We have 4 televisions in the house on an outside antenna.
We have 2 televisions in the TT on a batwing antenna.
We park our trailer in our driveway beside the house.
Every television gets something a little different.
The 4 in the house may get channel 13.1 but not 8.1. The one in the living room may get 8.1 but not 13.1. (same antenna).
The 2 in the camper do the same thing.
It's a 50/50 proposition.
Part of the success to an enjoyable television experience is the antenna. Yes, I agree. The other half is the television itself. Some televisions (even new ones) work better than others regards picking up television signals.
Perhaps the problem is not the camper, or the wiring in the camper, or the antenna on the camper. Perhaps it's the television itself.
Before making any drastic changes, considering swapping out the television in your camper with another television, maybe a small one from your house, and see if the response is the same or different. If a different television, same wires in the camper, responds better, then you know it's the television itself. It's an easy test to do. Try that first and see what happens.