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Located in Illinois, US, I recorded this http://loami-windmill.com/sounds/6m_noise.m4a on 28-June-2023 at 1603 UTC on 50.074MHz USB. The static has regular "pulses" where it gets slightly louder at a rate of a little more than once per second. While I've never heard anything like this, it sounds to me that it's clearly not man-made, but I have no idea what is causing it, or whether it's atmospheric, tropospheric or ionospheric. What might be causing it?

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    $\begingroup$ What makes you think it is not man-made? $\endgroup$ Jun 29, 2023 at 6:05
  • $\begingroup$ Yeah all that you describe, a human in a human environment observing noise using a human-made receiver pulsating at a human-perceptible rate points more to "human made". What is the pointer that says it isn't? $\endgroup$ Jun 29, 2023 at 12:04
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    $\begingroup$ I don't know for sure that it's natural, and you're right, I can't rule out that it's man-made. But of the man-made noises I recall hearing, none of them are soft, broad white-noise sounding. $\endgroup$
    – Duston
    Jul 2, 2023 at 14:02
  • $\begingroup$ Where was the antenna, and can you rotate it? Inside your house or outside? I'm thinking that it's picking up noise from something in your house (or a neighbor's). $\endgroup$ Jul 5, 2023 at 20:24

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Dustin, The fact that this is a regular timed noise argues that it is man made. When do your hear it, only night, only day, all the time? Do you live in an urban environment or rural? Could it even be coming from your own house? Shut off your house circuit breakers one by one to check. You can make a simple shielded loop antenna from coax, put it on a stick and use it to get a direction on the noise. If your radio is portable you can chase the noise down to satisfy your curiosity. 73s

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  • $\begingroup$ +1. I listened to this a couple of times, and it sounded like RFI from digital equipment (like a computer) that I've heard. It was somewhat broadband and the sound changed as the VFO was tuned. $\endgroup$ Jul 5, 2023 at 20:22
  • $\begingroup$ I can try shutting things off at my house. The nearest neighbor is at least 1500 (300m) away. I suppose it could also be something coming down the power lines. $\endgroup$
    – Duston
    Jul 12, 2023 at 20:57

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