After checking through my files I think these people in the ad are probably
selling something along the lines of the Tate ambient power system mentioned
on Geoff's Website. It has a US Patent number 4628299 although its for a
seismic warning device claiming that by monitoring RF one could detect
earthquakes. Its basically just a rectified, tuned resonant circuit.
Regards
Martin
http://www.geocities.com/CapeCanaveral/Lab/7919/