04 Crown Vic PI radio problem

In my work Crown Vic PI, I recently swapped out a POS aftermarket am/fm radio for an old radio that fits the slot (the stickers seem to indicate it was originally in an Explorer). The CD player and tape deck work just fine. The problem is with the radio stations - they seem to come in an out, as if the antenna plug was loose. I've checked it twice, and it's tight.

If the vehicle is sitting still, it doesn't seem to be as bad. The POS radio had reception problems (we thought it was the radio, and mostly it was), but not like this. Is it possible the antenna is lousy? The antenna plug not the perfect fit? Any known problems with 2004 Crown Vic PI radio problems? Any suggestions?

Thanks,

Gordon

There is an "antenna" module in the trunk, if it dies you can get poor reception.

check and make sure all your wires are copper and not aluminum. Aluminum wires will make your stations fade in and out. That's probably not the case, but I thought I'd throw that out there.