Has anyone used the CABLE in cable for Sat TV: YES. many
IS there as switch or something: YES
OK, how do we do it? (I suspect that is your real question)
Two answers: First the "official" answer
Somewhere in your RV is, most likely, a wall plate (I will describe the box of many buttons at the end) it has a SWITCH, a LIGHT an antenna connector (F-Connector) and a 12 volt accessory outlet (Very low current, might charge a cell phone or run a LED map light).
Remove it from the wall. ON the back will be two wires for 12 volt (Do not disturb) and 3 coax cables.. Disturb the one in the middle, in fact disconnect it.. then using a double female (Barrel) connector extend it out to your Sat Receiver.
IF the sat receiver has COAX OUT.. Connect that back to the center port on the back of the switch.
Job done.
My recommendations.
Forget that low cost RG-59 Cable completely leave it just as it is and run brand new RG-6, you can get the bulkhead (Through wall) connectors at any RV place or you can run to a ground block (Any RV or Electronics place including the proper isle at Lowe's et-al) in a basement compartment.
Mine is on the Brake Bell Crank Bracket under the hood.
Box of many buttons: One of the cables on the back is marked "CABLE", Instructions are the same as with the wall plate but you disconnect THIS cable instead of the "Center" one.