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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