[Amps] SB-220 Improvements

[Robert B. Bonner]

Yeah well if it is printed in QST it is approved by God himself isn't it?

You cant believe everything you read.  I agree with Lou, the 220 is best
converted to completely be on 6 meters by itself.

The loading cap needs to be only about 150 pF and the plate tuner needs to
be about 25 pF if even in the amp.  It is best with a pair of 3-500's to use
a couple plate cap only and bend the coil for resonance.

By itself the 220 will make great 6 meter power.  I think you might be
really disappointed in a conversion, plus by the time you are done will have
screwed up a good running box.

A single band 220 on 6 is worth a lot more than an HF one.

Good luck.

BOB DD

-----Original Message-----
From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com] On
Behalf Of Gudguyham at aol.com
Sent: Monday, January 15, 2007 7:32 AM
To: cgalbrai at umich.edu; jantree at satlink.com.au; Amps at contesting.com
Subject: Re: [Amps] SB-220 Improvements

 
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
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