From: "Gene McCalmont" 
Subject: RE: [drakelist] 4-NB Noise Blanker
Organization: RowdyHD Inc.


"Gene McCalmont"  made an utterence to the
drakelist gang
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Hi Al;
I'm sure you'll get lots of responses to this one, but it's cold and rainy
outside and warm here in the shack (the L-4B is a real nice space heater).
so, here are my thoughts.

The 4-NB is one of the best hardware based noise blankers I've experienced
on any radio including my new Orion. Like all hardware based blankers, it
works best on repetitive short duration pulse type noise, such as with auto
ignition or pulse type electrical line noise, say from an electrical motor.

It will not work on "white" or "pink" atmospheric noise
such as you would
expect a DSP unit to handle. It will be only marginally effective on long
duration pulse noise such as with electrical static from a nearby
thunderstorm.

Another nice feature of the 4-NB is that it can be "tuned" to your
individual rig. In fact, it must be tuned to your rig to operate correctly
and tuning is an easy enough process. Insertion of the 4-NB will cause some
minor signal loss, but most owners find it negligible.

The 4-NB works best with a first IF bandwidth of at least 8K. Use of
narrower first IF filters can lead to "AGC Pumping" which will effectively
desense the receiver in the presents of strong signals. The 4-NB WILL induce
distortion products when listening to very strong signals or in the presents
of strong adjacent signals in the 8K passband.

Also, there have been reports of the cable to the receiver shorting and
wiping out your second stage IF section. Shorting is most prevalent at the
cable/plug connection rather than internal to the receiver or the 4-NB. I
should suggest that you very carefully inspect the cable/plug solder
connection to make sure that there are NO possibilities of a short as the
cable is twisted to mate the plug with the receiver. The second IF FETs are
difficult to source and replace and the dual gate FET on the first
generation of R-4Cs is "unobtanium", although a NEC near equivalent is
available.

You should note as well that there were several "versions" of the 4-NB
available. All of the versions were essentially the same electrically. The
only real difference was the board to receiver cable connection points,
length and route. The "lighter color" (a lighter shade of green
)
with a shorter cable was made for the earlier generation R-4Cs without the
top shield. The darker green boards, with longer cables and different
connection point on circuit board were specific for the later R-4Cs with the
top shield. The longer cable was required to clear the shield and internal
AM filter mount. Either board will work with either generation R-4C,
however, you will find it difficult to route the shorter cable to the later
generation R-4C.

Hope all this helps.

Best regards;
Gene

W5DDW
Gene McCalmont
270 Oak Ridge Ln.
Argyle Texas 76226

n7ioh  made an utterence to the drakelist gang
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    I have been looking into buying the 4-NB for my R-4C.  My questions, how
well does this thing work and for what kind of noise is it best suited for. 
                                                 Thanks, Al, N7IOH

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