RADIO INTERFERENCE

Press, Volume LXXIII, Issue 21990, 14 January 1937, Page 4

RADIO INTERFERENCE

TO THE EDITOR Of THE PRESS Sir, —In reply to your correspondent “Fed Up,” who is complaining of amateur operators who are supposedly interfering with his radio reception, first I should like to enlighten him on the various wave-lengths used by amateurs throughout the world. These are 160 metres (not used in New Zealand). 80 metres, 40. 20, 10, and five metres. The reason that we do not use 160 metres is that this band is too close to the broadcast band and would cause too much interference. He says he hears most of the interference on 350 metres. This wave-length .is round about where the fourth overtones from the amateur stations operating on 80 metres would come in. As “Fed Up” should know, “superhet” receivers are definitely more powerful, selective, and sensitive than T.R.F. sets, and what can be heard on a “superhet” cannot always be heard on a T.R.F. set. Also, a “superhet” set will detect these signals by the incoming signals beating with the intermediate frequency of the receiver, and thus giving signals somewhere on the broadcast band. In New Zealand amateurs are all definitely working on the allotted Wave-lengths below 100 metres, but owing to the vagaries of radio transmission their signals are received on other wave-lengths, both in the broadcast and short-wave bands. Perhaps “Fed Up” remembers how 3YA had a harmonic on 1440 kilocycles and was jamming 3ZM. This was remedied only by installing certain apparatus called a Faraday screen. This, however, is costly, and as 99 per cent, of the " amateurs are men and boys of ordinary , means, to install these would be very hard on their pockets. I myself am an amateur of five years’ experience and have also a radio broadcast operator’s certificate and am a registered radio engineer However, if “Fed Up” still wishes to complain,.! would suggest that he can do nothing better than to interview our association’s publicity officer, Mr T. Danks (I believe he is on the telephone), and I can assure “Fed Up” that he will get the best of attention. If “Fed Up” wishes, he may obtain my address from your office and I will give him any further information.— Yours, etc., RADIO ENGINEER. January 13, 1937,