On 6/21/2012 6:58 PM, ZR wrote: > Differential mode filtering goes inside the outlet strip and ferrites on the > outside take care of common mode on my filters.
When power people talk about common mode, they're talking about voltage between neutral and the green wire. When RF people talk about common mode, we're talking about a current that is common to all three conductors and with no voltage between conductors. Commercial line filters work on the voltage between neutral and green, but do nothing to reduce what WE call common mode current unless the enclosure of the filter is integral to, and bonded to, either the noisy device or the device being protected the because the green wire bypasses the filter. Most noise on the power line that causes us grief is what WE call common mode, and the only good fix for that is a multi-turn ferrite choke wound with all three conductors. 73, Jim K9YC _______________________________________________ UR RST IS ... ... ..9 QSB QSB - hw? BK
