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K3 receiver desensing on CW during contest

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Mike K2MK

K3 receiver desensing on CW during contest

I had a great time with my K3 during the ARRL DX contest. I do S&P and I was
trolling around with my filter width at 50Hz. Absolutely outstanding. The
auto spot is equally outstanding.

At 50Hz width it was quite clear that many stations call off frequency.
Using RIT, I could see that it was typical for them to be 70Hz or more away
from the DX station but I could not hear them in my 50Hz passband. The real
problem was when one of them was S9 or greater. They completely swamped
weaker DX stations. Sound within the passband just blanked out. No band
noise and no DX station. And there was no recovery between dits and dahs. It
was actually easier to copy the DX station when people were calling directly
on top of him. You could at least hear him between the dits.

(Obviously if I was calling CQ instead of S&P I would have a wider passband
and I would have just worked the stronger off frequency station).

For my style of operating this was a disappointment. I tried AGC-F and AGC-S
but I forgot to try AGC off. I also varied the AGC THR and AGC SLP. I tried
NR off and on. (I was not using NB). I tried PRE and ATT off and on. I tried
riding the RF gain. I tried shifting the passband but shift doesn't work
well when the width is only 50Hz. Nothing helped. I also tried opening up
the passband. That didn't help either but I don't remember the results.

This was not a one time thing. It happened at least 20 different times on
different bands. I guess this is perfectly normal. I was just wondering what
operational trick is available to compensate.

73,
Mike K2MK

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Jim AB3CV

Re: K3 receiver desensing on CW during contest

What IF filters do you have installed?

jim ab3cv

Greg - AB7R

Re: K3 receiver desensing on CW during contest

In reply to this post by Mike K2MK

This is more than likely due to dirty signals on the TX end. I was
using a QS1R connected to the K3 IF and measured the width of some of
the strong signals. Some were as wide as 2.6 kHz!!!! Not very good
for a CW signal. In this case there is just not much you can do.

73
Greg
AB7R

On Feb 22, 2009, at 4:45 PM, K2MK wrote:

> I had a great time with my K3 during the ARRL DX contest. I do S&P
> and I was
> trolling around with my filter width at 50Hz. Absolutely
> outstanding. The
> auto spot is equally outstanding.
>
> At 50Hz width it was quite clear that many stations call off
> frequency.
> Using RIT, I could see that it was typical for them to be 70Hz or
> more away
> from the DX station but I could not hear them in my 50Hz passband.
> The real
> problem was when one of them was S9 or greater. They completely
> swamped
> weaker DX stations. Sound within the passband just blanked out. No
> band
> noise and no DX station. And there was no recovery between dits and
> dahs. It
> was actually easier to copy the DX station when people were calling
> directly
> on top of him. You could at least hear him between the dits.
>
> (Obviously if I was calling CQ instead of S&P I would have a wider
> passband
> and I would have just worked the stronger off frequency station).
>
> For my style of operating this was a disappointment. I tried AGC-F
> and AGC-S
> but I forgot to try AGC off. I also varied the AGC THR and AGC SLP.
> I tried
> NR off and on. (I was not using NB). I tried PRE and ATT off and on.
> I tried
> riding the RF gain. I tried shifting the passband but shift doesn't
> work
> well when the width is only 50Hz. Nothing helped. I also tried
> opening up
> the passband. That didn't help either but I don't remember the
> results.
>
> This was not a one time thing. It happened at least 20 different
> times on
> different bands. I guess this is perfectly normal. I was just
> wondering what
> operational trick is available to compensate.
>
> 73,
> Mike K2MK
>
> ______________________________________________________________
> 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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ROBERT CARROLL-4

Re: K3 receiver desensing on CW during contest

It seems that soundcard based "AFCW" has become popular with some
contesters, for reasons which elude me. There is great opportunity to
transmit wide, distorted cw signals if things are poorly adjusted.

Bob W2WG

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Gregory Fischer
Sent: Sunday, February 22, 2009 7:59 PM
To: K2MK
Cc: Elecraft Reflector
Subject: Re: [Elecraft] K3 receiver desensing on CW during contest

This is more than likely due to dirty signals on the TX end. I was
using a QS1R connected to the K3 IF and measured the width of some of
the strong signals. Some were as wide as 2.6 kHz!!!! Not very good
for a CW signal. In this case there is just not much you can do.

73
Greg
AB7R

On Feb 22, 2009, at 4:45 PM, K2MK wrote:

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Dave Hachadorian

Re: K3 receiver desensing on CW during contest

In reply to this post by Mike K2MK

The behavior you are describing is almost the same thing I
complained about a couple weeks ago. In my case I was trying
to sort out several signals calling me in a pileup, but it's
the same basic situation. Fast agc, even with the highest
threshold and slp=0, compressed them all into an
indecipherable mush.

