I've noticed that late at night I'm getting better signal than I do during the day, and I'm curious why. There are only 4 stations I really care about, and luckily they are all located in approximately the same direction. At night I get solid 100% signal quality on three of them and one varies between 96 and 100% with occasional dips to 90%. During the day three of them are still 100% and the other varies from 77% to 87%.
These numbers are good enough, so it isn't a serious issue, I just wonder why. As best as I can tell from the ground, my antenna is aimed directly at the three with the 100% signal, making it about 15* away from the one that sees slightly lower reception. So it makes sense that one is the weakest, due to the aim and the fact that station is about 50 miles away versus 35 or so for the rest. Perhaps I could fix this by having it aimed more towards the weaker one.
It may be that all of them get slightly weaker during the day for some reason, but the others are still strong enough that I see 100% no matter what. I'm wondering if it is possible something is affecting this one since it is VHF channel 7 and might have some source of interference during the day at frequencies just below it. The antenna (some channel master 7xxx model I believe) was installed in 2005, so it is designed for VHF as well as UHF - it used to receive a VHF low analog station just fine when first installed.