The SDR waterfall will not be very helpful with power-line noise, but
they are great at identifying switching power supply noises and
noises that pulse on and off in a regular pattern.
Most of the time, though, we are less concerned with "what is it" as
we are with "where is it?"
------------------------------------------------------------------------
*From:* RFI <rfi-bounces+w1rfi=arrl.org@contesting.com> on behalf of
Dave (NK7Z) <dave@nk7z.net>
*Sent:* Friday, December 30, 2022 12:08 PM
*To:* rfi@contesting.com <rfi@contesting.com>
*Subject:* Re: [RFI] Powerline noise question
Something else that might help you differentiate one source from another
source in the pile of other signals-- a portable SDR.
I now use an Icom IC-705 as my goto RFI hunt tool when mobile... Self
contained for power, and it has a waterfall!
The waterfall makes it a simple matter to ID one source, (most of the
time), then as you rotate your flag, or loop, you see only that source
dip... You know you have the right signal, and can DF only that one...
73, and thanks,
Dave (NK7Z)
https://www.nk7z.net <https://www.nk7z.net>
ARRL Volunteer Examiner
ARRL Technical Specialist, RFI
ARRL Asst. Director, NW Division, Technical Resources
On 12/29/22 20:07, Don Kirk wrote:
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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