[RFI] When AC filtering actually makes it worse

[Jeff Blaine]

Aaron,

My guess is that you have power adapters around your house which are taking 
a free ride on the house wiring.

Have you tried to hunt down the noise makers?  One quick (?) way is to get a 
portable AM radio, tune to an unused part of the band, and take a walk 
around your house holding that radio next to anything that connects to an 
outlet.  I would start with the adapters plugged into that power strip.

I have been kicking around using my QS1R for that purpose as well by 
powering the QS1R from the laptop's 5v (or other battery) supply.  A guy 
with this arrangement could roam from room to room with a small loop tied to 
the QS1R.  Looking at the wide band monitor in sdrmax, it would be cool to 
see the spectrum rise up as you closed in on a bad actor...

73/jeff/ac0c
www.ac0c.com
alpha-charlie-zero-charlie

-----Original Message----- 
From: Jim Brown
Sent: Monday, April 22, 2013 3:09 PM
To: rfi at contesting.com
Subject: Re: [RFI] When AC filtering actually makes it worse

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
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