[RFI] Mystery Noise (Aren't they all)

[Michael Carter]

Hi Wes,

Your comment about the RFI abatement when you powered
down the house is key:

"In conversation with the tech a few days ago I offered to battery power my TS-890 and turn off the whole house breaker.  When I did the noise went from S9+10 dB down to about S4, but it was still there!   I re-energized the house but opened the breaker to the shack and the noise was the same as with the whole house turned off."

The dominant RFI source is in your shack.  Start unplugging power supplies one at a time while keeping the radio
on the battery supply.  Be sure to disconnect UPS, if any, on both sides of the unit.  Once you've found the culprit
you can decide where to dig the hole in the yard to bury it.  More seriously, you can then start to look outside
the house for that S4 background noise.  Does the S4 background noise have the same audio and spectral
characteristics as the dominant big RFI, or is it just low level hash?

I have found that on 160 meters my Dell monitor and Intel NUC box generate a lot of obvious
noise, typically 20-30 dB over the background noise level when the computer and monitor
are shut off.  I am sure this RFI is conducted via cables rather than being picked up by
the antenna, so I have more bonding required as K9YC has advised.

73,
Mike, K8CN

________________________________
From: RFI <rfi-bounces+mike.carter=unh.edu at contesting.com> on behalf of Wes Stewart via RFI <rfi at contesting.com>
Sent: Sunday, January 28, 2024 10:50 PM
To: RFI at contesting.com <rfi at contesting.com>
Subject: [RFI] Mystery Noise (Aren't they all)

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I have been plagued for months with raucous noise, primarily on 160-meters. Our power co-op has a tech who maintains their com gear and fills in as their RFI guy.  I gave him a plug at a meeting with the CEO and suggested that he needed better equipment.  So he has the latest Radar Engineers 243, ultrasonic dish, etc. But he's struggled to find this particular noise and I finally got him into my shack and connected to my antenna, which pegged his meter and gave him a signature.
The problem with this organization is if he finds a suspect, he has to request a line crew which usually shows up when he's not around.  That was the case here; he identified a pole, they came out later and said they didn't find anything.  This was all unbeknownst to me and a few days later I happily reported the noise was gone.  He said, "Huh, that's funny, they said they didn't fix anything." Of course, it came back.
It has a strong 120 Hz component, but overlayed on that is a lower frequency modulation that is frequency sensitive.  In other words, if I tune for example to 1830 kHz I might hear the low frequency noise (Which I have dubbed rotating machinery) and then tune just +/- 10 kHz the low frequency stuff goes away and I'm left with the background stuff.
In conversation with the tech a few days ago I offered to battery power my TS-890 and turn off the whole house breaker.  When I did the noise went from S9+10 dB down to about S4, but it was still there!   I re-energized the house but opened the breaker to the shack and the noise was the same as with the whole house turned off.
I have limited test equipment these days.  In addition to the shack transceiver I have a Sony ICF-SW7600GR, which with just a loopstick antenna, has proved to be nearly worthless, and a TinySA Ultra, that I haven't tried.
This place has a smart meter which radiates prodigious garbage within a couple feet or so on the Sony RX on several bands, but falls off rather quickly with distance.  The RFI guy has suggested that I get a meter maid out here to pull the meter while I run further tests.
Any other suggestions?

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