppressed values from ment is enclosed within a sleeve of system. The ideal solution is to ones a maximum insulating material ; the termina- incorporate the suppressors in the unsuppressed components themselves where error of ro db is possible. It is tions for those intended for in- to note, however, that sertion in the coil lead or at the they will be out of sight. There interesting would be no difficulty in mould- there is no general falling off in distributor ends of the plug leads efficiency with in- consist of wood screw threads at- ing the coil lead resistor in the suppression rotor, or resistors in crease of frequency, the average tached to each end of the re- distributor zo db. sistor. Ignition cable is screwed the distributor terminals. The in- value being about the resistor in The distributed resistors, of into each end of the resistor, but corporation of plug resistance than the with resistors intended for attach- the body of the sparking plug much lower difficulties due to the concentrated type, gave equally ment to the sparking plugs one does present although the good suppression 40

sup- 1 1 1 crests and troughs on the I 1 1 1 pression frequency curves do not Il it---* HORIZONTAL POLARISATION coincide. This could be due to - -+ VERTICAL POLARISATION the distributed sup- the fact that 30 pressors are more efficient ; on the other hand it might have been found that concentrated resistors, equal in resistance to the dis- have given 20 L41 tributed, would equally good results. IMIIIIM_ It will be seen that the sup- 1i pression efficiency is extremely Ci ME low at frequencies around 300 inII Mc /s and 600 Mc /s, so low in fact the measurements were re- -III,IEMin that peated, but with the same re. sults. In the region of 300 Mc /s 0 100 200 300 400 500 the lengths of the H.T. leads or at least some of the longer ones, are FREQUENCY IN Mcia approaching the half wavelength Fig. 3. Effect of concentrated resistors on interference from Vauxhall " rz ". and so the possibility of standing waves on them has to be en- visaged. If this be so it means end at least has some form of elevated working temperature that the problems of ignition in- spade or screw -type terminal for (about 250 °C). It is possible to terference suppression at very connection to the plug. Little incorporate erosion resistors of not

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Ignition Interference - attractive alternative to the con- however, that little or no trouble more than r,000 ohms satisfac- centrated resistor. is to be. expected in fitting resis- torily, but it is not so easy to in- Effect on Engine Performance. tors to the popular type low- and crease this to the 5,000- 15,000- -It was widely held at one time medium -power vehicle, but that ohm value needed for suppres- that the use of resistance suppres- difficulties may arise with some sion. It would seem that further sors on engines had detrimental expensive, high -powered types. research on this point is called effects on performance, e.g., that Acknowledgment. - The mea- for. Distributed resistance cable it may cause difficult starting from surements at frequencies above in its commercial form is a com- cold, poor slow running, bad zoo Mc / s were made possible by paratively recent innovation. It acceleration and running at high the collaboration of the Radio consists of a central conducting speeds. Much of this was preju- Division of the National Physical core of graphited silk covered with dice, and now the general opinion Laboratory to whom acknowledg- a sheath of rubber. seems to be that on most popular ment is due ; and in particular to Conducting rubber cable has types of engines there is no Messrs. B. G. Pressey and G. E. been made but it is unsatisfac- adverse effect, even with resistors Ashwell. tory on account of the variability considerably greater than those References. of its resistance, which is very de- needed for suppression purposes. I Gill and Whitehead : " Electrical pendant on mechanical stress. It Interference with Radio Recep- In 1939 the Automobile Re- tion," J.I.E.E., Vol. 83, 1938. is also difficult to make the ohms - search Association carried out 2 George : "Field Strength of Motor per -foot low enough and to make tests on behalf of the Society of Car Ignition between 40 and satisfactory terminations. Motor Manufacturers and Traders 450 Mc /s." P. I.R.E., Sep- The earlier forms of the on a number of engines and tember, 1940. graphited silk cable were unsatis- vehicles of widely different types 3 Eaglesfield : " Motor Car Ignition factory for the same reasons, but using resistors from 5,000 to Interference.', Wireless Engi- neer, October, 1946. under the stimulus of the Fight- 500,000 ohms.' The conclusions ing Vehicles Design and Develop- 4 B.S.S. No. 833: " Radio Interfer- were that there was no effect at ence Suppression for Auto- ment Department of the Ministry moderate or high speed or under mobiles and Stationary Internal of Supply, a satisfactory form of appreciable load and that side - Combustion Engines." cable was evolved. The method valve engines in general were in- 5 B.S.S. No. 727: " The Charac- of termination used consists sensitive to the effect of suppres- teristics and Performance of of cutting back the rubber sors. Some overhead -valve engines Apparatus for the Measurement sheath by about an inch and were affected by suppressors at of Radio Interference." crimping the silk core to a single 6 B.S. Code of Practice: " Reduc- the lower speeds, the maximum tion of Radio Interference or multistrand copper wire of loss of power being 9 per cent. appropriate Caused by Motor Vehicles and size. The whole ter- Generally the loss was much Internal Combustion Engines." mination is then moulded in smaller than this. The effect was 7946. rubber, with the result that the found to be due to insufficient 7 Hendry : The Effect of Radio cable end is completely sealed turbulence and could be remedied Interference Suppression on from the atmosphere and the by the fitting of shrouded inlet Engine Performance." I.A.E. mechanical stress is taken by the valves. Factors such as mixture Report, March, 7939. moulding and not by the silk strength, ignition advance, spark- core /copper wire joint. E.R.A. Reports. ing plug gap, leaky plugs and Ref. M/ T28: " The Suppression of This construction has proved spark energy were found only to Short -wave Radiations from eminently satisfactory for military have an effect if the predisposing Automobile Ignition systems." purposes but it is hardly suitable condition of insufficient turbulence Rel. M /T44: " The Properties and for general civilian use. The leads was present, and even then their Performance of the E.R.A. are relatively expensive and the effect was small. Additional evi- Short -wave Receiver for Field replacement problem is difficult as Strength Measurements." dence in confirmation of these Ref. M /T47: "Short -wave Inter- each lead is made, so to speak, conclusions is provided by long to measure, Furthermore, ference from Ignition Systems." the experience with army vehicles. Ref. M /T62: " The Study of length of the moulding is such Some of the manufacturers of Capacity Spark in Automobile that on many vehicles, in which popular low- and medium -power Ignition Systems with Special the coil- distributor distance is vehicles report similar results ; on Reference to Short-wave Radio short, the actual length and, there- the other hand there is evidence Interference." fore, the resistance of the resistive that the performance of certain Ref. M / T63 : " The Radiated Short - part of the lead would be much Wave Disturbance from Auto- of the more expensive, high mobile Ignition Systems." too low unless cable with a higher powered vehicles is quite notice ohms -per -foot were Ref. M /T64: " Apparatus for the available. ably affected by resistors, even Measurement of Interference at This means duplication of cable by those of low value. A detailed Ultra High Frequencies." types which is undesirable. discussion on the reasons why Ref. M/ T75 : " The Capacity Spark What is wanted is a cheap and resistance in the ignition circuit Discharge of Ignition Systems." simple termination comparable in affects engine performance is out- Ref. M / T81: " Radio Interference from Automobiles in the Range its ease of fitting with those used side the scope of this ; paper 30 -220 Mc / s. on normal ignition cable. If this furthermore, the quantitative evi- Ref. M / T82 : " The Radiation from difficulty can be overcome then dence is not as extensive as one Automobile Ignition Systems at the resistance cable becomes an would wish. It would appear, Ultra High Frequencies."

www.americanradiohistory.com December, 1947 Wireless World Unbiased With the exhibits I had no fault studying the effects of broadcast to find at all, but in the case of one music on national output. These or two of the exhibitors-and I bovine statistics accord with my would emphasize that it was only findings regarding humans, which is one or two-courtesy seemed to be only to be expected as the cow is in as short supply as their goods so far more akin to us than Darwinian far as the home market was con- apes and monkeys. In infancy do cerned. In fact, in the case of one we not fall back on the cow's out- of them, it was only when I had put as our iron ration? There have, gone round the corner and bashed of course, been one or two notable my bowler into the semblance of a exceptions' to this rule, such as Radiolympressions sombrero and adopted a lisping Cas- Romulus, Remus and Kipling's IT is far too late to say anything tilian accent that I could get any Mowgli. about Radiolympia but it is none attention. I concluded it was, even As a result of my studies I am not too early to start thinking about the then, only because the young man in the least surprised to find that next show and what we should like on the stand was interested in bull- the cows' output is greater under to see there. As I cannot do that fights, of which I was fortunately the influence of chamber music. without some reference to the last able to give him a first -hand descrip- This is exactly what I should have show I have got to refer to it tion. It is only fair to say, however, predicted, for my colleague, a pro- whether you like it or not. that at most of the stands I got all fessor of industrial psychology, has Since one of the main objects of the information and help I wanted, the show was to encourage the ex- no matter whether I spoke with a port trade, I entered it with the eye Castilian lisp or the idiom of sele of the export buyer. My first im- Suffolk, so often debased by the By FREE GRID pression was distinctly painful as I ignorant into silly Suffolk. had the misfortune to sit down Lastly, I definitely did not like rather suddenly and heavily on that the " Klystron- effect " manner in portion of my anatomy intended for which we were bunched into Tele- proved to me clearly that had this that purpose. The cause of the vision Avenue from time to time type of music been provided by the trouble was apparently a banana - and then ejected in gulps or waves B.B.C. in their wartime music - skin deposited by one of the many after the principle of that famous while- you -work broadcasts, then it children one saw being reluctantly tube. Moreover, the period between is not at all improbable that the war dragged around the show by inter- admission and emission was too would have been over in half the ested parents. short to give viewers the oppor- time owing to the enormously in- In addition to this, however, I tunity of making comparisons. creased tempo of munitions produc- received a very painful mental im- tion. In fact, output might have pression in my self- appointed rôle of risen to such proportions as to have foreign visitor and buyer when I enabled us to finish the war without glanced aloft at the gaunt girders of Lacteal Lessons outside help. Olympia unadorned by their usual IWAS intensely interested to read Music of the " step lively " kind array of bunting and gaily painted in the Radio Times some time which was actually broadcast tended panels. I do not in the least blame ago (Oct. loth) a letter from a to produce exactly the opposite the organizers of the exhibition as farmer in which he claimed (I pre- effect to that desired. The workers, they doubtless had neither bunting sume that it was "he ") that his instead of getting on with the job, nor labour with which to put it up. cows gave their highest yield of became interested in the music, But all the same, if you are hoping milk when listening to chamber whereas, had chamber music been to sell goods to a customer it does music broadcast by the B.B.C. provided they would have pressed pay to dress well and put on a mil- whereas certain other types of pro- on with their work with all speed, lion- dollar look even if you have no gramme, such as swing, made them if only to finish the job and get shirt under your Palm Beach suit. away as quickly as possible. Any commercial traveller of repute !fr The great thing, of course, is to w11 bear me out in this. .P get the Government to profit by the If labour and materials are still lessons to be learned from my re- short when the next show is held, searches and apply them to the then most of us, I feel sure, would present economic crisis. They be willing to lend the yards and should instruct the B.B.C. to make yards of bunting, etc., which we an immediate start in the urgent hang out from time to time to cele- task of pumping out chamber music brate the end of a war to end war to the factories, thus enabling us to and such like things. As for save both our bacon and our basic. labour, well, I cannot help recollect- I am, however, having tremendous ing my early days before the mast difficulty in finding the correct Gov- in a whaler and feel sure that there ernment department to approach. are many more like me, as well as a Kicking the bucket. I have been referred from one to the good sprinkling of yachtsmen among other until I have completed the us wireless men, who would be only inclined to kick the bucket in a cycle and am well on in the second too pleased to do the job gratis and literal sense. lap. But I have not yet lost hope waive all our rights under the Work- I am particularly interested in the of eventually getting a select com- man's Compensation Act. matter since I have lately been mittee to sit on this idea.

www.americanradiohistory.com !OM Wireless N'urld December, 7947 Sidebands Again must know what frequency Why a Modulated Wave Must Have means, although it is quite an abstract idea. One thing that surely More Than One Frequency must be granted is that in a pure

By CATHODE RAY" To dispose of the last point first ; it must be understood that Fig. 3. Sample of carrier wave hand-keyed or even machine- IN " Channels of Communica- interrupted by morse keying. keyed morse represents quite a Here the carrier cycles that tion "' I referred to the old low frequency of modulation, so remain are identical with those in controversy about the physical it is difficult to make a receiver Fig. r, so where do side fre- reality of If letters I sidebands. selective enough to demonstrate quencies come in ? have received are anything to go loss of morse modulation due to by, it seems that this controversy wave train (that is, one having loss of sidebands. But it can be only a single frequency) every still rages, if not openly, then at done. least in the minds of some readers. cycle occupies exactly the same Although the sceptics can time. The only other requirement The cause of the trouble, you re- hardly deny that high modulation member, is the statement that it is that every cycle must have a frequencies are lost when the re- sine shape (that includes the is impossible to modulate a carrier is very ceiver made selective, they cosine, of course, because it has wave without producing waves of reply that the sort of modulation other frequencies. In particular, exactly the same shape). Prob- used, say for broadcasting, no ably nearly everybody one cannot vary its amplitude doubt does cause sidebands, will grant without producing other fre- that, too, but in case there is any quencies. hesitation it may be as well to It seems that many people are offer some reason for preferring prepared to take the word of the one particular shape to all others. As Fourier pointed out, a re- wise that this is so, but just can't Fig. 2. Simplest amplitude see it themselves. Others are modulation of Fig. r, in which peating wave of any other shape frankly sceptical. They say the modulating waveform itself can be analyzed into a combina- " Fig. r depicts a portion of un- is a pure sine of lower frequency. tion of sine waves whose fre- modulated carrier wave of a cer- quencies are exact multiples. But which can be tuned out, but that tain frequency ; what is to prevent a sine wave itself cannot be one from varying the amplitude just proves that it cannot really broken up into any simpler form. as in Fig. 2, and so conveying in- be pure amplitude modulation ; This is not just a mathematical see 1-3 _ formation without affecting the Figs. again, etc. fancy. If an oscillation is of sine frequency at all? This is What we have to find, then, waveform it can be tuned in at amplitude modulation we are is some convincing way of show- only one frequency, whereas if talking about; not frequency ing that you cannot do things like the oscilloscope shows it to have Fig. 2 or Fig. 3 on one frequency. modulation ! " Or they may show any other shape, then the com- Fig. 3, in which the carrier wave The usual book method is to ponent frequencies calculated by is keyed to convey morse signals. add together waves of two or Fourier analysis can be detected. Its cycles are obviously identical three different frequencies, which They actually exist. with those in the modulated yield something like Fig. 2, and Another significant fact is that carrier, and therefore of the same to say that therefore Fig. 2 must the natural way for things to consist of waves of these different oscillate, either electrically or TIME frequencies. If two parts of mechanically, when complicating hydrogen combined with one part effects are absent, is according to of oxygen are found to be water, a sine law. That is proved mathe- Fig. s. The familiar graphical then it is reasonable to suppose matically and confirmed by ex- representation of a pure unmod- that water consists of two parts periment. ulated carrier wave. of hydrogen combined with one There is one important con- part of oxygen. Or isn't it? This dition in the second requirement frequency. Why drag in side - back -to -front sort of proof doesn't bands, which seem to be an en- seem to satisfy everybody. tirely unnecessary and unreal Then there is the mathematical complication? approach. This may have to be They may also offer experi- made very circumspectly, like mental evidence, saying that even a banker's approach to a com- Fig. 4. Each of the equal time - when their receiver is tuned munist. I shall try to render it sharply to one frequency it can intervals is occupied by a single a little less abstract than usual. pure sine wave. But the wave still receive morse. But we are arguing about fre- train as a whole is not exactly Wireless World, June and July, X947. quency, and so even the sceptics sinusoidal!

www.americanradiohistory.com December, 1947 Wireless World 469

for singleness of frequency ; the scale, as at D or E, then it is still sible and calculating from a table sine shape must hold for every a sine wave of the same fre- of sines' the corresponding values cycle, no matter what part of the quency. of v ; when these pairs of y and t cycle one takes as the starting ` ` Ha ! " say the sceptics, are plotted as a graph the result point. In Fig. 4 each of the equal " That is just our point ! All you is a continuous pure unmodulated time intervals A, B, C, D, etc., do in true amplitude modulation contains one cycle, and each has is to expand and contract the Fig. 6. Starting from a sine shape, but I hope you 'will amplitude without altering the either a or c, there is wave train as a of any one whole cycle of pure agree that the shape or the duration sine waveform. It is whole cannot be called sinusoidal! cycle, and the result, as you have instructive to consider It is certainly not a natural mode just admitted, is a pure single - the cycle starting at b, of oscillation, and in practice frequency wave train." however. would not be found to be entirely But is it? Look at Fig. 6, free from harmonics. where two adjacent cycles of different amplitude are shown. Reckoning one whole cycle from either a or c, each has an im- wave such as maculate sine shape. But what Fig. r (extended about reckoning from b? The indefinitely i n unequal half- cycles and the nasty both directions join between disqualify that cycle of time). If you plot cosines in- completely. So any wave train stead of sins, the result is the of which Fig. 6 forms any part same except that it is a quarter of fails to meet the requirements for a cycle nearer along the time axis. a single frequency. It is no good You can complicate matters by saying that the two cycles in adding together as many sine and Fig. 6 are too different in ampli- cosine waves as you like, with as tude, and that you can draw an many different amplitudes and amplitude- modulated train that phases as you like, but so long as doesn't show any faulty joints. only one f is used for them all the The fact that the faults are too result is invariably a pure un- small to be seen by the eye does modulated wave train. You cannot mean that they are not there, not possibly obtain a graph like or even that they are negligible Fig. 2 -still less Fig. 3 -from an in radio communication. Nor is equation in which there is only it any good rounding off the sharp one f. angles with a pencil, because that But if you draw the graph of an destroys the purity of waveform. equation in which v equals Vpsin What we have shown, then, is 27rft plus equal -amplitude sines of that it is not possible to vary or two other frequencies equally modulate the ampli- above and below f, the result is Fig. 2 simplest case of am- A -E are tude of a carrier -the D Fig. 5. all pure sine wave without spoil- plitude modulation. Perhaps it waves, and are ing the pure wave- is because this is such a tedious assumed to re- form of the whole ; job to do, and the drawing has to peat exactly and and by every test- be done so accurately, that prob- continuously. mathematical, graph- ably not many students have That being so, ical, and experimen- actually taken the trouble. If A, D, and E are departure from everybody who is still not happy in frequency tal- equal sine waveform is about side frequencies would though different draw this graph, it might put an in amplitude. found to introduce B and C, though new frequencies. end to much of the uncertainty. equal to A in Bringing the It can be done either by drawing amplitude, differ mathematical a p - three pure sine wave graphs one in frequency. proach to b ea r above the other, the frequencies more directly; of the second and third being, if the graph of a voltage y varies higher and lower than that of the To deal with this simply, look with time t according to the first by an equal amount, and at Fig. 5. A is a single sine -wave equation then adding them all together vertically to make a fourth, cycle ; a sample from a continuous v = Vesinzir f t, succession. If it is compressed then it is a pure unmodulated which comes out like Fig. 2. Or or expanded along the time axis, wave of peak value Vo and fre- they can be added together as at B or C, then obviously the quency f. If you assume any con- numerically to give the data from frequency is altered. If it is ex- stant values of Vo and f, you can which the final graph is drawn, panded or contracted along the make a table; writing down as If the table is made out in degrees (instead of radians), substitute 36o for 1i in the amplitude axis only, strictly to many different values of t as pos- equation.

www.americanradiohistory.com 470 Wireless World December, 1947 Sidebands Again - The answer to that one is the One can usually grasp difficult by using a table of sines to definition of frequency, namely, ideas more effectively by visualiz- evaluate the equation- the rate at which a periodic wave ing them in a number of different v= V,sin2aft repeats. If a roo -kc /s carrier ways. There is a much neater + V2sin 2a(f + fm) t wave is modulated at 6 kc / s, each way of demonstrating the mul- +V2sin27r(f- fm)t successive cycle is slightly differ- tiple- frequency composition of a You can use any numbers you ent, and one has to wait for 3oo modulated carrier than by plot - like for V,, V2, f and fm, so long cycles of the loo kc / s to be shown ing the graphs, yet it seems to be in order to see the programme much less used. It comes direct round to where we came in. (300 from the basic idea of vectors, is the lowest common multiple of shown in Fig. 8, where OA is a 6 and roo.) By that time the car- line representing by its length, V, rier and modulating waves are in the peak voltage (or whatnot) of the same relative phase as at the the continuous oscillation, and its beginning, and the whole thing number of revs per second around repeats. Therefore, the funda- O represents the frequency. The mental frequency is + kc /s, and instantaneous voltage is then re- (b) the three component frequencies presented by the projection of OA in the modulated wave, 94, roo on the vertical axis, YY. At the IIII and ro6 kc /s, are respectively the moment shown by the full line it iz 3 4 5 6 7 8 9 10 11 12 282nd, 3ooth and 318th har- is zero, of course ; but, as OA (f) monics. So everything is fully rotates, its projection oscillates HARMONICS according to Fourier after all. A up and down about O sinusoi- Fig. 7. In the waveform gen- waveform consisting of harmonics daily. In the dotted position erated by an oboe (a) the funda- without the fundamental is, in OA the voltage is v,. mental cycle is not A, as might fact, of the Fig. 2 type. The Assuming now that a pair of be supposed, but B. This ap- sound waveform produced side frequencies pearance is because the funda- Y by an oboe (Fig. 7) is an ap- Fig. 8. The is added, the mental amplitude (b) is nearly vectors zero. Similarly in modulated proximate example. simple vector repre- waves the carrier frequency is So a typical amplitude principle. senting them not the fundamental, but a high modulator is - whether it m u s t rotate harmonic, and the side fre- knows it or not -a device .w respectively ' a quencies are other harmonics. for producing a little slower combination of VI and a little as V2 is not more than half V,. very high har- i faster than the You will see why later; fm, the monics, all of carrier - wave modulating frequency, is, of which are vector OA. course, normally much less than grouped symmetrically Supposing they f, the carrier -wave frequency. around one fixed frequency, are each half as long as OA, I hope that Fig. 6 has disposed even although the absentee then in Fig. 9, where the side - of the fallacy that it is possible fundamental or fundamentals frequency vectors AB and BC to modulate the amplitude of a may be varying over a very rotate about A and B respec- sine -wave train without spoiling wide range of frequency. The tively, the projection of the point the purity of waveform and there- fact that the proprietor or de- C on the vertical axis gives the by introducing other frequencies. signer of the modulator never Y result of adding the three wave But while you may now see that really intended to achieve this trains. there must be a slight (even if curious result, and may even Well, of course, the task of try- visually imperceptible) distortion deny that it happens that way, ing to visualize the movements of the cycles in order to make doesn't make any difference to it. of the point C -to say nothing their amplitude vary as in Fig. 2, Actions that appear to be quite of its projection on YY -with a you may quote Fourier against simple (such as varying the am- mechanism consisting of three me by pointing out that, accord- plitude of a constant- frequency pivoted links all rotating at dif- ing to him a distorted waveform oscillation) often have unforeseen ferent speeds, is not one that I can be analyzed into a funda- but inevitable results. The mo- would wilfully inflict on readers. mental and harmonics. Now the tives of an eater are generally The difficulty can be removed by frequencies of harmonics are, of much less complicated than the imagining oneself to be on vector course, exact multiples of the processes which subsequently go OA, so that relatively it is sta- fundamental frequency. Suppos- on inside him. tionary. Then, relative to OA ing Fig. 2 is the result of adding In common parlance one would and to oneself, AB is rotating in together pure sine waves whose say that in Fig. 2 there were 16 one direction at modulation fre- frequencies are, say, roo, 94, and cycles, but, strictly speaking, quency, and BC in the opposite 106, it consists of these and no every cycle of a periodic wave- direction at the same frequency. others. The harmonics of the form must be exactly the same as And now it is quite easy to see carrier frequency. however, are every other, or frequency has no that C oscillates between its 26o, 300, 400, etc.; certainly not meaning. Remembering this, the present position and O, as shown 94 or 1o6. So what price fallacy of the " single- frequency in Fig. ro, where it is performing Fourier? modulated wave " cannot arise. one complete cycle at modulation

www.americanradiohistory.com December, 1947 Wireless World 471 frequency. So the combination does not prove that the ingredient sible to arrive at Fig. 3 or any- of a carrier-wave vector of fixed is unnecessary. It can be left out thing remotely like it by adding length and these two side -fre- temporarily because water and together any number of con- quency vectors is equivalent to unmodulated carrier waves are tinuous waves of the same fre- an amplitude- modulated carrier - the same on both sides of the quency. In practice there is wave vector. Bearing that in bound to be some rounding -off of mind, we can now get off OA, so the starts and stops, or an infinite as to see that it is rotating at B C number of side frequencies would carrier -wave frequency, and we o be necessary. The neighbours of realize that the whole outfit repre- B amateur transmitters sometimes sents a zoo -per cent amplitude - observe that excessively abrupt modulated oscillation. Smaller o keying causes a very wide range depths of modulation are repre- C of frequencies to be radiated. B sented by shortening AB and BC. This is another example of the inexorable laws of nature. They Second Sideband Function o C Fig. ro. Here the always win against anyone who A rotation of the calls a process " amplitude modu- So the purpose of the second carrier -wave vec- sideband is now quite clear, it is lation " and tries to ignore the tor, OA, is tern - fact that it is also sideband pro- to balance out what would other- A porarily stopped wise be a certain amount of phase to make it easier duction. To insist that there is modulation. Note, in Fig. zo, to see that the only one frequency in a Fig. 3 how the phase of OB varies rela- resultant of the type of wave, and that therefore tive to OA. And whereas the c- -B4-i side - frequency there is no limit to the selectivity length of OC, representing the waves, AB and of the receiver that could be used, modulated carrier amplitude, can BC, is in phase is defeated by practical test. For with OA. The although the connection with the easily be shown to vary sinusoid - three -fold com- ally about A, the variation in bination is the mathematical theory of sidebands cir- length of OB is non -sinusoidal. A same as one vec- may not be obvious, tuning The difference is not very serious :CM tor, OC, varying cuits that are made more and AB in length. more selective do in fact show an if is small, but becomes more C and more marked as single -side- increasing sluggishness and in- band modulation approaches zoo ability to respond to stops and per cent. So if one sideband is B starts in the signal wave, and the removed, as happens during cer- extent of this agrees exactly with tain types of fading, there is dis- the sideband calculations. Slug- tortion. B gishness in response, and tuning - C out of sidebands, may seem to be It might look as if such distor- o B tion would be a drawback in the two quite different things ; but single -sideband system of com- they are just two different ways munication, which economizes in Atlantic, and readily obtainable of looking at exactly the same transmitter power by omitting the almost anywhere, so the original thing. Nothing can be done about carrier wave and one, sideband. product can easily be reconsti- the sluggishness except widen the But as a carrier wave has in any tuted at the receiving end. Water tuning to the extent that mathe- case to be supplied locally at alone contains no nourishment, matics indicates to be necessary to the receiving end in order to Y and an unmodulated carrier wave include the sidebands of the render the signals intelligible, no information. But they are desired signal. In television, it is quite easy to supply so needed to make the nourishment where stops and starts have to be much of it that the depth of or information fit for reception. very sudden, that means a con- modulation is always very What about Fig. 3? So far we siderable wideness. small. Sup- have been con- pressed - carrier sidering the B QUALITY " AMPLIFIERS comm;uni- simplest case of IA amplitude ABOOKLET " Amplifiers for V -i+Z4*Zi modulation, High Quality Sound Repro- Fig. 9. A simple amplitude - with only one duction " is obtainable from the modulated wave is represented General Electric Co., Magnet House, by the addition of three modulating frequency. Each Kingsway, London, W.C.2. The vectors, all rotating at differ- " cycle " in Fig. 3 is admittedly information it contains is based on ent rates to represent the a sine wave, so it may not be easy the articles by D. T. N. Williamson component frequencies. This Y to see why merely stopping and in our April and May issues. It is difficult to visualize all at starting a succession of them intro- also includes a design for an ampli- once, but see Fig. r o. duces other frequencies. But it is fier with PX4 output valves and a two -stage pre-amplifier with tone possible to discover a combination correction, suitable for gramophone cation is very much like the of continuous waves of different pickups. A simplified alternative dried egg trade ; for economy frequencies which, added together, bias circuit is given for the 15 -watt in transmission one ingredient is give a keyed carrier wave like amplifier using KT66 valves as removed at the sending end, This Fig. 3, whereas it is quite impos- triodes.

www.americanradiohistory.com 472 Wireless World December, 1947

Quality Design for a Nine -valve Receiver

THE receiver described in this article is the result of a series of experiments Superheterodyne spread over a period of several weeks. Their object was the in a phase-splitting circuit, its fere too seriously in one another's development of a moderately outputs being passed directly to business. priced quality receiver which, a pair of power triodes operating The receiver is designed only while possessing all the features in Class A push -pull. The " magic for the medium and long wave- of a modern design, did not con- eye " tuning indicator is fed from bands, since in the writer's opinion tain " gadgets " and was simple the A.G.C. diode in the ordinary the programmes of the B.B.C. and to construct. The circuit which manner through Res. a few of the near Continental finally appeared The use of the stations provide sufficient enter- to satisfy all superhetero dyne tainment. For the enthusiastic t h e conditions By S. A. KNIGHT principle in a S.W. listener there is, of course, the proved quite con- "quality" receiver communications receiver, but that ventional and the components may cause some misgiving, in is certainly not our concern at the used are types in plentiful supply view of the high degree of selec- moment. (with the possible exception of tivity normally associated with As already pointed out, the Fig. r. Circuit diagram of the main receiver which is built on chassis separate R2 i R from the power unit. A chassis size rein X gin 6 r- X tin is suit- RII able. CS_ TII L CI,=

SS C16 II---0- s

T, =-s-

P, L6

the output triodes, of which more this type of receiver. In the circuit is a fairly conventional will be said later). present case, however, the selec- one. The aerial input is applied On examination of the circuit tivity is not sufficiently high to through Cr and Sr to the primary of Fig. r, it will be seen that the interfere seriously with the quality windings of the aerial coils, where receiver consists of a conventional of the output, but it should not it is applied to the main grid superheterodyne ' as far as the be thought that this results in windings, tuned by the first detector V, -that is, radio -fre- interference. In actual fact a capacitor gang C2, by inductive quency amplifier, triode -hexode happy medium has been struck coupling. A.G.C. is applied frequency changer, I.F. amplifier in the design of the apparatus, and through the tuned windings to the and double-diode -triode for de- selectivity and quality-the cats grid of the R.F. amplifier, the tection, A.G.C. and A.F. amplifi- and dogs of the wireless world - lower ends of the coils being cation. After this a medium seem to have settled down to an returned to chassis, from the impedance triode (6C5) is used amicable agreement not to inter- point of view of R.F. through C4.

www.americanradiohistory.com December, 19¢7 Wireless World +7 i

R3 provides a standing bias of rude is sufficiently well main- first two stages on gramophone approximately 4 volts on the valve tained over the wave ranges to and there are no voltage changes grid, and the screen is supplied avoid the need for including on the receiver H.T. line. This through R5 from the main screen - series or parallel damping resist- may seem uneconomical at first voltage line. The output of the ances on the coils sight, but the current drawn by stage is applied to the grid of the It will have been noted, no the R.F. and I.F. stages is very mixer through a further tuned doubt, in considering these two small in comparison with the A.F. circuit (second gang C9), and stages that the wavechange switch end of the set and there is little A.G.C. voltage is again applied is of the three -position variety. object in switching out the former to the stage through the coil This is incorporated to enable the when the apparatus is being used secondary windings. A standing receiver to operate as a radio - on gramophone. S7, located before bias of about 2.5 volts is de- gramophone, the third switch the detector, automatically veloped across R8 for the hexode position being used for this pur- switches the pick -up into circuit section of the frequency changer, pose. The actual switch consists when the switch is set to the third the screen being supplied through of a three -bank unit of the Yaxley position. R6. or Oak type, each bank being The intermediate - frequency The oscillator section of this three -pole, three position. S1 and signal appears at the anode of the stage consists of the long- and S2 are located on the first bank, frequency-changer and is applied medium -wave oscillator coils L5 S3 and S4 on the second, and S5, to the first I.F. transformer, this and L6 respectively, switch banks S6 and S, on the third. In the being of the permeability -tuned S5 and S6, and the third tuning case of the former two banks the variety with fixed -tuning capaci- gang C18. The oscillator is of the additional pole is not used. The tors contained within the can. tuned -grid variety, back-coupled circuit diagram is drawn so that This type of transformer was from the anode through C1, and the set is switched to LONG chosen on account of the high degree of tuning stability normally found with dust - i r on cores for the adjusting elements. This is important in fixed tuned circuits, such as I.F. transformers, where the bulk of the receiver amplification is being carried out. The anode circuit is decoupled in the normal manner by R7 and C11, R, also serving to drop the H.T. to the required value of 25o volts. The I.F. amplifier valve is a variable -µ p e n - tode, cathode -bias being obtained across R12 (4 volts), and the the coil primaries, and the grid waves, the central position being screen voltage via R11. A.G.C. capacitor and leak are respectively MEDIUM waves, with the third voltage is obtained - through the C14 and R9. The medium -wave position as GRAM. In this third secondary winding of the I.F. padding capacitor P1 and the long- position it should be noted that transformer. wave padding capacitor P2 are con- the aerial and signal grids of the The second I.F. transformer is nected at the dead ends of the coil R.F. and mixer valves are earthed, similar to the first, and the anode secondaries to avoid an increase in but that the anode of the former circuit of V3 is decoupled in circuit minimum capacitance and valve and the oscillator circuit this case by R13 and C18. The also to ensure that their moving connections are still virtually output of the secondary tuned plates are at chassis potential. R10 switched as for the medium winding is applied directly to the is the anode load of the oscillator, waveband. This is arranged so signal diode of V4, and also and maintains the anode at about that no changes occur in the through C24 to the A.G.C. diode 105 volts. The oscillation ampli- normal operating conditions of the of the same valve. R16, C20 and

www.americanradiohistory.com 474 Wireless World December, 1947

Quality Superheterodyne - COMPONENT VALUES C21 form an I.F. filter circuit, and the diode load proper, con- Cl = 50o pF. R15 =91kû sisting of the receiver volume C2, C9, C13 = 3 ganged 50o pF R10 = 0.5 Mû; Vol. control (with tuning. switch) control R16, completes the signal - ¡ ¡ R17 = 2 MO diode circuit back to the valve "3, C4, C6, C7, C8, Cis, Cll, C12, C17, C18, C19, C31, C32 = O.I µF. R18 4 cathode. A of = part the A.F. C5 = 4 µF. R34 = I Mn voltage available across R19 is C14 = 5o pF. R20, R21 = 470 kû tapped off by the slider of the C15, C28, C30 = 0.05 F. R22 = 220 kn control and applied through C22 C10 = 200 pF. R23 = r.5 Mû and R17 to the grid of the triode C20, C21 = roo pF. R24 = 1500 û section of the valve, where normal C22 = o.006 F. R28, R27 = 27 kfû A.F. amplification takes place. C23 = 25 µF, 25 V wkg. R28 = 22 kS2 C24 3o pF. kS2 R17 has a value of 2 M f2 so = R28 = 33o that C25 = 0.01 µF. Rn = 35o û (5 watt) the shunting effect on is R16 C26, C27, C29, C33 = 8µF, 45o V wkg. R35 = 500 û (5 watt) small. C34 = 16 µF 450 V wkg. L1, L2, Wearite PA2, PAi The value of C24, the A.G.C. C38 = 5o µF, 5o V wkg. L3, L4, Wearite PHF2, PHFi coupling capacitor is quite small P1, M.W. Padder, max. 600 pF. L5, L6, Wearite P02, POI (3o pF) since a larger value makes P2, L.W. Padder, max. 25o pF. Ch Che ; Suitable A.F. Chokes. it difficult to peak the secondary T1, T2, T3, T4 = 7o pF; Aer. and TR1, Premier Radio, Type M.0.7 of the I.F. transformer due to R.F. Trimmers. TR2, Premier Radio, Type SP.351 the damping of the tuned circuit. T5, TO = 160 pF ; Osc. trimmers. (see text). Rl = 2 kf2 I.F. Transformers, 465 kc /s, per- The A.G.C. diode load consists of R2, R7 R11, R13, R31, R33 = Io k82 meability tuned. R19 R20 , and in series, a total R3 = 47o 12 V1, V3 = 6K7G value of r.47 MSI, and full A.G.C. R4, R5, R29, R30 = 270 kSI V2 = 6K8G is applied via R21, R4 and R5 to RO=5ki2 V4 = 6B6G the R.F. and F.C. control grids, Rs = 250 S2 V5 = 6C5G C15 providing decoupling. About R9, R10 = 47 kû Y63 two -thirds of the total A.G.C. R12 = 390 S2 V7,, V8 6PX4 voltage available (that developed Rt4 = 22 kS2 (2 watt) V9 = FWI20 /350 across R19) is applied to the I.F. amplifier through the I.F. trans- by C23, an electrolytic of 25 -1,LF Outputs are taken from the anode former and reduces the possibility capacitance. Little need be said and cathode circuits, and are of harmonic distortion arising in about the tuning indicator; the consequently in antiphase, being this stage. Since the diode load triode control grid is supplied approximately equal, since R25 = is returned to chassis, a small from the A.G.C. diode through R27. R26 is the anode decoupling delay voltage equal to that de- R28, and is decoupled by C30. The resistance, and therefore does not veloped across R18 is present upon triode anode load is R39, a enter into the matter of the anode the A.G.C. diode and A.G.C. is, resistance of I Am, and the load, and the small bias voltage therefore, inoperative on very target is returned directly to the developed across R24 (about 3.5 main H.T. supply line. volts) does nothing to upset the CH2 The output of the triode section normal working of the stage. of V4 is developed across R22, and Some doubts were expressed dur- is applied to . the phase -splitter ing the design of this stage as to whether the proposed valve (6C5G) would stand the heater - cathode voltage developed across Frig. 2. Circuit dia- R2b, since one side of the heater gram of the power has to be earthed to avoid hum. unit. A chassis size However, after several weeks of gin x 4in x tin faultless operation, the valve is suitable for this unit which connects seems to stand up to the voltage to the main chassis quite successfully, and the per- through a cable formance and reliability have been entirely satisfactory. ON VOLUME CONTROL form. (OR MAY BE The push -pull output circuit is SEPARATE) necessary from a quality reproduction point of view, for it through C25 and R23. The value cleans out the unpleasant com- of RY3 is 1.5 M 0, but the imped- ponents of distortion present in ance of the grid circuit is much the single -ended receiver and more than this from the point of avoids the necessity for exces- weak signals. The voltage across view of a voltage appearing sive decoupling. Directly heated R18, which is about 1.3 volts, is between grid and earth. Such a triodes are used, despite the also bias for the valve triode stage is therefore liable to hum attractions of tetrodes from the section since the leak R17 is re- pick -up and short grid -lead wiring point of view of power efficiency. turned to chassis. It is by- passed must be maintained at this point. The use of negative feed -back is

www.americanradiohistory.com December, 1947 Wirclrss World 475 off necessary with the off from each other (in pairs) by The first winding is stripped nearly always (it is a simple matter latter (which offsets the advantage aluminium screens, the switch in practice effect banks being similarly spaced and to strip these transformers of iron, of a smaller drive), and the wound speaker mismatch is placed as closely as possible to and the heater windings are of a slight of the bobbin) and considerably worse with tetrodes their respective coil sections. on the outside 6.3 - volt winding substituted than it is with triodes. In fact, The output triodes depend upon a valves available. If the from 18 S.W.G. enamelled wire. a transformer ratio that is the -volt with 4 -volt types (PX4 or equivalents) The number of turns- per slightly high is preferable when the while reducing the cannot be obtained, then the is easily determined triodes since, is removed (it was power output, it actually improves 2 -volt types may be used. The 4 -V winding only alteration in the receiver 3 t.p.v. in the writer's case), the quality. The output trans- should be is a multi -ratio type is then that of the bias resistance and so no difficulty former used in replacing it with of generous dimensions and will R35 and the fact that the heater experienced any speaker must be rated at 2 V, 4 A. The a 6.3 - V winding. This winding, match to almost not be centre -tapped, impedance. The anode -to -anode mains transformer used by the which need load of PX4 or equivalent valves is 4,000-6,000 f2, and the undistorted output obtainable is about 8 watts. TR, Components Employed The power unit, which is built on a separate chassis, is shown in Fig. 2 and requires little comment. It is quite conventional, i3 the mains transformer delivering CH, 350-0-350 volts at 150 mA. as H.T. plus 6.3 volts at 3 to 4 A I for the valve heaters, and 4 volts at 2 to 3 A for the output triodes, winding for the H.T. with a 4 -volt I T, I.F.T2 rectifier. The heater winding for the output valves is centre- tapped for the inclusion of the bias resistance Rab. H.T. smoothing is carried out by C33 and Cao (8 + 1612F)' and Che. 2 P The characteristics of most of the components are given in the I.F.T., V3 I F.T2 list of parts, and few additional 1 notes are necessary. All re- L__J L _ _ J sistors may be rated half -watt PANEL A except where the table indicates A.G.C. cir- / otherwise, and for the c/ cuits quarter -watt types are quite Q sufficient. Capacitors, with the T5 VS C exception again of the A.G.C. and e/ cathode by -pass circuits where the c negligible, O e//, voltages developed are L29 Cs & C/ preferably be rated at INPUT should SOCKET 350 to 45o volts D.C. working. un- The coils are of the Wearite ) screened " P " types, each con- Ss.5a C27 sisting of a primary and a 5,&52 S3&S, & S7 secondary winding, and are available with tags to accommodate postage -stamp type trimmers layout to_ the main receiver. Fig. (a) shows a convenient upper- chassis directly across the tuned wind- 3. The panels A' and B are ordinary H.F. (b) shows the under - chassis layout. ings. They are Aerial, tag boards of suitable size and hold all the appro- and Oscillator types resistance and capacitor capacitors, etc. may Transformer priate resistances and capacitors. Cathode resistors, for an I.F. of 465 kc s, covering be wired for s. the ranges zoo-600 and 800-2,000 metres. In Fig. 3 (b) is shown a the receiver valves is a Premier type SP 351 then feeds skeleton layout of the underside writer as V8, the remaining which delivers as L.T. 4 V at as far of the main chassis, where it will 2 A serving the rectifier 2 -3 A and 4 V at 3 -6 A 4 V at -3 be seen that the coils are divided 1 -2 A, 4 V at

www.americanradiohistory.com 476 Wireless World December, 1947 Quality Superheterodyne-. padder capacitor at the low - namely, the excellent balance at heater and the 4 V at 3 -6 A frequency end of the band. With comparatively low levels (below r supplying the output valves. a signal generator suitable watt), and the homogeneity of its These windings are ready centre - frequencies for the medium wave- high- frequency response. There is tapped. If 2 -V output triodes are band are 1,500 kc /s (200 no marked focusing of high frequen- m) and cies and used, the latter winding must, boo kc /s (Soo m), and for the long none of the detached of course, be halved waveband, " featheriness " often associated and re- 300 kc /s (1,000 m) with frequency responses up to centre- tapped during the winding and 15o kc /s (2,000 m). With 15,000 c /s. In a properly designed of the 6.3 -V heater. It is there- station alignment, the B.B.C. baffle the low frequency response is fore essential to get the output Light on 1,149 kc /s (261 m) and sensibly uniform down to 4o c/ s valves before modifying the mains the B.B.C. Third on 583 kc /s with no major bass resonance. transformer or specially buying (514 m) are suitable for the We can fully endorse the maker's one suitable for the purpose. medium claim to have achieved natural waveband, while the quality The output from the power unit weather-forecast station on of reproduction at a volume 25o level suited to the average living is taken through a short cable kc /s (1,2oo m) and the B.B.C. room. form to an octal plug which Light on 200 kc /s (1,500 m) are connects to a valveholder socket suitable for the. long waveband. mounted on the rear of the main Each trimming operation should Manufacturers' chassis. The mains supply is also be rechecked as the opposite taken through this point to the end of the wave range is adjusted. Literature switch on the receiver volume The tuning indicator makes a control. ILLUSTRATED catalogue of silvered useful alignment " tool " for these mica condensers from Londex Elec- purposes. trical Manufacturing Co., 459, Fulham Alignment A table of voltages follows Road, London, S.W.ro (available to taken from the writer's receiver manufacturers only). The trimming of the receiver which will assist anyone who Revised leaflet (MV12r) of Milliard is fairly critical, but calls for duplicates this receiver. Transmitting Valves for Amateur Com- no special skill or apparatus. munications from Mullard Wireless A good signal Service Co. (Transmitting and Indus- generator is re- trial Valve Dept.), Century House, commended for I.F. alignment, Cath- Shaftesbury Avenue, London, W.C.2. but actual signals may be utilized Valve Anode Screen ode for the aerial, R.F. Descriptive leaflets dealing with re- and oscillator ceivers Type trimming Vt 220 110 4.1 186A and Type 371A, and padding. In accor- from Philips Electrical, Century House, dance with usual practice, the Hex. 250 l Shaftesbury Avenue, London, W.C.2. V2 Ose. 10 95 2.6 trimming order is : (a), I.F. V3 220 100 3.8 Leaflet No. 32 (Insulating circuits ; (b), medium -wave Beads) oscillator, V4 140 1.3 from Steatite and Porcelain Products, aerial and R.F. trim- v5 40 Stourport-on- Severn, Worcs. mers in that order at the high - V6 230 3.5 Instruction frequency end of the band ; sheets MR14 for use of v l rectifiers for H.T. (c), medium -wave padder capaci- vy j 325 48.0* supply to radio receivers (Supplement r) and Westectors tor at the low- frequency end of Vy 350 R.M.S. (Supplement 3); also data sheet No. 42 the band ; (d), long-wave oscil- on ' Westalite " rectifiers Types 16K lator, and i6HT, from Westinghouse Brake aerial and R.F. trimmers Across R,, in power in that order at the high- frequency unit. and Signal Co., 82, York Way, King's Readings taken with no signal, Loco S2 per Cross, London, N.i. end of the band ; (e), long -wave volt meter, highest ranges in each case. Leaflet describing the " Derwil servicing cradle for receiver chassis from the Wilder Instrument Co., 75 -8r, Barker Model 148 Speaker Tooley Street, London, S.E.r. Leaflet giving details of the " Reveille " combined clock and radio Single -diaphragm Wide -range Reproducer receiver from Thames Valley Products, 28, Camden Avenue, DESIGNED primarily for - Feltham, Middle- high radiator, blends into the main dia- sex. quality sound reproduction in phragm, which is a 10 -inch cone of the home, this permanent- magnet impregnated woven fabric with Illustrated catalogue of mica and loudspeaker is constructed on the concentric corrugations. ceramic capacitors, hermetic seals, original dual drive principle evolved The speakers are individually con- metallized bushes and insulators for by A. C. Barker. The main voice structed and assembled, and each is radio and electronic equipment, from coil is coupled mechanically and subjected to critical aural tests, so United Insulator Company, Oakcroft electrically to a thin metal former that the number available is limited. Road, Tolworth, Surbiton, Surrey. which is cemented to the apex of The price is z 15 15s, and enquiries the diaphragm. At low frequencies should be addressed to BCM / the system vibrates as a whole, but London, W.C.1. Electrothermal Valve Retainers at high frequencies the metal former We have had an opportunity of IT was stated in our Radiolympia acts as a single turn of low inertia listening to thi., loudspeaker and show report that the valve retainers and vibrates independently of the the:e is little doubt that it ranks in made by Electrothermal consist of comparatively heavy speech coil. A performance with the best repro- moulded rubber and fibre -glass. This small concave area near the apex, ducers is incorrect as the former material is available today. In two re- not used, fibre -glass being the main which acts as the high- frequency spects it is outstandingly good, constituent employed.

www.americanradiohistory.com December, 1947 Wireless World Advertisements 33 BELLING -LEE QUIZ (No. I8) Answers to questions we are often asked by letter and telephone Interference. These questions came from people whose enjoyment was spoilt by various kinds of interference. There are still people in the trade who are inclined to shut their eyes to this matter. We wish we could have had time to take names ,X$ and addresses of enquirers but those who tried to get near our stand will 11 appreciate that this was impossible. Our engineers found themselves " in ., . ---'v_.-i'fi conference" with four or five at a time, `I Shows the Belling -Lee inverted " V " television aerial mounted in the attic. surrounded with interested listeners L605 Attic Model sells at E2 7s. 6d. eager not to miss a word. It must be admitted that many complaints Question 50. What sort of questions came from those who were using did you have to answer from Visitors to either an indoor aerial or none at all. your stand at Radiolympia ? In most cases, probably the cheapest 2 The " Winrod " L.581 is in 3 sections way would be the installation of and has a universal bracket providing Answer 50. Radio dealers ask out several fixing arrangements. Price I9s. 6d. this one, and wholesalers want to a *2 " Winrod " window mounting aerial L.581. This is not an anti - The post office engineers take a very know what questions the retailers keen interest and are really efficient. ask. We had a conference -all hands interference aerial, but any outdoor is better than none, and would on deck -on the stand on the last aerial Growing Amateur Interest. The be bound to improve the signal to Friday of the show before opening questions from the growing band of noise ratio. In really bad cases, a time. The greatest number of amateurs and their interest were most " Skyrod " anti -interference aerial enquiries related to television aerials, refreshing. Many had already seen might be necessary. our amateurs catalogue P.339 and and the forms of interference most with queries. Many were commonly associated with the recep- came to us complaints of long deliveries of our tion of television programmes. This aerial array. We would like to was followed general questions on by emphasise that we are all out to help interference, and the third group was Iu11161UIHI the radio amateur. He requires questions by amateurs. We will deal ° JI components of high quality such as with them in this order. were developed for war time radar Television. The interest in the and communications equipment and inverted " V " loft or attic aerial today are only applicable to the L.6o5 surprised us all. In this series highest grade electronic equipment - of questions, most came from people and to the amateur. We are very who already had television receivers, interested in both. but who were situated at the outside We had very few enquiries from edge, or beyond the useful service professional users of components, but area of Alexandra Palace. In other most of them already know and use A typical capacitor suppressor L.I I I8 ¡CT words; people who had a weak or for fitting at the source of interference, our products. An exhibition like unstable picture and who were e.g., electrical motors, rectifiers, etc., or Radiolympia is useful because it at the meter board. Price £I 7s. 6d. therefore liable to annoyance from brings us in touch with those with When the interference is known most forms of interference. It really whom we have no other contact to be coming from some appliance or must be appreciated that whereas except by letter -and after all, machine under the control of the many liberties may be with a letters cannot take the place of a taken person complaining, or of a friendly strong signal, a weak one requires visit. neighbour, the obvious thing to do is To be continued. not only the best possible aerial, but to have a suppressor fitted to the it must be erected with skill and not I " VIEWROD " (Regd. Trade Mark) appliance. If this is not practicable television aerials see illustration top left. a little craftsmanship and cunning. write to us or report the matter to 2 " WIN ROD " (Regd. Trade Mark) see illustration top right. Everybody, not only the viewer; the nearest post office who will give must realise that the aerial must be you form T.466G to fill up, and in paid for, its erection must be paid due course a specially trained sup- BELLING E LEE LTD for, and generally speaking you don't pression engineer will get in touch CAMBRIDGE ARTERIAL ROAD. ENFIELD. MIDDX get much for nothing these days. with you to investigate the matter

www.americanradiohistory.com Advcl"tiNcmcltls Wireless World December, 1947

QUARTZ CRYSTAL UNITS FOR STABLE FREQUENCY GENERATION FEATURES: Low temperature coefficient-less than 2 in 106 per °C. Patented nodal suspension. Mounted in vacuum V WIREMOUNTING BRITISH PATENT N?575290 performance independent of climatic conditions. Exceptionally high Q value. High stability. Small size, 3in. x tin. overall excluding pins. Fits standard minia- deaf aid valve The type /CFr200 unit illustrated above is representative of the wide ture socket. ronge of vacuum type units available for low and medium frequencies. SALFORD ELECTRICAL INSTRUMENTS LTD. P E E L W O R K S S A L F O R D 3 Phone. BLA. 6688 / 6 lines) Crams 9' Cab /es "Spark /ess , Manchester" Proprietors, THE GENERAL ELECTRIC CO. LTD. En8Iand.

