ELECTRICAL LEAKAGES

Radio Record, Volume II, Issue 6, 24 August 1928, Page 11

ELECTRICAL LEAKAGES

‘TROUBLE IN AUSTRALIA Action taken by officers of the Commonwealth Postmaster-General’s department a few days ago to overcome interference caused by an electric current leak from one of the Tramways Board’s power mains directs attention to a source of wireless interference to which,-so far, much too little attention has been given (says the Melbourne "Argus"). Although concrete cases of such information are seldom proved, it js generally accepted that power leaks cause a large portion of interference experienced in large cities. When they occur, listeners usually blame either the broadcasting station for poor transmission: or neighbouring amateur stations for causing interference, without realising: that. the real source of trouble is in their own electric tramway or

lighting service, and perhaps in their own homes. It is surprising how wide the range of some interference from electrical devices extends. JN recent experiments with supersensitive short-wave receivers, on wavelengths of about 20 metres, it has been found almost impossible to work while motor-buses and Cars are running in the neighbourhood, the electrical waves set up by the ignition equipment being sufficiently strong to operate the sensitive receiving apparatus. Such interference is seldom if ever heard on an ordinary broadcast receiver, but interference from electric fans and other apparatus using electric motors, old-fashioned electric are lights, battery chargers of the vibrating reed type, and violet ray machines is often so severe that it prevents reception.

COMMON cause of trouble, and one usually difficult to detect, is «a faulty contact between the socket prongs and the base of an_ electric

lamp, or the socket contacts and ping of a radiator or electric iron. If such a fault exists an intermittent eléctric are ig set up at the point, and while this are is burning it generally radiates powerful interfering waves. Proof of this can be had by turning off an electric light in the house. As the switch opens 2 momentary arc is caused, and a sharp click will be heard in the loudspeaker. The worst electrical interference I have ever heard occurs near the electric tram lines in Bendigo. Owing apparently to dirt on the rails, marked sparking occurs at the wheels of the trams in that city, and the resulting interference waves are so powerful that reception becomes impossible when a tram is in the neighbourhood.