WAVE-LENGTH QUESTION

Radio Record, Volume I, Issue 2, 29 July 1927, Page 13

WAVE-LENGTH QUESTION

~_~-_--_ UNDER 500 METRES BEST Interest has recently been caused by a revival of the discussion on the choice of the most suitable wave-lengths for conducting broadcasting services, and the use of wave-lengths of betweeti 1000 and 2000 metres (says the Mel‘bourne "‘Argus’") is once more being advocated. The subject is so manysided that the sharp differences of opinion which have occurred on the matter can be readily understood, but the weight of opinion seems to justify the action of the Australian broadcasting authorities who have abandoned the long waves for waves between 200 metres and 500 metres. There is no doubt that in some respects long wavelengths for broadcasting are eminently suited to Australian conditions. Long:-Wave Advantages, -Their chief advantage over shorter waves is that they are less subject to absorption, and hence travel further in the daylight than a short wave of equal initial power. This in itself is an obvious advantage, and there is no doubt that many parts of Australia not now. served in the daytime would get a good service if the existing ‘"‘A’’ class stations were replaced by long-wave stations of equal power and "fficiency. A further advantage of the long waves is that they are not so subject to fading and distortion arising from fading as

are short waves. It is well known, for | instance, that when 3L0 was on its long wave the areas in Gippsland, where fading and distortion are now so bad, then had a perfect service, Serious Disadvantages. But against these advantages of the long wave, there are serious disadvantages of more than equal weight. In the first place, an extremely large aerial system is needed at the transmitter of an effective long wave station. Experts consider that one of the’ reasons that transmissions froni Australian stations when they were on a long wave were unsatisfactory was that the aerials were far too small. A large aerial involves the use of extremely expensive high masts and a large allotment of ground, enormously increasing the cost of the station, There is, moreover, a_ tendency for distortion to occur as the wave length used for broadcasting is increased. Although there is no technical reason for believing that signals on a wave of 1700 metres should he much more subject to distortion than signals on 400 metres, there is no doubt that the quality of the transmissions from 8L0 since the wave length was reduced has been much improved. Short Wave Advantages. Although the daylight range of @ long wave station is greater than that of a short wave station, the night range and night signal strength at a distance of the short wave station, subject, of course, to fading, is far superior to that of a long wave station, and moreover interference from static is never so serious on short waves as it is on long oe -" ee

waves. The other advantages of thé short wave service are mainly economic ones, chief among them being that wave lengths between 200 metres and 500 metres have been adopted as standard for broadcasting, and the development of receivers for broadcast reception has been confined to equipment designed te work most efficiently on the standard wayve-lengths. In New Zealand there are so many thousands of receiving sets in use which are not constructed to tune to the long wave-lengths that any change to 2 longer wave-length than, say, 500 metres, would not be considered by the authorities.