First what antenna do you have.
I have a Winegard Sensar III with Wingman and Sensar Pro. YOU WILL NOT get reception as good as I do unless you have the same set up.. OR spend a whole lot on some very special antennas.
Jack, not as good. Sensar w/o Wingman or Sensar Pro, not as good. ROadstar, Not as good. in fact _______ not as good. per independent lab testing.
Now. the coax. usually roof to antenna. can get OLD. and as it ages bad things happen.. Next you have several connectors.
One at the antenna head
one at the roof or in the roof.. Short story. That connection in my RV had to be completely re-done. new ends (2) and a new double female (Barrel) connector to join them.
Then there is the connection on the switch/wall plate (2) and one at the TV as well.
Plus as others have said. Is there power to the Pre-Amp (light on on the wall plate or the proper buttons pushed and light on on a box with many buttons (Matrix switch).