[Elecraft] KNB2 - odd behavior

[Vic Rosenthal]

David Zatopek KT5V wrote:

> During SS this past weekend, I QSYed to a well-load 40 late Sunday and
> noticed an impressive and unusual level of S9 noise.  The NB1 was on at the
> time of the QSY (HI THRU).  The DSP denoiser and a tighting of filters
> helped, but the noise was pervasive and still S5.  On whim, I turned off the
> noise blanker and voila...no more noise (well no more than usual for my
> neighborhood).  Turned the blanker back on...noise level back up.  No
> difference between NB1 and NB2 and Hi/Low thru settings
> 
> I played with this some more with the same result.  Continued with the
> remainder of the contest.  Today, after turning the radio back on, I've not
> been able to duplicate the problem with any combination of NB or DSP setting
> tried so far.  Only difference, 40 CW is almost empty of signals here in TX
> tonight.  Any insights?

The NB can produce spurious signals when there are loud signals on the band.  In 
the contest, there were so many loud signals that the usual symptom -- sort of a 
  brapp brapp that follows the keying of the strong signal was replaced with an 
almost continuous noise.  In order for a noise blanker to work it needs to pick 
up signals over a wide bandwidth.  Turning on the noise blanker has a very 
severe effect on the receiver's dynamic range, which is why it's possible to 
turn it off!

-- 
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco