Okay, so the booster on the wall does only the antenna (which is coming down from the roof inside the wall) and when the booster is on, the signal comes out the TV1 connector on the front to your television. Usually, when you have an external 'cable' connection, it is attached to the 'cable' port on the back of the booster and that's the signal that comes out TV1 (and TV2, which is the same as TV1 on the front panel, via an internal splitter - intended to run inside the wall to a second TV placement, such as a bedroom, which your unit doesn't have so the cable isn't even there) when the booster is off.
I got the impression that you found an exterior coax port somewhere... Where does that come out on the inside?
2015 Rockwood Signature UltraLite 8282WS Platinum, GY Marathon LRD, TST 507RV TPMS
2005 GMC 2500HD CCSB D/A, Curt E16, Prodigy P2, Garmin RV760LMT w/BC-20 b/u cam