I want to install an external antenna for xm. I have one wire, it is currently used for cable tv signal. Is it possible to use this wire for the xm signal (using a combiner or what ever is necessary)?

Thanks

If you look around, you will be able to find a Diplexer type of combiner unit that will allow you to combine the signals into a single coax.

Thanks for the info. If you know of a specific one please give me a link to it. I see a lot that talk about satellite tv but not radio.

Will do. You might want to check with Crutchfield or maybe the xmfan webstore. I believe the diplexer units used for Satellite LNBs (1.5 GHz) will work in the XM band (2.4 GHz). Also, remember that the antenna is active and requires dc power through the cable, so you need to find a unit that blocks dc on the TV side but passes it on the Sat side.

Here is one designed for Sirius.
If your XM Receiver has the same connector that Sirius radios do, you should be able to use this.

SIRIUS CATV Cable Distribution Kit
The CATV Sirius signal distribution kit allows the connection of a special Outdoor Home Antenna using your preexisting Cable Television RG-6 Cable.

http://www.tss-radio.com/sirius-catv-cable-distribution-kit-p-4093.html

They also make one for DBS.