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From: phil@amdcad.UUCP (Phil Ngai)
Newsgroups: net.lan
Subject: Re: Fiber-optic Ethernet Extender
Message-ID: <11757@amdcad.UUCP>
Date: Thu, 22-May-86 03:58:58 EDT
Article-I.D.: amdcad.11757
Posted: Thu May 22 03:58:58 1986
Date-Received: Sat, 24-May-86 18:17:12 EDT
References: <373@imagen.UUCP> <3732@sun.uucp>
Reply-To: phil@amdcad.UUCP (Phil Ngai)
Distribution: net
Organization: AMD, Sunnyvale, California
Lines: 37

In article <3732@sun.uucp> djc@sun.uucp (David J. Cardinal) writes:
>If the buildings are adjacent, it is cheaper to just run the Ethernet
>(if you have a distance problem, I don't believe the fiber helps unless
> you get something smarter like a Vitalink or somesuch that does something

You believe wrong. If you will check your Ethernet or IEEE 802.3 spec
you will see that a coax segment has a length limit of 500 meters.
Coax segments can be connected together with repeaters. There can be
up to two local repeaters between any two stations. An Ethernet is
limited to 1500 meters of coax between any two stations. In addition
you get up to 1000 meters of point to point link between two halves of
a remote repeater. The max distance between any two stations is
therefore 1500 plus 1000 plus 50 * 6 = 2800 meters. In such a max'd
out system, there would be six 50 meter transceiver cables.

By the way, Belden 9880 is not rated waterproof. Belden tells me the
presence of pinholes in the PVC jacket can allow water to enter and
cause corrosion. You can use the teflon plenum cable but it costs $4
per foot. If you have conduit between buildings be sure that water
doesn't condense from the air moving between buildings.

Some electrical codes require a cable to be grounded at one point in
each building. DEC recommends this. If this causes ground loop
problems, then you can not run Ethernet coax trunk cable between
buildings.

Our production Ethernet does not use coax between buildings, although
we have an experimental Ethernet which does and works fine. For now.

By the way, why do people feel compelled to post on things they know
nothing about?
-- 
 Vote Yes on Proposition 51!

 Phil Ngai +1 408 749 5720
 UUCP: {ucbvax,decwrl,ihnp4,allegra}!amdcad!phil
 ARPA: amdcad!phil@decwrl.dec.com