[Amps] SB-220 Improvements

[Gudguyham at aol.com]

In a message dated 1/13/2007 9:36:33 P.M. Eastern Standard Time,  
cgalbrai at umich.edu writes:

I am  currently modifying an SB-220 for use on 6 meters by changing the 10
meter  section as per the QST article (SB-220 0N 6 METERS) and leaving the
rest of  the amp band positions unchanged on HF.




The Sb-220 Plate tune "C" capacity is too high at its minimum point for  
operation on 6 meters.  You can get it to work, but be prepared to have a  "hairy" 
time tuning it up.  You have to move the plate tune cap so slowly  to find 
the "sweet spot" that the motion of your breathing will take it out of  
resonance.  Also, you'll probably smoke the original parasitic  suppressors.  I don't 
advise this mod.  Using the proper value caps  and the right tank circuit, the 
Sb-220 makes a great 6 meter amp, but as a  retrofit to the original design 
its a compromise at best.  Been there   done that.  73 Lou