Didn't the Mythbusters ... And try using a large antenna to generate electricity from radio waves?
I think they used the antenna under power lines as an induction loop.
I think they also tried just seeing how much power you could get just from having a really big antenna - the result was not enough to power a radio.
'How shall a man judge what to do in such times?' 'As he ever has judged,' said Aragorn. 'Good and ill have not changed since yesteryear; nor are they one thing among Elves and Dwarves, and another among Men. It is a man's part to discern them, as much in the Golden Wood as in his own house.'