I'll tell you how I deal with it, but I'm not recommending
this for everybody:

agc off
config af lim = 30 (tech mode)
use preamp on 20m and higher
no preamp on 40
no preamp + attenuator on for 80/160
plug headphones into speaker jack, so you don't hit the AF
Limiter threshold. (There will be some hiss, but not too
bad.)
RF gain as low as possible
AF gain as low as possible to protect your ears.

WATCH OUT FOR YOUR EARS WITH THIS SETUP!!

I am hoping that the Elecraft folks will raise the AF
limiter threshold or allow disabling the limiter. If the
limiter is activated, all signals are horribly distorted.
Limiter threshold is abrupt and hard.

This setup is probably not for everybody, but it works great
for me.

Dave Hachadorian, K6LL
Yuma, AZ

----- Original Message -----
From: "K2MK" <[hidden email]>
To: "Elecraft Reflector" <[hidden email]>
Sent: Monday, February 23, 2009 12:45 AM
Subject: [Elecraft] K3 receiver desensing on CW during
contest

>I had a great time with my K3 during the ARRL DX contest. I
>do S&P and I was
> trolling around with my filter width at 50Hz. Absolutely
> outstanding. The
> auto spot is equally outstanding.
>
> At 50Hz width it was quite clear that many stations call
> off frequency.
> Using RIT, I could see that it was typical for them to be
> 70Hz or more away
> from the DX station but I could not hear them in my 50Hz
> passband. The real
> problem was when one of them was S9 or greater. They
> completely swamped
> weaker DX stations. Sound within the passband just blanked
> out. No band
> noise and no DX station. And there was no recovery between
> dits and dahs. It
> was actually easier to copy the DX station when people
> were calling directly
> on top of him. You could at least hear him between the
> dits.
>
> (Obviously if I was calling CQ instead of S&P I would have
> a wider passband
> and I would have just worked the stronger off frequency
> station).
>
> For my style of operating this was a disappointment. I
> tried AGC-F and AGC-S
> but I forgot to try AGC off. I also varied the AGC THR and
> AGC SLP. I tried
> NR off and on. (I was not using NB). I tried PRE and ATT
> off and on. I tried
> riding the RF gain. I tried shifting the passband but
> shift doesn't work
> well when the width is only 50Hz. Nothing helped. I also
> tried opening up
> the passband. That didn't help either but I don't remember
> the results.
>
> This was not a one time thing. It happened at least 20
> different times on
> different bands. I guess this is perfectly normal. I was
> just wondering what
> operational trick is available to compensate.
>
> 73,
> Mike K2MK
>
> ______________________________________________________________
> 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

w0mu

Re: K3 receiver desensing on CW during contest

I saw the same thing with a huge fairly weak pileup on 20m's today. This
really needs to get fixed asap. It makes working a pileup almost
impossible.

"A slip of the foot you may soon recover, but a slip of the tongue you may
never get over." Ben Franklin
-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Dave Hachadorian
Sent: Sunday, February 22, 2009 6:26 PM
To: Elecraft reflector
Subject: Re: [Elecraft] K3 receiver desensing on CW during contest

The behavior you are describing is almost the same thing I complained about
a couple weeks ago. In my case I was trying to sort out several signals
calling me in a pileup, but it's the same basic situation. Fast agc, even
with the highest threshold and slp=0, compressed them all into an
indecipherable mush.

I'll tell you how I deal with it, but I'm not recommending this for
everybody:

agc off
config af lim = 30 (tech mode)
use preamp on 20m and higher
no preamp on 40
no preamp + attenuator on for 80/160
plug headphones into speaker jack, so you don't hit the AF Limiter
threshold. (There will be some hiss, but not too
bad.)
RF gain as low as possible
AF gain as low as possible to protect your ears.

WATCH OUT FOR YOUR EARS WITH THIS SETUP!!

I am hoping that the Elecraft folks will raise the AF limiter threshold or
allow disabling the limiter. If the limiter is activated, all signals are
horribly distorted.
Limiter threshold is abrupt and hard.

This setup is probably not for everybody, but it works great for me.

