I don't know if it's an urban myth, but there was a story that a chap living near the crystal palace transmitter who found that his metal shed roof could provide enough juice to power a light bulb. The BBC spent some time trying to figure out what was causing a reception blackspot, and eventually tracked him down. The authorities take a generally dim view of people interfering with legitimate broadcasts, so he had to stop doing it.

I suppose you could argue that he was broadcasting a high power signal in exact anti-phase to the ligitimate transmitter. The fact that he needed negative energy to do it wouldn't trouble a court.