[K2] [Elecraft] Excessive PSK IMD with new K2/100

[Don Wilhelm]

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.
>>     
>