[Short Reviews]

Abstract

IT is not often that one branch of applied science reacts so unfavourably on another branch, and the difficulties which have arisen from the interference from power circuits and apparatus in the prevailing types of radio-receivers were scarcely anticipated. The problem assumed international magnitude, and has only within the last few years been brought down to a qualitative basis. Meanwhile the British Post Office has been investigating and advising on tens of thousands of cases per annum, and it is to them that we owe the idea that the interfering radio currents travel along power and other mains longitudinally, that is, along the wires in parallel; indeed, the impedance to earth of such mains may be megohms, thus conserving the disturbing energy. The variegated field has now been sorted, and a very complete guide offered by the present author, whose firm has been in the forefront, both in theory and practice, of interference suppression. In principle the methods are simple, the application of condensers to earth, with or without appropriate chokes, being most general; the economic design of units and their proper location, however, requires systematic thought. Much of the author's information is usefully tabulated.

Radio Interference Suppression

G. W.

Ingram

By. Pp. viii + 154. (London: The Electrical Review, Ltd., 1939.) 5s. net.