On Mon, 16 Dec 2013 07:46:16 -0500, Jerry Stuckle
wrote:

Then he has a problem in his ethernet. Properly installed, ethernet
creates virtually no interference.

Yes, that's the theory. If the cable isn't perfectly balanced, it
will become an antenna. Shielded ethernet adds additional
opportunities to radiate. Most of the RFI originates from ethernet
switches and routers.

One oddity are ethernet hubs. What goes in one port, goes out all the
other ports. With a switch, only data destined for a specific MAC
address on another port is passed. The problem is many older hubs
will send data to a port if a cable is inserted but not terminated.
They're not suppose to do that, but I've found a few old hubs that do
that. If you have an ethernet RFI problem, look into replacing hubs
with switches.

"Understanding and Eliminating RF Interference" by Jim Brown K9YC
http://www.audiosystemsgroup.com/RFIHamNCCC.pdf
Start reading at Page 20 for the ethernet radiation section.
Mo
http://www.audiosystemsgroup.com/publish.htm

This thread may also be of interest:
http://lists.contesting.com/_rfi/2008-11/msg00025.html

Note that 100baseT is quieter than 10baseT. With 100baseT, the data
is first 4B5B encoded at 125Mbits/sec. To reduce crosstalk, it is
then scrambled and MLT-3 encoded. The result is a 31.2MHz carrier and
a mess of sidebands. The necessary scrambling has the side effect of
reducing high power peaks, and evening out the power spectrum over a
wider frequency range, thus reducing the RFI power at any given
frequency. It's much the same idea as the "spread spectrum"
modulation of computer clocks, to spread the power over a wider
frequency range, to meet FCC Part 15 requirements. So, instead of a
carrier or birdie, you'll hear broadband noise, which I guess is more
tolerable.




--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558