I have an XM radio, and to hook it up to my car stereo means I have to use the provided receiver/antenna to get the signal...it hooks up to (if I remember right) the antenna in the back of the stereo unit, and splits with its own antenna, and the display unit....
Basically (it's been a couple years, have mercy) I had to set the radio station on my car stereo to a static-y station (the little receiver box gives you several choices), and fire up the display unit to whatever XM station you want at the time.
I should get the service turned on again....THAT would be sweet by the tub.....so long as I could get a SIGNAL, that is.....
Hope I didn't confuse you too much....I'm baffled by what I just said.