Recommended AGC settings for separation of signals in CW pile-ups

[Bob Henderson-2]

CQ WW CW is now over.  We used K3s at P3F this year.  While performance was
generally considered good, some questions were raised over the effectiveness
of the K3 in separating signals in large piles.

Similar concerns appear to have surfaced from other users including the guys
at 9L5VT and C6ATA.  Anecdotal evidence suggests the old TS930 and TS850
performed better in such circumstances.  I suspect the AGC systems of the
K3s used had not optimised.

Has collective experience of the K3 contesting community derived optimum
settings for the K3 AGC system in this kind of situation?

Thanks

Bob, 5B4AGN
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[Chester Alderman]

Bob -

I agree with the observation about the K3's effectiveness  in separating
contest signals in big piles as that was the only thing that irritated me
during CQWW CW contest. I have just started to try and optimize the AGC
settings for large signal conditions and so far, I'm not anywhere close yet.
If I can find anything useful, I will post it here. I certainly do hope
others who may already have optimized their K3 AGC for large signal contest,
will also post their information.

161,
Tom - W4BQF
 

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Bob Henderson
Sent: Sunday, December 05, 2010 4:39 AM
To: [hidden email]
Subject: [Elecraft] Recommended AGC settings for separation of signals in CW
pile-ups

CQ WW CW is now over.  We used K3s at P3F this year.  While performance was
generally considered good, some questions were raised over the effectiveness
of the K3 in separating signals in large piles.

Similar concerns appear to have surfaced from other users including the guys
at 9L5VT and C6ATA.  Anecdotal evidence suggests the old TS930 and TS850
performed better in such circumstances.  I suspect the AGC systems of the
K3s used had not optimised.

Has collective experience of the K3 contesting community derived optimum
settings for the K3 AGC system in this kind of situation?

Thanks

Bob, 5B4AGN
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[Olli Tuppurainen]

I use AGC THR=8, SLP=002 + AGC DCY SOFT. This sound OK with my modest
pileups ;)

Another issue is if you get someone loud to your zero beat ( or within your
roofing filter passband ) then hardware AGC will go up..

Olli
OH6CT

> -----Alkuperäinen viesti-----
> Lähettäjä: [hidden email] [mailto:elecraft-
> [hidden email]] Puolesta Bob Henderson
> Lähetetty: 5. joulukuuta 2010 11:39
> Vastaanottaja: [hidden email]
> Aihe: [Elecraft] Recommended AGC settings for separation of signals in
> CW pile-ups
>
> CQ WW CW is now over.  We used K3s at P3F this year.  While performance
> was
> generally considered good, some questions were raised over the
> effectiveness
> of the K3 in separating signals in large piles.
>
> Similar concerns appear to have surfaced from other users including the
> guys
> at 9L5VT and C6ATA.  Anecdotal evidence suggests the old TS930 and
> TS850
> performed better in such circumstances.  I suspect the AGC systems of
> the
> K3s used had not optimised.
>
> Has collective experience of the K3 contesting community derived
> optimum
> settings for the K3 AGC system in this kind of situation?
>
> Thanks
>
> Bob, 5B4AGN
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
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[Barry N1EU]

Bob Henderson-2 wrote

CQ WW CW is now over.  We used K3s at P3F this year.  While performance was
generally considered good, some questions were raised over the effectiveness
of the K3 in separating signals in large piles.

Bob, this topic has come up a few times in the past and is something that has my full interest during/after each cw contest.  I hate to say it, but I don't think there's much of a solution via AGC settings.  I typically run with AGC OFF and minimal RF Gain to try and maximize transfer of RF to AF rx dynamic range, but it honestly doesn't help much with the pileups.  Perhaps it's just the nature of K3's A/D/A.  I've used both the K3 and Orion in ARRL160 this weekend and my sense is that the similarly rx gain optimized Orion does a bit better in those situations where there are multiple callers on frequency.  

73, Barry N1EU

[Arie Kleingeld PA3A-2]

I also worked in the cqww, dealing with weak and strong signals.


I set my agc to agc-s with menu setting on 40.
Also on is the soft decay and I switched the agc pls to off.

This worked reasonably well. The agc is fast enouogh to recover from a
strong station, and slow enough to hold the gain constant when a station
is calling.
If stations call on exact the same freq (caused by riding the dx cluster
or some software program instead of finding the stations yourself), bad
luck. But I can manage that.

