Wednesday, February 23, 2022

QJ-PS30SWI low noise switching power supply with "noise offset" feature

In my pursuit of low receive noise I've been using a linear power supply but the one I have makes a loud audio hum sound that is a bit annoying. Searching for low noise switching power supplies I stumbled across the QJ-PS30SWI which I purchased for AU$120 from AliExpress.

The supply is quite low noise, but there are lines visible on the waterfall about every 2kHz if I turn the preamp on.

Unlike switching supplies I've used with HF receivers in the past, where there are broad bands of noise that drift up and down, in this case they are narrow and the "noise offset" control lets me move them away from the frequency I'm listening to.

The supply is very compact and has a fan that doesn't seem to run, presumably it does when it gets hot.

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