" ... .. ---

www.americanradiohistory.com October. T947 Advertisements reless World

The Research Engineer knows that the best speaker for any set is one that offers com- plete reliability plus true tonal fidelity. After exhaustive tests his advice is always the same -fit Rola and relax! RADIOLYM PIA OCT i-ii STAND 135 GRAND HALL ANNEXE

KEKS

SPEA FoR,15EF

SPEAK 0UALrIusirly TN STREET LONDON, W.1 BRIT ISH ROLA LTD 8, UPPER GROSVENOR

www.americanradiohistory.com Uctolier, z9¢7 Wireless World Advertisements r

s

The 50 -range Model 7 Universal AvoMeter, the pioneer of the compre- hensive range of " Avo " Precision Instruments, is the world's most widely used ccrnbination electrical testing instrument. Fully descriptive pamphlet available from the Sole Proprietors and Manufacturers :- THE AUTOMATIC COIL WINDER & ELECTRICAL EQUIPMENT CO., W I N D E R H O U S E D O LTD. U G L A S STREET N G Q Lo NI .5 W 1 TELEPHONE VCrOrAPLO4/9

www.americanradiohistory.com rele%% World ACI Cl

Ask your Dealer.

He will tell you

"IT LASTS ABOUT A MONTH LONGER"

www.americanradiohistory.com Uct ber. rn¢y Wireless World Advertase.ments 3

2rá`.

7y.. N,"., I 1 1 :.ä. `.

RADIOLYMPIC GAMES

by Christopher Stone

WHILE we all welcome the opportunity to see what's new, Radio exhibitions can be quite as exhausting as an Olympic

quarter -mile. So save your energy and put Stand No. 38 high on your visiting list. You can be sure of a genuine welcome from my friends at Bush and from them you will learn something of a new Bush development which I am sure is going to cause quite a stir in wireless circles. Mark my words - and the Stand Number ! Igoe zefr/tyoNlCdeYo- aáer BUSH RADIO at STAND No. 38 Radiolympia

royds

www.americanradiohistory.com October, 1947 4 .4dvertuements rcicaa World HAYNES RADIO

LIMITED at Radiolympia- Stand 53 HOME MARKET ITEMS OF INTEREST TO THE ENTHUSIAST

An equipment that will appeal to the QUALITY TELEVISION RECEIVER Type HR.77 of generous design using I4in. C.R. Tube. exacting needs of the technical critic.

UNITS. TELEVISION output stage and complete sound receiver with 5 MO I.F. amplifier Tuner Type V57, including six video stages. one common to sound, video and push-pull triode output. all tubes up to 15in. and 7,000 v. H.T. Three valve limiter and Time Base Type SS7, double time base of hard valve type suitable for for synchronising. separater for VS7 and SS7. All units interconnected by plugs and Power Supply Type Pl, producing all necessary heater, H.T. and E.H.T. supplies sockets. 9in., 12ín. and l4in./ I5in. tubes. Brown finish and provided C.R. Tube housings Type CCR9, 12 and 15. In three sizes to accommodate with aperture for control panel. Rubber mask and coil support included.

and E.H.T. transformers. TELEVISION COMPONENTS. Scanning coils for 35 mm. neck tubes, focus coils, line output transformers

and hermetically sealed types with ceramic TRANSFORMERS AND CHOKES for all commercial and amateur needs. Open, screened tushmçs.

circuits. By inland post I; -. AMATEUR STATION DESIGN. A 20-page bookie of transmitter layouts and

relay RELAYS AND U NDU LATO RS for morse recording and other high speed applications.

HAYNES RADIO LTD., Queensway, Enfield, Middlesex. HOWard 1171

NI A R C D N 11VI a s t e ry of Measurement is acknowledged throughout the world by users of Communications Test Gear.

FOR IMMEDIATE DELIVERY VIDEO OSCILLATOR TYPE TF 410C Workmanship and performance are equally precise in this A.C. operated heterodyne -type oscillator which combines the merits of a good audio - frequency beat oscillator with the cover of a video oscillator. The special precautions necessary in a wide range instrument have been observed. Brief Specification: Frequency Range: 20c /s -5 Mc /s; 30V -300N.V. Output: 1 watt; Attenuated Output: Full specification supplied on request. OLYMPIA -Stand No. 226 ' ee us at RADI ONI INSTRUMENTS LTD w Aur St Albans 6161,5 ST. ALBANS, HERTFORDSHIRE Phone: Office: VONMOUTH, BRISTOL. Avonmouth 438 Office: 30 ALBION STREET, HULL. 16144 Northern PORI IS SouthernHull Office : 109 EATON SQUARE,esterOLONDON, ROA6,5.

www.americanradiohistory.com October, 1947 %Wireless World Adt,ertasenit nts 5

w;;1z d/ ceeim l ACCURACY

//ey /Yrted er cos soi

An important section of the Cossor Organisation is devoted to the production of ellectronic indicating and recording equipment of the highest calibre, designed to fulfil the most critical of current scientific demands. Enquiries relating to problems arising in recording indicating and monitoring where effects can be made available as a voltage, should be addressed to : A. C. COSSOR LTD., Instrument Dept., Highbury, London, N.5.

www.americanradiohistory.com 1947 b .-ídz vrtisemcnts 'írletis 'orld October,

A WITCH DOCTOR MIGHT AS WELL TRY

A witch doctor might just as well try to find certain faults in a defective wireless set as a skilled engineer without a good test instrument. A Weston Model E772 Analyser will help you find radio faults in the easiest and quickest way. This instrument will save you time, trouble and money, and you \vill find it universally useful for a wide range of measurements. Features of the instrument are high sensitivity- 2o,000 ohms per volt on all D.C. ranges - simplified controls, robust construction, accuracy and dependability.

ANALYSE SYSTEMATICALLY WITH A WESTO N

1242 SANGAMO WESTON LTD. ENFIELD, MIDDX. Telephone : Enfield 3434 &

n\\\\iiniiiII111 rpm PRICES " flll/r SENIOR MODEL Type SC with Universal Transformer E5 15 6 R° Type SX minus Universal Transformer E5 2 6 o NE JUNIOR MODEL Type IC with Universal Transformer E5 0 0 Type IX minus Universal Transformer E4 10 6 AE `Ov LStEN BABY MODEL = Type BC with Universal Transformer E2 19 6 = pD10 - Type BX minus Universal Transformer E2 13 6 MINOR MODEL Type MC with Universal Transformer E2 5 6 Type MX minus Universal Transformer LI 19 6 %,,,oi///////l/li/IIIIIIII'

Now that Stentorian Extension Speakers are coming back to the shops the pleasure of listening again becomes complete. Just plug in one of these superb permanent magnet speakers to your set and you can enjoy its clear, pure tone anywhere in the house ; sitting room, kitchen, bedroom, wherever you happen to be. Ask your local dealer about them. Stentorian THE PERFECT FXTRA SPEAKER FOR ANY SET WHITELEY ELECTRICAL RADIO CO., LTD, MANSFIELD, NOTTS.

www.americanradiohistory.com October, 194,7 Wireless World Advertisements 7

To readers visiting Radiolympia we extend an in Radio, Radar and Television equipment, and invitation to meet us at Stand No. 80 Grand Hall, the Dubilier range of these important essentials where the famous Dubilier range of Capacitors has been continuously developed and extended and Resistors will be exhibited. Our chief for the past 36 years. To everyone interested technical people will be there to discuss your in how maximum efficiency has become an problems with you, and to outline developments integral part of every item in this Dubilier and extensions. range, a visit to Stand 80 Grand Hall is Capacitors and resistors are vital components recommended. UBILIE CONDENSER CO. (1825) LTD. DURILIER CONDENSER CO. (1925) LTD., DUCON WORKS, VICTORIA, ROAD, NORTH ACTON, W.3 Telephone : Acorn 2241 (5 lines) Telegrams : Hivoltcon, Phone, London Cables : Hivoltcon, London Marconi International Code D12A

www.americanradiohistory.com 5 1 i /remis, ul uts WireIfc. 'orId October, 1947

jjttc Thacstro DE -LUXE A new receiver of a very high order

RADIOLYMPIA PREMIERE ! SH They're NEW ! They're NEWS ! s4s Winners from the Pilot range . . new backed by the famous Pilot guarantee heading the .. planned for 1948. year's honours list!

The Little Maestro de Luxe. A SH545 First PILOT Post -war full size table model. First stunning walnut cabinet. An entirely new design. NEW time in England. A world- tested, all -wave 5 -valve superhet, high efficiency valves. NEW twin -scale tuning, separate housed in a beautiful walnut veneered cabinet. High indicator lamps for each band. Long and medium Fidelity, high sensitivity, with FLY WHEEL tuning. A set wave coverage. for connoisseurs. only. £22- I -0 PLUS P.T. E4 -14 -10 AC /DC models £ 13 -13 -0 PLUS P.T. E2 -18 -9 230'250 volts. 4.5 Watts output. famous Little For A.C. mains, 100/110, 200/225. And now the waves, 900/2400. 180/565, Maestro in colours! 1948 Reception on long, medium and short Edition of Radio's best -seller 13/54 metres. Flywheel tuning with concentrically mounted tone in powder blue, control. 8 inch permanent magnet speaker, illu- pastel green, or minated glass scale calibrated with station peach. names and wavelengths, with horizontal pointer. DC models AC / Automatic volume control. Provision for gramo. only. [12-5 -0 PLUS I?adio loud Pilot and extension speaker. P.T. E2 -12 -9 PILOT RADIO LTD., PARK ROYAL RD., N.W.I0 phone pick -up

No. 3 POINTS OF LOW CONTACT RESISTANCE IN MODERN CIRCUIT DESIGN

CLIN -TYPE B8A C I RADIO & TELEVISION VALVEHOLDERS SVA Standard Dimensions COMPONENTS .. . Easy insertion of valve Firmly retained Easy withdrawal . . . ARE USED BY Standard fixing centres I;" ALL THE LEADING SET MANUFACTURERS Hole diameter Designed to meet the requirements of the new all -glass type B8A Valves. Moulded body ... Plated saddle ... Screen ... and Sockets, - ensuring extremely low BRITISH MECHANICAL PRODUCTIONS LTD. contact resistance. A valve- retaining latch specially suit- 21 BRUTON ST., LONDON, W.1 able to these new all -glass valves.

Telephone : MAYfair 5543 A feature exclusive to Clix B8A Valveholders. Foremost in Valveholder design SEE OUR STAND (No. 127) AT RADIOLYMPIA

www.americanradiohistory.com October, rod¡ Wireless World Advertisements q

CORED SOLDER /i7 thc `ll) Ersin Multicore Solder is the only solder in the world con- taining three cores of extra -active non -corrosive Ersin Flux. Three cores of Ersin ensure speedy precision m soldering and flux continuity, thus saving time and v money and eliminating waste. No z extra flux required. -1 -I Ersin Multicore Solder is widely o used for all soldering purposes, m in the manufacture and mainten- (7 7-1 ance of Radio, Television and Elec- 0 tronic apparatus. Ersin v D C r v Multicore is most n r efficient for all -1 ro soldering pur- 0 poses in the home. z 3 -13

FOR FACTORIES. Nominal 71b. FOR SERVICE ENGINEERS FOR THE HANDYMAN. The o and I lb. reels. Made as standard and Maintenance Purposes.. Size Size 2 Carton provides approxi- T in and 9 gauges. 5 alloys Other I Self- feeding Cartons are supplied mately 3 feet of Ersin Multicore I specifications to special order. Bulk in 4 specifications. Prices as shown Solder. Price 6d. per Carton. m prices on application. below. (Not suitable for aluminium). v_ m NOMINAL 7 Ib. AND I Ib. REELS Alloys specially recommended for Radio Production ALLOY Equivalent MULTICORE Solidus Liquidus Recommended r Tin Lead B.S. Grade Colour Code °C °C bit temperature USES r o 60/40 K Red 183 High quality work requir- C 190 230 °C ing low melting point alloy m 45/55 M Crimson /Buff 183 227 267 °C Hand soldering. Radio. m - Telephone and Electrical Equipment - Batteries 40/60 C Green 183 238 °C v 278 I < o m STANDARD GAUGES SIZE I CARTONS Ersin Multicore Solder can also be supplied in any intermediate size High Tin Tin :Lead Alloy 60/40 --1 Standard Diam. Approx. Number of feet per lb. Diam. Catalogue Approx. List Price! N Wire in in ALLOY S. W.G. rn Ref. No. length (Subject) m Gauge Inches M, ms. 6040 45/55 40;60 3 IO 0.128 3.251 25.2 23.5 23.0 C 16014 14 44 ft. 6 0 m 12 0.104 2.642 38.1 35.2 34.9 C 16018 18 114 ft. 6 9 z z 13 0.092 2.337 48.7 45.3 44.5 -1 14 0.080 2.032 64.4 59.2 58.6 Standard 40/60 Tin,Lead Alloy 3 16 0.064 1.626 100.5 94.3 92.1 Catalogue Approx. List Price C 18 0.048 1.219 178.5 167.8 163.5 S.W.G. (Subject) Ref. No. i length r s. d. 19 0.040 1.016 257.5 240.4 235.5 20 0.036 0.914 318.0 302.5 291.0 C 14013 13 27 ft. 4 10 ñ 22 0.028 0.711 526.0 492.0 491.0 C 14016 16 60 ft. 5 3 o MULTICORE SOLDERS LIMITED m MELLIER HOUSE, ALBEMARLE STREET, LONDON, W.I. Tel.: REGent 1411

www.americanradiohistory.com io Advertisements Wireless World October, 1949

Radio ltd WILL BE AT RAIDIOIASPIAO models, McMichael STAI4Drange of McM' its best, is shown improve a comprehensive shown Craftsmanship aim Here will be British is in which 26 years experienceexp the past. of in the have produced what ethey RaIeherLSlough. Grams: 2085 : TEM Radierher, W.C.2. Tel Grams : LONDON. Slough 22311. STRAND, Tel Sales. Bucks.Bu Condon Office & $lough. - Radio Limited,Limited. McMichael

New and Improved Test Gear for Radio Engineers Electricians Radiolab ALL -PURPOSE TESTER (as illustrated). A.C. and D.C. multi range Meter. Models with 3/ in. or 6 in scale. High accuracy on Audio Frequencies Robust Plug and Socket range selection OTHER Radiolab Products include :- SERVICE VALVE TESTERS. Working condition tests with D.C. for H.T. and G.B. supplies. 4 in. Indicator. LABORATORY VALVE TESTERS. Nine simul- taneous volt and current measurements. Ideal for student use or demonstrations. HUM - METROHM INSULATION TESTER. 500 volts Insulation Test. Press -key controlled with facilities for earth and circuit testing. VAMPIRE (VOLTS- AMPS - POWER) A.C. TEST Everett SET. 4 RANGES CURRENT & POWER up to zo AMP. & 5 K.W., self-contained. 5o WATT Edgcumbe full scale range for testing small transformers, etc. RADIOLYMPIA ENTIRELY NEW rectifier circuit with 3f" Moving Colindale Works STAND 76 Coil Indicator, FOR SINGLE PHASE or 3 PHASE London, N.W.9 MAIN HALL Balanced Load CIRCUITS.

www.americanradiohistory.com October, r947 Wireless World Advertisements METALLISED CERAMICS Two additions to the S.P. range of FREQUENTITE bushes

R.50650 R.50764 * R.50844 *R.50855

C D TYPE A B E mms. mms. mms. mms. mms.

R.50650 9.5 9.5 6.4 6.25 275

R.50764 9.5 16.7 6.4 625 275

* R.50844 9.5 12.7 9.5 6.25 2.75

* R.50855 12.7 22.2 12.7 9.5 3.9

* Recent additions to the range

For full information and prices please write to : STEATITE & PORCELAIN PRODUCTS LTD. STOURPORT -ON- SEVERN, WORCS. Telephone: Stourport Ill. Telegrams: Steatain, Stourport. S.P.43

www.americanradiohistory.com 12 Advertisements Wireless World 0( !obey, 1917

Unsurpassed for use in Transmitter and other high voltage equipment

* A.F. A T T E N U A T O R, TYPE 1 3 5 8 Frequency Range, zero to 20Kc's. Input Impedance,

600 ohms Attenuation, 0-I10 dB in steps of I dB, _ 1% nominal voltage ratio. Internal Termination of 600 ohms at option. Dissipation. 2 watts.

* DIODE VOLTMETER, 1 TYPE 281 0.1 -150 volts, 50 cis. to 250 Mc /s. f 2% of F.S.D. Stable zero setting. Alternative model having additional d.c. voltage ranges available. PACITORS

: : '.:...

U.I.C. Ceramic Lead -through Capacitors are small In

dimensions and can be directly connected to the chassis, thereby keeping series inductance and resistance to an ab- solute minimum. Full technical data furnished on request. HIGH DISSIPATION RESISTANCE BOX, TYPE 1752 0 -1 meg. in 5 decades. 6 watts per resistor, 60 watts UNITED INSULATOR CO. LTD., per decade, except last decade which is 20 watts. OAKCROFT ROAD, TOLWORTH. Accuracy ± 5 %. Voltage limit 1,000 volts. SURBITON, SURREY. PRICES APPLICATION. ON Telephone. Elmbridge 5241 (6 lines) Telegrams: Colonel,. Surblton.

1)ueiiii LABORATORIES LTD. Uvt_-AJ-1..ta-ctra2-0(_ BOREHAM WOOD, I v- TELEPHONE: ELST0.EE 1137 C

www.americanradiohistory.com October, 1947 Wireless World Advertisements 13

We manufacture to customers' individual CHANNEL ISLANDS RADIO requirements. Model illustrated incorporates ENGINEERING CO. LTD. a 16 -valve double super- herrodync receiver, 4/5 Roseville House, Roseville Street, Auto -changer, High Fidelity pick -up and St. Helier. Telephone: Central 2598 Speaker. May we submit designs ? *Pure water flows from a pure fountain

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

Test imonials from users of the NEW `640' RECEIVER DvwYsT*:NE, ESPECIALLY FOR THE A MATEUR DESIGNED sensitivity, A RECEIVER Ref. I361J. " We compared general be a most remarkable rated Ref. 196 W. " It proves to and ease of control with two highly on producing selectivity, Receiver and yoJ are to be congratulated set, and we wish you givenf avow albiy such an outstanding " Ham " either mode0l. ompared mo e a U.. and the measured every success in this market." fact was much lower in either case comes up to the in several instances 196'SW The ' 640' fully carriers of very weak signals were Receiver o. If this set was for a Communications superior on the 640.' standards required We were slightly readily find especially on the "Ham "bands. exported even to the U.S.A., it would this nature, on top of each able to separate stations working almost enthusiasts." is extremely good. other. The signal -to -noise ratio very satis- on the production 216; N. " The receiver performed YouRef. are to be warmly congratulated Ref. very low feature being the very fine model." factorily, an outstanding of a Selectivity is ex- have had nothing but praisefor signal noise ratio. Ref. 196; B. " We crystal filter well are particularly pleased in the cellent and the the crystal gate. We while. Plenty of DX has been of the noise limiter." worth operation worked and the receiver has given "Your claims are fully justified, the Ref. 276/J. way." complete satisfaction." performance being excellent in every EDDYSTONE RETAILER ORDER FROM YOUR REGISTERED Manufacturer.: : RADIOLYMPIA & CO., LTD. OCT. I.11 STRATTON RD., WEST HEATH, BIRMINGHAM, 5 STAND No. 230 EDDYSTONE WORKS, ALVECHURCH harfecialle- Twin Speaker CORNER CABINET Height 42 ". Width 25.s ". Depth 184 ". Impedance 6 or 15 ohms, without Trans- former Cabinet in Solid Mahogany or Oak.

Sets a new Standard in life -like reproduction. Fitted with Wro /CS unit for the Treble and W12 /CS for Bass, with the new Wharfedale Separator. The Bass resonance is 35/40 CPS. and wide diffusion of high notes is achieved. Maximum input to Watts. The genera See it at impression on first listening to this Corner R AD I O LY MPIA Cabinet is one of stepping into the Concert STAND No. ISO Hall.

The Corner Cabinet is being demonstrated by :- WEBBS RADIO, 14, Soho Street, W.I. SIMON SOUND SERVICE, 48, George Street, W.I. PRICE £48 -10 -0 (Without Transformer) Made and Guarcn;eca bi WHARFEDALE WIRELESS WORKS, BRADFORD ROAD - IDLE - BRADFORD. Telephone: IDLE 461. Telegrams: Wharfdel, Idle, Bradford.

www.americanradiohistory.com October, 1947 VIVire14titi Oo orimi Advertisements 13

We want you to know.....

PRE -SET SWITCH SELECTED TUNING

THIS Is a feature of the 1947 Ferranti Models. It enables the listener to switch on any two AE RIAL TUNING stations of his choice on the TUNING OSC.

medium waveband, without RANGE 2 having to tune them in himself. The stations are pre -set and come in automatically correctly tufted. Pre-set tuning is done by means of adjustable dust -iron cored coils, which ensure high stability of tuning. A AERIAL OSC. negative temperature-coefficient con- TUNING TUNING denser to eliminate the effect of RANGE I temperature on tuning is a further contribution to stability. The pre -set adjustment is carried The wave-change switch manual tuning control to out by means of screws which are is a 5- position switch with a third station in the accessible at the rear of the chassis the three normal positions medium or long wave -band, without the necessity for removing for Short, Medium and Long three stations are available in- the cabinet back. The screws are waveband selection, and two ad- stantly by mere rotation of the used in conjunction with calibrated ditional positions, (which are marked wavechange switch, without the wavelength scales in order to make by two dots) to indicate the two pre- complexity and unreliability often timing adjustment easy. set stations. By turning the ordinary associated with push- buttons.

\ DETACHABLE ELECTROLYTIC CONDENSERS

A FEATURE which will interest all service men is the ease of replace- ment of electrolytic condensers made possible in Ferranti design. This enables condensers to be held in position by a screw -secured clip. When the screw is released either or both of the condensers may be re- moved and the connector unit ex- posed. The actual connections to the denser. A reliable con- recommend themselves to the mech- condensers are made by a spring clip tact is obtained. There anical designer and the service on the lead, and this can be detached are ocher features of engineer, but we should like-to talk to by hand and secured to a new con- Ferranti sets which will you about these at some other time -

FERRANTI Ferranti Ltd MOSTON MANCHESTER 10: & 36 KINGSWAY LONDON WC2

www.americanradiohistory.com 1b Advertisements Wireless World October, 1947

I S C A R R A D I O S D O M E S T I C R A D O

The makers of Britain's finest radio have in- creased their range, and are introducing new receivers worthy of the Masteradio reputation. You are cordially invited to our Stand. RADIOLYMPIA Stand No. 130

R A D I O G R A M S T E L E V I S I O N OM STAND 74 RADIOLYMPIA Rothermel "Quality" Products for QUALITY REPRODUCTION Everyone interested in high fidelity sound repro- duction is invited to inspect the unrivalled range oJ quality products on STAND 74. Rothermel technicians will be in attendance to answer all queries.

ROTHERMEL CRYSTAL ROTHERMEL NEEDLE "TORPEDO " MICRO- PRESSURE ADJUSTING PHONE E18.18.0 UNIT IO' , Plus P. Tax.

ROTHERMEL DE LUXE CRYSTAL PICK -UP E4.4.0. Plus Purchase Tlx

ROTHERMEL HOUSE, CANTERBURY ROAD, LONDON, N.W.6

/eXICOI: 'Phones : Maida Vale 6066 (3 lines) 'Grams : Rothermel London

www.americanradiohistory.com October, ¡947 ireless World Advertisements 17 next for discussion please...

The beauty of Spire Fixing (yes, we said ' beauty ' and meant it) is that it isn't fixed. It is a principle that can be adapted to almost any light assembly problem. There are already over 35o various Spire Fixings and fresh ones coming along almost daily. What can Spire do for you ? Isn't there some fumbling, fiddling, fastening problem it could,

` ? tackle ? A blind or awkward assembly perhaps ? An assembly that won't stay put' There may be an existing Spire solution - if not, we'll design one. Can we discuss it ?

THAT'S fixed THAT! The NU Types of Spire Fixings make blind assembly quick and certain. The NU is slipped over the edge of the sheet and the extrusion snaps into the bolt hole. If the bolt hole is some distance from the edge of the component a slot may be punched near the hole to enable the Spire Fix to be slipped into position. The NU fix gives a self -aligning assembly, the amount of float being varied as desired by altering the size of the bolt hole.

* A BETTER way of fixing Regd.

SIMMONDS AEROCESSORIES, LIMITED TREFOREST GLAMORGAN

9 B

www.americanradiohistory.com zö Advertisements WitrIos6. A% 'orld ()rlubf IQ 7";

EAs y S'E S TL1 foR Quick

C"() 1.a _ ' CS

The Rad. 20 model illustrated is ideal for schools, clubs, hotels, etc., where high quality reception of the normal broadcasting programmes is required. This equipment has proved to be outstanding in its class and will give reliable service due to the fact that only the highest quality components are used. A Three wave band superhet radio unit of the very latest design is incorporated, and provision is also made for microphone and gramophone inputs. Available for 200/250v AC mains Price £44 -15 -0. Generous Trade Discount. Other models are available 20 and 60 watt AC Amplifiers. Send for catalogue for full particulars of this and other models.

SELF -CONTAINED BATTERY OPERATED ELECTRONIC TEST METER gA,a4-/ta/fyejiais /wavte Efa 4,>rrhth The 17 ranges will give true readings of Bias and Screen, Anode and Mains voltages ; D.C. currents to I 1/2 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 10s. The versatile valve voltmeter for Experimenter and Serviceman ELECTRONIC INSTRUMENTS LIMITED I7 PARADISE ROADRICHMOND SURREY Telephone : Richmond 49 /7

www.americanradiohistory.com October, 1947 Wireless World Advertisements if)

THE COMPLETE SERVICE FOR MODERN SOUND RECORDING AND REPRODUCTION We have well - equipped workshops for the development and subsequent production of specialised equipment. We welcome enquiries for any type sound recording and reproducing apparatus, no matter what its particular application may be. Our new catalogue is now available, giving comprehensive details of our service and range of accessories, including :

Mobile and static single and dual Complete wire recorders. Stainless steel channel recording outfits. recording wire. Relay units to specification Loud- Recording amplifiers. Three circuit electronic speakers. Transcription motors. mixer units. Modulation meters. Microphones, crystal and moving Lightweight moving iron permanent sapphire coil. Desk and pedestal stands. pick -ups. Moving coil pick -ups. Boom stands. Steel and sapphire recording styli. Blank recording discs, 5in. -17in. Styli Containers. single or double sided. Miniature and normal shank re- producing sapphires. Disc envelopes and presentation albums. A design and printing service for labels. A complete range of accessories to meet every requirement of the recording engineer. * Our latest developments (of special interest to users of sapphire and delicate pick -ups, and the studio or theatre) the SIMTROL, a con- trolled micro -lowering movement easily fitted, for use with any pick -up, and THE SIMDICATOR, a Portable development of the Simtrol in- Dual Channel Recording and Replay Outfit corporating a novel and accurate STAND 209 vernier groove locating mechanism.

Call or write for lists and MEET US AT formal invitation - to t '

RECORDER HOUSE, 48-50, GEORGE STREET, PORTMAN SQUARE, LONDON, W.1 RADIOIYM PIA Telephone : Welbeck 2371'2 Telegrams : Simsale, Wesdo, London Cables : Simsale, London OCT. I I I

www.americanradiohistory.com 20 Advertisements U'ireles% World October, ¡947

/s

Recep ion conditions range from excel--

lent to very poor ; signal streng h from strong to vary weak, and to cope suc- cessfully with all such conditions, you need a pair of highly sensitive and dependable headphones.

If you want maximum reception results you should insist that your THE local dealer supplies you with a pair NEW of the rightly famous S. G. BROW J Type 'F' headphones. Sea, land and air WIT operators, servicemen, EDØYSTO exparimenters and radio amateurs all vouch for choir depandability. '640' TYPE 'F' (Featherweight) Receiver Price 255/- per pair. Communications ' F ' 1 YOUR LOCAL DEALER CAN SUPPLY. Descriptive Brochure "W.W." gives details of full range. Prices from 25/- up to ,105/- for Moving Coil Typa 'K' Brochure "W.W. " sent on request.

'Phone : ACOrn e 5021 C.4,7-° own* VICTORIA ROAD, NORTH ACTON, LONDON, W.3

THE ROMAC MODEL 126 Personal " RECEIVER

AVAILABLE FROM STOCK AT WEBB'S

Coverage 31 to 1.7 Mc /s. Electrical Band- spread throughout range. Nine valves. One R.F. and two I.F. stages. Efficient noise- limiter. 10, 20, 40, 80, and 160 metre amateur ban is calibrated. [he Romac Personal Receiver is an entirely Vacuum mounted crystal filter. new departure in portable radio. The Beat frequency oscillator. shoulder strap method of carrying has Fly -wheel control on band spread. Ingeniously been used to provide an The " 640 " has outstanding signal /noise ratio and " invisible " aerial. This convenient extremely good image rejection. Provision for feature is exclusive to Romac Models. external connection of " S " Meter. Price E17 3s. 8d. Plus E3 16s. 4d. Purchase Tax PRICE E42.0.0 Complete with I H.T. and 2 L.T. Batteries. PLUS PURCHASE TAX £9.0.7 Home and Export Enquiries should be directed to Write, phone o' call RADIO CORPN. LTD. 14 SOHO ST., OXFORD ST., LONDON, W.1. ROMAC Sets. 9 p.m. THE HYDE HENDON LONDON, N.W.9 Phone : GERrard 2089, Shop hours : 9 a.m. -5.30 p.m. a.m. -1 rel. No. COLindale 5401 (Three lines).

www.americanradiohistory.com October, 1947 Wireless Vi'orld Advertisements 21 EVERY RAo/ frisirmect

should inspect the wide range of high frequency heaters, welders and soldering machines on B.I.Callender's stand. These instruments are increasing production and reducing cost at many stages of radio and telecommunication equipment manufacture. Demonstrations will be given frequently each day throughout the exhibition. Also on view will be the new B.I.Callender's all -wave anti -interference aerial, radio frequency cables, radio capacitors, polyethylene moulded connectors

and a selection of solders and soldering fluxes.

5.1., . STAND No. 200 I NATIONAL HALL BRITISH INSULATED CALLENDER'S CABLES LIMITED NORFOLK HOUSE, NORFOLK STREET, LONDON, W.C.2.

www.americanradiohistory.com 22 Advertisements Wireless World October, 1947 INSTRUMENTS FOR EVERY MEASUREMENT

AMPLIFIER GAIN R! IIITORS Type 615 DIST'OR I ION GANG CONDENSER OUTPUT Type 301 A.F. MICROVOLTER Type 700 Type 2507 Type 610 LIMIT BRIDGE DISTORTION EQUIPMENT OUTPUT FACTOR METER POWER METER

cons Type 230 GENERAL INDUCTOMETER COMPONENT TESTING Type 302 Type 314 SHORTED TURNS TEST IMPEDANCE BRIDGE Type 620 Type 622 "Q" METER PRODUCTION "Q " TESTER Type 2502 PHOTOGRAPHIC FIDELITY TURNS ANA! Yf1A COUNT Type 400 8 PRESSURE TEST Type 1700 OSCILLATOR PHOTO FLASH VIBRATION Type 1400 & CONE ANALYSIS Type 1701 SOUND FREQUENCY RANGE CABIN ET PORTA FLASH Type 1200 LEVEL METER Type 802 Type 2100 STROBOFLASH Type 1702 OSCILLATOR MOISTURE METER MICRO FLASH Type 1201 Complete technical data available on reque t :- STROBOFLOOD DAWE INSTRUMENTS LIMITED vtiasint iic HARLEQUIN AVE., GREAT WEST RD., BRENTFORD, MIDDX. EALing 1850 201 RADIOLYMPIA -M.R. SUPPLIES Ltd We are proud of the confidence we bave built up with the Buying Departments o1 the largest industrial concerns. We offer no " cheap " material, we give fair descrip- tions, we stand by every item we sell and, nearly always, despatch same day as order In the peace and is received. STAND All Prices Nett. quiet of the TRANSFORMERS (all -flash- tested, 2,000 v.). All primaries tapped 200/220/240 r All continuously mted. Step -down to 22 v. 2 amps, 21/-. To 7, 11 and 15 v. at 2 National Hall amps, 22,/6. To 6, 8 and 14 V. at 4 amps, 36/ -. To 5, 12 and 17 v. at 6/8 amps, 51/6. To 7, 8 and 15 v. at 12 amps, 72/6. Auto -wound Voltage Changers, Gallery 100/110 to 200ß40 v. (tapped) and vice -versa, fully shrouded, 75 va 29/6, 120 va 323 3716, 250,100 va 77/6, 750 /1,1100 va (open) £e 6s. (care. 4/6). Power supply for radio and amplifiera: 450,/0/450 v. 150 m.a.6.3 v. 4 a., 6.3 v. 2 a., 5 v. 3 a., 49/6. RECTIFIERS (Selenium), by B.T.C. Rated for charging up to 12 v. (max. A.0 -.- 1.5 RADIOLYMPIA input, 17 v.). At amp, 12/6 ; at 4 amps, 23 :6 ; at 6/8 amps, 35/6 ; At 10/12 OCT. 1-11 amps. 45/6. Also for D.C. delivery of 30 v. 5 amps, 621 and 36 v. 10 amps, £4 17e. 6d. Also D.C. 25 v. 100 ma., 3/6 toelear. EUT types, 1,000 v. 4 m.a., 15/6 ; 2,000 v. 4 m.a., 25/-. "LOWTHER- VO'GT" fadio- gramophones and VARIABLE RESISTANCES. Sliding type, fully enclosed. 100 watts. 4 ohms 5 a., 10 ohms 3 a., 50 ohms 1.4 a., 100 ohms 1 amp., 200 ohms 0.7 a., 400 ohms 0.5 a. Electro- grams. These laboratory built instruments Rotary (panel mount) type, with 2lin. knob, 3 -hole mount, 4 ohms any one 27/6. are not only in a class by themselves, but represent 4.5 a., 23/6 ; 10 ohms 3 a., 28/6 ; 9 ohms 3 a., 23/6 ; 5 ohms 3 a., 22/- ; 100 ohms 0.9 a., 23/6 ; 230 ohms 1 a., 33/6 ; 920 ohms 0.4 a., 31/6 : 1,500 ohms the most advanced system or sound reproduction 0.25 a., 25/6 ; 2,100 ohms 0.25 a., 31/6 ; 3,000 ohms 0.25 a., 83/6, and many others. OUTPUT TRANSFORMERS. 25 -watt " W.W." model with 11 ratios from 12/1 yet evolved. to 75/1 with C.T. for push -pull. The perfect high -fidelity job, 59/6 (deep. 2/ -). Grampian " replacement " model, providing 8 ratios, tapped prim. and sec., 11/6. LOWTHER. range of Quality Tuners in chassis form, TEST INSTRUMENTS. The new B.P.L. " Super Ranger " from stock. A precision T.R.F., Superhet, Dual. instrument giving 28 ranges on Sin. 2- colour mirror scale. D.C. volts: 75 m.v., AC /DO volte: -10, 50, 100, 500, 1,000, 5,000. D.C. current: -1 ma., 10 m.a., -grade 100 m.a., 1 amp., 10 amp. A.C. current, 100 ma., 1 amp., 10 amps. (internal current LOWTHER High Quality Amplifiers, 5, 8 and transformer). Resistance:-0/10,000 ohms and 0/1 Megohm. Output -0 /60 15 watts max. output. db (at varying levels), £19 19e. Resistance boxes (Decade type), units 0 /10. 'feos 0 /100 ohms. With add. 100 ohms. Fitted m,,c Galva. In teak case. 16 by LOWTHER High -grade Amplifiers, etc., for Industrial, 71 by 6in., new, 65/- (d. 2,6). SHORT -WAVE RECEIVERS. The B.2 Receiver and Power Pack. Operation Hospital, Theatre, Factory, Dance Hall and the like. any A.C. mains and 6 -volt. Range 3.1 to 15.5 me /s (approx. 18 to 100 metres). Superhet with B.F.O. Receiver in metal housing 4j in. sq. by 9tin. Power Pack " LOWTHER-VOIGT " Corner Horn Reflector 4in. by Sin. by latin. With all leads, plugs, phones, etc., in steel transit case, £7 17e. 6d. (deep. 6/ -5. The best S.W. opportunity. We have a few of the Water- Speaker Type P.W.I. tight Transit cases only, fastened with six clips, stout keel, size lilla, by 9in. by 6in., at 7/6 each, poet free. LOWTHER Moving Coil Pick -up (Licenced under P.A. SPEAKERS (Recto). Reflected Horn type with 10 -watt P.M. M /coil Unit (15 ohms). Flare 12in. long, 14in. dia. On swivel mount and pillar. Ideal for Voigt's Fatent). mobile use. £7 12e. 6d. (deep. 5/ -). We have a few of the reflected Homs, less unit, new and perfect, standard P.A. thread, at £4 10e. (desp. 5/ -5. STEEL LOWTHER'S numerous other " Milestones in Quality " TRIPODS for these and other P.A. Speakers, the best type, extending to 121t., strong required byeveryloverof highfidelityreproduction. and rigid, 551- (desp. 3/6). SMALL UNIVERSAL L.V. MOTORS. 12 ;24 v. AC /DC. Length 31n., width 21ín. Ball bearing, }in. spindle. Approx. 3,000 r.p.m. Suitable for vertical or horizontal running. Very special offer, 17/6 each. (Please include sufficient for despatch.) FOR CALLERS ONLY. Cabinets ex Marconi TF 390 Sig. Generators, made of copper The Lowther Manufacturing Co., ideal for amplifiera, 23in. by Blin. by 10in., 35/ -. Vent-Axis Extractor Fans, com- plete, 24 v. AC /DC, 45/ , MOM Miniature Communications Receivers, with all Lowther House, St. Mark's Road, BROMLEY, KENT. recesaorles, brand new, sealed containers, £10 10s. M.R. SUPPLIES Ltd., 68, New Oxford Street, London, W.C.1. RAV. 5225. Telephone: MUSeum 2958

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

g/A/tX/Otiezt;/29

A Superb Instrument for the Perfect Reproduction of Gramophone Records

Here at last is an instrument which will give you the perfect record reproduction of which you have dreamed ... the full beauty of the quiet passages . . . the excitement of the finale ... the vigour of the bass ... the trill of the soprano. And the Collaro 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 dealers ... or write to address below for Illus- trated Brochure.

See the Microgram and the Collaro Gramophone Components on STAND 35 at RADIOLYMPIA OCT. 1 - OCT. 11

7L :- FAA, _.:

PRICES : De Luxe Model £ 19 19 0 Míiioqrum Plus Purchase Tax £4 8 8 Standard Model E16 16 0 1,,tatte au.api.te, Plus Purchase Tax £3 14 8 Trade Enquiries to :- Telephone COLLARO LTD., RIPPLE WORKS. BY -PASS RD., BARKING, ESSEX Rippleway 3333

www.americanradiohistory.com 24 Advertisements Wireless World October, '947

SEE US AT RADIOLYMPIA -STAND No. 87

The leading radiograms are fitted Ncitl Coodntaos 12" loudspeakers.

Type No. T2/1205/I5

CO 0 D .MA NS

OF EXCELLEN'E GOODMANS INDUSTRIES LTD LANCELOT ROAD, WEMBLEY, MIDDX

FOR THE RADIO SERVICEMAN DEALER AND OWNER The man who enrols for an I.C.S. Radio Course learns radio thoroughly, completely, practically. When he earns his Diploma, he will KNOW radio. We are not content merely to teach the principles of radio, we want to show our students how to apply that training in practical, every -day radio service work. We train them to be successful ! Write to the I.C.S. Advisory Dept. stating your requirements. Our advice is tree and places you under no obligation. You may use this coupon- INTERNATIONAL CORRESPONDENCE SCHOOLS Ltd. DEPT. 38, INTERNATIONAL BUILDINGS, KINGSWAY, LONDON, W.C.2 Please explain fully about your instruction in the subject marked X Complete Radio Engineering Radio Service Engineering NEW TYPES FOR Elementary Radio MIDGET RECEIVERS THE SCIENTIFIC 'na the following Radio Examinations: - HEARING British Institution of Radio Engineers AIDS VALVE P.M.G. Certificates for Wireless Operators METEOROLOGICAL City and Guilds Telecommunications INSTRUMENTS BRITISH MADE Wireless Operators and Wireless Mechanics, R.A.F. ETC. Name. Age

Address Greenhill Crescent. Phone HARROW HIVAC LIMITED Harrow on the Hil1.Middx 0895

www.americanradiohistory.com October, rqj] Wireless World I d-,'ertisements 25

STAND 34 WESTINGHOUSE METAL RECTIFIERS for H.T. supply to A.C. and A.C./D.C. receivers. Battery eliminators and trickle chargers. Television sound and vision receivers. De-ection and automatic volume control. A.C. measuring instruments. Condenser testing. H.T. supply to small electronic devices.

A completely new range of " double -voltage " Westalite rectifiers is now available for H.T. supply. These are very much smaller and lighter than the older type and are even more efficient.

WESTINGHOUSE BRAKE & SIGNAL CO., LTD., 82, York Way, King's Cross, London, N.I

www.americanradiohistory.com 26 Advertisements Wireleti% World 00 ,,/,(/ i y.Eï NTR CATE PARTS but not too intricate for Bullers Made in Three Principal Materials FREQUELEX An insulating material of Low Di- electric Loss, for Coll Formers, Aerial Insulators, Valve Holders, etc. PERMALEX A High Permittivity Material. For the construction of Condensers of the smallest possible dimensions. TEM PLEX A Condenser material of medium permittivity. For the construction of Condensers having a constant capacity at BULLERS LOW LOSS CERAMICS all temperatures.

BULLERS LTD., 6, Laurence Pountney Hill, London, E.C.4 Phone: Mansion House 9971 (3 lines) Telegrams: Butlers, Cannon, London"

"You're CERTAIN to get THE 'rYROGRI it at ARTHURS . (Patent Applied For) * VALVES : We have probably the largest Every Radio, Electrical, Motor and Model Engineer stock of valves in the Country. hates those fiddling small screws in awkward Let us know your requiremznts. corners! Here's the perfect solution -fits any NOW IN STOCK. screwdriver in. dia. approx., holds the screw AVOMETERS. Model 7 L19 IO 0 snug and straight, slips up the shank when not AVOMETER, 40 £17 IO 0 required. AVOMETER, Model VALVE TESTER (Complete) L16 10 0 L11 0 0 from Hard- TEST BRIDGE 6d. EACH L8 IO ware Shops Everywhere. AVOMINOR, Universal Model 0 AVOMINOR, D.C. Model L4 4 0 SIGNAL GENERATORS, A.C. L13 0 0 We stock: TAYLORS' METERS 15 AMP, 3 pin "CLIX" Foot Switch Plugs LI 0 0 Tcaserhms C.O.D. All orders sent by return of Post. or with order. London's Oldest Leading Radio Dealers.

EST 1919

ARTHUR GRAY GROPS- ELECTRICALLTD. , TELEVISION Our Only Address: & RADIO ENGINEERS. THE ACRU ELECTRIC TOOL MFG. CO. LTD Gray House, 150, Charing Cross Rd., London, W.C.2 123, HYDE ROAD, MANCHESTER, 12. Tel.: ARDwick 4284 Telephone: TEMple Bar 5833;4. P2

www.americanradiohistory.com October, 1947 "'fireless World Advertisements 27 of the P ick Take your NGS FTRA FER DE O na, V40111.0'S Ince rnatio Attend the Canadian it in Toronto Trade Fa

12, 1948 May

_ will be on world of of the the goods a every part spot! Dods from can comp the finest goods 1948. You order them re The Canada sponsored weron in _ together display s_ma Y Tr and seller tog many makers-manyfirst International bring buyer Fair Canada'sCanada's Trade Government International exhibits, Canadian Canadian on scale. the Full detailsfrom an international to attend available Pla a representative.rep etc., to to send Counsellor, in 194 Ortatìo ' and Commercialc nadau Canada Acting Bryan, o mme g 'Hughes, St. transportation,rap P LONDON: úaß s wt. G. COnr. y Scl Trade officeHouSeTrafaC Car GLASGOW:Govt. CanadianGa Canadian vechsler' gank Vincent 1' r , Martins MERLE GoLIVERPOOL: Trade Street. CO waterCSAND ADE p Building, pp .. DEPARTMENT CANADA

T ANNA ° r F

www.americanradiohistory.com 28 Advertasements Wireless World October, 1947

ALL -POWER CONSTANT VOLTAGE POWER SUPPLIES

This forward mounting Rack Unit, illustrated with cover removed, provides a constant out- put voltage of 300 D.C. at any current up to 600mA. The output impedance is a fraction of an Ohm, and the residual output ripple is less than 2mV.

This is only one of the many special Power Supply Units we are making to customers' requirements.

ALL -POWER TRANSFORMERS LTD. 8A GLADSTONE ROAD, WIMBLEDON, 8.W.19

TEL. : LiBerty 3303 LABGEAR -WINDING MACHINES= STRAIG11'l' WINDER

LraJlri .I.ly36 {r.il .

Very Wire clean in range 24 design to 47 swg Extremely Length ruggedly; Capacity WITH THIS SENSITIVE construc- ted GRAMPIAN MIKE Diameter Assured 7" The Grampian M.C.R. Type Microphone maximum voices ¡with that crystal clear- High Pro -, reproduces duction ness which gives full value to every word Power accentuates the " personality " of the and ' or Hand Those who still have "make do" Minimum speaker. fatigue to Driving microphones on their P. A. Systems facilities should take advantage of this up-to -date, Operator highly sensitive model which Grampian are now in a position to supply. The ALSO WAVE M.C.R. is mounted in a spring suspension frame with the Unit Assembly housed in WINDERS cast metal case. In crinkled blackand nickel standard finish. Write for details now. Type M. C. R. frequency \)`C\1- /.euJlel ä.1U16 II'. {l', G Range 80- 7,500 cycles. Q` Sensitivity Minus 45 d.b. Impedance 20 ohms. Size 24 ins. by 34 ins. frame, PRECISION MACHINES ENSURING OUTSTANDING RESULTS 6 ins. square with Base Adaptor threaded {t ins. 34 lbs LOUDSPEAKERS B.S.F. weight LABGEAR List L5 -0 -0 PLACE, CAMBRIDGE- GRAMPIAN REPRODUCERS LTD. Hanworth Trading Estate, Feltham, -WILLOW Middlesex Cambridg. Phone : Feltham 2657 Telegrams : Reamp, Feltham. 1: Phone : 2494 (2 fines) Grams : Labgear, Scienti fc Gis

www.americanradiohistory.com Wireless World Advertisements 21)

TAYLOR CIRCUIT ANALYSER. Model 20A. Audio and Magic -eye Indication. Pentode Detector in Prove. Ideal for fault finding. UNIVERSAL TAYLORMETER. Model 70A. Price £15.15.0. 50 rarges. Universal meter. Sensitivity THE TAYLOR JUNIOR. Model I20A. The 1,000 ohms per volt. Price L10.10.0. Pocket -size UNIVERSAL METER. 21 ranges. Sensitivity 1,000 ohms per volt, D.L. and A.0 Price L7.10.0. TAYLOR made

UN TAYLORMETER. Model 854. VERSAL Make a point of seeing these TAYLOR ALL -WAVE SIGNAL GEN- 90 Sensitivity 20,000 of ms per Ranges. ERATOR. Model 655. 100 Kc /s to end Price L19.19.0 vol , D.0 A.C. popular instruments among our 46 Mc¡-s. 6 scales. A.C. Mains- operated. complete range which will be Price L15.10.0. demonstrated at Radiolympia.

all to welcome leased shall be at We our friends 14IYMp1A RAD 1 19 TAYLOR CATHODE RAY OSCILLO- SIND TAYLOR VALVE TESTER. Model 45A /S. GRAPH. Model 30A. 31" Cathode Roy All tests on all usual English, American Oscillograph. Linear Time Base from and Continental Valves. Price L18.10.0. 10 to 10,000 cycles. A.C. Mains - HIRE PURCHASE TERMS Price operated. L27.10.0. ON ALL MODELS AND IMMEDIATE DELIVERY OF MOST.

TAYLOR ELECTRICAL INSTRUMENTS LIMITED, 419 -424, MONTROSE AVENUE, SLOUGH, BUCKS.

Telephone : Slcugh 21381 (4 lines).

Telegrams : "TAYLINS" SLOUGH

UNIVERSAL TAYLORMETER. Model TAYLOR A.C. BRIDGE. Mode, SCA. 40 ranges. Sensitivity 1,000 1108. Seven Capacity and seven ohms per volt, D.C. and A.C. First Resistance ranges. "Magic eye" grade accuracy. Price L15.15.0. balancing. Price L12.12.0.

www.americanradiohistory.com 3o Advertisements Wireless World October, 2947 DYNATRON THE SUPREME REPRODUCER

Since 1927 Dynatron have always made the finest radio gramophones for the radio enthusiast and music lover. The new Ether Conqueror Series again demonstrates this Dynatron supremacy.

3 cabinet styles Modern, Regency and Queen Anne from 160 guineas plus Purchase Tax. Regency Model.

All Models incorporate chassis Tuner T69a

and Amplifier LF59 : 12 valves : All Wave :

4 bands : Variable Selectivity : Whistle Filter :

Independent Bass and Treble controls : 9

watts output : 12" wide range loudspeaker : -4 Chassis available separately at 80 guineas plus

Purchase Tax. Deliveries : chassis ex- stock, radiograms in rotation. Write to us for Exhibitors at Radiolympia since 1931. Visit us at name of nearest Dynatron Dealer. Stand No. 6 Grand Hall just inside Main Entrance. DYNATRON RADIO LIMITED, RAY LEA ROAD, MAIDENHEAD, BERKS.

ve

New THE "ARNINE" A SHORT WAVE AERIAL The most suitable aerial for short wave band listening. Aerial sk' spans and down lead 441 consist of twin paral- lel feeder of 300 ohm impedance,polythene insulated. Pack in- Aerial cludes all the neces- sary insulators, fit- tings, etc. for easy that is erection. The Drayton "R.Q." is a 25 -waet motor unit geared to a final shaft, to which may be fitted for eccentrics, arms or cranks, gears, links or Operating Valves, pulleys for actuating valves or dampers, move- Dampers or Rheostats, ments, switchgear or other devices. Cinema Projectors, " R.Q." motors are available unidirectional or Rotating Screens, eoiyned reversing, with or without self- switching, for Illuminated Signs, roo /rto or 200)250 volts A.C. Small Working Models, Geneva Movements for Both types are fitted with an auxiliary two - way switch actuated by movement of the Drum -type Switches, final shaft, for operating auxiliary gear such Rocking Baths, Work ANTIFERENCE as fan motors, pumps, interlocking devices, Movement, Soldering L I M I T E D etc. and Welding Fixtures, Sales Division: FINAL SHAFT SPEEDS Continuous Turning, Reveling Max 600 R.P.M 27 min. per rev, Feed of Light Strip 67, Bryanston Street, Marble Arch, Unleireetional Max 280 R.P M. 80 min. per rev. Under Process. London, W.I. Send for List 302/xN Telephone : PADdington 7253;4 /5 Drayton Regulator & Instrument Co. Ltd., West Drayton, Mdx. A3

www.americanradiohistory.com Octobcr t917 Wireless World Advertisements 31 VISIT STAND 234 (NATIONAL HALL) FOR ALL- BRITISH PRODUCTS

RADIOLYM PIA A COMPLETE "HAM- SHACK" OCT. I -I I

The Q5/10 Receiver and the B4/40 Trans- i mitter, combine to give you everything you require for a complete station - when you want to operate - just switch on.

Q5 /10 COMMUNICATIONS RECEIVER B4/40 TRANSMITTER

5 Band 10 -Valve Superhet for A.C. Mains. A Complete 40 watt Four Band Trans- I R.F., 2 I.F. Beat Oscillator and 2 Audio Stages. mitter for Phone or C.W. 5 Amateur Bands completely spread on full vision S.M. Dial. * Four Bands 80 -40 -20.10 metres -single switch. Iron Cored Air Trimmed Inductances on Polystyrene * Two Tuning Controls only. Formers. * Built -in Modulator anc Power Pack. Adjustable Noise Limiter. * High efficiency Four Band Tank Coil Turret. Variable Selectivity Audio Filter. * Instant Crystal changing from front of panel. Dual Purpose Audio Amplifier. * Forty watts G.W. Thirty -five watts phone to KT8C Built -in "S" Meter. Final. Plug for External Battery Operation. * All essential circuits metered. Crystal Calibration Unit for Band Edge Checking * Provision for Low Impedance input from a V.F.O. (extra). * The whole completely housed in attractive black crackle finished steel cabinet 19 10 9_". also coverage coil unit. Available with general Nothing external except Microphone and Key.

PRICE: £52.10,0 (P1os Taxchase) PRICE: £75

If there is no " Q -MAX " dealer in your locality,

Prc v. BERRY'S Patent Spec. No. (SHORT -WAVE) LTD. 21011 25 HIGH HOLBORN, LONDON, W.C.1 will be pleased to send an illustrated cata- logue on receipt of THE IMPROVED " Q -MAX " CHASSIS a stamped addressed CUTTER (with Allen Key). envelope. POLYMAX " Sizes available : THE UNBREAKABLE 1" base), I (Octal), I .'t" I 1 ". (button i" and INSULATOR

IO LITTLE TURNSTILE, "Q -MAX" (ELECTRONICS) LTD., LONDON, W.C.I

www.americanradiohistory.com 32 Actvertìsesnents Wireless World Orlh,r, ry/; POINTERS FOR DESIGNERS

THE X6IM Triode -Hexode type, the An indirectly heated 6.3v. frequency changer of the per sec. (5 metres). OSRAM X6I M is suitable for operation up to 60 megacycles Outstanding features include:- cathode current, improving signal High conversion conductance for comparatively low to noise ratio. is apparent up to 5 volts R.M.S. Signal handling capacity is such that negligible distortion on the signal grid. used, making ganging of tuned Negligible " pulling " when tuned anode oscillator is circuits easy. KTW6I as IF amplifier, is designed to work in combination with Control characteristic distortion. giving maximum control on both valves with negligible A detailed technical data sheet is available on request. Osram VALVES COsramPHOTO CELLS CATHODE RAY TUBES Magnet House. Kingaway. London. W.C.2. Advt. of The General Electric Co. Ltd..

www.americanradiohistory.com W re ess World Radio and Electronics Proprietors: Branch Offices: ILIFFE & SONS LTD. 37th YEAR QF PUBLICATION COVENTRY : Managing Editor: 8-10, Corporation Street. Telephone: Coventry HUGH S. POCOCK, OCTOBER 1947 52ro. Telegrams : M.I.E.E. " Autocar, Coventry." Editor: MONTHLY COMMENTARY .. 351 IGNITION INTERFERENCE BIRMINGHAM : H. F. SMITH -I By W. Nethercot 352 SHORT WAVES FOR PLEASURE By Thomas King Edward House, New Street, 2. Editorial, Advertising Roddam ...... 358 Telephone : and Publishing Offices: HETERODYNING AND MODULATION By C. J. Midland 7191 (7 lines). Mitchell DORSET HOUSE, 359 Telegrams : STAMFORD STREET, NATIONAL RADIO EXHIBITION 1947 "Autopress, Birmingham." LONDON, S.E.,. Exhibitors at the Show .. 362 MANCHESTER : Telephone Plan and Guide .. 363 260, Deansgate, 3. Waterloo 3333 (5o lines). Stand -to -Stand Report .. 364 Telephone : Blackfriars 4412 (4 lines). Telegrams : UNBIASED By " Free Grid " " Ethaworld, Sedist, London." 387 Telegrams : TRANSFORMERS-OBVIOUS AND OTHERWISE " Iliffe, Manchester." A By " Cathode Ray " .. . . 388 Gu scow : TELEVISION RECEIVER CONSTRUCTION .. PUBLISHED -8 391 26B, Renfield Street, C2. QUALITY OF B.B.C. TRANSMISSIONS By H. A. Telephone : Central 4857. MONTHLY Hartley ...... 396 Telegrams : "Ilifle, Glasgow." Price: 1/6 WORLD OF WIRELESS .. 397 A LETTERS TO THE EDITOR 401 (Publication date 26th As many of the circuits and of preceding month) SHORT -WAVE CONDITIONS By T. W. Bennington apparatus described in these 403 pages are covered by patents, RANDOM RADIATIONS By " Dial'ist " . . 404 readers are advised, before Subscription Rate: making use of them, to satisfy ¡lornc and Abroad RECENT INVENTIONS 406 themselves that they would 201- Per annum. not be infringing patents.

Five of a kind The " Wearite " series of "P " coils is just one of a range of precision components Others are I.F. Transformers. Mains Transformers, Vibrators an3 Switches. at Radioiympia on See Stand No. 125 Wright & Weaire Ltd 2 Lord North Street, London, S W Telephone : A BBey 2126 Factory : South Shields, Co Durham 1635

www.americanradiohistory.com 34 Advertisements Wireless World October, 1947

VALVES AND THEIR APPLICATIONS

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

No. 10: Mullard OUTPUT PENTODE EL38

THE supreme merit of the cathode -ray tube, cathode circuit. Linearity is adjusted by varying as so often explained, is the absence of the damping of the output circuit. appreciable inertia in its moving part - the beam. Just so ; but if the beam is deflected electromagnetically, as in television, there comes into play the electrical equivalent of inertia -the inductance of the deflector coils. To make the beam fly back between lines it is necessary for the peak current through the coils to be reversed in less than 15 microseconds. This results in a back e.m.f., proportional to the current and to DEFLECTOR the inductance. The current must in any case 120n COILS 13n come within the handling capacity of a reasonable 6.5mM valve ; but in order to reduce it one must increase the number of turns on the coils (or the trans- former step -down ratio) ; and the inductance goes LINE NOLD up as the square of the number of turns (or ratio). Some EL38 Dala Heater voltage 6.3 V. So back e.m.f. is inversely proportional to current. Heater current ... 1.4 A. Peak -to -peak current x peak back- e.m.f., for Max. anode voltage 800 V. normal television equipment, is of the order of Max. screen voltage ... 400 V. Max. anode dissipation 25W. 250 volt- amperes ; so it is clear that the output Max. screen dissipation 8 W. valve must cope with fairly high signal values, At Va 250, Vg2 250,Vg1 -7:- such as 125 mA and at least 2,000 V. The EL 38 a top anode, Mutual conductance 14.3 mA/V. is a substantial pentode with -cap Anode a.c. resistance 21,000 12 rated to stand peaks up to 4,000 V., and cathode Capacitances current 200 mA. Sufficient deflection for a tele- Input 17.5 pF. vision tube can be obtained for a power supply Output ... .. 6.5 pF. of about 85 mA (to anode and screen) at 300 V. Anode -to -grid ... 1.2 pF. The design of such a stage, and particularly of the output transformer, is far too complicated to discuss in this space ; but see Cocking's Television Receiving Equipment, Chapter VI, or his Wireless World articles, " Electromagnetic Deflection " (July, 1946, p. 217) and " Line Time -Base and E.H.T. Supply " (July, 1947, p. 251). An ex- This is the tenth of a series written by M. G. ample of a circuit was shown in Wireless World, Scroggie, B.Sc., M.I.E.E., the well -known Consulting December, 1946, p. 405 -The Pye B 16 T tele- Radio Engineer. Reprints for schools and technical vision receiver. Another appears below. In colleges may be obtained free of charge from the the former the EL 38 is driven by a blocking address below. Technical Data Sheets on the EL38 oscillator (see No. 8 in this series) using an and other valves are also available. EF 50, but a triode will do. The amplitude of CO. LTD., the EL 38 output, which determines the width THE MULLARD WIRELESS SERVICE of the picture, can conveniently be controlled by TECHNICAL PUBLICATIONS DEPARTMENT, negative feedback, using a variable resistor in the CENTURY HOUSE, SHAFTESBURY AVE., W.C.2

Advertisement of The Mallard Wireless Service Co. Ltd. (M.V.M. 41)

www.americanradiohistory.com Wireless World Radio and Electronics

Vol. LIII. No. 10 OCTOBER, 1947 Price Is. 6d.

