- The Heathkit SB-220, two 3-500Z, amplifier made a notable impact in the world of amateur radio when it debuted in 1975.
Resources and modifications
QSK for the TL-922 and SB-220 mods
- Beautifully constructed amplifiers. Unfortunately, are not suited for high speed T-R switching, a necessary attribute for operating AMTOR, QSK-CW, or SSB-VOX modes.
- Heathkit SB-220 Amplifier modification by KE5YA
SB-220 Repairs and Modifications
- Heathkit SB 220 mods, replacing the Zener ZD1, replacing the plate-voltage voltage divider, adding a keying circuit for solid state transceivers