RADIO SERVICE

Waipukurau Press, Volume XXVIII, Issue 118, 13 May 1932, Page 6

RADIO SERVICE

Interference Aspects Dealt with authoritatively by A LEADING ENGINEER In a special paper contributed in response to a questionnaire by the Supply Eengineers’ Association, Mr. W. A. Waters, M.1.C.E., dealt with the subject of radio interference: — Strength of Signal.—The popularity of “B” Stations in their various country centres, while usually ascribed by listeners to “good .programme, and better transmission than ‘YA’ Stations,” is really a problem of human nature. The average listenered or potential listener to radio has in the past always associated this new art as mechanical music plus all sorts of other noises and defects in reproduction. The vast bulk of country listeners, until their attention is drawn to the fact, fail to realise that clear radio reception, free from extraneous noises, is merely a problem of the relative strength of the broadcast versus the interfering noises. The “B” Stations thus merely supply the requisite power for the areas they serve.

These interfering or unwanted noises, or as commonly stated, “interference,” are of many kinds, but for broad principles, can be classed as natural and man made. In the natural class we have “static ’ and in the “man made” class the whole gamut of radio interference, due to electrical apparatus of diverse kinds, and including interference of radio receivers themselves, both as regards internal defects and inherent design causing interference to be radiated into space by some receiving radio sets.

Unpreventable Interference. —“Static” will serve to name the type of radio interference that is beyond the skill of man to eliminate, that is radio interference of electrical storms, lightning, highly charged electrical atmosphere, etc.

In the “man made” class, there are a number of types of radio interference, which are serious to a listener who is forced by reason of his location relative to broadcast stations, to get his radio programmes delivered to the aerial at a very low ratio of signal strength. Quite a large number of these “man made ’ electrical interferences are of a type that are almost impossible to eradicate, except at prohibitive commercial expense which could seriously embarrass the electrical supply industry of New Zealand. Examples are—corona, salt spray , troubles, natural condenser effect of insulators, etc. Preventable Interference. —On the other hand, there are two distinct broad classes of electrical interference that are preventable and curable. Of these two classes, there is interference that originates on power supply lines of the class of 11,000 volts and lower. Usually serious interference on this type of equipment is very often an index of trouble developing, and most Power Supply Authorities track it down and effect repairs. This matter of trouble developing has been definitely proved by experience and on many occasions has resulted in maintaining the goodwill of the consumers affected, as well as effecting repairs to prevent an outrage on the part of system where it originated on lines.

There is being sold and used electrical equipment that causes a lot of objectionable interference with reception in a limited area under present day conditions of Radio in New Zealand. The average listener will clamour for a supply authority to go to a lot of expense to trace this class of interference (which is usually intermittent) that mars his reception, but, rightly so, most supply authorities decline. The consumer’s equipment that causes the trouble is a perfectly efficient piece of well organised apparatus, and until definite regulations are framed by the Public Works Department, will continue, to be sold and used.

The obvious remedy is to follow the trend in U.S.A., where many electrical manufacturers guarantee their equipment to be non-radiating. Certain equipment (such as beauty parlour apparatus, . medical equipment, fans and vacuum cleaners, certain small motors) are in this class of where prevention is better than cure. Any motor with a commutator on A.C. Supply sooner or later gives trouble with radio interference.

(To be continued.)