Can anyone answer me as to why out of the blue on my HD locals would I get a 771? I have 99.9% of the time a strength of 93-95 on transponder but for no reason (at least apparent reason) I get this error. It can be rainy, dry, calm, windy, night, or day and it happens. I have watched the signal and it goes from 93 to 0 while it is happening and then goes back and stays there for days or weeks until it happens again. Each time it happens it lasts maybe 10 -30 minutes and then goes as fast as it came.