It seems to me (presumptuous since my only satellite activity is reading the group!) that most of the responses suggest causes that would not be so sharply defined as Bill's observations. He says

Either 0.7 degrees OR 4-5 degrees

not a continuum of values. I would have to ask if there is any correlation with day of week, local weather conditions (also a continuum of values) or AO-7 mode immediately prior to the mode it is in when the observations are made (IIRC the mode can switch at random).

Can a correlation be made between the elevation at AOS and the signal level at nearest approach?

73 Pete K5GM AMSAT LM. Pete Jordahl, K5GM k5gm@amsat.org