The Radiation Efficiency of a Small Loop Antenna

Abstract

For cave radio applications, we are not normally interested in the radiation from a loop antenna because the distance over which we are working is small (relative to a wavelength) and so only near-field effects need to be considered. However, it is still interesting to consider the radiation field, and to express the radiation efficiency in terms of the specific aperture where, just as for near-field operation, the number of turns on the antenna does not affect the result. David Gibson explains radiation resistance, summarises the equations and shows how the skin effect in the wire and the proximity effect between turns of the antenna winding can be taken into account.