Here is _clear_ identification of a line noise source indicated by its
synchronization with the AC line as seen on an oscilloscope triggered by the
local AC line.
A single cycle of 60 Hz line is also shown to allow inspection as to the fixed
phase relationship between the arcing noise and the AC main reference waveform.
Also bear in mind we don't know which of the 3 phases in the distribution
network is the source of the arcing noise source.
This technique provides positive indication of an AC-line time-related as
opposed to say, video-related pulse train.
Years ago I noted a buzz in the 20 meter band that was _not_ AC line related,
perhaps a neighbors video system was leaking or something ...
I don't see how a "waterfall" display would provide this type of signal
discrimination using only the frequency domain.
A PC-based application known as Spectrum Lab could probably be used in lieu of
an actual oscilloscope to view synchronization of a 'buzz' noise source with
respect to the local AC line voltage.
de Jim WB5WPA
From: Jim Brown <jim@audiosystemsgroup.com>
To: rfi@contesting.com
Sent: Tuesday, December 12, 2017 11:56 PM
Subject: Re: [RFI] Visualizing Line Noise
Pete,
My tutorial on identifying RFI shows that a spectrum scope with a
waterfall display is probably the most effective tool for that. If you
haven't taken the time to study it, I suggest that you do. SDRs can be
bought for as little as $150, and the software is free.
73, Jim K9YC
On 12/12/2017 7:28 PM, N4ZR wrote:
> I recently ran across a neat little program called Soundcard Scope,
> which displays 0-20,000 Hz either oscilloscope style or as a vertical
> bar chart by the amount of energy on a given frequency. It seems to me
> this should be useful for characterizing line noise. Has anyone
> experimented with it for this purpose?
>
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