I live right in New Boston so I think I’m in pretty good range of it. I also have an extended antenna.I do have an SDS100 and DO NOT have a 325p2. However, a few years back I traveled to Portsmouth and Epping. I could pick up New Boston PD clearly on the NAC per db. The NAC may have changed. I would go to the transmitter site itself, and see what happens. Make sure that frequency is in SEARCH mode and not with a NAC programmed.
Could it be that you are slightly out of range of the P25 decode from it? Distant P25 signals on all my radios sound off with static / data sound until I'm in decode range. Since it's just a conventional frequency and not a trunked system, there is not much "programming" that could be wrong. Again not having this particular radio....