DTV has nothing what-so-ever to do with an RV antenna. If that's the route you chose then your support would be from the antenna manufacturer. In this case King Dome (King Controls). Don't blame DTV for the failure of the antenna you bought. If you use a DTV antenna connected to a DTV receiver you will not have any problems.
I assume you know that you cannot get ANY DirecTV HD programming from the Quest (any dome). Are you sure you are only selecting SD channels? Have you changed the receiver setup to show both HD and SD channels? If not, this is likely your first problem. With a 2nd assupmtion here, I assume you are not trying to get local Networks (ABC, NBC, ect.) after you have driven away from your home area. These channels are only available within a few hundred miles of home.
Please, a few more details.