I understand about the high loss cable issues. My Viewfinder is a 26' travel trailer. TV1 is connected to the wall plate with a 2' cable. The antenna is connected to the input of the wall plate with about a 3' cable, at most. The cable input connector on the outside is connected to the wall plate with an estimated 15' of cable and TV2 connector is connected to the wall plate with less than that, may be 10'.
I guess my first step is to test the cables and connectors. I'll connect my home Cable System to the cable input at the camper, disconnect the other end at the wall plate and connect it direct to the TV, if it still does not work, then it's the cable or connectors. Do the same with the TV2 by disconnecting the cable in the back of the wall plate and connecting it to TV1 output. Again if it still has problems, it the cable or connector...