[RFI] Apperent Power Line Noise

[John Pelham]

>> most people seem to say that Power Line noise gets worse with lower
frequency

Well, that's certainly not been my experience. I almost never hear power
line noise on any band below 15 meters. 15, 10 and 6 meters have been the
primary bands affected by the many sources of power line noise I've been
involved in fixing over the last 10+ years here in my Suwanee, GA power-line
hell.

I don't even yet know if such a frequency distribution means a particular
type of source. In my experience generally, the higher the frequency on
which the noise is strong, the closer it is. I'd guess yours is within a
mile or so, maybe.

73,
John, W1JA

-----Original Message-----
From: rfi-bounces at contesting.com [mailto:rfi-bounces at contesting.com] On
Behalf Of Edward
Sent: Monday, 01 November 2010 8:38 AM
To: rfi at contesting.com
Subject: [RFI] Apperent Power Line Noise

 

In the last few months, I have developed a strong noise problem here at the
N1UR QTH.  Here is the knowledge base so far.  I am in search of wisdom from
the group to help suggest a path of investigation.  Luckily the first Power
Company attempt was successful but did not fix the problem so I need some
help.

 

It has the classic buzz sound on AM.  No modulation of any kind, just buzz
with some intermittency occaisionally accompanied by some hard crackling
when it does.  Interestingly, in reading about this topic, most people seem
to say that Power Line noise gets worse with lower frequency.  This is the
reverse.  I hear nothing on 160 nor 80M. I can hear it there on 40M but
rarely affecting the meter vs. the atmospheric noise.  Its S2 on 20M.  S3 on
15M and S7 on 10M (with pre-amp on my FT1000MP). 

 

Antennas:  160 - Vertical T top.  80 - dipole at 65ft.  40 - 3 el. 20 4 els
at 80ft and 35ft.  15 - 6els at 70ft and 30ft.  10M 5 els at 70ft and 30 ft.

 

Its directional.  And essentially due east from the QTH.  I can turn
antennas on 10 - 40 to produce the above results.  All antennas show the
same thing - the peak reading due east and the expected null at about 90
degrees off the beam heading.

 

Its horizontally polarized.  I just happened to put up a 10M vertically
polarized antenna this summer and it is aiming almost right at it.  Its
right off the ground (boom is at 13 - 14 feet) and it hears absolutely
nothing even though the 30 foot high 5 el is blasting away at S7 pointed
exactly the same way - towards Europe.

 

Its wide band.  Obviously the strength is affected by the resonance of the
antennas I am using but it is heard from 30Mhz where I stop tuning down to
26 Mhz for instance on the 10M antenna.

 

What's east of here?  Well, I have underground line coming along my driveway
for about 800 feet. The pole that goes up to the line is due east.  As is
the road power line which runs parallel to the property along the east side.
There are 2 houses at about 1400 and 1800 feet respectively.  Then there is
a gap of woods and another couple of houses and another road line at about
3,000 feet and finally a medium voltage line at about 5,000 feet.  All of
that is in the beam path.  I have lived here for 8 years and been very
active.  This noise just occurred in the past 4 months maximum.

 

Occurrence.  It is not on all the time although its on at all times of the
day and night when its on.  It is affected by weather tending to turn off
when it rains but not always (seems to depend on the strength of the rain
and how long its been wet).  It was off completely for a couple for a couple
of days last week with some especially wet weather but then other times its
on even though its raining lightly.

 

I did some driving around and listened to 10M AM in the areas that I could
that are near the lines but can hear nothing in the region described.  But
of course the antenna is vertically polarized.

 

My next plan is to set up a 2M and 6M antenna on the tower at approximately
20 feet and see if I can hear the noise there (goal to get the smallest
antenna I can use as a horizontal antenna driving around that I know is
picking it up at the same time as what I am hearing).

 

But I am interested to hear the wisdom of the group.  Thoughts on the higher
frequency affect? Does that steer me in a potential type of source
direction?  Horizontally polarized.assume that means its radiating on nearby
wires .thoughts?  Weather affecting but not exclusively rain vs no rain?
For instance as I write this at 7:30am, its not raining and it is off yet
yesterday there was light rain on and off all day and it was on most of the
day and night (last checked around 9pm).

 

Appreciate any and all guidance.

 

Thanks.

 

Ed  - N1UR

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