MONTHLY COMMENTARY The National Radio Exhibition EVERYONE concerned with the National television, but in general wartime developments Radio Exhibition is to be congratulated. were restricted to the higher frequencies, for which The Radio Industry Council, as organizers, the peacetime applications are still limited. The are now embarking on their first venture in this real advance of the industry has been in individu- direction, as the Council was formed since the last ally trivial matters of " know -how ; " under the pre -war show was held. They have introduced stress of war it has learned many lessons that many changes of principle, all of which we con- affect the details of design and production. Wire- sider to be for the better. The industry, collec- less components and equipment generally are tively and individually, also deserves the highest better designed and better made than ever before. praise for its courage and resourcefulness in carry- More efficient methods of production have in turn ing through, in the face of present -day obstacles, resulted in economies, with the result that prices the idea of a show that is actually larger and of compare favourably with those in other fields. wider scope than its immediate predecessor of " Miniaturization " and " tropicalization " are 1939. The show has now grown up ; though it is two clumsy words that nevertheless represent im- actually the seventeenth of the series, it would portant wartime advances. By learning how to have attained its majority some years ago had it make small components economically the industry not been for the war. has found means of greatly expanding the appli- Ideally, an annual exhibition should aim at en- cations of radio and radio -like equipment ; the couraging the widest possible section of the general hearing aid is one of the first examples that comes public to take an intelligent and serious interest to mind. By mastering the problems of making in radio matters of every kind. A secondary but apparatus that will resist extremes of temperature highly important function is that the show should and humidity, the whole world has been made a be regarded by those in all radio circles-including potential market for the exporter. The contribu- professional, industrial and trade -as the focal tion of the radio industry towards the restoration point of the wireless year. Pre -war shows did of our national export/ import balance is already little to satisfy these requirements ; at the worst, considerable ; there is no technical reason why it they tended more and more to publicize the less should not be larger. We have the knowledge, the solid aspects of broadcasting, and at the best they production capacity and the still more important did little more than mark a period in the calendar asset of fertility in technical ideas. of production of broadcast receivers. Educational exhibits are not lacking, but this is a Rome was not built in a day, and it would be side of the exhibition that could be expanded in unreasonable to expect the perfect exhibition to future years. The possibilities of the cinema are emerge fully developed out of the chaos of war. already being exploited with advantage in explain- But so many steps in the right direction have been ing some of the more subtle points of recent taken that we can look forward to the future of developments. This technique, used with skill and radio shows with some confidence. imagination, might be extended in many directions. The critical visitor to Olympia will no doubt Two or three "conventions," to be held at look for signs of the influence of the war years on Olympia, have already been arranged ; here, again, current practice. In our view, the most important is an idea that should be developed. Every en- effects of that period will not be in matters that couragement should be given to those who wish to are evident superficially. True, radar technique plan meetings to coincide with the annual has contributed several details of circuit design to exhibition.

www.americanradiohistory.com %0'íre lesti World October, 1947 Ignition Interference and the plug gap breaking down at 1. -Its Nature, Magnitude 5 kV. Increasing resistance re- duces the amplitude of the current Measurement and at about r,000 ohms changes the discharge from oscillatory to By W. NETHERCOT, M.A., B.Sc., F.Inst.P. unidirectional. With 25,000 ohms in circuit it is indistinguishable, (British Electrical and Allied Industries Research 'Association) except for the steep front, from the subsequent inductive dis- ALTHOUGH extensive in- The circuit is shock excited by charge. vestigations on interference the breakdown of the gaps G, and These records were obtained from the ignition systems of G. The distributor gap breaks with the resistor inserted at the motor vehicles have been made down at about 3 kV and the sparking plug. A resistor inserted over many years by organizations sparking plug gap anywhere be- in the coil- distributor cable or at such as the Post Office, the tween approximately 3 and i 2 the distributor end of the plug B.B.C. and the Electrical Re- kV, depending on engine condi- cable reduces the rate at which the search Association, little quanti- tions. When the sparking plug self- capacitance C, discharges to tative information has been pub- breaks down the energy stored in the same degree as does a similar lished. The Electrical Research the capacitance resistor inserted Association has issued many re- C, and the H.T. at the plug end of ports on this subject to its mem- cables, both of With the spread of television, the H.T. cable bers but the information contained which are charged the question of interference but, whereas the ; to the breakdown prevents therein has not been published from motor - vehicle ignition latter voltage of the the rapid dis- at least since Gill and Whitehead's systems will become increas- paper in J.I.E.E., 1938.' It is the plug gap, is rap- charge of the purpose of these articles to sum- idly dissipated, ingly important. These articles charged H.T. marize the information contained giving rise to the contain a summary of present- cable the former in these reports and to give an up- so- called " capa- day knowledge on the nature does not, and this to -date picture of the situation at city " component of ignition interference, its is the reason why present obtaining. of the ignition measurement and suppression a single resistor spark. The cur- in the coil -dis- Origin of Interference. - The rent is oscillatory tributor cable is ignition circuit is essentially a and has a complex wave shape ineffective as a suppressor at spark generator. It can be repre- with a high peak value, but frequencies above 8o - 100 sented approximately by the cir- decays rapidly, due to energy dis- Mc/s. cuit shown in Fig. i. L is the in- sipation in the dielectric of C the The upper limit of the frequency ductance of the H.T. winding of gaps G, and G2 and the R.F. re- band of the radiation depends on the coil or magneto and C, is its sistance of the circuit. ' For nor- the rate at which the gaps G, and self- capacitance. 1, and l2 are the mal motor vehicles the current G2 become conducting at break- cables joining the coil to the dis- oscillates at a frequency between down. Theoretical considerations tributor and the distributor to the 3o and 5o Mc / s. The discharge indicate that the voltage should sparking plug. For magnetos lasts only for a microsecond or fall to a negligible value in an ex- with integral distributor 1, can be less but the peak current may be tremely short time and this is several hundred amperes. A suc- borne out by experiment. The fall cession of such discharges may is too rapid for accurate measure- occur due to current chopping ment ; some tests made by the before the final inductive dis- author with a high -speed oscillo- charge in which the amplitude of graph on the breakdown under the low- frequency current is only impulse of a i millimetre gap a fraction of an ampere. The in- (which is of the order of the spark- ductive discharge contributes a ing plug gap) have shown it to s Fig. 1. Essential circuit of negligible amount to the radio take place in less than 4 x io ignition system. interference except possibly at the sec., and it is probably consider- lowest frequencies. ably shorter than this. One of the omitted. G, is the distributor Spark Discharge. -The capacity oscillograms is reproduced in gap and G2 the sparking plug spark discharge, and the effect of Fig. 3. gap. C2 is the self- capacitance of resistors on it, has been Frequency Distribution. -Mea -. The capacit- suppressor the sparking plug. studied oscillographically by the surement has shown that ignition ance associated with the distribu- author. Fig. 2 shows tracings of interference has a continuous fre- tor gap is not shown. some of the oscillograms obtained quency spectrum from normal References are to a bibliography to be up to at published with Part 2. on a typical ignition system with broadcast frequencies

www.americanradiohistory.com October, ¡947 Wireless World 353

least 65o -Mc / s. It is not serious value of the interference. This is (2o- r2oMc /s) had a bandwidth of at the lower frequencies, except the well -known method of assess- rot kc / s and both had output to radio equipment situated with- ing the " annoyance " effect of meters of the type mentioned in the vehicle, but rises rapidly in interference to radio reception, above except that the discharge intensity above ro Mc / s and is and it has been standardized by time was increased from the speci- very strong at television fre- the British Standards Institution fied value of 15o milliseconds to quencies. At one time it was and accepted by the C.I.S.P.R.' 50o milliseconds. thought that the intensity de- It is necessary The response of creased progressively with increase that the equipment a meter of this of frequency above roo Mc /s but should be ade- .r 3 type to a succes- more recent measurements, both quately sensitive to sion of pulses is a here and in America, have shown both interference

www.americanradiohistory.com s 354 Wireless World October, 1947

Ignition Interference- a level of about 3oµV /m, as frequencies between 22 and 48 suitable for the sound transmis- measured at the television aerial, Mc / s and at distances between 3 sion. Although a bandwidth of was just tolerable. and 141 yards from the side of the loo kc/ s is greater than the audio Many television aerials are road (ground level). The corre- bandwidth of television receivers, situated considerably more than sponding attenuation with dis- 3oft from motor vehicles tance curves shown in Fig. 5. 4 are = 70 and are often screened to The order of levels observed and f 0 iANCE 3 TOI some their relatively slow o- 60 extent from the attenuation > direct radiation by the with distance indicate that motor 50 TDS t A; 25 presence of ; vehicles can cause interference' J 40 buildings T, furthermore the residual over a wide area. 30 >!e 1,1T,5 M\ field from many vehicles Fig. 6 shows the results of tests 1 at 20 on a number of vehicles stan- 26 28 30 3 34 36 36 40 42 44 46 411 after suppression is less at a than 5oµV /m. dard distance of 3oft and a stan- FREQUENCY Mold In view of these facts dard speed of 3o m.p.h. At 15 the figure of 50µV / m is Mc /s the strength of the inter- Fig. 4. Frequency variation of average ference field is about 15 db below peak -field strength of interference from not an unreasonable one motor vehicles. and although the specifica- tions on radio interference COMiCIAL the pre -war subjective tests car- are in course of revision, it is un- liklikt-- ried out by the E.R.A. showed likely that the revised ones will Iin, 4sMc/s that the limiting signal-to- inter- call for a higher degree of sup- ference ratio for tolerable sound pression.' Practical tests have .lMIWK reception as measured in the way shown that ignition interference to described above was independent television is reduced to a tolerable Cligna, of the type of interference and level by the simple methods well approached 4o db, the well -known known before the war.' o MIEN= 50 60 70 limit for lower frequencies. The Magnitude of Interference. - corresponding limits for the vision The frequency range below Izo FIELD STRENGTH IN db ABOVE i.&V/m transmission were found in most Mc / s has hitherto excited most Fig. 6. Interference due to motor cases to vary from 20-35 db. interest for in it lie not only the vehicles. Some recent television ser- 70 tests by the vice but also that at 45 Mc /s and it will be ob- 60 B.B.C. a n d other import- served in the latter case that r the E.R.A. on 50 ant services ; mV /m is rarely exceeded (the the subjective 40 i\tte4_ e.g., police maximum field recorded was z aspect of igni- 50 radio cars. mV /m) and that only 40 per tion interfer- The E.R.A. 20 Eall -`-"----_ cent of the private cars tested ence to tele- 21 Me/s has made an exceeded 10 MEN 3o µV /m. vision re- extensive sta- A series of measurements ceivers of the 40 60 120 I6o 200 tistical survey between 43 and r r8 Mc /s at 3oft post-war type of ignition in- DISTANCE FROM ROAD IN YARDS from the line of traffic on Western have indicated terference b y Avenue is shown in Fig. 7, which that when the Fig. 5. Variation of average peak - measuring the also shows the results of controlled receivers a r e field strength from motor vehicles radiation from tests on a number of vehicles at fitted with with distance from road. motor vehicles frequencies of 5o, 8z and 103 audio and at selected Mc/s. video noise limiters they are points near roads such as the In the latter the vehicles were more sensitive on the vision than Great West Road and Western stationary at Soft from the aerial the sound channels, probably due Avenue which have fairly high and the engines run at a speed to a reduction of the signal -noise traffic densities and ratio in the latter. More compre- on which the aver- hensive tests are needed on this age speed is be- point and arrangements to this tween 3o and 40 SO effect are in hand. m.p.h. In addition Tolerable Interference Level. upwards of roo - 40 Before the war BS833 specified separate vehicles, that the interference level in the both private and VALUES OBTAINED ON WESTERN AVENUE frequency band 1.5 to 15o Mc / s, commercial, have 3°- e CONTROLLED TESTS, VEHICLES STATIONARY measured at ground level 3oft been studied under

I I I from the interfering source, should controlled condi- 10 I 1 60 not exceed 5oµV /m(4). In the tions. 40 50 70 BO 90 100 110 12 tests mentioned above the peak Fig. 4 shows a FREQUENCY IN Mess field of the television service was series of measure- 3ooµV / m and the interference ments made on Fig. 7. Comparison of interference measurements from the vehicles, suppressed to Western Avenue at on stationary and moving vehicles.

www.americanradiohistory.com October. 1947 Wireless World 355 which produced the maximum the inductance and radiation These tests were made on 1940 reading of the output meter. fields and the fact that at short model Vauxhall " 1z " and " 14 " Results of Tests. -The agree- distances from a vehicle its dimen- cars with a pulse field strength ment between the two sets of sions become comparable with measuring set designed by the measurements is satisfactory, hav- such distances. Interference radi- N.P.L. It consists essentially of ing regard to the different condi- ated from the vehicle body arrives a tuned half -wave dipole aerial, a tions of test. The results show at the aerial from different direc- frequency changer, an I.F. ampli- that the interference level falls tions and the magnitude of the fier tuned to 35 Mc /s with a band- progressively with frequency in- sum of these is a function of the width of 2.5 Mc /s and a cathode crease over the range ray indicator unit. The fre- to 118 Mc / s ; at I w quency ranges are 20 to 3o and 40 43 A - -* VERTIAL POL'RISATION 118 Mc /s the level is e to 65o Mc / s. about zo db lower than 111111 8 01 sb90 f4 iE11L' Figs. and 9 show respectively that at 43 Mc /s. Fig. the variation of the interference > 70 t14.043Elijil Mr 4 shows that the level with frequency for the " rz " and 60 6-6 HORIZONTAL POLARISATION increases with f re- ---- " 14 " cars. It is seen that the quency in the range 26 30 0 leo I ZOOCO 300 1 400 S00 600 7C curves are series of crests and to about 43 Mc /s and troughs with variations in level of so it appears that the FREQUENCY IN Mqs up to 3o db but that the average band most susceptible level does not fall off with in- Fig. 8. Variation of interference with fre- to interference is that quency for unsuppressed Vauxhall " rz " crease of frequency which is in in which the television car. accord with George's results. service operates. Some difficulty was experienced It should be mentioned that all phase differences which depend on in determining the peak ampli- the figures given above refer to the distance of the aerial from the tude of the interference as the in- the vertically polarized compo- vehicle. dividual peaks, as seen on the nent of the ignition field. (Tele- However, in general, the nearer C.R. screen, varied over the en- vision aerials receive vertically the aerial is to the vehicle the gine cycle by as much as ro db, polarized radiation.) more severe is the interference ; on with occasional peaks, recurring For reasons which bave already the average the mutual interfer- about once a second, about 5 db been stated it is unnecessary, ence between two vehicles passing above the general maximum peak when considering interference in one another under normal road level. A change of frequency of relation to television, to measure conditions is about twice as much a few Mc /s was often enough to at distances less than 3oft from as when they are separated by 3oft. change completely the character TABLE I of the peak -to -peak distribution. The ratio of the horizontally to Distance in feet of Interference expressed as db above the vertically polarized compo- aerial from 1µV /m nents of the field is a function of Vehicle centre of the frequency, but appears to vehicle 30 35 40 45 50 80 100 Mc/s obey no simple law. With one or two exceptions it is well below Vauxhall " 12 " 6 52 49 51 57 65 40 37 ro db. 15 48 43 46 50 58 42 44 30 45 43 47 51 51 39 34 Table II shows the distribution Of of radiation around the " 14 " Vauxhall "14" 6 38 45 45 46 65 45 42 car. The aerial positions A, B, 15 35 39 36 41 56 43 37 C, D are shown in Fig. ro ; the 30 33 31 38 37 55 36 32 normal measurements were made at A. the source of ini rteronce, but for Interference above 120 Mc / s.- It is seen that the distribution police radio cars, which must Very little information operate in close proximity to about ignition interfer- 90 11111.11 1111.lT.N.. other vehicles, shorter distances ence above 120 Mc / s is Il.yyiitr are of more interest. available ; the only Ro %0`yyES Table I shows how the level of comprehensive results 70 Z!'p PO ARISÁ71

www.americanradiohistory.com 356 Wireless World October. 1947

Ignition Interference- way along the cylinder block, to the engine, the interference tion of the frequency. It is prob- may reduce the interference con- level may be reduced by 8 -21 db. able that the distribution is affec- siderably. A further reduction Redesign of the layout of the ig- ted very largely by the car body. may be obtained if advantage is nition system on the lines dis- Fig. II (a) and (b) shows the taken of the screening effect of cussed above may in some cases variation of the field strength of the interference with distance at TABLE II 175 Mc /s and Soo Mc /s respec- tively. They show that slightly Interference level in db above higher levels are obtained with 1 µV /m the greater aerial height but the Frequency in Mc /s Polarization tests were not comprehensive A B C D conclu- enough to permit definite 55 Horizontal 74 68 75 69 sions to be drawn about the effect 55 Vertical 79 79 78 75 of polarization, aerial height and 175 Horizontal 79 79 81 81 frequency on the attenuation with 175 Vertical 85 82 88 88 distance. They indicate no special relationship between these 300 Horizontal 84 79 78 86 factors on the average the 300 Vertical 82 88 85 86 level is reduced by about 3o db 500 Horizontal 93 83 89 82 as the aerial is moved from 500 Vertical 95 86 94 90 Io to zoo yards from the cars. This is about To db greater than proximity to the metal mass of avoid the necessity for the use that found for the frequency band the engine. The farther the leads of suppressors. up to 5o Mc /s which suggests that can be kept from the bonnet, so Engine conditions, the type of is the interference likely to be sparking plug and its gap width smaller because of the reduced affect the interference mainly in coupling between them. so far as they affect the break- The type of body affects the down voltage of the sparking plug magnitude of the interference con- gap, and the magnitude of the dis- siderably ; fortunately the modem charge current. C A trend in pressed steel body design Spark Gap Length.-Increasinn leads to reduced interference. On the gap width of the sparking many new vehicles the hinged part plug increases the breakdown of the bonnet is in one piece as voltage but often this increase is compared with the four-sectione 1 less than linear. With some en- type in which the between in- loo Fig. ro. Positions of measure- bonding e---e VERTICAL POLARISATION AERIAL 'HEIGHT 10' dividual members 90 b- -....a .. u 6'- ment for results shown in Table II. 0.0 was very indifferent :e 80 ignition interference at ultra -high from an R.F. aspect. 0 70 frequencies will be much more re- More efficient screen- LT_o 60 artigliiiiiiiMMIll ing is the result, m stricted in area than at the lower < 50 11111,..ifill NI -1 frequencies. with consequent re- of the in- 40 .r -4 HORIZONTAL POLARISATION AER AL HEIGHT re --=- Factors affecting Magnitude. duction +--4- .. , 6' - is so Referring to Fig. 6 it will be ob- terference. It still 40 80 120 160 200 240 280 served that there is a great varia- common practice to mount ignition coils DISTANCE Of AERIAL FROM VEHICLE IN FEET tion in the strength of the interfer- (a) (FREQUENCY 175MCJs ence from one vehicle to another ; on bulkheads in- stead of on the for instance at Soft distance the loo field strength from some vehicles engine and this gives á : -* VERTICAL POLARISAtION. AERIAL' HEIGHT IO' a long distributor 90 - is less than 25 db above TµV /m, á 80 with others it is as high as 66 db ; lead and circulating e i.e., a ratio of about Too to T. path for R.F. cur- :4 70 There are a number of factors rents. E.R.A. tests w ao 1111115462 ---- which account for this variation. so a-N HORIZONTAL POLARISATION AERIAL HEIGHT 10' The layout of the ignition system Fig. rr. Variation of 1C n , 6' 40 _ + - -+ and its relation to the vehicle interference with dis- 1 1 I I' 30 body have a large effect on the tance of aerial from 40 80 120 lao zoo 240 280 magnitude of the interference. In vehicle and aerial height above ground. DISTANCE OF AERIAL FROM VEHICLE IN FEET general the longer the H.T. igni- (b) (FREQUENCY 500Mcrs ) tion leads the greater is the inter- ference, at least for frequencies up have shown that if the coil is suit- gines it is possible to increase the to that of television. Reduction of ably mounted on the engine so as gap widths considerably without the length of these leads; e.g., by to reduce the dimensions of the noticeably increasing the interfer- location of the distributor mid- radiating circuit and to confine it ence, since the breakdown vol-

www.americanradiohistory.com (Jctober, '947 Wireless World 357

tage, once the engines have tion performance, loose connec- changer where a further conver- attained normal working tempera- tions in the high tension circuit sion to 5 Mc /s is made. The main ture, changes very little with and large distributor gap due to amplification then takes place at appreciable variation of gap worn rotors are to be avoided. this frequency. The dverall band- width. Relatively little can be done to width of the receiver is 5o kc /s On at -3 db, which allows for crystal the other hand, additional affect the magnitude of the inter- tolerances in transmitter and re- spark gaps in the circuit should ference by sparking plug design ceiver and also permits the system be avoided since each gap break- which anyway is controlled by to operate, when required, with down on the ignition circuit pro- other considerations. several headquarters' transmitters duces a R.F. voltage and current Engine conditions influence the in different locations and on slightly impulse. Also any additional gap interference appreciably ; the different frequencies, but all modu- in series with the sparking plug effects are rather complicated but lated from a common source. This may be partially or wholly addi- in general maximum interference system was described in our issue tive with it of February, 1946. and so increase the occurs at rapid acceleration from The main interest in the mobile peak voltage of the system and low speed and at wide throttle transmitter is perhaps its extreme the magnitude of the discharge under heavy load such as occurs compactness. Miniature components current. For this reason, apart when ascending gradients at high are used throughout as well as from deleterious effect on the igni- speed. miniature valves. The working fre- quency is extracted from the crys- tal oscillator in one operation and then amplified by two successive Mobile Radio - stages, the last of which drives the Telephone final amplifier, which delivers be- tween 8 and io watts Marconi 100 - Mc /s from send to receive is effected by a press- button switch on the hand to the aerial. Anode Equipment microphone. This changes over the modulation is employed. A NEW V.H.F. radio -telephone short vertical designed by Marconi's Wireless aerial from one Telegraph Company for use by set to the other. police and fire services was demon- Each of the two strated recently in London. This sets is entirely equipment operates in the 78 to loo - self -contained and Mc/s band and consists of mobile includes its own units for installation in patrol cars, rotary trans- vehicles and launches and a fixed former. installation of considerably higher Transmit- power for headquarters' use. ter and receiver Perfectly reliable two-way corn - units are very munication was maintained between compact: each a car and a temporary fixed station measures 8in in the centre of London, while wide, 15 +in deep signals were actually received in the and 71in high. car in the heart of London from the They are as- Company's works in Chelmsford. sembled normally Reliable communication was also side -by -side on a maintained between Chelmsford and shock - absorbing the temporary headquarters' station. carrier located in Transmitter No interference of any kind was the luggage boot of the car. Quick (right) and re- caused by adjacent and passing release fittings and rear plug and ceiver units of motor cars, this freedom from the socket connectors allow rapid servic- Marconi radio- effects of the ignition systems being ing of the units. telephone entirely due to the effectiveness of An additional facility provided is Whilst the same receiver, but with the noise limiters in the receiver. that the audio output from the a different power unit, is used in the The radio car was not fitted with modulating a m p l i fi e r, which headquarters' installation this trans- suppressors of any kind, yet there amounts to about ra watts, can be mitter is a comparatively high - was no interference when operating switched at the remote control power one and delivers about 50 on the move. unit to a loudspeaker mounted out- watts of R.F. to the aerial. This The mobile equipment is powered side the car and the microphone is has separate drive and power am- from the 12-volt car battery and then used for traffic control pur- plifier units, the former being consists of a double superheterodyne poses. crystal controlled and by means of with crystal- controlled oscillator and The receiver is unusual in that, doublers and tripiers, all of which a crystal -stabilized transmitter, both though it is a double superhetero- are small V.H.F. pentodes, the out- working on spot frequencies. There dyne, it has only one oscillator. As put is raised to the operating fre- are no external tuning controls of previously mentioned this is crystal quency after which two stages of any kind. The few controls that controlled and the third harmonic high -power amplification are em- are needed are all located on a small is taken out in the anode circuit and ployed. remote control unit which can be injected into the first frequency Various other applications are mounted on the instrument panel, changer. The first I.F. is about visualized for this new Marconi or anywhere else convenient. 45 Mc /s. After passing through equipment such as ship -to -shore This control unit carries the one transformer the signal, with and ship -to -ship communication in switches for starting up the trans- the original injected oscillations, harbour work, such as tug boat mitter and receiver, but changeover is passed to a second frequency services.

www.americanradiohistory.com relititi N'ori1 October, 1949 Short Waves for Pleasure and -so, who was first violinist at Radio Engineer Takes a Busman's Holiday the Argyle Theatre in Birkenhead before the war ! I never was in By THOMAS RODDAM Birkenhead and I don't know any first violinists, and nor do 99 per 1OMEONE lent us a flat in a few minutes the receiver had cent of the listeners to the over- Stockholm for a month. This drifted completely away. At a seas service. Can't a quick pro- S isn't going to be a description rough estimate it drifted at least gramme summary, free of the of non -austerity life in Sweden, five band -widths, and it certainly Boys at the Bolivar atmosphere, although that would be a subject went on drifting for an hour. That be slipped in after the news to gloat over. The flat had a radio meant that for the first half-hour bulletins? set in it, one of those all -wave it needed retuning every five Reverting to a more technical minutes, and then at increasing 4 jobs which form an essential item point : can't Mr. Bennington help, of furniture nowadays. The aerial intervals. Of course, we should too. I don't want to sit down system was simply five floors never have switched off, but with Tremellen charts or the height of central heating, and it austere habits die hard, and in month's ionospheric predictions to seemed to do some good. On this practice we tried to remember to find which band to tune to. It is equipment we tried to get some switch on half -an -hour before we nice to know that in East Africa entertainment. tried to listen. I should tune to the r9 -metre Of course, there was the local This question of drift is well - band, but an indication that station, which came roaring in as known, and there are quite a lot listeners i,000 kilometres east of 1 all local stations do. The only of cunning ways of compensating London should tune to such and trouble was that the programmes for it, according to the literature. such band, based on the current seemed to consist of short gramo- In receiver production, however, propagation conditions, would be phone recitals and long talks in it -seems as though the cost of fit- most useful. As it is, I had to what was presumably Swedish. ting a short -wave range has ex- check the 19 -metre band, to make Entertainment value -to us -- hausted the manufacturer. One sure that the poor signals on 25 practically zero. The rest of the solution which I haven't seen de- metres weren't absorption rather medium -wave band was pretty scribed is to fit a heater inside the than penetration, and then hunt dead at all normal hours : the box with a suitable cut -out around 31 metres to find the pro- hour of darkness which forms the switch, to bring the whole thing gramme. Again, most listeners Swedish utility night in summer up to its steady temperature don't know that when the signals was needed for sleeping. The quickly. If the drift was all over go bad they must change wave- long -wave band is, of course, stiff in five minutes, that would be bands, and they certainly don't with the caterwaulings of radio tolerable, but the slow creep after know which way to go. beacons, which form an interest- an hour is an abominable My short period of complete de- ing commentary on the popularity nuisance. The other really trying pendence on broadcasting on short of the newer navigational aids. thing is this ticklish tuning ; find- waves has been most instructive The receiver, by the way, was ing a station by searching a band to me. It has brought out the calibrated with the names of too is tolerable, but having to hold seriousness of the defects, both medium -wave stations and 25 ones breath while doing it is not. in receivers and in B.B.C. infor- long -wave stations : it seemed a The receiver market in Europe mation, of which I was already lot of marking for just one usable is open to British receivers. Quite vaguely aware. It would be well programme. a lot of countries have long -wave if receiver designers could be made local stations, so that American of Short Waves to depend completely on their own Shortcomings competition is not so serious the receivers for a time, so that they This left us the short -wave Germans are, for the moment, out would make more serious attempts band. Twelve megacycles in 8 of the market. It is essential, to cure their defects. inches, or 7¡ turns of a small however, that the receivers should knob. Actually, as the scale was be good. Europeans do listen to Electro- plating not very linear, the useful range the B.B.C., because they want to ACOMPREHENSIV] collection ran to about 2 Mc /s per turn, improve their English. If they of data for those concerned which means than to tune to with- suffer as I did, they will get bored. with the design, erection, mainten- in i kc /s of the carrier, the knob Then, of course, there are the ance or operation of electro- deposi- had to be adjusted to within to programmes. Three times within tion plants is to be found in the minutes of arc. It is possible to 3o minutes we were given the " Handbook of Industrial Deposi- This book, just issued by do this, but it is not éasy, and I same cricket scores on the same tion " we our publishers on behalf of our asso- don't think a non -technical programme. In case missed ciated journal, Metal Industry, con- listener could, or would, manage that, an hour later there was a fines itself to the practical aspects it. Certainly my wife couldn't and sports bulletin. But I could of the subject, and does not deal just wouldn't try. Of course, it never find Tommy Handley : I with theory. The Handbook costs really didn't matter, because after was told I should remember so- r5 /- (postage 7d).

www.americanradiohistory.com October, 1947 Wireless World Advertisements 33

istfrija Ito iseg 61786 guEt

CHANGE SOCKET CHANGE CONNECTIONS OTHER WORK PERFORMANCE NECESSARY CHANGE TYPE FROM TO FROM OLD TO NEW SOCKET SOCKET 6P8G

REALIGNMENT SLIGHTLY 6K8G INTIOCTAL NO CHANGE NO CHANGE WILL BE REDUCED NECESSARY I GAIN

i

RATED CHARACTERISTICS BOTH 6P8G and G2,. cT 6K8G are triode - G4v 03, 6P8G 6K8G Heater Voltage 6.3 6.3 Volts hexode types with A. Current 0.8 0.3 Amps International Octal 2 Anode Voltage 250 250 Volts bases, and no change U Current 2.2 z H 2.5 mA. of connections will be Screen Voltage 80 100 Volts necessary. The inter - C D 6 P 8 G a Osc. Anode electrode capacitances G2H GIT Resistor 50,000 40,000 Ohms. G4H G1H of the two types are Conversion 0.65 0.35 mA/V. different however, AH AT Hexode Input and G3H Capacity 7.5 5.5 m.m.f.d. it will be necessary to CAP Hexode Output realign the oscillator Capacity 21.5 5.5 and I.F. circuits after Osc. Input 6 K 8 G KEY C Capacity 17 7.0 Brimariring.

BRI Nest- '101( which ,firs a service can offer class dealers whose customers those ve ose flPIMAQ radio sets valves designed round RADIO VALVES are in shorter RADIOLYMPIA which OCT. I-11

STANDARD TELEPHONES AND CABLES LIMITED, FOOTSCRAY, SIDCUP, KENT.

WATCH THIS SERIES FOR THE BEST ADVICE

www.americanradiohistory.com 36 Advertisements Wireless World October, 1947 TYPE A.D. /47 VPdatill9 DiAmoth.56 AMPLIFIER

This is a 10-valve amplifier for recording and 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 feed -back. 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 over- load indicator switch, scratch compensation control and fuse. All inputs and outputs are at the rear of the chassis.

C.P.20A. 15 WATT AMPLIFIER

for 12 volt battery and A.C. Mains operation. This improved version has switch change -over from A.C. to D.C. and " stand by " positions and only consumes 5 amperes from 12 volt battery. Fitted mu -metal shielded microphone transformer for 15 ohm microphone, and provision for crystal or moving iron pick -up with tone control for bass and top and outputs for 7.5 and 15 ohms. Complete in steel case with valves. As illustrated. Price E28 0 0

PORTABLE DANCE BAND EQUIPMENT

This I5 -watt amplifier, has a response 35- 25,000 cps. mixing arranged for pick -up and microphone, large output transformer for 4 -7.5 and 15 ohms. Complete in 3 -part leatherette case as illustrated, with 2 -10in. P.M. Speakers, moving coil microphone and collapsible floor stand, retails at 40 gns.

"SUPER FIFTY WATT" AMPLIFIER complete in louvred steel case, 362 gns.

257 -261, THE BROADWAY, WIMBLEDON, LONDON, S.W.19

TELEPHONES : LIBerty 2814 and 6242 -3

TELEGRAMS : " VORTEXION, WIMBLE, LONDON."

www.americanradiohistory.com 'October, r947 rrle%s N'orld Hetero dyning and Modulation frequencies respectively. The Do Additive and amplitude of these voltages is Multiplicative Mixing equal to half the carrier voltage when M = I. These are the well - Amount to the Same Thing ? known sidebands. The modulation frequency is usually low compared with the By C. J. MITCHELL, A.M.I.E.E. carrier frequency, but in the case of the superhet frequency changer FREQUENCY changing in a the modulation factor would alter- employing multiplicative mixing, superhet can be accom- nate between plus and minus. the modulation frequency is very plished in two ways, (a) by This would result in frequency close to the so- called carrier adding the signal to the oscillator doubling, for each trough due to frequency ; the lower sideband and then rectifying the resultant the negative half -cycles of the due to this modulation is the voltage, or (b), by employing one cosine term would become a peak. required intermediate frequency. voltage to modulate the other ; The envelope would not be truly It is rather interesting at this in this case the modulation pro- sinusoidal in form but would be point to study a graph of a modu- duces two sidebands, the lower of similar to the shape of the output lated voltage ; when an R.F. which is the required intermediate voltage of a full -wave rectifier. voltage is modulated at an audio frequency. Method (a) is usually If equation (I) is multiplied out frequency, the sidebands are not referred to as additive mixing, it becomes :- while the second method is called V.t = sin 2nfct sin 2nfct cos 21rfmt . . (la) multiplicative mixing. If this Vmax + MV., process is studied carefully it In this form the equation shows will be seen that there is a very that there is the unmodulated apparent in a graph, but when a close connection between the two carrier voltage, plus what is voltage is modulated at a fre- methods, and additive and multi- apparently another voltage whose quency near to its own, a graph of plicative mixing amount to almost frequency is not obvious because the resultant voltage reveals the the same thing. Frequency chang- ing is really a multiplicative Fig. ï (a). 6o -kc /s process, irrespective voltage modulated of the way in at to kc /s. (b) 12o- which the oscillator and signal (a) ./ I 1'.-.'11i1'- kc/s voltage modu- voltages are combined. Simple lated at t to kc /s. In addition of these voltages does this case the side - not produce a difference frequency, MODULATION ENVELOPE - IIOkc/s bands can be seen in and it is only after rectification i\ the graph. The aver- that the intermediate frequency r\ f\ i\ iRi age level varies at / l r\ ¡\ lá,i (b) \\ the difference -fre- appears as a voltage. quency (lower side - The reader will probably agree band) and the kink that amplitude modulation is a in each alternate purely multiplicative process, for it is the product of two sinusoidal half cycle of the carrier wave is the R.M.S. value of a modulated quantities. It only requires the the sum -frequency voltage (upper carrier voltage is being multiplied application of a little elementary sideband). by a factor which is varying in trigonometry to change the form magnitude at the modulation fre- of the second term into something two sidebands quite clearly. The quency. The equation to a which shows the frequencies envelope of an amplitude- modula- modulated carrier voltage can be present. ted wave is shown in Fig. I (a) ; written down in the form :- the ratio of the carrier frequency to the modulation frequency is 6 : I VLn,t Vmnx sin znfct (I + M cos 2nfrrtt) . . . . ( I ) in this case. Fig. r(b) shows the where V1,,,t = the instantaneous result of modulating the carrier value of the carrier voltage, fc = From the identity : sin A. cos B at a frequency close to its own, the the carrier frequency, fm = the = sin (A + B) -l- z sin (A - B), ratio between the two voltages modulation frequency, M = the we can re -write the second half being II : 12. It is seen that the depth of modulation. M = I when of equation (Ia) as follows : the depth of modulation is loo MVm,,:= sin (277fct + 2nfmt) + 21'IVmAx sin (2nfct 2nfmt) per cent. 2 - 2n sin 27 Ant)] The constant I at the beginning = IMV max [sin (fo + fm)t + (fc - (2) of the second term is present be- This shows the existence of two cause the modulation factor varies equal voltages whose frequencies whole curve moves up and down between zero and 2 (when M = I), are equal to the sum and difference about the datum line at a fre- and if this constr nt were omitted, of the carrier and modulation quency equal to the difference

www.americanradiohistory.com 36o Wireless World October, 1947

Heterodyning and Modulation - Equation (3a) shows the exist- adding the ordinates together is frequency. The average level ence of a voltage whose fre- extremely laborious and not always line is the lower sideband, usually quency is equal to the average of very instructive. More informa- employed as the I.F. in a superhet. the two frequencies concerned, tion can often be obtained by The upper sideband is not so multiplied by a sinusoidal term representing the voltages vec- - obvious, but it will be noticed that whose frequency is equal to torially and adding the vectors a little kink appears in each alter- half the difference frequency. together. It is generally under- nate half -cycle of the resultant How, then, does the resultant stood that vectors of different voltage, and if this kink appeared envelope vary in amplitude at frequencies should not be added together, we are Fig. 2. When two sinusoidal but provided voltages of equal amplitude considering instantaneous con- ande different fre- ditions only, then it is quite quency are added together, permissible to add vectors to- the resultant voltage is modu- gether. lated at the different fre- The series of vectors shown in quency. Notice that this Fig. 3 represents the conditions modulation is not sinusoidal. instant by instant, when two -4 on the same portion of the wave the difference frequency ? The alternating voltages of different in each cycle it would appear to be answer is simple ; the second term frequency are added together. a second harmonic. Its position is in (3a) passes through two peak Consider each vector to be rotating constantly shifting, however, so it values per cycle ; one positive in a counter -clockwise direction ; is not harmonically related to the peak and one negative peak. The all the vectors shown in Fig. 3 (a) carrier voltage ; its frequency is positive peak results in a maxi- are rotating through 271a radians not exactly equal to twice the mum value of the resultant volt- per second, and those in Fig. 3 (b) carrier frequency, but very nearly age, and the negative half-cycle are rotating through 2 of b radians so. It is the sum frequency, so produces another maximum, the per second. The instantaneous this kink is the upper sideband. only effect of the minus sign voltage is proportional to the (zoo per cent modulation is shown being to reverse the phase of the vertical component of the vector, in order to accentuate the side - resultant voltage. Notice that so the voltages pass through their bands). although rectification has not yet peak values as the vectors reach Now let us consider the so- been performed, the combined a vertical position. Each vector called additive process. Fig. 2 voltage is the result of a voltage is virtually a snapshot of the con- shows the result of adding together with a frequency equal to the ditions at regular time intervals, two equal voltages of slightly average of the two individual fre- the snapshots being taken each different frequency. The resultant quencies, which is being multi- time vector " a " has made one voltage rises and falls between plied by a sinusoidally varying complete revolution ; vector " b " zero and 2V at the difference factor whose fre- 1 frequency. If we write down the quency is equal to equation to the resultant voltage half the difference (d)r1iiiiiiii!tit it is seen that there are no voltages frequency. Thus frequencies equal to present with simple addition of (b) f \i the sum and difference frequencies, two sinusoidal Ae- and although the contour of the quantities results in envelope is varying at the differ- multiplication. ence frequency, this does not Where, then lies 1 I indicate the presence of a voltage the difference be- (c) I f7r>ttd<Ì 1 '\ of that frequency. The envelope tween additive and of an amplitude -modulated carrier wave varies at an audio frequency, but there is no A.F. voltage present Fig. 3. Heterodyning in the carrier wave. and modulation. (d) If we express the two voltages in the form : multiplicative mixing ? is rotating at a lower speed than Va = Vmax sin 2 ofat The process of plotting many vector " a " so it appears in a and Vb = Vmax sin 2nfbt, then cycles of two voltages and then different position each time and is adding them together produces rotating clockwise with respect the result: to the reference vector " a." The resultant voltage, instant Va (sin +2nfat + sin 277fbt) (3) +b = Vmax by instant, is shown in Fig. 3 (c) since and it is seen that the resultant (A + B) voltage is modulated at the differ- sin A + sin B = 2 sin cos (A - B), we may re -write 2 2 ence frequency. It is interesting equation (3) as follows : to note that the modulation is not sinusoidal, and that the phase of fb) -J b) Va +b 2V max sin 2n (fo + cos 2n(fa .. (3a) the resultant voltage does not 2 2 remain constant. The voltage

www.americanradiohistory.com October, roc Wireless World 361

Heterodyning and Modulation- almost the same as suppressor - The back radiation from the lower is both amplitude and phase - grid modulation ? The modula- unit is passed through a bass cham- modulated. The contour of the tion is accomplished by varying ber to apertures at floor level. envelope is shown in Fig. 3 (d) the gain of the valve, the only We have heard one of these loud by re- speakers in operation; the multiple drawing the resultant vec- difference being in the method sound sources give an attractive tors all in a vertical position. by which the effective gain is spatial effect not found in single If the two voltages are not varied. On the other hand, it cone units mounted in a plane equal, then the contour of the can be argued that the modulation baffle. The bass response is smooth envelope tends to become sinu- in the case of a Class " C " modu- and unobtrusive, indicating the soidal ; this can be shown quite lator is an additive process fol- absence of any marked resonance. Without easily by the vector method, but lowed by rectification ; the carrier tone control the output in it is extremely laborious to show and modulator voltages being the upper middle register was pro- this by plotting sine added together minent on some gramophone re- I, cordings but should be well suited waves. Further, the phase before being ap- to compensate for sideband cutting modulation cannot be seen ANODE plied to the grid when the loudspeaker is used in when the sine waves are CURRENT of the valve; conjunction with the average radio plotted. If a normal am- rectification receiver. No trace of cabinet vibra- plitude- modulated wave is then takes place tion could be detected with inputs dealt with by within the of the order of 4 to 6 watts, repre- the vector valve. senting the maximum acoustic out- put which be method -that is, TIME The could tolerated in the - author average living room, having regard the of vectors does not ven- to the high flux density and effi- the carrier and Fig. 4. Class ture to lay down ciency of the units employed. the two side - "C" grid any hard and The price of the Wharfedale bands are plot- modulation. fast rules con- corner cabinet loudspeaker, imped- ted, then since cerning this ance 6 or 15 ohms, without trans- the upper-side- question of additive and multi- former, is L47 Tos. Transformers of RF AND AF INPUT any ratio can be supplied to order. band vector is FED IN SERIES TO plicative mixing, nor to dispute rotating in a GRID CIRCUIT any The separator unit, with cross -over accepted conventions. The at T,000 c/s is available as a corn- counter - clock- object of this article is to point out wise direction with respect to the similarity of the two methods, the (arri. vector, anI the and in conclusion, to suggest that lower -slue band vector is rotating frequency changing and modula- in a clockwise direction at the tion are both multiplicative pro- same speed, the resultant vector cesses, irrespective of the method is not phase modulated, but employed. remains vertical. The result of adding together two alternating voltages of differ- ent frequency is to produce a Wharfedale voltage which is amplitude -modu- lated at the difference frequency, Corner Cabinet L.S. and an actual alternating voltage Twin Loudspeaker with of this frequency does not appear until after rectification. Frequency Separation Most people who cling to the DESIGNED to fit in the corner of convention that there is a distinct a room the new Wharfedale difference between additive and corner cabinet loudspeaker is avail- multiplicative mixing, will agree able in mahogany, or oak of any that modulation is a multiplica- shade to order. Solid wood of the tive process. If suppressor -grid order of Tin thickness is employed modulation is employed, the gain for the exterior walls of the cabinet of the valve is being varied, and to achieve the requisite rigidity at low frequencies, and internal divi- since the output of an amplifier sions are of thick material. is equal to the product (input x A type Wrz unit with cloth sur- gain), the multiplication in this round is used for low frequencies and case is obvious. a Wro /CS unit for frequencies above When Class " C " grid modula- r,000c /s. Frequency division is by tion is employed, the effective means of a choke -capacity potential Wharfedale corner cabinet loud- gain is varied by varying the bias divider and a volume control em- speaker. The dimensions of the on the grid of the modulator ploying a tapped choke is also pro- front are 44 in x 25,j- in and the valve. An increase in bias results vided. The high -frequency unit is depth is al in. at the top, and is fitted with a dif- in a smaller fraction of the input fuser for the forward radiation and ponent for use with pairs of similar wave running into the conducting a reflector which directs part of the existing loudspeakers of 3 to 15 region of the valve, as can be back radiation through a triangular ohms impedance. The price is seen from Fig. 4. Is this not aperture in the top of the cabinet. £3 15s.

www.americanradiohistory.com 362 Wireless World October, 1947 Exhibitors at the Show List of Stand -holders with References to the Plan Opposite

Name Stand Ref. Name Stand Ref. Name Stand Ret. 206 B6 Ace Radio .. 55 D3 Electronic Engineer- Partridge, Wilson.. Acoustic Products iii C2 ing . . .. 216 B6 Peerless Radio .. 307* - D6 ' Acoustical Mfg. .. 147 CI Electrothermal .. 32 D5 Peto Scott .. .. 8 Aerialite .. .. 78 D3 Emor .. .. 314* - Petter Radio .. 102 C2 25 Aerodyne .. 7 D6 Erie.. . 41 C4 I- 'hilco .. , .. C5 .. & A5 Albion Elec. Stores 107 C2 Everett, Edgcumbe 76 D3 Philips .. .. 56 & 227 C5 Music Allander . 135 CI Pianomaker, Amplion .. 85 C2 Farnell .. .. 203 B5 Seller & Radio 12o C2 . C2 Antiference .. s D6 Fel ß ate .. .. Retailer . .. 124 Armstrong 205 B6 Ferguson .. .. 26 C5 Pilot .. .. 39 C4 Automatic Coil Ferranti .. .. 57, 77 D3, D3 Plessey .. .. 65 C3 Winder .. 113 D2 & 215 & B6 Portogram .. .. 56 D3 Fidelity .. .. 309* - Practical Wireless .. 239 A6 B.B.C. 243&244 Ai & Bi Fitton .. 114 D2 Puckridge, F. .. 308* - B. I. Callender's .. zoo B5 Franklin Electric .. 143 Di Pye ...... 58 & 229 D3 & At B.S.R. .. .. 222 B5 Fulham Electrical.. co D5 B.T.H. .. .. 213 B6 " Q -Max " .. .. 234 A6 Baird .. 50 D4 G.E.C. .. .. 70 & 221 C3 & B5 Oualrad .. .. 241 A5 Balcombe .. .. 28 D5 G.P.O. .. .. 302, 303 - Barclay Stuart .. 204 B5 & 304* R.G.D. .. . 36 D4 Beethoven .. .. 61 C3 Gamma Electronics 238 A6 R.M. Electric .. 51 D4 Bell & Croyden .. 117 D2 Garrard .. .. 24 C5 R.S.C. Radio .. 45 C4 D2 Belling & Lee 33 D4 General Elec. Radio 217 B5 R.T.R.A. .. .. loo Bennett Power Prod. 122 C2 Goodmans .. .. 87 C2 R.W.F. . 503 C2 321* Gramophone Co. .. 59 C3 Radio Instruments 52 D4 Bernards(Publishers) - Cr Bird, Sydney S. .. 31 D5 Grampian .. .. 79 D2 Radiomobile 144 Board of Trade .. 84 C2 Radiospares .. 73 D3 British Centralab .. 74 D3 Hale Electric .. 67 C3 Rainso Raidio .. 305* - British Mech. Prod. 127 CI Haynes Radio .. 53 D4 Regentone .. .. 4o C4 British Moulded Hobday Bros. .. 116 D2 Relay Services .. 32o* - Plastics .. 3o D5 Hunt, A. H. .. 88 C3 Ripaults .. .. I D6 British Rofa .. 135 Di Roberts .. 43 C4 British Tungsram 132 CI Imhot .. .. 62 C3 Romac .. 129 Cs Invicta .. .. 69 C3 Brush Vacuum C4, C3 Cleaner 121 C2 S.T.C. .. .. 47, 64 Keith Prowse .. 89 C6 & 228 & A5 Brown Brothers .. loi Da 14o Dx Kerry's .. .. Salford 75 D3 Bulgin 3 D6 Kleergaze .. .. 357* Burgoyne .. .. 208 B6 q8 - Scharf, Erwin 306* - Kolster- Brandes .. D4 Scott, Geo. L .. 109 C2 Bush Radio . 38 C4 L.E.S. Distributors.. 148 CI Shannon & Bishop 104 C2 B6 Cable & Wireless .. 223 B5 Lee Products . 207 B6 Simon Sound Service 209 Celestion .. 86 C3 London Elect. Mfg. 9 D6 Sless (Tools) .. 322* - Champion Electric 68 C3 London & Prov. Sobel! . .. 19 C5 Cole, E. K... .. 46 & Iio C4 & C2 Factors .. .. 523 C2 Static Condenser .. 2 s B6 Collaro 35 D4 Long & Hambly .. 146 C1 Steatite .. 18 C5 Concordia Elect. Lowther Mfg. .. 323* - Sterling Cable .. 128 CI Wire .. .. 236 A6 Lugton .. .. 141 Di Stratton .. .. 23o A6 Cossor, A.C. .. 15 & C5 & A5 224A McMichael .. .. 6o C3 T.C.C. .. .. 5 C6 Cossor Radar .. 224 A5 McMurdo . 42 C4 T.C.M. Co. . . 518 D2 Coventry Factors .. 145 CI Marconi Instruments 226 A5 Tannoy .. .. 17 C5 Crypton .. .. 237 A6 Marconiphone .. 37 D4 Taylor Elect. Inst. 119 D2 Marconi's W.T. .. 225 A5 Tenaplas .. .. 133 Di Dagole .. . 66 C3 Masteradio.. .. 13o Ci Trix .. .. 20 C5 Dallas .. 137 Dx Metropolitan Police 2 I I B6 Truvox .. 81 D2 Dawe .. . 205 B5 Metropolitan Vickers 233 A6 Tucker Eyelet .. x34 DI Decca .. . 14 D5 Micramatic Elect. De La Rue.. .. 44 C4 Inst. .. .. 21 C5 Ultra .. .. 53 D5 United Insulator .. Cs Dibben .. .. 505 C2 Midland Bank . 313* - 526 8o D3 Min. Civil Aviation 235 A6 Dubilier .. V.S.E. Construction 4 C6 Duratube & Wire .. I1 D5 Min. of Supply .. 240 A6 Radio .. iz D5 Mullard .. .. 71, 112 D3, C2 Varlet' .. 202 B5 Dynaport Vidor .. .. 27 D5 Dynatron .. . 6 C6 & 214 & B6 Multicore .. .. 23 C5 Vitavox .. .. 54 D3 E.I.B.A. .. . 324* - Murphy 72 & 220 D3 & B5 CI E.M.A. .. 318* Re- Webber, J. M. .. 149 - Music Trades 34 D4 E.M.I. .. .. 29 & 212 D5 & B6 view 108 C2 Westinghouse .. Eastick .. .. 115 D2 Weymouth.. .. 142 D5 Econasign .. .. 316* - National Prov. Bank 312* - Wharfedale .. 15o C2 Ediswan .. 29 & 212 D4 & B5 New London Elec- Wingrove & Rogers 539 Dr Electrical Inst. 218 B5 tron Works .. 22 C5 Winter Trading .. 138 Dx Electrical & Radio Wireless & Electrical Ossicaide 232 A6 Trader 536 Dx Trading 106 C2 Overseas Reception 82 & 83 D3 & C3 Electrical & Radio - Wireless World and logical Inst. .. 231 AS Page Engineering .. 63 C3 Wireless Engineer 242 A5 Electro Dynamic .. 31I* - Parker Radio .. 315* -- Wright & Weaire.. 125 Cx

www.americanradiohistory.com October, 1947 Wireless, World 363

41d! A.. .".. _ r,il 1

Q

ar PLAN and GUIDE 2 2 By using this sçuaredrplan in conjunction with I 1061 f ID 104103IOáJ the references given in the list of exhibitors on the opposite page any stand on the ground ¡ 87 81 floor of the exhibition can readily be located. 88 86 83 82 Stands in the accompanying list which are sit- uated in the gallery of the National Hall are indicated by an asterisk. The Television Avenue, n 68 69 70 71 ï2 73 74I where some 30 receivers will be demonstrated, 76 is located at the Addison Road end of the 3 Grand Hall ga'ilery, in which are also the exhibitors offices. 61 60 58 7 56 55 154 A

.111111,

45 46 47 48 49

TELEVISION STUDIO

40 39 37 35

24 25 26 27 2E 29 21 22 23

2244 224 I 223 20 EIAMMERSMITH R0. ENTRANCE S

17 13 12

Wireless World

1

ADDISON RD. ENTFIANCE 6

`-- 237 236

1 J D A B i

www.americanradiohistory.com Wireless World Octobrr, r947 ational Radio tand -to -Stand Report

IN the followng pages we give o report of individual exhibits I printed in arder of trade names. Overseas readers should note that, where prices are given, purchase tax (abbreviation P.T.) is shawr separately : this tax is applicable only on the home market. This review is intended to serve not only as a guide for r sitars but also os o permanent record of the ndustry's programme for 1947-48.

ACE (65) system " in which one position of much sharper cut -off than usual is Domestic receivers shown by this the tone control switch widens the available when the load is taken by firm include an eight -valve super- I.F. band -width to zo kc /s. conventional projector speakers. het (Model Afioo ) covering medium Ace Radio, Ltd., Tower Road, In the labyrinth loudspeaker a 10 and long waves with bandspread Pound Road, London, N,W.zo. smooth response down to 3o c / s has tuning ou seven short-wave ranges, been obtained by fitting the charac- and a three -waveband, five -valve ACOUSTIC PRODUCTS (111) teristics of the unit with those of a superhet (Model B5o) for export In the range of " Lectrona " loud- folded acoustic tube of less than the only, operating from a 6 -volt speaker units shown, the speech -coil usual length. The type SLI5 is battery. former and high -frequency cone are ruggedly designed for P.A. work and Most of the receivers in this year's moulded in one piece. A non -mag- a twin labyrinth (Type CL2) is range will be fitted with the netic chassis reduces leakage field - available for domestic reception. " fidelity bandwidth expansion an important point where the 'unit Acoustical Manufacturing Co., is to be installed near a C.R. tube. Ltd., Ermine Street, Huntingdon. " Lectrona " There are Bin and loin permanent loudspeaker magnet which (78) with die -cast types are available AERIALITE frame. in four colour-coded flux densities This firm specializes in aerials ranging from 6,45oo to 9,500 lines and associated equipment and an per sq cm. interesting feature of their display Acoustic Products, Ltd., 50-58, is the " miniatures " showing the Britannia Walk, City Road, Lon- various types of television and rod don, N.I. aerials mounted on chimney stacks. The latest form of the Mastatic ACOUSTICAL MANUFAC- anti -interference aerial with screened TURING (147) down -lead is included, together From the wide range of electro- with a range of car aerials for acoustical equipment shown by this mounting on the roof, on the side firm the MB32 amplifier and the of the scuttle, on the rear bumpers labyrinth loudspeaker may be or below the running board. selected for special mention. A selection of " Ashton " cables, Overloading by unskilled opera- co -axial and balanced -twin aerial tors or announcers is mitigated in feeders is also included. the MB32 amplifier by a compressor Aeriafite, Ltd., Castle Works, circuit which comes into operation Stalybridge, Cheshire. before the overload point and limits distortion to less than 4 per cent. AERODYNE (7) A phase -shift bass -cut filter with a The Model 303 A.C./D.C. is a 4- valve plus rectifier superheterodyne of the midget type covering 16 -5u metres in addition to medium and Ambassador auto radio - long waves. It is designed for gramophone with 5 -valve rro V as well as the usual Zoo -25o V. all -wave receiver chassis. It is priced ß14 14s (3 38 3d P.T.). Larger table models are also shown, including a battery receiver, and there is a console radio- gramo- phone. l rrodyne, Ltd., Platina Street, l.nndun, E.C.2.

AI >t. .'.t''id I13rr..,with handspread tuning and mates reevivrr hlexlel Cris. www.americanradiohistory.com thtulrz'r, 1947 OVirnietik World

- Exhibition 1947 THIS Exhibition, which is the 15th of the series, it She fast to he held since the débBde of 1939, when the shcw was closed prematurely on the imminence of war. It is beeng held at Olympia, West London, from 1st so 11th October, avid

is open doily from 1 1 .0 a.m. to 10.0 p.m. (except Sunda!). Admission costs 2 6. The, show is logger thon in pre-wet days, and covers a wider field, embracing communication and electronic equipment as well as broadcast receiver.-. Demonstrations of the performance of broad:ast receivers in the hall is impracticable. but the loudspeakers of the sets on show are fed with B.B.C. programmes try a high -impedance --, line. Performance of the television receivers shown con, however, be studied, as the television programme is distributed at R.F. after being ALBA (28) received by a central station working with a long tilted -wire aerial erected on the roof A new table model superhet type of Olympia. Elaborate measures have been taken against interference. A 3 -mV signal Dari with bandspread tuning on is " piped " to each exhibitor through a separate cable. six wavebands below 31 metres and with continuous tuning between 3z`- AMBASSADOR (114) pick -up is also made and has an out- coo metres, zoo -55o metres and Boo - For the home market Ambassador em- of some 7.5V at goo c /s. 2000 metres, is among the wide is showing a range of receivers put A portable receiver covering range of broadcast receivers and bodying a 5 -valve superhet circuit. shown by This covers 9.7 to x,900 metres in medium and long waves is designed radio- gramophones this There i" Alba midget re- six ranges with bandspread on the for dry- battery operation. firm. In the new a mains unit which is chú;vcti ceiver, Model Cr52, single -ended short waves. An extra short -wave also valves are employed and range replaces the long in the export to be suitable for any all -glass portable set; it is for A.C. casts, the superhet circuit consists of version,. This chassis is available in table, Amption (5932), Ltd., 230. Tot- triode- hexode frequency changer, Road, London. W.1, combined I.F. and A.F. amplifier, console, radio- gramophone and tenharn Court diode-pentode output stage and half - bookcase styles. wave rectifier. There are three The radio -gramophone is an wavebands and the plastic cabinet attractive set having an automatic record-changer and storage space measures Bin X 4 1in x 4 }in. The price is ß13 53s (i,2 585 9d P.T.). for 300 records. A. J. Balcombe, Ltd., -58, A new r4 -valve A.M. -F.M. re- 52 covering 2.75 metres Tabernacle Street, London, F.C. o. eiver is shown to 2,000 metres. It is a double ALBION ELECTRIC STORES (107) superhet on the short waves, has a As wholesalers this company is noise limiter, a six -gang tuning con- not exhibiting products cf their own denser and 52 -watt push -pull output manufacture but shows a selection stage feeding twin loudspeakers. of receivers and components by well - R. N. Fitton, Ltd., Radio Works, known manufacturers. Hutchinson Lane, Brighouse, Yorks. Albion Electric Ste res r.5, Albion Street, Leeds. AMPLIOM (85) A magnetic pick-up at Lr 9s 6d ALLAMDER (121) (+ 6s 8c P.T.) in which steel, fibre. With the exception of the A4 52 cr sappl ire needles can be used, is midget for A.C. / D.C. operation 11 a product of this firm. It has an Allander receivers have a 5- val-+e output of about 5 V A_ crystäl - superhet chassis covering long, medium and short waves for hone ose as.d with medium - and tv-o short-wave bands for export Model A400 is a ra Ea-gram). phone with an automa:ic recoxi changer, models A43o anc A421 are consoles, the latter being an A.C. / D.C. set. There are :wo tAb e models, one for home arxl one for Export. Allender Industries, Ltd., 4S, Avenue Street., Bridgeton, Glasgott.

An:basador buokzaxe :ncde]ofthe$etirsq;,5 rece.sers,

Above. tical M.a-lufaclurinp 3o-watt13.pe MI332 an[on'IAtie vcCurl[ Cemptessien -in labyrihtb, " Concert" lotul- www.americanradiohistory.comker Type 366 Wireless World October, 1947

B.B.C. (243 & 244) One of the two B.B.C. stands is devoted to engineering. Here is displayed the various processes in the production of sapphire record- ing and reproducing needles. The exhibit includes a projection micro- scope with a magnification of 25o for inspecting the finished cutter. Another section of the stand is de- voted to a display depicting the technical processes through which the signal passes between the micro- Beethoven Model U2038 A.C. /D.C. phone and the aerial. receiver. The two stands of the B.B.C. are (Above) Armstrong RFto3 chassis linked by a photographic display of 411011=4 =C +nd (left) Antiference folded dipole come of the outstanding events dur- with feeder made of 3oo -ohm ing the first twenty -five years of flat -twin line. broadcasting in this country. The ARMSTRONG (205) Corporation's 25th anniversary will Receivers in chassis form are pro- be celebrated in November. duced by this firm. The RFro3 has British Broadcasting Corporation, an R.F. stage, triode- hexode fre- Broadcasting House, London, W.I. quency- changer, one I.F. stage and duo-diode -triode detector, A.V.C., B.S.R. (222) and A.F. stage. This is followed In addition to heat -frequency by a phase -splitter, a push -pull A.F. oscillators and their standard triode A.F. stage and a push -pull range of P.A. amplifying equip- tetrode output stage delivering ment, this firm is showing a flew to W. The set covers '17.9-50m, ribbon microphone (Type RBMx) with 195-530m and 800- 2,000m in three floating suspension and built - bands. On gramophone 6 -db bass in 50o-ohm line transformer, a lift is provided. The gramophone motor and pickup, in tone control which , gives treble lift. The chassis is the die -cast turntable is rim - priced at ¿i8 18s (+ P.T.). An driven and the pickup standard A.C. /D.C. model at the same price needle resonance around 4,500 c / s has a 6 -W output. has been eliminated, and a direct Similar chassis, the EXP83 and disc recorder; Type DRr3. The re- Avo Electronic UNI83, but with a simpler corder is housed in a transportable Testiarter and A.F. wood (right)- High- sensi- system, are available. instrument case and cuts discs tivity multi -range Armstrong Wireless and Tele- up to rain, 96 grooves per inch. test set. vision Co., Ltd., Warlters Road, The 15 -ohm cutter requires s watt London, N.7. for average modulation. A light- weight play -back . pickup is pro - AVO (113) vided and the equipment includes The Electronic Testmeter is a swarf- removal brush, spiralling new valve -voltmeter type of instru- handle and automatic cutter lower- ment for voltage and current mea- ing lever. surements up to ro kV D.C. and Birmingham Sound Repro - 2.5 kV A.C. On D.C. the input ducers, Ltd., Claremont Works, Old resistance is over roo MÛ total and Hill, Staffs. on A.C. the upper frequency limit is B.T -H. (213) Belling -Lee valveholder for B8A- zoo Mc / s. Other facilities pro- The aerial scanner and console based valves. vided are A.C. power output, deci- of bels, radar equipment developed for capacitance son pF to 50 µF merchant shipping are shown on ANTIFERENCE (2) and resistance 0.2 to r,000 MSZ. A television aerial of the com- this stand. There is also a standard There are 49 ranges all told. test -bench for use with X -band pressed dipole type is 'shown by Among the more recently intro- Antiference for Use indoors and waveguides. duced test apparatus is the AVO Crystal valves are shown and where space is limited. The Uni- Valve Characteristic Meter fitted point aerial is an anti -interference some miniature crystal receivers, as with a multiple selector switch for well as examples of silicon and ger- aerial system without the customary " wiring " the valveholders to suit matching transformers. The design manium crystals. any valve and an overload cut -out Radio -frequency heating equip- necessitates the use of a fixed length which protects the whole instru- of screened downlead; one receiver ment, a resistance -welding control ment. There is also a wide -range unit, a photo -electric relay a.iid an only can be fed. signal generator covering 5o kc /s The Amine short -wave folded electronic timer are on view as well di- to 50 Mc /s and having a switched as industrial valves, including pole is made throughout of 300- coil turret and a multi -range high - ohm polythene thyratrons. There are also work- insulated flat twin sensitivity test set of the well - models feeder. It is available for all ing of a compensated thyra- the known Avometer style having a re- tron motor -speed control and a amateur and most of the short-wave sistance of 20 Ml per volt. The broadcast bands. remote -position control servo sys- Douglas series of fully automatic tem. Other Antiference specialities in- coil winding machines are shown. clude. a range of motor British Thomson -Houston Co., Car aerials Automatic Coil Winder and Elec- Ltd.; Rugby, Warwick. and all kinds of aerial accessories. trical Equipment Co., Ltd., Winder Antiference, Ltd., 67, Bryanston Flouse, Douglas Street, London, BAIRD (50) Street, London, W.I, S.W.I. Four television receivers are

www.americanradiohistory.com October, 1947 Wireless World 367

shown by this firm. The smallest one new design now serves for both. BOARD OF TRADE (84) is the Garrick with a 12 -in C.R. Other items of interest include The Export Promotion Depart- tube. In addition to vis.on and a new B8A valveholder, a variety ment of the Board of Trade is re- sound it includes a broad :ast re- of co -axial plugs and sockets for sponsible for this stand, which con- ceiver covering 15 -50 m and zoo - television and car radio feeders, sists entirely of an export enquiry

55o m with push -button control and many different . kinds of 'terminals, bureau where visitors from overseas 3 -W output. The set costs ,162 15s fuseholders and a delay switch. are especially welcome. (plus 437 os 6d P.T.). Belling L' Lee, Ltd., Cambridge Board of Trade (Export Promo- The Adelphi and Lyric models are Arterial Road, Enfield, Middlesex. tion Department), 35, Old Queen of similar general design bat have Street, London, S.W.I. móre elaborate cabinets and cost BELL & CROYDEN (117) BRIMAR (47) £183 15s (plus L4I 165 4d P.T.). Hearing -aids are shown on this The Grosvenor has a picture z2in stand. There are two lightweight Prominence is given on this stand by r9in with a flat viewing screen. battery models, one with internal to the new :octal all -glass valve, The receiver has Ix wavebands and batteries and the other with a which, by virtue of the improved 3o An automatic separate battery unit. A mains unit characteristics with the pinchless -W output. record form of changer is fitted and a recording is available so that batteries can be construction, especially at can be if saved when mains are accessible. the television frequencies, is likely unit provided required. to replace many of the The price is not fixed but stated to There is a mains model also for current types office and home use and an audio- even for gene:al -purpose use. This be about ¡I,5oo. valve has a grooved centre John Logie Baird, Ltd., 4, Upper meter is being shown. spigot Grosvenor Street, London, W.I. J. Bell and Croyden (Savory arid Moore, Ltd.), 1x7, High Street, BARCLAY ,STUART (204) Oxford. Specialists in the production of in- jection, compression and transfer BENNETT POWER PRODUCTS moulding for the radio industry, this (122) firm is showing a variety of coil Among the range of broadcast re- formers, tuning knobs and escutch- ceivers shown on this stand is a eons as examples of the type of work set including a time- switch which they are prepared to produce to can be set to switch on at any pre- customers' requirements. determined time. The set is un- Barclay Stuart (Plastics), Ltd., conventional in appearance in that Spencer House, South Place, Lon- it is built to look like a clock. don, E.C.2. Bennett Power Products, Gerrards Cross. Bucks. BEETHOVEN (01) (200) This 'exhibit comprises all -wave B.I. CALLENDER'S Bevelling tool used by the B.B.C. for table model receivers, radio- gramo- In addition to a selection of wires, grinding tFe facet round the cutting phones and television sets. special cables and wave guides, a edge of the sapphire tips of recording Very impressive is the ARG1188 range of R.F. heaters designed for cutters. radio -gram with its 9 -valve superhet pre -heating moulding powder, sol- chassis, I2in loudspeaker and auto- dering and welding thermoplastics matic record changer. The II-49- is shown. Powers range from 0.2 to metre band is divided into nine 5 kW, and in all but the last size band -spread ranges with an addi- the pre -heaters are fitted with elec- tional one covering 5o to roc metres trode assemblies on top of the cabi- for export. For the home market this net. Process timers are included. is replaced by a long -wave band; An all -wave anti- interference both cover the medium waves. aerial has been developed for use on A T.R.F. circuit, with five R.F. the usual long, medium and short stages, is used in the television set, waves. A boft dipole is coupled to the first two being commor_ to the a receiver transformer through an sound channel. It has a in tube, 8o -ft coaxial cable, polyethylene in- which in the Model T918 disappears sulation being used throughout. into the cabinet when not in use. B.f. Callender's Cables, Ltd., Beethoven Electric Equipment, Norfolk House, Norfolk Street, Lon- Ltd., Chase Road, London, N.W.xo. don, W.C.2. BELLING -LEE (33) An unusual aerial possessing direc- tional properties and described as mew the inverted " V " is now included in the range of television aerials made by Belling and Lee. It is de- signed to fit in the roof space of a si house in localities where a reason- ably good signal is available. It can also be erected externally on a pole. There is a new Skyrod " whip " aerial, now r8ft long, one for win- dow -frame mounting, known as the Winrod, and a telescopic car aerial for mounting on the side of the scu t Ile. Instead of one set of transformers A.I. Callender's all -wave anti - for the Skyrod and another for the interference aerial system. Baird . ('rarrick " television }ìliminnise anti- interference aerials receiver. www.americanradiohistory.com ;,6S Wirrle,cy VVorld October, 194.7 which locks into the valveholder brated volume control so that it can warming -up period and effects and prevents the valves in a re- be pre -set for a particular pro - economies in current consumption ceiver from falling out in transit. gi amme. as well as in time. Shown also is a range of new The Magneta Time Co. are showing Measuring Tin x 41in x 21in, the miniature valves intended mainly on this stand a range of P.A. equip- " Playboy ' personal portable for use in small portables and hear- ment with outputs of ro - roo W. weighs only 311b and covers ing aids. British Vacuum Cleaner and En- medium and long waves. Separate The Brimar replacements scheme, gineering Co., Ltd., Goblin Works, tuning scales calibrated in station which is being demonstrated, shows Leatherhead, Surrey. names are provided and an auto- how obsolete multiple valves may matic on -off switch is incorporated be replaced by modern types com- BROWN BROTHERS (101) in the lid. bined with metal rectifiers. These well -known traders are Burgoyne Engineering Co., Ltd., Standard Telephones and Cables, showing a representative display of 2-3, Robert Street, London, N.W.r. Ltd., Connaught House, Aldwych, receivers and equipment by some of London, W.C.2. the leading manufacturers. BUSH (38) of sets BRITISH MOULDED PLASTICS Brown Brothers, Ltd., Brown's A feature of many the Buildings, Great Eastern Street, shown by this firm is " Bi -Focal (30) London, E.C.2. Tone." This is an arrangement This company make a wide whereby the audio -frequency re- variety of plastic mouldings for the BULGIN (3) sponse is broadened when the radio industry and the great This company has always been volume control is turned down for advances made in the technique of noted for the extent and versatility the reception of strong signals. The plastic moulding are well exemplified of the vast range of components and broadening is obtained by negative by the inclusion of some early parts they manufacture. Of special feedback and is arranged to improve examples for comparison with the interest is the series of really minia- the quality of local reception with- present -day article. ture intervalve transformers. out complicating the operation of British Moulded Plastics, Ltd., There were well over zoo different the set. Avenue Works, Waltham;;tow types of switches, but nevertheless It is used in the AC2 table and Avenue, London, E.4. some new models have been added, SUG3 console models, which are BRITISH VACUUM (121) including a series of press switches priced at £20 545 5d (plus £4 9s 7d The Goblin Time -Spot receiver in- operating against a return spring P.T.) and £25 OS rod (plus £5 8s 2d clu&s a time -, ;witch and a calî- and key-actuated toggles. P.T.) respectively. They are both Other new items comprise a series three -band sets of the four -valve of moulded signal lampholders type for A.C. operation, but A.C./ giving easy access to the bulb for D.C. models are being produced. replacement, 8- and r2 -pin plugs Portable sets, both battery and and sockets and a safety mains con- mains, are shown. The BP90 is an nector for television sets; removal example of the former and the of the back of the set automatically DAC90 one of the latter. It is for breaks the mains supply. A.C. / D.C. operation with a frame Fuses, plugs and jacks, connectors aerial. of many kinds, knobs, coils and I.F. Export models are the EAC9r and transformers are also shown. EAC95. D.C. models are available A. F. Bulgin and Co., Ltd., By- and vibrator power -packs for 6 V pass Road, Barking, Essex. battery operation can be supplied. They BURGOYNE (208) cover two short wavebands and the medium. The EAC95 has Products as diverse as coaxial - an R.F. stage and a scale indicator cable connectors, electric soldering permitting accurate resetting. irons and a personal portable come Television within the scope sets include the model of this firm. T9r, reviewed in our last issue, and The " Seven Second " solder gun, a similar set with a larger (sain) as its name implies, reduces the tube. Bush Radio, Ltd., Power Road, London, W.4. .

C. & W. (223) A two -way wireless telegraph cir- cuit is operating between the Cable Wireless stand and the company's station at Barbados. Among the latest equipment on show are a high -speed photo -electric

Coasor Model 477 A.C. band- spread receiver.

('.amatole )hreotelcgraphy transmitter- receiver used on ;the stand o' ('.able &.Wireless to demonstrate natio picture transmission and recéptíon. www.americanradiohistory.com October, 1947 Wireless World \ 369 'telegraphy transmitter, capable of CLIX (127) V.F. stage and a strip -built 3 -Mc /s handling up to Boo words a minute, Some new valveholders have been stagger -tuned I.F. autplifier. and a photo -telegraphy transmitter- added to the Clix range of speciali- In the Model 902, there is a ro -in receiver. The latter, which was ties; there is one for the miniature tube with 6 kV for E.H.T. and the designed by C. & W. and manu- all -glass lock -in type valve, with or set costs £78 ris. (plus £r7 53s 9d. factured by the G.E.C.; transmits without centre spigot, and the B8B P.T.). The Model 901 has a is-in photographs, maps, etc., measuring and B9C which are eight - and nine- tube giving a picture 1 z f in by loin x Tin in about ten minute's. A pin models respectively, the latter 94in. The E.H.T. supply of 9 kV device, normally used for monitor- being for the EF50 style of valve. comes from a high -voltage coil ing, has been fitted to the console One other new item in the Clix pulsed at line frequency. The set models on show whereby the picture range is a moulded M.E.S. lamp - includes an all -wave sound receiver. being transmitted on a closed cir- holder for scale illumination. It is Among the many broadcast sets cuit from one set to the other is so designed that the lamp always shown the Model 477AC is of par- seen as it is being built up on makes a good contact and cannot ticular interest in having five S.W. Teledeltos " aluminium -foil paper. become loose. hands as well as medium and long. Cable and Wireless, Ltd., Electra In addition there is a vast range Push -button waveband selection is House, Victoria Embankment, Lon- of plugs and sockets, terminal strip used and there is flywheel tuning. don, W.C.2. connectors and many different types There are several battery sets, in- of valveholders on laminated and cluding the Model 481B, which is CELESTION (86) ceramic plates. specially designed for rural areas. All loudspeakers in the Celestion A. C. Cossor, Ltd., Highbury. range British Mechanical Productions, are of dústprobf design and Ltd., 21, Bruton Street, London, Grove, London, N.S. are treated to withstand tropical W.x. climates. They range from a 24 -in COVENTRY FACTORS (145) unit weighing 31oz to a r8 -in repro- COLLARO (36) A wide range of equipment i ducer capable of handling 40 watts. Equipment for gramophone and shown by this firm of wholesalers. Universal output transformers and radio -gramophone manufacturers, Receivers, components and acces- cabinet extension loudspeakers, are pickups, record players, motor and sories by manufacturers not exhibit- also shown. automatic record changers are shown ing at Olympia are to be found o Celestine, Ltd., 145, London on this stand and also the " Micro- this stand. Road, Kingston -on- Thames, Surrey. gram " portable electric gramophone Coventry Factors, Ltd., for A.C. mains with House, Leicester CENTRALAB (74) 24-watt output. Row, Coven Collars), Ltd., Ripple Works, By- Piezo -electric pickups, micro- pass Road, Barking, Essex. phones, headphones and loud- speakers are being exhibited, here. The De Luxe Crystal Pickup has an CONCORDIA (238) output of x.3 V R.M.S. Cables, flexes and wires of all and costs kinds are made by this firm and the £4 45 (+ P.T.) . The Torpedo micro- phone has an of exhibit gives some idea of the range output -54db and and variety of costs ßr8 18s. A hearing -aid type their products. The wide use of nylon, glass and with an output of -5x db at too c / s asbestos has a rising characteristic to in the manufacture of insulated about wires to -day is well 3,soo c /s. It is priced at 25s. The exemplified. loudspeaker shown is of the " pil- Concordia Electric Wire and low " type for use in hospitals. Cable Co., Ltd., Long Eaton, Nr. Volume controls, sapphire gramo- Nottingham. phone needles, and vibration pick- up units are among the other ex- COSSOR (15 & 224A) hibits. The television receivers shown by British Ce'ntralab, Ltd., Canter- this firm include a C.R. tube incor- bury Road, London, N.W 6. porating an ion -trap to avoid ion burns on the screen. The time - CHAMPION (68) bases include automatic linearity A range of five receivers- includ- controls, there is a cathode -follower ing a car radio -is shown. The " Comet" (three wavebands) and " Planet " (two wavebands) sets are compact A.C. /D.C. superhets in plastic cabinets, with built-in aerials. The Model X49 is designed for export, has three waveranges (medium and two short) and is housed in a walnut cabinet. Champion Electric Corp., Cham- pion Works, Seaford, Sussex.

