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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