Richard,
I forgot to mention that electric fence RFI typically has
a definitive repetition cycle similar to what you described
and often goes away during rain.
73
Frank
W3LPL
----- Original Message -----
From: "Don Kirk" <wd8dsb@gmail.com>
To: "Richard" <richard@karlquist.com>
Cc: "rfi" <rfi@contesting.com>
Sent: Friday, December 30, 2022 4:07:12 AM
Subject: Re: [RFI] Powerline noise question
Hi Rick,
Sorry that my last message was blank as I typed it on my cell phone and
then accidentally deleted the text prior to hitting the send key.
You can use your MF/HF loop to do some triangulation on the source but you
often need to get far away from existing power lines to avoid receiving
conducted signals along the lines versus the signal direct from the
source. As an example when out in the country I will often walk out into
the middle of farm fields to get away from overhead power lines when
obtaining bearings. As you get closer to the source you can go higher in
frequency if it really is power line noise (arcing hardware). As an
example you can go to 40 meters then 20 meters and then 10 meters as you
get closer to the source as a form of attenuation and to also help you get
multiple wavelengths away from objects that might otherwise skew your
readings. Adjustable RF gain and/or attenuators are also very helpful.
If it really is power line noise (arcing hardware) you should be able to
hear the source using an AM receiver with a 3 or 4 element yagi when you
are within approximately 0.25 miles of the source (and sometimes upto 0.5
or more miles away). Make sure the yagi is tuned for the frequency you are
using in order to assure the correct antenna pattern. When you get very
close to the suspect pole you will typically need to throw in 20 to 30 dB
of attenuation in order to determine the exact pole (in rare cases you
might even need 40 dB of attenuation).
One thing that is great is that it sounds like your source has a specific
pattern that will help you differentiate it from other sources but if the
pattern is always a very specific 0.9 second pattern that never changes
regardless of what day you listen, etc. that makes you wonder if something
else is going on, but the fact that it goes away when it rains is typically
a good indicator that it's indeed power line noise (arcing hardware).
Don (wd8dsb)
On Thu, Dec 29, 2022 at 10:46 PM Don Kirk <wd8dsb@gmail.com> wrote:
>
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