Reg Edwards wrote:
Roy. as you know, radio propagation through the ground follows exactly
the same laws as propagation through anything else.

Sure. The only real differences among salt water, dirt, and air are the
loss -- which is a big difference -- and propagation velocity.

All is governed by the resistivity, permeability and permittivity of
the medium, at a partcular frequency, and the geometry of the
interfaces between different mediums.

The problem of finding solutions to paricular problems lies only in
entering input data into a general purpose, number crunching computer
program, which I'm sure versions of it already exist.

NEC-4 can handle antennas and propagation in two media of infinite
extent separated by an infinite plane boundary. Neither one has to be
air. While this doesn't imitate some real situations very well, it can
produce some good insights into propagation and the performance of
antennas embedded in a medium other than air.

Roy Lewallen, W7EL