The cable connection is for cable only and cannot be used as it stands for the use of satellite. Cable and satellite are not the same.
Also, turning the Winegard power supply on or off does not change this rule.
Now, depending upon how your coach is wired you may be able to modify the cable wiring to make it work with your satellite system or you may have to run a new cable or run the cable through a window depending upon how handy you are.
If you coach has a video control center with push buttons that allow you to select TV, VCR, Aux, Cable, etc. then the coax from outside runs to the back of this controller. You can remove the coax cabled Cable and run that directly to the satellite receiver. You now can't use cable unless you reconnect to the controller (you can also add and A/B switch to that cable and send one output to the satellite receiver or back into the controller.
If you don't have this then you coax cable most likely runs to that Winegard power supply wall plate. But again you cannot use that as it stands. You would need to remove the wall plate and look for the one cable that it connected to the circuit board and labeled cable. Remove this coax and run it directly to the satellite receiver. Again, no cable now but you could also setup an A/B switch for this connection that would allow to use either with the push of a button.
A few RV's are setup such that the Cable input runs through a series of splitters to get the signal to all TV's. If this turns out to be the case in your RV then the Cable input cannot be used at all for a satellite connection.