Goblin Time -Spot Receiver. d

(Left) Bush export Models EAC95 Cossor Model pes televlalör, and litios are externally the same. receiver (top) srxt Burgoyne (Right) Safety trains connector " Y'layboy " p..nnmal portable made by Bulgin for television sets. Model www.americanradiohistory.com R473. October, 1947 . 370 Wireless World

COSSOR RADAR (22a) being the fully insulated and pro - Cyldon dual capa- Marine radar equipment similar to tected input and output connectors. citor on ceramic Partridge, Wilson and Co., Ltd., base for minia- that installed in R.M.S. " Queen ture I.P. trans- Elizabeth " is shown in a facsimile of Davenset Works, Evington Valley formers. a ship's chart room. Examples of Road, Leicester. for " Gee " navigational equipment DAWE (201) aircraft are also shown. Highbury An enormous range of measuring Cossor Radar, Ltd., and test apparatus is exhibited on Grove, London, N.S. this stand. The Modulated R.F. Oscillator Type 8ozA is unusual in CRYPTON (237) having an aperiodic buffer amplifier This exhibit comprises battery between the master oscillator and chargers. The AI will charge up to /s- will the output. It covers Iokc 6 cells at I A and the A63 deal 5o Mc /s and is direct reading up to with 36 cells at 8 A. Other models 3o Mc /s; the accuracy is ± r4 per cover all intermediate requirements. cent up' to To Mc / s and ± 3 per Most patterns have selenium metal cent to 3o Mc /s. rectifiers but some use valves. A new R.C. oscillator, type 400C, Crypton Equipment, Ltd., 1, covers o.!- I,000c /s with an Victoria Street, London, S.W.I. accuracy of ± o.i c/s or ± 3 per is roo mW into Dynerr,;\. (31) cent. Its output convertor CYLDON 5 kf) for a distortion of under 3 %. ound -proof All kinds of variable condensers, A Decade Inductometer, Type Met. from the high -voltage transmitting Dubilier car- 23oA, provides inductances up to types to miniature air- and mica - bonized rod and III.r mH in ro -all steps with an . precision wire- dielectric 'trimmers, are made by wound t accuracy of ± 2 per cent. The resistors. this firm. One of their latest pro- inductors used are dust -cored and ductions is a miniature twin -mica- readjustment for higher accuracy dielectric trimmer for inclusion in at a particular frequency is possible. fin square I.F. transformer cans. Among the other apparatus on In addition there is shown a small view are output power meters, model- making press described as the valve voltmeters, impedance bridges, Prestacon which can be used for the distortion meters, stroboscopes, and production of small brackets, punch- vibration meters. ing shaped.holes and for bending. Dawe Instruments, Ltd., Harle- Sydney S. Bird and Sons, Ltd., quin Avenue, Great West Road, Cambridge 4rterial Road, Enfield, Brentford, Middlesex. Middlesex. DECCA (14) DAGOLE (88) Full frequency range recording The redesigned type " S " volume and reproduction is the keynote of controls have centreless-ground the exhibit, which culminates in the shafts and a new type three -finger " Decola " standard model electric spherical contact spring. reproducer with a frequency range Wire -wound resistances of all of 3o to 14,000c /s. A portable self - types are shown including standard contained electric reproducer, 0.2 and o.3 -amp voltage droppers, known as the " Deccalian," while coated in cement or heat- resisting not on the ambitious scale of the Davensct Model H battery charger paint. Other types are available in " Decola," nevertheless has many for A.C. mains ; output 15 volts 2.25 A. ratings of s, 5, Io and 20 watts. refinements, including the latest Dagole and Co., Ltd., 5, Torrens Decca lightweight pick -up with Street, London, E.C.I. sapphire stylus. DALLAS (137) The ' Double Decca " portable. This firm of wholesalers is showing in its latest guise, provides recep- a large variety of receivers and tion in short as well as medium and amplifiers of various makes, as well long waves, and operates from A.C. as test gear, transformers, aerial or D.C. mains, or from internal bat- equipment, and recording ap- teries. The L.T. battery receives a paratus. trickle charge when the set is being J. E. Dallas & Sons, Ltd., used on mains. Dallas Buildings, Clifton Street, Decca Record Co., Ltd., 13, London, E.C.2. Brixton Road, London, S.W.9. DE LA RUE (44) DAVENSET (208) The many ways in which plastic Here are shown the latest models materials is one form or another are of Davenset battery chargers for now used in radio apparatus is v ell both A.C. and D.C. supplies. Some exemplified by this exhibit. A of the units are very versatile and special display is made of Delaron will accommodate several banks of resin -bonded laminated board, Dela- accumulators while charging them flex insulating sleeving and other at different voltage and current De La Rue plastic specialities. rates. Individual control of each De La Rue Insulation, Ltd., Im- is provided. The latest circuit perial House, . 84, Regent Street, selenium rectifiers are widely used. London, W.I. This firm also continues to make their well -known range of Davenset DIBBEN (105) and chokes, one qervicing equipment, P.A. gear, " three- waveband mains transformers bp) Double Decca i attefies stable for mains or battery operation and of the chief features in their design receivers, hnudspeakers, ccalian" portable electric record reproducer. www.americanradiohistory.com October, 1947 Wireless World 37' and valves by many of the well - equipment for Geiger counter known manufacturers are to be seen measurements. on this wholesaler's stand. Dynatron Radio, Ltd., Perfecta Horace Dibben, Ltd., Upper Works, Ray Lea Road, Maiden- Banister Street, Southampton, head, Berks. Hants. E.D.C.C. (311) DUBILIER (80) This firm has long specialized in Here can be seen a most compre- the production of small machines hensive selection of capacitors and for converting a D.C. voltage to resistors for use in communication, A.C., or stepping up a D.C. supply television and transmitting equip- to a higher voltage. Such machines ment. Many of these are designed are essential for operating radio, tropical Dawe instruments to satisfy the most stringent television and P.A. equipment when Type 8o2A modu- conditions. the right kind of supply is not laid on. lated R.P. oscillator. The new series of Drilitic electro- Their range of equipment also in- lytic capacitors now -includes some cludes soundproof cabinets and anti- double types in cylindrical metal interference filters which are effec- cases with the case negative in some tive from so to 2,000 metres. A but insulated in others. The Nitro - special type of machine with excep- gol series of impregnated paper tionally good voltage regulation is capacitors in sealed metal cases has supplied for television sets. been enlarged and improved, and The exhibit includes petrol - there are a number of special tele- electric generating sets, constant - vision models for 3.5 kV to ro kV current charging dynamos and small working voltages. rotary transformers for operating metallized paper, mica from car bat- Push -buttons repla Paper, mobile equipment the usual range swit. and ceramic capacitors in a wide teries. in this E.I.C. test se range of styles and values are also Electro Dyriamic Construction included in this section of Dubiliers' Co., Ltd., St. Mary Cray, Kent. exhibit. A fine display is also made of re- E.I.B.A. (324) sistors. There are high -stability The Electrical Industries Benevo- carbonized ceramic rod types for lent Association, the object of which general purpose use, wire -wound is to help the non -manual members precision models for instrument con- of the industry who " fall on bad struction, ultra -high resistances, times," is using this stand as an in- power resistors and volume control formation bureau. o potentiometers in a profusion of Electrical Industries Benevolent sizes, types and characteristics. Association, 32, Old Burlington Dubilier Condenser Co. (5925), Street, London, W.I. Ltd., Ducon Works, Victoria Road, E.I.C. (218) London, W.3. Among the several test sets shown DURATUBE (11) on this stand is one with range .5 i.w A comprehensive display of wires selection by push- buttons. De- and cables insulated with Duratuf scribed as the Test Set 5PB it is a S " Y.V.C. includes screened universal meter for measuring cur- types suitable for communication rent, voltage, resistance and capacit- equipment. Other applications of ance. The ranges are : current up extruded P.V.C. shown are decora- to 50o mA ; A.C. and D.C. volts up tive strips, plaited covered tinsel to r ,000 ; resistance up to 2 MG with wires for carrying handles on port- internal battery and capacitanc able receivers, and thread for bind- from Soo pF to o. r F. The meter w ing wiring assemblies. resistance is I,000 ohms /volt. Cryptrn Model A6z Duratube and Wire, Ltd., Faggs This firm make a portable electro- battery charger. Road, Feltham, Middlesex. static voltmeter with a single range and full-scale deflection of 6 kV for DYNATRON (6) E.H.T. measurements in television. The Ether Conqueror models Electrical Instrument Co. (Hil- shown on this stand inclpde a z2- lington), Ltd., Boswell Square, Hil- valve receiver covering ró -32 m and lington, Glasgow, S.W.2. 30 -85 m as well as the medium and long wavebands. The harmonic dis- E.M.A. (318) tortion at 5 W output is claimed The Electronic Manufacturers' to be less than o.s per cent. Spin Association, which aims at promot- tuning is fitted and there is variable ing the welfare of the British elec- selectivity with bandwidths of 5, so, tronics industry, defines electronic 55 and 20 kc / s. Independent bass apparatus as including all equip- and treble tone controls are fitted. ment " depending for its function in The model KI29M is priced at ¿i68 whole or in part on the emission of (plus P.T.) and includes an auto- a stream of electrons, including matic record -changer. apparatus incorporating thermiotiic Another model including a tele- valves." "The stand of E.M.A. is for vision receiver costs £325 Sos (plus the use of its members as a club P.T.). The tuner and amplifier with room for the purpose of meeting loudspeaker are available separately business associates. in chassis form at 484 (plus P.T.). Electronic Manufacturers' This firm is also showing.a range Association, Vernon House, of A.F. amplifiers, and special- Sicilian Avenue, London, W.G.s. www.americanradiohistory.com Wireless October, 1947

E.M.J. (212) dude marine radio transmitters as provides continuous tuning from Electronic devices shown on this well as marine and light radar 3o Mc / s to 600 kc / s. Land ïnc_ Jude examples of recent equipment,. and there is a working The Model 640 is also new and is mitron television camera develop - model demonstrating the principles essentially an amateur's receiver as ents and a new film scanner. of the " Rebecca " system of beam its coverage is 31 to 1.7 Mc/ s. An here is also a scale model of one approach for aircraft. eight -valve superhet circuit is em- the E.M.I. mobile television vans. Tape and portable disc recording ployed with one R.F. and two I.F. A range of R.F. dielectric heaters apparatus is shown and there is also stages with crystal filter. The price . r pre- heating plastic moulding a section explaining the scope of the is X42 (L9 os 7d P.T.). wders is represented and applica- training courses in electronics pro- The other set is intended for ex- ons in other industries are Indi- vided by E.M.I. Institutes. port and is described as Model S659. ted. Radio aids to navigation in- Electric and Musical Industries. It has two tuning bands, each with Ltd., Hayes, Middlesex. two ranges, covering Io to 5o metres and I TO to S75 metres respectively. E.M.I. SALES & SERVICE (29) In addition there is a full range Community aerial systems for of the short and ultra -short wave Erie Ccramicon "' Feed - blocks of Hats are represented components for which Eddystone are th`rra " capacitor. among the various systems of R.F. so well known. and A.F. programme distribution Stratton and Co., Ltd., Eddy- shown. There is a series of P.A. stone Works, Birmingham, 31. amplifiers from 12 to Zoo watts, and a wide variety of aids to service EDISWAN (49 & 219) ranging from tools to test gear. Magnetically -deflected television F'.M.I. Sales & Service, Ltd., tubes with screen diameters of Tin, Works, Hayes, Middlesex. gin and 12in are shown, as well as R.K. Sheraton t mag- a range of Mazda valves. These pcaker E.R.I.C. (231) include miniature A.C. /D.C. types y Edis- This firm is showing a variety of with the BSA hase taking 0.1 A otan. apparatus which includes R.F . heater current. The miniature A.C. tuning coils, I.F. transformers, types include an R.F. pentode with turfing units, power transformers, g,,1= 7.5mA /V and fitted with the vibrator units and loudspeakers. I37G base. This is the 6F1 and In addition there are complete there is a double- diode, the 6D2 on receivers and radio -gramophones. the same base. They have three wavebands, four in Both magnetic and piezo -electric the export models. There is also a pickups are shown. The former television set with a I2 -in tube. has an output of 0.7 V R.M.S. at A multi -range high -impedance 1.000 c / s and is priced at 275 6d 5 V, valve voltmeter covers -1,000 ( + 6s 3d P.T.), while the latter has A.C. and D.C. an output of 1.7 V R.M.S. and costs Electrical and Radiological In- 505 ITS 5d P.T.). Mazda Ctctul- and BRA - (+ base type valves show- strument Co., Ltd., 54-56, Church The B.T.H. Senior R.K. loud- ing the reduction of Road,' London, W.3. speaker is of the permanent- magnet size with the latter. type with a curved cone. It is rated (118) EASTICK to handle To W peak ; it has a funda- The Eelex range of standardized mental resonance at 45 c / s and plugs and sockets and spring -loaded covers 30- 12,000 c /s. It costs testing prods manufactured by this L6 15s without transformer. company are exhibited on this This exhibit also includes the stand. As wholesalers they are also loudspeakerphone, an electro -ence- showing a comprehensive range of phalograph with an automatic wave proprietary components and acces- analyser, industrial valves and sories. metal -to -glass seals. J. J. Eastick and Sons, Ltd., 12, Edison Swan Electric Co., Ltd., Errol Street, London. E.C.I. 155, Charing Cross Road, London, EDDYSTONE (230) W.C.2. Three new sets occupy prominent ELECTRON (22) places on the Eddystone stand. The Insulated aerial wire is being Model S68o communications receiver shown on this stand as well as is an improved version of the D.C.C. one- to four -way telephone " 504." It is a nine -valve super wire. There is also a rod aerial having two R.F. and two I.F. costing 21S with 25ft lead -in. stages, the latter incorporating a New London Electron Works, I + crystal filter giving a 45 -db attenu- Ltd., F3oleyn No.td, T,ondon, E.6. ation r kc / s off resonance. Use of this filter is optional. This receiver ELECTROTHERMAL (32) Retaining devices made of moulded rubber and fibre -glass material to prevent valves from fall- ing out of their holders in mobile ' and transportable sets are shown, together with various other applica- tions of asbestos and glass -fabric insulating materials to radio equip- ments. R c :into -radiogram Model rot hernial Engineering, Ltd., Alt.. ;(17 and (right) "Radio- Elect ;inte "` teceiver Mood A33 270, Neville Road, London, E.7.

www.americanradiohistory.com bctóber, 1947 Wireless World 373

EKCO (46 & 110) P.T.). and the valves are arranged FERRANTI (57, 77 & 215) In accordance with the policy of as frequency-changer, I.F. stage, Ranges of battery, 4 -V A.C., 6.3- this firm to extend the trading cycle detector, A.V.C., and 1st A.F. V and o.15 -A valves are shown by in new models from one to two amplifier, and tetrode output. this firm as well as high -voltage years, none of the sets to be pro- Hale Electric Co., Ltd., Radio rectifiers and both g -in and s2 -in duced in I947/48 will supersede any Works, Talbot Road, London, W.13. television C.R. tubes, There are of the receivers so far produced in also cold- cathode tubes, crater the 1946/47 period. EVERETT, EDGCUMBE (78) lamps, stroboscopic lamps and elec- Table models are represented by a Among the exhibits on this stand trometer valves for industrial appli- standard all -wave set with no frills is an All- purpose Tester. This is a cation. (A.C. and battery versions), by a multi -range A.C. and D.C. meter, A cloth-guiding device and a yarn - receiver of superior specification and with voltage, current and ohm- breakage detector are shown, and performance falling between the meter ranges. The Model A has a there is a hyperbolic computator. This A23 and A28 models and by the meter with a 31 -in scale length; the " Radiotime " combined programme Model E one with a 6 -in scale. setting alarm clock receiver for The Vampire is a new rectifier - those who need a " second set." type A.C. test set having one voltage Those requiring a " luxury " and four current and power ranges. radio -gramophone will find their A 500 V insulation and earth cir- needs fulfilled by the Model ARG37 cuit conductivity tester called the with Garrard automatic record " Hum Metrohm," derives its changer mechanism, push -pull out- power from a battery through a buzzer, and rectifier. put stage and 39 to ro,000 -c /s I2- transformer inch loudspeaker. Valve testers are shown, including an elaborate model for educational Television receivers, car radios to and export models complete the estal.lishments. It is designed facilitate taking characteristic curves firm's exhibit. operation of the E. K. Cule, Ltd., Ekco Works, and to permit the Southend valve in certain circuits. -on -Sea, Essex. Everett, Edgcumbe and Co., Works, London, Everett Edgcumbe EMOR (314) Ltd., Colindale Model E MI- purpose A three -waveband superhet built N.W.9. Tester. in the form of a globe, with circum- FARNELL (203) ferential tuning scale and loud- This firm is showing close toler- speaker grille at the top, is the a principal exhibit. Tuning is effected ance silvered -mica capacitors and range of chokes, transformers and by rotating the globe, and sub- resistances. There are also loud- sidiary controls are in the f ant of speakers, electric soldering irons and sleeves concentric with the support- radio tools, including a ratchet ing rod, which stands 4 ¡ft high and screwdriver and B.A. socket set. is adjustable to Gft. A. C. Farnrll, Ltd., 15, Park Emor Ltd., 45, Kilburn Radio, Place, Leeds, 1, Yorks. High Road, London, N.W.G. Ferguson Mains Mint FERGUSON (26) Moder 203V. ERIE (41) The Model 20IRG is a 6-valve Some new ceramic double -cup plus rectifier receiver with push -pull condensers rated 5 kVA are shown at output of 6 \V and three wavebands. for use in transmitting and radio -' stage included and there heating equipments. These' will An R.F. is R.F. is an automatic record changer. carry comparatively heavy There is a smaller radio -gramophone currents with working voltages -the 46IRG, with 3.¡W output. ranging from 5 to ro kV. Three Among the table models there is capacitances in of two tempera- each an A.C. / D.C. set, the 2o3U, which ture coefficients are so far available, covers medium and long waves. It viz 20 to 39 pF and 51 to 1oó pF has a plastic cabinet and is normally Elston output Iespectively. V A transformer and designed for 200 -25o mains. replacement wind- Included also is a new ceramic model for roo -rro V is available. of the circular rotor type ing shown by trimmer The price is £r5 (3 4S Gd P.T.). Farnell. designed to exclude all dust from The Model 204 is designed for ex- the rubbing surfaces, thereby port and there are three versions of greatly improving both stability and it --one for A.C. supplies, one for I noise factor. Other new "Cerami- A.C. / D.C., and one for 6 -V battery Everett Edg- cons " comprise lead -through and A Model cumbe Hum operation. television set, Metrohm. stand -off condensers in which the 80C, is being shown, fixing busts serves as one connec- Thorn Electrical Industries, Ltd., tion, the other being the insulated 105 -109, Judd Street, - London, bush or pillar. W. C.'. The exhibit contains many varie- ties of carbon rod and wire -wound vitreous enamel resistors as well as carbon track potentiometers. Erie Resistor, Ltd., Carlisle Road, The Hyde, London, N.W.9. ETRONIC (87) The Model RAG4o receiver is - being shown here. It is a three Eddystone Model ;Sao-, , band set costing L18 18s ( + ¿4 Is 3d communicationns : tel (left) Enaupoult-, i ng a crystaf' www.americanradiohistory.com 74 Wireless World October, 1947

characteristic of G.E.C. sets this year and in the Model BC4S5o and its A.C. /D.C. version BC4855 " piano -key " station selection re- quiring vertical instead of horizon-

} erranti Tesvac tal pressure are provided. These H.F. Unit' are also a feature of the BC4750 Model N.A. luxury table model and its radio - and auto -radiogram versions (Light) G.E.C. television and Bram ,-uadcaa receiver Model BT7o91 C4758 and BC4758R. with (below; communication General Electric Co., Ltd., Mag- delver, Model BRT400. net House, Kingsway, London, W.C.2.

G.P.O. (302, 303 & 304) Designed to illustrate the work of the Post Office in many fields of communication this stand provides made by this firm. Radio- gramo- visitors with an opportunity of see- phones in wood cabinets are also ing some of the apparatus produced shown. by the research engineers at Dollis Fidelity Radio, rr, Blechynden Hill. One such piece of equipment Street, London, W.ii. is the frequency -range limiter. This G) demonstrates the effect of suppress- FRANKLIN ELECTRIC (143) ing the upper and/or lower side - The components shown include bands. capacitors of the dry electrolytic, A cable fault -locator is shown for silvered-mica, paper, and ceramic which is claimed an accuracy in the types, as well as carbon and wire - location of faults in a radio -fre- wound resistors, both fixed and quency cable to within z per cent variable. Rotary and toggle in distance up to ro miles. switches are on view and a feature is The process of inverting the trans- made of windings for transformers, mitted frequencies symmetrically chokes and field coils. about a central frequency and cor- Franklin Electric Co., Ltd., ira, recting them at the receiving end Howland Street, London, W.I. is demonstrated visually and aurally. This method of frequency inversion FULHAM ELECTRICAL (10) was introduced during the war to Silvered ceramic fixed condensers help safeguard confidential tele- ranging in capacitance from r to phone conversations. 400 pF are shown on this stand. Another aural and visual demon- :.,mma all-wave universal receiver. They include models with positive stration shows how various types of Below) Garrard Model RC7o auto- and negative temperature co- signal are affected by fading and matic record changer. efficients and combination of these noise peculiar to long -distance S.W. two types will provide a capacitance communication. The use of this of exceptional stability or, 'if re- equipment to simulate fading, etc., quired, one having a predetermined permits the examination of radio- temperature co- efficient. telephone systems in the laboratory Fulham Electrical Components, under controlled conditions. Ltd., 459, Fulham Road, London, Enquiries from listeners and -4 S.W.ro. viewers regarding electrical interfer- ence are invited. G.E.C. (70 Si 221) General Post Office, London, Communication equipment on the E.C.x. main stand includes a 1-kW F.M. broadcast transmitter and portable GAMMA (238) V.H.F. transmitter- receiver, also A 5 -valve A.C. / D.C. receiver with last corrects automatically the posi- with frequency modulation. The a long -wave band for home use tional information obtained from BRT400 communication receiver is and an extra short -wave range in lieu for navigational aids such as Gee, a 53 -valve superhet with two - export is shown with a signal choice Decca, Loran, into range and bear- frequency stages covering 15okc /s of cabinet styles. There is i ing. It shows also the track and to 35 Mc /s in six bands. It is also an inter -office communication distance to a chosen destination. equipped with every circuit refine- equipment having a control unit, The Tesvac is a portable H.F. ment and is fully " tropicalized." separate amplifier and station units. unit with an output at 4 Mc /s for A magnetic tape recorder having The design permits a " pageing testing the degree of vacuum in any a playing time of 35 minutes and call " to be sent out. glass or partly glass system. The using oxide -impregnated plastic Gamma Electronics, Ltd., 12, exploring electrodes are held near tape is shown, and there is a typical Green ford Road, Greenford, Middle- the glass and the degree of vacuum sound reproduction system, suitable sex. can be judged by the nature and for large factories, with a power out- GARRARD (24) colour of the discharge. put of 500 watts. The G.E.C. Gramophone motors, record - Ferranti, Ltd., Hollinwood, 5 -kW industrial R,,F. heater is also changers and pick-ups for every ap- Lanes. shown. plication are shown. The new Flat -ended 9 -inch C.R. tubes are Model S radiogram unit makes use FIDELITY RADIO (309) employed in the G.E.C. television of Laminated a constant speed drum drive plastic cabinets in a sets (BT7o9z and BT7o94) which motor mounted on a unit plate with wide range of colours are available include three -waveband broadcast automatic stop and for the small table model Type E mag- receivers receivers. Louvred cabinets are a netic pickup. The friction driving

www.americanradiohistory.com 04'06., 1947 Wireless World 375

wheel is interchangeable and the coupled acoustic chambers and a HOBDAY (118) unit can be supplied to give 78 die -cast streamlined housing is A representative display of radio r.p.m. on hoc /s mains. It is provided. and television receivers and acces- claimed that the drum drive gives Graonpian Reproducers, Ltd., sories made by the leading increased manu- torque for heavy record- Hampton Road, Hanworth, Felt - facturers is shown by this firm of ings, and the same motor is used ham, Middlesex. wholesalers. A certain quantity of in the new Model RC7o record test equipment is also exhibited. changer. This plays ten loin or H.M.V. (59) Hobday Bros., Ltd., 22-27, Great rzin records. (not mixed) and the The Model 1604 table model radio - Eastern Street, London, E.C.z. operation time between records is gramophone is of special interest. four seconds. It includes an automatic record HUNT (88) Garrard Engineering and Manu- changer of compact design and takes The activities of this company are facturing Co., Ltd., Newcastle up no more space than a conven- devoted to the manufacture of Street, Swindon, Wilts. tional table model receiver. Other capacitors and their exhibit com- table models are the Model 1119 GENERAL prises specimen of the many ELECTRICAL RADIO push- button A.C. (217) mains transport- varieties of fixed capacitors, semi - able and the Model 1115 for A.C. / variable trimmers and associated Those seeking receivers and radio - D.C. mains with built -in aerial. The apparatus now is production. gramophones with specifications console above Model 1605 radio- gramo- Among the many types of fixed the average will find much to phone with pull out front gives easy interest them on this stand. The condensers are tubular paper-dielec- control and access to the record tric types, some of which" are seven -valve three- waveband receiver changer from armchair level. Model GER /É7 has two I.F stages miniature pattern employing the and sensitivity A Io -in tube is used in the Model the is stated to be 1804 television which costs ¿61 19s 81AV on the two short -wave ranges, (+ ¿14 Is rid P.T.) while the Model which cover 52-23 metres 30- and 1803 at ¿94 los (+ X21 209 P.T.) 120 metres. The third waveband is employs zoo -55o a r5 -in tube giving a metres. Other models in- picture x corporating size rz }in loin. record players are avail- Future developments are fore- able. A radio -gramophone Model shadowed by the display of an elec- GER /G24 is also shown, in which a simple trical gramophone reproducer with turntable for playing special a frequency range of 3o records is provided in to 15,000 addition to a c/a and a 43 -valve r2- waveband record changer. Separate amplifier channels combined radio- gramophone and are provided for 16 -2,000 television receiver for both c/s and z,000- 16,000c /s, and there designed are three A.M. and F.M. reception. loudspeakers with separate The Gramophone Co., Ltd., controls for bass, middle and top frequencies. Hayes, Middlesex. General Electrical Radio Go., 92, HAYNES (53) Charlotte Street, London, W..r. The Model HR77 televison re- GOODMANS (87) ceiver shown by this firm has a 14 -in Among the high- quality loud- cathode -ray tube. There are six speaker units shown on this stand R.F. stages and one V.F. stage and the twin -diaphragm model with a the detector is of the full -wave type. frequency range of 45-15,000c/s Hard -valve time -bases are used and may be selected for special mention. the sound side is unusual in having A range of bass reflex cabinet a push -pull triode output stage. The speakers for high quality reproduc- price is ¿Iv) (+ JJ26 139 4d P.T.). tion has been developed, the largest A wide range of chokes and trans- of which incorporates the twin -dia- formers is shown including some phragm unit. Among P.A. equip- with Crystalloy cores. Scanning and ment be focus coils for television are on may mentioned the new view, cabinet units and a diffuser loud- and there are E.H.T. trans- speaker with a high -efficiency drive formers of the hermetically sealed type for outputs up to 7 kV. unit designed to handle 5 watts. Haynes Radio, Ltd., Queensway, Goodmans Industries, Ltd., Lan - celot Road, Enfield, Middlesex. Wembley, Middlesex. ('l'op right) Equipment for simulat- GRAMPIAN (79) ting fading shown by G.P.O. It enables radio- telephone systems A high -grade r2 -inch loudspeaker to be examined in the laboratory with curved -sided cone is among the under "working" conditions. new products shown by this firm of (Right) H.M.V. table radiogram P.A. equipment manufacturers. It Model x604. has a power handling capacity of 15 watts and the Alcomax magnet (Below) General Electrical Radio develops 24,000 lines /cma in the Model GER /G9 radiogramophone. diameter gap. Two circular diffuser loudspeakers are also shown. They are of the reflector plate type and designs are available L for suspension from or direct- móunt- ing on the ceiling. The Type DPI moving coil micro- phone employs a pressed duralumin diaphragm and aluminium speech coil weighing only 56o milligrams. Response correction is provided by www.americanradiohistory.com October, 7947 373 Wireless World

nrotallised paper form of construc- It has orle R.F. and one I.F. valve, tion developed by iiunts, 110 ulded and fly -wheel tuning. A similar ruina and silvered mica condensers, set, the 1IR4oT, is an export mortel large capacitance paper condensers designed for tropical use. in rectangular metal cases alai an There is a wide range of small extensive range of dry clectrolytics. sets, including some reflex types, included also is an imposing dis- and many are available as export play of small preset trimmers some models with tropical components. on ceramic bases. Kolster- Brandes, Ltd., Footscrey, The exhibit includes the capacit- Sidcup, Kent. ance and resistance bridge manufac- KERRY'S (140) tured by this company. Among the items featured on this A. H. Hunt, Ltd., Garrett Lane, stand are a number for which this London, S . IV. tß. company -formerly East London Rubber Co. -are the sole wholesale IMHOF (82) include the in instrument distributors. They This tirtn specializes " Roberts" portable combined Marcaniphone " personal" port- cases :old handles. The cases are of analyzer and the able Model Yr7fì finished valve and circuit welded sheet steel and are unit, Type A14, range of colours. The Hutchings mains in a wide for converting all -dry portables to i for instance, measures I\ p) ))221i, mains operation. z i) in I ny t Sin by rofin, costs 69x, finished in Kerry's (Gt. Britain), Ltd., War - and can be supplied London, E.15. light grey, brown, yellow, red or ton Road, black. Receivers and radio- gramo- KLEERGAZE (317) phone cabinets are also macle. A preparation for applying to the .1llred Imhof, l.trl., II2 -116, New glass screen of a television set, or O.rfrd Street, London, the dial of a radio set, to prevent condensation and misting is shown INVICTA (89) on this stand. it has the additional Receivers for the home market as quality of imparting a high polish. well as for export are shown on this Kleergaze. ;;oa, Sackville Street, stand. Among the former is a tele- London, W.I. vision receiver in a console cabinet L.E.M. (9) fitted with a 0-in tube and having a (+ P.T.). This firm specializes in the manu- T.R.F. circuit. It costs55 of silvered mica fixed capa- an attractive walnut facture Housed in citors and these are made in is a -waveband A.C. cabinet four ranging from I to one range covering.the capacitances superhet with 10,000 PI:. The working voltage of Phis irwicta Model 30 trawler mont. This set is the Model supe^he elvers the the standard pattern is 350 D.C., .tt1 and costs 417 ( ¿.i 13s, sd P.T.). for trawler band. svavel,ancl A.C./ hut there is a range available There is a three- 750 volts D.C. and a limited selec- a self- contained D.C. superiet and for operation at 5.000 volts. receiver, the price of tion all-dry hat wry The silvered mica construction en- which is L13 55 (L2 16s rid P.T.). two A.C./ ables close tolerances to be achieved Shown for export are production. ll.C. .1ivevalve superhets, one for even in quantity (Below) Imhof radio - London lìl,'rtrieal .Manufacturing ,gramophone cabinet. 1 w; 250 volts A.C. supplies and a Co., Ltd., I510, Fulham Road, Lon- model incorporating band - six -valve W. ro. spread tuning. don, S. Invicta Radio, Ltd., Parkhurst L.E.S. (148) Road, London, N.7. The exhibit of this firm of whole- sale distributors consists entirely of K.B. (48) proprietary articles, and is intended The television set exhibited is the for the trade visitor only. a CV .to with a t2 -in tube giving a pic- L.E.S. Distributors, Ltd., 15, ture tain by8in. It is a super- Alfred Place, London, W.C.I. heterodyne employing 19 miniature valves and a temperature-compen- LEE PRODUCTS (207) satcd oscillator. Kits of parts and circuit diagrams There is a radio- gramo- for the construction of radio re- phone w i t h automatic ceivers are shown. They are avail- record -changer and storage able for export as well as for the space for records. The pick- home market and include amplifiers, up is of light weight and has T.R.F. and superhet receivers.

a sapphire needle; the loud - Lee Products - (Great Britain), speaker is provided with an Ltd., Radio House, East Street, .T acoustic laiivrinih and a Brighton, Sussex. 4 liai er. The re- -,,,--+`..,' -Y/; --^', high -note il ceiver has four hands with LONDON & PROVINCIAL for r4 FACTORS (123) ' baudsprieet 5-15.4 including i s l i to Mc; s. Fly - Proprietary equipment, Mc and n. intercommuni- 1, a'lrel tuning_ is used and receivers, test gear. -r then, is an internal frame cation units, battery chargers, aerial for local reception. loudspeakers, rotary couvcrtors, There is a similar receiver aerials and components in great without t h e gramophone variety are shown by this firm. equipment. London and Provincial Factors, The BR4o is a 7 -valve 7 -band set Ltd., 230, 'Tottenham Court Road, with baudsread on five S.W. bands. London, W.1. www.americanradiohistory.com October, 1947 lOirrhti!: ;i7

LONG & HAMBLY (148) police fora:,, lire services, dock and Specialists in moulded rubber harbour authorities. parts, the company are showing, Marconi's Wireless Telegraph 'Co.. among other items, masks for tele- Ltd., Marconi House, Chelmsford, vision and C.R. tubes, valve re- Essex. tainers, a wide range of grommets and rubber -metal lxmded parts. MARCONI INSTRUMENTS (228) Long and Hambly, Ltd., Em- Two items of test equipment that pire Works, Slater Street, High will attract the interest of most Wycombe, Bucks. radio service technicians, are the LOWTHER (323) TF888 Receiver Tester and TF868 Receiver and amplifier units for Universal Bridge. The former is a high -quality reproduction are shown versatile test set comprising a crystal -checked signal generator, Marconi Instruments uni- by this firm. The Type DT /4 func- versal bridge Type TF868. tions as a straight receiver for local an A.F. tone source and an output station reception, and as a superhet meter. The frequency range is with variable selectivity for more 75 kc /s to 5o Mc /s and the A.F. distant programmes. Types LEI/2 generator produces i,000c /s for modulating the R.F. output, or as a and LES are straight and superhet separate units respectively for those who do signal for A.F. testing. Battery or mains operation is not require the dual tuner. optional. Three A.F. amplifiers are avail- The able, Type B5F with single PX25 TF868 provides facilities for output valve, Type Awl,' with the measurement of inductance from t rtH PX4s in push -pull, and Type A15F to loo H; capacitance from with two P)(25s in output r pF to ioo µF and resistance from the stage. o, r fl The latter to 10 M11. The single dial amplifier employs separ- gives direct readings without the ate rectifiers for the H.T. supply to complication the output valves and the preceding of multiplication stages.. factors. In addition, test sets of various Lowther Manufacturing Co., Low- kinds ther House, St. for use in receiver and com- Mark's Road, ponent production are shown and Bromley, Kent. demonstrated. LISGTON (141) Marconi Instruments, Ltd., St. The display on this stand, which Albans, Herts. is mainly of interest to dealers, is divided into four main categories: MARCONIPHONE (37) receivers, public address gear, test A " personal " portable (Model gear and servicing replacements. Pi7B) with a four -valve superhet circuit is Among the P.A. equipment is a among the range of Mar - high -quality record reproducer and coniphone receivers which this year the test gear includes are for the most part of compact a 6,000 -volt design with electrostatic meter for television ser- built-in aerials. Model vicing. Lugtons Ti4A, on the other hand, is in- are sole distribu- for tors of Leland instruments for tended long- distance reception England, Wales and Northern as well as quality of reproduction and covers 13.5 to 52 metres in Invita Model TLzt Ireland, television receiver. Lugton and three waverauges with hand -spread Co., Ltd., zo9-z1z, tuning in Tottenham Court Road, London, addition to the normal W.C.I. medium- and long -wave ranges. The corresponding ARG14A radio - MARCONI (225) gramophone includes a record - The exhibits on this stand are changing mechanism of new design. concerned with the " heavier " side The Model VT50A television re- of the radio industry. Here are ceiver incorporates a ro -in tube and shown some gives a picture size of 8 1-in x . typical examples of the S equipment used in broadcasting A display of export models, trans- stations, for navigation on the sea mitting and receiving valves, a and in the air, for high speed point - cathode -ray tubes, H.T. batteries to -point communication and for and accessories, such as pickups and use. record players, completes the Marconi V,H.F. mobile mobile radie -telephone transmitter There is a complete 5 -kW medium exhibit. and receiver unit. wave broadcast transmitter with Marconiphone Co., Ltd., Hayes, some typical microphones for use Middlesex. in studios, a horn -type aerial for a MASTERADIO (130) V.11. F. television link and, among This exhibit comprises a wide the .tir navigation equipment, is a range of equipment including car light veight communication and sets, radio -gramophones and tele- automatic direction finder for air- vision receivers. There are special 410416 craft. The Marconi Radiolocator export models and aerials for car +II Si for use in merchant ships gives a sets. P.P.T. picture of everything " seen " - e , Masteradio, Ltd., ro -so, Fitzroy W by the radar transmitter. Place, London, N.W.I. 7I411 The versatility of Marconi equip- 616 ment is further emphasized by the MoCARTHY (120) new V.H.F. mobile transmitters and T.R.F. amplifiers are used for of both sound and vision in receivers designed for the use the tele- Í i_ www.americanradiohistory.com vision receiver shown by this firm. luxe radio -gramophone embodying pression. Accurate polythene There are four R.F. stages in the every up -to -date feature there is a mouldings are a speciality of this vision channel with the first com- television set which is also an all - firm and samples are on display. mon to sound channel. It in- wave receiver covering 13.3 to 2,000 Metropolitan -Vick, rs Electrical the Pk., Manchester. cludes a 9 -in magnetic -type tube and metres, It is a console type and is Co., Ltd., Trafford un- fitted with a 12 -in. tube. derives its E.H.T. in a rather MINISTRY OF CIVIL AVIATION usual manner by rectifying the out- Shown also is a range of export specifi- (235) put of au R.F. oscillator. Exten- models with similar circuit ex- cations to those mentioned but The slogan of the Ministry's sive use is made of miniature valves. is safety in the air." There of giving continuous tuning from 9 to hibit " Shown also is a range super- is a replica of a civil aviation area heterodyne broadcast receivers, all 55o metres, Ltd., Igo, control room which provides a live of which have negative feedback. McMichael Radio, of Strand, London, W.C.2. demonstration of the movement Felgate Radio, Ltd., 6, Studland in what is known in aero- W.6. aircraft Street, London, -MoMURDO (42) nautical circles as the. South East NI:MICHAEL (80) This firm is showing a range of Flight Information Region. The In addition to a wide range of Amphenel valveholders in both controller and radio operators are mains receivers and radio- gramo- bakelite and ceramic materials, in- actually handling traffic and the phones, McMichael has a special cluding the BSA and B7G types. movements of all aircraft in and out sets. The .out- There is also a range of A.F. of London which are being handled display of battery which standing model is a battery radio - amplifiers, among which a i5 -W by -Control Headquarters (of gramophone providing a radio model is interesting in view of the this stand is a sub -section) are de- 17i metres as use of an R.F. oscillator to generate picted on a wall map. coverage of 16.5 to Ariel well as the medium and long waves. heater current for the early- valves Ministry of Civil Aviation, It has a ro -in speaker and a spring in ordet to reduce hum. Huse, Strand, London, W.C.2. motor capable of playing a- 12 -in McMurdo Instrument Co., Ltd., MINISTRY OF SUPPLY (240) - winding. Q.P.P. out- Victoria. Works, Ashtead, Surrey. record on one The purpose Of the exhibits on put is used and the consumption is MEICO (21) this stand is to show the research - 12 mA H.T. and o.5 A L.T. There micro - and development work done by the is a table model receiver and a con - The Meico moving -coil phone is shown and also two audio Ministry for the War Office, Air solette with the same chassis. Ministry and industry. In addition to a twin -speaker de amplifiers, the Model Uro for A.C./ D.C. mains giving ro watts, and the On the air side is shown the latest Model 5A for A.C. mains rated at 5 V.H.F. aircraft communications waits. Examples of power trans- equipment in contrast with that formers, coil winding and sheet used during the - Battle, of Britain. metal work undertaken by this firm The latest equipment, the.TRr92o, complete the exhibit. which operates in the loo- r24 -Mc /s Micranwtic Electrical Instrument band, is a combined transmitter - Co., Ltd., Meico Woxks, Congleton, receiver of exceptionally small Cheshire. dimensions. The main unit, ex- cluding cables, weighs approxi-

METROVICK (233) - mately 22 lb. With a load of Radio test gear and the " Sea - 45 ohms the transmitter has an out- scan " marine radar equipment, put of 4 -5 watts. Receiver sensi- developed to meet the Ministry of tivity is of the order of r5 IX for Transport specification, are shown. A.G.C. threshold. Another item of The test gear includes examples of interest is a daylight -viewing skia- signal generators, valve voltmeters, tron which has been designed to miniature oscilloscopes, etc. There meet the -need for the daylight oper- M:eastuing she bit temperature of a soldering rn while .:n use by means of a pyrometer, are also an electronic industrial pro- ation of A.C.R. (Approach Control demonstrated by Multicore. cess timer, and examples of the ap- Radar) in aerodrome control towers. plication of " Metrosil " non -ohmic The H2S simulator described in

resistances in spark and surge sup- February Wireless . World is shown. Among the ground equipment is shown the No. ro set, described in our June and September issues last year, and the proximity, or V.T., fuse. Ministry of Supply, Shell Mex House, Strand, London, W.C.2. MULLARD (71, 112 & 214) Receivers, valves and C.R. tubes are displayed on this stand. The receivers are of all types from the MUS22I, with a plastic cabinet, and

Interior ofOssi-

caide - Model RP7 hcarins aid.

Morph + Ato2R radio -gramophone and (right) VI r6 console television receiver. www.americanradiohistory.com October, 1947 11'8r'less World i''t

for A.C. / D.C. operation, to the that is, the " cabinet " is little PARKER RADIO (315) MTS315 television console model more than a baffle plate carrying the A table model and a radio-gramo- giving a picture join by 8in which controls and tuning scale on. the phone are the principal products of includes also an " all -wave " re- front and the enclosed receiver on this firm. The Model S/ AD/3 ceiver. The MAS281 five -valve A.C. the back. The set itself is of the A.C. / D.C. superheterodyne, cover- set includes an R.F. stage specially four -valve type and negative feed- ing short, medium and long waves, designed for a good short-wave per- back is used in the A.F. circuits. is housed in a mahogany cabinet formance. There is a radio -gramophone, the lain x 9in xó}in and costs X14 3S bd In addition to the home models, AIo2R. The receiver has three (plus £3 3s P.T.). In the Model there is a range of special export wavebands and fly -wheel tuning. A RG / AC / Q radio- gramophone a types covering the medium- and larger model, the Aso4 has an auto- Class A push-pull output stage is short-wave bands and designed to matic record changer and the re- employed and the pick -up is a withstand extreme heat, cold and ceiver has an optically projected Lexington moving coil. humidity. tuning scale effectively Soin long. Parker Radio Manufacturing Co., Among the wide range of valves Murphy Radio, Ltd., Welwyn 756, Harrow Road, London, shown are r.4 -V miniature types on Garden City, Herts. N. W. ro. the B7G base and the sub - miniature types for hearing aids are of special OSSICAIDE (232) PEERLESS (307) interest. There are also special tele- A 3 -valve R.C. coupled circuit is Communication type receiver vision types and low -power trans- used in the latest Osray hearing chassis with alternative A.F. output mitting valves. aids. They are housed in neat stages, designed to meet the require- Measuring instruments, including moulded cases of small size with ments of discriminating technical C.R. oscilloscopes, and transmitters self -contained batteries. Consump- users, form the principal exhibit. are being shown as well as Ticonal tion is very low, being 70 mA L.T. The 16-valve Model 1546 receives magnets, air -dielectric trimmers and and r.5 mA H.T. Models are shown medium and long waves in addition high -stability resistors. ' also with separate battery cases. to four short -wave ranges covering Mullard Wireless Service Co., Ossicaide, z, Upper Richmond 3 to 6oMc /s. An R.F. stage with Ltd., Century House, Shaftesbury Roud, London, S. W.15. bandpass aerial filter precedes the Avenue, London, W.C.2. frequency changer, which is fol- OVERSEAS RECEPTION (82 & 83) lowed by two I.F. stages with vari- MULTICORE (23) With the slogan for the exhibi- able selectivity, including a crystal The Ersin Multicore three -core tion "Britain Builds Radio for the gate." The A.V.C. circuit in- solder is being shown, but a major World," it is very fitting that the part of the stand is occupied by de- central feature of the west end of monstrations of the use of the the "Grand Hall should be the solder in radio production. One of reception rooms set aside for over- these is a conveyor at which girls seas visitors. from the Bush Radio factory are Overseas Reception and Informa- assembling and soldering coil units. tion Office. Another consists of an illustration PAGE (83) of the way in which the solder is A bedside lamp incorporating a used by A. H. Hunt for soldering loudspeaker is among the range of the ends of tubular paper capaci- extension loudspeakers made by tors at the rate of 500 joints per this firm. The "Switchmatic hour. control unit will operate any num- Apparatus for the measurement ber of extension units and enables of the hit temperature of a solder -., the set or any individual speaker to ing iron while a joint is being made be switched on or off from the ex- is shown. tension point. A range of 5 -, 6f Multicore Solders, Ltd., Mellier and 8 -in loudspeakers for set manu- House, Albemarle Street, London, facturers is also shown.. W.x. Page Engineering Co., Ltd., MURPHY (72 & 220) Franklin Road, Portslade -by -Sea. This firm is showing broadcast and television receivers. Of the latter, there are the Vi Le and Vi j6 table and console models with 9 -in and 12 -in tubes respectively. Inter- ference limiters are included. The Aroo is a small set se designed that the controls are actes- cible from either side. It is for A.C. operation and embodies miniature technique. A full-scale set is the A122, but is unusual in -being of the baffle type; (Above) McMichael batter radio -gramophone and nes portable receiver. V.H.F. aircraft transmitter - receiver exhibited by the Ministry of Supply is shown on the right. A rear view of theuáin unit withdrawn from the calsi{tet is given above. The transmitter and receiver ,ccupy the top deck with the rower supply unit beneath.

Mullard A.C.'D.C. receiver Type MUS221. www.americanradiohistory.com -1 f- -f

....,

38,0 Wireless World October, 1947 dudes an inter -station noise limiter. ¿4 145 rod P.T.), an A.C. three - PHILIPS (16 & 227) A.F. unit employs band set and the HU52 at ¿22 15S Except for the cheapest table Tho standard shown 6L6 valves in push -pull; negative (plus L4 17s rod Y.T.) for A.C./ model, the television receivers seven - feedback is variable. The whole of D.C. use. They are four -valve on this stand all include a - valve three -band broadcast receiver. the receiver is " tropicalized " to superheterodynes , with triode mtt the severest conditions. hexode frequency- changer, one I.F. Two picture sizes are available, 7kin stage, duo -diode- triode detector, by bin and loin by 8in, and the sets Peerless Radio, Ltd., 374, Ken- both sington High Street, London, W.14. A.V.C. and A.F. stage, and tetrodo include interference limiters in output valve. sound and vision channels. PETO SCOTT (8) In the H52 and HU52, the wave- The receivers are mostly table A range of A.C. and A.C. / D.C. bands are 15- 51.7m, 170 -55orn and models and include a small A.C. / sets is exhibited on this stand. They 750- 2050m. There are also SU5r, D.C. set -the 2o9U. Most, however, include the H52 at ¿22 1s (plus S51 and H51 models otherwise are four - or five -valve types for A.C. similar but covering 12.5 -47.5m mains. .1 high -fidelity radio-gramo- 47.5 -170m and 17o -55om. phone has a push -pull output stage An all -dry battery portable and twill loudspeakers. The receiver weighing r4 41b costs ¿r4 14s 9d is of the seven -valve type. The (plus L3 2S rod P.T.) including. sui ornatic record- changer wil I handle batteries. There is also a radio - a mixed batch of up to eight loin gramophone. and rain records. Peto Scott Electrical Instruments, R.P. induction heaters are shown Ltd., Addlestone Road, Weybridge, on Stand 227. The F12 /I has an Surrey. input of 5 kW and the FVroo an input of loo kW. A Mass Chest PETTER (102) X -Ray Unit and a Therapy unit A comprehensive range of pro- with an output of Soo W at 6 m are prietary components and acces- on view as well as a welding control sories is shown by this wholesale unit. firm, which specializes in meeting Philips Electrical, Ltd., Century the needs of the service -man. The House, Shaftesbury Avenue, Lon- company has the sole agency for don, W.C.z. London and Eastern Counties for the Advance signal generator. PILOT (39) Pattogram Transconti- Petter Radio and Electrical Sup- Among the new receivers shown nental table-model radio - is the Little gramophone. plies, 201 -7, Forest Road, London, for the first time E.17. Maestro De Luxe, an A.C. / D.C. _ 4 -valve (plus rectifier) superhet rif PHILCO (25) with separate scales for the medium The Model A r7o8CG television re- and Iong waves. Housed in a wal- ceiver shown on this stand is of the nut cabinet it costs 413 13s T.R.F. type with three R.F. stages (La 18s 9d P.T.). in the vision channel. A 9 -in tube is There is the Little Maestro, also used and the cabinet has folding an A.C. / D.C. superhet with a 4- doors covering the tube when not valve chassis. A choice of cabinets in use. In a larger model, the is provided with prices varying -- A17o7, the tube is mounted on 'a slightly, ' the average is ¿12 5s hinged panel and disappears when ( ¡2 ras 9d P.T.). Both are minia- out of action. ture sets with concealed aerials. The Model D -537RG is a table A table radiogram with the model radio -gramophone of the modest dimensions of r5in x r 1 }in x Pilot Little Maestro de Luxe AC./D.C. receiver. letter -box " type. The receiver is r5 }in is also new and like the other of the four -valve + rectifier type Maestros, has a 4 -valve (plus recti- with three wavebands. fier) superhet chassis, but for A.C. A four -band set, the A747W has mains only. It provides for short-, an R.F. stage and covers 4.5-30 medium- and long -wave listening Mc /s on short waves. A tetrodo and costs ¿32 (L6 17s 8d P.T.). output valve is used and there is a Pilot Radio, Ltd., 31 -37, Park C.R. tuning indicator. Royal Road, London, N.W.Io. A new four -valve portable using miniature valves is on view. It PLESSEY (65) covers medium and long waves with Components for the receiver built -in frame aerials. manufacturer include trimmers, There are also some large radio - chokes, electrolytic condensers, drive gramophones. mechanisms, variable condensers, ' Q-Max " communication re- Philco Radio and Television Corp. switches, vibrators and transformers. ceiver Model Q5 /xo. of Gt. Britain, Ltd., 204, Great Scanning coil assemblies, line and Portland Street, London, W.x. frame transformers, focus coils, etc., t are also available for the television set maker. Plessey television components, Loudspeakers include types with focus coils, scanning trans- formers and de- centre -pole magnets and reduced ex- flector coils. ternal field, suitable for use in tele- vision set::. The Plessey record- changer has an overall height above the table of 4iin and depth below of only 4.n. standard performance

Philco car www.americanradiohistory.com_radio ^ Octóbcr, 19¢7 Wireless World 381 of eight mixed ro -in or r2 -in records dials with bands which can with a much -simplified mechanism, be set R.Q.D. (36) as a reminder when to switch on An attractive and the special clutch device safe- the set. ten-valve radio - guarding the pickup arm mechanism gramophone fitted with an auto- F. Puckridge and Nephew, Ltd., matic record is a useful feature. Mount -changer occupies a pro- Vibrators Works, 96, Upper Clapton minent place on this stand. of both synchronous and Road, London, E.5. It is a non- synchronous types are shown. five -band superhet haying three Plessey Co., Ltd., Vicarage PYE short-wave ranges, 13.8 to 52 metres Lane, (58 & 228) inclusive, Ilford, Essex. A new range and the usual medium - of receivers with and long -wave built -in frame aerials but mains facilities. Other fea- POLAR (139) operated tures include variable I.F. band- is shown for the first time. width, This company specialize in the Two are 3 -valve 8 -watt push -pull output production of (plus rectifier) stage and tone variable condensers superhets, one for A.C., the other control. An export and condenser drives for set manu- for A.C./ D.C. operation facturers. Their and the well -known bar third is a 4 -valve (plus rectifier) construction is retained for the transportable for frame of the A.C. /D.C. mains. standard and minia- All cover short, medium and long ture types. A three-gang assembly waves and have of provision for ex- the latter kind measures 2}inx ternal aerials when needed. I /in x r tin only. The exhibit The capacitance includes the new of Polar con- Baby " Q " all -dry portable and a densers is largely decided by users' 4 -valve requirements, super. A car radio set for but there is an upper 6- or sz -volt supplies with manual limit normally imposed by space tuning and considerations loudspeaker measures in both the standard 5Iin x 5 {in x 6 }in only. and miniature patterns. It is a 4- In the valve superhet with vibrator and former it is 532 pF and in the latter rectifier H.T. supply 362 pF. and the price is ¿12 128. ({z 14$ zd P.T.). Several different types of reduc- Two television receivers tion mechanism with are remote and shown, one is a table model and the Pye transportable integral drive are shown, together other a A.C. /D.C. with console. Both have the receiver, a series of air- and mica- same T.R.F. Model K47C, and circuit for sound and car -radio set dielectric trimmers. vision, 9 -in magnetic com- Wingrove and tube and noise pared in size with a Rogers, Led., Mill limiters. The table set costs ¿42 matchbox. Lane, Old Swan, Liverpool, 8s 8d Lancs. 13, (,Ç9 P.T.) and the console L'52 2OS (II r5s sod P.T.). Pye, Ltd., Radio Works, Cam- PORTADYNE (12) bridge. The model 1.157 receiver is of the three -band type for A.C. /D.C. "Q-MAX " (234) operation, with self - contained Components for the construction aerial for local reception. It costs of short -wave transmitters and re- ¿r9 r7s 6d (+ ¿4 5s 6d. P.T.). ceivers and complete instruments There is an export model, the 1157E, such as the B4/40 transmitter with which has two short-wave bands and 10 -, zo -, 4o- and 8o -metre tank coil medium waves. turret are shown. The Q5/ r0 com- ,/i An A.C. 5 -valve set (including munication receiver is a five -band rectifier) is the A548. This has also ten -valve superhet for A.C. mains three bands with plug and costs ¿22 I5 (-i- L4 for external battery opera- 54s sod P.T.). tion. A four -valve all -dry short- Portadyne Model A548 receiver. Another 5 -valve set, an A.C./ wave receiver is available at ¿12 12s D.C. model, has one medium and (+ ¿2 17s 5d P.T.) and covers xi to one short -wave band only. It can 35o m. be supplied with medium and long "Q-Max" (Electronics), Ltd.,. wavebands as an alternative. It is Io, Little Turnstile, London, priced at ¿13 28 6d (-{- P.T.). W.C.I. Dynaport Radio and Television, Ltd., Portadyne Works, 18 -19, QUALRAD (241) Gorst Road, London, N.W.Io. This firm is showing a range of re- ceivers including an A.C./ D.C. PORTOGRAM (58) model-the Midgetuned -with pre - This firm is showing a wide range tuned circuits. There is a 6 -valve of receivers and radio- gramophones. A.C. /D.C. set with a push-pull out- The Transcontinental Table -Model put stage; also a range of com- radio -gramophone ponents. has an output of Philips 8 W from a push-pull Qualrad Products, Mocel 563A stage and is a Ltd., 29, Red television receiver. three -band superheterodyne. The Lion Street, Richmond, Surrey. Corner Console has an output of 3 W (A.C. /D.C. Peto -Scott Model) and 4W (A.C.) HE7r receiver. and is designed to fit into the corner of a room. Portogram Radio Electrical In- dustries, Ltd., Preil Works, St. 4# Rule Street, London, S.W.8. PUCKRIDGE (308) Here is shown the Radio Listening Polar miniature two -gang cup._ Reminder, a device with denser compared in size with an three clock ordinary Yale key, www.americanradiohistory.com 7 Wireless World October, 1947

RADIOMOBILE (144) The car radio receivers shown on this stand embody a six -valve superheterodyne receiver covering the medium and long wavebands. In the Model zoo station selection is effected by four push- buttons. The preselected combination can be changed without dismantling any part of the set and four more selected in a matter of minutes. Change from medium to long waves and tone adjustment for speech or music are likewise push- a rotary (Top left) Radiomobile push -button button operated, but car -radio equipment, Model too. (Above volume control, combined with an right) Role Regal " extension loud- on/off switch, is used. Noise filters speaker. are included in the circuit and igni- tion suppressors are not normally required. The Model zoo costs valves in push -pull feeding up to 12 L27 6s (L6 16s 6d P.T.). There is watts to a 12-in loudspeaker. An a companion set with manual tuning R.I. miniature pickup with sapphire priced at L23 2s (LS 15s 6d P.T.) needle is used. and a range of car aerials. The Airflo " television receiver Radiomobile, Ltd., Cricklewood Model T484 employs zr valves plus Works, London, N.W.2. three rectifiers and the vision re- ceiver fully modulates the rz -in tube RADIOSPARES (73) tor a signal of zoo eV. The picture This company specializes in the size is loin x 8M and the price Li ro distribution of replacement parts (+ L26 9s 5d P.T.). designed in many cases especially Components shown include pick- for use in the repair of radio equip- ups, valveholders with beryllium ment. upper contacts, transformers and Radiospares, Ltd., 29 -23, Fitzroy chokes. Street, London, W.z. Radio Instruments, Ltd., Purley Way, Croydon, Surrey; RAIMO RAIDIO (306) Among the products of this firm R.M. ELECTRLC (51) are extension loudspeakers and re- Among the receivers made by this mote control units. Thcy have also Above) R.G.D. two of more than usual in- De radio hearing aid to -valve firm are the -Phone radio- terest. One is a quality local - which enables phones to be con- gramophone. station receiver made for rack nected to the external L.S. sockets mounting and having an 8 -valve of an ordinary receiver ; volume T.R.F. circuit with push -pull out- control is included. put giving.4 watts, with bass and A range of cabinets is shown. treble tone controls. The other is Rairno Raidio Products, rb, Old an R.F. feeder unit for use with any Torquay Road, Paignton, Devon. existing amplifier. It is a superhet covering 16 to 5o metres with . REES MACE (45) medium and long wavebands and Modern versions of the Rees Mace consists of a frequency changer, I.F. " Cameo " and " Gnome " receivers are shown and also a Model SC7o " Cameo - and combined detector, A.G.C. and gram " A.F. stage. It is in chassis form. battery portable for which un- A.C. /f.C. portable R.M. Electric, Ltd., Team Valley, usually high sensitivity is claimed. radio- gramophone Gateshead, rr, Durham. The " Cameogram " universal mains (R -S.C. Radio). çortable radio gramophone mea- Vernon of this equipment is shown R.T.R.A. (100) sures only r7 ¡in x 14in x loin, yet in which the long waves are replaced The advice bureau provided by includes two internal loudspeakers; by a 50- to r45-metre band and all the Radio (Sc Television Retailers' the four -valve + rectifier receiver parts are fully tropicalized. Association at this stand is open operates on three wavebands. There is a seven -valve three-wave- both to traders and the public. Full R.S.C. Radio, Ltd., 40, Welbeck band auto radio- gramophone and a particulars regarding membership of Street. London, ¡V r. receiver fitted with a r2 -in the organization representing the television (40) tu! giving a to -in x 8 -in picture. country's radio retailers are avail- REGENTONE A superheterodyne circuit is used able for traders, whilst the public Table model, console and radio- with six valves in the vision chain can obtain information about gram versions of a number of super- five, seven and three in the sound, the fre- R.T.R.A. members in any locality. heterodyne chassis with quency changer being common to Radio and Television Retailers' and eight valves are shown. Models both. Magnetic scanning is used. Association, 18, Woburn Square, with tropicalized components are Radio 'Gramophone Development London, W.C.r. available for export. Co., Ltd., Pale Meadow Print Regentone Products, Ltd., Eastern Works, Bridgaorth, Shropshire. R.W.F. (103) Avenue, Romford, Essex. A lounge and enquiry bureau for R.I. (52) the benefit of members of the Radio RELAY SERVICES ASSOCIATION Tw,) important additions have Wholesalers' Federation are pro- (320) ern malle to the range of " Airfln " vided at this stand. Designed to represent a living rcei.,er.c. The Model RG488 is a Radio Wholesalers' Federation, room, the stand of the Relay Ser- of Great Britain is rada gramophone w:th two PEN4 5 58, Cordon Square. London, W.C.r. vices Association www.americanradiohistory.com Urtober, 1947 Wireless World 383 fitted with the various types of SALFORD (75) SCOTT (109) loudspeaker installed by the relay A quartz -controlled oscillator for companies. This firm is showing silicon -steel the calibration of radio receivers is laminations for transformers, Relay Services Association of Gt. chokes one of the most interesting exhibits. and relays as well as types for Britain, 25, High Street, Tunbridge The fundamental is rookc /s and meters Wells, Kent. and motors. the useful range of harmonics ex -. Geo. L. Scott and tends Co., Ltd., RIPAULTS (1) to about 3o Mc /s; there is Cromwell Road, Ellesmere Port, provision for A.F. modulation. The principal activities of this Cheshire. Quartz crystals in evacuated con- company are devoted to the manu- tainers are shown SHANNONS facture of cables, wires, insulated with frequencies & BISHOP (104) ranging from 4 kc /s to 15 Mc /s. The activities of this firm are de- and screened sleeving, resistance The Type JCF/2oo with voted to the distribution line -cords and the assembly of cable a fre- to the quency of rookc /s is adjusted to trade of certain proprietary receivers, forms for the radio industry. They o.or per cent test apparatus also produce tag connectors and as standard and and accessories. higher accuracies can be supplied if There is shown also the Leak ampli- small presswork to manufacturers' required. fier requirements. Thermostatically - con- having a push -pull output stage trolled units on international octal with negative feedback giving 15 Ripaults, Ltd., Southbury Road, bases are watts with Enfield, Middlesex. available and some types o.r per cent distortion have an overall stability of 5 parts and a linear response. ROBERTS (43) per million over a wide ambient Shannons and Bishop, ltd., 182, Wardour This firm is showing portable re- temperature range. Street, London, 17,r. ceivers. The P4D is a four-valve Selenium-rectifier type photocells battery model, comprising fre- of high sensitivity for use in the con- trol of industrial quency- changer, I.F. stage, diode - processes are also triode detector and A.F. stage and shown, and the exhibit will include tetrode output valve. It is housed toroidal dust -cored coils, decade in a rexine- covered case and 'weighs switches, slow -motion drives, small 19} lb. measuring instruments, the " Selec- The P5A has a circuit of similar test" A.C. /D.C. testing instru- general form but is designed ment, "Miniscope " C.R. oscillo- for scope A.C. mains operation. This one and G.E.C. resistance and weighs only 17} lb. capacity bridge. Both sets have internal frame Salford Electrical Instruments, aerials for medium and long wave- Ltd., Peel Works, Silk Street, Sal- bands, and provision is made for the ford, 3, Lancs. connection of an external aerial for the SCHARF (308) S.W. band. Sapphire - pointed gramophone . Roberts' Radio Co., Ltd., Creek needles of straight, Road, East Molesey, Surrey. trailer and miniature type are shown, also a new lightweight pick -up (No. 520 ROLA (135) retailing A complete range of energized at 355 plus P.T. and Erwin Scharf, 49, De Beauvoir permanent magnet loud - Road, speakers, the latter including units London, N.i. with Alcomax II magnets, forms the SCOTLAND YARD backbone of (211) the exhibit. These The part played by radio in pro- speakers are suitable for incorporat- viding speed in the communication ing in receiving sets or as extension system of the Metropolitan Police is units, though for the latter purpose shown on this stand. The V.H.F. the ready -made Rola " Regal " in equipment, employing R.Y. television receiver plastic frequency Model cabinet will meet most re- modulation, which is fitted in patrol T484. quirements. cars, is seen British in situ. Rola, Ltd., 8, Upper Metropolitan Police, New Scot- Grosvenor .Street, London, W.z. land Yard, London, S.W.r. ROMAC (129) A personal portable and a car radio receiver are Ene principal ex- hibits. The Model 126 portable is a 'Si superhet covering 193 -888 metres. A layer -built H.T. battery gives 30 -40 hours' service and L.T. is sup- plied by a type U2 dry cell which lasts 6 -8 hours. Wires embedded in the shoulder carrying -strap are used .... as an aerial. The weight is 4 4lb and the dimensions 9 }in x 5 }in x tin. p In the Model zoo car receiver two units are ILA Electric employed, the " control " radio feeder uni unit on the dash containing the with ope short

