THE BEST AERIAL

Shannon News, 23 November 1928, Page 4

THE BEST AERIAL

GUIDE TO DIMENSIONS.

In a casual walk round any of the suburbs one cannot fail to be impressed with the great diversity in form and size of the wireless aerials above the houses, ‘ writes " 3BI) ” in the Melbourne Argus. Even listeners of considerable experience often fail to select and instal a type of-aerial which will give them the best results that can be obtained from their apparatus. "While a large aerial will undoubtedly pick up wireless signals loudly, it will also receive powerful impulses from atmospherics, and experience shows that the degree of interferendft caused by the atmospherics increases with the size of the aerial. A small aerial, while giving relatively weak signals will generally produce a result which.is almost, entirely free from atmospheric disturbances. Moreover a large aeriai markedly affects the selectivity of the tuner in the receiver. So much energy is collected from strong local stations by an unavoidable process known as shock excitation, that interference is caused with weaker signals, and if the aerial is very large distant reception becomes impossible. Two main factors should govern the size of the aerid.l used. They are the type of receiver to be employed, and the distance of the site of installation from the nearest broadcasting station. If a very insonsitive receiver, such as a crystal set, or „a onevalve set is used ,effective distant reception will be impossible, and the owner must concentrate on getting the best possible results from his local stations. A large aerial which will pick up a great deal of energy to actuate the x-eeeiver strongly is therefoM needed.

For use with a cyrstal set or a onevalve set, especially in the country, it is generally wise to make the aerial as largo and high as curcuxnstances permit In the metropolitan area an aerial 30ft. high and 50ft. long will usually give excellent loud-speaker signals from the local broadcasting stations, while if the tuner is carefully designed, and perhaps supplemented by a wave trap ,very weak signals can be heard from inter-State stations.

A slightly smaller aerial should be used with a three-valve set ,and the size still further reduced as the number of valves in the receiver is" increased, until when an aerial is needed for such receivers as supw-hetero-dyno sets of five or six neutrodynes, a short length of wire “in the room with the set will permit satisfactory receptions from both local and interstate stations.

In the country when the of interference from a nearby station is reduced, larger aerials can be used. The factor governing the size of the adrial then becomes the amount of interference which is caused by static. It. will often be found wise to erect two. aerials in the country. One should be long, and high, and should be used whenever interference is not caused by static, while a much smatie-r one can be used in sultry and hot weathei’, when static is prevalent.