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Re: OT: Strange network cable problem



On Fri, Sep 21, 2001, Nadav Har'El wrote about "Re: OT: Strange network cable problem":
> You know that wires for 100Mb/s ethernet are called "Category 5" UTP
> (unshielded twisted pair), right? This category 5 (and I'm sure some of the
> EE'ers on this list can explain it much better than I can) has to do with
>..

After writing the above from-memory-account of how UTP works, I looked for
a good short reference on how UTP works, what kinds of noises/crosstalk can
occur despite the differential signaling, and so on, and I found

http://www.ora.com/reference/dictionary/terms/U/Unshielded_Twisted_Pair.htm

It should be an interesting read to anyone attempting to build UTP wires
(or even terminate UTP wires) him/herself.

One particularly interesting paragraph says:

 "A Category 5 cable installation requires more than just Category 5 cable.
  For example, installation practices (such as not untwisting a pair more
  than 1/2 inch when terminating it onto a connector) must be met. ..."

This is easy to get wrong if you terminate a UTP wire for the first time
by yourself, and didn't know that the twisting was so important.
Or, again, the wire itself can simply be faulty from the start: a twist
which is not tight enough, or not twisted properly (see the above reference)
is likely to make a cable worthless for 100 Mb/s transmission.



-- 
Nadav Har'El                        |       Friday, Sep 21 2001, 4 Tishri 5762
nyh@math.technion.ac.il             |-----------------------------------------
Phone: +972-53-245868, ICQ 13349191 |I am the world's greatest authority on my
http://nadav.harel.org.il           |own opinion.

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