1817

The Problem The directional response characteristic of single unit loudspeakers is very pronounced at the higher audio frequencies which are audible only in a comparatively narrow channel directly in front of the reproducer with a corresponding lack of intelligibility and brilliance elsewhere. This feature is particularly troublesome when high quality sound reproduction is required in public halls, theatres and small cinemas where the size and expense of a large dual channel loudspeaker system is often not justified.

It is for such installations that the Vitavox Bitone Reproducer The Solution in this has been designed. High frequency reproduction instrument is handled by a small multicellular horn and moving coil pressure unit, this assembly providing adequate coverage and at the same time because of its high efficiency, a rising high note characteristic which is an advantage in auditorium reproduction. A 12" moving coil cone type loudspeaker operating in a vented enclosure reproduces low frequencies and a cross -over filter network is fitted to divide the frequency spectrum correctly between the two units. The whole assembly is mounted in a polished Walnut finished cabinet 'as standard, Oak and Mahogany veneered models being available to special order, and can be relied upon for applications where quality of performance rather than first cost is the main consideration.

S P E C I F I C A T I O N A N D P R I C E S Power Handling Capacity: Model 610-10 watts: Model 620-20 watts. Si..: 32'a21 "x20'. Terminating Impedance: 7'5 ohms. Filter Attenuation: 12 d.b. per octave. H. F. Distribution (apps): 60 °: 40 °. MODEL 610 - £42 0 0 MODEL 620 - £50 0 0

VITAVOX LTD., WESTMORELAND ROAD. LONDON, N.W.9. TEL t COLINDALE 8671 -3

www.americanradiohistory.com December, 1947 Wireless World 477 WORLD OF WIRELESS Radar & D.F. Nomenclature Amateur Activities Reception of French Television TERMINOLOGY suggested modifications the tele- AMATEURS AND THE THE need for overhauling our vision transmissions may still break INDUSTRY terminology in the field of through in the immediate vicinity THE principal guest and speaker position- finding by radio was of Alexandra Palace. at the October luncheon of the stressed by C. E. Strong, O.B.E., above Radio Industries Club was the new chairman of the I.E.E. CQMPONENTS EXHIBITION John Clarricoats, general secre- Radio Section, in his inaugural THE fifth annual private exhibi- tary of the R.S.G.B. After a address. tion of components and test brief outline of amateur history and He suggested that there were two gear to be organized by the Radio achievements he spoke of the press- main branches of the tree of which Component Manufacturers' Federa- ing need for valves, components, radio is the root and trunk. The tion will be held from March 2nd to sets and accessories for use on the first, generally known as radio- 4th in the Great Room, Grosvenor wide range of frequencies allocated communication, and the second, House, Park Lane, London, W.I. to amateurs at Atlantic City. embracing the whole field of direc- As in former years the exhibition, He estimated the present strength tion and range determination by which is promoted to acquaint of the amateur movement in the radio, he suggested should be called equipment manufacturers with the British Isles at about so,000 and " radiolocation." Whilst realizing latest developments that this represented a potential that the term had been used before in the com- home market of at least £25o,000 ponent and instrument section of per annum. In addition, he in a different sense and, too, that it the industry, will be open to visitors pointed had such " important historical by invitation out that there is a considerable ex- associations," he felt it would be only. port market awaiting the right type hard to find a more comprehensive of equipment. one. We would then speak of EUROPEAN DX CONTEST ` ' communication systems " and AN All- European DX contest has FRENCH TELEVISION " location systems ". been arranged by the Nether- suggestion an Developing still further the idea, lands amateur radio society that attempt Mr. Strong proceeded to sub -divide THEmight shortly be made to link (V.E.R.O.N.). During the contest, the British and French television radiolocation itself so that from the European stations will attempt to main branch came on the one side services for an interchange of pro- work as many different countries grammes lends added interest to an all time -sum methods giving range, outside Europe, whilst amateurs in which he called " range determina- account of an R.A.F. wartime in- the other continents will endeavour telligence activity which has just tion," and on the other time- differ- to work European stations. ence methods giving direction, come to light. The telegraphy contest will be As a result of information received which be called " direction deter- held from 18or G.M.T. on Novem- mination." The latter is further through Intelligence sources a tele- ber 28th to 2359 G.M.T. on Novem- vision receiving centre was set up to divided into " direction giving " ber 3oth, and the telegraphy and " direction finding." The first contest intercept transmissions from Paris would include Gee, Decca, omni- during the same hours from Decem- during the German occupation. range beacons, overlapping beam ber 12th to 14th. Fill details and Wing Cdr. G. T. Kelsey, O.B.E., course beacons and all systems the rules for the contests are given who is now with E.M.I., secured transmitting azimuth information, in the October R.S.G.B. Bulletin. two of the company's television sets while the second would embrace all Logs must be sent to the QSL and, with a curtain array consisting the counterparts of the above. The Bureau, V.E.R.O.N., Post Office of 32 dipoles slung between two branches were then further split Box 400, Rotterdam, Holland, on 15oft masts, successfully received the into broad -based and narrow -based or before December 31st. transmissions which were monitored systems. for two years. The special aerial TELEVISION-S.B.A. was found to be INTERFERENCE necessary to eliminate the powerful INTERFERENCE from the signals from the B.B.C. television sound trans- nearby radar missions with Standard Beam Ap- stations. in aircraft flying proach reception T h e transmis- in the London area was reported sions, usually news recently. reels of bomb The Ministry of Civil Aviation damage in France, has now issued a notice to airmen provided (No. 267, 1947) outlining modifica- useful tions to the marker beacon receiver I21125D which is particularly prone PARIS interval to the interference when using a signal received at horizontal aerial. No interference Beachy Head -a has been experienced with receivers distance of r 8 o 121125A, R1125B and RII25Cwhen miles - during the using a dipole aerial. German occupation It is stated that even with the of France.

www.americanradiohistory.com 478 Wireless World December. 1947

World of Wireless is to become vice -president of the every respect. " -Charles R. Denny, - National Broadcasting Company. chairman of the Intemational Telecom- information on the success of R.A.F. munications Conferences, reporting to raids. F. T. Cotton, chief valve engineer President Truman. of the Cossor valve and cathode -ray tube subsidiary, Electronic Tubes, RADIO AIDS TO NAVIGATION Ltd., High Wycombe, has resigned to OBITUARY ABROCHURE containing short take up the position of head of the We regret to record the deaths o1:- technical descriptions of all the physics laboratory of Ekcn- Ensign W. Densham, one of the small group radio aids to civil aviation demon- Electric, Ltd., the electric lamp sub- of technicians which assisted Marconi strated by the Research and sidiary of E. K. Cole. He joined th, during his early experiments in this Development Establishments of the Cossor organization in 1932. country. He joined the Marconi Co. Ministry of Supply during last Dr. Hilary Moss is assuming respon- in 1899 and took part in the pioneer sibility for the research' and develop- work in the Isle of Wight, at Poldhu, year's international conference has Clifden and in the U.S.A. He held by H.M. Stationery ment engineering division of Electronic been issued Tubes, Ltd technical and administrative posts in Office. Entitled "P.I.C.A.O. De- the company and retired in 1939, but monstration of Radio Aids to Civil B. N. MacLarty, O.B.E., M.I.E.E., returned for three years during the war. Aviation, September 1946," it is head of the B.B.C. Design and Installa- He was 70. priced 5s. tion Dept., who has been with the cor- F. S. Hayburn, at the age of 69, poration since 1926, has resigned to be- He joined the Marconi Intemational A complete set of the technical come a deputy engineer-in -chief of papers read before the London con- Marine Communication Co. in 1904 and Marconi's W.I. Co. He was one of the became managing director in 1933. ference is available in three volumes band of Marconi engineers who started Two years later he relinquished that entitled " P.I.C.A.O. Demonstra- the broadcast transmissions from position in order to become foreign tions- Technical Papers on Equip- station 2MT at Writtle in 1922. He envoy for the Marconi group of com- appears (standing left) in the photo- ment and Systems." Price L4 4s panies He retired in 1944. graph on page 456. the set. Individual papers, obtain- Air Comdre. H. Leedham, C.B., able at is 6d each, or the bound O.B.E., managing director of Ericsson volumes are available from the WHAT THEY SAY Telephones, Ltd. From 1929 until 1935 C.E.R.C.A. Central Office, Room he was head of the Radio Division, 211, Ministry of Civil Aviation, Unanimous. -" I am pleased to be Royal Aircraft Establishment. During Ariel House, Strand, W.C.z. able to advise you that we feel that the war he was successively director of all three conferences [at Atlantic City] radio production and director of radio E.I.B.A. were successful and that the new Inter- research and development at the Min- national Telecommunications Treaty istry of Aircraft Production. He joined THE annual report of the Electri- Ericsson's in September, cal Industries Benevolent Asso- and the new International Radio Regu- 1945. ciation, which helps radio as well lations, both of which were signed by all of the 78 countries participating in IN BRIEF as electrical non -manual workers in the conferences, are satisfactory in times of misfortune, records that Nearly 11,000,000 broadcast receiving the number of cases dealt with last licences were in force in Gt. Britain year (253) showed an increase of and Northern Ireland at the end of 25 per cent on the previous year. September. 25,05o of the 10,950,650 The amount paid out to members licences were for television receivers. of the radio industry last year was Servicing Certificate. -Of the 65 en- over £2,000. The income from the trants for the Radio Servicing Certifi- radio industry was, however, less cate Examination held in May, 41 passed in both written and practical sections. than 25 per cent of that amount. This examination was the first to be One regular source of income is held jointly under the auspices of the from the collections taken at the Radio Trade's Examination Board and Radio Industries Club luncheons, the City and Guilds of London Insti- which last year amounted to £189. tute. The proceeds (L218) from the Radio International Broadcasting.-Accord- Industries Ball, held at the Royal ing to a survey by the American State Albert Hall during the Olympia Department Great Britain leads the show, were devoted to the E.I.B.A. list of 55 nations as the biggest user of international short -wave broadcasting. The survey shows that at the end PERSONALITIES of last year the percentages of the Sir Ernest Fisk, managing director orld's international broadcasts used of E.M.I., Ltd., was elected president by the U.K., U.S., Russia and France of the International Federation of the were 16.56, 9.21, 6.o9 and 3.83, respec- Phonographic Industry at the recent tively. annual general meeting in Brussels I.S.M. -A typographical error ap- attended by the representatives of peared in our summary of the Atlantic twelve countries, including . mon. City frequency allocations in issue. The the U.S. and. Germany working ..,wxout- eznausting the tube and without a.._, _wnuvau last month's by using the arrangement in my registering apparatus." last of the frequencies than allocated to industrial, C. R. Denny has resigned From the foregoing remarks may be inferred that the chairmanship of scientific and medical from the arrangement of Marconi's receiver is a reproduction of my equipment should have the U.S. Federal Com- POPOFF. munications Commission lightning recorder.-Yours, ,4e., - A. been 5,850 Mc / s. This which he has held for the Torpedo School, Cronstadt, Russia, Nov. 26, 1897. frequency, which comes at years. He served the top end of a new past three will be used as chairman of the Inter- Alexander Stepanovich Po'ov (born 1859, dies 1906) amateur band, national Telecommunica- with a tolerance of ±0.6 with a facsimile of his claim made in a letter to The per cent. tions Conferences, Atlantic ago. The significance his four Electrician exactly 5o years of City, during the and ciscussed in our leading arti le. The a half months' duration of early work is School Broadcasting. - the three conferences which portrait is from an engraving issued by l'Union Inter- The Central Council for ended on October znd. He nationale des Télécommunications. School Broadcasting has

www.americanradiohistory.com December, 1947 Winless World 479

been dissolved and a new body, the Desmond (GSVM), president, and School Broadcasting Council for the W. A. Scarr, M.A. (G2WS), executive United Kingdom, formed. Similar vice-president. councils have also been formed in Scot- B.I.O.S. now T.I.D.U. -Enquiries land and Wales to guide the B.B.C. about reports in the B.LO.S. series in undertaking broadcasts to schools. have in the past been made to In an endeavour to raise the standard the British Intelligence Objectives Sub - is of reception in schools the Council Committee, 32 -37, Bryanston local education Square, giving advice to London, V. r, and applications to authorities. It is of interest to recall examine the original documents made that the recent McNair Committee's to Documents' Unit, I3oard of Trade, report on education stressed the need use Lansdowne House, Berkeley Square, for teachers to be trained in the London, W.I. These two units have of broadcast equipment in schools. been merged and are now known as Poland. -A change of wavelength has the Technical Information and Docu- been notified by the Polish broadcast- ments Unit, German Division, Board ing authorities. Warsaw II, which, of Trade, 40, Cadogan Square, London, since reopening last December, has S.W.t been temporarily operating in the American its Production. -According to medium waveband, has returned to figures given at the New York meet- pre -war wavelength of 5339.3 metres. ing of is the U.S. Radio Manufacturers' Its power is to kW. Warsaw i Association the estimated production of operating on 395.8 metres with a power broadcast and television receivers of 5o kW. during 1948 will be between 13,000,000 Telecommunications Courses. -A BELGIAN TELEVISION. -- A Pye and s5,000,000. syllabus of courses and examinations mobile television station recently U.S. Radio electrical Week.- America's third in telecommunications and toured Belgium. The only failures annual National Radio Week, which subjects has been issued by the City throughout the 500 - mile tour, ended on November for the 1st, brought to a and Guilds of London Institute during which the station operated close the year's campaign organized by 1947-48 session. The courses include for 15o hours, were the U.S. Radio Manufacturers' engineering, elec- two miniature Associa- telecommunications valves tion to increase receiver sales, for trical installation work, electrical en- which the slogan service was " Radio in gineering practice and radio authorities to arrange lectures and Every Room ". work Details are also given of the classes in polytechnics, service work, clubs, etc. Mr. I.P.R.E. -At the first annual dinner final examination in radio Thomson, whose address is Box 846, conducted jointly by City and Guilds of the Institute of Practical Radio En- Stockholm 1, Sweden, is in urgent need gineers, and the Radio Trade's Examination of manufacturers' it was stated that there were literature containing now 800 members and goo Board, for the Radio Servicing Certifi- illustrations of modern electronic students. cate. The raising of the standard and status equipment as a help in explaining war - of service has been coined expressions technicians was given as one Jamaican Broadcasting.-It or idioms which are of the primary aims of the institute. decided by the Jamaican Government quite unfamiliar to Swedish students. to discontinue broadcasting from its Amateur and to Prefixes are given in alpha- own transmitter in Kingston betical order on a card measuring invite applications for private broad- 8t x rolin INDUSTRIAL NEWS Cable and Wire- published at sixpence by R. casting under licence. Martin and Co., Bridge Street, Work- "Cossor Courier," dealer less has intimated that the company the journal tech- sop, Notts. of A. C. Cossor, Ltd., has reappeared would be willing to provide the after nical facilities but is not prepared to B.W.I. Transmissions. -The Trinidad a break of over nine years. The undertake the programme side. Broadcasting Company has arranged first issue, dated Autumn, includes, in two special amateur transmissions from addition to details of the 1947 -48 range International Television. -A meeting its short-wave station VP4RD. " Radio of receivers, some interesting figures on of television technicians of various Trinidad," working on 9.625 Mc / s with Cossor's wartime production. countries was held at Cannes in Septem- a power of Soo watts, will radiate these Decca. -A new publication, Music, ber as part of the Comité International programmes on November 30th from la Diffusion Artistique, Littéraire has been. produced by the Decca pour i000 to two G.M.T. and on December Record Co., and will be issued et Scientifique par la Cinéma. The 1st from 0830 to 0930 G.M.T. Recep- British representative was A. G. D. quarterly, price 2s. Its scope will not tion reports will be welcome by the be confined to recorded music, but is West, past president of the British Trinidad Broadcasting Co., Ltd., Society. The oppor- intended to " bridge the gap between Kinematograph Broadcasting House, Port-of-Spain, the essentially academic type of review tunity was taken to form a Comité Trinidad, B.W.I International de Television (C.I.T.), and the ' popular' music paper ". with R. Barthelemy (France), Dr. A. I.S.W.C. Broadcasts.-Details of the " Marconi Mariner " is the title of a Castellani (Italy), Professor F. Fischer special short-wave transmissions from new journal to be published bi- monthly (Switzerland), and A. G. D. West overseas broadcasting stations for by the Marconi International Marine (Great Britain) as founder members. amateurs, arranged by the. Inter- Communication Co. The first issue, national Short-Wave Club, are given in July- August, of this purely staff Wire -to -Disc Transcriptions.-Equip- the club's duplicated four -page monthly ment for the production of personal journal includes details of Seamew and news -sheet, ' Internatiònal Short-Wave Seagraph equipment. disc recordings installed by Modern Radio," issued from its headquarters, Messages, Ltd., at their recently opened ioo, Adams Gardens Estate, London, Multicore distributors in New York studio at g, Piccadilly Arcade, London, S.E.r6. have ordered five tons of Ersin Multi- S.W.i, includes wire recording appara- core solder-sufficient for too,000,000 tus for preliminary rehearsal. High - Amateur F.M. -Australian amateurs joints. quality transcriptions from wire to disc have been granted permission to afford the opportunity of selecting the employ frequency modulation for optimum performance and effect con- transmissions between 27.185 and siderable economies in recording 27.455 Mc / s, on 5o Mc / s and above. CLUBS materials Pulse transmission is permitted on, and Battersea. -The London Short -Wave Technical Literature Wanted. - above, 166 Mc / s. Club now meets on Fridays at 8.o at Language classes in technical and R.S.G.B. Officers. -The following " The Crown," Battersea Park Road, scientific English are being started members have been nominated for London, S.W.it. It is affiliated to the in Sweden; F. P. Thomson, election at the annual general meeting International Short-Wave Club, the "A.M.Brit.I.R.E., has been appointed of the Radio Society of Great Britain secretary of which is A. E. Bear, too, by the Stockholm educational to be held on December 19th: V. M Adams Gardens Estate, London, S.E.i6.

www.americanradiohistory.com 480 Wireless World December, 1947

World of Wireless - - Meetings are normally held at 7.30 at MEETINGS the Charles Street United Baptist B,irkenhead. -The December meet- Church, but that on December 2nd will Institution of Electrical Engineers ings of Wirral Radio the Amateur be at the Drill Hall, Ulverscroft Road, Ordinary Meeting. Speech Com- Society will be held on the 3rd and in order that the radar equipment may -" 17th 7.30 Y.M.C.A., Whet- munication under Conditions of Deaf- at at the be inspected. Sec.: O. D. Knight, 16, ness or Loud Noise," by W. G. Radley, stone Lane, Birkenhead. Sec. : B. Berners Street, Leicester. C.B.E., Ph.D. (Eng.), on December O'Brien, G2AMV, 26, Coombe Road, 4th. (Joint meeting with the Physical Irby, Heswall, Cheshire. Romford.- Meetings of the Romford Society.) Birmingham. annual general and District Amateur Radio Society -The are now held on Tuesdays at 8.o at the Radio Section.-" The Design and meeting of Slade Radio will be held Y.M.C.A., Operation of High -power Broadcast November 28th the Parochial Western Road, Romford. on at Sec.: R. C. E. Beardow, G3FT, 3, Transmitter Units with Their Outputs Hall, Broomfield Road, Erdington. On Geneva Gardens, Chadwell Heath, Combined in Parallel." by T. C. Mac - December r2th the club will hold a Essex. namara, A. B. Howe, M.Sc., and D.F. contest. Sec.: C. N. Smart, rro, P. A. T. Bevan, B.Sc., on December Birming- Woolmore Road, Erdington, Sutton and Cheam. -Meetings of the 3rd. ham, 23, Warwick. Sutton and Cheam Radio Society are Informal lecture on " Commercial held on the first and third Tuesdays Disc Recording and Processing," by Birmingham.- Having obtained B. E. G. premises 220, Moseley Road, Bir- of the month at Ye Olde Red Lion, Mitten, on December 9th. at The above meetings will be held mingham, 12, the Birmingham and Cheam Village. Sec.: R. G. Finch, at District Short -Wave Society now meets 26, Sunnymede Avenue, Carshalton 5.30 at Savoy Place, London, W.C.2. on alternate Thursdays for practical Beeches, Surrey. Cambridge Radio Group. - " Indus- work, in addition to the monthly meet- trial Applications of Electronic Tech- ing at the Hope and Anchor Hotel, Walworth. -A radio club has been niques," by H. A. Thomas, D.Sc., on Edmund Street, Birmingham. Sec.: formed by the Walworth Men's Insti- December 2nd, at 6.0, at the Cambridge- N. Shirley, 14, Manor Road, Stechford, tute and meets at the Avenue School, shire "Technical College. Birmingham, 9, Warwick. John Ruskin Street, London, S.E.5, on " New Possibilities in Speech Trans- Wednesdays and Fridays at 7.0. Sec.: mission," by D. Gabor, Dr. Ing., on Bradford. -A discussion on " who P. Senechal, 92, Grove Park Road, December r6th at 8.15 at the Cavendish should be the members of the R.S.G.B." Camberwell, London, S.E.5. Laboratory will be held by the Bradford Amateur Radio Society on December 9th at 7.30 West Bromwich.-A series of talks North -Western Measurements Group. at Cambridge House, Horton Lane, covering many aspects of amateur -" The Design and Construction of a Bradford. A social evening is proposed radio has been arranged for the coming New Electron Microscope," by M. E. for December 23rd. Sec.: W. S. Sykes, meetings of the West Bromwich and Haine, B.Sc., on December 16th, at 6.0, G2DJS, 287, Poplar Grove, Great District Radio Society which are held at the Engineers' Club, Albert Square, Horton, Bradford, Yorks. on alternate Mondays at 7.30 at the Manchester. Gough Arms Hotel, Jowett's Lane, Rugby Sub -Centre. -" New Possibi- Brighton. -The December meetings West Bromwich. Sec.: R. G. Cousens, lities in Speech Transmission," by D. of the Brighton and Hove Group of the G3BCS, 38, Collins Road, Wednesbury, Gabor, Dr. Ing., on December 8th, at R.S.G.B. will be held on the 1st and Staffs. 6.45, at the Rugby Corporation Elec- r5th at 7.3o at the Golden Cross Hotel, tricity Showrooms. Western Road, Brighton, Sussex. Wolverhampton. -Details of the Town Representative: J. R. D. Sains- winter's programme arranged by the Radio Society of Great Britain bury, G8HV, So, Lansdowne Place, Wolverhampton Amateur Radio Annual general meeting on December Hove, Sussex. Society, which meets on alternate 19th at 6.30 at the I.E.E., Savoy Place, Mondays, are obtainable from the London, W.C.2. Eastbourne. -The recently formed secretary, H Porter, G2YM, 221, Park Eastbourne and District Group of the Lane, Wolverhampton. R.S.G.B. meets on the first Friday in Institute of Physics the month at the Friends' Meeting " The Travelling-Wave Tube," by House, Wish Road, Eastbourne. Sec.: R. Kompfner, on December r7th at 5.3o in the Rooms of the Royal Society, R. F. Nugent, G3FTS, 12, St. Burlington House, Piccadilly, London, Anthony's Avenue, Eastbourne, Sussex W.I. Grimsby. -The Grimsby Amateur Radio Society has been granted a Institution of Electronics 15o -watt licence (G3CNX) for its trans - North -West Branch.-" The Electron mitter-a T1131. Meetings are held and other Constituents of Matter," by each Thursday at 7.45 at 115, Garden Prof. R. E. Peierls, F.R.S., on Decem- Street, Grimsby, Lincs. Sec.: R. F. ber 12th, at 6.30, at the Reynolds Hall, Borrill, G3TZ, address as above. College of Technology, Manchester. Non -members may obtain tickets from Harrogate.- Premises have been L. F. Berry, 105, Birch Avenue, Chad - obtained at the rear of 31, Park Parade, derton, Lancs. and the Harrogate and District Short- wave Radio Society now meets there British Sound Recording Association every Wednesday at 7.30. Sec.: K. B. " Factors in the Reproduction of Moore, 2a, Wayside Crescent, Harro- Gramophone Records," by W. J. gate, Yorks. Lloyd, B.Sc., on December 19th at 7.0 Kentish Town.-The St. Pancras at the Royal Society of Arts, John Radio Society now meets on Mondays Adam Street, London, W.C.z. and Thursdays at 7.o at the L.C.0 British Kinematograph Society Evening Institute, Holmes Road, Manchester Section.-" Electronics in Kentish Town, London, N.W.S. A for Industry," by J. Baggs on December third evening is being arranged be- znd, at 10.30, at the Manchester Geo- ginners. Sec.: H. Brown, 84, Blenheim Society, r6, St. Mary's Par- Gardens, Willesden Green, London, graphical N.W.2 MURPHY RADIO is continuing the sonage, Manchester. development of Service equipment. Leicester. -The subjects of the lec- The latest Army set to be made is Television Society tures at the December meetings of the " Impressions of American Tele- Leicester Radio Society are: " Army this WS3I, a F.M. transmitter- vision," by T. M. C. Lance, on Novera -. Radar " (2nd) and " Dielectric Charac- receiver operating in the extra high - ber 28th at 6.o at the I.E.E., Savoy teristics and their Importance " (16th) frequency band. Place, London, W.C.a.

www.americanradiohistory.com December, 1947 Wireless World Advertisements 35

%/tualG` O A.D /47 AMPLIFIER

.111, ,._ = _ - ` -... . .

1.101. .

This is a 10 -valve amplifier tor recording ana play -back purposes for which we claim an overall distortion of only 0.01 per cent., as measured on a distortion factor meter at middle frequencies for a 10 -watt output

The internal noise and amplitude distortion are thus negligible and the response is flat plus or minus nothing from 50 to 20,000 c/s and a maximum of .5 db down at 20 c /s.

A triple- screened input transformer for 71 to 15 ohms is provided and the amplifier is push -pull throughout, terminating in cathode -follower triodes with additional feedback. The input needed for 15 watts output is only 0.7 millivolt on microphone and 7 millivolts on gramophone. The output transformer can be switched from 15 ohms to 2,000 ohms, for recording purposes, the measured damping factor being 40 times in each case.

Built -in switched record compensation networks are provided for each listening level on the front panel, together with overload indicator switch, scratch compensation control and fuse. All inputs and outputs are at the rear of the chassis.

Send for full details of Amplifier type AD /47 257/261, THE BROADWAY, WIMBLEDON, LONDON, S.W.19.

Telephones . LIBerty 2814 and 6242/4. Telegrams " VORTEXION. WIMBLE. 'LONDON.'

www.americanradiohistory.com 3b Advertisements Wireless World December, 1942 the fltphoiiíc Etcctrocram For record connoisseurs, the world over, we have the pleasure to announce the Polyphonic Electrograrn, incorporating the Phase Inverter Speaker and a specially designed six valve paraphrase push -pull Amplifier with triode output and negative feedback, together with individually controlled tone compensating channels via electronic mixing giving up to 26db Bass Lift., 15db Treble Lift from linear response, as required. Control without raising the lid via finger tip instrument panel; this instrument compares favourably with anything on the market, regardless of cost, and is provided with ample space for a high fidelity Radio Feeder Unit. PRICE: Non -Automatic model .. £65 plus P.T. Automatic model .. .. f80 plus P.T.

Barnes & Avis, Reading; Bowers & Wilkins, Worthing; AGENTS. Binns Ltd., Newcastle; Dalton & Sons Ltd., Derby; Clark & sons, Isle of Wight ; C. C. Gerry, Newquay ; 'fickle & /tickle Ltd., Reading (and branches) ; Thomas Lynn & Sons, Andover; Merriotts Ltd., Bristol; Needham Engineering Ltd., Sheffield; Pank's Radio, Norwich; Sound Ltd., Cardin; Bernhard Smith, Barnstaple; Sound Services, Jersey, C.L; Precision ; Services, Edinburgh Seals Ltd., Southsea ; G. E. Samways, Hazel Grove ; Weybridge Radio Electric, Weybridge; West End Radio, Farnham; Valiance & Davidson Ltd., Leeds (and Branches).

57, St. Martin's Lane, W.C.2 %ounb Zates tò. (Temple Bar 4284u Works : Farnham, Surrey (Farnham 6460¡3).

- s I L , . - -F-1 - -i- - - EILIECTIRONICI

There is increasing scope for ambitious men and women in the new fields opened up by Electronic Science. The Correspondence and College Courses provided by E.M.I. Institutes which cover recognised diplomas such as the City and Guilds, etc. are written and supervised by E.M.I. * scientists who are specialists in Electronic Science. Courses are already available in such subjects as Basic Radio, Basic Television, etc., and the prospectus is being constantly extended. E.M.I. basic training fits you for entry to CAREERS in such fields as :- SERVICE ENGINEERING, OPERATING, DESIGN AND DEVELOPMENT, TECHNICAL SALESMANSHIP, TEACHING, etc. With this basic training you can eventually become a specialist in Television, Radio Communications, Radar, Navigational Aids, Audio Frequency, Medical and various Electronic applications. There are also short courses for Executives, Amateurs, Students, etc. For full details apply to your local " H.M.V." Radio dealer or direct to :- The Principal: PROFESSOR H. F. TREWMAN, M.A. (Cantab), M.I.E.E., M.I.Mech.E., M.Brit. I.R.E. LIMA. INSIII!1IES LID Dept. 16, 43, Grove Park Road, Chiswick, London, W.4 * The E.M.I. Group includes "H.M. V. ", Marconiphone and other important electronic interests. E.I I

www.americanradiohistory.com December, 7947 re less World Television Receiver DETAILS of all units comprising the television receiver have now been Construction given, including those of the framework which carries them and links them with the C.R. tube, 10.- Operating Notes and Conclusion deflector and focus coils into a complete receiver. To conclude nections to a low- voltage tube, rated for a voltage other than the description it remains only to since much less voltage drop in 6.3 V the separate winding is describe the operation of the set the leads is permissible. The needed in any case. The float- as a whole and to deal with a few MWzz -7, for instance, takes o.6A ing- heater circuit is a simple way points which have arisen out of at 6.3 V, and if a drop of 5 per out of the difficulty and in no enquiries made by readers. cent in heater voltage is permis- case in which the writer has tried Of these last probably the com- sible, a resistance of 0.52511 can it has it led to any undesirable monest relates to the use of be allowed in the wiring. A 2 -V effects. cathode -ray tubes other than the tube may take 2 A heater current There are a few tubes, notably Mullard MW22 -7. Some notes on and the resistance for the same pre -war ones, in which heater and this were given in Part 6, but percentage drop must be no more cathode are joined internally. there is a demand for some ampli- than 0.05 f1. The conductors used With these it is necessary to feed fication of them. The MW22 -7 in the heater connections all the the signal to the grid. This has a tetrode gun and the heater way back to the transformer must entails the use of a phase -reversing is rated for 6.3 V and is run from be of ten times the cross -sectional stage and, of course, there must the same heater winding as the area in the case of these low - be a separate heater winding for other valves. The heater is thus voltage tubes. the tube. earthed and as the V.F. signal is The next point arises out of the The phase- reverser, shown in fed to the cathode of the tube the permissible heater -cathode voltage Fig. r, is an anode follower giving cathode is considerably positive rating of the tube. With the con- phase reversal and a gain of about with respect to the heater. Most nections given in the earlier de- unity. The direct connection to other tubes have a triode gun. scription the heater -cathode voltage the grid of the tube is reasonably This occasions no difficulty, for it has a maximum safe because of the use of the leads merely to the omission of a of about 130 V. potential- divider output which connection between +H.T.2 and Some tubes are limits the amount by which the a tube electrode. Most other tubes +H.T. , not rated for as grid can be carried positive in the have a heater rated for a voltage 4Tkn much as event of a valve failure. 3W this. other than 6.3 V, usually 2 V. When this is so, With this arrangement R23; R2a This again causes no difficulty for cathode feed can and C2, of Fig. I, Part 7, are no TO SCREEN longer necessary, but their reten- GRID OF Va 4 7kn bieµF Fig.!. PART 7 3W tion does no harm. If they are omitted L5 must be joined directly to the anode of V6. The " V.F. Output " socket is, of olMn BµF course, connected as F usual through TO V.FFUTPUT 47 C R TUBE C, of Fig. r, Part 6, to the frame Fig.! PART 7 i GRID time -base " Sync " socket. Some alteration is needed to the wiring of the Brightness control. The leads to the two ends of R,, 2Mfl ()IMO Fig. I, Part 6, must be reversed. and its slider and C; must be taken to the cathode of the tube instead of to the grid. Resistot R, should be joined from grid to - H.T. instead of from cathode to +H.T.2 Fig. r. Circu't diagram of anode -follower phase reverser for use with a C.R. tube having heater and cathode These modified connections for joined internally. a tube having heater and cathode it can be met by providing an be retained by the simple expe- joined internally can be used, of appropriately rated winding on dient of providing a separate course, with any tube, but when the mains transformer. heater winding on the mains trans- heater and cathode are not joined It should be pointed out, how- former and connecting it to the it is much simpler to adopt ever, that it is necessary to use tube heater only and to nothing cathode feed. heavy leads for the heater con- else. As such tubes are usually When all units are completed

www.americanradiohistory.com 482 Wireless World December, 1947

Television Receiver Construction- a rough and ragged note to a clean ness are the only panel controls. and connected together the time one of lower intensity and prob- The former because occasional comes to receive a picture. If it ably higher pitch. readjustment during a programme is at all possible the individual Incidentally, this note sounds may be necessary to compensate units should be tested indepen- very like an inter -station hetero- for the change of resistance of the dently to make sure that there is dyne whistle and it is extremely focus coil as it warms up and the nothing seriously wrong with any difficult to make it completely in- latter since it is advisable to black one. If the whole equipment is audible. It comes from the mech- out the picture before switching put into operation at once in an anical vibration of the line -scan off. untried form the location of any transformer and can be reduced The focus drift is normally fault may prove quite trouble- by putting the transformer into a small and it is less with a C.R. some. heavy box packed with sound - tube having a tetrode gun than Start off with Brightness, Con- absorbent material. Care must be with one having a triode gun, trast and Picture Width turned taken to preserve insulation, how- since the latter usually needs a right down (fully anti -clockwise) ; ever. The whistle is, of course, heavier focus current. switch on and give the valves time greatly reduced when the equip- In normal operation the proper to warm up. Turn up Picture ment is housed in a cabinet and procedure is to see that the Width gently until the time base these remarks about its audibility Brightness is right down, switch is heard to sing quietly. Turn up apply to the use of the set without on and allow a couple of minutes the Brightness until the raster just a cabinet. for the valves to warm up. Then appears. Now adjust Height and The next step is to adjust turn up Brightness to the require Width so that it is roughly of the Frame Hold and the picture level. At the end of a programme, right size and Focus for maximum should then lock in and be seen turn Brightness right down and line sharpness. as a complete steady picture. switch off. Now adjust Height, Width and Before concluding, it may be as Adjustments Line Linearity for the proper pic- well to make some mention of the It is assumed that the receiver ture size and for an even horizon- effect of mains voltage variations, has previously been aligned with tal scan. Focus will probably since these can be sufficient nowa- a signal generator, so the signal need readjustment from time to days appreciably to affect the per- should appear when Contrast is time during this process. formance. It is quite common for turned up. It will probably be a When approximately right, a nominally zoo V supply to be confused jumble of black and turn down Contrast and adjust anything from 220 V to 260 V and white marks. Adjust Line Hold Brightness so that the raster is at periods of heavy load it may so that the line time base locks just not visible. Turn up Con- well fall below 220 V. The most in. A recognizable picture should trast so that the picture appears. noticeable effect of a change of now be found but probably mov- It will now be found that the mains voltage will be on picture ing more or less rapidly vertically. frame fly -back lines show in dark width and with any serious drop Also the " singing " of the line - parts of the picture; therefore, in voltage it may not be possible scan transformer will change from turn down Brightness until they to obtain the full width. just disappear. Contrast must It is inadvisable to .alter the then be increased somewhat and tapping on the mains transformer Brightness turned down a little to correct for the drop, unless a more. This is continued until the voltmeter is used to keep a check best picture is secured. Some on the voltage, since it can result Focus adjustment may be needed in the valves being over -run when during this process. the voltage rises. Unless a voltage- regulating is If Contrast is not advanced far transformer enough a clean picture will be fitted, the best thing is to adjust obtained but it will be " thin " the transformer tap for the aver- and either it will be very dim or age voltage. the frame fly -back lines will show. If it is advanced too far the pic- WIRELESS WORLD DIARY ture will become what is often COPIES of the Wireless World termed " soot and whitewash." Diary for 1948 will be distri- The scanning spot will defocus on buted through stationers and book- and sellers shortly. Readers are advised whites there will be no detail to place their orders at once as sup- in the blacks. plies are limited. Once the correct setting of Con- The 8o -page Reference Section of trast is found, this control will the Diary has been completely re- THE MAZDA TYPE 27Ml photo rarely need readjustment, for the vised and now contains a consider- electric electron multiplier has nine day -to -day variations are best able amount of additional informa- stages rated at roo V per stage. controlled by Brightness. Having tion. Base connections for some At 5o V, the current amplification 40o valves, including the new is one million times and the lumin found it, final adjustments to B.V.A. Standard B8A, are included. ous sensitivity is ro pA/lumen. Height, Width, Linearity and The Diary, which shows one week The base is a small shell ri-pin Focus can be made. at an opening, costs 3s 8d, includ- sub -magnai. Normally, Focus and Bright- ing purchase tax.

www.americanradiohistory.com December, 1949 Wireless World 483 New "All- stage" Valve Details of the grid wires are aligned behind the grid wires, Sargrove - Tungsram and a method has been found of doing Type UA -55 this without optical aids. It is claimed DESIGNED pri- that a ratio of anode marily to re- to screen current of duce the cost the order of io : r is of valves used in re- maintained through- ceivers manufactured out the life of the by the E.C.M.E. sys- valve. tem (see W.W.. With a screen April, 1949) the Type potential of + 15 V a UA -55 is capable of high-impedance volt- performing all the age amplifier with a SPEAKERS OF stage functions in a slope of 4.5 mA is ob- straight or superhet tained. The anode - DISTINCTION receiver and is yet of grid inter -electrode comparatively small capacity is of the The extensive range of TANNOY dimensions and order of o.o9 pF per Sound Equipment now available robust construction. Effective section, and it is therefore neces- embodies the latest technical developments in design and per limitation of size has been sary to use somewhat unconven- fo rm an ce. achieved by accepting a reason - tional circuits for R.F. and I.F A neutralized cir- Here are two examples of dis- ably small output (of the order of amplification. tinctive Loudspeakers. The one r watt) when the valve is used as cuit using a capacity centre tap shown above is Type LSH /200 /H a power amplifier. on the secondary of the input a weather -proof Re- entrant Horn The valve is a combination of transformer may be employed giving first - class quality re- two beam tetrodes disposed sym- with one half production. Gzx Gut Ay metrically on either side of a com- of the valve, I mon cathode. The heater is rated the other half Ax. at 55 V, roo mA and is therefore being used as I! convenient for series connection second detec-

HALF ANODE IN ANODE LEAD SCREEN GZy This is Type LS A Bowl ALL-GLASS BASE /CIR /5. "E"SCREEN Loudspeaker suitable for Ceiling or wall mounting, combining the latest developments in speaker design with artistic appearance

