After-market antenna in Factory Installed Hyunda Santa Fe?

[Woland]

I've been an XM subscriber for years, and about six months ago I bought a 2010 Hyundai Santa Fe. The built-in XM is nice, but it drops out WAY more than the Roady 2 I have installed in my Subaru Outback. Driving the same route, the Outback hardly ever loses the signal while the Santa Fe loses the signal repeatedly and sometimes for 30 seconds or more. This is in rural Massachusetts with a decent amount of tree cover on country roads. The Outback's radio can handle it, but the Hyundai can't.

Is it possible to get an aftermarket antenna and wire this to the factory installation? And will it make a difference, or is the factory-supplied antenna as good as it's going to get on the Hyundai?

Other than this one issue (and obviously, it's a big one) the Santa Fe is a terrific car and the XM interface on the radio is very nice.