I recently installed an Alpine CDA9833, JLA E6450, BA speakers....in a Cadillac Seville 2002. The factory antenna has two antennas mounted, one on the front windshield and one on the rear window. There is a power module in the headliner for the antennas. When power is applied to the module, I get crackling noise on FM, but AM is clear. When no power to module FM is clear, but NO AM at all.
The module needs power for AM because there is no ground plane for the antenna, but the amplification of the signal causes the noise that is probably always present in FM, to amplify to an unacceptable level. Plus this Alpine head unit probably picks up better a "+/-" situation.
I now have a toggle switch mounted to the power line to the antenna module. I switch power on/off depending on AM or FM. Anyone have any filter ideas or anything other than having to turn the power on and off?
Whoa that's an odd problem. Why don't you dump those antennas and install a reg one? You can purchase a powered antenna with remote control. I did that.