| Author |
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James Knott
Guest
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 Posted:
Tue Dec 07, 2004 7:24 pm Post subject:
Re: Cable ends: how important is standard? |
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Phil Partridge wrote:
| Quote: | Agreed. Coaxial is unbalanced (lets ignore twinax, which has two central
conductors)
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Many years ago, I used to work on a system that used triaxial cable, which
had two separate shields. This was used on the one of the earliest
computer networks (Collins computers). That network dates back to the mid
60s and used time slots, rather than the packets that are common today.
All the devices, such as tape and disk drives, were connected on a ring,
which ran at 8 Mb/s. The network consisted of two rings and devices could
be attached to either ring, under program or manual control. When a device
wanted to transmit, it was assigned a time slot, which the receiving device
was told to listen to. |
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glen herrmannsfeldt
Guest
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| Posted:
Thu Dec 09, 2004 3:07 pm Post subject:
Re: Cable ends: how important is standard? |
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Watson A.Name - "Watt Sun, the Dark Remover" wrote:
| Quote: | "glen herrmannsfeldt" <gah@ugcs.caltech.edu> wrote in message
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(snip regarding length of mispaired cables)
| Quote: | My usual numbers are 3m for 10baseT, 0.3m for 100baseTX, and
0.03m for 1000baseT. It depends, though, on exactly which
pairs are mispaired.
Oh, gee, you make this mistake so often that you have a usual
number for it? ;-)
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It is the approximate length I have read here when people
say that a cable doesn't work, then divided by 10 and 100.
Or, about 1/10 the wavelength for 10baseT, and then 1/10
and 1/100 of that. About the same either way.
While the frequency doesn't go up by a factor of 10, the
faster standards are a little more sensitive, so I use a
factor of 10, anyway. If you get to where the difference
between 20cm, 30cm, and 40cm makes a big difference, you can
measure them yourself.
-- glen |
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glen herrmannsfeldt
Guest
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| Posted:
Sun Dec 12, 2004 8:22 am Post subject:
Re: Cable ends: how important is standard? |
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David Lesher wrote:
(snip)
| Quote: | If you are punching down PLUGS, you need to be "dope-slapped" {in
the words of Click & Clack} as you can buy patch cables cheaper than
make them....and get a better cable.
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Buy them on eBay, and they can be cheaper than the connectors
for do it yourself cables. I have bought them for school networking
projects, 100 cables for about $30.
For unusual lengths, though, it is still useful to make my own.
| Quote: | That said: note that the lay alternates COLOR WHITE COLOR WHITE etc.
[1] Well, almost... since the twists are different rates, the pairs
are different lengths. This is of zero interest since the difference
is so small, EXCEPT to the standards folks working on the latest
NTP protocol. Seems that there, the few nanoseconds of difference
DOES matter.
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For a round trip connection the total time will be the same
either way. For a patch cable (2m or so) the difference
should be less than 1ns. For a longer cable it could be
a few. You don't have that much control over the rest of
the network, though.
-- glen |
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Watson A.Name - \"Watt Su
Guest
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| Posted:
Sun Dec 12, 2004 8:45 am Post subject:
Re: Cable ends: how important is standard? |
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"Robert Redelmeier" <redelm@ev1.net.invalid> wrote in message
news:v20td.41224$Al3.31459@newssvr30.news.prodigy.com...
| Quote: | David Lesher <wb8foz@panix.com> wrote:
As long as you make both ends the same, they are functionally
equal. [1] That said, 95% of the folks use 568B; except
some USG contracts still call for 568A.
The residential std now calls for -A to get USOC compatibility
for pair one (blue) _and_ pair two (orange).
If you are punching down PLUGS, you need to be "dope-slapped"
{in the words of Click & Clack} as you can buy patch cables
cheaper than make them....and get a better cable.
_FULLY AGREED_. If you don't know what a split pair is,
nor why it's bad, then you've got no business with crimpers.
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I've noticed that the last several hundred patch cables we've received
have all been Cat6 (said on the bag), with the special two-part plugs
and the weird cable that doesn't say anything about what category it is
(says 4/23, tho). These have been both systimax and another brand made
in thailand. To do these yourself seems like it's masochistic, since
the whole plug is different and needs new supplies and crimpers, etc.
Probably new, more precise technique, too.
We're getting ready to move into our new 90,000 sq ft bldg, with over
600 drops all Cat6, with all Systimax supplies. Looks like I gotta get
the boss to let me order a bunch of cat6 Systimax stuff. ;-)
Everything I've done up to now has all been cat5e. I read that the
Crisco gear will cost over $200K just for this site. And they have the
nerve to complain about me spending a few bucks for tools.
Everything's running late, no carpet on the floors yet, still a lot of
finish work to be done. No labels on the jacks yet(!) I don't know if
I'll be asked to work over the xmas vacation. Bummer. Damn
contractors!
> -- Robert |
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