[Elecraft] k3 NR Audio level increase

[Steve Ellington]

Bob
When in USB/LSB, NR does tend to totally null out carriers. CW does make 
that "wup-wup" sound as it's notched out. I'm not sure why NR would be 
acting as an "Auto Notch" but this does seem to be the case.
Don't know about your red light...Do you have a mic connected?

Steve Ellington
N4LQ at carolina.rr.com
----- Original Message ----- 
From: "Bob Cunnings" <bob.cunnings at gmail.com>
To: <Elecraft at mailman.qth.net>
Sent: Saturday, April 25, 2009 7:39 PM
Subject: Re: [Elecraft] k3 NR Audio level increase


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 <bob.cunnings at gmail.com> 
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@mailman.qth.net/msg58245.html
> [2] http://www.mail-archive.com/elecraft@mailman.qth.net/msg60930.html
>
> On Sat, Apr 25, 2009 at 12:55 PM, Joe Subich, W4TV <lists at subich.com> 
> 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
>>
>
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