The only thing that annoyed me was that the signals within the roofing
filter (400Hz) and outside dsp passband pumped the agc just a few times
to many (the hardware agc so I understand).

Wouldn't it be nice if this could be switched to different settings in a
menu or so.
Same thing for bringing the notch into the agc-loop.

73,
Arie PA3A
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[Don Wilhelm-4]

  Arie,

I don't think you would like the consequences of reducing the Hardware
AGC action.
Those same strong signals that now pump the HAGC would then overdrive
the ADC and really create chaos.

73,
Don W3FPR

On 12/5/2010 10:32 AM, Arie Kleingeld PA3A wrote:
> The only thing that annoyed me was that the signals within the roofing
> filter (400Hz) and outside dsp passband pumped the agc just a few times
> to many (the hardware agc so I understand).
>
> Wouldn't it be nice if this could be switched to different settings in a
> menu or so.
>
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[AD4C2009]

Oh well,I don't like to argue anybody or disagree anybody but I was at the contest as well and and I could easily separate CW stations that were off  between 100 200 Hz with my K3 using the 400Hz roofer and the DSP set to 100Hz and also moving the Shift acordingly,.no problem at all with the selectivity and also I used the great help of the APF as well.
If it has to be with the AGC or not,these are my settings that has been working for me in any case:
 
AGC DCY.....SoFt
AGC HLD.....0.05
AGC PLS.....OFF
AGC SLP.....0.07
AGC THR.....007
AGC-F.........080
AGC-S.........020
 
To help in the RX filtering I have set my RX EQ this way:
 
0.05 at minus 16
0.10 at minus 16
0.20 at minus +0
0.40 at +3
0.80 at +3
1.60 at minus 16
2.40 at minus 16
3.20 at minus 16
PITCH at 400 (I like to hear better at low pitch)
 
With these settings my K3 is super selective and have no ringing noise even at 50Hz DSP bandwiith.
In those conditions I can work any contest no matter how crowded it will be.
 
AD4C
 
 
 
 
 


"If freedom means something,it is the right to tell others what they don't want to hear" –George Orwell

--- On Sun, 12/5/10, Tommy Alderman <[hidden email]> wrote:


From: Tommy Alderman <[hidden email]>
Subject: Re: [Elecraft] Recommended AGC settings for separation of signals in CW pile-ups
To: [hidden email]
Date: Sunday, December 5, 2010, 10:47 AM


Bob -

I agree with the observation about the K3's effectiveness  in separating
contest signals in big piles as that was the only thing that irritated me
during CQWW CW contest. I have just started to try and optimize the AGC
settings for large signal conditions and so far, I'm not anywhere close yet.
If I can find anything useful, I will post it here. I certainly do hope
others who may already have optimized their K3 AGC for large signal contest,
will also post their information.

161,
Tom - W4BQF


-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Bob Henderson
Sent: Sunday, December 05, 2010 4:39 AM
To: [hidden email]
Subject: [Elecraft] Recommended AGC settings for separation of signals in CW
pile-ups

CQ WW CW is now over.  We used K3s at P3F this year.  While performance was
generally considered good, some questions were raised over the effectiveness
of the K3 in separating signals in large piles.

Similar concerns appear to have surfaced from other users including the guys
at 9L5VT and C6ATA.  Anecdotal evidence suggests the old TS930 and TS850
performed better in such circumstances.  I suspect the AGC systems of the
K3s used had not optimised.

Has collective experience of the K3 contesting community derived optimum
settings for the K3 AGC system in this kind of situation?

Thanks

Bob, 5B4AGN
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[Dave Hachadorian]

>CQ WW CW is now over.  We used K3s at P3F this year.  While
>performance was
>generally considered good, some questions were raised over the
>effectiveness
>of the K3 in separating signals in large piles.
--------------------------------------------------------------------------------------
This is a subject that keeps coming up, over and over again.  The
most recent discussion was on the K3 Reflector, and below is my
November 23 posting on the subject "Mushy Audio on CW."  The only
solution I have found that works well is to turn AGC OFF, and use
an external audio amplifier, so that you can keep the K3's AF
gain at a low level in order to defeat the K3's ridiculously
distorting AF Limiter.
-----------------------------
23 November 2010

The K3 does indeed have major problems if you are on the
receiving end of a pileup.

