Coaxial cable has been around for quite a while. It was developed around the 1920’s by the military. Coaxial cable is different from other electrical cables and wiring in that many cables and wires are used to power electronics such as light bulbs and motors, where coaxial cables are used to send signals to control things. These two purposes have different amounts of power or electricity needed to draw through them. The powering cable assemblies have a larger draw on electricity, and therefore emit a strong electromagnetic field. These fields interfere with the smaller field that the signaling cables emit, which is smaller since they require a smaller draw of electricity. For example, the field from the cables that power a plane motor might confuse a cable in charge of signaling communication, and accidentally allow bomb doors to open and drop bombs unintentionally. Therefore, a shielded and more secure cable was needed, which the military developed and called the coaxial cable.
The term “coaxial” comes from the construction of the cable: “two axis”. This refers to the fact that there are two conductors in this cable, a center wire, and conducting foil that goes around it, which share the same “axis”. The center wire can be copper, or copper-coated steel, and it is surrounded by a foil conductor, with a dielectric material in between the two conductors. The dielectric is key to making sure that the center and foil are equidistant from each other, providing a buffer that is crucial to the cable’s function. Encompassing all of these is a braid sheath, usually made of a wire material. Some models of coaxial cable have extra layers of this metal braiding. Outside of the braid is a jacket material, usually black in color, which protects the cable from environmental harm, as well as protecting users from coming into contact with the conductors while in use.
One reason why it is acceptable to use copper-coated steel (CCS) instead of standard solid copper in the center of the cable is because steel adds strength to the core integrity of the wire. The pulling tension or pulling strength of CCS cables is up to 75 lbs. of force. Copper conductors can withstand pulling tensions up to only 35 lbs. Also, since the signals are usually at very high frequencies, up to hundreds of millions of Hertz (signals in the cable are turning on and off at a hundred million times per second) there is an effect that takes place called the “skin effect”. This means that the electrons are traveling so fast down a conductor that they will travel mostly on the surface or outside of the conductor.
A great amount of stability is required to ensure that the foil runs equidistant from the center wire for proper functioning. This can make installation of coaxial cables a tricky thing. There are many restrictions that must be followed. If the cables is pulled, bent, or strained too far in any manner, it will end up not functioning. This is one reason why wire harness assemblies come in handy, since they ensure that all the cables and cable assemblies will be resistant to environmental harm, by being strapped into place for safety and organization.