Minimising Interference

Radio Record, Volume V, Issue 5, 14 August 1931, Page 28

Minimising Interference

No Substitute for a Good Aerial ewe HCHNT research has conclusively proved the fallacy of the common belief that a short indoor serial is a desirable adjunct of the modérn sensitive radio recelver, states the chief engineer of Philips Lamps, Lid. (N.Z.). For all but local reception there is a8 much difference in performance between outdoor and indoor serials as between an expensive and a cheap set. The development of "Interference technique" has proved that there is no man-made interference which cannot be eliminated at its source, but the listener himself can exert quite a useful measure of control of conditions at the receiving end. The one object to be kept in view is obtaining the highest ratio of signal strength to interference level; any means, therefore, of inereasing signal Strength or reducing interference strength is a step in the right direction. It has been established experimentally that by far the greatest proportion of the radio interference experienced in towns, including the clicks and bangs caused by the making and breaking of electrical circuits, the crackling, rasping and whirring noises from electrical machinery reaches the receiver by way of the lighting and power mains, gas and water pipes, gutters, etc., these noises being propagated from the ground upward. An indoor aerial operated right in the midst of the interference must obviously be affected -by it to a ‘marked extent. By adopting a high outdoor aerial we accomplish simultaneously a twofold effect, firstly by increasing the signal strength of the distant station and secondly we decrease the coupling between the aerial and the ground interferences. Yn addition to being well above the interference mentioned, a good aerial has the down lead carefully placed, remote from any power or _ telephone wires, house gutters, etc., while a really good earthing system is well worth while, and attention to these points re sults in a great improvement in the ratio of signal strength to interference level, adding greatly to the enjoyment of distant broadcast programmes