
This is everything I presently know about ARCnet cabling, presented here
because most of you are probably like me and without an ARCnet manual.

NOTE:  Please, if you have any useful information about ARCnet cabling
       that is not mentioned here, send it to:
                       apenwarr@tourism.807-city.on.ca

Any information about those "neat little boxes with the red lights that
blink when there's network traffic" would also be appreciated.

I only have two ARCnet cards, wired together by a simple coax cable with no
terminators or anything at all.  I haven't tried any setup but my own.  Use
this information at your own risk, but think about it first.

                                  -- Avery



To: Avery Pennarun <apenwarr@tourism.807-city.on.ca>
Date: Sun, 23 Oct 94 15:32:29 -0400
From: "Stephen A. Wood" <saw@hallc1.cebaf.gov>

Here is my guess about how to wire ARCNET networks.  ARCnet seems to want to
use 90 ohm cable (as opposed to 50 ohm for ethernet).  Also, ARCnet cards
appear to have an input impedance of 90 ohms (as opposed to infinite for
ethernet.)  Therefore, the cable is plugged directly into the card rather than
using a T with either another cable segment or a terminator on the other side.
It would thus seem that an ARCnet network can only consist of two nodes.  When
I bought my two cards at a garage sale, they came with little box with four
BNC connectors on the outside.  The shields of the four connectors are all
grounded together, and the center conductors were connected by the following
resistor network.

              |
              |
              R
              |
         ---R-+-R---
              | 
              R
              |
              |

Where R is 47 Ohms.  A little math shows that if you terminate three of the
outputs with 90 ohms (A cable or a terminator), the remaining input see's
90 ohms.  Therefore this box is impedance matched to 90 ohm cable.  So this
box can be used to connect 2 to 4 nodes together.  Perhaps this box should
even be used when only two nodes are in use so that cards to see too much
signal from the other card??

Clearly one could daisy chain such splitter boxes together, although one would
quickly lose signal.  So perhaps amplifiers are needed if more than 4 nodes
are to be used.

---------------------------------------------------------
Stephen A. Wood				       CEBAF/SURA
Internet: saw@cebaf.gov                            MS 12H
Bitnet:   saw@cebaf                12000 Jefferson Avenue
                                   Newport News, VA 23606


From: jmorriso@bogomips.ee.ubc.ca (John Paul Morrison)
To: apenwarr@tourism.807-city.on.ca
Date: Fri, 28 Oct 1994 23:33:08 -0800 (PDT)

The "little box with four BNC connectors on the outside" is an Arcnet
passive hub. They're worth about $5 (just so you don't get ripped
off).

I don't have specs at my fingertips. Basically, don't use too many
passive hubs (or none at all, apparently passive hubs are A Bad Thing.
On the other hand, they're a really cheap way to do things.)

Arcnet active hubs are available, they are analogous to Ethernet
twisted pair hubs. You can plug either a single station or a passive
hub into each port on the active hub. If you plug in a passive hub,
that lets you connect three more stations.

The maximum distance between two stations is 600 m or
300 m to a hub (probably to an active hub).

I don't know what the ET1 and ET2 are for, but I've heard that some
arcnet cards can be configured for longer distances; maybe that's what
those jumpers do, but I'm just speculating.

The coax cable used is RG62.

Some Arcnet cards can use twisted pair; they have two RJ11 jacks, and
jumpers to select between twisted pair and coax.  I don't know much
about this configuration. I think you run twisted pair between each
station in a ring like topology. I don't know how they are terminated,
but I have seen RJ11 terminators along with the cards, so they must
need to be terminated.

---------------------------------------------------------------------------
BogoMIPS Research Labs  --  bogosity research & simulation  --  VE7JPM  -- 
jmorriso@bogomips.ee.ubc.ca ve7jpm@ve7jpm.ampr.org jmorriso@ve7ubc.ampr.org
---------------------------------------------------------------------------


From: jojo@repas.de (Joachim)
To: Multiple recipients of list <linux-arcnet@tourism.807-city.on.ca>
Subject: Re: Arcnet cards

Some word on cableing. You don't need 90 Ohm cable. The following cables are
valid for arcnet:

RG-62  93 Ohm  up to 610 m
RG-59/U 75 Ohm up to 457 m
RG-11/U 75 Ohm up to 533 m
IBM Typ 1 150 Ohm up to 200 m
IBM Typ 3 100 Ohm up to 100 m

So normaly you can use you TV antenna cable (75 Ohm) for short distances.

Greetings from Dreieich
---------------------------------------------
repas GmbH          |  Joachim Koenig
Voltastr. 8         |  jojo@repas.de
63303 Dreieich      |  Phone +49-6103-390877
Germany             |  FAX   +49-6103-390810

