MANY Re task the cable for Sat, but I do not recommend that, in fact I recommend AGAINST it.
Run a new RG-6 cable you can run it to a bulkhead connector (Get one at any RV store) or a ground block (RV store or Radio Shack) which can be mounted in a compartment where you can pass the cable in or in the case of my Class A Gasser under the hood on the brake bell crank bracket (it gets funny later)
That is the Satellite in.
Park cable is left alone as is ANTENNA on your mnulti-swich (Box of Many Buttons or BOMB)
IF you have only a wall plate (not a BOMB) then it selects ANT or Cable. Leave it alone and let it do its thing or better yet replace with a Sensar PRO (optional serious upgrade about 100 bucks plus DIY or Labor).
Again run the new RG-6 for the Sat Antenna.
Feed the TV via HDMI off the sat receiver.. To watch SAT select proper input on TV"s menu.. To watch OTA select ANTENNA or TV and select source with the wall plate.