Can't say with absolute certainty but that's not gonna stop me from offering an opinion :act024:
If, the XM receiver/decoder is housed in a chassis that doesn't do anything more than receive/decode satellite frequencies & data, it absolutely should not generate heat - at least not to a concerning level. It should be right around the heat generated by an LED cluster, which is to say pretty darn low. There simply isn't enough switching happening inside a pure receiver to cause appreciable heat build up.