Coaxial cable: design, history, types, and common uses

Structure and key characteristics

A typical coaxial cable consists of four layers: a central conductor (solid or stranded), a dielectric insulator surrounding that conductor, an outer conductor or shield (braid, foil, or both), and an outer protective jacket. The most important electrical parameters are characteristic impedance (commonly 50 ohm or 75 ohm), attenuation (loss per unit length), capacitance and voltage rating. These properties determine suitability for particular frequencies and transmission distances. Coax is commonly used for carrying radio frequency signals and cable television signal transmission.

How it works

The cable confines the signal's electromagnetic field between the inner and outer conductors so that the wave propagates with predictable velocity and minimal external coupling. That field confinement is why coaxial lines are less prone to external electromagnetic interference and why they can be routed near other equipment with limited cross talk. More on the field behavior can be found in discussions of transmission-line theory electromagnetic field and shielding effects interference.

History and development

The basic concept of a concentric transmission line emerged alongside late 19th and early 20th century advances in telegraphy and radio. Practical coaxial cables were developed as manufacturing, insulating materials and connector technology improved, enabling reliable wideband RF links. Coaxial designs were widely adopted in mid‑20th century broadcast and radio systems and later used in early computer networking standards before higher‑speed and lower‑cost alternatives became common network history.

Common types, standards and connectors

• Impedance: 50 Ω types are typical in radio and data systems; 75 Ω types are standard for television and video distribution.
• Construction: solid versus stranded center conductors; single braid, dual braid, foil-plus-braid shields for improved isolation.
• Popular cable families: RG‑series (legacy naming), low‑loss foam‑dielectric types for long runs, and flexible coax for patch cables.
• Connectors: F‑type connectors for consumer TV/cable, BNC for instrumentation and some video, N‑type and SMA for higher‑frequency RF applications.

Applications, advantages and limitations

Coaxial cable remains widely used for cable television distribution, broadband Internet (last‑mile and in‑home wiring), satellite and antenna feedlines, closed‑circuit television, and various RF test and measurement setups. Advantages include controlled impedance, effective shielding, and good performance at high frequencies. Limitations are greater bulk and cost compared with twisted pair, increasing attenuation with frequency and distance, and sensitivity to poor connector terminations. For practical installation advice and standards references consult industry sources high‑frequency resources.