[Elecraft] Noise Blanker

[Ron D'Eau Claire]

The Noise Blanker does a GREAT job with high amplitude, fast-rise-time
impulse noise. It counts on a very sharp leading edge on the noise
pulses to 'trigger' it. That's how it discriminates between noise and
signal. A lot of noise lacks the fast rise time needed to trigger it. 

Auto ignition noise is a great example of the sort of noise that it will
kill effectively, although I've found that a lot of what sounds like
"hash" on the lower bands is also handled by the KNB2 very nicely. It's
not always obvious what noise has the requisite waveform just by
listening to it. 

The noise blanker literally punches "holes" in the signal path, turning
off the signals for a brief period during each noise pulse. That sort of
action creates artifacts of its own that can show up as other forms of
noise and distortion. That's why Elecraft cautions users to leave the
noise blanker OFF whenever it is not needed. I'm not certain that is
what is causing your odd sounds, but it's something to consider. Does
the KNB2 add the noise with a dummy load connected to the K2 antenna
input? 

Ron AC7AC
K2 # 1289

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"Postal Guy" wrote:
  Although I'm still very impressed and satisfied with my new K2, I've
yet to notice much of a difference in using the Noise Blanker. I could
'see' a slight difference using the Spectrogram program but could not
hear much of one. Switching to hi or low threshold did'nt change much of
anything either. I just thought that maybe there was'nt any electrical
noise to filter out around here.
  
  Unrelated to the KNB2, after seeing the suggestion about swapping out
the R1 resistor (control board), I changed mine to 49k and heard some
improvement, (and still found little use for the KNB2), so I changed it
again to 39k and can hear even more of an improvement.

  However, now when I try the KNB2, it actually ADDS interference noise.
In hi-threshold, it adds some clicking/popping sounds; in lo-threshold,
it adds a "roaring hiss" sound. Not that I really found a need to use it
anyway, but has anyone else experienced this? So far I dont mind the
trade-off, but I would like to see a remedy for this, other than going
back to the 51k value.