There is really no setting of AGC that will keep multiple callers
from mushing together.

The only good way to use the K3 in a pileup is to turn AGC OFF,
but there is a major problem with that too - extreme distortion
when loud signals hit the AF Limiter threshold.

The only immediate answer, short of adding external equipment,
is to turn AGC OFF, and ride the RF gain so that weak signals are
readable, but loud signals stay below the AF Limiter threshold.

K3NA has published an article on setting receiver RF and AF gain
with AGC turned off:
http://wiki.contesting.com/index.php/Setting_receiver_gain_controls

Unfortunately, K3NA's procedure doesn't work well with the K3.
There is no single setting of RF and AF gain that will keep weak
signals readable and loud signals out of the harsh AF Limiter.
If you have an extremely sensitive set of headphones (lots of
audio for low driving power), the K3NA procedure helps quite a
bit, but you will still be reaching for the RF gain control quite
frequently.  I tried plugging my headphones into the SPEAKER AF
output, so that I could turn down AF gain and keep loud signals
out of the limiter, but managed to blow up the fragile speaker
amplifier chip, but that's another story.  I don't recommend
using the speaker amplifier for anything other than the internal
speaker, or an efficient external non-amplified speaker.  Sooner
or later you will be looking at a $100+ repair bill for the
speaker amplifier chip.

I complained about mushy pileup audio a long time ago, and the
Elecraft folks did make some changes to the AGC parameters, but
the problem was not solved.  Here are the best AGC settings for
pileup use that I can find:
AGC DCY = SOFT (supposedly reduces IMD)
AGC HLD = 0.20 (supposed to be like riding the RF gain if agc is
  set SLOW)
AGC PLS = NOR
AGC SLP = 000 (makes loud signals louder than weak ones)
AGC THR = 008 (the highest threshold before AGC action begins)
AGC-F = 120 (the default, but the best agc setting is SLOW
  anyway)
AGC-S = 020
AGC FRONT PANEL SELECTION = SLOW

Although the above settings are the best with AGC that the K3 can
do, I still find them inadequate for dealing with a pileup. After
a lot of experimentation, here is what I have come up with as a
workaround solution:
AGC OFF
AF LIM = NOR 030
Use an external audio amplifier (sound card). Then you can keep
the K3's AF gain turned way down, keeping loud signals out of the
AF Limiter.  I have back to back 1N5818 Schottky Diodes across
the sound card output as a soft limiter for ear protection.  I
connect the K3's LIN OUT to the sound card, and set LINE OUT =
PHONES so that I can still use the K3's AF Gain control.

This has all been discussed previously on the main Elecraft
Reflector.  You can search the MARC archives for "K6LL pileup."
The message with "workaround solution" in the subject discusses
the external audio amplifier.


Dave Hachadorian, K6LL
Yuma, AZ

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[David Gilbert]

Ideally, AGC settings could be accomplished by user-defined macros so
that a single keystroke (either from the logging program or from
something like AutoHotKey) could be used to select between full sets of
AGC characteristics on the fly depending upon the situation at hand.  I
understand Elecraft's reluctance to expose the DSP code to carelessly
created commands, but I'd vote to make an exception for AGC.  Possibly
some kind of protection scheme could be incorporated to limit the range
of input values.

73,
Dave   AB7E



On 12/5/2010 8:32 AM, Arie Kleingeld PA3A wrote:

> I also worked in the cqww, dealing with weak and strong signals.
>
>
> I set my agc to agc-s with menu setting on 40.
> Also on is the soft decay and I switched the agc pls to off.
>
> This worked reasonably well. The agc is fast enouogh to recover from a
> strong station, and slow enough to hold the gain constant when a station
> is calling.
> If stations call on exact the same freq (caused by riding the dx cluster
> or some software program instead of finding the stations yourself), bad
> luck. But I can manage that.
>
> The only thing that annoyed me was that the signals within the roofing
> filter (400Hz) and outside dsp passband pumped the agc just a few times
> to many (the hardware agc so I understand).
>
> Wouldn't it be nice if this could be switched to different settings in a
> menu or so.
> Same thing for bringing the notch into the agc-loop.
>
> 73,
> Arie PA3A
> ______________________________________________________________
> 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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[Dave Hachadorian]

This thread is not about copying signals that are separated by
100 Hz.  We are talking here about multiple nearly-on-frequency
callers in a pileup.  In those circumstances, with most rigs, you
can separate the signals by amplitude, or slight pitch or other
CW idiosyncrasies.  The K3's agc has a problem dealing with that.
Signals are compressed together, such that you can't copy anyone,
unless you reach for the rf gain control.  If you turn agc OFF,
you have to deal with the crazy AF Limiter.


