The reflector [and I] have received several messages with links to various
sites that write about synchronous noise blankers. My original question was
directed at finding out if anyone on the reflector currently had fabricated
and used such a device. I am still hoping that someone will appear who has
done so.
I want to add to the links presented previously one that is to an article in
the Longwave [LWCA] Home Page library. This link is to a very interesting
and well written article that discusses listening methodology for NDB'
[non-directional beacons] which are found below 500 kHz or so. The folks who
have an interest in hearing these beacons have been working on methods to
minimize the effect of power line [and other] noise on their listening
frequencies for some time. The discussion covers material that we generally
do not see in the ARRL books and the ON4UN book. In Chapter 6 of this
article Sheldon Remington, KH6SR, covers synchronous noise blankers and
provides some references and a circuit diagram for generating the control
pulse for such blanking.
http://lwca.org/library/articles/kh6sr/index.htm
In his article he implies that one can use the noise blanking circuits
already in a receiver, but control the blanking by an externally generated
synchronous blanking control pulse. He implies this will be more effective
than using the internally generated control pulse. It may be that one does
not want to dig into one's radio but still wishes to blank noise pulses.
Happily, John Reed, KA5QEP, has produced another article in the same library
that discusses building an external circuit that will "slice" the offending
pulses out of the RX input signal as it goes to the receiver. It uses the
same synchronous control generator as the Remington article.
http://www.lwca.org/library/articles/jtreed/gate/gate1b.htm
The parts and circuitry look simple to acquire and fabricate. I would
suspect that it would work excellently to remove electric fence pulses from
beverage inputs and other RX antennas that we employ, as well as perhaps
removing other significant spikes that plague us on Topband. Unfortunately,
so far that is all I have -- a suspicion . In the interest of not
reinventing the wheel and in finding out why something that looks good
doesn't work well without me having to fabricate it I posted my question. My
first Law of Life is => "Trauma Teaches [but it doesn't have to be your
Trauma]".
Again, if anyone has tried something like this I really would appreciate
hearing your assessment of its value for you.
Tod, K0TO
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