OK, I have a Roady XM Radio that I move between vehicles. I installed the "hardwire" kit that includes a small transformer inside the fairing. Initially, this was connected, both hot and ground to the Cigar Lighter connectors...I also took the step of connecting the ground wire to the radio ground as an alternative. The magnetic antenna is on top of the radio and I use a 1/8" jack for the direct wire into the radio. I use the Tune Trapper antenna.
When powered up, the XM radio prevents the radio from receiving the signals from AM/FM/WB.
I also tried using the Cigar Lighter directly with a different power cable, same problem.
Finally, I plugged the XM Radio into the 12V jack on my JumpStart Battery Pack...no interference.
Any suggestions? Is it a gound issue? Should I try running the ground back under the seat?
This does not happen in my truck.
/Bill