Dave Hachadorian, K6LL
Yuma, AZ




-----Original Message-----
From: Hector Padron
Sent: Sunday, December 05, 2010 9:22 AM
To: [hidden email]
Subject: Re: [Elecraft] Recommended AGC settings for separation
of signalsin CW pile-ups

Oh well,I don't like to argue anybody or disagree anybody but I
was at the contest as well and and I could easily separate CW
stations that were off  between 100 200 Hz with my K3 using the
400Hz roofer and the DSP set to 100Hz and also moving the Shift
acordingly,.no problem at all with the selectivity and also I
used the great help of the APF as well.
If it has to be with the AGC or not,these are my settings that
has been working for me in any case:

AGC DCY.....SoFt
AGC HLD.....0.05
AGC PLS.....OFF
AGC SLP.....0.07
AGC THR.....007
AGC-F.........080
AGC-S.........020

To help in the RX filtering I have set my RX EQ this way:

0.05 at minus 16
0.10 at minus 16
0.20 at minus +0
0.40 at +3
0.80 at +3
1.60 at minus 16
2.40 at minus 16
3.20 at minus 16
PITCH at 400 (I like to hear better at low pitch)

With these settings my K3 is super selective and have no ringing
noise even at 50Hz DSP bandwiith.
In those conditions I can work any contest no matter how crowded
it will be.

AD4C







"If freedom means something,it is the right to tell others what
they don't want to hear" –George Orwell

--- On Sun, 12/5/10, Tommy Alderman <[hidden email]>
wrote:


From: Tommy Alderman <[hidden email]>
Subject: Re: [Elecraft] Recommended AGC settings for separation
of signals in CW pile-ups
To: [hidden email]
Date: Sunday, December 5, 2010, 10:47 AM


Bob -

I agree with the observation about the K3's effectiveness  in
separating
contest signals in big piles as that was the only thing that
irritated me
during CQWW CW contest. I have just started to try and optimize
the AGC
settings for large signal conditions and so far, I'm not anywhere
close yet.
If I can find anything useful, I will post it here. I certainly
do hope
others who may already have optimized their K3 AGC for large
signal contest,
will also post their information.

161,
Tom - W4BQF


-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Bob
Henderson
Sent: Sunday, December 05, 2010 4:39 AM
To: [hidden email]
Subject: [Elecraft] Recommended AGC settings for separation of
signals in CW
pile-ups

CQ WW CW is now over.  We used K3s at P3F this year.  While
performance was
generally considered good, some questions were raised over the
effectiveness
of the K3 in separating signals in large piles.

Similar concerns appear to have surfaced from other users
including the guys
at 9L5VT and C6ATA.  Anecdotal evidence suggests the old TS930
and TS850
performed better in such circumstances.  I suspect the AGC
systems of the
K3s used had not optimised.

Has collective experience of the K3 contesting community derived
optimum
settings for the K3 AGC system in this kind of situation?

Thanks

Bob, 5B4AGN
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[Arie Kleingeld PA3A-2]

I agree with you Don.

But how much chaos would it be? I hove no idea.

There are a lot of things that we can set by menu in the K3. Absolutely
wonderful how we can manipulate threshold, slope, pulse, decay,
releasetime and holdtime. Would it be wrong te try out a menu selectable
threshold for the hardware agc?
Just wondering how this would work out in a CQWW.

73,
Arie
>
> I don't think you would like the consequences of reducing the Hardware
> AGC action.
> Those same strong signals that now pump the HAGC would then overdrive
> the ADC and really create chaos.
>
> 73,
> Don W3FPR
>
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[Barry N1EU]

I'm one of the biggest proponents of AGC Off on the K3, but I honestly don't find that it helps much with multiple nearly-on-frequency callers.  It helps greatly with relief from AGC riding by neighboring key clickers, but not so much with sorting out the nearly-on-frequency pileups.  That just seems one of the very few things the K3 doesn't excel in.