R.F. . amplifier and frequency wave band. changer, while the " loudspeaker " Salford unit contains I.F., detector and out- crystal calibrator. put stages, as well as the non -syn- chronous vibrator and power recti- fier. Romac Radio Corporation, Ltd Romac" rais" The Hyde, London, N.W.r.. personal www.americanradiohistory.comportable. Wireless World October, 1947 dimensional S.T.C. (64 & 228) ground to very close Several new types of rectifier have limits after manufacture. Tele- Included also is an extensive been developed by Standard metallized phones for use in radio, television range of standard type These insulators for use as hermetic seals and electronic equipment. bases in include L.T. rectifiers for battery and a profusion of ceramic T.C.C. Metalmite different models various shapes and sizes for the mul- tropical -type chargers, several insu- a series of rod - tifarious uses to which ceramic miniature for H.T. supply and in modern capacitor. type units for the E.H.T. supply lating materials are put in oscilloscopes and television sets. radio equipment. also has a display Steatite and Porcelain Products, This company Severn, Worcs. of quartz crystal oscillators and Ltd., Stourport -on- (Left) Truvoa" Wafer" folr industrial loudspeaker chassis. resonators, equipment STERLING CABLES (128) applications of radio heating, part the in- transmitter A comprehensive range of of a r3o -kW broadcast sulated wires and cables using and compact radio- telephone sets rubber and plas- in aircraft and in rubber, synthetic for installation tics made by this firm is shown. vehicles. Their products also include co -axial Audio equipment, such as moving - applica- P.A. amplifiers cables for high frequency coil microphones, and wires and cables with and test -room instruments, including tions oscilloscope, are special tropical insulation. a new double -beam Sterling Cable Co., Ltd., 25, also included. Enfield, Middlesex. Standard Telephones and Cables, Queensway, Ltd., Connaught House, Aldwych, T.C.C. (5) Ceramic lead -through and by- London, W.C.2. Every variety of fixed capacitor pass capacitors made by United and electrolytic types Insulators. SOUND SERVICE (209) in paper, mica SIMON for radio and television equipments A comprehensive service to sound and is to be found on this stand. Minia- record studios - professional ture and tropical styles are included. amateur -is represented by acces- high instruments of For conditions of extremely sories and complete humidity T.C.C. have a range of all types. described as 48, George super -tropical models Simon Sound Service, and Metal - Portman Square, London, Metalboss, Metalpack Street, mite in sealed aluminium cases, the Four S.T.C. Uni - W.r. last being a miniature type. plates assembled as SOBELL (19) especially for television a bridge rectifier + rectifier) Designed Model 7r 7 (six valves C.R. oscilloscope for measuring in- stages and push -pull equipment and struments. has two I.F. purposes is.a range of high -voltage output valves ; there are four wave- 'in drum scale ex- (75o V to 15 kV) capacitors bands. A rotary moulded bakelite cases. poses only one wave -range at a time. there An interesting type is the ex- In addition to the table model Picopack series of 717G in dwarf console tremely small is the Model electrolytics which measure only cabinet and Model 717AG with include a for radio o.34in in diameter and separate compartments for 35o volts D.C. receiver, record changer and record r aF size have auto- Telegraph Condenser Co., Ltd., storage. Both models Farm Road, London, W.3. matic record changers. Wales A combined television and broad- TANNOY (17) cast receiver (Model Tro7) has an new products for in which A number of interesting tuning device sound amplification and distribution the broadcast tuning scales are which are shown. contained in a sliding panel The " Commercial " radio- gramo- Trix 6- channel hides the picture tube and television phone, which is intended for school electronic mixer. controls when they are not in use. installations comprises -in 8 -in and similar The television set gives a ro x a playing desk, a newly designed picture and includes impulsive noise 25- or 6o -watt and radio chassis and a suppression on both sound amplifier assembled in a wooden vision. cabinet. Designed for low record Sobell Industries, Ltd., Langley wear, the " Commercial " moving - Park, Nr. Slough, Bucks. iron pick -up uses standard needles -sprung quick release STATIC CONDENSERS (210) with a rubber dielec- mounting. The frequency response The firm is showing paper level in rectangular metal is claimed to be substantially tric capacitors to 8,000 c / s. cans and also of the tubular type. from 5o with voltage Tannoy Products (Guy R. Foun- They are available Canterbury Grove, ratings up to 20 kV. tain, Ltd.), Static Condenser Co., Ltd., London, S.E.27. lvokingham, Berks. TAYLOR (119) a very STEATITE (18) This exhibit consists of of the many different comprehensive display of multi- Specimens instruments and forms of ceramic insulating ma- range measuring by this firm for the specialized test equipment such as terials made -ray oscil- radio industry are displayed on this circuit analysers, cathode stand. Of special interest are such loscopes and bridges. as variable condenser The Model 2oA circuit analyser record -replaying products re- Simon 14 -watt spindles and threaded coil formers, provides facilities for checking unit, taking up to Alin discs. www.americanradiohistory.com October, 1947 ircle%* 0®'IP lII

ceiver performance; it contains an extensive range of soldering and amplifier and loudspeaker and is connecting tags is included mains operated. in the exhibit. Sobel! Model The Model 30A cathode -ray Geo. Tucker Eyrlet Co., Ltd., Trod receiver oscilloscope has a 3h -in tube, an in- Walsall Road, Birmingham, wltb(right)con- put amplifier, b 22, trot panel down linear time base Warwick. for broadcast covering io c/s to ro kc /s and pro- reception and vision for synchronising. The price TUNGSRAM (132) (below) up for is L27 Ios. Valvés made by this firm cover television. Taylor Electrical Instruments, a very wide range of types and re- Ltd., 419 -424, Montrose Avenue, placements for most makes are Slough, Bucks. available, So far as possible lists have been TELCON consolidated, and the (118) valves included are adequate for R.F. cables with Telccthene di- most purposes. electric are shown and include The American and international types suitable for use at ro,000 octal range covers Mc /s. the, requirements The range includes coaxial of most industrial control devices, and twin -wire types. Transmission amplifiers, domestic and car radio lines intended for the amateur receivers. transmitter Octal -based " E " series are shown and have im- valves are being continued, and pedances of 15o S2 and 300 O. There there is a range are of miniature button - also other cables, including based valves with standard ß7G pin high- voltage types for C.R. tube arrangements for personal portables H.T. leads. and hearing aids. Various high -permeability alloys British Tungstarn Radio Works, and glass -sealing alloys are also Ltd., West 'Road, shown. London, N.17. Telegraph Construction and Main- ULTRA (13) tenance Co., Ltd., 22, Odd Broad Among a wide range of broadcast .Street, London, E.C.2. receivers this exhibit includes the TENAPLA8 Model A511 auto- radio -gramophone. (133) covers A selection from the wide range It 18.8- 6Mc /s, I,5oo -545 of thermoplastic extrusions kc /s, and 300- 15o kc /s and has an in poly- output froth push thene and polyvinyl- chloride is -pull tetrodes of shown. 6 watts. A metal rectifier is used Tenaplas, for H.T. Ltd., Upper Basildon, The Nr. Pangbourne, Berks. T49 table model has flywheel tuning and the set is in three sub- TRIX (20) units, two of which are hinged to A.F. amplifiers with outputs allow ready access to the interior for ranging from 15 W to over 500 W servicing. The cabinet is of are among the P.A. equipment pro- moulded plastic material in two duced by this firm ; the model V885 shades of brown. is unusual in giving a 20 -W outpu t Ultra Electric, Ltd., 62, Bucking- with AC /DC operation. Gramo- ham Gate, London, S.W.1. phone units and receivers are shown as well as horn -type loudspeakers, UNITED INSULATORS (128) and there. are 4- and 6- channel Among the latest products of this electronic mixers firm is a silvered -mica twin capacitor Trix Electrical Co., Ltd., r.5, available up to 200 pF designed for Maple Place, Tottenham Court use as the base of an I.F. trans- Road, London, W.I. former. Two sizes are made, one for midget I.F.s measuring din TRUVOX (81) square and one for standard types of A reduction of weight of 40 per ijin square. cent and a depth roughly one - A departure from the traditional quarter of the diameter are advan- tubular, disc and cup shapes for tages of the novel method of con- small ceramic capacitors is made by struction adopted in the " Wafer " the introduction of a wafer pattern series of loudspeakers. The magnet for capacitances of from lo pF to is enclosed within the dept i of the ioo pF. cone Taylor Model soA circuit and the magnetic circuit is United Insulator Co., Ltd., Oak - analyser. completed by the chassis itself. croft Road, Tolworth, Surbiton, High- quality pickups shown in- Surrey, clude a ribbon type with a fre- quency range claimed to he linear V.B.E. (4) between 25 and 20,000 c/ s, a Radio receivers and portable am- moving coil covering 4o tc 16,000 plifiers are the main interest of this c /s, and a "Ferrocoil," also with firm. detachable sapphire needle, suitable The V.S.E. lightweight portable for use without pre -amplification in amplifiers are designed to operate normal radio -gramophones. on A.C. or D.C. mains, Igo -250 Truvox Engineering Co., Ltd., volts, and the " Junior" model at Truvox House, Exhibition Grounds, /24 is rated at ro watts with two Il'rorbley, Middlesex. CLi3 valves in push -pull. The V.S.E. 16 -watt TUCKER EYELET amplifier uses four (134) CL33's in parallel push -pull. This firm manufactures all types V.S.E. Construction lets for the radioindustry. Co., Ltd., An www.americanradiohistory.com5-7, Denman Street, London. W.I. October, 194; WflreleSs - World

WESTINGHOUSE (34) ( + ras P.T.) is shown. It is a VARLET (202) covering The latest pattern Westalite recti- accumulators with capacities four -valve superheterodyne of Dry and long waves and includ- fier is now made in a variety of r,o a.h. to 32 a.h. for radio pur- medium most requirements of a ing batteries and loudspeaker types covering poses are shown and there is H.T. and E.H.T. supply in radio of 4 a.h and 4 V weighs 41 lb. -aid model . are hearing are two television sets, equipments. These models which measures 3 /in by 3 1in by i in There lighter and more efficient Models 369 and 370, with 9 -in and smaller, and weighs 1 lb 8 oz. earlier types. Ltd., r2 -in tubes. They are superhetero- than Varley Dry Accumulators, in all. Westinghouse are showing seven Road, Barking, Essex. dynes and 19 valves are used for 13y5ass Ltd., West Street, Erith, units, HT43 to H.-r49 inclusive, Vidor, A.C. receivers and a special (27) use in VIDOR Kent. of r6H tubular rectifiers for receiver measuring range A " pocket " VITAVOX (54) E.H.T. supply in C.R. equipment only 81in by 3 1in and costing ¿17 A wide range of microphones, and television sets. Two r6H loudspeakers and P.A. equipment is units in a voltage doubling circuit shown. It includes the " Bitone " will give over 8,000 volts D.C. at reproducer with multi -cellular H.F. 8 mA. horn and r2 -in L.F. cone speaker A 16K miniature rectifier is avail- combined with cross -over filter net- able giving 15o volts D.C. at a few work. milliamps for use in test apparatus, The " 55o " series of multicellular also some improved copper-oxide horn loudspeakers are designed as Westectors in miniature and her- " tweeters " for high-quality domes- metically sealed types. tic reproducers, and are available Westinghouse Brake and Signal in 3- and 6 -cell sizes. Co., Ltd., 82, York Way, London, Vitavox, Ltd., Westmoreland Ni.. Road, London, N.W.9. WEYMOUTH (142) Vidor Model CN 369 WEARITE (125) A new range of dust -Core coils in four -band receiver. I.F. transformers with dust -core cans measuring tin by ¡in by rin is trimmers are shown in several types. shown on this stand. These K -type In the 55o -type the size is 3 1in by coils cover 33 -2.000 m and there are lain square and the coils have a Q air -core models for 12 -35 m. for three wave- of 115 at 465 kc/s ; two different de- Several coil packs grees of coupling are available in bands are made and include switch- permea- different models. The M400B type ' ing and trimmers. There are is if fin by 4-1-in square and is for bility tuners Of both the straight frequencies of 46o kc /s, 1.6, 2.r, and and superheterodyne types. They 4.86 Mc /s, the Q ranges from go to can be supplied to cover any two 15 120. bands between r5o Ike /s and Miniature A.F. transformers mea- Mc / s. only thin diameter by Weymouth Radio Manufacturing suring Street, Wey- r 1TSin high are shown, and include Co., Ltd., Crescent microphone, intervalve and push - mouth, Dorset. are ceramic pull types. There WHARFEDALE (150) switches, a range of rotary -type A new cabinet -type loudspeaker mains transformers and chokes. is shown. containing aerial and designed for schools Coil packs, Known as the "Varitone" it em- oscillator coils for three wavebands, unit with are on view, ploys an 8 -in moving coil together with switching at 45 c/s and the the well -known range of P a bass resonance as well as phase inversion opening at the coils. bottom of the cabinet is fitted with Synchronous and non- synchron- closed when repro- vibrators are shown, and there 'a door which is ous ducing speech. ar,, Vibro power units, containing corner cabinet, buffers and R.F. filters. The twin speaker Vitavox Type "B" moving -coil micro- transformer, for which a frequency range of 40- phone. Wright and Weaire, Ltd., 2, Lord a London, S.W.I. r8,000 c / s is claimed; employs North Street, ro -in unit for high and a r2 -in unit (Below) W estinghouáe recti- with elec- fiers ; tyyppes shown are 16K, WEBBER (149) for low frequencies, an 16H1'71 and HT43. The exhibit of this firm consists tricaI separator unit giving a cross- of various proprietary makes of over at about r,000 c / s. This broadcast receiver, battery chargers, separator, which is suitable for loud- H.T. and L.T. batteries. speaker impedances of 2 to 15 ohms J. M. Webber and Co., Ltd., 244, and will handle 3o watts, is avail- Tottenham Court Road, London, able as a unit, price ¿3 15s. W.z. IVharfedale Wireless Works, Bradford Road, Idle, Bradford, Yorks. WINTER TRADING (138) These wholesale distributors and factors are exhibiting equipment by n.any of the well -known manufac- turers. Components form a large (Right) Weymouth K -type part of the exhibit. coils. Winter Trading Co., Ltd., 6, Harrow Road, London, W.2.

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

' AN .0,,/I i--MW Alwr a -1= 7 - Thy, .I . I I wi i 7 I ill , _- n I r r, i i F. J , AL I - i A / S .r AI

MP MOW / mir aM NNW NW III I a IN 7A i / I Ì . Al " imiIr aim i . a ir i w AMP, alimh i i - JIL.. aa a A - / í "

STAND No.36 GRAND HALL

You'll see television at its brightest and clearest when you meet the modern R.G.D. tele- vision receiver-No. 2547 T.R. - making its first public appearance at this year's " Radiolympia." This new instrument is presented as a worthy companion to the famous radio -gramophones which for years have been acclaimed the " Aristocrats of Radio." All television models and the seven and ten valve all wave auto- radio- gramophones -746G, 1046G and 1048G - will be demonstrated daily throughout the exhibition.

RADIO GRAMOPHONE DEVELOPMENT CO. LTD. BRIDGNORTH SHiROfl'SHIRE LONDON BIRMINGHAM MANCHESTER Temporary Service premises: Sales and Service: Saks and Service: 48, Nine Elms Lare, S.W.8 187, Corporation Street, 4 12, Cateaton Street, 3 Tel : MACaulay 5592 Tel: CENtral 2403 Tel: BLAckfriars 1951 D

www.americanradiohistory.com 1947 38 Advertisements Wireless World October,

444a ki si

o\NN. co\\»

A23 A.C. yuperhet and U49 axeand p\ A 2 8 Bandspread ACIDC Superhet 22 A52 A.C. Superhet plus £3.16.9d. tax (boths. 15 A.C. Superhet 32 gns. plus £4. 9 26 gus. plus £5.'7.5d Battery Superhet gns models) tax plus £á79d. tax \ plus £7.4.6d. tax \\O\ ,\,,\\\\\\\\\\\\\\\\O\O\\\\O\\\\\\\\\\\\\\\\\\\O\\\\\\\O\O\\\\\\\\\\\\\\\\\\\\\\\\\`\\\\ \\\\ \ \\ \.O \ \\\ \

"Second Set" for TS46 Table Tele- "Radiotime" for U29 vision. Price to be plus N A.C.' mains Consolei 32 8ns riá, tax plul £áe3ánr4gus.£3.3.3d. tax announced £7.4.6 tax \ plus £53 \\\o\\\\\\\\a\\\\\\\s\\\\\\\\\\\\\\\\\\\\o\\\\\\ \o\\\\o\\\\\\os\o\\ae\ooo\\.\\\\\o\\o\\o\\\\\o\\\\\\\\ ! a f1 i N 4 I r

N

plus TSC3oA Television V RG35 A.C. Radio- ARG37 A.C. Auto- TSC48 Television 120 gns. Radio. Price tobe Console 66 gus. gram Radiogram plus tax r.8sgd.,ax plus £27r .rod. tax announced £15.15.4d. AAI.AAO\\O\VVAAAV\VVV"Y.a\V\VAAAAAAAA\VA\.UNO.AAVV \\\\VAV`l\.\AVAAVVAAVVV\OI.A\Ov\.AA\O\VAAAAOAV\ N Ekco Television In- door Aerial £z.io.od. N free of tax

Ekco Car Radio CR32 Car Radio Switch Clock Aerials CA57 27i- 2r gns. plus £4.14.rod. ES3i Extension Speaker CC65 tax £3.1o.0d. free of tax £5 plus £1 .2.0d. tax CA7 i 31,, 6

\\`l\\\\ NVNL\\L., 1\NlLN . WAMNNja m`\\ \\\\\\N\ \ `` \\\\\\ Quality plus reliability and outstanding performance . . . these are the characteristics of Ekco Radio and Television. Those who know Ekco's background will affirm that this is the result of a combination of brilliant scientific conception, painstaking development and the maintenance of a standard of electrical and mechanical efficiency unsurpassed in the industry. See them on Stand 46.

\\\\\\o\\\o\\\\\\\N\\ 0000 \o \\oo\oo\oo\o\o\\\m\o\o\o oo\\\\\N\\\\ oo\\\\ :\\\s E. K. COLE LTD EKCO WORKS SOUTHEND -ON -SEA

www.americanradiohistory.com October, 1949 Wireless World 387

is, I understand, a rather less refined version of the expression recently made famous in government circles. I chanced to be on a visit to a Unbiased friend living near London Airport where, of course, domestic wireless By FREE GRID reception during the passing over- head of a plane is made virtually impossible. I was listening to a talk Juan Fernandez, I determined, therefore, to avail in the B.B.C.'s "Quiet Hour " myself of the privilege whereby on series when the roar of an approach- payment of L5 a train may be ing plane was heard and I stretched 1947 stopped by pulling the communica- SOMETIMES amid the turmoil of out my hand to turn the volume up, tion cord, and I took from my wallet but before I could do so modern life with its incessant the it increased jangling necessary pound notes to hand automatically. By the time the of telephones and clatter of to the guard. To me this typewriters, I find myself longing seemed, plane was overhead the whole place and still does seem, a simple enough was filled with the stentorian for the solitude of Alexander Selkirk business roar as he transaction whereby one of the broadcaster reading the late sat on the beach at Juan Fern- pays, although stiffly, andez wondering with some rather for a Poet Laureate's " Into the silence." satisfac- service rendered. But not bit of tion what particular crisis he was a With the passing of the plane the it ! Those who talk of the red missing at home. There must be tape reader's voice gradually died down that is likely to be rampant when in happy synchrony with the many like me in this respect and I the railways senti- am happy are nationalized seem ments expressed in the poem. Long to be able to tell every- to imagine that it is non body that I -existent have found at least one now. The contrary is true, for not place where one is as much cut off only did from the guard refuse to accept the outside world as the unfor- my but the whole time -wasting tunate Mr. Selkirk, is in 45 and that a and money- wasting m..chinery of the British railway train. law, for which you When travelling in one and I pay, had of these to be set in motion solely to fulfil archaic monsters the other day I the requirements suddenly of red tape. In remembered that I had not the end, of course, I had to pay over told Mrs. Free Grid I should be exactly the same /J5 (plus needless away for a few days. Reaching costs) which could have automatically for been paid the 'phone I was in the first place without any fuss brought up sharply by the realiza- or bother. tion that for no apparent reason, As a result of my experience, I despite all our much vaunted carrier- cannot help reflecting that if current system, not a single train in marooned railway travellers cannot this country is fitted with a tele- have a telephone service, Peace, perfect phone call box nor even they might peace. a telegraph at least be provided with a broad- station. I was, I reflected, far more cast listening service (headphones cut off than was Mr. Selkirk who before the poem had come to its only, of course). This is especially appointed end could at least have put messages in necessary I was up and doing, bottles now that the newsprint carrying out an investigation into and thrown them into the cuts mean that it is no longer sea-that is if he had possessed any pos- the innards of the set to see what sible to buy a newspaper with suffi- produced this bottles. cient phenomenon. In addi- reading matter to while away tion to the aerial lead -in I found a Thinking of bottles reminded me the tedium of a long journey. that I could obtain one of these from pair of leads running up to the roof the dining car, stick a message and where I discovered a carefully posi- a ten shilling note inside if and hurl tioned microphone. This picked up it out as we rushed through a way- Conversational the noise of the approaching plane side station. The dining car atten- and triggered off a special A.V.C. dant pointed out, however, that this Counterblast arrangement, rather in the manner of Vogad -faithfully dealt with by THE factory -made wireless set ' ` Cathode Ray " in the issue of that enhances the furnishing Wireless World for July zoth, 1939, scheme of almost every British which brought a super amplifier home, be it cottage or castle, con- temporarily into circuit. tains very little that has not origin- Needless to say I at once saw the ated in the fertile brain of an immense possibilities of the invention amateur. Even where the originator for something far more pressing than of an idea has been a member of the overcoming the noise of planes. I research staff of some radio manufac- hurried home and set about the turer, he has generally first thought necessary alterations to my receiver of it when in his bath or at some and I am glad to say that I was able similar moment of his time not pur- to test it out the very next after- chased by his firm. noon at one of Mrs. Free Grid's in- Recently I had further proof of terminable " at homes." The Red tape run riot. the above when there was demon- receiver rose nobly to the occa- strated to me a receiver specially de- sion. For the first time in my life I was a breach of the company's regu- signed to fill a very pressing need of succeeded in listening to the B.B.C. lations regarding the hurling of an unorganized section of the listen- programmes throughout the whole bottles from windows whereby plate- ing public for whom no manufac- of the afternoon's interminable pro- layers might be injured. turer cares a sailor's farewell, which ceedings.

www.americanradiohistory.com October, 1947 388 Wireless World Transformers Obvious and the same too. But if the resistance is connected across a secondary winding having twice the number of turns, as in Fig. 2, the primary voltage is one half and the primary current is twice that through the secondary resistance, so the resistance of R looked at from (a) (b) (c) the primary side is one quarter of R. More generally, the voltage M Cs across the primary of a perfect t : n transformer is t/n of that across the secondary ; the load current is n times as much ; so the impedance is t /n2 times the impedance across the secondary. Splitting impedance up into its components, resistance and in- multiplied (d) (e) (f) ductance are effectively by t /n2, and capacitance by n2. Fig. i. These are some of the "transformer " couplings explained. The If the coupling is less than too resistance RA is converted by them to per cent, the problem is not so L2R8/M2 (a) w2L2 /R (d) simple but still quite manageable. (b) Rs (e) t /w2Cs2Rs One considers the transformer as Csz z z w2L12 /Rs of a perfect one ()c C2( R .. - t / (w Ce Rs)) (f) a combination (representing the proportion that the terminals in each case. (w = 2irf ). - measured between is coupled) with inductances in series (representing the uncoupled AFEW months ago, while the point explained in any element more tary book. (I am now looking MAGNETIC reading one of the /LEAKAGE learned articles in this forward to receiving numerous journal*, I came across the follow- autographed copies of elementary the passages on this ing statement : books with subject prominently marked.) " The aerial or other source of The author of the article showed signal is usually coupled to the several examples of the sort of r first valve via some network circuit he had in mind, reproduced consisting of at least one cir- here as Fig. t. There will be no 100 to resonance ; this cuit tuned difficulty in identifying d as a COUPLING acts as a transformer, and the transformer, but how about a ? Fig. 3. An incompletely coupled aerial therefore appears to the of the things that the books resistance having One transformer can be represented valve as a do explain is how resistance (or as a combination of a completely some value RA which depends impedance) is, in effect, transformer and two ratio." any other coupled on the transformer transferred from one winding of completely uncoupled coils -4 of which can be " trans- As it was not an article for a transformer to another. If (either the coupling is ferred " to the other winding, to beginners, the make only one). author quite roo per cent, rightly proceeded and the ratio . is parts of the windings), as in Fig. 3. 1 on his argument t : r, then from Going back to our very simple without further t h e primary's case in Fig. 2, there is no change explanation of point of view it in principle if the winding with is all the same is this fact ; but the smaller number of turns 2I a resis- it struck me in I whether made common to both, giving that it tance is connected an auto -transformer (Fig. 4a). passing Fig. 2. Interposing a perfect might not be across the second- Simpler still, if the ratio is t : t, t :2 transformer has the effect prim- obvious to all how resistance R ary or the as in Fig. 4b, then it is quite of dividing the The ratio a single tuned by 22, so far as the terminals ary. obvious that the resistance, re- circuit can act on the left are concerned being t : t, voltage ferred to the primary (which in as a transformer, and current are this case happens to be the having seen voltage too) is R. nor did I remember on both sides, so secondary, the same current What about the inductance in * " Noise Factor," L. A. Moson May 1947 impedance) is obviously parallel, you say ? Well, if the p. a71. (i.e., the

www.americanradiohistory.com October, r947 Wireless World 389

ticular frequency. Making Z the same in both circuits, the equiva- BY CATHODE RAY Otherwise lents work out as : RP XP2 RP2 XP Rs= Xs= RP2 +XP2 RP2 +X122 Things Not Appearing on the Diagram Rs2 +Xs2 Rs2 +Xs2 RP- XP= Xs These are extraordinarily useful transformers we have been in Fig. r looks like a step -up or thinking about are low formulae. And very often, frequency step - down auto - transformer, especially in ones, with substantial iron cores high- frequency because no tapped coil is visible. circuits, they can be simplified. and many turns, their primary But they all depend on well -known inductances are generally If the series reactance is con- so large principles, all of which we have siderably greater that the current taken by them than the re- already used in connection with sistance -say at least five times (the " magnetizing current ") : can Fig. 4. They are greater -or the parallel reactance be neglected in comparison with (r) The impedances of in- the current re- is much less than the resistance, ductances and then Rs2 sulting from con- 1:2 I:I + Xs2 is nearly the same capacitances. as Xs2, and it is accurate enough necting l o a d. These depend on But the doubt- to say : frequency, and XP2 ful - looking as they tend to Rs = Xs = XP " transformers " cancel one an- RP in Fig. r were z other out they RP s definitely in- are given oppo- - XP = Xs (a) (b) tended for high site signs : frequencies, in which case the XL (inductive reactance) = cul., ohms complicating Xe (capacitive reactance) (co = 2nf) R = - effect of the --s- R wC parallel induct- (SLIGHTLY (SLIGHTLY (2) The usual ance can be CED) REDUCED) dis- rules for com- In a tuned circuit the reactance posed of even bining impe- more perfectly, is cancelled out by one of the (c) (d) dances is series opposite kind, leaving resistance by tuning it ; and in parallel. only. RP is what is called the i.e., connecting Fig. 4. Working back, via an Any number of dynamic resistance, or " reject - in parallel with auto-transformer, to the direct impedances of connection of a load resistance ance " ; while " Diallist's " name it an equal impe- R. the same kind for dance of Rs is " acceptance." the op- (R, XL or Xc) Armed with posite kind -capacitance (Figs. in series can the three principles 4c be reduced to one, summarized above, one can easily and ib). by simple addition. Reactances From the point of view of the of the opposite kind can be supply terminals, the currents reduced in the same way if XIS through L and C, being in nearly the signs are observed ; but opposite phase, nearly cancel out, R and X have to be " added at leaving the equivalent of a high right -angles " (Z = VR2 + X2) or resistance, known as the dynamic by the magic j if you prefer it. i resistance, though " Diallist " In Fig. 5a, if the length of Rs (very sensibly, it seemed to me) represents the resistance, and (a) suggested that it might be called Xis an inductive reactance in the " rejectance," seeing that it series with it, Z represents by its is the net impedance of a rejector length the magnitude of the circuit. Whatever it is called, total impedance, and by its angle XLP this resistance can be merged with the phase. If R and L are in the parallel load resistance R, parallel, the procedure is the same, which is thereby reduced. The except that the lengths have to effect of the tuned circuit on the represent the reciprocals (Fig. 5b). supply being represented now by (3) Putting Figs. 5a and 5b an adjustment of the value of R, together, it is easy to see that it Fig. 5. The well -known vector there is no longer any need to show is possible for the impedance to diagram (" completing the paral- the mutually cancelling L and C, be the same in both. In other lelogram ") method of adding and we finally arrive at Fig. 4d. words, given R and X in sedes, resistance and reactance (a) in series and (b) in parallel. If the A r : r transformer can hardly it is possible to substitute another be considered a transformer at all, R and X in parallel which are resultant Z is the same in both because it has no power to change cases, then Xis and Rs in series equivalent. And vice versa. But are equivalent to XLP and RP the effective load resistance. And as X depends on frequency, they in parallel -a very useful dodge none of the arrangements shown are equivalent at only one pat-- in circuit calculation. .

www.americanradiohistory.com uctooer, 1947 390 Wireless World

Transformers-Obvious and series, so can be larger than other- by varying the tapping on the Otherwise - wise. Cs and C might be the coil ; i.e., the ratio of the trans- reduce the examples in Fig. s irreducible output and input former. It is a type of transformer (except the recognizable trans- capacitances of valves, for very commonly used to couple to grid circuit in a valve former, d) to their equivalents. instance. - anode Take a, for a start. Assuming This suggests a new line of oscillator, and is then known as Rs is relatively small, RP follows thought, which I shall try to the Hartley circuit. But an circuit, at once as Xs2 /Rs (which of develop next month ; but in the alternative is the Colpitts bourse is w2L2/Rs), and XL and meantime there is a way of which is similar except that the Xc cancel out at resonance. looking at Fig. rc that may be capacitance, instead of the in- So this is a suitable circuit for more helpful than this series - ductance, is " tapped " (Fig. 6b). matching the usually low resis- parallel- series business. Fig. 6a The ratio is then determined by tance of an aerial to the high input is obviously a tuned transformer, the ratio of Cl to C2, remembering impedance of a valve. It is the in which the terminals are con- that the reactance of the two corresponds to that of equivalent of a Rs : X step -up nected to the primary winding in series transformer. (" X " in this can and R is across the secondary. C in Fig. 6a. it, be either the L or the C kind, R can be converted to any other In case you haven't noticed because when in tune they are value, seen at the terminals, Fig. 6b is Fig. ic. equal). Circuit f is just the same, except that there is already a parallel BOOK REVIEW is necessary inductance, L2. So it inverter the reactance of L5 and L2 Elementary Radio Servicing. By The testing of the phase- that 260 circuit is particularly badly done. in parallel tune with C. The William R. Wellman. Pp. +xi. Macmillan & Co., Ltd., St. In the first place the circuit shown in a ; conversion formula is as Martin's St., London, W.C.2. is not of the self- balancing type it but as L5 can-in fact must - Price 2rs. is claimed to be, but is one in which be greater than is needed to tune THIS book is intended to meet the balance depends on the main- with C by itself, the object of the requirements of those who tenance of the correct ratio of two this circuit would be to get a have had instruction in the theory resistances in relation to the gain bigger step -up ratio than with a. and practice of wireless apparatus of a stage. In the second place, but who are inexperienced in fault- after a lengthy discussion on volt- finding. The arrangement of the age checking, there is a brief refer- hook is unusual; it is divided into ence only to checking the balance chapters dealing with different parts with an A.F. input, but no indica- of the equipment, but each chapter tion at all of what is to be done if consists of a few pages only of gen- the circuit is then found to be un- eral explanation together with a balanced. number of so- called ' Job Sheets ". In a section headed " The Volt - These are followed by a number of Ohm-Milliammeter " there is no re- (a) (b) questions for the student, but ference whatever to the milliam- answers are not given. meter and the use of this instrument Fig. 6 (a) is obviously a trans- The Job Sheets are really potted in fault- finding receives no men- former. (b) is an alternative instructions for testing particular tion at all. form, tapped on the capacitance parts of a circuit or particular com- The book is of American origin side. ponents. For instance, the chapter and the references to circuit tech- American practice. on A.F. amplifiers has four sheets ; niques are to stage, for a Although the ground covered is e is same as except for a pentode output Circuit the f for a triode wide, the treatment is superficial. , reactance is capaci- 25L6 beam-power stage, that the series push -pull stage, and for a self - W. T. C. tive, and the formula is modi- balancing phase- inverter circuit. fied accordingly. Under the heading " Procedure " Circuit c is a little trickier, the author almost invariably starts BOOKS RECEIVED because Rs and Cs in parallel must by advocating voltage measure- first be converted to series ments and he gives figures of the Radio Test Instruments. -By Rufus to be expected at various P. Turner. Most of the material in ; the series reactance voltages equivalents designed equip- this American book has appeared dur- then partly cancels out with the points in normally ing the past five years in Radio News, reactance of L. The balance ment. and is concerned mainly with the build- The examples quoted above show ing of test gear -from Simple current (which must be inductive) tunes some confusion of thought on the and voltage meters to signal gener- C, and the series resistance is con- part of the author, for there is no ators. 221+xv pages, with 582 diagrams verted to its parallel equivalent. difference from the fault- finding and illustrations. Ziff, Davis, Ltd., The conversion means point of view between pentode and Grampians Building, Western Gate, This double W.6. Price 25s. that with normal component beam tetrode stages. The only dif- London, ference between the two stages C. & W. Press Handbook. -The values it is suitable for smaller third edition of this booklet includes, e quoted lies in the applied voltages. ratio transformations than a, in input in addition to cable tariff rates, details Furthermore, defects the radio facilities afforded and f. An advantage is that in coupling capacitor are treated in of the cable and high- frequency apparatus, by Cable & Wireless and its associated very one only and the impression is thus companies throughout the world. 36+ xii where the difficulty is to avoid given that they are peculiar to that pages. Cable & Wireless, Ltd., Electra excessively low reactances, L is one instead of being equally applic- House, Victoria Embankment, London, tuned by two capacitances in able to both, W.C.2.

www.americanradiohistory.com October, 1947 Wireless World Advertisements 39 BELLING -LEE QUIZ (No. 16) Answers to questions we are often asked by letter and telephone What are you showing NEW SKYROD. . Q. 4 6 at Radiolympia ? A. 46. NEW ELIMINOISE. The new Belling-Lee " Skyrod " will be 18 feet long, in three sections, of high tensile alloy, for chimney mounting. Instead of one set of transformers for the " Skyrod " and another for the " Eliminoise," there will be one set only, which will normally be used with the " Skyrod," but may also be used with a horizontal aerial, or attached to the cross bar of a television dipole (Belling -Lee U.K. patent No. 520628) to enable the reflector to be used as an anti -interference aerial. As we have been unable to improve the electrical design, this has been left as in the original " Eliminoise," the per - formance of which has never been equalled. We have, however, considerably improved the mechanical design of both the aerial and receiver transformers. They have been " stream- lined " inside and out. All parts necessarily so, are easily accessible and much time will be saved in installation. A very real facility has been added to the receiver " Eliminoise which is intended to be fixed to the skirting board, and is provided with a coaxial output, the new Belling -Lee coaxial plug and socket being incorporated. The lead to the receiver consists of a 5ft. coaxial cable with its appropriate plug to the transformer, the set end terminating with two O.Z. 118in. dia. plugs soldered on, the junction being a polythene mould- ing. We would remind readers that the wave bands covered are I0 -56 ; zoo -56o ; I,000 -2,000 metres.

The above illustration is of our new The illustration "Eliminoise," Kit No. L308K, including (left) shows the new Transformers, Cable, Aerial and Earth Skyrod" mounted THERMAL CUTOUTS for the wire, Insulators and a Receiver connec- on a chimney. ting lead. U.K. Patents No. 4718, Kit No. L618. protection of fractional h.p. motors 479118. are being shown and demonstrated, a television ; incidentally, every em- motor being run which may be stalled ployee of every exhibitor should We are by a brake. have also showing a full range The action of the cut- his car suppressed. of TELEVISION AERIALS in- out being brightly illuminated is cluding the comparatively new observed through a powerful lens. AMATEURS will find that they INDOOR TELEVISION AERIAL Cutouts are a rapidly increasing are interested in practically every- thing shown and FOR ATTIC OR LOFT. This is part of our production, and our will be made specially welcome. intended for districts where field engineers will be glad to discuss these Our AMATEUR AERIAL KIT is strength is strong. with engineers already fairly well It has very of firms who are known. distinct minima, which can be used interested. against interference. Can be used COMPONENTS include a full A range of FILTERS FOR range of ; indoors, or is supplied with metal THE TERMINALS improved SUPPRESSION OF H.F. INTER- single, double and mast and lashings for chimney multi PLUGS FERENCE is shown. Most of these AND SOCKETS ; a comparatively mounting. If you do not already have been re- designed since last new range of COAXIAL PLUGS know them, see also the " WIN - Radiolympia, to take care of the AND SOCKETS, single, twin " T " ROD " WINDOW AERIAL and higher frequencies now more section and couplings ; FUSES AND the " CAROD " CAR AERIAL. com- monly in use. FUSEHOLDERS, including a fairly new miniature panel fuseholder ; A.B.8A VALVEHOLDER has been SPARKING PLUG SUPPRES- also GLASS SEAL TERMINALS. added to the range of other well - SORS and DISTRIBUTOR SUP- We are proud of our produc known types which include HIGH PRESSORS are available to prevent tion, but, although in general our VOLTAGE VALVEHOLDERS. motor cars from interfering with deliveries are as good as most, we are anything but proud of them, f nor are we complacent. We do our best and crave your patience ¡Radiolympia '1947 although we are ourselves impatient.

STAND No. 33 BELLING S LEE LTD1 CAMBRIDGE ARTERIAL ROAD. ENFIELD. MIDDX

www.americanradiohistory.com Advertisements Wireless World October, 1947

RADIO TELEVISION RECORDS MOBILE TELEVISION UNIT TELEVISION EMITRON CAMERAS V.H.F. RADIO - TELEPHONE EQUIPMENT FILM CHANNEL DISC & COMMUNICATION TRANSMITTERS & MULTIPLIER PHOTO CELL & REPLAY RECEIVERS MARINE & AIRBORNE RADAR MAGNETIC TAPE RECORDING VELOCITY MODULATED OSCILLATORS EQUIPMENTS DIELECTRIC PRE -HEATERS

For the Design, Development & Manufacture of ELECTRONIC EQUIPMENT ON the E.M.I. Stand in the Electronic Section RECORDING GEAR of Radiolympia the following Companies are A variety of Recording Gear is displayed in- exhibiting : cluding a Portable Magnetic Disc Recorder, and E.M.I. Engineering Development Ltd., a Magnetic Tape Broadcast Recorder, both E.M.I. Research Ltd., with replay apparatus. E.M.I. Factories Ltd., E.M.I. Institutes Ltd. COMMUNICATIONS EQUIPMENT On this Stand the technical enthusiast will find Several examples of the numerous Communi- a wide range of highly interesting electronic cation Transmitters and Receivers developed by equipment. E.M.I. are also on view, including a V.H.F. TELEVISION Radio -Telephone equipment. The Television Section includes examples of the most recent Emitron Camera developments; SPECIAL EQUIPMENT the space available to typical pulse generating equipment ; a scale model It is not practicable within of an E.M.I. Mobile Television Van and one of display more than a selection of the varied the very latest achievements of E.M.I. Research electronic equipment produced by E.M.I., which Laboratories - an entirely new Film Channel. includes Television Transmitters; Monitoring and All of these items were developed in the E.M.I. Studio equipment for complete Television in- Laboratories, first in the field with Electronic stallations ; Emiscope Cathode Ray Tubes for Television. radar and other purposes; Velocity Modulated Oscillators covering centrimetric wave-lengths for RADAR and marine navigation and for Infra -red Other sections of the Stand show examples of airborne viewing apparatus ; specialised Electronic specialised electronic devices developed and and Measuring instruments and a wide assortment of produced by E.M.I. for war -time purposes intricate Radio -Testing instruments. now being applied to peace -time uses. Exhibits for However, qualified staff will be in attendance on include " Rebecca " - the beam system the exhibition and will be light- weight radar equipment this Stand during aircraft; marine and pleased to give information and answer enquiries and other such gear. from both overseas and home visitors as to the ELECTRONIC HEATERS full field of Research, Development and Manu- The application of electronic technique to facture covered by the E.M.I. Group. industry is exemplified by the range of R.F. Dielectric Pre -Heaters also exhibited on the NOTE: Students and technicians will be interested to Stand. The models shown were specifically find on this Stand full information about E.M.I. designed for the plastic moulding industry, Institutes, the new College which has been estab- but many other industrial applications are now tablished by E.M.I. to provide elementary and possible. advanced tuition in electronic science. VISIT STAND NO. 212 AT RADIOLYMPIA Electric & Musical Industries Ltd M A I N F A C T O R I E S AND HEAD O F F I C E HAYES MIDDLESEX ENGLAND BRUSSELS BUENOS AIRES CALCUTTA COPENHAGEN DUBLIN ;UBSIDIARY COMPANIES AT ATHENS AMSTERDAM BARCELONA SHANGHAI SINGAPORE STOCKHOLM SYDNEY WATERFORD WELLINGTON STANBUL MILAN PARIS RIO DE JANEIRO SANTIAGO

www.americanradiohistory.com uctober, 1947 Wireless World 391 Television Receiver 8- Receiver Unit Construction high frequencies the use of high- conductivity material for the chassis must be con- sidered essential. As the R.F. currents do not penetrate deeply into the material, it would be eco- nomical to use steel with copper or silver plating. However, it is simpler to use sheet copper, and the thickness needed is governed by mechanical considerations. As shown in the photographs, the vision and sound chassis are of channel section and are bent from pieces of No. 20 gauge cop- per sheet. Cross screens, cut away to clear the valveholders, In this view are fitted, of the com- and No. 26 gauge is plete receiver adequate for these. The two the R.F. unit is shown tilted chassis are bolted together after up for access to its underside. the cross screens have been The focus and brightness con- fitted and it is, of course, neces- trols can be seen fitted to a sary to use countersunk -head small panel which can be mounted The earthy heater, adjacent in- screws for those in the adjacent in any convenient place. ternal screen and centre spigot are faces of the chassis. all joined together on the valve- are the earthy heater, The V.F. stage is carried in a internal holder. In addition, there are a compartment above the rear of screen, grid and cathode connec- short lead from "` internal the main chassis. This economizes tions, while on the output side screen " to chassis, one very in space and brings the V.F. out- there are the non -earthy heater, short lead from " internal screen, put close to the base of the C.R. anode and suppressor con- screen ' to chassis, and one very tube. For this, brass is adequate, nections. The second internal - short one from the centre spigot but there is no objection to cop- screen connection falls immedi- to the cross- screen. This last con- per if it is preferred. ately beneath the cross screen. nection is important. It is essential to pay particular This last is earthed by a short The screen and anode de- attention to obtaining very short lead soldered to the chassis on coupling capacitor is mounted on direct leads, and it is especially the input side of the cross screen the cross screen on the output side important to make sound soldered and the suppressor is similarly and the o.00r -µF main bias -re- connections to the chassis for all earthed, but on the output side. sistor by -pass capacitor is held by earth points. The earthy- heater tag is earthed the same screws on the input side. A small hole is drilled through the cross screen adjacent to the earthy ends of the capacitors This sketch shows the and a wire passed through it is main dimensions of soldered to the two capacitors, to the chassis. the screen and to the suppressor tag on the valveholder. The H.T. side of the decoupling capacitor is joined directly to the screen tag on the valveholder and also supports one end of the de- coupling resistor. The 50 -pF cathode capacitors are supported in the wiring over 3' - 3' 2'/ the valveholder 14' and soldered directly with the shortest leads to The cross -screen divides the to the chassis as closely as pos- the cathode tag and the internal - valveholder leads into two groups sible to it and a short lead is run screen tag adjacent to the which fall into adjacent compart- along adjacent to the chassis for heater. The main roo-S2 bias ments. On the input side there the live heater lead. resistor is soldered across the

www.americanradiohistory.com 1947 392 Wireless World October,

Television Receiver Construction- should not taper at all until it will enable sound joints to be o.00r -µF cathode capacitor with is close to the end, and it should made with ease. It is worth tak- the 33 -52 resistor from the un- then have a blunt, wedge -shaped ing a little trouble to acquire the earthed end to cathode. nose. The whole flat end of one knack, for bad joints will be a It is necessary to provide some side of the wedge can then be perpetual source of trouble. It support for the H.T. ends of the placed in contact with the chas- will probably be hard to obtain 220 -lì anode and screen de- sis. an electric iron with the right The sort of bit that is satisfac- shape of bit for the job, and it tory, and the simplest way of is best to use a plain one heated SOLDERING chassis or a blow- IRON soldering the leads to the by a bunsen burner are shown in the sketch. A small lamp. area is scraped quite clean, say, The photographs which illus- with the end of a screwdriver, and trate this article show the details a piece of rosin -core solder about of the wiring where they are im- lin long is placed on the clean portant. They are substantially patch. The iron must be clean the same in all compartments, and really hot. It is placed on there being only minor differences top oft-he solder, which it melts brought about by the trap cir- almost instantly, and pressed cuits. CHASSIS against the chassis. After some The coils themselves are un- CLEANED 5-to seconds the copper chassis screened since in view of the low PATCH will locally be hot enough, and stage gains they are far enough Illustrating the kind of soldering - a slight rub of the iron will make apart for magnetic coupling to be iron most suitable for making the solder take. The previously small and the cross partitions pro- sound joints to a copper chassis. tinned lead is then slipped under vide screening for the electric the nose of the iron and held per- fields. They are double wound, coupling resistors. There are fectly still while the iron is re- not to provide a band -pass effect, many ways of doing this. The moved and the solder cools. for this is obtained by stagger one adopted is particularly neat, All this sounds rather difficult, tuning, but to save coupling but a little troublesome because but it is not, and a little practice capacitors and to provide separate 1 specially made. the supports are B.A. BRASS SLUG A short length of -,min insulat- IIb LONG ing rod has a 2 B.A. thread run on it and a small hole drilled lengthwise down its centre. A "--Ye" DIA. PAXOLIN TUBE tightly fitting piece of wire is pushed through the hole and the -THREAD GUIDE FOR SLUG whole forms a lead- through in- sulator which is secured in a hole in the cross- screen by two 2 B.A. half -nuts. v; Now it will be clear from the above that there are a good many connections to the chas- soldered 'h6 sis. If this job is tackled in the right way and with the right R i is difficult tools there nothing "D" CROSSBAR about it, but it is impossible to 4 make good joints if one adopts 68.A. an ordinary soldering tec nique. This is because of the high heat conductivity of copper, which PAPER makes it difficult to raise the tem- INTERLEAVE perature of a small piece of the chassis sufficiently. average soldering iron is The TINNED !' quite useless for the job. It is COPPER WIRE essential to have a big heavy bit so that it can store an adequate THREAD THREAD BINDING quantity of heat ; the smallest satisfactory bit weighs about TUBE TIGHT PUSH FIT IN BASE % alb. It is essential to have an Ì contact area between LIGHT GROOVE % adequate TO LOCATE WIRE and the chassis so that the i = the bit i ai-e- heat can flow rapidly from the . ° " iron " to the chassis. A long These drawings show the details of the R.F. coil construction. Winding tapered bit is useless. The bit data is given elsewhere.

www.americanradiohistory.com October, 1'949 Wireless World 393

These three photographs show in detail the arrangement and wiring of the R.F. stages. The centre one shows T2 coupling VI (right) to V2 (left), while the right- and left -hand pictures show the same compartment from different angles. earth return circuits for the anode photographs the sound -channel The other coils are mounted by and grid circuits of adjacent coils, the rejector and one vision - a Paxolin plate which has two valves. This helps considerably channel coil are mounted in the holes tapped 4 B.A. for fixing in obtaining stability at high fre- usual way by a 6 B.A. screw screws and a hole fitting tightly quencies. through the chassis into a short on the outside of the coil former. Drawings of the coil details are metal rod passing through holes The former is pushed into this given. They are wound on a } -in in the side of the former. hole and flooded with shellac. outside diameter ,din wall Paxo- Li lin tube and fitted with o B.A. L z brass slugs for tuning. An in- i ,üüüunupu umüüi'11 II ,¡¡¡¡¡¡¡¡¡¡ ternal " thread " is provided by Ij 3I8 I\' IbIIÌÌIIÌÍÍIIIIIIIIIÍÍÍIIIIIIU III+ the simple expedient of cutting l; II lil away two segments of the wall of , the tube and winding this with thick thread ; this should be done with the slug in place. 4" Thin wire is used for all the vision -channel coils, since losses are unimportant as the circuits must be heavily damped to L5 & obtain 41' LS L4 the bandwidth. The effect of coil losses is, therefore only to modify the damping resistors needed. This does not apply to circuits operative on the sound channel, either in the sound amplifier or as rejectors. Heavier wire is used here, but in spite of the higher losses as compared with copper, brass slugs are retained in the in- terests of uniformity. Copper slugs are better in theory, but the difference is not enormous and o B.A. copper rod is not easy to obtain. Two forms of coil mounting are Details of the detector filter and the various correction coils are given used. As can be seen from the here.

www.americanradiohistory.com October, 1947 394 Wireless World

'Television Receiver Construction- COIL WINDING DATA Winding details of all coils, in- Note. In all multi-winding assemblies, all windings are in the same direction, cluding the V.F. correction coils, anode windings with one turn of shellacked Table. They are and grid windings are overwound on are given in the paper between for insulation ; adjacent ends are grid and anode on the one not difficult to make, but are hand and earth and +H.T. on the other. somewhat tedious because there are rather a lot of them. Com- Wire Winding Winding Resonant The R.F. coil formers are nearly ponent (S.W.G.) 1 -2 3-4 Freq'cy Remarks all alike, and the labour is re- (turns) (turns) (Mc /s.) duced by carrying out similar T1 36 D.S.C. 21¿ 15 43 Winding 1 -2 is interwound operations on all coils in turn with 3-4 at earthy end with- rather than completing each one out interwinding insulation. The T2 36 D.S.C. 11 11 43 individually. best procedure T3 36 D.S.C. 10 10 41.5 Sound coupling coil of 1 turn is to cut all the formers to length, inserted in wiring ; to be remove burrs from the ends, mark disconnected while adjusting off the positions of the slots for T3. T4 36 D.S.C. 9 9 47 Winding 3-4 is tapped for connection (5) at 1 turn from (4). T5 36 D.S.C. 13 13 46 Ts 26 D.S.C. 12 41.5 T7 (a) 26 D.S.C. 13 41.5 T7 (b) 26 D.S.C. 12 41.5 T8 26 D.S.C. 10 41.5 Lr, L2 36 enam 84 L3 38 enam 108 L4 38 enam 90 L5 40 enam 112 copper wire, about No. zo gauge. be put into the former and then In most cases the tags are in pairs thick thread should be wound into opposite one another. The two its thread, through the slots cut tags of a pair should be placed in the walls of the former, and in their grooves and held in place tied tightly. This will be found by a tight binding of thin thread. to provide quite a good screw The whole former should then be thread and is sufficiently robust given a coating of shellac var- for the purpose. Unless the ends nish. of the slugs are tapered slightly When dry, the slugs should be and smoothed, it is not recom- fitted. These are lin lengths of mended that a slug be removed o B.A. brass rod with a saw -cut completely after it is fitted. The across one end. The slug should (Continued on page 395)

EF EL 33 EL 38

G} o o AO o This close -up of T3 clearly shows the coupling loop to the sound H° O °H channel. It is formed in the 0 o wiring. M C

GI= TOP CAP the thread holding the slugs, and A = TOP CAP 1 then cut the slots with a minia- ture hacksaw. If the former is then slipped on a piece of din EF 50 MW22-7 brass rod, the segments are easily A - ANODE

removed with a sharp, narrow- G GRID chisel. bladed C m CATHODE A few formers have holes for fixing bars, and these can now be H - HEATER drilled. The solder tags should S INTERNAL SHIELD be attached next. A small V- M - METALLIZING groove should be put in the for- OR INTERNAL SHIELD mer where each tag is wanted A2 -SIDE CAP with a small triangular file. The For convenience the base connections of the valves used are given here, tags are short lengths of tinned in all cases looking at the underside of the valveholder.

www.americanradiohistory.com October, 1947 Wireless World Advertisements 41

Moth inside and outside the radio business, the name

Philips is synonymous with Dependability. And, throughout

the changing years, no reputation has been - or ever will

be - more jealously guarded.

The latest radio receivers, radiograms and television

receivers, to be seen and heard on Stand No. 16 at

Radiolympia, are outstanding examples of Philips

craftsmanship - worthy of the name they bear.

PHILIPS 2.4e- ..g-.0erzeZe/4 MezeZá and itóton

PHILIPS ELECTRICAL LTD., CENTURY HOUSE, SHAFTESBURY AVENUE. LONDON, W.C.2 R9ooD

www.americanradiohistory.com 42 Advertisements Wireless World October, 1949 '

Indoor Suspension Loud- speaker -Type LS /T/ IOC. Fitted with two 8" units and covers a wide area. ers...

IS" Single Cone Loud- speaker -Type LS /30C. 12" Single Cone Loud- Totally enclosed. speaker -Type LS /10 /C. For wall mounting. OPEN BOTH SIDES and suitable for centre hang- Single Unit Loudspeaker - ing in Hall or Workshop. Type LS /SC. Ideal for medium power Public Address. Dual Unit Loudspeaker - TypeLS /HF /IOC. A medium capacity general purpose speaker 'or wall mounting. Sp eakers or o f Cabinet range a particular ide er output-eachtor

otters d1eba)a being d STAND 17 NO r,gt large OY SOU Dual Unit Loudspeaker - 'lust hall S PN Type LS /HF /5C. Designed for tloo óca dance RADIOLYMPIA mounting on wall or across a ,i small corner. combination speech, éoCCas,ob °. pos or rg ° P m OCT. 1 -11 For s ts C h aPhes\ways private et fi 'TAN is the Equipment Registered Trade Mark of Equipment manufac- tured by

GUY R. FOUNTAIN, LTD. The Largest organisa- tion in Great Britain specialising SOLELY in Sound Equipment.

www.americanradiohistory.com October, 1947 Wireless World 395 Television Receiver Construction - reinsertion of a slug with any roughness on the end is likely to RC 2o cut the thread. a V OUTPUT Winding is easy. The turns are -4 COPPER OR given in the Table, and they are BRASS SCREEN spaced by eye so that the full coil fills the winding space available, starting and finishing about one R19 turn spacing from the tags. After putting on one winding, the coil ,CZi is given a light coating of shellac, and when it is in the tacky stage one turn of thin, previously shel- R 20 lacked, paper is put over it. This forms the interwinding insulation R21 and is held firmly in place by the outer winding which is the same Rz4 as the inner in most cases. A BRACKET FOR second light coat of shellac com- VALVE HO LDER pletes the coil. CI7 OF V8 In T, the feeder -coupling coil needs no special insulation, and is interwound with the grid coil at its earthy end. The end of the *turn coil is held down by tying it with thread. On the outer winding of T, there is a tapping one turn from the earthy end of the outer winding. This is not The V.F. side of the set is shown here. A vertical screen separates the terminated on the former but is detector chokes Lr, L2, L3 from the output V.F. components. run straight to Ts. In all cases the inner winding the connection around the coil. tances. Anything but minor is the anode one and the outer the It must be emphasized that as variations in wiring, or the use of grid one. It should be noted that the valve and other stray capaci- valveholders of widely different the coupling coil in series with T, tances are relied upon entirely for pattern will alter the capaci- is a single turn over the middle of tuning, the inductances needed in tances and so the inductances Ts done in the wiring by looping the coils depend on these capaci- required. The slug adjustments are provided mainly to correct for unavoidable changes of this kind, but the range of adjustment ob- tainable in this way is not very large. It is possible, therefore, that in a few cases some adjustment to the turns may be needed. It is unlikely that lower capacitances will be obtained, so that such ad- justment is unlikely to be more than the removal of one turn. It will be necessary only if it is found that a circuit will not tune to a high enough frequency with the slug fully in. A signal generator or calibrated test oscillator is needed for align- ment. The cathode -ray tube can be used as an output meter, even with an unmodulated oscillator, for with the D.C. couplings used the brightness depends on the D.C. output of the detector. The Brightness Control should be kept so adjusted that the brilliance is low and the signal -generator out- put kept at a suitable level. signal generator should A general view of the underside of the sound and vision channels. The

www.americanradiohistory.com 396 Wireless World October, 1947

Television Receiver Construction - Te, and adjust T, for maximum An interesting point mentioned have its output cable terminated output at 41.5 Mc /s. Reconnect by Mr. Bishop was the provision in the proper resistance to suit it the coupling coil and adjust TB of perforated desk tops in talks and the signal from it applied be- for minimum output at 41.5 studios to avoid sound reflections tween the grid of V, and chassis. Mc/s. into the microphone when Ts is then tuned for maximum Then go to the grid of V, and speakers drop their heads. output with an input of 46 Mc /s. adjust T2 for maximum output at On the matter of recorded pro- Then connect the signal genera- 43 Mc /s, and finally connect to grammes Mr. Bishop said they tor between the grid of V. and the aerial socket and adjust T, sometimes had difficulties in chassis, and tune T, for maximum for maximum output. at 43 Mc /s. bringing artistes to the microphone output at 47 Mc /s. Then adjust Leaving the signal generator con- when they were wanted. Pro- T8 for minimum output at 41.5 nected, adjust T, (a) and (b) for grammes were recorded only when Mc /s ; this trimmer should be maximum output from the sound it was impossible to achieve a live critical. Readjust T. at 47 Mc /s channel with an input at 41.5 broadcast ; improvements in the and then T. at 41.5 Mc /s. Mc /s. A pair of phones can be quality of recording and reproduc- Transfer the signal generator to connected from the sound output tion were constantly being made the grid of V2'and chassis; discon- tag or an A.F. amplifier and loud- and they had gone to considerable nect the coupling coil on T. from speaker can be used. expense to design and construct entirely new equipment, which was now in use. Mr. Bishop gave his assurance Quality of B.B.C. Transmissions that a feeling of healthy discon- tent could be said to animate his Chief Engineer Interviewed department. The economic situa- tion of the country imposed By H. A. HARTLEY severe restrictions on what they were READERS will recall my rection is introduced into the A.F. trying to do. In reply to a specific criticisms of the quality of chain, but this is seldom a cure for question, Mr. Bishop denied that they restricted B.B.C. transmissions and acoustic problems : if the auditor- the band -width of the reply of the Corporation's ium itself kills the extreme top, their transmissions because of in- Chief Engineer in Wireless World then no amount of tone correction ternational repercussions on the of January -March last. Mr. can put it back. Certain of the problem of interference. Bishop has since been good smaller studios at Broadcasting enough to give me a detailed House, reconstructed since the account of the Corporation's engi- war, give excellent results. MANUFACTURERS' neering approach to the problems. Throughout the war period there LITERATURE Readers will be glad to know that was practically no acoustical re- ILLUSTRATED brochures (for manu- Mr. Bishop and his colleagues are search, and owing to the extreme 1 facturers only) have been received far from satisfied with what they difficulty of getting either build- from The Plessey Co., Ilford, Essex, have already achieved and are ing materials and deal with the following: Electra or labour for re- lytics, Chokes and Transformers, continually striving to do better, building it will take a long time to Drives and Couplings, Miscellaneous although in fairness it should be bring all the studios acoustically Components. pointed out that he does not up to date. Nevertheless, Mr. think that conditions are as bad Bishop Bulletin B528D from Muirhead and puts improvement of Co., Eimers End, Beckenham, Kent, as I made out. studios near the top of his list of describes the Muirhead -Wigan Decade High-fidelity enthusiasts have priorities. Oscillator with a frequency range of strongest grounds for complaint On outside broadcasts and S.B.s rcis to over loo kc/s. in the transmission of orchestral a limiting factor is Post Office " Sobell Television Dealer's Manual " programmes, and Mr. Bishop is lines. The line from B.H. to -including typical questions asked by fully aware of the shortcomings Brookman's Park is the public and some model answers. A flat to few there. The principal difficulty is r5,000 c copies are available to other dealers /s, and many of the im- on application to Sobell Industries, the present lack of suitable studios portant trunk routes are flat up Langley Park, nr. Slough, Bucks. for large orchestras and with good to 8,000c /s, but on other routes acoustical properties. The main it is not always possible to achieve Catalogue of " Ashton Radio Cables," orchestral concerts in London this including all types of screened leads for figure. pickups, microphones, car radio, etc., originate in the Maida Vale studio, Distortion has sometimes been from Aerialite, Ltd., Castle Works, the People's Palace and the allowed to creep in in control and Stalybridge, Cheshire. Albert Hall. The loss of the monitoring, but the B.B.C. en- List of ex- Government electronic and Queen's Hall was a grave blow to gineering operating staff, greatly radio equipment from Clydesdale musical London. The acoustical expanded during the war, is fully Supply Co., 2, Bridge, Street, Glasgow, performance of the Maida Vale alive to these dangers. In war- C.5. studio could undoubtedly be im- time it was impossible to give ade- Brochure " From Wet to Dry " proved by structural alterations, quate training to new staff, but describing Varley dry accumulators. and both the People's Palace and this is now being done in the En- Instructions for care and charging of the Albert Hall were technically gineering Training Dept. under the batteries are given. From Varley " difficult." In certain cases cor- Dr. Dry Accumulators, Ltd., By -pass Sturley. Road, Barking, Essex.

www.americanradiohistory.com October, 1947 Wireless World 397 WOULD OF WII {ELESS Exhibition Plans . Radio Facilities Extended + International Organizations

RADIOLYMPIA exclusive use of the Press for two - FINAL arrangements for the first way radio communication prompted post -war National Radio Ex- the question " Is the P.M.G. lending hibition, which opens at Olympia a more sympathetic ear to applica- on October ist (preview September tions for new licences? " It is 3oth), have now been made. learned from the G.P.O. that fre- We give below a few of the de- quencies over 67 Mc /s will be tails regarding special sections. issued to certain specified classes of Conventions. - The convention applicant where it is known that the hall situated in the National Hall ordinary line telephone cannot gallery is being used during the possibly give the required service. RNNERSß afternoon session -3 to 5 -on Octo- As has already been mentioned in ó ber znd, 6th and 7th for conven- previous issues tugs and railways tions organized by have been allocated power the Radio Whole- frequencies. greater salers' Federation, Radio & Tele- Other classes of undertaking to A mr `' expected Gives considerablycons usually Con- vision Retailers' Association and which permission may be granted than uipme °A eQ as our Television are : C.P.C. Society, respectively. - electricity undertakings, from sa me and fitted oe the It is available for exhibitors' road vehicles of public utility, hired structed model carrying meetings at other cars and taxi att A.C. pgeel times. services, port controlgram°Phone Television Avenue. -Some twenty authorities, professional cars and for with latest and manufacturers are exhibiting over communication between works and controls, ngec$al £1-position thirty receivers in the specially con- sites in constructional under- amp and change- pilot either gramo-ramo- structed television avenue which is takings. switch providingcircuit for fed with the B.B.C. programme at What is believed to be the first over microphone. T four R.F. from a central pre -amplifier. taxi service to employ a radio- and In phone high-gain shPUII This 25o -foot long avenue is situ- communication system in this vt parallelarallel o 10 v aloes. valves in total of ated at the Addison Road end of the country was recently licenced in valves a loW impe- Grand Hall gallery. Cambridge. for ercircuits. Films.- Throughout the The maximum power ape andan other exhibi- of the cen- dance of this Full details request. tion there will be six sessions daily tral station in the Press scheme will sent on models in the cinema located in the Grand be 15o watts, the mobile stations 25 SEE US AT Hall gallery. The hour -long exhibi- watts and the pack sets one watt. tions begin at 11.3o, 2, 3.3o, 5, The maximum range of all stations RADIOLYMPIA STÑQD 6.3o and 8. The main films. being licensed by the G.P.O. for such 20 shown and the concerns exhibiting schemes is at present limited to 15 them are: - miles. " The Decca System of Naviga- Er I.B.U. AND tion " (Decca). " Electronics " I.B.O. and " Electronics in Industry " THE merits and demerits of these (B.T -H.). " They're Called Elec- two organizations caused a trons " (Ediswan). " North Sea clash at an early meeting of the Work of Coast Stations " (G.P.O.).- Atlantic City Conference when the " Radar Record " and " Radar International Broadcasting Union Goes to Sea " (Metrovick). " R.D.F. applied for admission to the meet- to Radar" (Ministry of Supply). ings. The application met with Admission to the shows is free strong opposition from delegates but tickets must be obtained from from the countries belonging to the the exhibitors. International Broadcasting Orga- Electrons at Work and Play. nization formed just over a year This " novelties " section includes- ago. demonstrations of radar, infra -red, The main reasons given for the radio control of a model train and exclusion of the Union were: transmission of sound on light. r. It is a deceased organization ; The section is located at one end of 2. It includes Franco Spain the National Hall gallery. At the (which is not represented at the opposite end is a promenade from conference) among its members ; which visitors can see the produc- 3. It should give way to the tion of programmes in the B.B.C. I.B.O. whose aims are identical and television studio. which has a greater number of mem- bers ; EXTENDING RADIO 4. It suffered Axis influence dur- FACILITIES ing the war and permitted the Con- THE TRIX ELECTRICAL CO, LTD. THE recent announcement that trol Office to pass to German 1-5 MAPLE iE ACE TOTTEMRAM COURT ROAD IOMDON, WI the Postmaster -General had Administrators. ïf.'fPdOdf:MUSEUM 507 CRAMS E(JR(ff: MEMO. WE5D0.l11NUUN. allocated seven frequencies, for the Sir Stanley Angwin, head of the

www.americanradiohistory.com October, 1947 398 Wireless World at regular World of Wireless - dard S.B.A.C. aircraft racking, porting from set positions British delegation supported the re- were shown by Marconi and by intervals and giving observations on commendation from the Executive Standard Telephones while G.E.C. the upper atmosphere by the use of Sub -Committee that the Union had a lightweight V.H.F. radio radiosondes every six hours. should be admitted as an observer. telephone designed especially for The ships' radio equipment is This was ultimately adopted by installing in privately owned civil operated by a Chief Radio Officer, twenty -four votes to twenty with aircraft. It is hoped to describe the six radio Petty Officers and two seventeen abstensions. outstanding exhibits in greater radar Petty Officers, who, like the Britain is not a member of either detail in our next issue. remainder of the crew of fifty, have been selected from the R.A.F. and organization and in giving support SHIPS to the recommendation Sir Stanley WEATHER Merchant Navy. stated that while he " deplored the IN compliance with an inter- The radio gear includes beacons, national agreement signed in D.F. sets, radar apparatus for fol- existence of two separate broadcast- bal- ing organizations in Europe he alsó London last year eight nations are lowing the flight of radiosonde is an obvious attempt to establish and operate weather loons to a height of 40,000 feet, and deplored what the five to suppress one of them (the reporting ships at thirteen stations Loran. In addition to Great Britain main transmitters there are four life- U.I.R.). . . ..Until a single unified in the North Atlantic. broadcasting organization can be is manning two stations and has for boat transmitters and the equipment part of the purpose converted four corvettes carried by the balloons. These set up in Europe, forming audio a larger world organization, and into floating meteorological obser- transmit C.W. modulated at stations. Each ship will be frequency (700 -1,000 c /s). The conforming to I.T.U. accepted rules vation sets of membership and voting, the at sea 27 days and will be relieved inductance in each of the three U.I.R. should be allowed to con- by a sister ship before proceeding (one each for pressure, temperature tinue to exist." to her base at Greenock. and relative humidity) is varied byl In addition to their primary task a mumetal armature the position of AIR RADIO of undertaking meteorological obser- which with respect to the coil is con- OUTSTANDING among the radio vations the ships will also provide trolled by the meteorological ele- equipment displayed at the radio navigational aids for trans- ment (pressure, aneroid capsule; recent exhibition of the Society of atlantic aircraft and air -sea rescue temperature, bi -metal coil, humid -' British Aircraft Constructors at facilities, for which purpose they ity, gold- beater's skin). daffodil Radlett, Herts, were two radio com- are painted the well -known AIRCRAFT RADIO passes, one by Marconi's W.T. Com- yellow. a G.E.C. -Salford The reports provided by the ships OPERATORS pany and the other of design. They work on the M.F. will supplement those of meteoro- AMORE advanced knowledge and L.F. bands. logical reconnaissance aircraft and radio, higher operating speeds The present tendency is for merchant shipping. Their main and a higher pass standard gener- are that they will be re- ally will, in future, be required of ordinary aircraft routine communi- advantages for cations-as opposed to direction those sitting the examination the Civil Aircraft Radio Operators' finding -to be carried out on en- and tirely separate equipment built combined radiotelegraphy form. Separate re- radiotelephony licence. largely in unit will ceivers and transmitters, all fully The proposed changes, which miniaturized and fitting the stan- probably be introduced at the be- ginning of next year, raise the oper- ating speeds as follows : - (1) minute (375 characters in 3 mi utes) (2) Code; 20 groups per minute (60 groups of five letters in 3 minutes). (3) minute groups of2ffiverfigurepern minutes). These changes have been made in accordance with the proposed re -, vised Air Navigation (Radio) Regu- lations.

