Where does the noise I can hear on my 28 MHz receiver come from? I'm not talking about the inherent noise produced by the internal circuitry of the radio, I mean the noise received by the antenna. It's always there, no matter where I am, even if I am in the middle of nowhere and there are no nearby noise sources. If it were noise from outer space, then it would be blocked by the ionosphere when there are skip conditions, but when there is skip the noise is still there. Is it dead people?

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    $\begingroup$ Hi Andrew, atmospheric noise is known as "QRN" in ham radio, so I took the liberty of editing your question to put QRN in the title to help future searchers. $\endgroup$
    – rclocher3
    Commented Mar 17, 2021 at 16:02
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    $\begingroup$ When there is "skip", you also get a path to RFI/EMI noise from around the world. $\endgroup$
    – hotpaw2
    Commented Mar 17, 2021 at 19:01
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    $\begingroup$ I question whether outer space noise would be blocked at 28MHz in any conditions. It certainly isn't at 21MHz where you can hear solar storms and noises from Jupiter. $\endgroup$
    – Duston
    Commented Oct 29, 2021 at 13:04

1 Answer 1


Atmospheric noise does not go as high as 28MHz, it becomes less dominant above 10MHz, see figure: https://en.wikipedia.org/wiki/Atmospheric_noise

At 28MHz it is the thermal noise of the earth, either directly picked by the antenna or coming from further and reflected. Thermal noise formula: https://en.wikipedia.org/wiki/Noise_temperature

At 28MHz most of the noise may be man made, mainly from switching power supplies, mainly from led lights.

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    $\begingroup$ I see that you've been around a couple years, but nobody said hello to you back then, so hello and welcome to ham.stackexchange.com! $\endgroup$
    – rclocher3
    Commented Mar 19, 2021 at 0:27
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    $\begingroup$ Hello : ) yes i am often ignored $\endgroup$
    – Andrew
    Commented Mar 19, 2021 at 9:52

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