Originally Posted by rootofjesse
My memory is not great, but I do not recall having this much trouble - four weeks with almost no reception of UHF. Usually, dry and windy winter days are when I have dropouts. KYW used to be a sure thing, and it does not lock most of the time now. Also, there are zero obstructions or trees. The knife-edge I have is a mountain about a mile away, and it has trees. My only conclusion is we have had so many dry, red-flag days, and somehow the dryness is affecting signal badly.
Perhaps you are correct about no trees, but remember that multipath is about obstruction; it results because of a reflected signal (off a tree or building or whatever) that gets to the antenna (from any angle, not just the direction the antenna's pointing) via a longer overall path than the direct signal (refracting over that mountain), and thus arrives later. It could be from trees in a neighbor's yard or nearby wooded area. When the reflected signal (which could possibly be stronger than the direct) is at a constant delay, modern tuner design can choose the stronger signal through signal processing. When the delay varies over time (as trees wave about), the tuner can't cope, thus dropouts or total signal loss.
ADTech is correct, the whole geometry can change from year to year.
My coping mechanism is slight adjustment of antenna direction (I mean very slight) to try to null out all but the strongest signal. Of course, higher is better, but I prefer to keep my antenna in my attic to avoid deterioration due to weather. Most of my troubles went away when a big stand of white pine trees owned by my neighbor were cut down.