Hi Glen,
Let me try to answer your inquiries from the perspective of a
networking manufacturer.
When we do our EMI testing, we use the cable that would normally be
used with the product. That means that if the product is meant to be
used with Cat. 5 Unshielded Twisted Pair (UTP) cabling, it is tested
with UTP.
We presently have available 100Base-T products that MEET the class A
requirements using Cat. 5 UTP.
Incidentally, most if not all of the networking manufacturers use
shielded ports that are tied in to ground somehow within the product,
even if the specified cabling is UTP. The reason for this is that
noise radiated within the box will couple onto the UTP if it is not
shielded at the connector. The cable shielding is not necessary if
the design is done properly.
If you have more questions, please let me know.
Sincerely,
Ron Fotino
Principal Compliance Engineer
Cabletron Systems, Inc.
______________________________ Reply Separator _________________________________
Subject: Ethernet Compliance
Author: Gassaway Glen <[email protected]> at !INTERNET
List-Post: [email protected]
Date: 5/28/96 2:41 PM
We have a decision to make on one of our systems regarding 10 base T LAN
cabling. It is intended to carry 10BaseT (10Mb/s) traffic, but we want to
install it with the capability to upgrade to 100BaseT (100 Mb/s). The
question is whether or not to use shielded cabling.
We know that the industry standard in the US and in most of the world is to
use unshielded twisted pair cabling (like cat 5). Because of this, most
hubs, routers, etc. have unshielded, ungrounded connectors on them. We can
buy shielded twisted pair cables and connectors, but obviously the shield
will not be grounded when simply plugged into an ungrounded jack.
The question is whether or not unshielded 10 base T or 100 base T will meet
FCC\CISPR Radiated limits. The limits applicable to our product are class A
FCC.
Could anyone on the net offer some guidance about this issue?
Thanks in advance
Glen Gassaway
Motorola GSTG
EMAIL: [email protected]
