NB/NR Noise Blanker/ Noise reduction

[Deni F5VJC]

Yes let's not get this confused... the K3 NB (Noise Blanker) does a
great job with impulse noise from my  local electric fence QRM.

However,  the NR (Noise reduction) always seems to reduce the audio and
does very little to enhance the recovered audio.

This is my subjective opinion.
--
73, Deni
F5VJC



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[Steve Ellington]

This is amazing....We have some who complain about NR increasing the audio
and some complaining about it reducing audio!
I think the K3's NR is the best I've seen thus far. Contrary to some
"experts" opinion, it works great with narrow cw filters and not only
reduces noise but "Peaks" the CW signals. Someone said it makes CW "mushy".
I say it does just exactly the opposite. It sharpens the AF response and
enhances CW, especially weak signals that are down at the noise floor.
Have had a lot of rigs, the IC-7800's NR is pretty good too. The PRO series
NR is terrible. Keep in mind I'm talking about CW here. Keep that AGC
threshold up high and the SLP low....It makes the NR really bring up those
CW signals nice and LOUD like they should be.
N4LQ
Steve Ellington
[hidden email]
----- Original Message -----
From: "Deni" <[hidden email]>
To: <[hidden email]>
Sent: Monday, April 27, 2009 6:18 PM
Subject: [Elecraft] NB/NR Noise Blanker/ Noise reduction

> Yes let's not get this confused... the K3 NB (Noise Blanker) does a
> great job with impulse noise from my  local electric fence QRM.
>
> However,  the NR (Noise reduction) always seems to reduce the audio and
> does very little to enhance the recovered audio.
>
> This is my subjective opinion.
> --
> 73, Deni
> F5VJC
>
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>
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> Please help support this email list: http://www.qsl.net/donate.html 

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[Deni F5VJC]

Yes you're right Steve!

After reading your comments below,  I have now set my AGC THR high and
SLP low, this REALLY does improve the NR function on both CW and SSB.
(previously I had my AGC settings more or less at default values)
Maybe others may wish to try this.

Thanks.

73, Deni
F5VJC

Steve Ellington wrote:

> This is amazing....We have some who complain about NR increasing the
> audio and some complaining about it reducing audio!
> I think the K3's NR is the best I've seen thus far. Contrary to some
> "experts" opinion, it works great with narrow cw filters and not only
> reduces noise but "Peaks" the CW signals. Someone said it makes CW
> "mushy". I say it does just exactly the opposite. It sharpens the AF
> response and enhances CW, especially weak signals that are down at the
> noise floor.
> Have had a lot of rigs, the IC-7800's NR is pretty good too. The PRO
> series NR is terrible. Keep in mind I'm talking about CW here. Keep that
> AGC threshold up high and the SLP low....It makes the NR really bring up
> those CW signals nice and LOUD like they should be.
> N4LQ
> Steve Ellington
> [hidden email]

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[Deni F5VJC]

Hello Gordan, well my AGC settings are now THR 008 and SLP 000

I'm not saying this is best or optimum but it certainly improves the
action of NR.
I'm still experimenting, but found ( thanks to Steve), that the default
AGC values for me gave ineffective NR.

Be aware that you may find strong signals could be too loud with these
AGC settings.
I use my RF gain control,  and usually it's between 11 and 1 .

73, Deni
F5VJC

Gordan Hribar wrote:
 > Hello Deni!
 >
 > Please could you repeat again this AGC settings?
 >
 > 73,
 > E72X, Gordan,
 >
 > --- On *Tue, 4/28/09, Deni /<[hidden email]>/* wrote:
 >
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[GW0ETF]

If I look at the audio response in Spectrogram while feeding in a noise source at the antenna the trace shows definite nulls when NR is switched in. In SSB at max width (2.7kHz) the number of nulls vary with the settings as follows:
F1-# 9
F2-# 7
F3-# 4
F4-# 3

As # is increased from 1 to 4 at each F setting the depth of the nulls decreases and it's almost flat at #4. However RF gain and AGC slope settings drastically affect the depth of these nulls but at maximum the nulls are about -30db which would presumably affect the 'loudness' of a signal if it happened to fall in one of the holes? I don't have time at the moment to investigate further how the AGC settings affect the nulls but backing off the RF gain definitely flattens the response.

According to Lyle back in 2007 the F parameter indicated the number of taps (?) in the adaptive filter and the second number the amount of signal 'bleed through' to reduce distortion effects. I'm not sure my limited knowledge of dsp and filters ties this in with what I see in Spectrogram.....

Having said this I must admit I tend to use filtering in preference to NR even though I seem to be able to get NR to work pretty well.

73,

Stewart Rolfe, GW0ETF

Steve Ellington wrote

This is amazing....We have some who complain about NR increasing the audio
and some complaining about it reducing audio!........