Dave Hachadorian, K6LL
Yuma, AZ

----- Original Message -----
From: "K2MK" <[hidden email]>
To: "Elecraft Reflector" <[hidden email]>
Sent: Monday, February 23, 2009 12:45 AM
Subject: [Elecraft] K3 receiver desensing on CW during contest

>I had a great time with my K3 during the ARRL DX contest. I do S&P and
>I was trolling around with my filter width at 50Hz. Absolutely
>outstanding. The auto spot is equally outstanding.
>
> At 50Hz width it was quite clear that many stations call off
> frequency.
> Using RIT, I could see that it was typical for them to be 70Hz or more
> away from the DX station but I could not hear them in my 50Hz
> passband. The real problem was when one of them was S9 or greater.
> They completely swamped weaker DX stations. Sound within the passband
> just blanked out. No band noise and no DX station. And there was no
> recovery between dits and dahs. It was actually easier to copy the DX
> station when people were calling directly on top of him. You could at
> least hear him between the dits.
>
> (Obviously if I was calling CQ instead of S&P I would have a wider
> passband and I would have just worked the stronger off frequency
> station).
>
> For my style of operating this was a disappointment. I tried AGC-F and
> AGC-S but I forgot to try AGC off. I also varied the AGC THR and AGC
> SLP. I tried NR off and on. (I was not using NB). I tried PRE and ATT
> off and on. I tried riding the RF gain. I tried shifting the passband
> but shift doesn't work well when the width is only 50Hz. Nothing
> helped. I also tried opening up the passband. That didn't help either
> but I don't remember the results.
>
> This was not a one time thing. It happened at least 20 different times
> on different bands. I guess this is perfectly normal. I was just
> wondering what operational trick is available to compensate.
>
> 73,
> Mike K2MK
>
> ______________________________________________________________
> 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

wayne burdick

Re: K3 receiver desensing on CW during contest

Administrator

In reply to this post by Mike K2MK

Mike,

The K3 is virtually desense-proof, with a BDR of ~140 dB. But to take
advantage of this, you need a narrow crystal filter -- the closer to
the DSP bandwidth the better. This is exactly the situation that we had
in mind when we designed the 200-Hz 5-pole filter. For CW pileups, you
can't beat it.

What crystal filter were you using at the time?

Of course if the transmitting stations are "wide" due to key clicks,
there may be situations where no amount of filtering can help (for any
receiver). The DSP noise blanker and NR may be useful sometimes -- you
might give this a try.

Wayne
N6KR

On Feb 22, 2009, at 4:45 PM, K2MK wrote:

> I had a great time with my K3 during the ARRL DX contest. I do S&P and
> I was
> trolling around with my filter width at 50Hz. Absolutely outstanding.
> The
> auto spot is equally outstanding.
>
> At 50Hz width it was quite clear that many stations call off frequency.
> Using RIT, I could see that it was typical for them to be 70Hz or more
> away
> from the DX station but I could not hear them in my 50Hz passband. The
> real
> problem was when one of them was S9 or greater. They completely swamped
> weaker DX stations.

w0mu

Re: K3 receiver desensing on CW during contest

I have the 200, 400, 1000 and 2.7

I do not recall which one I was using at the time. At least the 400hz.
Keep in mind these signals were all s7 and below, most well below.

I was fresh blood on 20m this morning and got spotted. It was an ugly
pileup. The adjacent qrm was not an issue.

When I could get one letter and had one or two people calling it was fine
when 5 or more the signals all were the same strength and as Dave said mushy
like. I did have to rit off and pick off those not zero beat.

All my pileup training goes against having super narrow filters as you want
to hear those on your sides too.

This issue had nothing to do with wide signals or clicks.

I don't think it is desense either it is more of an overload of the audio
circuitry where all the signal levels are being capped or captured to a
specific level. While the pileup was maybe S3 when I picked out station and
he was all alone the signal would come up considerably.

Why I don't know.

There was no local noise issues and no hams close by causing issues.

Just passing on what I experienced. Overall the radio is great on CW. I
worked so many very weak stations easily that I contribute to the fine
receiver in the K3.

"A slip of the foot you may soon recover, but a slip of the tongue you may
never get over." Ben Franklin
-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of wayne burdick
Sent: Sunday, February 22, 2009 7:27 PM
To: K2MK
Cc: Elecraft Reflector
Subject: Re: [Elecraft] K3 receiver desensing on CW during contest

Mike,

The K3 is virtually desense-proof, with a BDR of ~140 dB. But to take
advantage of this, you need a narrow crystal filter -- the closer to the DSP
bandwidth the better. This is exactly the situation that we had in mind when
we designed the 200-Hz 5-pole filter. For CW pileups, you can't beat it.

What crystal filter were you using at the time?

Of course if the transmitting stations are "wide" due to key clicks, there
may be situations where no amount of filtering can help (for any receiver).
The DSP noise blanker and NR may be useful sometimes -- you might give this
a try.

