HFU HF Underground
General Category => General Radio Discussion => Topic started by: IQ_imbalance on November 21, 2021, 1827 UTC
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Just purchased a small ultrasonic humidifier for my office since the desert-like humidity levels play havoc with my sinuses. I was pleasantly surprised that the wall briquette and the device did not hash up my radios....at least the bits of HF, VHF, and UHF I'm currently monitoring.
That is all!
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Well that's certainly good news!
Nowadays I figured everything would generate RFI.
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You might have gotten lucky with a decently filtered switching wall wart power supply. 8)
For those note so lucky, a good quick read on improving wall wart regulation and filtering:
http://www.dxing.info/equipment/wall_warts_bryant.dx
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You might have gotten lucky with a decently filtered switching wall wart power supply. 8)
For those note so lucky, a good quick read on improving wall wart regulation and filtering:
http://www.dxing.info/equipment/wall_warts_bryant.dx
Interesting reading, but quite outdated : it's about wall warts in the old way, with transformer on the 50/60 Hz mains frequency. Those old wallwarts were not so bad!
Nowadays, all wall warts are of the switching type : first, change the mains current to a high voltage continuous current, then use switching at some frequency between 30 and 120 kHz, where the transformer can be of light weight, then pass the output through diodes and (hopefully) capacitors. A switching PSU is a much more complex device, and can send HF noise on both the AC input and the DC output. The very bad ones are hardly producing 'DC' current, and can destroy the connected device rather quickly.