[Elecraft] Noise blanker and APF test recording

[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
> 
> 
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