Barry N1EU

Dave Hachadorian wrote

This thread is not about copying signals that are separated by
100 Hz.  We are talking here about multiple nearly-on-frequency
callers in a pileup.  In those circumstances, with most rigs, you
can separate the signals by amplitude, or slight pitch or other
CW idiosyncrasies.  The K3's agc has a problem dealing with that.
Signals are compressed together, such that you can't copy anyone,
unless you reach for the rf gain control.  If you turn agc OFF,
you have to deal with the crazy AF Limiter.

[Guy, K2AV]

It's not NEARLY on frequency.  It's EXACTLY ON FREQUENCY.  I know what
I'm hearing.  I can hear a hertz in the area around my usual 450 Hz
spot.

This problem is getting worse as frequency accuracy is getting to half
a hertz on modern rigs (half a hertz measured on my K3), and people
use packet spots to arrive on frequency.  These people are frequently
EXACTLY on the same frequency. Not close, EXACTLY.  Research by Bell
Labs in the 1930's suggests that with no other clues for the ear to
separate them (as in diversity RX) that 3 to 6db is the minimum
difference to allow the ear to separate two signals on volume alone.
Or stated differently, your ear probably needs something an S-unit
difference to discern two signals exactly on frequency with no other
separation information in the signal blend.

As to the AGC, all the options are what everybody was hugely clamoring
for so everybody could "do it their way."  So you got what you wanted.
The flip side of that is that all these variations have to have a
value set BY YOU. Not by Elecraft, BY YOU.  All you guys that wanted
all this flexibility, stand up now and be counted and defend yourself.

Someone was touting their Orion as having a better AGC.  TenTec went
through the AGC options torture as well. There are those who
SPECIFICALLY abandoned the Orion because they could do AGC better on a
K3.

As best as I can tell, I can set the K3's AGC to mimick any rig's AGC
I've ever operated by picking a set of option values, including my
75A3.  So if the K3 AGC is supposed to be worse than rig XYZ, whose
fault is that?

The truth is that the K3, by offering all the options, has allowed the
complexity of the problem to be exposed and put Elecraft on the
bleeding edge of original development with a responsive company that
will actually try out new stuff that emerges.  One would think you
guys would LOVE that for the unique opportunity it really is.

73, Guy.


On Sun, Dec 5, 2010 at 11:50 AM, Dave Hachadorian <[hidden email]> wrote:

