[RFI] Mains filter for test bench

[Christopher Brown]

Actually there are EMI filters that do filter all conductors.  They are
EMI only filter bricks (not surge/emi outlet strips).  I have multiple
examples here of sealed filters with one or more inductors on the
"green-wire".

Just not common.


Now, of we are talking Surge/EMI outlet strips, I have never seen a
product for sale that filters ground lead.  Only place I do see it is
commercial grade "EMI filter only" stuff.



On 11/7/12 3:53 PM, Jim Brown wrote:
> On 11/6/2012 4:38 PM, Missouri Guy wrote:
>>  From what I've read, there's some question of whether or not to
>> run the grounding wire, along with the "hot" and neutral
>> wires, through a say, a 2.4"i.d. #77 mix toroid.   There are no other
>> grounding conductors at the test bench.
> 
> Even the best power line filters provide NO attenuation of common mode 
> noise on the AC line, because the green wire bypasses the filter.  
> (While power filters SAY that they attenuate common mode, they define 
> common mode differently than we do (they define it as noise between 
> neutral and green, while the proper definition is a signal that is 
> common to all conductors on a cable).  AND -- most RF noise on the AC 
> line is common mode noise, and lots of baseband noise is power-related 
> leakage current on the green wire.
> 
> Thus, the ONLY good defense for RF noise on the AC line is a serious 
> ferrite choke formed by winding all three conductors around a #31 
> toroid, using as a guide  the measured data for single conductors in 
> appendix one of http://audiosystemsgroup.com/RFI-Ham.pdf
> 
> For baseband (power-related) noise, the best defense is bonding from 
> chassis to chassis of all equipment, AND fixing any missing or improper 
> bonds of the green wires inside equipment. The proper connection of the 
> green wire is directly to the chassis or shielding enclosure, never to 
> the circuit board first. Another common mfg error is a chassis 
> connection that fails because there is paint between the chassis and the 
> connection lug (VERY common in Astron power supplies).
> 
> 73, Jim K9YC
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