The input connection labeled "Cable" is for either cable TV or can be used as an antenna connection. This system should be wired to distribute the signal to both front and rear TVs.
The connection labeled "SAT" is not a distributed signal. The reason for this is Satellite TV needs power at the dish. This power comes from the Satellite Receiver box, so it needs a straight through connection. So, the "SAT" line goes straight from the connection inside the trailer to the connection on the outside.
Use the "Cable" connection to get your antenna signal to both front and rear TVs.
I am taking from your post that you do not have a factory mounted over the air antenna. If you do have a factory installed antenna it should be wired into the cable connection. There is a small button on the wall plate. When you push the button on and off a light should light You need to make sure the light is on when using the over the air antenna and off when using cable.
2008 Chevy Silverado 2500 Duramax Crewcab
Jeep Commander - sold
Flagstaff V-Lite WRB26