[Elecraft] KNB2 - looking for experience with mods that made it effective

Don Wilhelm w3fpr at embarqmail.com
Wed Oct 9 17:41:48 EDT 2013


Stan,

First check the KNB2 to be certain it is working.  With no antenna on 
the K2 and the preamp on, tap a metallic object (screwdriver) against 
the case of Q21 - you should hear clicks (ignore the 'rushing' sound of 
the screwdriver acting as an antenna).  Turn on the NB and the clicks 
should be reduced - you may have to switch it to Low Threshold.

Once you verify that the KNB2 is working, you can proceed with the 
mod(s).  Most have found that increasing the value of C11 is sufficient 
- solder another .001 uF capacitor across the leads of C11 as a test (or 
a permanent solution).

A caution, those mods may not be effective against the type of noise you 
have.  The KNB2 works quite well on impulse noise like automotive 
ignition noise, but does not work well with noise sources with a slow 
rise time.  The KNB1 is similar (the K3 NB is different).  The KNB2 will 
do nothing to reduce powerline noise or the noise from various household 
appliances.

If the KNB2 cannot handle your particular noise source, you may have to 
add the KDSP2 with its Noise Reduction algorithm which is effective on 
such things as powerline noise.

73,
Don W3FPR
On 10/9/2013 5:06 PM, Stan AE7UT wrote:
> I just recently built the KNB2 and it does not seem to be very effective for
> the noise pulses near my house.
> I also put a the KNB1 in my K1 with disappointing results.
> I'm comparing this to my K3 and KX3 that almost completely eliminate the
> noise.
>
>
> Doing some internet research there appears to be a couple of mods that
> people embrace.
> I was looking at LA3ZAs site and he shows two mods.
>
>



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