[RFI] Reducing RFI from Switching Power Supplies

[WD8ARZ]

Most of the electronics in my home is protected by putting a UPS 
(uninteruptable power supply) between them and the wall outlet.

Avoid the cheap low end low power units. They dont last long, fail 
sooner, and can run hot.

Choose a size from a good vendor that has the capacity to run the items 
it is powering for about 15 - 30 minutes with out AC power.
Those better models have excellent switching time, larger or multiple 
batteries, run cool, and have excellent filters / suppression built in.

Plus many will adjust to provide the right voltage and 60 cycles needed 
for more sensitive devices, especially computers.

When the UPS is going dead, it switches off giving a clean break to the 
equipment.

So not only do you provide isolation and suppression of a lot of RFI 
from switching power supplies, you also improve the survivability of 
those switching supplies that are still powered on when the device they 
run are off, thus making them vulnerable to power line transients.

Keep in mind that even though a lot of power supplies and electronics 
have built in spike suppression from MOV's (metal oxide varisters), 
those MOV's will no longer be working after several hits, even one large 
event can disable them. Same for those external power strips with spike 
protection built in. The better external power strips will have 
suppression devices that include chokes / filter design, and not just 
mov's.

Ups units are better choices as they have all the mov / filter / choke 
designs in them, but also the battery that absorbs and isolates a lot of 
problems, along with voltage / Hz adjustments.

No, I cant say what UPS units to avoid or to get. That changes so much 
in a short period of time as the models are changing all the time.

73 from Bill - WD8ARZ