[RFI] 160m-5mhz noise?

Paul Christensen w9ac at arrl.net
Sun Nov 8 10:08:02 PST 2009

> Just to say that switch mode supplies CAN be made to be as RF quiet as any 
> linear supply.

While a switch-mode supply can be made as quiet as a linear supply, 
oftentimes they are not.   The quality power supply brands are generally not 
a problem.  The problem more often is from an Asian import "brand "X" 

I have two-switch mode station supplies that are completely RF quiet.  My 
prior point was that as more switch-mode technology is deployed, a larger 
number of poorly-designed supplies will exist around our neighborhood 
households, especially when poorly-designed switch-mode technology is 
embedded into our "quality brand" appliances -- appliances exempt from a 
certification requirement.

It's also true that more well-designed supplies will be around us -- but 
those supplies are not the problem unless they fail in a mode that produces 
RFI.  I've never seen a linear supply fail in a mode that produces S9 noise 
at a distance of 500 feet.  At most, the output filtering may develop noise 
or ripple and its generally contained to the DC power bus, but unless its 
some extremely abnormal condition, the noise/ripple does not propagate like 
a switch-mode supply.

Paul, W9AC 

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