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k3 NR Audio level increase

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G4POP

k3 NR Audio level increase

I see that the dramatic increase in audio level when NR is turned on has been mentioned a couple of times but I can find no solution for this mentioned in the forum and the latest firmware 3.11 has not cured it.

At this point I find NR totally un-usable unless I want to risk perforated ear drums!

Terry G4POP

Pete Harris G3OBV

Re: k3 NR Audio level increase

Terry

I agree, it is an effect I have recently noticed. I have not had my K3 very
long so I am not quite familiar with all the various options available so I was thinking it was something
I have done. A quick check using Speclab indicates about a 20dB increase.

Pete G3OBV

________________________________
From: G4POP <[hidden email]>
To: [hidden email]
Sent: Saturday, 25 April, 2009 9:03:53 AM
Subject: [Elecraft] k3 NR Audio level increase

I see that the dramatic increase in audio level when NR is turned on has been
mentioned a couple of times but I can find no solution for this mentioned in
the forum and the latest firmware 3.11 has not cured it.

At this point I find NR totally un-usable unless I want to risk perforated
ear drums!

Terry G4POP
--
View this message in context: http://n2.nabble.com/k3-NR-Audio-level-increase-tp2702048p2702048.html
Sent from the Elecraft mailing list archive at Nabble.com.

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Don Wilhelm-4

Re: k3 NR Audio level increase

In reply to this post by G4POP

Terry,

I do not experience anything like that on my K3. What NR parameters are
you using?
Are you attempting to use NR at a narrow bandwidth when this occurs?
If so, I can understand why that might occur.

Lyle has explained previously that the NR is implemented in the K3 as
"signal enhancement" rather than a strict noise reduction. In other
words, the passband is examined for content that correlates, and the
result is amplified. If the bandwidth is narrow, it is possible that
the entire passband content (including noise) will appear to be a signal.

73,
Don W3FPR

G4POP wrote:

> I see that the dramatic increase in audio level when NR is turned on has been
> mentioned a couple of times but I can find no solution for this mentioned in
> the forum and the latest firmware 3.11 has not cured it.
>
> At this point I find NR totally un-usable unless I want to risk perforated
> ear drums!
>
> Terry G4POP
>
>

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N2TK

Re: k3 NR Audio level increase

In reply to this post by G4POP

Checked again the NB on CW and SSB on both rigs with 3.11. I do not see this
problem at all. Is it possible the AGC setup that does this?

73,
N2TK, Tony
#311
#1435

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of G4POP
Sent: Saturday, April 25, 2009 4:04 AM
To: [hidden email]
Subject: [Elecraft] k3 NR Audio level increase

I see that the dramatic increase in audio level when NR is turned on has
been
mentioned a couple of times but I can find no solution for this mentioned in
the forum and the latest firmware 3.11 has not cured it.

At this point I find NR totally un-usable unless I want to risk perforated
ear drums!

Terry G4POP
--
View this message in context:
http://n2.nabble.com/k3-NR-Audio-level-increase-tp2702048p2702048.html
Sent from the Elecraft mailing list archive at Nabble.com.

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Bill W4ZV

Re: k3 NR Audio level increase

N2TK wrote

Checked again the NB on CW and SSB on both rigs with 3.11. I do not see this
problem at all. Is it possible the AGC setup that does this?

Most likely it's due to setting RX EQ to positive settings for some bands:

http://www.mail-archive.com/elecraft@mailman.qth.net/msg71174.html

73, Bill

Joe Planisky

Re: k3 NR Audio level increase

In reply to this post by Don Wilhelm-4

Don,

Try this:

1. Set mode to CW, BW to 2.00, RX EQ = flat.

2. With no signal tuned in, hold NR and set to F4-4. Tap NR twice to
turn off NR.

3. Tune in an S9 signal, or better yet, use a signal generator (I use
an XG2).

4. Set RF gain to max, AF gain for a comfortable volume.

5. Tap NR to turn on noise reduction. (You might want to keep one hand
on the AF gain control :-)

On my K3 (with FW 3.11), turning on NR under these conditions boosts
the audio output voltage by 17.2 dB according to the built-in AFV meter.

Using less aggressive NR parameters results in less of a boost, down
to 6.3 dB at F1-1.

Now tune in a weak signal (say, S3) and repeat the steps. The boost
is still there, but very much reduced (On my rig at S3 and NR=F4-4,
the boost is 6.3 dB, at NR=F1-1 it's 1.4 dB)

Now imagine trying to copy a signal that rapidly fades between S3 and
S9 with NR on.

