[Elecraft] KNB2 does not work on my power line noise

[Tom Hammond]

GM Roger:

What S-meter reading do you get from the line noise at your QTH?

All noise blankers must have a minimum signal level from the noise before 
they can properly sense it and begin the blanking process.

If your QTH is very quiet (other than the line noise), then even a minute 
amount of line could sound terrible, but still be below the minimum 
blanking level.

Since your NB did work correctly at your frien'ds QTH, but not yours, this 
could be the cause... line noise, yes, but too low-level to allow for 
blanking. In which case, there also a good chance that you be able  to hear 
most signals (even most of the weak ones) thru (or even above) the line noise.

Of course, the NB does depend upon the 'content' of the noise as well, but 
I've found that (for my line noises), if my NB won't blank it, it's NOT 
because of the content but because of the level.

73,

Tom    N0SS

At 09:39 AM 2/29/04, you wrote:
>I have a KNB2 for my K2.  The PC board says 1999 ELECRAFT REV D.  The 
>microcontroller says NB102.  I sometimes have power line noise at about an 
>S5 level, usually between storms.  After a storm the noise goes away for a 
>few days to a week.  The noise blanker has absolutely no effect on the 
>noise.  It doesn't matter if I use NB1, NB2 or LO THR.  It's as if the 
>blanker was still off.  I recently built a K2 for a friend and this past 
>week he raved about how the noise blanker on his K2 completely removed his 
>power line noise (also about an S5).  He lives about 15 miles away so it's 
>not the same noise. I haven't bothered with my noise blanker for a long 
>time since it does nothing.  Yesterday, remembering my friends rave 
>report, I looked into my noise blanker problem again.  It still did 
>nothing for the noise.  I found a suggestion on the reflector that 
>recommended changing C11 from 0.001uF to 0.0068uF and C12 from 0.0068uF to 
>0.047uF.  I made the changes and still no noise reduction at all.  I then 
>took my K2 over to my friends house.  He turned on his K2 and let me hear 
>his power line noise. It sounded just like mine.  He turned on his noise 
>blanker and the noise was
>gone.  I then connected my K2 to his antenna turned on my noise blanker 
>and the noise was gone!  I guess my noise is different enough for the 
>noise blanker not to work on it.  Does anyone have any suggestions for me.