.The twin lead from the antenna connection goes in one end and
the coax goes on the other. The coax then goes to a plug in unit in the
house which is connected to the TV.

I would buy an inexpensive 300 ohm to 75 ohn transformer and a piece of 75 ohm
coax cable. Unhook the twin lead at the antenna and hook it into the new
transformer. Hook the new coax into the other end of the new transformer and
run it right to your TV. You have to bypass BOTH the amplifier (at the antenna)
AND the power supply (plugged in at the back of your set).

If that fixes your problem, you could either replace the amplifier, or, it may
in fact be a "good enough" signal, especially since you say it is only a
back-up.

John