TRENDS IN RADIO

Shannon News, 7 December 1928, Page 3

TRENDS IN RADIO

OF PROGRAMMES.

Some of the lines along which broadcast transmission and reception are moving are discussed in an article reprinted from a trade journal by the Literary Digest, New York. “Beamcasting, ’ ’ arid the storing of programme items by phonograph for use later in the day are among the possibilities suggested. Radio, says the writer, is at present in the engineering stage of its development. Contributions are becoming less and less the product of individuals, and more and more that of wellorganised laboratories. Radio has great present capabilities, but also, unfortunately ,some sharply defined limitations. It is most important to the industry that the effects of these latter should be reduced.

For instance, broadcasting of sound in the United States is seriously limited by scarcity of channels to operate in. The present ten-kilocycle is really closer than is desirable for the best quality of sound with transmitters operating even under the best conditions. However, porhap3 50 per cent, more channels could be pi’ovided if stations suppressed part of ‘ their sidebands. “Chain” stations rigidly synchronised on the same -wave-length by crystal control to prevent heterodyne squealing would help in the same direction. Beam-casting of sound has possibilities in some regions, notably along coasts whore the beams can be directed toward important sectors. The same method may yet be employed to reduce interference between . stations on nearly the same wave-length. ‘ ‘ The phonograph is being considered for storing up programmes, especially those of events occurring in the daytime, for broadcasting at convenient times, The phonograph, as at present developed,” the writer declares, “is capable of so much better sound-qual-ity than is the transmitting apparatus Of even the finest stations, that, so far as the ultimate listener is concerned, it is as good as the original source of sound. It is even probable that the use of the phonograph will result in ovei'-all improvement in transmit-tiug-quality, because records can be made over and over until a sufficiently good one is obtained, whereas sounds are now sent out whether good or poor.

“The evolution of loud-speakers continues, with stretched thin metal diaphragms 3ft. or 4ft. in diameter as the next commercial form. Some A these may be elliptical in shape, with the actuating mechanism at one of the foci. Entirely new principles of operating loud-speakers ,: J .h as magnetostriction, or change of dimensions of iron when it is magnetised, are being developed. The practically discarded type of horn speaker is being improved and may return to large usage, this time capable of delivering . low notes.

“The alternating current set., which can be plugged directly into a light socket and has no outside batteries or eliminators has great popular appeal. The limitations of the set are in the A or filament-lighting current, .which is still not nearly so satisfactory as storage battery current. Strenuous efforts are being made by valve-mak-ers, however, to bring out a valve which will, be lighted by alternating current, yet which shall be free from the alternating bias produced by the voltage-drop across the filament. This bias would cause a serious growl in the speaker, but for the design of the audio system, which automatically prevents the amplification and passing-on of the low notes. Even if this biasing difficulty can be overcome and the fulltone range is obtainable, the A.C. set will still offer certain difficulties on power-liues where theTe is much voltage fluctuation.”