| Author |
Message |
Watson A.Name - \"Watt Su
Guest
|
 Posted:
Sun Jan 30, 2005 8:03 pm Post subject:
Weird Test |
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I tested a short run with my Fluke 2000, and it gave me an error I'd
never seen before. I got the excessive delay skew, 95 where the max is
50nS. Usually the cables have only a few nS, less than 5 between pairs.
Anyway, I cut it off and repunched it down and the problemn went away.
When I think about it, having 95nS delay skew between pairs means that
at about a foot per nS, there's 95 extra feet on that pair! And we all
know that can't be. :-/
--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@ |
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Goonerak
Guest
|
| Posted:
Sun Jan 30, 2005 9:56 pm Post subject:
Re: Weird Test |
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| Quote: | When I think about it, having 95nS delay skew between pairs means that
at about a foot per nS, there's 95 extra feet on that pair! And we all
know that can't be. :-/
|
Maybe there was a distortion in the space-time continuum in that particular
section of cable ;) |
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Dmitri(Cabling-Design.com
Guest
|
| Posted:
Mon Jan 31, 2005 7:37 am Post subject:
Re: Weird Test |
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Watson A.Name - \"Watt Sun, th wrote:
| Quote: | I tested a short run with my Fluke 2000, and it gave me an error I'd
never seen before. I got the excessive delay skew, 95 where the max is
50nS. Usually the cables have only a few nS, less than 5 between
pairs.
Anyway, I cut it off and repunched it down and the problemn went away.
When I think about it, having 95nS delay skew between pairs means that
at about a foot per nS, there's 95 extra feet on that pair! And we all
know that can't be. :-/
|
Consider it a fluke ;-)
delay skew is definitely a cable-only related parameter, so you are
correct: re-punching would not have fixed the problem. IF there was a
problem indeed.
When technology-related explanations are exhausted, it is usually wise to
look into human-induced possibilities. Like, someone's playing a practical
joke or some error in operating the machine
--
Dmitri Abaimov, RCDD
http://www.cabling-design.com
Cabling Forum, color codes, pinouts and other useful resources for
premises cabling users and pros
http://www.cabling-design.com/homecabling
Residential Cabling Guide
-------------------------------------
##-----------------------------------------------#
Article posted with Cabling-Design.com Newsgroup Archiv
http://www.cabling-design.com/forum
no-spam read and post WWW interface to your favorite newsgroup -
comp.dcom.cabling - 1169 messages and counting
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Dmitri(Cabling-Design.com
Guest
|
| Posted:
Mon Jan 31, 2005 7:46 am Post subject:
Re: Weird Test - A second thought |
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|
On a second thought though:
The way Fluke cable testers work (they don't call it DSP for nothing) is:
the tool sends a short pulse into the cable and, by doing the Digital
Signal Processing magic, devise all the parameters from the way the pulse
is distorted when it hits the other end.
You've mentioned it was a short cable. It must have been the case when the
signal is so strong that it travels the same piece of cable twice, and
some echo showed up exactly 95 ns after the first signal, which means that
it is actually 95ns/3 (traveling DSP-remote-DSP-remote instead of just
DSP-remote), which is conveniently within the spec.
Just my 2c.
--
Dmitri Abaimov, RCDD
http://www.cabling-design.com
Cabling Forum, color codes, pinouts and other useful resources for
premises cabling users and pros
http://www.cabling-design.com/homecabling
Residential Cabling Guide
-------------------------------------
Watson A.Name - \"Watt Sun, th wrote:
| Quote: | I tested a short run with my Fluke 2000, and it gave me an error I'd
never seen before. I got the excessive delay skew, 95 where the max is
50nS. Usually the cables have only a few nS, less than 5 between
pairs.
Anyway, I cut it off and repunched it down and the problemn went away.
When I think about it, having 95nS delay skew between pairs means that
at about a foot per nS, there's 95 extra feet on that pair! And we all
know that can't be. :-/
--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@
|
##-----------------------------------------------#
Article posted with Cabling-Design.com Newsgroup Archiv
http://www.cabling-design.com/forum
no-spam read and post WWW interface to your favorite newsgroup -
comp.dcom.cabling - 1170 messages and counting
##-----------------------------------------------## |
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Watson A.Name - \"Watt Su
Guest
|
| Posted:
Mon Jan 31, 2005 8:00 am Post subject:
Re: Weird Test - A second thought |
|
|
"Dmitri(Cabling-Design.com)" <info_at_cabling-design_dot_com@foo.com>
wrote in message news:y_gLd.291380$B07.38281@news.easynews.com...
| Quote: | On a second thought though:
The way Fluke cable testers work (they don't call it DSP for nothing)
is:
the tool sends a short pulse into the cable and, by doing the Digital
Signal Processing magic, devise all the parameters from the way the
pulse
is distorted when it hits the other end.
You've mentioned it was a short cable. It must have been the case when
the
signal is so strong that it travels the same piece of cable twice, and
some echo showed up exactly 95 ns after the first signal, which means
that
it is actually 95ns/3 (traveling DSP-remote-DSP-remote instead of just
DSP-remote), which is conveniently within the spec.
Just my 2c.
|
I can 't remember if it was 45 feet or 54 feet long.
Methinks it was just Fluke. :-P
| Quote: | --
Dmitri Abaimov, RCDD
Watson A.Name - \"Watt Sun, th wrote:
I tested a short run with my Fluke 2000, and it gave me an error I'd
never seen before. I got the excessive delay skew, 95 where the max
is
50nS. Usually the cables have only a few nS, less than 5 between
pairs.
Anyway, I cut it off and repunched it down and the problemn went
away.
When I think about it, having 95nS delay skew between pairs means
that
at about a foot per nS, there's 95 extra feet on that pair! And we
all
know that can't be. :-/
--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@
##-----------------------------------------------##
Article posted with Cabling-Design.com Newsgroup Archive
http://www.cabling-design.com/forums
no-spam read and post WWW interface to your favorite newsgroup -
comp.dcom.cabling - 1170 messages and counting!
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