The quality reading refers to signal quality, not picture quality, with a digital channel, as long as the signal is received above a certain signal strength and quality, then the picture will to all intents and purposes, look perfect. A very slight reduction caused by bad weather could well cause the picture to start breaking up and pixellating though, so you ought to perhaps look at tweaking the dish alignment or LNB skew to see if you can improve the signal quality reading.
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PS. Please consider where you are posting your questions, as i had to move this from the links section.