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
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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