[RFI] Mains filter for test bench

[Jim Brown]

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