A coaxial (coax) cable consists of an outer hollow cylinder, made from copper or another electrically conductive material, and an inner, single-wire conductor. The cylinder and the wire share a common geometric axis, hence the name.
Radio Frequency
When a radio frequency (RF) signal travels through a coaxial cable, the electromagnetic field carrying the signal is contained between the cylinder and the wire. The outer cylinder serves as a shield for the wire inside.
Attenuation
The design of a coaxial cable means large, metal objects do not affect RF transmissions. The electromagnetic field is contained wholly in the cable itself, so the signal cannot leak away (attenuate) and cause power losses, and is unaffected by any external electromagnetic interference.
Insulation
The space between the cylinder and the wire is filled with air, or another insulating material. Coaxial cables filled with air are better at preventing signal loss, provided the space between the conductors is free from moisture.
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