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Can Anyone Identify This EMI Source?

F1R

Well Known Member
This is a short recording of a radio interference tone on 122.8 that has been an intermittent pain and distraction around the airport at CEQ3 for a number of years. Does anybody recognize the tone?

https://youtu.be/YtfD87eAoJo?t=5

A Rocket w/Garmin SL30 & GX60 , Lake 250 with 2 of Garmin XL 250 and a Chipmunk all get blasted with the same tone.
Sometimes on the apron and runway, sometimes in the air in close proximity to the airport.
 
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The city is just off the LH wing a couple of miles. We have no MRI within 60 miles. In the foreground however is an almost new large pig farm.

In the city there are several pipe manufacturing facilities. Also pipe coating plants. Perhaps they have a high frequency welder that has un shielded wiring or a non enclosed power supply.
 
Arc welders are giant spark gap transmitters. Very broadband.
Sounds like 60Hz ish modulation.
Take a handheld and drive near the plants (during operation)
Can you email the audio? I can take a look the spectrum.
 
Possibly the pig farm. Pigs are susceptible to stray voltage/current. I was on a pig farm recently and saw the mitigation gear they use - quite sophisticated. I have no idea how it works or what it does but it was a significant installation. There was a unit in each barn.

Jack
 
Arc welders are giant spark gap transmitters. Very broadband.
Sounds like 60Hz ish modulation.
Take a handheld and drive near the plants (during operation)
Can you email the audio? I can take a look the spectrum.

There is an "add on" for Firefox (Video DownloadHelper) that will allow one to download and convert (for a fee) to MP3 HQ (256 KBPS). The file is 500K so it could be emailed. Send me a PM with your email address and I will send you the file.
 
I’m curious

There is an "add on" for Firefox (Video DownloadHelper) that will allow one to download and convert (for a fee) to MP3 HQ (256 KBPS). The file is 500K so it could be emailed. Send me a PM with your email address and I will send you the file.

I’m curious about this. Could you send me the mp3? I can run a Fourier Transform to get the peak frequencies up to 0.5 the sampling rate.

Thanks,
Sam
 
Looking at the spectragram, it looks like 3-phase 60Hz pulse modulations (the black dots in the spectragram) spread across some harmonics in the audio band.

I'm still guessing some big honkin' industrial welder or similar.

I can get a deeper look once IT gets my good audio analysis SW with 3D spectragrams installed on my new laptop. This is from freeware Audacity:
 

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Thanks Mike,

That is greatly appreciated. There are currently a few professionals involved in the hunt which is looking at several possible sources. Presently the on airport suspect is the Constant Current Regulator for the rwy lights. It may proceed to surrounding area equipment. So far it has not been able to be heard with a hand held VHF radio. Only the 3 ships previously mentioned.

The next few weeks will hopefully find the source and cure the problem.
 
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