OK, once again I've been a bit vague [img]smile.gif[/img]
On the SkyFi unit, there is no "tuner". Or rather, the "tuner" (i.e. the module that Thump is showing mounted under the rear deck.....excellent location for the Pioneer tuner BTW) is built into the display unit.
Obviously, that display isn't gonna do much good if it is mounted in your trunk
The SkyFi "car kit" includes a cradle to hold the SkyFi display. You have to run the XM antenna connection to this cradle. Separately available is an RF modulator that connects ONLY to the cradle with power and audio signal (i.e. 1/8" mini plug).....the XM antenna does NOT attach to the RF modulator. Rather, the RF modulator attaches (thru some adapters) to your AM/FM antenna input on the head unit. The antenna wires on the RF modulator are about 4 feet long....long enough to make it from about anywhere underdash to the head unit, but NOT long enough to reach from the trunk.
I mounted the RF modulator on the steering column shielding under the dash. Its out of the way (once you zip-tie the wires up) and works.
That said, it isn't a great RF modulator (sound-quality wise). If your head unit has an aux input on it, then you definitely wanna bypass using the RF modulator altogether and just wire the Skyfi cradle directly into your head unit.