On my last TT I just drilled a hole in the side near the TV and used a pass through connector that you buy from and RV shop. Then just ran a short length of coax from there to the tv. Then just sealed the outside waterproof box.
U.S. Army Retired Desert Shield/Storm Vet
2014 Silverado Crew Cab
2009 28ft Flagstaff V-Lite
1996 Impala SS 1972 Chevelle SS