[RFI] Device Generating RFI Fix

WD8ARZ wd8arz at ix.netcom.com
Mon Aug 7 08:34:41 EDT 2017

Many of today's electronics use AC Switching power supplies. That method 
avoids the use of transformers saving on cost, weight and size of the 
device. Instead 'switching' power supplies circuits are used. That 
method of chopping the a power source to achieve the voltage and current 
from the device as needed to run that equipment, does generate a lot of 
spurious signals. Some of them are radiated as radio frequency energy 
(RF). A lot of interference can be generated by such devices and be 
received by other devices, especially when other devices are close to a 
radiating piece of equipment.

Unfortunately, many such power supplies do not use a true on / off 
switch that mechanically disconnects the power supply from the a.c. 
mains. Thus turning the device "off" may not in fact remove power from 
the switching power supply. It is left running to support the 'instant 
on' feature. To remove the interference from such a device requires 
pulling the power cord out of the ac outlet to truly turn it off.

So when looking for a radiating interfering signal, pull the power cord 
to truly test if that device is the problem or not. Good luck on such a 
quest of find that type of interference .... 73 from Bill - WD8ARZ

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