Noise blanker and APF test recording

[wayne burdick]

A brief K4 audio sample can be downloaded using the link at the end of this email.

This recording hows how the new K4 noise blanker algorithm can reveal a signal buried under loud noise. It also highlights the effectiveness of the audio-peaking filter (APF) when listening to a very weak CW signal.

This was recorded on 17 meters, CW mode, in a 1 kHz bandwidth. Both receivers are turned on, tuned to the same frequency, and the recording is stereo. There's a slight delay between main and sub RX audio as the settings change; this is due to tapping A>B to copy the main RX NB and APF settings to the sub RX.

Things to listen for (T in seconds):

T0:    S-9 noise masking very weak carrier

T7:    Noise blanker turned on so that only atmospheric noise remains; carrier now barely audible

T14:   APF turned on, 30 Hz BW; carrier clearly audible

T23:   Carrier disappears, leaving band noise only

http://ftp.elecraft.com/K4/K4_audio_samples/K4%20NB%20demo%201.mp3

73,
Wayne
N6KR


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[Drew AF2Z]

Thanks, Wayne. The effectiveness of the K4 NB will be a major factor for
me.

FWIW, I have found the K3 NB to be vital in my locality and have
depended on it a lot (for hundreds of CW QSOs in the recent SKCC event),
its major fault being key "clicks" from adjacent CW signals leaking
through when NB is engaged. I'm wondering how well the K4 handles nearby
signals when the NB is on, compared to the K3.

Also, I'm wondering how well the K4 NB might handle real key clicks
produced by mis-adjusted transmitters, of which there seem to be many
these days.

73,
Drew
AF2Z


On 02/22/21 16:14, Wayne Burdick wrote:

> A brief K4 audio sample can be downloaded using the link at the end of this email.
>
> This recording hows how the new K4 noise blanker algorithm can reveal a signal buried under loud noise. It also highlights the effectiveness of the audio-peaking filter (APF) when listening to a very weak CW signal.
>
> This was recorded on 17 meters, CW mode, in a 1 kHz bandwidth. Both receivers are turned on, tuned to the same frequency, and the recording is stereo. There's a slight delay between main and sub RX audio as the settings change; this is due to tapping A>B to copy the main RX NB and APF settings to the sub RX.
>
> Things to listen for (T in seconds):
>
> T0:    S-9 noise masking very weak carrier
>
> T7:    Noise blanker turned on so that only atmospheric noise remains; carrier now barely audible
>
> T14:   APF turned on, 30 Hz BW; carrier clearly audible
>
> T23:   Carrier disappears, leaving band noise only
>
> http://ftp.elecraft.com/K4/K4_audio_samples/K4%20NB%20demo%201.mp3
>
> 73,
> Wayne
> N6KR
>
>
> ______________________________________________________________
> Elecraft mailing list
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>
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> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

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[wayne burdick]

I should have mentioned that the K4 also has a panadapter noise blanker that's very effective. It removes pulse noise that would otherwise cause the panadapter noise floor to rise, where it might obscure weak signals.

The display NB can be turned on automatically at the same time that the receiver blanker is turned on (AUTO setting), or turned on/off manually. Either way, the level settings for the display and receiver blankers are independent and per-band.

While recording the noise sample I just provided, I had the display NB on as well. It knocked the noise level on the panadapter down by about 20 dB. Weak signals could be clearly seen.

73,
Wayne
N6KR

>

> On Mon, Feb 22, 2021 at 2:15 PM Wayne Burdick <[hidden email]> wrote:
> A brief K4 audio sample can be downloaded using the link at the end of this email.
>
> This recording hows how the new K4 noise blanker algorithm can reveal a signal buried under loud noise. It also highlights the effectiveness of the audio-peaking filter (APF) when listening to a very weak CW signal.
>
> This was recorded on 17 meters, CW mode, in a 1 kHz bandwidth. Both receivers are turned on, tuned to the same frequency, and the recording is stereo. There's a slight delay between main and sub RX audio as the settings change; this is due to tapping A>B to copy the main RX NB and APF settings to the sub RX.
>
> Things to listen for (T in seconds):
>
> T0:    S-9 noise masking very weak carrier
>
> T7:    Noise blanker turned on so that only atmospheric noise remains; carrier now barely audible
>
> T14:   APF turned on, 30 Hz BW; carrier clearly audible
>
> T23:   Carrier disappears, leaving band noise only
>
> http://ftp.elecraft.com/K4/K4_audio_samples/K4%20NB%20demo%201.mp3
>
> 73,
> Wayne
> N6KR

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[Jim Brown-10]

On 2/22/2021 1:14 PM, Wayne Burdick wrote:
> This recording hows how the new K4 noise blanker algorithm can reveal a signal buried under loud noise.

Hi Wayne,

Have your beta testers (or other users accumulated any experience
blanking with any of K1JT's modes?  I've got a couple of solar farms as
neighbors that make weak signal work tough on 6M during the day, and
other sources in one of the homes that makes a mess during the evenings
(I suspect something home entertainment related). It's especially
problematic when trying to stretch meteor scatter to it's practical limit.

73, Jim K9YC
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