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From: ed%mtxinu@mtxinu.UUCP
Newsgroups: net.dcom
Subject: Re: Thin Ethernet really works...
Message-ID: <1@mtxinu>
Date: Thu, 24-Apr-86 02:03:00 EDT
Article-I.D.: mtxinu.1
Posted: Thu Apr 24 02:03:00 1986
Date-Received: Sun, 11-May-86 16:32:41 EDT
References: <735@hoptoad>
Lines: 34

In article <735@hoptoad.uucp> gnu@hoptoad.uucp (John Gilmore) writes:
>I can see why 3Com pushed Thin Ethernet -- it's easy and the parts
>are available locally.  For all I know, Radio Shack has what you need.

I didn't check radio shack since I didn't think they would have the
stuff.  TV cable is *not* Ethernet cable.  TV cable is 75 ohm and uses F
series connectors, Ethernet is 50 ohm.  A local electronics store
(Al Lasher's in Berkeley) had most of the parts I needed.  They didn't
stock the BNC-to-N adapters, though.

Neither did they have RG-58/CU cable, which is what 3Com recommends.
They did have RG-58/AU, which is slightly less flexible, has lower
capacitance and a higher propogation speed.  It works, too, at least
for our small network (Vax, microvax, sun, PC).

>Why did xeroX go with expensive custom cabling originally?  They figured
>that standard TV style thin cables wouldn't permit a big enough network?

There are differences in the physical and electrical characteristics
of the cables.  The thin stuff is *much* more fragile than the thick,
and stinger-tap transcievers (like everyone but 3Com sells) are easier
to install on the thick stuff.  On the other hand, thin cable cost me
about $80 for 500 feet (of the aforementioned RG-58/AU);  Inmac
sells RG-58/CU for $.23/foot ($115/500 ft) in bulk and thick cable
for $1.40/foot ($700/500 ft - both prices are for 500-1000 foot lengths).

The electrical differences relate to things like total network length
and distance between nodes.  I don't know the details.

-- 
Ed Gould                    mt Xinu, 2910 Seventh St., Berkeley, CA  94710  USA
{ucbvax,decvax}!mtxinu!ed   +1 415 644 0146

"A man of quality is not threatened by a woman of equality."