I have mentioned using a LISN, Line Impedance Simulation Network, in
measuring RFI/EMI before.

An Email asked what in the devil is a LISN.

A Wiki discription
http://en.wikipedia.org/wiki/LISN

An operation manual with schematic diagram.
http://www.ets-lindgren.com/manuals/4810.pdf
Please note that F1 and F2 are, in my opinion, misplaced,
F1 should be before the L1/C3 and F2 should be before
L2/C4. The opening of the fuses because of a failure
in C13 or C14 will place unexpected voltages at S1.

A LISN is not a very accurate simulation of any AC mains
that I have ever seen, but it is a standard so EMI labs can
do similar tests. It is very useful for testing the EMI that
leaks back in to/on to the AC mains.

An unusual little RFI probe that can be used with a LISN.
http://www.edn.com/archives/1998/060498/12DF_04.pdf

A very detailed explanation of EMI certification:
http://www.navair.navy.mil/e3/Documents/mil462d.pdf

And for those silly enough to want to measure the RF noise
directly on an AC main, or telephone cable, see page 26:
http://www.nato.int/docu/stanag/aectp/aectp-500-2.pdf
I must caution anyone wishing to build such a unit to stop
and consider the risks. Improperly construction or use
will result in electric shock or electrocution. For over
90% of my home RFI sniffing I have found a 19uH inductor
wound on a pill bottle to be as effective. This probe is very
good for the really sneaky and hard to find RFI sources.

The diagram shown is for illustration only and neglects
required safety components. If you build it as shown,
and use it, you will get fried! I am not going to describe
the unit I built because this is a hobby and I don't want
to help someone hurt themselves.

This probe is very useful when trying to "denoise" a large
device, such as anything with variable speed drives.

Current probes also exist, but I don't have any links to these.
They are much like a clamp on ammeter and are much safer
to use.

Separating Differential Mode Noise from Common Mode Noise
Page 46.
http://www.hottconsultants.com/pdf_files/APEC-2002.pdf
There are slicker ways to do this, but this is the only link I have.

In most cases even serious high levels of RF noise can be attenuated
to a level where we can still listen to all but the weakest SW
signals.

You do not have to be an EE to solve 99+% of your RFI woes,
understanding how RF spreads into the various conductors in
your house and an understanding of the appropriate filter
technology will allow you to almost certainly reduce the RFI
significantly. It is important to understand and accept that this
is an iterative process, that is many passes will have to be made,
with each pass finding and reducing ever lower levels of RF noise.

And many times you will think you are done, only to realize at a
later date that more noise remains.

Now, if there was just a way to make a living reducing RFI in the
real
world. Too bad the NSA isn't hiring.

Terry