The SB-220 amp tunes really sweet on 80 and 40 meters. While turning the load and tune you can see a a nice swing on the meter and you can identify the peak output easily without missing it. On 20 its a little more critical but still not bad. On 15 and 10 meters you had better be sober, steady, and don't blink an eye or you will miss that sharp peak in output. After the peak it drops off quickly. Vernier tuning would have been nice for those bands. Surprisingly the "el cheapo" (as everyone calls them) Ameritron amps do have vernier tuning to their credit. As far as numbers, I am in awe of how many SB-220 amps were bought. They are for sale everyday in multiples on just about every sales venue dedicated to ham radio. There are probably 4 to 6 each week on EBAY, every week without fail. Several on other venues as well. Anyone know how many were sold? And to think they were kits in the late 60's to late 70's and you had to build them! Seems like old time hams knew how to solder. I built 2 new ones myself way back when.