[RFI] Power line RFI situation
Mon, 18 Mar 2002 16:14:35 -0500
"...goes away when it snows or rains..." - hardware, hardware, hardware - 95+%
of the time.
This is a very common problem with feeders and loose or corroded connections or
the mounting hardware. Yes, it can be fixed but expect to uncover the problems
in "layers", i.e., you will eliminate one or more only to find others that were
being masked. I do my initial locating by DFing using a 6m beam then pull out
the topo map and try to locate the problem(s) first using the AM broadcast
band. I then switch to an AM aircraft rcvr; you're using a small beam is vy
good. Be aware and observe that different sources frequently have different
"signatures" and that because of the various (complex) resonant structures, you
are likely to find nulls in the frequency spectrum. Corona, BTW, from 100KV
and up lines will almost always get worse with rain, etc. Corona is usually a
"hiss" as opposed to the stacatto of lower voltage spans.
Expect "officials" to initially ignore you - unfortunately, many have little
knowledge or experience and it is always easier to pass the buck. The real key
is to be able to talk directly with a troubleshooter that is willing to work
with you, and if you can actually locate affected poles, it does wonders at
establishing credibility. This can be a frustrating effort, but it usually
works better in the long run than going immediately to a Public Service
Commission or the FCC - but sometimes is necessary,
There are quite a few very capable people (including a few EMI professionals) on
this reflector who will be more than willing to try to help.
BTW, the ARRL book is good, but buy also a copy of "AC Power Interference
Manual" by Marv Loftness - ISBN: 0-0653760-2-8 .
Keep us informed; this issue is a problem almost all of us have.
73, Tom - WA2BPE
"Rob Atkinson, K5UJ" wrote:
> Hi everyone:
> I just recently started reading the mail on this list and it seems to be a
> great resource. I'm sending this mail out to the list as a sort of status
> report regarding my particular problem. I hope that as things progress I
> can send updates and get advice with a few of you guys being familiar with
> my situation. I live in an old neighborhood of St. Charles Illinois, a
> suburb of Chicago. A river (the Fox river) flows through the middle of
> town. My qth is about 100 feet from the east bank. High voltage power
> lines on poles run along the east bank of the river. The city of St.
> Charles owns and maintains the municipal power grid. They bill us for
> electricity which they purchase from Commonwealth Edison. So the city is
> responsible for fixing powerline problems.
> After being qrt for about 18 years I set up a HF station late last summer.
> I was dismayed to find a S7 level line noise, loud enough to make a lot of
> qsos unworkable on 80, 40 and 20. It's not so bad on 15 and 10. For the
> first several months I was preoccupied with solving some grounding, rf
> feedback and antenna bugs. Lately I have gotten around to tackling the ac
> noise problem which was next on my list after finally getting the shack set
> up and the station problems fixed. I had taken a stab at it last fall to
> the extent that I naively called the city electrical dept. to complain about
> the noise. A young man called back a few hours later to tell me he drove
> around my neighborhood & listened on his car radio for noise and didn't hear
> anything. He suggested I make sure the noise wasn't coming from inside my
> house. I told him okay, and realized this wasn't going to be so easy. I
> had figured the noise was from outside because it went away when I
> disconnected by antenna. I got a copy of the ARRL RFI Book and started
> reading it.
> A couple of weeks ago I went around with a mw am receiver to DF the noise.
> One way I know it's from outside my house is that I've observed that it goes
> away when it snows or rains. The rest of the time it's there night and day.
> The mw rx was too sensitive and nondirectional.
> Over the weekend I found an old Alinco 2m/70 cm HT that receives air band on
> AM. I found a battery pack for it that will
> take a charge so I have been walking around with it using a loaded 5/8 w.
> duck. I have it tuned to a bit above 108 Mhz and have also been driving
> around with it connected to a 1/4 w. g.p. on the roof of my car. I've found
> a couple of potential sources. I went to radio shack yesterday. They sell
> a cheap 20 buck 6 el. yagi for the FM broadcast band. I bought one along
> with a receive only balun and am going to use it to DF the problem with the
> 108 mhz AM rx. S7 noise is unacceptable. I could live with it if it were
> maybe S1 to S3. But at S7 I can only work guys with beams and/or linears.
> Anyone with 100 w. and a dipole is briefly workable but no fun and after a
> few minutes I usually end the qso. I plan to drive around
> St. Charles for several hours noting the possible sources (there's one real
> bad one on the other side of the Fox river from me) then go back with the
> yagi to try to isolate the pole(s). Then contact the city electrical dept.
> & put everything on the table & see what they do.
> What do you all think about this plan so far? Anyone else in this situation
> where you are working with a municipality instead of a utility? Tnx 4 your
> help & 73--GL with your own noise problems too.
> Rob Atkinson
> St. Charles IL
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