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 |
aurie@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