[RFI] Interference from AC units

Jim Brown jim at audiosystemsgroup.com
Mon Aug 29 08:13:07 PDT 2011

On 8/28/2011 7:22 PM, Larry Parker wrote:
> My next big headache is the new undercounter puck lights that have a 
> 20 khz transformer converting 120vac to 12vac. 

These are very nasty RFI generators. They are NOT transformers, they are 
switching power supplies.  The FCC and ARRL are seriously asleep at the 
switch to have allowed the proliferation of these RFI generators.  You 
MAY have some success by winding multiple turns of the AC line cable 
around a #31 toroid to form a common mode choke.  See my RFI tutorial 
for guidelines for tuning the choke to the frequencies where you are 
experiencing the greatest RFI trash.

73, Jim K9YC

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