Well, as for the recent shift in the direction of goodness... I’ve seen seasonal atmospheric conditions cause greater shifts.
As for my signal checker: it reports both signal strength and signal quality. The bar on the application changes color according to signal quality, with red being bad, green being good and blue being the best (verging on being too strong).
To save you from having to page back, and to illustrate what I am saying about the color changes:
The software itself can be downloaded from here
; but I am told it will not work with other manufacturer’s cards. The name of the app itself is TuneFinder.exe.