And Ed is at the southern edge of the North Carolina mountains, where there are a lot of translators for analog signals. Maybe some of them are interfering with his desired signals at night because of tropospheric enhancement.
I have a similar problem with WUNF-DT out of Asheville, which is on ch 25. Out of Columbia, WOLO (analog) is also on channel 25, and I'm in the middle. During the day, I can usually get decent reception on WUNF-DT if I aim my antenna carefully, because I have line-of-sight to its transmitter on Mt. Pisgah, whereas there's a slight rise in terrain between me and Columbia. At night, however, the signal from WOLO increases and usually swamps out WUNF-DT.
Which specific channels are giving you problems, Ed?