HOW TO - Ethernet Cables
Parts: You'll need several feet of CAT 5 cable, RJ45 ends and an RJ45 crimper to complete this. You'll also need a nice cut-off plier. A wire striper and a cable tester are greatly helpful aswell.
Cable: First, start off with good quality cable, it has to be UTP (Unshielded Twisted Pair) Category 5 cable, don't skimp on this (Shielded works too, but isn't necessary). Bulk cable comes in many types, there are 2 basic categories, patch and riser cable. Patch cable is meant for desktop use, it is more flexible and resiliant than riser cable, its easier to work with, but really meant for shorter lengths. Riser cable is meant for longer runs through walls and ceilings. Your likely going to want patch type cable. Plenum cable is not needed unless you plan to do a very professional job and will be running wires through walls, ceilings and air conduits etc.
Here is what the internals of the cable look like:
There are 8 color coded wires. These wires are twisted into 4 pairs of wires, each pair has a common color theme. One wire in the pair being a solid or primarily solid colored wire and the other being a primarily white wire with a colored stripe (Sometimes cheap cable doesnt have any color on the striped cable, the only way to tell is to check which other wire it is twisted around). Examples of the naming schemes used are: Orange (alternatively Orange/White) for the solid colored wire and White/Orange for the striped cable. The twists are extremely important. They are there to counteract noise and interference. Each pair has a different twist ratio, I believe this has effects on signalling at higher speeds, so it becomes important to wire according to the color codes.
RJ45 Ends: The RJ45 end is a 8-position modular connector that looks like a large phone plugs. There are a couple variations to these plugs, there are models that deal with round or flat or even oval cables, cat 5 should be round. There is also variation in the contacts used in the plug. One type, for stranded wires, which is what would normally be used in a patch cable, has contacts that actually pierce the wire. The second type of contact is for solid wires, typically used in riser type cable. This contact has fingers which pierce the insulation and make contact with the wire by grasping it from both sides. Now I just learned about all these variations recently, so I'm not sure how harmful it is to use the wrong type. It's also pretty impossible to tell in the store what type it is, if the plugs aren't labeled. But the general jist, if possible, use connectors that say stranded for patch type cable, and solid type plugs for riser type cable. I also discovered that you can get plugs that have an extra piece that acts as a wire quide, you fed the wires through it, then insert the piece into the plug, looks pretty handy, I haven't tried it yet. There are many more variations but they are not very important, btw you can add strain relief boots if you want. Here is a diagram and pinout:
Ethernet Cables: Now, on to the cables. There are two basic cables. A straight through cable, which is used to connect to a hub, and a cross-over cable used to operate in a peer-to-peer fashion without a hub. Since you are making your own cables, I will assume you understand which cable you need.
Standard, Straight-Through Wiring (both ends are the same):
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Wire Diagram | Signal* |
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Transmit+ |
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Transmit- |
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Receive+ |
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Unused |
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Unused |
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Receive- |
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Unused |
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Unused |
Cross-Over Cable:
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If you look closely, you will noticed that the green and orange pairs are swapped or crossed, these are the transmit and receive pairs.
Procedure: To create the cable, strip off about 2 inches of the cable sheath. When you get to the second side, cut the wire to length and make sure it's more than long enough for your needs. Remember, a cable should not extend more than 100m (~328ft). When uplinking between hubs, you usually need a very short cable <1m, check the hub's specifications.
Next untwist the pairs, dont untwist them beyond what you have exposed, the more untwisted cable you have the worse the problems you can run into.
Now you want to align the colored wires according to the diagrams above. When nicely aligned, hold them in line together and trim them all to the same length, about 1/2" to 3/4" left exposed from the sheath. And then you want to insert them into the RJ45 end and make sure each wire is fully inserted and in the correct order. The sheath of the cable should extend into the RJ45 end by about 1/2" and will be held in place by the crimp. Crimp the end with the cripmer tool and once again verify the wires ended up the right order and that the wires extend to the front of the RJ45 end and make good contact with the metal contacts in the RJ45 end. If you have a cable tester, put it to use, and verify the proper connectivity of your newly made cable.
That should be it, if your cable doesn't turn out, look closely at each end and see if you can find the problem. Usually a wire ended up in the wrong place or more commonly, one of the wires didn't extend to the front of the RJ45 connector and is making no or poor contact. If you see a mistake or problem, cut the end off and start again.
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