Been there, done that...
Well, with one of those JVC FM transmitters that you are supposed to use to connect a cd changer via the radio... I plugged it into the car antenna, and it was powerful enough to be picked up within about 80 Meters...

Very silly in car parks... =)

Jazz
(List 112, Mk2 12 gig #40. Mk1 for sale 4 gig #30, apply within)