Hidden Earth is the UK annual caving conference.  This year it will take place on 24-26 September in Leek, Staffordshire.  Lectures are scheduled for Saturday 25th.  See http://hidden-earth.org.uk/ for details.

David Gibson has written extensively on earth loop antennas and other aspects of underground electronics in the CREG Journal.  See http://bcra.org.uk/creg/jnl/index.html for contents lists. His paper on What We Don't Know About Earth-Current Propagation appeared in 2003 in issue 54 and his lecture will deal with his latest theoretical analysis of this subject.  He currently works for a manufacturer of mine safety equipment - underground electronics is a hobby which is why the update has been delayed.  He is not (as far as I know) a radio amateur.

I will ask him if he is interested in a collaborative venture.

73

John F5VLF