RADIO INTERFERENCE

Hawke's Bay Tribune, Volume XXII, Issue 148, 8 June 1932, Page 10

RADIO INTERFERENCE

CAUSES AND REMEDIES. ELECTRICAL FAULTS RESPONSIBLE. Radio interference from electric power mains has become sufficiently serious to lead the Public Works Department to circularise power boards, seeking their co-operation in eliminating the trouble where possible. At present there are no regulations governing the matter. Irregularities in electrical circuits and apparatus are among the causes of interference. Tramways also provide their quota, although the trouble in this case is not always as serious as may be imagined. It is stated that the lighting circuit in a tramcar will cause more interference than the traction circuits, the smaller current forming a spark, whereas the traction current forms an arc. Most interference troubles are due to continuous or intermittent sparking at contacts, cither intentionally, as in the case of motors, switches or flashing signs, or unintentionally, as in the case of faulty or partially broken conductors. One of the most prolific sources is the average house lighting circuit, because of the comparative lack of attention it receives. The use of a sensitive alternating current operated receiver in a house will very quickly prove the existence of faulty switches, refrigerator, or vacuum cleaning motors or other appliances. A likely source of trouble is a loose contact in a plug connecting apparatus to the circuit, or in a fuse which has not been tightly set up in position. Flexible cords to radiators, portable lights, irons, vacuum cleaners, and so forth, will also cause trouble if they have reached the stage when some or all of the internal conductors are broken, or when the insulating material has become sufficiently damaged to allow leakages between wires, or from one wire to earth.

The best way of successfully avoiding the trouble is to remove the source, or, if that is not possible, to provide suitable filtering apparatus at the point at which the interference originates, for sparks act in much the same way as the old type of spark transmitter, and radiate interfering signals, but of indeterminate wave length.