73
--
Joe KB8AP

On Apr 25, 2009, at 4:35 AM, Don Wilhelm wrote:

> Terry,
>
> I do not experience anything like that on my K3. What NR parameters
> are
> you using?
> [...]
> 73,
> Don W3FPR
>
>
> G4POP wrote:
>> I see that the dramatic increase in audio level when NR is turned
>> on has been
>> mentioned a couple of times but I can find no solution for this
>> mentioned in
>> the forum and the latest firmware 3.11 has not cured it.
>> [...]
>> Terry G4POP
>>
>>

Gary, W7TEA

Re: k3 NR Audio level increase

Joe, following your instructions, I cannot duplicate this on my rig
listening to a S-9 signal. I do find that if AGC-THR is set
below 5, the audio drops significantly when initiating NR at
my preferred setting, 2-1. Decreasing the AGC SLP increases
the audio with NR engaged.

Gary W7TEA

<quote author="Joe Planisky">
Don,

Try this:

1. Set mode to CW, BW to 2.00, RX EQ = flat.

2. With no signal tuned in, hold NR and set to F4-4. Tap NR twice to
turn off NR.

73,

Gary W7TEA K3 #1001, #5763

Dave Hachadorian

Re: k3 NR Audio level increase

In reply to this post by Joe Planisky

----- Original Message -----
From: "Joe Planisky" <[hidden email]>
To: <[hidden email]>; <[hidden email]>
Cc: "G4POP" <[hidden email]>
Sent: Saturday, April 25, 2009 2:58 PM
Subject: Re: [Elecraft] k3 NR Audio level increase

> 1. Set mode to CW, BW to 2.00
---------------------------

If the snr is marginal, why would you set BW = 2.0?

Dave Hachadorian, K6LL
Yuma, AZ

.
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Joe Planisky

Re: k3 NR Audio level increase

The settings and steps are intended to demonstrate the issue, they're
not necessarily typical operating settings. Don had suggested that
perhaps the cause was related to using NR with a narrow bandwidth. I
wanted to demonstrate that it happens at wide bandwidth as well.

73
--
Joe KB8AP

On Apr 25, 2009, at 8:21 AM, Dave Hachadorian wrote:
>
>
> If the snr is marginal, why would you set BW = 2.0?
>
> Dave Hachadorian, K6LL
> Yuma, AZ

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Merv Schweigert

Re: k3 NR Audio level increase

In reply to this post by N2TK

I have the problem also for some time, it is signal strength
dependent, the signal must be loud enough and when you
hit the NR function with a high setting the audio increases
greatly, Easiest way to prove it is with a variable strength
signal fed into the receiver and setting the NR to a setting
if 4. Will clean your ears out for sure. It does it on other
settings as well but less of an audio increase.
By the way thats not how an audio peak filter works if thats
what its trying to simulate.

Merv KH7C

> Checked again the NB on CW and SSB on both rigs with 3.11. I do not see this
> problem at all. Is it possible the AGC setup that does this?
>
> 73,
> N2TK, Tony
> #311
> #1435
>
> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of G4POP
> Sent: Saturday, April 25, 2009 4:04 AM
> To: [hidden email]
> Subject: [Elecraft] k3 NR Audio level increase
>
>
> I see that the dramatic increase in audio level when NR is turned on has
> been
> mentioned a couple of times but I can find no solution for this mentioned in
> the forum and the latest firmware 3.11 has not cured it.
>
> At this point I find NR totally un-usable unless I want to risk perforated
> ear drums!
>
> Terry G4POP
>

Joe Planisky

Re: k3 NR Audio level increase

In reply to this post by Gary, W7TEA

Good catch, Gary. AGC settings are the missing piece and probably why
some people aren't seeing this. With an S9 signal, NR=F4-4, BW=2.00,
I get the following results for different settings of AGC THR and AGC
SLP when NR is engaged:

