POWER LEAKS AND HETERODYNE INTEREFERENCE.

Radio Record, Volume V, Issue 5, 14 August 1931, Page 4

POWER LEAKS AND HETERODYNE INTEREFERENCE.

QUR Mailbag and DX columns provide, we think, a means for the expression of the views of listeners. From time to time interesting points are raised therein, and.in not a few cases some definite good has een accomplished as a result. Few subjects are more consistently @iscussed than interference, for not only has it been responsible for #he ruination of many an otherwise good programme, but also it has een definitely responsible for the loss of sales to dealers. Interference can be classed into two groups-man-made and jatural-but it is the former we are concerned with as the latter is wtite beyond control. Of the former there are three classes, electrical sturbances, heterodyne interference, and the "howling" valve. Now, } has been said truthfully that all man-made static can be controlled. 3ut what is the position obtaining in this country? Very far from tisfactory. When one turns on a powerful receiver, the result, pecially if the set is in a town area or near power apparatus, fs most distressing. A series of gurgles, splutters and roars makes Ustening quite impossible. If it is absent, then the chances are that the annoying, unvarying whistle we call heterodyne is there to mar one’s enjoyment. In countries where radio is more developed, these ‘orms of interference have been thoroughly suppressed. In several gountries it is an offence to operate machinery capable of radiating high¢requency power that can mar someone’s enjoyment of radio. And. guite rightly, too. Inexpensive filters, which will effectively eliminate ili noise, can be fitted to most apparatus, and it is our contention that t is high time some such legislation were introduced into this country. Radio is no mere plaything that need be operated only when the ether is clear. It is a utility that is in operation continuously. ‘A. DISTRESSING case is brought to our notice this week. In a certain city suburb residents near the tramline cannot listen when a tram is approaching or leaving. On being asked to suppress the noise the authorities stated that they were the first in the field and therefore radio must give way to them, though they admit that much of: the goise could be eliminated at a moderate cost. They absolutely refuse to do anything, even if listeners were to contribute a portion of the cost. KY Ancadd . feats Fed.

Frankly we cannot understand this egotistical attitude, but we can appreciate the fact that it is high time legislation to deal with cases such as these was introduced. We understand the broadcasting gystem is under revision, and we are confidently looking to the mouldérs of the new system to introduce legislation to deal effectively with cases such as these. It is our firm belief that listeners as a whole are more concerned with improving radio from this angle than they are in who shall provide them with their daily fare. With a clear atmosphere they can reach out and get exactly what they want, whereas now, being in many instances restricted to one programme, they find cause for complaint, simply because one programme cannot please everyone. Listeners will be. disappointed if this question is shelved when the long-awaited broadcasting legislation is brought down. At the present moment it is a punishable offence to make a receiver oscillate so that it annoys a neighbour, yet a local body or a private person can blot out a whole programme, and all that can be done is to ask the offenders if they would please instal filters. Surely the case is reminiscent of the "man-of-war without guns" that we read of in early New Zealand history. ANOTHER source of interference is that caused by two stations operating on almost identical frequencies and coming in at, relatively the same strengths. The result is a whistle called the heterodyne beat. This completely mars the programme of both stations, and because of this the frequency of 1YA has been changed within the last week or so. Heterodyning stations show a deplorable lack of co-operation on the part of the broadcasters in the areas concerned. In Europe there are some hundreds of broadcasters, yet the ether is orderly and hetero~ dyne whistles are not serious. But they were until a conference was called of engineers of all the principal countries and the "Prague Plan" evolved, This separates broadcasters on approximately the same power and wavelength, and arrangements are made to keep careful track on the outputs of all stations. Broadcasters off their allotted frequencies are asked to explain, and if this state continues they are ordered off the air. A somewhat similar system operates in the United States of America and Canada, where there are some 760 stations on the air, But in New Zealand and Australia the Governments merely "keep in touch," and with no more than 80 odd stations, we find that there is frequent heterodyning, and that now, one of the most powerful stations -. has to move because of a newcomer and blot out a popular Anferican. Elsewhere we call attention to the fact and ask the co-operation of listeners in preparing a report on the subject. We believe that if a comprehensive report could be handed to the Governments of the two countries much could be done to alleviate the present unsatisfactory state of affairs.