Coaxial cables are cables that consist of two conductors that share an axis. The inner conductor is usually a straight wire; the outer conductor is the wire's shield, which is usually a braided wire or a metal ribbon. It is used primarily for radio and television signal transference. The combination of the center conducting wire and the outer conducting shield keeps other cable noise out and the signal in.
Types
Different types of coaxial cable rated by the U.S. government are designated by the letters RG and then a number. RG stands for "radio grade" and are from when the Army used most of its coaxial cable for radio transmission. The numbers were chosen arbitrarily. The most common RG designations are RG-6, RG-8, RG-11, RG-58, and RG-59. The main difference between them is the impedance. RG-8 and RG-58 have a 50-ohm impedance, while RG-6, RG-11, and RG-59 are 75 ohms.