THR=2, SLP= 0 +10.0 dB
THR=2, SLP= 5 + 2.7 dB
THR=2, SLP=10 - 6.0 dB
THR=2, SLP=15 -15.5 dB

THR=4, SLP= 0 +15.2 dB
THR=4, SLP= 5 + 9.6 dB
THR=4, SLP=10 + 3.6 dB
THR=4, SLP=15 - 3.8 dB

THR=6, SLP= 0 +16.6 dB
THR=6, SLP= 5 +13.3 dB
THR=6, SLP=10 + 7.9 dB
THR=6, SLP=15 + 1.5 dB

THR=8, SLP= 0 +18.3 dB
THR=8, SLP= 5 +15.6 dB
THR=8, SLP=10 +11.7 dB
THR=8, SLP=15 + 7.0 db

73
--
Joe KB8AP

On Apr 25, 2009, at 8:21 AM, W7TEA wrote:

>
> Joe, following your instructions, I cannot duplicate this on my rig
> listening to a S-9 signal. I do find that if AGC-THR is set
> below 5, the audio drops significantly when initiating NR at
> my preferred setting, 2-1. Decreasing the AGC SLP increases
> the audio with NR engaged.
>
> Gary W7TEA
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Steve Ellington

Re: k3 NR Audio level increase

So where's the problem? Everything seems to be working properly. With a
high THR and low SLP, louder signals are LOUD and NR just helps make it more
obvious because there's not so much noise to distract your hearing.
Remember, AGC used to be called AVC Automatic Volume Control, back in the
old days. If you choose a high threshold, THR, that means that AVC does
almost nothing. AVC becomes MVW, manual volume control, ....Meaning knobs
must be turned (AF).
Steve Ellington
[hidden email]
----- Original Message -----
From: "Joe Planisky" <[hidden email]>
To: "W7TEA" <[hidden email]>
Cc: <[hidden email]>
Sent: Saturday, April 25, 2009 1:22 PM
Subject: Re: [Elecraft] k3 NR Audio level increase

> Good catch, Gary. AGC settings are the missing piece and probably why
> some people aren't seeing this. With an S9 signal, NR=F4-4, BW=2.00,
> I get the following results for different settings of AGC THR and AGC
> SLP when NR is engaged:
>
> THR=2, SLP= 0 +10.0 dB
> THR=2, SLP= 5 + 2.7 dB
> THR=2, SLP=10 - 6.0 dB
> THR=2, SLP=15 -15.5 dB
>
> THR=4, SLP= 0 +15.2 dB
> THR=4, SLP= 5 + 9.6 dB
> THR=4, SLP=10 + 3.6 dB
> THR=4, SLP=15 - 3.8 dB
>
> THR=6, SLP= 0 +16.6 dB
> THR=6, SLP= 5 +13.3 dB
> THR=6, SLP=10 + 7.9 dB
> THR=6, SLP=15 + 1.5 dB
>
> THR=8, SLP= 0 +18.3 dB
> THR=8, SLP= 5 +15.6 dB
> THR=8, SLP=10 +11.7 dB
> THR=8, SLP=15 + 7.0 db
>
> 73
> --
> Joe KB8AP
>
>
> On Apr 25, 2009, at 8:21 AM, W7TEA wrote:
>
>>
>> Joe, following your instructions, I cannot duplicate this on my rig
>> listening to a S-9 signal. I do find that if AGC-THR is set
>> below 5, the audio drops significantly when initiating NR at
>> my preferred setting, 2-1. Decreasing the AGC SLP increases
>> the audio with NR engaged.
>>
>> Gary W7TEA
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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G4POP

Re: k3 NR Audio level increase

In reply to this post by N2TK

I am talking about SSB with a bandwidth between 1k and 3.5k ( I have the 250, 1k, 1.8k, 2.7k & 6K filters installed)

No mater what NR setting is used I get the same effect to a lesser or grater degree

Strange that some of you have this problem while others do not?

Terry

N2TK wrote

Checked again the NB on CW and SSB on both rigs with 3.11. I do not see this
problem at all. Is it possible the AGC setup that does this?

73,
N2TK, Tony
#311
#1435

-----Original Message-----
From: elecraft-bounces@mailman.qth.net
[mailto:elecraft-bounces@mailman.qth.net] On Behalf Of G4POP
Sent: Saturday, April 25, 2009 4:04 AM
To: elecraft@mailman.qth.net
Subject: [Elecraft] k3 NR Audio level increase

I see that the dramatic increase in audio level when NR is turned on has
been
mentioned a couple of times but I can find no solution for this mentioned in
the forum and the latest firmware 3.11 has not cured it.

At this point I find NR totally un-usable unless I want to risk perforated
ear drums!

Terry G4POP
--
View this message in context:
http://n2.nabble.com/k3-NR-Audio-level-increase-tp2702048p2702048.html
Sent from the Elecraft mailing list archive at Nabble.com.

