Heinz,
When I got my new car in 2009, I wanted to use a radio without an external aerial. I installed a powered internal aerial and it did work, but only where there was a pretty strong signal. So much so that in Ireland it would frequently stop receiving until you entered a better signal area. After about 4 months, I installed the usual external aerial and all problems with reception vanished!!
I use a Sony radio and have the front speakers in the footwell as usual and the rear speaker output I have wired to a 3.5mm socket mounted on the rear bulkhead behind the seats. I use a set of earphones from Starcom(
www.starcom1.com) which just attenuate the wind noise leaving all road noise and horns etc audible. I find they are really superb and are very safe.
I hope this is of use. PM me if you want further information
Cheers!
