"D Ray"

Depends on the stucture and where you're located. I have XM's indoors
that work great with no access to windows.

On my encouragement a co-worker bought a Roady2. It worked fine in his
car. He then bought a 12V wall-wart and tried it in his apartment in
downtown DC. It works fine - in fact conventional AM/FM are very poor
in his apartment.

XM has quite a few repeaters around DC and that helps. The building where
we work in the suburbs is solid concrete with metal interior walls. Even
in my north-facing office XM works fine - doubtless due to a repeater.

XM has enough repeaters in the DC area that I can hear them in every
mall's multistory parking garage I've tried.

YMMV