This is all fairly new to me, too, but I've noticed that a signal strength of 50 (Mercury II Receiver) seems to be the threshold. A dip below that to 47-48 and I start to get some pixelizing. At this point in time, Montana
PBS seems to be the only channel I want to watch that sometimes dips that low. All of the others come in mid 60s or above and the picture is perfect. Clear weather, of course, but in the Baja desert we don't get clouds or rain too often.