PERSONALITIES Sir Edward Appleton received the honorary degree of Doctor of Laws of RADIOSONDE St. Andrews University, Dundee, equipment (above), during the recent meeting of the with Bakelite cover British Association for the Advance- removed, as carried ment of Science at which he was a aloft by 6 -foot dia- speaker. meter balloons. On W. E. Benham, B.Sc., F.Inst.P., the left is the ap- who was until recently with P.R.T. paratus for receiv- Laboratories (now Airmec Labora- ing the automatic tories), has been appointed to the transmissions from board of Gamma Electronics, Ltd. the balloon on 27.5 D. C. Birkinshaw, B.B.C. television Mc /s. Both superintendent engineer at Alexandra -28 Palace, has, we regret to record, an visual and aural attack of infantile paralysis. Although means of checking a comparatively mild attack, it will the received A.F necessitate him being away for some signal are provided months.

www.americanradiohistory.com October, 1947 %Vireless World 399

Harold Bishop, C.B.E., B.Sc. (Eng.), WHAT THEY SAY 1802 B.B.C. chief engineer, was recently In the interests elected a Fellow of the City and Guilds Useful but Fallible. -" Electronic de- of better of London Institute (F.C.G.I.). vices will be accepted by the British qualify... R. C. Hiscock has resigned his shipmaster merely as useful, though position as general sales manager of fallible, aids, and never in substitution Birmingham Sound Reproducers to for the traditional methods and prin- take up an appointrrfent with the ciples of good seamanship." -From the Plessey Co. He has been succeeded by Report of the Officers' (Merchant Norman Miers Navy) Federation. The lABYRiNTH International Short Waves. -" Of the total of 300,000,000 people throughout the world who daily listen to some form of broadcasting, less than three IOHD SPEAKER per cent hear any form of direct short- wave broadcasting. " -B r i g a d i e r (TYPE S. L. 15) General Stoner, Chief Communications Engineer, United Nations, speaking at for Music U.N.E.S.C.O. international radio net- ... Societies -Schools work conference in Paris. ' Theatres Quality P.A. and Radio -meteorology.-" The most - - striking manifestations of these effects (the bending of radio waves round the all music lovers curvature of the earth) were noticed during the war, when it was found A partitioned cabinet to form a folded that, under certain fine -weather con- pipe -the back of the unit coupled to ditions, it was possible for a coastal radar station to receive echoes from a it in such a way that the quarter and ship which had passed well beyond the half wave resonances are under in- horizon. . . . The need to correlate dependent ' Q ' control RT. HON. OLIVER LYTTELTON radio phenomena with meteorological - cabinet conditions has prompted the radio - acoustic resonances arranged to the new president of the Radio physicist and Industry Council the meteorologist to join in succession to forces in attacking the problems of cancel pipe anti -resonances. The result Alfred Clark. He was President of what is practically a new subject, is a smooth bass response down to the Board of Trade and Minister of radio -meteorology." -Sir Edward Production during the war. Appleton in his address as president 35 c.p.s. of the Mathematics and Physics Sec- tion of the British Association meeting A number of radio personalities were in Dundee. among those recently decorated by U.S.A. with the American Medal of Freedom. Among them were :- IN BRIEF Sir Frank Smith, who was during the war controller of telecommunica- Licence Figures. -Of the 10,883,500 tions equipment, Ministry of Supply, broadcast receiving licences in force in and chairman of the Ministry's Great Britain and Northern Ireland at scientific advisory council. He received the end of July, 21,zoo were for tele- the Medal with Silver Palm, vision receivers. Dr. R. L. Smith -Rose, superin- Ferry Radar. -It is proposed by the tendent, Radio Division, N.P.L., re- Wallasey Corporation Ferries to install ceived the Medal with Silver Palm for radar gear for the guidance of vessels his work on radio propagation. when close to the landing stages. Dr. H. G. Booker, who was head No Outside Aerials.-Tenants of new of the mathematics section of T.R.E., council houses at Saffron Walden, received the Medal with Bronze Palm Essex, will not be permitted to erect for his work on micro -wave radar. outside aerials. The housing commit- tee reported that outside aerials are Dr. H. G. Hopkins, radio -physicist, not needed for new sets. In view of received the Medal with Bronze Palm protests by one councillor it has been for his contributions in the field of decided to consider applications from radio direction finding. householders with old sets and from Dr. E. T. Paris, principal director short-wave enthusiasts. of scientific research (defence) in the Unlicensed Transmitter. -At the Ministry of Supply, received the Medal Wirral Justices Court on August 28th, with Bronze Palm for his work on the Reginald C. J. Maude, of West Kirby development of radar communications Cheshire, was fined L10 for operating and other electronic equipment for the an unlicensed transmitter. The postal MEET US AT Army. authorities stated that transmissions W. Ross, M.A., who is principal were on 16o and zoo metres. scientific officer on radio navigational Consol Tables have been prepared by RADIOLYMPIA aids (Ministry of Transport), received the Ministry of Civil Aviation so that STAND NO. 147 GRAND HALL ANNEXE the Medal with Bronze Palm for his bearings may be plotted from the services in the field of radio and radar, stations at Bushmills and Stavanger especially when serving as liaison when the specially prepared charts are officer in the U.S.A. not available. J. M. C. Scott, secretary of the Electron Jubilee. -The special ex- EICVLJSTIGAL Ministry of Supply U.S.W. Propaga- hibition arranged at the Science tion Panel, received the Medal with Museum, South Kensington, London, ACOUSTICAL MANUFACTURING CO., LTD., his Bronze Palm for work on radio S.W.7, to mark the jubilee of the dis- HUNTINGDON Telephone: HUNTINGDON 361 propagation. covery of the electron by J. J. Thom-

www.americanradiohistory.com October, 1947 460 Wireless World

World of Wireless Grimsby.-The Grimsby Amateur - Radio Society has now moved to new son, will be opened on September 27th. REVIEW OF THE premises at 115, Garden Street, Industrial organizations and the uni- Grimsby, where meetings are held versities have helped in providing the SHOW every Thursday at 7.45. The club's exhibition, which is designed to show transmitter, a T1131, will soon be the principles underlying the applica- A DETAILED REVIEW of operating. Sec. : R. F. Borrill, G3TZ, tions of the many devices in which the technical progress and tendencies 115, Garden Street, Grimsby, Lines. A electron plays an essential part. as revealed at Olympia will be of the handbook on the exhibition is obtain- Liverpool.- Weekly meetings Museum or by post from included in our November issue Liverpool and District Short -Wave able at the Club are held on Tuesdays at 7.3o at i the Institute of Physics, 47, Belgrave is zd. St. Barnabas Hall, Penny Lane, Liver- Square, London, S.W.r, price pool. On Monday evenings practice Worked His Passage. -When the telegraphy 43 (total 796), radio com- morse is transmitted on 3,562 kc /s from wireless operator on the Union Castle munication 13g (3,97o), and technical 7.o to 7.30, call G3BHT. The club's liner Roslin Castle had to be left at electricity 6o (6,522). The number of own transmitter (G3AHD) will soon be service work Freetown, Sierra Leone, because of ill- candidates for the radio operating on 3.5 Mc /s. Sec. : B. G. ness, a Cable and Wireless operator examination increased by 33 to 289. Meaden, G3BHT, ro, Alfriston Road, from Ascension Island who was delayed West Derby, Liverpool, 12, Lancs. in Freetown on his way home took on INDUSTRIAL NEWS Slough. -The local group of the the operator's job and the vessel was R.S.G.B, recently staged a show of able to proceed. T.C.C. A new factory- Whiteside amateur equipment during the town's Out of Date. -A number of Maxi- Works-at Bathgate, Linlithgow, Scot- Holidays -at -Home carnival and secured mum Price Orders have been revoked land, recently started production of several prizes in the model engineer- of with the pub- T.C.C. condensers. When in full pro- ing competition. A transmitter was by the Board Trade r,000 people. lication of the Miscellaneous Maximum duction it will employ operated on 7 Mc /s throughout the ex- Price Orders (Revocation) Order, 1947 Ultra. -The London County Council hibition. (S.R. and O. 1947, No. 1749), as they is purchasing £33.550 worth of school Stourbridge.- Meetings of the Stour- no longer serve any useful purpose. radio equipment from Ultra Electric. bridge and District Amateur Radio The revoked Orders are :- Gamma Electronics, Ltd. -The offices Society are held on the first Tuesday Radio Valves (Maximum Prices) and works of this company, which has of each month at King Edward School, Order, 1942 (S.R. and O. 1942, No. been reorganized, have been trans- Stourbridge, at 8.o. Sec.: W. A. Higgins, G8GF, Street, 1934), controlling prices of valves im- ferred from Greenford, Middlesex, to 35, John ported under lend -lease; Burwood Road, Hersham, Walton -on- Brierley Hill, Staffs. High Tension Dry Batteries (Maxi- Thames, Surrey. (Tel.: Walton -on- Worthing. -Although full member- mum Prices) Order, 5942 (S.R. and Thames 4483). ship of the Worthing and District O. 1942, No. 2512), controlling prices Page Engineering Co., Ltd., has Group of the R.S.G.B. is for members of 120 -volt lend -lease batteries; moved from 119, Maple Road, Sur - of the Society, visitors are welcomed Imported Wireless Receiving Sets biton, Surrey, to Franklin Road, to the monthly meetings. The next (Maximum Prices) Order, 1944 (S.R. Portslade -by -Sea, Sussex. (Tel.: Port - meeting will be held on October 2nd and O. 1944, No. zoo), controlling slade 7253). at Oliver's Café, Southfarm Road, prices of American receivers. Worthing. Sec.: G. W. Morton, 42, Diamonds. -A monthly abstract of Southfarm Road, Worthing, Sussex. I.E.E. Meetings. -As in the past few articles on the properties and industrial years, admission of non -members of the applications of diamonds is obtainable Institution to its meetings will again free from the Industrial Diamond In- MEETING S be permitted. Those " interested in the formation Bureau, St. Andrew's House, proceedings, but who may be unable 32 -34, Holborn Viaduct, London, E.C.r. Institution of Electrical Engineers to claim admission to any of the A Montreal firm of radio representa- Ordinary Meeting. -Presidential ad- classes of membership " may therefore tives offer to act for European manu- dress by P. Good, C.B.E., on October receive an admission card to meetings facturers wishing to export to Canada. 9th. on completing the application form Letters sent to this office will be Radio Section.- Chairman's address (obtainable from the secretary) and on forwarded. by C. E. Strong, O.B.E., B.A.I., on payment of Li for the session. October 15th. Broadcasting Stations. -The third re- CLUBS Discussion on standardization in the vised edition of our booklet " Guide electrical industry to be opened by the to Broadcasting Stations " is now avail- Birkenhead.-Seventy -four members president on October 27th. The above meetings will be held at ' able. In addition to the geographical have been enrolled during the past and frequency lists of world short-wave year by the Wirral Amateur Radio 5.30 at the I.E.E., Savoy Place, stations and European medium- and Society which meets twice a month in London, W.C.z. long -wave transmitters this edition in- the Y.M.C.A., Whetstone Lane, Birken- London Students' Section. -" The In- clude` other useful information for the head. The annual general meeting will fluence of Propagation on the Uses of broadcast listener. The 1,40o entries be held on October 8th at 7.30. Sec.: Radio Waves," by E. M. Hickin, chair- have again been checked against the B. O'Brien, G2AMV, 26, Coombe Road, man, on October 20th at 7.o at the frequency measurements made at the Irby, Heswall, Cheshire. I.E.E. B.B.C. Tatsfield Receiving Station. Cambridge Radio Group, -" Further Copies are obtainable from booksellers Birmingham. -The last of this Education for the Engineer," by R. W. or direct from our Publisher, price is season's D.F. tests organized by Slade Wilson, B.Sc. (Eng.), chairman, on (postage id). Radio will be held on September z8th. October 21st at 6.o at the Cambridge- The Club's fortnightly meetings are shire Technical College. Anti -Interference.-The Canadian held on alternate Fridays at 8.o in the North -Eastern Radio and Measure- Government has prohibited the use of Parochial Hall, Broomfield Road, ments Group.- Address by V. Z. de unscreened diathermy apparatus after Erdington. The next meeting is on Ferranti, M.C., on October 20th at 6.15 January 1st. All new equipment must October 3rd. Sec.: C. N. Smart, fro, at King's College, Newcastle. be frequency stabilized and include Woolmore Road, Erdington, Birming- North -Western Radio Group.-" New harmonic suppression. ham, 23, Warwick. Possibilities in Speech Transmission," City and Guilds Exams.-Although Farnborough. -Details of the pro- by D. Gabor, D.Ing., on October 22nd last year there was an overall decrease gramme arranged by the R.A.E. and at 6.30 at the Engineers' Club, Albert 92 in the total number of examinees Farnborough District Amateur Radio Square, Manchester. of Midland Radio Group. Prac- (14,941) in the five subjects comprising Society, which meets on alternate South -" the telecommunications group, there Mondays in the R.A.E. Assembly Hall, tical Waveguides," by L. G. H. Hux- was an increase of 98 in telephony Farnborough, at 7.30, are obtainable ley, Ph.D., on October 27th at 7.o at (total 2426) and 52 in transmission and from the Sec.: P. R. Burkitt, Park the James Watt Memorial Institute, lines (1227). The decreases were: View, Priory Street, Farnborough. Birmingham.

www.americanradiohistory.com October, 19 4.7 Wireless World 401

LETTERS TO THE EDITORR 1991 More Views on Loudspeaker Damping These MR. LANGFORD -SMITH has E Hlis Z° = o raised a very interesting point in - - Hl r Hl his letter on the damping of moving - Re- arranging, coil Cases speakers. It seems that a more E I comprehensive picture of the effect u of source impedance on the frequency -Hl. +ZM(Zo-f-r) Electric Fire response as well as on the transient )1sa response is It may now be seen that the term required. A case which merely houses its contents The Zm(Z° I moving coil is a generator of r) should be made as small mechanical energy, to which the HYIa is doing only half a ¡ob. We specialise mechanical " Ohm's Law " can be as possible, as it is desirable that u in building cases that do a selling applied. It is presented with a should be independent of Z. It job as well. complex mechanical load, which can appears that the effect of the driving be divided into two parts. circuit impedance is to introduce (I) A number of reactances, each into the driving circuit a voltage in with a resistive component to series with the back E.M.F. of the represent losses. The various sus- coil dependent on the cone impedance, pension stiffnesses will appear as capa- which prevents the back E.M.F., Make citive reactance, and the cone and being equal to the driving voltage E. coil masses as inductive reactance. As only the sum of Z° and r appears This part will have large and rapid in the equation, it would seem to be of variations with frequency, and will little value to reduce Zo much below become very small at the principal r. It may also be seen that the Radio Cabinet resonance points. For example, at stronger the field the better the the bass resonance, the total cone linearity of response. We can develop and style an individual mass will resonate with the sus- The approach to the problem is to modern case, exclusive to you, or work pension stiffnesses in series. minimize variations in Zm by in- to rigid specifications, or supply standard (2) The radiation resistance of the creasing the radiation resistance cone. By definition, the power and /or decreasing the cone reactances. cases from stock. radiated will be Rua where u is the The bass resonance is being dealt velocity of the coil. R varies only with in this way in several modern slowly with frequency in a well - speakers by using acoustical reson- designed speaker. Thus to obtain a ance to increase the radiation resis- smooth frequency response u should tance at low frequencies. This is be made independent of frequency. also why the exponential horn type The sum of (I) and (2) is the total speaker is still supreme for quality loading on the coil, which varies reproduction. greatly with frequency. Thus for u J. H. D. WALTON. to be independent of frequency it Swindon. should be independent of the load Amplifier Case into which the coil works. THE correspondence on loud- Turning now to the electrical side, speaker damping which has an equation can be derived connect- We use only materials of the finest arisen as a result of Mr. F. Langford- quality. And we guarantee to deliver ing the coil velocity with the driving Smith's comments on my remarks E.M.F. (E). in the April issue is very interesting, every order on time. Send today for Force on coil = HII.. .. (I) in that it demonstrates the con- free booklet. Mechanical load (Zm) = Hit fusion which may be caused by an . (2) over -simplification of the equivalent u circuits and electrical analogues of Back E.M.F. in coil = - Hlu electro- mechanical apparatus, and Where H = field strength in gap, by the use of a term -in this case l = length of wire in field, I = " Damping Factor " -which is not current through coil, u = velocity a clear description of the effect to of coil. which it refers. The equivalent circuit of the ideal INSTRUMENT CASES loudspeaker postulated by Mr. Langford-Smith is a resistance whose dissipation is equal to the o energy radiated. Such a system re- quires no damping as there is no RADIOLYMPIA possibility of energy storage. A prac- OCTOBER Ist - OCTOBER Ilth E© -Hlu tical loudspeaker, however, has an SEE US AT equivalent circuit which may con- STAND 62, GRAND HALL sist of a network as shown in Fig I Let the coil resistance be r and The symbols R and L represent have internal impedance the source the physical resistance and induct- Ltd., Z°, then applying Kirchhoff's law to ance of the speech coil winding. ALFRED IMHOF, the driving circuit, and substituting The speech coil performs the dual I 12, New Oxford Street, London, W.C. I. for I from (2), function of a motor (shown as M) Museum 5944.

www.americanradiohistory.com 402 Wireless World October, 1947

Loudspeaker Damping - amplifier to negligible proportions. Loa:, c /s, it was not thought desir- The relationship between the able to attempt control above this coupled to a generator (itself) shown may as G. coupling relative amounts of electrical and frequency, and the upper range in the diagram The be with a of this motor -generator is loaded by mechanical damping in any particu- dealt by separate radiator. a complex mechanical resonant sys- lar loudspeaker must surely deter- tem (the diaphragm and suspension) mine the effect of a given percentage which has the properties of inertia change in the amount of electrical damping. This must vary consider- R (rn), compliance (Cm) and mechani- cal resistance (rm), with which is ably with loudspeaker constants and may account for the somewhat lumped the acoustical radiation re- LOUD divergent views on matter. 1 IORI sistance which is Mr. Langford - the SPEAKER Smith's ideal loudspeaker. venture to suggest, however, that Due to the complex nature of this it is normal for the suspension mechanical system and the fact that resistance to be very low, and H. F. e Olson states (" Elements of Acousti- it can store energy, the generated o E.M.F., e, bears a complicated cal Engineering," Van Nostrand, OOUTPUT p. 112) be o TRANS. phase and amplitude relationship to that it may generally o VOLTAGE PROPORTIONAL neglected. If this is so, the electri- TO VELOCITY the current, i, which causes the (eh) generating motion, and it is by cal damping would have a marked virtue of this relationship that the effect on the behaviour of the system, and it is my experience that mechanical properties of the vibra- R /10 SCALED REPLICA tory system are reflected back into this is usually the case. OF PHYSICAL R While the question of loudspeaker IMPEDANCE OF the electrical system as Zm, the LOUDSPEAKER " motional impedance," determin- damping is being discussed, it may L /10 ing along with R and L the be of interest to Wireless World readers to know a method has apparently complex impedance at that .lá the terminals of the loudspeaker. been evolved by the writer which The fact that this "motional imped- makes use of the generated E.M.F. in an electro-mechanical vibratory ance " is not really an impedance Fig. 3. but a generated E.M.F., is the key system to control the motion of the to the question of loudspeaker system. The method, which is a The system is still undergoing of suggestions damping. The current due to e development put development and should ultimately forward by Messrs. P. d'E. Stowell provide a close approach to an ideal and M. K. Taylor, consists basic- radiator. ally, as applied to a loudspeaker, of D. T. N. WILLIAMSON, extracting the generated E.M.F. (which is proportional to speech coil Research Department, velocity), and using it to control the Ferranti, Ltd. velocity by means of a negative Edinburgh. feedback system. The extraction of the generated E.M.F. is achieved The " -tron " Family by a simple bridge network as in I\VAS very much interested in the Fig. 3, and requires no special Fig. I. " Unbiased " column of your attachments to the loudspeaker. February, 1947, issue relative to the The system demands a high -grade suffix " tron." which provides the damping is amplifier with very low phase shift For a considerable number of limited only by the impedance of R, of the type described in the April years, I have had a hobby of col- L and Ro (the output resistance of and May issues. It has been made lecting the uses of this suffix in the amplifier), and the percentage to operate satisfactorily over a fre- newly coined words. Since writing electrical damping is therefore quency range of Io -I,000 c/s using an article on the subject for an determined by the relative values a standard 1z -in loudspeaker, the American periodical, Electronic of Ro and the impedance, R + jXL,. coil velocity of which was made Industries, January, 1946, I have Taking the term " damping fac- proportional to input amplitude and continued my collection and it now tor " at its face value, it would be totals about 200. It ranges from only reasonable to expect that an 100 " aeriotron " to " zyklotron " and 4 increase in the value of this factor covers words beginning with every would produce a corresponding pro- letter of the alphabet except J, W, portional increase in the effective- o Fig. 2. X and Y. W. C. WHITE. ness of the damping. This is not General Electric Company, so, however, and the relationship, Schenectady, N.Y., U.S.A. simplified by neglecting the reactive components, is of the form shown in 10 20 10 40 "Push -pull Phase-splitter" Fig. 2. The optimum value assigned DAMPING FACTOR to this curve is a matter of per- FOR many years now I have made sonal choice, but a figure of so completely independent of fre- up for my own interest most of which I put forward when the quency. By suppressing the radia- the L.F. amplifiers which have ap- cathode follower output stage con- tion from the back of the diaphragm peared in your pages, and a few days troversy was at its height (W. W., and adjusting the frequency charac- ago completed the new phase- August, 1944) seems reasonable as teristics of the amplifier circuits, splitter described in the August it produces 91 per cent electrical the loudspeaker could be made to number. damping. ' Damping factors " of have any desired radiation charac- This amplifier, after a period of this order appear as a by- product teristic. Since the behaviour of a most careful listening, is in my when negative feedback is applied 12111 diaphragm loudspeaker departs opinion just about as near perfec- to reduce non -linear distortion in an from that of a rigid piston above tion as anything of the sort I have

www.americanradiohistory.com October, 1947 Wireless World 403

made up for myself or heard in com- balance the two output valves, also mercially made amplifiers. The ap- it is very inexpensive. paratus is very easy to make and G. POTTER requires no special instruments to Tenterden, Kent. RE- ENTRANT HORN Short -wave Conditions TYPE 42 REH Expectations for October By T. W. BENNINGTON (Engineering Division, B.B.C.) DURING August the average day- The E and Fi layers will not con- time maximum usable fre- trol transmission for any distance in quencies for these latitudes were these latitudes, and Sporadic E is somewhat higher than during July, not likely to be much in evidence, while the night -time M.U.F.s were so that medium -distance communi- considerably lower than during that cation on high frequencies will not month. This was in conformity with often be possible. the normal seasonal trend, and the Below are given, in terms of the M.U.F.s should now continue to broadcast bands, the working fre- vary in that manner towards the quencies which should be regularly winter. The night -time decrease was, usable during October for four long - The new 42REH has advantages however, greater than would have distance circuits running in different of complete weather -proofness, been expected, because on a large directions from this country. (All smaller overall length, better number of nights conditions were times in this article are in G.M.T.) weight distribution and conse- disturbed. In addition, a figure in brackets is quently greater ease in handling, Daytime working frequencies were given for the use of those whose which make this one of the most therefore fairly high, though not primary interest is the exploitation popular of the new F.I. loud- high enough to allow much use of of certain frequency bands, and this speakers. The horn is designed such frequencies as the 28 -Mc /s indicates the highest frequency for use with the standard F.I. band. Night -time working fre- likely to be usable for about 25 per L.S.7 Unit and allows for this quencies were such that those as low cent of the time during the month unit to be driven to 12 watts as II Mc / s were required on some for communication by way of the input. A spun aluminium cover paths. Sporadic E was prevalent- regular layers: - over the unit has room for though somewhat less so than during housing a suitable matching July medium -distance Montreal : 0000 11 Mc/s (18Mc/s) -and com- 0500 9 transformer. munication on very high frequencies (15 ) 0800 11 The construction has been de- was frequently possible by way of 1000 17 or 21 Mc/s (30 ) 1200 26 signed so that the whole this region. It is not expected that (39 ) unit 2000 21 or 17 Mc/s (29 is assembled and held together this situation will last much longer. 2200 15 (22 ) LARGE 2300 11 with ONE NUT only. The (19 ) first i. days of the month , This construction enables a were relatively undisturbed, but Buenos Aires : 0000 15 , . (22 number of units to be packed later there were some ionosphere 0200 11 , (19 for export in a space which storms of very long duration and, 0600 15 , or 17 Mc,s (24 21 is a of on certain days, of marked severity. 0800 (31 fraction that normally 0900 26 (43 required ; assembly is a The most disturbed periods were 2000 21 (32 matter a 2100 17 (26 of few minutes un- 12th, i4th, 16th -23rd and 24th- ) 2300 15 ,. (23 skilled labour. 27th. ) This unique feature will recom- Forecast. -During October the Cape Town : 0000 11 (20 ) mend itself to all export daytime M.U.F.s should continue to 0500 15 (22 21 0600 (41 ) buyers particularly. increase, and should, in fact, reach 26 0700 1 ) values which will be near the peak 1800 21 (32 ) The 42REH is not of the " loud- hailer " type 17 of of those for the present sunspot 1900 (26 ) speaker, but is designed to cover a range 2100 15 of frequencies considerably greater cycle. Long -distance communica- (22 ) than those needed for purely " announcing " tion on very high frequencies will be Chungking : 0000 11 (17 ) purposes : i.e., it is suitable for all normal quite often possible in all directions 0100 9 (16 ) requirements of high power reproduction from this country. The 28 -Mc /s 0300 11 (18 ) of music as well u speech. 0500 17 or 21 Mr/s (24 ) Dimensions assembled ... 22in. amateur band, for example, 0700 dia. x 24ín. should 26 (36 Bell diameter ...... 22in. 1300 21 ) be regularly usable at the appro- (30 Cut-off frequency ...... 175 1500 17 (25 (' ) Effective Air Column 42in. priate time of day, and the month 1700 15 Weight Horn only 8 lbs. will be ; propitious for the establish- 1900 (18 j Shipping space ... One -23in. x 23m. x I8in ment of contacts over long distances 11 12 -33ín. x 33in. x 27in. on 5o or 56Mc /s, though not, of Ionosphere storms are often pre- course, as a regulak feature. valent during October and some Night -time working frequencies are periods of poor communication are expected to decrease somewhat as therefore to be expected. At the compared with September. Fre- time of writing it would appear that FILM INDUSTRIES LTD. quencies as low as 9 Mc / s will be- such disturbances are more likely to 60, PADDINGTON ST., W.1 come the optimum for a few occur within the periods ist, 6th - Telephone: WELbeek 2385 night -time circuits, though fre- 7th, 9th -i3th, 16th -18th and 25th - quencies lower than this are unlikely 28th than on the other days of the .71t I to be really necessary. month. w. w. I

www.americanradiohistory.com .404 Wireless World October, '947

vided with a R.F. amplifying stage. Without at least one such stage- RANDOM RADIATIONS or, at any rate, a bandpass input from the aerial to the first valve- By "DIALLIST" it is hardly possible to eliminate second -channel interference entirely. Both the R.F. stage and the band - Eventful Years so far come my way. First, the small sets, those whose basic price pass filter have one big drawback RADIOLYMPIA again, after (and by " basic " I mean the price in these hard times : each means an eight exhibitionless years! I before purchase tax is added) has extra section in the variable tuning find it hard to believe that so much been kept down to somewhere near capacitor and additional coils. time has passed since we were the ß15 mark. To produce such a Variable capacitors larger than the there ; but passed it has and the set is not easy to -day, if it is to two -gang are expensive and not world has changed not a little in be efficient and easy to handle. The easy to obtain. Very possibly they those years. When the last exhi- price limit reduces the possible are difficult to come by mainly be- bition was held the word " radar " number of valves (excluding the cause the demand for them is had not been coined and R.D.F. rectifier, which after all, need not comparatively small. I have never was known only to the little hand be a valve), to four at the outside. believed that the cost of a wireless devoted to its early developments. Now, it is almost an axiom of wire- set of the larger type mattered very Very little was known about the less that the more highly efficient much, for the man who wants a centimetre waves, though investiga- you make the circuit of a receiver, really good receiver is quite pre- tion of their possibilities for short - the more difficult it is likely to be pared to pay for it. distance communications was going for any but an expert to get the best forward. The magnetron and the out of it. Designers were thus faced Sutton tube were still to be in- by the double problem of getting Shocks and Switches vented. And who could have the last ounce out of a small num- A FRIEND of mine was discon- guessed that the crystal would stage ber of valves and of making the certed the other day by re- a comeback as the most effective de- combination handleable by the ceiving a pretty shattering electric tector of microwave transmissions? wettest -nosed of wet -nose listeners ! shock when he thought that he Who would have dreamt that we In both these essentials they have had taken all the proper precautions should before long be pouring wave- succeeded pretty well. to prevent such a thing. His A.C. lets through such radio -plumbing as mains set had died on him and, the wave -guide or launching them having removed the chassis from into the ether from aerials so queer The Bigger Sets the cabinet, he was making a pre- as the " cheese " or the " horn "? For years I've been urging that it liminary examination, with aerial The square pulse we knew from its is of little use to try to popularize and earth disconnected and the set use for the frame sync and line sync short -wave listening if the short- switched off. A visual inspection of television ; but few can have fore- wave ranges of broadcast receivers disclosed nothing amiss, so he de- seen the importance that pulse tech- have tuning arrangements so coarse cided to connect up aerial and earth nique was to have, or that some that only by the exercise of con- in the faint hope, which most of us form of pulse -modulation would siderable manual skill and the cherish at such times, that there make it possible to modulate a patience of Job can a desired station was nothing really wrong and that single carrier with several speech be brought in. I'm glad to see the set was just being pernicketty. channels simultaneously. All those quite excellent bandspreading With the bare end of the earth wire things and more have happened arrangements provided on the S -W in his left hand, he put his right since the last Radialympia and range in several of the bigger sets. on to the chassis in order to turn many of their applications will be This should be a popular feature it into a convenient position. It there for all to see. and I hope it will meet with the was at that moment that he bought success it deserves. There is, a genuine fourpenny one. The set though, just the chance that many was switched off, wasn't it? Yes, Broadcast Receivers potential buyers have come to the but there happened to be an insu- conclusion, after so many years of lation defect in the mains transfor- To the majority of those who that to Olympia the new broadcast clumsy tuning arrangements, mer primary circuit and it chanced flock the short waves are not their cup of that the two -point plug at the end and television receivers will be the Really one could hardly most interesting of the exhibits. tea. of the set -to -mains flex was so in- wonder if it were so : have you serted in its socket that the switch That is as it should be. The bulk ever tried " exploring " the r9- E- of the space is occupied by those in the receiver was in the neutral metre band with a small superhet lead. The chassis was thus very who live by selling receivers and, of the " broadcast " type built in this year it is be a radio much all alive -oh, even though the though to years gone by? I put the word switch in the set was at " off." The rather than just a broadcasting ex- in inverted commas, since its main object must be to exploring shock, as you'll see, could just as hibition, I've known dials on which the easily have smitten one who was maintain, renew or arouse interest whole band occupied less than a in apparatus designed for entertain- not engaged in looking for a fault quarter of an inch ! Let's hope that at all, but was merely connecting ment in the home. There will be such absurdities are things of the in I am sure, to every- his earth lead, holding the wire plenty, interest past and that the man in the street one hand and feeling with the one amongst the broadcast receivers will be convinced that short -wave and the television sets, though one fingers of the other for the socket listening can he an enthralling or spring -clip in the set. sighs rather to think what there hobby. Given the right kind of set, might'have been, had there been no is. post -war restrictions, no purchase it certainly tax, no shortage of labour or of Safety First materials. Several points have The Missing Stage Personally, I've never much liked struck me particularly in the de- It is, in a way, surprising to find the single -pole mains switch used signs of the receivers which have how few of our receivers are pro- in conjunction with a two -pin plug,

www.americanradiohistory.com }; October, 1947 Wireless World 405 for it is an even chance whether or not you connect up in such a way that the switch breaks the phase Interesting lead. Ideally, the receiver switch should always be of the double -pole variety, for " off " ought to mean that the set is completely discon- Display of nected from the supply. Some well - designed sets have this safeguard, but far too many don't. It is sound New practice to use a three -point plug Components and socket for the mains connec- tion, making sure, of course, that the phase pin of the plug is wired to on the the lead from the switch in the set. It's rather surprising, when you come to think of it, that the wiring regulations in force should allow the use of any flex -connected apparatus containing a single -pole switch in conjunction with a two - point plug. The three -pin plug is CBULGIN) eventually to become the standard domestic fitting, but it may be years before its adoption is univer- sal. STAND No. 3 MERCHANT SHIP EQUIPMENT (Grand Hall) 1 /TORE rigorous requirements for Vl the radio equipment of British merchant vessels are foreshadowed at Radiolympia by the issue by the Post Office of * A new range of PRESS switches especially suitable for personal three specifications. In a foreword midget receivers. Available in five types, for flush mounting. Also it is stated that the G.P.O., in con- suitable for refrigerators, lobby lights, etc., where circuit is required sultation with the Ministry of on opening or closing of a lid, cover, or door. interests and Transport, shipping A new co -axial flex connector designed for car radio uses. Also radio equipment manufacturers has * improve- available for flush panel mounting. Types with integral fuse are decided that technical included. ments of the apparatus now in general use is needed to cope with * The range of toggle -switches now includes over 200 types. All present -day traffic congestion. A types have been improved by new methods of manufacture and by series of specifications, in keeping standardisation of specialised raw materials. Of particular interest with modern standards, stating the are the 5.258 and 5.259 general-purpose types. minimum performance that will be * A unique range of key-operated toggle-switches designed for required to secure the P.M.G.'s security purposes. Certificate of Approval for each * A new range of moulded signal lampholders. These are of simple major item of ship radio equipment, construction and are designed to facilitate easy access to the lamp - has been issued. The titles are:- bulb. Radio for Merchant Ships : Per - new (P.200) is Pp. 49; * For television requirements, a mains connector formance Specifications. available also 8 and 12 -pin plugs and sockets. The P.200 fixes to price is. the cabinet -back and breaks the mains supply on removal of the : Per- Radio for Merchant Ships back, thus ensuring absolute safety to the user. formance Specification for a Motor Lifeboat Radio Equip- ALSO ON DISPLAY ment. Pp 9 ; price 3d. A COMPREHENSIVE RANGE OF OUR STANDARD RADIO Radio and Radar for Merchant AND TELEVISION COMPONENTS, INCLUDING CABLE Ships : A Performance Specifi- PLUGS AND SOCKETS, CAPACITORS, COILS, FUSES, cation for Climatic and Dur- RESISTORS, TRANSFORMERS, ETC. ability Testing. Pp 6; price 2d. Of these specifications (which are issued by H.M. Stationery Office) first-mentioned is the most im- portant ; it deals with several different types of transmitters and "The Choice receivers, as well as with D.F. gear. Eventually all marine equipment will be required to conform to these specifications. Due notice will he given of the date after which new A. F. BULGIN A CO., LTD. installations must -conform ; also of the date on which existing installa- BYE -PASS ROAD, BARKING, ESSEX. be brought into con- tions must (5 lines) formity. Telephone RIPpleway 3474

www.americanradiohistory.com 406 Wireless World October, 1947

echo signal at the centre of the strobe interval. RECENT INVENTIONS F. C. Williams, E. L. C. White, and D. Blumlein (legal representative of A. D. Blumlein). Application date A Selection of the More Interesting October 15th, 5943. No. 582503. Radio Developments MEASURING RELATIVE VELOCITY WIRING SYSTEMS switching the earth contact between THE relative speed of a craft in pursuit of another is shown by re- a wireless the points E, and E,. 'TIIE assembled parts of set Standard Telephones and Cables, flected pulse signals on a calibrated are connected up in circuit through meter of the centre-zero type. strips of a metallic paste, which is laid Ltd., and E. O. Willoughby. Applica- tion date May 2nd, 1941. No. 581724. Each of the twin grids of a tetrode in grooves previously made in a chassis detector, forming part of the radioloca- of insulating material. The paste is TUNING CIRCUITS tion set carried by the pursuit plane, is made by mixing finely powdered copper VARIABLE separately coupled to the echo- with amyl acetate, in which some cel- THE stability of a valve oscillator luloid has been dissolved. As the ace- is adversely affected by the vary- O1 tate evaporates, the celluloid binds the ing shunt impedance value of the nor- copper particles into a firm mass of mal tuning circuit at different frequen- R1 good conductivity. The chassis is of cies. One known method of compen- synthetic resin. sation is the use of an inductance coil At unavoidable cross -over points with a Q- factor that is inversely pro- apertures are made to connect one of portional to frequency, but this has D2 the upper grooves with another formed certain disadvantages. i in the under-surface of the chassis. Re- According to the iikvention, the pro- cesses are shaped to take the bases of blem is solved, in the case of a capa- Ol the principal components, and are fitted city -tuned circuit, by connecting across with rubber packing to force the ter- a part or the whole of the circuit an minals into firm contact with the con- auxiliary resistance in series with an ducting strips. auxiliary capacity. The specification Murray field Nominees, Ltd., and P. contains an analysis of the conditions Plowman. Application date, Oct. 13th, required to keep the shunt impedance D 5944. No. 583285. of the corrected circuit constant, as the tuning control is varied, without in- APPROACH BEAMS curring undue losses at the lowest fre- THE inner quency, and gives specific formulæ for ends of the radiators A, the values of both the auxiliary com- B are connected through a half - ponents in terms of the conductance of (c) wave non -radiating reactance Z, so the main circuit at its upper and lower that the currents in both limbs are limits of frequency. A. C. Lynch. Application date, July loth, 1944. No. Di D, D, Beam 585365. A B C switching AUTOMATIC STROBING device. Vradar equipment, as used on fighter Pulse indications of relative velocity. enemy I planes for intercepting receiving aerial, one directly, and the bombers, the echo signal from other a selected target is isolated through a circuit which reverses and distinguished from other the signal voltage and introduces a signals by a strobing voltage, time lag equal to the pulse repetition which first searches for the frequency less half a pulse -width. Both desired signal and is then parts of the split echo signal are also automatically locked to it, so equalized in amplitude, before they that only this signal can reach their respective grids. One grid appear on the C.R. screen to thus receives a part of each echo signal show the instantaneous posi- directly, whilst its twin grid receives a tion of the quarry. An part of the delayed and reversed echo auxiliary voltage is then signal from the previous pulse, both to " draw -out " the in- combining to control the anode current applied that is fed to the indicator. dicating spot along the time- In the diagram the transmitted (b) base, and to add lateral exten- pulses (a) sions or " wings," which serve are marked O, the direct echoes R, and to indicate the instantaneous the delayed echoes D. Diagram (a) of the same sign, i.e., positive or nega- range of the bomber, as the fighter is shows the signal conditions for con- tive. The outer ends are fed from the " homing " on to it. Control voltages stant relative velocity, and (b) those inner wire of a coaxial transmission are used to cut out undesired ground that occur when the pursuer is gaining line T, the outer conductor of which reflections, and for other purposes. on his quarry. In diagram (c), A and is connected to a horn- shaped reflector The master control voltage is initi- B show the corresponding grid voltages, of rectangular cross -section. The line ated by each exploring pulse, and is and C those when the pursuer is losing assembly is tuned to the operating fed to a delay network, from which ground. frequency by an adjustable stub or the other operative voltages are tapped J. Forman and Pye, Ltd. Application loop L. off. The duration of the " searching date April 17th, 1941. No. 581166. The direction of the radiated beam strobe " is gradually increased until, r depends upon the distribution of the in the course of its " drift " along the standing wave system along the limbs time -base, it overlaps the desired echo The British abstracts published re- here are prepared with the A, B, relative to the sides of the signal. The coincidence of the two on permission of the Controller of flecting horn, and this will alter as the the grid of a gate valve then allows H.M. Stationery Office, from position of the voltage node at the that signal alone to appear on the in- specifications obtainable at the earthing point is changed. The axis dicator. Simultaneously the " drift " Patent Office, 25, Southampton of the maximum lobe can accordingly control is cut out, so that the strobe Buildings, London, W.C.2, price each. be swung from X to Y, in order to stays locked to the signal. . A fre- lì- define an approach path D, by rapidly quency- discriminating circuit holds the

www.americanradiohistory.com October, rq¢ ' Wireless World Advertisements 43

199E

ACKNOWLEDGED e-e-4//4 THROUGHOUT THE WORLD

MÛT US AT P

_ c

RADIOLYM PIA OCT. 1.11

STAND No. 41 GRAND HALL

E

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

Telephone : COLindale 8011 -4. Cables . RESISTOR, LONDON.

Factories : London England Toronto, Canada Erie Pa., U.S.A.

www.americanradiohistory.com 44 Advertisements Wireless World October, 1947

MIIIIPP11111111111111111

1.1 MORE THAN = 1,500 DIFFERENT TYPES u C S machine tools

Is* 1-*Itylo" 0 suivsw orwittlikw, t MOM 411111) ESCIL11011 CONIIINIESTA.S. 91/011EINI4 IRIEILP1N I'VE iii MAID Government Surplus machine tools available NOW at attractive prices. NIEVIRIEIRILANIDO YOUR opportunity to get better equipment and increase production. weVir DISPOSAL CENTRES, where records of all l' machines available may be inspected, are open to the public for enquiries from 10 a.m. to 4 p.m. OIFIFSCIE Monday to Friday inclusive :- 4 BIRMINGHAM C.M.L. Buildings, Great Charles Street k 4 BRISTOL 8/9 Elmdale Road, Bristol 8. CARDIFF Imperial Buildings, Mount Stuart Square. GLASGOW 21 Glassford Street. LEEDS 10 Bank Street, off Boar Lane. LONDON Room 0088, Ground Floor, Thames House North, Millbank, S.W.1. MANCHESTER Britannia House, Fountain Street. REPRODUCERS &LIFIERS LTD. F RE DE RIC K STREET WOLVERHAMPTON ISSUED BY THE MINISTRY OF SUPPLY

www.americanradiohistory.com October, 1947 Wireless World Advertisements 45

a ON DON CENTRA 1 RADIO STORES

Special Offer ®f Ex-Govt. Receivers, ei-cv 10 -VALVE COMMUNICATION FRACTIONAL H.P. A.C. MOTORS Model 'AN!APA -1. Ex- U.S.A. RECEIVER -Type R1155 AMERICAN AIRCRAFT RADAR UNIT Brush type. 220- 250 v. 50 cycles approx. 5,000 r.p.m. Overall diem. 10 x 41n. }in. spindle ex- tends lin. both ends Post 2/6 extra.37 6

A new AIRBORNE G.P. TRANSMITTERS delivery! Type 1154. A few only to clear. These seta are equal to new, need only a power pack for Complete with 4 valves. Frequently coverage: 600 ko /s, immediate use (see " W.W.," July, 1940). Freq. range 200 kc /s, 10 me /s, 8 me /e, 2.35 me /e, 8 me /s, 2.5 mc/s. 7.5 mes. or 1,500 kcs., complete with 10 valves, including Power Input 1,200 v., 200 m /a. H.T. 6 v. 4 amp. L.T. magic eye. Enclosed in strong metal box.... 5 Chassis size, 15in, x Skin. x 8lin. In metal cabinet, Each receiver is aerial tested. £p 1.r1 Supplied in strong wood case, with metal bound cornere Careiage and packing 7/6 extra. No C.O.D. easily adapted and carrying handles, for £5.17.6 115v. 500 cycles. Complete with 31n. Cathode Itay 'rube Amateur use. Lees Power Pack 11 valves, Power pack, etc. In black crackle meta/ POWER PACK 220 -250 v. A.C. for above Packing 10/- extr,. is available to CALLERS Carriage and case. Brand new and boxed. With full DA 10.0 ONLY instructions. Care. paid. ñY

Type R1147B 4 -VALVE SUPERHET RECEIVER 7 -VALVE U.H.F. RECEIVER Ex- G.P.O. TELEPHONE CHASSIS Range approx. 200 megacycles TRANSMITTERS Type 18 Mk. III

On table stand with screened lean and Jack Plug. New. 13/6

RADAR VIEWING UNITS Consisting of gin. diameter Electrostatic C.R. tube, 7 valves including four EF50, potentiometers, resistances and other associated components. to metal cabinet 18 x 8 x 78in. Bargain price £3,7.6ir0 TELEPHONE LINE or UNISELECTOR A Real Opportunity! SWITCHES Beautifully constructed and fitted with micro- condenser 4- or 6 -bank, It drive. Valve type two EF50, two EF36, one each EBC33, constants. Have EL7, ELIO. In black metal case 8 x 7 x Range 6.9 me /s. Complete with valves, 465 61n. Bet, complete with valves £2.763K . V various applications Ka. IF. Carr. paid ...... 37 6 Including a u t o matit tuning, cir- Exceptional Offer! cuit selection, etc. 6 -VALVE SKIORT -WAVE RECEIVER VOLT -OHM METER Operates on 25.50v. Precision -built Communication Type 28/6 1,000 Type 30/- R20 ohms per volt. Super Quality Heavy Duty TWIN- Range 0- ELEMENT SLIDING RESISTANCES 600 volts 5.4 ohm at 20 amp 47/6 and 0 -1 12 ohm at 10 amp. 39/6 megoh m 70 ohm at b amp. 35/- Single Element 14 ohm at 5 amp. 13/6 Resistance In damp- ELECTRO MAGNETIC COUNTERS -proof ca p- Ex- G.P.O., every one perfect, electro- magnetic, 600 ohm 811n. x 71n. x coil, counting to 9,999, operated from 25v. -50v. 71n,,l0ustra- D.C., many industrial and domestic applications tion shows /5/6 hinged lid 217. Range : removed. OSCILLATOR UNITS. Type 10-80 me /s Complete These units contain very useful componente: two EF50 Valves, three P.O. type Relays, numerous Condensers Suitable with all Including two 20v. 25mfd. Electrolytic., Resistors, for AO 100.250 v. or 6 -v. battery operation. Meta instructions. Potentiometers. etc. rectifiers, B.F.O., Built -in Speaker, Super Slow motion Brand new. Bargain £1.12.6 dial. Provision for phones, etc. A real super job in grey prim metal cabinet. Complete with Valves and £5.10.0 Vibrator ready to use £18.0.0 We do not issue lists or catalogues Corsage and peeking 12 +6 extra.

ION DON CENTRAL RADIO STORES, 23, LISLE ST. (GERrard 2969) LONDON, W.C.2 Closed Thursday 1 p.m. Open all day Saturday.

www.americanradiohistory.com 46 Advertisements U.'ü1rclecs World October, 1947

S E R I E S 1 0 0 MULTI -RANGE TEST SET by

A Service Engineers' Universal Testing Set with a sensitivity of 10,000 Ohms per Volt. The Instrument is housed in a strong metal case with carrying handle, and is complete with one pair of leads having detachable bull -dog clips and test prods.

Ranges : AC /DC Volts : 10, 25, 100, 250, 500, 1000. D.C. Milliamps : 2'5, 10, 25, 100, 500. AC /DC Microamps : 100 Microamps on the 10V range.

Resistance ranges : 0 -1 Meg. (13,500 Ohms mid scale). 0 /10,000 Ohms (135 Ohms mid scale).

Frequency Range : 15 to 20,000 Cycles per second.

Accuracy : 3% on D.C. Ranges. 4.)% on A.C. Ranges (for sinusoidal waveforms). 5% on Resistance Ranges (Compensated for normal variation of cell voltage). Size: 9 "x5¢ "x4 ". Terminals : Socket head type.

MEASURING INSTRUMENTS (PULLIN) LTD THE S. S. WHITE COMPAYY BRITANNIA WORKS ST. PANCRAS WAY CAMD°_N TOWN LONDON NI W.I. Address all enquiries to Dept. 1, Electrin Works, Winchester Cable Address: WHICODEvTA, WESDO.. PHONE. LONDON Street, Acton, London, W.3. Telephone: Acorn 4651 -4 Telephone: EUSAON 4758 -4755

Robert Sharp & Partner: te. 735

www.americanradiohistory.com October, 1947 Wireless World Advertisements 47

Modal Y2VU. A 21" KINGSTON -ON- THAMES SURREY ModelP84. An 18" dia- diameter Speaker, TELEPHONE: KINGSTON 5656-7Z-9 meter Speaker with a weighing only 3 ozs. peak power handling capacity of 40 Watts; designed for small suitable for public personal radios. address purposes.

www.americanradiohistory.com 48 Advertisements Wireless World October, 194'7 Stabilised Insulation BY MODERN IMPREGNATION METHODS

HYMEG Synthetic Insulating Varnishes are HYMEG recognised tied widely used for their mechanical rigidity, improvement of electrical properties of windings ; heat, moisture, oil, acid and alkali HIGH-SPEED PRODUCTION resistance as well as for the considerably reduced 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 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 modern 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. WA. Telephone : MAYfair 9171. VIANUFAC'l'URERS OF HIGH- PERFORMANCE tNSULA'l'ING VARNISHES AND ENAMELS

SPHERE INSTRUMENTS ISOLATION ...VIBRATION Introducing the ALL WAVE TYPE NEW

1 606 SIGNAL VIBRATION GENERATOR ELIMINATORS A portable Signal Generator for I AC. Mains operation. Specially 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 [EQuIFLEx' receivers and amplifiers. Equiflex "Mountings are This is a specially designed MOUNTINGS invaluable Generator embodying several new and unique features and Improve- for the mounting ments, which radio engineers will find and suspension of machines, invaluable. AN PR 0 0 V CT All "SPHERE " Test -instruments are entirely British made ® equipment, instruments, with highest quality materials and workmanship and carry a SIX Months' guarantee. electrical apparatus, motors, etc., and wherever elimination of vibration and shock is required. Continuous Frequency Built In ladder attenuator, coverage from 110 Kilocycles with fine control, giving SPECIAL FEATURES to 56 Megacycles, in six I Volt maximum, in five steps, bands. In multiples of 10 Microvolts. Flexible in all directions at an equal deflection. Can be e Exclusive "SPHERE" "SEE Radio and Audio Frequency loaded on any side, thus eliminating vibration in Vertical, AT A GLANCE" Band Voltages can be switched via Horizontal and Longitudinal planes employing best quality and Attenuator indicators. single Test -lead. natural rubber spring elements and complete with snubbing Variable control of 400 device. Special Fittings made to suit customers' require- C.P.S. audio, from 0 to I Volt. ments. FOR RADIO SERVICE, RADIO ENGINEERING Also available as previously advertised, the ALL -METAL AND LABORATORY USE. construction comprising an ingenious Damped Spring System. Write for List No. SOS S.G. Write for illustrated brochure, and SPHERE RADIO LIMITED send us details of your requirements. Radio Instrument Manufacturers A. WELLS & CO. LTD. (Dept. W.W.), HEATH LANE, WEST BROMWICH STIRLING ROAD, WALTHAMSTOW, LONDON, E,17 'Phone : Larkswocd 2691

www.americanradiohistory.com October, 1947 'írIess 'oeId Advertisements 49 PREMIER RADIO COMPANY MORRIS & CO. (RADIO) LTD. ALL to 167 POSTORDERS LOWER CLAPTON RD., LON DON, E.5. 'Phone : Amherst 4723. ALL to 169 CALLERS FLEET STREET, LONDON, E. C.4. 'Phone : Central 2833. Terms of Business : Cash with order or C.O.D. over LI. Send 2d. stamp for list. RADIOGRAM CABINETS BAKELITE CABINETS PREMIER PEDESTAL PLAYING DESKS

MIDGET RADIO KIT. Build your own midget radio. .4 complete set of parts, including valves, loudspeaker and iuxtructluns. In fact, a verythhu except cabinet wry to build 4 -valve Medium and Long Wave T.R.F. radio operating on 200.2511 v. mains, A,C or 11/C. Valve line -up. 6K7, 6J7, 25.46, 25Y5. Wavelengths covered 200 -557 and 700 -2,000, Size 10 x 6 x Sin. Com pletely drilled chassis. Price. including tax, £7 7e. 6d. SUPERHET MIDGET RADIO KIT. A complete kit of parts for a 5 -valve .superhet. Covers Dignified appearance and 16 -50 and 200 -557 good ork,,r reship. Size metres, AC DC 200 -250 v. 6K8, 61{7, 6Q7, A well made mahogany finished pedestal cabinet, S11hn. high, 18)1n. .33 aide. 25A6, 2515. cmo- deep, French polished. Size, 10 x 6 x 61n. twining a quality electric walnut. Completely drilled chassis. Price gramophone motor and plek-up Price £26. Abo available complete including tax, £B in upper compartment, and record space wiveeredth electric motor with auto .stop, or with 5e, in louer £30 3e. 94.. An attractive brown bakellte cabinet as illustrated above Height, 30in. Width, 161n. Depth, 15ín. Price electric motor, auto atop and magnetic pick -up, £18 18s. can be supplied for either kit at a cost of 25 £32 13s. 4d. -. RECORD PLAYERS. Consist of a High Quality electri. gramophone with Rotherntel Crystal Pick -up. £35 2e. id, or METAL RECTIFIERS. motor 200,250 v. 50 cycles with speed e it h n recurd -mixer changer, Output Volts Current regulator, 121n. turntable, automatic start and stop. £45 7e. Bd. Type Fripe Quality 100 ...... 40 m /a. 11.W. 5 - magnetic pickup, mounted on a strong metal FERRANTI 1 MILLIAMP METERS. 31in. external frame, Price St0 ...... 40 ass, a, H.W. or V.D. £8 19e. Od. Identical Model but will! diameter, flush mounting, with self- contaiced Westing- 5.- Rothermel '125 ...... 65 mia, H.W, or V.D. 5 - Crystal pickup, 510 19s. Od. louse bridge rectifier. Seale marked 0 -1(3 volts with AUTOMATIC RECORD 36 .. , . 75 PLAYERS. A reliable automat io l'ut y' d irisions, fitted in well -made wooden box 6 x 5 x 5in. .. m /a. Bridge 1 6 16 ti record mixer changer, 200/250 v. 50 cycles, with rejeee 35 -. .. .. -. 1 amp. Bridge 12 6 48 ...... 11 amp. Bridge 25 - and repeat hanism, mounted on a strong met:,! frame. D C TO A'C CONVERTERS. Input. 18124 v. ITC. 16 ...... 5 amp.,, Bridge 30 - Price ng20. Output., 2101 v. 50 cycles 100 watts, £5. la ...... 8amps. Bridge METERS. A huge purchase of military surplus meters 376 allows us to offer the POWER PACKS. Input, 21.0 -240 v. 50 cycles. Output, 4 ...... i amp. H.W. following bargains- Beet makes. 5 - Bakelite eases, prices 270 v. 80 ne a, 6.3 v. 3 -5 a, Fully smoothed. Contained are approx.} original cost. ill substantial screening box, with wave valve. ALUMINIUM CHASSIS. Substantially made of bright Range Ext. Bolo Fitting Type Price full alonsinlum, four sides. £2 lOs. wit Diem- Movement -.r31x2in. .. 4'6 91v41x2in. .. 56 300 v. 3)' 8 MIA Flash M.I. A/C .... 7 6 MAINS TRANSFORMERS. All 230 v. 50 cycles input. IO x8 x2yiu. .. 7,- 12x 9x211n. .. 7;9 500 M/A 3' - Proj, M/C D/C .... 126 Type 2. v. 2 amps. (Excellent for rewinding.) -40 15 -. 14 x9 x21in. .. 5 3 16 x 8x2)in. .. 2'6 40 v. 2" 5 M/A Flush M/C D,'C .... 7 6 Type 4, -005.0 -065, tapped at 760 and 6911 v., 500 millt- 20 x 8 x 21ín. .. 10,8 22 x 10 x 21ín. .. 13/6 2)A 0' - Flush Thermo .,., 76 uigsa with L.T. torn. 4 v. 3 a. twice, 4A £3 15e. 21' - Port H, Wire ..., 7 6 v. 10 a. and 4 v. a. MANSBRIDGE TYPE CONDENSERS. Huge purchase Type 9. -6 10 3KV 31" 21 M/A Flush M/C D/C .... 20 - G . 1 of military .surplus paper condensers. Super Type 3,- 51111 -0 -5 0 v. 150 m, 0 4 0 . 2 ) 1 4 v a, 4 v , 5 a, quality 20A 2" 25 oil filled. MIA Flash M/C D/C ..., 7 6 35, -. 40A 2' 121 MIA Flush M/C D/C .... 7.6 Type 450 -0 -450 v. lapped at 300 v. 150 in/a, 4 v. Working Price Per 5.- Capacity 25A 3 }" 5 MIA Flush N/C D/C .... 7.6 3 -5 a, 4 v. 3 -5 a. 30' -. Voltage Size Each Doz. 25A 25 M A Proj. M/C D/C .... 7 f4 Type v 250 in a, 4 v. 5.5 a, 6.3 v, 5 -7 a, 2mt. .. .. 1,000 41 x 11 x 1 2,6 35.-306-0-300 20,- SUPER OUTPUT TRANSFORMERS. By means of a 1 mf. .. .. 600 31 x 11 x 1 1/9 14/- series parallel arrangement wherein the maximum OSCILLCGRAPH POWER UNITS. -Input, 230 volts, TYPE 103 ROTARY TRANSFORMER. Normal rating winding to used for each ratio extremely high efficiency Consist of kit of parts incorporating nains trancfornnem is 19 v. 1), C Input. Output, 300 volts 30 m, a and 6.5 volts is obtained. Any valve single or pushpu0 may be matched to any voice Coil (2 to 30 ohms) type metal rectifiers voltage doubling condensers .. 3 a. D, C. By applying between 200 and 250 volte D/C Mo.15. 15 watts, 30 -. Type 406.-Output, 10110 v. and 6.3 v., 20// -. to the 11.7. output side, the two low -tension windings PREMIER MAINS TRANSFORMERS. R.A.F. 1155 RECEIVERS. Brand new. complete, may be used to charge accumulators- The 19 -volt side All primaries are tapped for 200- 230 -250v, mains 40 -10o will charge a 6 £17 10e. -volt accumulator at 2 -3 amps the 6.5 side cycles. All primaries are screened- All LYS are centre a 2 -volt accumulator at 1 -2 a. With a 1.2 -volt Input to lapped. A POWER PACE (230 v. input) for above, £2 10e. the 19 -volt side, 180 v. at 30 m'a and 4 v. at 3 a. may I.lat No. Output. Nie SHORT -WAVE CONDENSERS. High -grade ceramic be obtained. N ith a 6 -volt input to the 6.5 side, 160 v. SP.175A. 175-0-175 v. 50 m/a. 6.3 v. 2-3 a., 5 v. 2a 25- insulation, super midget type, single ganga available in at 30 m'a may be obtained- By extending the spindle OP.175B. 175-0-175 v. 50 m/a. 4 v. 1 a. 4 v, 2-3 a. 25 - 10, 20, 50, 75 (75 pf. has double spindle fm ganging), which is flush with the frame and applying 200 to 250 v. SP.250A. 250-0-250 v. 60 m/a. 6.3 v. 2-3 v. 5 v. 2a. 25 - Price 2, 6. D/C mains to the 300 v. side, the unit becomes a powerful SP.250 B. 250-0-250 v. 60 m/a. 4 v. 1-2 a., 4 v. 3-5a. 25 - high -speed electric motor, suitable for small drilling SP.300A. 300-0-300 v. 60 m/a. 6.3 v. 2-3 2 -GANG. in 4, 8, 9.6, 27.1, 50, 75 p.f. Price 5,' a., 5 v. , machines, etc. Similarly, It may be used with 6 or 12 v. 2a. 160 25 - 0-GANG. Full size, p.f. Trice Input to the 6.5 v. or 19 v. side. It employs a powerful SP.300 B. 300-0-300 v. 60 m/a. 4 v. 2-3 a-, 4 v. WAVE CHANGE SWITCHES. Available with any of ring magnet and is of substantial construction, costing 3-5 a., 4 v, 1-2 a. 25 - following wafers: 2 -pole 3 -way, 3 -pole 3 -way, 4-pole originally over £5. A fortunate purchase enables us SP.301A. 300-0-300 v. 120 m/a. 5 v. 2-3 a., 6.3 v 2-uay, 0 -pole 4 -way, 1 -pole 4 -way, with shorting bar; to offer these fine unite at 10, -. 3-4 a. 28 - 2 -pole 5 -way [ 1 gang, 4/- ; 2 -gang, 5/6 ; 3-gang, 7 /-, Philips Amplifiers. Military surplus, soiled condition. SP.301B. 300-11-300 v. 120 rnla 4 v. 2-3 a., 4 v 2-3a., 4 3-5 a TYPE 100. -A rotary transformer with completely Perfect working order, 12 -volt battery operated, speech v. 28 - oothed output, contained in a soundproof metal only, output 6 watts, push, pull output. Incorporate SP.350A. 350-0.350 v. 100 m'a. 5 v. 2-3 a., 6.3 v niug box. Input 6 V. D /C; output 220 v. 50 mis '220 v. 60 ma vibrator pack, 35/- 2-3 a. 29 - úP . 30 / -. 3 Valves for sauce (024 and two EL35), 35/-. High SP.350B. 3511-0-350 v. 100 rn'a. 4 v. 2-3 a., 4 v output carbon hand mike for same, 5 0-3 a., 4 v. 3-5 a TYPE 113, -A rotary transformer, input 6 or 12 volta. 29 - SP,351 350-0-350 v. ISO m'a. 4 v. I-2 a 4 v \\' ith 12 v. input, output Is 600 v. 250 m /a, with 6 v. SHORT -WAVE BATTERY KIT- A complete 2-3a.,4v.3-6a Input, output is 300 v. 200 m /a, 30,' -. kit of parts for a 2 -valve receiver, covering 15 -600 metres, 36 - 8P.351A. 350-0-350 v. 150 m'a. 4 v. including valves, coils, drilled chassis, H.T. and L.T. dry 2.3 a., 4 v 500 MICROAMP METERS. Moving coil, 2in. diameter 3-6 a., 4 v. 1-2 a., 4 v. 1-A. batteries to last approximately 6 to 12 months. Ilnsh mounting, Available by the followingmanufac- A pair SP,352. 350-0-350 v. 150 m/ of double headphones and full instructions- Price a. 5 v. 2-3 a., 6.3 v tnrers; Met.-Vick 500 ohms; Ferranti 79 ohms: 2-3 a., 6.3 v. 2-3 a 10 e. An extra coil can be suppliedPP coveringv rm g 0004,900 36,- Weston 116 ohms. Either type 2 1 /- Specialpe quotations4 metres SP.375A. 375-0-375 v ISO m / a. 8.9 v. 2-3 a , for quantities. The following accessories are available metres,, at 4,-. above a to convert the meter into multlmeter.. Set five SUPERHET TUNING PACKS. Completely wired and BP.375B. 375-0-375 v. 250 m/a. 4 v. 2.3 a., 4 v multipliers plus /minus 2) per cent. to read 10 v., 50 v.. aligned- 13 -40, 40 -120, 190.570 metres. R.F. otage, 2-3 a., 4 v. 3-6 a 46r- 100 v., 250 v., 1,000 v., 7/6 the set. Bridge type metro 465 he.; if connections only. Complete with 3 -gang SP.425A. 425-0-425 v, 200 m/a, 6.3 v., 2.3 a rectifier, Separate 0.10,000 ohms 10/-. scale chart., condenser, calibrated, engraved Perspex dial, and S'M. 6.3 v. 3-5 a., 5v. 2.3 a. 47 - 1,000 ohms. Present resistance, and fixed resistor to drive. I.ita wound polystyrene insulation, permeability SP.425B. 425-0-425 v. 200 ma. 4 v. 2-3 a., 4 v 1) battery, convert meter into ohm -meter with v. 3/6. tuned I.F's, 7 Ice banal width. Price complete £3 17e. Bd. 2.3 a., 4 v. 3-6 a. 47-

www.americanradiohistory.com 5o Advertisements Wireless World October, 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 dis- °13t tributors who will endeavour to Fpg 1Ht RADIO HEART meet your requirements. AMME"' All the principal com- ponents of a factory - RESPONSE CURVE (onnoi sear PICK -UP made 3 wave superhet receiver, matched and 10 DO assembled, ready for wiring. Tested and 10 proved for reliability, sensitivity and many .117.6 exceptional qualities. Easy to build ; saves time ; no snags. FREQUENCY i. s TOP CURVE TRANSFORMER LOWER CURVE DIRECT FROM PICK UP Let us send you details. RESISTIVE LOAD 10000011 COUPLED loon ON SEC OF TRANSFORMER

1. Every " Connoisseur " pick -up is hand Sole Manufacturers:- tested and passed to ± 2DB of above response curve. MORGAN,OSBORNEaCO.LTD 2. Our new type damping material work- Warlingham SURREY/'0°zs6ra" ing in gap direct on to armature does not affect bass resonance point. is 3. The required downward pfessure RAYTHEON CONTRIBUTIONS to development of Hearing Aids 1.1/3 ozs. which has been acR- sieved with- out counter -balancing or springs. 4. Being a constant velocity device Bass ?lLoze compensation is required in the amp- PP' aelltoPteei lifier and alternation of high .fre- quencies to suit individual recordings. IN HEARING AIDS... 5. Output direct from pickup .1 volt. With transformer coupled .5 volt.

In compactness, ease of control, dependability, economy of operation, convenience of servicing, fidelity of tone, and all -round superiority, the Hearing Aid of today is far bigger value than that of yesterday. A great contribution to this advance is the reduced battery drain, long life, small size and all -round reliability of the Raytheon Flat Hearing Aid Valve. New production techniques and specially designed valve manufacturing equipment which have made this possible are typical of Raytheon service to Hearing Aid makers and users. Another reason why 90% of all Hearing Aid Tubes In use throughout the world today are marked with the name RAYTHEON! For detailed information on Raytheon Hearing Aid Valves write to Submarine Signal Company (London) Ltd., Artillery House, Artillery Rcw, Apply to :- London, S.W.!, England, or to: Albion Electric Stores, 125, Albion Street, Leeds 1, or to Lawton Brothers (Sales) Ltd., Henry Square, RAYTHEON RAYTHEON MANUFACTURING COMPANY Ashton -under -Lyne. INTERNATIONAL DIVISION Made by : A. R. SUGDEN AND CO. 60 EAST 42nd STREET f.rtvN/l iM fIKGtNiNN (ENGINEERS) LTD., BRIGHOUSE, YORKS. ,rre NEW YORK 17, N. Y., U. S. A.

www.americanradiohistory.com October, 1947 Wireless World Advertisements 51

There is increasing scope for ambitions men and women in the new fields The opened up by Electronic Science. Correspondence and College Courses provided by E.M.I. Institutes which such as the cover recognised diplomas City and Guilds, etc. are written and supervised by E.M.I. * scientists Electronic Science. who are specialists in Courses are already available in such subjects as Basic Radio, Basic Television, etc., and being constantly extended. the prospectus is E.M.I. basic training fits you for entry to CAREERS in such fields as :- SERVICE ENGINEERING, OPERATING, DESIGN AND DEVELOPMENT, TECHNICAL SALESMANSHIP, With this basic TEACHING, etc. training you can eventually become a specialist in Television, Radio Communications, Navigational Aids, Audio Frequency, Radar, Medical and various Electronic applications. There are also short courses for Executives, Amateurs, Students, etc. For full details apply to the E.M.I. Stand No. 212, Grand Hall, Radiolympia, 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. E.M.I. INuuuitES LID Dept. 16, 43, Grove Park Road, Chiswick, London, W.4 * The E.167.1. Group includes "H.M.V. ", Marconiphone and other important electronic interests.

KOIECTRIC LTD OFFER A PRECISION BUILT r HAND COIL WINDING MACHINE (WITH INTEGRAL CLUTCH MOTOR DRIVE IF DESIRED) For Solenoid and Choke Coils, etc., up to 6" dia. x 7 " long. Field Coils, etc., up to 12" A/C corners. Armature Rewinding, etc. (16 SWG to 45 SWG) ATTRACTIVE FEATURES INCLUDE :- I. TWO SPINDLE SPEEDS I -I AND 31-1 2. TURNS COUNTER WITH INSTANT RESET, ADDS AND SUBTRACTS LARGE EASILY READ FIGURES. RECORDS UP TO 100,000 TURNS 3. ALUMINIUM HEADSTOCK FITTED WITH PRE- a CISION BRONZE BEARINGS. ALL GEARING TOTALLY ENCLOSED, OUTSIDE OILING TO ALL BEARINGS 4. QUICK RELEASE TAILSTOCK WITH BALL THRUST LIVE CENTRE 5. NON- REVERSING TOGGLE CLUTCH WITH MACHINES AVAILABLE FOR EARLY DELIVERY INSTANT RELEASE 6. SMOOTH AND EFFORTLESS IN OPERATION KOLECTRIC LTD., 20, AVONMORE RD., LONDON, W14 V

www.americanradiohistory.com 52 Advertisements W'ireleaa World October, 194;

METERS at PRICES BELOW IP PRESENT DAY COST

Panel- mounting moving-coil meter illustrated is in Black Bakelite case, 214" I t ". 0 -40 volts.

Also available are : Voltmeter Milliammeter

,, I 0-75 M.A. 21/4" x l'iz 0 -20 Volts. I ;;;" Voltmeter Ammeter 21 "" x 17s" 50 -0 -50 Amp. 2! -8" x I !.2" 0 -600 Volts. Milliammeter Oil Pressure Gauge 0- 1601bs. 3" x 11/4" 0 -50 M.A. 214" >- 2',"

Illustrated folder and trade prices on application to : PIFCO LTD. PIFCO HOUSE WATLING ST. MANCHESTER, 4

Denco Quality Electrical and General Accessories (Leicester) Ltd., have inadvertently manu- RADIO COMPONENTS, RECEIVERS. TELEVISION, ETC., FOR THE DIS- factured and sold Plugs which they have CRIMINATING BUYER. now discovered infringe certain Patents owned by British Mechanical Productions Watch for announcements of some new, interesting additions to our Ltd., and which are marketed by the latter range and enquire at our nearest Company under the trade mark CLIX. approved stockist for full details of our products. The matter has been settled by payment Receiver is our latest The DR20 of an agreed sum by way of damages. contribution to better radio enjoy- ment. A 6 valve (plus Magic Eye) Superhet with TEN wavebands, and Electrical and General Accessories band spread tuning of all shortwave (Leicester) Ltd. state that they have dis- broadcast bands. continued the manufacturing of the in- Specially designed for export and fringing articles, and that they have none suitable for use in any part of available for distribution. the world.

