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Thread: Unknown RFI

  1. #1

    Default Unknown RFI

    I have an ignition/spark type interference that is strongest on 20 meters. I can null it out by using the NB on my Kenwood 830S. It starts around 8:00am and goes off around 6:00pm seven days a week. I live near a few horse and cattle farms that use electric fences but the beat of the interference is about 8 to 10 times per second which I think is to fast for electric fence. On of my neighbors has an invisible fence for their dog but I don't think that would be cycled off every day. I am also about 5 miles from a large coal powered power plant that uses very large electro-static precipitators. One other business nearby is a large chicken farm with four or five large enclosed pens. I'm not sure if these pens would use any type of equipment that would produce this type of noise. The fact that it is turned on and off every day promptly around 8 am and 6 pm leads me to believe that it is the power plant. I can upload a file with sound and video of the noise if someone would like to see it.
    I would appreciate any comments that might help me with this issue.

  2. #2


    When RFI corresponds to certain times, it is always related to human activity rather than a hardware fault like power line micro arcing. Start by turning off all power on your property to eliminate your devices as possible culprits. If hitting the mains breaker changes it, go one breaker at a time and see what circuit its on. Then, one outlet at a time and so forth.

    Once you have established its not you, you need to determine if it is related to power line hardware failing (like micro-arcing on an old insulator or ground wire). I can assume that this is not the case for you as the issue relates to specific times, but will detail it a bit anyhow for other readers. Very bad power line noise usually manifests itself as a 120Hz hum (at least for a 60Hz mains because arcing happens at the positive and negative peaks). However, it can also come through as random pops with similarly slow frequency. Power line noise usually corresponds to weather rather than time as moisture tends to inhibit arcing whereas dry weather or cold winter weather will usually intensify it.

    So, we ruled out power line noise and the possibility it comes from your property. It occurs at distinct times and is broadbanded suggesting it is a human-controlled device, and by that repetition rate, I would guess its definitely arcing or a high power pulsed current being it definitely contains harmonics.

    My recommendation: Hop in your car and tune around in the AM broadcast band till you find it on the radio and drive around until the noise gets strongest. Then, you can tune to a higher frequency where the strength is lower and repeat the process. This is where a radio with an RF gain is really handy. Every time you get closer, turn the gain down (or install a worse antenna) and hunt a little further.

    If you find the source, DO NOT be rude when approaching the guilty party. A kind explanation and a willingness to help solve the issue usually results in faster resolution than pointing fingers and making threats. If it does turn out to be the industries down the road with big bucks on the line, there are laws in place regarding harmful interference....
    Last edited by brandon lind; Wed 29th Jan 2020 at 16:16.

  3. #3


    After researching electrostatic precipitator power supplies, My first course of action would be to call the power plant down the road and ask them at what times the device is in operation. Sounds like the most likely cause so far.

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