trying to couple to large structures is an interesting experiment, both
for receiving and transmitting (only by induction of course :). think
about power lines, phone lines (but unfortunately nowadays most are very
short, and the rest is done via fiber), natural gas pipelines, railways
etc. this is an example rx experiment:
http://www.youtube.com/watch?v=sWsdaSmWg7E , these structures are usually
very well grounded at regular intervals, but still some vlf will slip
through the ground system, so they can be also used for tx too. a few
miliamps at 9kHz into a large structure is detectable from a few hundred
meters.
actually the "utilities-assisted earth mode" works not only on transmit.
a loop antenna near a long conductor will pick up a stronger signal (and
also more qrm, so this doesn't always raise S/N).
this might not be ham radio (or not radio at all), but is very interesting
nevertheless
VY 73
Jacek / SQ5BPF
|
