Re: Ground wave transmission, was G-line

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Ed Phillips <evp@xxxxxxxxxxx>

"Original poster: robert heidlebaugh <rheidlebaugh@xxxxxxxxxxxxxx>

A burried dipole or coil antenna is not the same as two stakes in the
ground. An insulated antenna burried above the water table projects an
immage antenna the same distance above the ground as the antenna is
burried
down so part of the power is an air wave and part is a ground wave so
the
total power at the reciever is lower than a above ground antenna. This
was
tested for NASA to develop a hardened antenna system for missile sites.
In
Majave desert dipole antenna were burried  in the desert beyond normal
TV
reception range only 4 ft down and were able to recieve clear TV
signals.
The antenna were lengths of net fence wire one role long each way in a
trench made with a cat tractor. Yagi and 1 meter ferrite antenna were
also
tested  in bore holes, with good results. The fence wire was large an
worked
best. Tests were done in 1962.
      Robert   H
-- "

	I understand about the buried antenna but question the image antenna
bit.  That analogy applies to the radiation pattern of an antenna above
a perfect (infinitely conducting) ground plane but not to an antenna
embedded in lossy soil.  Dry sand is pretty low loss material but
there's nothing above it to reflect in your example.  Some of the Space
Shuttle Imaging Radar (SIR-B in partiular) were able to see far enough
through the sand in the North African desert to image ancient
underground drainage channels.

Ed