TVFool results vary by day?
 

Was going back and working on reception issues and redid the TVFool report from a couple months back.

The results are significantly different for some channels. +_ 5 db. So, how is this derived? Is it taking into account the weather etc?

Weather is not factored into the Longley-Rice model used by TVFool. http://en.wikipedia.org/wiki/Longley%E2%80%93Rice_model

The transmitter database was updated earlier this month, it's possible an antenna change or power increase/decrease made it's way into the data.

Thanks. I looked a little further, not sure why one went up but it looks like my problematic WDAF took a major dive, probably cut their power as they have not been at full power for a couple months.