Yes, many noises can sound the same. Also, many noises do NOT propagate for
any significant distance from the source. For the most part, if a noise is
conducted onto the AC mains in the differential mode, it decays at nearly 60
dB/distance decade from the source. Our testing engineer and I recently had a
chance to visit a local solar farm. At the fence, near the inverter
electronics, we found S9 noise, but it was inaudible on a portable SW receiver
when we were 10 feet away, so noise can decay rapidly with distance.
This is a problem that electric utilities encounter all the time. They get a
complaint, go to the area, find noise and fix it... well... fix most of it, but
the noise sources they fixed were not ones the amateur could hear.
There are several ways to get reasonable correlation.
For sparking noise sources, get a noise signature at the affected station and
compare it to noises in the field.
For sources that come and go in a regular pattern, ie 1 second on, 3 seconds
off, it is reasonable to assume that a similar noise found in the field nearby
is the source.
For switching power supplies, the spacing between the noises vs spectrum can be
a clue, but many devices could have similar spectral signatures.
If you can clearly hear the noise on a mobile antenna at the ham station and
can clearly hear it all the way to the suspect source, that can also be a
reasonable correlation.
Ed
________________________________
From: RFI <rfi-bounces+w1rfi=arrl.org@contesting.com> on behalf of Frank W3LPL
<donovanf@starpower.net>
Sent: Saturday, December 31, 2022 6:56 PM
To: Richard <richard@karlquist.com>
Cc: rfi <rfi@contesting.com>
Subject: Re: [RFI] Powerline noise question
Hi Rick,
I never attempt to guess based on the sound of the RFI, I always
use geolocation techniques to discover the location of the source.
Good luck!
73
Frank
W3LPL
----- Original Message -----
From: "Richard" <richard@karlquist.com>
To: "Don Kirk" <wd8dsb@gmail.com>, "Frank W3LPL" <donovanf@starpower.net>
Cc: "rfi" <rfi@contesting.com>
Sent: Saturday, December 31, 2022 9:49:50 PM
Subject: Re: [RFI] Powerline noise question
I have attached an mp3 of the noise to my reply.
I hope it propagates to Don, at least.
73
Rick N6RK
On 12/31/2022 8:55 AM, Don Kirk wrote:
> Hi Richard,
>
> how a conventional Xenon tube flash circuit works in photography. Can
> you upload a recording of your noise burst so we have a better idea of
> what you are hearing/seeing? But as others have said I never try and
> guess what the source is other than to try and determine if it is power
> line related noise because if it's not power line noise then I might not
> pack my vehicle with as much VHF and UHF DF gear.
>
> Don (wd8dsb)
>
>
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