Here is a copy of a post I made in a similar topic. Hope it helps.
Satellite TV is NOT Cable. In most cases you will not be able to use that connection due to the way the manufacturer wires a trailer for cable (splitters, amp, etc.).
The best option, if you can a way, is to create a new input for your satellite coax connections. Many RV's are wired with a Cable input PLUS a Satellite input and this is the very best option. If the satellite receiver is in a slide-out you might consider drilling a hole through the wall to the outside where you can install a outside coax connection with a weather cover. If it's not in a slide you might be able to easily route a cable through a storage area, wall, floor, cabinet, something, to get a cable from outside to the receiver location.
As mentioned above, some trailers send the Cable signal directly to a wall plate where a small button or slide is used to turn on the power supply for the roof top OTA TV antenna and, when turned off, allows Cable TV to come through. If you are lucky and the manufacturer did not install any splitters along the way then this connection can be modified for use by both Cable and Satellite. To find out you would need to remove the wall plate and determine which coax goes to the outside cable connection (usually labeled) and remove that from the wall plate. Connect a coax extension from that wall plate to the receiver and see if it works. If it does not then you are done. If it does work then you can add an A/B switch to that coax and send one coax to the receiver and loop one back to the wall plate to allow the Cable connection to work as well when necessary.
