Members of the Cave Radio & Electronics Group have been using and investigating 
earth loop antennas for some time. The theoretical basis of such an antenna has 
not been clear to us, but Dr David Gibson of CREG is proposing to give the 
following lecture at the Hidden Earth conference in the UK this autumn.

How earth-current antennas really work
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With cave radio equipment such as the HeyPhone and Nicola system there
has been a trend away from the use of induction loop antennas towards
earth-current antennas, i.e. long wires grounded at both ends. However,
the popular explanation for how these antennas work is fallacious. They
do not operate by allowing the current to flow in a 'big loop' in the
ground and in fact, they do 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, or how to design a better one. Back in 2003, I wrote
an article for the CREG journal entitled 'What We Don't Know About
Earth-Current Propagation'. It has taken me some time to get to grips
with the problem but this talk will now go some way to filling in the
gaps in this knowledge and will describe a method of experimentally
rating earth-current antennas for effectiveness.

-- 
David Gibson