K3 Cw pileup problem: effects of Noise blanker?

[ni0c]

I've been thinking about the recently reported "cw pileup" problem,
wondering why this apparently wasn't noticed before-- particularly by
the VP6DX operators.

I'm using a K3 with a single receiver, and use the three narrowest
roofing filters, operating CW almost exclusively.  In combing through
large pileups (notably during the recent K5D operations), I've sometimes
noticed a blurring or smearing effect caused by multiple signals in a very
narrow bandwidth.  I'm not certain of this because it is such a dynamic
intermittent problem; however it seems to be ameliorated when I turn off
the noise blanker.  (The K3 NB is so effective, compared to noise blankers
on other receivers I've used, that I tend to have it on all the time).

My guess is that the VP6DX operators probably never needed the noise blanker in their (presumably) quiet QTH.  

It may be that the solution to this problem may be different for those using
a single receiver K3 versus the dual receiver.  It may be that the solution could be as simple as disabling the NB when switching from VFO A to VFO B.

Forgive my tardy input to this conversation; however I woke up very early this morning with these thoughts in mind.  (I wish I had some thoughts about solving the world's economic problems.)

73,
Chuck Guenther  NI0C
K3/100 s/n 1061
 
 
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[Dave Hachadorian]

The VP6DX operators mostly ran with agc OFF on all modes.
There was a discussion of this subject on the Elecraft
reflector in March of 2008, e.g.
http://www.mail-archive.com/elecraft@.../msg51762.html .
This thread contains a good discussion of why agc should be
OFF when running a pileup. That being said, there is a K3
firmware change now in pre-beta testing that seems to
improve performance of slow agc in a pileup.

I doubt if the VP6DX folks were using the noise blanker. I
think all of us have come to expect some dynamic range
degradation and distortion when the nb is switched on in any
rig.

Dave Hachadorian, K6LL
Yuma, AZ


----- Original Message -----
From: "ni0c" <[hidden email]>
To: <[hidden email]>
Sent: Friday, February 27, 2009 10:24 AM
Subject: [Elecraft] K3 Cw pileup problem: effects of Noise
blanker?

> I've been thinking about the recently reported "cw pileup"
> problem,
> wondering why this apparently wasn't noticed before--  
> particularly by
> the VP6DX operators.
>
> I'm using a K3 with a single receiver, and use the three
> narrowest
> roofing filters, operating CW almost exclusively.  In
> combing through
> large pileups (notably during the recent K5D operations),
> I've sometimes
> noticed a blurring or smearing effect caused by multiple
> signals in a very
> narrow bandwidth.  I'm not certain of this because it is
> such a dynamic
> intermittent problem; however it seems to be ameliorated
> when I turn off
> the noise blanker.  (The K3 NB is so effective, compared
> to noise blankers
> on other receivers I've used, that I tend to have it on
> all the time).
>
> My guess is that the VP6DX operators probably never needed
> the noise blanker in their (presumably) quiet QTH.
>
> It may be that the solution to this problem may be
> different for those using
> a single receiver K3 versus the dual receiver.  It may be
> that the solution could be as simple as disabling the NB
> when switching from VFO A to VFO B.
>
> Forgive my tardy input to this conversation; however I
> woke up very early this morning with these thoughts in
> mind.  (I wish I had some thoughts about solving the
> world's economic problems.)
>
> 73,
> Chuck Guenther  NI0C
> K3/100 s/n 1061
>
>
> ______________________________________________________________
> 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 

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[Guy, K2AV]

I'm really having a really hard time identifying with any of the AGC & NB
complaints.

I used the second-to-last alpha test firmware (not latest) installed to my
K3 in the recent ARRL DX CW on 40m from NY4A and was simply delighted. I can
nearly or effectively remove key clicks with certain choices of  *digital
only* NB coupled with same bandwidth narrow roofing and DSP.  The K3 front
end plus these settings turned the usual 40m incoming cr*p into a zone where
not copying a QRP signal was the exception as long as there wasn't a
stronger station calling. At most there were a dozen or two signals all
weekend calling that were not pulled out.

It was, frankly, astounding.  And *very* beneficial to score (1700 Q's on
40m).

I did not experience AGC pileup distortion of any kind. With the key click
nullification I was able to work 3/4 of the contest USING SLOW AGC, albeit
set to its fastest decay. No theory here, just what happened.

