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Author Topic: Power line noise  (Read 397 times)
KD5SCG
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Posts: 19




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« on: December 12, 2002, 09:00:55 AM »

I'm just setting up my hf station and I'm sort of worried about power line interference. The reason I am worried is that when I drive by the transformer directly behind my house in the ally, it completely blocks out any AM station I am listening to. What will it sound like on an ssb reciever and how can I detect exactly where it is coming from. I do have an am capable scanner but no directional antenna. Who should I contact if I do have power line noise problems.
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K0BG
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« Reply #1 on: December 12, 2002, 09:43:27 AM »

Contact your power company. The FCC has taken a hard stance against such man-made noise, and most power companies have been more responsive of late as a result.

You really don't need a directional antenna. Just use a cheap AM radio like a $5 Radio Shack special.

Good searching.

Alan, KØBG
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W1ID
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Posts: 2




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« Reply #2 on: December 12, 2002, 09:51:34 AM »

As someone else pointed out, call your power company. Some have websites where you can report what you are experiencing. Power poles have numbers attached to them. Next time you drive by take note of the pole number (if any) and the closest street address. I would also drive around other power poles in the neighborhood to make sure you have the one creating problems. Line noise travels great distances at lower HF. If you could verify the problem with a portable VHF scanner near the pole, that would do it. That should be all the info they need. The big question is when they intend to fix it. My experience with the local power company is not very good. It takes about 2 months of prodding to get them to act. They say they don't have the manpower. A poor excuse to shun their responsibility. I know the FCC is now putting pressure on power companies to correct line noise interference but some of them still don't get it.
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N8FVJ
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Posts: 692




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« Reply #3 on: December 12, 2002, 10:16:09 AM »

Use the verbage- 'The transformer is creating interference due to a poor contact. The continued arcing could lead to transformer failure & possible PCB oil loss. I have created a daily log in a bound book to note your progress in this serious matter.'
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AC5UP
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Posts: 3822




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« Reply #4 on: December 12, 2002, 12:25:57 PM »

Something as modest as a Walkman style radio tuned to the top or bottom of the AM band can get you pretty close to the source of your line noise. Rotate the set for the deepest null in the noise rather than listening for a peak, and trust your readings instead of assuming the obvious...

A few years back I thought I'd traced a noise source to a ground-mounted power transformer (we have underground utilities and that's GOOD!) but the null angles didn't exactly point toward the transformer. The power company came out with a VHF setup that narrowed it down to a yard across the street with an electric fence charger installed to discourage the dogs from digging their way out. An electric fence charger in a residential area was the last thing I'd have suspected, but one look at the hot wire running through the weeds and a rusted pipe as a ground rod told the story.

The fence charger was 40 over on 75 Meter Phone...

- AC5UP
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WB9RAA
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« Reply #5 on: December 12, 2002, 01:21:28 PM »

Plus most likely its not the fault of the power company itself. Many times its a neighbors appliance.
So look for patterns. Every morning at 7am or Saturday evening. It can be shavers saws, wash machines, furnance motors, who knows.

Every morning driving to work I used to heard AM radio noise like digital signals much like X-10 controlling bursts at 7:45 - 7:50ish. I would of guessed it was some ComEd equipment sending data.

Bottom line keep a log book of date/times and amplitudes. And Talk/visit with you neighbors, ask if you can come in with your $5 AM radio!
-Ed-




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WB2WIK
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« Reply #6 on: December 12, 2002, 01:40:39 PM »

I also wouldn't fret about this until it actually becomes a problem.

In my neighborhood, there is such severe power line noise that AM broadcast radios barely work; however, it's much weaker in the HF spectrum and rarely bothers me for amateur radio work.

I wouldn't worry until you actually get on the HF bands, and see what kind of local noise level you have.

WB2WIK/6
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WB6BYU
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Posts: 13005




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« Reply #7 on: December 13, 2002, 03:45:21 PM »

If you DO find that you have a problem, an AM broadcast
receiver does make a reasonably good DF receiver.  In
most cases the ferrite rod antenna runs horizontally
the width of the case, and signals will be weakest when
the END of the rod is pointing at the signal.  So if
you rotate the AM receiver to minimize the noise, the
likely location is in the direction of one of the edges
of the case.  (It will not, however, tell you WHICH
edge is pointing at it, but if you take several
bearings from different points, you should be able to
figure it out.)

One problem with using an AM Broadcast receiver for
tracking power line noise is that the power wire act
as long antennas, and you may find a "hot spot" that
actually is some distance from the problem.  (If you
think of the current distribution on a long wire
antenna, current peaks - where radiation is greatest -
are 1/2 wave apart.  At 1 MHz this is 500' (150m).

Also, when you get close to the source it may be
difficult to take a bearing because the noise activates
the AGC regardless of the direction the radio is
pointing.

Once you have a good idea of the general area to look,
a VHF AM receiver with directional antenna is better
for pinpointing the exact source.  If you have a
scanner, the only addition may be a directional
antenna.  This need not be hard to build.  First, check
your scanner manual to see what modes it uses on which
frequency ranges.  (If you can switch in AM mode on
any frequency, so much the better.)  You then need an
antenna for a frequency where the scanner works on AM.
Something in the 240 - 400 MHz range might be a good
choice, though if you can switch to AM on a ham band
you may have other uses for the antenna later.

A convenient sized antenna is about 3' (1m) long.  This
will accomodate more elements (and have better
directivity) as the frequency goes up, but even 3
elements on 2m will be quite useful.  You can make a
simple one by sticking pieces of aluminum wire or
brazing rod through a piece of PVC pipe for the boom.
Exact dimensions will depend on the frequency you want
to use, but www.cebik.com has some good designs for the
ham bands.

You will find you have to be closer to the noise source
to hear it with the VHF receiver, but you now can swing
the antenna vertically and horizontally to find the
strongest signal.  BE CAREFUL AROUND THE POWER LINES -
DO NOT LET THE ANTENNA TOUCH ANYTHING!

Then call the power company and report the nearest
pole number.

You may be able to use another type of detector - your
ears.  There is a loose splice wire on a line about
1/4 mile from my house, and I can hear it jingling as
I walk down the road.  In fact, I can hear it from my
house on a quiet night (we're in the country).  There
is a high level of RF noise coming in the powerline,
especially on 80m and 160m.  The noise was pretty high
on a long wire fed against ground, but a balanced
dipole or loop was no problem (even if I didn't use a
balun).
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KB0NLY
Member

Posts: 1




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« Reply #8 on: December 18, 2002, 03:23:08 AM »

I always read about power line noise and reporting the pole number to the power utility, that makes me think a bit, i have yet to see a number of any kind on any power pole here.  I have lived in the country, and i have lived in several towns over the years, but have yet to see any kind of individual id on a power pole.

Is it required for the power company to number them?  Or is it an optional practice that not all utility companies use?

73,

Scott, KBØNLY

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