THOSE TWENTY-TWO WAVELENGTHS

Evening Star, Issue 23699, 5 October 1940, Page 4

THOSE TWENTY-TWO WAVELENGTHS

NECESSARY FOR COMPLETE SERVICE TWO MAJOR REQUIREMENTS If it were possible for an overseas listener to be so situated that ho could receive everything radiated m tliu 8.8. C. shortwave service throughout the entire 24 hours of one day, he would find that in the course of the day he had received no fewer than 22 different wavelengths. Ho would find, too, that this total included at least one wavelength in each of the bands normally available for shortwave broadcasting. The 8.8. C. might well be asked “ Why do you confuse the listener in this way? Why are so many wavelengths required?” At the present time the 8.8. C. overseas service comprises four separate programmes. Two of them are primarily intended for reception in distant parts of the world, and two for reception on the Continent of Europe. Under these conditions, the 8.8. C. must meet two major requirements in its broadcasts to overseas listeners* The first is that the wavelengths used must be suitable for any particular transmission path, and the second that different wavelengths in the same band will be required if two . programmes are to be simultaneously broadcast to areas requiring that band.

To fulfil both these requirements the engineers must not only choose the correct wave band for a given service, but must arrange for more than one wavelength in the chosen band to be available to carry the different programmes. Transmission 2 provides a clear example of how these requirements are met. One programme service, in English, is carried on 13.93 m (GSJ) and 16.86 m (GSG) for India, Burma, and Malaya, and on 1£).82m (GSF) and 25.53 m (GSD) for the Far East. The second overseas service, including various foreign languages, is simultaneously radiated on 16.84 m (GSV) for Canada, 13.97 m (GSH) for Africa, and 13.92 m (GST) for South America. One of the two foreign language programmes in the European service is radiated 0n'25.53m (GSE) and 49.59 m (GSA); the other programme is simultaneously radiated on 25.38 m (GSN) and 49.10 m (GSL). Thus for this one period of the day—transmission 2 is in operation from 10.40 to 14 G.M.T.—no fewer than 11 different wavelengths are required in order to provide satisfactory reception of the 8.8.C.’s four overseas programmes in all parts of the world. Later in the dayi (when, generally speaking, rather higher wavelengths are required for most of the transmission paths), a further group of wavelengths is necessary. In order, however, to avoid confusing the listener, the 8.8. C. tries as Tar as possible to keep the wavelengths to which listeners are accustomed directive over the area concerned.