[RFI] thrashing SMPS

[bill K7WXW]

I am currently in the second (or third) phase of taming the EMI/RFI that 
plagues my 
middle-of-the-city-garden-lot-antenna-surrounded-by-RF-sources station. 
I learned pretty quickly that fixing it wasn't going to be a matter of 
simply swapping out every power supply or having a warehouse full of 
ferrite ready to wrap around every wire I could get my hands on. Don't 
ask me how I learned.

As others have suggested, I first looked to my radio table, saw how much 
noise the cheap SMPS connected to USB hubs, etc were generating and got 
myself a hefty RF quiet linear 14VDC power supply, and set up a DC power 
distribution system.  While I could have kept some of those supplies, it 
was easier to have one power supply and a distribution system that 
managed it all.That cleared a bit of noise away.

The situation in the rest of the house, which is infested with devices 
that use SMPS, was not so simple.Tossing power supplies or dispensing 
hunks of ferrite without having any idea whether either is (a) necessary 
or (b) makes a difference caused my parsimonious heart to ache, so 
evaluating each and every one of the beasts on its own merits was a 
must.  When I tried fixing a noisy source, sometimes ferrite worked. 
Sometimes a SMPS had to be replaced. Sometimes, as with the goofy 
integrated charger and stand that my dear wife chose for her iPhone, it 
had to be lived with. Each fix ended with a round of checking the 
result. When I got through it all, the overall noise level at my 
receiver had dropped a bit more.

So while I think there's a lot to be said for switching out switchers, I 
am a big fan of doing so in a thoughtful way, mostly because I am really 
cheap.

73 de Bill K7WXW








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