[Elecraft] [KX3] equalization in DATA-A mode?

[Paul Dickson]

My KX3 is connected to my computer through a SignaLink USB device.
I only operate digital modes, either with fldigi or wsjt-x, and always
in
DATA-A mode.   The waterfall display in both these programs shows a
pronounced increase in levels at the low and high ends of the audio
passband.   So much so that the background noise goes into "yellow",
or even "red".

A picture of this is at http://imgurl.org?di=5S2I

That was taken with no antenna connected at all, VFO at 14070,
in DATA-A mode.   Bandwidth was set to 4kHz.  The radio has the
ATU and roofing filter options installed.

Since DATA-A is supposed to disable all equalization and compression,
I thought at first that the SignaLink was introducing this, but if I
use the PBT knob to descrease the bandwidth to 2 kHz, the "yellow"
regions move toward the center - though the effect is most pronounced
whan the BW is 4kHz.  This makes me think it is an artifact of
the DSP algorithms.

If I change the mode to SSB so I can re-enable RX EQ, I can dial-down
the ends a bit.

Also notice that outside of the silent region just outside the chosen
bandwidth, the noise level rises again.  This is not generally a
problem
so far.

Is this expected behavior?   It makes it difficult to see signals that
fall
toward the ends of the passband.  In extreme cases I retune the VFO to
make them fall in the center.