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
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