[RFI] power line bypassing

[Jim Brown]

On 2/12/2011 9:05 PM, Chuck wrote:
> A friend tells me he has an AC lines conducted noise problem from his
> next door neighbor's well pump. In the past, I have heard of people
> putting bypass caps onto their service entrance panel.Is his best answer
> to apply bypassing? If so, what is recommended?

You didn't say what frequency, or what the noise sounds like.  The first 
thing I would work on is making sure that the neutral and green wire are 
not bonded together at the pump. Also make sure that no 120V motors are 
running between one side of 240 and the green wire.  Both are recipes 
for noise. Also, try to figure out what kind of motor and motor 
controller it is.  If it is speed controlled, what kind of controller?

The best cure for most conducted noise is a good common mode choke, and 
the most effective common mode chokes are formed by winding multiple 
turns of the cable around the "right" ferrite core.  The choke MUST be 
very close to the noise source to be effective.  Conducted noise is 
really RADIATED noise -- the wire that conducts it becomes an antenna, 
so the choke works by killing the current.  You MIGHT do some good with 
caps at the entry panel, but I suspect that the wiring that's doing the 
damage is between the pump and the panel, in which case the caps 
probably won't help.

For more, study http://audiosystemsgroup.com/RFI-Ham.pdf  Also, study 
the tutorial on Power And Grounding for Audio and Video Systems at 
http://audiosystemsgroup.com/publish.htm   While it's written for those 
systems, the same laws and rules of good engineering apply, and the same 
dumb electrical wiring mistakes cause problems at both audio and RF.

73, Jim Brown K9YC