In Reply to: E34 & new sound system problems posted by Dave on April 03, 1999 at 21:01:28:
I had the exact same problem after putting a new Hi-Fi in my '89 535i, ie. poor radio reception. The aerial is integrated with the defrost wires in the rear window and uses a dedicated amplifier which requires power. If you have the Bentley manual you'll see in the stereo wiring diagram that the aerial amp is powered by the amp in the trunk. Since you've changed your stereo, there is no power to it. The stereo shop that did my install tried all sorts of things to solve the problem, until I showed them the diagram. So, you need to find a white wire and attach it to the power antenna out on your new deck. That's al it took to fix mine. As I had the system installed professionally, I have no grounding problems, the sound is very clean & solid.