Actually, much powerline noise is rather steady, so it will show up as a solid
block on a waterfall. That is diagnostic that the noise is not coming from a
switcher, but will not differentiate conclusively between electrical noise and
perhaps noise caused by something not powerline-related at all. The waterfall
will not really identify 60- or 120-Hz modulation, so demodulating in AM and
looking at the resultant audio is an important step.
From: RFI <firstname.lastname@example.org> on behalf of Jim Brown
Sent: Monday, June 6, 2022 1:45 PM
To: email@example.com <firstname.lastname@example.org>
Subject: Re: [RFI] Power Line Radiated Interference Limits
On 6/6/2022 4:28 AM, Hare, Ed, W1RFI wrote:
> You can also make a .wav or .mp3 file and run it through a free program
> called 'Audacity" and analyze that spectrum, with the understanding that your
> receiver bandwidth is usually limited below 200 Hz or so, so that 120-Hz
> component may be reduced in amplitude.
The best diagnostic tool, by far, to identify power line noise, as
opposed to electronic noise, is a broadband WATERFALL of either a
receiver's IF or RF. Powerline noise and lightning static is arcing, and
will show up as horizontal lines on a slow waterfall.
Electronic noise is the harmonics of square waves used in switch-mode
power supplies and other power control electronics like variable-speed
motor controllers, which show up as vertical humps of noise spaced at
10-50kHz, and microprocessor clocks, which sound like carriers and show
up as narrow vertical lines.
Power line and other impulse noise is present at all frequencies, but is
best chased at the highest frequencies where it can be heard.
Traditional techniques apply. Electronic noise must be chased on the
frequencies where it is heard.
More on this in this here.
73, Jim K9YC
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