Wayne
N6KR

On Feb 22, 2009, at 4:45 PM, K2MK wrote:

> I had a great time with my K3 during the ARRL DX contest. I do S&P and
> I was trolling around with my filter width at 50Hz. Absolutely
> outstanding.
> The
> auto spot is equally outstanding.
>
> At 50Hz width it was quite clear that many stations call off frequency.
> Using RIT, I could see that it was typical for them to be 70Hz or more
> away from the DX station but I could not hear them in my 50Hz
> passband. The real problem was when one of them was S9 or greater.
> They completely swamped weaker DX stations.

---

http://www.elecraft.com

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Steve Ellington

Re: K3 receiver desensing on CW during contest

In reply to this post by wayne burdick

I think what they are seeing is this: Strong signals that fall slightly
outside the DSP's audio passband are still pumping the S-meter and the AGC
is desensing the receiver. The DSP is acting more like and audio filter than
an IF DSP. In other words, the DSP's audio bandpass is very steep but it's
IF bandpass is broad. This is with the 200Hz roofing filter installed but we
are dealing with this 50Hz issue. To illustrate, tune in an S-9 carrier
using the 50Hz filter. Tune off his signal 60Hz. The audio is gone but the S
meter still reads S-9 telling me that the slopes for audio and IF are
different.
Also, at 50Hz BW the Passband tuning is indeed useless since it tunes in
50Hz increments. Can that be reduced?
Steve Ellington
[hidden email]
----- Original Message -----
From: "wayne burdick" <[hidden email]>
To: "K2MK" <[hidden email]>
Cc: "Elecraft Reflector" <[hidden email]>
Sent: Sunday, February 22, 2009 9:27 PM
Subject: Re: [Elecraft] K3 receiver desensing on CW during contest

> Mike,
>
> The K3 is virtually desense-proof, with a BDR of ~140 dB. But to take
> advantage of this, you need a narrow crystal filter -- the closer to
> the DSP bandwidth the better. This is exactly the situation that we had
> in mind when we designed the 200-Hz 5-pole filter. For CW pileups, you
> can't beat it.
>
> What crystal filter were you using at the time?
>
> Of course if the transmitting stations are "wide" due to key clicks,
> there may be situations where no amount of filtering can help (for any
> receiver). The DSP noise blanker and NR may be useful sometimes -- you
> might give this a try.
>
> Wayne
> N6KR
>
> On Feb 22, 2009, at 4:45 PM, K2MK wrote:
>
>> I had a great time with my K3 during the ARRL DX contest. I do S&P and
>> I was
>> trolling around with my filter width at 50Hz. Absolutely outstanding.
>> The
>> auto spot is equally outstanding.
>>
>> At 50Hz width it was quite clear that many stations call off frequency.
>> Using RIT, I could see that it was typical for them to be 70Hz or more
>> away
>> from the DX station but I could not hear them in my 50Hz passband. The
>> real
>> problem was when one of them was S9 or greater. They completely swamped
>> weaker DX stations.
>
> ---
>
> http://www.elecraft.com
>
> ______________________________________________________________
> 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
>

Merv Schweigert

Re: K3 receiver desensing on CW during contest

In reply to this post by w0mu

Have to ditto whats been said, I have to run with AGC off, audio set about
3 o'clock and use the RF gain. That seems to work fairly well, I use the
400HZ filter most of the time. Not sure what the problem is but the audio
goes to pot in a hurry in a pile up. Sounds strange and no pure tone to the
signals. Was beginning to chalk it up as my problem with old age, not
knowing how to set parameters or ??
I have bought new headphones of several types thinking it was an audio
problem here, but so far nothing works, I agree mine does not seem
to be desense as I can get within a few hundred HZ of very strong signals
and copy a single weak signal fine.
Merv KH7C

I have the 200, 400, 1000 and 2.7

I do not recall which one I was using at the time.  At least the 400hz.
Keep in mind these signals were all s7 and below, most well below.

I was fresh blood on 20m this morning and got spotted.  It was an ugly
pileup.  The adjacent qrm was not an issue.

When I could get one letter and had one or two people calling it was fine
when 5 or more the signals all were the same strength and as Dave said mushy
like.  I did have to rit off and pick off those not zero beat.

All my pileup training goes against having super narrow filters as you want
to hear those on your sides too.

This issue had nothing to do with wide signals or clicks.

I don't think it is desense either it is more of an overload of the audio
circuitry where all the signal levels are being capped or captured to a
specific level.  While the pileup was maybe S3 when I picked out station and
he was all alone the signal would come up considerably.

Why I don't know.  

There was no local noise issues and no hams close by causing issues.

Just passing on what I experienced.  Overall the radio is great on CW.  I
worked so many very weak stations easily that I contribute to the fine
receiver in the K3. 


