[RFI] EMI/RFI AC line filter design info?

Cortland Richmond ka5s at earthlink.net
Tue Sep 24 16:23:20 EDT 2013

I have spent about 30 years doing EMC engineering, with some of the 
safety type thrown in, because safety and power line EMC filtering 
cannot be separated.  We Amateur Radio operators are perhaps uniquely 
qualified, among those who use radio equipment, to design and build our 
own, but when it comes to power line filtering, the SMART choice is to 
find filters that are already qualified by test, listing and recognition 
of Nationally Accepted Test Laboratories (NRTL's) as safe when used for 
that purpose.

We used to say "UL Approved" though there are now a number of NRTL's 
whose mark is accepted by the various jurisdictions who have electrical 
and fire safety regulations. Luckily, we need not pay list price, there 
being enough such filters available excess to the needs of overly 
ambitious manufacturers.  Some we can install ourselves but some, if we 
want (among other things) Homeowner's or Renter's insurance to cover 
damage from an unfortunate occurrence, we should not.

When installers or manufacturer's representatives modify an appliance or 
add a filter to one, THEY assume liability for the consequence if it 
fails. or the installation is done improperly.

Buy two and test one, but have an authorized representative or installer 
put in the one you will USE.  Cheap is rarely good enough after 
something bad happens. If you *must* install one yourself, don't modify 
the appliance yourself if a licensed electrician can; add it outside the 
appliance with NRTL approved and marked wiring stubs and using good 
electrical wiring practices including to-code wiring and enclosures.

Dead is a one-time thing. Live and be safe.



On 9/24/2013 1021, Ray, W4BYG wrote:
> The Corcom info was interesting but at $55 apiece totaled more than I want
> to spend.  I need a couple.   Thus, I prefer save the money and build/test
> them myself.

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