Re: CAT 5
On 11 Dec 1997 bruce@va.debian.org wrote:
> Isn't it funny how so few of these cables are shielded?
> Shielded cables, grounded only at one end (to prevent ground loops),
> would be much better about static, atmospheric noise, radio pickup,
> and induced currents from near lightning strikes. I did up my home
> and office that way to keep the interference from the network out of
> my ham radio. It works the other way, too.
Actually, that is probably why they are called UTP -> Unshielded Twisted
Pair. The tight twisting of the two pairs in CAT 5 cabling is what keeps
the noise out of the transmission (and gives the required impedance).
But.. if you do happen to put strong singal sources near your cabling,
especially ones that are at 10MHz or 100Mhz or any harmonic of those two
you will likely get problems anyhow. UTP doesn't do much for keeping noise
from leaking out of the cable but it is fairly tolerant to normal abient
noise.
Shielded Twisted Pair (note, the twists are still important) is better,
especially in noisy environments, but TP ethernet was designed to work
without a sheild on the cable. AFAIK there actualy isn't a ground pin in
the spec that you could connect the shield to anyhow and an ungrounded
sheild isn't worth much. I also imagine that sheilding a TP cable will be
difficult to do properly because adding the extra ground 'plane' will
effect the impedance of both pairs.
As you said, with CAT 5 and 100Mbit it's VITAL that the pairs are used
properly. Otherwise you get the transmit line leaking into the recieve
line and vise versa and that will probably prevent 100Mbit and mess up
10Mbit.
Jason
Studying Vector Calculus
--
TO UNSUBSCRIBE FROM THIS MAILING LIST: e-mail the word "unsubscribe" to
debian-user-request@lists.debian.org .
Trouble? e-mail to templin@bucknell.edu .
Reply to: