When XM and Sirius proposed merging, an interesting factoid popped out that you'd never figure out from the company PR. They really do directly broadcast from satellites to receivers across the US, but interestingly (and somewhat secretly), they also operated *hundreds* of terrestrial transmitters to fill in coverage around the US. The reason that this information came up during the merger hearings was that XM (and Sirius to a much lesser extent) had been illegally operating over 200 ground repeaters at output power much higher than they had been licensed for.
In an attempt to not piss off the FCC, Sirius very quickly moved to shut down or reduce transmitting power at their ground repeaters. XM has a bigger problem, as the positions of their two satellites give fairly poor signal on the West Coast and parts of the East Coast.
I have XM in my car, and definitely noticed poorer reception within 2 weeks after reading about this. I live in the Silicon Valley and I can only assume that some of the ground repeaters here were shut down.
This may be what's happening to you as well, as they tweak the system and infrastructure. Atmospheric effects can certainly have an effect on the reception, although, because it's digital, you won't really hear a degradation of sound until it completely cuts out.
When I first got XM years ago, I could listen to something like CNN, stop at a light under a bridge and it would continue playing for most of a minute before it cut out. These days, CNN will conk out within 10-15 seconds when I'm in an obstructed position.
David Fung
