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Our radios and computers have been converging for a long time now.  At some point you are going to need to create your own Ethernet cables for any number of reasons. Store bought Ethernet cables are grossly over priced so here is how you can make your own.

It isn't enough for all eight conductors to have end to end continuity.  For Ethernet to work properly the twisted pairs of wire must be terminated with the correct pin-out.  The two standards for Ethernet cables are 568A and 568B. Electrically, there is no difference between the two. The only difference is in the way the colored pairs are arranged. The tables below lists the ordering for the two standards.

If you are observant, you'll notice that the difference in the two standards are pins 1,2,3 & 6. As it turns out, these are the only pins that Ethernet uses. Pins 4,5,7 & 8 are not utilized in an Ethernet connection. The orange pair is transmit and the green pair is receive. In the illustrations and instructions that follow, we'll be using the 568B standard. 568B seems to be the more prominent pin-out but you'll commonly see both kinds of cables in use. Again, there is no difference electrically as long as both ends of the cable are crimped the same way. Now, lets get to the step by step instructions for creating your Ethernet patch cable.

Begin by stripping about two inches of the outer insulation away from the inner conductors and spread apart all eight wires. Take care not to damage any of the insulation on the individual conductors.

Next, arrange the conductors either for 568A or 568B going from left to right and cut off the excess length leaving about 5/8 inch of the inner conductors extending beyond the outer insulation. The image below shows the conductors arranged per the 568B standard and ready for the RJ45 connector. Note the ordering of the colored pairs.

Carefully slip the RJ45 connector over the inner conductors. The tab on the RJ45 plug should be facing down and the orange pair of wires should be on the left.

Visually inspect your work. Without letting the plug slip off of the end of the cable make sure that none of the wires slipped out of place while you were inserting them into the RJ45. The individual conductors should extend all the way to the tip of the plug and be positioned directly below the metal contacts. When crimped, the contacts will pierce through the insulation on each conductor making direct contact with the wires.

In order for the cable to be properly mated and have the best mechanical connection to the plastic RJ45 plug, the outer insulation should extend inside the RJ45 connector. When crimped, a small plastic wedge will gently "bite" into the outer insulation gripping it. This will help to keep the RJ45 plug firmly connected to the end of the cable.  The photo below shows a properly seated RJ45 ready to be crimped. Note how the gray outer insulation is visible inside the clear plastic RJ45 connector.

The next photo shows an improperly prepared cable. The outer insulation is not inside the RJ45 and therefore won't have a strong mechanical connection when crimped. This is wrong!

The last step is to crimp the RJ45 onto the end of the cable using a crimping tool. Repeat this procedure for the opposite end of the cable and you are finished.

Ethernet Crossover Cables

Ethernet crossover cables are just a normal patch cable with the transmit and receive pairs reversed on one end. They are used when you need to network two computer NIC cards to each other when an Ethernet switch or hub is not available. They are also used to connect switches or hubs together when neither device has a built in crossover port. In order to construct your own Ethernet crossover cable, simply crimp one end of the cable as 568A and the other end as 568B.