Interference with Radio Supply by Electric Lighting

Abstract

IT is well known that when direct current supply is used for electric lighting, the contacts of- the switches and fuses often get badly corroded after a few year's operation. This usually causes little, if any, inconvenience in the lighting of the house or in the use of electric appliances, but if a radio receiver be installed the loud speaker produces most unpleasant noises. This is often attributed quite wrongly to some fault in the set. In many cases the noises are got rid of by having the electric wiring overhauled. According to a paper in the Electrical Review of June 1 by V. Z. de Ferranti, many domestic electrical appliances also cause bad radio reception. As examples he gives electric bells operated from the mains, children's electric toy trains, a bad contact in an electric fire and, worst of all, any piece of equipment driven by a motor. He points out that it is far easier to supply equipment which can be trusted to cause no interference than to eliminate by special devices the interference caused by equipment already installed. The special devices are often expensive. He estimates that there are now two and a half million mains-operated radio sets in Great Britain. Collectively, they take about 150,000 kilowatts and the average demand is about two hours a day. In addition, the demand for this load is outside the busy hour of supply and it is therefore desirable to the electricity companies. There is quite an appreciable number of small house-holders who have availed themselves of electric supply primarily in order to be able to use it for radio receiving sets.