You cannot use the coach "Cable In" connection for satellite TV as it came from the factory, but there is a chance that the cabling could be modified to be used for either satellite only or with an A/B switch or similar inside the coach you could choose which input you wanted. You might need to find an RV tech to re-wire things or check with a Gulfstream owners forum to see how Gulfstream wired their coaches.
If you have a video control center (usually a black box with a variety of buttons for TV, Aux, VCR, etc.) the rewiring job can be easily accomplished by you.
What I post is my 2 cents and nothing more. Please don't read anything into my post that's not there. If you disagree, that's OK.
Can't we all just get along?