[Elecraft] K3: Unexpected AGC action

[Dave Cole]

Hi,

I have a K3, and am seeing what looks to be some sort of unknown, and 
unexpected AGC action when I have AGC off, on both the K3, and within 
Windows.

I am trying to triage this to the radio, the computer, or WSJT-X.

Here are the test conditions:

WSJT-X used as the software for testing.  K3 is feeding audio directly 
to the computer via a USB cable, Windows 10.  I believe I have AGC off 
in Windows...

Here is what makes me question the AGC:

1.  K3 bandwidth set to 4KHz.
2.  WSJT-X showing 0-4000 Hz in waterfall.
3.  If I reduce bandwidth using the control on the K3 I see:
        a.  A reduction in the level shown by WSJTX input meter.
        b.  An INCREASE in noise on the waterfall.

This is totally unexpected to me...  I would expect to see the waterfall 
stay the same brightness, and the waterfall width reduce, while the 
input meter drops.  Why the brightness change?  Is this happening within 
WSJT-X?

-- 
73, and thanks,
Dave (NK7Z)
https://www.nk7z.net
ARRL Volunteer Examiner
ARRL Technical Specialist
ARRL Asst. Director, NW Division, Technical Resources