Folks:
Somewhere on the ARRL website is a downloadable CD file, that is the report
of an Navy Postgrauate School Team, that for decades has studied and
ameliorated HF and other RFI sources of noise, particlarly power line
sources, that were of concern in Military applications. These guys are
the best. The reports described the field procedures, and equipment
selection that they used to find, characterize and ameliorate sources of RF
noise, usually generated in AC power distribution systems. A couple of
things stand out in my mind reading from their report, and hearing their
talks at Ham Club meetings, and conferences.
1. High tension transmission lines (we are not talking about HV distribution
lines) are rarely sources of RFI. I interpreted some of the follow up
discussions on this by the experts, as saying that if there are insulator,
or arcing and sparking problems in High tension lines, the consequencese
are severely destructive and costly to the power companies, and the power
companies fix and correct promptly else they lose equipment and dollars
2. Dirty insulator surfaces DO NOT cause HF interference to radio systems.
Washing of such by the power companies temporarily reduces the RFI
generation but the removal of contaminants on the ceramic insulator surface
is not what is going on. The noise generation often sources from the
(corroded) metal joints, the clevis pins, and interconnecting hardware,
particularly so in the chain or stack, of ceramic disk types of insulators.
The noise is ofen caused by repeated burn through, arcing on each rise and
fall of the AC wave, between semiconducting/insulating corrosion layers in
the metal fittings. The insulator washing detail, if it reduces noise, does
so because the soaking of the hardware to a great degree makes the
corrosion layers conductive, therefore there are less arcs and sparks
between them. If you have a noise problem and it is suspected with good
reason that a ceramic insulator chain is the problem, you can argue
effectively a case for the power company to replace the old insulator(s)
with a new type called, Epoxilators that are noise free.
So, I dont think the 115KV lines are going to cause you any problems.
The disk on the ARRL page is a great download and read.
Sincerely, Pat Barthelow aa6eg@hotmail.com
http://www.jamesburgdish.org
Jamesburg Earth Station Moon Bounce Team
http://www.cq-vhf.com
From: kd4e <kd4e@verizon.net>
Reply-To: kd4e@verizon.net
To: k4zw@comcast.net, rfi@contesting.com,TowerTalk
<towertalk@contesting.com>
Subject: Re: [TowerTalk] [RFI] 115 KV Lines
Date: Tue, 22 May 2007 09:24:37 -0400
We are on an approx. 330' wide 1500' long 10ac lot.
There are 45K lines up one side that are about 10yrs
old, they were in place when we bought the property.
They are very quiet and the only hassle is one may
not erect anything permanent on that land and whatever
is there is subject to truck damage should they ever
need to service their wires.
The only antenna hassle is that one should avoid any
long-wire antennas parallel to the lines.
I wonder if the windmills may cause some flutter to
ground-wave signals from that direction the same as
airplanes sometimes do to TV signals?
BTW: I copied this to the TowerTalk list as there
are some folks there who likely have good info for
you.
> Wonder if anyone on the list has experience with nearby 115 KV
> transmission lines? I have a 43-acre property that I?m getting ready
> to develop, including an HF station. Last week I received a call
> from an engineering firm that is working on a wind generation farm on
> a nearby mountain. The problem, they want right of way permission to
> run the 115 KV transmission lines on my property either along the
> road or at the back of the lot. My first reaction was oh no! One of
> my office colleagues use to work for a power company in the Midwest.
> He suggested it might not be as bad as it sounds because 115 KV lines
> typically don't have transformers and lightning arrestors like you
> find in residential neighborhoods. Still, the thought of something
> like that nearby (within 200? ? 2000? of my antennas) conjures up
> thoughts of potential RFI. I know I would not have bought the
> property had the lines been there to begin with. I realize there is
> no way to speak to the specifics of this case but what are your
> general experiences with lines like this and RFI? I haven't built on
> the lot yet but I was getting ready to put up the first two towers
> soon. Now I'm wondering whether I should proceed or ditch this
> location and look for another if they gain approval for right of way.
> It?s a perfect location in all other respects so I really hate to
> bail. Any thoughts or experiences you can share would be greatly
> appreciated. Ken K4ZW
--
Thanks! & 73, doc, KD4E
Personal: http://bibleseven.com/kd4e.html
Ham QTH: http://bibleseven.com/steel/cjb-steelhouse-index.html
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