I give up. It's power line discharge.
Dave - WØLEV
On Wed, Dec 4, 2019 at 11:24 PM Michael Morgan <michael@aa5sh.com>
wrote:
I was hoping to get some help identifying a potential source for some
RFI
that started a few weeks ago. I posted some pictures and audio clips
from
20 and 40 meters on my webpage. Thought it may be easiest there I
hope it
is ok. https://www.aa5sh.com/?p=328
I tried to get some screenshots from my 7610. On 20M the Noise
Blanker
does a decent job of removing the noise but on 40M it is a bit two
random.
I have tried turning the main breaker off to my house and use a
portable
radio (Recent RS-918) off a battery and the noise is still there. I
did
walk around my property and noticed no real differences. The odd
thing is
it's kind of random. It has been going to 30 Mins or so and it just
stopped for a minute while I've been typing this email for a minute
or so
then started back up.
Then at lunch today I took a break and remoted home since I saw where
10M
was open and there was no noise for that 30-40 minutes.
I appreciate any guidance you can provide. In my years of radio
anytime I
have had noise problems I have always been able to narrow it down to
wall-wart or battery charger.
73
Michael, AA5SH
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One very last try: Copy to Word. Eliminate image. Copy test with no
image. Paste to email. If this doesn't work, I give up:
In your third image, the audio spectrum, the groups (first peak of
first
group to first peak of next group) is 17.5 ms.
The period on one cycle at 60 Hz is 16.67 ms. Very close. The sound
clip
also sounds suspiciously like 60 Hz discharge from the power
distribution
somewhere in your vicinity. I usually detect this at 120 Hz as the
discharge occurs at both the + and - peaks of the sine wave. But not
in
this case. In the time domain, I also usually detect an exponentially
decaying envelope for each discharge. No so in this case. But,
considering the period and sound, I'd guess its due to power
distribution
discharge in you area. Walk the power lines with your battery-powered
radio. When you find a pole that is particularly, kick the pole hard
and
observe any change in the character of the sound on your radio. If no
change, its not at that pole. Continue searching. Also, damp weather
usually exacerbates the discharges as does dusty conditions.
Dave - WØLEV
--
*Dave - WØLEV*
*Just Let Darwin Work*
*Just Think*
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