[Elecraft] K2 / KPA ALC problem. Are power levels sensed at the same point?

[Don Wilhelm]

Chris,

If you have both the KPA100 and the KAT100 in the system, the power 
output is measured with the KPA100 wattmeter.
If the KAT100 is used on a K2/10 than the KAT100 wattmeter is used for 
power output measurement.
Take both the KPA100 and KAT100 away and the base K2 uses a simple diode 
detector to measure power.  That detector will only be accurate when 
working into a 50 ohm non-inductive load (dummy load or antenna with 
some properly tuned antenna tuner.

Try to break the problem down into pieces to be certain what is 
happening.  First thing is to get the wattmeter in the KPA100 properly 
calibrated (no KAT100 at that point),
Then work on the value of R98 to stabilize the power control loop. Once 
that is accomplished, then look at the ALC action - if you still have 
excessive ALC on SSB     with the KPA100 in-circuit (11 watts or above), 
then look to the ALC changes for the KSB2 board.

Attempting to do things in any other order may lead to erroneous 
conclusions.

73,
Don W3FPR

On 12/6/2013 1:36 PM, Chris Kimball wrote:
> Rob,
>
> Thanks for your helpful comments.
>
> My setup has a KAT-100 in it and the KAT-100 is, apparently, is the source
> of the power level measurement, not the KPA-100.   I've got the Elecraft
> dummy load and your suggestion was great.
>
> At this point it looks like the R98 replacement is the way to go.  I'm
> getting a bipolar distribution of output power under "Tune" at a power set
> level of 5w, with a display of either 4.4 or 6.4 W and nothing in between.
>
>