[GRLUG] CAT5 Cables

[Casey DuBois]

On Wed, Apr 30, 2008 at 11:33 AM, Greg Folkert <greg at gregfolkert.net> wrote:
>
> On Wed, 2008-04-30 at 08:56 -0400, Adam M. Erickson wrote:
> > I apologies if writing about cables on a LUG sight is upsetting
> > anyone, I just have to inform anyone who might not know.
> >
> > Cat5 Crimper $20, Cat5 Ends $7,  500' Cat5 Cable $50, - If you
> > purchased these at Lowe's you could always make it yourself.
> >
> > It is a good investment:
> >
> >  1. If a end breaks you just have to crimp on another end.
> >  2. Make the exact length that you need.
> >  3. Could you find a crossover cable on the weekends?
> >  4. Make a cabling for your friends and family, or just the people you
> > really care about.
> >  5. Lowe's is open on the weekends.
> >  5. "Save Money"
> >
> > Same amount of supplies and tools would cost $400 dollars for a kit at
> > Best Buy and $700+ at best buy for prepared lengths that = 500'.
> > Stores sell there cables for $17-$30 for about 20' of cable. It cost
> > the same stores $2 to bring it in.
>
> For those of us that manage wiring plants with bandwidth and EMI/RFI
> guarantees, most of the time these guarantees require the use of
> certified patch cables at both end of the link.
>
> Is there any way *you* can guarantee these qualities in you self made
> cables are within the certified limits for a given professionally
> installed wiring plant:
>
>     1. Impedance load
>     2. Capacitance load
>     3. Resistive load
>     4. Contact end integrity for Attenuation (contact signal drop),
>        NEXT (Near End Crosstalk) and PSNUM (Power Sum Crosstalk)
>     5. Stress reliefs on each end to ensure cables don't bend more than
>        a certain arc.
>
> There are qualities, though these are the big ones.
>
> At CAT3 (10Mbit and 16Mbit token ring) these really don't matter much
> (Voice and up to 20MHz clocking).
>
> As CAT4 and CAT5 don't exist in the real world, no matter.
>
> At CAT5e, these begin to matter, at 125MHz clocking (100Mbit Ethernet
> use 4/5 encoding), things like Impedance and Capacitance begin to
> interfere with signaling. Impedance affect the ultimate distance an
> "Ethernet" signal can travel, though a cable with capacitance can
> literally short the signal via RFI crostalk between each wire. CAT5e
> generally has greater twist in the pairs and twisting of the 4 pairs as
> they go down the cable to combat both this capacitance and also to
> thwart EFI/RFI outside interference. CAT5e is really the last of the
> cabling you and I can make that work. CAT5e cables are generally good
> upto 150MHz, but not are guaranteed, some do work for 1GBit, but lots of
> re-tries and drops do occur. On 1GBit, it uses all four pair of cable to
> "mux" the signals, and get the throughput up. vs 100Mbit, only using 2
> pair. CAT5e can be usable upto 250Mhz.... but Your Mileage May^H^H^H
> *WILL* Vary GREATLY.
>
> At CAT6 and beyond, typically ONLY are possible to be made in a
> manufacturing environment. Why? Tolerances required are not repeatable
> except in jigs and machines set to certain "crush torque" and stripping
> of wire without nicking them and so on.
>
> (yes these links are wikipedia, but they are correct and point to good
> references)
>
> http://en.wikipedia.org/wiki/Category_3_cable
> http://en.wikipedia.org/wiki/Category_5e_cable
> http://en.wikipedia.org/wiki/Category_6_cable
>
> http://en.wikipedia.org/wiki/Structured_cabling
> http://en.wikipedia.org/wiki/TIA-568B
>
> --
> greg at gregfolkert.net
> PGP key 1024D/B524687C 2003-08-05
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>
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>

I have a good story to go along with this thread.

I was working with a wiring company that got a service call @ 2:30AM
for a connection being down, after driving an hour to the location and
working the issue for another hour he discovered a bad crimp and
broken tab were the issue.

Savings $10
Service Call Cost $300+

For NON critical applications making your own is fine but for a
connection that runs your business using a certified cable that costs
a couple extra bucks is worth it.

Casey