The Action of Short-Wave Frame Aërials

Part I (1) An electromagnetic wave incident on a tuned rectangular frame aërial comparable in dimensions with the length of the wave is considered to cause a circulating current which may be resolved into a "direct" current component due to the primary action of the wave, and an "indirect" current component due to the current in adjacent parts of the frame. This treatment leads to the conclusion that the resultant current is dependent on the dimensions of the frame and on the angle of incidence of the wave. (2) For each particular width of the frame less than one wavelength there are at least two critical heights for which the frame current will be a maximum. That is, for each particular width less than one wavelength there are at least two critical frame areas for best reception, and any variation of these areas will result in decreased signal strength. (3) The resonant current which circulates in a tuned frame aërial under the influence of an electromagnetic wave is not the maximum current that can be produced in the frame by the incident wave. By formatising the frame, that is, by properly adjusting the height and width of the frame, the current may be increased to a very much larger value. Part II (1) The transmitter, which is capable of working on wavelengths from 7.54 to 8.80 meters, is described and the chief difficulties in its design are discussed.