Interesting you mention frequency shift. Something I am noting is that whatever the baseline Signal Quality is, it will be that and "bounce" to 99. For example Tolo, on AMC5 (I think) baseline quality is in the mid 30s. But it will "bounce" to 99 and back...
And it seemed to me that the signals here are stronger at night. Could this be a temperature factor in the LNB, or the product of too many margaritas while setting the LNB?
Re the bounce to 99, I've seen that a few times, and I don't know what causes that. I'm guessing it means a marginal signal and you're losing lock, getting it back, etc, but I don't know. On my Twinhan PC card receiver, if the freq drifts even a couple MHz, I completely lose lock, I'm guessing because it has a very tight tuning window, or perhaps the software doesn't try to search for it. With most of the STBs I have, plus my TT3200 PC card, if the frequency drifts, usually the receiver will follow the drift. Usually, the only problem I have is that if I'm trying to lock a narrow band transponder, and there is another similar signal nearby, it will often lock on the wrong transponder. This usually happens with those 3978 SR newsfeed s that are often quite close together, and/or those PBS scpc signals with 4444 SR values. When my KUL1 would drift, I'd generally lock onto the wrong transponder. But most receivers will tend to search for signals. With STBs, if I'm locked onto a newsfeed transponder, and it goes off line, often I'll see the signal go away, then the receiver searches for a while, then locks onto another newsfeed with the same parameters, but when I check the transponders out with my Twinhan, I'll see that it is locking on a signal that might be 10 or 12 MHz away, and receiving it just fine. My TT3200 even searches further than that. For example, I can be locked on a 4080H transponder with my BUD, then switch polarity to vertical while watching the transponder. I'll initially lose lock, then about 15-20 seconds later, it will be locked again on a 4060V transponder that has the same SR. The S/Q of the lock is pretty much the same even though the receiver is tuning 20 MHz off freq.
Anyway, with most receivers, once you lock a transponder, freq drift doesn't affect your ability to receive channels very much with most receivers. With my Twinhan though, I have to be right on freq, or reception will suffer.