If it is a bad cable, simple test would be to run a cable loose from the tv and out the window to the roof antenna. Re-program tv and test if thats a bad cable you will now know that you have to replace inside the walls.
Rod & Linda From Wisconsin
1- Labs (Ronnie)
2011 Eagle 320RLDS
2015 Chevy Silverrado 2500
14,000#/1400 Equal-i-zer 4-way sway bars
www.rodsrvneeds.com (for all your RV needs)