This is a HUGE subject. I expect that most of the comments will be
subjective descriptions of how well a noise blanker worked for a
particular person in a particular location, on various kinds of noise.
It would be nice if we also had some details about the real workings of
the noise blankers. For example, I can think of perhaps four ways to
describe how each noise blanker works.
How is the blanking triggered? From a pulse detector in the IF of the
same receiver the blanking is done in, or in a dedicated noise receiver?
(In almost every amateur rig it will be the former, but this is not
necessarily the best way to do it)
Is the triggering threshold adjustable? Or can it be changed a bit using
selected resistor values?
Is the delay from the trigger to the blanking fixed, and what is the
delay? Or is it adjustable.
Is the duration of the blanking fixed, and what is it? Or is it adjustable?
Where is the blanking done, and how much is the signal attenuated during
the blanking? If the blanking occurs after many gain stages and filters,
the noise can get spread out in time and require a longer duration
blanking than if the blanking was done at at earlier stage in the signal
chain. In most every amateur transceiver the noise blanker will be in
the IF system long after a strong noise pulse can distorted and spread
out. It would be better to have the blanker right at the antenna input,
but then of course the triggering would have to be done with a dedicated
noise receiver. What sort of envelope shape does the blanking have as it
turns on and off.
And here is another that just occurred to me: Does some characteristic
of the triggering, such as the noise pulse amplitude, dynamically change
the delay or duration of the blanking?
Just some things to ponder. Much of what I have mentioned is not
applicable to amateur equipment, but we can dream. The questions of
delay and duration of the blanking are relevant and can be determined
with the right instrumentation.
DE N6KB
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