[K2] K2NB noise blanker performance testing

[Douglas Furton]

Can anyone suggest a controlled set of tests that might verify if a K2NB module is working properly?

I built and installed a K2NB for my K2 sometime ago and whether or not the module performs properly has always nagged at me -- especially since there is something in my neighborhood that now and then emits considerably RF noise that splashes across a wide range of frequencies.  The noise sounds just like broad-band ignition/pulse noise, the type of noise a noise blanker should effectively blank.  But my K2NB module doesn't seem to be able to get it, even though NBers on a couple other of my rigs zap it effectively.

There are two possibilities: either I did not build my K2NB quite properly (because it does seem to limp along and blank some noise in certain circumstances), or the K2NB doesn't quite live up to its billing as a "high performance" noise blanker.

I'm interested in running some sort of objective test that is able to discern if my K2NB is working up to spec.  

Doug
K8EXB

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[Don Wilhelm-4]

  Doug,

One way to check the operation of the KNB2 is to turn on the preamp and
tap on the side of Q21 with a metallic screwdriver.  Turn the NB on and
the clicks produced should be significantly reduced.  If not, try
changing the threshold and check again.

The K2 NB works great on sharp impulse noise like ignition noise from a
gasoline engine, but it will not do much with the slower rise time noise
from a diesel engine, although the two sound similar to some ears.

If the KNB2 is working, but not effective on the noise you have, you can
try increasing the value of C11.  Try tacking an additional .001
capacitor to the leads of C11 on the bottom of the board.  Be aware that
too large a capacitor at C11 will "punch holes" in the IF stream which
will lead to signal distortion when the width of the 'holes' is great
enough.  You are free to experiment within those constraints. (C11, and
for NB2 C12, control the width of the hole placed in the signal path).

73,
Don W3FPR

On 9/27/2010 8:16 AM, Douglas Furton wrote:

> Can anyone suggest a controlled set of tests that might verify if a K2NB module is working properly?
>
> I built and installed a K2NB for my K2 sometime ago and whether or not the module performs properly has always nagged at me -- especially since there is something in my neighborhood that now and then emits considerably RF noise that splashes across a wide range of frequencies.  The noise sounds just like broad-band ignition/pulse noise, the type of noise a noise blanker should effectively blank.  But my K2NB module doesn't seem to be able to get it, even though NBers on a couple other of my rigs zap it effectively.
>
> There are two possibilities: either I did not build my K2NB quite properly (because it does seem to limp along and blank some noise in certain circumstances), or the K2NB doesn't quite live up to its billing as a "high performance" noise blanker.
>
> I'm interested in running some sort of objective test that is able to discern if my K2NB is working up to spec.
>
> Doug
> K8EXB
>
> ____________________________________________________________
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