"A slip of the foot you may soon recover, but a slip of the tongue you may
never get over." Ben Franklin
-----Original Message-----
From: [hidden email]
[[hidden email]] On Behalf Of wayne burdick
Sent: Sunday, February 22, 2009 7:27 PM
To: K2MK
Cc: Elecraft Reflector
Subject: Re: [Elecraft] K3 receiver desensing on CW during contest

Mike,

The K3 is virtually desense-proof, with a BDR of ~140 dB. But to take
advantage of this, you need a narrow crystal filter -- the closer to the DSP
bandwidth the better. This is exactly the situation that we had in mind when
we designed the 200-Hz 5-pole filter. For CW pileups, you can't beat it.

What crystal filter were you using at the time?

Of course if the transmitting stations are "wide" due to key clicks, there
may be situations where no amount of filtering can help (for any receiver).
The DSP noise blanker and NR may be useful sometimes -- you might give this
a try.

Wayne
N6KR

On Feb 22, 2009, at 4:45 PM, K2MK wrote:

I had a great time with my K3 during the ARRL DX contest. I do S&P and 
I was trolling around with my filter width at 50Hz. Absolutely 
outstanding.
The
auto spot is equally outstanding.

At 50Hz width it was quite clear that many stations call off frequency.
Using RIT, I could see that it was typical for them to be 70Hz or more 
away from the DX station but I could not hear them in my 50Hz 
passband. The real problem was when one of them was S9 or greater. 
They completely swamped weaker DX stations.


---

http://www.elecraft.com

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

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Help: http://mailman.qth.net/mmfaq.htm
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n9adg

Re: K3 receiver desensing on CW during contest

I believe that I encountered this a couple of times while in VP5 last fall... there wasn't a roar of stations, the radio just sort of sat there and 'hummed'.

I turned the radio off, then back on, rechecked all of the settings, and kept going.
Brian N9ADG

--- On Sun, 2/22/09, Merv Schweigert <[hidden email]> wrote:

> From: Merv Schweigert <[hidden email]>

> goes to pot in a hurry in a pile up. Sounds strange and no
> pure tone to the
> signals. Was beginning to chalk it up as my problem with
\
______________________________________________________________
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Steve Ellington

Re: K3 receiver desensing on CW during contest

In reply to this post by Merv Schweigert

Merv

Try going into the Config and setting your AGC THR down to 003 and see if that improves. I had mine too high at one time and it caused stronger stations to distort.

Steve Ellington
[hidden email]

----- Original Message -----

From: [hidden email]

Cc: [hidden email]

Sent: Sunday, February 22, 2009 11:31 PM

Subject: Re: [Elecraft] K3 receiver desensing on CW during contest

I have the 200, 400, 1000 and 2.7

I do not recall which one I was using at the time.  At least the 400hz.
Keep in mind these signals were all s7 and below, most well below.

I was fresh blood on 20m this morning and got spotted.  It was an ugly
pileup.  The adjacent qrm was not an issue.

When I could get one letter and had one or two people calling it was fine
when 5 or more the signals all were the same strength and as Dave said mushy
like.  I did have to rit off and pick off those not zero beat.

All my pileup training goes against having super narrow filters as you want
to hear those on your sides too.

This issue had nothing to do with wide signals or clicks.

I don't think it is desense either it is more of an overload of the audio
circuitry where all the signal levels are being capped or captured to a
specific level.  While the pileup was maybe S3 when I picked out station and
he was all alone the signal would come up considerably.

Why I don't know.  

There was no local noise issues and no hams close by causing issues.

Just passing on what I experienced.  Overall the radio is great on CW.  I
worked so many very weak stations easily that I contribute to the fine
receiver in the K3. 


"A slip of the foot you may soon recover, but a slip of the tongue you may
never get over." Ben Franklin
-----Original Message-----
From: [hidden email]
[[hidden email]] On Behalf Of wayne burdick
Sent: Sunday, February 22, 2009 7:27 PM
To: K2MK
Cc: Elecraft Reflector
Subject: Re: [Elecraft] K3 receiver desensing on CW during contest

Mike,

The K3 is virtually desense-proof, with a BDR of ~140 dB. But to take
advantage of this, you need a narrow crystal filter -- the closer to the DSP
bandwidth the better. This is exactly the situation that we had in mind when
we designed the 200-Hz 5-pole filter. For CW pileups, you can't beat it.

What crystal filter were you using at the time?

Of course if the transmitting stations are "wide" due to key clicks, there
may be situations where no amount of filtering can help (for any receiver).
The DSP noise blanker and NR may be useful sometimes -- you might give this
a try.

Wayne
N6KR

On Feb 22, 2009, at 4:45 PM, K2MK wrote:

I had a great time with my K3 during the ARRL DX contest. I do S&P and 
I was trolling around with my filter width at 50Hz. Absolutely 
outstanding.
The
auto spot is equally outstanding.

