THE WIRELESS WORLD

Otago Daily Times, Issue 23107, 5 February 1937, Page 3

THE WIRELESS WORLD

NEWS AND NOTES By Magna Vox Items o£ local interest are Invited by Magna Vox" for publication in this column. It is necessary that such matter should reach this ollice by Tuesday of each week for insertion on the following Friday 2BL Sydney.—74o K.C., 405 metres. 2FC, Sydney.-610 K.C., 476 metres. 3AR, Melbourne.—77o K.C., 390 metres SCL, Adelaide.—73o K.C.. 411 metres. 4QG, Brisbane.—Boo K.C.. 311 metres IYA, Auckland.—6s K.C.. 526 metres. 2YA. Wellington.—s7o K.C., 526 metres 3YA, Christchurch. —720 K.C.. 416.4 metres. 4YA, Dunedin.—79o K.C.. 379.5 metres 4YO. Dunedin.—ll4o K.C., 261 metres. ANSWERS TO CORRESPONDENTS F. I. M„ Dunedin.—(l) Yes, you could substitute glass valves in the audio end with very little trouble. An 80 would probably cause a small drop in the voltage available In the receiver, but this would be compensated by a lower field resistance. Actually the voltage given with the 80 would be sufficient without the change, as there would be an almost inappreciable difference in performance (2) So far as is known, the life is about the same, r should say that only time will tell.

" Voltage,” Middlemarch. —You will find it preferable, and handier, to use a voltage divider of some 20,000 ohms, and the taps can be slid along the divider until the correct voltages are shown on the voltmeter. This will make the arrangement of the voltages easy. You will find that this method works quite well unless B class amplifier is used. The current on the portion of the resistor which develops the C bias is domposed of two parts—the steady current from the generator and the current from the receiver. The latter one should be steady it the bias is to be steady, and with a B class amplifier the current increases with the output of the amplifier. The small amount of variation of B current in the usual set with the change of volume control will usually be swamped by the steady current down the voltage divider, so that a substantially constant voltage will be developed for C bias. " Earthworm,” Oturehua.—Whether you can operate the set without an earth will depend on whether the chassis is earthed to one or both mains by condensers. If this is the case, it is possible to get a shock from the chassis, which may or may not be severe. If, as you state, your set operates well without an earth—and, in your case, there is no necessity, so far as the set is concerned, to provide an earth—the set will not be harmed. An earth, however, would be advisable from the other point of view, and the hum should not be present if an entirely separate earth is provided. Should a hum make itself heard, the set should be checked by a serviceman, as the noise is an Indication of a definite fault, which should be rectified before any permanent harm is done.

CZECHOSLOVAKIAN SHORTWAVER The Consul-General in Sydney for Czechoslovakia advises that the shortwave station Praha is now broadcasting daily on 49.05 metres between 8.25 and 10.30 p.m.. the programmes including at 10.15 p.m. news in English. The same station is engaged on experimental transmissions on 25.26 metres daily between 3 and 5 p.m. In addition. on Tuesdays and Fridays or each week the station broadcasts on 25.26 metres a programme directed to the so-called American zone. These special transmissions, which extend from 1 to 3 a.m., include press news in English at 2.40 a.m. The station is owned by the Czechoslovakia Radio Journal, whose headquarters are at Praha, and it is understood that the hours quoted by the Consul-General are Eastern Australian standard time THE NEW 2YA The promise that the 60-kilowatt transmitter at Titahi Bay would give daylight coverage of the whole Dominion is apparently to go unfulfilled (comments a writer in the Timaru Herald). In Timaru at least its signal strength is lower than that of 3YA or 4YA, stations with only onesixth of its power. It is not strong enough to rise above the Morse, and in the inner area does not get above the interference level, and the prevailing feeling among listeners is one of disappointment. The modulation is good, and fading is scarcely noticeable, but it appears that a good deal more wattage or a different typo of ariel is needed if 2YA is to be a Dominion station. WIRELESS WORLD TRADE The twenty-ninth report of the Imperial Economic Committee consists of a survey of the world’s trade in electrical apparatus, including, of course, wireless. It is extremely interesting to note from this report that wireless apparatus now accounts for no less than one-quarter of the value of world trade in electrical equipment. It appears that the estimated number of wireless receiving sets in use throughout the world at the end of 1935 was 56,000,000. This represents an increase of between 60 and 70 per cent, over a period of four years. The United States and Europe (excluding Russia) account for some 85 per cent, of this figure. Ninety per cent, of the wireless trade is concentrated in the hands of four countries. Of these, the two leading countries, the U.S.A. and Holland, account for about two-thirds of the trade. Germany is third, and Great Britain, which is responsible for about one-tenth of the trade, is fourth. It appears that the Empire takes only about one-third of the total exports of the Homeland, her biggest customer being Holland. By far the largest part of her wireless exports consists of transmitting apparatus and valves, the majority of these valves being of the transmitting type.