Ax INTER -HALF SCREEN Gzx \TANNOY/ cQUIPMENT- Ay- -SOUND "E" SCREEN Glx H R. FOUNTAIN LTD INTER -HALF SCREEN GUY t " THE SOUND PEOPLE " Gzy Gly Constructional details of the UA -55 'TANNOY" Is the registered valve and (top right) section show- trade mark of equipment manu in rio- 220 -volt mains supply lectured by and ing arrangement of electrodes circuits. A central screening plate GUY R. FOUNTAIN LTD. with extensions between the leads tor. Alternatively, the two WEST NORWOOD, S.E.27 to each section of the valve is halves may be arranged as an GIPSY HILL 1131 connected to the cathode and is amplifier of the Colebrook R -C The largest Organisation In Great Britain shaped to act also as the beam - coupled type, when stable gains specialising SOLELY In Sound Equipment. forming plates. In cross -section it of the order of 30o can be ob- Branches at Manchester, Belfast, Newcastle is " E " shaped and shields the tained at 465 kc /s. on -Tyne. Birmingham, Bristol. Glasgow, etc. first and second grid supports In circuits where the input can from the anode. The accelerator be applied to both control grids

www.americanradiohistory.com Wireless World December, 1947

New " All-stage " Valve - simultaneously, variable - mu Cathode -ray Tube Data characteristics can be obtained by Types applying dissimilar voltages to Characteristics of some Ex- Service Surplus the screens. Otherwise, remote Compiled by D. W. Thomasson cut -off characteristics can be ob- TI1E following list gives some 4 -V heaters, taking about I A, tained by supplying the accelera- of the more important and are of the electrostatic focus tor grid potential through a com- data on some of the C.R. and deflection type. The figures paratively high series resistance. t ubes now available in the surplus given are average values, but With anode and screen market. All the types given have considerable variation may be strapped, a high -slope low- imped- ance triode is obtained. One half as an Size Operating Conditions Sensitivity of the valve can be used Type Screen Base oscillator under these conditions, L D V1 V2 V3 Vt11O I6 X-axis Y-axis the other half being employed as this ar- NCI G. M. 9.1 160 25 0.8 0.135 0.8 - 3 100 90 a tetrode mixer. With 4 10 3`<0 480 of NC6 G. - 12.1 350 75 1.45 0.6 3 rangement and a line voltage NC7 G. S. 12.2 630 230 1.7 1 6 6 40 1490 1270 only 9o, a conversion conduct- NC12 G. S. 12.3 420 160 1.8 0.8 5 6 3 550 1000 0.7 mA /V is claimed, NC14 B. - 12.3 420 160 2 0.35 2 2.5 20 600 1140 ance of 0.8 1.5 3 150 150 current of 9 mA. NC16 G. M. 12.4 200 70 0.8 0.12 with a cathode NC19 G. M. 9.1 160 25 0.8 0.135 0.8 - 3 100 90 When the two sections are con- VCR97 - - 12.3 420 160 2 0.35 2 2.5 20 600 1140 nected in parallel and both screen VCR138 G. S. 12.3 340 85 2 0.35 2 2.5 - 750 350 from a 9o- VCR139A G. M. 12.4 200 70 1.5 0.25 1.5 1.5 3 170 170 and anode are supplied VCR522 G. M. 9.1 160 25 0.8 0.135 0.8 3 100 90 volt H.T. line, the valve functions - as a power amplifier with a slope and NOTES.- Screen type; G = Green, B = Blue, M = Medium persistence, S = Short of 7 mA /V at .- 5 volts bias persistence. gives over one watt into a load The connections given in the lists of bases are liable to alteration. The effective con- of 2,500 ohms with an anode dis- nections will usually be as shown, however, as the changes usually involve taking two leads to a common connection to avoid the necessity of strapping them externally. The sipation of 31- watts. addition of a suffix letter is sometimes used to indicate more extensive changes. It may seem rather wasteful to The dimensions given are the overall length and the effective screen diameter (mm). final use a valve of this type as a Symbols : V1 = first anode, V2 - focus anode, V3 = final anode, V11162, maximum power rectifier, but the makers anode potential in kilovolts ; Ii,, beam current (pA). The sensitivities are given in mm/V. consider that this is economically l2-WAY S.C. 12 -PIN SPIGOT BRITISH 9 -PIN justified if specimens which do not meet the required standards for general circuit use, and which would normally be rejected, are earmarked for use as rectifiers. Resistors must be used in series with the first and second grids to limit current, and the D.C. output voltage is subtantially the same as the R.M.S. input voltage for currents up to 20 -25 mA, the value drawn by the simple two - valve receiver illustrated on page 438 of the November issue. BASE CONNECTIONS A special nine -pin valveholder is necessary. The possibility of British Standard 9 -pin Base 8 9 using existing nine -pin holders 1 2 3 4 5 6 7 but it was -- was considered, 9.1 X1 Y1 A2 IL 1l :\ Al decided that it would be less ex- C A,1 pensive to go for optimum design Standard 12 -way side contact (B.E.G. type) and to call for a in the valve 1 2 3 4 5 6 7 8 9 10 11 12 Caps special holder. The pitch circle H H At A2 Coa. X2 A3 is x fi / i6in in diameter and the 12.1 M - - pins, Tmin in diameter and fin C 12.2 M - H H A1 A2 Coa. Y2 X2 A3 Xt Yl - long, are spaced 36 degrees apart C except the anode pins, which are 12.3 M C H 11 Ai A2 Coa. Y2 X2 A3 X1 Y1 - spaced at 72 degrees. 12-pin spigot-type base of the UA- 11 12 Full characteristics 1 2 3 4 5 6 7 8 9 10 55 are given in a paper which will be read at the Brit. I.R.E. discus- 12.4 C M H H A2 - Y2 X2 A3 X1 Y1 - ; C = Cathode ; Coa. = Coating ; sion meeting on Dec. firth. Ad- SYMBOLS : M = Modulator (grid) ; H = Heater ; A1, A3 = Anodes from Xl, X2 -X -axis deflector plates ; Y1, Y2 = Y -axis deflector plates A2. vance copies are obtainable numbered from the cathode. (Anodes one and three may be strapped internally, the At Sargrove Electronics, Sir Richard's connection being omitted. Xt and Y1 may be similarly treated. These variations are Bridge, Walton -on- Thames. unpredictable. )

www.americanradiohistory.com December, t947 Wireless World 485

experienced between different are not equivalents. This may tubes of the same type. be due to different minimum spot It may be noted that, while sizes or similar f, .ctors relatively some of the types given are unimportant for many ai plica- closely similar as far as the quoted lions, but is often a matter of characteristics are concerned, they construction. Short -wave Conditions Expectations for December By T. W. BENNINGTON (Engineering Division, B.B.C. Cabinet Gram °phoneTP, 614 RC) DURING October daytime maxi- usable during December for four incorporates AmplifieC mum usable frequencies for this long- distance circuits running in dif- specialty latitude increased very consider- ferent directions from this country. illustrated) T 614 repro- ably, and during the last week of All times in this article are in Amplifier Fidelity ecords, NEwned Sh the month reached very high values, G.M.T. In addition, a figure in designed gramophonera Uophÿ n response, for example, a measured value of brackets is given for use of the of those duction frequency bass, treble 47 Mc /s at 1200 G.M.T. on 31st. whose primary interest is the ex- of control ties. Inputs Contrary to expectation night -time ploitation of certain frequency separate frequencies. Inputs M.U.F.s were, on the average, no bands, and this indicates the highest middle lower than during September. frequency likely Inc. and ASlternatively 614) to be usable for for layer (CP. Had it not been for a large about 25 per cent of the time during controls.record TWIN amount of ionosphere storminess the month for communication by single ble, new With daytime working frequencies would way of the regular layers:- Also speaker for have higher Sound been much than they model. full Montreal : 0000 '3 Mc /s (14 Mc /s) list of were. Even so, frequencies like the this AGI 0300 7 , (12 illustratedIncluding 28 -Mc /s amateur band were more 0900 9 or 11 Mc /s (16 Write or less regularly usable, while it is 1100 17 or 21 Mc /s (26 quipmenl reported that a Dutch amateur 1300 26 (38 1800 21 , (29 , established contact on 5o Mc /s with 2000 17 or 15 Mc /s (22 ,' two amateur stations in Capetown. 2200 11 (18 Night -time working frequencies were 2300 i) (15 relatively high for the time of year. Buenos Aires :0000 11 Mcls 16 Mc/s Sporadic E decreased very consider- 0500 9 ,, (14 ably in the frequency of its occur- 0700 11 (18 rence during the month. 0800 21 (28 0900 20 (40 , Conditions were very disturbed 1900 21 , (32 during the first three weeks of the 2000 17 or 15 lYlc/s (22 month, the worst periods of iono- 2200 11 (18 sphere storminess being rat/ 3rd, Cape Town : 0000 11 Mc /s (16 Me /s 9th /r6th, r8th /2oth and 24th. 0300 0 (156 Forecast. Daytime M.U.F.s are 0500 11 (20 - 0600 17 (29 , expected to be somewhat lower in 0700 26 (40 ., December than in November, due to 1700 21 or 17 Mc /s (29 , peculiar " 2000 15 (21 the mid -winter " effect 2200 11 in the Northern Hemisphere. Day- 18 time working frequencies will, how- Chungking : 0000 7 Mc/s ever, still be_ relatively high, though 0400 ) 14 0500 11 16 , the period when high frequencies are 0600 17 or 21 Mc/s (21 . usable will be somewhat shorter 0800 26 (30 .. than during November. The 1200 17 or 15 Mc/s (24 .. 1700 11 or 9 i1lc/s (15 ,. 28- IVIc /s amateur band should still 2300 7 ., ( C3 be regularly usable over daylit , paths, but conditions will not be so Ionosphere storms are not par favourable for long -distance con- ticularly frequent or of exception- tacts on 5o Mc / s, which is not to ally long duration in December . say, of course, that none will occur. though those which do occur an Night -time M.U.F.s will fall to their often particularly troublesome after lowest values for the winter, and darkness, because of the already loin night -time working frequencies, ionisation prevailing during the which will be as low as 7 Mc /s over winter night. At the time of writing some long -distance circuits, will re- it would appear that disturbances main in use for longer periods than are more likely to occur within the THE TRIX ELECTRICAL CO. LTD. at present. periods 2nd/5th, 8th/9th, r3th / Below are given, in terms of the r4th, 22nd /23rd and 30th /3rst 1 -5 MAPLE PLACE1OTTENHAIII COURT ROAD LONDON, w.1 5i17 6N/MIi OMIT TRIEADIO, 1'IESDO, LONDON. broadcast bands, the working fre- than on the other days of the TfIf.*DNf;MUSEUM quencies which should be regularly month.

www.americanradiohistory.com Wireless World December, zq¢] Additive and Multiplicative Mixing

THE recent article' by C. J. Mit- By J. W. WHITEHEAD, is apparent that both types of mixing are multiplicative, the term chell is a very useful contribution B.Sc., M.I.E.E., A.Inst.P. to a difficult subject. There can be " additive " being really a misnomer ; very little doubt that the multi- and furthermore, it is clear that plicative and additive processes frequency, and q /tar is a local modulation, frequency changing, and are the same thing. In each case oscillator frequency, then (p - q) /tar the heterodyne reception of C.W. the mixing is performed by a valve can be the intermediate frequency of are all different versions of the same -by an " anode bend " or other a superheterodyne receiver. thing, the difference lying only in device of non -linear current /voltage Let us now proceed to the " multi- the relative values of p and q. characteristic in the case of " addi- plicative " mixer. Consider a tetrode It could perhaps be appropriate tive " mixing, and by a " linear " valve with two concentric grid.,. to make constructive comments on modulator such as a tetrode, pentode, Each grid has its own effect on the a few points in Mr. Mitchell's article. hexode or heptode, in the case of anode current, but they will also On p. 36o at the top of column z " multiplicative " mixing. produce, together, effects which it is stated that the resultant fre- To take the first case first, it is neither of them can produce singly. quency of two beating oscillations worth while to examine closely Let the mutual conductance of is the average of the two components. the significance of the term the portion comprising cathode, I feel that Mr. Mitchell should have " additive." It is true stated more clearly that that the two oscillations this applies only to the are added together in the on case in which the corn - input circuit of the non- Furthe r Thoughts Heterodyning ponent oscillations have linear device, but that is equal amplitudes. It can not all. The fact that and Modulation be shown that the result- the current /voltage char- ant oscillation is to some acteristic is not linear extent frequency modu- indicates at once that multiplication inner grid and anode be g1, and lated at the beat frequency between must occur within the device. let that of the cathode, outer grid the limits (using my notation) For example, suppose we have a and anode be g2, both slopes being the same electrode ¡p and valve possessing a current /voltage measured at p --Bi (p characteristic of the form potentials. Now suppose the bias {i q)1 i,,= a-- bv+cv2 to the inner grid to be made more where a and b are constants and y negative by an extent Vol. The p{i +B(P )] is the total signal input, and suppose anode current will fall and the outer i.e., the mean angular frequency tends this to be part of the valve will behave as to p rather than to (p + q)/2, and v =A sin pt +B sin gt (p >q) though the emissivity of the cathode in fact is only equal to (p + q)lz Then i, = a + b (A sin pt + Bsin qt) is reduced, and accordingly its when A = B. + c (A sin pt + B sin qt) 2 slope will be less, depending on the Mr. Mitchell further states (p. 361, Expanding this expression we value of Vol. By suitable design, col. 1) that a wave -form diagram obtain terms in sin pt, sin qt, sin2pt it can be made directly proportional of the resultant of two beating sin'gt, and the product sin pt. sin qt. to Vv1, and we may write the new oscillations does not reveal a The last -mentioned can be resolved, slope , as KVgig2. Now apply a phase- shift. If such a diagram is as Mr. Mitchell points out, into terms steady voltage change VO2 to the drawn, a closing -up of successive involving (p - q) and (p + q). In outer grid. The anode current will half -cycles is revealed as we move other words, through the multiplying change by KV01g2 VD2, i.e. the from positions of maximum to action of the valve, the output current anode current is proportional to minimum resultant amplitude, and contains, amongst other things, com- the product of the voltages applied the reverse as we move from re- ponents of angular frequencies (p -q) at the two grid circuits. But the sultant minima to maxima. Pre- and (p + q), and also p. These voltages need not be steady ones. sumably, this could be regarded as represent a carrier wave of frequency They are usually in the form of a both a progressive shift of phase p /tar flanked by sidebands of res- fixed bias plus an alternating voltage, and as an indication of frequency pective frequencies (p q) /tar and and so Vol and V0, could be written modulation. for (p + q) /zar. Or, if you like, the as (C + A sin pt) and (D + B sin qt). We can derive an expression valve has modulated p with q. The resulting anode current will the instantaneous phase ¢ by splitting If p is of radio frequency and q is then be : (A sin pt + B sin qt) into terms of audio frequency, the output I. = g2K (C + A sin pi) (D + B sin qt) current contains what we generally regard as a normal modulated wave ; = g2KI CD + CB sin qt + DA sin pt + -AB cos (p - q)t - 2B cos (p + q)t] but if p and q are both of radio frequency and are separated by a Again we have our carrier p and few hundred cycles per second, then its sidebands (p - q) and (p + q). involving sums and differences of the output current contains an audio A point here is worthy of note. half -angles. It is that frequency term (p - q) /tar which is If the angular frequencies p and q are zero, then tan tan . t not present in the input circuit, ¢= A Bp2q and we have a case which is identical la = g2KCD. with the heterodyne reception of On applying signals of frequencies Lastly, it is stated on p. 36o, col. 2, C.W. telegraphy. Similarly, if p /2/r p /ear and q /tar, the only additions that "the simple addition of two represents an incoming signal to the anode current are alternating sinusoidal quantities results in ones. No rectification occurs. multiplication." This is not trae, Wireless World, October, 1947. From the foregoing, therefore, it and I do not think that the author

www.americanradiohistory.com December, 1947 Wireless f,ti'o r Id 487

Additive and Multiplicative Mixing - ing manner readily to demonstrate ,937 really means this. What I feel he the effect of the multiplying together means to say is that the resultant of two oscillations. of two beating oscillations is another Take two tuning forks of the same oscillation of varying amplitude frequency and load one with a Record and phase which can therefore be small piece of sealing wax or chewing regarded as a modulated wave. gum. On sounding them simul- Modulated waves, as we usually taneously, the ear at first detects a understand them, are composed of beat tone of one or two cycles Storage at least three oscillations, whereas per second, but as the amplitudes heterodyne action need involve only decay and become very small, the two Nevertheless, it is possible beat tone vanishes. This is accoun- to derive mathematically an ted for by the fact that the input/ expression for a modulated waveform output characteristic of the ear is which approaches closely to that non -linear for large inputs, and so resulting from the superposition of " multiplication " occurs and the Here, to end your record storage two oscillations of roughly equal difference frequency is apparent. problem once and for all, is the new frequency. For small inputs, the characteristic lightweight portable 'IM R A K'. Two tuning forks of almost equal is sensibly linear and so no beats Holds up to so records, to" and frequency can be used in the follow- are heard. is ", yet requires little more space than a medium -sized table lamp. LETTERS TO THE EDITOR Is No The First Aerial . Damping Speaker Coils Longer Modulation and Frequency- Changing

Who Invented the Aerial ? Loudspeaker Damping WITH reference to the article IAM very pleased to note the published in your September increasing recognition of the issue on the invention of the aerial, advantages of a high intensity mag- Every record easy to get at. Every I beg to inform you that a group netic field for damping loudspeaker of Russian scientists has written an speech coils. division individually numbered. Records open letter of protest to the com- I, too, share the belief that when held firmly in position by resilient, mittee which is organizing in Italy the effective resistance of the speech plastic covered, sprung -steel divisions the celebration of the 50th anniver- supply circuit is low relative to the and cushioned at points of contact. sary of Marconi's invention of wire- D.C. speech coil resistance, then less telegraphy. According to the little is to be gained from the point Russian professors the real inventor of view of damping by further re- of wireless telegraphy should be the ducing the input resistance. Ani Russian physicist Popov. I have In the case of triodes operating replied to the above open letter, at a higher load line than the usual repeating the statements made by makers' rating, for example, with a Popov himself on board the Italian PX25 (at 400V ; R. approximately Problem cruiser Carlo Alberto in July, 1902 1,too l2) operating at a 5,000-12 load (statements already reproduced by line, we have a drive -to -load ratio Wireless World). But now I beg to of about I : 4i. Even if the speaker add the following facts :- is so efficient that its D.C. resistance At the first Berlin international is half the dynamic impedance, the wireless conference in 1903 a Rus- ratio of drive -to -load D.C. resistance sian delegation, which included is still t : 2t, and this without cir- Finished in a wide choice of gay Popov, was present. As one of the cuit complications. If, by feedback, colours. And you can add on new Italian Government delegates, I the input impedance is reduced to racks just like a unit bookcase. Now made during the conference an offi- zero, the D.C. resistance of the cial statement about the invention speech coil still exists and currents available at most record shops, price of wireless telegraphy and about the due to back -E.M.F. cannot exceed 29/6d., plus 6/5d. tax. Optional dust- long examination made by the proof plastic cover 7/9d., plus i /8 }d. tax. patents offices of Russia, of Ger- 3+ =1.45 of their previous value. 2 The new many, of England and America A reduction of input resistance to upon Marconi's patent application one -third or one -quarter of its for wireless telegraphy by electric natural value will allow very nearly RAIL waves. This examination lasted this maximum effect. MADE BY THEI about one year and the fundamental From the point of view of dimin- MAKERS OF THE patent for wireless was granted to ishing harmonic distortion, hum, FAMOUS IM NEEDLES Marconi on June 2nd, 1897. No- etc., which in some circuits is re- For details of your nearest supplies body was able to contradict my duced in the same ratio as the statement, which made a clear re- write to Alfred Imhof, Ltd., Dept. W3, apparent amplifier output imped- 112, New Oxford Street, London, W.C.I. ference to the aerial. will ance, it be obvious that it may Museum 5944. Rome. LUIGI SOLARI. well be desirable to use much more

www.americanradiohistory.com 488 N'írcles% World December, 1947

was changing, and the output circuit Letters k.o the Editor - commercial production, as it feedback than that needed for judged to be a little ahead of its is now tuned to the lower sideband damping purposes alone. time. This opinion you will under- frequency, (the audio difference It is possible to overcome the stand when you look at the enclosed frequency) produced by multiplying damping limitation reaulting from Specification [No. 231,992] and see the carrier by the lower and upper the D.C. speech coil resistance if that the application date is sidebands. Rectification is also this resistance is neutralized (in 29/1/1924. similar, the output circuit being part) by something corresponding to P. G. A. H. VOIGT tuned to the lower sideband frequency mains radio - frequency reaction, only London, S.E.r9. produced by multiplying the operating at A.F. and without input voltage by itself. The tuning Heterodyning and Modu- difference frequency from this pro- Such circuits naturally involve an duct will, of course, be zero frequency: element of possible instability in lation i.e. it will be D.C. which frequency responses can " go IWAS interested in the article by Evesham. K. R. STURLEY crazy " and which may also lead to C. J. Mitchell on heterodyning [This subject is also referred to a region of overdamping. and modulation, and the view he on p. 486. -En.1 Imagine a speech coil so solidly puts orward that modulation and frequency changing are the same process accords with my own. Effective Use of Amateur The only difference between the Frequencies two is that with modulation the out- 1 T the present time we hear quite put circuit is tuned to accept the LI a lot about vicious spirals in carrier and both sidebands, whereas connection with economic affairs. with frequency changing the out- May I, as an old amateur, venture put circuit is made selective to a to suggest that amateur radio is at band of frequencies centred about present in the throes of a vicious the lower sideband frequency. spiral of a rather different type, and I do not like his suggestion that it looks to me rather like this: addition can be shown to be multi- Every month between roo and plication as I think this view is apt 15o new licences are issued in this to confuse the student. It is merely country, which means that by 195o a mathematical wangle to change there will probably be about ro,000 Diagram reproduced, by permis- sin A + sin B into amateur transmitters in the small sion of the Patent Office, from + - B) area of the British Isles -and there 2 sin (A B) cos (A Specification No. 231,972. (P. G. 2 2 will be fewer channels for them. A. H. Voigt.l More amateurs, fewer frequencies ; and to say that addition is therefore this is by no means the whole story. damped that it becomes virtually a multiplication. Multiplication, as British amateurs are now allowed rigidly fixed object, the diaphragm I would understand it, is the multi- inputs up to 15o watts (except for vibration characteristics will then plication of the original input the first 'prentice year of operation). be quite different from those frequencies ; i.e. it would be represen- Increasing congestion in the ama- obtained when the coil is able to ted by sin A x sin B and the result teur bands sorely tempts every move. This may, or may not; be an is the sum and difference and amateur to go to the limit of the improvement on the original design. frequencies represented by (A + B) power and employ his full 150 watts Circuits of the general type shown and (A - B). Pure addition cannot (and some !), in order to make hini- by D. T. N. Williamson in his letter produce _ these sum and different self heard. (Wireless World, October, page frequencies ; if these are required Even this is still not the whole must followed multi- 402) and evolved according to sug- addition be by story ; much of this high -power gestions by P. d'E. Stowell and plication, and this is performed by operation in congested bands is by M K. Taylor can produce such A.F. the rectification process. Taking means of telephony, so that one reaction effects if thrown slightly the simplest rectifier, the square powerful phone station spreads over out of balance. It will be remem- law type, the expression for anode enough kilocycles to accommodate bered that the circuit involved current is : twenty telegraphy stations. placing the loudspeaker in one arm I. = a + aiE0 + a2E2p.. .. (r) The temptation to " pile on the of a bridge in which any unbalance If E,0 = El sinw,t -)- E2sinw2t watts " is aggravated by the pre- voltage was fed back into the (we can neglect any bias voltage sent crazy Gadarene rush to work amplifier, so that if the back - there may be) the second term in (r) DX -a procedure which seems quite E.M.F. due to coil vibration was gives a2 (Ejsinwyt -i- E2 sines 2t)2 purposeless, since any individual excessive or deficient, this feedback which contains the term with a good aerial, a good receiver remedied matters. 2a2Elsinwtt x E2sinw2t and a few hundred watts can work I have no doubt that the three thus providing the sum and difference any part of the world to order; gentlemen named would be inter- angular frequencies (col ± w2). there is little cleverness and no ested to know that some years ago With the multiplicative frequency merit in doing so. I must also 1 patented a circuit in which the changer such as the pentode with make mention of another abuse of loudspeaker formed one arm of a suppressor grid injection, or the the amateur bands: this is the bridge and in which unbalance volt - heptode, etc. selfish employment of high -power tage was fed back into the ampli- I,, = (a0 + a,Ect) (b. + b1Ea2) (2) telephony for local or semi -local fier so that at resonance the appro- where neglecting bias communication. priate frequency was automatically = Eisinw,t Two years ago you published an diminished, etc, etc. The circuit and article from my pen forecasting, did actually work, the effect on Eo2 = E2sinw2t more or less, the state of affairs in multiple voices being to make them The term b,b2E,sinwlt x E2sinw2t the amateur bands as we see (or seem to go down the horn, and to will be obvious from the above rather, hear) them to -day I sug- sort themselves out better. The Incidentally, detection is by the same gested there that if action were not circuit, however, never went into process as modulation and frequency taken among amateurs themselves

4.4 www.americanradiohistory.com December, 1949 Wireless World 489

to rationalize their operation, then Apart from being telescopic, the amateur radio would choke itself to mast is also rotatable, allowing the death by sheer weight of numbers. aerial to be swung for " maximum " To -day that is more true than ever. irrespective of the orientation of the RE- ENTRANT What it will be like by 195o, I boat. shudder to think. The power Lupply is obtained from Can British amateurs discipline a carbon pile regulated rotary con- HORN themselves in time? Or is amateur verter which is driven by the boat's radio, as a pleasant scientific hobby, z4V D.C. battery supply. doomed to extinction? If any of your readers have had TYPE 42 REH That, flatly, is the choice before experience of installations us. of a simi- ' ` ETHERIS." lar nature it will be most interesting to hear of the results obtained. Television Afloat C. E. TATHAM. Tr may be of interest to some of Langham Radio Services, your readers to learn that a Pye Cambridge. Di6T console television receiver has been successfully installed in a Aerial Aesthetics 35-foot four-berth cabin cruiser, JUDGING from the photograph Golden Spray," on the River Cam. of the model of the television Consistently excellent results have relaying site appearing in your last been obtained on the waterways in issue, there is little wonder that the and around Cambridge and about 3o proposal, put forward earlier in the miles north at Redmere. Further- year, to erect a television relay The new 42REH has advantages more, a picture of reasonable enter- station near White Horse Hill on the of complete weather -proofness, tainment value has been obtained Berkshire Downs aroused so much smaller overall length, better whilst sailing in The Wash between antagonism. weight distribution and conse- King's Lynn and Hunstanton. Con- The designers of these and other quently greater ease in handling, sidering the aerial is mounted on a aerial masts and towers might do which make this one of the most 20 -foot telescopic steel mast, 6 feet well to examine some of the long - popular of the new F.I. loud- of which is inside the boat, this span bridges. If the civil engineer speakers. The horn is designed could be regarded as a tribute to the can design bridges that are pleasing for use with the standard F.1. sensitivity of the receiver used. to the eye, why cannot the electri- L.S.7 Unit and allows for this The Antiference aerial used cal engineer, justly proud of his unit to be driven to 12 watts lends itself admirably for this job circuit design, take interest in the input. A spun aluminium cover due to the ease of -dismantling when appearance of the work as a whole? over the unit has room for the mast is telescoped after nse. Cambridge. P. G. BRIGGS. housing a suitable matching transformer. The construction has been designed so that the whole unit per cent, and 2 per "CONCERTO" AMPLIFIER cent at r3 watts. is assembled and held together The price is £277 ros and the makers with ONE LARGE NUT only. DESIGNED for the reproduction of are Charles Amplifiers, me, Palace Gate, records, this amplifier has eight London, W.8. This construction enables a triode valves and a rectifier. The first number of units to be packed stage is a pre-amplifier for moving -coil for export in a space which pickups, and can be switched out when is a fraction of that normally the input is from moving -iron or crystal RADIO'S ENEMY No. 1 required ; assembly is a pickups. The output stage consists of matter of a few minutes un- two PX25s in push pull, and negative ACOMPREHENSIVE survey of existing skilled labour. feedback is applied over three stages, knowledge on all kinds This unique feature including the phase -splitter. of radio noise is made will recom- in a special mend itself to all export Separate tone controls for " Treble " report (No. 15) just issued by the buyers particularly. and " Bass " are provided. The Department of Industrial and Scien- tific Research. The types of inter- The 42REH is not of the " loud- hailer " type ference dealt with are summarized of speaker, but is designed to cover a range in of frequencies considerably greater than the main chapter headings: those needed for purely "announcing " receiver, thermal, cosmic, atmos- purposes : i.e., it is suitable for all normal pheric and man -made. Two later requirements of high power reproduction chapters are on the influence of of music as well as speech. Dimensions assembled ... 22in. dia. x 24in. noise on reception and on measure- Bell diameter ...... 22in. ments. Suppression is not treated Cut -off frequency ...... 175 at any length. Effective Air Column ... 42in. Weight Horn only . 8 lbs. In the concluding " Recommenda- Shipping space ... One -23ín. x 23ín. x I8in tions " is is stated, " The survey 12-33in. x 33in. x 27in. shows that in no section is the Separate " Treble " and " Bass " knowledge complete ; in fact, it indi- tone controls are provided in the cates a wide field for further investi- " Concerto " model made by gation." l P0 Charles Amplifiers. " Survey of Existing Information FILM INDUSTRIES LTD. and Data on Radio Noise over the 60, PADDINGTON ST., W.1 " Treble" control provides both cut Frequency and boost, while the " Bass " has six Range I -30 Mc /s," con- Telephone: WELbeek 2385 steps, from linear to full boost at 8db tains 126 pages and 57 figures; it is per octave. issued by H. M. Stationery Office. w.w. l2 It is claimed that the overall dis- Kingsway, London, W.C.2, at 3s ( tortion for an output of 7 watts is 1.3 (by post 3s 4d). D

www.americanradiohistory.com Wireless World December, 1947

done, though with the present limited A.F. band imposed on RANDOM RADIATIONS short-, medium- and long -wave transmitters, I doubt whether the By " DIALLIST " public would regard the results as spectacular. Something, again, materials that are now scarce, might be achieved in the moderately The More the Merrier ! though once they were plentiful priced sets in the way of lessening IT is a rather amazing thought that enough. The spirit seemed to be: the content of znd or 3rd harmonic one person in every hundred of If we can't get this, we'll make do in the output: but would the man the whole population of Great with that and jolly well see that the in the street be in raptures over Britain visited the Radio Exhibition job's as good as ever it was. An- that? Again I permit myself to during its ten days' run. Never- other important point is that one of be doubtful. More efficient valves? theless it was so, for there are forty- the things we had perforce to learn We already have quite a few three- four million-odd of us and the during the war was how to make valve-plus-rectifier superhets. Valves attendance at Radiolympia was sets of all kinds that were easy to making a smaller drain on sources 440,320. Had the show been held handle and could be relied upon to of H.T. and L.T. supply? Already in school holiday time the figure stand up to hard wear. The know- the mains set costs no more to run might have been a good deal higher, ledge gained in wartime has been than a single small electric light for schoolboys (and schoolgirls too) receiver, bulb. Battery users would be put into the peacetime improvement are great wireless enthusiasts, as all which at its best is a sound, well - pleased; but such an of us know who either have children designed piece of work mechanically would hardly be as sensational now- of our own or number other people's as well as electrically. adays as it might have been some amongst our friends. That the years ago, for battery sets are fast attendance was so large -nearly becoming fewer and fewer. No, it's double that of any pre -war exhibi- What Next ? not easy to think of any likely im- tion-seems to me to be due to four provement on existing methods of main causes. The first, and pos- Come to think of it, how and long- and medium -wave broadcast where are spectacular improvements which could cause a sibly the most important, is that receivers to- reception so many veteran receivers are now possible in broadcast furore. The most probable " sen- crying out to be placed on the day? Increased sensitivity? To- sation " of a future Radiolympia is retired list. The second, that many day's receiver brings in pretty well F.M., of which the ordinary listener visitors rather expected to find all the stations that the ordinary in this country has heard little breath -taking advances due to war- listener is likely to want. Selec- yet. time progress. The third, that tele- tivity? Most respectable sets will vision was a prominent feature and separate stations with channels The Popular Televisor that interest in this department of 9kc /s apart. Unless we discover In television receivers, though, I wireless is more lively than ever. some new method of transmitting feel that the improvement since the The fourth, that it was a genuine we can hardly ask the broadcast previous radio exhibition has been radio exhibition and not just a show receiver to do more than that. phenomenal. I'm thinking par- of broadcast receiving equipment. Higher fidelity in reproduction? ticularly of the moderately priced Whether or not that's a correct Here, perhaps, something might be instruments, made up in compact diagnosis, all the world and his wife form and with all but the most were certainly there. On some of straightforward controls preset, the most crowded days the hall be- which give an image of round about came so packed that one could have seven and a half inches by six. I believed almost any attendance have an idea that that size of image figure! is going to make a very wide ap- peal, so long as our transmissions Sound, but Not Spectacular are limited to 405 -line definition. that course there were those who People have begun to realize Of it is about the largest you can do crabbed the show. There always in average are. One cynic told me that the with, comfortably the only important advance he'd been living room of to -day, if you're not able to discover in broadcast re- to spoil results by viewing at too ceivers was in their prices -the kind close quarters. Compare the best of thing that has to be said by a of the 7$ x 6 or 8 x61 vision re- fellow with a reputation for mor- ceivers of to-day with medium - dant wit, no matter how far it may priced sets of 1939, and I think you be from expressing his real opinion. must agree that there has been a I agree that there weren't any spec- very remarkable advance. Their tacular developments- things to clear, contrasting, steady pictures; knock the non -technical visitor all their effective limiting of the snow- of a heap, as did, for example, the storm effects due to ignition inter- all -mains receiver, the screen -grid ference; their simplicity of opera- valve, the pentode, the moving -coil tion-all these make them com- loudspeaker, the ganged tuning pletely different things from most condenser and the pickup in their of the television of pre -war days. respective years. But there were A Moot Point plenty of good things there, if you COMPRESSED SPEAKER HORNS. looked for them. What, perhaps, Film Industries have re- designed One thing the manufacturers do interested me most was the way in their re- entrant loudspeaker horns not yet seem to be at all certain which so many makers had man- to save space in export packing ; about is the form that the great aged to turn out good jobs of work 8o of them now go in a case of public is going to want its tele- whilst making little or no use of 24 cubic feet vision receivers to take. Will the

www.americanradiohistory.com December, 1947 Wireless World 491 most popular set eventually prove to be the SV, the VML, the VAW, TOGGLE-S 11 'l _TCHES or the VAWRg? I'm beginning to change my mind about that. I used to think that Mr. and Mrs. Everyman's ideal was to have a single piece of furniture which would be the complete provider of entertainment in the home and that they would not really be satisfied with anything less than the televisor cum all -wave radio receiver cum gramophone unit. I still believe that there will be a big demand for such instruments by those who have the money to pay for them and living rooms large enough not to be overweighted by their necessarily rather large cabinets. But something tells me that the small vision plus accompanying sound only model is going to have bigger sales than any other in the immediate future. And it's not just its modest price and its small size that may be the deciding factors. Many people do not want to put all their eggs into one box, so to speak. They prefer to be able to have the broadcast receiver in one room and the televisor in another when they want to do so. Others, again, already have broadcast receivers or radiograms with which they are quite satisfied.

Another One On Magnets for every purpose .. . YOU may recall that some months maximum reliability, experience has proved the need for separate ago I suggested a simple little FOR problem about two steel bars of switching in all types of apparatus. For this and many other require- exactly the same size and appear- ments, over 200 types of BULGIN switches are available, including ance, one of which was magnetized " ON- OFF," " CHANGE -OVER," single- and double - pole, dolly-, whilst the other was not. How rotary -, key- operated, biased- action, rotary- selector and press -button could you quickly tell t'other from which, supposing that you had no models, suitable for a wide range of voltage and current ratings. instruments of any sort or kind, no Smooth, clean, rapid make- and -break actions and made from materials other bits of iron or steel, not even only of the highest grades obtainable. BULGIN switches are produced a piece of string? The answer in nickel, Florentine-bronze and gun-metal finishes. given was : arrange them like a T. Then if there is no attraction, the cross piece is the magnet. If there SELECTIONS ILLUSTRATED ARE LIST is, the magnet is the upright. I DATA was surprised that no one wrote in NO. for 6 to say that he could produce a pair S.253 Rotary-action, single -pole, make -and -break, -250V. 3A. wkg. of steel bars answering the descrip- S.257 double -pole, change -over, for 6 -250V. 1A. wkg. tion given on which this test would S.258 Toggle -action, single -pole, make -and- break, for 6 -250V. 3A. wkg. fail. Any offers? S.265 change -over, for 6 -250V. 2A. wkg. S.270 double -pole, change -over, for 6 -250V. 1A. wkg. -break, for 6 -250V. MULLARD VALVE DATA 5.277 make- and 3A. wkg. S.301 change -over, for 6 -250V. 2A. wkg. AREVISED edition of the Mull - ard Wall Catalogue has been issued for use by retailers by Mull - ard Wireless Service, Century House, Shaftesbury Avenue, Lon- don, W.C.2. A very useful new section is that dealing with substitution types. E CO. LTD. BYE- PASS-RD. BARKING Full details of alterations to base A.F.BULGIN and associated circuits connections Telephone : R/Ppleway 3474 (5 lines) are given in cases where these are necessary.

www.americanradiohistory.com 492 Wireles% World December, 191.7

will be gratified to find that the BOOK REVIEWS author uses only simple mathematics, and deduces the wave pro- Radar System Engineering. Edited vide a basis for design. There is perties mainly from physical by L. N. Ridenour. Pp. 748 + sufficient matter to make up what reasoning. The student thus gets a xviii, with 446 illustrations. ought to have been a separate good appreciation of general prin- McGraw -Hill Publishing Co., volume, of military and historical ciples, in which he is aided by Ltd., Aldwych House, London, interest. Space would then have excellent diagrams. But this pro- W.C.2. Price 37a 6d. been released for filling in some cess is limited, and the reader has THIS volume is the first in a passages which are somewhat super- for the moment to take many monumental publication -a ficial and descriptive, and for prac- results on trust. series of twenty -eight, recording the tical design data. Present -day The fourth chapter introduces one work of the Radiation Laboratory radar engineers are more interested to the many practical devik es which of the Massachusetts Institute of in present and future equipment have been developed -terminations, Technology, which was the great than in what was done during the couplings, bends, transformers, etc. American wartime centre for radar war, and may be disappointed at -and to some associated microwave research and development. Circum- having to reorientate this for them- apparatus. Examples are drawn stances in this country having re- selves instead of having it done for from equipment designed for use at stricted systematic publication of them. This criticism, applied to 9 -cm and 3 -cm wavelengths, but it our work in this field to Part III A a work that announces itself as a is a pity that so much reference is of the I.E.E. Journal, appreciation record of war work, may on that made to in x Tin and z jtin will be felt for the acknowledgment account be a little unfair ; but see- x tin guides as standards for the in the Foreword that the Radiation ing that the general principles of 9 -cm waveband ; these have little Laboratory Series records the col- radar have already been written -in to recommend them and are now lective result of work done not only some respects better -it is a pity obsolescent. in the U.S.A. but also in Britain that the Radiation Laboratory staff In the next chapter waveguide and in the Dominions, and that it is could not have been retained long techniques of a more advanced dedicated to all who contributed in enough for them to have reached a character are described. Impedance any way, anywhere, to what was more forward- looking viewpoint, at in waveguides and its relation to perhaps the most remarkable co- which they would have turned their corresponding ideas in coaxial lines operative development enterprise backs on details of merely historical is treated well, but the reader will ever carried out. interest and been able to concen- not gain much idea of when he may Most of the other volumes in the trate on quantitative data of more use the formula for intrinsic imped- series are devoted to specialized use to the practical radar engineer. ance and when that for total im- principles and techniques, and since M. G. S. pedance. He will be more troubled many of them have applications far later (p. 196) when he finds the beyond radar the aim has been to The Principles & Practice of Wave formula for total impedance used point out the general applicability Guides. By L. G. H. Huxley. under the name of intrinsic imped- of the work reported, avoiding any Pp. 328 -i-xi; 148 figures. Cam- ance. Detailed treatment is given of special emphasis on radar. The bridge University Press, zoo, series and shunt junctions, and of present volume is intended to apply Euston Rd., London, N.W.I. such elegant devices as ring switches this work specifically to radar. Price zis. and T.R. cells. The first eight chapters are is the first of a new series of Chapter 5 treats the modes of devoted to the broad principles of THISmonographs to be published by oscillation and some of the applica- radar, and include such matters as the Cambridge University Press tions of cavity resonators. The dia- the radar range equation, the pro- under the heading " Modern Radio grams are good, but it is not made perties of radar targets, limitations Technique," the aim of which is to clear which characteristic numbers of pulse radar, the alternative of describe the advances in radio are allowable for the different c.w. radar, and the gathering, pre- technique made during the war. It modes, and the E,,, and Eo,l are sentation and use of radar data. is based on courses given by the wrongly stated as being the funda- The last two deal with two special author at the Radar School of the mental E -modes for rectangular and techniques which hitherto have not Telecommunications R e sear c h circular resonators respectively. had much notice -moving target Establishment. Thus far the mathematical treat- indication and radar relaying. The The fact that a single hollow ment has been deliberately kept seven intervening chapters are on conductor could act as an efficient simple in order not to obscure the radar design, first in its compon- transmission line for waves of suit- physical arguments ; in the final ents and then as complete systems. ably high frequency has been known chapter a purely analytical treat- This work has been divided for many years, but prior to the ment is given, supplying the basic among the team of experts respon- war this waveguide had hardly mathematical theory of the subject. sible for the whole series, and has emerged from being a laboratory The change is abrupt, and may come been ably carried out. In spite of curiosity. The development of as a shock to the reader who thinks an apologetic note about continued centimetre -wave radiolocation, how- that he has learned everything shortages, the volume is to British ever, required also intensive prac- without much mathematics, but it eyes a handsome one, doing credit tical and theoretical work on wave - certainly has to be tackled if he is to the ambitious scheme of which it guides, and it is with these develop- to have a sound understanding of forms a part. ments that the book is mainly con- the subject. While acknowledging the value of cerned. It is a good book, thoroughly up most of the material thus presented, The first three chapters describe to date, and comprehensive, but it the reviewer cannot help feeling the various modes possible in is spoiled by quite a number of that it does not quite fulfil expecta- rectangular and circular guides and errors, both of a major and a minor tions aroused by the title. The con- the simpler properties of wave pro- nature ; none appear to be printer's siderable sections on the tactical pagation in them. Those who have errors. The layout and production use of radar during the war seem previously been alarmed by the of the book are attractive, and the completely out of place in an en- seemingly difficult mathematics re- price is not at all excessive. gineering work that claims to pro- quired in the study of this subject H. R. L. L.

www.americanradiohistory.com December, 1947 Wireless World Advertisements 37

1998 ACKNOWLEDGED THROUGHOUT THE WORLD

RESISTORS CERAMICONS Hi -K CERAMICONS POTENTIOMETERS SUPPRESSORS VITREOUS ENAMELLED WIRE -WOUND RESISTORS Erie Resistor Ltd., The Hyde, London, N.W.9, England,

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www.americanradiohistory.com 38 Advertisements Wireless World December, 1947 Stabilised Insulation BY MODERN IMPREGNATION METHODS

HYMEG Synthetic Insulating Varnishes are recognised and widely used for their mechanical HYMEG rigidity, improvement of electrical properties of windings ; heat, moisture, oil, acid and alkali resistance as well as for the considerably reduced HIGH-SPEED PRODUCTION stoving time necessary. Now, special methods of continuous conveyor impregnation and baking developed with the use of HYMEG have still further reduced processing times to a fraction of those previously believed necessary. Often faster than infra -red baking with none of the defects, reduced handling, absence of special jigs, with complete freedom from blistering, bubbling and porosity, are some of the advantages claimed and substantiated for HYMEG High Speed Production methods.

After much research in our laboratories and in conjunction with many well - known specialist 1YMEGLAS. manufacturers, we have now evolved the Hymeglas system of Insulation which comprises modifications of Hymeg as used for coil impregnation to meet GLASS FIBRE INSULATION SYSTEM the varying conditions applying to each field of manufacture. This integrated system of development is;successful in enabling machines to be designed and operated without weak links in the chain of insulation below 200 °C. Thus the fullest advantage is taken of modem glass fibre insulation by providing a degree of bonding and insulation at every point in which the uniting of Hymeg impregnation with the Hymeg as used for subsidiary insulations gives a solid homogeneous winding of equally efficient characteristics and heat resistance throughout. Hymeglas therefore virtually eliminates any risk of insulation failure and enables motors and the like to operate under abnormal conditions for long periods without risk of electrical breakdown. Due to the excellent space factor of glass fibre as compared with the more usual asbestos and mica Class B insulations, it is often possible in redesigning with the Hymeglas system to employ larger copper sections with well -known advantages. The Berger Technical Service -the research work of which produced " HYMEG " and " HYMEGLAS " is available to advise manufacturers on all problems of insulation. Get in touch now with- LEWIS BERGER & SONS LTD. (Est. 1760) 35, BERKELEY SQUARE, LONDON. W.1. Telephone : MAYfair 9171. 6IANUFACTURERS OF HIGH- PERFORMANCE INSULATING VARNISHES AND ENAMELS Five & Ten Metre Converter

AS DESCRIBED IN THE CONSTRUCTIONAL ARTICLE IN THE No.5 EDDYSTONE SHORT WAVE MANUAL If your receiver covers the recommended I.F. of 1.6 Mc /s (187.5 metres) the Converter will allow efficient reception of FIVE & TEN METRE AMATEURS AND TELEVISION SOUND Uses modern V.H.F. Valves EF5o, EF54 and EC52. FROM STOCK

5 & IO METRE CONVERTER UNIT Assembled and tested (less valves) .. .. £IO 10 0 VALVES Types EC5z, EF5o, EF54.. .. 3 0 I I

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STREET, OXFORD STREET, WEBB'S RADIO, 14, SOHO The necessary power supply of 6.3 volts I amp. and 25ov. H. T. can usually use WEBB'S LONDON, W.1 Phone : GERrord 2089 be supplied from your receiver. If this is inconvenient Power Pack "23013o, ' size 6in. x 6in. x 4in. ... PRICE E4 10 0 Shop hours 9 a.m. -5.IS p.m. Sots. 9 a.m. -1 p.m.

www.americanradiohistory.com December, 1947 Wireles s World Advertisements 39 Wharfedale NEW GOLDEN 10 inch LOUDSPEAKER... During the last six years hundreds of Wharfedale Golden Units have been supplied, and are still being supplied, to the B.B.C. and G.P.O. It was selected by reason of its level response. The new model is fitted with precision die -cast chassis, improved spider, and Alcomax i i Magnet increasing the flux density from io,000 to 12,500. Delivery 4 -5 months. Speech coil Made and Guaranteed by 3 or 15 ohms WHARFEDALE WIRELESS impedance WORKS BRADFORD ROAD, IDLE, BRADFORD PRICE 75/- Telephone : IDLE 461. Telegrams : Wharfdel, Idle, Bradford

THE NEW KOLECTRIC HIGH SPEED PRECISION AUTOMATIC COIL WINDING MACHINE

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A few features : Totally enclosed headstock. Ease of operation and setting. Winding of 2 coils simultaneously if required.

nfinitely v a r i a b l e micrometer w i re gauge adjustment. Wire gauges 25-50 S.W.G. Winding Speeds up to 3,000 R.P.M. Carriage setting Write us for full information of this NEW DEVELOPMENT IN COIL handle. WINDING. Enclosed drive, with pedal control.

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www.americanradiohistory.com 40 Advertisements Wireless World December, 1947

The ('laur«cleristics Te111

S. G. BROWN, Type 'K' Moving Coil Headphones, with the following outstanding characteristics, supply that High Fidelity Reproduction demanded for DX work, monitoring and laboratory purposes, etc.