DENCO, OLD ROAD, CLACTON, ESSEX V

www.americanradiohistory.com October, 1947 Wireless World Advertisements 53

1817

The Probte mThe directional response characteristic of single unit loud- speakers is very pronounced at the higher audio frequ -ncies which are audible only in a comparatively narrow channel directly in front of the reproducer with a corresponding lack of intelligibility and brilliance elsewhere. Th s 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.

The Solution It is for such installations that the Vitavox Bitone Reproducer has been designed. High frequency reproduction in this 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 rag 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 wette; Model 620-20 watt". .Size: 4fMalik. 32"x 21 "x 20 ". Terminating Impedance : 7'S ohms. Filter Attenuation : 12 d.b. per octave. R. F. Distribution (appx): 60° x 40 °. RADIOLYMPIA MODEL 610 - £42 0 0 OCT. 1.11 MODEL 620 - £50 0 0 STAND No. 54 GRAND HALL VITAVOX LTD., WESTMORELAND ROAD, LONDON, N.W. 9. TEL t COLINDALE 8671 -3

TELÇONRF CABLES for all Television and Radio requirements CABLE CHARACTERISTICS CODE Zo CAPACITY ATTENUATION K25 300 4.6 /1 /4F At I Mc;'s ohms 0.15 db ,!I00 Ft. per foot IO 0.4 50 tt 1.0 Dimensions 0.44" x 0.09" TYPE : FLEXIBLE TELCOTHENE TRANSMISSION LINE Further details A of this and other R. F. Cables on application

THE TELEGRAPH CONSTRUCTION & MAINTENANCE CO. LTD. TELCON Founded

Head : 22 ST., 18641E.C.2. Tel : LONdon Wall 3141 Once OLD BROAD LONDON, Enquiries to TELCON WORKS, GREENWICH, S.E.IO. Tel : GREenwich 1040

www.americanradiohistory.com 54 Advertisements Wireless World October, i947 9a ecot& iitahePP-4pi For Amateur Radio Enthusiasts ! TRANSMITTING INDUCTANCES. Consisting of 21in. dia. ribbed Ceramic Former 5in. long, having 26 grooves. At present wound with haw: and v Oak blow 26 turns 14 SWG silver plated wire. With 5 plug ceramic sub -base 5 socket ceramic mounting base. Price 12/6 complete. BRAND NEW DIAPHRAGM ASSY., for "Parmeko" folded Horn The know -how in the manufacture of P.A. Speakers. (15 ohm speech coil as used on " Loud Hailer "equipment). A very useful spare. Price 5 -. TEST METER TYPE S. Consisting of 21in. dia. flush fitting 6 amp Thermo -coupled R.F. Meter in 2(in. x 4 {in. x 7in. enamelled steel box, pre -set pot., and "Pye " socket. In original manufacturers carton together with connecting lead consisting of length of (in. dia. co -ax fitted with " Pye " plug each end. Brand new. Price 17/6. exiny o EPICYCLIC DRIVES. Small back of panel mounting by 2 4BA Screws. COIL PICK-UPS (7 /16in. hole required in panel) complete with knob and pointer. Depth MOVING back of panel l } in., fin. dia. x (in. spindle. Price 2/6. ; l in. dia. Price 1/3. is the result of FLEXIBLE COUPLERS. Best quality NATIONAL JX100 5 -pin J Valve Sockets (Ceramic) Price 5/ -. long experience 2 -GANG Yaxley Type Ceramic Switches. 2 pole 4 -way, twice. Just the job for band switching Tx. Price 5/ -. and precision CLASS C WAVEMETER NO. 1. Small metal case, no valve but Price watch - making containing 1,000 kc Crystal. 10/ , POTENTIOMETERS. Wire- wound, 5 watt type with tin. dia. spindle. standards which 100 ohm, 2,000 ohm, 15,000 ohm, 25,000 ohm. Price 3/6 ea. DITTO, but pre -set type (Short }in. spindle with screw driver slot) give a finely con- 2,000 ohm, 5,000 ohm, 10,000 ohm, 50,000 ohm. Price 3'6 ea. structed instru- POTENTIOMETERS (Carbon) in stock. 5,000 ohm, 25,000 ohm, 50,000 ohm, 2 megohm. Price 3/6. Ditto, but midget type. 100,000 ohm, / -. ment the details megohm, I megohm, 2 megohm. Price2 500 OHM 50 Watt Pots, all ceramic insulation, Price 3/6. A beautiful job of which are shown for bias on audio stages. 2,000 OHM 50 Watt Pots. All ceramic insulation. All ceramic insulation, and winding in the sectional Price 5/.. 5,500 OHM 50 Watt Pots. protected by vitreous enamel. Complete with Knob and skirt. Price 7/6. diagram. POTENTIOMETERS. Large Slider type, .4 ohm, 25 amp. Ideal for Charger Boards, etc. Price 7/6. Ditto, but 8.5 ohm, 5 amp. Price 5 / , DE LUXE MODEL Robust design!''Accidental dropping on record L.F. CHOKES. Low resistance. No information available, but wound will not damage Pick -up Extremely low moment of inertia (80 milli- with 22 SWG enamelled wire, and would be O.K. for L.T. circuits or re- grams total weight of movement) Pure sine wave with no harmonic winding. Core size 2x2x2f¡in. Postage 1/- extra. Price1 / -. distortion Automatic needle or sapphire changing opens new fidelity CO -AX PLUGS AND SOCKETS. All brand new and unused. changer without in. co -ax cable field to the amateur Can be used with normal record Details and prices of Plugs complete with various lengths of l fear of damage. Price (without sapphire) E5.10.0, plus 24/6 P.T. will be supplied on request. PLUG -IN HEADS Available in both 48 HEAD, junior and De Luxe RADIOMART types to fit Collaro B RM NGHAM, and Garrard arms, thus providing easy change -over from Magnetic types. Input conversion may be required. (See our Technical Brochure.) Price 49/6, plus 11 /- P.T. Separate Ejector for De Luxe type,

30/10, plus 6/10 P.T. ;IIIIIIIIIIIIIIIIImIIIIlmmiillllit1119111111 III Sapphire Needle with specially tapered shank, 15/3 (incl. P.T.) PRE -AMPLIFIERS having an inverse of the recording characteristic incorporated are available for use with pick-ups. These are necessary with some amplifiers. Price complete with valve and input Transformer, See the full range of E6.1.0. Announcing The NEW LEXINGTON TRIMMERS IS -WATT HIGH FIDELITY AND AMPLIFIER PADDERS Designed in our laboratories for use with our own Pick -ups, also including latest miniature type; as an Audio -channel for high quality local station radio feeder units. AT RADIOLYMPIA The amplifier is available NO. completely constructed or the STAND 1111, necessary circuit diagrams and technical details can be supplied to technical amateurs who prefer to do their own construction. In addition technical details and circuit are also available showing the construction of a high quality RADIO FEEDER UNIT incorporating local stations and television sound bands for use with the above amplifier, making a perfect combination for the connoisseur. Prices and details of the above will be sent upon request. This service is introduced at the request of the many satisfied users of our Pick -ups. Illustrated Technical Brochure upon request. ß Export and Trade Enquiries invited. TRANSMITTING HANWAY WORKS NEAREST STATION TOTTENHAM COURT COOPER ROAD UNDERGROUND MANUFACTURING CO. SYDNEY S. BIRD & SONS, LTD. . R weI_` CAMBRIDGE ARTERIAL ROAD, ENFIELD, MIDDX. lrw+9 NMJ ó DOMINION HANWAY WORKS, " u 'Phone : Enfield 20712. 'Grams : Capacity, Enfield." ~ HANWAYST., LONDON,W.1 OXFORD STREET NEW.OXFORDSTREET 9779 1MARiNCtr Telephone ; MUSeum fTA. ICROSSI\\ ROAD SALES OFFICES -Top Floor

www.americanradiohistory.com (llulur, rq.ij reless World Advertisements 55

. \\\\\ 111.11111.11.11111111111111111111111111111111MIN ,o\á °\ °i r\ '; TRANSFORMERS , . ` `? á \o 4 j COILS AND CHOKES eZietesirlo

BE SURE TO VISIT OUR STAND NO.51, MAIN HALL

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

Quaidy Here's a feast for you. Our new 1948 Range caters for every purse and each model provides a new revela- tion in sound production.

RADIO SETS Reynolds " Quality Eight." N -valca 3 waveband superhet, twin chassis. Outstanding c:,biuet, bristling with new features. PRICE 34 GNS. Plus Tax. " Finest reproduction I have ever heard in a table REYNOLDS " MASTERPIECE " model."-Radio enthusiast with 27 years' experience. Also the "ALL-INDIA EIGHT." RADIOGRAM 10 -valve 3 wave superhet As above, but with entirely new tone specially designed for Indian conditions. Price on AMPLIFIER Model T40 circuit. 12ín. speaker, request. South African and 10 watts output. Musical reproduction is Australian models also amazing. You available. Export Our famous 140 now in use every- must hear this I prices on request. where. For details see previous issues or write. "It's unbelievable. " -Symphony Orchestra Conductor. PRICE 115 GNS. Plus Taz. REYNOLDS CONCERT GRAND AMPLIFIER The ultimate in sound reproduc- Model TI2 tion. 16 valves, twin 12ín. speakers, auto - record changer for The smartest AC /DC 30 mixed l0in. /12in. records, plays Amplifier on the both sides, featuring ultra -sonic market. Outstand- reproduction, 40 watts output. ing performance, 10 "This is not Radio, it's the real watts output. thing. " -Everyone who has heard it. PRICE 395 gns. PRICE 18 GNS.

REYNOLDS UNIVERSAL MANUFACTURING CO., LTD., 410, DUDLEY ROAD, EDGBASTON, BIRM INGHAM, 16 V EXPORT AND TRADE ENQUIRIES WELCOMED Telephone : SMEthwick 0201

www.americanradiohistory.com October, 1947 56 Advertise_i.erts Wireless World

KNOBS D/ LS 6 POINTERS L P A I N/ T 0 N / / °NORTUAM PION

PAINTON & CO LTD KIN 3STNORPE i NORTHAM?TON Telephone Ncrthomp/on 2820 Tc/e9ron78Ceif1VOrthamplsn

/%/ /O /// %// // / / / / / // / / // / / / // % /// /? J/'. /// ///// /// ///%// %/ /O /// ////O / ///'/ %/ // O /O ' r /////9//// .a/9/ , //d 90 .. /. SYLMAR RADIO LTD. r5/ are now distributors of 40/ iaiairaaiaiaoiari / / id /a//ai /',' T.R.E.L. PRODUCTS 113, CHARING CROSS ROAD, (Tolworth Radio & Electrics Ltd.) LONDON, W.C.2 SUPERHET TUNING UNIT. 16 -50, 200 -550, 1,000-2,000 m Consisting of 2 -gang Condenser, Silver Screen Dial, printed in blue, Drive, IFs., Coils, etc. Completely wired and aligned on Broadcast signals. Price. with circuit, E5 Ss. Od. Obtainable through Retailers. The VIBRATOR PACKS. 12 volt Input, 210r. 70 mA. out- Wired for 6KM put consisting of Input Smoothing, TAYLOR & 6K7 Valves. Vibrator, Transformer, Rectifier, Speciale to and two 20 - mfd. Conds., etc. order. Size 8 ¡in. x 3)in. x4kin. Limited quantity only, 32/6. JUNIOR NOW IN PRODUCTION. MODEL 120A The inexpensiveT.R.F. Battery Receiver, retailing at E7/17/6, Plus Tax El /15/-. - A REAL ALSO 5 Valve AC /DC Med. and Long Wave Midget, in Handsome UNIVERSAL Bakelite Cabinet. Latest Super- het. circuit. Excellent per- METER formance and superb quality. LI0/I0 / -, Plus Tax £2/6/8. SPECIFICATION Packs. Complete 3 -Wave Coil Ranges with trimmers and wavechange 21 GET OUR QUOTATION for all switch, 30/ -. Sensitivity ; 3,000 ohms pee volt D.C. and A.C. --, ooiuirements. T.R.F. Coils, Medium and Long wave. Complete with circuit, Measures from 5 mV to 5,000 welcomed. 616 pair. P R I C E volts D.C. 0.2V to 0,000 volta Retailer's Enquiries A.C. 20, A to 500 mA. D.C. : Coils. 3 Aer. and 3 Superhet 0.5 to 200,000 ohms with Phone : PROspect 6651. Osc. Set of 6, I2 / , internal battery. Sin. P.M. Loudspeakers, 17/6. £T -10 -0 Sise only 41' x at' x 1 15 10'. Ex -Govt. Surplus. Cond 0.1 mfd. 6d., 0.01 mfd. 6d., 10 for particulars of full mage of mfd. 450 v. Z9, X5 mfd. 25 v. 1,19, 50 mfd. 12 v. 1/9. Valveholders, Write Octal 6d., Mazda type 4d. Resistances, all values 2/6 doz. Radio, Television, Electronic, Electrical inetromente and component., ROAD, M. ALLEN (Radio), Ltd., 113, Charing Cross Road, SYLMAR RADIO LTD. t97 RICHMOND, URREY London, W.C.2. Tel.: Gerrard 8734

www.americanradiohistory.com October, r947 Wireless World Advertisements 57

' Zr

1°QA\\\` °,\ .,..A.\

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. 5,N , r3F(;,,aMOZART I We are confident that for ease of control and absolute fidelity of reproduction these models will be found to AG* have no equals -that, in fact, you will pronounce them THEM ß to be `technically outstanding'. A\ x , 414/VE'g

SOBELL MODEL 516 We can't, of course. T.G. TABLE Not just like that. But RADIOGRAM Monobult we do say that if you Takers use Truvox Equipment with amplifiers of com- parable quality you Pater will Roll top gives easy access to Speakers get realism as dramatic gramophone turntable. The receiver is a 5 -valve as if the composer were super -het. operating from 200/250 volts, 4o /zoo cycles per second indeed conducting A.C. supply. Wave range : 16 -5o metres; 193 again. -577 metres; 800 -z, 140 metres. New Truvox loud- speakers, new gramo- phone pick -ups, results SOBELL Cabinet Speakers of years of specialist MODEL 717 endeavour will be 7-VALVE shown for the first time RECEIVER High at Radiolympia on Fidelity Piekups Stand 81. We hope that you will see them there, but if you can- Built with a push -pull not, a postcard will output stage giving 8 watts bring satisfying litera- P.A. undistorted output. Incorporates a IO" Equip- atu re. ment loudspeaker. Covers long, medium and two short wave h ranges. Voltages as for 516 T.G. TRUVOX ENGINEERING CO. LTD. RADIO Exhibition Grounds Wembley Middx.

TWO YEARS' FREE ALL -IN SERVICE IN THE HOME Advt. of Sobel' Industries Ltd., Langley Park, near Slough, Bucks.

www.americanradiohistory.com 58 Advertisements Wireless World October, 1947

H.P. RADIO SERVICES LTD.

Manufacturers of LOUDSPEAKERS LAMINATIONS

A IRMA S TER" 5 -valve 4- vavebund AC SCREENS SUPERHET CHASSIS AND LOUDSPEAKER In Dimensions 14," .: 8" x 3 ". Highly finished in Cream RADIOM ETAL Cellulose. zoo -25o volts. AC Mains 4o /too cycles. Wave- bands 12-30m., 30-60m., 200- 550m., 900- 2,000m. Speaker 8" High Grade Moving Coil PM. Power Output 4, watts. PERM ALLOY Mains consumption 6o watts. Pickup sockets. Extra LS sockets. Wide range tone control. Highly selective. Very sensitive. Ideal for incorporating in Radiogram. Dial SILICON ALLOYS dimensions 8," x 5i" edge lit. Price .. £17.12.0 Large Art Photographs available to genuine enquirers. ELECTRICAL SOUND & TELEVISION PATENTS LTD. 12, Pembroke Street, London, N.1. Terminus 4355 2 4, Manor Way, Boreham Wood, Herts Elstree 2138

BALL DRIVE to -watt AUDIO AMPLIFIER. Dimensions 94"x 6f". Overall height 6, ". Two Channel Input. Tone SMOOTH, RELIABLE & VERY POWERFUL Control. Heavy duty Output Transformer matched to 3, 8 Epicyclic friction drive, ratio 6 : t and 15 ohms. Valves EF36, 5Z4, KT66. Intended for the record enthusiast. Highest possible efficiency, overall May be used to increase ratios on other drives or Eminently gain, stability and equality of reproduction. spindle (i" shaft). suitable for Concert Work, booster amplifier, standby fcr attached direct to component amateur transmitters, paging system, etc. PRICE 3/3 RETAIL Amazing value. Price Large Art Photographs available to genuine enquirers.

SAFE DELIVERY AND COMPLETE JACKSON SATISFACTION ALWAYS GUARANTEED BROS (LONDON) LIMITED KINGSWAY WADDON SURREY 55, County Rd., Walton, Liverpool, 4 TELEPHONE: TELEGRAMS: WALFILCO, Tel.: Aintree 1445 CROYDON 2754.5 PHONE, LONDON

www.americanradiohistory.com October, T947 Wireless World Advertisements gg

Sound linde rstandtng

A portable Beat frequency Oscillator of outstanding merit, widely used by all the leading government and indus- trial laboratories. Range : 0 -16000 c.p.s. Output : 0.5 watts. Weight : 30 lbs. Total Harmonic Distortion : Less than 1% at full output. Output impedance : 600 ohms. Calibration accuracy: 1% or 2 cycles, whichever is the greater. Vernier Precision dials and built in output meter 0-20 volts. Suitable for use in sub -tropical climates ; very stable under reason- ably constant ambient temperature conditions. Meet us at Radiolympia !National Hall)

PRECISION

BUILT

INSTRUMENTS BIRMINGHAM SOUND REPRODUCERS LTD. CLAREMONT WORKS: OLD HILL, STAFFS. PHONE: CRADLEY HEATH 6212/3 LONDON OFFICE: 115 GOWER STREET, W.C.I. PHONE: EUSTON 7515

NI-W. 72

/l=

Superspeed Special Rosin Cored Solder is essential to the Radio and Electrical trades because - I. Chemically activated rosin core ensures correct degree of "wetting" and spreading. 2. Increased fluidity accelerates production. 3. Allows more mtPderate soldering iron -bit temperatures and minimises the risk of physical damage and alteration to the electrical values of small pre - erspeed calibrated components, such as capacitors, resistors, coil windings, etc. 4. Ensures complete mechanical bonding of joint metals, maintaining perfect SPEC /AL 1 electrical conductivity. 5. Reduces to a minimum the solder required per joint and cuts down waste. 6. Residue is non -corrosive, solidifies to a semi -transparent film of high electrical insulation value, is non- hygroscopic and unaffected under tropical ROSIN CORED SOLDER conditions. 7. The heating of the activated rosin core does not cause any deleterious Sole Manufacturers: fume deposits or unpleasant odour. H. J. ENTHOVEN & SONS LIMITED, 230 THORNTON ROAD, WEST CROYDON, SURREY Telephone: THOrnton Heath 2462

www.americanradiohistory.com bo Advertisements Wirelr.ss World October, 1947 % ALLANDER

MODE L 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 -inch traverse-magic eye and 2 -gear control. Instant unerring selection of the required range. Automatic volume control frequency 5 -VALVE ALL -WAVE SUPERHET and an I F trap are incorporated in the circuit. Sockets are provided for gramophone pick -up FOR A/C MAINS -MODEL A.410 and extension speaker. Guaranteed for one year from date of purchase. PRICE 22 GUINEAS (Plus Purchase Tax -L4 - 19 - 4) DC /AC Model shortly available. (AN ALL -SCOTTISH PRODUCT) r

_, =,,.._ RADIOLYMPIA ALLANDER OCT. III

GLASGOW, S.E., SCOTLAND ALLANDER INDUSTRIES LIMITED, AVENUE STREET, BRIDGETON,

2000

BRIERLEY -RIBBON" AND "ARMATURE" PICKUPS

Government surplus Loud- speakers manufactured by the undermentioned firms, now being offered for sale at reduced prices, are of non- standard type, designed for RIBBON TYPE ARMATURE TYPE Services purposes and Fixed point pressure of . oz. Fixed point pressure of } oz. Output Voltage 10 to 5 mV. Output Voltage I to Iv. conditions. No spares are Price in U.K. £8 16s. 10d. Price in U.K. £7 10s. 8d. including special mumetal screened including mumetal screened trans- available and no repairs can transformer and Purchase Tax. former and Purchase Tax. Floating Element " design prevents any tone arm resonances. be undertaken. Permanent Point will play 10,000 to 20,000 records and will not be damaged by cracked records or careless handling. Quality of Reproduction. This cannot be stated easily in specifica- tion data, but both Pickups -particularly the ' Ribbon " type -are far superior to any type hitherto available. We recommend how- ever, that direct comparison be made whenever possible. VITAVOX RESLO Demonstration Centres are being arranged. At present they may London, W.I. Messrs. be heard at Webbs Radio, Soho Street, U Rawlinsons, 2 Caunce Street, Blackpool (Voigt speaker used here). VITAVOX LTD., RESLOSO ND LTD., Amplifiers, Pre -amplifiers and Low Pass Filters available. Full Westmoreland Road, 359, City Road, information on any product sent on request. London, N.W.9 London, E.C.I

1. H. BRIERLEY LTD., 46 Tithebarn Street, LIVERPOOL, 2 Tel.: Colindale 8671 -2 -3 Tel.: Terminus 1140

www.americanradiohistory.com October, 1947 W irelcss World Advertisements 61 Delivering th got is durit g ItADI®LYMPIA It is our experience that Radiolympia does not provide ideal aural conditions ; you can look but you cannot usually listen to the best advantage. Therefore, we respectfully suggest you look by all means at anything and everything, but listen to really amazing reproduction, at a reasonable price, at your nearest Sound Sales agent ; alternatively, you will be more than welcome at our London office and showrooms. In the meantime, the enormous order book from Home and Overseas necessitates every available moment being devoted to production. AUTOMATIC CHANGER POLYPHONIC RADIOGRAM

E94 I7s, 6d , plus Purchase Tax. NON -AUTOMATIC POLYPHONIC RADIOGRAM

E77 I2s. 6d , p'us Purchase Tax. PHASE INVERTER SPEAKER E14 7s. 6d

OVERSEAS STOCKISTS Zo tt nb %Rtes South Africa: S. Machani:k & Co., 58 Strand Scre at, ttb. Capetown. 57, St. Martin's Lane, W.C.2. (Temple Bar 4284) Kenya: Campling Bros. & Vanderwal Ltd., Salisbury Road, Nairc bi. Works : Farnham, Surrey. (Farnham 6461/2/3).

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

ALL - BRITISH VIBRATORS

NO. S-PO Py coCa `, e\ o` SOO o` 450 tece\e a R`e a teke ßOe\GP

c cr ac C c`l Qool agas Wimbledon Engineering is a the first British firm to devote its resources to the design and manufacture of Vibrators, and the careful investigation of their growing 1 ' applications. If you have a problem which may involve the use of Vibrators, we shall be glad to put our specialised knowledge at your disposal. WIMBLEDON ENGINEERING LIMITED GARTH ROAD LOWER MORDEN SURREY TELEPHONE : DER WENT 4814 5010.

CRC i

www.americanradiohistory.com 62 Advertisements Wireless World October, 1947

et

INST3U1w1ENT.' 1CKWOOD but NOT The newest addition to the - Advance - range of Laboratory" Signal Generators places an instrument of labors- íß#tì tory class within the financial scope of every radio Price ! service engineer and experimenter. The discerning engineer will appreciate its accuracy and stability, its exceptionally wide which covers all frequencies required for radio and television receivers, and its accurate attenuating system which enables sensitivity measurements to be made on highly sensitive receivers up to 60 Mc /a. Send for fully deacrptive pamphlet.

Range: 100 Kc /s-60 Mch on fundamentals (up to 120 Mc/h on Second Harmonic). Accuracy

Guaranteed within ± 1 Attenuation: Constant im pedance system embodying u matched 75 obme transmission ne. Stray Field: Less than 3 microvolts at 60 megacycles. `, Illuminated Dial: :1 Total scale length 30' Power Supply: 110 -210- 230 -250 volts. Dimensions: 13' X IO1'x 72' deep Weight: 15 lbs. The New

The " Aristocrat " Planned for the connoisseur requiring a high quality cabinet suitable for a quality receiver. ADVANCE COMPONENTS, LTD., Back Road, Shernhall Street, Walthamstow, As good as pre -war and embodying all that is London, E.17. Telephone : LARkswood 4366/7 best in British craftsmanship and design. For 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 A WIDE RANGE OF where possible.

Dimensions: Length, 40 in., Height, 32 in., Depth, 171 in. Capacity approx. 12 cu. ft. Weight, I cwt. approx. Concealed castors. Sloping baffle. Slag wool and felt lining. Felt lined lid. Ample OKERIN accommodation for large receiver and amplifier and heavy duty speaker. WAX DI-ELECTRICS Interviews by appointment only. Details and Prices ready November 1st, 1947 -created in our own laboratories and manufactured & CO. in our own works -supplies LOCKWOOD almost every requirement of Electrical HARROW, MIDDX. LOWLANDS ROAD, Industry. Grades have been designed Telephone : BYRon 3704 for operation under the most severe and varied conditions, and many are resistant to Resistors produced mould and fungus growth. by the cracked car- bon process remain Special types are evolved as new demands O stable to ± r% of arise, and technical discussion on manufac- initial value. turers' problems is welcomed. *Tolerance ± i% Telephone . Temple Bor 5927 +2 %f 5% L o w temperature ASTOR BOISSELIER co- efficient. O & LAWRENCE LTD Sales Dept.: Norfolk House, wyn nrróow resistor Norfolk Street, London, W.C.2 élWELWYN ELECTRICAL LABORATORIES LTD. Welwyn Garden City, Herts. Telephone : Welwyn Garden 38168. Y

www.americanradiohistory.com Uctobc°r. Wi reless World Advertisements 63

411R41e;i: C QUARTZ CRYSTAL UNITS FOR STABLE FREQUENCY GENERATION

FEATURES Low temperature coefficient -less than 2 in 10" per `C.

Patented nodal suspension. Mounted in vacuum ; V WIREMOUNTING BRITISH PATENT N °. 578290 performance independent of climatic conditions. Exceptionally high Q value. High stability. Small size, 3in. x ¡in. overall excluding pins. Fits standard minia-

the type ICF 200 unit illustrated above is representative of the wide ture deaf aid valve socket. rangeof 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 16 lines / Crams 9' Cab /es "Spark /ess , Manchester" Proprietors. THE GENERAL ELECTRIC CO. LTD. England.

GOOD LOOKS ... . GOOD LISTENING

TABLE MODEL '4756'

BRIEF SPECIFICATION 5 valve 6 waveband A.C. Superhet. Electrical Bandspreading on principal S.W. Bands. New design output circuit giving ex- ceptional wide frequency response. A f really outstanding receiver for Short Wave listeners who also appreciate '_ quality reproduction. Plus £4.18.11 Tax. £23 Ambassador RADIOLYMPIA SEE THE NEW AMBASSADORS -STAND NO. 114 GRAND HALL ANNEXE AMBASSADOR RADIO Works. HUTCHINSON LANE BRIGHOUSE YORKS

www.americanradiohistory.com 64 WIRELESS WORLD CLASSIFIED ADVERTISEMENTS October, 1947

Rate 6,'- for 2 Imes or less and 3- for every additional mains superhet receivers, 2 ew and 1 line or part thereof, average lines 5 -6 words. Box AC mw bands, brand new ex- factory; £15/10 Numbers, 2 words plus 1 -. Press Day : November 1947 ea; 6 %in P.M. speakers, new, boxed, 21/- ea; issue, first post Wednesday, October 8th. No responsibility lpartrf a Je flews Truvox microphones, 13/6 ea; volume controls, aooepted for errors. less switch, 1/6 ea. -Uncle Tom's Radio Cabin, 5, Seven Stars Court, Manchester, 4. [8427 finest amplifier I have yet heard; WARNING " Readers are warned that Government THE1 better than many at twice the price." - surplus This is a about components which may be offered for sale what satisfied customer states our amplifier, built to " W.W." (May issue) through our columns carry no manufacturer's design; quality parts only used, producing guarantee. Many of these components will have superb results; price £25/10; kits of parts can been designed for special purposes making them also be supplied; pre -amplifier, elec. motor and unsuitable for civilian use, or may have de- pick -up and 12in speaker extra.-Enquiries to teriorated as a result of the conditions under Radio Trades Manufacturing Co., Laurel which they have been stored. We cannot House, 141, Little Ealing Lane, W.5. Eal. undertake to deal with any complaints regarding 6962. [8331 any such components purchased. UNIVERSAL ELECTRONIC PRODUCTS, 36, Marylebone High St., London, W.1. NEW RECEIVERS AND AMPLIFIERS Tel. No. Wel 4058. Our U.E.7 amplifier is FOR sale, brand new Marconi U.S.W. signal designed for the connoisseur who requires generator, type T.F'. 390G, as delivered the best possible reproduction together with from Marconi, in full working order. -Apply the highest standards of workmanship and Box 2202. [8212 materials; 10 watts undistorted output from COMMUNICATION receivers. -As soon as 9 valves (triodes) in double push pull with civilian supplies recommence we shall be independent controls for treble and bass; we at your service. -A.C.B. Radio 44, W idmore invite you to hear this instrument demonstra- Rd., Bromley, Kent. [4528 ted; 26-d stamp for details. [8264 WO Defiant 6 -valve superhet chassis, wit h RECEIVERS, AMPLIFIERS -SECOND -HAND loin speakers, one Lowther dual H.Q. 88 L.F., pertet t, 55gns; B28/ ('11100, tuner.- Pioneer Films, 348, Gray's Inn Rd., AR.offers. -Box 2223. [8246 W.C.1. Terminus 7311. [8305 Till R.A.F. receivers, excellent condition, Ltd., announcement. -When 16 to 4,000 metres; £15. DEGALLIER'8,token imports American receivers is per- INDIVIDUAL DESIGN IN nearly new condition, realigned and cali- mitted we shall have these; information will be brated, guaranteed working order; £17/10. Cir- in this column when available, please watch PARTRIDGE Precision Built TRANS- cuit diagram and component value, 1/6 post free. future issues. [7541 FORMERS wound to suit individual CAN be supplied with output stage /power new 1947 model Hi -Fi units, requirements pack and loudspeaker; £27/10. AMPLIFIERS;with triple tone controls, built to custo- now incorporate :- FULLY modified, as follows, becomes an all mer's specification. - Broadcast & Acoustic Silver plated turret terminals giving round stiper set with high quality output. Equipment Co., Ltd., Broadcast House, Tomb - a low potential drop and carrying up D.F. parts removed, new front panel, bass and land, Norwich 26970. [6433 treble boost with separate tone controls, R.C. POCKET size, all -dry 51w receivers, 11i/2x to 15 amps. Adequate room on each coupled push -pull output (2- PX4s), gram in- 9i/4x1%in, brand new c/ w, 4 spare for easy soldering of several external put, other refinements, complete with loud- valves, 'phone and aerial, by Crosley's, speaker; £35. -Write for details. U.B.A., weight approx. 71b, price £7 each. - circuit wires. R1155s already purchased, modified and ser 201, Long Lane London, 8.E.1. Carbot, Ltd., Firm clamping of the laminations by viced and power packs supplied. -R.T.S., Ltd., HIFI, :Ltd. -May we send you details of 8, Gladstone Rd., Wimbledon, S.W.19. Tel. our latest " Hifi " quality amplifier, de- means of scientifically designed pres- Lib. 3303. [7003 signed for use with moving coil pick -ups and sure die -castings. receiver for sale, condition good; £65.- to satisfy the most discriminating of music AR88Paul's Radio, Nolton St., Bridgend, Glam lovers.-150, High St., Lye, Worcestershire. Interlocked fixing feet providing FOR sale. -AR88, brand new cond.; £60.- SANDRINGHAM " 2 -wave midget radio, alternative mounting. Sherwood, Queen's Proni., Douglas, I.o.M. " t..7 attractive moulded cabinet, in walnut, C100, recent model, perf. cond., spkr.; £65 cream or green £9/13/ 6, inc. tax; can'. Illustrated above is mounting style N or offers. -L$ Molesworth Ave., Coventry. paid; c.w.o. or .O.D.; s.a.e- catalogue other " DN " which can be employed if ALLICRAFTER Super Sky -Rider, 11- valve, lines. -Radio Unlimited, 16, Carnarvon Rd., XX gil. cond.; offers.-Haines, Laceby, Grimsby. l,eyton. [8205 desired on all components wound to C.It.100 late model, 12 valves, inc. noise announce the first in their amp- special requirements. limiter; offers £30; ¡Manchester).-Box NUPLANSlifier series, the all- triode 4 watt A.C. 2225. [8240 amplifier, highly sensitive, bass and treble con- receiver, 9 ' coils, spare valves, Xtal, trol.- Plans, details 2/6, from E. N. Bradley, HROS- meter, etc.; good condition; £50.- ' Whinnie Knows Escalls °' Cliff, Sennen, AVAILABLE STOCK Box 2531. [8289 Cornwall. S.a.e, for list of Testgear plans. EX -RADAR set, 5in e.s., c.r.t., 26 valves, A.C. -D.U. 3 -wave 5v superuet re- A comprehensive range of mains and 6H6, 681,77, 6SJ7, 100 kc /s, crystal; OSMORceivers, excellent reproduction and sen- £10. -Box 2526. audio components is now available [8271 sitivity, attractive cabinet, early delivery, EDDYSTONE 358X 90'kr -30mc, Xtal gate, as shipping waveband if required; write for from stock, and we can despatch new; £45. -19, Patten Rd., Wandsworth, literature; trade enquiries invited.- Morgan, small quantities of these per return. London, S.W.18. [8224 Osborne & Co. Ltd., Southview Rd., Wading- 7 it v 10 -160m communications RX xtal, ham, Surrey. [7286 We would stress that before ordering BFo a /eter, limiter, a.v.c., complete in SPECIAL offer for limited period only. you send for our list detailing these cabinet; £45. -Box 2030. [8165 " Banks " Fidelity 10 -watt 7 -valve ampli- amplifier, components. Our stock now covers WAT7' Cellaro turntable and fier mic. gram radio input A.C. mains, with 15 pickup. 12in Goodman's speaker in all valves and carrying case attractively finished almost all normal requirements, and cabinet; £25 lot. -Box 212. [7747 black crackle. A real bargain, £16/10 from by availing yourself of this service IIALLICRAFTERS 5.27, 27.8 to 143 rocs stock. -F.S.R , Ltd., 87a, Upper Richmond AM /FM 110 -230 volts, good condition; Rd., S.W.15. Putney 1665. [8248 you will save the inevitable delay in offers over £35. -Box 2209. [8227 'LT OLLEY'S RADIO STORES for latest the production of a special component. Comms. recurs., 5 waveband, £13/10; iZ high- fidelity radio and auto -radiograms, 1155 modified, £14/10; tested.- Ptppet. makes include Sound Sales Polyphonic The latest addition to this range is a Busketts Way, Ashurst, Southampton. Decola, R.I. Marconi, Ekco and Cossor, prices High Quality matching transformer receiver, accurately lined up and com- from 55gns; also large stock of full frequency R1155plete with power pack and loudspeaker range recordings.-285, Camberwell Rd., Lon- for moving coil pickups (available in a in separate don, S.E.5. Tel. Rod, 4988. cabinet; £16. -Box 2206. [8218 [8181 variety of ratios to suit any im- 01191 (similar AR88), new, complete with PARKER RADIO offer semi -midget 3 -wave- handbook; best offer over £50, or would band superhets and table model receivers, pedance pickups). Type 402 /PU exchange good radiogram. -Box 2033. [8174 housed in mahogany veneered cabinets; trade priced at 45/ -, employing mumetal PHILIPS communication receiver, and export enquiries invited; receivers manu- one RF, core, overall dimensions 2in. x tin. two IF, L /W, M ¡W, short 5.6 -18 m /es. factured to specification; meet us at Stand a.c, power pack, as new; offers. -Box 2028. 315 Radiolympia.- Parker Radio Manufac- x !tin. AM A.C. amplifier 25 watts, twin turing Co., 756. Harrow Rd.. N.W.10. [8270 Partridge Output Transformer, speakers, high-fidelity m/c mie. and 'AKER'S. -New 7 -valve ' Wireless World -, -t. ^ml. maker's offers. wound to the specification of Mr. guarantee; -Fin. 4065. Quality amplifier with tone control stage, " 8 " communication receiver, S. 8 watts push -pull triode output. price includes D. T. N. Williamson (Wireless World. TROPHYmeter, B.F.O., 1.3- 43mcs, ex. super Quality triple cone, 12in permanent cond.; May, 1947), E4 3s, Od. offers £15. -hill, 96; (folly St., Blackburn. magnet speaker, with large output transformer DDYST'ONE 358X 90ke to 31mcs, with and all valves; also as above but with 15 E power pack, in beautiful condition.- Offers watts tetrodo'output, ideal for realistic repro. to 2, Logie Rd., Causeway Head, Stirling. duction or public address; 21/d stamp for RADIO Te Abbey 2244 television receiver H.M.V. model parties., prices, etc.- Baker's Selhurst Radio. %Phone: 905, recently overhl'd by H.M.V., per- 75, Sussex Rd., S. Croydon- Croydon 4226. fect order; £50 or near. -Tel- Sanderstead SILVER DRAGON.- Aitnough we have not 3395 after 6.30 P.m. [8168 been able to secure stand space at Radio - 450A, 12- valve, 65 me /s, 550 lympia we certainly have the finest receiver HOWARDkc /s, Xtal first -class condition, new PARTRIDGE condensers, instructions; collect which will be available, 10m- 2,000m communi- alignment cations sensitivity, variable selectivity, band - Glasgow; offers. -Box 2529. [8286 spread, top and bass compensated controls, ex- LTD MOUNTED 50watt Savage amplifiers, pander, 10 watts P.P. output, exquisite cabinet TRANSFDR!NERS RACK-suitable relay service, transmitter mod., etc. work. -Details from The Moreton Chevnev Co.. 76-8, FRANCE, LONDON, S.W.1 factory installation, -Details from Adams Ltd., Darkhouse Lane, Coseley, Bilston, Staffs. PETTY Radio, Long Buckby, Rugby. [8037

www.americanradiohistory.com October, 1949 Wireless World Advertisements 65 TROPHY communication receiver (46mc SPECIAL a.c. 12v General Motors car radio, 9- 550kc) model, condition as new, Sonic Fine Investments! valve, 5 wavebands, including medium complete with speaker; £22 or near offers. and 4 short wave Macdonald, - with bandspread; 12 watts Fodderty Cotts.. Dingwall, Ross- MOTORS. Elertradis Micro output; one microvalve sensitivity; 5 press - shire. [8162 Motors for Instrument work button station selectors; best offer over £25. Walkie- talkie sets No. 38, short range and models tin. x -Apply Mr. Babani, Bernards (Publishers). 4 R/T communication, 3 complete and re- weight only 10 ozs. 12.24 Ltd., The Grampians, Western Gate, London, cently netted, in working order; 1 spare set, volts; work from dry cells or W.6. Shepherds Bush 2581. [8298 instruction supplied, £14 /10. -P. Brooke, The going abroad, disposing of 40 Temple, Goring, Berks. [8187 A.C. Mains through transformer, laminated ENGINEER, fields, ball bearings, watt amplifier with separate pack built .C.A.. AR88 comms. rec., 540 kc /s to 32 totally enclosed, small vee with pulley, centrifugal Partridge transformers and oil capaci- R 6 wavebands, BFO, 100 watts out- relay speed governor on shaft tors. 807 p.p. output, Lexington m/c pick -up put, L,S. terminals and 'phone jack, as new, removable for second shaft drive. Precision with 2 sapphires and input transformer, voltage 110 to 250v, in stages; highest offer to made ex W.D. stock. Worth 45/ , Price 2I /- B.-T.-11. 1947 12in speaker p.m. 100 valves Simpson, 40, Mowson Lane, Worrell, Sheffield. each. Limited stocks. inc. Acorn and U.H.F. p.a., valves only at HALLICRAFTER Sky me Champ, 31 /s, 500 BOAT MOTORS. 12 -volt D.C. work off three 60% list price; kit of components inc valves. kc /s, good condition, new, boxed, for 8 superhet; £20; 41 v. dry cells. Weight only 10 ozs., precision -valve must be sold within 3 Tx1154M, 4 -band, £7/5, R1155, new, 14/10; weeks with 25% price made, totally enclosed, as new, IS / -. reduction, -Box 2152. rot. trans., 12v input. 450v 70m /A and pro 30W amplifier (Partridge transformers, rata output, Hancock, Petre MOTORS. D.C. 230 -volt D.C. 1/12 h.p., 22/6.- 198, St., 1,500/2,000 r.p.m. etc 1, output 2.27; 500 Ferranti meter Sheffield, 4 [8293 shunt wound by Croydon, 150ma, pre -amp treble and base boost, turn HR.O., 4 coils, £45, Hammarlund, '6 25/ -. 1/40 h.p. 110 v. or 220 v., 17/6. 1/30 h.p. table a.c, in leather case. Marconi p.u, B.T.H bands, £35, each with separate 110e to 12 -volt with 4 -hole base plate, 75/-. mike. floor and table stands; screened ext 250v p.s.; T33 transmitter and 2.000v p.u., MOTORS A.C. 230 volts 1/3 h.p., 4,000 r.p.m., mike lead 60yis on reel; centre contact for £25; Lustaphone, 701 -; valves, etc.; s.a.e. 50 cycles, E9. I, 27 h.p. 230 volts A.C. /D.C., quirk connection. Speakers, 15ohm Bake', for details.- Nelson, 24, Kings College Rd.. 4,000 r.p.m., E3 IS. B.T.II.. Epoch. R.K.; 2 rect. units for field N.W.3. 1,20 h.p. 230 volts A.C./D.C., Primrose 4806, [8175 sewing machine type, square construction, excitation. Horns. Rect. 52inX 18inx72in, AC. 5 -valve 8 -watt push pull amplifiers, hex liar, '8inx50in. round 28inx34in: also enclosed with pulley, belt and bracket, E4 10. negative feedback, complete with large Murphy B25 converted to pentode o,p.; offers' multi -ratio output transformer, £9; ditto 10- MOTOR PUMPS. Lesdix 12 volts D.C. for -Meldrum, Stansted, Ex. 'l'el. Stansted 3341 watt 6V6, £10; a range of feeder units' caravan or bungalow ; lift 31t., throw loft., MORSE EQUIPMENT T.R.F. and superhet from £5 / 5. -R.T., 64. S,t. handle 100 gallons per hour, ES 10. 230 volts MORSE practice equipment for classroom or Leonard's Rd., London, S.W.17. [8253 A.C. Stuart Turner model, individual tuition; keys, audio oscillators radio and television re- 120 g.p.h., E6 6. and M.V. combined E7 10. Foot valve strainer, 21/.. for both batt. or main operation. -Webb's -1-1 ceiver, model 904.3 wavebands, ac 200/ Radio, 14, Soho St., W.I. Ger. 2089 [2291 50, perfect picture and sound reproduction, LABORATORY INSTRUMENTS. Portable NEW MAINS EQUIPMENT thoroughly overhauled by makers; sacrifice at Weston Substandards Model 155, A.C. ammeter mains transformers, chokes. £85; 350 mains and battery valves, 25grs. 100 amps zero adjuster, mirror scale, in polished VORTEXIONetc., are supplied to G.P.O., B.B.C., 1r 200 asstd. condensers, lengths /lmm sleeving, wood case 7in. x 61in. Model I multi -range D.C. L.P.T.B.; why not you? Wound to any speri other com- 0.00001- 32m1d, 500v, hundreds of voltmeter by Weston, 3 v. 150 v. 750 v. zero fication, prompt deliveries; imitated but tin ponents; send for lists. -E. A. Porritt, 13 adjuster, mirror scale, in carrying equalled. -Vortexion, Ltd., 257 -261, The Broad and 27, Rd., Forest Hill, S.E.23. case. Weston way, Wastdale Model I Ammeter 15 Wimbledon, London, S.W.19. Tel communication re- 3- -75-300 -1,000 mA 5 -15 -150 SPECIAL offer, Midget amps with external shunts liberty 2814/6242 -3. [8365 ceiver and power pack. M.C.R.1 5 -valve to match above Volt- TEST EQUIPMENT superhet., complete with aerial and earth meter. INSTRUMEN'T'S equipment, lightweight headphones, range WHEATSTONE BRIDGES. Ex- G.P,O., in 20 -3,000 metres, £9110; receiver P.109 with new condition, 200 ohms 3 -ratio arms MOST makes is stock, some on easy terms. receiver P.25 with 11 valves, and moving 24 valves, £10; coil galvo, flush panel type 25 -0 -25 on ebonite Write for details and proposal forms to The £5; C.R.T. units, microameters, milliameters Instrument Co., 244, Harrow panel 9in. X 63in., with leads and fitted in strong Rd., London, W.2 voltmeters, etc., very low prices; send fo- list; TAYLOR valve testei, model 45A. as new. - trade Wi'kinson, Wholesalers. 204, carrying case (bin. X 7kin. X 6in., with carrying supplied.- offers. -Box 2151. i 8202 Lower Addiscombe Rd.. Croydon. Add. 2027. handle, E6 10. Silmilar type without galvo, E5 S. D.C. SALE, Wee Megger, unused, in metal case, OVERWHELMING demand for some of our MOVING COIL BRIDGE GALVO. with leads; £5. -Box 2210. [8230 lines has caused delay in replying to ocr Flush panel, 2;; in., scaled, 25 -0 -25, new, 75//- each. FOR sale, Mullard Master testing set -D and has also cleared out some of customers GALVOS. D.C. moving coil suspension mirror Slade. Mount St.. Battle, Sussex. [8274 our disposal bargains; there are, however, still ALEC DAVIS. 8 Percy St., Tottenham galvo, reflecting type, by Tinsley, 100 ohms, a number of attractive items of appeal to the Court Rd., W.1, offers the following bar sensitivity 2.', micro amps I amateur enthusiast but remember stocks are per in. of scale at I gains;- - limited, so don't delay: R.A.F. radar ampli- metre, in polished wood case with glass front INDICATORS. -Type 62A, almost complete lier, model 1124, complete 6 -stage U.H.F. amp- door, E8 10. G.P.O. Linesman's Galvo, 25/ -. receiver for vision, £10: type 6A, £5; type lifier with 6 valves, 3 Westectors. 3 I.F. stages Vertical Testing Galvos, W.4889, £5; type 184A, with two tubes Sin 6 pre -set R.F. setting, makes an ideal base HAND MAGNETO GENERATORS, and 21/in, £6; test set type 74. wonderful for television or F /M, experiments. compo- output bargain. at £10. nents alone worth £10, our price, £4110 ea.; approx. 70 volts 25 m. A.C.A, perm. steel magnet wound armature WAVEMETERS. -Type APW.1095 covers class D. No. 1 wavemeter, a few left only, driven by gearing in handle, /s I0 /- ea. 3- magnet type 1,220/1.540 kr and 2,000/3,410 kris, in- complete with all spares and crystal check 12/6, postage I). extra. corporating 0 -100 micro-ammeter, £2115; type D., corn unit at £515; aerial couplers, type G.P.O. MAGNETO BELLS. APW.1252, mains driven, in copper lined case we have Two coils and plete, at £1115; R.A.F. dinghy sets, gongs 3/6. Postage 9d. 22/30 kc /s, with -'magic eye " indicator £5 a small quantity of these portable transmit- OSCILLATORS. -Type 37, mains driven, £6; ters, ideal for amateur field day work when B ELLS. Tangent I /C230 /250 volts A,C. 6in.gong, type 145, brand new, £5; type 231, 25/ -_ modified, hand driven generator gives 6 volts as new, 42/-. EX- GOVERNMENT aerial poles, made in two and 400 volts, 6J7 and 6v6 valves, neon in RELAYS. G.P.O. Relays for almost all purposes. sections length 14ft complete. fitted with alu- our price, 3 -stage amplifier dicator. £2/5; Send us your inquiries. Thermal delay relay minium base, bargain at 21/ -, carriage paid; panels for 1T4 type valves complete with con- attachment, 7/6. Mercury Relay motors densers. resistors and vol. control, can be made Tubes, " On -off," 12volt at 21/ -; 24 -volt motors at into midget portable by adding tuning device 5 amp, 7/6, postage I / -. 17/6, new; large selection of components and condensers; plugs and sockets, single- and (20/- worth of components). to clear at 7/6 FANS. D.C. Table Fans, 110 volts, 10in, blade multi -pin, coaxial for all requirements; all each; send stamp for complete bargain list; and guard, 45/ -. 12in. blade and guard, 55/.. Oscil- terms, cash with order or c.o.d. over £2. -- types cable and flex. [8156 lating pattern, 12in., 65/.. Wall Fans, I8in. blade, model 666H, 1,0000 volt, as new; Orders to Dept. W.W., Ariel Trust. Ltd., 188. 200/220 volts D.C., 740 Vanxh,'l Bridge Rd., London, S.W.1 [8106 r.p.m., 75/ -. TRIPLETToffers over £6. -15, Smirrells Rd., Bir- WESTERN Electric receivers, R1585. 12- TRANSFORMERS. Double wound 230 volts mingham, 28. - [8198 valve U.S.W. type. 34 -58 mes, seven to 12 v. 3 amps, 32/6. 230 volt to 20 v. 2 amps, new Thrush capacitance resistance 9001, three 6AK5, EBC33, 12A6 valves, 4 THEbridge, 2% accuracy, price 131,-ígns de- 30/ -. 230 volts to 4 v. C.T., 71 amps. 17/6. tails gladly supplied; from stock.-F,S.R., Ltd., R.F. stages, F.C. and ose., 2 I.F.s det and B .T.H. TRANSFORMERS. 200/230/250 volts and these sets are 87a. Upper Richmond Rd., S.W,15 Putney output, B.F.O. limiter- input, 2 volts 20 amps and 75 volts 6 amps, 15 taps converted for use as 6 or 12 volt car 1665. [8247 easily output, 65/ -. radio, or A.C. mains receivers, giving 6 me- WESTON analyser model E665, complete dium wave stations on selector switch (pre- B ATTERY CHARGERS. We have a large stock with valve adaptors, recent overhaul by selected); for 6 volt car radio 12A6 is re- of Chargers by leading makers, various sizes, metal makers, £11/10; Weston output meter, model 695, £3 Waverley Csockford Park Rd.. placed with 6V6GT; no other components or bulb rectification. Send us your inquiries. /10.- required except power unit and speaker; wiring Addiestone, Surrey. [8170 ran be modified in 30 minutes by most ama- TELEPHONES. Wall type constructors' parts, sale, model 7 Avo meter, A16 /10; uni. teurs, with full instructions how to convert. ex- G.P.O., comprising cabinet Bin. x bin. x 3in., FORversal Avo Minor, £6/10; Taylor 85B £5/5 ea.; speakers, 3i,4in or 61 ;:in. £1 ea.; 6 bracket mike, transformer and condenser, mag. signal generator, with dummy aerial, £13'10 volt or 12 volt or A.C. mains power unit, bell, switchhook and contacts, hand mag., ringer (all as new). -" Radiolert," 17. Laughton Rd.. £2 /5 ea.; 8 -valve U.H.F. receivers. I.3108. P.O. type receiver terminals and connection Dìnninglori, nr Sheffield, Yorks (Tel. Din. 30/- ea.: 12aivalve L3078, 35/- ea.; P.43A 11 pair. ningtan 337.) [8195 diagram, 35/- per G.P.O. Candlestick Tele- 1Q11.A.F. valve, 35/- ea.; receiver type 50A 14 valves, receiver and signal generators wavenieters. phone with cord, IS / -, postage 1;6. W1191Á 100 kcs -20 nags, crystal check £3 ea.; R.3601. 14 valves, £3/10; R3084, 14 inserts, valves, £3; L3585, 23 valves, £4; all con Spare mike 2/6 each. battery operated, 4 -valve 220TH HL2.2, PM2. meta with valves; s.a.e. for details; P.A. METAL BOXES. Ex -W.D. stock,9in. x 9in. X 8in. mod. 1,000 cps, in transit case, £7/10; U.S speaker units; P.M.M.C. 15 ohm handle 20 with 2 front fasteners and loops for carrying Army v h.l. signal generators. I.E. 19A, 100. watt. £1 ea., less horn; 2 -gang condensers strap, plinth for panel, 12'6. 156 nies, crystal or M.O., inc. f a meter, bat- 0.0003 or 0.00015, 4/6 ea,; 3- gang, 0.00015 tery box, 3 9003, 2 9002, 1 155, 2 0.1 m.a 5/ -; 9 -way Yaxley switches, 1/6 ea., 12/- doz.; Please include postage for mail orders, meters, new in transit case, £7; radar wave. rotary converters, 12 volt D.C.. 275 volt 110 meters, 180 -260 kes an 200 -250. with rect., ma, 500 volt 50 ma, complete in case with 6,15. Y63, EA50, £315; smaller version, smoothing, £1 ea.; numerous components and £2 10; Monitor units, would convert to score Government surplus radio, etc.- send for list; ELECTRADIX RADIOS «ü It tube, trans, T.B. valves, £3/10; similar a e. pease: menial terms to dealers. -H. Eng- 214, Queenstown Road, London, S.W.8 but 80v 1,000 a /s, £2/5. lish, The Maltings. Rav'eigh Rd. Hutton. ,JAMES W. GRAHAM, M.1 R f': Radio Engi- Brentwood, Essex. 'l'el. Brentwood 1685. [8126 Telephone: MACaulay 2159 neer. 98. South SL. Perth. 18177

www.americanradiohistory.com 66 Advertisements Wireless World October, 1947

WEE-MEGGERS, brand new, ex Govt., 250 - volt complete in leather case; list price RADIO £12. our price, £8, post free. -Auto Collections, -COULPHONE HENRY'S W.4. " The Return of Post Mail Order Service," Ltd. 126, St. Albans Av., Bedford Park, 58 DERBY STREET, ORMSKIRK, LANCS. LF. UNITS. Comprising 1T4 Valve with holder, Tel. Chiswick 1601. Taylor Bridge, 'Phone : Ormildrk 496. Midget iron-cored I.F. 465 N.C.'s, Condensers and AVO oscillator, £11/10; : Ormekirk baffle, Telegrams Coniphona, Resistors. All in midget aluminium can. New. £12/10; as new. R.K. speaker, NEW GOODS ONLY. 15/- cacti. rectifier, £4/10- Selenium rectifier for speaker -up. C.W.O. or C.O.D. Post Free over 5 /-. B,F.O. UNIT. Comprising 185, with holder, Midget field, 10 / -; E.M.I. hypersensitive pick MAINS TRANSFORMERS B.F.O. In can, Condensers and Resistors. Al in £3/15; 500 volt precision megger, £7/10; PRIMARIES for 200/30/50 volts. Universal 4, ti and midget aluminium can. New. 12/6 each. Avo Minor (universal) in case; £6/10. -Box 6.3 v. L.T.'n. 300 -0.300 v. 60 rnA., 23/6 ; 350.0- ELECTROSTATIC VOLTMETERS, :lint scale, panel 2527. [8283 350 v. 100 mA., 28/6 ; 450 -0 -450 v. 200 MA. IOTA is the 4 8 4 v. 4 a. 4 v. 4 a., ; 450.0 - mounting, 0 -5,000 volts. £3 5s. SIGNAL generators. -Model v., a. C.T., C.T., 45/- precision job for service engineers; range 4b0 v. 200 m.4., 6.3 v. 4 a. C.T., 6.3 v. 4 a. C.T., Slow Motion Drives. MUIRHEAD 8/6. 100 kc /a to 50 me /s, individual calibration 6 v. 3 a., 45/- ; 450.0 -450 v. 200 mA., 6.3 v. 8 a. 3 EP/CYCLIC low Motion Drives, 6-1. 2/6. accuracy better than 1/, ; 12 months' guar- C.T., 4 v. 2 a. C,T -, 4 v, 2 a. C.T., 6 v. a., 47/6 ; 1,250 -1,000 -760.0- 750' 1,000.7,260 v. 300 mA. (no BULGIN Jack Sockets. 1/9. antee, H.P. terms available; write illustrative leaflet as below; price £12/12. Servicometer, L.T.$), 112/6 ; 4 or 6.3 v. 6 a. C,T, (Filament), 17 /6 BULGIN Pilot Indicators. 1/9. Model 1212, the new instrument for all radio Auto (Filament), 4v. to 6.2v. 4a. (or vice versa) 13'6 BULGIN Signal lamp Indicators. 2/6. engineers, speedily locates faults, hum, dis- SMOOTHING CHORES VALVES BVA and CAR RADIO Trans. 6 v. snail type. 12,6. tortion, etc., measures inductance tuning 16 H. 40 mA. 360 ohm., 6/ -. coils, measures capacitance, checks aerial, 20 H. 60 mA. 425 ohm., 6// -. TUNOSRAM PLUG SUPPRESSORS, 1/6.: Dynamo Cond., 3/6. earth installations for efficiency; H.P. terms 15 H. 90 mA. 240 ohm., 7/ -. SENT C.O.D. ELECTROLYTICS. 8 mid. 350 v.w., 3/8 ; 8 mid. available; write as below; price £13/17/6. 20 H. 100 mA. 425 ohm., 12/6. 600 v.w., 8 x 8 mid. 500 v.w., ; 16 mid. 20 H. 200 mA. 150 ohm 21/6. 4/- ; 6/- Instrument cases : 20 different new types 500 v.w., 5/- ' 16 x 8 mid. 500 v.w., 9/. 16 x 16 mid. and sizes available, all finished black crys- 30 H. 200 mA. 360 ohm., 25/ -. 350 v., 7/6 : 25 x 25, 2/ -. Best makes. Not surplus. tonne enamel, complete with handle and OUTPUT TRANSFORMERS HEADPHONES, movie; coil, 100 ohm with plug. pr, panel; prices from 7/6 to 35/6, see below. Midget Power Pen., 6/8. Std. Univ., with C.T., 7/6. Large Univi., with C.T., Heavy Duty Univ.. 7/6. Design calibration repair : We can undertake 12/6. for 3, 8 and Heavy Duty, THROAT MICROPHONES moving coil, pr. 7/6. any work applicable to test equipment and 150., 22/6. Extra 37/6. pro- SPECIAL (to author's specification), for quality BULGIN Midget Intervalve Trans., 4 -1, 4/6. necessary to service maintenance, factory amplifier, described in April and May issues of 4 -pole 8-way switches, small, 4/6. duction, medical requirements, etc.-Radio "The Wirleess World," 67/6. 2 -pole 2 -way switches, small, 2/6. Development Co., Moretonhampstead, Devon. COILS, COIL PACKS, ete. . HFRANKS, 58, New Oxford St., W.C.1. TYPES OF ENGLISH ANI) AMERICAN WEYMOUTH TRY. COILS M. and L., with cet, ALL Mus. 9594.-Offers the following pair 9/6. " P " Type, 2/9 ea. VALVES IN STOCK, INCLUDING 185, IT4, 384, only, ac main - G.T. equipment to callers comprising SUPERHET 3 W.B., with cot., 405 ko/e., pair 11/6. 3Q5, 6A7, 25A60, 25Z6, 35Z5. 52K7, 955, U17, driven oscillators, type 37, 22 to 70mc /s, com- 00IL PACKS. Completely aligned, 36/6. MX40, 6.17, MKT4, 5 -pin and 1R5, eta., eta., at B.O.T. WEYMOUTH plete with 6 valves, 807 valve in output stage 138 TUNING (FEEDER) UNIT. With R.F. stage. prices. and milliammeter in output circuit; receiving Completely aligned, station named scale, £9 15s. units, type 69; C.R. power units, type 526; I.F. TRANSFORMERS. Midget, 18/9 pr. Standard. performance meters, type 53874; at mains 15/-pr. 2-GANG CONDENSERS. .0005 L /T'r. It will pay you to send ror our Liss. wavemeters, type W1252; battery wavemeters, J.H. MIDGET type W1095; receivers, type 1147; ac mains 11/6 ; W /Tr.,12,'6. 3 -gang LITr.,16 /6. power packs for 1147; receivers 3132; indica- KITS. 5v. S /bet. 3 W.B., A.C., £1210s. WITH ORDER or C.O.D. ( over El) CASH tor modulators, auto transformers; receivers, MUIRHEAD PRECISION REDUCTION DRIVES. TRADE SUPPLIED. 54 1, 12/6. J.B. Fall Vision, 8: 1, 12/8. type 76A; battery driven amplifiers, large SUNDRIES assortment of volt, amp and milliammeters, LINE CORD. .3 amp. 600 per ft., 2 w., 2/3 yd. ; neutralizing units with RF meters. metal rec- 3 w., 2/6 yd. P.B. Wire, 3d, yd. HENRY'S RADIO tifiers, relays, vibrator packs, inter -coin sets, MAINS DROPPERS. 3 a. 0000, 4/6 : 2 a. 1,0005? signal generators dc to ac converters; Brown's 43. CARBON RESISTORS (5052 to 5 M52). I u. 5, HARROW RD., W.2. A type headphones; E.M.I. cathode -ray tubes; 6d. i I w., Bd, 6 -valve receivers incorporating Clystron unit; EDDYSTONE SHORT WAVE GEAR. PAD 1008:9. ac power units suitable for 1155 receiver ; a ROMAC SUPER CAR RADIO. VIDOR PORTABLES. quantity of Lorenz transmitting gear, ideal Send Old. stamp for new 24-page Catalogue. for conversion. Sangamo synchronous motors, self -starting, 200 -250v ac 50 cy, consumption 25swatts, size 21yinx 2i¢ geared 1 rev 60 mins, can be reset to zero by friction drive from front or back shaft, %inxl /10in, to run clock- wweimmsmoNNI @RR] issesimm.. wise, ideal movements for making electric clocks, time switches, etc., nickel- plated finish, MIDLAND INSTRUMENT Co. price 22/6 ea; 12 to 1 dial trains to fit above sppindle, 2/6 per set extra; ChawithChamberlain and RECEIVERS. No. 18 SET, complete with four valves, Hookllam synchronous motors enclosed ready for use from 2 -volt L.T. and 120 -volt H.T. rotor, similar specification as Sangamo, con- supply. Superhet, range 6 to 9 mica, calibrated slow- sumption 3 watts, price 27/6 ea, complete with motion drive, with other controls, etc., suitable for 12 to 1 dial train, [8474 phones or small speaker, front panel 'Axe 94in. x Sin. rHANSMITTING EQUIPMENT An attractive receiver offered at a fraction of original NEW 1190 ex-R.A.F. TX covers, 160, 80, cost. 36/- poet free. 40, 20, complete with V.T. 31s (2); £75.- JONES PLUGS witn sockets to fit, 10 -way, 3/6 , 52 -way D. R. Metcalfe, Cambridge Rd. Dover 1124. 4 /6. A.m. trimming, etc.. tools. set of fom, 2/6. ,1_20.0 15 watt 'phone and CW trans- MOVING COIL METERS, high grade 0 -1 m /A., flush ntter. relay operated, 3-stage V.F.O., panel mtg., 3tin. dia, 25/ -. Moving coil meters, fitted 3stage band switched exciter, 80/ buffer thermocouple for R.F. 0.2 amp., to match above, 15/ -. doubler, 2 -35T's in P.Y., crystal mike, 6J7- Both meters brand new boxed. 6J5-2-6J5'a in P,P., 2 -6L6's in P.P., 2- TZ40's in EX-A.M. D.R. MASTER UNIT gyro compasses, P.P., H,R.O. with all band- spread coils; contains three motors, 24-v., one a convertor supplying best offer over £200. -Blake, 140, Broadway, A.C. current to the motor gyro, plus a wealth of other Leigh on-Sea. [8299 gear, cost over 550. condition as new. 705-. crate and A PAIR of new American ducal sectional carriage, 7/6 extra. MINOR' dia. aerial masts (or would make one 40ít). weight only 71b each, 20ít high, EX -GOVT. UNITS, fitted 11 vaivesVR65A (4), CV6 (21, INSULATION from ground and with copper VR67 (2), VR92 (2), VR54 (I), also relays, var. couds. TEST SET insulated 66ft 50 resistors and 40 condensers, coils, chokes, etc., doublet, halyards, guys, ground pegs, all made mounted on chassis 12in. x Sin, x 2iin., fitted louvred' Compact and inexpensive up complete and ready to erect, and finest cover, condition as new, 40/ -, earr. paid. without sacrificing accuracy and reliability. Weighs only quality; LS /15 per set.- IIarri o, Stroads, 31b. Height allows for full awing of generator handle. Berks. [8379 EX-A.M. POWER UNITS, type 667, fitted 11 valves, Pangbourne, (2), (2), 6X50 (1), (1), ÇV188 (2), Ranges up to 20 megohms 5011 volts. 5U4G 5Z40 6V60 NEW LOUDSPEAKERS CV173 (I), V11,91 (1), VU120 (1), also three trans- CONTINUITY quality, precision -built speakers, formers (80 -v. 2000 -cy.), four chokes, v- controls, high TESTER HIGHTiconal magnets, detachable dia- voltage condensera, resistors, etc., steel case, 12in. x Phis latest addition to phragms die -cast chassis, twin cone.- Broad- 12in. x 8115., weight 35 lbs., brand new, unused, 701-. the Record Ohmmeter cast & Acoustic Equipment Co., Ltd., Broad- catriags 5/- extra. range Is enclosed in a cast House, Tombland. Norwich 26970. [6435 loudspeakers provide NO. 19 A.B. VARIOMETERS, Includes variometer, moulded bkelite case of Duplex b m/A meter rectifier, 4-v. 10 m/A h/w rectifier, midget pleasing appearance. REXONAXthose qualities most sought after by en- 750 -ohm w/w v.control, .001 mid. 5000 -v. mica condo., Equipped with self -con- thusiasts of better sound reproduction.-Full knob and enclosed dial, etc., enclosed in metal case, tained dry battery. Speci- details and demonstrations from main distri- x 51h., weight 6 lbs., 5 / -, post 1 / -. ally designed test spikes butors, Lowther Mfg. Co., St. Mark's Rd., and leads con he supplied, Bromley, Kent. Tel. Ravensbourne 5225, 18413 ALARM UNITS, consists of high grade 2 -4 -v, belt also a"test and carry" LOUDSPEAKERS. SECOND -HAND VE55 valve, 2000 ohm relay, mains switch, 4 mid. case in which the instru- sonde., prey. switch, jack, westector, coils, resistors, HARTLEY -TURNER 215, pert., £7; output conde., etc., chassis med., enclosed In wood case, ment may be used with- transformer, 15,-. -Box 2207, [8220 out remov41. Ranges: - 64in. x Olin. x din., brand new boxed, 15/ -, poet 1 / -. 0/3 -0/30 ohms. 0 /30- T_TARTLEY- TURNER duode, 43 obma, with New August lists, 2d. with S.A.E. sill rectifier, Osborne, 30, Forester 0/300 ohms. O 500- £5.- no C.O.D. Ender 11,50,000 ohms. 0.1000- Road, Bath, [8223 Orden over 80 /- post paid, 20/- 0 /200,000 ohms. G.E.C. 10 -watt p.m. 15 -ohm units on 42in IMP RECORD ELECTRICAL 4 all -metal exponential horns; as new; CO., LTD.. offers. -Box 2226. 18242 Moorpool Circle, Birmingham, 17 8roadheath, Altrincham, Cheshire. HARTLEY- TURNER, energised, 2,000ohm Tel.: Altrincham 3221,2. Grams : "infusion," Altrincham. 20watt field, £3110.- Howard, 7, Berke- Tel.: HARborne 1308 or 2664 LONDON : 28, Victoria St., S. W.1. Phone: Abbey 5148. ley Square, Bristol, 8. [8251

