Making Your Own Ethernet Cables Is Not A Casual Project

I’m a great fan of do-it-yourself. Setting up a computer network is a lot of fun, even if you’re getting paid to do it. Making your own Ethernet cables is not fun, though.

An RJ-45 Ethernet cable contains 4 pairs of color coded wires, and each wire is not much more than the thickness of a really thick piece of hair. Ok, a really, really thick piece of hair – but one that won’t bend like hair – and you’ll wish it would too.

You have to identify each wire by color, untwist each pair of wires just enough so the individual wires will fit into the end of the plug (or jack if you’re doing interior cabling), get each wire in the correct sequence side by side, insert the 8 wire set into the plug / socket simultaneously and squarely, and crimp everything perfectly. I say simultaneously because you won’t be able to insert each one individually – those wires, as thin as they are, are not going to bend for you.

Oh yeah, I forgot, you have to strip the outer sheath enough – just enough – to separate the 4 pairs. Don’t nick any of those wires when you strip the sheath. And you do know that all 4 pairs of wires don’t go in perfect sequence – one sequence is “green / white-green / white-orange / white-blue / blue / orange / brown / white-brown”. So you have to untwist the orange pair (orange and white-orange) just a little more, because its halves have to fit on either side of the blue pair (white-blue and blue).

There are four color sequences – two for straight-thru cables (connecting jacks and plugs), and two more for cross-over cables (jacks and plugs again). Each sequence has one pair separated by another pair (as the orange pair is separated by the blue pair above).

Make one mistake, and your cable is toast. Untwist one pair just one turn too much (the twists are critical to functionality – they are NOT decorative), or switch one pair of wires (a white-orange stripe looks a lot like white-brown in dim light), and it won’t work. You have to cut the plug off, and start over from the beginning.

And just because it works today, don’t expect it to work tomorrow. Move your computer, flex the cable or put pressure on the plug, and just one micro-disconnection could make the cable not work. Or worse, the cable might work just 90% of the time. You do want a 100M network, right? Not 50M (if the cable doen’t work 100% of the time, you may get an effective rate of 50M). One day you’ll want Giga-Bit too.

Add up the cost of cable, plus the plugs, plus the crimping tool (if you want a quality cable, prepare to spend quality money), plus the time you spend trying to figure out why it doesn’t work, plus a second trip to the store, because you got stranded cable, but connectors (plugs or jacks) for solid cable (you can’t mix solid and stranded components!). Then a third trip to the store because you ran out of connectors – once you crimp one, it’s done. One mistake, cut the bad one off, and throw it away.

There is one, just one, situation where I would make my own cable ends. If I had an electrician pull cabling inside the walls, it may be cheaper to use bulk cable. When you have that done, by the way, have 2 or 3 times as many cables pulled as you need right now. Pulling 2 or 3 cables (tied together) is no more expensive than pulling 1.

If you decide to go the luxury route, and have the electrician attach the end connections (my preference), make sure he knows more about this than I do, make sure he’s licensed, and make sure he tests each cable, and gives a written report for each one. And make sure he labels each cable, so you know which one goes to the master bedroom, or to the office!

Always terminate a cable inside the wall, with a jack, then run a patch cable between the jack and the computer. Please don’t run end to end plugs, with cables running thru holes in the walls. If you’re going to attach the cable ends yourself, attach the ends to secured points inside the walls (the back side of each jack), where they don’t move, and make a strain relief to protect the connection from even the weight of the cable. Always, and I mean always, run pre made and tested patch cables, from the jacks, to the computers.

If you must terminate the cables yourselves, whether to save money or for convenience, or whatever reason, get the right equipment. LANShack sells Cat6 equipment including the Sentinel Cat6 Modular Plug Assembly, and the appropriate tools. If you’re going to have reliable Gigabit Ethernet, or a large quantity of custom length cables, that’s where I would start.

But for a single patch cable, go back to the store, and buy a tested, pre-made cable. You’ll be glad you did in the long run.

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