NOTE THESE CHARACTERISTICS. D.C. RESISTANCE, 47 Ohms. IMPEDANCE, 52 Ohms at 1,000 c.p.s. UNIVERSAL COUPLING SENSITIVITY, 1.2 x 10 -'= Watts at 1 kc. -.0002 Dyne /ems. CONSTANT VELOCITY * Descriptive Literature on request. TROPICAL BAKELITE INSULATION MATERIAL TYPE "K." PRICE £5.0.0 PER PAIR. FINEST QUALITY Compensates for both axial and angular misalignment and Supplies now available. * provides accurate "ganging." For details of other S. G. Brown PRICE 2/9 RETAIL Headphones (prices from 25/- Order from your Local Dealer. to 60/ -) ask for illustrated Brochure " W.W." HEADPHONES WHICH UPHOLD BRITISH PRESTIGE. JACKSON

Phone BROS (LONDON) LIMITED ACOrn 5021. l` ) J`S KINGSWAY WADDON SURREY TELEPHONE: TELEGRAMS: WALFILCO. VICTORIA RD., NORTH ACTON, LONDON, W.3 CROYDON 2754 -5 PHONE, LONDON

r r.' aaiaaaoai , THE BRIERLEY " RIBBON " PICK-UP ia a /aaaaa . aa ia / o o /ai/ /i /aiiaiao /i io ; aiaaar // aai /aai ; / /ao The high frequency resonance of this pick -up is over 20,000 cis and is ` i ,/,`" irr vi orr ar o/ , ri largely self- damped. These features have been realised by decreasing °agar , the mass cf the moving parts rather than increasing their stiffness. i/// ./a¡p// // Jl The frequency response is ± 2 dbs. up to 20,000 c/s with the coupling i transformer in circuit. We do not however urge you to consider this 113, CHARING CROSS ROAD, a matter of very great importance. The important point is : how much of this frequency range can be used before the better tonal LONDON, W.C.2 quality is marred by scratch, fizziness and even distortion which increase as the frequency range is extended 2 Omitting for the moment the sad story of the " advance " in recording technique and other matters having considerable bearing on the COILS subject, we ask you to consider the importance of ensuring distortion - SHORT WAVE less reproduction not merely at a few selected frequencies, but over the whole frequency range. FOR Iii Closely related to this is the question of longitudinal damping of the moving parts. It will readily be realised that to obtain a low point BETTER restoring force and negligible stiffness for lateral movement of the moving parts -essential where low point and record wear demand RESULTS small downward pressure -and at the same time adequate longitudinal damping, presents a problem in itself far more important from a STOCKS performance point of view and much more difficult to realise than a frequency response extending even to 200,000 c /s. AVAILABLE From time to time -as space permits -we propose to touch on the more interesting and the more relevant design features of pick-ups and to show why the BRIERLEY " RIBBON " PICK -UP ha the widest useful frequency range. For the moment we point out that this pick -up operates with a per- manently fixed downward pressure of oz. It is entirely free from resonances throughout the whole range -due to a great extent to the exclusive use of the " Floating Element " design. The permanent point cannot be damaged by cracked records and will play 10,000 to 20,000 records (depending on the type and composition of the records). The weight of the aluminium ribbon is about 0.15 milligram and the total mass of the moving parts is 6 to 8 milligrams most of which is concentrated near the axis of rotation giving a very low effective mass INTERCHANGEABLE COIL SET comprising the at the point. The output voltage is between 1/150 and 1 /100th of a " IVALEK " wave ranges : -24 Meters, 20 -36 Meters, 30 -80 Meters. volt ; is no trouble whatsoever from hum and the instrument is following -12 there 3/6 each. not delicate. Price in U.K. complete with special mumetal screened 9/- per set of 3 coils. MEDIUM WAVE COILS of Radio, Television, coupling transformer and including Purchase Tax, £8 16s. 10d. Coll and see our exceptionally wide selection Electronic and Electrical instruments and components. Full information on " Ribbon " and " Armature " Pick -ups, Low Pass Filters, Pre -amplifiers and Amplifiers sent on request. M. ALLEN (Radio) Ltd J. H. BRIERLEY (GRAMOPHONES & RECORDINGS) LTD., 46 Tithebarn Street, LIVERPOOL, 2. 113. CHARING CROSS ROAD, LONDON W.C.2. Tel.: Gerrard 8734.

www.americanradiohistory.com 1)1 1( 1111)( 11) IT Wirele,%s Wurld Advertisements 41

" DECISION BY MAJORITIES IS AS MUCH AN

I EXPEDIENT AS LIGHTING BY GAS." Gladstone.

The majority of discerning people quote Lectrona Loud- speakers as the best on the market.

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Made in Three Principal Materials FREQUELEX An insulating material of Low Di- electric Loss, for Coil Formers, Aerial Insulators, Valve Holders, etc. PERMALEX A High Permittivity Material. For the construction of Condensers ort the small- est possible dimensions. TEMPLEX A Condenser material of medium permittivity. For the construction of Con- densers having a constant capacity at all Bullers tem peratu res. BULLERS LOW LOSS CERAMICS BULLERS LTD., 6, LAURENCE POUNTNEY HILL, LONDON, E.C.4

www.americanradiohistory.com 42 Advertisements Wireless World December, 19./7 ...VIBRATION ISOLATION EXCELLENT SELLING LINE High Fidelity S.H.E.F.I. Moving Coil Pick -ups NEW VIBRATION ELIMINATORS

[HEQU!flE__i " Equiflex " Mountings are MOUNTINGS J invaluable for the mounting AN PRODUCT and suspension of machines, ® equipment, instruments, electrical app -atus, motors, etc., and wherever elimination of vibration and shock is required. Retail Price, including Transformer - £2,0.0 SPECIAL FEATURES Plus 8/11d. Purchase Tax. Generous Trade Discounts. Flexible in all directions at an equal deflection. Can be The only Moving Coil Pick -up with high level output. loaded on any side, thus eliminating vibration in Vertical, Will operate average receiver. No Pre -amplifier. No Shielded Horizontal and Longitudinal planes employing best quality Transformer. No Hum Problem. Genuine High Fidelity repro- natural rubber spring elements and complete with snubbing duction flat to 1,200 c.p.s. with bass boost below 250 c.p.s. to device. Special Fittings made to suit customers' require- allow for drop in recording level of 6 db. per octave. Available for home trade and export. Immediate delivery in ments. beautiful plastic finish. Also available as previously advertised, the ALL -METAL This is one of many other electrical appliances. construction comprising an ingenious Damped Spring System. Overseas enquiries are invited. Agency arrangements may be made. Write for illustrated brochure, and send us details of your requirements. BROOKS & BOHM LTD., A. WELLS & CO. LTD. (Dept. W.W.), 90, VICTORIA ST., LONDON, S.W.I. VIC.9550 -1441. STIRLING ROAD, WALTHAMSTOW, LONDON, E.17

'Phone : Larkswood 2691

THE ROMAC MODEL 126 Personal " RECEIVER

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Manufacturers of LOUDSPEAKERS The Romac Personal Receiver is an entirely LAMINATIONS new departure in portable radio. The shoulder strap method of carrying has SCREENS ingeniously been used to provide an " invisible " aerial. This convenient In feature is exclusive to Romac Models. RADIOM ETAL

Price £17 3s. 8d. Plus C3 16s. 4d. Purchase Tax.

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Home and Export Enquiries should be directed to . SILICON ALLOYS ROMAC RADIO CORPN. LTD. ELECTRICAL SOUND & TELEVISION PATENTS THE HYDE HENDON LONDON, N.W.9. LTD. 12, Pembroke Street, London, N.1. Terminus 4355 Tel. No.: COLindale .5401 (Three lines). 2/4, Manor Way, Boreham Wood, Herts Elstree 2138

www.americanradiohistory.com December, 1947 Wireless World Advertisements 43

We send you Greetings and Best Wishes for the New Year. The past months have been difficult for the trade, and we thank you for your patience and understanding. During the coming year we sincerely hope to meet the many demands for our receivers, and look forward to your continued co- operation. iffelfficitael Radio Ltd London Office & Sales: 190 STRAND, W.C.s. Tel: TEMPLE BAR 2085. Grame: RADIETHER, LONDON. McMichael Radio Ltd., Slough, Bucks. Tel: Slough 22311

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SELF -CONTAINED BATTERY OPERATED ELECTRONIC TEST METER 74x,(4(4=4r,9ife, aa,e'azCG nreahvte Efae-td4E4saG The 17 ranges will give true readings of Bias and Screen, Anode and Mains voltages ; D.C. currents to 11/2 Amps, and Resistances to 100 Megohms. Voltage multiplier 0 -5000 v. D.C. and V.H.F. probe for 200 Mc /s also available. PRICE £24-IOs. The versatile valve voltmeter for Experimenter and Serviceman ELECTRONIC INSTRUMENTS LIMITED Telephone: Richmond 49 /7 1 7 PARADISE ROAD-RICHMOND SURREY

www.americanradiohistory.com 44 Advertisernesats Wireless World December, 1917

RAYTHEON CONTRIBUTIONS to development of Hearing Aids

goat E+Ti &tree lot gd^Eewried Caa cKdtead BIG umommairri THE COMPLETE SERVICE FOR SOUND RECORDING AND REPRODUCTION

* Mobile and Static Continuous Recording Outfits. * Recording Amplifiers. * Moving-Coil and Crystal Microphones ** Sapphire Pointed Reproducing Styli and Cutters. * BIanK Recording Discs from Sin. to 17ín. Single or Double sided. * Light- weight moving iron, permanent sapphire and moving coi' pick -ups. A big factor in making the modern Hearing Aid such a neat, * Label and Envelope Service. compact instrument is the great reduction made possible in size of * A comprehensive range of accessories to batteries. In 1939 valves used in the average Hearing Aid drew almost meet every requirement of the sound recording engineer. one -third of a watt from the " A " battery. Today, thanks to Raytheon And our latest development (of special developments in valve and ** design construction., drain on the " A " interest to users of sapphire or delicate battery is 80 per cent less, battery life ten times greater, so that batteries pickups)-The Simtrol. can now be much smaller, with many times the life. Because of this This is a controlled micro -movement and other important developments Raytheon is supplying more than easily fitted for use with any type of 90 per cent of all Hearing Aid valves in use today. pick -up to eliminate the danger of Ask for complete information. Address your inquiry to Sub- damage to the record or pick -up. This is achieved by a vernier lowering action of marine Signal Company (London) Ltd., Artillery House, Artillery the pick -up head to the record. Row, London, S.W.I, England, or to : Write for comprehensive lists or call at South African Distributors: Lynch -Wilde (Africa) (Pty) Ltd., Jo'burg. Recorder House for demonstration.

RAYTHEON RAYTHEON MANUFACTURING COMPANY RECORDER HOUSE, 48/50 GEORGE ST. INTERNATIONAL DIVISION PORTMAN SQUARE, LONDON, W.I. 60 EAST 42nd STREET rie (enir4 Telephone: WEL 2371/2 Telegrams: Simsale, Wesdo. London d/ NEW YORK 17, N.Y., U.S.A.

The ROTH ERMEL "Vibromikerr SPHERE INSTRUMENTS for all Stringed Instruments Introducing the ALL WAVE

_TYPEBGB SIGNAL I GENERATOR A portable Signal Generator for AC. Mains operation. Specially v developed by SPHERE as a high class instrument, for general Laboratory and Workshop use, it Is the ideal instrument for the aligning and testing of radio receivers and amplifiers. This is a specially designed Generator embodying several new and unique features and Improve- ments, which radio engineers will find invaluable. ROTHERMEL 'Vibromike' is a contact microphone All "SPHERE " Test -instruments are entirely British made with highest quality materials and workmanship and carry a SIX Theof the bender type designed for amplification of all Months' guarantee. instruments, and is widely used special stringed for Continuous Frequency Built In ladder attenuator, orchestral effects. The crystal generating element is coverage from 110 Kilocycles with fine control, giving housed in a hermetically sealed case, and is therefore to 56 Megacycles, in six I Volt maximum, In fivesteps, protected against adverse humidity conditions. When bands. In multiples of 10 Microvolts. Exclusive "SPHERE" " Radio and Audio Frequency used with instruments such as violins, guitars, mandolins, . AT A GLANCE" Band Voltages can be switched via etc., the output voltage is from .05 v to .1 y and higher, and Attenuator indicators, single Test -lead. Any amplifier having high impedance input will be found Variable control of 400 satisfactory for use with the Vibromike. C.P.S. audio, from 0 to I Volt. A full range of ROTHERMEL Crystal PRICE [4 10 0 FOR RADIO SERVICE, RADIO ENGINEERING and other products in most leaf complete with 8ft. of AND LABORATORY USE. catalogue form will be sent on receipt flexible shielded cable. of 6d. to cover postage, etc. Plus Purchase Tax. Write for List No. SOS S.G. LTD. SPHERE RADIO LIMITED R. A. ROTHERMEL Telephone : Rothermel House, Canterbury Rd., MAIDA VALE 6066 Radio Instrument Manufacturers lines) London, N.W.6. (3 HEATH LANE, WEST BROMWICH

www.americanradiohistory.com December, 1947 Wireless World A dvertisements 45

The leading radiograms are fitted with Goodmans 12" loudspeakers.

Type No. 72/1205/15

f?F EXCELLENCE GOODMANS INDUSTRIES LTD. LANCELOT ROAD, WEMBLEY, MIDDX.

TWO OUTSTANDING MODELS ,...,..,. , FROM THE

is 15 Watt Quality Amplifier Special Amplifier RANGE OF The Rad. 20 model illustrated ideal for Schools, designed primarily for the high quality repro- Clubs, Hotels, etc., where high quality reception duction of Gramophone records. Incorporating a of the normal broadcasting programmes is re- built -in variable scratch filter, bass and treble lift quired. A Three wave band superhet radio unit of controls and negative feed back. A maximum out- QUALITY the very latest design is incorporated, and put of 15 Watts is obtained, but low average is also made microphone and deterioration provision for listening levels may be run without gramophone inputs. Available for 200.250v. in quality. The valve line up is ECC 32 Twin :-2 A.C. mains. Triodes, 2 EF 50 Pentodes, 2 EL 37 Pentodes, I 5U4G Rectifier. AMPLIFIERS Retail Price £44.15.0 Price £29.15.0 WODEN TRANSFORMER CO. LTD., MOXLEY ROAD, BILSTON, STAFFS. Phone : Bilston 41959

www.americanradiohistory.com 46 Advertisements Wireless World December, 1947 or w

MENT... but NOT

The newest addition to the 'Advance °range of "Laboratory'' Signal Generators places an instrument of labors- wry class within the financial scope of every radio Price ( +ervice engineer and experimenter. The discerning engineer will appreciate its accuracy and stability, its exceptionally wide range which covers all frequencies required for radio and television receivers, and its accurate attenuating system which anables sensitivity measurements to be made on highly sensitive receivers up to 60 Mc /s. Send for fully descriptive pamphlet.

Range : 100 Kc /s-60 Mc /s *.rt. on fundamentals (up to 120 Mc /s on Second Harmonic). Accuracy: AOVAnce Guaranteed within -L 1 %. Attenuation: Constant impedance system embodying a matched 75 ohms transmission THE GRAMPIAN 461 RECEIVER AMPLIFIER line. This new high -grade reproducer has been specially designed for use in Small Stray Field : Less than 3 Factories, Hotels, Clubs, Swimming Pools, Municipal Buildings, etc., where microvolts at 60 megacycles. Illuminated Dial: it is desired to broadcast Radio or Gramophone Records and provide amplification of speech by use of a microphone. Let us send you further details. Total scale length 30'. Power Supply : A dual wave -band superheterodyne with Power Amplifier having an 110 -210 -230 -250 volts. output of 15 watts. Provision is made for both pick -up and micro- Dimensions : phone inputs with separate volume controls and high and low 13 "x 10i'x 71" deep. impedance outputs. It is of extremely robust construction in an Weight : 15 lbs. attractively finished onetal case. Price List L42 0 0 Plus L2 2 0 Purchase Tax A.C. Mains ONLY HAVE YOU HAD DETAILS OF OUR wigt) f LOUDSPEAKERS NEW LINES ADVANCE COMPONENTS, LTD., Back Road, Shernhall Street, GRAMPIAN REPRODUCERS LTD. Hampton Road, Hanworth, Middlesex. Phone : Felthom 2657 Walthamstow, London, E.I7. Telephone : LARkswood 4366,7 Scientific G.6A.

in WIRING IS EASIER A Specialists QUICKER WITH ,A SPECIAL' Waxes

Most applications of wax in the manufacture of electrical components demand special characteristics which can be met from the regular range of

To the amateur assembler, the OKERIN WAXES " ham," the serviceman and the Et COMPOUNDS manufactLrer, the Special Radio " PYROBIT " Electric Soldering or designed to specification. Grades are Iron is the first essential tool. available for arctic or tropical service - Light weight, perfect balance and stable, moisture - proof fungi - resisting. - handy shape double the pleasure For expert advice, samples, etc., please and speed of wiring. Telephone TEMple Bar 5927

See one at your Radio, Electric or ASTOR BOISSELIER Hardware Shop or write for full details. & LAWRENCE LTD P.4

(Sales Dept.) THE ACRU ELECTRIC Norfolk House, Norfolk St., Strand, London, W.C.2 TOOL MFG.CO. LTD. 123 HYDE ROAD, MANCHESTER 12.Tel:ARD.4284

www.americanradiohistory.com December, x947 Wireless World Adverttsemënts 47

\\ ;\:,... \

TRANSFORMERS,

COILS AND

CHOKES

R.M. ELECTRIC LTD., TEAM VALLEY, GATESHEAD II, ENGLAND

UMETA` REGD.. MAGNETIC SCREENS The high permeability of MUMETAL makes it the outstanding material for the production of all types of magnetic screens. We are in a position to fabricate boxes and shields of practically any shape or size for the screening of delicate instruments and equipment from both um- directional and alternating magnetic fluxes. A complete range of standard MUMETAL shields is available, examples of which are illustrated. Our technical experts will be pleased to assist in the solution of all screening problems. Your enquiries are invited. TELco

THE TELEGRAPH CONSTRUCTION & MAINTENANCE CO. LTD. Founded 1864 TE LC ON E.C.2. LONdon Wan 141 Head Office : 22 OLD BROAD ST., LONDON, Tel: METALS Enquiriesto: TELCON WORKS, GREENWICH, S.E.I0. Tel: GREenwich 1040

www.americanradiohistory.com 48 Advertisements Wireless World December, 1947

For reception or transmission. Load factor UNIVERSAL IMPEDANCE BRIDGE 500 watts at 100 m : /s. Aerial spans and MODEL UB 202 down lead consist of twin parallel feeder of 300 ohm impedance, polythene insulated. This is a self contained universal bridge which measures resistance at DC, Capacity and Inductance at 1000 Cycles. The necessary Pack includes all the necessary insulators, bridge voltage and null detectors are incorporated in the instru- fittings, etc., for easy erection. ment. Measurements in condensers can be carried out with applied polarising voltage and inductances can be measured with superimposed DC. Model FDA20 - E3 2 6 FDA40 - E3 12 6 Resistance Range .01 ohm to I megohm Capacity Range 10 p.s. to 1000 m.S.d.s. Inductance Range 10 µH, to 1000 Henries ANTIFERENCE For particulars of this and our full range LIMITED of measuring instruments write to :- BRITISH PHYSICAL LABORATORIES Sales Division : HOUSEBOAT WORKS, RADLETT, HERTS 61, Bryanston St., Marble Arch, London, W.1 Telephone : PADdington 7253/4/5 Telephone : Radlett 5674 -5 -6

Have you heard THE CONCERTO ? .tothicid FOR YOUR PICK -UP AND SPEAKER Qualify & This Is the Finest Record Producer available because - I Distortion is only 14% at 6 4. Separate Bass and Treble TRANSFORMERS- watts, 2% at 12 watts. Controls with aDaub.'e bass MAINS (Independently Certified Figures) Boost Circuit. A. F. TRANSFORMERS 2. Hum Level is negligible. 5. 12 months unconditional 3. It will take any type of pick- guarantee. THERMAL DELAY up- moving coil-moving 6. 9 Valve Circuit-8 Triodes CIHOKES, iron -crystal. plus Rectifier. HING PRICE ,27,10/0 The "Concerto"-the Amplifier that is making itself heard POWER RESISTANCES_.__-: CHARLES AMPLIFIERS LTD., 1E, Palace Gate, GlLde

Kensington, London, W.8. (Phone : WEStern 3350) 70.phe,,: WOOtw /CN /422 -/426 CAMBRIDGE ROW WOOLWICH SE18

Subject to the provisions of the Control of Engagement Order, 1947. R.A.F. MORSE OSCILLATORS A VACANCY occurs (Valve Buzzers Type 2). A 2 valve battery C Iell for the appointment of a Telecommunications Valves) Engineer in the States of Jersey Harbours and Airport Committee's operated Morse oscillator, ready for instant Telecommunications Department. Ga1rr. and use without adaptation. Packing 2/6 Candidates must be of British parentage and be between the ages of 35 and 45 years, with administrative experience, possess a professional Incorporates note selector control, volume control, phone, key and ` qualification in electrical or radio engineering or have equivalent interference jacks. ize 9" X 8" x 8f ". Power supply required, HT 60v., experience,, being accustomed to staff control and station organisation. GB 4)v., LT 2v. (Provision for internal fitting). Price complete with 2 Preference will be given to candidates having experience of the latest valves (PMILF and PM2A) 27/. (carriage and packing 2/6). technical developments in connection with civil aviation ground station Government surplus who stock, brand new condition. Complete kit equipment and have a knowledge of telephone systems and line consisting of oscillator, valves, heavy -duty Morse work. A good knowledge of aeronautical, key and pair of marine and line operational S. G. Brown phones for plus carriage and packing. work is essential, an operational qualification being an advantage. 32/. Wooden transit cases 2/6 extra. The commencing salary will be £460 per annum, rising by annual increments of £20 to the maximum of Watch next month's announcement of the release of the L560. Burgoyne Seven Second Solder Gun. Applications in writing, giving full details of experience, should be addressed to the Superintending Engineer, Telecommunications MAIL ORDER PP LY CO. Department, States Airport, Jersey, C.I. 24 New Road, LonSUdon, E.I. Stepney Green 2760 -3506,

www.americanradiohistory.com December, 1947 WIRELESS WORLD CLASSIFIED :\DVERTISEMENTS 49 Bate 6/- for 2 lines or less and 3/- for every additional C.A AR.88 lf, in perfect condition; line or part thereof, average lines 5-6 words. Box offers over £40. Numbers, 2 plus Day : -Box 3902. [8671 word. 1 / -. Press deanery 1948 R1155, issue, that post Thursday. December 4th. No responsibility 6V6 output, mains power pack, £14' accepted for errors. moved district without mains.-Tunstall Rectory, Sittingbourne. [8741 -WATT amplifier, Callaro turntable and WARNING 15 pickup, 12in Goodman's speaker to tfeaders are warned that Government surplus cabinet; £25 lot. -Box 212 components which may be offered for sale ' 7ALKTF- TALKIE, 2 complete transmitter- through our columns carry no manufacturer's W[7747YY11 receivers, as new; £5 ea, or nearest offer. guarantee. Many of these components will have 14 Commercial Rd., Totton, Southampton. been designed for special purposes making them BOILED only. -£44 Grampian radio unsuitable SHOP-ampi. model 461, £29/10; £23/10 Vortex. for civilian use, or may hare de- ion 15watt ampl., teriorated as a result of the conditions £16 /10.- Wilson, Alnwick. under 'DECEIVER, type BC348 -Q, as new, which they have been stored. We 200 kc /s cannot to 18 me /s, 2 R.F., 2 I.F. Xtal gate, undertake to deal with any complaints regarding 100 i dial; best offer over £30. -Box 4012. any such components purchased. MID West console, 18 valves, 5 wavebands, walnut case, £80; Howard Send receiver. NEW RECEIVERS AND AMPLIFIERS 6 valves, 4 wavebands, metal case -WAY amplifiers with instruc- TWO for inter-comm. or tion manual, £25. -Box 4010. [8725 baby alarm, with speaker in attractive COMMUNICATION receivers, 8 -valve R.109, cabinet; £12/12. as new in original packing case, complete WHITE, 95, Friern Rd., London, with circuit and working instructions £6, DE.S.E.22. plus cgs. t8762 5/- and pkg. -Box 4013. ' [8734 WAVE -BAND radios, illuminated dial, IRELESS WORLD " 2 -R.F. quality 2 choice of sprayed cabinets, £9; e.a.e. WVV tuner for use with " Wireless World please. -Box 3909. [8707 quality amplifier, new, £5/10 less valves, which WAKE the easy way with the Reveille are easily obtainable-Box 3538. [8589 clock -radio £12/12 retail; send for leaf- FOR sale, Hammarlund super preoomm. re- let.- Thames Valley Products, 28, Camden ceiver, recently overhauled completely by Ave., Feltham, Middx. [8786 Webbs, pereect cond.; best offer over £40.- AMPLIFIERS; new 1947 model Hi -Fi units, Villiers, 45, Abbey Rd., Sompting, Sussex. with triple tone controls, built to custo- SOUND SALES console radio, 3 wavebands, mer's specification. - Broadcast & Acoustic variable selectivity, phase inverter speaker, Equipment Co., Ltd., Broadcast House, Tomb. slightly shop soiled; reduced to £50.- Wallace land, Norwich 26970. [6433 Heaton, Ltd., 127, New Bond St., London, W.I. POCKET size, all -dry 5/w receivers, llikx Known the world over as el-VALVEVALVE " Wireless World" quality am- 91/4x11/zin, brand new c /w, 4 / spare makers of the finest trans- plifier, with tone control, 15 watt tetrode valves, 'phone and aerial. by Crosley's, output, by Bakers Seihurst Radio; used only U.S.A., weight approx. 71b, price £7 each. - formers, we export even to few hours. -.tones, Motor House, Falcon Av., Carbot, Ltd , 201, Long Lane London, S.E.1. Edinburgh, [8406 OSMOR A.C.-D.C. 3 -wave 5v superhet re America and to New York 1AC.A. console receiver, 12 valves, p.p. ceivers, excellent reproduction and sen- , output, 12ín speaker, motor tuning, sitivity, attractive cabinet, early delivery, component firms at that band -spread, cabinet 35inx37in, shipping waveband if required; write for nice condi- - tion; £75; going abroad; other household literature; trade enquiries invited.-Morgan, convincing proof of the quality items.- Please write, Osborne & Co., Ltd., Southview Rd., Warling - BM /GFX, London, W.I. B0342 and BC312 communications receivers, ham, Surrey. [7286 of British products and of complete -New 7 -valve " Wireless World " and in proper working order, BAKER'S. PARTRIDGE transformers in £18, or for 230v A.C., £19/10 plus carriage Quality amplifier with tone control stage, and deposit on packing; 8 watts push-pull triode output, price includes send for details. - super Quality triple cone, 12in permanent particular. Barton, 41, Bedminster Down Rd., Bristol, 3. magnet speaker, with large output transformer QUALITY I I i Push-pull amplifier, PX4'a, 6 and all valves; also as above but with 15 watts output. 2 h.f. tuning unit bass watts tetrodo output, ideal for realistic repro- boost 10 DB. on P.U.; 2 large oak Howe duction or public address; 2,4d stamp for box battles with Baker speakers; nearest to partite., prices, etc. -Baker's Selhurat. Radio, £40. -J. Richardson, 70, Norbury Hill, 75. Sussex Rd., S. Croydon. Croydon 42ka,. OUR EXPORT DEPARTMENT S.W.16. Pollards 2578. [8772 " THE finest amplifier I have yet rieura; 0. 5 -valve 8 -watt push pull amplifiers, 1 better than many at twice the price." - negative feedback, complete with large This is a states is at the service of all OVER- multi -ratio output transformer £9; ditto 10- what satisfied customer about watt 6V6, our amplifier, built to ' W.W." IMay issue) £10; a range of feeder units design; quality [tarts only used, producing SEAS BUYERS and we welcome T.R.F. and superhet from £5 /5. -R.T., 64. St. Leonard's Rd., London 8.W.14. [8253 superb results; price E25/10; kits of parts can enquiries. -STAGE also be supplied; pm-amplifier, elec. motor and your THREE resistance capacity minia- pick -up and 12ín speaker extra. -Enquiries to ture amplifiers with three tested 1T4 Radio Trades Manufacturing Co., Laurel midget valves, 20/- each, post free; in alu- House, 141, Little Ealing Lane, W.5. Eal. minium case, 22/ -; spare 1T4 valves, guaran- 6962. [8331 teed 6/- each; holders, 6d each.- Littler 24, GOODSELL, Ltd., 40, Gardner St., Stanley Rd., Whalley Range, Manchester. Brighton, 1. -For highest quality repro- For Home Buyers our Con- DE luxe RCA portablè amplifier 50 watts, duction use the Williamson amplifier as per for 2 controlled microphones, high and specification, £20/10; best quality compo- sulting and Supply services are low impedance, Monitor phones, £50, 20 nents, including transformers and chokes, oil watt amplifier for superb gramophone repro- reservoir and smoothing condensers, per -amp available as usual and we would duction, £20. 2 electric turntables with for same, fitted E.F.37 valves in 4 position pick -ups, £5 each. Can be seen between I base and treble control circuit, £2/10; special remind you that PARTRIDGE p.m.-2 p.m. or after 6 p.m. -Tel. Kensington pre-amp for moving-coil pick -up using E.F.37 0808 or write 21, Sloane Avenue, S.W.3 for first stage and E.F.37 in tone control as Precision Built TRANS- CRYSTAL radio receiver, complete with above, £414. [8791 headphones and aerial and earth wires FORMERS wound to suit your E1 /1; extra 'phones, SPECIAL offer : Midget communication re- 4/11 pair; the set will ceiver and power pack (M.C.R.L), 5- individual requirements are comfortably work up to four pairs; self -ener- valve superhet, complete with aerial and gising telephones, no batteries required, sold earth equipment, lightweight headphones; still available. separately at 2/6 each; four are needed for range 20-3,000 metres in four bands. operates 2 -way communication; twin wire, 3d yard; 60 on any voltage between 97 and 250 A.C. or microamp meters, two mounted in one case. D.C.; £9(10; send for one now before stocks 10 / - aerial dummy loads, 43 ohms 100 watts, are exhausted; large stocks held of C.R.T. standard 4 -pin base, 2/- each; 0 -3 amp thermo Units, metres, switches, fuse holders, etc.; ampmeters basic movement 3.5 ma, 7/6 each; low prices; send for 6 -page list; trade sup- 0 -6 amp thermo ampmeters, basic movement plied.-L. Wilkinson. Wholesalers, 204, Lower Catalogue will be sent on request, 3.9 milliamps, 10 /- each; 0- 110 -230v trans- kddiscombe Rd., Croydon. Add. 2027. (8624 formers, 4 -0 -4v at 6 amps output, 10/6; neon RECEIVERS, AMPLIFIERS - SECOND-HAND detailing components available aerial current indicators, 3/6. -Park Radio "L'DDYBTONE 504, complete speaker, as from stock. of Manor Park, 676 -8, Romford Rd.., Eli. 1À new; £52. -Box 4040. [8775 MORSE EQUIPMENT perfect condition, 550 kc /a to MORSE practice equipment for classroom or AR.77E,30 me /s; £25. -Box 3743. [8637 individual tuition; keys, audio oscillators ALKIE- TALKIE TX /RX, new, c/w all for both butt. or main operation. -Webb's Radio, 14, W extras; 12gns. -Box 3746. [8647 Telephone.- Abbey 2244 Soho St., W.I. Ger. 2089. [2291 V ac /do midget superhet, m & s wave, as TEST EQUIPMENT `O new; £12.-BM/CXRJ. London, W.C.1. 4 MPLIF11R, A.C., G.E.O. gram /mike, 15 INSTRUMENTS watts: good condition, £10. -Box 4009. MOST makes in stock, some on .terms. -Write Skychfef, '37; 18-5, 5 -1.5, 1.5- for details and list of radio and electrical mc, 240v, Parker, 5, Wentworth PAR °.IDGE 1CRAFTER10.5 £14.- spares, new and ex-Govt., to The Instrument Hill, Wembley. [8731 Co., 244, Harrow Rd., London, W.2. HR.O. receiver, fitted S. meter, crystal, etc., TRANSFORXIERS LTD AVO ao oscillator, all-wave, as new; E10.- including 7. coils, spare valves, phones 16, Thurlow Gdns., Wembley. and power new condition, [8733 unit; £53.8B5x 76 -8, PETTY FRANCE, LONDON, S.W.I (WING death owner, radio test equipment; £12. -67, Mill Rd., Leighton Buzzard.

www.americanradiohistory.com 5o Advertisements Wireless World December, 1947 TAYLOR model 65b sig. gen., new; list price.- BM /CRJR London, W.C.1. [8804 WESTON analyser, E772, perfect condition; £16 /10.- Poole, Kenneth House, Dogpole, RELIANCE yhrewsbury. [8720 TAYLOR model 30 C.R.O., as new; offers POTENTI OM ETERS over £20.- Haworth, 98, Swinley Lane, %Vigan, Lance. [8636 FURZEHILL Laboratories oscilloscope, type 1936 as new, £33 or offers; owner going abroad.-Box 4038. [8770 AVO model 7 meter, as new, £16/10; Avo valve tester, overhauled by makers, £12. -R. K. Wilson, Alnwick. [8730 COSSOR 339A oscillograph and Rola G12, 2,500 ohms. -Offers to Rushton, 8, Broad Walk, Wilmslow, Cheshire. [8656 TAYLOR 65 oscillator, 100 service charts, valves, etc.; lot £20.- Driscoll, 13, Land Lane, Marston Green, Birmingham. [8753 wESTON E772 20,000 OPV analyser, £6/15 spent on overhaul by makers in October, with circuit selector and English valve adap- Types T.W. and S.G. -Box 3907. [8704 T.W. Wire -wound track tors(;offers.CdMBINED signal tracer and V.V. meter in - kit form, £10 /10; lists of range of test Rating : 5 watts (linear) Max. instruments available. -L. A. MacLachlan & 3 watts (graded) do. Co., 16, Thistle St., Stirling. [8578 21N thermocouple moving coil milliammeters, Ranges : IO 0- 100,000 SI (linear) 100 0- 50,000 S2 (graded) 0- 350m /a, new ex -Gov.; a bargain at 5/6 each, £3 per doz.. post free. -J. McMillan. 100 0- 10,000 0 Non- induc- 5. Oakfield Road, Bristol, 8. [8767 tive RADIO SERVICE, of Birmingham, can RJsupply from stock all Aso instruments, S.G. Composition track - list also Sphere and BPL signal generators; Rating : I watt maximum. prices. -R -J Radio Service, 264a, Rocky Lane, Birmingham, 22B. [8728 Range : 2,000 ohms. to 2 megohm:. valve tester with latest type roller PERMANENT NEEDLE Avocontact selector panel for 1.4 -volt valves Characteristics : (either type) £16; B.P.L. all -wave mains oscillator with Linear, log., semi-log, inverse log., non- variable L.F. output in makers wrappings, £20 inductive, etc. or best offer. -Box 3744. [8643 voltmeters, moving coil, DOUBLE reading for full details to 0/15, 0/250, 21kin dial, standard pocket Write type; trade and wholesale only.-Harris & ERWIN SCHARF Russell, Ltd., 80, Tottenham Court Rd., Lon- don, W.1 (Museum 6061). [8724 RELIANCE NOW ready! -New Nuplans multimeter, to 49 -51a, DE BEAUVOIR RD., measure AC /DC, V, mAs and snips., re- Manufacturing Co. (Southwark) L'd. sistance 0.1 meg., capacitance 1,000v, for 0 -1 Sutherland Road, Higham Hill, N.1. mA, 100 ohms M/C meters. -Full plans, ? /6.- LONDON, Bradley, Whinnie Knowe, Sennen, Cornwall. Walthamstow, E.I7 rel.: Clissold 7713 -0941. Cables: Echovox, London. DYNATRON audio oscillator, improved Telephone : Larkswood 3245 ecroggie design, auto. oso. control, 45- 18,000 cycles in 11 calibrated steps, metered output 0 -2.5v, 0 -25v, unused, £16. Baldwin "Muter " capacity tester 5eunf to 4nF, £4 -Gerry, 36, Bank Street, Newquay. [8784 MICRO amperes. -Model 505. D.C., Turner GOVT. SURPLUS. UNUSED Electrical Instruments, F.S.D. 100-0-100, EX -GOVT. EQUIPMENT OFFERS moving coil, zero set screw, dead beat, 2'43in LOUD HAILER MICROPHONE, made dial, 3i /4in diameter, moulded bakelite case, by " Ardente." Has On -Off switch, and is Govt. surplus, new, in original cartons, 1st complete with 50ft. cable. Ideal for remote grade; 30/ -.- Below. control use. Only 24/6 (carriage, etc., 2/ -). CONDENSERS AMMETERS. -Range 0 -100, moving coil with EX- R.A,F. TX /RX UNITS. Operate leads and shunt, by Victoria Instrument Co.. between 155 -185 me /s. Complete with . . . 31/2in flush fitting, bakelite case. zero set screw, of all lypes dead beat, Govt. surplus, new, in original car- following valves : 2 type RK34, I type EF50, tons, 1st grade; 251 -.- Below. 4 type SP4I, 3 type DI, and 20 watts rotary VOLT meters.-Range 0120, moving coil, by transformer. Only 39/6 (carriage, etc., 5/ -). We can offer, FOR IMMEDIATE Victoria Instrument Co., 31/2in flush fitting EX-R.A.F. AMPLIFIERS. Contains valves very bakelite case, zero set screw, dead beat, Govt. types QP2I and 210 LP, Ideal for adding DELIVERY from generous surplus, new, in original cartons, 1st grade; amplifier stage to take gramo. pick -up, etc. stocks, a wide range of ultra -high 22/6.-Below. BRAND NEW. Only 25;- (carriage l'EDDINGTON ENGINEERING Co., High St. etc., 216). quality fixed paper Condensers, Teddington, Middx. Kin. 1193-4. [8583 EX - R.A.F. MODULATOR UNITS, CLYDESDALE for bargains in ex- Services from .001µF to 8µF. Also STOCKS TYPE 2. Range 2400 -6250 kc /s.. Complete electronic equipment. Unused Wheatstone with 210 LF valve and 0 -500 microamp D.C. Conden- Bridge WA10771, 20-0 -20 galvanometer range of small, genuine MICA 0 -210 can be extended, our price only 50/ -, moving coil meter calibrated for percentage modulation. BRAND NEW. Onls sers from .00001 (10 pf) to .01µF cart. paid; unused AN /APA1 C.R. indicator 65;- and repeater amplifier unit 3BP1 C.R.T., in ad- (carriage, etc., 3/6). (I0,000pf). Prices are exceedingly justable case, amplifier with 11 valves, etc., WAVEMETERS, CLASS D. No. 1 MK. II our price only 97/6, case. paid; set of plugs Frequency ranges 1.9 -8 me /s. with check moderate. for AN /APA1 at 7/6; as new, A1134, 2 valve, frequencies up to 25 me /s. Incorporates 2 stage, pre -amp or intercom unit, our price are invited for manufac- dual crystal 100/1000 kc ¡s, and is accurate to Enquiries only 15 carr. paid. within 2 kc's. Complete with valves and CLYDESDALE SUPPLY Co., Ltd., 2, Bridge turers requirements, wholesale vibrators, crystal, intstruction book, etc., in St.. Glasgow, C.5. [8710 teak carrying case. BRAND NEW. Only and export only for bulk W AVEMETERS.Special-- offer of ex -Govt wavemeters, suitable for general nee, all £6 /IS 1-, or a few only available without spares quantities, and for scheduled de- in working order and calibrated. Type 061 at 85/- (carriage, etc., 3/6). contains temperature controlled 1 me /s crys- T1154 TRANSMITTER KITS. The com- liveries over a period, as required. tal, and covers 1 to 25 me /s with very high plete Master Oscillator Tuning Unit and the precision, £20 each; Type 10T/67 contains Output Unit for P.A. for the famous TI154 Condensers of close or very close 100 Ws and ' mots crystals, with switched Transmitter. Add the valve assembly and tolerance can be supplied within tuned circuits directly calibrated 30/86 mole, build your own TX covering 10-5.5 me /s, £4 /10 each; Type 10T /69 contains 100 ko /s 5.5 -3 me /s, and 500 -200 kc's. Circuit details about one week. and 1 mo /s crystals with 2 sets switched tuned BRAND NEW IN MAKERS' circuits directly calibrated 25/130 me /e, main supplied. Type G57, 100 kc to CARTONS. Only 49/- (carriage, etc., 6/6). operated, £8/10 each; /s C.W.O. please. S.A.E. brings current lists Please request our 4 page bulletin CONSEVEN 011147 24 mo /e, £5 each; s.a.e. for details.-BM/ RICBF, London, W.C.1. [8716 NEW LOUDSPEAKERS THE RADIO CORNER CLAUDE LYONS LTD. A MPLIFIERS, speakers at wholesale prices; 138 GRAY'S INN RD., LONDON,W.C.1 Li example: 5watt, push -pull, £8; lOwatt (Terminus 7937) 180, Tottenham Court Rd., London, W.1 quality, £14; 15watt R.8. portable with twin speakers and microphone, £26; record -playing (2 mins. from High Holborn, 5 mins. from and 76, Oldhall St., Liverpool 3, Lancs. units of every description; Goodmans 12in King's X) speakers, £5119; Rola 8fn, 21/ -; s.a.e. list. - Open until I p.m. Saturdays. Radio Unlimited, 16, Carnarvon Rd., Leyton.