www.americanradiohistory.com October, 1947 Wirrless World Advertisements 67 1OIJANTITY extra large magnet Rola loin 10066 speakers surplus. -Pioneer Films, 348. Gray's Inn Rd., W C.1. Terminus 7311. Sl3I1ND amplifying equipment, large amount Vou'ie SORE tri et it at of matched equipment, mainly Tannoy, detailed list on request.- Thompson, 25, West St., .Scunthorpe, Lines. [8250 FOR sale.- Hartley -Turner duode de luxe loudspeaker, mounted on large heavy baffle, with built -in field rectifier and out put transformer; price £15 complete. -Write 137, Longland Drive, N.20. Tel. Hil. 7556. VALVES RADIOGRAPHIC, LW., 66, Osborne St., Glasgow, C.1. Tel. Bell 3776. ESTABLISHED 25 'IMF_ TRANSMITTING valves: 866/866A, 27/6; 811. 35/ -; 814, 52/6; 100TH, £511916; 807, and you can be sure that you can DEPEND 12/6; PT15, 25/ -; rack mounted power packs; on it. 200,250v in, 6V5A 160v, 60ma out, £311916. ROTARY beam aerials, complete, £7/10, plus AVO METERS AND INSTRUMENTS 10 /- carriage; rotary transformers, Model No. 7 E19 10 0 etc smooth- Valve THE " FLUXI TE " QUINS AT WORK ing units, 4/11; 500kc crystals, 9/6; Pyrex Tester with Valve Data LI6 10 0 teed- through insulators, 2/6; multiple crystal Signal Generator E13 0 0 "These boxing bouts give me a pain holders, 9d each; R1155 last I.F. transformer. Universal "Avominor" E8 10 0 Listen! He's socked him again, 2/6 each. TAYLOR METERS. S.A.E. for list; extensive stocks of all types Model 70A, 50 Ranges, AC /DC EIO IO 0 Go on I Swing your of right ! .. radin equipment. -Radiographic, Ltd. " Junior " Model 120A, AC /DC, 1,000 ohm That's all for tonight, VALVES. -Send for monthly lists. -Valve Service, 11, Salisbury E7 10 0 Our set will need St., Pelaw- onTvne CONDENSERS. A few examples. FLUXITE that's plain, new RX and 'l'X valves CRTs mostly 2 gang .0005 with Trimm, 2(; I 120 American for sale by amateur, x 21 x } 12 6 3 Gang 6A('7, 6AB7, 807, 813, RK34, SUP1; s.a.e. for .0005 less Trimm, 3 }x3 }x2 IO 6 list. -Cobb, 34, Cbalkpit Lane, Dorking. 4 gang .0005 less Trimm, 5¡ x 3 x 2I 5 9 I.F. new and unused 955s 25/ -, 956s TRANSFORMERS. Others in stock. ACORNS27/6; Pye Midget, See that FLUXITE is Baby Q portable, £15/15; Wearite, 465 kit, Iron Core, pr., always by Philips mie microphone, with heavy chrome, 21 0 extending you in the house garage floor stand, £8. -Box 2150. [8201 Wearite, 465 k /c, Cap. Tuned, pr. 20 0 - - - VALVES. -1s your work held up tor valves, Denco, Midget, 1 -6 m /c, Iron Core, pr. 21 0 If so, we may be able to help you; we Service, 465 and 110 k /c, workshop have large stocks Cap. Tuned, pr. 12 6 - wherever speedy of all types available at list DENCO " MAXI Q" COILS. Poly- prices; send for monthly lists -- Scott's Valve Service tricot. styrene Formers, Iron Core, ranges 5 -10, soldering D), 14. Gardner . is needed. Used for St Brighton 9 -30, 20-68, 50-188, 167-727, LARGEST and most comprehensive range in 500-1760 metres, over 40 years in Government the country, British and U.S.A. types. at Chassis Mtg., Aerial, H.F., and Osc. 4/- each. Board of Trade prices; send for lists (valves WEARITE " P " COILS. All ranges works and by leading available), free, s.a.e.; valves sent c.o.d.; re available, Aerial, H.F. and Osc. ea. 3 0 engineers tailers not supplied. S WATT W /WOUND Variable Tapped RANSOM, and manufacturers. Bond St , Brighton. [7223 Resistance, 50, 100, 150, 200; 250 ohm Of all Iron - HOVE Valve Service. -We may be able to each I 9 help you with your radio valve MA1 NSTRANSFORMERS.A few examples mongers-in tins, 10d., 1/6 & 3/ -. troubles; many " liard to get " types in Woden, 250-0 -250 stock; give us a trial; mail orders v. 80 m /a, 6.3 v. 3 a., 5 v. 2 a. only; all 32 6 goods sent C.O.D. post paid. -54, Fallowfield Woden, Crescent, Hove 4, Sussex. [8190 350 -0 -350 v., 120 m ¡a, 6.3 v. 3 a., 5 v. FOR sale, gin television 2 a. 39 6 CRT, Mazda CRAM.. Varley, new, in sealed makers' cartons, £8115; 300-0 -300 v., 70 m /a, 6.3 v. 4 a, 5 v. 3 a. TO CYCLISTS ! Your wheels 2nd hand focus scanning and deflection roil 30 0 assemblies, £2/10; rubber masks, 15/ -.- A. Varley, 425 -0-425 v., I50 m, a, 6.3 v. (C.T.) will Gordon Galloway & Co., 120a, Mydrlleton Rd. 42.5v.3a.4v.(C.T.)4amp 0 NOT keep round and true Bowes Park, 55 London, N.22, Bowes Park 3472 Varley 350-0 -350 v. 200 m /a, 6.3 v. 5 a. 5 v unless the spokes are tied with DYNAMOS, MOTORS, ETC. 3 a., 4 v. (C.T.) 4 amp 52 6 ROTARIES, 110. 230 D.C. to 50 -250 A C., L.F. CHOKES. Some of many. 50c/ s 200w. fine wire at the crossings AND -25, Glenmore Rd., Birkenhead, Varley 3 Hny. Tapped Chokes 13 6 quantity capaeitator type; small Varley, 5 Hny. 50 ohm, 250 m/a SMALLmotors (new), surplus.-Pioneer 18 6 SOLDERED. This makes Films, Varley, 20 Hny., 250 ohm, 120 m/a 18 6 a much 348, Gray's Inn Rd., W.0.1. Terminus 7311. Brentford charging set, 15 Hny., 250 ohm, 60 m/a 6 6 consisting of lhp S /WAVE stronger wheel. It's simple-with PGTROLJ.A.P. engine coupled to 13- 32volt 20amp TUNING CONDENSERS. generator, complete with regulator, ammeter, Ceramic Insulation, suitable for ganging, FLUXITE -but IMPORTANT. cut -out, etc., £20; 12volt 100a.h. accumulator. I 00 pf., 4,6 ; 160 pf., 5/- ; 200 pf., 5/6 ; 15 pf., £5; carriage extra. -Box 2023. [8148 4/9 ; 50 pf., 2 9. chargers for home and export, ELECTROLYTIC COND. A few of BATTERY4 models, 2- 6 -12v, 1, 2, or 4amp do any many Capacities. mains voltage; generous trade terms. Write T.M.C., 8 mid. 450 volt, Canned for 4 0 catalogue. Tel. Hoddesdon 2659.-The Dubilier, 8 -8 mfd. 500 volt, Canned 6 o The FLUXITE puts Banner Electric Cd., Ltd., Hoddesdon, Herts. GUN GENERATORS: Dubilier, 8 -16 mfd. 500 volt,Canned 8 6 12v input, 250v output, T.M.C., 8 -16 mfd. 450 volt, Canned ideal car radios, 15/ -; 12v input, 275v 6 3 Dubilier, 16 mfd. 500 volt, Canned 6 6 FLUX ITE 100m.a. and 500v 50m.a. output, this can be T.M.C., 32 mid. 450 volt, Canned 5 9 reversed for 12v charging, £1 ; cases, aluminium where you want 8 ?1inx4'liri >lOin, with panel and chassis, 4/6; Hunts, 40 -40 mfd. 150 volt, Canned 7 0 Dubilier, 8 mfd. 500 volt, steel ditto, 8in x6in x10in, 3/6 ; condensers, "Drilitic" 4 0 it by a simple l6mfd, 250v, 1/9; 250mfd 12e, 1 /6; )mfd, 1/ -; A few Ex -Govt. Lines. all single hole fixing; heavy toggle switches, pressure. Price 1/3; 60m.a. h.t. chokes, 3!6; double wound Oil Filled Cond., .01 mfd. 4000 v. 2 0 l.t. chokes, 3/ -; 0.01 micas, 6d.; 5watt re- .03 mfd. 2500 v. I 6 sistors, 24, 30, and I mfd. 2500 v. 2 6 1 '6, or filled, 2/6. 60 100ohm, 9d.; meters, 31 /0ní 0- 1m.a., 30/ -; 2in, 0- 30m.a., 22/6; 21$in Mainsbridge Cond., .5 mfd. 1000 v 2 0 0- square, 0.5amp, thermo -couple, £1; . 31yin, .1 mfd. 5000 v. 5 9 ALL MECWANICS wfEL YE 0 -300v, M! I, 17/6; 12v relays, break 40amp. 8 mfd. 750 v. 6 9 bakelite cased, 2/6; heavy duty cut -outs, transformers, 4/ -; CHOKES IS Hny., IOO ohms, 300mfa 12 6 230e in, outputs 1,500v 10m.a., 9 Hny. 250 ohm, 120 mfa 7 9 2v 2amp, 400 x,400v 100m.a., 6.3v 7amp., D /SPACED 4v lamp, 4v 1.5amp, 5v 1.5amp, for television TRANSMITTING COND. or oscilloscope, 55/ -; other types in stock; Split Stator, Ceramic Mtgs., 150 pf. each Sector 4 headphones, 1 / 6 each; 230v d.c. 1 / 15hp 9 FLUXI motors, 30! -; 5/megohm v.c., 1/6 ea.; call or also .0002 mfd. D;spaced straight at I 9 send postage. -J. W. Hutchins, 29, Buxton Rd., R.I155 RECEIVER. 5 NM/ Bands co%ering IT SIMPLIFIES ALL SOLDERING Willesden Green. London, N.W.2. Willesden 16 to 4000 Metres, 10 Valves includes Magic 1533. 18137 Eye, R.F. Pre -selector stage, each set has GRAMOPHONE AND SOUND EQUIPMENT been thoroughly tested 15 gns. Write for Book on the ART OF " SOFT- CAPEHART auto. record changer, pert. or Power -pack and Output Stage ... E5 IO 0 SOLDERING and for Leaflets on CASE- der; £10. -1, Browning Way, Heston, Mx HARDENING Senior pick -up, new, with STOCK LIST now available, send 2.h stamp. STEEL and TEMPERING ROTFÌERMELlatest hi- fidelity cartridge, 50/-.-Hunt, TOOLS with FLUXITE. Price td. each. Stagsden, Bedford. [8200 and auto radiogram units, cabi- STERN RADIO LTD. FLUXITE LTD. SINGLEnets, chassis, amplifiers, speakers, pick- 115, FLEET STREET, E.C.4. ups, midgets, etc.; s.a.e. catalogue; trade in- W.W.), Bermondsey (Dept. Street, S.E.I quiries invited.-Radio Unlimited. 16, Car - Telephone: CENtral 5814 narvon Rd., Leyton. [8184

www.americanradiohistory.com October, 1949 68 Advertisements Wireless World 12 P.U. and transformer, 55/-; A.C. TYPEgram. motor, 200 -250v, £6/10; model THE LATEST 25 P.U., 30/-.-Box 2032. [8172 NEW Collard microgram, unused. in carton, coat E20/10/8, accept 16 gas-Win- wood. 12. Carnarvon Rd., Leyton [8206 Specialists VOIGT moving coil pick -up with diamond stylus; almost new; £14/10.- .Joseph Enock, Ltd., 273a, High St., Brentford. tone control and filter TRANSFORMERS,chokes for all " W.W." circuits. -R in Clark, 30, Langland Crescent Stanmore ddx Wor 5321 [7532 HAYNES quality radiogram, comprising 112 unit, 6 watt amplifier, Simpsons turn- table, Haynes speaker in oak cabinet. £55; 2046. HIGH POWER - HIGH QUALITY reason for selling moved to D.C. -Box TRANSLANTIC SIX, 3 -wave, 5 valve, radio- gram chassis with Bin energised speal-er; PICK -UP also Collard se gram unit with pick -up, auto - Permanent stop; £24. -Radio Unlimited. 16, Carnarvon With - Rd., Leyton. s.a.e. list. [7832 Jewel Point Sapphire CONSOLE radiogram cabinet in polished PUBLIC ADDRESS lJ mahogany by Camio, good condition. in- GOLDRING PRODUCTS cluding part radio set; £7/151 -; also modern walnut console type radiogram cabinet with INCLUDE: motor, good condition; £13/17/6. -Cle 4480 UNIVERSAL Convertogram, comprising PICK -UPS SYSTEMS Garrard A('/ DC mixed autochanger (loin and 12in any order), perfect condition, in console cabinet (walnut) with ample re- PICK -UP HEADS cord storage compartments; £21- -300, Higham Hill Rd., E,17. l.arkswood ?,25. 'DROVED supremacy! The new Felicity SOUND BOXES Senior cabinet speaker; clean bass e AMPLIFIERS sponse. Felicity 15 -watt amplifier resnonse 30 to 14,000 cps., 0.1 % distortion; matched for JEWEL POINT oil pick -up.- Details from : Felicity Sound from 150 W to IkW Reproduction. Ltd., 87a, Upper Richmond Rd.. SAPPHIRE NEEDLES S.IV.15. Putney 1665. [8249 tracking gear, Dralowid D.T.7 cutting V.G.bead, V.G. synchronous motor and turn- table, 78 230 A.C., in wooden case, as new; Meet us at Aeco recording motor and turntable, 33(1/3- 78 A.C. /D.C. Rothermel spherical sound cell RADIOLYM PIA microphone and socket, offers; few reground STAND No. 306 NAT. HALL GALL. sapphire Stylus, 12/6 each. -Box 2144. [8188 W. Bryan Savage Ltd Snund Recording Assoc. von BRITISHcovers all interests of the professional WESTMORELAND ROAD, LONDON, N.W.9 and amateur rerordine eneinee- and chart, ERWIN SCHARF reproduction enthusiast. Radiolympia edition 49 - 51a, DE BEAUVIOR ROAD, Telephone Cobndole 7131 of " The Sound Recording Journal," 2/8. post LONDON, N.) free. -Details of information bureau, meetings. publications and membership application form Telephone : CLISSOLD 7713 -0941 from 1lon. Secretary. BCM /BSRA, London. W.C.I. [7772 j[- QTARR quality : A new product and e 17 new standard of fidelity with the Starr sapphire stylus for miniature pick -ups. 1116 each, from leading London dealers; provincial G. L. PRODUCTS enquiries invited, samples c.o.d. direct. Starr AMAZING supply pick -ups and transformers plus sap- phires; " Connoisseur " plus. 90/ -: " Lev'ng- ton Junior " plus. 120/ : W. x- W " Coil," -: add -on eram units (H.M.V. Columbia. BARGAIN 152/ 4 etc.) plus from 12 "ns. Loudspeakers : Superior EX- GOVERNMENT (Truvox licence) Bin. 25/ -: various loin. 35/ -, 60 / -; Goodmans 12in, l'5/ -; in heavy mahog- any, 225/ -; Hartley, 180 Pullin Series 100 1% METRE 10 VALVE Universal meter. lOgns. Starr quality pro- gramme: Send 4d stamps for copy autumn bulletin and reprints technical articles.- Starr, SUPERHET UNITS 8, Dartmouth Park Ave., N.W.5. 18259 COMPONENTS -SECOND -HAND, SURPLUS Matt has it. VALUE! AC /IO chassis Twin input, 8 gns. Portable case amplifiers P.P. outputs. AC /18 Concert and SPECIAL offer : headphones with lead and jack plug. 5/6 per pair (boxed 2 pairs); recording Gram., 13 gns. AC /I8HG for Mic. speakers, P.M. (less trans.), 4in 17/6. 5in and Gram., 18w., IS gns. AC /25 Prof. Mic.and 15/6, 8in 22/6; output trans. to match 5/6 Gram. P.A., 25w., 18 gns. Write for "Sum- each; condensers, 0.1, 0.01, 9/- doz; 2, 4, 8, mary " leaflet illustrating and describing this GNS. 16mfd, 8 +8 canned, 6/6; 16mfd electrolytics popular range. (chassis mounting), 7/6 each; line cord. 0.3 LargerAmplifiers,for mic.,gram. and film, speakers 2 -way 1/6 per yd, 3 carriage paid amp (60 ohms pr. ft), and all P.A. Accessories. The " Wharfedale, way 2/6 per yd; volume controls (Centralab) Separator " now available. Cash with various values, LIS 3/6. W/S 4/9; crystal Order pickups, Rothermel, de luxe, £2/16/3 (Inc. Sp teal discounts P. tax); 2 -gang condensers, 0.0005 (not BOOSTERS. Made for a telephone concern to Trade, Radio midget), 5/6; television cable (aerial lead in), are offered at cost. For AC mains with power Soothes, etc., n 1/6 per yard; large assortment of B.V.A. and trans., tondrs etc., all working. Valves, Rect. IDEAL FOR Iota of 25 or more U.S. valves always in stock; let us have your CONVERSION IN1 receivers. 6J5, 6F6. Output 3;w. Makes ideal amp. for enquiries. experimenters, etc., or can be used from TELEVISION UN TS MATT Radio Service, 29, Castle St., Kingston- shack, radio, actual a two -stage amplifier 5 I -F., on- Thames. Kingston 8353. [8375 gramo., mid., Circuit comprises: 1 Pre. Amp. Osc. Mixer control, all on chassis 7 x 4 inches, Video Amp. 1.F. Frequency 12 Megs. TRANSFORMERS, chokes, from quality am- with vol. Det. Coiling - number available, cannot be made at Co-axial input 6r output plifiers; s.a.e. for list to Willis, Limited Band -width 4 Mega wood, St. Georges Rd., Winsford, Cheshire. this price to -day. Complete E6 IOs. Odd. sockets. External source of L.T. à H.T. supply RILEY Elect. Eng. Co. (Hull), Ltd., offer, is required. Manufactured to stringent Govt. new components, kits, everything for the specification by such famous makers as R.O.D., home constructor; lists; competitive prices. - Many new lines are offered in the Autumn List. -Pye, and Murphy. Brand new and unused, and 69a. Church St., Sutton-on -Hull, Yorks. [8243 Eliminators from 65/ -, multi -ratio output trans., trans. In manufacturers sealed cartons. Complete e -WAVEBAND superhet coil packs with 30/ -. Chargers, vibrator with 10 Mazda valves. el circuit (long, medium and short), 22/6 Small chokes, 2/6. Speaker Trans., 2/9, etc., etc. each; long and medium TRF coils, 6/- pair; Full catalogues of G.L. Products. 3d. Circuit Diagrams supplied Free toits each set. wave coils Sold separate at ll -. long, medium and short superhet 7/- per pair; 2 -short and medium waveband superhet coils, 7/- per pair; ultra short wave General Lamination Products Ltd., WIRELESS INSTRUMENTS coils, Polystrene formers, adjustable iron TEL. (LEEDS) LTD. 22262 cores, 5/6 per pair; send P.O. with 6d post- Winder House, Bexleyheath, Kent 9 Ave.. Brighton 54 -56 THE HEADROW, LEEDS, I age to Davis. Windlesham 3021) i 1, Sussex. [7957 (Bexleyheath

www.americanradiohistory.com October, 1947 reles World Advertisements 6g

ALIGNED INSTRUMENTS SERVICES, 1, Colworth Rd., I.eytonstone, E.11. FROM RADIOLYMPIA 40 COIL pack : A superhet coil pack with an h.f. stage, uses 9 iron cored coils in a 16 -50. 200 -500 and 800 -2,000 metres circuit for TO OUR 465kc /s, i.f., complete with circuit diagram, aligned and gain tested; this coil pack enables the amateur with no signal generator to con- struct a first -class all -wave receiver; price RADIO BOOK DISPLAY £3110. Circuit diagram only, 2/6, post free. (No. 27 BUS DOOR TO DOOR) 30 COIL pack series : A famous series of precision -made coil packs now too well known to need description. Superhet types : Model Radar Engineering, by Donald G. 30, 16-50, 200 -550, 800 -2,000, at 42/ -; 30A, Fink, 35s., postage 9d. 12 -30, 30 -75, 75 -200. at 42/ -; 30B, 16-50, 200- 550, at 30/ -; 30C. 200 -550, 800 -2,000, at 30/ -: 30S. 12 -30, 30 -75, 200 -500, at 42/ -. 'T.r.f. Wave Guides, by L. G. H. Huxley, types: Model 30D, 16 -50, 200 -550, 800 -2,000, 2Is., postage 6d. .rt 35/ -; 30E, 12 -30, 30 -75. 75-200, at 35/ -; 30F, 16 -50, 200 -550, at 27/6; 30G, 200 -550, 800 -2,000, at 27/6. Each is complete with Television Receiving Equipment, circuit. Circuits only, 2/6. [7370 by W. T. Cocking, Its. 6d., coils, frequency bands between 50- HR.O.960 kc /s; £1 each; offer for 50 enter- postage 4d. tained. -Box 2143. [8185 " VOU'LL probably get it at Smith's, Edg Wireless Direction Finding, by 1 ware Rd.!" Everything for the construe- tor, from a 1 /10watt resistor to a radiogram PEERLESS TYPE 1546 CHASSIS R. Keen. 45s., postage 9d. cabinet; lowest prices, biggest variety. -Near Metropolitan Music Hall. Pad- 5891. 1.8005 Communications -type high fidelity Radio Engineering, by F. E. resistors, from 1 mego to 50,000 Receiver employs numerous 50,1'000megos, 5/4, !/, 2, 5 watt. 15,000 lmfd, importan Terman, 30s., postage 8d. oil filled condensers, 750 volt and 1,000 volt features including dc. working.- Wembley Electrical Appliances, :- Radio Tube Vade by Ltd., Exhibition Grounds, Wembley Park. 6 wave ranges. -Mecum, packs, brand new, not Govt. surplus, P. H. Brans, I2s. 6d., postage 6d. POWERinput 200 -240e ac, output 350v dc, 80rna 6o mcs. to 15o kcs. 6.3v ac, overall size 61/2x 6x4), with mains lead crystal control The Practical Radio Reference less 5Z4 valve, 54/6; cash with order or c.o.d.- S.T.L., 32, Grafton Rd., New Malden, Surrey. variable selectivity Book, 8s. 6d., postage 6d. I.f. smoothing chokes, 6 independent base MINIATURE hen- and treble control ries, 40 nt.a., 350/- per 100; quotations pre -amplifier for moving coil pick Short Wave Wireless Com- for large quantity from stock. -Ace Electronics -up Ltd., Purley Way, Croydon, Surrey. Tel. Croy- zo watts output munication, by A. W. Ladner and Ion 3444 -5 -6. [8124 employs a total of 16 valves C. R. Stoner, 35s., postage 8d. WEE- MEGGERS, brand new ex -Govt. 250 volt, in leather case, list price £12, cur price £8 post free; second -hand ditto, £5; -and a completely new Peerless Electronics for Engineers, by special price for quantities. -Auto Collections, Receiver Markus and Zeeluff, 30s., postage Ltd., 126, St. Albans Ave., Bedford Park, W.4. Tel. Chiswick 1601. [8123 8d. toy to build! -The 5 -valve ac APERFECTor ac /dc 3 -wave Superhet Assembly (all Radio Handbook Supplement, main components ready mounted on chassis) forms the foundation of a powerful receiver 2s. 6d., postage 3d. at a price you'll like; send postage now for fall details. -N Il 4 c6 Parkhill Rd N W 3 Wireless, and from 5- to 50-watt, mains or Coils, Chokes AMPLIFIERSbattery, radiogram components, motors, Transformers, by F. i. Camm, cabinets, changers, chassis, speakers, pick- 6s., postage 4d. ups, players, micrograms, midgets kits, microphones, etc.; s.a.e. catalogue. -Radio Unlimited, 16, Carnarvon Rd., Leyton. [8204 The Wireless World Valve Data, Selenium rectifiers by S.T.C. and 2s., postage 2d. 15,000Westinghouse, 5 types, 30 m.a. to 220 MA., 50 to 360 volts, all new tested stock, substantially discounted for quantities. -Apply WE HAVE THE FINEST STOCK for full technical data and prices, Partridge, Wilson & Co., Ltd.. Davenset Electrical Works, OF BRITISH AND AMERICAN Leicester. [8120 COPPER wires, enamelled, tinned, cotton RADIO BOOKS. COMPLETE and silk covered, all gauges; B.A. screws, LIST ON APPLICATION nuts washers, tags; bakelite and ebonite panels, tubes, coil formers; headphones, flexes, solder, etc,; list s.a.e.; trade supplied.-Post Radio Supplies, 33, Bourne Gardens, London, E.4. Tel. Clissold 4688. [8231 THE MODERN BOOK CO. ALARGE quantity os radio components, in- eluding condensers, flexible couplings, 3 (Dept. W.27) pole 3 -way switches, line cord, multi range ohms meters, screened wire single and twin, S- 19 -21, Praed Street, London, W.2 core flex., 2- and 4 -way fuse boxes, etc. - 'Phone or call L. Goodman (Radio), Ltd., 9, Percy St., Tottenham Ct Rd., W.1. Mus. 0216. K.A have for disposal the following items: TYPE 1047 RADIO -GRAM CHASSIS 10,000 0.1mfd condensers, 350v tubular; 5,000 250 m.a. fuses, cartridge type; 3,000 Specification includes: - EDDYSTONE .640' gin Yaxley switch handles; 30,000 single -pole Io stage 4 -way and 8 -way wafers; 500,000 Hellerman superhet circuit sleeves, all sizes.- Prices on application to Io valves (including magic eye) We are now booking orders for this A.K.A. Supplies, 30, Berkeley Rd., Clacton- RF amplifier on-Sea. State quantity required please. [8210 first -class communications receiver. 2 KITS of radio receivers from £7/8 ; 4- and IF stages Demonstration model on view at 5- valve, new materials, table models, 4 wave bands wmi-midget; our latest kit. -Wylwyn Star 1947 our Show Room. has connections for gramophone pick -up, ex- Io Watts push pull output tensions to loudspeaker A.V.C. 6 hours aver- tropicalised components EDDYSTONE '504 ' in stock. age time for constructing; fu.ll details dia- grams with each kit; c.w.o. or c.o.d. -Isher 52 Page Catalogue of Components & woods, Reme House, 81, Plungington Rd. Meet us at Accessories I,'- Post Paid. Preston. Tel. 3348. Estd. 1936. [6788 STAND NO. AMATEUR selling up!- Universal Avominor with 5a shunt, £5; D.104 crystal mike. RADIOLYMPIA National B.T.S. £3; telescopic mike stand, 3'/2ín M.C. Hall £1 OCT I-11 307 Gallery The Radio Firm of the meter, 100 -0- 1000a, SOl -; ' Avodaptor " valve South. tester, 10/ -; all above, together with 21 valves 63, London Road, Brighton I, (many newt, 66 switches 43 vol controls, 25 electrolytics, 36 trimmers and tuning, and 100 PEERLESS RADIO LIMITED Sussex. other condensers, 200 resistors, chokes, trans- 374 KENSINGTON HIGH ST., LONDON, W.14 formers, coils, plugs, etc., etc., £35; s.a.e, for Phone : WEStern 1221 list.- Madge, 267, Porters Ave,, Dagenham.

www.americanradiohistory.com o Advertisements Wireless World October, z9¢7

GEE ELECTRIC, 15, Little Newport St.. London, W.C.2 Tel, Ger. 6794. -A few of the many lines held in stock : 32mfd 650vw YOU tropical condensers, 12/6; 4mfd 800vw paper condensers, 5/ -; 5mfd 2,500vw paper conden- RELIANCE sers, 7/6; Sin page speaker p.m., 16 /6 each; 31/2in p.r.t., as per last month's issue, £4110; POTENTIOMETERS can become this month's special ex -Gov. modulator unit type 76, containing relays, i.i i. fuse holders, also condensers, tr,urslormers, resistors, and valve holders, all new. bargain price to clear, A first-class 27/6 each; trade supplied. 17806 GOODSELL, Ltd., 40, Gardner St., Brighton, Sx.- Demonstrations of the new Armstrong lt.F.103 4 -hand feeder units using Denco tur- rets, I.F.T.s as last month's advert, details upon request; Denco catalogues 7d, No. 1 Bulletin 3/21/2; 1d stamp for list of components for con - structors; Williamson amplifier as per specifi- ENGINEER cation with all Partridge transformers to speci- fication, £20/10, including valves; general test and frequency response cheek, usual guarant,e; We are specialists in Home. pre -amplifier with 4-position bass hit and 4- Types T. W. and S.G. Study Tuition in Radio, position treble lift using E.F.37s, at £2110; a few Desna) C.T.3 coil turrets, 6 bands, ex- As recently specified in the " Wireless World" Television and Mathematics. stock. 18403 Post coupon now for free NEW STO metal rects., bridge cony. 12v la 11/ -, 1.5a 14/ -, 2.5a 19/6. 4a 231- all "TELEVISION RECEIVER" booklet and learn how you p.f. 5a 31/ -, p. 1/, 8 -10a 37/9, p. 1 / -, 24v 4a Two 1,000 ohms T.W. linear can qualify for well -paid 42/1, 8a 64/10, 16a 126/5, 30v 5a 57/10, 50v 5a 81/6, 90v 5a 151/3, all p. 1/3; trans. 200 - Two 2,000 ohms T.W. linear employment or profitable 250in. for 6 -12v charger, 2.5a 25/ -, p. 1 / -, 5 -ba One 10,000 ohms T.W. linear spare -time work. 48/ -, p. 1/6, 8.10a 75/ -; care. 2/- replace- ments for valve chargers, state snake and Two 2 megohms S.G. linear type and d.c. o/ p, 150w slider res., 1.15a One 100,000 ohms S.G. linear 22/6, p. 8d., 40w fluorescents from £6/9/6; 230/1/50 1/4HP ind. motors, £9/5/ -, 1 /3rd do. "HIGH QUALITY AMPLIFIER" T. & C. COLLEGE £1015/ -; all goods adv. in Aug. issue still RADIO available; terms, c.w.o. or ptoforma; c.o.d. One 25,000 ohms T.W. linear post goods only-Pearce, 66, Gt. Per ,:y St , North Road, Parkstone, Dorset W.C.1. (Nr. Angel). [8262 Two 100 ohms T.W. linear in new and unused ex- Service are now available. BARGAINSequipment. -Indicator units type 6C, con- taining one 3in cathode ray tube. 2 VR91 For full details of all types write to Post in unsealed envelope, ad. stamp) (EF50), 2 VR54 (ECCC31) valves, 20 various :- resistances, 4 potentiometers, 8 condensors. Please send me free details of your Home- co -axial input and output sockets, etc., new Study Mathematics and Radio courses and unused, in maker's sealed carton 5gns RELIANCE each, carriage paid; 40 feet lengths flat twin R.F. feeder ribbon cable with connector, 300 Manufacturing Co. (Southwark) Ltd. NAME ohm impedence, new and unused, in maker's ex- R.A.F. type Sutherland Road, Higham Hill. original carton, 8/6 post paid; Walthamstow, E.I7 ADDRESS 256, oil filled 4kva, input 230 volts, 50 cycles, output 18kv, weight approx. 41/2cwt, in maker's Telephone : Larkswood 3245 W, W.64. sealed crate, £15 carriage forward. -Wireless Instruments (Leeds), Ltd., 54 and 56, The Headrow, Leeds. 1. 'rel. 22262. 776 PORTER, Ltd.- Radio, guaranteedf JACK equipment, ex-R.A.F. 69 receivers, 10 LASKY'S RADIO valves, 6 type EF50, 4 type 6Q7, also genera- Miniature 1.4 volt Button Base Valves. Multerd, new, tor, coils, relays, rectifiers, etc., 70/ -; Philco- boxed, and at official list prices. Masteradio, 6 -volt vibrator packs, complete CRYSTAL PICK -UP DE91, F.C. Equivalent 186, 15 /10 each. with synchronous vibrators, 15/ -; RGD /Elmo D L92, output. Equivalent 384, 14/ -each. push-button type radio tuning ac 12 -20 -colt DAP91, D. Pen. Equivalent 1S6, 15/10 each. motors, small. new boxed, 20/ -; de /do genera- DF91, H.F. Equivalent 1T4, 14/- euch. tors, 6 volts input 230v at 50ma out. The complete set 59/8. post 9d. put, new 17/6, super 12 volt Input model, 250 Miniature Valve Holders. Button base, 1/- each, volts 120ma output, ideal for PA. 19/6; ex- 9'- doz. receiver model, R.3067, with 11 valves .0001 2 -gang Tuning Condensers, ceramic R.A.F. Miniature 6.3 types, 155 -185 mes, amazing, 30/ -, complete insulation, size Ili . wide, lüw long, llin. high, 8'6 each. with valves, cash with order. postage extra.- E -gang Tuning Condensers, with Jack Porter, Ltd., Radio, 22 -31, College St., Miniature .0005 17871 trimmers, size 1 ¡in. wide, 210,. long, 11in. high, Worcester Tel. 2442. 13.9 each. switches; 5 -bank, 25 -way, per Wearite Miniature I.F. Transformers, 465 Re/s. Iron - SELECTORbank 20/- each; toggle switches, telephone cored. high Q. Size, 113, 16in. x 13 /16in. x 13 /l6in. jacks, press switches, 20 -way tag boards, E.S. Wearite "P Coils, l'.A , PHF, and PO, all types, holders, lead ends, E.S. holders, screwed, Vax 3'- each. ley type switch, 3 -pole 2 -way, each 18r'- per Miniature Intervalve Transformers. Size, lin.x dozen; voltmeters, 0 -40, ampmeters, 0 -50, 15/- fin. x Im.. 4 6 each. volt, 6/- each; each. per pair; condensers, 8mld 700 WITH Gf'1 CRYSTAL Miniature 2 /in. Speakers, M.C. Celestion, 27/ condensers, 4 +4, 500 volt, 3/6 each; conden- Miuiature H.T. Batteries. 67i volts. Size, 31íu. x dozen; Slydlock 11íu. x afin., 18/9 each. sers, lmfd 250 volt, 6/- per New stock of energised moving roil speakers. fuses, 15amp, 15/- per doz; rotary switches, Sin. 3 ohm V /C, 1,000 ohm field, Pentode trans., 5-section, 10-pole, 15 /- each; 10- section, 20- The ACOS G.P.I0 combines purity of re- 29/6, Rota. pole, 25/- each; 0.0003 tuning condensers, 3/- production with extreme reliability. A 6lin. 3 ohm V /C, 1,500 ohm field, no trans., 23/ -, Rohl. each; relays, 200 ohm, 3/- each; Octal plug unique flexible assembly renders the crystal Bin. 3 ohm V /C, 2,000 ohm debt, Pentode trans., tops, 1/- each; postage extra; delivery by re- 85' -, Celestion. turn.- Particulars, Denfords Engineering Co., virtually unbreakable, while a needle - l0ln. 3 ohm V /C, 1,500 ohm field, Pentode trans., Ltd., Box Trees Mill, Wheatley, Halifax, pressure adjustment is incorporated in the Rola. 36/6, ,Yorks, - [8221 base. Resonance -free response from 50- AMMETERS FIRST-GRADE MOVING COIL, by trans, tapped output, Ultra leading manufacturers, 21ín., 0-20 Res., .005 ohm SPEAKER 8,000 cps. Output l5 v. at I,000cps. Needle midget 5/ -. midget 5/6, standard 8/ -; Internal shunt can be removed, 10 /- each. pressure I} As above, 0.1 amp., 11.6 each. Y.P. output (6L6 valves, A/A load 6,600 THIS MONTH'S SPECIAL BARGAIN. ohms) output 7.5 and 15 ohms, 21/ -; Ferranti ozs. (adjust- 12 -volt Vibrator Power Unite. P.P. output, heavy duty 2 -1 (massive job), able). Vibra- Made for use with communication receiver P.C.R. 12/6; Varley heavy duty P.P. driver, 2.5 -1, tion -free arm Absolutely complete with 4ft. long battery leads 15/ -; chokes. ultra midget 40ma 5/ -, midget in two large crocodile clips, 1 spare 100ma 8/6, heavy duty movement. terminating 50mä 5/6, standard Flexible coupling A protects vibrator, 2 spare indicator bulbs. Manufactured by 150 -200ma 12/6; 5v superhet fully drilled Screened lead. Slack crackle crystal B against breakage. Pye. Totally enclosed in metal case. chassis, 111/5x 51/2x 21/2in, 7/ -; Rotherme, Price in Great finish. Size, loin. long, 61n. wide, Sin. high. crystal pick -ups, S.8 and 5.12, 52/8; Avo (Brit. Pat. 579,524. Pats. Price 59/6. Brand New, Boxed and Unused. capacity bridge, £11; Muirhead fluted instr, Britain 44/- (in- pend. abroad). Licensed by Postage extra. knobs, diameter 21/in, 2/6; black inatr, pointer cluding P.T). Brush Crystal Co. Ltd. Send ld. stamp for our current list and bulletin knobs, 1 / -; single core screened cable, per yard Obtainable only from TERMS : C.O.D., Fro Forma, or C.W.O. 9d; twin ditto, 1I -; nuts /screws, 4, 6, 8BA Radio Dealers 6/- gross (2 gross in all); Centralab volume RADIO controls, 5.000 to 2 meg, long spindle, switch, LASKY'S 6 / -; comprehensive lists monthly, 21,!,d stamp COSMOCORD LTD 370, Harrow Road, Paddington, W.9 enquiries, postage extra all orders. ENFIELD: MIDDLESEX (Opp. Paddington Iiospital.) Tel.: CUM 1979. O. GREENLICK. Ltd., 34, Bancroft Rd., Cam- E.1. Tel. Step- Moa. -Sat. 9 a.m. to 6 p.m. Thursday Hulf-day bridge Heath Rd., London, Hours: ney Green 1334. [8428

www.americanradiohistory.com October, '947 Wireless World Advertisements 71 A. RYALL, 65, Nightingale Lane, Lon- don. S.W.12. -Mail order only; special announcement, owing to restricted space, we e `' are now quite unable to give details and RADIO VALVES er e55ed prices Of our numerals lines in radio com- BULLs ponents and various units, all new and un- 246,HICH T. HARLESOfg dwl9 e r used; kindly send for our fully descriptive m-P list, ready now, enclosing large stamped ad- BRIMAR,-1D8, 513 250A, 6136, 6K8 6K7, 6827, dressed envelope; items available include 68N7, 677, 6V6, 7135, ^B7, 7B8, 706, 7Y4, SD2, switches, resistances, Mansbridge and mica 9D2, 10D1, 11D3, IIDS, 1281(7, 26Z4, 16D2, 1D6. G reatly condensers, relays, co-axial cable, h.f. units, COSSOR.-2P, 4TPB, 4T8P, 138PA, 4186P, 41MPT, meters, test sets, high resistance 'phones and 42 OT-DD, 42PTB, 203THA, 210DG, 210LF, 220OT, microphone, 507, This phrase was used by a leading Electrica. instrument boxes with panel, 220P, 220PA, DDL4, MP/PEN, MS/PEN, Paxolin panels, control panels, rotary trans- MSTEN-B, Mt-8/PEN, 0M4, OMB, 0M9. PT10, Instrument concern in connection with formers, amplifiers, volume controls, h.t. and 8130, 13VPA, 41MHL, 418TH, 202VP, 202VPB, I.t. vitreous resistances, interference suppres- 210DDT, 2158G, 22011PT, 41MRC, 40SUA, 42-0T, TRANSFORMERS sors, radio control boxes, and the like.- Please OM10. send for our full list. [8358 HIVAC,-XD, xH, XL, XP, X861, XY. CONDENSERS, 0.1mfd, 350e, 5/6 doz; 250 MARCONI OSRAM.-CRT-E4102/11/7, D41, 1/42, and m.a. fuses, 3/6 doz; Chnttertons, 2/6 D63, DA30, DL63, DL74M, DN41, OT1C, 01750, stick; 2 -pole 5amp panel switches- 3/6; drive 1130, H63, HA2, 111)24, HL2, KT2, KT41, KT44 CHOKES cord, Id yd.; Yaxley switch handles 0,6in, KTlil, KT83, KT66, K771, KT74, KTW61, KTW63 10,1; wafers only, 4- and 8 -way, 4/- doz; KTZ41, KTZ83, KTZ73M, L63, LF2, MH41, ML4i M84B, M8P4, N14, P2, PX25, QP2l, 823, U10, 1316, us, and is assorted Ifellerman sleeves, 6/- lb; various sol- supplied by praise to which we 1717, U18;24 1131, 1750, U52, 1374, VMP4171, VM846, have become accustomed. Our modern dering tags, 2/- gross; 9 -pole 3 -way Yaxley, 10/ -; bargain parcels of assorted radio com- W21, X61M, 565, X71M, Y63, DG2, DS, HL2K, factory is fully equipped with vacuum and ponents, each LIB, 1.85B, MKT4, 1123, Z22, 301, 302, 303, 004, impregnators, guaranteed to contain goods to U14, MX40. pressure and all the latest the value of £1, price 10 /- each: rash with test equipment. order; money back is dissatisfied. -Harold King MAZDA,-AC2PenDD, ACOPEN, ACSPENDD. Radio, Clacton Rd. SL Osylh Essex. [8211 AC6YEN, AQ'P, ACPen, ACP4, ACTH1, ACVP1, POWER RATINGS 8 V.A. to ELECTRON iC PRODUCTS DI, DD207. DD620, HL21DD, 11123, HL23DD. -1TNIVERSAL HIA1, HL41DD, HL42DD, 11L133DD, HLDD1320, (G8UQ), 36, Marylebone High St., Lon- P41, Pen25, Pen 45D11, Pen Pen453DD, PenDD4020, 8 K.V.A. don, W.1. Tel. No. Wel 4058. High perfor- 46, mance QP25, QP230, 80215, SP41, 81.2220, TH41, TH233, AUDIO RATINGS 3 watts to tuning units, covering 16 -50, 200 -550 TH2321, TP22, TF25, TP26, U403, 17116, UU7, V914, and 1,000 -2,000 metres, complete with I.F. VP23, VP41, VP1:33, VP1322, DCP, DC80, DD41, 200 watts. transformers, valve holders and attractive dial, DDI01, 11210, ITY5,300. fully aligned and tested; type A : for 61(8 OUTPUT TRANSFORMERS TO MULLABD.-2D4A, 2D13C, 5U4, 5Y3, 6C6, 6D8. and 61(7 valves price (less valves) £5/8/6; 627, 61,6, 6Q7, 6R7, 164V, AZl, AZ31, CCH35, CL33, Mr. D. T. N. Williamson's Specification. type B: as above but with addition of third Cyl, Cy1C, CY31, DF51, DL35, D030, DW2, EA50, L3. 10. O. valve holder (for 6Q7), together with volume E834, EBC33, EBL21, EC52, ECC31, ECC34. control, wired, aligned and tested, price (less ECC35, ECH21, EC1135, EFS, EF6, EF9, RFS7. PROMPT DELIVERIES valves)' £6 /10 / -; postage 2/6; R1155: If you EF39, EPOS, EF64, EL2, EL3, F.L32, EL33, ELIO, are not satisfied with the performance of your EM34, EM35, FC13, FC13C, F W4/600, HL13c,1W4/500, set write for details of our conversion; out KBC32, KF35, KK32, KL35, Pen4VA, Pen428, works are available for the construction of PenA4, PM2, PM2HL, PM4DX, PM12111, AUSTIN MILLS LTD. specialist type receiving or transmitting equip- QP22B, 8P4, SP413, 8P13, 8P13c, T6D, TDD2A, ment to specification; prototype and develop- TDDl3c, TH4B, TH21C, TT4, 1152, VP2B, VP4, ment work [8263 VP4A, VP18A, 1)F33, DW4/350, ECC3., EF22, LOWER CARRS, undertaken. EL35, E1.00, HVR2, liVR2A, PM5B, PM22A, P51220, LYDESDALE for bargains.- Ex -U.S. Nos-y 81'13c, IJBL21. UCH21, UY21, ITY31, 6C6, CBL31, C 4 8.1(.8 power unit 3 valves supplied, I)L02, DAF01, DF91, EBL31, EF36, EM4, TH30C, STOCKPORT etc_; our pi-ice 30 %- each, phis 5/- C. & P.; VP13C. A.S.B.7 or 8 reroiver units, 12 valves sup- 452, 1012, years STO PHILLIPS.-C7, CIc, 328, 329, 340, 367, Established 20 Phone : 3791 plied. etc., our unite 75/- each, plus 7/6 1038, 1120, 1561, 1729, 1738, 1821, 1904, 1905, 1914, C. & P.; ('.L.Id.43 AAX, 12v Rx. unit, 10 1920, 1926, 2050. valves supplied, etc., our price 4216 each, plus 7!6 C. & P.; AN /APAI, C.R. indicator TUNGSRAM.-5X4, 6B5, 625, 6V6, 6X6, 25Y5, 25Z5 and repeater amplifier unit; 3in CRT and 11 807, APP41:, 1)D13, 1)D818, EC112, EF12, BIN 1111SMsees valves EL5, E1,11, EM4, EPA, HL13, HP33, HP1018 anrplied. etc., our price £4/19/6 each. HP1118, HP2018, HP2118, HP4106, HR210, MH1118 plus 12/6 C. & P.; ex- R.A.F. R.1124 Rx., 6 L0210, LL2S, P2018, PP6E, 8P2BS, BP4B, 8P4S valves supplied etc , one Price 30'- each, 88210, VP48, VR105/311, VR150,30, HIA, HP211C The B.P.L. Wobulator plus 5/- C. & P.; B.38. 3 W.B.Rx., 5 30 LL4, LP 220. metres. 6 valves and metal rect. with speaker, A.C. AMERICAN.-OZ4,1A4, 1A5,1B4, ID7,1 D8,1E6, 1E7, mains, or 6v operation, complete with 1F4, 1F5, 1E6, 1E7, 11.06, 2 etc, 106, 1H6, 126, ILN5, pairs phones, our price £15115, plus 184, 155, 1T4, 1T6, 2A6, 2A7, 2B6, 2B7, 3B7/1291, 15'6 carriage and packing. -- Clydesdale 5U4, 5V4, 5Y3, 5Z3, 5Z4, 6A3, 6A4, 6A6, BAB7/1853, Sunnis- Co., Ltd.. 2, Bridge St., Glasgow, (''.5. 6AC7/1852, 6AE5, 8AE6, 6X05, 6X06, 6A67, 684, TRITD RAr)lllí RAF's, Ltd., the Leicester 6357, 688, 6C4, 6C5, 6C6, 6C8, 6115, 6D6, 6E6, 6E7, 1 soeri :1 lists ffer from their comprehen- 61,6, 6F7, BFB, 6(16, 6116, 625, 627, 6J8, 6K6, 8K7, sive sleeks: Mains transformers, 250- 0 -250v 6K8, SILO, 6L6, 6L7, 6N7, 6Q7, 6P6, 6R7, 68X7, 60ma. 4v 2a. 6.3v 2a, 19/6; 3-gang 0.0003 6807, 68E7, 6827, 68K7, 68L7, 68N7, 6T7, 6V6, 13X6, midget tuning condensers with super sm drive, 6Y6, 625/12y.5, 7A6, 7A7, 7.130, 7B6, 7B7, 7B8, 7C6, 8/6; 3 -gang standard type 0.0005, 7/6; split 706, 707, 7117, 787, 7Q7, 7Y4, 10, 12A, 12X5, 12A6, stator types. 20 +20, 2/6; 75 +75. 3/6; 1504 12137, 12C8, 12J5, 14H4, 12K8, 12Q7, 128(17, 12887, 150. 51 -; 3- waveband FM r'ials wills glass and 128K7, 1287Ç7, 12807, 128E5, 128117, 12Z5, 14117, epicyclie drives, 12K7, 15, 17, 20, 22, 26X6, 25Y5, 2524, 26, 29, 30, 31, 7inx4in iscutcheon, 12/6; 32, 33, 34, 3526, 37, 38, 39,'44, 41, 42, 43, 46, 48, 49, 1. 1 5: /6; 0 -500 microamp m/c meters. li¡,in 50, 53, 55, 57, 59, 71A, 77, 79, 80, 81, 83, 89, 807, dial 7/6. Owing to the impossibility of 866A, 954, 955, 1156, 117Z6, I299A, 1626, 9001, 9002, listing many separate items we offer a special 9003, 9004, 9005, 9006, 1-V, 3X8, 6E5, 14B7, I4Q7, bargain parcel of ex -Gov. components having a 35,15, and 101 mare types retail value of over £5 for only £1, aver 50 Order C.O.D. above listed members or equivalents useful items, our selection, but Su tisfartinn (suhject to stoc..l. Please enquire for any valve you guaranteed or money refunded; latest lists of require, even if lint listed. We may have it. Old many other lines free on request; trade sup- and new types are arriving daily. plied. -Frith Radiocraft, 1411., 69-71, Church Gate, Leicester. Tel. 58927. [8404 THIS MONTH'S SPECIALS : CLEARANCE sale. -Weymouth 3-wave veil "Introducing Radio Receiver Servicing," 7/6. packs, 30/- each Weymouth midget i.f.s, "Unities" Scratch Remover Kit, 5/6. Spring 1.5/- per pair; Weymouth type 3 -wave roils, Winder and 5 ass. gauges of Spring Wires, 2.15. Test 7/- per pair; Weymouth constructional draw- Prods, Y.V.C., insulated. 3 8. Wire and Cable ex- R.A.F., 1 Weymouth circuit with Strippers, 15/ -. Telescopic Aerials, 10/ -, ings. /6; free all the doe. above; 2 -speed drives. 21 -; snerisl voltage drop- Aluminium, 16; -. Steel Service Sheets, 10 6 per A frequency Modulator which operates Voltmeters, ex -Gov., new, Dual Range 0.250, 0 -15 pers vitreous enamelled, tapped for 100, 110, moving coil, Res. 34512 per v., complets with ease, in conjunction with any make of signal 150, 200 and 250 volts- 0.3amps, a beautiful 18,9. Set of Tools, complete illiteme) 211 -. Trimmer job, 6/6 each; electrolytic condensers, new and generator and C.R.O. The essential Tool Kite, in wallet, 301 -. Chassis Unit, ready wired not surplus goods, 16x8k450 volts, 616 each; for a battery 3- valve, 261 -. Headphones (new), requisite for the visual alignment of 16x8x4x4, 570 volts, 7/6; 25Omfdsxl2 volts. pair 9í -. Flikodisk, isms law calculator, 7/6. wireless sets. Yet another first -class 1,000mfdsx6 volts, 4i -; 1,500mfdsx35 "Jackson " Full Vision 3-wave Band Diele, and Drives, volts. 15/- each 25mfdsx25 volts, 1/9; 2 -gang complete with escutcheon and glass 6 x 3, 13 / -. B.P.L. product in their range of Instru- 0.0005, with drum. 2 -speed drive, 16 /6; 2 -gang "Special" AB -mefxil Ratchet. Screwdriver with exten- 0.0005. 9/6; the new Osmor coil pack, a very sion lever handle, 21/ -. Aso Mains Oscillators, £13. ments of pioneer design. neat and efficient 33/ -; Summersby Avo Valve Testera, £16 10s. Test Bridge, M. pack, Minor, Full details from the manufacturers. tuning coils. 2 waveband on one former, ad- Aso Universal Minor, £8 10e. Ave D.C., justable iron dust core, superhet type only, £4 4s. Wee- Megger, £13 18s. 3d. 7/- per Summersby midget coils, very pair; STOP PRESS' : Taylor Portable Valve BRITISH PHYSICAL high Q (1701, adjustable iron core, superhet type only, range available, 13 -35. 35 -100, 200- Tester, Model 47a, new, L25 LABORATORIES 550, 800 -2,000 metres, 6/6 pair; Summersby The Houseboat Works, RAF/LETT, Herts. i.f.s, 465 kcs, Q 160, 15/- pair; write for our J. BULL & SONS (WW), Phone: Radiett 5674 -56 list; all orders under £5 must include postage. -Castle Radio, 86, Abbeyville Rd London, 246, High Street, Harlesden, N.W.10 S. W .4 [8143

www.americanradiohistory.com 72 Advertisements Wireless World October, '947 11i4IDLAND RADIO COIL PRODUCTS.-Coil IVY packs, IQ /AO 3 -band s /het, 33/ -; IQ /HO 3 -band s /het with RF stage, 50/ -; IQ /SO SW 00016 tuning 10, 25, 2045, 40, 100m, 33/ -, all tested, guaranteed free blue print; IQSS superhet coils, 0005 tuning, 12- 2,000m. AE HF Osc, 2/6 ea; IQS. 00016 tuning, 10 -25. 20, 45, 40, 100m, 2/6; IQA TRF SW. double wound with reaction as IQS types, 2i3; per- meability tuned IF'l'S. super job. 15/- pr.; also tuning hearts, etc., 3d for data and lists; louvred instrument eases, steel, 18x8x7in, open one end, 12/ -; moving coil mies. special job. low price, details stamp; electric Hawaiian guitar. plays into most radios, professional job and finish, £616, stamp for description; 10 watts push -pull amplifier for mie gram or guitar, ac mains. £8/8; stamp for details; exclusively mai. order c.o.d. service; trade enquiries invited. full .- Midland Radio Coil Products. 19. Newcomen Rd., Wellingborough. [8152 SELENIUM H.T. and L.T. metal rectifiers and battery charger kits, new goods with ?WA(' l/fFft/L full warranty, add postage, 6d up 15/ -, 1/- above; new small space type selenium H.T. rectifiers for 250e 60ma ac -dc receivers 9/ -, NEW FOLDER- 120v 25ma for eliminators 7/6, 350- 0 -350v for tells you all about the wmpicte ac sets 13/6, 5ma instrument rectifiers for Ava range of Henley SOLON Llectric 12/6; selenium L.T. rectifiers with instruction ALL -WAVE Soldering Irons, for the standard voltage sheet, 12v lamr 8/6, 12v 1.5amp 10/6, 12v ranges of 200/220 and 230/250: 65 watt 2amp 12/6. 12v 3amp 18 /6. 12v 4amp 25/ -. and 125 watt models fitted with oval - 12v 5amp 27/6, giant, finned 12v 6amp 32/6, SIGNAL- tapered bits or pencil bits and 240 watt 24v 2.Samp 32/6; many other types, including models fitted with oval -tapered are conversion rectifiers for valve type garage bits chargers; charger kits, no rheostat or ammeter Type available. needed, foolproof running, 12v 3amp rectifier GENERATORS 5&6 Write to -day for the new folder ref. Y.ro with 50watt transformer and ballast /indicator These high -quality precision instruments 200- describing bulb for 2v to 12v charger, weight 71b, 45/ volts AC DC ditto 2amp rect. 32/6, ditto 6v 2amp only 240 volts AC Type 5, 100 -250 a 100 to 30 Mc /s G.t1 Li. 30/ -, heavier type 12v 4amp rect. with 75watt Type 6, have coverage of KO trans and ballast bulb for 2v to 12v charger in 5 ranges. Calibrated by hand against a 62/ -, ditto but 5amp rectifier and 140watt standard frequency accurate to 0.01°ó. Con- trans. 78' -; trickle charger rectifier 2v 0.5amp structed in B.A.60 alloy and finished black sOLON type with transformer 'for 2v trickle charger and cream. Price 14 Gna. Type 5 or 6. ELECTRIC SOLDERING 13/6, heavy duty transformer, rectifier, ballast Immediate delivery. bulb for small commercial charging, for 1 to IRONS 20 cells one amp 95/-. ditto 2amp £6/5, ditto Illustrated leaflets on application to : 1 to 12 cells 2amp 95/ -, guaranteed one year; ammeters, 0 -6amp flush 12/6. slider resistances 16ohm l0amp 14/ -, crystal diodes 2/6, trans- R.R. DE VELOPMEnT W. T. HENLEY'S former, 2 rectifiers, 2 condensers for 120 - tees, /... 20ma eliminator with 2v trickle charger 39 6. LTD TELEGRAPH WORKS CO. LTD. crystal and m /c. mikes. -Champion, 43, Up- LABORATORIES (Engineering Dept.) lands Way, London, N.21. Tel. Lab. 4457. BARIIARD ROADBRADFORD 51 -53 Hatton Garden, London, E.C.I RADIO CLEARANCE, Ltd., 27 Tottenham Ct. Rd., W.1. Mus. 9188. -Ex -Army 3b sets, 5 -valve trans. -rec., range 7.4 -9 me /s, com- plete with 2v valves and junction box (as used in tanks, with No. 19 set). 45/ -: 3 snare 4 -VALVE COMMUNICATIONS RE- valves in metal case (1 -ATP4, 2- ARP12), CEIVER (Type 3 /II). 10 / -; 2 section rod aerials in canvas case, 8 /6; A complete 4 -valve Superhet, covering 3 -16 - - Fourth Edition mains trans., 230v 50 c/s primaries, secs 300- 0 -300v, 200mA, 5v 3a, 6.3v 2.5a, 6.3s me /s, in 3 bands. Employs 2 7R7 and 2 7Q7 3a, 25/ -; 300- 0 -300v 200mA, 5v 3a, 6.3v 4.5a, Loktal valves. A most efficient set. Operat- 22/6; 2,000v 2mA, 2v 2a, 4v 2a, 21/ -; ing voltage 90 -100 at 8 -10 m /a, 6.3v. L.T., 41v. RADIO RECEIVER smoothing chokes, 2.5í1 200mA, 7/6; 20H G.B. Supplied complete with phones and full 400mA, 18/6; H.F. chokes, covers S and M.W., circuit details in steel transit case. BRAND SERVICING AND 1 /6; U.H.F., 1 / -; Mansbridge conds., lmf NEW and UNUSED. Only 79/6 (carriage, 350e 8d., lmf 1,000v, 1/3; 2mí 300v, 10d; etc. 5/ -). 4mf 600v, 4/6; 4mf 1,500v, 5/ -; 0.25mí MAINTENANCE 2,000v 1/9; 0.5 2,500v, 2/ -; lmf 3,000v, I0 -VALVE I.F.F. /RX 3/6; 0.5mí 1,200v, 1/ -; 0.25mf 400v, 5d; TX UNITS By E. J. G. Lewis. A new edition all wkg. V; ex- R.A.F. visual indicators in A few only. As used by R.A.F. in conjunction of this outstanding book giving bakelite case, inc. 2 complete Weston moving with Radar. Complete with 10 valves and coil meter movements, 300 micro amps rotary transformer. Only 39;6 (carriage, expert practical information on F.S.D., 6/11; 0 -30mA moving coil meters, etc. 5/ -). the technical details of servicing 2'/in scale, flush fitting, 8 /6;' telescopic aerials, 103in extended, 15in closed, ideal EX R.A.F. POWER UNITS and maintenance. 8s. 6d. net. for car aerials, dipoles, etc., 9/ -; air dielec- tric variable condo., 30 P.F. fain spindle, Complete with 20 watts rotary transformer. "This book is practical, replete with facts, 9v. input, 450v. output. Contains and well arranged. " -Wireless World. 1/ -; 50 P.F. ceramic base diff. 2/ -; 50 P.F. cooling straight, 2 /-; electrolytics can type, 8mí 170v, blower, resistances, etc. BRAND NEW. 2/3; 50mfd 12v, 1/9; 100mí 12v, bakelised, Only 19/6 (carriage, etc. 3 6). Ready Shortly 1 / -; metal rectifiers, 12v la bridge, 4/6; 250v 60mA H.W., 4/6; headphones, moving coil, T 1154 TX OUTPUT UNITS slightly used, 10 /6 pr; single earpieces bal The complete output FUNDAMENTALS anted armature, low rec., 1/6 ea; switches, unit for the R.A.F. 1p 1p T 1 154 Transmitter. Made to replace faulty 3w 1/9, 9w 2/6, 1p 6w 2b 3/ -, 2p 6w items OF RADAR 2/6, 2p 5w 3b short spin 2/9, 2p 5w 2b 3/6, but never used. These are BRAND 3p 3w ceramic 3/6, 4 bank switch with 3 -2p NEW in maker's cartons and chock -full of wafers 1 81, Transmitting Gear. Contains coil condenser By Stephen A. Knight, F.R.S.A. 4w and -lp 4w on /sin locator, with 21, /in spindle, 6/6; mica conds. 0.0001 -2 -3 -5 assembly for power amplifier for all frequency A useful book surveying the prin- 4d, 0.001 -2 -4 -5 5d, 0.01 6d, 0.005 1,0001, ranges, .0002 mfd Transmitting Condensers, ciples of radar, and showing how it wkg. 7d, 0.0001 3,000v wkg. 9d, resistors Station Selecting Mechanism, Variable In- vitreous 5w wire ended 552, 4512, 47011, 1K, ductance, Stud Switching, Short Wave Coils, has from radio - developed ordinary 3.9K 4.7K, 6.8K, 8.2K, 22K, 27K, 1/- ea wire Instrument Type Coloured Knobs, etc., etc. engineering. A book of special wound VC no SW, 3012 11/2w 2/ -, 20012 3w, Only 24/6 (carriage, etc. 3/6). Illustrated 40012 3w, 500f/ 2w, 1K 3w, 2K. 10K, 20K, leaflet available. interest to radio engineers and 25K, all 3w 2/6, 500 /50011 3w 3/6, 5K /50K students of radar and television. 3/6, 50011 15w 4/ -, 50k 10w shielded type C.W.O. please. S.A.E. brings current lists. precision job, 7/6; carbon mike buttons About 7s. 6d. net. 4in dia, 1/6; ceramic conds, 2, 10, 20, 25, 50, 100 P.F. 6d; silver micas most values THE RADIO CORNER Obtainable through booksellers 10-6,000 P.F., 6d; volume controls carbon, no SW, 10K, 20K, 50K, 100K, 5O0í, lm, 2/-; 138 GRAY'S INN RD.,LONDON,W.C.1 trimmers ceramic 1 -15 P.F. 6d, 3-50 P.F. 9d, (Terminus 7937) double U.I.C. type 15-45 P.F. ea 8d, single (2 mins. from High Holborn, S mins. Pitman ' ' Books 3 -25 P.F. 4d; padders 150 P.1'. 1 / -, 750- from Kings X). r 1,250 P.F. 1 / -; 0.2a droppers 3/6; single screened wire, rubber ins stranded centre 8,1 Open until I p.m. Saturdays. yd; I.F. trans 465K kc /s 14/- pr. [8261

