When using that All Powerful UNsharp Mast filter (when you don't have time for Doodlers SUPER SHARPEN technique
) USE THAT
THRESHOLD SETTING!
With the threshold set at "0" it shorpens EVERYTHING - including Jpeg artifacts and noise and grain and other non-disirables.
Best way to learn this adjustment is to grab a picture and put the RADIUS at about "2" and the AMOUNT at "200%" or so. The move the THRESHOLD from "0" on up in steps... you'll soon see whats going on.
(Normal starting point for smaller sized images like we use here at PSC is around 75% AMOUNT, RADIUS .7 pix, and THRESHOLD at around 2~5. But it is like spice: your choice and if you overdo it you'll wreck the flavor of the meal!)