Coaxial cable is an electrical cable consisting of an inner conductor surrounded by an insulating spacer, then surrounded by an outer conductor. Coaxial cables are often used to transmit radio frequency (RF) signals.  Coaxial cables provide protection of signals from external electromagnetic interference (EMI) and radio frequency interference (RFI).  They effectively guide signals with low emission along the cable length.  Physical size, frequency performance, attenuation, power handling capabilities, flexibility, and cost are all aspects of coaxial cable design.

Insulator Dielectric

The insulator dielectric surrounding the inner conductor may be solid plastic (polyethylene or PE) or a foam plastic. The dielectric controls some electrical properties of the cable.

The Shield

A typical coaxial cable has a braided copper mesh forming the shield, allowing for flexibility.  Cable television (CATV) distribution systems use such cables, as they provide a lower signal loss. 

The Jacket

The outer jacket of a coaxial cable is typically comprised of polyvinyl chloride (PVC).

The Connectors

RF connectors are the primary choice of termination for coaxial cables. 

Impedance

Most coaxial cables have a characteristic impedance of 50, 52, 75, or 93 ohms.  75 ohms is most commonly used for broadcast television and radio.

Where Used

Short coaxial cables are commonly used to connect home video equipment, in ham radio setups, and in measurement electronics.  Long distance coaxial cable is used to connect radio networks and television networks, though this has largely been superseded by other more high-tech methods of fiber optics, T1, and satellite. It still carries cable television signals to the majority of television receivers, and this purpose consumes the majority of coaxial cable production. Micro coaxial cables are used in a range of consumer devices, military equipment, and also in medical equipment.