www.americanradiohistory.com Oclobcr, 1947 Wireless World Advertisements 73 !TARRY JAMES PRODUCTIONS, 270, Leith Walk, Edinburgh, 6. -Mail order only; c.o.d or cash with order: H.f electro, lyrics- 500v blocks, 8mfds, 3/6; 8 +8 5 /6; tubular, 4/9; 16mfds, 4/9; 25tnfrls, 25volt, GALPI N S 2/1 0.01, 0.05 and 0.1, 8d. each; volume ELECTRICAL STORES controls 14 and 1/ meg, 4/9; multi -ratio speaker transformers, 6/6; loudspeakers, 19/9; 2 -gang condensers, 0.0005, 12/ -; valve holders, 408 HIGH STREET, LEWISHAM, LONDON, S.E.I3 5 -, 7 -pin and Octal, 6d.; Amphenol type, 9d.; Telephone : Lee Green 0309. Near Lewisham valves c.o,d., most English and American types Hospital. in stock ; let us have your enquiries for any - TERMS : CASH WITH ORDER. NO C.O.D. I hing in radio. [8219 SUPREME RADIO, 746b, Romford Rd., Manor Park, London, E.12. -Send for list MAINS TRANSFORMERS. Ex Govt. (New). D.C. TO A.C. ROTARY CONVERTERS. of components for everyday servicing, Govt. Tapped Input 200/250 volts 50 cys. 1 ph. Output 24 volts input, 50 or IOÖ volts 500 cycles at 30J surplus job lines; tubular condensers, 0.1- 350/0/350 v. 180 m/a 6.3 v. 4 a. 5 v. 3 a. 4 v. 4 a., watts output. Condition as new, 75/- each, C F. 500vw, 0.002 1,000vw, resistances 2w, 10,000 37/6 each. 1/6 post. Another 500/0/500 v. 150 m/a EX -NAVAL CATHODE RAY RECTIFIER 12,0000 5w 4.000 -5,000, W.W., all short 6.3 v. 4 a. 5 v. 3 a. 4 v. 4 a., 47,6, post 1/6. Another UNITS. New and unused, sold for components 12 nds, 2/6 doz; 10w 10,00012 5/6. 5w 2,000.0 6, and 24 volts 10/12 amps., 45/- each, post 2/ -. which consist of : -2 x .5 mfr 2,500 v., I x .1 3' -, 3,30011 5/ -, 0.25mid with clip 9/- doz, Another 141 and 171 volts at 30 amps. (auto 5,000 v., 6 x 2 mf. 800 v., 2 x 8 mf. 800 v. 15 0.5nitd can 8/ -, 0.25 350vw 8/ -. 8mhl 39/- wound), E4 /IS -, post 2 6. Another 700 /0/7C0 v. volume controls, various values, approx. 100 doz; worse tappers, 1 ors, 1 /6; Westert /6; 80 m a 12 v. I a. 4 v. 2 a., 30 -. Another 350/0/350 small condensers and resistance, smoothing choke meter rectifiers, 5/6; earphones with head- v. 200 m a 6.3 v. 20 a. 5 v. 3 a., 45/ -, post 2/6. and 9 v. holders, including 3 EF50 and I tube band, 50(1, M.C. mike 3 4/6; inserts, /-; test Another 4, 6.3 v. and 12.6 volts 12 All meters 21,2in flush type, C''or- at amps 45/ -, base. components wired and with the addi- Iby Pullin), £1; post 2 6. actual plug and socket, I /6; 4 -pin American Another 171 and 20 volts at 30 amp., tion of mains transformer would make a good 95 -, post 3/6. oscilloscope. Price 45/ -, carriage paid. UX v /holders, Ceramic, 1/- doz; L.F. trans. VOLTAGE 1 / -; 2,00012 W.W. v /cs, less sw, 1/6; Mazda CHARGER TRANSFORMERS LARGE RECTIFIERS FOR CHARGING. v /holders, 3/6 doz; 0.5 mica p.I.s, 1/6 doz; (AutoWound), tapped 0, 110, 200, 220, and 240 6 or 12 volts at 6/8 amps. Complete with mains anchor tags, 3/- gross; A.W. glass dials, 3 6; volts 350 watts, 55 / -, post 1/6. 500 watts, 70/ -, transformer for 200/250 volts 50 cy. I ph., ES 2 6, Paxolin panels ld per way ; assorted W.W. post 2! -. 1,000 watts, L5 /5 / -, post 2/6. 1,500 carriage paid. resistances, 1 -2w, 2/6 dos; carbon resistances, watts, E7 I5' -, post 3/6. 2,000 watts, L8; 15 -, EX -GOVT. NEW MAINS DIMMER RE- low, 1k -2.2 meg, 3/- doz; v /cs, 4/6; 0.2 post 5/ -. Double Wound 2 to 1 ratio (120/240 or SISTANCE, worm wheel control 700 watts doz, vw 250vw condensers 2/6 0.05 -0.1 500 vice versa, 4,000 watts, E12/10/ -, C F. variation from full to Blackout. Price L3/10/-each. 4/6 doz, 0.1 500vw 4/6 doz; 0.01- 1,000vw AUTO WOUND TRANSFORMERS (Mains EX -GOVT. VARIOMETER for 19 ; 4/6 doz; s.a.e. all enquiries; c.w.o.; send 6,1 No. sets extra all orders under £5, no c.o.d. [8394 Boosters) tapped 0, 6, 10, 19, 175, 200, 220, these contain C.T. Westector, .001, 5,000 v., 225, 240 and 250 volts at price RADIO'S wireless 1,500 watts (New ex condenser, etc., 7/6 each. Complete in SOCTIIERN bargains. - Govt.), E5 /I0 post 5; -. case with dial. Latest radio publications, " Radio Repairs -, metal graduated Manual," 2/6; " Car and Portable Radio LARGE MAINS TRANSFORMERS, Ex Govt. EX -GOVT. VARIABLE RESISTANCES. 450 .7 Manual," 2/6; " Radio Valve Manual," equiva- (New) Input 200/250 volts 50 cys. I ph., in steps (New), ohms, carry amp., 30/- each, 4,000 lent and alternative British and American of 5 volts. Output 30/35 volts at 100 amps. ohms, carry } amp., 37/6 each. valve types, 3/6; " Radio Circuits," receivers, Price E12 -, C /F. EX- R.A.F. R.F. UNITS TYPE IIOA. New power packs and transmitters, tally illustrated, AUTO WOUND TRANSFORMERS and unused, consisting of 5 valves, including 2/ -; " Amplifiers," fully descriptive circuits. (Voltage Changer) tapped 0, 10, 20, 25, 90, 130, grounded grid 750 m /cy. tube, small 12 volt motor 2/-; " Short Wave Handbook," 2: -; " Manual 150, 190, 210 and 230 volts at and numerous other components, would make of Direct Disc Recording," 2/ -; "Test Gear 1,000 watts. (It will be seen that almost any voltage can very useful crackers, 45/. each, 5/- carriage. Construction Manual," 1j 6; " Radio Pocket be EX- R.A.F. RADAR IMPULSE formulae, colour code and tables, etc., obtained from this Transformer.) Price ES 10 -, TRANS- Book," FORMERS (new, boxed). We have no actual 1 / -; " Ten Hows for Radio Constructors," 1 / -; post 5/ -. data on these, them an Bulgin Radio Service Manual," 2/6; " Radio MOTOR GENERATORS EX. GOVT. 11/12 but believe to have output of 15,000 volts at 3 kW. for a micro second. Constructor's Manual," 3 / -; " Television Con- volts D.C. Input 230 volts 30 m /a. Output A strictor's Manual," 3/6; " Radio Aerial Hand- complete with all smoothing chokes, condensers, bargain for the experimenter at 7/6 each. P.F. book," 2 /6; " Ultra Short Wave Handbook," etc.), 30/- each, 2/- post. EX- G.P.O. VERTICAL TYPE GALVANO- Hints Manual," 2/6; " Radio Ditto 450 volts 50 m /a, METERS, centre 2/6; " Radio output, 35/ -, carriage 2/6. Ditto 24 volt Input. zero reading 30/0/30, 7/6 each, Reference Handbook," cloth bound, fully com- post I / -. Mallory 12 volt, vibrators, 450 v. 5 m/a output, 32/6 each, carriage 2 6. new and prehensive, covering all available data, 12/6; unused, 7 6 each. Electrolytic condensers, 80 Radio Resistor Chart," resistor values at a MAINS TRANSFORMERS EX GOVT. mf. 350 volt wkg., 5/6 each, post 9d. 1 manuals : Input 230 volts 5o cys. 1 ph. glance, / -. American service Output 121 volts L.T. RECTIFIERS (new), 6 volts, lk amp., Uroaley-Belmont 1 & 2), Sparton C.T. at 25 amps., (parts 45/- each, carriage 5' -. 7/6 each, 12 v. I) amp., 10/6 each, 9d. post. Instru- Emerson, Stewart Warner -Fada, 12/6 per METERS BY 3d per ALL WELL -KNOWN MAKERS. ment Rectifiers, S.H., 10 or 20 m/a types, 4/6 each. volume, postage on all publications Ex Govt. new boxed 1st grade book. All items advertised postage extra. Moving Coil. SHUNT WOUND D.C. 110 volt motors, 0 to I m /a, 21/- ; 0 to 40 volts, IS/- ; 0 SOUTHERN RADIO SUPPLY, Ltd., 46. Lisle to 10 1,500 r.p.m. approx. -1 h.p., condition as new, St., London, W.C,2. Gerrard 6653. [Soda amps., I5 -; Oto5m'a,17/6; Oto20m/a, 17/6; 17/6 each, post 2/ -. WANTED, EXCHANGE, ETC. 0 to 50 m, a, 20, -, all 2in fsd. 0 to 3 m, /a, 22/6 ; EX- G.P.O. Permanent Magnet Moving Coil American valve required. -Write Box o to 50 m,a, 22/6 ; 0 to 200 m /a, 22/6 ; 0 to 4 speakers (makers Tannoy), suitable for extension 12SC72528. [8284 amp. Thermo Coupled, 30/- ; 0 to 20 volt A.C., or small P.A. work, fitted, in wooden cue. WANTED, " Wireless World " Indexes for calibrated 50 cys., 25 - 0 to 3,500 volts Electra - 9in. x 9in. x 7in., as new, 27/6 each. 1942 -3 -4.- Lewis, Whiteway, nr. Stroud. static, 35/ -. All 21in. fsd. EX- R.A.F. I.F.F. UNIT (Model 3002), complete WANTED, " Wireless World," Aug. 18th, D;C. TO A.C. ROTARY CONVERTERS. 10 valves, types 1939. 2974. with 3X70E, IEF50, 4VR65. 25th, 1938, June 8th, -Box Ex Govt. (New) 110 volts D.C. to 230 volts 50 2XYT6IA and rotary converter 12 volts input. WANTED urgently, 1 Index to Vol. 40, cys. I phase at .85 amps., E12 10; -, C /F. 450 volts 40 m'a These 1944, " W.W."-Price to A. C. Cossor, output. units are as Ltd., Highbury Grove, N.5. [8276 ELECTRIC LIGHT CHECK METERS for new. Price complete, 57/6 each, carriage paid. rotary converter, 500w, 24v to Garages, Subletting, etc., all for 200/250 volt A.C. EX- R.A.F. MICROPHONE TESTERS. These WAN'T'ED,60v input, 220v 50cy 3pdr output, con- mains. 5 amp. load, 15 - each, 1/6 carriage. consist of a Ferranti 24in. in coil 0 to I m/a trolled speed tssential. 'del. Chancery 8760. 10 a., 17/6, x 1/6 ; 20 a., 25/ -, x 1/6 ; 30 a., 30/ -, meter with Westinghouse Rectifier incorporated, WANTED, power units, type 38 and /or 41, x 1/6 ; 40 a., 35r -, x 1:6 ; 50 a., 40/ -, x 1/6. Also a calibrated at present 0 to IO volts, microphone supply for ex -A.M. TR1148a. -J. H few only, Prepayment Meters, 21 amp. load only, transformer, jacks, etc., all contained in polished Bárrance, 49, Swanage Rd.. Southend -on -Sea. 27;6 each, carriage 2,6. teak case, size 6jin. x 51in. Price 32/6 each. urgently required, enameled, all WIREgauges 24 to 46 s.w.g.. Litz wire offered in exchange if required. -Weymouth Radio Mfg. Co., Ltd., Crescent Works, Weymouth. WE buy for cash, new, used, radio, electri- The many man -made setbacks to our cal equipment, all types; especially IRON DUST post -war plans had, by the end of 1946 wanted, radios, radiograms, test equipment, brought Mr. Voigt motors, chargers, recording gear, etc. -If you CORED COILS to the verge of a want to sell at the maximum price, call, write breakdown. or 'phone to University Radio, Ltd.. 22, Lisle of Exceptional Efficiency and Stability Although since St., Leicester Sq., W.C.2. Ger. 4447. AERIAL AND OSCILLATOR, short, medium, or mn then he has taken REPAIRS AND SERVICE wave, size tin. x lin. 7/6 pair. things very quietly, MAINS transformers rewound, new trans- AERIAL AND OSCILLATOR, medium or long wave he has not re- formers to any specification. size fin. x lis. 6/9 pair. covered sufficiently long wave serin I MOTOR rewinds and complete overhauls; first - DUAL WAVE COILS, medium and to take class workmanship, fully guaranteed, and ILL 9/6 Pair. an active F. M. ELECTRIC Co., Ltd., Potters Bldgs., LF. TRANSFORMERS, Standard Frequency 465 part in Radiolympia. He much regrets Warser Gate, Nottingham. Est. 1917. Tel. 3855. Kr Is. Size. tin. di:un, x 1 fin. high. 9/6 each. missing his many friends this year, and transformer rewound and con MINIATURE ROTARY SWITCH. 4 pole. s way. 3'9 thanks his "allies The Lowther specification; prompt de. each. Manufacturing Co. who MAINSstrutted to any iron supplied are exhibiting livery.- Brown, 3, Bede Burn Rd.. Jarrow. 3460 All coils fitted with adìualahle cores, and LOWTHER VOIGT repairs, British, American, with circuit diagram. RADIO PERMS : Cash trial orner or e.v.v. on orders over El. LOUDSPEAKERany make; moderate prices.-Sinclair (Gallery, Nat. Hall Stand 323) Speakers, 12, Pembroke at. London, N.1. for to accept messages Terminus 4355. [3308 MONOCHORD RADIO arranging LOUDSPEAKERS repaired; transformers. (Established 1929) rewound; prompt VOIGT PATENTS clock coils, chokes, 17, Streatham Hill, London, S.W.2 attention; prices quoted. -E. Mason, 5, Balham Phone: Tulsa Hlll 101112 LTD. Grove. Balham. London. S.W. [7667

www.americanradiohistory.com 74 Advertisements Wireless World October, T947 measuring instruments skit- ELECTRICALfully repaired and recalibrated.- Electrica Instrument Repair Service, 329, Kilburn Lane, HARTLEY- TURNER London. W.9. Tel. Lad. 4168 [6935 "DICK-UPS, rep:acement coils for Garrard HIGHEST FIDELITY SERVICE type, etc.; 5/3; trade enquiries invited. - Radiocratts, 10, Goodmayes Rd.. Goodmayes. Essex. 'l'el. Seven Kings 4557. [7919 ANNOUNCE for 1948 REWINDS and conversions to mains and CONDENSERS output transformers, fields, etc., from 4) 6 Speaker Model 215. Local- Distance T.R.F. pp equipment a speciality. -N.L. Rewinds. 4, Receiver Unit. Brecknock Rd.. N.7. 'Tel. Arnold 3390. [6283 of all types . . . " SERVICE with a Smile. "- Repasrers of all 28 watt Amplifier and Versatile Tone -Con- Power Unit. 1,-.3 types cf British and American receivers: trol and Pre -Amplifier coil rewinds; American valves, spares, line Unit. ceird.- F.R.I., Ltd.. 22, Howland St.. W.1. FOR IMMEDIATE The "BOFFLE" and Museum 5675 11575 We can offer, "VERMEX" Speaker Balanced Whistle - to moving coil speakers. cones, DELIVERY from very generous Cabinets. Filter. REPAIRScoils fitted field rewound or altered; Styluses. speaker transformers, clock coils rewound, stocks, a wide range of ultra -high Pick -Up and Jewelled guaranteed satisfaction, prompt service; no mains trans. accepted. quality fixed paper Condensers, L.S. REPAIR SERVICE, 49, Trinity Rit., AND Upper Tooting, London, S.W.17. [4819 from .00I µF to 8µF. Also STOCKS STURDY rewinds, mains transformers, of small, genuine MICA Conden- chokes and fields; we give prompt delivery " NEW NOTES IN RADIO " and guarantee satisfaction; 14 years' expert sers from .00001 (10 p') to .01µF Fifth Edition. A complete guide to High Fidelity ence; prices on request.- Sturdy Electric Co., Price 3/6d. 2d. Postage. Ltd., Dipton, Newcastle-on- Tyne. [4316 (10,000p`), Prices are exceedingly Reproduction. t and transformer repairs LOUDSPEAKER"almost by return of post "; we offer the moderate. Supplemented by the - quickest service in the trade, at competitive HARTLEY - TURNER Recommended prices. Send ld for our monthly service bul- Enquiries are invited for bulk letin, Dept. W,- A.W.F. Radio Products, Ltd., Record Catalogue and a series of Borough Mills, Bradford, Yorks. Tel. 22838. quantities, and for scheduled de- Technical Bulletins. repairs, any make, reason LOUDSPEAKERable prices, prompt delivery, to the trade liveries over a period, as required. Your name on our Mailing List and quality fans; 25 years' combined experi ence with Rola, Magnavox, Goodmans, Coles Condensers of close or very close will ensure that you receive all tion. -Sound Service Radio, 80, Richmond information on High Rd.. Kingston -on- Thames Kin. 8008. [4977 tolerance can be supplied within the latest REWINDS, mains transformers, speaker field Fidelity Reproduction as issued. coil, chokes, high -grade workmanship, 7 about one week. day delivery; new transformers constructed to You can see and hear all these new and exciting customers' specification, singly or in quanti- products at any time at our showrooms, which ties.- Metropolitan Radio Service Co., 1021. will be open late during the Radio Exhibition, Finehlev Rd.. N.W.11. Speedwell 3000. [3719 which is quite near us. HOUR service, 6 months' guarantee, any 24 transformer rewind, mains output. CLAUDE LYONS LTD. and Liss., etc., all types of new transf., c I supplied to specificalion; business headin;; 180, Tottenham Court Rd., London, W.1 H. A. HARTLEY CO. LTD. service, card for trade prices. -Majestic Win l Bournemouth. and 76, Oldhall St., Liverpool 3, Lancs. 152 Hammersmith Rd., London, W.6 ing Co., 180, Windham Rd., COIL specialists . -Tuning and oscillator coils, Telephone : RiVerside 7387. I.F., L.F. and mains transformers re RPL/P.36 wound and wound to specification; wavewiud ing, L.S. repairs. -Electronic Service, (lt.T.R.A.), 17. Arwenack St., Falmouth, LRS /DELIVERY from STOCK Cornwall; and 49, Uxbridge Rd., Ealing, W.5. REWINDS, mains transformers, layer wound wax impregnated, O /l' trans- MORSE CODE '-AVOMETER Model i ... £19 10 0 formers, chokes fields, clock coils, pick -ups, (Carr Ifni packiug 2 /6 extra) fractional hp motors, competitive prices, TRAINING prompt delivery ; guaranteed work. -W. Groves. Avominor DC Test Meters' ...... 'a Ge. Manufacturing Electrical Engineer, 154, Ick Avominor AC /DC Test Meters* ... £8 10 ' Meld Port Rd.. Birmingham, 16. [4547 There are Candler -Armatures fields, transformers, Morse Code `Plus 1/- Regd. poet and supplied on Easy Terms If REWINDS.pick -ups. vacuum cleaners, gram. motors, Courses desired. speakers refitted new cones and speech coils. for Stuart Centrifugal Electric Pumps Al; guaranteed and promptly executed. New BEGINNERS AND for all pumping purposes, garden fountains, etc. vacuum cleaners, most popular makes, Send No. to. zoo galls. p. h...... IS 10 6 stamped addressed envelope for list of radio OPERATORS. spares and c.o.d. service. -A.D.S. Co., 261 -3 5, Send for this Free Lichfield Road, Aston, Birmingham, 6. 18238 inc. foot valve and strainer, cary. paid. STUART repairs.- L. Cottenham for "BOOK OF FACTS" adJustable fountain Jet, 5/3. LOUDSPEAKERyour loudspeaker repairs. all types re- Morphy Richards Cyldon Door Chimes ... 49/a paired at keen competitive prices; field coils it gives lull details con- l'est Free. rewound to any resistance; quick service and cerning all Courses. guaranteed satisfaction. -Send to L. Cottenham, The LONDON RADIO SUPPLY CD Loudspeaker Repair Factory, Wfiel-ley Lane, THE CANDLER SYSTEM CO.; (The L.R. Supply Co. Ltd.) si. 1925 Bradford. Yorks. Enquiries will receive im- mediate attention. [8350 (Room 55W), 121 Kingsway, London, W.C.2 BALCOMBE .USSEX RADIO SERVICE a 'tELE- Candler System Co., Denser Colorado, U.S.A. NA'l'IONALVISION CO -Trace service engineers: immediate service any district; rewinds to all types transformers, armatures, motors. le ud- speaker cones, speech coils fitted, British and SEND US YOUR LIST American components and valves; enquiries invited for contract trade service: multiple ROTARY of requirements, and we will immediately let transformer winding. -63. High St. St. John's you know which items -usually 99.5 % -we Wool N Ws Primrose 6725 16752 WARD CONVERTERS can supply FROM STOCK, and the prices. T EGAILIER'S, Ltd.- Service with a gutar- changes in supplies and prices 1/ antee. If you cannot get your receiver For Radio, Neon Signs, Tele- Present constant serviced. let American specialists do the job; make the issue of a worth -while Catalogue first class workmanship only: specialising in vision, Fluorescent Lighting, almost impossible, but we DO carry the most Air -King, Belmont, Challenger. Delco, Detrola, -ray, comprehensive stocks of Radie Components, de Wald, Emerson, Ferguson, Garod, Hamtner- X Cinema Equipment and Valves, Material and Test Equipment in the lund, Hallicrafter, Lucille, McMurdo Silver, innumerable other applications trade ! Midwest, Majestic. Pilot, Philco, Scott, Spar - ton, Zenith, R.C.A , etc., also any British set; For a new experience in PROMPT and diligent our service We also manufacture: send your enquiries today, due tc lack of accommodation - attention branches are still dispersed; therefore apply for Petrol Electric Generating Plants, H.T. PRINTING your name and address in block forwarding instructions before despatching sets; capitals, and enclosing lid. stamp. s.a.e. with all enquiries.- Degallier's Ltd., Generators. D.C. Motors. etc., up to

1 25 BCM i DE1.19, London. W ('.1 8043 K.V.A WIRELESS SUPPLIES UNLIMITED MISCELLANEO US SPEECH disability; Mr. 11. V. Ilemery con- CHAS. F. WARD 264 -266, Old Christchurch Road, suits at Wigmore Hall Studios, W.I. chassis panels to your own LERDSCROFT WORKS, HAVERHILL, SUFFOLK BOURNEMOUTH, Hants. ALUMINIUMspecification from 3/9 each.- M.E.A,D Telephone: Haverhill 253 & 4. 13, Bence Lane, Darton, Barnsley. [8290

www.americanradiohistory.com October, 1947 Wireless World Advertisements 75 W. " bound volumes, 1929 -38, " Harms FF worth Wireless Encyclopedia" (3 bound volumes).-14, Southlands, Newcastle -on -Tyne. SALE. -Copies of journals, inc. " W W.," B.T. Elec. Eng., also books; s.a.e. details -R. Rowlands, The Laurels, Hawarden, Chester BRAND new 9.M surplus 2-volt radio ao cumulators ARMSTRONG J at ess than hall the usual price 8/6 post paid; trade supplied. -Dept. 8.. Enfolds. High St., Metsem,' Norton. Som. STAND No. 205 SMALL quantities of the following wire for sale, 28swg, D.S.C. Eureka. 34swg

En.S.S.C. Constantin, 34, 36. 38, 40. 42swgs, Overseas Buyers are - cordially invited to visit copper enamelled S.S.C. -Box 2977. [8456 Lat.ESSPAH.- Paxolin- Laminated ba kehte, our stand and inspect the excellent design and 1 etc., squares and strips, wide variety, useful for workshop; per lb, 3,6; special workmanship of our new range of Radio Chassis. assorted 51b sample parcel, 12/6, post free.- The Television Development Co., 4, The Model Parade, High Rd., Kilburn, N.W.6 Tel. Mai EXPI25. 14 -VALVE ALL -WAVE RADIOGRAM CHASSIS 3991. [8257 giving continuous wave -band coverage from 11.9 m. upwards. Wave-band expansion. -GOVT. elec. lamps, brand new. ring R.F. Pre -amplifier. Two I.F. stages with variable selectivity. Electronic bass and treble EX makes; one million in stock at approx. lift controls. I S watt push -pull output. For 200 -250 v. A.C. mains. 75 per cent off list prices; 2 volt to 230 volt; 0.2 watt to 1.500 watts; various caps; Prefocus Model RF103. I0-VALVE ALL -WAVE RADIOGRAM CHASSIS. Projectors, 12 volt to 230 volt; send for list; 10-Valve circuit. R.F. Pre -amplifier. Wave -band expansion (Short wave -band covers over special prices for export, etc -Auto Collections, 20 "). Large glass scale. 3 stages A.V.C. Treble lift control (operates on both radio and Ltd., 126, St. Albans Ave., Bedford Park, W.4. kramophone). Plus 6 db. Bass lift of Gramophone (to restore bass cut on some records). Tel. Chiswick 1601. [8122 10 watt push -pull output. For 200-250 v. A.C. mains. Prov. Price 18 tube, lin 20 gauge 9d ft, Plus P.T. bgns. DURALUMIN13ft 9/ -, 7 /16in 16 gauge aluminium tube 6d ft, max 12ft lengths; aluminium Model UNI -103. 10-VALVE ALL -WAVE RADIOGRAM CHASSIS chassis 18 gauge 10x8in 5 /6, 12x9tn 6/ -, FOR D.C. -A.C. MAI NS. 10 -Valve circuit. R.F. Pre -amplifier. Wave -band 16x8in 6 /6, 20x8in 8/ -, 22x10in 10 /6; all expansion (Short wave -band covers over 20 "). Large glass scale. 3 stages A.V.C. 21/2in depth; Treble aluminium sheet 22 gauge 1/4, lift control (operates on both radio and gramophone). Plus 6 db. Bass lift on Gramophone 20 gauge 1/9, 18 2/ -, 16 gauge gauge 3/. (to restore bass cut on some records). 6 watt push -pull For v. sq ft; all postage extra; also in stock alumin- output. 200-250 D.C.A.C. mains. . ium angle, 4's,`á, r/s, lin; flat strip, moulding, Prov. Price send s.a.e. for list of aluminium, etc-Fan- gns. thorpe, 6, Hepworth's Arcade, Hull. [8285 Model EXP83. 8 -VALVE ALL -WAVE RADIOGRAM CHASSIS RADIO and electrical accessories ex stock incorporating wave -band 6BA expansion. Large glass scale. Treble boost control. Gram. brass lockouts, 1 /10 per gross switching. High quality push -pull output gives 10 watts audio. For 200 -250 v. A.C. mains. (minimum 20 gross); a varied selection of BA screws, nuts, bolts, etc. (list on application). Price Paxolin strip and tubing, 2/- per lb; twin Plus P.T. 14 nS. screened flex, 50 /- per 100 yards; 50,000 Model UNI -83. 8 -VALVE ALL -WAVE RADIOGRAM CHASSIS ohm wire wound volume controls, 25/- per incorporating wave -band expansion, e.g. the 16 -50 mm- band covers just over 20 inches dozen ; coil and valve screen tins, 1 9/16inx on the large glass scale, treble control, gram. all 1s6iinx41/4in, boost switching, controls work on both 3/- per dozen; tinned copper radio and gram., high quality push -pull output giving 6 watts audio. For 200 -250 v. D.C. wire (minimum 561b), 2/- per 1b; radio or A.C. mains. chassis, 8inx61,/,inx21/2in, £5 per 1007 Price trans Plus P.T. 14 gns. mitter racks, 21in x 19ín x17in, 15/ - each JOHN DOWN'l'ON & Co., 89. High St., Epp - ing, Essex. Tel. Epping 2163. [8282 WORK WANTED NSTRUMENT gear ending capacity. -Lloyd & Ramsden, Huntingdon St., Nottingham. L]UHT press capacity available up to 25 tons. and assemtly. in London area. -Box All new Models All Models can 1437. [8074 WE make wireless and radiogram cabinets be heard during for home and export; immediate de- can be seen liveries.-Radiac, Ltd., 26, Brondesbury Rd., business hours London, N.W.6. Maida Vale 8792 [8025 on our stand CAPACITY available press tools, plastic at our Show- moulds, jigs and fixtures; production, %in at Radiolympia capstan capacity. -Blair Tool Products, 112, rooms Greyhound Lane, Streatham S.W.16. [7959 %WINDERS, 74a, East Hill, Wandsworth, 461.1ssssssi FO S.1V.18, are now able to quote you for your light press walk, blank form or pierc- 1 ings, milling, turning and guillotining, [8382 enthusiasts! Have that new high OUAL1TYfidelity set you are contemplating de- signed and /or built by a specialist; all types of apparatus built to requirements -Write for quotation to BCM /HIFIDEL, London, W.C.1. ARMSTRONG TEILEVES 7o r8.; COMPANY LTD. and tracing work for radio and DRAWINGelectrical engineering, jig and tool and light engineering, photoprinting; full sets of Warlters Road, Holloway, London, N.7. NORth 3213 drawings undertaken to commercial or Minis- try standards.- Drawing & Tracing. Ltd., 456a, Ewell Rd., Tolworth, Surbiton 'Phone Elm - bridge 7406. [7703 TELEVISION aerial installations and aerial maintenance, full range of antennas sup- plied and /or installed by experts; removals "ENGINEERING and re- erections arranged; our pre -war Trade Service Dept. is now open. -Brochures from COVENTRY OPPORTUNITIES' Wolsey Television, Ltd., 87, Brixton Hill. This unique handbook S. W.2. 'pulse Hill 1240. 17320 shows the easy way to BUSINESSES FOR SALE OR WANTED RADIO secure A.M.1.Mech.E. manufacturing radio business in A.M.Brit.I.R.E. A.M.I.E.E., ACTIVEMidland industrial city, with retail side. COMPONENT SPECIALISTS SINCE 1925 City and Guilds, etc holding exclusive pre -war American agencies, extensive export sales with wide -world demand, 2 -gang .0005 mfd. Condensers, Ise WE GUARANTEE - grade 1119 I amble of expansion; £25,000. -Box 2592. "NO PASS -NO FEE." EASTBOURNE (the " sun -trap of the Slow Motion Drive, dial, glass and Details are given of over 15o south "I; electrical and radio business escutcheon, 3 wave -band, 7in.x4in. 11,9 Diploma cour ses in all for sale as going concern; shop, charging - well Toggle Switches, Q.MB., S.P. on -off branches of Civil, Siech., room and large -fitted workshop; hstsy Elec., Motor, Aero,. Radio, position; rent £90 p.a., 14 years lease; Metal Rectifiers, 12 -volt I amp. L.T. 10/- Television and Production £1,500; " all at " s.a.s'., ofd-established.- Signal Lamps, Red or Green type, D49, Sole Agent, George Howard, P.A.I., P.A.S.I., Engineering, Tracing, Building, BuIcin, 2 9 each, or 24/- dozen. 56, Grove Rd.. Eastbourne 3569. 18272 Govt. Employment, R.A.F. FINANCIAL PARTNERSHIPS Latest L ist. 3d. post paid. Maths., Matriculation, etc. I.Er"l'IfICAL radio engineer seeks active Safeguard your future; vend T'd pt. a tcrship London business, £200 -£1,000 191, DUNSTABLE ROAD, 'or your copy at once-FREE. call.h),-: also wiring, appliances, office ad- LUTON. 387, SHAKESPEARE HOUSE, rnmtstration and export experience; travelled. Phone Luron ?6 7, linguist. -Box 2203. [8214 17, STRATFORD PLACE, LONDON, W.

www.americanradiohistory.com 76 Advertisements %Vireless World October, 1947 WANTED a working partnership in small progressive radio electrical business in West Country, some capital available. -Write Several Fine Offers! HILL & CHURCHILL LTD. Box 2530. [8288 SITUATIONS VACANT EX -ARMY No. 38 SET Holloway, - BOOKSELLERS NORTHERN Polytechnic, N.7. (Walkie- Talkie). Complete with valves, two mikes, two pairs phones, junction box, Body immediate appli- throat THE Governing invite haversack, sectional aerial, range 7-4 to 9 Mc/s, SWANAGE, DORSET. cations for appointment as full -time lecturer in radio engineering; salary scale: £300x E4.5.0, carriage paid. Available from Stock: £15 -£525, plus £36 -£48 London allowance, CLASS D WAVEMETER - together with other allowances in accordance Complete with crystal, valve and vibrator, Zworykin and the "Electron Optics with the Burnham Award; forms of applica- spare valve and vibrator, brand new, in transit & others. Electron Microscope " - - 60 - tion, together with full particulars, will be case, E3.19.6, carriage paid. Bernard "Electronics and their appli- forwarded on receipt of a stamped addressed PERFORMANCE METER No 2 Lovell, ed. cation in Industry and foolscap envelope. -It. II. Currell. Clerk. For A.C. mains 230v operation, complete with Research " ------42 - IIROWN Agente for the Colonies.-Appli- 1 cations from qualified candidates are these valves : 2, EF50, I, EC52, I, 5Z4G, I, EA50, Chute in Industry " 25 "Electronics invited for the following post: - I, Y63, Magic Eye. This instrument is brand new Kiver "Television Simplified" 27- BROADCAST Officer required by Gold Coast and built into a grey steel case, size 9x IOx8ins. -, 7/6 Huxley "Wave Guides" - - - 21 - Government for 1r/1 to 2 years, with possible Splendid bargain. To callers, 45/ or extra permanency; salary according to age and for carriage and packing. war service in RADIATION LABORATORY SERIES scale £600 to £970, including MCRI Receiver, with power pack, phones, etc., overseas pay; outfit allowance £60; free pas- I (ready shortly), free. No. sages; candidates should have hail thorough EF.5.0, carriage "Radar System Engineering" 37/6 training in theory and operation of wireless U.S. Navy Indicator, No. AN /APAI, with C.R. Other volumes to follow. broadcast transmitters and in studio tech- Tube and I I valves. Callers, £4.I0.0, or carriage Postage extra nique; should understand thoroughly the free £4.17.6. system of distributing radio programmes by R1147 UHF Receiver, with 7 valves, 39/6, carriage wire and have thorough knowledge of super- heterodyne free. We have a large selection of shortwave receivers; knowledge of etc gramophone disc recording desirable. We stock full range of Standard Components, -Apply for details and prices'_ English and American Books on at once by letter, stating age, whether mar- Send for our List " W.W." ried or single, and full particulars of quali- CHARLES BRITAIN (Radio) LTD RADIO and TELECOMMUNICATION fications and experience, and mentioning this E.C.2. paper, to the Crown Atrents for the Colonies, 2 Wilson Street, London, CATALOGUE ON APPL?CATIOAN 4, Millbank, London, S.W.1, quoting MIN/ (Phone : BIS 2966.) 13418 on both letter and envelope. [8341 ADIO service engineers required for car radio installation and maintenance: all parts t l' K torsi emnlovment.-Box 2812. [8374 EQUIRED urgently, competent radio ser- & COILS R vice engineer, able to drive; good oppor- TRANSFORMERS tunity for right man.-Box 2534. [8314 radio television engineer re- y Ideal for TO SPECIFICATION. QUALIFIEDquired; excellent, onnort,unities to keen C,. high and low capable man. -Write Robert Bennett, Ltd.. 73. " voltage testing ; 1/30. MANUFACTURED OR REWOUND Stroud Green Rd.. NA. [8366 W\ \`, , 100;850 A.C. and D.C. FACTOR LTD., position is offered to an ex- Allowance made on old modela JOHN APERMANENTperienced and skilful radio and television Send interesting leaflet (11.14) on Electrical and service engineer; wages for (Formerly Stanley Cartel! Ltd.), good and conditions; Radio Testing, from all Dealers or direct. Harrow district. -Write full details to Box 9-11 East Street,TORQUAY, Devon 2985. [8472 R UNBAKEN MANCHES TER I 'Phone: Torquay 2182 Air Ministry has vacancies in the THEMeteorological Office organization for a number of civilian Radio (Meteorological) Mechanics to maintain radio and radar equip- ment. APPLICANTS must possess a knowledge of BROOKES CRYSTALS the fundamental principles of radio and radar and have hail practical experience in the use EST. 1929 LTD. of tools, filing, drilling, hard and soft soldering, wiring, and in the maintenance and use of 'Radiospares' electrical radio and radar instruments, includ- FOR ing cathode ray oscilloscopes PREFERENCE will be given to former R.A.F. HIGH PERFORMANCE personnel, and any other ex- Servicemen pos- utility Parts sessing the requisite qualifications; staff se;ected OSCILLATORS will be required to serve at any station at home or abroad, and in the case of appoint- AND ments at horns units, will generally be expected The to make their own arrangements for accommo- RESONATORS dation; successful applicants will be engaged on a temporary non- pensionable basis only at Serrice Engineer's commencing weekly wages (in the United King- ACCURACY GUARANTEED dom) of £6 5a per week (inclusive) for ap- pointees aged 21 and over. First Choice APPLICATIONS should be addressed to Air 51 -53 Greenwich Church Street, Ministry (S.5.11), Bush House, North -West Wing, Aldwych, London, W.C.2. (8450 S.E.10 'Phone: GRE. 1828 RADIO service engineer 'required, able to London, drive, good wages and conditions for right man. -Thorogood Radio, Ltd., 44-5, Tamworth Rd., Croydon, Surrey. Tel. Croydon 7417 -8. [8313 laboratory assistant with some CALLING AMATEURS JUNIORknowledge of physics and some electrical with BUCCLEUCH POSTWAR TELEVISION training.- Write, giving details of experience, age, etc., to : A. H. Hunt, Ltd., Bendon Precision Built Equipment The advance in Radio 1 ethnique offers unlimited Valley, S.W.18. [8354 l'HASS'S SMOOTH BLACK opportunities of high pay and secure poste for those charge hand for high frequency 171" o 10" x 21', 919. Radio Engineers v-ho have had the foresight to become WORKINGand power test department; preferably 17-x15 x2 ", 819. Haw you can do this quickly with knowledge of high power PANELS- CRACKLE technically qualified. oscillators; 19'x08",4/ spare time it fulls explained in our West London; age, experience and wages re- -. and easily In your 10-x7 ", 6/9; unique hand hook. quired, to : Box 2885. [8378 la'a8f', clerk required by large 7/9; Full details are given ot A.M.1.E.E, A.M.Brit.I.E.E., progress 19" x 10 }', 8/9. MALEradio manufacturers, S.E. London area; ANGLE BRACKETS, 12I" long, pr.7/6. City & Guilds Exams., and particulars of up -to -date must have experience of purchasing progress; Radio (All in Bright Aluminium, same coat.) Courses in Wireless Engineering, Servicing. write, stating age, experience and salary re- COMPLETE RACK ASSEMBLY Short Waves, Television, Mathematics, etc., etc. quired, to Box 2597. [8329 (Rigid 4-Piilar), 53', 93/51.8111", £2 /5e. Chassis, etc., to order, "NO PASS -NO FEE' !'f ENTL1' SEAN required immediately to Id ,q. inch. We Guarantee Jf handle export matte's in connection (Include aldea when costing,) Prepare for to- morrow's opportunities and post -gar with radio receivers; it is essential that he PUNCHING CHARGES UP TO 1", 2d. competition by sending for your copy of this very understands the radio market and has suit- VALVE HOLES, 1 ", 15- or 1f-, 6d. formative 1l2 -pose guide NOW -FREE. METER HOLES, etc., 1/6. able contacts. Box 2886. [8380 SQUARE HOLES, 2/ -. BRITISH INSTITUTE OF ENGINEERING established firm of quality radio BUCCLEUCH RADIO MANUFACTURERS WELLmanufacturers require sensible works TECHNOLOGY (Dept. 388, 1 & 2 MELVILLE TERRACE, EDINBURGH, 9 manager, able to maintain production and '6'ramx: Tlotm," C'dinturgl,. 17, Place, London, W. keep in Stratford records thereof the customary manner; Factory: il'/t- ,,field St.. Rrtiot.0. h. state age, exp. and salary required. -Box 8150.

www.americanradiohistory.com Uctober, 19¢7 Wire less World Advertisements 77 CrALESMAN to take over small radio de- t partment; experience and some tech- nical knowledge essential; write fully, stating salary req.; W. London district-Box 2813. RADIO engineer -operator required for radio station in North London; applicants must have good servicing knowledge of com- MWILSO$ T° munications receivers, be able to receive morse at 25 -30 w.p -m. and have good typing speed. -Write Box 2595. [8327 DURING

DRAUGHTSMAN- ILLUSTRATOR wanted 1LJ for 'l'echnigen Publications; practical knowledge of radio essential; write, with full " RADIOLYMPIA" particulars of career, age and salary required, to Lewis George Laboratories, 222.229, Ham ,one are holding a mersmith Rd.. 1V.6. [8357 JUNIOR laboratory assistant, 20 -22, with some knowledge al chemistry, preferably up to Inter -B.Sc. standard, for raw material and process testing-- Write, giving details of SPECIAL experience, age etc., to : A. H. Hunt, Ltd., Bondon Valley, S.W.18. [8353 TRANSFORMER designer required for de- velopment dept., S.E. Lanes radio firm, for EXHIBITION work on transformers up to Skva; capable of full design responsibility; qual. degree std. or nl Grad. LE.E.- Apply, stating age, experience and salary required, to Box 2811. [8369 14ARGI: organization in West Middlesex re- 307 HIGH HOLBORN quires field service and workshop engin- LONDON. \V.C.1 eers with good television and radio teeluw.al knowledge; smart appearance, car, an advan- tage, but not essential.-Reply, stating details Last exp., age and salary reqd., Box 2145. gear superintendent required for ex TESTpaneling radio component factory, subu RADIO RECEIVERS ban, Surrey; qualifications, degree or equi va lent, previous experience in development of mechanised testing desirable; salary £500 and AMPLIFIERS upwards, according to qualifications and ex perience. -Box 2537. 1831e built from our BLUE PRINTS I' Et ELUPMEN'P engineer required for lab - 1J oratory investigation and measurements also the *^ 3 WAVE BAND in connection with development of cables for radio frequencies; university degree or equiva- lent; salary up to £400 per annum. -Apply UNIT SYSTEM OF RADIO AC /DC 200/250 Volt Personnel Manager, Standard Telephones & Cables, Ltd., North Woolwich, E.16. [8279 CONSTRUCTION RADIO. -A vacancy arises for a junior en- *^ Two -Colour Plastic Cabinet gineer with engineering degree or Higher National certificate and with some experi- TELEVISION CHASSIS Built -in Hemoscope Aerial ence of receiver design for production; age * about 25 years, West Middlesex district. -Ap- ply, giving age, details of education and ex- COIL UNITS and perience, with salary required, to Box 2533. Full Vision Illuminated required to call on customers of POWER PACKS MANradio component manufacturers; some Tuning Dial technical knowledge essential ; previous ex- perience unnecessary; only ex- Servicemen Miniature in size (10)" x 6" x 6 "), but gigantic in under 35 years of age in easy reach of Wem- You are cordially performance and tone. bley district should apply; give full particu The " Comet " is obtainable in Light Walnut, Dark lars, age, exp., salary required, to Box 2599. first-class, urgently re- invited to call, Walnut, Back, Maroon, Cream, or pastel shades of DRAUGHTSMAN, and green. quired for local engineering concern blue, pink with experience in machine design and /or jig see, and listen Price £14.14.0 and tool work; 5-day week; excellent work- ing conditions.- Write, stating age, Plus E3.5.4d. pur. tax. experience and salary required, to : Personnel Officer, Write for full particulars. Ferguson Radio Corporation, Ltd., Great OPEN UNTIL 8 P.M. Ca mbridgc Rd., Enfield. [8348 REQUIRED by large radio manufacturer in Greater London area engaged on modern high -speed production of complex receivers, OCTOBER lst_llth C £AM!O chief of test and assembly foreman; also superintendent of radio production with ex- tut' minute's walk front Chancery Lan, ELECTRIC CORPORATION perience of chassis assembly, roil winding Underground Station Seaford, Sussex. 'Phone Seaford 3235, 67 and assembly methods. -Write full details. salary required to Box 2538. [8317 Ex part : Agents MURP1fY RA OW, Ltd., have a vacancy 307 HIGH HOLBORN. Geo. Vint & Co., Ltd., for a senior rng:ricrr having consider LONDON W.C.I. Phone.HOL6orn 124, Seymour Place, London, W.I. able experience in the development and design 463/ of communication receivers and allied equip ment. -Apply in the first place in writing, giving full particulars and stating salary re- nnired, to : Personnel Department, Murphy " "din Lid.. Welwyn Garden City, Herts. for TECHNICAL advertising assistant for pub- LONDEX RELAYS Reify department of imro "tañt radio valve manufacturer; duties would include writing REWINDS for copy for advertisements. booklets, press articles; Send your burnt -out A.C. and D.C. every facility fo^ keeping in touch with latest radio developments. -Write in confidence. giving transformers to be rewound. 2 VA Coil consump- details of experience, present position, and tion from 2 to 600 salary required, to Box 2976. [8449 No technical data wanted. volts and tested to are invited for the position Post Transformer well packed, APPLICATIONS rmuprehensive 2000 volts, Aerial of manager. having know ledge of design, production and rewi ni ling of labelled with your name and change-over Relays, small electrira.I and radio transformers: pre- address and marked mercury Relays, mea- vious practical especieuw essential ; South suring Relays and London district. -Write full details please. stet - " For Rewind " ing salary required to Box 5052, Frost Smith time delay Relays. Adve.. OA. Finsbury Pavement. London, E.C.2. A new " Telecraft " Cone and for telecommunications research speech coil will improve your Midget Relay ML,C Ask for leaflet REQUIREDcompany near Maidenhead. engineer or RE /WW physicist to [undertake standardization and Loudspeaker. special measurements for the establishment and development of special purposes measuring ap STD, paratns if required; salary scales, with annual SOUTHERN TRADE SERVICES, LTD. LONpEXLTp increments. and pension fund. -Apply in writ- of RELAYS MANUFACTURERS 6258 -9 ing, Box No. 856. Vorlands. 18 -20, Regent St.. 297/299, HIGH ST., CROYDON 207 ANERLEY ROAD - LONDON S.E.20 London, S.W i [8473

www.americanradiohistory.com 78 Advertisements Wireless World October, 1949 COMPETENT radio service engineer re- Special Offer! quired, with experience on all makes of receivers ; television knowledge useful ; North London area. -Apply Ferguson Radio Cor- EVERY COIL poration, Great Cambridge Rd., Enfield. [8347 is tested ans supplied with its test card A typical .<_ Weather 14ft. AERIAL MAST RADIO mechanics.- Vacancies exist for ex- test card of the S.A.2 (medium wave aerial coil) is -proofed perienced mechanics (preferably ex -Ser- shown below. paxolin Consists of two lengths of vice) for the repair of test equipment; special knowledge of test equipment an advantage, FINAL TEST on coil TYPE S.A.2. tubing paxolin tubing 21Iin. and 31in. but not essential; assisted travel from Not- Inductance, 170 dia, respectively, with 3'xfin. tingham, Leicester anti Melton Mowbray is given. wall. The smaller -For details, apply to the Establish- Frequency Metres Capacity Magnifica- tube fits ment Officer, Central Ordnance Urpo), Old tightly Dalby tion (Q) K_Aluminium into the larger, both Leicestershire. [8343 having metal ends. When WANTED for service in Indian State, dry S50 545.4 500 mid. 80 ferrule healthy climate signals officer to act as 650 461.5 355 80 fitted the aerial mast has an second in command police communications. Applicants 700 428.6 305 80 over -all length of 14f t. Ideal most have technical experience 800 375 235 70 operating and servicing medium power trans- for a transmitting or receiving mitters and receivers and have 900 333.3 185 65 served m the 1,000 300 150 50 aerial, but has Allied Forces in a rank not lower than ser- many other geant.- Applications, with full particulars 1,100 272.7 124 45 Paxolin uses also. May be fixed to and salary expected, to Box 2938. [8411 1,200 250 104 30 CHIEF storekeeper 1,300 230.8 88 tubing the ground or to a fixture required, age 35 -45 25 years; applicants should be experienced ,400 214.3 73 00 3%4 "die such as a chimney, wall, in modern methods of storekeeping of large 1,500 200 63 80 etc. Very sturdy. The price quantities of radio and similar components and capable of handling mixed labour; the Tested by E. M. Date 21 -7 -47 for the complete article is position offers good prospects and salary in Complete coverage 13 Aluminium only 21 - carriage paid. accordance with experience. -Write, stating from metres to 2,000 base age, experience and salary required, to the metres. Labour Manager. Bush Radio, Ltd., Power 411 coils fitted with adjustable iron dust cores. ALEC DAVIS Rd. Chiswick, W.4. [8342 For full details of our products write for our catalogue. tockists of Government Surplus Radio Gear. designers, age 30 -40. cap - -aECHANICALt able of completing mechanical design of 8, PERCY ST., TOTTENHAM COURT fixed or mobile transmitters to electrical in- A. SUMMERSBY, RD.. LONDON, formation supplied. supervising detail draw- W.C.1. MUSeum 2453 ings, preparation of stock lists and purchasing MILL LANE, MARGATE, KENT specifications, location South -West London. - Margate 2409 Write, stating age, experience, salary required and when free to commence, to Group Staff Officer 1311, Philips Lamps, Ltd., Century House, Shaftesbury Av., London, W.C.2. TELECOMMUNICATIONS engineer required by Standard Telephones & Cables, Ltd.. NEW North Woolwich, 1,.16, for the design and de- GOODS ki.9110Built up velopment of radio frequency testing equip- Aluminium Chassis, punched for 5 valves, chassis. ment for carrier telephone and television and transformer 8 8 8- Waveband Coilpaek by famous maker, I Factory assembled units cables; applicants should possess on honours degree in engineering or physics anti have hail with dust -cored coll, to fit above chassis £1 15 0 oModel ASO. All -Wave 5v. Superhet experience on comparable work; salary up tt Dust -cored I.F. Tram Special High " Q " radiogram chassis 12 gas., plus PT £450 per annum according to qualification'- 985 K.0 per pair 17 8 54 - or with magic eye), £13.5.0, anal experience. -Apply Personnel Manager. Circuit Blueprints and all other components for the plw, 57i -. constructor. Send for list. Model 92A. 4v. chassis. for coil -winding shop urgently Special for W.W." Television Receiver, All -dry portable long and FOREMANrequired for " med. wave, £9.15.0, plus PT 4213. new factory in South Wales, E.F.50 Valves les -Govt. but perfect) .. each 12 8 Model 88. 15 -watt istortionless amplifier, made small transformers, chokes, and F.H.P. American Sin. Cathode Ray Tubes, from finest quality material and each unit carefully motors; first -class equipment; gond prospects Magnetic type with flat screen, complete checked for wave Orin with oscilloscope. £25. of advancement for right man; accommodation in shielded assembly with coils, focus and brilliance controls. Long persistence, Tuning Inductances. 3 available; only persons with many years' shop ideal No, 100. -wave coil kit with for photography. Data with RN stage with instructions and circuit, 2 experience nova apple.- Please reply in first each .. each £2 10 0 gas. 0 -1 mA Meters, 311t. scale, res. 100 ohms, Series 1 Coils. High -grade inductances on low loes ' nstance. stating fully, previous experience, by world famous maker. The perfect basic formers to cover 12- 2000m. Ae. 11F or Osc. names of previous : Guar. employers, to Box T., e/o meter. Shunts and multi's to your order matched 1 per cent. Ranges and siae similar to Smith', re. .Aberdare. Libra 18360 each £2 P coils. 2 6 each. senior jig and tool 5 0 The TEL.ERAQIO Co., DRAUGHTSMAN,urgently required to fill interesting and 157, Fore Street, Edmonton-, N.18. progressive vacancy in new light engineering MORTON & DISMORE 'Phoneare : Tottenham 3386. factory in South Wales; only highly experi- enced people need apply; excellent working 52c Oldchurch Rd., Chingford, E.4 conditions and high remuneration and accom- modation found within reasonable period. - Please reply in first instance, stating fully, pre vious experience, names of previous employers and salary required, to (Box No : - T) Smith's Library, Aberdare, [8361 3.ß.0® MI10 ENTHUSIAST with a knowledge of ampli- 100 kcs. fier construction and testing, electronics SPECIALISTS IN SHORT WAVE and preferably some experience of manufac- QUARTZ and high -class broadcast equipment offer a ture of light mechanical instruments, aged wide range of components for the con- between 21 and 35, required for development CRYSTAL structor and enthusiastic amateur. anti production work on a new type of sound recording instrument, progression possible for In addition to our range of equipment bearing the right technician ; extreme enthusiasm UNIT the well -known Trademarks of Eddystone, Ray - most essential qualification. -Write with detail, of experience, mart, Hamrad, Labgear, etc., we have a large and age, etc., to Boosey & Type varied stock too numerous to Hawkes, Deansbrook Rd., Edgware, [8426 detail in the space are invited for the position available. For example we are usually able to APPLICATIONSof senior engineer to take charge of e Q5 /100 offer Communications Receiver, tested and laboratory principally engaged upon the design realigned in our workshops, including such well - and development of electronic devices; appli- known types as the NATIONAL H.R.O., R.C.A. cants should hold first -class honours degree in tor Secondary Frequency Standards AR88, etc. Your enquiry for any particular engineering or science item and have bed at least Accuracy will receive our careful attention. In P.A. Equip- six years' development experience; salary range better than 0.01%. * New : ngles of give a ment we can offer a complete outfit comprising £700 -£900 per annum, according to qualifica- cut temperature coefficient of 2 parts in A.C. operated Amplifier with Push -Pull D.A.I00 tions and experience.-Applications should be a million per degree Centigrade temperature 12in. addressed to the Personnel Manager, Airmec change. * Vitreous silver electrodes fired dires: output, two P.M. Speakers in Cabinets with Laboratories. Cressex, detachable horns and stands, high Wycombe. Bucks. on to the faces of the crystal itself, giving perman- Mixer Panel, Gramo- THE ENGLISH ELECTRIC VALVE Co., phone Turntable and microphone. Complete ence of calibration. *Simple single valve circuit Ltd., Chelmsford, require immediately one strong harmonics outfit E75. senior scientist gives at 100 km. intervals up to ! and three assistant scientists 20 Mm. Octal based mount of compact For the Short Wave Amateur we stock for work in their research department; candi- * dimen- several sions PRICE 45/- Post Free types of transmitting and receiving valves in- dates should he graduates in science with ex- cluding the EIMAC 100TH at E6, S.T.4074A(RK34) perience in research, development or experi- Full details of the Q5 /100, including circuit, mental of at E2, 5C/í00(813) at £7/15/ -, Mullard RGI /240A manufacture vacuum devices; for are contained in our leaflet QI. Send scam- the senior post considerable experience of this to-day for your copy M.V. Rectifiers at 20/ -. V.H.F. receiving types type will be required, a knowledge of the pre- include 9002 -11/10, 9001. 6AK5 -15 / -. paration of photo -sensitive surfaces would be THE QUARTZ New component gist W -W." sent on request. an advantage; salary raid would be commen- CRYSTAL Co., Ltd. surate age, qualifications 63 -71 Kingston Road, with and experience. NEW 44 WIOMORE R4 BROMLEY, KENT -Please address applications to Central Per- MALDEN, SURREY sonnel Services, English Electric Co., Ltd., Telephone : MALden 0334 Phone RAVensboume 0/56 Queens house. Kingsway. W. C.2. 18275

www.americanradiohistory.com October,' iç&p Wireless World Advertisements 79 RADIO and electronic draughtsman for lay- SVCE. mech. desires employment in London out work, etc., used to mechanical de- --7 Does t ese -Middleton, 169, Gloucester Place, N.W.I. sign of electronic equipment, required for Re- EX -RADIO of icer, 17 years at sea, 3 years search Section; West London district; 38- ACCURATELY and QUICKLY fitting maintenance ashore requires hour, 5 -day week. -In applying give full shore position. -Box 2598. [8334 -` Chassis, Brake's, Shrouds, C seden- details of experience, qualifications, age and t j 12 yrs.' wide experience radio sor and Transformer alias - salary required, to Box 2596. [8328 4 TREPANNING dteel or Aluminium. ENGINEER,industry. development, research, technical SENIOR development engineer required in 'AAAAAA :1 Five sines-12" to 36' admin., seeks position. -Box 2941. [8421 television design laboratory; good ITf Full parliudarr from RADIO mechanic desirous to train for honours degree in Physics or Engineering and ,_la A. A. TOOLS (W), specialized work, good radio and electrical at least 4 years' industrial experience of tele- / 1874 WHITEACRE ROAD knowledge, 10 yrs.' practical exp. -Box 2532. vision receiver development essential.-Appli- r" ASHTON-UNDER-LYNE VOREMAN small radio factory desires cations, giving full particulars of training change, 20 yrs. exp., pref. radar, lab. or and experience, to Personnel Manager 1155 - OWNERS design,- Jackson, 12, Robert St., N.W.1. (Laboratory), Murphy Radio. Ltd., Welwyn The best of seta break down, and a, it Is difficult RA.F. F /S. wireless electrical mechanic, Garden City, Herts. [8352 to buy spares for 1155's, we suggest that to married, 27 yrs age, A.I.D. and civilian buy a parcel of 25 spares, including I.F. Trans- exp., requires responsible position any branch oSAOCIATED electrical Industries lt e- formers, R.F. Coils, B.F.U. Coil, H.F. Choke, etc., etc., radio; S. England preferred. -Box 2539. search Laboratory for long -term research is a sound idea. We can offer such a parcel for 26,,6 'rXPERT service engineer, 12 years' ex- at Aldermaston Court, Aldermaston, Berk- post free, e.g. lees than the cost of the LF. Trans- perience with leading manufacturers, 5 shire; graduates or equivalent required for formers. We are able to make this offer because we scars' radar research. good organiser, desires posts in electronics section; sound knowledge bought a big stock of new parts which were not needed post abroad. pref. in Colonies. -Box 2808. of electronic circuitry and practical experience when the Air Ministry contract for 1155 receivers was WORKS manager, young, energetic, seeks essential, for work on design and construc- completed. All parts are new and exactly as used in post, administrative, technical, commer- tion of all types of electronic for use your set. Order new to avoid disappointment. circuits BULL'S E 5- 001 "y. DEPT., 42.46 WINDMILL HIL L, cial; fully conversant design, organization. pro- in the Laboratories. -Reply, stating full.quali- RUISLIP MANOR, MIDDLESEX duction, quality control, labour handling. - flcations and salary required, to the Manager Box 2981. [8465 RADIO service engineers for employment engineer, 35, 15 yrs. exp. trans- in works and in field; vacancies exist in The Popular RADIOmission and reception, installation and a well -known company with excellent pros- I I I: o Q U -BEC" maint., wide exp., excep. refs., desires post in pects, primarily in the London area; appli- S 1 Universal Coil Canada or Australia; pres. sal. £500, accept cants should have a comprehensive knowledge /f N. \'a ,/ Former again less cur opportunity. -Box 2943. [8424 of radio servicing and a minimum of 2 to 3 available by re- MAN. 25, desires post in radio trade; I.C.S. years retail or industrial experience in re- l' ® °°f turn of post! " Complete Radio " diploma, spare time pair work; 5 -day, 44 -hour week; wages / \, Send 2/6 & 2ád. exper., keen, conscientious, hard- working; any- according to experience and at prevailing post thing with prospects considered. -Gortacar, levels.-Apply stating age, giving full details i/ 'o EVANS Clonelly, Enniskillen, Co. Ferm, N.I. [8446 E. W. of experience .I é no and wages regd. to Box 2536. go r I I I' o ° 5, Betkingham EX- FOUEMAN of Signals (W.0.2). 23; KINGSTON - UPON - HULL Education Rd., LEICESTER pre- s9rviee experience, direct from Authority, Municipal Technical College. PEGO DESIGN school to Army; 5 years' Army experience REQUIRED, in October, 1947, a full -time of communications; good at inat -ho. and ex- assistant radio instructor for appointment to es ptional ability to learn quickly; wishes to the Kingston- upon -Hull Municipal Technical PHOTO- ELECTRIC CELLS inter radin or other telecommunications trade College; candidates must have a First -Class in good progressive job.- Box 2810. [8367 for engineering student, age 30, ex- P.M.G. Certificate in Wireless Telegraphy, seeks and theoretical and practical knowledge of Talking Picture Apparatus. RADIOtonsire commercial experience, radar is essential; practical experience with position with technical firm: good organiser, modern radio equipment (marine and air- Caesium Photo- Emissive Cells Only. administrator; able to take complete charge craft) an advantage; salary will be in accord- dept., and bear responsibility; experienced RADIO - ELECTRONICS LTD., export procedure; keen to enter trade; at ance with the Burnham Scale for Technical eressent in dead-end, non -technical employ- Institutions, 1945; particulars of appoint- St. George's Works, South Norwood, ment: London area. -Box 2541. [8321 ment and application forms to be returned London, S.E.25. WELL -KNOWN radio engineer, M.I.E.E., within 14 days of the date of this advertise- desires another managerial post in indus- ment) can be obtained on receipt of a stamped .,. addressed foolscap envelope try or with a trade association, etc., in which from the Die-- bra his abilities and knowledge of the industry can for of Education, Guildhall, Kingston-on-Hull. be used to the full, experience of radio, radar, OVERSEAS AIRWAYS COR- television and electronic instrument develop- BRITISHPORATION have vacancies for ground ment and production, a good, responsible post radio operators, medically fit and willing to with real prospects is required, -Box 2540. serve on a world -wide basis overseas. The upper engineer (British) with many age limit is 40 and preference will be given ROTARY CONVERTORS ' EXECUTIVEyears administrative experience in sales, to single men. Basic rate of pay £5115 to ' publicity, marketing and installation of sound £6 /10 a week, plus allowances overseas graded 220 D.C. to 220 A.C. %. equipment and radio, seeks position in Belgium according to the local standard and cost of Deails from- as large manufacturers' branch director /mana- living. The initial tour of duty is three years, BEETHOVEN ELECTRIC EQUIPM ENTLTD. ger, capable of establishing, equipping and and successful candidates will be required to Beethoven Works, Chase Road London N.W.10 staffing works and securing materials and or- serve in any part of the world at the discretion ganizing manufacture from the start, fluent of the Corporation. Essential qualifications: French, own car, many contacts in Northern Postmaster -General's First or Second-class Cer- Europe, keen and persistent worker with wide tificate or equivalent service experience. Can- VALVES AVAILABLE experience and good grounding. -Firms in didates not holding certificates will be given At B.O.T. prices, British and American, these are only terested in widening their export field sub- proficiency tests on ground radio operating. - a selection of oar 10.000 valves held in stock. Please stantially please write Box 2937. [8408 Applications in writing to Staff Appointments send for our comprehensive Valves Available List. free, Superintendent, Stratton House, Piccadilly, enclosing B.A.E. for reply. Postage 6d. extra C.W.O. TUITION W.1, stating age, certificates held and giving or C.O.D. British National Radio School brief' details of radio operating experience. Re- Mollard -KF32, KF3S, KBC32, K1.:35, FC2A, VP2, THE plies will be sent only to candidates called VP2B, SP2, PM12M, TDD2A, PM2A, PM202, PM22A OFFERS you a career. for interview. Mark envelopes " Ground Radio PM22D, QP22B, RM1, EM4, EM31, EM35, EF6, EF9. WRITE to -day for free booklet describing on: Operator " [7960 EF36, EF37, ECU, EC53, EF39, EE50, EF54, EC31, wide range of training courses in radio, Radar, B.C. invites applications for a number of EB34, EBC3, EBC33, EL2, EL:3, EL33, ECC32, telecommunications, principles, mathematics, appointments of Programme Engineers EL35, EL37, ELSA EF22, TH4B, VP4, VP4A, 8P4, correspondence and 2D4A, 21)4B, 354V, 164V, Pen4VA, PenB4, Pen4DD, physics, and mechanics; (Grade D), on a salary scale 8375- E20 -C475 VPI3A, day classes for the new series of C. & G. exami. TH3oC, FC13, FC13C, VP13C, 5P13, SP13C, " (minimum age 21), for duty at the Corpora- 2D130. EL13, HL13C, TDD13C, CL33. Pen428 nations; we specialise in turning " operators tion's studio centres; candidates who must CBL31. into " engineers," and for this purpose our be of British nationality and parentage, must Meada-P220, Sl'220, HL2, SP22, HL22, VP23,111,23 " Four Year Plan " (leading to A.M.hE.E, and possess theoretical knowledge in electrical en- TP22, TP25, TP26, Pen220A, Pen25, QP230, QP23. A.M.Brit. I.R.E., with 9 C. and G. Certifi gineering to Ordinary National Certificate or 8P1320, V914, DD41, DD620, ACHL, AC2HL, HL41, cates as interim rewards) is unsurpassed; ' our City and Guilds (Radio Communication, Grade ACP, AC /SGVM, AC /VP1, VP41, SP41, 8D42, SP61, guarantee has no strings attached. " -Studies II) standard, including a knowledge of ACTH1, TH41, AC /HL /DDD, HL/41DD, HL /42D0, Director, B.Sc., A.M,I.E.E. M.Brit. I.R.E., acoustics and low frequency speech input PA20, PP5 /400, ACPen, ACHiIPenDD, AC6 /Pen, 66, Addiscombe Rd., Croydon, Surrey. [6811 Pen45, Pen45DD, Pen46, ME920, HL1320, TH2321, equipment; they must have pronounced artis- RADIO training -P.M.G. exams. and I cs.r. tic leanings towards, and a certain minimum TH233, TP1340, DD207, DD10i, 00215, 8215VM, Diploma; prospectus free - Technical of HL21DD, HL23DD, HL /DD1320, HL133DD, VP133, standard appreciation of, all branches music ME91. College, Hull. [0611 and /or draina; selected candidates will be Pen383, Pen453DD, RDIAO Engineering. Television and Wire a Octale-lAI, 1115, ICS, DF33, DL35, 1A, 106, required to serve probationary period of six 13111.21, UCH21, UY21, 2A8, 2B7, 15, 26, 27, 30, 31, less Telegraphy comprehensive postal months, which will include a three months' 32, 33, 34, 87, 39/44, 42, 46, 71A, 77, 78, 79, 83, 84. courses of instruction.-Apply British School training course at the Cornoration's Engineer- 89, 2103, 2151, 6,15, 6L7, 9138, 605, 6E6, 6116, 6E7, of Telegraphy, Ltd., 179 Clapham Rd., Lon- ing Training School at Evesham, Worcester- ORB, 637, 6Q7, 6L6, 606, 6D6, 691, 6U7, 6C8, 6B7, don S.W.9 (Estd. 1906). Also instruction at shire; confirmation of appointment will be 6115, 6R7, 6K6, 6F8, 638, 6A6, HAGS. schon in wireless for II.M Merchant Navy subject to passing a qualifying technical ex- GT Range- 128A7, 12A1í, 12J5, 14A7, 12B7, 12U7, and R.A.F. [9249 amination at the end of the training course; 12118, 128E7, 12895, 12J7, 128J7, 12117. 35Z4, Institute of Practical Radio Engineers entry- to the permanent staff (contributory 50L0, 35L6. THEhave available Home Study Courses cover- Pension Scheme) is subject to two years' Obsolete Types. -PM6D, TDD25, DC2 /SG 80410, ing elementary, theoretical, mathematical. qualifying service. -Applications, stating age, P51256, 410LF, P650, D025, HL20, P5116, AC064, practical and laboratory tuition in radio and and experience, should reach 118, DCSO. text is suitable qualifications Reclaers- FW4500, CYl, CY31, UY31, 40SUA, AZ1, television engineering; the the Engineering Establishment Officer, Broad- AZ31, UU6, UU7, UUe, DW2, U14, U31, U50, U52, coaching matter for I.P.R.E Service entry and casting House, London, W.1, within 7 days of U76, U17, U74, GU50, 43IU, U21, 1D0, 2525, 5Z4 progressive exams.; tuitionary fees at pre-war the appearance of this advertisement. [8390 6115, 25Z4, 5Y3, 5V4, 5U4. rates -are moderate. -The Syllabus of Instruc- SITUATIONS WANTED II-1. tional Text may be obtained, post free. from RANSOM, 20. Fairfield Rd., Crouch End, EXPD. radio relay engr, regs, change; cap- 39, BOND STREET, BRIGHTON. Phone Brighton 5003 the Secretary, able of taking full control. -Box 2525. N.8. [6722

www.americanradiohistory.com Ro i(lzlerliselllenls Wireless World lIi lober, 1947 ofedeate ú x-R. A. F. Transmitter Receiver for LOUDSPEAKING short waves 2040 metres. Provision for crystal con- EQUIPMENT trol. Uses standard head- phones and microphone. Battery operated, requir- For ANY ing standard 120 volts h.t. and 2 volts I.t. Includes 9 valves standard English CAR or VAN types. Six valves in -`f receiver and three in transmitter Circuit RX, 2r.f., der., 2 Audio CARRIAGE dGnó and Power. TX Osc. P.A and Modulator. PAID . . . This reliable mobile system com- THE STAMFORD RADIO CO. bines high quality reproduction As used by with power, compactness and 199 Stamford Street, Ashton -u -Lyne, Lancs. economy in operation. Police Telephone : ASHton 1964 The equipment consists of : Forces, Type 615 AMPLIFIER for 12 or 6 v. acc. Power output 10 -15 Military watts. Type PMXR LOUD- Police, SPEAKER PROJECTOR, (»or/mi., ríf weatherproof, powerful, effici- Crown ent -built along the same lines Agents as the famous -LOUD HAILER." Type CMH3 hand held MICRO- for the MAINS TRANSFORMERS PHONE, unbreakable, has re- Colonies -A. F. TRANSFORMERS mote control switch and high etc. etc. SWITCHES intelligibility. THERMAL" DELAY Write for full details and for HOKES demonstration. L91W415115,. SMOOTHING POWER RESISTANCES ARDENTE ACOUSTIC l(ad' bt LABORATORIES LTD. WOOLWICH ,412-/426 COMPTON, Nr. GUILDFORD, SURREY. Guildford 3278 -9 cnMnninGE HUW WOOLWICH ' SE'IS And now .. all that a good amplifier should be the Models At ailaLle CHARLES AMPLIFIERS' MODEL 'CONCERTO' By extending the range job will find in these - models everything they 9 Valves Double Bass Boost. of Lustraphone Moving Coil Microphones, users want in terms of good 2 ^,, Distortion at 7 Watts. Separate Bass & Treble Controls. anxious to obtain the reproduction and last- Hum level 65dB. 12 months Guarantee. best instrument for the ing dependability. Incorporates a switched pre- amplifier so that any kind of pick -up can be used -moving -coil- moving -iron or crystal. Price £27.10.0 complete. MON' ING-COIL CHARLES AMPLIFIERS LTD., 1E, Palace Gate, MICROPHONES Kensington, London, W.8. (Phone : WEStern 3350) LUSTRAPHONE LIMITED DEMONSTRATIONS 9.30 to 6. SATS. 9.30 to I p.m. 84, Belsize Lane, London, N.W.3 ,url 551.5 S T A M P F O R D E T A I L S O F ALL OUR PRODUCTS

M.O.S. FOR COANDUGIPATIONS RECEIVERS below A few examples from our range of Govt. surplus receivers detailed TYPE CCMMUNICATIONS RECEIVERS, complete wit Is 11 valves, s R1155 (ER-R.A.F.) snoolard con- brawl new and unosed. £17 10 - (rb I s.1v Mc s.1. ln excellent OSCILLOSCOPE dition. £1b 15 k..IyM /+). Model It 11 8( (latest service nit.ils.). £1710 (.200 k la N ') ,ith galyes, TYPE MORS MINIATURE COMMUNICATIONS RECEIVERS complete UNIT kv power p.m k, i lt, n ,oil., et.. Brand new and unused. £10 9,13/1011 1Lki) ". Ivey. Power INDUSTRIAL NEEDS RECEIVERS, compee , TYPE PCR1 COMMUNICATIONS Me. pack and built -in ill. speaker. Brawl ne w and unused. £1717-/lan he ..Hi 8-1. and Bases a no with Interchangeable Amplifiers Time with TYPE No. 3 II MINIATURE COMMUNICATIONS RECEIVERS, plot" unused. £3 19,6 1:1.1- wide range of accessories cover every application. 1 valves, phone.v, but lees power supply. Brawl new .un1 15.5 Mes s.). No loose wires, no unwanted controls, no complex FREQUENCY MODULATION COMMUNICATIONS RECEIVERS, TYPE BC003D button and manual switches, but standard snap -on units give rigid complete with Ill valves, poker supply t20 =28 M.' +.1, push tuning, £6,196. yl 'apply and assembly with tailor -made performance. TYPE AC71, BUSH O.P. RECEIVER. complete with 5 valves. pow ive . 1'o -day s built. in speaker, in line wooden cabinet. \ ln.mestie l ype re, Mn'. 1 value, 25 gus. Brand new and unused, £17 17,- 1150 he s -18 +.1. LYDIATE ASH LABORATORIES 2;d. stamp will bring you our latest illustrated catalogue. Please add RESEARCH AND DEVELOPMENT tNG.NE Ev carriage and packing to all remittances. Nr. BROIVISGROVE ORDER SUPPLY CO. Stepney Green Telephone Rubey 168 169 MAIL 24 New Road. London, E.I 2760 & 3906

S.E.I, by Tun CORNWALL PRESS LTD., Paris Gorden, Stamford Street, the Publishers, Icing AND Soso LTD., Dorset House, Stamford Street, London, In Great Britain for : St s Cu. Printed ZEALAND : Gorden s Botch, Ltd. INDIA A. H. heelur World " enn be obtained abroad from the following- At'nTRA1.1.A and NEW London, 8.E.1. "\Wireless S (S.A.). Ltd. 1'v,TEU STATES: The Iuternatiom,l Newu Cu. : Ned Oa, son Sons 1!_NAOA: Imerrial N east',,.;t:.ad oaí:.,1,1n, 1.1.1. Solo AFRICA Central Aneucv,I.td.;William

www.americanradiohistory.com Octobe7. 1947 Wireless World Adterti.:ements

THE TELEGRAPH CON.2NSER CO.,LTE) CAN" NORTH ACTON LON D N W.3. Telephone:ACORN 0D61

www.americanradiohistory.com Advertisements October, 1947

THE EDISON SWAN ELECTRIC CO. LTD. 155 CHARING CROSS ROAD, LONDON. W.C.2.

www.americanradiohistory.com