tom@wcc.oz (Tom Evans) (07/12/89)
Sorry about the wide posting, but this affects Unix, PC and Mac Lans. Your Cheapernet consists of cables and "Tee" pieces. If any cable or Tee piece goes bad, your net comes down (or gets sick). I bought four "Brand A" Tee pieces from an electronics store. The centre pin diameters varied. They consistently had one "tight" and one "loose" socket. At least pins and pin-sockets were gold-plated. After complaining, I got six "Brand B" ones. These have tin-plated everything. The pins are loose, and break contact when you move them. The outer-shield mechanics are so bad as to give intermittent SHIELD continuity. The pin and surround diameters are all wrong - they connect to each other badly, and to real BNC connectors terribly. I have to call them "Brand A" and "Brand B". They are both NONAME - not a single identifying mark anywhere. Acceptance test. Join all your Tee pieces together in a line. Put a terminator (or a short) on one end and a multimeter on the other. Wobble the lot. If the resistance changes, you've got a problem that could cost you hours in real-life. Try your cables as well. --------- Tom Evans tom@wcc.oz | If "the Network is Webster Computer Corp P/L | the Connector" and 1270 Ferntree Gully Rd | the connector is Scoresby VIC 3179 Australia | broken... Australia | 61-3-764-1100 FAX ...764-1179 |
glen@aecom.yu.edu (Glen M. Marianko) (07/13/89)
In article <335@wcc.oz>, tom@wcc.oz (Tom Evans) wrote about the trials
and tribulations of using T connectors in thin ethernet.
Just to echo a bit, several months back someone mentioned a bad
T causing problems on his net. Wiseguy that I am, I thought how
could you possibly have a bad T? Well, living through one does
open up one's eyes!
This is a VERY serious problem. I suspect that if one uses BNCs
and Ts from the same manufacturer, they stand a better chance of
interoperating better. I can't confirm this, however.
I don't know if there is a BNC "standard" that describes the OD of
the center pin, but one can visually see that it does vary between
manufacturers.
What I have noticed about Ts is that the brand name ones (like Amphenol)
that one gets bundled with ethernet cards work better. I guess you
get what you pay for. Cheap Ts can go for as little as $1.50 in
reasonably small quantities, yet brand names can be advertised as
high as $15!
Anyone who found a reliable combination, (at a good price - better yet),
please post your sources. Thanks!
--
-- Glen M. Marianko, Supervisor of Data Communications and Hardware Support
glen@aecom.yu.edu - {uunet}!aecom!glen - CIS: 76247,450aurie@rhea.trl.oz ( Radio and Satellite Networks) (07/17/89)
In article <335@wcc.oz> tom@wcc.oz (Tom Evans) writes: >Your Cheapernet consists of cables and "Tee" pieces. If any cable or >Tee piece goes bad, your net comes down (or gets sick). > >I bought four "Brand A" Tee pieces from an electronics store. >The centre pin diameters varied. They consistently had one "tight" ^^^^^^^^^^^^^^^^^^^^^^^^^^^ One thing to note about BNC connectors is that there is TWO generic types 75 ohm - with thin centre pins 50 ohm - with thicker centre pins (Its all a question of ratio of diameters - the higher the ratio and higher the impedence) If you use a 50 ohm female connector with a 75 ohm male then you don't get a very good connection the other way around is a bit more serious ( and is known in the trade as raping the connector) -- Alistair URIE Radio and Satellite Networks Phone: +61 3 541 6370 Telecom Research Laboratories Fax: +61 3 543 3339 770 Blackburn Rd. Clayton Vic Mail: aurie@rhea.trl.oz AUSTRALIA
pat@hprnd.HP.COM (Pat Thaler) (07/18/89)
Glen Marianko writes: > Just to echo a bit, several months back someone mentioned a bad > T causing problems on his net. Wiseguy that I am, I thought how > could you possibly have a bad T? Well, living through one does > open up one's eyes! > > This is a VERY serious problem. I suspect that if one uses BNCs > and Ts from the same manufacturer, they stand a better chance of > interoperating better. I can't confirm this, however. > I don't know if there is a BNC "standard" that describes the OD of > the center pin, but one can visually see that it does vary between > manufacturers. > To quote from the 10BASE2 "cheapernet" standard: "High-quality versions of these connectors (per IEC 169-9) are recommended in order to meet dc loop resistance and reliability considerations." In addition to the IEC spec, there is a Mil spec, but I don't know the number off-hand. These specs cover dimensions. I think they also cover plating type and thickness. Improperly installing connectors on the cable can also lead to problems. Pat Thaler
childers@avsd.UUCP (Richard Childers) (07/20/89)
glen@aecom.yu.edu (Glen M. Marianko) writes: >What I have noticed about Ts is that the brand name ones (like Amphenol) >that one gets bundled with ethernet cards work better. I guess you >get what you pay for. Cheap Ts can go for as little as $1.50 in >reasonably small quantities, yet brand names can be advertised as >high as $15! >Anyone who found a reliable combination, (at a good price - better yet), >please post your sources. Thanks! Use MILSPEC Amphenol connectors and use a VOM to check the connections. I was taught to do this and never had problems that couldn't be fixed in a few minutes ... >-- Glen M. Marianko, Supervisor of Data Communications and Hardware Support > glen@aecom.yu.edu - {uunet}!aecom!glen - CIS: 76247,450 -- richard -- * Truth : the most deadly weapon ever discovered by humanity. Capable of * * destroying entire perceptual sets, cultures, and realities. Outlawed by * * all governments everywhere. Possession is normally punishable by death. * * ..{amdahl|decwrl|octopus|pyramid|ucbvax}!avsd.UUCP!childers@tycho *