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April 11, 2024. Your computer has done you in!

That terrible band noise you are hearing in your homebrew rig is not a CME (corona mass ejection) or EMP (electromagnetic pulse) from North Korea. No, it is your computer power supply.

I was hearing something in my SDR radios that also was heard in radios like my KWM-2. It was a constant noise that drove me nuts. Thoughts for the source drifted back to when the nice-looking divorced woman down the block was growing weed in her garage and the noise from the grow lights was S9.  But she had moved. 

My non-scientific research on the Mean Well power supply caused me to make this video and share that with you.

I have 3 computers in close proximity at one of the operating positions which are used for SDR work. Two are Windows 10 machines and one is a Linux Mint 20. Two of the machines are noise generators but the third has no RF Hash from its switching power supply.  This non-hash computer is a small form factor refurbished HP that was bought at Amazon for $75. 
 
The noise is loud and fills the spectrum with blips. So, if you are hearing noise go beyond just powering down the computer as it may not be off, and you will hear the noise. Either flip the power switch on the power supply to "OFF" or unplug it. 
 
Many computers have a Wake on LAN capability and even though the computer is powered down and appears off -- its power supply may be active awaiting a Wake on LAN signal.



A replacement power supply that is "clean" starts at about $100 which is a trade off at buying a refurbished computer at $75 that doesn't have the noisy switcher. 

73's
Pete N6QW


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