I've tried to do this before, it never worked particularly well.
In the early 90's (possibly late 80's?) I made a crystal radio from some old cheap chinese AM transistor radio, I put a battery snap (pp3) on the earth and connected this to the radiator. I was astounded to find it didn't need an aerial! The ferrite rod inside was enough. Used to listen to Radio1 on that late into the night, until I got bored or fell asleep and rolled my ear over onto one of those horrible crystal earpieces!
Interestingly, now that I have my own home i've been experimenting more, when I moved in we removed the old gas fire but left the aluminium flue in place, this is insulated from everything by brickwork. Measured with a fluke 175 there is about 500mV DC with respect to earth on it at all times, even after breifly shorting it out. Works quite well as a CB aerial too!
Have a look here, from what I can tell, these crazy russians aren't playing with a live transmitter, they're playing with a disused antenna not far from a transmitter, just look at that spark!...
http://englishrussia.com/index.php/2...-plasma-radio/
Dave.