For what it's worth:
We bought a printer server made in France, it requires STP (shielded) cable for
CE compliance. We use it to test our 10/100 Ethernet ports. So at least one
French/EU entity believes in STP cable.
I also have a small 4 port 10/100 hub at home, it requires STP to pass. Uh, I
haven't bought any STP cable yet. :)
I do have a little interesting EMI experience:
I'm an amateur radio operator and have HF (1.8 to 30 MHz) equipment in my van.
I am picking up noise every ~100 kHz or so in several bands, up to 15 dB above
the noise floor, from a few meters outside my house. The regular pulsing noise
is present even if the 10/100 Ethernet is idle (all computers off), but the
Toshiba cable modem is always on. Cable modems uplink on 5 to 50 MHz, right
through prime ham radio real estate. But, there could be other sources to
blame, I'll find it when I get enough time....
Eric Lifsey
Please respond to lfresea...@aol.com
To: david_ster...@ademco.com, chris_al...@eur.3com.com, c...@prodigy.net,
cet...@cetest.nl
cc: emc-p...@ieee.org, gary.mcintu...@worldwidepackets.com,
john_mo...@eur.3com.com (bcc: Eric Lifsey/AUS/NIC)
Subject: RE: Conducted Emissions on Telecom Ports
Hi all,
just thought I'd throw a few Euros in...
First, until folks in the computer world know what shielded cable means (
anything less that 40 dB is lossy insulation;-))) ), I'd stear clear of
specifying them. This is 20 years of experience talking, and shields seem to
cause more problems ( 'cause they are missinstalled ) than they fix: right Ken
J?
Second, the probability of interference ( or immunity ) from LAN wiring depends
a lot on where they are routed. If LAN wires are bundled with phone wires,
interference will result... Conducted emissions control on LANs will minimize
this. Remember, the LAN can act as a path for noise to leave the PC, it need not
be direct LAN sourced noise! Poor layout of a LAN card causes this....
Third, I've tested a bunch of LAN cards from different folks.... There is a huge
difference between vendors. Not all cards have the ability to terminate a shield
properly.
I would suggest that vendors comply with conducted limits deemed appropriate by
the power that be, without applying any form of shielding. If you disagree with
the powers that be, join the committee that develops the requiremnt in the first
place! I say this as a LAN product end user... and someone active in the
committees that write the requirements for my products.
Thanks,
Derek.
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