At 50Hz width it was quite clear that many stations call off frequency.
Using RIT, I could see that it was typical for them to be 70Hz or more 
away from the DX station but I could not hear them in my 50Hz 
passband. The real problem was when one of them was S9 or greater. 
They completely swamped weaker DX stations.


---

http://www.elecraft.com

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wayne burdick

K3 receiver & CW contest condx -- AGC settings, etc.

Administrator

In reply to this post by Merv Schweigert

> When I could get one letter and had one or two people calling it was
> fine.
> When 5 or more the signals all were the same strength....

I'll discuss this with Lyle, KK7P (our DSP engineer). I don't think
this has anything to do with "desensing" if a narrow filter is being
used. I can't imaging what might cause it with lower-level signals. The
ADC has plenty of resolution, and the DSP has plenty of horsepower, so
there should be no difficulty in separating out multiple stations in
close proximity.

There are only two things I can think of: the AGC may be set too
"flat", or, if a speaker is being used at moderate to high output, that
perhaps the RFC47 mod hasn't been done (on the RF board). In any case,
we'll look into it.

tnx
Wayne
N6KR

---

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w0mu

Re: K3 receiver & CW contest condx -- AGC settings, etc.

Wayne,

100 percent headphone operation here. I have not done the RFC47 Mod. I
have it but I was not going to tear the radio apart with no backup. I have
my 2nd K3 on the way in the brown truck. I am going to build that first and
then do the mods on the older K3.

Any suggested settings for serious contester types for the radio?

I am not sure what AGC PLS does but mine was set to auto. Maybe off would
be better?

AGC Thr was 5 I will try 3 as suggested.

AGC fast was 120 maybe faster?

"A slip of the foot you may soon recover, but a slip of the tongue you may
never get over." Ben Franklin
-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of wayne burdick
Sent: Sunday, February 22, 2009 9:58 PM
To: 'Elecraft Reflector'
Subject: [Elecraft] K3 receiver & CW contest condx -- AGC settings, etc.

> When I could get one letter and had one or two people calling it was
> fine.
> When 5 or more the signals all were the same strength....

I'll discuss this with Lyle, KK7P (our DSP engineer). I don't think this has
anything to do with "desensing" if a narrow filter is being used. I can't
imaging what might cause it with lower-level signals. The ADC has plenty of
resolution, and the DSP has plenty of horsepower, so there should be no
difficulty in separating out multiple stations in close proximity.

There are only two things I can think of: the AGC may be set too "flat", or,
if a speaker is being used at moderate to high output, that perhaps the
RFC47 mod hasn't been done (on the RF board). In any case, we'll look into
it.

tnx
Wayne
N6KR

---

http://www.elecraft.com

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Bill W4ZV

Re: K3 receiver desensing on CW during contest

In reply to this post by Mike K2MK

Mike I believe there are two separate parts to your post:

> At 50Hz width it was quite clear that many stations call off frequency.
Using RIT, I could see that it was typical for them to be 70Hz or more away
from the DX station but I could not hear them in my 50Hz passband. The real
problem was when one of them was S9 or greater. They completely swamped
weaker DX stations. Sound within the passband just blanked out. No band
noise and no DX station. And there was no recovery between dits and dahs. It
was actually easier to copy the DX station when people were calling directly
on top of him. You could at least hear him between the dits.

The K3 will desense for signals about S9+25 that fall *within* the roofing filter but *outside* the DSP WIDTH passband. Elecraft made a modification ("hardware AGC" in the mod kits list) about a year ago which improved this problem and raised the threshold from a little over S9 to S9+25 (or maybe +30). I don't know your S/N but if it's ~280 or less you should install this mod. In my opinion, the threshold for this mod could still be raised a little more based on my experience with Orion which has a very similar front end to the K3. You didn't mention which filter you were using but even if you had the 200 Hz filter installed, you could have desense from S9+25 signals about +/- 150 Hz from your center frequency. There's simply not much that can be done about this until SHIFT resolution is changed from 50 Hz to 10 Hz. Then you could possibly use SHIFT to put the strong interfering signal on the XFIL passband slope.

> For my style of operating this was a disappointment. I tried AGC-F and AGC-S
but I forgot to try AGC off. I also varied the AGC THR and AGC SLP. I tried
NR off and on. (I was not using NB). I tried PRE and ATT off and on. I tried
riding the RF gain. I tried shifting the passband but shift doesn't work
well when the width is only 50Hz. Nothing helped. I also tried opening up
the passband. That didn't help either but I don't remember the results.

> This was not a one time thing. It happened at least 20 different times on
different bands. I guess this is perfectly normal. I was just wondering what
operational trick is available to compensate.

