Oh ya, I know the XM antenna has nothing to do with the HD reception (and I plan to remove my Antenna-X shorty and reinstall the factory whip).
I'm just hoping that the antenna relocation to the roof will improve the XM reception.
I'm not dropping signal... even in places where the SC-C1 used to drop.
Frankly, I'm amazed at the difference between the Sirius SC-C1 and the new XM SXV200V1 tuner. The Sirius used to drop signal on the overpasses on the 210 between the 605 and 57, and the Mission overpass, plus it would drop under the power lines that cross near Sierra Madre in Pasadena. The XM tuner has never dropped. The only time I haven't had signal was on restart when parked against the north wall at Lowe's in Chino Hills... but once it connected, I did not drop crossing the north wall of BevMo'.
Like I said, I'm just hoping for more consistent tone on the XM channels. Sirius was consistent, the traffic channels were very clear. SM is a bit "muddy" on those channels... yet the music channels are good. I'm hoping that perhaps they are on a different transponder... but if you don't think it will improve, then I see no reason to move it to the roof.