If you're saying that your're getting a snowy picture when you connect the receiver (outside your RV) to the coax and connected the TV inside the RV to that same cable, then you definitely have a bad connection somewhere. The picture coming off the output of the receiver should be entirely free from "snow". Digital images such as those with satellite TV don't get "snowy"; they are either all there or they aren't there at all. The snow is coming from something in your system. Most likely one of the connectors on the coax is bad; that's pretty common.
That kind of problem with a coax will degrade the picture and add the snow you are observing. However, it will totally DESTROY the satellite signal if you try to send it down that same cable. That is why you can't get any signal if you move the receiver inside.