A POPULAR BROADCASTER By tho death of Mr William Farquhar Young station 3YA loses one of the most successful broadcasters who have spoken at Christchurch. The late Mr Young had all the attributes that go to make a popular speaker at the microphone. He had a rich bass voice, faultless diction, and an intimate and conversational manner, making a listener feel that Mr Young was speaking to him personally and not to a public meeting. As an outstanding singer and elocutionist, he frequently illustrated his remarks by a snatch of song or by an excel lently delivered excerpt from Shakespeare. Possessing also considerable histrionic ability, he had the gift of reproducing the voice and manner of some of the persons of whom he spoke. Most of Mr Young’s talks were of the reminiscent type, and as the greater part of his life was spent in Dunedin his remarks had a special interest ’for local listeners especially those whose memories go back to the ’nineties. In those days Dunedin was exceptionally rich in vocal talent, and it was good to hear Mr Young’s tribute to the singers whose names are now only familiar to the few. One specially interesting talk was that in which Mr Young described a public demonstration of the phonograph which took place in the City Hall in Dunedin some 45 years ago. Often in his talks did Mr Young refer with real feeling to the fact that some old acquaintance had gone to that bourne from whence no traveller returns. Now ho himself has embarked on the last journey, and to many Dunedin listeners it will be a real regret that they will no longer have the privilege of hearing his voice over the air again. TELEVISION DEMONSTRATION The first public demonstration of big screen television by the new Baird system was given at a London cinema early last month. An audience of 3000 saw a variety programme which is being televised regularly during the ordinary film shows on to a screen above the stage. Actually, the artists televised were in a small studio in another part of the building, and television was effected by land line on to the screen. The picture suffered a little from immediate comparison with the perfection of the 24ft cinema picture. The television pictures w'erc dimmer and less distinct, but impressed the large audience. It was obvious, however, that television is not nearly advanced enough yet to be used on such a scale. The screen, which measured Bft by Gift, looked tiny on the big cinema screen, and there was not room in it for more than a single head and pair of shoulders at a time. The picture was clear in tho centre, but shadowed at each side, and there was a constant play of vertical lines

over it which bothered the eyes. Mr George Lansbury and Mr Baird, both of whom addressed the audience, were little more than blurred outlines. It was noticed that Mr Baird’s spectacles caught‘“the light every now and then and obscured his face. Nevertheless, now that the transition from the small to the large screen has been accomplished, rapid improvement is expected. All the voices came through excellently.

NOVEL RADIO ORGAN Nearly three thousand pipes ranged in three chambers (the accompanying, the solo, and the percussion); a grand pianoforte: a mobile four-manual console; any kind of sound effect, from the smash of falling crockery to the ‘‘ clop ” of horses’ hoofs; an “ electrone ” These are the principal features of the new theatre organ that has been installed in St. George’s Hall, the home of the variety department of the 8.8. C. Were the listener sitting in the auditorium of St. George’s Hall, he would see little evidence of the existence of the instrument—he would see the console on the stage; the grand pianpforte; he would see that, on either side of the hall, at gallery height, are what look like partition walls which, as he watches, resolve themselves into a series of thick vertical slats. Sin or 9in in width, that operate as the organist desires crescendo or diminuendo —in other words, the swell shutters. But he would see none of the tall, stately pipes that are orthodox evidence of an organ’s existence. Behind the shutters, however, are three chambers, in which are all the pipes necessary to satisfy the conventionally minded. To drive air through these pipes, the'services of two 7£ h.p. motors are required. It is, of course, essential that the pressure of the air passing through the pipes should be regulated with minute accuracy and thereafter kept constant and also that the air in the organ chambers should be brought to and kept at a constant temperature. All the unorthodox effects of the organcrockery smash, xylophone glockenspiel, cow bells, steamer syren, side drum, bass drum, bells, marimba harpare to be found in the percussion chamber. To dispel illusion, it may bo added that no crockery is used in the “smash.” When the effect is required the organist presses a button, thereby releasing air from'a normallyinflated bellows. A taut chain on which a number of metal plates are suspended is thus slackened, allowing the plates to collapse together. ULTRA-SHORT WAVES It has often been assumed that the useful range of waves of ultra high frequency (very short wavelength) is that of the visible distance between the transmitting and receiving points Because of this quasi-optical property of these frequencies, television services, which use them mainly for the reason that there is not enough room in other parts of the band, have only been given an effective service range of about 30 miles. Since serious work has been done with these short wavelengths it has been frequently noted that much greater distances have been covered The possibility of useful long-distance communication is increased by the reception in South Africa of the sound signals which accompany the London television signals. This does not mean that communication over long distances with wavelengths of this nature is an immediate practical undertaking, but it again shows that in wireless communication, even at this date when the practice and theory are comparatively well known, it is dangerous to affirm that anything cannot be done. The lesson was learned, or should have been learned, over 30 years ago. when transatlantic communication was first considered. Many of those who claimed to know all about it stated with decision and proved to their own satisfaction that it could not be done. Ye* it was done, and since then many “ impossible ” things have become common practice. In the future, no doubt, many more will be found practicable, although with the growth of research and a wider knowledge of the underlying principles of the properties of waves of all frequencies the chances of emphatic statements being made by those who claim any knowledge of the subject will become more remote. If these ultra-high frequencies do become of value for long distance work there will be compensating disadvantages mostly in the nature of interference. One of the principal advantages claimed for the use of such frequencies was that because they were useless outside a relatively restricted local area the same wavelengths could be employed in many parts of even a small country. These frequencies are finding increasing use for aerial navigation, particularly for giving ’planes accurate and certain information of their positions in places where erroneous advice would probably result in an immediate accident. Interference of such a nature as would give the wrong indication or prevent the proper signal being given clearly would be a serious matter. Most of these aeroplane systems use highly concentrated directional radiations when the ultra-high frequencies are used, and most of them are sent in an upward direction, but with the chance that they mav be reflected back to earth again, as those signals which went to South Africa must have been there might be some awkward combinations. The saving factor is that signals of this type need only be used over comparatively short distances, and therefore the local transmission would be almost certainly of great strength compared to an interfering impulse.