Mounting an exterior coax connection to motorhome

A cable would not be run from the BOMB to an antenna. That needs to run directly to the receiver. If that's where the BOMB is located as well that's fine but you don't connect that cable to the BOMB. The "output" from the receiver connects to the BOMB for TV viewing on multiple TV's.
Does your coach have wiring currently for a TV located outside in one of the bays? If so, and you are not using it you can re-purpose that cable for a run from your dish to your receiver. Let us know.