Hi,
I recall seing a small allotment site many years ago,
(for those who don't know that term, its a plot of land set
aside by the local authority for use by local folk who rent
plots to grow stuff for themselves, usually veg/flowers)
and mentioned to someone there about the lights in one or
two huts, they seemed to be left on for a long time, surely
the batteries must be costing someone a bit much.
These places don't normally have any mains electricity.
I found out later, that the lights i wondered about were
actually powered by a close nearby local radio transmitter,
some folk had made loops of wire around the inside of their
huts, and fed small filament lamps.
The company running the transmitter had found out about this,
and they had altered the arrangements on their transmitting
ariel, so that this no longer worked.
Also, my parents had a crystal set on their house-boat many
years ago, and when in the right place they could both listen
to the BBC directly from a loudspeaker, not loud so they told
me, but quite audible by them both when sitting by the set.
I have often wondered about charging batteries from unusual
sources, although i've never tried radio waves. I have wondered
about earth currents, but from the few tests i have done they
seem very variable. The highest i have personally measured was
about twenty volts, i think that was near a hospital (?)
maybe they had their own substation ... ?
Earth currents seem to be fairly low impedance but are usually
only a few volts, maybe a small transformer could step up to
charge a battery. I might look at that again.
I have heard that some people who live on boats near pylons
can get strip lights to work on their boats. Where i've seen
this before, they haven't lit properly, just dimly and flicker.
But maybe some people have put ariels or something on them.
Regards, John