www.americanradiohistory.com December, 1949 Wireless World Advertisements 51 HIGH quality, precision -built speakers, ELECTRIC repeater motors, new, ideal ex- Ticonal magnets, detachable dia- perimenters ,adaptable for A.O. /D.C. 6/50 phragms, die -cast chassis, twin cone.-Broad- ELECTRADIX BARGAINS volt or remote control, Government surplus, cast & Acoustic Equipment Co., Ltd.. Broad- 5/- each, post 8d; quotation for quantities. - cast House Tombland. Norwich 26970. [6435 MOTORS. D.C. 2.30 volt, 1/12 h.p., 1,500/2,000 F. R. Lucas, 22, Hengrove Rd., Bristol, 4. AMAGNAVOX 66, 2,000 ohm field, 'Voigt r.p.m., shunt wound, by Croydon, 25/- ; a few BATTERY chargers for home and export, 1VI H.C. horn, Hartley Turner 750 ohms needing minor repairs, 12/6 each, postage 2/6 4 models, 2- 6 -12v, 1, 2 or 4amp dc, any field, infinite baffle corner deflector with 12in extra. mains. voltage; generous trade terms; write 25w p.m. unit; latest types 12in R.K., Celes- for catalogue.-Tel. Hoddesdon 2659. The tion, Wharfedale WIOCS.-Burley, Balaclava MOTOR BLOWERS. Keith Blackman, 24 volts Banner Electric Co., Ltd., Hoddesdon, Herts. Rd., Derby. [8742 D.C., 5" inlet and outlet, a robust machine, O. ALL types of rotary converters, electric S /18 /6.-New Baker Super Quality 12in motors, battery chargers, petrol -electric cv Auditorium permanent magnet speaker. METERS D.C. generator sets, etc., rotary transformers, input Moving coil Weston Meters. 12v dc, output 600v 250ma; price with triple cone, manufactured by Bakers tin. dia. flush fitting, full scale 500 micro amps. at £4/10 Selhurst Radio, the pioneer manufacturers of each nett, post paid; J.A.P. No. 2A engines, moving coil speakers since 1925, wide fre- Scaled for 15 volts and 600 volts will measure 1.2 b.h.p. at 2,600 r.p.m., complete and ready quency range, even response, ideal for quality 15 v. but need external rises for high voltages, for use, £17 nett, ex works. -Ward Lordscroft reproduction, fitted with magnet, having ex- 20/-, Works, Haverhill, Suffolk. Haverhill 253/4. ceptionally high flux density in the air gap, VALVES suitable for public address equipment when CIRCUIT BREAKERS. N.C.S., 71 amps. LARGESTAthe and most comprehensive range in quality consideration; A.C. enclosed type, 21/ -. Ellison make mounted country, British and U.S.A. types at end1d tamp for leaflegivtrsg ails on sub -base, D.P.O/L 200/230 v. A.C. single phase, Board of Trade prices; send for lists (valves above and constructional details of a new 200 amps. 15ín. x 13ín. x I2in., weight approx. free, s.a.e.; valves sent c.o.d.; re- acoustic chamber designed to extend loud 50 lbs., ditto 300 amps. 171in. tailers not supplied. x I4in. x 15ín., RANSOM, Bond speaker frequency range. weight approx. 89 lbs., 220 volts, 1,000 St., Brighton. [7223 amps., PHOTO electric cells, first grade, £8/19/6. -New Baker super power cinema per- S.P. 50 cy. D.P. with no volt hold -on coil, loose G.E.C., manent magnet speaker with 18in triple cone handle, C.M.G.8, 4 -pin, top cap, 35/- each; A.M. - of new design, giving wide frequency response switchboard mounting oil switches by surplus, new condition, each tested in sound free from objctionable resonances; speech is Ferguson & Palin. All offered at very low prices head circuit for full sensitivity. -Bryce Elec- clear and natural and music is reproduced to clear. trical Co., 246, Stockport Rd., Manchester, 19. with exceptional realism; fine engineering job, GRAMOPHONE AND SOUND EQUIPMENT extremely sensitive; ideal for public address SWITCHES. SIMON SOUND SERVICE can supply your equipment when power handling capacity, plus Dewar key panel needs. [8712 realistic reproduction, is required; prompt type, 8 -pole C.O. P1155.-Customers assure us that our delivery per pass. train. -Bakers Selhurst Radio. flush fitting, 5/ -. fully modified version is the. best all - 75, Sussex Rd., S. Croydon. (Croydon 4226.) Yaxley 3 -pole round set available to -day. LOUDSPEAKERS. SECOND-HAND 3 -way, 3/6 ; 8-pole, COMMUNICATION results with local station WESTERN Electric 555w 200v 8e1ä, per- quality; 10 valves, 16-4,000 metres, d.f. re- I-way, 3/6. D.P.C.O. toggle 250 v. 1 amp., switch moved, new -pull fect; £10.-Clissold 5255. [8678 flush panel, front panel PX4 push quality Goodman T/12 loudspeakers, unused; 3/3 ; 8 -way Lucas sWitchbox, 3/6 ; amplifier, bass and treble boost (separate con- TWO£5/10 each. -BCM /Tech, London, W.C.1. 6 -way, 3/ -. trols), gram input, other refinements, com- VOIGT unit, horn, power pack; £20, working. plete with speaker; £35. -Altham, Little Shelford, Cambridge. TRANSFORMERS. B.T.H. 200/230/250 v. WRITE for full details, or call for demon- A.E.C. twin -cone IIi /Fi 12ín loudspkr, as 50 cy. input, 2 volts 20 amps. and 75 v. 6 amp. stration. new; £7.- Meldon, Highfield, Sidmouth. with IS taps output, 9" x 6 ", weight 60 lbs., 70/-, R1155 circuit and values, 1/6 post free. VOIGT H.C. corner horn with bass cham- carriage paid by England and Wales. Auto - WE can offer to modify your R1155 in the ber; £12, no offers. -Duffy, 93, Rutland transformers, 230 volts/I 10 volts, 85 watts, 25/- same way, or to your special requirements; re- alignment, Gardens, Harringay, N.4. [8695 150 watts, 35/- ; 300 watts, 65/- ; I kW., E7 ICs. calibration and repairs WHARFEDALE W10 /CS, £4; Voigt H.C. to all communication and quality receivers; corner horn and base chamber, offers. first-class work with first-class instruments by - MOTORS. Electradix Micro experts. -R.T.S., Ltd., 113, Hazel Rd., Huyton, Lanes. [8754 Motors for Instrument work 8, Gladstone Rd., Wim- 12 -inch triple Done speaker, 15 bledon, ß.W.19. Liberty 3303. [8795 BAKERohms, complete with infinite baffle cabinet and models tin. x 11in., weight PRAMERO 30 -watt cinema amplifier; in the white, new, £6110. -Box 3539. [8590 only 10 ozs., I2/24 volts ; Vitavox Bi. tone; both items brand new; EXCHANGE Goodman's Axiom 12 twin cone work from dry cells or A.C. offers for both. -Box 4041. [5776 H1 /Fl, new, for Hartley Tamer 215; Mains through transformer, laminated fields, ball TRANSFORMERS, tone control and filter cash adjustment.- Furness. Braeknowe, Pit- bearings, totally enclosed, small vee pulley, chokes for all ' W.W." circuits, -R. 'ochry, Perthshire. [8773 centrifugal relay speed governor on shaft remov- Clark, 30, Langland Crescent, Stanmore, highest efficy. quality American able for Middx. Wor 5321 [7532 second shaft drive. Precision made UNLIMITED, TWOspeakers, both perfect, Jensen M -10 ex -W.D. stock. Worth 45/ -. Price 21;- each. RADIO, 16, Carnarvon Rd., auditorium 12ín Bohm 15-25w in bass-reflex Limited stocks. Leyton.- Radiograms players, amplifiers, cabinet, pressure type unit l6ohm 5w a/ain speakers, micrograms, cabinets, accessories; mouth, sound P.P. 60w pri., everything for radio and gram; s.a.e. list. sales trans., TELEPHONES. Wall type constructors' parts, MICROPHONES.- 6,000 and 3,000 A -A, esc., 2- 4 -8 -16- 250 -500, ex- G.P.O., Quantity of S.T. & C. type comprising cabinet 8in. x 6in. x 3in., 402I0 for sale, very good condition; im- feedback C.T. coil, as new unused. Tel. bracket mike, transformer and mag. Finch. 2315. -W., 76, Holders Hill Rd., N.W.4. condenser, mediate despatdh; price £6/10 each.-Douglas DYNAMOS, MOTORS, ETC. bell, switchhook and contacts, hand mag., ringer Price, Cottage, Claybrooke Grange, Rugby. C. /A.O. conversion. Special offer of un- P.O. type receiver terminals and connection RECORD player Birum -Invar sync. motor used single phase marine type motor diagram, 35/- per pair. G.P.O. Candlestick with Marconiphone pick -up, Autostop, alternators, input 220v D.C., output 230v A.C., Telephone with receiver and cord, I5 / -, postage 110-250v, in solid walnut case.-£10 or better 50 c /s, 3.5 amp, £20 each; 220v D.C. to 230v 1/6. Spare mike inserts, 2/6 each. offer : Sleator, The Craige, Sennen, Cornwall. A.C., 50 c /s, 0.87 amps, £9/10 each; 110v iii. fidelity recorder D.C. to 30v A.C. 50 c /s, 0.87 amps, £8 BUTTON MICRO- TRANSPORTABLE,and playback; 13 -valve triple purpose am- each; carriage extra; s.a.e. for details -BM/ PHONES provide inter- plifier; R.C.A. dynamic and ribbon micro- RXBF London, W.C.1. [8715 esting experiments for phones; sound investment; £125 or near offer. SANGAMO synchronous motors, self starting, G3BNL, 53, Old Steine, Brighton. [8782 making outside listeners, RADIOGRAM comprising 200 -250v A.C. 50 cy., consumption 21/, sound transmission, etc. W.W. Monodial watts, size 2%inx2in, geared 1 rev. 60 mine, receiver, 12-watt Quality amplifier, B.T.-11. can be reset to zero by friction drive from These ex- G.P.O. Voice Units speaker, Garrard induction motor, and mag- front or back shaft, 5/8xl /10in, to run clock- are under lin. diam., filled netic pick -up housed in high quality oak cabi- wise, ideal movements for making electric carbon granules and fitted net; best offer over £60. -Box 374] [8633 clocks, time switches, etc., nickel -plated finish, mica diaphragm, 3/6 each. equipment and accessories, price 22/6 ea.; 12 to 1 dial trains to fit above Special Transformer and RECORDINGblank discs, cutters, radio units, mixer spindle, 2/6 per set extra; Chamberlain & Condenser, 5/ , Instruction Leaflet with each units, a complete recording equipment for Hookham synchronous motors with enclosed Button., G.P.O. Mike insets, 2/6. £75; send 3d in stamps for descriptive cata- rotor, similar specification as Sangamo, con- logue to University Recording Co., 113, Milton sumption 3 watts, price 27/6 ea., complete CRYSTAL SETS. A charming production in Rd., Cambridge. . [8476 with 12 to 1 dial train; f/3.5 lenses, 2in focus, COMPLETE recording gear, previously used Bakelite. The Lesdix Boudoir Crystal Set ; neat professional outside by well -known makers, ex-Govt. stock, as new, bakelite cue, fitted condenser, coil, semi -perm recordings, recording fitted in oxidised mount, flange, etc., ideal for m/c 30w amp. 3 -channel mixer and pre -amp. detector, terminals ; all aerial tested before ribbon, mov. coil and Xtal mikes, playback projectors, enlargers, cameras, etc., price 27/6 despatch, each, postage 6d; to callers only, Bendex 6 15/-. Headphones sensitive to crystal equip., all accessories; £125 or will sell indi- wave -band receivers, type R.A.I.B., Bendex reception with headband and cord, 12/6. vidual items.-Grimsdyke 1652 (Harrow). type R.A.10 receivers; receiving units, type GERMAN portable comm. receiver 12 -120 69; C.R. power units, type 526; performance MAGNETS. D.C. Electric magnets, weight metres, 3 wave bands, 100 -230v a.c. or meters, type 53874; A.C. mains wavemeters, 10 oz., lift on 2 volts, le lb., 4 volts 3 Ib., 6 volts 12v d.c., Tungsam range footless valves, built - type W1252; battery wavemeters, type W1095; 4 Ib., new, surplus, 7/6 each. Permanent powerful in speaker, B.F.O., etc.; £22 or exchange receivers, type 1147; A.C. mains power packs flat bar magnets, 2 1in. x lin. x tin., drilled 2 holes transcription motor and ribbon mike. -Rey. for 1147; indicator modulators, auto trans- each end, for any pole pieces, 2/- pair. The nolds, Garden House Hotel, Cambridge. [8788 formers; receivers, type 76A; battery driven wonder Midget magnets. Alni perm. disc ; sH.E.F.I. moving -coil pick -up is now avail- steel able for home amplifiers, large assortments of volt, amp and diam., ein. thick, with 3 /16ín. centre hole, both trade and export; it milliammeters, neutralising units with R.F. combines for the first time high fidelity with relays, vibrator packs, 3/6 each. Large stock of Horseshoe magnets. high output voltage, enabling it to directly meters. metal rectifiers, Send Leaflet inter -corn. sets, signal generators D.C. to A.C. for special Magnet " W.W." replace normal moving iron pick -ups without converters; 12 and 24v D.C. tet 230v A.C. any extra amplification; it has an exception. Sun Vic delayed action control, 3,500 watts, ally clean response with no undesirable reson- blower motors, G.E.C. gas -filled mercury ELECTRADIX RADIO ances thereby reducing needle scratch price relays; Brown's A. type headphones; E.M.I. 214, Queenstown Road. London, S.W,B including transformer. 40/- each retail, plus cathode -ray tubes- 6 -valve receivers incorporat- (late Queen's Road) 8 /11 purchase tax; wholesale and retail en- ing Clystron unit, etc. -H. Franks, 58, New quiries invited; illustration sent on request. - Oxford St., W.C.1. Tel. Mus. 9594. [8726 telephone: MACaulay 2159 Brooks & Bohm, Ltd., 90, Victoria St., S.W.1.

www.americanradiohistory.com 52 Advertisements Wireless World December, 1947 SIMON SOUND SERVICE have recorders in stock. [8713 YOU PROFESSIONAL recording equipment; to the trade, recording machines, blank discs, cutters, trailer needles, etc., from stock; record. MIDLAND INSTRUMENT Co. ing amplifiers. matching transformers, ribbon can become and m.c. microphones; full trade terms. -Sound OFFER GOVT. SURPLUS STOCK Discs (Supplies), Ltd., 83a, Bold St., Liverpool. CD.P. Recorder with control panel, 2 extra VIBRATOR PACKS, input 6 -v., output 90 -v. 20 m /A.. cutting heads, high fidelity crystal play- contacts require cleaning,Mherwise in perfect condition, -class back pickup, Standard Telephones 4017C fitted H.T. rectifier, a REGULATORS, first / VOLTAGE 10 -. microphone and battery pre -amplifier, £50 or ver. resistor etc., 3'6, 36/- don. SELECTOR near offer; would consider selling separately. - SWITCHES, 12/24 -v. impulses and homes, operating llimant, 21, Limes Ave., 11)11 Hill, London, yaxley switch, brand new, 3/6. 30/- doz. CON- RADIO N.W.7. [8685 NECTORS, 5C/430, bakellte 2 -way, 9d., boxes of 50, N'MEW U.B. microphones, R.C.A. ribbon on 12/6. STEATITE Interlocking beads, No. 2, 10/- lb. desk stand with grip switch £7/10; ELIMINATORS. 200/250 -v. A.C. output 120-v. Shure T.17 carbon with lead and plug, 15/ -; 30 -m /A. D.C. fitted neon stabiliser, brand new, 40/ -. LINGI EEtt Electrovoice 600 moving coil with lead and ATTENDATOR units type 17, fitted control knob with, plug, T.30 mikes, 6/- pair; T.45 pointer, Beale marked 0 -100, brand new boxed, 3/8, £2; throat 2, consists of Pang - 36!- dos. MAGNIFIER unite type mouth mikes, 5 /- .- Harris, Btrouds, transmitting ver. condo. and tapped plated toile, We are specialists in Home - bourne, Berks. [8673 2/6, 24/- doz. CERAMIC car. condo. 50-p.f., 1/, BRITISH bound Recording Association wlrewound resistors, 23 ohm. Study Tuition in Radio, of 10/- doz. VITREOUS covers all interests the professional 16 amp., 5 / -. 48/- dos. MICROPHONE transformers Television and Mathematics. and amateur recording engineer and awaits No. 2, 2/6, 20/- do'. NO. 18 RECEIVERS complete reproductipn enthusiast. Radiolympia edition with 4 valves, 6 to 9 mks., 2 -v. and 120 -v. 35; -. Post coupon now for free of The Sound Recording Journal," 2/8. post NO. 813 RECEIVERS, complete with 8- valves, 2.4 to booklet and learn how you free. -Details of information bureau, meetings. 6.7 m /ca. 6.3 -v. and 260 -v. 60/ -. TONES PLUGS with and membership application form sockets to fit, 10 -way, 3/6, 36/- doz. 12 -way, 4/6, can qualify for well -paid fpublicationsrom Hon. Secretary BCM/BSRA, London, 48/- dos. ELECTRIC PANS, 12 -v. brand new boxed, employment or profitable w.C.l. [7772 30/ -, 215 doz. MOTOR GENERATORS, 4 types, you interested in reproducing woad 12 -v.600 or 760 watts, 24 -v. 360 or 500 watts, 30 / -each. spare -time work. ARE to plus 5/- carriage. IRONCLAD 5 -amp. A.C. mains as nearly as possible the original and 4- doz. Ex -GOV. ALL - I position switches, 5/ -, 48/- doing this at a reasonable cost If so, we DRY BATTERIES, fully guaranteed by us, as previously invite you to either come to our demonstra- advertised, 00 -v. phis 1) -v. 5/- ; sealed cartons of tions or write for full particulars; demonstra- 8 batteries, 30/- : 46 -v. batteries, 511n. x Silo. x T. C. RADIO COLLEGE tions daily, 9.30 -10.30 a.m, 6 p.m. -6.30 pm., lila., 3/ -. 30/- doz. NO. 19 SET AERIAL VARIO- & excepting Sat.- Rogers Developments Co., 12, METERS, 3/6. 36/- doz. D.R. MASTER 'UNIT, Macclesfield St., Shaftesbury Ave., W.I. (8743 24 -v. gyroscope compasses, consists of three motors. North Road, Parkstone, Dorset Ltd., manufacturers of direct one a convertor supplying A.C. current to the motor TECHNIFON.disc recording equipment and accessories, gyro, fitted compass card, plus a wealth of other precision built traverse gear complete with gear, originally cost over £80. Our price, 70/ -, plus first class cutting head, we manufacture and 7/6 for carriage and packing. (Post in unsealed envelope, rd. stamp) specialise in sapphire stylii, our standard types Hundreds of other interesting Radio and Electronic fit the most popular pick -ups on the market lists, 2d. with s.a.e. your Home - items, send for our Nov./Dec. Please send me free details of and inc. a push-in model for lightweight Orders over 30/ -, post free. No C.O.D. under 20/- Study Mathematics and Radio courses. pick -ups we manufacture specials in quantity please. to specification. Technifon, Ltd., 99, Belgrave Rd., London, S.W.1. Vic. 8814. (8706 NAME COMPONENTS- SECOND -HAND, SURPLUS Moorpool Circle, Birmingham, 17 VALUE! Matt has it. HARborne 1308 or 2664 ADDRESS Tel.: W.W.66. SPECIAL offer : Headphones with lead and jack plug, 5/6 per pair (boxed 2 pairs); speakers, P.M. (less trans.). 4in 17/6, Sin 15 /6, 8 in 22/6; output trans. to match 5/6 each; condensers, 0.1, 0.01, 9/- doz; 2, 4, 8, 16mfd, 8 +8 canned, 6 /6; 16mfd electrolytics (chassis mounting), 7/6 each; line cord, 0.3 THE amp (60 ohms pr. ft), 2 -way 1/6 yer yd, 3- way 2/6 per yd; volume controls (Centralab) various values, L/S 3/6, W/S 4/9; crystal Specialists pickups., Rothermel, de luxe, £211613 (inc. BRITISH NATIONAL P. tax); 2 -gang condensers, 0.000.5 (not midget), 5/6; television cable (aerial lead in), 1/6 per yard; large assortment of B.V.A. and RADIO SCHOOL U.S. valves always in stock; let us have your in enquiries. ESTE). 1940 MATT Radio Service, 29, Castle St., Kingston - on-Thames. Kingston 8353. [8375 FRITH RADIOCRAFT, Ltd., The Leicester A privately owned personally con- Specialista, offer from their comprehen- ducted coaching service by post HIGH POWER - HIGH QUALITY sive stocks: - TUNING gear drives as fitted to the famous American TIRO communications receiver, complete with spindles and stator carriers, less dial, price £11616; rotary converters, input SERVICE SATISFACTION 24v dc, output 230v ac, 50 cycles, 00 watts, in steel cases with carrying. handle, ideal for PUBLIC ADDRESS mobile amplifiers, etc., the best converter we have ever offered, £3115; battery communica- SINCERITY tions receivers, R.A.F. Type 1224, 5v a'het, RF stage, 1 to 9 me in 3 bands, Muirhead dials, Mazda Octal valves, guaranteed tested SYSTEMS and in perfect order, £11; RCA modulation ORIGINATORS of the B.N.R.S. transformers, 250 watts, primary 10,4000, secondary 4,3500, for pair of 8135, £5; sleeving i/,, 1, li/x, 2mm, 36 yds, 2/6 144 yds FOUR YEAR PLAN 10/-; tuning condensers, standard 3 -gang 0.0005 ceramic insulation, %in spindles at both ends for clockwise or anti -clockwise AMPLIFIERS operation, 7/6; midget 3 -gang 0.0003 with Covers full syllabus of A.M.I.E.E., SM drive and logging device, size only 11/2in Brit. I.R.E., and C. & G. xllkinx3in, 8/6; meters 3in, flush types, A.M. from ISO Wto IkW 0.20v ac, 10- 0 -10ma dc, 1 -0 -1ma dc, 0 -12e RF thermocouple, all at 12/6; ditto, 0 -12e dc, Radio and Telecommunications dc, all at 15/ -; 0 -20e do 350 -0 -350 millivolts a cost of owing to the impossibility of listing many Examinations at separate items we offer a special bargain parcel of ex -Gov. components having a retail value of over £5 for only £1; over 50 useful PER DAY items, our selection, but satisfaction guaran- 8d. teed or money refunded; latest liste of many W. Bryan Savage Ltd supplied. 'other items free on request; trade Free Booklet from : FRITH RADIOCRAFT, Ltd., 69-71. Church WESTMORELAND ROAD, LONDON, N.W.9 Gate, Leicester. Tel. 58927. [8761 Studies Director, B.N.R.S., GANG condensers, escutcheons, transformers 66, ADDISCOMBE Rd., CROYDON Telephone : Colindale 7131 etc., to be sold regardless of cost-Send stamped addressed envelope for full particulars Phone : Addiscombe 3341 to Retail Sales, Ltd., 6, Chiltern Parade, Syca- more Rd., Amersham, Bucks. [8670

www.americanradiohistory.com December, 1947 Wireless World Advertisements 53 BRITAIN (RADIO), Ltd CHARLES TEST set No. 102 in grey metal case, size 10 %inx9s/ainx8?4in with hinged lid and snap fastener; contains a.c. mains, 200 -250v 50 cps ARMSTRONG mains transformer metal rectifier, two new valves DET19, 6.75, also numerous volume controls, Raymert knobs complete with all connectors, mains lead, spare fuses and lamps; the chassis is of the Cradle type and the whole outfit is just the job for making an instrument; brand new and unused with circuit diagram, only 27/6, plus 5/- carriage and packing. RECEIVING set R1224.- Communications receiver for battery operation from 120v h.t., 2v l.t. frequency range 1 to 9 me /s (30 to 300m); 5 -valve superhet circuit, r.f. stage, Muirhead dials; brand new and complete with all valves, price £7/10; carriage and packing 10/ -; order yours now as we only THE "FLUXITE QUINS" AT WORK have a very limited supply; cash with order only. "What's all this soot?" came a yell. SPECIAL parcels (enabling the amateur to "O1's handiwork, I can tell." obtain small components at less than whole- Cried EE sale prices). -No. 1, 12 assorted volume con- "Well, by jiminyl trols, new, less switch, 5.000 ohms to 3 meg, He's flopped down the chimney 17/6 ea; No. 2, valveholders, 24 asstd, lncl And taken our FLUXITE as loctals, octals 5 and 7 -pin, etc., I0 / -; No. 3, welll" mica condensers, 0.0001 to 0.01, 36 for 12/6; No 4, metal cased condensers, 0.001 to 0.5, Model RF103 72 for 27/6; No. 5 resistors, 1 and 3/, watt 100 ohms to 6 meg, 72 for 12/ -; callers always welcome; trade supplied; terms, cash with See that is always by order, c.o.d. or pro forma. 10 VALVE ALL -WAVE FLUXITE FULL component list available on request; SUPERHET you in we are expecting many new bargains to be - the house - garage- in stock before this advert appears; be sure to obtain our latest list of ex -Govt receivers, RADIOGRAM CHASSIS. workshop - wherever speedy etc. -Charles Britain (Radio), Ltd., Radio Douse, 2, Wilson St., London, E.C.2. Tel. soldering is needed. Used for Bis 2966. [8760 SOUTHERN RADIO'S wireless bargains; over 40 years in Government latest radio publications. SPECIAL FEATURES AMATEUR transmitters' construction manual, works and by leading engineers 2/6; radio repairs manual, 2/6; car and port- 10 VALVE CIRCUIT. able radio manual, 2/6; radio valve manual, R.F. PRE -AMPLIFIER. and manufacturers. alternative and equivalent British and Ameri- Of all Iron - can valve types. 3/6; radio circuits, receivers, WAVE BAND EXPANSION. transmitter, power packs, etc., illustrated, 2/ -; mongers-in tins, 10d., 1/6 & 3/ -. short wave handbook, 2/ -; ultra short wave LARGE GLASS SCALE. handbook, 2/6; manual of direct disc recording, 2/6; test gear construction manual, 1 /6; 3 STAGES A.V.C. radio pocket book, colour code formulas, etc., TREBLE 1 / -; ten hows for radio constructors, 1/ -; Bul- LIFT CONTROL. gin radio service manual, 2/6; radio construe- (Operates on both radio and gramo- TO CYCLISTS! Your wheels tors manual, 3/ -; television constructors phone.) manual, 3/ - radio aerial handbook, 2/6; radio will NOT keep round and true hints manual, 2/6; amplifiers, fully illustrated PLUS 6 db. BASS LIFT ON GRAMO- circuits, 2/ -; radio resistance chart, resistance PHONE. (To restore bass cut on unless the spokes are tied with values at a glance, 1 / -; radio reference handsome records.) book, cloth bound up to date information on fine wire the crossings all aspects of radii), 12/6. 10 WATT PUSH -PULL OUTPUT. at AND AMERICAN service manuals, Crosley- Belmont, Sparton Emerson, Stewart-Warner Fada, 12/6 SOLDERED. This makes a much per volume; postage extra on all publications; send 21/2d stamp for complete list of publica- stronger wheel. It's simple-with tions. To export buyers we can confidently EX -ARMY throat mikes, brand new, with lead recommend RFI03 to any firm abroad FLUXITE -but IMPORTANT. and jack plug, 4/6 each, post 6d; Lufbra adjustable hdle cutters, for use on wood, metal who contemplates making a high -grade and plastics, list price 5/ -, post 6d. Radiogram or Console radio receiver. EX-R.A.F. Morse keys, 2/6, post 4d; Mar- coni naval pattern keys, 5/ -, post 8d; mains The transformers, 280 -0 -280 volts, tappings 5v and lively short -wave performance The FLUXITE GUN puts 6v, 17/6, post 1/2; input transformers, ratio coupled with the excellent quality repro- 1:9.9 mu metal core, 4/6 post 1 / - ratio duction ensure an outstanding performance. 1 :7 mu metal core, 4/6, post 1 / -, ex- Govern- FLUXITE ment pattern, brand new; A..0 motors (200/ where you want 250 volts), constant speed, ideal for light work, We will gladly make any alterations approx. 1/2 hp, 2,000 rpm, consumption under to the specification to meet individual 1/2 amp, weight 201bs approx., £2/15 each it by a simple plus 5/- carriage and packing; ex -Army head- requirements. sets, carbon mikes and moving coil earphones, pressure. Price guaranteed perfect, 12/6 per set, post free. To home buyers demonstration SOUTHERN RADIO SUPPLY, Ltd., 46, Lisle 1/6, or filled, 2/6. St., London, W.C.2. [8735 model now available to interested UNIVERSAL ELECTRONIC PRODUCTS, callers to hear, and technical specifica- ALL MECHANICS W/ML VI 36, Marylebone High St., London, W.1. available Tel. Wel. 4058. tion now on request. HIGH performance superhet tuning units covering 16 -50, 2-00-550 and 800 -2,000 It is hoped that a number (very limited metres, complete with i.t. transformers, dial will be and drive, completely wired, aligned and unfortunately) available for early ested; Type A," £51816; Type " C, ;' with delivery. FLUX! R/F stage added. £8; postage 2/6 extra. Our works are available for the construction The above model is for A.C. Mains. IT SIMPLIFIES ALL SOLDERING of transmitting or specialist type receiving equipment to specification. [8794 We also have a similar model Type UNI 103 Write for Book on the ART OF "SOFT" RELAYS. -New boxed Govt surplus, 2,000 ohm, 1 make, 1 ch'over, 200ohm 2p for DC /AC Mains. SOLDERING and for Leaflets on CASE- make, 2/3; 500ohm 4p ch'over, 2/9. HARDENING STEEL and TEMPERING YAXLEY types. -2p 6w ceramic, 8/6; 1p 2w, * * * 1 / -; 1p 3w, 1p 6w, 2p 3w, 1/9 each; 2p 9w, TOOLS with FLUXITE. Price II d. each. 3p 2w, 4p 2w, 2/3 each; 3p 3w 2b 5p 4w 3/ - -Brent & Salisbury, Regent St., Burnham - FLUXITE LTD. on -Sea, Som. [8739 dust cores, in varions sizes, for dis ARMSTRONG TELEVISION CO. LTD. Dept. W.W.), Bermondsey Street, S.E.I IRONposal; send samples of your requirements WARLTERS ROAD, HOLLOWAY, LONDON, N. for quotation. -John Downton & Co., 89, High St., Epping. Tel. 2163. [8700 'Phone : NORth 3213

www.americanradiohistory.com December, 1947 54 Advertisements Wireless World bargains of interest to constructors RADIOand Servicemen' send for list. -Kemp The Wise Men Rush, Too! Radio Supplies BCM /KRAE, London, W.C.I. AUTO COLLECTIONS, Ltd., 126, St. Albans Ave., W.4 `Chiswick 1601); or 15, Law- C.D.P. Tho reception given to " New Notes in Radio " (6th edn.) offer following has been most cordial. A very large number of readers rence Bt., Northampton, the ex -Govt. brand new goods: - RECORDER have expressed surprise and gratification at the packing inpt. 24v is of robust construction and is built to give years of so much useful knowledge into so little space, and the 5,000 ROTARY transformers T.29, of service without the necessity of renewals word has gone around that it le a wonderful three -and- 16 amp, outpt. 1,230v 200 mA, lots of 100 efxpenceworth. Wise men are hurrying to get their copies (4 £1; 10 Q3' 30/ -; 5 h? £2; 1 (u' 50/ -; super- before the edition is ezhausted. posing transformers (4 windings), 50/- per 100; gals. earth rods, 12/- doz.- Above. electrostatic This compact guide to high- fidelity reproduction (3s. 8d. post 10,000 VOLTMETERS, ammeters, ; 25/ -; tree) is mainly valuable to you became it shows you how v /mters, 5,000v, lots of 12 L £1 6 to to assess the claims made by those who claim to be experts 1 (Y: 30/ -; ammeters H.F., 200 mA or 350 in the subject. Hartley- Turner were the world originators mA, Ferranti & Weston 2ìn proj. m /coil, 5/6. of high-fidelity reproduction, and we don't now need to -Above. shout the odd^ from the housetops. 5,000 HYDROMETERS, unbreakable glass, size approx. 9inxlrfain, worth 6/- retail, 144 But this being a reputed free country, others (B 2/6; 12 @ 3/ -; 1 I4 3 /6.- Above. are at liberty to muscle in on our specialised WEE meggers, 250v, in leather case, few left, field of endeavour-4f they can. We do not list £12, our price £8; enorm. quan. emery mind at ail; rather do we get a good deal cloth (med.), U.S. Army " Wetordry " proofed of amusement from the remarks of those who (safety walk), in rolls 50 yds.x24in, £4 ea. or have completed "Ls grand tour des salmi 12 (L £3; also large quan. lacquer, aircraft h[R a Londres." These sound tourists can instruments, pressure gauges, steam gauge tee and hear for themselves and are not glasses, crowbars, climbing irons, prefocus deceived ; but those who have to depend lamps and all sorts elec. lamps.- Above. on the written word are in a position of some LARGE quantity condensers, resistors, R.F. The C.D.P. recorder is suitable for studio uocaialnty. and I.F. coils, service sheets and public and serious work, and will produce address equipment for sale, cheap, owner going excellent piano recordings. The addition ' New Notes " helps you to choose wisely by explaining the abroad. -Write Box 4021. [8738 of a new balanced armiture cutting head necessary attributes of any high -fidelity equipment. VALVE ex- R.A.F. units, rotary trans - (now fitted as standard) places the machine Hartley-Turner speakers, amplifiers, radio tuners and 111 former, 450v 0.05a; gears, relays, parts, in the highest category for workmanship, pick -ups have these qualities because knowledge and 2 chassis; in case 12inx12inx8in, wt 321b, to be essential. Not ail high quality recording and reliability. experience showed them other £3/10; cis 5/ -. -54, Station ltd., Countesthorpe. equipment is no well designed, and it is desirable that you selec- £32 should know your -ray around. H. RADIO carry comprehensive Price B&tics of component parts for the service with run -out groove device E5 extra engineers and components specialist; trade Should present users of the C.D.P. recorder only; stamp for list.-Huntley St., Darlington. experience trouble through low voltages in kit for 4 -valve a-c. T.R.F. M. and To Uvee still waiting for their Haraey- smooth- the present-day electricity difficulties, BASICL. rcr., incl. mains transformer, as for advice to overcome Turher leallda --orr apologies. We had ing, bin spkr., polished oak cabinet, 12inx9inx please contact thought interest our work would 2 condenser with drive, this. not in 7in, coils, -gang recording unit supplied, Amplifier. be so intense and widespread. But no valves, drilled chassis; £6. -Box 4026. 18746 Complete TELEVISION aerial equipment, 5 types fully Microphone Recorder. one trill be overlooked. waterproofed aerials available, poles, Please write for details. lashings, all types of feeder in stock; send for brochures; aerials installed. -Wolsey Television, BOURNE H. A. HARTLEY CO. LTD. Ltd., 87, Brixton Hill, S.W.2. Tulle Hill 1240. Smith's, Edg- 152 HAMMERSMITH RD., LONDON, W.6 " TTOU'LL probably get it at INSTRUMENTS 1 ware Rd.! " Everything for the construc- BOURNE, LINCS. TELEPHONE : RIVERSIDE 7387 tor, from a I / 10watt resistor to a radiogram RPL/P150 cabinet; lowest prices, biggest variety. -Near Phone 224 Metropolitan Music IIall. Pad. 5891. [8005 SUPPLIERS of high-grade radio components including television and high fidelity radio equipment; all types of radio and electronic HENRY'S apparatus built to your specification; large stocks of close tolerance resistors.- Rogers De- OPPORTUNITIES velopments Co., 12, Macclesfield St., W.1. se GUARANTEED SERVICE APERFECT joy to build! -The 5 -valve or ac/dc 3 -wave Superhet Assembly (all IN RADIO main components ready mounted on chassis), Single and multiple types, forms the foundation of a powerful receiver ELECTROLYTIC& Get this ! can and tubular, large stocke by leading manufacturera. at a price you'll like; send postage now for FREE Book full details.-N. R. S., 66, Parkhill Rd., N.W.3. METERS. Complete range of AYO and TAYLOR by S.T.C. and be Selenium rectifiers "ENGINEERING instruments, Including signal generators, can 15'000 5 types, 30 ea.a. to 220 supplied stock. Westinghouse, OPPORTUNITIES" from m.a., 50 to 360 volts, all new tested stock, volte, -Apply ELECTROSTATIC VOLTMETER. 0.6000 panel substantially discounted for quantities. reveals how you can mounting, by leading manufacturer, 30n. scale. Ex- for full technical data and prices, Partridge, Govt.. but new and guaranteed, ready for use, 85 /-only. Wilson & Co.. Ltd., Davenset Electrical Works, become technically-quali - VALVES. We have a large stock of many difficult Leicester. [8120 fied at home for a highly - types, including 384, IR6, 185, IT4, 6A8, 6K8OT, tuner, no tuning con- 3QSGT, MKT4 6 pin, 851,6GT, AC6 PEN DD, DDT, PERMETEORBILITYdenser required, single waveband, 2 or 3 paid key -appointment in FC2A, 26A80, 26YOO, etc., etc., at current controlled bands, wire frequency coverage, small size. the vast Radio and Tele- prices. Send s.a.e. for full lists, including details of 2 waveband I /Ç' vision Industry. In 108 VALVEHOLDERS. 4, 6, 6, 7, and Octal, English Midget iron -cored coils and and Paxolin dos.; Amphenol 7/6 doz. coils.-Meteor Electronics. Gloucester Row. pages of intensely inter- American, 5/- Weymouth. [8800 CERAMIC. Inter. Octal, and 6 pin tux 116 each. spares. -Al] new stock at esting matter, it includes Button type forlT4, etc., 1/ -each. Acorn type 2/-each TELEVISIONmanufacturers' list prices. Everything full details of our up -to- aerials indoor INTRODUCING THE RUCO TUNING ASSEMBLY. for the constructor. Valves, the- minute home study 15 -2000 m., Includes, chassie 465 kir. I.P's., coil pack, end outdoor, 80ohm feeder cable, focus and 3 wave awitching, trimmers, paddess, drive and drum, scanning coils, e.h.t. mains transformers, courses in all branches of dial, .0005 three gang with wide spaced ow. section, condensers, Mazda CRM 1171 12in and CRM RADIO and TELEVIS- V /holders and small components necessary to complete 91 9in cathode ray tubes. Radio : 1,000 valves, the circuit of a 6K8 G Frequency changer, and 6K7O condensers, cabinets, R/G and table types. ION, A.M. Brit. I.R.E., I.F. Amplifier. Provision is made for A.V.O. feed te 13 & 27. write for lists, state. -E. A. Porritt, A.M.I.E.E., City & I.F, and H.F. stages. Wired, tested and aligned. Wastdale Rd., Forest Hill, S.E.23. For 1292. Guilds, Complete with drawings. £5. JAMES PRODUCTIONS, 270, Special Television, Servicing, This Unit makes radio construction a very simple ARRY IT7 Leith Walk, Edinburgh, mail order Sound Film Projection, Short matter. specialists, cash with order or c.o.d.- Electro- THE "Q" COIL PACK. A really midget pack of lytics B.I. 500v 8mfds, 3/6; 8- 8mfds, 5/6; Wave, High Frequency, and outstanding performance. Sire 31in. x lin. x 2ie., 16mfds, 4/9: 16 -8mfds 6/6: bias 25v 25mfds, General Wireless Courses. employing 6 separate high " Q " coils, wound on 2/2; condensers, 0.01, 0.05, 0.1 500v, 8d; ultra midget low losa plastic formers, with adjustable 2 -gang, 12/ -, with trimmers. switch and trimmers, ready fur variable, 0.0005 We Definitely Guarantee iron cores. Complete 13/6: coils M. & L. with circuit, 8/6 pair; use. With circuit, 33,- only. T.R.F. chassis. 4/6; loudspeakers, 5in P.M., rc NO PASS -NO FEE" 19/6; 61/in energised, 29/6; volume con- If you're earning less than L10 a week, this A stamp will bring our comprehensive List. trols, standard values, with switch, 5/6; less enlightening boot is for you. Write for your switch, 3/6; mains transformers, 350- 0 -350v copy today. It will be sent FREE and without Cash with order, or C.O.D. (over £1>. 6.3 or 4v L.T. 80m /a, 30/ -; output mult.i- ratio, 9/ -; midget pentode, 5 /6; valve holders, obligation. 5 -, 7 -pin and octal, 7d; Amphenol type, 9,1; INSTITUTE OF droppers with feet and sliders, 3a 800 ohms, BRITISH 5, HARROW ROAD, W.2 4/9; 2a 1,000 ohms 3/9; line cord, 3 -core, ENGINEERING TECHNOLOGY PAD 1008/9 3a 60 -70 ohms. per f[, 9d; valves, large stock, 388b, Shakespeare House, of English and American types; please order 17/19, Stratford Place, London, W.I. c.o.d.; give us your enquiries, s.a.e. for lists

www.americanradiohistory.com December, 194i Wireless World Advertisements 55 TELEVISION RF chassis, new ex- Govt., Headline seen in recent papers : bandwidth 4 me /s 5 EF 50's, diodee ato 30,000 cathode follower, £12 1802 -LONG also similar little used chassis tuned to sound "LIFE VALVES frequency; £9. -Box 4044. [8780 "RESEARCH SUPPRESSED." CELLULOID battery lead identification tags, I. the interests of better obtainable in multiples of 25 in the fol- We at BULLS wonder how much truth lowing markings: H.T. -, H.T.+1, H.T. +2, quality... there is in it -what we know is-our H.T. +3, H.T. +4, G.B. -{-, G.B. -1, G.B. -2, VALVES are certainly LONG -LIFE G.B. -3, G.B. -4 L.T.- L.T. +; 25 tags 1 /6; Products. c.w.o., samples ld.-J. H. Charlesworth & Son, BRIMAR. -1D5, 1D6, 5B/250A, 686, 6116, 6K7, 14, Hightown, Crewe [8675 6817, GSN7, 6T7, 6V8, 7B5, 7B7, 7B8, 7C6, 7Y4, COPPER wires, enamelled, tinned, cotton 8D2, 9D2, 10D1, 11D3, 11136, 128B7, 2524, 16D2. and silk covered, all gauges; B.A. screws, COBSOB. 4TPB, 4T8P, 138PA, 1SVPA, 40811A, nuts, washers, tags; bakelite and ebonite The LABYRINTH 411111L, 41MP, 41MPT, 41MRO, 418TH, 42 -OT, panels, tubes, coil formers; headphones flexes, 420T -DD, 42PTB, 202VP, 202VPB, 203THA,210DDT, solder, etc.; list s.a.e.; trade supplied.-Post 210D0, 210LF, 2158G, 22011P7, 2200T, 220P, 220PA, Radio Supplies, 33, Bourne Gardens, London, DDL4, MP/PEN, MS /PEN, M8 /PENB, MV8 /PEN, E. 4. Tel. 0M4, 0M8, 0159, OM10, PT1O. Clissold 4688. [8231 HIVAC. -XD, XII, XL, XP, X8á, XY, XW. Tin boxed Post Office type relays for aale of types LOHD SPEAKER MA11008I/08HAM. -CRT- E4102/8/7, D41, D92, at a fraction cost, D83, DA30, D02, DL63, DL74M, DN41, GTIC, G1150, available include some with i, in dia. high H30, H63, HAS, 10D94, HL2, MINK, KT2. KT41, current contacts, high sensitivity contacts KT44, KT61, KT63, KT86, KT71, KT74, KTW81, adjustable by thumbscrew; also twin coil KTW83, KTZ41, KTZ63, KTZ73M, L2B, L89, LP2, high speed relays. Send s.a.e. for details.- L86B, MH41, MKT4, MIA. M84B, M8P4, MX40, BM /RXBF, London, W.C.1, [8714 for Musk Societies-Schools N14, P2, PT25H, PX25, QP21, 823, U10, U14, 1118, TELEVISION I.F. transformers, 9.2 to 10.6 ... UI7, U18/20, U31, U50, 1(52, U74, VMP4G, VM84B, mega frequency or band easily modified W21, X6115, X65, X7IM, Y63, Z22, Z63, 301, 302, as required, variable inductance trimmers, Theatres Quality P.A. and 303, 304. exceptionally well and - made for stability pre- - MAZDA.-AC2PenDD, sA.06PEN, ACOPENDD, cision, 10 /6 each, post free.- Television ACOPEN, AC/P, AOPen, ACP4, AOTH1, Dl, DCP, Co., DCSG, DD41, DD101, DD207, 1313620, 11210, HL21DD, Development 4, The Parade, High Rd.. all music lovers HL23, HL23DD, HIAI, 1TL41DD, 1IL42DD, Kilburn, N.W.6. Mai. 3991. [8802 HI183DD, HLDD 1320, P41, PenS6, Pen46DD, Pen46, Q s.w.g, tinned copper wire, twin-screened Pen463DD, PenDD4020, QP26, QP230, 80215, ßP41, 1 O flex, 4-core screen flex; brass screen cans A partitioned cabinet to form a folded 8142, 8P2220, TH233, TH2321, TP22, TP26, TP28, 4%i inx15/sx1 %min; Paxolin tubes, 11 /fin o.d. U403, ÚU7, V914, VP23, VP41, VP138, VP1322, x lt/gin i.d.x6ft; Paxolin panels, 5%sinx3lkx pipe -the back of the unit coupled to UY6/300. r %sin, 16i linx2%Ginx3¢, and 6inx2%iux%in; MULLARD.-2D4A, 2D13C, 5174, 5Y9, 605, 606, hard fibre rod, %in square. it in such a way that the quarter and DUD, 6Lß, -John Downton 6J7, 6Q7, 8117, 164V, AZI, AZ31, OBL31, & Co., 89, High St., Epping. Tel. 2163, [8702 0(01135, CL33, 071, 0210, CY31, DAF91, DF33, half wave resonances are under in- DF51, DF91, DX91, 13135, DL92, 13024, D026, ALARGE quantity of radio components, in- 1)030, DW2, DW4/350, EA50, EB34, EBC3, EBC33, cluding condensers, flexible couplings; 3 dependent ' Q ' control cabinet EBL21, EC52, ECC31, ECC32, ECC34, EOC35, EOH21, pole 3 -way switches, line cord, multi range - ECH35, SF5, EEO, EF22, EF36, EF37, EF39, EF50, ohms meters, screened wire single and twin, S- acoustic resonances arranged to EF54, EL2, EL3, BL32, EL33, EL36, EL38, SL50, core flex., 2- and 4 -way fuse boxes, etc. - EMS, EM34, EM35, F013, F0130, FW4 /500, HL13e, 'Phone or call L. Goodman (Radio), Ltd., 9, HVR2, HPIt2A, 1W4/200, KBC32, KF35, KK32, Percy St., Tottenham Ct. Rd., W.1. Mus. 0216. cancel pipe anti-resonances. The result KL35, Pen4VA, Pen428, PenA4, P112, PM211L, KITS of radio receivers from £7/8; 4- and PM4DX, P1512M, PM224., PM220, QP22B, ßP4, 5- valve, new is a smooth bass response down to SP4B, 11P13, materials, table models, 8P13c, TOD, TDD2A, TDD19c, TH4B, semi-midget; our latest kit. -Wylwyn Star 1948 TH300, TT4, U22, VP2, VP2B, VP4, VP4A, VP13A, has 35 c.p.s. VP130, UBL21, UCH21, 1.Y21, ÚY31. connections for gramophone pick -up, ex- PHILLIPS -C1 CIO, 328, 329, 340. 287, 452, 1012, tensions to loudspeaker A.V.C., 6 hours aver- 1038, 1120, 1581, 1729, 1738, 1821, 1904, 1905, 1914, age time for constructing; full details, dia- 1920, 1926, 2050. grams with each kit; c.w.o. or c.o.d. Isher- TUNGSRAM, -6B8, 6J5, OVO, 6X5, 25Y5, 807, woods, Reme House, 81, Plungington Rd., APP4C, APP4G, D1313, DD818, ECH2, EF12, Preston, Tel. 3348. Estd. 1936- [6788 11E2, EL5, EL11, E504, EZ4, HIA, ELIO, HP13, Gl00DSELL, Ltd., 40, Gardner St., HP2110, HP1018, HP1118, HP2018, HP2118, Brighton, Sussex. -Ex- stock, Denen C.T.3 HP4106, HR210, 15111118, LD210, LL28, LIA, coil turrets, £6/10, complete; 4 -band feeder LP220, P2018, PP6E, 8P2B8, SP4B, ßP48, 88210, units using Denco C.T.2 turrets from £9/9, VP48, VR105 /30. with B.V.A. valves; AMERICAN.-0Z4, 1M, IAS, 184, 11)7, 1E6, details upon request; 157, Denco No. 1 1F4, 1F5, 1E6, IF7, 1GO, 1118, 1LC6, 7LN5, 185, Bulletins, 3/21/2, Id stamp for 1T4, 175, 1 -V, SAO, 23.7, 2B6, 2B7, 2X2, SAO, 387/1291 constructors' component list; Williamson am- 3Q5, S174, 5V4, 529, 5Z3, 6Z4, 6A3, 6A4, BAb, plifier as per specification, £20/10, including 6457 /1853, 6A07/1852, 6.055, 6058, 5A05, 6AG6, valves; pre -amp for above, with 4 position bass 6A07, OAKS, 684. 887, 6B8, 804, 6C5, 608, 608, and treble control, using E.F.37s, £2/10; 6136, ODO, 6D8, 6E5, 6E8, 8E7, 6E8, 8E7, 8E8, 806, " Q-Max " components in stock; ld stamp for 8118, 6J5, 817, 818, 8K8, 8E7, 6K8, 13L6, 8L8, 6L7, list. [8792 657, 6Q7, 8P6, 8117, 88A7, 8807, 68F7. 8807, 86117, RADIO components. -50 brand new useful 61317, 88117, 88L7, 68147, 8887, 88117, 677, OVO, components 6%6, 8Y5, 7A03, 7A7, 7E5, 7B6, 7B7, 788, 705, 708, to a list price value of £20 707, 7117, 787, 7Q7, 774, 10, 12A, 124.6, 12A6, 12B7, for only 50 / -; our assortment includes P.O. 1208, 12J5, 12K7, 12K8, 12Q7, 128137, 12887, 128117, standard relays, air dielectric condensers, 128Q7, 1213E5, 128117, 1225, 144.7, 14138, 14Q7, 15, selenium rectifiers, wire wound potentio- 17, 20, 22, 25A8, 26E5, 25Z4. 28, 27, 28D7, 29, 80, 31, meters, transformers, chokes, electrolytics, 32, 88, 34, 35A6, 3555, 36, 37. 38, 39/44, 41, 42, 43, jacks, insulators, signal lamps, plugs and 46, 48, 49, 50, 53, 55, 67, 69, 77, 79, 80, 81, 89, 84, 89, sockets, tag panels, i.f. transformers, r.f. 807, 832. 868A, 954, 966, 958, 1I7Z6, 1299A, 1626, chokes, block condensers, etc., etc.; our pur- 7198, 9001, 9002, 9003, 9004, 9006, 9008, and 101 chase of a complete Ministry of Supply store more types. makes this unprecedented offer Order 0.0.D. above listed numbers or equivalents possible; order (subject to stock). Please enquire for any valve a sample parcel and come back for more.- you require, even It not listed. We may have It. MM. O. 8., 24, New Rd., London, El. [8745 Old and new types are arriving daily. NEW S.T.C. selenium rectifiers, f.w. bridge THIS MONTH'S SPECIALS : Iona damp -proof finish, 17v 1.5a, 12/1; Taylor Meters on easy terms. Service Sheets, British, 2a 15/5, 3a 21/6, 4a 25/ -, all p.1., 30v 2a 10/6 per doaen. Electric Motor, to work off 31 28/6, 4a 38/ -, 50v 4a 53/8, all post 9d; to 8v. battery, 12/8. Batteries, ex-A.M. heavy duty type, Tin sq, Al cooling fins, unite, Inert 120 v., 10/9, 50v. 5/9. Morse Tappers, 17v 6s, 34/1, p 1 / -; 16v 10a 43/8, p 1 / -; 33v 1 /11. Wail Telephones, complete installation, 2 6a 63/8, 30v 10a 71/2, 28v 20a 139/3, instruments, etc., £3 15a. 0.5 mA Lnminona 11ín. 52v 6a 89/8, 90v 6a 141/ -, 110v 6a Heten. 12/6. Radio Maintenance and Servicing 166/4. all p 1/3; replacements for Philips & Tungar Book, 8 /6. Midget Speakers, 2(n., works the M.o.R.I., and all valve chargers, state make, type, also as extension, 7/6. Trimmer Tool Kits complete No. outfit for set aligning, 31/-. Vidor Portable Elec. input and output. h.w., push -pull and Cooler, with oven (no tax), £2 2s. 6d. Mousetraps, doubler recta, for all duties; specialised recti- " ADDRESSING the PUBLIC" electric. hygiento (no wattage). fying equipment for labs, schools, 12/6. Sunray Lamp etc.; kits, P.A. "Collard." complete with goggle,, £5 16s. IOd. incl trans, rect. and rheostat, 16v 10a The Fundamentals of good Technique ' Vibro-Aro" Metal Engraving Pen, 15 / -. Waffle £6/12/6, 17v 6a £4/12/6, special 16v 5a Machine, electric, tax tree, £5. 5s. Unmet :Pressers, £3/2/6, vent steel ease 7/6 extra; 4a £3, electric, 28/6. Pen Torches, chromium plated, com- case 7/6; 2a 38/6, case 7/6; transformers, 130w 3/6d POST FREE atg30 Tie Pressers, for 17v 6a 47/6 p 1/3; 220w for 16v 10a 65/ Oafits, -, ,8, and 18/6. 'Mechanical p and pp 1/8 90w for 17v p Fingers, American tool for difficult jobs, 9/-. 4a 35/6, 1/ -; Radiograph Library, 10 complete books (unrepeatable) 150w slider res, all values, 24/6, p 8d.; fluor- 36/ -. escent fittings comp with tubes and starter Stop Press : Avo Battery Oseillatore,e, £12,plus 5/- care. gear, 40w from £6/9/3, 80w from £8/8; Television Sets : Baird', " Garrick " Model, 12in. 80w twinlamp, £17/2/6; all carr. extra; one combined. only 12- Acvusica tube. radio Cryataltone Electric Record Delooreany 15volt, 200watt output. Players, £18 5e. 8d. petrol generator with volt and ammeter, £15; Write at once please, to BULLS (WW) illus. list 2d stamp; c.o.d. post goods only, ACOUSTICAL MANUFACTURING CO., LTD., otherwise c.w.o. or pro forma; trade supplied. - HUNTINGDON Telephone: HUNTINGDON 246, High St, Harlesden, N,W.10 Pearce, 66, Gt. Percy St., London, W.C.1. 361 (Nr " Angel. ") [8759

