kx3/wsjtx, multiple notches?

[Tox]

Hello,

Between the kxpa100 and getting a fan dipole just above roofline, I'm
finally able to make ft8 contacts fairly consistently in North America
when my local broadband noise source isn't operating.

There are times though when one of a couple adjacent stations a mile
or two from me either swing their beam over my dipole, or crank the
knob, and desense my kx3 pretty solidly.

I'm slowly learning how to tune the skirts and wield the notch, so can
sometimes work the one edge of the ft8 range, but there are also times
both of them are active at the same time, and trying to grab a 400kc
slice in between them to work hasn't panned out so far.

Is there a way, either in-radio, or with wsjtx, to do *two*
controllable notch filters, so the world doesn't disappear into the
shadow of +18s?

Thanks,

Scott
AD6YT



--
Scott Small
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

[Jim Brown-10]

On 2/24/2020 10:27 AM, Tox wrote:
> There are times though when one of a couple adjacent stations a mile
> or two from me either swing their beam over my dipole, or crank the
> knob, and desense my kx3 pretty solidly.

I've got big antennas and am surrounded by big signals when I work FT8,
but I get by just fine.  Those strong signals are causing AGC in the rig
to reduce RF gain. What we need to do is drive the computer audio system
harder from the radio so that weaker signals are still within range of
the A/D converter in the computer's sound card. The fundamental settings:

1) Full RX bandwidth, let WSJT-X separate the signsls
2) Reduce RF gain (or use ATTEN) to prevent overload
3) Set audio level feeding the computer so that, when those strong
signals are present, the green bar on the left reads about 75-80 dB but
doesn't turn red (which indicates digital clip).

Yes, I know that #3 is not what the instructions say. But I have a LOT
of weak signal QSOs on 160M and 6M because set up that way.

73, Jim K9YC
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

[Jim Brown-10]

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


______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]