I don't know if it's still in use nowdays,but there is/was a very low
frequency antenna buried in the ground from coast to coast along the
U.S.A./Canadian Border.I read about it in either one of my Popular
Science or Popular Mechanics magazines which dates back to the 1950's or
1960's.If I sort of remember,that antenna is intended for U.S.Navy to
use.Maybe it is an ULF antenna,I still have that magazine floatin around
here somewhere.
cuhulin