[AMRadio] QRM fron Neighbor's Security System


Paul Christensen w9ac at arrl.net
Fri Jan 22 09:56:25 EST 2010


> "Years ago my young son bought one of those scooters with his own
> hard-earned money..."

Steve,

The switch-mode chargers used for scooters are notoriously noisy.  I had a 
similar issue with the neighbor to the side of me.  These supplies offer 
little or no common-mode filtering between the switcher circuit and the AC 
line.

In my own home, several SMPS have caused interference.  I have been 
replacing SMPS types with used, industrial linear supplies (e.g., Lambda, 
PowerOne, etc.)   Many SMPS designs are fine and produce no interference. 
The most problematic chargers seem to be imported from Asia and/or are 
imbedded into our household appliances where they are exempt from Part 15 
certification.  Part 15 requires an entire re-write since the proliferation 
of microprocessors and SMPS devices in common household appliances over the 
past decade.

Paul, W9AC

 



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