This could be a second issue (i.e. separating multiple strong stations) which Dave K6LL has identified. I haven't experienced it as yet because unfortunately I haven't had many pileups of strong stations calling me! However I believe Dave W6NL has determined that AGC THR and AGC SLP settings of 5 and 5 are best for this separation issue. I leave my AGC PLS set to NOR and have not experienced any problems that I felt were related to it.

As an aside, I never use AGC-S for any mode and have AGC-F set to 120. Using Extreme Isolation EX-29 headphones, I select AF GAIN LO in the CONFIG menu, set my front panel AF GAIN to 9 o'clock (NEVER higher than 11 o'clock), set PRE/ATT so I can hear band noise when antennas are selected and then back off the front panel RF GAIN to a comfortable audio level. In the contest this weekend with ATT on my TX array and PRE on my Beverages (using both antennas for diversity), I typically had RF GAIN for both Main/Sub set from 2 o'clock to noon.

The K3 was wonderful on Topband in the contest, especially the first night when QRN was low enough to use both my directional TX array and Beverages in diversity. It appears I set a new USA record with 434 QSOs and 79 countries for 102,858 points, breaking the old record of 81k set by N4PN at W8JI's station in 2006.

73, Bill

Mike K2MK

Re: K3 receiver desensing on CW during contest

In reply to this post by Mike K2MK

Hi Wayne and all:

My filters are 200, 400, 1.0, 1.8 and 2.7 and they are all CW enabled. I
was using headphones and my sub RX was off. My serial number is 2208 and the
radio was factory assembled (including the sub RX).

I did not hear key clicks when this was happening. The off frequency
transmissions were clean. I also made a point of observing the signal
strength of the offending stations and they were usually S8 or S9. Not the
20db or 40db over S9 that I was expecting.

I thought it was interesting that recovery was noticeably slow on the DX
station's frequency when this was happening. However, under normal
conditions when US stations were calling directly on top of the DX station,
recovery was fast. Hence the ability to copy the DX station through the dits
when the QRM was on frequency.

Maybe a passband shift could of helped. I would like to see the shift limits
changed to something less than 50Hz. Maybe 10Hz on CW and 50Hz on other
modes.

I appreciate the interesting ideas from K6LL and W4ZV. Unfortunately I'll
have to wait for the next busy contest to try them out. This just isn't the
type of condition you can experience under normal band conditions.

73,
Mike K2MK

wayne burdick
Sun, 22 Feb 2009 18:26:03 -0800

Mike,

The K3 is virtually desense-proof, with a BDR of ~140 dB. But to take
advantage of this, you need a narrow crystal filter -- the closer to
the DSP bandwidth the better. This is exactly the situation that we had
in mind when we designed the 200-Hz 5-pole filter. For CW pileups, you
can't beat it.

What crystal filter were you using at the time?

Of course if the transmitting stations are "wide" due to key clicks,
there may be situations where no amount of filtering can help (for any
receiver). The DSP noise blanker and NR may be useful sometimes -- you
might give this a try.

Wayne
N6KR

On Feb 22, 2009, at 4:45 PM, K2MK wrote:

Bill W4ZV

Re: K3 receiver desensing on CW during contest

K2MK wrote

I thought it was interesting that recovery was noticeably slow on the DX
station's frequency when this was happening. However, under normal
conditions when US stations were calling directly on top of the DX station,
recovery was fast. Hence the ability to copy the DX station through the dits
when the QRM was on frequency.

Mike this definitely sounds like desense but I'm surprised you experienced it with only S8-9 signals. I'm not sure what you mean about differing conditions on and off the center frequency. Desense will affect everything inside the roofing filter.

What speed AGC were you using (F or S) and what were your AGC-F and AGC-S CONFIG settings? I NEVER use AGC-S on either CW or SSB and like at least 120 dB/sec for AGC-F. Also, help your AGC do its job by not running RF GAIN fully clockwise (as mentioned in my previous message).

73, Bill

P.S. As I said before my K3 worked extremely well coping weak signals in the midst of massive ones on 160 this weekend. I smiled when I saw the following comment from OL0W(OK1DSZ):

"Only for fun, when the band was already closing, I decided to try what I will
be able to work with QRP. Using longer callsign OK1DSZ and the power reduced to
5W I spend about 10 minutes calling several east coast big guns. The award for
the best ears goes to W4ZV, who was worked as easily as with the kilowatt
earlier in the night. K8PO and W2FU were worked with several repeats. The
others just kept CQing without any reaction with exception of K1TTT, who
apparently heard something, but not enough for the QSO."

