New RFI - 24khz spacing on 80m

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raydeeoh
Posts: 10
Joined: Sat Feb 13, 2021 6:23 pm

New RFI - 24khz spacing on 80m

#1

Unread post by raydeeoh »

Hi all,
Wondering if anyone has seen anything like this before and, if so, what is the likely culprit. I was away for two weeks, came home and turned on the radio to find this wonderful new noise all across 80/75m with approximately 24khz spacing between signals.

I'm using a Hermes Lite 2, powered by a 12v battery, not connected to house mains at all. I've shut down everything that is connected to the house mains in the shack and still see the same signals.

Any advice/direction is greatly appreciated!
73,
Robert VE7ZN
Screenshot-2022-11-23-151016.jpeg

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KA1GJU
Posts: 264
Joined: Tue Aug 11, 2020 2:16 pm

Re: New RFI - 24khz spacing on 80m

#2

Unread post by KA1GJU »

Looking at QRZ.com, you have two immediate neighbors that could have a SPS (Switching Power Supply) running a cordless screwdriver, charging batteries in a UPS, or ??? Any UPS's in your QTH? Or one attached to your Internet connection from street. We have fiber to the house, but the converter box has a battery and charger to keep phone/Internet up during power outages.
To check if it's your USB cord, place a small whip antenna on the feedline and sweep the USB cord. An open ground on a USB cable made me chase my tail for a few hours on SDRC Superstation #1. But it made one heck of a mess of the spectrum!

How big is the antenna and how close to which neighbor?

73 Kriss KA1GJU
73 Kriss KA1GJU Home of the KA1GJU Super Station SDRC Servers in NH, USA (FN42mw & FN43na)

raydeeoh
Posts: 10
Joined: Sat Feb 13, 2021 6:23 pm

Re: New RFI - 24khz spacing on 80m

#3

Unread post by raydeeoh »

Kriss,
Thanks for the input. It's very strange because mid February this year, it suddenly "went away". Then, about 3 weeks later it came back. I decided I would create a little written blurb about it including some pictures and an explanation that this interference was causing problems with the Emergency Communications Net which meets every night on 3720KHz.

I went to every house on my block and the houses behind me, met with the homeowners and calmly and in a friendly manner went over the issue. Suddenly, a couple of days later, it disappeared and thus far, hasn't returned. Hopefully it won't but we'll see...

It definitely is some sort of switching PSU/Charger but what and where? VERY hard to track down...

73,
Robert VE7ZN

User avatar
KA1GJU
Posts: 264
Joined: Tue Aug 11, 2020 2:16 pm

Re: New RFI - 24khz spacing on 80m

#4

Unread post by KA1GJU »

Actually, VERY easy to track down... with the right tools!
SDRC is what I use along with an active 1m loop antenna. Since the loop has VERY sharp nulls, one plots them on a very zoomed in Google map in the satellite view and you can plot lines using buildings, trees, towers, etc off in the distance as reference points to aid in transfering the loop nulls to paper. Then take another reading from somewhere else. Your lines will now have crossed, getting you close to the source. Keep repeating until you find the source.

The loop I have is made from 1/2" Andrews LDF4-50 hardline and the amplifier came from Everett, N4CY, who occasionally sells batches of them on the groups.io SDRC site. For out in the field work, I can use my FT-817 on battery power and use my ears, but having SDRC with the scope and large S-meter... easy peasy!

73 Kriss KA1GJU
73 Kriss KA1GJU Home of the KA1GJU Super Station SDRC Servers in NH, USA (FN42mw & FN43na)

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