I am assuming the TV works fine with the cable input connection.
When using the OTA ANTENNA you need make sure the TV PANEL small switch is pushed IN and shows a small LED light ON. This provide 12VDC up to the antenna where the pre-amplifier is located...
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Also your TV menu has to set to ANTENNA and a digital scan for signals has to be done first...
Your older Trailer may not have the BATWING crank up antenna that has the added dipoles...
It should look like this google image
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this antenna shown in the photo is pointing toward the transmitting station to the right of the picture. The added dipoles are for UHF frequencies reception...
Roy Ken