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Joe Subich, W4TV-4

Re: k3 NR Audio level increase

In reply to this post by Steve Ellington

> So where's the problem? Everything seems to be working
> properly. With a high THR and low SLP, louder signals
> are LOUD and NR just helps make it more obvious because
> there's not so much noise to distract your hearing.

It's not working as it should ... there should be no volume
change when engaging NR. Noise reduction should work on the
audio AFTER AGC. If anything, the test results below should
show a very slight drop with NR due to the removal of the
unwanted (broadband) components but the peak level should
not change.

This NR problem is the flip side of the issue with the notch
filter ... Notch is working AFTER the AGC where it should
work before AGC while NR is working before the AGC where it
should work AFTER the AGC.

73,

... Joe, W4TV

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Steve Ellington
> Sent: Saturday, April 25, 2009 2:00 PM
> To: Joe Planisky; W7TEA
> Cc: [hidden email]
> Subject: Re: [Elecraft] k3 NR Audio level increase
>
>
> So where's the problem? Everything seems to be working
> properly. With a
> high THR and low SLP, louder signals are LOUD and NR just
> helps make it more
> obvious because there's not so much noise to distract your hearing.
> Remember, AGC used to be called AVC Automatic Volume Control,
> back in the
> old days. If you choose a high threshold, THR, that means
> that AVC does
> almost nothing. AVC becomes MVW, manual volume control,
> ....Meaning knobs
> must be turned (AF).
> Steve Ellington
> [hidden email]
> ----- Original Message -----
> From: "Joe Planisky" <[hidden email]>
> To: "W7TEA" <[hidden email]>
> Cc: <[hidden email]>
> Sent: Saturday, April 25, 2009 1:22 PM
> Subject: Re: [Elecraft] k3 NR Audio level increase
>
>
> > Good catch, Gary. AGC settings are the missing piece and
> probably why
> > some people aren't seeing this. With an S9 signal,
> NR=F4-4, BW=2.00,
> > I get the following results for different settings of AGC
> THR and AGC
> > SLP when NR is engaged:
> >
> > THR=2, SLP= 0 +10.0 dB
> > THR=2, SLP= 5 + 2.7 dB
> > THR=2, SLP=10 - 6.0 dB
> > THR=2, SLP=15 -15.5 dB
> >
> > THR=4, SLP= 0 +15.2 dB
> > THR=4, SLP= 5 + 9.6 dB
> > THR=4, SLP=10 + 3.6 dB
> > THR=4, SLP=15 - 3.8 dB
> >
> > THR=6, SLP= 0 +16.6 dB
> > THR=6, SLP= 5 +13.3 dB
> > THR=6, SLP=10 + 7.9 dB
> > THR=6, SLP=15 + 1.5 dB
> >
> > THR=8, SLP= 0 +18.3 dB
> > THR=8, SLP= 5 +15.6 dB
> > THR=8, SLP=10 +11.7 dB
> > THR=8, SLP=15 + 7.0 db
> >
> > 73
> > --
> > Joe KB8AP
> >
> >
> > On Apr 25, 2009, at 8:21 AM, W7TEA wrote:
> >
> >>
> >> Joe, following your instructions, I cannot duplicate this
> on my rig
> >> listening to a S-9 signal. I do find that if AGC-THR is
> set below 5,
> >> the audio drops significantly when initiating NR at my preferred
> >> setting, 2-1. Decreasing the AGC SLP increases the audio with NR
> >> engaged.
> >>
> >> Gary W7TEA
> > ______________________________________________________________
> > 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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Don Wilhelm-4

Re: k3 NR Audio level increase

In reply to this post by Joe Planisky

Joe,

I tried your suggested settings, and yes I found an increase in audio
volume. I also observed that the NR worked as a squelch at that
aggressive setting. I normally use F1-3 or F1-4 for NR and have no
problem.

I don't use NR when attempting to copy a weak signal. When the weak
signal is down in the noise level, the NR algorithm cannot distinguish
between the noise and the signal with certainty. My ears do a better
job despite the noise, so I turn NR off when digging for the weak ones.

