Looks like there are two antennae mounted in the glass of my 02, one is in the front winidshield, upper right hand corner, and is a basic "t". There is another one in the rear window above the defroster. It has several more lines and "branches". Does anybody know which one is the FM antenna and what'* the other??

These are both radio antennas and are part of the Diversity Antenna System used on this vintage of Bonneville.

The rear antenna receives both AM and FM signals while the front receives only FM. When the radio is turned on, it also turns on the antenna module (located inside centre above the rear window). When AM or FM is selected, it connects the rear antenna directly to the radio, but when FM is selected the radio sends an enable signal to the antenna module. Superimposed on this enable signal is the signal strength which is received by the radio tuner. The antenna module performs two functions. It switches between the front and rear antennas, monitoring the radio signal strength and combines both and phase aligns them to create one strong signal.

Interesting arrangement.... I'm surprised they made it so complex!! Thanks for the info... So I guess I'f I was installing XM and using their "Sure-Connect" solution, I could mount it on either antenna and should get similar results,...

THanks again for the reply!

There is some interesting information available on the internet. Basically, it is supposed to provide the best signal and reduce/eliminate noise from ghosting.

I wasn't aware of this new SureConnect system until you mentioned it. I looked at the installation manual from XM though and I would suggest the rear antenna would be your better choice (based on the Bonneville Diversity Antenna system). Again however, I haven't looked very deeply into it.

Hey , I finally installed my XM. I used the XMFM1 modualator so I avoided the Sureconnect and the cassette adapter. I couldn't get to the antenna wire in back of the radio (due to the Dock-n-Lock design) without taking the dash completely apart. It looks like I probably could have reaced it if I pulled the top of the dash off, but I wasn't willing to go THAT far. As it was I took most of the stack apart and pulled the glove box out and dropped the headliner in the back and along the passenger side.

The way the XMFM modulator works is that it is connected inline with the antenna wire going to the back of the radio. So it had 2 leads, one intended to plug directly into the radio and the other to plug into the original antenna wire that goes to the antenna. When XM is turned on, it isolates the antenna and just feeds XM signal into the radio.

I ended up installing the XMFM modulater at the antenna module above the headliner in the back. There are three antenna wires coming into that module. (one for the front antenna, one for the rear antenna and one going to the back of the radio HU up front) The problem here is that the wire for the front antenna and the one for the HU are similar wires. The difference is that one had a yellow sleeve around the end. The one with the yellow sleeve went to the radio. I was able to remove the module by dropping the headliner a bit and removing the single 10mm bolt. I needed the GM antenna adapters for the XMFM1 unit (to convert from the large (standard) plug to the mini plug that GM uses). The problem I ended up with was that the lead coming off of the XMFM1 modulator to go to the radio was a male lead. When I unplugegd the antenna wire from the antenna module that went to the radio, it was also a male. The same sitation was true for the other side of the XMFM1 modulator that was suppsoed to go to the Antenna and the antenna module plug, they were both female. I had to mod the adapter cable to give me a a Male large end to a male mini plug and another to be a female large connector to a female mini connector. (basically just swapped the ends of the two GM adapters). It was a bit of a hassle with all of the trim pieces (I pulled off both A piller trims, the passenger side B piller and pulled away both C piller trim pieces to route the wires and to get into the headliner) but everything worked out fine, no wires showing. I used some wire taps to pull power from the cigar lighter and hid that under the hush pad on the driver'* side. I used some velcro and mounted the XMFM modulator on the inside of the roof above the rear drivers side hand hold (the "Oh-No" Handle) and courtesy light.

My battery ended up going dead, so it'* on the charger now, (I thought the run down protection would prevent this....) But all in all no major issues and the sound quality is good. It was interesting that I originally had the modulator connected backwards (before I realized that I would need modified adapter cables) and it still worked, it just didn't provide great sound quality.

Sorry for the long post.....