For a quick and easy reading, the WSJT-X waterfall is quite useful. Just
drop the rig into AM mode and see the bright line at 120 Hz and
harmonics every 60 Hz across the whole pass band (at least at my QTH).
Be sure to set Start to 0 Hz. You can roll over the waterfall or the pan
with the cursor and read out the frequency.
I've also used Spectrum Lab to capture audio artifacts.
Soundcard Oscilloscope is useful to identify when you have multiple
sources by observing the pulse trains and measuring the times between
pulses. https://www.zeitnitz.eu/scope_en
Cant have too many tools.
73,
Steve
W1SRD
On 6/6/2022 13:24, Hare, Ed, W1RFI wrote:
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.
Ed
________________________________
From: RFI <rfi-bounces+w1rfi=arrl.org@contesting.com> on behalf of Jim Brown
<jim@audiosystemsgroup.com>
Sent: Monday, June 6, 2022 1:45 PM
To: rfi@contesting.com <rfi@contesting.com>
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.
http://k9yc.com/KillingReceiveNoise.pdf and
http://k9yc.com/KillingRXNoiseVisalia.pdf
73, Jim K9YC
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