We don't watch TV very much, but the first time we tried a cable hook-up, picture quality was horrible on both the front and bedroom sets. I checked using a DVD player as a source and it was fine. I concluded that the coax from the cable connection in the rear stow-bin to the video distribution box was the problem.
Since I had no documentation to show where it ran, I decided to get rid of the bedroom TV (never watch TV in the bedroom, even at home). I put a new coax from the stow-bin connector into the cabinet where bedroom TV had been, then mated it to the feed between that cabinet and the distribution box.
It's worked fine ever since - still rarely use it though. We've never even bothered to get a D-A converter for the OTA antenna and have never cranked the antenna up in three years!
Frank and Eileen
No longer RVers or FR owners