Get Ready for London on Short Wave

Radio Record, Volume I, Issue 5, 19 August 1927, Unnumbered Page

Get Ready for London on Short Wave

Easily Made Adapter To Work On Your Present Set According to the latest cablegrams from Home, Mr. Gerald Marcuse, the well-known London amateur transmitter, will commence world-wide broadcast concerts on an ultra-short wavelength on September 1, New Zealand broadcast listeners by the thousands will regret that their ordinary receiving sets will not tune down to the ultra-short wave-lengths which have such a phenomenal range. However, "‘The Radio Record" has much pleasure in placing before its readers an inexpensive device which will instantly convert any ordinary broadcast receiving set into an ultra-short wave receiver without interfering with any wiring of the ordinary set. The device has been exhaustively tested in Wellington and has proved an unqualified success.

"* ’ RQ SAT SANTI This wouderful short-wave adapter comprises a unit with one valve and socket, simple tuning coils. a variable condenser, radio-frequency choke, a small fixed condenser, grid leak and grid condenser, and three insulated flexible cords fastened into an old valve base. ‘The unit can be assembled without any skilled technical knowledge. : HOW IT IS CONNECTED. To connect the ultra-short waveleneth adapter in circuit with the

| 7] AAS AUT Red SAU SANTI sUHUUUHIAIA TS ASAI ANIA -ordinaty broadcast receiving set is the work of a few moments. The detector valve of the set is removed from its socket and placed in the socket of the adapter. The old valve base attached to the adapter is inserted in the detector valve socket of the ordinary set, and the aerial aud earth ate transferred from the ordinary broadcast receiving set to the shortwave adapter. Nothing could be simpler. No battery cortnections ate changed. The loud-speaker remains plugged in, as usual, into the ordinary receiving set. The audio valves in the sect are used as is customary. APPLIED TO ANY SET. The short-wave adapter can be applied to any broadcast receiving set-neutro-dyne, super-het, BrowningDrake, tuned radio frequency, three-coil regenerative, etc. Once the adapter is connected to the broadcast receiver all the tuning is accomplished on the — single variable condenser in the adapters, Novices should note the radio-frequency amplifica-

dll t ws HUVUHITUAT tion, in the common application, is not practicable on ultrashort wave-lengths, therefore the radio frequency valve, or valves, are not required when using this adapter. [ff one rheostat controls all the amplifying valves of your set, then the radiofrequency valve, or valves, can be removed from their sockets when the adapter is being used. If there is a separate rheostat for the radio-fre-quency valves, then the A battery current can be shut off from hese valves

to save current. Ag stated previously, the audio valves ate required. ONLY DETECTOR AND AUDIO, Therefore, all that is necessary for _ operating your set in conjunction with the adapter is the use of the detector valve (which is transferred to the adapter), and the audio-amplification valves, which remain in their customary sockets in your ordinary receiying set. The simplicity of the whole arrangement does not impair its efficiency, as the adapter is designed on

thoroughly approved technical principles. In practice, if correctly constructed, the adapter will be found to be thoroughly efficient and easy to manipulate; in fact, easier than the ordinary broadcast receiver, as there is only one condenser to operate for the whole outfit, the condensers in the broadcast receiver not being used, although they are not disconnected in any way. The parts embodied in the adapter ate not in any way intricate, The

ultra-short wave tuning coils may be purchased in any of the four New Zealand centres. Some very efficiently made sets of coils to suit the adapter are sold at a most reasonable figure. If, however, the broadcast listener possesses a little skill, and desires to make his own coils, he has no difficulties to overcowe, It is advisable that those who are not familiar with coil construction should purchase their coils ready-made. There are three coils, all of which

may be wound on the same tubing, The tickler should be at one end, the secondary in the centre, and the primary at the other end of the coil. The best wire for the purpose is No. 26 double-cotton-covered for all coils, The primary coil should have about five turts, the secondary ten, and the tickler six turns. ‘The tickler should be wound to within one-eighth of an inch from the secondary coil, and at least an inch should separate the primary from the secondary.

Still better results can be obtained by making the primary coil variable to increase selectivity in tuning The coils may be of the spider-web or the pancake type. Another method of Witiding ‘the coils is known as ‘"pinchwinding."’ The coils should be wound on bakelite tubing, three inches iu diameter. To cover two or more wayebands the coils should be made on the plug-in principle to facilitate changing the coils. In dealing with ultra-short waveMULALLY ft AA AAT ANN

lengths, it is important that only the best variable condenser be used. It must be of the low-loss, straiglit-line frequency type of the highest grade, with a capacity of .00025 microfarads. Those who purchase interior quality condensers Should not expect good results, for efficiency cannot be obtaimed with poor quality condensers. Importauce must be attached to the selection of a good vernier dial for operating the variable condenser. Ultra-short wavelengths are strikingly sharp when it comes to tuning on them, and a vernier condenser control is, therefore, essential. THE VARIABLE RESISTANCE. Importance 1s also attached to the variable resistance (8). This resistance has a critical effect in the operation of the adapter, aud slfould be of the smoothest-working type. This . variable high resistance is shunted across the tickler coil, and thus eliminates an additional yariable condenser, greatly simplifying the tuning and reducing the cost of the adapter. The variable resista Nd Ua Yi 4 Ali RAT i MITTEN a

ance should be of 200,000 or 500,000 ohms. The most suitable is the Bradley type of variable resistance, owing to its smoothness in operation. The.controlling knob should be on your right-hand side of the panel when facing the adapter. GRID-LEAK AND CONDENSER. There is nothing revolutionary about the grid-leak (5) and fixed condenser (6). The best variable grid-leak, of (Continued on Page 3.) bm

Get Ready for London: on. the Short Wave

This article is continued from the cover, and describes the process by which any skilful operator may adapt any yalve set for the reception of short-wave London broadcasts. As from September 1, Mr. Gerald Marcuse will broadcast for Antipodeon listeners. There is also available on the market reliable apparatus for short-wave reception. Enthusiasts are invited to send records of receptions.

