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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.
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I buy cables because I would go through 5 - 10 cables a day and by the time I made them, tested them, labelled them, I could be doing 101 other things.
It's not to say that you can't do it, you can. It's just a matter that the amount of time you spend doing it just makes it a hell of a lot cheaper in the long run to buy them.
This is ESPECIALLY true when dealing with CAT7 or STP. On a 20Mb line (Probably a 100Mb link) the chances of having a problem though are pretty low provided you terminate it cleanly.
Curiosity was framed; ignorance killed the cat. -- Author unknown
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.
Solid core has slightly better propagation properties (the 100M limit implies solid core for example) however it also acts similar to a wire coat-hanger. Like any metal it weakens as it bends and after a period of time it'll grow weak, thin and even completely break.
Stranded is similar to a braided rope, it can withstand constant reconnections (user area, especially common with laptops), movements (telcom closets when you're moving the cable mess to access equipment ports) and the stress that will wear down the solid-core cables.
Do yourself a favor and make sure that if you create your own patch cables:
There's nothing wrong with making your own patch cables, and it could potentially save you big bucks (compared with buying a $35 patch cable at a local store). However if it's not done right you will kick yourself down the road -- or more likely blame the network electronics, server, network cards, or whatever you normally blame. :)
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
Why is this modded interesting? I thought the parent was trying to be funny. Somehow I doubt EMF harmonics has anything to do with the nice round values like 6 and 10 ft, that are commonly found at compusa, best buy, etc
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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
Here's a link to a page explaining the reasons for this.
3 things about computers: they're alive, they're self-aware, and they hate your guts.
You miss the point.
The domain is successful Ethernet via the TIA TSB specs using the IEEE recommendations for connectivity with the signaling method employed. Good signal, no weird phase shifts or nullings, and no discriminator problems (e.g. via NEXT).
Standing waves are inevitable in non-DC cable connectivity and are a red herring unless propagation effects signal discrimination, or unwittingly becomes an antenna for other problems. In my experience (50K+ end point terminations), it's not been a problem. With a few discrete components, I can make any Ethernet cable into a wicked antenna. But the question would be: why would I do that? Standing or sitting waves (pun intended) may change ground-level, but that's when STP or 'screened' cabling is an alternative. If you need shielding because of ground-based level shift, use fiber. In fact, fiber is just about as easy to terminate as UTP these days.
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The rule of thumb I use: After you cram each wire into the connector, if you can't see light glint off the cut end of each wire when looking through the end of the connector, they aren't in right. Looking at the sides or the top or bottom of the connector won't do.
Hint: The injection molded ones are made by robots.
Gigabit Ethernet all but eliminates half-duplex (it's technically in the standard, but nobody implements it properly, and autonegotiation is required), so collisions are no longer a concern.
The length restriction is still in the standard, but most of the time it will still establish a link at 110 meters of Cat5, let alone Cat5e or Cat6.
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Strictly speaking, 100m is a fuzzy limit.
It's a hard limit for half-duplex. The CD part of the CSMA/CD Ethernet standard can't wait indefinitly. So they picked numbers that were just longer than the standard. Back in the old days, they would actually let you run fiber at half-duplex. I was working on an old 3-Com network that was set up by the lowest bidder. They had copper (full duplex) running at 200+ meters, but the fiber they had laid (before the copper, they had to retrofit the copper because the fiber didn't work) would fail because it would sense collisions when there weren't any and retransmit until it collapsed. One quick setting to "full" and they went from 10 Mbps copper to 100 Mbps fiber and things magically got better. So yes, the distances as far as signal level and quality are fuzzy, but if you run half-duplex (not that anyone does anymore), there is a hard limit just past. And no, I don't remember the number. Back then, I looked up the spec and calculated it by hand, but I don't remember it and figure someone has it on a web page you could find if you were interested.
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