You might be interested in the 1918 article on underground antennas.
http://www.rexresearch.com/rogers/1rogers.htm

"Roy Lewallen" wrote in message
...
Michael wrote:
This has been done since the beginning of radio. Nothing new. However, I
am
interested in the sand antenna. I would love to hear more about working
antennas that exist entirely below ground. I am guessing but would say
this
would not work on any band above 160 meters. I know the Navy has made
huge
underground radiators at frequencies like 50 khz. I would be surprised
to
hear that something as high as 1.8 mhz could be made to work.

I recall reading some years ago about underground antenna experiments
done by the military. I believe the were done well into the HF range. A
trench was dug, the antenna put into the trench but not in direct
contact with the soil, then the top was covered. The objective was to
make a concealed antenna for relatively short range communication. The
signals were much weaker than for an above-ground antenna (~30 dB if I
recall correctly, but I might not), but still usable for the purpose at
hand. This shouldn't be surprising.

Roy Lewallen, W7EL