Trees and tree leaves do a real fine job of reducing or blocking Tv reception and so do buildings and other obstructions.
If you have a thick dense tree , use the tree to reduce or block the KVMD UHF 23 to the north. Get the antenna close to the tree to block reception to the north.
Buildings also do a good job of reducing or blocking Tv reception , use your house to reduce or block KVMD 23 to the north. Get the antenna close to the house. To block reception to the north.
Amplifier gain is not the problem. A higher gain amplifier will not help.
The noise figure of the amplifier needs to be lower. All electronic devices generate noise , Amplifier noise masks the signal.
Stay with the AP8700 preamp for now. And move the 91XG to locations that reduce and block the signal to the north.
Look at the locations of the transmitters on the tvfool radar map plot and position the antenna for the most obstruction to the north.
And at the same time you need to shoot for a clear shot to XETV.
Its a balance.
_______________
Another antenna to try is the Channel Master CM4228HD UHF antenna.
http://sollidsignal.com ,
http://www.amazon.com ,
http://www.channelmasterstore.com.
______________
A amplifier booster that has a Ultra Low Noise Figure is the KT-100 adjustable gain remote power amplifier booster.
http://www.kitztech.com.