How Earth-Current Antennas Really Work

Abstract

With cave radio equipment, there has been a trend away from the use of induction loop antennas to the use of so-called earth-current antennas, i.e. long wires grounded at both ends. Both the HeyPhone and Nicola system use this type of antenna. However, the popular explanation for how this antenna works is fallacious. The antenna does not operate by allowing the current to flow in a 'big loop' in the ground, nor is it a 'conduction mode' of operation. In fact, it does not depend, fundamentally, on current flow in the ground at all. The fact that the popular explanation is wrong is important because, if we do not understand how the antenna works, it is difficult to know the best way to use it, nor how to design a better one. In this short note, David Gibson outlines a more useful model - that of the Grounded Horizontal Electric Dipole - but without the mathematical justification, which will be given in a future article.