Bob, I can only assume you mean mount an XM antenna in the rear window...like inside the car on the rear parcel shelf? I have seen some people do that with limited success, the signal cannot get 100% of what it needs inside the car. If you really dont want to have an XM antenna outside your car, if you look around, there may be some alternatives, but i really havent heard of any. I mounted mine on the outside of the car just above the rear glass, and just tucked the antenna wire under the rubber weatherstripping and then ran it underneath the side door weatherstrip to get inside the car. It doesnt get pinched and it comes into the car without any "body mods" (ie: drilling). but to answer your question ( i think) ,the antenna you will need comes with the kit you buy.