Coaxial cables are the most common type of transmission line used to connect wireless equipment. They create a circuit where the cable’s inner conductor forms the go path, and the outer conductor, usually a protective braid, forms the return path.
The distance between the inner and outer conductors of a coaxial cable is vitally important. An insulative (dielectric) material, such as a foam, is used to keep the conductors at the required spacing. This however means that coaxial cable must be handled carefully; crushing or tightly bending the cable may seriously impact performance.
One of the most important considerations in RF cable selection is its loss per metre, known as attenuation. Generally speaking larger diameter cables incur less loss per metre than smaller cables. Bigger is not always better however, as the diameter increases the maximum supported frequency decreases. Flexibility and practicality also becomes quite a serious concern as the size increases.
There are three main classes of cable types based on their intended application. Feeder cables are large diameter cables designed to span long distances, such as interconnecting roof mounted equipment to a system within a building. Jumper cables are shorter cables not usually more than a couple of metres, typically used to interconnect system components. Patch cables are very short leads used to provide strain relief and connect very small types of coaxial connectors.