www.americanradiohistory.com 56 Advertisements Wireless World December, 1947

STOCKS wop't last for ever; send 21/pd s.a.e. for lists and see last two months' advte.; new extension speakers in cabinets, 32/ -; mike transformers, 2/6; midget switched meter or 'phone jack sockets, 2/9; tool boxes, power units, meters, s.m, driven etc. -Dept. W.W., Barnes Radio & Wholesale, 2. Elmdale Rd., FOR RADIO VALVES Penn, Wolverhampton, [8662 AT last, the coil pack that we have been At B.O.T. prices. British and American, these introducing, looking for, a super efficient coil pack a selection of our 10,000 valves held in stock. Please completely screened and fitted with an 1.F. send for our Comprehensive Valves Available List, free, Radio Receiver Servicing filter, 3 or 4 waveband, complete with cir- enclosing S.A.E. for reply. Postage 6d. extra, C.W.O. new, or C.O.D. By E. M. SQUIRE. Gives a useful working knowledge of cuits, test sheet, the Albion coil pack, receivers and equipment. Second Edition. 7,6 net. delivery from stock, prices from 36/6; electro- MULLARD.-ñK32, KF35, KBC32, KL36, FC2, servicing lytics condensers, 16x8x500 volts, 7/ -; 8x450 F02A, VP2B, SP2, PM12M, TDD2A, PM2A, PM202, volts, 4/ -; 250mfdaxl2 volt 2/ -; 1,000mfdax PM2HL, PM22D, QP22B, EM1, EM4, EM34, E3135, 6 volts, 4I -; 2 gang condensers, 9/6; full EOH35, ER32, EFB, EF9, EF22, EF36, EF37, EF39, Radio Simplified range of Summersby high gain coils, 3/3 each, F.F50, EF64, EC31, EC52, EC63, EB34, EBCB, EB033, By JOHN CLARRICOATS. A simple and well -illustrated I.F.s Q160, 15/- per pair; Weymouth con- ECC31, LL2, ELI, EL38, EL35, EL37, EL38, EL50, introduction to radio for beginners. Second Edition. 4/6 net. structional drawings, 1/6 per cent; 2 -speed ECC35, EOC32, PM24A, TT4, TH9B, V74, VP4A, drives for 2 gangs, 1/6; speakers, etc. Send VP4B, BPS, SP4B, 2D4A, 2D4B, TDD4, 354V, 904V, stamp for list; terms cash with order or c.o.d. 104V. PEN4A, PENA4, PENB4, PEN9DD, TH30C, Short Wave Radio over £2, plus 6d postage.-Castle Radio 11, PC13, F0130, VP13A VP130, BP13, SP1SO, 2D13C, This is a compre- HL13, HL130, CL33, PRN428, CBL1, OBL31, ECH21, By J. H. REYNER, B.Sc. (Hons.), etc. Millill Lane, Margate. (8683 EBL21, hensive survey of short waves and their application in radio joy to build! High -class 5- UBL21, 1801121, UY21. and television. Fourth Edition. 10,6 net. valve ac or ac /dc 3 -wave superhet of MAZDA.-P220, BP22, VP23, HL22, TP22, TP26, unusual sensitivity and power, set of blue- TP26, PEN220A, PEN25, PEN220, QP230, 0E75. parts available; HL23, 90215, S216VM, HL21DD, HL23DD, HI42DD, Upkeep and prints 5/- (refundable), all AC/PEN, AC3PEN, AC6PENDD, ACOPEN, PEN44, Radio special bargains: 21in scale 0 -1 ma 1st grade PEN45, PEN46DD, PEN46, ME920, HL1320, TH233, m/c meters, 27/6; 5 ma meter rectifiers, 7/6; TP1340, DD207, DD101, SP2220, BP1320, V914, Repairs selenium rectifiers, 250v 45ma, 5/ -; 1st class DD41, AOHL, AC2HL, 41HL, of useful hints on ACP, ACP4, ACSGVM, By ALFRED T. WITTS, A.M.I.E.E. Full p.m. speakers, R & A, 8in, 21/-; Rola ACMG, ACVP1, VP41, SP41, SP42, P4I, SP61, ACT$1, and their correction. 6th Edition. 7/6 net- the location of faults 61/2in 19/ -; 5in, 17/6; o.p. trans., 5/6; TH41 AO/HL/DDD HL41DD PEN453DD ME91' new high " Q " iron -cored coil packs, 3 -wave, PP6/400. 33/ -; shrouded mains transformers, 300 -0 -300, AMERICAN RANGE.-16, 18 26, 80, 31, 32, 34, 37, Cathode Ray 6v and 5v, 27/6; filament trans. 6.3v 1.5 amp 89/44, 41, 42, 43, 46, 71A, 76, 77, 78, 79, 80, 83, 84 89, output, 12/6; postage extra under £5; terms, 9161, 6J6, 6LT, 8A4, 6W7, 8D8, 6T7, 6A7, 6,16. BAB, Oscillographs c.w.o. or c.o.d. any value; send postage for 6118, 6C5, 61rB, 6116, 61C7. 637, 6K8, 6B7, 6K6, BR7. By J. H. REINER, B.Sc., A.C.G.I., D.I.C., etc. A guide to Rd., London, 608. OKB, BFB, 638, 6AG6, 6 Q7, BVB, 606. 6D6, of the cathode ray tube. special list.- N.R.S., 66, Parkhill 6117. 808, 2546. the numerous practical applications N. W.3. [8664 8/6 net. Rd., RECTIFIER$.-DW4/360, 1W4/360, FW4/600, SUPREME RADIO, 746b Romford DW4/600, CY31, UY31, 11E30, R2, DW2, AZl, AZ31, Manor Park, London, E.12. 'Phone inquiries invited. UUB, U117, 1310. U14, U81, 0360, 1762, 1176, U17, A Dictionary of Ilf. 1260. Manufacturers D74, 431U, TDB, 6U4, 5Z3, 67A, 5Y3, 5V4, 606, 25Z4, 2 gang condensers with feet, 9/6; line cord 267,6, 26Z6, 35Z4, 50L6. Terms 60 -79 Cl it, 20/- doz yds; tubular condensers, OCTALB.-%66, KTW61, KTW62, KTW63, KTZ63, Electrical Smtd can or M.A., A.M.Iost.C.E., A.M.I.E.E. Fourth 0.1 0.01 0.05 500w, 416 doz; 1183, LO3, D63, DH63, DIOS, KT81, KT63, KTO6, By S. R. ROGET, type l6mfd 4/3 173, %76, W76, %61, KTZ41, DL74M, KT74, KTW74, Edition. 12/6 net. cardboard, 39/- doz; can ea, 16x8mfd 7/- ea, 16x16mfd 7/3 ea, 8x %71, KT7S, KT71, Z62. ea; SxBmfd W. ?. 8x8 mid 7/3 ea, 24x8mfd 7/3 RRIàIAR.--80A1, 20D2, 16D2, 11D3, 11D6, 10D1, London, 6/- ea, 4mfd 15 /- doz; condenser clips 4/6 941, 9132, 841, 8D2, 7A3, 7D5, 7AS, 4D1. doz; resistances sizes from 2200 to 2.2 meg LOCTALB.-7A7, 7C5, 7CO3 7C7, 7135, 784 7B7, 7E8, P Kingsway, 1w, 3/- doz; assorted ww, handy sizes 2/6 7Y4, 1LB4, ILA4, 1LN5. Parker Street, doz; volume controls 50k short spindle, 12/- ww 12/- doz; standard V /cs with H. RANSOM, doz; 2,000 34, BOND BRIGHTON. Phone Brighton 5603 sw 100k and 50k 42/- doz, doz lots only; STREET, 5k up to 2 meg, 4/6 ea; 250k less aw, 2/6 ea; all wave glass dials, 8inx5in, 3/6 ea; 1 +1 condensers 350e w do 250v an 6/- doz; Midget knobs less grub screw, 1/- doz; Octal valve holders, 3/6 doz; 4 pin Ux Ceramic holders, 12/- doz; anchoring tags, 3/- gross; WINDING grid caps with lead, 1/6 doz; ditto on panel with 570 res. 4/- doz; Paxalin panels with tags 3- 4 -8 -11 ways, 3 ways let; 0.002 condensers 1,000v w short ends, 1/6 doz; 1 w carbon REWINDING res. 27,00012 75,0000, 4/- doz; 10,00012 6w, 5/- doz; 10,000 and 20,000 2w short ends, AND 2/6 doz; coractual plug and socket, 1/6 ea; meter rectifiers 5ma, 5/6; Westectors 1/8; earphones 50n, 4/6 pr; earphone inserts or mikes, 3/-; test meters, etc. All service material cash with order; no c.o.d.; s.a.e. LOUDSPEAKER all enquiries; 8d extra postage orders tinder £5. [8684 selenium metal rectifiers, charger kits, A New NEWetc., no surplus goods, all new stock, add REPAIRS postage 6d up to 15 / -, 1/- above 15/-, Rec- tifiers, selenium cell, 12v 3amp 211 -, 12v 4amp GRAMOPHONE BY 25/1 12v 5amp 27/6; giant 12e 6amp, aluminium fins, fume proof finish, 33/6, 24v 2.5- amp 32/6, 24v 5amp 43/6, also 6v 0.5amp UNIT 6/ -, 6v 2amp 9/6, 12v 2amp 12/6, 12v 1.5amp 10/6, 12e 0.7amp 7/6; interesting data and circuit supplied; many other L.T. types, in- Specially designed for use with "TELECRAFT" cluding rectifiers for converting valve type (TRADE MARK; garage charger to metal rectifier. H.T. rec- Lightweight pickups tifiers. new small selenium type, 250v 60ma 9/6, fit any ac /dc receiver, for 350- 0 -350v 60- chokes, transformers, ma 13/6, 120v 20ma 7/6, 110v 60ma 9/6; * Heavy cast, non -magnetic, crystal diodes 2/6; 5ma instrument rectifiers 12 in. turn -table for Avo- Avominor 12/6; charger kits, 2v 0.5- fields, etc. amp rectifier with transformer for 2v trickle * Hightorque,frequencycon- charger, ideal trickle charger for 2v cell, 13/6, trolled motor, 200 -250 volts guaranteed one year; 12v 3amp rectifier with 50watt transformer and ballast bulb for 2r 50 cps. to 12v charger, weight 71b 45/ -, ditto with * Robust direct mounting 2amp rect., 35/ -; ditto with 4amp rect. and 75watt transformer, £312; ditto 12e 5amp plate 14 in.x 12 in. rect. and 120watt trans, £4; heavy duty type chargers for commercial charging, transformer, Price (Exl. Pickup) £6 0 0 Southern Trade rectifier, ballast bulb for one to 20-cell lamp charger, 95/ -; ditto one to 12 cells 2amp, Purchase Tax Extra £I 6 0 Services Ltd. 95/ -; ditto one to 20 cells 2amp, £6/5, guar - anteed one year; slider resistances 0.5ohm 10amp, 14/ -; ammeters, 0-ham , 12/6; elim- 297/299, HIGH STREET inator kit, transformer, 2 condensers, 2 rectifiers for 120v 20ma and 2v trickle charge, CROYDON 39/ 6; Rothermel ' Bullet " microphones. B.B. LTD. 58/6; Lustraphone m/o mikes 78/6; 80watt fluorescent chokes, boxed and bitumen filled, 'Phone : CRO 4870 WEST 230v, 19/6; tapped 21 /- .- Champion, 43. Up- 39/43, HILL, S.W.18 lands Way, N.21. Lab. 4457. PUT 8765

www.americanradiohistory.com December, 1947 Wireless World Advertisements 57

GA. RYALL, 65, Nightingale Lane, Lon - don, S.W.12. -Mail order only pc Cages extra, c.o.d. £1 or over, please send large en- N S velope for our full list; U.H.A. make metal GALPI cased 500v tubular 0.1mí, 7/6 dozen; Silver ELECTRICAL STORES mica, 200p1, 300pí, 400pí, 500pí, 4/6 dozen; 500v wkg, Micamoulde d 0.004m!, 4/- dozen; 408 HIGH STREET, LEWISHAM, LONDON, S.E.13 Mica 0.01mi, 3 -2/ -; Manabridge 1mí 500v wkg., 3 -2/ -; all condensers guaranteed; Am- Telephone : Lee Green 0309. Near Lewisham Hospital. phenol type British 5 -pin valve holders, 4/6 dozen; U.S.A. paxolin 4-5-6-pin, 3/6 dozen; Volume controls, 10,000 medium spindle, 1 /6; TERMS : CASH WITH ORDER. NO C.O.D. 250,000ohm short spindle, 1/6; Bar type 3 gang, 0.0004mí short spindle, 5/-;5/ -; Twin EX- R.A.F. CALIBRATOR UNITS TYPE 18. MAINS TRANSFORMERS, EX -GOVT. In- ceramic 0.0003mí, 5/6; Bar type gang These units consist of 1 -100 k/c Xstal 2 -EF 50 put- 230 volts 50 cys. I ph. Output 12* volts 1 100 0.0004mí, 5/ -; Resistors, /watt, r/2watl., valves and numerous other components (new C.T. at 25 amps., 45/- each, carriage 5/ -. ohms to 2 meg level assortment, 40 -5 / -; Plastic group boards, drilled, less tags, 9w, boxed), 35/- each, P /F. METERS ALL BY WELL -KNOWN MAKERS types, 3 -1/6; Switches 8B.2P. 6w, 2 /- ;:5B.2P. EX- U.S.A. ARMY HAND DRIVEN GEN- Ex -Covr. new boxed 1st Grade Moving Coil. 6w, 2/6; 2B.3P. 3w, 2/3; Res. panels, 5 -way ERATORS (as new). Output 162 volts at 0 to 1 m/a., 21/- ; 0 to 40 volts, 15/- ; 0 to 10 with 25mf and three res., 113; Twelve -way 60 m /a, 3.1 volts at .3 a., complete with all smooth- amps., 15/- ; 0 to 5 m /a., 17 6 ; 0 to 20 m /x.,17/6 group boards with 9 -lwatt and 1/zwatt re, 2/ -; ing and circuit diagram, 35/- each. Ditto, 425 0 to 50 m /a., 20/- ; all tin. fed. 0 to 3 m /a., 22/6 ; all new; twenty types in stock; Octal plugs, volts at 115 m /a, 105 volts, 32 m /a, 6.3 volts at 0 to 50 m /a., 22/6 ; 0 to 200 m/a., 22/6 ; 0 to 4 cap and socket, 3 -2/8, with tags 3-3/ -. (8579 2.5 amps., 6.3 v. at .43 amps. at 55/- each. amp. Thermo Coupled, 30/- ; 0 to 20 volts A.C., SELECTOR switches. 5 -bank, 25 -wáv, per A SPECIAL LINE OF VOLTMETERS. calibrated 50 cys., 25/ -; 0 to 3,500 volts Electra - bank 20/- each; toggle switches, telephone First -grade Moving Coil 0 to 20 volts, tin. static, 35/, All 2¢in. fsd. jacks, press switches, 20 -way tag boards, E.S. square Tax- face, new boxed, 10 /- each, in lots of 3, 25/ , L.T. RECTIFIERS (new), 6 volts, I} amp., holders, lead ends, E.S. holders, screwed, R.A.F. 7/6 ley type switch, 3 -pole 2 -way, each 18/- per EX- MICROPHONE TESTERS. These each, 12 v. 14 amp., 10/6 each, 9d. post. In- dozen; voltmeters, 0 -40, ampmeters 0 -50, 15/- consist of a Ferranti 21in. m/coil O to I m/a meter strument Rectifiers, S.H., 10 or 20 m/a. types, per pair; condensers, 8mfd 700 volt: 6/ each; with Westinghouse Rectifier incorporated, 4/6 each. condensers 4 +4, 500 volt, 3/6 each; conden- calibrated at present 0 to 10 volts, microphone MAINS CHOKES, 9 by., 100 m /a.,6 /6. 20 hy., sers, lmfd 250 volt, 6/- per dozen; 8lydlock transformer, jacks, etc., all contained in polished 120 m /a., IO;6 each ; 30 hy., 150 m /a., 22/6 each. fuses, 15amp, 15/- per doz; rotary switches, teak case, size 6 }in. x 5 }in. Condition as new. MAINS TRANSFORMERS, 230 volts, 50 cys. 5- section, 10 -pole, 15/- each; 10- section, 20- Price 32/6 each. pole, 25/- each; 0.0003 tuning condensers, 3/- I ph. input. Output 500/0/500 volts at 250 m /a., LARGE RECTIFIERS FOR CHARGING. 6 5 v. 3 a., 47/6 each. Another with two windings each; relays, 200 ohm, 3/- each; Octal plug or 12 volts at 6/8 amps. Complete with mains tops, 1/- each; postage extra; delivery by re- of 6} volts 5 amps., 30/- each; another with 350/0/ Denlord, Box Trees transformer for 200/250 volts 50 cy. I ph £5/2/6, 350 v., 180 raja., twice three 6.3 volt windings turn.-Part(culara. H. 8. F. paid. Mill Wheatley, alifax Yorks. (8221 carriage and two 5 volt windings, 42/6 each ; another 50 $ADIO CLEARANCES, Ltd.. 27, Tottenham EX -GOVT. NEW MAINS DIMMER RE- volts at approx. 50 amps., also a 5 volt winding, Court Rd., W.1. Mus. 9188.- Electrolytics, SISTANCE, worm wheel control, 700 watts E3/15/ -, each C /F. All the above Transformers are 8mí 170v 2/3, 8mí 450v 3/3, 16124mí 350v variation from full to Blackout. Price E3 /10/ -each. very large type, so please allow 3/6 for carriage. 5 /6, 16+16m1 350v 5/6, 32mí 350v 4/ -, 25mf EX- GOVT.VARIABLE RESISTANCES'(sew), 25v 2/ -, 50mí 12v 1/9, 100mí 12v 1/ -, 100mí 450 ohms, carry .7 amp., 30/- each, 4,000 ohms, D.C. TO A.C. ROTARY CONVERTERS. 24 volts input, 50 or 100 volts 500 cycles at 300 6v 1 / -. Meters 030ma 21kin scale Such carry é amp., 37/6 each. mounting 8/6 0 -750 micro amp plug in 21/2in MAINS TRANSFORMERS. (New). Tapped watts output. Condition as new, 75;- each, C/F. scale for use with thermo- 9/6, calibrated volts 50 cys. I ph. Output350 EX -NAVAL CATHODE RAY RECTIFIER visual indicators, 2 types input200/250 /0/350 -couple. Ex-R.A.F. v. 180 m /a. 6.3 v. 4 a., 5 v. 3 a., 4 v. 4 37/6 each. UNITS. New and unused, sold for components still available type 3 containing 2 complete a., which .5 2,500 1 .1 Weston 300 micro amp movements 5/- cross- 1/6 post. Another 500 /0 /500 v. 150 m /a., 6.3 v. consist of :-2 x mf. v., x over as used with R1155 with 4 a., 5 v. 3 a., 4 v. 4 a., 47/6, post 1/6. Another 5,000 v., 6 x 2 mf. 800 v., 2 x 8 mf. 800 v. 15 needle type, 100 2 60 micro amp movements 5/11. P.M. 6, 12 and 24 volts, 10/12 amps., 45/- each, post 2/-. volume controls, various values, approx. speakers, brand new and boxed, 5in less trans, Another 141 and 17/. volts at 30 amps (auto small condensers and resistance, smoothing choke 16/11; Sin with trans, 19/11; Bin with trans, wound), L4 /15 / -, post 2/6. Another 700/0/700 v. and 9 v. holders, including 3 EF50 and 1 tube 25/ -; 10in with trans, 39/6. Ex-Admiralty 80 m /a., 12 v. I a., 4 v. 2 a., 30/ -. Another 4, 6.3 v. base. All components wired and with the addi- S.M. dials, ratio 100/1, fit 3'isin spindle, 7/6. and 12.6 volts at 12 amps., 45/ -, post 2/6. Another tion of mains transformer would make a good Epicyclic B.M. drives 6 -1 ratio, fit standard 17$ and 20 volts at 30 amps., 95/ -, post 3/6. oscilloscope. Price 45/ -, carriage paid. 14in spindle, 2/ toggle switches D.P. D.T., CHARGER TRANSFORMERS LARGE RECTIFIERS FOR CHARGING. - 2/3, VOLTAGE 2/11 D.P. S.F. 2/6; D.P. B.T. bakelite, (Auto Wound), tapped 0, 110, 200, 220 and 240 6 or 12 volts at 6/8 amps. Complete with mains Metal rect. 12v la bridge, 4/8; 250v 60ma 350 1/6. transformer for 200/250 volts 50 cy. 1 ph., L5/2/6, H.W., 4/6; tuning condensers 0.0006 2 gang volts, watts, 55/ -, post 500 watts, 70/ -, small size, 11/6 volume controls wirewound, no post 2/-. 1,000 watts, E5/5 / -, post 2/6. 1,500 carriage paid. switch, 3w type, 15011, 20011, 40011, 5000. watts, L71151-, post 3/6. 2,000 watts, £8/15/ -, post EX -GOVT. VARIOMETER for No. 19 sets ; 1K, 2K, 10K, 20K, 50K, 2/6 2 gang wire - 5/ -. Double Wound, 2 to 1 ratio (120/240 or these contain C.T. Westector, .001, 5,000 v., wound, 500/50011, 2.5K/2.5K. 5 /50K, 3/6 ea; vice -versa), 4,000 watts, E12/10 / -. C/F. condenser, etc., price 7/6 each. Complete in 2w 30f1 mini., 2 / -i 5001 15w, 4/ -; 50K, 10w, AUTO WOUND TRANSFORMERS (Mains metal case with graduated dial. fully shielded precision type. 7/6; volume con- Boosters), tapped 0, 6, 10, 19, 175, 200, 220, 225, EX- R.A.F. R.F. UNITS TYPE 110A. New trols, carbon, no switch 10K, 20K, 50K, 1,500 unused, consisting of 5 valves, including miniature 240 and 250 volts at watts (new ex- Govt.), and 100K, IM, 2/ -; ganged IM/IM, 3/6; £5 /10 / -, post 5/ -. grounded grid 750 m /cy. tube, small 12 volt motor carb., 1K, 20K, 100K, 500K, 1/8. 'witches, TRANSFORMERS (Volt- and numerous other components, would make and 21/sin spindle, 3- AUTO WOUND 4 -bank with 9in locator age Changer), tapped 0, 10, 20, 25, 90, 130, 150, very useful crackers, 45/- each, 5/- carriage. wafers 2p 4w and 1 wafer 1p 4w, 6/ -' 1p 3w, 190, 210 and 230 volts at 1,000 watts. (It will be EX- R.A.F. RADAR IMPULSE TRANS- 1 /9; 1p 9w, 2/6; 2p 2w, 2/-; 1p 10w ÌB, 3/6; (new, We have no actual 2p 4w 3B with long spindle, 3/6; 2p 5w 3B seen that almost any voltage can be obtained from FORMERS boxed). short spindle 2/9. Tubular conchs., 0.01 1000v this Transformer.) Price ES /10/ -, post 5/ -. data on these, but believe them to have an output 6d, 0.02 35áv 6d, 0.04 350v 6d, 0.05 500v EX- R.A.F. I.F.F. UNIT (Model 3002), complete of 15,000 volts at 3 kW. for a micro second. A 6d, 0.1 350v 7d, 0.1 500v 9d, 0.1 600v bakel- with 10 valves, types 3X70E, IEF50, 4VR65, bargain for the experimenter at 7/6 each. P.F. iced 6d, 0.25 350v 1 / -, 0.25 500v metal cased rotary converter 12 volts input. SHUNT WOUND D.C. 110 volt motors, bridge '2XYT61A and 1 / -. Meter rectifiers. Westinghouse 450 volts 40 m /a. output. These units are as 1,500 r.p.m. approx A h.p., condition as new, ima 6/11, selenium 400v 60ma 5(6, mica new. Price complete, 57/6 each, carriage paid. 17/6 each, post 2/.. conchs. 0.0001 -2 -3 -5 4d, 0.001 -2 -6 5d, 0.01 6d, 0.0001 3000v wkg. 9d, 0.005 1000v 7d, silver micas most values 10- 6000pí 6d, ceramic conde. 2- 10 -25 -50-100pí 6d. Valveholders 4p UR, 5p Brit., Mazda Octal, 6d' Int. Oct. Pax., 6d; CALLING AMATEURS amph., 8d; EF50 type Pax. Bd. Micalex 1 / -, ceramic 1 /6; special offer Int. Oct. amph. with EDDYSTONE '640' with BUCCLEUCH 2 'kw res. (100K and 68011) wired across pins Prec'sion Built Equipment 8d; smoothing chokes, 2.5H 2OOma, 7/6; high CHASSIS SMOOTH BLACK filled, We are now booking orders for this STEEL voltage condensers, 0.1 12.000v test oil 17r xle'x2r, 9/9. 6/ -; 0.0005 2 gang tuning condensers with first -class communications receiver. 17'x10'2', 8 /9. epicyclic drive, 10/6; maasbridge condensers PANELS -CRACKLE 1m1 350v 8d 1,000v1/3 2m1 300v 10d, 4mf Demonstration model on view at 19' x 3)', 4/ -. 600v 4/6, 0.25m1 2.000v 1/9. 0.25 2,500v 2/ -, 19' x 7', 6/9 ; all working V. cathode ray Indicator units with our Show Room. 19' x 81', 7/9 ; (non -persistent), 7 valves (4 EF50 and 19' x loi', 8/9. bin tube ' in stock. 3 EB34) available to callers only at £211916; EDDYSTONE '504 ANGLE BRACKETS, 12l' long, pr.7 /6. ex-army 38 sets, 5 -valve trans -rec. complete (A5 in Bright Aluminium, same nest.) valves and junction box (as used 52 Page Catalogue of Components & COMPLETE RACK ASSEMBLY with 5 2v (Rigid 4-Pillar), 63', £315e.31í', £2 /6s. 19 2 section aerials I in tanks with sets). 45/ -' Accessories /- Post Paid. Chassis, etc., to order, Id sq. Inch. for same .7 /6; throat mutes, 3/6; carbon (Include aides when costing.) mikes, power type with switch in handle, 6/ -; B.T.S. PUNCHING CHARGES UP TO )', 2d. power units with rotary trans., and carbon VALVE HOLES, l', 11' or 1I', 6d. pile voltage reg., input 24v, output 300v The Radio Firm of the South. METER HOLES, etc., 1 /6. 30ma, 6.5v 3.5a with 12v in will give 200v SQUARE HOLES, 2/ -. 30ma, 15 / - Vit. res. 10w 50011 1/6, 20w with 63, London Road, Brighton I, BUCCLEUCH RADIO MANUFACTURERS clips 2K, 8iß, 2/ -; 40w 14K tapped at 2K, 3/ - Sussex. 1 & 2 MELVILLE TERRACE, EDINBURGH, 9 metal rect. 12v tha, bridge, 3/6; mains 'Grams: ' Therm," Edinburgh. droppers 0.2e 1,00010, 3/6 (with 2 adjustablee Factory: Wheat ieid SI., Edinburgh.

www.americanradiohistory.com 5.8 Advertisements Wireless World December, 1947 JV. NEWSON, G3GY, 28, Market Place, North Walsham, Norfolk.- Everything for ARE YOU LOOKING FOR LASKY'S RADIO transmitter, constructor and short wave enthusiast. Components by Eddystone, Den - THESE? DECEMBER SPECIALS co, Labgear, Harnrad, Raymart and other PICKUPS. well -known makers from stock. All new goods. Connoisseur, with transformer, 78/9. S.R.1, móWng Ex-A.M. Receivers, Type 151626, brand new and Wide range of transmitting and receiver coil with transformer, 79/9. Rothermel, crystal, senior unused, consisting of 4 units. valves at list prices. S.a.e. with enquiries plse. model 56/ -, 8 /12 52/8. Amplion, crystal, 51/7. Rapid post svce., c.w.o. or c.o.d.-Tel. 219. Magnetic, 36/ -. B.T.H., Piezo electric, 81/8. Magnetic Receiver 'Unit 185, Containing ten valves, 7 EF50. THE American I.F.F. responser unit with 33/9, (Mitring super magnetic 30/7. Pickup head 3 EB34, 1 Relays, 6 Pot /meters, dozens of Neon, 2 6 68117 all -metal H.F. pentode valves, 2 fits all tone arms, 25/7. Cosnioeord, crystal, 44/ -. resistances ¢, }, 1 watt, condensers, toggle switches, All prices include tax. Delivery immediately from stock valveholders, and other components. 6116 all -metal double diode valves, and 2 type 7193 valves; also includes 2 200 ohm MICROPHONES. Receiver Unit Type 170. Containing three valves multicontaet mechanically cam operated relays, Crystal type, ehaftesbnry, 1H35./-d. Rothermel, 12 gas EF50'a, I relay, 2 pot /meters, resistances, condensers various pie sockets, and a host of fixed con- Carism type, Mleeo, 70/ - mike, 30/ -. and other components. Maria coil type. Mieeo, Lnstraphone, 104/-. densers, and 1/4, 1 1 and 2 watt high -grade 105/. /s, Reel,,, Power Unit Type 565. Consisting of Motor generator, carbon and wire wound resistances; the above 110/ - Ribbon type. Shaftesbury, 12 gas. 20 watts 24 volts, 1.74 amps to 180 volts .04 amps, also includes a 12 volt dynamotor with an Microphone stands. Trix spring action. heavily 1 relay, 1 power regulator, type 6, condensers and output of 400 volts complete with step -down chromium plated, heavy base, 95/ resistances. gear ratios suitable for driving instrument lathes; a real bargain at each plus SOLDERING IRONS. R.F. Unit Type 108. Consisting of Lecher Bars and 50/- 4/- Pyrobit. 200/220 v. 45 watts. Instrument type, 22/ -. packing and carriage. details of co-axial sockets. -For further Wireless type, 22' -. Model 6GB, 200/220 v. 65 watts, The four units completely housed in strong metal other Government surplus bargains send 25 /2d 22// -. box. Size: length, 19 14n.; width, Sin.: depth, stamp to Uncle Tom's Radio Cabin, 5, Seven Solon, 200/220 v. or 230/250 v. 65 watts. Pencil 7 1la Original cost over £30. Weight, 35 lbs. Stars Court, Manchester, 4. [8680 Bit, 18.9. Straight Bit, 17/3. Lasky's price 57/6, carriage 5/- extra. SPEAKER trans. tapped output, ultra - Else, 200/220 v. 60 watts, 12'4. midget, 5/ -, midget 5/6, standard 8/ -; L.L.P. 230/250 v. 60 watts, 18/9. TEST SET TYPE 238 P.P. output (6L6 valvés, A/A load 6,600 - PYROBIT SPARES. Consisting of calibrator unit type 115, containing ohms), output 7.5 and 15ohms, 21/ -; P.P. Elements. Instrument 230 v. 45 w., 3/6. 9 EF50 and 3 EA50 valves, ceramic valveholders, modulation trans. for 807 valves, audio power Wireless, 230 v. 45 watt, 4,,6. resistances and condensers, coils, switches, 230 volt 30 watts, 2 -1, at 12/6; chokes, ultra-midget Universal. Fits either 200/220 v. or 230/250 v.50 wort, 50 cycles power pack including mains transformer 40ma 5/ -, midget Soma 5/6, standard 100ma 4/6. 325.0 -325, 250 m /A, 6 v. 2 a., 6.3 v. 4 a., 250 m/A 8/6; hy. duty 150/200ma 12/6; tuning BITE. smoothing choke, 8 mid. 500 vw and 16 mfd. 500 vw assembly, assembled and fully wired for s.m.l. Large Instrument, 4/ -. Small pencil, 6d. condensers, 5Z4 Rec. valve, screened cable and con- waves. On chassis, dial, pointer, I.F.s coils, Sundries. Screened cable, single 7dd, yard, twin 1/- necting pings, pot /meters and dozens of other com- padders, etc. Series heater wiring for use with yard, heavy twin covered 2;9 yard. Wander plugs, ponents. Amazing value. Totally enclosed in strong or black, Banana plugs, 4d. Crocodile width, 6k8g, 61c7g valves, complete, factory tested and red 214. metal cabinet. Size: length, 191in.; Sin.; clips, 45. Alligator clips, 25 amp., 9d. Jack plugs, depth, 7¢1n. Entire set and leads in wood carrying aligned, with circuit 85/ -; 5v superhet fully 11%X51,2x2 %in, AVO 2,11. Double circuit jacks, 2/3, insulated. Tone or case with handles and hinged lid. Total weight, 55 lbs. drilled chassis, 7/ -; volume plates 2tin. square, chrome or black, 6d. Brand new and unused. Can never be repeated. capacity bridge, £11; single core screened Indicator plates, chrome or black, llin. x }in. Lasky's prise 90,- carriage 5/- extra. cable, per yard 9d; twin ditto 1/ -; nuts/ Output Gram, Input Mike, Aerial, Key, filaments, 6d. screws, 4, 6, 8 BA 6/- gross (2 gross in all); Send ld. for our latest bulletin of other ex- Service .lack discs chrome, marked Gram, Mike or radio, 1/ - bargains, also our current list of radio components. Centralab volume controls with switch, 5,000 - And all other lines you need or are ever likely to need We guarantee satisfaction. It will pay you to pay us a ohms to 1 meg, 6 / -; English and American in radio. Prompt 0.O.D. or C.W.O. Service. visit. paxolin valveholders, 8/- per doe; slow motion Please irírl,ede extra for packing and postage. drum drives, 3/ -; Epicycle drives, 3/3; SML dials, coloured 4x31/2 2/ -, 5x55/ 2/6; 2 -gang RADIO condensers, 0.0005mfd 11 / -, ditto Tiny Tim LASKY'S fitted trimmers, perspex dust cover, 2x11/2x VALLANCE'S 370, Harrow Road, Paddington, W.9 11/4in, 17/6; 2 -gang, 0.0001mfd 6/ -, 2 -gang 144, BRIGGATE, LEEDS, 1 (Opposite Paddington Hospital.) 'Phone C1TN 1979 split stator, 0.00017mfd, 6 / -; 3 -gang, 0.0001- Rhone: 29428 and 29429. mdf, 7/6; condensers: Electrolytics, 24 plus Staff call signs G2H1IV, G6SX, 02AHV, G3BDD, Hours : 9a.m. to 6 p.m. Thurs. close half -day. Smfd, 350v, 7/6; 450v, 7/6; 20 plus 20mfd, G3A13I1, 150v, 7/6: 32mfd, 350v, 5/ -: 25mfd, 25v, 2/6; paper, 2mfd, 1,000v, 3/ -; 4mfd, 100v, 9.1; drive assemblies; square plane MIL with escutcheon, glass, pointer, etc., 11/6; ditto full vision, SML 12/6; relays, 400ohm 12v 3/ -, 100 -25ohm 6 or 12v 3/6; line cord, 3way 0.3amp per yd 3/ -; ditto 2 way 2/ -; Weymouth all wave coil pack with circuit, brand new, 36/6; Weymouth midget Lc. I.F. trans. 465 Kcs, brand new, pr. 18/9; standard I.F. trans., pr, 15/ -; ditto I.F.s 2Mcs, each 2/ -; M/L t.r.f. coils with reaction, circuit, pr. 7/6; M/L i.e. t.d.f, pr. 10 /6; SML, aer & osc, pr 10/6; sleeving, all colours, 1/1.5 mills. 35/40 yard reels 1/6; Bernards publication stockist, television constructors' manual, 3/6; car and portable radio ditto, 2/6; radio constructors, 3/ -; etc,; court prehensive lists monthly; 2 //,d stamp enquiries; postage extra all orders. O. GREENLICK, Ltd., 34, Bancroft Road. Cambridge Heath Road, London, E.1. Tel. Stepney Green 1334. [8799 WANTED, EXCHANGE, ETC. WANTED, Sound Sales tri- channel amplifier. -Box 4019. [8740 Oct., '47; state price. -Stutfield, Bow - TIN" larFt/l WW.,down Farmhouse, Greenham, Newbury. WANTED, double or triple spring gramo- 'MINOR' FOLDER' phone motor; details, price. -Box 41143. NS U LATI O N yFwtells you all about the complete Col paid for data, 11102 (Murphy), 1940. - TEST SET range of Henley SOLON Electric á Watt. 19, Willowbank Gdns., Belfast. standard voltage WANTED, electrical A.C. 230 -volt disc re- Jompact and inexpensive Soldering Irons, for the cording turntable, Simpson type preferred. without sacrificing accuracy and reliability. Weighs only ranges of 200 /220 and 230. z50: 65 watt -Box 3898. [8657 01b. Height allows for full swing of generator handle. and 125 watt models fitted with oval - ANTED, Voigt corner reflector speaker. Ranges up to 20 megohm. os: , -cita. tapered bits or pencil bits and 240 watt W -Webb, 32, Kenninghall Rd., Benchill. CONTINUITY models fitted with oval- tapered bits are Manchester. [8781 TESTER available. WANTED, Proc. I.R.E., Jan., Feb., March, rills latest addition to Write to -day for the new folder ref. Vac) 1945, for binding. -Waterton, 245a, Mag- the Record Ohmmeter describing dalen Rd., S.W.18. [8641 range Is enclosed in a WANTED, service sheets, any type, age. - moulded bakelite case of Offers to Thompson, Rose St., Ohl Pen - pleasing appearance. shaw, Co. Durham. [8765 Equipped with self-con- WANTED, universal record- changer, new or tained dry battery. Speci- price Brandon, ally designed test spikes second -hand; good paid.- and leads can be supplied, 428, Upper Richmond Rd., S.W.15. [8721 also a "test and carry" second -hand Cossor oscilloscope, ease in which the instru- WANTEDmodel 339. -Write with full details re- ment may be used with. garding age and condition to Box 3910. [8664a out removal. Ranges: - OUANTITES of ex -Gov. valves, types 013 -0/30 ohms. 0/30- ooee VR53, VR56 and VT52 or equivalents, 0/300 ohms. 0/500- wanted for cash. -N.R.S., 66, Parkhill Road, 0150,000 ohms. O'1000- London, N.W.3. [8768 0/200,000 ohms. W. T. HENLEY'S required, half bard. 0.002 or THE RECORD ELECTRICAL CO., LTD., TELEGRAPH WORKS CO. LTD. URGENTLY0.003 phosphor bronze strip, 2in wide or Broad heath, Altrintham, Cheshire. (Engineering D p'.) multiples.-Price, samples and quantity avail- reI.: Altrintham 3221 /2. Grams : Infusion," Altrintham. able, to Rev Motors, Ltd., Lever Bridge, LONDON : 28, Victoria St., S.W.1. Phone: Abbey 5148 5I -53 Hatton Garden, London, E.C.I Bolton. [8674 D 26

www.americanradiohistory.com December, 191L7 Wireless World Advertisements 59

URGENTLY needed for export, M.E.A. pat - terns 72, 74 and 4a laminations; Scott's U.S.A. RADIO Aircraft RECEIVERS pattern 130 and 4a laminations or equivalent in iron; 39a gauge copper wire, enamelled. - to Offers to A.W.F. Radio Products Ltd., 1/ou'íe SURE qet it at Type CCT -46145 Borough Mills, Bradford. [8526 TATE buy for cash, new, used, radio, electri- Made by Stromberg -Carlson T cats equipment, all types; especially wanted, radios, radiograms, test equipment, motors, chargera, recording gear, etc. -It you want to sell at the maximum price, call, write or 'phone to University Radio, Ltd., 22, Lisle St,. Leicester Sq., W.C.2. Ger. 4447. WANTED to complete files, " Wireless World," 1940, May, Aug., Dec.; 1941, Feb., Mar., Apr., May, July, Aug., Sept.; 1943, Apr., Oct.; furthermore QST, 1940, May; 1941, whole year except May and Aug.; 1942, whole year; 1943, Oct., Nov., Dec.; Weymouth M. & L. Waves Permeability 1944, whole year; 1945, whole year except Tuning Onit,with integral W/Band switching, Nov. and Dap; offers, including postage, and s /het or TR F, 2}" x 3}" x 44 48/9. 5/Het stating condition of copies, to James Steffen - Coil Pack, S.M. & L. Waves, 36/6. Screened sen, Ehlersvej 8, Hellerup, Denmark. [8703 Iron Cored Coils, A, HF or Osc., 5 ranges REPAIRS AND SERVICE cover between 33 to 2,000 metres, 4/9 each. MAINS transformers rewound, new trans- Complete Perm. Trim I.F. Filter, l' sq. x £6 formers to any specification. 465 k /cs, 4/9. Plus 5 - Carr. and pkg. MOTOR rewinds and complete overhauls; first - class workmanship, fully guaranteed. '00035 MFD. Midget Variable Twin Gang F. M. ELECTRIC Co., Ltd., Potters Bldgs., Cond., 12/9. Medium Waveband, 520 -1,500 )Cc /s Warser Gate, Nottingham. Est. 1917. Tel. 3855. rewound con- Varley L.F. Choke, 20 Hy. 250 ohms 120 m /A, These Ex- Government 6-valve receivers are MAINS transformer and to any specification; prompt de- 18/6. Mains Transf. 350 -0.350 130 m /A, brand new in original cartons. Overall dimen- structed livery.- Brown, 3, Bede Burn Rd., Jarrow. [3460 6.3 v. 4 a., 5 v. 2 a. (both tapped at 4 v.), sions approx. 101" x 41" x 51" high containing LOUDSPEAKER repairs, British, American, 40/ -; 425 -0-425 150 m /A, 6.3 v. (C.T.) 4 a., removable plug -in dynamotor for 24/28 volts any make, moderate prices.- Sinclair 5 v. 3 a., 4 v. (C.T.) 4 a., 55/. Thermal with an output of 250 volts. Valves are one Speakers, 12, Pembroke St., London, N.1 Delay Switch, 4 v. and 6 v., 10/6. I2K8, three 12SK7, one 12SR7 and one 12A6, Terminus 4355. [3308 three Permeability -tuned I.F. transformers, instrument repaira. Electrical test TEST Wearite I.F. Transf. 465 k /cs. Standard, 20/- Input aligning condenser and main tuning instruments repaired and recalibrated. pair. intended Quick service guaranteed work.- Electrico, 99. Midget iron -core, 21/- pair. ' P " condenser originally for use with Coils, remote control but easily adapted for direct George St., Croydon. [8698 all ranges, A, HF, Osc. or BFO, 3/- each. S /Het iron -core tuning. Illustration shows metal cover and repaired; transformers, Coil Packs, Condenser screen removed. LOUDSPEAKERSclock coils, chokes, rewound; prompt S.M. & L. Waves or 13 -35, 34 -120, 200.550 attention; prices quoted. -E. Mason, 5, Balham metres, 42/ -, We have also the U.S. R- 1/ARR -1 AIRCFAFT Grove, Balham, London, S. W, [7667 RADIO HOMING ADAPTOR EQUIPMENT measuring instruments nkil Electrolytics Dubilier 8 mfd. 500 v., 4/- ; which can be used in conjunction with the ELECTRICALfully repaired and recalibrated.-Electrical 8 -8 mfd. 500 v., 6/6 ; 16 mfd. 500 v., 6/6 Lane, ; above receiver on 234258 mcs. l his contains instrument Repair Service, 329, Kilburn 8 -16 mfd. 500 v., 8/6. T.M.C. 8-16 mfd. 4 acorn tubes type 954 and all permeability London, W.9. Tel. Lad, 4168. [6935 450 and to mains and 450 v., 7/6 ; 32 mfd. v., 5/9. It is use on 12 24 volts. REWINDS conversions tuning. for or 35 /. output transformera, from 4/6; pp equip- Plus 5/- carr. and pkg. Price ment a speciality. -N.L. Rewinds, 4, Brecknock Westinghouse 0 -I m/A Meter Rectifier, 10/6. Rd., N.7. Tel. Arnold 3390. [6283 Indicators and in stock (,her Receivers are: SERVICE with a Smile. " -Repairers of all Ex -Govt. 0/Put Transf. 60-I, It" a 11 x I} ", R.1147 30/- plus 5/- carr. & pkg. " t. types of British and American receivers; P/Pull Intervalve Transf. 2.5-1 each half, A.M. 6A Indicator coil rewinds; American valves, spares, line I }"x I}", 3/-. Midget 0/Put 32 -I, 82.15 plus 5/- pkg. lx carr.& cord.-F.R.I., Ltd., 22, Howland St., W.1. 1" x l' x }", 3/. L.F. Chokes, 5 Hy 100 A.M. 62A 810 plus 6/3 carr. & pkg. Museum 5675 [1575 ohms, 150 m /A, 6/9. 15 Hy., 100 ohms, to moving coil speakers, cones. m /A, 12/6. Double- spaced Trans- or altered; 300 REPAIRScoils fitted field rewound Condensers, split- PF coils rewound, mitting stator, 150 speaker transformers, clock half, 4/9. Straight type 200PF, 4/9. ALEC DAVIS guaranteed satisfaction, prompt service; no each mains trans. accepted. Mains Transf. 250. 0-250. 70 m /A, 6 v. 1} a.. 8, PERCY STREET, LONDON, W.1. L.S, REPAIR SERVICE 49, Trinity Rd., 5 v. 3 a., 19/6. '0001 MED. Twin Gang Midget Variable 'Phone : MUSeum 2453 Upper Tooting, London, 13.W.17. Balham 2359. repairs, vac rewinds, elec Cond., 5 / -. LOUDSPEAKERtrio clocks, gram motors and pick -ups rewound and repaired; for real service send to: Rd., Man Laycock Bros., 36, Bt. Stephens -k Send 21d. stamp for Catalogue-No- cheater Rd., Bradford, Yorks. [8507 vember Supplement now available. When STURDY reminds, mains transformers, please cover packing and postage. chokes and fields; we give prompt delivery ordering, ARE IN STOCK :: od guarantee satisfaction; 14 years' experi- ,THESE ence; prices an request. -Sturdy Electric Co., Ltd., Dippton Newcastle-on -Tyne. [4316 STERN RADIO LTD. Radar Engineering, by Donald G. Fink. DEWINDIÑG of all types of transformers, 35s. Postage EH. AL chokes, etc.; quick service; motor rewinds 115, FLEET STREET, E.C.4. The Mathematics of Wireless, by R. of all types; replacement bobbins supplied; new Stranger, 7s. 6d. Postage 5d. transformers to any epeclfioation.-Radio & Telephone: CENtral 5814 Transformer Services, 570, Manchester Rd., Television Explained, by W. E. Miller. hlollinwood, Lanas. [8638 3s. 6d. Postage 2d. LOUDSPEAKER and transformer repairs Television Today, by Roy C. Norris. 21s. almost by return of post' ; we offer the Postage 6d. quickest service in the trade, at competitive T. prices. Send Id for our monthly service bul- Wireless Servicing Manual, by W. Ltd., Cocking. 10s. 6d. Postage 6d. letin, Dept. W- A.W.F. Radio Products, Borough Mills, Bradford, Yorks. Tel. 22838. Radio Aids to Navigation, by R. A. Smith. repairs, any make, reason. 9s. Postage 5d. LOUDSPEAKERable prices, prompt delivery, to the trade ROTARY The Wireless World Valve Data. 2s. and quality fans; 25 years' combined experi- Postage 2d. ence with Rola, Magnavox, Goodmans, Celes- WARD CONVERTERS in tion. -Seund Service Radio, 80, Richmond Electronics and Their Application 8008. (4977 Research. Postage Rd., Kingston-on-Thames. Kin. For Radio, Neon Signs, Tele- Industry and 42s. mains transformers, speaker field 9d. REWINDS,coil, chokes, high -grade workmanship, 7- vision, Fluorescent Lighting, Mathematics Applied to Electrical day delivery; new transformers constructed to Engineering, by A. G. Warren. 21s. customers' specification, singly or in quanti- X -ray, Cinema Equipment and Postage 6d. ties. -Metropolitan Radio Service Co., 1021, innumerable other applications Foundations of Wireless, by M. G. Scraggie Finchley Rd., N.W.11. Speedwell 3000. [3719 7s. 6d. Postage 4d. HOUR service, 6 months' guarantee, any 2 'm transformer rewind, mains outputs We also manufacture:- and i.f.s., etc., all types of new transi., etc., Petrol Electric Generating Plants, H.T. We have the finest stock of British and supplied to specification; business heading or American Radio Books. Complete list service card for trade prices. -Majestic Wind- Generators, D.C. Motors, etc., up to on application. ing Co., 180, Windham Rd., Bournemouth. 25 K.V.A. COIL specialists.- Tuning and oscillator coils, THE MODERN BOOK CO. I.F., L.F. and mains transformers re- F. WARD (Dept. W29) wound and wound to specification; wavewind- CHAS. ing, L.S. repairs.- Electronic Services LERDSCROFT WORKS, HAVERHILL, SUFFOLK 19 Praed London, W.2. -21, Street, (R.T.R.A.), 17, Arwenack St., Falmouth, Telephone: Haverhill 253 & 4. Cornwall; and 49, Uxbridge Rd., Ealing, W.S.

