Ok the place where you hook up an antenna (Where it comes out of the wall) is this a wall plate with a 12 volt outlet (Which by the way is mostly useless) an Antenna conneciton a switch and a light?
If so then remove it carefully, there should be 3 cables on the rear (minimum 2) looking at it from the rear, cables down they are
ROOF (Antenna)
Cable in (park inlet)
TV-2
(optional) TV 3
TV-1 is the front outlet.
Disconnect the 2nd cable and hook a screamer to it (Cable tracker transmitter) you can get a cable tracker at Harbor Freight for little cash.
Then trace the line with the receiver.