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I've had some luck tracking down power-line noise sources by going to higher
frequencies, where the noise doesn't travel so well along the power lines.
I recall tracking down one cracked insulator using a receiver at 1.3 GHz
(AM mode) and a small, hand-made helical antenna.
<P>The advantage of the higher frequency is that the noise pretty much
is all radiated within a few wavelengths of the source, so you don't have
to spend a lot of time checking out different poles. if it's dark,
you can also look for sparks and corona -- you'll need some good binoculars
for this -- but first you have to narrow the search area.
<P>One thing often mentioned is that one could hit telephone poles with
a small hammer (even the palm of a hand may work) and listen for a change
in the sound of the noise. This does work, but a 1.3 GHz beam will also
pinpoint many sources down to the area of the pole they occupy.
<P>Cortland
<P>tduffy wrote:
<BLOCKQUOTE TYPE=CITE>owner-rfi@contesting.com wrote:
<P>> >From k3lr Sat Feb 28 19:16:26 1998
<BR>> Received: from migate.ampr.org (sapgate.freeway.net [206.153.72.61])
<BR>> by dayton.akorn.net
(8.8.5/8.8.5) with SMTP id TAA23191
<BR>> for
<rfi@contesting.com>;
Sat, 28 Feb 1998 19:16:25 -0500
<BR>> (EST)
<BR>> X-BBS-Msg-Type: P
To: <rfi@contesting.com>
<BR>> Date: Sun, 01 Mar 98 00:14:10 +0000
<BR>> Message-Id: <5939@migate.ampr.org>
<BR>> From: i4jmy@migate.ampr.org
<BR>> To: rfi@contesting.com
<BR>> Cc: thomas@cybrzn.com
<BR>> Subject: Re: Line Noise
<BR>>
<BR>> Message-Id: 5939_migate
<BR>> From: i4jmy@n8it.#nwmi.mi.usa.noam
<BR>> To: rfi@contesting.com
<BR>>
<BR>> Hi Guys,
<BR>>
<BR>> the real drama is not the line noise, but to depend on
someone else
<BR>> will, for the "official" search and solution.
<BR>> Read books can't solve the problem if who materially
search and
<BR>> repair "has no hears" and/or follows other purposes (to
delay).
<BR>> Here, you can forget to be considered by the electrical
company if
<BR>> complaining as a private citizen. In my country to force
the
<BR>> electric
<BR>> company (just one is existing) to act against a line
noise problem,
<BR>> there is nothing else than the official way.
<BR>> Apparently easy, this official way is practically long,
bureaucratic
<BR>>
<BR>> and still doubtfully effective.
<BR>> So, who suffers the interference must send a written
complaint to
<BR>> the
<BR>> office of regional department for telecommunication,
an office that
<BR>> is depending by the communication ministery.
<BR>> The complaint must be detailed because other than veryfing
what is
<BR>> descripted, this office won't do.
<BR>> The need to find out the exact source of noise, before
starting the
<BR>> official procedure, is the obvious consequence to have
a chanche of
<BR>> success, but this is a big challange without specific
<BR>> instrumentation
<BR>> and experience.
<BR>> Weeks or months after the complaint, notified to compliant
and to
<BR>> the electrical company to send representatives in the
date of
<BR>> veryfy,
<BR>> they will go in the indicated area. If the noise is present
when
<BR>> they
<BR>> check, they will give a term within the noise has to
be eliminated.
<BR>> Since a deny to act brings to a legal action, I know
the electrical
<BR>> company even replaced all the insulators along 7 Km power
line to
<BR>> solve a problem they couldn't fix in a short time otherwise.
<BR>> As it is easy to understand, apart our specific situation
described
<BR>> above, pointing at the real source of the noise is probably
a big
<BR>> help in any case, expecially when it is possible "get
in touch" with
<BR>>
<BR>> the electrical company without need of a third entity.
<BR>> Localizing a problem, infact, could make not so titanic,
long and
<BR>> expensive the work to fix the noise, and the electrical
company
<BR>> won't deal, at least, in the search of the originating
device.
<BR>> It is practical to realize that in 99% of the cases they
won't gain
<BR>> anything by fixing their line noise, while to do it they
have an
<BR>> economical cost to pay.
<BR>> Speking about our specific problem it is mainly affecting
10 meters,
<BR>>
<BR>> but this could be a matter of radiation angle and orientation
<BR>> between
<BR>> our antenna and the line that is also radiating, I think.
<BR>> I investigated the problem along the line with an antenna
that is
<BR>> flat in gain and responding to the electrical field (short
active
<BR>> antenna), along some 10 KM the line is noisy from 0.1
to 30 MHz and
<BR>> more.
<BR>> When the line arrives to substations, the derivated lines
are noisy
<BR>> by only few hundred meters, less if in between there
are
<BR>> transformers.
<BR>>
<BR>> The line is a 150KV AC, not the highest voltage and power
around
<BR>> here, but looks like if once it was a main line (old
line).
<BR>> The noise is higher and lower point to point and sometimes
stops,
<BR>> just like if something is intermittently arcing.
<BR>> Wet and humid weather often produce a NO NOISE period,
dry weather
<BR>> causes a rise in the noise.
<BR>> Looking with powerful binoculars, all the surface of
each glass
<BR>> insulator (composed by 8 conical stacked ones) is covered
by a
<BR>> reddish powder. The powder density is maximal around
the metal
<BR>> junctions and decreasing toward borders.
<BR>> A qualified employed in the electric company (informally)
told me
<BR>> they check the lines, in search of this interferences,
with special
<BR>> infra-red binoculars (can be performed in daylight).
<BR>> I couldn't find anyone else having such a tool.
<BR>> Is there anyone who tried infra-red or alternative method
without a
<BR>> big expense ?
<BR>> Any practical suggestion is welcome.
<BR>>
<BR>>
<BR>> 73,
<BR>> Mauri I4JMY
<BR>>
<BR>> e-mail i4jmy@migate.ampr.org
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