[RFI] Any Issues with newer heating cooling systems

Jim Brown jim at audiosystemsgroup.com
Fri Aug 28 09:21:40 PDT 2009

On Thu, 27 Aug 2009 22:49:35 -0500, Mike - KM0T wrote:

>The fan would be variable speed.

Modern variable speed motors are notorious for REALLY severe RFI. 
They work by first rectifying AC to get DC, then creating a chain of 
square waves whose width is modulated to control the motor. It is 
certainly possible, with good circuit design and implementation to 
do this without creating RFI, but noisy variable speed motors are 
all too common. 

I would approach this with caution. 


Jim K9YC

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