[John Candle]

I believe the problem is multi path , Try pointing the front of the antenna down , this will tilt the top UHF reflector in more of a downward direction so there will be less reception from reflections off of planes. Another thing to try is a variable attenuator , Antennas Direct 1296F . dialing down the signal strength also dials down the reflected signals and the tuner will be better able to filter out the reflected signals. If you have any amplifiers connected , remove them completly. Another thing to try is move the antenna to the outside.