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Handmade vs. Commercially Produced Ethernet Cables
An anonymous reader writes "We have a T1 line coming into our satellite office and we rely fairly heavily on it to transfer large amounts of data over a VPN to the head office across the country. Recently, we decided to upgrade to a 20 Mbit line. Being the lone IT guy here, it fell on me to run cable from the ISP's box to our server room so I went out and bought a spool of Cat6. I mentioned the purchase and the plan to run the cable myself to my boss in head office and in an emailed response he stated that it's next to impossible to create quality cable (ie: cable that will pass a Time Domain Reflectometer test) by hand without expensive dies, special Ethernet jacks and special cable. He even went so far as to say that handmade cable couldn't compare to even the cheapest Belkin cables. I've never once ran into a problem with handmade patch cables. Do you create your own cable or do you bite the bullet and buy it from some place?"
I've learned the hard way when setting up a couple of clusters: You MUST use custom-made, cut to length cables to prevent a huge rats nets in the server room. Buying precut cables is a disaster. I had to rip out and completely rewire one cluster because I made that mistake.
However, you need to TEST the cables. And not just by plugging in and making sure it works, but a full ethernet validation tester.
I've been very happy with the Fluke Cable-IQ qualification tester, which doesn't just make sure that the wiring is correct, but actually tests the cable up to gigabit speed to make sure everything is kosher.
Test your net with Netalyzr
We had a contractor come in and rewire our facility. They ran raw CAT 6 and hand terminated it, then TDR'd each run.
Your boss is unclear on the tools needed and the difficulty...just simple hand crimpers were all they needed. There's going to be
an impedance bump at the RJ anyway...the cable's not twisted there.
As to making them yourself or buying patch cables? It's way cheaper to buy them (I like L-Com) but if you need one *right now*,
(or a custom length) it's cheap to have a crimp tool, some RJs and a roll of cable handy in the corner of the office.
While it may be cost effective to crimp and cut your own cable when you are making less than 20 dollars an hour once you are making 20 dollar+ just buy it.
I promise you I can make more than $20 worth of test-worthy cables in one hour.
Dewey, what part of this looks like authorities should be involved?
Depending on wages and such, the commercial cables could easily have 10x the labor and still be cheaper.
Nerd rage is the funniest rage.
Yes, you can use handmade cables that are as good as mass-produced factory cables. But that really isn't the issue.
It's just not worth the time spent to cut and crimp your own lines anymore. In my experience, it was a more common practice years ago in IT. That may have had something to do with the fact that there weren't nearly as many PC's or ethernet ports in buildings as there are today.
My advice: Find a good supplier (i.e. not one that charges $800 for a 6 ft. adamantium-coated cable) and do something else with the rest of your time.
I can't agree with this - if the termination of a transmission line is correct at each end, then the length has no matter at all for any frequency (in theory, not accounting for increasing losses with frequency, but then there's a reason for length restrictions in the CatX/Ethernet standards).
If you're talking about a *tuned* line (eg a stub or a tuned antenna feeder), then length is important. But we're not. If you've got problems with harmonics or matching and reflections then your ethernet cards are probably bottom-shelf knock-offs.
The problem with premade-lenght cables is you're going to run into tangles if many changes are made, and are going to end up coiling. Make that coil too tight and you're going to cause crosstalk. A custom job with all cables neatly following defined routes with no coils, twists or kinks is going to make life easier in the long term.
-- Sig Sig Sputnik
Orange and white, Orange. Green and White, Blue. Blue and White, Green. Brown and White, Brown.
Use pieces (cable, plugs, jacks) certified for the speed you want to carry.
Once you get those two down, understand not to untwist more of the cable than absolutely necessary to get it into the connector, get it correctly into the cable, and get a good solid crimp on it - and TEST IT after you crimp both ends - odds are it's more than sufficient to carry as much GigE traffic as you care to move.
Once you have a stock of pieces on the shelf, it's WAY more cost effective from an employers perspective to make a single cable than to sit down, fill out a purchase order, have that purchase order pass through several hands during processing, follow up with the paper order, wait a week to have that single cable shipped to you. ESPECIALLY if that cable is a statistical anomaly and needs to be replaced.
If you're wiring a patch panel for the first time, however, order a hundred or so cables of various length and save yourself the hassle.
Glonoinha the MebiByte Slayer