I just added the 2.1 KHz 8 pole BPF to my K-3. I already have the 2.7 KHz 5
pole, and the 400 Hz 8 pole for cw.
I can get it to operate manually as expected. When I adjust the DSP
bandwidth, I observe the following:
As the DSP readout goes narrower, the filters switch to match the DSP
bandwidth. This is very cool, so I can change Xtal filters as I adjust the
DSP from 4.0 KHz (broadest) down to 50 Hz (narrowest). In cw all 3 filters
can be activated, based on my filter setup.
My question is, what happens when I adjust the DSP bandwidth broader than
2.7 KHz? It appears that all the fixed filters drop out, as I begin to hear
broader audio if I'm listening to someone using ESSB, for example?
And I also start picking up QRM that I had tuned out at the narrower
setting. So can I receive a station transmitting with a 4 KHz bandwidth and
hear him across that entire audio range without adding a 6 KHz filter?
One more interesting observation; when I shift the DSP either higher or
lower, at a specific one of the 2 (2.7 or 2.1 KHz for SSB) the selected
filter remains the same and does not seem to change. This is a great way to
knock out a closer interfering signal within a selected filter like the 2.1
KHz 8 pole.
The other night another K-3 owner who also works for Elecraft, explained to
me that the Xtal filters operate on the first mixer (hence "roofing
filters") and the DSP operates on the 2nd mixer, after the roofing filter
does its thing.
This appears to be the uniqueness of the K-3 architecture.
73,
Ron
S/N 1997
AE6RH
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