Re: kx3/wsjtx, multiple notches?

Posted by Jim Brown-10 on Feb 24, 2020; 6:48pm
URL: http://elecraft.85.s1.nabble.com/kx3-wsjtx-multiple-notches-tp7658581p7658584.html

On 2/24/2020 10:37 AM, Walter Underwood wrote:
> Instead of a notch, I’d try low-cut and high-cut to narrow in on the signal.

Note that K1JT strongly advises to set wide bandwidth and let WSJT-X do
the filtering in the digital domain. All it takes to make that work is
to use the audio drive the way I've described.

Think about it this way. The A/D in the sound card is good for about 90
dB of dynamic range. The green bar tells us how far the signal level is
from the BOTTOM of that range. Let's say that a strong signal is 50 dB
over S9, and it takes over the AGC in your KX3. If the audio drive TO
the computer sets the green bar to 30 dB, it would take a 20 dB over S9
signal to be within range of the A/D.

But if we set the green bar to 80 dB, S9 is still 30 dB above the bottom
of the A/D, and at 6 dB per S-unit, we can decode signals down to S4 (or
to S4 if you call an S-unit 5 dB).

73, Jim K9YC


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