Our RV had the optional SAT Prep...
One coax in the roof is connected to the rooftop antenna.
Another, dedicated second coax goes from the entertainment cabinet - down to the front driver's side bin (off door side) and works perfectly.
A dedicated coax is easiest/simplest and provides the best signal feed to the receiver. By not moving the cable coax, you don't lose any function. Ours runs up inside the pillar next to the windshield.
The 12v socket (pictured) would be for the portables that need 12v feed...but our Tailgater has power on the coax.
BTW, King says the Tailgater will work out to 75' of coax...but we have used up to 150' of coax to clear trees with no problem (camping in a heavy wooded area).
Best luck