> This thread is not about copying signals that are separated by
> 100 Hz.  We are talking here about multiple nearly-on-frequency
> callers in a pileup.  In those circumstances, with most rigs, you
> can separate the signals by amplitude, or slight pitch or other
> CW idiosyncrasies.  The K3's agc has a problem dealing with that.
> Signals are compressed together, such that you can't copy anyone,
> unless you reach for the rf gain control.  If you turn agc OFF,
> you have to deal with the crazy AF Limiter.
>
>
> Dave Hachadorian, K6LL
> Yuma, AZ
>
>
>
>
> -----Original Message-----
> From: Hector Padron
> Sent: Sunday, December 05, 2010 9:22 AM
> To: [hidden email]
> Subject: Re: [Elecraft] Recommended AGC settings for separation
> of signalsin CW pile-ups
>
> Oh well,I don't like to argue anybody or disagree anybody but I
> was at the contest as well and and I could easily separate CW
> stations that were off  between 100 200 Hz with my K3 using the
> 400Hz roofer and the DSP set to 100Hz and also moving the Shift
> acordingly,.no problem at all with the selectivity and also I
> used the great help of the APF as well.
> If it has to be with the AGC or not,these are my settings that
> has been working for me in any case:
>
> AGC DCY.....SoFt
> AGC HLD.....0.05
> AGC PLS.....OFF
> AGC SLP.....0.07
> AGC THR.....007
> AGC-F.........080
> AGC-S.........020
>
> To help in the RX filtering I have set my RX EQ this way:
>
> 0.05 at minus 16
> 0.10 at minus 16
> 0.20 at minus +0
> 0.40 at +3
> 0.80 at +3
> 1.60 at minus 16
> 2.40 at minus 16
> 3.20 at minus 16
> PITCH at 400 (I like to hear better at low pitch)
>
> With these settings my K3 is super selective and have no ringing
> noise even at 50Hz DSP bandwiith.
> In those conditions I can work any contest no matter how crowded
> it will be.
>
> AD4C
>
>
>
>
>
>
>
> "If freedom means something,it is the right to tell others what
> they don't want to hear" –George Orwell
>
> --- On Sun, 12/5/10, Tommy Alderman <[hidden email]>
> wrote:
>
>
> From: Tommy Alderman <[hidden email]>
> Subject: Re: [Elecraft] Recommended AGC settings for separation
> of signals in CW pile-ups
> To: [hidden email]
> Date: Sunday, December 5, 2010, 10:47 AM
>
>
> Bob -
>
> I agree with the observation about the K3's effectiveness  in
> separating
> contest signals in big piles as that was the only thing that
> irritated me
> during CQWW CW contest. I have just started to try and optimize
> the AGC
> settings for large signal conditions and so far, I'm not anywhere
> close yet.
> If I can find anything useful, I will post it here. I certainly
> do hope
> others who may already have optimized their K3 AGC for large
> signal contest,
> will also post their information.
>
> 161,
> Tom - W4BQF
>
>
> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Bob
> Henderson
> Sent: Sunday, December 05, 2010 4:39 AM
> To: [hidden email]
> Subject: [Elecraft] Recommended AGC settings for separation of
> signals in CW
> pile-ups
>
> CQ WW CW is now over.  We used K3s at P3F this year.  While
> performance was
> generally considered good, some questions were raised over the
> effectiveness
> of the K3 in separating signals in large piles.
>
> Similar concerns appear to have surfaced from other users
> including the guys
> at 9L5VT and C6ATA.  Anecdotal evidence suggests the old TS930
> and TS850
> performed better in such circumstances.  I suspect the AGC
> systems of the
> K3s used had not optimised.
>
> Has collective experience of the K3 contesting community derived
> optimum
> settings for the K3 AGC system in this kind of situation?
>
> Thanks
>
> Bob, 5B4AGN
> ______________________________________________________________
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>
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> Please help support this email list:
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> ______________________________________________________________
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> Post: mailto:[hidden email]
>
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>
>
>
>
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[Don Wilhelm-4]

  Arie,

If the ADC is overloaded, the digital output will be garbage, and there
will be nothing to resemble any form of a signal out of the receiver.  
In a contest like CQWW where there are lots of extremely strong signals,
you would work fewer stations if the ADC were allowed to overload.  Lots
of lost points while waiting for the digital bits to settle down and
recover.

73,
Don W3FPR

On 12/5/2010 12:00 PM, Arie Kleingeld PA3A wrote:

> I agree with you Don.
>
> But how much chaos would it be? I hove no idea.
>
> There are a lot of things that we can set by menu in the K3.
> Absolutely wonderful how we can manipulate threshold, slope, pulse,
> decay, releasetime and holdtime. Would it be wrong te try out a menu
> selectable threshold for the hardware agc?
> Just wondering how this would work out in a CQWW.
>

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[Don Wilhelm-4]

  Dave,

The signals can be separated by amplitude if you set the AGC slope
correctly - unfortunately, that is not the default settings.
See the article dealing with the K3 AGC on my website www.w3fpr.com.

73,
Don W3FPR

On 12/5/2010 11:50 AM, Dave Hachadorian wrote:

> This thread is not about copying signals that are separated by
> 100 Hz.  We are talking here about multiple nearly-on-frequency
> callers in a pileup.  In those circumstances, with most rigs, you
> can separate the signals by amplitude, or slight pitch or other
> CW idiosyncrasies.  The K3's agc has a problem dealing with that.
> Signals are compressed together, such that you can't copy anyone,
> unless you reach for the rf gain control.  If you turn agc OFF,
> you have to deal with the crazy AF Limiter.
>
> .qsl.net/donate.html

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[KK7P]

The AF Limiter in the K3 is designed to allow you to
protect your hearing when you have the AGC off and gain
cranked up to hear the signal buried in the noise just as
your neighbor with his beam bore-sighted on your QTH and
running the Alpha amplifier starts transmitting on that
same frequency.

