The above graphic is one way.. I prefer to run a nice NEW quality RG-6 line from some handy access point (You can route the cable into the utility channel where you other wires and plumbing run, then down through an existing hole in the floor to the wet bay on both Trailers and Motor homes, or on a motor home down the "A" pillar under the dash then out via an existing foam filled hole in the firewall to under the "hood") and provide an external connection point.
Mine is on the Brake Bell Crank Bracket under the hood.