The antenna on the roof is only used for XM radio. If you don't subscribe to XM, then the antenna is unnecessary as you have noticed. The antenna for AM/FM is embedded in the rear window like the defroster grids.

 

The black antenna on the roof is for OnStar.

 

I think you're both right. I'd be surprised if we don't soon see the details design changes through the years. This is a great forum.

 

My 2000 STS was equipped with OnStar and had no antenna on the roof...

 

The antenna is a tri configuration
It provides Onstar 1)GPS/2)Cell as well as 3)XM.

 

Interesting. The OnStar antenna in my 2000 STS is under the rear package shelf and looks like the square black gps antenna.

 

First of all, OnStar uses two separate antennas.

Up until about 2004, GM was using a glass mounted antenna for OnStar voice communications with a GPS antenna mounted under the rear shelf. This changed in the 2005 model year where both became part of the same assembly and was mounted on the roof.

The roof mount antenna prior to 2005 was an XM radio antenna. In 2005, this was also integrated into the single roof mounted antenna (if the vehicle was XM equipped).

The 2005+ roof mount antenna has either two or three coax cables. Two if you only have OnStar, three if you have OnStar and XM.

In vehicles with a roof mounted XM antenna and glass mounted OnStar antenna, the roof mount XM antenna will have either one or two coax cables depending on the generation of XM installed. In vehicles with two XM coax cables, one was for the satellite signal and the other for a terrestrial signal. The later generation was able to combine both signals into one coax.

In your case, the small mast has come off the antenna base. This mast is responsible for OnStar voice communications only. If you don't subscribe to OnStar, this won't matter. If you don't replace it though, you will get moisture and contaminants in the area where the mast connects and may cause future performance problems if you decide to subscribe down the road.

 

I do not have XM radio and the RPO list on the spare tire cover indicates an XM radio delete. I have an antenna on the roof that looks like a black hockey puck with a shark fin sticking out of it.

 

In your model year, the antenna looks the same whether you have OnStar and XM or just OnStar. The difference will be inside the antenna and the number of coax cables coming from the bottom. This was the style of roof mount antenna GM used from 2005-2008 (in most, if not all vehicle lines). In the STS, we're now seeing the new style which is colour matched to the body.

 

Got it...thanks for the education!

 

Noticed my "fin" was missing this morning on my 2008 SRX. Is there an aftermarket replacement available from anyone? Any idea what the replacement cost is?

 

The blade alone can be replaced. There is a trick to getting the bloody stub out but the new one slips right in in place of it. With postage and all it was about $25 from GMPartsDirect. There is a little locking tab that you can push in with a sharp pointed object and the blade turns out to the left.

Been there. Done that.

 

Thanks for the great info. Like I said, the old one is out.. so someone knew the unlock trick

Any idea what it's called on GMPartsDirect? All I could find was the whole assembly for $66.74 (Antenna assy - W/digital audio - W/digital audio)