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When scanning through UHF, I find that there are a few frequencies that made a sound similar to a fast drum (~300 bpm?) Here are a list of the frequencies:

  • 451.200 MHz
  • 454.280 MHz
  • more coming soon

Is that what it sounds like for 60Hz in the US? If not, what does it sound like? I tried searching for it on YouTube but all that came up with was, "10 hours of 90kV Electrical humming For Concentration Relaxing" and stuff like that.

There isn't any of the noise in VHF, so it gives another clue. ARRL says that if you tune to an empty frequency on AM in a car, it is similar to the power line noise. Should I try that? It also says to use a oscilloscope to see 120 bursts per second. That way, if it is at 120 bursts per second, it means it matches up with power line noise. Can I do it with a multimeter? (with an Arduino, maybe?)

I read the FCC frequency allocation table and saw that it is something called MedRadio. Google says it is for medical devices. I want to know what the interference is.

This is the link to the audio recording: audio

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    $\begingroup$ Don't wildly speculate! 451 MHz is so far from powerline frequencies that it's almost certainly unrelated. From your KC3WCR callsign, I'd infer you're in the US (added that tag, location is obviously relevant here). So, just look up to which service that frequency is assigned by the FCC, search for "FCC frequency allocation table". You'll find the type of service that is there. $\endgroup$
    – Marcus Müller
    Commented Apr 20 at 11:16
  • $\begingroup$ Outside of amateur radio, aircraft and marine emergency communications (and both only for 100 years of compatibility reasons), and maybe a few CB stations, and US-American "talk radio" nobody uses AM; it's technologically very obsolete. So, you tuning an AM receiver to anything but bands used by AM broadcast radio, amateur radio, approaching aircraft and ships, and hearing something that sounds "strange" on your AM radio means very little, but that your AM radio wasn't designed to make sense out of these transmissions. $\endgroup$
    – Marcus Müller
    Commented Apr 20 at 11:26
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    $\begingroup$ So, your question "should I do that? Can I do it with something else?" cannot be reasonably answered, without asking you "do that, to which end?"; we can't know why you want to do that. Can you tell us what the purpose of attaching an oscilloscope there would be? I ask so explicitly because you have a bit of a history here asking questions about things, presuming that they are a problem, and after people have spent a lot of time asking you what the actual thing is that you're asking, you delete the question. That's not a great way of asking questions, in your own interest: $\endgroup$
    – Marcus Müller
    Commented Apr 20 at 11:29
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    $\begingroup$ Please state exactly what the reason you're asking this is. Are you debugging a problem with a receiver getting overloaded by interference? Are you trying to figure out how to make sense of the signal there? Do you know what is there, but are experiencing a problem with the system you know is there? We can't guess that! Please edit your question to explain the purpose of your measurement. Without knowing why you want to measure, nobody can tell you how to measure. $\endgroup$
    – Marcus Müller
    Commented Apr 20 at 11:31
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    $\begingroup$ Since that is not 60 Hz power line RFI, I suggest that you edit your title. Perhaps something along the lines of "What is this signal?". $\endgroup$
    – Mike Waters
    Commented Apr 20 at 18:58

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I know the sound well; it is a control/data channel for a P25 or EDAC trunking system used by police, sheriffs, and federal law enforcement.

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  • That is almost certainly some kind of digital transmission.

Someone with suitable software could decode it and listen to it.

It could be voice or data. It's apparently too narrow for a video signal.

The use of the 450-454 MHz band is allocated primarily for non-Federal use to the land mobile radio service. The Federal agencies use this band for land mobile communication systems that are shared with State and local public safety partnering agencies for mutual aid responses such as fire fighting, emergency response, and law enforcement operations.

  • I've had to listen to powerline interference for over 50 years, and I can tell you that it most certainly is not line noise.
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  • $\begingroup$ Sorry, I was unable to copy the URL to link the quoted part in this answer to the PDF document. $\endgroup$
    – Mike Waters
    Commented Apr 20 at 19:00

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