It seems that a lot of people confuse noise Blanking and Noise Rejection.
NOISE BLANKER (NB)
My NB is extremely effective on ignition noise and my neighbor's weed
eating electric fence. The S9+ fence disappears and with not much
distortion.
I am not sure what the difference between the so called Hardware and the
Software options are, but sometimes one seems to work better than the
other. NB is effective against very short impulse type noise that can
be somewhat irregular. NB does not work on band noise but does
sometimes help static crashes.
Usually older hardware implementations have a separate wide bandwidth
detector near the front of the receiver and if an impulse is detected, a
switch shuts off the signal path near the front end for a short period
of time. In effect, it puts a hole in the signal reception to prevent
the pulse from getting spread by the narrow band filters and detectors.
If a system has sufficient dynamic range to not be saturated by the
impulse then the impulse can be identified in one signal path and used
to blank a second delayed signal that you then use for detection. This
approach can completely remove the short impulse from the signal you hear.
It works very well. Sometimes my electric fence is S9+. The NB makes
it disappear into the S1 to 3 background. I often have to set it at 8
or 9. The Orion V2.059d is better than my K2 and that is pretty good.
NOISE REJECTION
The Noise Rejection is an attempt to remove background noise and
everything else that is not signal. There are many different algorithms
for this. It works better if the bandwidth is set larger than the
signal bandwidth so the algorithm can get a grip on the noise in order
to remove it.
It is not just a BW reduction approach although sometimes it sounds that
way. TT has tried several different schemes. I am not sure how the
current approach works on cw. It works quite well on weak SSB and often
makes an unreadable signal pop out of the noise, although it sounds a
bit distorted. I am not sure that it works that much better than
adjusting the threshold and Bandwidth just right but it is a lot quicker.
NR does not work on impulse noise and other stuff that may saturate the
filters or detectors.
I like the idea of identifying the noise and subtracting it from the
signal. I think it works and will work better in the future. I thought
it worked better on a earlier version but it worked poorly on some of
the interim versions. It is better now in V2.059d but more distortion
than I like on SSB.
Aloha,
John KH7T
The
Max wrote:
> /Just some thoughts....could not handle the clumsiness of the
> 1.3..however ext T/R delay is rite on.../
> /on the 2.059d if you set the T/R at max (100) and the QSK delay at
> 100 the transmitter will switch over and u sit there and have to wait
> for the qsk to switch...on the 1.xxx versions they were pretty much in
> line./
> /Q: does the Digital NB do anything???I have been operating without it
> and there is no difference. Should it work independently of the NR?/
> /This is hard to tell but I find the hardware NB to be less effective
> in the 2.XXX version. ( am I dreaming?)./
> //
> /Don't do SSB. so no feed back from me./
> /73/
> /Max/
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