I am thinking you issue is related to ingress. As a former Cable tech. (15yrs in service/install) I have had this problem many times. Ingress is caused by outside interfeance ie: electric motors, cb radios, air traffic.... there are many caused for ingress. My yrs in cable have taught me that one of the main causes of this is poor wiring (RG-59 cable as opposed to RG-56) RG 56 cable has better sheilding and allows less ingress. most likely your RV was built with RG-59 cable, less sheilding and cheaper to buy. Bad fittings are another cause, push on fittings vs screw on fittings. screw on fittings are the way to go. metal braid hanging out of a fitting acts like an antena and picks up interferance which in turn, you see on your TV. Your TV may be another issue, most newer TV's have less sheilding in them and will cause ingerss as well. There few fixes for your issue, Use RG-56 jumpers from your prewired outlets with screw on fittings, usually you can go to your local cable co. and they will give them to you. (they rather you get it from them so they don't have to roll a truck ). You can also try getting a cable box. You don't need one that is provided from your cable co. just one that will act as your tuner instead of your TV. this has better sheilding than your TV and more likely to block out ingress. You can get them by looking on-line under cable products. They are pretty cheap and will work anywhere. These are just a few quick fixes that may solve the issue.