[Elecraft] KX3 S meter calibration

[robertsmith at vom.com]

I'm sure this question has been asked before, but I can't find any information 
about it.

In measuring the calibration of the S-meter in my KX3, I discovered it is extremely 
accurate, but only with the pre-amp engaged. With it engaged, S9 is indicated at 
exactly 50 uV (within the resolution of the display).  It is also very accurate up 
and down the S-meter range, with 6dB corresponding exactly to an S unit.  

I would have expected it to be calibrated with both the pre-amp and attenuator 
disengaged.  Is there some reason it's calibrated this way?

Also, when the firuware is available that automatically accounts for engaging the 
pre-amp or attenuator, will the indication be referenced to the pre-amp on or off?
 
Bob Smith, NY4Y