Dave . . . I bought my wife an XM radio awhile back. I found that contrary to what Sudonim said (sorry Andy) that reception for XM is quite good here . . . but I've never done a head-to-head reception comparison with Sirius and XM while they're side-by-side. That said, I occasionally lose XM . . . particularly in downtown Bangor, under bridges, etc.
However, to address your question . . . assuming that the model you bought has the wireless connection feature . . . my wife has had similar issues. I resolved most of these issues by a) doing what Andy suggested and trying a different FM frequency to tune to and b) positioning the wires so that they were not crimped and were not near any of my bodyparts (I found that the wires bunched together caused some static and some static would be generated whenever my knee or hand got too close to the wires -- not enough to make the music unlistenable but enough of a hiss to cause it to be a distraction.
I suspect a hardwired XM radio set-up would improve the situation.
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