73,
Don W3FPR

Joe Planisky wrote:

> Don,
>
> Try this:
>
> 1. Set mode to CW, BW to 2.00, RX EQ = flat.
>
> 2. With no signal tuned in, hold NR and set to F4-4. Tap NR twice to
> turn off NR.
>
> 3. Tune in an S9 signal, or better yet, use a signal generator (I use
> an XG2).
>
> 4. Set RF gain to max, AF gain for a comfortable volume.
>
> 5. Tap NR to turn on noise reduction. (You might want to keep one hand
> on the AF gain control :-)
>
> On my K3 (with FW 3.11), turning on NR under these conditions boosts
> the audio output voltage by 17.2 dB according to the built-in AFV meter.
>
> Using less aggressive NR parameters results in less of a boost, down
> to 6.3 dB at F1-1.
>
> Now tune in a weak signal (say, S3) and repeat the steps. The boost
> is still there, but very much reduced (On my rig at S3 and NR=F4-4,
> the boost is 6.3 dB, at NR=F1-1 it's 1.4 dB)
>
> Now imagine trying to copy a signal that rapidly fades between S3 and
> S9 with NR on.
>
> 73
> --
> Joe KB8AP
>
>

Bob Cunnings NW8L

Re: k3 NR Audio level increase

In reply to this post by Joe Subich, W4TV-4

Apparently NR *is* upstream of AGC, since a while back NR was
disallowed unless AGC was enabled [1] in order, according to K2VCO, to
prevent instability [2].

By the way, I can observe this instability (a "wup-wup" oscillation)
in LSB/USB modes with an S9 carrier, and AGC settings on the "light"
side (high threshold, low slope, with THR=8 and SLP=0 being the
extreme). I ran into this tuning through shortwave BC stations with NR
enabled with THR and SLP set to 5. I'm using firmware version 3.11.

What seems odd to me is that although I can reproduce the audio level
increase cases observed by others when NR is enabled, the S-meter
indication doesn't change - I suppose that the S-meter pickoff point
is upstream of NR?

On the flip side you mention, if notch filtering was before AGC as you
wish, would you expect the S-meter indication to change when the notch
filter is active?

Bob NW8L

[1] http://www.mail-archive.com/elecraft@.../msg58245.html
[2] http://www.mail-archive.com/elecraft@.../msg60930.html

On Sat, Apr 25, 2009 at 12:55 PM, Joe Subich, W4TV <[hidden email]> wrote:

>
> It's not working as it should ... there should be no volume
> change when engaging NR. Noise reduction should work on the
> audio AFTER AGC. If anything, the test results below should
> show a very slight drop with NR due to the removal of the
> unwanted (broadband) components but the peak level should
> not change.
>
> This NR problem is the flip side of the issue with the notch
> filter ... Notch is working AFTER the AGC where it should
> work before AGC while NR is working before the AGC where it
> should work AFTER the AGC.
>
> 73,
>
> ... Joe, W4TV
>

Joe Planisky

Re: k3 NR Audio level increase

In reply to this post by Steve Ellington

Heh. My voltmeter's hearing doesn't tend to get distracted by noise.

On Apr 25, 2009, at 11:00 AM, Steve Ellington wrote:

> So where's the problem? Everything seems to be working properly.
> With a high THR and low SLP, louder signals are LOUD and NR just
> helps make it more obvious because there's not so much noise to
> distract your hearing. Remember, AGC used to be called AVC Automatic
> Volume Control, back in the old days. If you choose a high
> threshold, THR, that means that AVC does almost nothing. AVC becomes
> MVW, manual volume control, ....Meaning knobs must be turned (AF).
> Steve Ellington
> [hidden email]
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Steve Ellington

Re: k3 NR Audio level increase

In reply to this post by Don Wilhelm-4

Interesting. For CW I always use the NR to dig out the weak ones. The effect
is amazing. I believe the reason we all see this differently is due to AGC
settings. THR, SLP etc. really affect the NR.
Steve Ellington
[hidden email]
----- Original Message -----
From: "Don Wilhelm" <[hidden email]>
To: "Joe Planisky" <[hidden email]>
Cc: <[hidden email]>
Sent: Saturday, April 25, 2009 5:14 PM
Subject: Re: [Elecraft] k3 NR Audio level increase