www.americanradiohistory.com 6o Advertisements Wireless World December. z947 AREWIND service which duplicates or modifies as required; transformers, loudspeakers, etc; prompt returns. Raidel Services, LO 49, Lr. Addiscombe Rd., Croydon. Cro. 6537. (3O CJO CRYSTAL PICK-UP PICK -CPS, replacement coila for Garrard type, etc., 5/3; rewinds to clock coils, SPECIALISTS IN SHORT WAVE fields, transformers, etc., replacement Marconi, and high -class broadcast equipment offer a H.M.V., mains transformer coils, 18 / -; 48- wide range of components for the con- hour service; trade enquiries.-Radiocrafts, 10, structor and enthusiastic amateur. Goodmayes Rd., Goodmayes, Eases. Tel. Seven Kings 4557. [8505 in addition to our range of equipment bearing COILS and transformers manufactured to the well -known Trademarks of Eddystone, Ray - specification single or quantity; rewinds mart, Hamrad, Labgear, etc., we have a large and to all types of coils, transformers, etc.; quali- varied stock too numerous to detail in the space fied consulting engineers available to help available. For example we are usually able to solve your problems; first -class service and offer Communications Receiver, tested and delivery.-Millett & Holden, Ltd., 2, Pembury realigned in our workshops, including such well- tr Rd., Westcliff-on -Sea, Essex. [8480 known types as the NATIONAL H.R.O., R.C.A. REWINDS.-Armatures, fields, transformers, AR88, etc. Your enquiry for any particular item pickups, vacuum cleaners, gram. motors, will receive our careful attention. In P.A. Equip- speakers refitted new cones and speech coils, ment we can offer a complete comprising All guaranteed and promptly executed. New outfit WITH CRYSTAL vacuum cleaners, most popular makes. Send A.C. operated Amplifier with Push -Pull D.A.100 timbie 12ín. P.M. Speakers stamped addressed envelope for list of radio output, two in Cabinets with spares and c.o.d. service.- A.D.S. Co., 261 -3 -5, detachable horns and stands, Mixer Panel, Gramo- Turntable and microphone. The ACOS G.P.10 combines purity of re- Lichfield Road, Aston, Birmingham, 6. (8238 phone Complete production with NATIONAL RADIO SERVICE & TELE outfit E75. extreme reliability. A VISION CO. -Trade service engineers; unique flexible assembly renders the For the Short Wave Amateur we stock several crystal immediate service any district; rewinds to all types of transmitting and receiving valves in- types transformers, armatures, motors, loud- virtually unbreakable, while a needle - cluding the EIMAC 100TH at E6, S.T.4074A(RK34) pressure adjustment is incorporated in the speaker cones, speech coils fitted, British and American components and valves; enquiries at E2, 5C/100(813) at L71151 -, Mullard RGI /240A base. Resonance -free response from 50- invited for contract trade service; multiple M.V. Rectifiers at 20/-. V.H.F. receiving types 8,000 cps. Output 1.5 v. at 1,000 cps. Needle transformer winding. -63, High St., St, John's nclude 9002- 12 /10, 9001, 6AK5 -15/.. pressure lk Wood, N.W.8. Primrose 6725. [6752 New component list "W.W." sent on request. ozs. (adjust- DEGALLIER'S, Ltd. -Service with a guarantee. If you cannot get your receiver 44 WIDMORE R4 BROMLEY, KENT able). Vibra- serviced, let American specialists do the job; tion -free arm first-class workmanship only; specialising in 'Phone flVensbouine 0/56 movement. Air -Ring, Belmont, Challenger, Delco, Detrola Flexible coupling A - Screened lead. protects de Wald, Emerson, Ferguson, Garod, Hammer crystal B against breakage. lund, Hallicrafter, Lucille, McMurdo, Silver. Price In Great (Brit. Pat. 579,524. Pats. Midwest, Majestic, Pilot, Philco, Scott, Spar The Popular Britain 44/- (in- pend. abroad). ton, Zenith, R.C.A., etc., also any British set; ' U -BEC" Licensed by Universal cluding P.T). Brush Crystal Co. Ltd. due to lack of accommodation our service Coil branches are still dispersed; therefore apply for Former again Obtainable only from Radio Dealers forwarding instructions before despatching sets; available by re- s.a.e. with all enquiries.- Degallier's, Ltd.. turn of post! BCM /DEG9, London, W.C.1. [8043 Send 2'6 & 21d. COSMOCORD LTD MISCELLANEOUS post ENFIELD: MIDDLESEX SPEECH disability; Mr. H. V. Hemery con- E. W. EVANS sults at Wigmore Hall Studios, W.I. 5, Beckingham Feb. '43, Dec. '46; offers. -K. Oliver REGS Rd., LEICESTER WW.,5, Ennismore Ave., Guildford. [8747 DESIGN LARGE quantities of new unused Ifni -Radio cables, various patterns, for disposal. - Box 2984. [8471 up -to -date beautifully kept 10in records, "ENGINEERING 70 all in covers; E9/10, or near offer. - OPPORTUNITIES" Box 3748. [8853 This unique handbook OR sale, " W.W.," Jan., '41 -Dec., '46. shows the easy way to Offers to Thompson, Rose St., Old Pen - shaw, Durham. [8765a nre` secure A.M.I.Mech.E. EX-A.M. battery units, insert, 60v 5/9, 120v A.M.Brit.I.R.E., A.M.I.E.E.. 10/9, post free-Bulls (W.W.), 246, High City and Guilds, etc. Kad`,rgPn,.tR St., Harlesden, N.W.10. [8652 i WE GUARANTEE VOLUMES 1 to 6 ' Wireless World," bound - publisher's covers; offers,-12, Grove "NO PASS -NO FEE." Park Avenue, Bristol, 4. [8766 ` Details Ql` are given of over 150 MIDGET set cabinets, inside 10,4inx5inx Dipl ,ma cour ses in all 51 /zin, whitewood to finish yourself, un- branches of Civil, Mech., cut; 8/- post free.-9, Wicklow Av., Stockport Elec., Motor, Aero., Radio, OBA steel, fibre ring, lockouts, single and Television and Production twin flange fixing, 2/6 gross (minimum Engineering, 20 gross). -John Downton & Co., 89, High St., Tracing, Building, Epping. Tel. 2163. [8701 THE , Govt. Employment, R.A.F. HM.V. console cabinet, 45fnx25Mx231n, Maths., Matriculation, etc. heavily built; E10; can be seen by ap- SERVICE ENGINEER'S Safeguard you future; send pointment; buyer to collect. -Sculley, 52, for your copy at once-FREE. Ridgeway, Hayes, Kent. [8846 B.t.E.T., 387, SHAKESPEARE HOUSE, REPLACEMENT radiogram chassis, cabi- FIRST CHOICE 7, STRATFORD PLACE, LONDON, W.I. nets, speakers, amps. pick -ups; also mobile and static P.A. equipment.- Radio, Unlimited, 16, Carnarvon Rd., Leyton. [8631 WW., 20 clean bound vols. from Vol. 18 (1926- 1935), £9/10; massive condenser, 100 p.f., 7,000v flashover, £2 /15.- Tranmer, THE "WILLIAMSON" AMPLIFIER " Wandsworth," Burniston, Scarborough. If you are very critical of the reproduction the Continent; D5 school -boy coil, from the average " quality " amplifier, this is TOURcrystal 1, 2 and 3 valve, circuit enclosed; the instrument for you. The designer claims 5/- each from your dealer. -If unobtainable, this to be " virtually distortionless, "to which write Douglas Electronic Industries, Ltd., Announce we would add that the "attack" and Brinklow, Rugby- [8639e and transient response sets quite a new standard. ALUMINIUM chassis panels, any size, 2 NEW KITS We are now producing this amplifier to plain or punched to your requirements. specification with chassis 18 s.w.g., 4 sides, 6x4x2 3/9, 10x6x2 Model 55. 4 valve highly sensitive, first-grade components in 16 s.w.g. 13, Bence Lane, chassis form at 4/6; also in -Mead. 3 wave, battery superhet. Darton, Barnsley. [8650 Components E6, plus P.T. 25/6. Valves 36/, £27.10.0 LARGE quantity of 6BAx11/2fn r.h. plated B'prints 4/-. We shall be happy to arrange demonstrations steels screws; also 6BA brass lockouts; brass also 88. Distortioniess S valve 14 by appointment. other sizes 2, 4, 6, SBA in stock; MODEL watt send us a note of your requirements. Orders are handled in rotation. -John quality amplifier. being strictly Downton & Co., -89, High St., Epping. Tel. approx. Valves 4 gns. A limited number of acoustically designed Components 03 2163 (8699 B'prints 4/ -. cabinets are also available. sure of good reception. -Radio ALLVAYSCraft, 19/6; O.Q. 21/6; Radio News For full details of these new designs send 4d. & Q.S.T. /8; (International),a stamp to MORTON DISMORE k, aturdays E. 55/ Oldchurch Rd., Chingford, E.4 25/21 Post . The TELERADIO Co., 52c full list of all other American magazines, Fore 8 treat, Edmonton, N.18 Phone : SIL. 4987. 157, send s.a.e. to Willen, Ltd. (Dept. 52), 120 'Phone: Tottenham 3386. St, Georges Rd., London, E.10. [8879

www.americanradiohistory.com December, 1947 Wireless World Advertisements 61 RADIO cabinets (midget), hand -made, french polished, chrome speaker grill, Ex- M.O.B. BARGAIN exclusive design, 12x7x6 internal, dial-cut to COULPHONE RADIO "'The Return o Pos. Mall right. 4x3144; 32/6 inc._ dial; c.w.o.; photo Order Service." on 58 DERBY STREET, QRMSKIRK, LANCS. NEW AND UNUSED request to interested uyers. -Burman, 64, Phone: Reighton Rd. Clapton, London. E.5. [8696 Ormsldrk 498. Grams: Coolphone, Ormakir] magazines available. -F.M. and NEW GOODS ONLY. ARICANTelevision, 30/ -; Radio Craft 19/6; C.Q C.W.O. or 0.0.D. Poet Free over 5 / -. MAINS TRANSFORMERS (Amateur Radio), 18/6; Q.B.T. (Amateur PRIMARIES Head i.rití.l Sets Radio), 21/6; Radio News, 25/ -; Audio Engi for 200/30.60 volts. Universal 4, 6 and d.3 v. LT.'.. 300.0 -300 v. 80 mA., 23/6 ; 850.0- V neering, 17/6, incl. one year.-For full list of 350 v. 100 radio and other magazines s.a.e. Willen, Ltd. mA., 28/6 ; 450.0 -450 v. 200 mA. 4 v., 8 a. O.T., 4 v. 4 a. O.T., 4 y. 4 a., 48/-; 450-0 - (Dept. 52), 120, St. George's Rd., E.10. [8239 450 v, 200 mA., 6.3 v. 4 a. O.T., 8.8 v. 4 a. O.T. MieroplLO11 / PLASTIC precision moulding.-Lustroid. 5 v. 5 a., 45/- ' 460 -0 -450 v. 200 mA,, 8.3 v. 8 a. Ltd., Coatbridge, can offer to manufac- O.T., 4 V. 2 a, QT., 4 v. 2 a. QT., 5 v. 8 a., 47/8 ; POET FREE turers almost all materiale : injection and 1, 250 -1,000. 760.0.760 -1,000.1,260 v. 300 mA. (no compression moulding, free technical advice 115/- ; 4 or 8.8 v.6 a. O.T. (Filament), }17/6 and design, prompt quotation, minimum pro- Auto (FUament), 47. to 6.3v. 4a. (or vice verso) 13/6 ' duction delay. -Apply to sole representatives SMOOTHING CHORES VALVES in England and Wales : Foreman & Ellams, 16 H. 40 mA. 380 ohm., 5/ -. BV A an i Ltd., 91 -3, Charterhouse St., London E.0.1. 20 H. 60 mA. 425 ohm., 6/6. MIA an AM Tel. Clerkenwell 3735 and 5, Rumford Place, 15 H. 90 mA. 240 ohm., 7/ -. SEAT C.O.D. Liverpool 3. Tel. Central 1701 (3 lines). 20 H. 100 mA. 425 ohm.. 13/6. ELECTitIC hand drilling machines, inde- 20 H. 200 mA. 150 ohm., 22/6. pendent of mains, 57/6, operates from 30 H. 200 mA. 350 ohm., 25/ -, any 6v or 12v battery, 1,250 r.p.m., on 6v OUTPUT TRANSFORMERS and 2,000 on 12e; can be used for drilling Midget Power Pen., 5 /6. Std. mini., with O.T., 7/6. or easily screwed to bench and used with standard chuck attachments (rotary wire forts 8and i5uitn 22 /6.1EExttra Beevey Doty, 87/6. brush, grinder polishing mop, etc.), fitted with SPECIAL (to author's specification), for quality amplifier, described in April and May berms of Reliance chuck 0 to y4in capacity, ex- Govern- "The Wireless World," 67/6. ment ball race motor, stout leads and quick - grip weight numerous COILS, COIL PACKS, ate. clips, 7%Ib, testi- WEYMOUTH monials available for inspection, carriage 1 /8. TRH, COILS M. and L., with cct, Pair 9/6. ' P " Type, 8/9 es. -E. A. Mason, 153, Manchester Drive, Leigh - SUPERHET on -Sea, Essex. [8642 8 W.H., with cot 465 ko /s pair 11 /8. MOVING COIL EARPIECES WEYMOUTF0,1L PACKS. Completelyalltmed. 3818. WORK WANTED SUPER FEEDER UNIT. 5 waveband. R.F. Stage gear cutting capacity.-Lloyd Magic Made to the stringent specification of Eye. Complete with 5 valves 218 18e. INSTRUMENT& Ramsden, Huntingdon St., Nottingham. I.F. TRANSO'. rumgo,. 18,9 pr. 05.01 darn, 17/6 pr. the Tank Regiment by the leading LIGHT press capacity available up to 25 J.B. MIDGET 2-GANG CONDENSERS. uuuo t/Tr. tons, and assembly, in London area. -Box 11/6 : w /Tr.,12,8. 3-gang L/Tr., 15/6. British manufacturer. Ordinarily KIM 4v. 1437. [8074 MUIRH would cost several pounds retail. CAPACITY available for assembly, wiring. EAD RPRECISION REDUCTIONN DRIVES. 64: 1, 12/6. J.B. Full Vision, 8 : 1,12/8. Despatched in their original packings. testing radio chassis; large or small quantities. -Box 4028. [8755 SUNDRIES Send for our Hats of new and unused ex- can undertake design, research and LINE CORD. .3 amp. 6052 per ft., 2 we 2/8 yd. Govt, Radio Equipment. 8 we 2t6 yd. P.R. Wire, 8d. yd. WEconstruction of radio and electronic MAINS equipment; let us quote you first.-Box 4030. DROPPERS. .3 a. soot 4/6 ; 2 a. 1,00Oí2 4/8. CARBON RESISTORS (5Ót3 to 5 M(2), i w. WIRELESS INSTRUMENTS SMALL firm has capacity for manufacturing 6d. ; 1 w., 9d. (LEEDS) LTD. radio chassis metal cabinets and metal fittings; presswork a speciality; individual or EDDYSTONE SHORT WAVE GEAR. 54 -56, THE 1 HEADROW, LEEDS, quantity orders.-Box ROMAC SUPER Tel. 22262. 3742. [8634 OAR RADIO. VIDOR PORTABLES, yvE make wireless and radiogram cabinets Send Std. stamp for new 24 -page Catalogue. for home and export; immediate deliveries.-Radiac, Ltd., 26, Brondesbury Rd.. London, N.W.6. Maida Vale 8792. [8025 FOXWINDERS, 74a East Hill Wandsworth, 8.W.18, are now able to quote you for your light press work, blank form or piero- I tags, milling, turning and guillotining. [8382 CABINET81 -Large modern factory now has Were capacity available for additional radio cabinet manufacture; we have every facility for "We large-scale productions; let us quote you. - rrtpre55ed3I Box 3745. [8645 E'T' us build that new radio for you; encl. Greatly L receiver is specially designed, under laboratory conditions, to fulfil your most by a leading exacting requirements. -For further details This phrase was used E.D.C.O 24 Belmont Circle. Harrow. Middx Electrical Instrument concern in LARGEALondon old- established public company in connection with with extensive experience of mass - production woodwork and exceptional facilities and resources for the production of radio and gramophone cabinets would welcome enquiries TRANSFORMERS from the trade. -Enquiries to Box 3900. [8665 RAWING and tracing work for radio and D electrical engineering, jig and tool and and light engineering, photoprinting; full sets of drawings undertaken to commercial or Minis- CHOKES try standards. -Drawing & Tracing Ltd., 456a, Ewell Rd., Tolworth, Srbiton. 'Phone Elm- bridge 74na .7703 supplied by us, and is praise to which CAPACITY available for large quantities of we have become accustomed. Our electrical and radio instrument assembly, ALL -WAVE wiring, and final test' 1- 10.000 instruments modern factory is fully equipped efficiently produced; collection and delivery of with vacuum and pressure impreg- components and completed instruments. -E. A. Porritt, 13 and 27, Wastdale Rd., Forest Hill, SIGNAL- nators, and all the latest test 8.E.23 For. 1292. [8635 equipment. RESEARCH engineers with well equipped electrical and mechanical laboratories and GENERATORS Type 5&6 drawing office, are prepared to undertake the POWER RATINGS 8 V.A. to design and /or fabrication of special scientific These high -quality precision instruments 200- 8 K.V.A. and industrial equipment; the organisation is 240 volts AC Type 5, 100 -250 volts AC /DC suited to the design or research on the indus- Type 6, have a coverage of 100 Kc /s to 30 Mc /s AUDIO RATINGS 3 watts to trial electronic and.other fields, also the design in 5 ranges. Calibrated by hand against a and construction of specialised and ancillary 200 watts. apparatus. standard frequency accurate to 0.01 %. Con- -Box 3525, [8559 structed in B.A.60 alloy and finished black LARGE firm of woodworkers are develop- and cream. ing mills, machining, veneering, as- Price 14 Gns, Type 5 or 6. sembly and finishing shops for specialised Immediate delivery. AUSTIN MILLS LTD. production; these shops will be controlled Illustrated leaflets on application to: by men of long technical and practical ex- LOWER CARRS, perience; these nervices will be available shortly and we invite enquiries from firms of gocd standing or their accredited agents; P.R. DEVELOPME11T STOCKPORT the plant is most modern and capable of fabrication of a high -class production; tech- LABORATORIES LTD Established 20 years. Phone : STO 3791 nical service available to prospective clients immediately. -Box 2594. [8325 BRRTIARD ROAD BRADFORD

www.americanradiohistory.com 62 Advertisements Wireless World December, 1947 BUSINESSES FOR SALE OR WANTED AMERICAN RADIO, television, musical instruments and records; sound, well -established business_ 100 kcs. COMMUNICATION RECEIVERS N.W. London, excellent position, large premises, held on long lease at low rent, increas- QUARTZ B.C.312 - BRAND NEW ing turnover; only substantial principals need Here is your chance to obtain a super communication apply. '-Box 3901. [8669 receiver of American design and manufacture. These LANCASHIRE coast.-01d-established radio CRYSTAL seta are absolutelynew and still in the Makers' original and electrical business with excellent liv- waterproof packing cases. Each case contains ing accommodation included. Sole agent for UNIT A-One brand new 80.312 Receiver. leading makers; £3,000 plus e.a.v. Vacant B-A complete set of nine spare Valves. possession on completion. -General Business Type C-A set of eight spare Brushes for the Dynamotor. Transfer Co.. 88, Mosley St., Manchester, 2. D-Four spare Fuses and two spare Dial Lamps. SITUATIONS VACANT E- Complete Technical and Operating Manual. Vacancies advertised are restricted to persons Q5/100 BRIEF SPECIFICATION. or employments excepted from the provisions SIX WAVE BANDS. VALVE LINE UP. of the Control of Engagement Order, 1947. With illuminated Dial. 087 -let R.F. Valve. CROWN Agents for the Colonies.- Applica- for Secondary Frequency Standards 687-2nd R.F. Valve. tions from qualified candidates are In- Accuracy better than 0.01 %. FREQUENCY COVERAGE. 6C5-R.F. Osc. Valve. vited for the following post: - * * New angles Band A - 1,500- 3,000 KCS. 6L7-Mixer Valve. INSPECTOR of Wireless Telegraphs re- of cut give a temperature coefficient of 2 parts in B - 3,000- 5,000 KCB. 887 -1st LF. Valve. quired for Post Office Department, Hong a million per degree Centigrade temperature C - 5,000- 8,000 RCS. 687 -2nd I.F. Valve. Kong,- for 3 years with prospect of per- change. * Vitreous silver electrodes fired direct D - 8,000. 11,000 KM. 6R7 -Ind Dei.. and A.V.C. manency. Commencing salary in scale £475- on to the faces of the crystal itself, giving perman- E -11,000. 19,000 KOS. 6C5-0.W. Ose. Valve. £575 a year according to age and experi- F -14,00048,000 KOS. 6F0 -Audio Output. ence of calibration. * Simple single valve circuit ence. Cost of living allowance on salary of gives strong harmonics at 100 km. intervals up to The set receives its power from a D.O. Dynamotor £475 is £200 for single man and £270 for operating on 12.14 volts, the input power being 50 -60 20 tics. * Octal based mount of compact dimen- married man. Outfit allowance E60. Free PRICE 45/- Post Free watts. This generator compartment is conveniently passages 27 -35 sions. be removed co that a and quarters. Candidates, mounted on hinges and can easily be with ship station Full details /100, including mains power pack can be fitted in its place if necessary. years, must conversant of the Q5 circuit Two sets of 'phones and a speaker can be plugged Into survey, inspection and licensing, and radio are contained In our leaflet Q1. Send stamp the front panel. legislation generally. Must be able to read to -day for your copy. BET, Berne correspondence in French and be INCLUSIVE PRICE FOR£25 THE COMPLETE familiar with British Post Office methods. THE QUARTZ CRYSTAL Co., Ltd. Experience of radio traffic desirable. Prefer- 63 -71 Kingston Road, 10/- carnage extra ence given to candidates possessing City and BULL'S "EX- GOVERNMENT" DEPOT. Guilds certificates in radio communication and NEW MALDEN, SURREY Telephone : MALden 0334 42 -98. WINDMILL HILL, RUISLIP MANOR, MIDDX. P.M.G. first -class certificate. -Apply at once by letter, stating age, whether married or single, and full particulars of qualifications and experience and mentioning this paper to the Crown Agents for the Colonies 4, Mill - bank, London, S.W.1, quoting M/N/18571 on TRANSFORMERS & COILS both letter and envelope. Applications from General Post Office employees should be sub- TO SPECIFICATION. mitted through official channels. [8801 EXPERIENCED radio service engineer re- MANUFACTURED OR REWOUND quired; television an advantage. -State ROTARY CONVERTORS F e, experience, salary to Cropley, 8, Upper JOHN FACTOR LTD., naigh St., Epsom- [8723 220 D.C, to 220 A.C. Details from -. Cattell Ltd.), ENGINEERS wanted to test television re- (Formerly Stanley ceivers in accessible West London area. s` BEETHOVEN ELECTRICEQUIPMENTLTD. Road. N.W.10 9 -I I East Street, TORQUAY, Devon -Please write stating age, experience, and Beethoven Works, Chase London, 'Phone: Torquay 2162 salary required, to Box 4045. [8787 engineer required for development JUNIORof radio components by progressive company in Surbiton area; degree or equivalent in electrical engineering essential.-Box 3903. TUNIOR laboratory assistant with some BROOKES CRYSTALS eJ knowledge of physics and some electrical training. -Write, giving details of experience, LE EST. 1929 LTD. age, etc., to: A. H. Hunt, Ltd., Bendon TE VISION Valley. S.W.18 [8354 The advance in Radio Technique offers unlimited WORKING manager required for test de- opportunities of high pay and secure posts for those partment; must be conversant with the who had the foresight to become YpUR complete testing of marine and commercial Radio Engineers have Fox radio apparatus; only those with experience technically qualified. How you can do this quickly need apply.-Box 3899. [8663 and easily in your spare time is fully explained in our JUNIOR laboratory assistant, 20-22, with unique handbook. Cystc,l some knowledge 36 chemistry, preferably Full details are given of A.M.LE.E., A.M.BriLLR.E. up to inter-B.Sc. standard, for raw material City & Guilds Exams., and particulate of tip-to-date and process testing.- Write, giving details of courses in Wireless Engineering, Radio Servicing, leciuireynents experience, age. etc., to : A. H. Hunt, Ltd. Short Waves, Television, Mathematics, etc., etc. Bendon Valley, S.W.18. [8353 CHARGE -HAND required for collwinding We Guarantee "NO PASS-NO FEE" and transformer assembly department; pre- Prepare for to- morrow's opportunities and post -tear vious experience of coilwinding essential; ex- competition by sending for your copy of this very cellent opening for keen and enthusiastic informative 112 -page guide NOW-FREE. worker. -Apply to Personnel Department, 51/53, GREENWICH CHURCH STREET, Ltd., Blyth Rd., Hayes. BRITISH INSTITUTE OF ENGINEERING E.M.I. Factories, TECHNOLOGY (Dept. 388) LONDON, S.E.10. 'Phone: GRE. 1828 Middx. [8654 GRADUATE development engineer, with 17, Stratford Place, London, W.1 laboratory experience in electronic development; preferably of amplifiers for very low frequencies, biological amplifiers and electronic instruments; eastern outskirts of Lon- don. -Write full details and salary required to IRON DUST Box 3747. [8651 SERVICE engineer with good basin theory COVENTRY CORED COILS and mechanical sense required for trade of Exceptional Efficiency and Stability repairs to quality radios, sound projection and RADIO long AERIAL AND OSCILLATOR, short, medium, or recording equipment, P.A. installations, etc.; SPECIALISTS SINCE 1925 wave, size lin. x lin. 7/8 Pair. small private workshop with latest electronic COMPONENT AERIAL AND OSCILLATOR, medium or long wave, and mechanical equipment. -Precision Services, size lin. x lin. 6/9 pair. Ltd., 8, Hill St., Edinburgh, 2. Tel. 34311 -2. 1948 DUAL WAVE COILS, medium and long wave aerial RADIO trade. -Representatives wanted in and h.f. 9/6 pair. Midlands, Eastern and South Eastern LIST OF RADIO COMPONENTS I.F. TRANSFORMERS, Standard Frequency 465 counties, already calling upon wholesalers and Kc /s. Size, 11n. diem. x 18 in. high. 9/6 each. -selling, established line; MINIATURE ROTARY SWITCH, 4 pole, 3 way, 8/9 retailers, to carry fast NOW READY each. generous commission terms; technical know- Silvered Mica. .0001 mid., 4/- doz. ledge desirable; particularly suited to compo- CONDENSERS, representative. Box A.C.23547, Send for your copy to-day, PRICE 3d. post AVOMETER, Model 7, 519/10/ -. nents -Write details of hundreds of latest All coils fitted with adjustable iron gores, and supplied Samson Clarks, 57 -61, Mortimer St., W.I. paid- Contains with circuit diagram. MURPHY RADIO, Ltd. have a vacancy new components. TERMS : Cash with order or C.O.D. on orders over £1. for a senior engineer having considerable experience in the development and design MONOCHORD RADIO of communication receivers and allied equip- COVENTRY RADIO (Established 1929) ment. -Apply in the first place in writing, giving full particulars and stating salary re- D'UNSTABLE ROAD, LUTON, BEDS. 17 Streatham Hill, London, S. W.2 quired, to : Personnel Department, Murphy Phone : Tube Hill 1051/2. Radio, Ltd., Welwyn Garden City, Herts.

www.americanradiohistory.com December, 1947 Wireless World Advertisements 63 SENIOR development engineer required in television design laboratory; good honours degree in Physics or Engineering and QUALITY REPRODUCERS at least 4 years industrial experience of television receiver development essential.-Appli- cations, giving full particulars of training and experience, to Personnel Manager (Laboratory), Murphy Radio Ltd., Welwyn Garden City, Herts. [8352 appointment offered to assistant LONDONphysicist with a leaning to radio and electrical circuits; applicants should have appropriate theoretical qualifications, and not less than two years' experience, and will be required to develop the electrical aspects of plastics evaluation in a large chemical manufacturing company; the work offers pros- pects for promotion; commencing salary range 6375- £500. -Box 3526. [8560 RADAR company in the Manchester area PORTABLE AMPLIFIERS. P.P. require engineer to supervise preparation AC /18 Twin gram inputs, 15w. 134 gns. of technical handbooks on radar and similar ... apparatus; technical grade required is at least AC /IBHG With mit stage ...... I5} gns. equivalent of C. and G. final; ability to write AC /25 Mic and Gram, 25w. ... 18} gns. PEERLESS technical descriptions and initiative to develop and use new ideas are essential some know- CHASSIS AMPLIFIERS TYPE 1047 RADIO CHASSIS ledge of drafting and printing is desirable. - Reply, giving full particulars of experience, AC /I0 Single EL6, twin gram. ... 8} gns. Those who visited our stand at Radiolympia age and salary required, to Box 3905. [8691 AC /8Q Quality recording, P.P. ... I5} gns. were quick to appreciate that this chassis, with circuit and electro-mechani- AC /WW Wireless Spec. 211 ELECTRONIC World ... gns. its workmanlike design and generous specifica- L cal engineers required for research and All these, described provides the some- development work; good academic and many others, on separate tion, enthusiast with qualifica- leaflets, available upon request. thing out of the ordinary at a reasonable price. tions essential, apprenticeship or industrial or research experience desirable; knowledge of Among its principal features are:- any of the following subjects would be of assist- TO THOSE INTERESTED IN HOME ance, radar and television pulse techniques, CONSTRUCTING Io stage centrimetric components, time -base generators, superhet circuit. ac and do amplifiers, feedback amplifiers, ser- A new impedance matching Transformer. to valves (including magic eye). vors especially low power electro- mechanical, Twelve ratio for quality output stages in single RF stabilised power supply units, data transmis- P.P. Type amplifier. sion systems. gyroscopic applications, table or OP4. 37/6. 2 IF stages. form layouts; some mathematical ability is FULL CATALOGUES DEALING WITH 4 wave bands. desirable.-Write, with full details of qualifications experience, age and salary required, AMPLIFIERS, TRANSFORMERS, SPARES. to Watts push-pull output. to the Personnel Manager, Sperry Gyroscope If your name is not on our register send 3d. Tropicalised components. Co. Ltd., Great West Rd., Brentford, Middx. in stamps at once. M.I. ENGINEERING DEVELOPMENT, Communications enthusiasts should Ltd., have several vacancies for junior HOME - EXPORT - DEALERS write for details of our 1546 Chassis. engineers, and engineers mainly between the ages of 22 and 28; the work requires qualifications of degree standard, or very definite GENERAL LAMINATION PRODUCTS LTD. PEERLESS RADIO LIMITED practical experience in the development field; 294, BROADWAY, BEXLEYHEATH, KENT. 374, Kensington High St., LONDON, W.14 the particular vacancies are for laboratory development and design work at Hayes on various Phone: WEStern 1221 electronic products, including (a) civilian radar equipment, (b) commercial communication receivers and transmitters (c) R.F. generators THE "PER IMET" ELECTRODE for heating purposes, (d) high- quality sound -SPECIALITY GRINDING reproduction, (e) car radio receivers, (f) radio of - Soldering and Brazing Tool receiver componnet, (g) cathode ray tubes, eta: (: fives perfect Joints ou all electrical and in,,trumen please state clearly your age, qualifications and TUNGSTEN CARBIDE work. Operates from 4 or 6 volt Accumulator or Trans experience, salary required and the vacancy or to high precision fine termer. Price Complete with cable and spare Electrode.. type of work in which you are interested, limits including 15 ,'- poet free. addressed to Personnel Department, E.M.I. grooves, forms surface and cylindrical Mains Transformer with tappings for 3 heats, 100 Va Factories, Ltd., Blyth Rd., Hayes, Middx. grinding. output, Price 35'- delivered. SITUATIONS WANTED works manager or similar post S.T. Ltd., 24, Upper Mulgrave Details on request. ASSIS'T'ANTwanted by chief engineer of development. HOLBOROW & CO., company. -Box 3549. [8603 Rd., Cheam, Surrey. Vig. 4250 71, Weymouth Bay Avenue, Weymouth, RADIO engineer, 29, seeks post design or supervisory, experienced electronic & mech anical design; adaptable. -Box 4039. ASSISTANT works manager or similar position, 18 years with leading radio mantes. all branches of production; London area preferred; age 34. -Box 3906. [8697 HILL & CHURCHILL LTD. Prectston -ARMY wireless mechanic seeks opening EX in radio or electronics, little civilian ex- BOOKSELLERS perience, but keenly- interested. -L. A. Law, WOOtLtvolh Bentham, Purton, Swindon. [8692 RA.F. F. /Sgt., experienced radar meth.. SWANAGE, DORSET seeks progressive post in development of Available from : FOR EXPORT ORDERS civilian radar and television; certificates Radio - Stock Comm., 1 and 2, City and Guilds; released Dec. -Box 4121. [8798a. Van Nostrand's "SCIENTIFIC executive, 43, with 26 yrs.' ENCYCLOPEDIA" (a complete ENGINEERradio experience all branches manufacture, specialised knowledge large scale servic- science library in one volume) 2nd We are well equipped for ing, seeks change; 14 yrs.' present employer, edition completely revised highest refs. -Box 4027. [8749 the production of high service engineer, 10 years exp. 1946 65'- EXPERTwith large firm, 5 years exp. public grade veneered cabinets address design, installation and repairs, factory Williams "Thermionic Valve Circuits" 12,6 trained, car radio installation and repairs, seeks "A.R.R.L. Handbook 1947" 13'- in quantity. We invite position abroad, South Africa preferred. -Box 4020. [8737 Lewis "Radio Rece'ver Servicing enquiries for Radio -Gram TUITION and Maintenance " - - - 8;6 Cabinets, Consoles, and RADIO Engineering, Television and Wire- Sarbacher & Edson "Hyper& Ultra High less Telegraphy comprehensive postal Frequency Engineering " - - 36,/- courses of instructiod,-Apply British School other repetition wood- of Telegraphy, Ltd., 179, Clapham Rd., Lon- Rider "Inside the Vacuum Tube " 30,/- don, S.W.9 (Estd. 1906). Also instruction at "Cathode Ray Tube at work. school in wireless for H.M. Merchant Navy and R.A.F. [9249 Work " ------25/- ' ENGINEERING opportunities." -Have you Harrison "Klystron Tubes " - - - 17/6 Timber Licence required L had your copy of this tree guide to Postage extra. A.M.I.Mech.E., A.M.I.E.E., and all branches of engineering, building and plastics? Become STAVRIDI CRAIES technically trained on " no pass -no fee " terms BAXTER & Ltd. for higher pay and security. -For free copy CATALOGUE ON APPLICATION 9 Commercial Road, Edmonton, London, NIB write B.I.E.T. (Dept. 387B), 17, Stratford Place. London, W.I. [8939

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www.americanradiohistory.com Wireless World RADIO AND ELECTRONICS

VOLUME LIII

JANUARY - DECEMBER 1947

Published from the Offices of " WIRELESS WORLD " ILIFFE & SONS LTD., DORSET HOUSE, STAMFORD ST., LONDON, S,E.1

www.americanradiohistory.com GENERAL INDEX To facilitate reference the month of issue as well as the page number is given. The General Index is followed by a Classified Index under the headings of Books, Design, Electronics, Manufacturers' Products, Miscellaneous, Modulation, Organization, Propagation, Radar, Recording, Sound Reproduction, Television, Test and Measurement, Transmission, Valves and Thermionics, Illustrations and Authors. References to Authors, Books and Illustrations appear only in the Classified Index. A.F. Millivoltmeter, G.E.('., 14, Jan. Channels of Communication, by " Cathode Exhibitions (continued) A.V.C. Calculations, by S. W. Amos, 46, Feb. Ray," 223, June ; 261, July (News), 19, Jan. ; 196, June; R.C.M.F., Adcola Miniature Soldering Iron, 462, Dec. Charles Amplifiers " Concerto " Amplifier, Guide to, 137, Apr. ; R ..C.M.F. Report, Additive and Multiplicative Mixing, by J. W. 489, Dec. 177, May ; R.S.O.B. (News), 217, Whitehead, 486, Dec. Cinema Television (News) 335, Sept. June ; 440, Nov. (Correspondence), 489,Dec. ( ircuit Conventions, by Ray," 129, Exports, Domestic Receiver (News), 335, Aerial Aesthetics Sept. - - Coupling in Wide -Band Amplifiers : Apr. Design Data -11: 50, Feb. Colonial Broadcasting, 214, June Inventor, Marconi or Popov ? 338, Component Design Trends, R.C.M.F. Exhibi- F.M. and Dictatorship (Correspondence), 447, Sept. (Editorial), 453, Dec. ; (Cor- tion, 177, May Nov. respon;dence), 487, Dec. Condensers Vacuum, by H. A. H. Griffiths, -- Long Distance (News), 440, Nov. -, Is a Big One Worth While ? by M. G. 23, fan. - -- Receiver Design, by Thomas Roddam, Scroggie, 314, Sept. Consol (N. Ireland) Service Commences 1 : 143, Apr. ; (Correction), 181, May ; System, Amateur Station G8JG, 459, (News), 67, Feb. 2: 203, June - Dec. Corrosion in Steel Chassis, Preventing, 22, Facsimile in U.S.A., 419, Nov. Aerials, Television, by N. M. Best and R. D. Jan. Filters, Tuned A.F., by H. E. Styles, 242, G. Beebe, 293, Aug. ; (Correspondence), Crystal Pickups, by L. J. Wheeler and K. July 282, Aug. ; (Correspondence), 344, Sept. ; 448, Nov. Lockyer, 412, Nov. 308, Aug. ; 344, Sept. Air Navigation (News), 18, Jan. ; (Editorial), -- Valves, 89, Mar. First Steps in V.H.F. Exploration, by 79, Mar. ' Cathode Ray," 15, Jan. Radio, S.B.A.C. Exhibition, 398, Oct. ; DAVENTRY 5XX Closed (News), 97, Mar. Forest, Lee de, 40th Anniversary, 226, June 417, Nov. Deflector Coil Efficiency, by W. T. Cocking, French Television (News), 335, Sept. ; 477, Aircraft Radio Operators' Licences (News), 460, Dec. Dec. 398, Oct. Degrees for Ex- Servicemen (Correspondence), --- Terms of English Origin (Correspond- All -India Radio (News), 296, Aug. 191, May ; 308, Aug. ence), 21, Jan. Amateur Frequencies (News), 216, June ; Design Data : Frequencies for Television (Correspondence), 479, Dec. 10. Wide -Band Amplifiers, 25, Jan. 112, Mar. Effective Use of, (Correspondence), 11. Aerial Coupling in Wide -Band Frequency and Wavelength Classification Amplifiers, 50, Feb. -488, Dec. (Editorials), 117, Apr. ; 157, May ; Societies and Clubs, List, 32, Jan. 12. R.C. Coupling, 131, Apr. (Correspondence), 259, July - Transmitter Licences (News), 249, July 13. Corrected R.C. Coupling, 170, May -Amateurs and the Industry (News), 477, Dec. 14. Resonant R.F. Chokes, 246, July O.E.C. Compact Receiver, 206, June American Colour Television, 192, May 15. Link Coupling, 291, Aug. 297, Aug. Designing an F.M. Receiver, by Thomas G.P.O. and Radio Facilities (News) 397 Oct. F.M. Allocations (News), O.B.S.E. and R.T.R.A. Service - Mien's -Amplifier, High -Quality, by D. T. N. Roddam : 1, 143, Apr. ; (Correction), Register (News), 296, Aug. Williamson, 118, Apr. ; 161, May - 181, May ; 2 : 203, June 267, July Garrard High -Fidelity Pickup, 138, Apr. Amplifiers, Hum in High -Gain, by P. J. Direct Recording Gear, German Listeners (News), 217, June Baxandall, 57, Feb. : (Correction), 97, Domestic Recordings (Correspondence), 258, Mar. July ; 309 Aug. Wide -Band, Design Data -10: 25, Dolci AC /DC Midget, 206, June H.M.S. l'nutleeard, by G. M. Bennett, 80, -, Mar. Jan. 11: 50, Feb. Appointments Bureau (News), 336, Sept. HaS Trainer, by G. W. A. Dummer, 65, Feb. City Allocations (News), E.C.M.E. Automatic Receiver Production. Heterodyning and Modulation, by C. J. Atlantic Frequency 123, Apr. ; Dec. Mitchell, 359, Oct. ; (Correspondence), 439, Nov. (Correction), 478, 87, 479, E.M.I. Developments (Neves), Feb. 448, Nov. ; 488, Dec. ; (Article), by Australian Amateur Frequencies (Neves), 297, Aug. Dec. Institutes (News), J. W. Whitehead, 486, Dec. E.C.M.E.. E.R.A. Report on Interference from R.F. High Audio Frequencies, 415, Nov. Automatic Receiver Production, 326, 122, Apr. Heaters, Sept. High -Quality Amplifier, Design for, by EDITORIALS : D. T. N. Williamson, 118, Apr.: B.B.C. Charter, 1, Jan. 181, May ; 187. B.B.C. and F.M. (News), 05, Mar. Broadcast Licence Changes, 1, Jan. Hum in High -Gain Amplifiers, by P. J. May Wave- Classifying Frequencies and Baxandall, 57, Feb. ; (Correction). Charter (Editorial), 1, Jan. ; (News), lengths, 117, Apr.; (Correspondence). 97, Mar. - 18 Jan. 259, July Jubilee, by P. P. Eckersley, 454, Dec. " Elevated Electrode," 453, Dec. - Transmissions, Qualty of (Correspond- In the Air, 79, Mar. I.B.U. and I.11.0. (News), 397, Oct. : 440 ence), 22, Jan. ; 75, Feb. ; 112, Mar. ; ? 157, May Nov. Live or Recorded (News), 150, Apr. ; 191, May ; 308, Aug. ; Marconi Jubilee, 195, June I.E.E. Premiums 336, Sept. (Editorial), 157, May ; (Article), by Meaningless Superlatives, 157, May - Officers (News), 337, Sept. H. A. Hartley, 396, Oct. National Radio Exhibition, 351, Oct. Radiocommunication C on v en ti on 247, July - 95, Mar. ; 158, May ; List. of Papers. Television Progress (News), Radio Exhibition Plans, 235, July B.I.O.S. now T.I.D,U, (News), 479, Dec. Reading Wireless World, 313, Sept. 181, May and F.M. (Neese), 67, Feb. Report on Interference (News), 215. B.R.E.M.A. Reflections on Olympia. 407, Nov. June B.S.R.A. Conference (News), 95, Mar. or Circuitry ? 39, Feb. ; Symmetry Ignition Interference, by W. Barker Model 148 Speaker, 476, Dec. (Correspondence), 112, Mar. ; 192, Nethercot, Bass Compensation, by J. Ellis, 319, Sept. May 352, Oct. ; 463, Dec. Restoring, 257, July Variable -Mu, 39, Feb. Imhof Record Storage Unit, 329, Sept. Board of Trade Manufacturing Control What is a Broadcasting Station ? 273. Indian Receiving Licences (Nsws), 217, June (News), 96, Mar. Aug. India's New Broadcasting Plan, by " Radia- Boy Scouts' Licences (News), 216, June Wire versus Wireless, 79, Mar. tor," 139, Apr. (News), 190, Interference from R.F. Heaters, R.R.: \. Brit. I.R.E. Radio Convention Ekco A28 : Teat Report, 54, Feb. May ; 248, July ARG37 Radiogramophone, 334, Sept. Report, 326, Sept. Broadcast Licence Changes (Editorial), 1, - C36 Console, 181, May -- Radio (News), 188, May Jan. CR:32 Car Radio Receivers, Interlacing, by W. T. Cocking, 124, Ala. and CR60 International Frequency Allocations (News). Reception for Schools, 327, Sept. 115, Mar. ; (Correction), 186, May -Broadcasting at V.H.F., by Thomas Roddam, V49 AC /DC Receiver, 334, Sept. 439, Nov. (Correction), 478, Dec. 70, Feb. Radiogramophone, 115, Mar. Meeting on Marine Radio Aids (N, in Australia, 245, July " Radiotime " Set, 169, May 248 July - Jubilee, by P. P. Eckersley, 454, Dec. Electro Acoustic Industries P.M. Miniature Standardization (News), 296, Aug. (Neves), -Bush Television, Model T 91 : Test Report, Loudspeaker, 71, Feb. Telecommunications Conferences 323, Sept. Electron Jubilee, Science Museum (News), 96, Mar. ; 187, May 399, Oct. - Television Committee (C.I.T.), 479, Is it Overworked ? by Dec. CABLE and Wireless Nationalization " Electronics," Research (News), 188, May " Cathode 43, Feb. ; (Corres- Ionosphere (News), 133, Apr. Ray," Review, by T. W. Bennington, 108. 220, Tune ; 259, July Calculus and Decency (Correspondence). 21. pondence), - Mar. " (Editorial), 453, Dec. Jan. " Elevated Electrode 1psophone Robot Phone Recorder, 130, Apr. Car Radio Purchase Tax (News), 296, Aug. : Exhibitions B.I.F., 135, Apr. B.I.F., 1948 Is a Big Aerial Worth While ? by M. G. 336, Sept. Scroggie, 314, Sept. Careers in Radio, by A.. U. Thor, 151, Apr. ; (News), 337, Sept. ; Institute of Elect- (Correspondence), -220, June ronics (News), 190, May ; N.P.L., Cathode- ray.Tube Data, by D. W. Thgmas- 307, Aug. ; Olympia 189 May ; 335. JUBILEES and Anniversaries (News), 215. son, 484, Dec. Sept. ; 383, Oct. ; Physical Society June 2

