Posted by
John Huffman on
Jan 13, 2005; 6:46pm
URL: http://elecraft.85.s1.nabble.com/KPA100-80m-poor-quality-SSB-tp372990p372999.html
However, my 80M SSB distortion turned out to be a different solution.
Like Stewart, I saw the jumpy power output on 80M as I varied the output from 11
to 100+ watts. It was not smooth and either was my SSB signal. The problem
persisted through the implementation of the solution listed below.
> a) A 1k resistor is fitted across RFC3.
>
> b) R4 in the HV bias supply is changed from 100k to 39k.
I also, with Gary's help, modified the KSB2 ALC -
"If the SSB RF output goes as high as 150-200w, there is a problem with the
ALC on the KSB2 and I know just what to do to correct that. R9 should be
changed to 1.5K, and the trace to Q1 is cut and a 1K resistor is inserted
across the trace. The 1K resistor should be a small 1/8w or SMD type, or cut
the leads really short to fit in the limited space between Q1's base and pin
6 of the KSB2 where the base circuit normally goes. This gives the ALC the
extra control it needs to hold the SSB PEP RF output in check."
It was better, but not completely gone.
The cure, for me, was the Power Control Mod on the Elecraft web site -
www.elecraft.com/Apps/Power_Control_Mod.html
1.6K ohms looked best when I tested, but used a 1.3k because that was what I
had. Locals have pronounced my 80M SSB distortion cured.
Hope that helps...
73 de NA8M
John
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