http://www.myradiostore.com/antennas...enna-xmt4.html
This is the one I use for XM and it has been leaps and bounds better than the stock one. Aside from tunnels, I never loose signal.
A couple of pointers on it..
1. Mount it as close as possible to your AM/FM antenna if you are rf broadcasting your satellite signal to your AM/FM radio.
2. Mount the antenna on the drivers side. It is less likely to be caught up in trees on narrow roads and be broken. That was a $60 lesson for me, and you get it for free. :lol: