It is assumed you are referring to the PBS station out of Philly, WHYY on real and virtual channel 12.
It is about 99.9% likely that your diagnosis of LTE interference is incorrect. There's simply no way that 700 MHz signals are going to disrupt a VHF channel 12 with the pre-amplifier you have in use. It's front end has a U/V diplexer circuit that will attenuate UHF and LTE signals by > 30 dB before the VHF signals are amplified. Another U/V diplexer is on the output to re-combine the separately amplified frequency bands before sending the signals down stream. However, if you want to try the filter if you've already ordered it, it can go anywhere in the distribution scheme as long as it does not block operating power between the amp and its power inserter. Additionally, 700 MHz signals are not going to cause interference into other frequencies that are less than a third of the frequency of the wireless system. If they do, there's either a fault in the system or something is very poorly designed and implemented, probably on the receiving end.
Since your issue is in the evening hours, it's far more likely that you have a local electrical, electronic or lighting interference issue.
If not for that amp's dual signal path configuration, then Chuck's suggestion would indeed be spot on assuming the intermods occur in the amp. Of course, they could always be occurring in a tuner, also.
In any event 700 MHz signals at two miles is extremely unlikely to be strong enough for interference concerns anyway unless you had both a high gain UHF antenna aimed dead at the tower plus a high gain preamp. The power levels coming off cell towers isn't all that strong at that distance.
Tech support for Antennas Direct
Last edited by ADTech; 11-09-2017 at 09:22 AM.