— ‘ ‘of the condenser is connected between i about three olims resistance, should be used. Shunted across it is the common type of fixed condenser of .00025 microfarads capacity. -Vaives vary a great deal in characteristics, and a variable grid-leak will ensure the best results. . RADIO FREQUENCY CHOKE. A special short-wave radio frequency choke (10) may be purchased readymade, or could be made to order by any radio mechanic for two or three ‘shillings, Those who desire to make their own radio frequency choke will -require No. 26 double cotton-covered wire. This should be wound haphazard, ‘ without any evenness, one hundred times around a small, wooden reel with flanges half an inch in diameter, and the core about a quarter of an inch in diameter. ‘This choke, howerer, should be purchased readymade, if possible, for the factory-made article is generally of the boney-comb or duolateral wound type, which gives a very low distributed capacity, and is infinitely more efficient for radio-fre-quency currents on short wavelengths. BY-PASS CONDENSER. The customary by-pass fixed condenser (9) should not be omitted, It is of .0001 microfarads capacity. The condenser is counected at one side between the radio frequency ckoke and the variable resistance. The other side the A- (or F-) of the valve and the A- of the connecting cord which goes to the ordinary receiving set. TO CONNECT TO SET. Connecting the adapter to the ordinary broadcast receiving set is a most simple process, Take an cld_ valve, one that has outlived its usefulness, or procure a "‘dud" valve from one of the big radio houses, which always have a few burnt-ont or defective valves on hand. Remove the glass Bulb from the valve, using care for fear of cuts on the-face or hands, The insulated flexible wires which connect the "Ax," "A-," and "P’’ terminals of the adapter valve socket should then be soldered inside the old valve base .to the corresponding prongs of the base. In the UX200A and UX201A_ type valves the thick prongs are for the A battery, and when the pin on the side of the valve base is pointed towards you, the thin prong on your left-hand side of the pin is the P prong. .No connection is made, inside the old valve base, to the other thin prong-G. It is advisable, however, to note which way the A battery is connected, in your ordinary receiving set, to the detector valve socket, with respect to plus and minus. Care. should be taken to see that the flex cords are well soldered and insulated inside the old valve base, so that the bare wites cannot coiwe into contact with each’ other, and thereby cause a short-circuit. After they have been well soldered the inside of the old valve base could be filled with melted sealing-wax, resin, pitch, or plaster of paris. The flex cords should then be bound together with adhesive tape just above thé top of the old valve base. The cords can also be plaited into a cable. | , THE CONNECTING CORD. The flexible insulated wire cords which connect the adapter to the receiving set can be two or three feet in length, It is a matter of convenience for the best position to place the adapter, The most satisfactory position for the adapter is the closest to the aerial lead-in. If it is to be placed on top of the receiving set little rubber tips glued underneath the cabinet of the adapter will prevent scratches on the top of the receiving se ’ TUNING THE ADAPTER. To tune the adapter very little skill is necessary. ‘The tuning condensers of the receiving set are not touched, the attention being centred on the ver-nier-controlled single tuning dial of the adapter and the knob of the variable resistance. The latter should be turned backwards and forwards, while the condenser dial is moved very slowly. in search of a ‘‘carrier’® wave. When the whistle of the "carrier" is picked

up it is cleared up by careful manipulation of the yariable resistance and the tuning dial. With a little practice the wovice will sliortly become quite adept. It is advisable to keep a "Jog" of the dial readings of the condenser, so that stations once found will be promptly located again. THE SAME AERIAL, Ne change in the length of the ordinuty aerial will be necessary for tuning the short-wave stations. The standard broadcast aerial will serve the purpose withent any reduction in iength.

/ LOTS OF SHORT-WAVE STUFF. Listeners will find quite a lot of short-wave broadcasting is available at various times of the day. The Schenectady station, 2XAI, is heard regularly every Sunday afternoon in New Zealand, transmitting band, orchestral, vocal, and other items. Following are the principal short-waye broadcast stations which are frequently heard in New Zealand at irregular times :- . Metres. QEAD, Sehenectady, U.S.A..,. 20 QXAG, Schenectady, U.S.A. ... 26,02 PCJJ, Holland wecccscscseeeees »» 80.2

‘OSA, Schenectady, U.S.A.... 52.79 WGY, Schenectady, U.S.A, . =89 REN, Russia cee esecsseeesseceeeeee Ad WLW, Cincinnati, U.S. sereee O23 KDKA, Pittsburgh, | USA, .. 68 WGY, Schenectady, RS.AL we ay HWE, Perth, W estern Aust.... 106 And now, from Kngland, comes the news that Mr. Gerald Marcuse, the world-famed Tondon amateur transmitter, is to give Australians and New Zealanders regular high-class broadcast concerts transmitted on a short wayvelength. As he is to commence in a fortnight, uow is the time to render

your receiving sect able to pick up tl.c London concerts, by means of the "Radio Record short-wave adapter." It may be said, generally, that reception of short-wave transmission calls for skill, and presents some problems. The service about to be broadcast by Mr. Mareuse is of an experimental nature, but it is uuquestionably of the first importance, and will certainly prove a stepping-stone towards the attainmenut of regular Empire broadcasting. We will be glad to have details of the experiences of any listeners who get resulis on London shortWaye transmission.