Don,
Toss this into the mix:
Three phases times 2 ppc (pulses or strikes per cycle) gives those
six 'peaks' seen in the 16.66 ms cycle duration between the cursors
in that screen capture.
Take a look and see if I missed or misinterpreted something.
de AA5CT
.
.
On Friday, January 10, 2020, 7:18:32 AM CST, Don Kirk <wd8dsb@gmail.com>
wrote:
Hi Ken,
Thanks for the additional 17 second recording with no human voice on top of the
noise, and this is what I really needed. I looked at the audio using my 100
MHz digital oscilloscope, I looked at the audio using "Audacity" software, and
I looked at that audio using "Soundcard Scope" software, and all 3 methods
yielded the same results. I have attached the screen shot from "Soundcard
Scope" as it's a good representation of what I see. There is indeed a
repeating pattern that happens at a frequency of 60 Hertz.
If you do FFT analysis on the signal you will also see strong component at 120
Hertz and other related harmonics in addition to the strong 60 Hertz component,
but I'm not convinced that means anything as you can also imagine you are
seeing bursts at a frequency of 360 Hertz too (looking at what I would call
major peaks for each small grouping I see a frequency of 360 Hz), and 360 Hz is
also one of the dominant frequencies in the FFT plot (spectrum plot) generated
with the Audacity software.
Would love to hear comments from others regarding their opinion of what they
see in my attached plot. As I previously stated, it's interesting to look at
the audio signature but what counts is locating the offending device using DF
gear versus guessing what it might be. It will always be a guess (sometimes an
educated guess) until you find the device.
Keep us posted on what you find, and let me know if there is anything else you
might need.
73,Don (wd8dsb)
Bottom line is that I am seeing repeating pattern at a frequency of 60 Hertz.
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