[RFI] When AC filtering actually makes it worse

[Jim Brown]

On 4/22/2013 12:17 PM, Aaron Kreider wrote:
> I think what happens is that my AC is poorly grounded - so my coax 
> shield stops working. Does that make sense? 

No. But we don't know enough about your situation to offer further 
specific advice.

That said, the following is GENERALLY true:

1) Power line filters at OUR end of things rarely do much good because 
most noise is RADIATED by wiring connected to noise sources and then 
picked up by our radios, and filters can do NOTHING about that.

2) Noise is best filtered at the source.

It is VERY common for wiring mistakes in homes to CAUSE noise radiation. 
Some of the common wiring errors are:

3) A poor, missing, or improperly connected earth connection at the 
point where power enters the home.

4) Improper bonding (connections) between neutral and the green wire in 
the home.  There MUST be ONE, AND ONLY ONE bond between Neutral and 
Green, and is MUST be where power enters the home. It is rather common 
for additional bonds to be present in certain laundry equipment.

5) Failure to bond all grounds together in the home.  Absolute rule -- 
we can have as many earth connections as we like, but ALL of them MUST 
be bonded together by short, fat copper.

6) Mis-wired power outlets.

I encountered #3, #4, #5, and #6 in the home I bought when I moved to 
California, and the power system noise was quite high. ALL of the faults 
were the result of the stupidity of the so-called "qualified 
electrician" who wired the place, and all were missed by the third-party 
"home inspector" we hired to verify that the home was in good condition. :)

As soon as I found and corrected those wiring problems, the noise got 
down to very reasonable levels, and now all I hear is what is picked up  
by my antennas when I point them to a neighbor's noisy solar 
installation, and to what I suspect are grow lights in the direction of 
my EU Beverage.

It is also very good practice to use serious common mode chokes on all 
antennas.  See my RFI tutorial at http:// k9yc.com/publish.htm On the 
same page, there is also a Power and Grounding "White Paper" which 
details proper wiring practices for North America. While that document 
is written specifically for pro audio and video installations, the same 
laws of physics and building codes apply.

73, Jim K9YC