This is my tough RFI case story.
Prior to the ARRL CW DX Contest about ten years ago S9 continuous
day and night RFI appeared but only on 160 meters. There was no trace
of RFI on any other band. It was so strong that it was impossible to
hear replies to CQs on 160 meters during European openings.
Using my Beverages I was able determine that is was radiating from a
source northeast of my QTH, but I was unsuccessful finding it my car radio
tuned to 1700 kHz. During the contest I took off on foot attempting to
walk directly under every power line approximately NE of my QTH.
I could hear it weakly in a few locations, but they were obviously not
the source.
I decided to walk home via the shortest route after a few hours of futile
search. One of the roads I walked down was through a newer community
with large lots and buried power lines. Much to my surprise, I heard the
RFI fairly strongly on a road with a buried power line. I walked over to
a fence about 50 feet off the road and the RFI steadily increased in
intensity as I approached it. I soon discovered an electric fence wire
running along the top of the fence and the RFI was even more intense
when placing the portable radio close to the wire.
Fortuitously I noticed a person outdoors at that property and I asked about
their electric fence. They said they had stopped using that fence charger
years ago. We walked over the the fence charger and it was completely
disconnected from the electric fence wire. I asked if I could walk along
the fence wire that she agreed that we could walk it together.
I walked along the wire with the owner and discovered that that RFI was
strongest where it ran near an adjoining property with another electric
fence enclosing some cattle. We walked over the the neighbor's fence and
the RFI became extremely intense, obviously that was the source of the
continuous non-pulsing RFI. Fortunately the neighbor was also home and
agreed to unplug his fence charger and the RFI disappeared!
Unfortunately that property owner said it would be unsafe to disable his
fence charger for more than a few hours. Apparently cattle aren't as smart
as horses when it comes to avoiding an electric fence. He agreed to
disconnect the charger until he could no longer observe his cattle after dark.
Voila, RFI resolved! Or so I thought... The owner was initially uncooperative,
and refused to replace his faulty fence charger or allow me to purchase a new
one for him. It took a week of intense "social engineering" before he fixed
himself. And he was an electrician!
73
Frank
W3LPL
----- Original Message -----
From: "Hisashi T Fujinaka" <htodd@twofifty.com>
To: "Don Kirk" <wd8dsb@gmail.com>
Cc: "RFI" <rfi@contesting.com>
Sent: Wednesday, March 10, 2021 4:22:07 PM
Subject: Re: [RFI] Difficult power line RFI find.
Nice work!
I've lost steam now that I'm just using FT8 and don't have to listen to
the radio. I'm also in the middle of town and have given up on tracking
down noisy houses.
I tended to use MFJ equipment, knowing I might have to modify it to work
the way I wanted it to, so I liked seeing your equipment in the video.
The 122MH beam/receiver from MFJ, for example, has no attenuator and
according to another ham, needs a balun as well as improvements. I got
the ultrasonic dish, and all I hear is 60Hz hum but it gave me the dish
I wanted as a starting point.
These reports are appreciated because it reminds me of the projects I
should be tackling to improve my gear even if I don't go out to look for
problems all the time.
--
Hisashi T Fujinaka - htodd@twofifty.com
BSEE + BSChem + BAEnglish + MSCS + $2.50 = coffee
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