making cables - what am I doing wrong?

I'm making ethernet cables which don't quite work and it's drivign me crazy. I can't quite explain under what conditions they work and don't work. It seems that they do work with almost all (or juts all) 10 mbit boards but don't work with the newer 100mbit boards. I've used two different sources of cat 5e cable, in one case it's not clerly labeled for speed, in the other it says that it was tested for Gigabit networks. Results are the same. So it must be the heads I'm using? Is this even possible? Or could it be the crimper? Because I've tried heads from two different sources -- doesn't seem to make a difference. When I plug such cable between a 100mbit Linksys router and a 100mbit PCMCIA card the light on the switch goes on for couple of seconds, blinking very-very fast and then disappears. If I replace the PCMCIA card with an old one 10mbit card it works fine. Please help, I'm getting scared.

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You are probably untwisting the pairs too much. the twist of the pairs needs to be maintained right up until the last millimeter. Also possible you are using connectors designed for stranded wire with solid wire, or vice versa. If you are making patch cables, I submit that you can buy them for far less money from various online sources than what your time and materials are costing you.


Reply to
Dale Farmer

How are you building the cables? Sounds like a classic case of not building them to 568A or B...

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Reply to
William P.N. Smith


It is much more likely mispairing. The untwist requirement for

100baseTX isn't quite that bad. Cat5 is supposed to be good enough for gigabit, but even gigabit won't be that sensitive until you are close to the maximum length. I thought the Cat5 spec. was closer to 0.5in, or about 12mm. 100baseTX will likely work with significantly more, and 10baseT even more than that.

Mispairing means that the two wires used by a signal aren't a twisted pair. For 10baseT and 100baseTX ethernet the pairs are (1,2) and (3,6). Normally ethernet cables are wired with (1,2), (3,6), (4,5), and (7,8) as twisted pairs as required for gigabit. If you didn't do that, then that is the problem. A mispaired cable will work to about 10m on

10baseT and about 1m on 100baseTX (depending on which pairs you actually use it could be more or less). (And probably about 0.1m for gigabit.)

-- glen

Reply to
glen herrmannsfeldt

The cables you are using should get you 1Gbit/s no problem. Sounds like you might be making a straight-through cable without actually placing all conductors into their standard-defined positions. Check your color code with either T568A or T568B pinouts:

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make sure you use the same pinout on both ends of the cable. One other thing: very often people use heads designed for stranded cable on a solid conductor one. This usually results in higher attenuation, but could actually have other symptoms as well. Check with the supplier of your plugs - make sure you are using the correct type for your cable.

Cheers! Dmitriy


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Yes, you are right. I wasn't doing it according to the spec. I didn't realize that the pair that was used had to be tweasted and that that pair wasn't consequtive (3,6). Very, very stupid of me. Thank you very much for getting me straight.

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