[Elecraft] K2 Requested vs. Indicated Power Output

[W3FPR - Don Wilhelm]

Dan,

First, are these measurements into a 50 ohm dummy load or into an antenna? 
If you are using an antenna, such variation is to be expected - and may be 
much more than what you indicated.

20% accuracy is not unusual for wattmeters in general - check the ARRL lab 
tests of several wattmeters if you doubt that statement, yes, some are 
better, but several are not, so the 20% difference that you are seeing is 
not really that unusual.  I don't recall seeing a spec on the accuracy for 
the K2 indication.

Be aware that the ALC needs some time to settle too - wait several seconds 
to see what the display settles to before drawing conclusions.  There will 
always be some hysteresis in the firmware calculations and the analog to 
digital conversions that must be done for the computation - sorry, but I 
can't put a number for that variable.

I assume you are using the base K2 - without the KAT2 or KPA100.
You may be able to improve the accuracy by carefully trimming R67 and R68 on 
the RF Board.  Also you may want to try different 1N5711 diodes at D9 - 
there can be some variation from diode to diode.

73,
Don W3FPR

----- Original Message ----- 
I have a question concerning the power level requested and the indicated 
power delivered by the K2. How close should the indicated power track the 
requested power level?

My K2, #4473, is very close at about 2 watts, but below or above this 
requested power level it varies in the amount of difference between the two. 
This difference is on all bands but by different amounts.

An example would be:
At 2 watts requested, K2 indicates 1.9 watts when tune is pressed.
At 7 watts requested, K2 indicates 8.5 watts when tune is pressed.
At 10 watts requested, K2 indicates 12 watts when tune is pressed.

This is representative of all bands, the values of indicated power is 
different on each band. My indicated power on all bands at 10 watts 
requested is greater that 10 watts indicated when tune is pressed. I know 
that the power level you set is only a requested power level; what I don't 
know is the degree of accuracy I should expect from the indicated power.