Then surely something is causing the signal degradation. Must be a faulty LNB. 30% is when there is heavy rain, for normal LNB. And normal Signal Quality for the same will be 80-90% in normal weather.
When TS technician came to see, did he use some digital meter to record the signal ??? On that its should be min 75%.
I guess even LNB skew plays imp role here and depends on ur location.
Even i have a issue that is not solved, i have 2 HD STB, and one STB signal goes down by 20-30% and other STB remains fine. Technician came and checked and fine tuned it once, but now it happens again, however its temporary and get fixed. It happens mostly in the afternoon and by evening or night its back to normal