My Bullitt has the XM/Sirius radio factory option. The reception is pretty bad. Everytime I do something as simple as going under a bridge on the interstate it cuts off. The other day I was sitting at a light and it cut off, granted I was under a intersection where there was several overhead bridges (think the LA mixmaster), but the nearest bridge was at least 70 feet overhead. Haven't had this trouble with the Explorer or the wife's PT, both have antenna mounted on the roof.