[RFI] FW: Quiet Switching Power Supply?

[Paul Christensen]

>"Unless you're in a screen room or 100 miles from civilization, the
background noise is going to cover up any minuscule noise that the best
switchers for ham use are going to emit. "

Dale, that's probably true when using coaxial lines and resonant antennas
but all switching supplies emit RFI - some more or less than others.  

When using open feeders that run across the length of a home, any small
amount of RFI can be detected, including RFI emitted from the best ham
switching supplies.  On receive, balanced feeders cannot cancel all noise
sources, since the arrival angle to the line is inconsistent.
Trans-positioning the line may sometimes help.  

At my home QTH, coax is run through the house to feed a motorized,
symmetrical  balanced tuner that's located outside and away from home RFI
sources.  Problem solved but it requires an extra level of cost and
complexity.

Just my opinion, but for ladder line/open feeder runs through a house or
apartment, I would stick with linear supplies and linear wall-warts for
accessories.

Paul, W9AC