From: gwt 
Subject: Re: [drakelist] 4-NB Noise Blanker


gwt  made an utterence to the drakelist gang
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I second Gene's comments. The BEST hardware based noise blanker in 
existence! It was the reason I bought my Drake twins back in '79. Back 
then I lived in the big city where line noise was the order of the day. 
Being a 160M guy, and wanting to have a chance to work SSB DX, I bought 
a used set of twins. Best move I ever made! It opened up new horizons 
for me as far as weak signal reception went.
I now own two sets of "C lines" and have for over 25 years. I do not 
have any "modern" rigs of any kind. Don't need them! What I've got works 
fine. And the big bonus is - I can fix them myself, when something goes 
wrong.
What else could you ask for!
George KE4HJ

Gene McCalmont wrote:

>"Gene McCalmont"  made an utterence to
the drakelist gang
>----------------------------------------------------------------------
>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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