> Joe,
>
> I tried your suggested settings, and yes I found an increase in audio
> volume. I also observed that the NR worked as a squelch at that
> aggressive setting. I normally use F1-3 or F1-4 for NR and have no
> problem.
>
> I don't use NR when attempting to copy a weak signal. When the weak
> signal is down in the noise level, the NR algorithm cannot distinguish
> between the noise and the signal with certainty. My ears do a better
> job despite the noise, so I turn NR off when digging for the weak ones.
>
> 73,
> Don W3FPR
>
> Joe Planisky wrote:
>> Don,
>>
>> Try this:
>>
>> 1. Set mode to CW, BW to 2.00, RX EQ = flat.
>>
>> 2. With no signal tuned in, hold NR and set to F4-4. Tap NR twice to
>> turn off NR.
>>
>> 3. Tune in an S9 signal, or better yet, use a signal generator (I use
>> an XG2).
>>
>> 4. Set RF gain to max, AF gain for a comfortable volume.
>>
>> 5. Tap NR to turn on noise reduction. (You might want to keep one hand
>> on the AF gain control :-)
>>
>> On my K3 (with FW 3.11), turning on NR under these conditions boosts
>> the audio output voltage by 17.2 dB according to the built-in AFV meter.
>>
>> Using less aggressive NR parameters results in less of a boost, down
>> to 6.3 dB at F1-1.
>>
>> Now tune in a weak signal (say, S3) and repeat the steps. The boost
>> is still there, but very much reduced (On my rig at S3 and NR=F4-4,
>> the boost is 6.3 dB, at NR=F1-1 it's 1.4 dB)
>>
>> Now imagine trying to copy a signal that rapidly fades between S3 and
>> S9 with NR on.
>>
>> 73
>> --
>> Joe KB8AP
>>
>>
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Don Wilhelm-4

Re: k3 NR Audio level increase

Steve,

My AGC THR is 008 and the SLP is 02 if that makes any difference to your
conclusions.
FWIW, a narrow bandwidth with NR off is best for weak signal reception
for me. The narrow bandwidth itself reduces the noise substantially and
my ears have to do the rest.

73,
Don W3FPR

Steve Ellington wrote:
> Interesting. For CW I always use the NR to dig out the weak ones. The effect
> is amazing. I believe the reason we all see this differently is due to AGC
> settings. THR, SLP etc. really affect the NR.
> Steve Ellington
> [hidden email]
>
>
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Bob Cunnings NW8L

Re: k3 NR Audio level increase

In reply to this post by Bob Cunnings NW8L

I've only just now noticed that the "oscillation" when NR is enabled
that I hear when tuning through an S9 carrier in USB/LSB happens only
when VOX is enabled. In fact, I just now noticed that the red TX
indicator is illuminated when this happens - although there is no
indication of power out on either the K3 or the outboard power meter.

So with AGC SLP=5, THR=5, NR enabled, VOX enabled, tuning through S9
carrier triggers this on USB/LSB, but not CW.

Very strange.

Bob NW8L

On Sat, Apr 25, 2009 at 3:20 PM, Bob Cunnings <[hidden email]> wrote:

> Apparently NR *is* upstream of AGC, since a while back NR was
> disallowed unless AGC was enabled [1] in order, according to K2VCO, to
> prevent instability [2].
>
> By the way, I can observe this instability (a "wup-wup" oscillation)
> in LSB/USB modes with an S9 carrier, and AGC settings on the "light"
> side (high threshold, low slope, with THR=8 and SLP=0 being the
> extreme). I ran into this tuning through shortwave BC stations with NR
> enabled with THR and SLP set to 5. I'm using firmware version 3.11.
>
> What seems odd to me is that although I can reproduce the audio level
> increase cases observed by others when NR is enabled, the S-meter
> indication doesn't change - I suppose that the S-meter pickoff point
> is upstream of NR?
>
> On the flip side you mention, if notch filtering was before AGC as you
> wish, would you expect the S-meter indication to change when the notch
> filter is active?
>
> Bob NW8L
>
> [1] http://www.mail-archive.com/elecraft@.../msg58245.html
> [2] http://www.mail-archive.com/elecraft@.../msg60930.html
>
> On Sat, Apr 25, 2009 at 12:55 PM, Joe Subich, W4TV <[hidden email]> wrote:
>>
>> It's not working as it should ... there should be no volume
>> change when engaging NR. Noise reduction should work on the
>> audio AFTER AGC. If anything, the test results below should
>> show a very slight drop with NR due to the removal of the
>> unwanted (broadband) components but the peak level should
>> not change.
>>
>> This NR problem is the flip side of the issue with the notch
>> filter ... Notch is working AFTER the AGC where it should
>> work before AGC while NR is working before the AGC where it
>> should work AFTER the AGC.
>>
>> 73,
>>
>> ... Joe, W4TV
>>
>