www.americanradiohistory.com VINO Monitors, by W. A. Roberts, 73, Whistling Meteors, D. W. Heightman, Personalities (continued) Feb. T. W. Bennington, 219, June; 399, Oct. ; Brown, O. F., 248, July ; Albert Parsons, 258, July Cadell, Air Comdre. C. S., 217, June ; Who Invented the Aerial ? Luigi Cockburn Dr. Robert, 249, July ; TTERS TO THE EDITOR : Solari, 487, Dec. Cotton; J. H., 216, June ; Denny, Aerial Aesthetics, P. G. Briggs, 489, Licence Changes, Broadcast, (Editorial), 1, C. R., 478, Dec. Donisthorpe, Dec. Jan. H. de A., 217, June ; Entwisle, G. W., Amateur Frequencies, "Etheris," 488, Licences, Broadcast, (News), 96, Mar. ; 68, Feb. ; Fisk, Sir Ernest, 478, Dec. 133, Apr. ; 189, May ; 217, June ; Dec. ; Fortescue, Prof. C. L., 19, Amateurs on E. H. F., E. R. Westlake, 249, July ; 298, 297, Aug. ; 337, Jan. ; Garro- Jones, G. M., 67, Feb. ; 258, July Sept. ; 399, Oct. ; 440, Nov. ; 478, Gill, A. J., 68, Feb. ; Goyder, C. W., Amplitude Control in R.C. Oscillators, Dec. 217, June Hopkins, Dr. H. G., 399, E. J. B. Willey, 219, June Link Coupling, Design Data -15 : 291, Aug. Oct. ; Howe, Prof. G. W. O., 249, Calculus and Decency, E. M. Crook, Loudspeaker Damping (Correspondence), July ; Jackson, Prof. Willis, 248, " Cathode Ray," 21, Jan. 309, Aug. ; 343, Sept. ; 401, Oct. ; July ; Jefferson, H., 189, May ; Careers in Radio, R. J. Woodhams, 447, Nov. ; 487, Dec. ; (Article), by Jones, Eric E., 217 June ; Kirke, 220, June H:. A. Hartley, 398, Oct. H. L., 249, July ; Lyttleton, Rt. Hon. Degrees for Ex- Servicemen, O. S. Oliver, 399 Oct. ; MacLarty, B. N., Puckle, 191, May ; 308, Aug. µ IS OVERWORKED (Correspondence), 74, 478, Dec. ; llacauley, T. A., 189, May ; Domestic Recordings, A. J. Little, Feb. Moss, Hilary, 478, Dec. ; Paris, Dr. 258, July ; D. W. Melons, 309 " Magic Eye " Indicators, by G. O. Thacker E. T., 399, Oct. ; Paterson, Sir Aug. and B. Y. Walker, 30, Jan. ; (Corres- Clifford 248 July ; 297, Aug. ; Educating the Public, T. H. Kinman, pondence), 150 Apr. Pete; Major L. H., 217, June ; Pul- 192, May Magnetic Recorder, JPele -Tech Abstract, 88, ling, M. J. L., 440, Nov. ; Reid, Electronics, L. Wafer, 259, July Mar. Andrew, 217, June ; Renwick, Sir F.M. and Dictatorship, P. P. Eckers- Tape Recording, 335, Sept. Robt., 189, May ; Ross, W., 399, Oct. ; ley, 447, Nov. Units, by " Cathode Ray," 339, Sept.; Rowe, Albert P., 249, July ; Scott, French Terms of English Origin, E. - (Correction), 447, Nov. J. M. C., 399, Oct. Smith, Sir Frank, Aisberg, 21, Jan. Magnetophon Recorder, B.I.O.S. Report, 399, Oct. ; Smith -Rose Dr. R. L., Frequencies for Television, D. W. 128, Apr. 336, Sept. ; 399, Oct. Strong, C. E., Heightman, 112, Mar. Mains Transformer Protection, F. R. W. 336, Sept. ; Watson -Watt, Sir Robt., Frequency Bands, W. E. Webber, Strafford, 51, Feb. ; (Correction), 94, 19, Jan. ; 68, Feb. ; 249, July ; 259, July Mar. Williams, Dr. Emrys, 336, Sept. ; Heterodyning and Modulation, M. G. Marconi Jubilee (News), 188, May ; (Editor- Williams, Dr. F. C., 19 Jan. ; Williams, Scroggie, 448, Nov. ; t. R. ial), 195, June J. H., 217, June ; Williams, R. C. G., Sturley, 488, Dec. Memorial (News), 297, Aug. 96, Mar. Loudspeaker Damping, F. Langford - or Popov, Aerial Inventor ? 338, Sept. ; Philco Car Radio, 94, Mar. Smith, 309, Aug. G. N. Patchett, (Editorial), 453, Dec. ; (Corres- A536W Receiver, 169, May P. J. Walker, C. J. Mitchell, pondence), 487, Dec. A746ARG Radiogramophone, 334, Sept. E. J. James, 343, Sept. J. H. Television Link, 284, Aug. -Philips 20911 Miniature Superhet, 64, Feb. D. Walton, D. T. N. Williamson, -Marine Radio Aids Conference (News), 187, 462A Receiver, 169 May 401, Oct. ; A. E. Cawkell, May - F0509 Communication Set 188; May J. S. Smith, 447, Nov. ; P. G. Maximum (News), 400, Oct. - MZ600 Transmitters 202, June Price Orders A. H. Voigt, 487, Dec. Measuring Gear at Stockholm, 320, Sept. -Physical Society's Exhibition, 196, June µ- Confusion, G. F. Dalton, L. Bain- Merchant Ship Equipment, 405, Oct. Pickup, Sensitive S.E.S., 10, Jan. bridge Bell, W. R. Ferris, 74, Metal Lenses for Radio, by " Cathode Ray," Variable Resistance, 66, Feb. Feb. 84, Mar. -Pickups, Moving Iron, by E. H. Francis, 285, " Magic Eye " as Null Indicator, Micovac Test Meter, 445, Nov. Aug. D. A. Ward, 150, Apr. Microphone Pre -Amplifier, by R. Selby, 239, Police Radio, 457, Dec. " Magnetic Units " : A Correction, July Popov or Marconi ? Aerial Inventor 338, " Cathode Ray," 447, Nov. Mobile Radio Telephone, 357, Oct. Sept. ; (Editorial), 453, Dec. ; (Correa- Protecting Pilot Lamps, B. J. Axien, Modern Marine Radio, by D. F. Bowers and ' pondence), 487, Dec. 75, Feb. E. F. Cranston, 221, June Positive and Negative, by A. B. Vaughan, 260, Purchase Tax on Listening, R. C. Moving-Coil Headphones, S. G. Brown, 56, July Bell, 344, Sept. Feb. Pre -Emphasis and De- Emphasis, by " Cathode Push -Pull Phase Splitter, G. Potter, Microphone, Lustraphone, 140, Ray," 183, May 402, Oct. Apr. Projection Television, 227, June Quality of B.B.C. Transmission, Moving -Iron Pickups, by E. H. Francis, 285, Protecting Pilot Lamps (Correspondence), 74, H. A. Hartley, 22, Jan. ; 191, Aug. Feb. May ; H. Temple, 75, Feb. ; Mullard MAS305 Receiver, 206, June Provincial Television (News), 187, May H. Bishop, 112, Mar.; F. Multitone MT3 Miniature Hearing Aid, 220, Purchase Tax on Kits (News), 132, Apr. Duerden, 150, Apr. ; G. R. W. June Push -Pull Balance, by W. T. Cocking, 408, Lewis, 308, Aug. Murphy A104R Radiogramophone, 206, June Nov. Shorthand Circuit Symbols, V. E. 122C Baffie Set, 334, Sept. - Phase Splitter, by E. Jeffery, 274, Walker, J. E. Perrin, 191, May Aug. ; (Correction), 318, Sept. ; Squegger, H. J. Round, 258, Judy ; N.P.L. Annual Exhibition, 307, Aug. (Correspondence), 402, Oct. L. Bainbridge Bell, 309, Aug. National Certificate in Physics (News), 247, Standard Valves, J. Sparrow, 22, July "Q" COIL Pack 416, Nov. Jan. ; R. G. Parr, 74, Feb. ; Naval Radio Expansion, by G. M. Bennett, 6, Quality of B.B.C. Transmission (Corres- W. Galbraith, 150, Apr. Jan. pondence), 22, Jan. ; 76, Feb. ; 112, Super -regen. in St. Helena, J. H. Gear, by G. M. Bennett, 62, Feb. Mar. ; 150, Apr. ; 191 May 308, Jameson, 21, Jan. - Wireless Reserve (News), 187, May Aug. ; (Editorial), 157, May ; (Article), Symmetry or Circuitry ? J. H.. 112, New Receiving Valves, Mazda and Mullard, by H. A. Hartley, 396, Oct. Mar. 228, June Superheterodyne, by S. A. Knight, 472, Technical Assistants, W. H. Cazaly, Noise Factor, by L. A. Moxon, 2 : 11, Jan. ; Dec. 75, Feb.; Thomas Roddam, 113, (Correction), 77, Feb. ; 3 : 171, May Mar. R.C. Coupling: Design Data -12 and 13: 131, Television Aerials, F. R. W. Strafford, OBITUARY : Denham, W., 478, Dec. ; Apr. ; 170, May J. N. Pateman 344, Sept. ; Hayburn, F. S., 478, Dec. Heaver, Oscillator Control, by B. J. Solley, 321, N. M. Best, 448, Nov. E. F., 68, Feb. ; Leedham, Air Sept. Afloat, C. E. Tatham, 489, Dec. Comdre. H., 478, Dec. ; Miles, Lt, -Col. Oscillators, Amplitude Control in and Thunderstorms, E. G. Hill, W. G. H., 189, May ; Odhams, E. L., - (Correspondence), 219, June - 344, Sept. 189, May ; Vyvyan, R. N., 68, Feb. R.C.E.E.A. Officers (News), 134, Apr. Cinema Merger ? James N. Olympia 1947 (Editorials), 235, July ; 351, R.C.M.F. Report (News), 215, June - Roe, 447, Nov. Oct. ; 407, Nov. ; (News), 335, Sept. ; R.F. Chokes, Resonant, Design Data -14: Deflector Coils, W. J. Dawson, List of Exhibitors and Stand -to -Stand 246, July - 309, Aug. Report, 362, Oct. ; Show Review, 423, Tuning Wand, A. and H. White, 265, Synchronization, A. W. Keen, Nov. - July -220, June R.G.D. 746G Radiogramophone, 334, Sept. The -tron Family, L. H. Bainbridge P.I.C.A.O. Report (News), 215, June R.S.G.B. Council (News), 134, Apr. Bell, 150, Apr. ; W. C. White, Permanent Magnets, by " Cathode Ray," 300, D.F. Contest, 259, July 402, Oct. Aug. - Officers (News), 479, Dec. Thyratron Action, Wm. H. P. Leslie, PERSONALITIES : Angwin, Col. Sir Membership (News), 67, Feb. " Cathode Ray," 220, June Stanley, 68, Feb. ; 189, May ; 297, -R.T.R.A. and G.R.S.E. Service -Men's Tuned A. F. Filters, Thomas Roddam, Aug. ; Appleton, Sir Edward, 216, Register (News), 296, Aug. 308, Aug. ; Henry Morgan, June ; 249, July ; 297, Aug. ; 398, Radial Time Bases, by G. W. A. Dummer and 344, Sept. Oct. ; Bareford, Dr. C. F., 68, Feb. ; E. Franklin, 287, Aug. Universal Transformer, A. E. Brown, Barrell, W. S., 440, Nov. ; Barton, Radio Aids to Marine Navigation (News), 215, 112, Mar. F. S., 440, Nov. ; Bedford, L. H., June V.H.F. for Trunk Communications 336, Sept. ; Benham, W. E., 398, Oct. ; Radio- communication Developments, I.E.E. (Wire or Wireless) ? D. A. Bell, Birkinhaw, D. C., 398, Oct. ; Bishop, Convention, 158, May ; List of Papers, 308, Aug. Harold, 399, Oct. Booker, Dr. H. G., 181, May a www.americanradiohistory.com Radio Compasses, 417, Nov. Standard Frequency Broadcasts (News), 132, Thrush Capacitance Resistance Bridge, 25 Exhibition Plans (Editorial), 236, July Apr. ; 439, Nov. July - Telephony for Tugs (News), 296, Aug. Valves (Correspondence), 22, Jan. ; 74, Transformers, Obvious and Otherwise, -Radio Industry, by D. A. Bell, 27, Jan. - Feb. ; 150, Apr. " Cathode Ray," 388, Oct. Interference Conference, C.I.S.P.R. Superhet Foundation Kit, 290, Aug. Tropical Broadcasting, by " Radiator," 13 - (News), 67, Feb. Superheterodyne, Quality, by S. A. Knight, Apr. Navigation Aids, by J. A. McGillivray, 472, Dec. Tuned A.F. Filters, by H. E. Styles, 24 - 146, Apr. Super-regeneration in St. Helena (Correspond- July ; 282, Aug. ; ( Corresponde on the Royal Train, 29, Jan. ence), 21, Jan. 308, Aug. ; 344, Sept. -RANDOM RADIATIONS, by " Diallist," Super-regenerative V.H.F. Receiver, by Tuning Circuits, by " Cathode Ray," 44 35, Jan. ; 76, Feb. ; 114, Mar. ; " Cathode Ray," 15, Jan. Nov. 154, Apr. ; 182, May ; 231, June ; Symbols, Shorthand Circuit, by A. W. Keen, 266, July ; 310, Aug. ; 348, Sept. ; 99, Mar. ; (Correspondence), 191, May ULTRA U51 AC /DC Superhet, 334, Sep 404, Oct. 450, Nov. ; 490, Dec. Symmetry or Circuitry ? (Editorial), 39, UNBIASED, by Free Grid, 34, Jan. ; 7 Receiver Remote Control, by J. F. O. Feb. ; (Correspondence), 112, Mar. ; Feb. ; 102, Mar. ; 136, Apr. ; 23 Vaughan, 212, June; 346, Sept. 192, May June ; 268, July ; 299, Aug. ; 34 46 RECENT INVENTIONS, 38, Jan. ; 78, Sept.; 387, Oct.; 446, Nov.; Feb. ; 116, Mar. ; 156, Apr. ; 194, TECHNICAL Apprentices, T.R.E. and Dec. May ; 234, June ; 272, July ; 312, S.R.D.E. (News), 440, Nov. Aug.; 350, Sept.; 406, Oct.; 452, Assistants (Correspondence), 75, Feb. ; %66R Communication Receiver, 36, Jan. Nov. - 113, Mar. V.H.F. Aircraft Equipment, 306, Aug. Rediffusion Response Curve Tracer, 226, June Telecommunication Engineering & Manu- Broadcasting, by Thomas Roddam, 7 Rees Mace EL80 Universal Receiver, 115, facturing Association (News), 133, Apr. Feb. Mar. Telegraph Key Design, Marconi's, 61 Feb. Super- regenerative Receiver, 77, Television E.H.T. Supply, by W. T. Cocking, - " Cathode Ray," 15, Jan. All -Dry Portable, Feb. - SC 70 Portable, 206, June 207, June Transmitter- Receiver, 269, July (News), 440, Aerials, by N. M. Best and R. D. -Vacuum Condensers, by H. A. H. Griffith Research,- T.R.E. and D.S.I.R. Nov. - Beebe, 293, Aug. ; (Correspondence), 23, Jan. Roberts Fault Analyser, 170, May 344, Sept. ; 448, Nov. Vairadio Heavy Duty Converter, 228, Jun Rotating Dual Aerial System, 459, Dec. Afloat (Correspondence), 489, Dec. Valve Equivalent Generator, Circuit Co - and Thunderstorms (Correspondence), ventions, by " Cathode Ray," 12 - 344, Sept. Apr. S.B.A. Interference with Television (News), O.B. Vehicle, 241, July Prices (News), 18, Jan. -- Type B8 477, Dec. Receiver Construction : - Standardization, A.V.A. Safety in the Air, by J. A. McGillivray, 146, - 1. Deflector Coils: General Principles, 176, May Apr. 2, Jan. Voltmeter, by H. W. Baxte-, 9, Jan. -Tungsram All -Stage Valve, 483, 2. Line Deflector Coils : Winding - (Correction), 56, Feb. Sargrove Dec. Data, 40, Feb. ; (Correspond- Variable -Mu (Editorial), 39, Feb. Schools, Broadcast Reception for, 327, Sept. ence), 309, Aug. Resistance Pickup, 66, Feb. Sensitive Photo- Electric Relay, 270, July 3. Frame Coil Winding and Deflec- -Vitavox " Bitone " Loudspeaker, 153, Apr. Service -Men's Register (News), 296, Aug. tion Yoke Assembly, 103, Mar. ; SHORT -WAVE CONDITIONS, by T. W. (Correspondence), 309, Aug. WEATHER Ships (News), 398, Oct. 36 Bennington, 8, Jan. ; 53, Feb. ; 88, 4. Frame Time - Base and Sync Wharfdale Corner Cabinet Loudspeaker, Mar. ; 140, Apr. 176, May ; 232, Separator, 164, May ; (Corre- Oct. ? June ; 264, July 277, Aug. ; 329, spondence), 220, June What is a Broadcasting Station (Editorial Sept. ; 403, Oct. 448, Nov. ; 485, 5. Line Time -Base and E.A.T. 273, Aug. Dec. Supply, 251, July Whistling Meteors, by G. R. M. Garrott, 14 Short Waves for Pleasure, by Thomas 6. Cathode -Ray Tube Mounting, Apr. ; (Correspondence), 219, June Roddam, 358, Oct. 278, Aug. 258, July Shorthand Circuit Symbols, by A. W. Keen, 7. The Receiver Unit, 330, Sept. Wire Broadcasting, Multi- Broadcast Ltd., 31 99, Mar. ; (Correspondence), 191, May 8. The Receiver Unit, 391, Oct. Jan. 9. 420, Nov. or Wireless ? by Thomas Roddam, 236 Sidebands Again, by " Cathode Ray," 468, Power Unit, 308, Aug. and Conclusion, - July ; (Correspondence), Dec. 10. Operating Notes Mar. Simple Valve Voltmeter, by H. W. Baxter, 9, 481, Dec. versus Wireless (Editorial), 79. 56, (News), 215, June -Wireless World, Reading (Editorial), 313 Jan. (Correction), Feb. Television Relay Stations Six -Metre Transatlantic Signals, by R. Signal Generator, 250, July Sept. Woden Amplifiers, 111, Mar. Naismith, 186, May ; (Correspond- - Synchronizing, by W. T. Cocking, 90, 18, Jan: ; 67 ence), 258, July ; (News), 18, Jan. Mar. WORLD OF WIRELESS, - ; ; 132, Apr. 187 Sobell 516 TG Radiogramophone and 717 Terminology (News), 477, Dec. Feb. ; 95, Mar. ; July ; 296 Receiver, 257, July Test Prod, Clip -on, 240, July May ; 215, June 247, ; 335, Sept. ; 397, Oct. ; 439 Squegger (Correspondence), 258, July; 309, The -tron Family (Correspondence), 150, Apr. ; Aug. Aug. 402, Oct. Nov. ; 477, Dec. CLASSIFIED INDEX (All entries except Bo oks, Illustrations and Authors also appear in the General Index.)

Radio Navigation : Radar and Positio BOOKS Handbook of Industrial Deposition, 358, Oct. in Marin A.R.R.L. 1947 Handbook, 220, June I.E.E. Report on Radio Research, 336, Sept. Fixing Systems for Use Navigation, 42 Feb. Amplifiers for High- Quality Sound Repro- Marconi Instrumentation, 247, July (St G.E.C., 471, Dec. Metre Second System of Electrical Radio Operating Questions and Answers duction, -Kilogram- Edition), by Arthur R. Nilson and An Introduction to Transmission Lines, by Units, by R. K. Sas and F. B. Pidduck Aug. C. J. Mitchell (Review). 83, Mar. (Review), 345, Sept. J. L. Hornung, 295, Radio Receiver Servicing and Maintenance B.B.C. Year Book, 216, June Music and Sound Systems in Industry, by 238, Bomber Offensive, by Sir Arthur Harris B. E. Benson, 218, June Edition), by E. J. G. Lewis, J4thuly (Review), 113. Mar. Official Used Radio Set Values (Wireless by Rufus P. Turner, British Standards Year Book, 1946, 19, Jan. Trader), 19, Jan. Radio Test Instruments, C. & W. Press Handbook. 390, Oct. P.I.C.A.O. Demonstration of Radio Aids to 390, Oct. Calculating Machines, by D. R. Hartree, 342, Civil Aviation, Sept. 1946, 478, Dec. Radio Valve Vade Mecum, 1947 Supplement, 83, Mar. Sept. Plastics for Electrical and Radio Engineers, 31, Capacitors, Their Use in Electronic Circuits, by W. J. Tucker and R. S. Roberts Reference Data for Radio Engineers, Jan. ; 459, Dec. by M. Brotherton, 284, Aug. (Review), 37, Jan. by Richard -Ray Tube Handbook (2nd Edition), Mechanics for All, Edited by Leroy School Broadcasting in Britain, Cathode Practical Palmer, 459, Dec. by S. K. Lewer, 284, Aug. A. Beaufoy, 414, Nov. 155, Through the Ages. by Alfred Professional Electrical Service Valve Equivalents, R.S.G.B., Communication Practical Training of Apr. Still, 295, Aug. Engineers, I.E.E. and R.I.C., 292, 238, July Drafting for Electronics, by L. F. B. Carini, Short -Wave Listeners' Annual, 342, Sept. Principles gand Practice of Wave Guides, by Sound Motion Pictures Recording and Electrical Transmission in Steady State, by L. G. H. Huxley (Review), 492 Dec. Reproducing, by James R. Cameron Paul J. Selgin, 238, July Principles of Radar, Massachusetts Institute (Review), 422, Nov. Electronic Developments, by K. G. Britton, of Technology (Review), 222, June Survey of Existing Information and D. 238, July Principles of Radio for Operators, by Ralph on Radio Noise Over the Frequcr. Elementary Radio Servicing by William R. Atherton, 238, July Range 1 -30 Mc /s, D.S.I.R., 489, L Wellman (Review), 390, Oct. R.C.M.F. Export Catalogue, 18, Jan. Television, R.C.A. Papers, 322, Sept. Evolution of Activated Resin Solder, Enth- Radar Engineering, by Donald G. Fink Television Bibliography, R.C.A., 134, Apr. oven, 290, Aug. 345, Sept. Television Explained, by W. E. Miller, 459 Science, Institute of Physics, (Review), Experimental Radar System Engineering, Edited by L. N. Dec. 247, July Receiving Equipment, by W. T. F.M. Radio Handbook, Edited by Milton B. Ridenour (Review), 492, Dec. Television Radio Aids to Marine Navigation, 19, Jan. Cocking, 89, Mar. Sleeper (Review), 260, July by Milton S. River by G. Windred (Review), Radio Amateur Call Book, 26, Jan. Television Simplified, Gas -Filled Triode, (Review), 422, Nov. 36, Jan. Radio -Craft Library 414, Nov. 4 www.americanradiohistory.com in and Its Usess Tin Research Institute, 22, Lustraphone Moving -Coil Microphone, 140, Positive and Negative, by A. B. Vaughan, Jan. Apr. 260, July Trader Year Book, 1947, 134, Apr. Marconi's Mobile Radio Telephone, 357, Oct. Pre-emphasis and De- emphasis, by " Cathode Two -Way Radio, by Samuel Freedman. 414, Telegraph Key Design, 61, Feb. Ray, 183, May Nov. --- Radio Compass, 417, Nov. Radio Industry, by D. A. Bell, 27, Jan. Mazda 6: Milliard Receiving Valves, 228, June Radio on the Royal Train, 29, Jan. Morgan Osborne " Q " Coil Pack, 416, Nov, Rotating Dual Aerial System, 459, Dec. DES ION Safety in by A. McGillivray, 146, Calculations, by S. W. Amos, 46, Feb. Mullard MAS305 Receiver, 206, June the Air, J. A.V.C. Multi- Broadcast (Engineering) Ltd., Wire Apr. omponent Design Trends, R.C.M.F. Exhi- Short Waves for Pleasure, by Thomas bition, 177, May Broadcasting, 31, Jan. Multitone MT3 Hearing Aid, 220, June Roddam, 358, Oct. Design Data : Symbols, by A. W. Keen, 10, Wide -Band Amplifiers, 25, Jan. Murphy A104R Radiogramophone, 206, June Shorthand Circuit 99, Mar. ; (Correspondence), 191, May 11. Aerial Coupling in Wide -Band -- 122C Baffle Set, 334, Sept. 258, July ; 309, Amplifiers, 50, Feb. Philco Car Receiver, 94, Mar. Squegger (Correspondence), 536W Receiver, 169, May Aug. 12. R.C. Coupling, 131, Apr. -A T.R.E. and S.R.D.E. 13 Corrected R.C. Coupling, 170, May A746ARG Radiogramophone, 334, Sept. Technical pprentices, -Philips 209U Miniature Superhet, 64, Feb. (News), 440, Nov. 14. Resonant R.F. Chokes, 246, July (News), 477, Dec. 15. Link Coupling, 291, Aug. 462A Receiver, 169, May Terminology - F0509 Communication leceiver, 188, Transformers, Obvious and Otherwise, by Designing an F.M. Receiver, by Thomas -- May " Cathode Ray," 388, Oct. Boddam, 1 : 143, Apr. ; (C`orrection), MZ600 Transmitters 202, June Tuning Circuits, by Cathode Ray," 442, 181, May ; 2 : 203, June Nov. Steps in V.H.F. Exploration, by " Cath- Plessey Miniature VJI.F. Transmitter- First Receiver, 269, July Variable -mu (Editorial), 39, Feb. ode Ray," 15, Jan. Weather Ships (News), 398, Oct. High -Quality Amplifier, Design for, by D. T. - Premier Superhet Foundation Kit, 290, Aug. Pye Radio Telephony for Tugs (News), Whistling Meteors, by G. R. M. Garratt, 141, 118, Apr. ; 161, May N. Williamson, (Correspondence), 219, June ; Bum in High -Gain Amplifiers, by P. ,l. 296, Aug. Apr. Vehicle, 241 July 258, July ; (Correction), Television O.B. Baxandail, 57, Feb. ? 236, -R,G,D.746G Radiogramophone, tá34, Sept. \Vire or Wireless by Thomas Roddam, 97, Mar. ; (Correspondence), 308, Aug. Magic " Indicators, by G. O. Thacker Radiolympla, 364, Oct. ; Show Review, June " Eye 423, and B. Y. Walker, 30, Jan. ; (Corres- Nov. lta,ìiovision V55R Communication Receiver, MODULATION pondence), 150, Apr. Mixing, by J. W. Microphone Pre -Amplifier, by R. Selby, 36, Jan. Additive and Multiplicative 239, July Rediffusion Response Curve Tracer, 226, June Whitehead, 486, Dec. Bees Mace All-dry Portable, 77, Feb, B.B.C. and F.M. (News), 95, Mar.; 187, May Noise Factor -3: Design of Receivers or by Thomas Amplifiers for Minimum Noise Factor, SC70 Portable, 206, June Broadcasting at V.H.F., Roddam, - EL80, Universal Receiver 115, Mar. 70, Feb. by L. A. Moxon, 171, May Modulation, by C. J. Push -Pull Balance, by W. T. Clocking, 408, Roberts Fault Analyser, 170, May Heterodyning and Nov. Sobell 516 TO Table Radiogramophone and Mitchell, 359, Oct. ; ( Correspondence), Phase Splitter, by E. Jeffery, 274, 717 Receiver, 257 July 448 Nov. ; 488, Dec. ; (Article), by Southern Electronic Industries Sensitive J. W. Whitehead, 486, Dec. Aug. ; (Correction), 318, Sept. ; Pickup, 10, Jan. Sidebands Again, by " Cathode Ray," 468, (Correspondence), 402, Oct. Dee. Quality Superheterodyne, by S. A. Knight, Standard Telephones V.H.F. Aircraft Equipment, 306, Aug. 472, Dec. IZAT ION Receiver Remote Control, by J. F. O. Technifon Direct Ìtecording Gear, 267, July ORGAN Thrush Capacitance Resistance Bridge, Air Navigation (News), 18, Jan. Vaughan, 212, June; 346, Sept. Aircraft Radio Operators' Licences (News), Symmetry or Circuitry ? (Editorial), 39, 258, July Ultra U51 A.C. /D.C. Superhet, 334, Sept. 398 Oct.. Feb. ; (Correspondence), 112, Mar. ; Clubs, 32, Jan. 192, May Vacuum Physical Laboratories Vacuum Con- Amateur Societies and List, Test Prod, Clip -on, 240, July densers, 23, Jan. Australian Broadcasting, 245, July Tuned A.F. Filters, by H. E. Styles, f42, Valradio Heavy Duty Converter, 228, June B.B.C. and F.M. (News), 95 Mar.; 187, May Vitavox " Bitone " Loudspeaker, 153, Apr. Charter 1947 -1952 (Editorial), 1, .Tan. ; July ; 282, Aug. ; (Correspondence). - :10s. Aug.: 344. Sept. Wharfedale Corner Cabinet Loudspeaker, 361, (News), 18, Jan. Oct. Board of Trade Manufacturing Control White A. & H., R.F. Tuning Wand, 265. (News), 96, Mar. ELECTRON ICS July !toy Scouts' Licences (News), 216, June G.E.C. Radio Compass, 417, Nov. Woden Amplifiers, 111, Mar. Broadcast Licence Changes (Editorial), 1, Interference from R.F. Heaters, E.R.A. Jan. Report, 326, Sept. Car Radio Purchase Tax (News), 296, Aug. Is "Electronics" Overworked? by "Cathode MISCELLANEOUS 336, Sept. Ray," 43, Feb. ; (Correspondence), Aerial Inventor, Marconi or Popov ?, 338, Colonial Broadcasting, 214, June ; 259, 220, Joie July Sept. ; (Editorial), 453, Dec. ; (Corres- Frequency and Wavelength Classification " Magic Eye " Indicators, by G. O. Thacker pondence), 487, Dec. (Editorials), 117, Apr. ; 157, May ; and B. Y. Walker, 30, Jan. ; (Corres- Air Navigation (Editorial), 79, Mar. (Correspondence), 269, July pondence), 150, April Amateur Frequencies, Effective Use of', G.P.O. and Radio Facilities (News), 397, Oct. Marconi's Radio Compass, 417, Nov. (Correspondence), 488 Dec. I.B.U. and I.B.O. (News), :397, Get. ; 440. Sensitive Photo- Electric Relay, 270, July Broadcasting Jubilee, by F'. P. Eckersley. Nov. 454, Dec. LE,E. Radiocommunication Convention, 95, MANUFACTURERS' PRODUCTS Careers in Radio, by A. U. Thor, 153, Apr. : Mar. ; (Survey), 158, May ; (List of Adcola Miniature Soldering Iron, 462, Dec. (Correspondence), 220, June Papers), 181, May All Power Transformers' Television Signal Channels of Communication, by " Cathode Report on interference (News), 215, Generator. 250, July Ray," 223, June ; 261, July - June \udix Broadcast Equipment for Schools. Circuit Conventions, by " Cathode Ray." Interference, Radio (News), 188, May 327, Sept. 129, Apr. International Frequency Allocations (News), II.T: H. Crystal Set, 462, Dec. Elevated Electrode (Editorial), 453, Dec. 439, Nov. ; (Correction), 478, Dec. Barker 148 Speaker, 476, Dec. Exports Table, Domestic Receivers (News). - Standardization (News), 296, Aug. Brown, S. G., Moving -Coll Headphones, 56, 335, Sept. Telecommunications Conference, Mos- Feb. Facsimile in U.S.A., 419, Nov. cow (News), 96, Mar. Bush T91 Television Receiver, 323, Sept, Forest, Lee de, 40th Anniversary, 226, June --- Telecommunications Conference, Atlan- n icon " Switchmatic " No, 700 Remote H.M.S. Vanguard, by G. M. Bennett, 80, tic City (News), 187, May Control Unit, 346, Sept. Mar, Marine Radio Aids Conference (News), 187, harles Amplifiers " Concerto " Amplifier, Ignition Interference, by W. Nethercot, 352. May 489, Dec. Oct. ; 463, Dec. Merchant Ship Equipment, 405, Oct. Dulci A.C. /D.C. Midget, 206, June is a Big Aerial Worth While ? by M. G. Naval Radio Expansion, by G. M. Bennett, 6, E,C,M.E. Automatic Receiver Production. Scroggie, 314, Sept. ,Tan, 123, Apr. Magnetic Units, by " Cathode Ray," 339, -- Wireless Reserve (News), 187, May likco A28 Table Receiver, 54, Feb. Sept. ; (Correction), 447, Nov. Purchase Tax on Kits (News), 132, Apr. - C36 Console, 181, May Mains Transformer Protection, by F. R. W. B.('.E.E.A. Officers (News), 134, Apr. - CR32 and 'CR60 Car Receivers, 115, Strafford, 51, Feb. ; (Correction), 94, R.C.M.F. Report (News), '215, June Mar. ; (Correction), 186, May Mar. R.S.G.B. Council (News), 134, Apr. ARG37 Radiogramophone and V49, Marconi Jubilee (News), 188, May ; (Edit- Radio Exhibition Plans (Editorial), 236, A.C./D.C. Set, 334, Sept. orial), 195, June July - - Radiogramophone, 115, Mar. Merchant Ship Equipment, 405, Oct. Radio Interference Conference C.I.S.P.R. Radlotime " Set, 169, May Metal Lenses for Radio, by " Cathode Ray." (News), 67, Feb. 1.Icctro Acoustic Industries P.M. Miniature 84, Mar. Research T.R.E. and D.S.I.R. (News), 440, Loudspeaker, 71, Feb. Modern Marine Radio, by 1). F. Bowers and Nov. Electronic Instruments Micovac Test Meter. E. F. Cranston, 221,,June Service-Men's Register (News), 296, Aug. 445, Nov, N.P.L. Annual Exhibition, 307, Aug. Standard Valves (Correspondence), 22, Jan. ; G.E.C. Compact Receiver, 206, June National Certificate in Physics (Nuns), 247, 74, Feb. ; 150, Apr. A.F. Millivoltmeter, 14, Jan. July U.I.R. and O.I.R. (News), 397, Oct. ; 440, Radio Compass, 417, Nov. Naval Radio Gear, by G. M. Bennett, 62, Feb. Nov. -Garrard High -Fidelity Pickup, 138, Apr. Permanent Magnets, by " Cathode Ray," What is a Broadcasting Station ? (Editorial), Imhof, Record Storage Unit, 329, Sept. 300 Aug. 273, Aug. Londex, Remote Control Unit, 346, Sept. Police Radio, 457, Dec. \Vire versus Wireless (Editorial), 79, Mar. 5

www.americanradiohistory.com PROPAGATION Television Relay Stations (News), 216, June SOVIET Receivers, 297, Aug. Frequencies for Television (Correspondence), Synchronizing, by W. T. Cocking, 90, Standard Telephones & Cables D810 Trans- 112, Mar... - Mar. mitter, 80, Mar. Ionosphere Research (News), 188, May Strong C. E., 337, Aug. Review, by T. W. Bennington, 108, TEST AND MEASUREMENT Super- E mitron Tube for E.M.I. Television -- Mar. Electronic Instruments Micovae Test Meter, Camera, 44, Feb. -h..rt -Wave Conditions, by T. W. Benning- 445, Nov. ton, 8, Jan. ; 53, Feb. ; 88, Mar. ; Measuring Gear at Stockholm, 320, Sept. VITAVOT Loudspeakers in H.M.S. Van- 140, Apr. ; 176, May ; 232, Time ; Noise Factor, Methods of Measurement, by guard, 81, Mar.

. 264, July; 277, Aug.; 329, Sept.. ; L. A. Moxon, 11, Jan. ; (Correction), 403, Oct. ; 448, Nov. ; 485, Dec. 77, Feb. WASHINGTON -New York R.F. Cable. 131, Six -Metre Transatlantic Signals, by R. Physical Society's Exhibition, 196, June Mar. Naismith,186, May ; (Correspondence), R.C. Oscillator Control, by B. J. Solley, 321, 258, July ; (News). 18, Jan. Sept. Tropical Broadcasting, by " Radiator," 139, R.C. Oscillators, Amplitude Control in, Apr. (Correspondence), 219, June AUTHORS Rediffusion Response Curve Tracer, 226, \C_, 16, Feb. RADAR June H.S Trainer, by G. W. A. Dummer, 65, Feb. Simple Valve Voltmeter, by H. W. Baxter, 9, BAXANDALL, P. J., 57, Feb. H. W., 9, Radial Time Bases, by G. W. A. Dummer and Jan. ; (Correction), 56, Feb. Baxter, Jan. E. Franklin, 287, Aug. Standard Frequency Broadcasts (News), 132, Beebe, R. D., with Best, N. M., 293, Aug. Apr. 439, Nov. Bell, D. A., 27, Jan. RECORDING Test Prod, Clip on, 240, July Bennett, G. M., 6 Jan. ; 62, Feb. ; 80, Mar. Domestic Recordings (Correspondence), 258, Bennington, T. Si., 8, Jan. ; 53, Feb. ; 88, July 309, Aug. VALVES AND THERM IONICS Mar. ; 108, Mar. ; 140, Apr. ; 176, ; ; 264, ; 277, Ipsophone Robot Phone Recorder, 130, Apr. Cathode -ray Tube Data, by D. \V: Thomas - May 232, June July Magnetic Tape Recording, 335, Sept. son, 484, Dec. Aug. ; 329, Sept. ; 403, Oct. ; 448, Crystal Valves 89, Mar. Nov. ; 485, Dec. SOUND REPRODUCTION Mazda & Mulard Receiving Valves, 228, Best, N. M. and Beebe, R. D., 293, Aug. B.B.C. Transmissions, Quality of (('orrea- June Bowers, D. F., and Cranston, E. F., 221, June pondence), 22, Jan. ; 75. Feb. ; Sargrove -Tungsram All -Stage Valve, 484, RAY," 13 Jan. ; 43, Feb. : 112, Mar. ; 150, Apr. ; 191, May ; Dec. ' CATHODE 129, Apr. ; 183, May ; 223, 308, Aug. ; (Editorial), 157. May ; Standard Valves (Correspondence), 22, Jan. ; 84, Mar.: (Article), by H. A. Hartley, 396, 74, Feb.; 150, Apr. June ; 261, July ; 300, Aug. 339, Oct. Valve Prices (News), 18, Jan. Sept. ; 388, Oct. 442, Nov. ; 468, Dec. B.S.R.A. Conference (News), 95, Mar. Valve Standardization, B.V.A. Type BBA, Cocking, W. T., 90 Mar. ; 124, Apr. ; 207, Bass Compensation, by J. Ellis. 319, Sept. 176, May June ; 408, Nov.. 460, Dec. Crystal Pickups, by L. J. Wheeler and K. G. Cranston, E. F., with Bowers, D. F., 221, Lockyer, 412, Nov. June High Audio Frequencies, 415, Nov. Loudspeaker Damping (Correspondence), 309, ILLUSTRATIONS " DIALLIST," 35, Jan. ; 76, Feb. ; 114, ; 154, Apr. ; 182, May ; 231, Aug. ; 343, Sept. ; 401, Oct. ; 447, B.B.C. Station at Ottringham, Nr. Hull, 455, Mar. ; 266, ; 310, Aug. ; 348, Nov. ; 487, Dec. ; (Article), by H. A. Dec. June July Hartley, 396, Oct. B.T. -H. Crystal Set, Fountain Pen Size, 462, Sept. ; 404, Oct. ; 450, Nov. ; 490, Magnetophou Recorder, B.I.O.S. Report, Dec. Dec. 128, Apr. Baird's Telecicrome Cathode -Ray Tube, 45, Dummer, G. W. A., 65, Feb. Moving -Iron Pickups, by E. H. Francis, 285, Feb. Dummer, G. W. A., and Franklin, E., 287, Aug. Bareford, Dr. C. F., 68, Feb. Aug. Multitone MT3 Miniature Hearing Aid, 220, Bedford, L. H., 336, Sept. June Belgian Television, Pye, 479, Dec. ECKERSLEY, P. P., 454, Dec. Variable -Resistance Pickup, 66, Feb. Brookman's Park Masts, 454, Dec. Ellis, J., 319, Sept. C.B.C. International Short -Wave Station, FRANCIS, E. H., 285, Aug. TELEVISION 216, All Power Transformers, Television Signal June Franklin, E., with Dummer, G. W. A., 287 Generator, 250, July Cadell, Air Cmdre. C. S., 217, June Aug. Bnshmills, Ulster, 95, ; : American Colour Television, 192, May Consol Transmitter at Free Grid, 34, Jan. ; 72, Feb. 102, Max. B.B.C. Television Progress (News), 247, July Mar. 136, Apr. ; 230, June ; 268, Judy.; Bush Model T91 Television Set., 323, Sept. DECCA Navigator, Map Showing English, 299, Aug. ; 347, Sept. ; 387, Oct. ; Cinema Television (News), 335, Sept. Scottish and Danish Chains, 146, Apr. 446, Nov. ; 467, Dec. Deflector Coil Efficiency, by W. T. Cocking, 461, Dec. E.M.I. Fisk Solariscope, 449, Nov. GARRATT, G. R. M., 141, Apr. 23, French Television (News), 335, Sept. ; 477, Electron Microscope, Metropolitan Vickers, Griffiths, H. A. H., Jan. Dec. 44, Feb. Frequencies for Television (Correspondence), Entwisle, G. H., 68, Feb. HARTLEY, H. A., 396, Oct. 112, Mar. Ever Ready Model " C " All -Dry Transport- Interlacing, by W. T. Cocking, 124, Apr. able, 20, Jan. JEFFERY, E., 274. Aug. International Television Committee (C.I.T.), FACSIMILE Newspapers, 97, Mar. KEEN, A. W., 99, Mar. (News), 479, Dec. Horns, Marconi Television Link, 284, Aug. Film Industries Compressed Speaker Knight, S. A., 472, Dec. Projection Television, Dr. Starkie's Inst. of 490, Dec. with L. J.. 112. Physics Paper, 227, June G.C.A.. Ground Controlled Approach, at LOCKYER, K. G., Wheeler, Provincial Television (News), 187, May London Airport, 133, Mar. Nov. Pye O.B. Vehicle, 241, July G.E.C. Mobile Field Unit for Television Interference with Television (News), McGILLIVRAY, J. A., 146, Apr. S.B.A. Radio -Relay Link, 247, July Oct. 477, Dec. Television Relay, 439, Nov. Mitchell, C. J., 359, Television Aerials, by N. M. Best and R. D. - Moron, L. A., li, Jan. ; 171, May Beebe, 293, Aug. (Correspondence), JONES, Eric E., 217, June 344, Sept.; 448, Nov. NAISMITH, R., 186, May -- and Thunderstorms (Correspondence), KIRKE, H. L., 249, July Nethercot, W., 352, Oct. ; 463, Deg 344, Sept. LYTTLETON, Rt. Hon. Oliver, 399, Oct. E.H.T. Supply, by W. T. Cocking, 207, " RADIATOR," 139. Apr. - MAGNETRON Assembly, Marconi, 43, Feb. Roberts, W. A. 73, Feb. June Receiver Construction. Mazda 27M1 Photo -Electric Electron Multi - Roddam, Thomas, 70, Feb. ; 143, Apr.: ; ; 358, Oct. - 1. Deflector Coils: General Principles, plier, 482, Dec. June 238, July 2, Jan. Micro-Wave Tower for Federal Telecommuni- M. G., 314, Sept. 2. Line Deflector Coils : Winding Data, cations Laboratories, New Jersey, 132, SCROGGIE, 40, Feb.; (Correspondence), 309, Apr. Selby, R., 239, July Aug. Muirhead Picture Transmitting Unit, 82, Mar. Solley, B. J., 321. Sept. 3. Frame Coil Winding and Deflection Murphy WS31 F.M. Transmitter Receiver, Strafford, F. R. W.. 51, Feb. 242, ; 282, Aug:. Yoke Assembly, 103, Mar. ; 480, Dec. Styles, H. E., July (Correspondence), 309, Aug. 2MT, 455, Sr 1. 4. and ORIGINAL Writtle Transmitter THACKER. G. O., and Walker, BA., Frame Time Base Sync Separ- Dee. ator, 164, May ; (Correspon- Jan. U., Apr. dence), 220, June PIONEERS of Writtle Days, 456, Dec. Thor, A. 151, `i. Line Time -Base and E.H.T. Sup- Pocket Ohmmeter, 248, July ply, 251, VAUGHAN, A. B., 260, July July Popov, Alexander Stepanovltch, 478, Dee. Vaughan, J. F. O., 212, June 6. Cathode -Ray Tube Mounting, 278, Post Office S -W Transmitter at Criggion, Aug. 168, May B. Y., with Thacker, G. O., 30, 7. The Receiver Unit, 330, Sept. Pye Radio -Telephone Equipment, 296, Aug. WALKER, 8. The Receiver Unit, 391, Oct. Jan. 9. Power Unit, 420, Nov. RADIOLYMPIA Television Studio 441, Nov. Wheeler, L. J., and Lockyer, K. G., 412, Nov. 10. Operating Notes & Conclusion, 481, Radiosonde Equipment for Weather Ships, Whitehead, J. W., 488, Dec. Dec. 398, Oct. Williamson, D. T. N., 118, Apr. ; 161, May

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