David,

The only other thought I have is that perhaps the KPA100 PA transistors are not operating at exactly the right point of their characteristic curve. The only thing that will change the portion of the curve for the PA transistors (i.e. the operating point) is the bias. The bias setting given in the KPA100 manual is good for most applications, but that does not say it cannot be optimized for a particular set of transistors used in a specific application. I would suggest that you alter the bias setting *slightly* on either side of the manual suggested setting to see if you obtain any improvement. Good luck with your experiments.

73,
Don W3FPR

dberkley wrote:
Don,

At first I thought your suggestion didn't affect anything since I already
had dressed the leads fairly well.  However, in bypass mode (less than 10
watts) the IMD is now back to -30 dB.  Also, after running for about 15
seconds, the IMD at 25 watts now drops to about -27 dB.

So there is now a noticeable difference between bypass and KPA100 mode and,
I suspect, a difference in my SSB performance as well.  Any other good
thoughts like that one?

Tnx and 73,  David
K2MUN


Don Wilhelm-4 wrote:
David,

The KPA100 can be coupling back into the KSB2 option.
Remove the right side panel and tuck the ribbon cable and speaker cable up into the space at the top of the KPA100 instead of letting it dangle near the KSB2 board.

I will not guarantee that it will help, but it often makes a difference on SSB, and can also help on data modes.

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