Flowrs780, I’m going to start with a description of the system in my 2020 23FB FC. You’ll see why.
I have a King Omni Pro mushroom antenna on the roof, connected to a a Winegard power injector wallplate beside the telly. The other wallplate input is a coax from the outside cable jack. There’s an output to the telly and another to the JL marine head unit (radio tuner which powers the speakers).
I’ve never gotten acceptable reception, radio or TV. I called WInegard, and they told me the antenna is not theirs. I called King, who told me that those antennas are limited, because digital broadcast signals are very directional because there’s no way a 360 degree element can be robust enough to pull in faint signals. The antenna is not designed for FM, and forget about AM.
When the Airstream rep asked me about the whip antenna for the radio, I told him the trailer never had one. He consulted with an associate, who verified this but said my system is installed as Airstream intended, so there must be a damaged cable. I’m not about to put a bunch of elbow dents into the roof to take apart the antenna, so I scheduled a dealer service appointment for December.
If, as Mollysdad indicates, the Winegard wall plate switches between inputs, you could move the cable input to the antenna input and switch on the injector to try to get a boosted signal from your directional TV antenna hooked up to the cable jack outside.
On my own trailer, I don’t hold out much hope, between the lack of documentation, the hodgepodge of OEM’s, and the unfamiliarity of the Airstream people at JC and the dealer. It reminds me of the car stereos back in the 80’s, that the factory used to fill the hole in the dash until the buyer got fed up and got something mail order to install themself.
(That man in that tiny can)
(Same man, Bigger can)