Coaxial Cable – the best cable for TV ever

Coaxial Cable

“AT&T is proud to follow in the footsteps of Espenschied and Affel as we continue to drive innovation.” by Dave Belanger, Chief Scientist at AT&T Labs

In the early 1920s it was clear to communications engineers that high-frequency transmission line were paramount to the success of any further developments in communications, since ordinary wires and cables simply could not cope. Two engineers at Bell Laboratories, Lloyd Espenschied (1889-1986) and Herman A. Affel (1893-1972), came to the rescue. Together they created the coaxial cable which is capable of carrying high-frequency (or broadband) signals successfully. Instead of having just single strands of copper covered by a jacket of a flexible plastic they widened their working diameter to include as insulating spacer and a conducting shield, which gives the cable a very distinctive cross section.
Running through the very center of the cable is the conductor which carries the signal. Wrapped around this is the inner dielectric insulator and Wrapped around that is a conducting shield that reduces electromagnetic interference from any external sources, meaning that the signal stays clear. The shield can be made from layers of braided wire (which allows flexibility but creates gaps) or can be a solid metal tube (which is rigid but more secure). Usually, the whole cable is coated in some sort of vinyl material.

Coaxial Cable was invented by English engineer and mathematician Oliver Heaviside (patented the design in 1880). In 1884, Siemens & Halske patent coaxial cable in Germany. First modern coaxial cable patented by Lloyd Espenschied and Herman Affel of AT&T’s Bell Telephone Laboratories in 1929.

Coaxial cable design choices affect physical size, frequency performance, attenuation, power handling capabilities, flexibility, strength, and cost. The inner conductor might be solid or stranded and stranded is more flexible. To get better high-frequency performance, the inner conductor may be silver-plated. Copper-plated steel wire is often used as an inner conductor for cable used in the cable TV industry.


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