Note that the AF Limiter level is completely adjustable
when AGC is OFF.  At its highest setting it clips just at
the threshold that the audio amplifiers in the K3
otherwise limit/clip.

In fact, when AGC is ON, the AF Limiter is still present
but set to this highest level.

So, if it bothers you, please set it higher :-)

Enjoy!

73,

Lyle KK7P (at 38,000 feet enjoying in-flight WiFi)
> you have to deal with the crazy AF Limiter.
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[Barry N1EU]

Guy, K2AV wrote

Or stated differently, your ear probably needs something an S-unit
difference to discern two signals exactly on frequency with no other
separation information in the signal blend.

My experience, which seems to be shared by several others, is that even signals of greater than an S-unit difference in strength cannot be discerned.  Weak and strong signals are all blended indiscernibly together.

Barry N1EU

(bottom posted to first show context of response)

[Dave Hachadorian]

Hi Lyle,

Thanks for entering the discussion. It's great that the company
guys monitor these reflectors.

Even at its maximum 030 setting, the AF Limiter is problematic.

The K3's AF Limiter is a HARD limiter that has an abrupt onset
and causes extreme distortion.  In fact, once the AF Limiter
threshold has been hit, the louder the signal is, the less audio
comes out of the headphone amp, at least as measured on my DVM.
Once the limiter is hit, there is absolutely no hope of pulling a
signal out of the pileup.  One absolutely must reduce AF or RF
gain to pull anything out at that point.

A soft limiter on the other hand (such as a pair of back-to-back
Schottky Diodes) doesn't cause that extreme distortion, and
allows a much wider usable dynamic range, albeit with some minor
fuzz on very loud signals.

There is no way, despite K3NA's excellent attempt
http://wiki.contesting.com/index.php/Setting_receiver_gain_controls
to set the K3's RF and AF gain controls to accommodate the
dynamic range of signals encountered on the bands, without riding
the RF and/or AF gain controls.  Maybe it is possible with
super-sensitive headphones, but not with any that I have tried.

The most successful method of dealing with pileups that I have
found (other than agc OFF, and constantly riding the RF gain) is
to use an external audio amp with a soft limiter.

I wonder if there is a place in the K3 to put a pair of limiting
diodes, ahead of the AF Limiter?

Dave Hachadorian, K6LL
Yuma, AZ





-----Original Message-----
From: lyle johnson
Sent: Sunday, December 05, 2010 11:18 AM
To: Elecraft Reflector
Subject: [Elecraft] AF Limiter (was Recommended AGC settings for
separation of signalsin CW pile-ups)

The AF Limiter in the K3 is designed to allow you to
protect your hearing when you have the AGC off and gain
cranked up to hear the signal buried in the noise just as
your neighbor with his beam bore-sighted on your QTH and
running the Alpha amplifier starts transmitting on that
same frequency.

Note that the AF Limiter level is completely adjustable
when AGC is OFF.  At its highest setting it clips just at
the threshold that the audio amplifiers in the K3
otherwise limit/clip.

In fact, when AGC is ON, the AF Limiter is still present
but set to this highest level.

So, if it bothers you, please set it higher :-)

Enjoy!

73,

Lyle KK7P (at 38,000 feet enjoying in-flight WiFi)
> you have to deal with the crazy AF Limiter.
______________________________________________________________
Elecraft mailing list
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Post: mailto:[hidden email]

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http://www.qsl.net/donate.html 

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[Jan Erik Holm]

Exactly, I have noticed this too but never said anything before.
It did happen a few times during the SAC CW contest that I operated,
never had time to take part in CQWW CW. The radio do have
a problem in this respect and I can see that 5B4AGN has found
it too.
Something is going on but what it is I of course do not know.
The old FT1000MP had something similar and someone called it
AGC IMD of course this K3 radio is a different animal.

