Aerials for use on aircraft: a comparison between fixed and trailing types on the 900-metre waveband

Although trailing aerials have been used satisfactorily on aircraft for many years, the increasing speeds of modern aircraft have made it necessary to discard them in favour of fixed aerials. The paper reviews briefly the past development of aircraft aerials, and describes an investigation into the characteristics of the two types which was designed to provide data on which the design of equipment for medium-frequency operation on fixed aerials could be based. Measurements on typical examples of both types are described, and the values of effective height, radiation resistance, loss resistance and capacitance are discussed and compared. The increase in transmitter power which would be necessary in order to obtain the same performance with a fixed aerial as that formerly obtained with a trailing aerial is calculated. Some particulars are given of equipment whch goes some way towards meeting this requirement, and an estimate is made of its probable performance. Possible future developments in aircraft aerials for medium frequencies are discussed.