Barry N1EU

Re: K3 receiver desensing on CW during contest

In reply to this post by Bill W4ZV

Bill W4ZV wrote

This could be a second issue (i.e. separating multiple strong stations) which Dave K6LL has identified. I haven't experienced it as yet because unfortunately I haven't had many pileups of strong stations calling me! However I believe Dave W6NL has determined that AGC THR and AGC SLP settings of 5 and 5 are best for this separation issue.

I don't see why SLP of 0 and THR of 8 wouldn't be the best settings in this case, in order to minimize compression? Perhaps Wayne/Lyle could weigh in on this.

I have to echo W0MU and K6LL's experience - I was using AGC-F, 500hz filter@300-400hz dsp. I've noticed it in previous contests and the past weekend as well. For whatever reason, the 40M/20M pileups this weekend were HUGE at times, the biggest I've ever encountered. My typical experience was that I could work off the s8+ callers (thanks to SLP 0), but was eventually left with a sea of "mush". I easily could read the first character or two of the early callers but they were soon swallowed up by the "mush". It was impossible to pick out an individual caller, even after reducing RF Gain.

73,
Barry N1EU

Mike K2MK

Re: K3 receiver desensing on CW during contest

In reply to this post by Mike K2MK

Hi Bill:

Here are my CONFIG settings related to the AGC. The only ones I played with
during the contest were SLP and THR. I always use AGC-F but did occasionally
try AGC-S.

AGC-HOLD 000
AGC-PLS NOR
AGC-SLP 010
AGC-THR 005
AGC-F 120
AGC-S 020

The differing conditions I described were the situation of everyone calling
the DX close to his frequency versus one strong station calling 70Hz off
frequency. When even strong stations called the DX right on frequency I was
able to hear signals through the QRM. When strong stations called 70Hz off
of the DX frequency the receiver went quiet and took about 1/4 to 1/2 second
to recover after he stopped sending.

73,
Mike K2MK

Bill W4ZV
Mon, 23 Feb 2009 05:31:37 -0800

K2MK wrote:
>
> I thought it was interesting that recovery was noticeably slow on the DX
> station's frequency when this was happening. However, under normal
> conditions when US stations were calling directly on top of the DX
> station,
> recovery was fast. Hence the ability to copy the DX station through the
> dits
> when the QRM was on frequency.
>

Mike this definitely sounds like desense but I'm surprised you experienced
it with only S8-9 signals. I'm not sure what you mean about differing
conditions on and off the center frequency. Desense will affect everything
inside the roofing filter.

What speed AGC were you using (F or S) and what were your AGC-F and AGC-S
CONFIG settings? I NEVER use AGC-S on either CW or SSB and like at least
120 dB/sec for AGC-F. Also, help your AGC do its job by not running RF GAIN
fully clockwise (as mentioned in my previous message).

73, Bill

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Darwin, Keith

Re: K3 receiver desensing on CW during contest

Having 1/4 to 1/2 second recovery time does not sound like AGC-F. By
chance, did you have the CW text decode feature engaged? Did you have
NR engaged?

- Keith N1AS -
- K3 711 -

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of K2MK
Sent: Monday, February 23, 2009 11:00 AM
To: [hidden email]; Elecraft Reflector
Subject: Re: [Elecraft] K3 receiver desensing on CW during contest

Hi Bill:

Here are my CONFIG settings related to the AGC. The only ones I played
with during the contest were SLP and THR. I always use AGC-F but did
occasionally try AGC-S.

AGC-HOLD 000
AGC-PLS NOR
AGC-SLP 010
AGC-THR 005
AGC-F 120
AGC-S 020

The differing conditions I described were the situation of everyone
calling the DX close to his frequency versus one strong station calling
70Hz off frequency. When even strong stations called the DX right on
frequency I was able to hear signals through the QRM. When strong
stations called 70Hz off of the DX frequency the receiver went quiet and
took about 1/4 to 1/2 second to recover after he stopped sending.

73,
Mike K2MK

Bill W4ZV
Mon, 23 Feb 2009 05:31:37 -0800

K2MK wrote:
>
> I thought it was interesting that recovery was noticeably slow on the
> DX station's frequency when this was happening. However, under normal
> conditions when US stations were calling directly on top of the DX
> station, recovery was fast. Hence the ability to copy the DX station
> through the dits when the QRM was on frequency.
>

Mike this definitely sounds like desense but I'm surprised you
experienced it with only S8-9 signals. I'm not sure what you mean about
differing conditions on and off the center frequency. Desense will
affect everything inside the roofing filter.

What speed AGC were you using (F or S) and what were your AGC-F and
AGC-S CONFIG settings? I NEVER use AGC-S on either CW or SSB and like
at least 120 dB/sec for AGC-F. Also, help your AGC do its job by not
running RF GAIN fully clockwise (as mentioned in my previous message).

73, Bill

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