Jim SM2EKM
------------
On 2010-12-05 17:50, Dave Hachadorian wrote:

> This thread is not about copying signals that are separated by
> 100 Hz.  We are talking here about multiple nearly-on-frequency
> callers in a pileup.  In those circumstances, with most rigs, you
> can separate the signals by amplitude, or slight pitch or other
> CW idiosyncrasies.  The K3's agc has a problem dealing with that.
> Signals are compressed together, such that you can't copy anyone,
> unless you reach for the rf gain control.  If you turn agc OFF,
> you have to deal with the crazy AF Limiter.
>
>
> Dave Hachadorian, K6LL
> Yuma, AZ
>
>
>
>
> -----Original Message-----
> From: Hector Padron
> Sent: Sunday, December 05, 2010 9:22 AM
> To: [hidden email]
> Subject: Re: [Elecraft] Recommended AGC settings for separation
> of signalsin CW pile-ups
>
> Oh well,I don't like to argue anybody or disagree anybody but I
> was at the contest as well and and I could easily separate CW
> stations that were off  between 100 200 Hz with my K3 using the
> 400Hz roofer and the DSP set to 100Hz and also moving the Shift
> acordingly,.no problem at all with the selectivity and also I
> used the great help of the APF as well.
> If it has to be with the AGC or not,these are my settings that
> has been working for me in any case:
>
> AGC DCY.....SoFt
> AGC HLD.....0.05
> AGC PLS.....OFF
> AGC SLP.....0.07
> AGC THR.....007
> AGC-F.........080
> AGC-S.........020
>
> To help in the RX filtering I have set my RX EQ this way:
>
> 0.05 at minus 16
> 0.10 at minus 16
> 0.20 at minus +0
> 0.40 at +3
> 0.80 at +3
> 1.60 at minus 16
> 2.40 at minus 16
> 3.20 at minus 16
> PITCH at 400 (I like to hear better at low pitch)
>
> With these settings my K3 is super selective and have no ringing
> noise even at 50Hz DSP bandwiith.
> In those conditions I can work any contest no matter how crowded
> it will be.
>
> AD4C
>
>
>
>
>
>
>
> "If freedom means something,it is the right to tell others what
> they don't want to hear" –George Orwell
>
> --- On Sun, 12/5/10, Tommy Alderman<[hidden email]>
> wrote:
>
>
> From: Tommy Alderman<[hidden email]>
> Subject: Re: [Elecraft] Recommended AGC settings for separation
> of signals in CW pile-ups
> To: [hidden email]
> Date: Sunday, December 5, 2010, 10:47 AM
>
>
> Bob -
>
> I agree with the observation about the K3's effectiveness  in
> separating
> contest signals in big piles as that was the only thing that
> irritated me
> during CQWW CW contest. I have just started to try and optimize
> the AGC
> settings for large signal conditions and so far, I'm not anywhere
> close yet.
> If I can find anything useful, I will post it here. I certainly
> do hope
> others who may already have optimized their K3 AGC for large
> signal contest,
> will also post their information.
>
> 161,
> Tom - W4BQF
>
>
> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Bob
> Henderson
> Sent: Sunday, December 05, 2010 4:39 AM
> To: [hidden email]
> Subject: [Elecraft] Recommended AGC settings for separation of
> signals in CW
> pile-ups
>
> CQ WW CW is now over.  We used K3s at P3F this year.  While
> performance was
> generally considered good, some questions were raised over the
> effectiveness
> of the K3 in separating signals in large piles.
>
> Similar concerns appear to have surfaced from other users
> including the guys
> at 9L5VT and C6ATA.  Anecdotal evidence suggests the old TS930
> and TS850
> performed better in such circumstances.  I suspect the AGC
> systems of the
> K3s used had not optimised.
>
> Has collective experience of the K3 contesting community derived
> optimum
> settings for the K3 AGC system in this kind of situation?
>
> Thanks
>
> Bob, 5B4AGN

______________________________________________________________
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Post: mailto:[hidden email]

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[Barry N1EU]

It is fundamentally essential to use very high isolation headphones to achieve K3NA's dynamic range goal (i.e., to hear the weakest and strongest signals with AGC OFF without kicking in the limiter).  It IS achievable.  It's not a matter of sensitivity.  

Barry N1EU

Dave Hachadorian wrote

There is no way, despite K3NA's excellent attempt
http://wiki.contesting.com/index.php/Setting_receiver_gain_controls
to set the K3's RF and AF gain controls to accommodate the
dynamic range of signals encountered on the bands, without riding
the RF and/or AF gain controls.  Maybe it is possible with
super-sensitive headphones, but not with any that I have tried.