greg@duke.cs.unlv.edu (Greg Wohletz) (12/16/89)
To quote from some cabletron documentation:
When making up networks requiring shorter cable run, Ethernet
standard length 23.4m, 70.2m, and 117 meter cable sections should be
used. These cable sections may be connected together to form a cable
segment by using a barrel connector. Use of non-standard cable
lengths may result in impedance mismatches causing reflections to
occur. These reflections may cause data errors.
My question is how critical is this? I have some cable runs that will
probably be around 100 meters, should I be sure they are 117 meters?
--Greg
greg@duke.cs.unlv.edulars@salt.acc.com (Lars J Poulsen) (12/16/89)
In article <1425@jimi.cs.unlv.edu> greg@duke.cs.unlv.edu (Greg Wohletz) writes: >To quote from some cabletron documentation: > When making up networks requiring shorter cable run, Ethernet >standard length 23.4m, 70.2m, and 117 meter cable sections should be >used. These cable sections may be connected together to form a cable >segment by using a barrel connector. Use of non-standard cable >lengths may result in impedance mismatches causing reflections to >occur. These reflections may cause data errors. > >My question is how critical is this? I have some cable runs that will >probably be around 100 meters, should I be sure they are 117 meters? The connections WILL cause some (hopefully minor) impedance mismatches. The standardized cable lengths are selected to prevent standing waves from the resulting (hopefully weak) reflections. The more carefully your connectors and taps are done, the less important the lengths will be. But if it doesn't cost you anything, why not go with the spec and get the extra help from self-cancelling reflections ? -- / Lars Poulsen <lars@salt.acc.com> (800) 222-7308 or (805) 963-9431 ext 358 ACC Customer Service Affiliation stated for identification only My employer probably would not agree if he knew what I said !!