The most exceptional reduction was one period, about two hours, where a 20+
over clicky EU station was right below me, and was so close I had to use 350
width for running. With NB off had S6-8 key clicks, NB on had S1 S2 S3 band
bottom.  I used slow AGC during this time and worked QRP stations and weak
Russians through it.  Slow AGC was easiest to listen to (no idea how to
express technically what I mean).

There used to be that "next unworkable layer", stations you could hear were
there, but just could never pull out.  The unworkable layer was workable
this contest. The end of workability occurred with the station dropping into
absorbtion, as I now know is a very clean and transparent transition that
doesn't sound like anything else on HF.  You could hear it happen.  I
suspect it sounds like a vhf beacon signal dropping into solar noise though
that is a very old memory for me.

We worked Russians on 40m at 1130Z when it was 1:30 or 2:30 in the afternoon
their time, which were only a whisper above a remarkably constant and
unjunky noise level.

More specifics on click removal:

The clicky station must be well down on the skirts of the roofing filter for
the trick to work and the best results seem with DSP width set at the TRUE
bandwidth of roofer.  Both my "250" 8 poles measure out ~ 330.  350/300 DSP
width was best. Narrowing DSP below Roofer width seems to mildly worsen
results. I presume getting the clicky station well down the roofer skirt
makes sure that within the DSP IF the click appears as a detached click
rather than a clickish aspect of discrete signal that is inside the DSP IF.

There is one necessary artifact to nullifying key clicks, and that is a
discernable notch on a very weak signal, that with a little help from fast
deep QSB can break a dash into two dots, or turn a dash into a dot.  I
figured that out very early and made upward tweaks on my callsign
correctness paranoia to compensate.  I will take that mild mental adjustment
with a smile anyday over frequencies rendered useless for weak signal work
by key clicks.

I cannot comment on use of 5 poles for this.  For running bandwidth reasons
I use 400/"250" 8 pole roofers in both RX, set to kick in at 450/350 Hz
width settings.

I did not use IF NB, or use NR at any point in the contest. I do not find NR
at all useful on CW, confirming Lyle's statement that he did not see how it
would be useful, everything else optimal.  Be careful that in messing with
the AGC for these complaints I don't understand, you don't UNDO what I used
last weekend.

73, and thanks for a real edge in the contest past.

Guy, K2AV

P.S.  Puhleeze, 10 Hz step for shift and width on CW.

----- Original Message -----
From: "ni0c" <[hidden email]>
To: <[hidden email]>
Sent: Friday, February 27, 2009 5:24 AM
Subject: [Elecraft] K3 Cw pileup problem: effects of Noise blanker?


> I've been thinking about the recently reported "cw pileup" problem,
> wondering why this apparently wasn't noticed before-- particularly by
> the VP6DX operators.

> My guess is that the VP6DX operators probably never needed the noise
> blanker in their (presumably) quiet QTH.
>
> It may be that the solution to this problem may be different for those
> using
> a single receiver K3 versus the dual receiver.  It may be that the
> solution could be as simple as disabling the NB when switching from VFO A
> to VFO B.
>


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[Bill W4ZV]

Guy, K2AV wrote

It was, frankly, astounding.  And *very* beneficial to score (1700 Q's on
40m).

For those like me who temper rhetoric with results, the following may be of interest:

2009 ARRLDX CW - US/VE 3830 Claimed Scores 23Feb2009
US/VE M/M HP
Call     40m Q/M  
~~~~~~~~~~
NY4A   1700/114
W3LPL 1688/122
NR4M  1616/119
K1XM  1552/115
K3LR   1516/124  
K1RX  1389/116

Finishing #1 in QSOs in this list is impressive, even more considering other stations had more hardware and operators (e.g. W3LPL had 4 on 40m alone).  Congrats to Guy and his K3!  Something was definitely working well at NY4A.

73,  Bill  W4ZV

[Jim Brown-10]

On Fri, 27 Feb 2009 23:29:51 -0500, Guy Olinger, K2AV wrote:

>I can nearly or effectively remove key clicks with certain choices
>of  *digital only* NB coupled with same bandwidth narrow roofing and DSP.

VERY interesting, Guy. Many thanks. I think I understand that this version
of software/firmware is not yet released?

73,

Jim K9YC



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