I can tell you about my two trailers.
The '75 Argosy 28 has a spring-coiled base whip in front on the street side and the wire runs under the skin behind the back of the curved front side window and up into the front overhead compartment.
The '79 Excella had an outlet inside the credenza. Both the stereo and the TV outlet were spliced into the overhead main TV antenna. On my front gaucho model, this is inside the credenza just aft of the stereo-8-track. A PO at some time removed the (trouble-prone) electrically actuated TV antenna and put a batwing style antenna on top. This is not tied into the stereo at all presently, so it ony picks up extremely strong signals. That's fairly low down on my list of things to fix as the old receiver picks up my XM Roady XT satellite receiver just fine. I like mixing 70's technology with 21st century technology.