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

Sun Feb 29 13:08:01 2004

Hi Roger,
    I can lend moral support maybe with some anecdotal results I have
obtained with power line noise.  I have been battling Public Service Co. of
New Hampshire for two years trying to be able to hear on the VHF bands
again. I had tremendous noise situations with over 20 different beam
headings to discrete sources. After two years, I am still in the battle.
    On a given pole, there is usually not one, but seven or eight leaks. The
more leaks on the same heading, the less effective your noise blanker will
be. Playing around with receive levcels can help abit as some have said.
(Preamp switched on or off)  The levels for blanking certain noise will
vary.  I had a crew come out to a pole that was 600 ft from my antenna and I
sat there listening to it with a small beam and portable AM receiver, for
three hours while they worked on the pole. They found 7 different problems,
and there was still some weak noise being generated after all their work.
The line crew finally said (no joke) that the best way to fix this pole is
to drive a truck into it at night when no one is watching. They felt there
was leakage inside the pole. Well it did not bother me anymore, and that was
two years ago. (It was a 7 kv line)  Other power line problems have been
more prolonged. I frequently would notice that my noise blanker (OMNI V) was
ineffective, but after they worked on the pole, the noise blanker was very
effective on the remaining noise on the same beam heading! I would also
watch the noise in early morning. It would start with a quiet band as the
dew covered the lines and hardware. As the Sun heated things up the noise
would start. My antenna is very sharp on 144 MHz so I would see just a
single pole at a time. The blanker was very effective with the threshold set
way back. As time progressed, the noise blanker would need more and more
advanced blanking settings  to eliminate the noise. Finally, the noise could
not be eliminated. Generally the OMNI V will get rid of two or three
sources. Any more leaks and it starts getting ugly. I have seen the same
situation on many radios. The K2 and a Yaesu 50 MHz box all do the same
thing. The Yaesu blanker was real bad on some noise. I figured it was
worthless. I was very surprised one day to see it all disappear when the
blanker was turned on. This was right after a power co. crew had been
replacing faulty insulators. They had removed some of the leaks, and only
one or two must have remained!
    If your blanker worked at ur buddy's QTH, I would chalk it up to a very
ornery power pole! The more pulses generated, the more they will blend and
merge into a more random noise that the blanker cannot deal with. There was
one pole that required five trips with line crews and two trucks. It has
finally been fixed for the most part after only 1 1/2 years.
    Good Luck. I dealt with the power company for one year with no results
at all. I finally involved the ARRL and Riley Hollingsworth's office. That
got their attention. It is still an uphill battle. All my noise is on 50 and
144 MHz. At times I hear it on 432 MHz. Now that is bad.  Best DX for my
line noise on 50 and 144 is TEN MILES. 3-5 miles is typical with line of
sight and 34.5 KV lines. I find that the higher voltage lines pollute much
worse than 2-7 KV lines.  I am beginning to think that it is impossible to
clean up 34.5 kv lines at all.  As long as the power companies insist on
using ceramic bell insulators, the problems will persist. Polymer insulators
tend to work, but they do not like them since they have length of life
issues. Ceramic insulators will last for many decades. Of course they will
sound like a buzz saw, but they won't fall down.

73
Dave Olean K1WHS
----- Original Message -----
From: "Roger Marrotte" <[email protected]>
To: <[email protected]>
Sent: Sunday, February 29, 2004 3:39 PM
Subject: [Elecraft] KNB2 does not work on my power line noise


> 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.
>
> Roger, W1EM
>
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