Do It Yourself: Roll Your Own Network Cables

You never know when you'll need that extra bit of cable, and for a few dollars in parts you won't have to worry about it.

By Aaron Weiss | Posted Apr 14, 2006
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by Aaron Weiss

Sooner or later, whether it's while you're perched up on a stepladder with your head holding up a ceiling tile, or after someone in building services has decided that a broom closet needs to be the new intern's office, you're going to need to run some cable and you're not going to have the right length on hand. Even if your supply closet is usually well stocked, it can't hurt to know how to make your own network cable on the spot. With a little practice you can finish the job in less than ten minutes.

Supplies

Bulk Cat5 Cable, RJ-45 Plugs, and Crimper
Bulk Cat5 Cable, RJ-45 Plugs, and Crimper

You need Cat 5 cable, of course. You can buy it in bulk at electronics stores and online. Or if you already have some cable with damaged connectors, snip them off and start anew. Cat 5 comes in a wide variety of jacket colors, but is most commonly found in blue – use any one you like.

You also need RJ-45 connectors – the plastic plugs at the end of the cable. You can also find these at many electronics stores in packs of 25, 50, or 100, often for less than $10.

Finally, you need a crimping tool that supports 8-conductor modular plugs, sometimes also called an RJ-45 crimper. Radio Shack’s “Professional Crimping Tool” (Item #279-405) will do the job for $33, but you can find equally good solutions for half that price on eBay and at online retailers.

Step 1

Grab one end of the cable and, if necessary, snip it to get a straight cut. You need to strip off about one inch of jacket. If your crimper has a jacket stripper, simply shove the cable end into the stripper until it stops, squeeze the crimper gently, and twist the cable as the razors slice through the jacket. Remove the cable and pop off the cut end of jacket. Strip 1 inch of cable jacket
Bundle of twisted pairs

Step 2

With the jacket stripped, you’ll find four twisted pairs of wires. Each pair is represented by a solid color and a striped color each of brown, green, orange and blue. Separate these pairs so they are unbundled.

Four twisted pairs

Step 3

Now separate the pairs, so that you have eight individual wires. Using nimble figures, arrange the eight wires into the exact sequence represented in the wiring diagram labeled 568B.

It can take some practice to configure the wires into sequence. They can be unruly and need some twisting. You want the wires to be as close together as possible. Sometimes it helps to flex the wires lightly to better manipulate them into position.

This wiring sequence, known as 568B, is the most common arrangement for Ethernet cable.

568B Wiring Diagram

Step 4

When the wires are in sequence, double check against the diagram in case one or two slipped out of position. Using the cutter on your crimper, or a pair of scissors, cut straight across the tips of the wires so they are clean and even.

Grab an RJ-45 plug, with the latch side facing down.

RJ-45 Plug
Guide the wires into the plug, being careful not to let them slip out of sequence. As the cable enters the plug, each wire should slip into its own channel, allowing them to glide smoothly into the plug. Push the cable as far as it will go. You should have about 3/16 inch of cable jacket inside the back of the plug. The wire ends should reach as far as possible toward the front edge of the plug. Wires inserted into RJ-45 plug

Step 5

With the wires pushed into the plug, fit the plug into the crimping slot in the crimping tool. While holding the cable in place with one hand, use your other hand to squeeze the crimping tool with reasonable force. This will press the pins inside the plug into the wires and fasten the plug onto the cable. Crimping RJ-45 Plug

Step 6

Now flip the cable around and assemble the other end. Chances are you want to make a standard, or “straight-through” cable, in which case you should assemble both ends exactly the same.

Alternatively, you could opt to build a crossover cable — a less common cable configuration sometimes used to directly network two devices without a hub or switch in between. To assemble a crossover cable, complete one end following steps 1-5. For the other end, you will change the wiring sequence by swapping the green and orange pairs. This is called a 568A arrangement.

 

Technically speaking, you can make a straight-through cable using either 568B or 568A, as long as both ends are the same. Mixing arrangements produces a crossover cable. Be sure to clearly label any crossover cables you make, because they will not be compatible with straight-through cables.

568A Wiring Diagram

Conclusion

Test your cable in a network segment that is known to work. Because small mistakes can cause erratic or non-functional cable operation, it may take a few practices tries to get it right. The most common problem is lack of contact between the pins in the RJ-45 plug and the wires, particularly if the wires have not been pushed in far enough. If your connection is poor, simply snip off the RJ-45 plug and try the assembly procedure again.

If you want to get fancier and arguably more reliable cables, you can also add strain relief boots to your supplies, as well as a handheld cable tester.

Article courtesy of Practically Networked

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