According to Wikipedia, NPTV operates three transmitters. WENH, licensed in Durham, NH operates on real CH-11 and sources several virtual channels 11.1 through 11.4.
When I measure the distance between your approximate location and the WENH tower, using Google Earth, I come up with about 119 miles.
It's clear that you are seeing the signal via a tropospheric path and that's subject to weather / atmospheric conditions. I doubt you'll be able to get reliable reception of their signal. It may be the subject of a DXing hobby though...
(Do you want to build a really big rhombic array?
http://forum.tvfool.com/showthread.php?t=2865)