Noise Blanking is indeed a very interesting subject:
I have tested and measured different circuits for IF noise blanking and then
developed my own version of an effective noise blanker circuit for my home-brew
transceiver, the HBR-2000. You will find a description of some of my research
and my blanker design at
As much as I appreciate having a very good noise blanker, nothing takes the
place of eliminating the source of the noise. Particularly today with the over
abundance of switching power supplies radiating from nearly every house on your
block which most noise blanker do nothing for.
North Vancouver, BC CANADA
On Dec 24, 2013, at 11:40 AM, Ken Brown <firstname.lastname@example.org> wrote:
> 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
> DE N6KB
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