Coaxial cable

RG-59

Oheaviside

Coaxial cable cutaway

Transmission line element

Transmission line schematic

Coaxial cable, or coax cable, is a type of electrical cable consisting of an inner conductor surrounded by a concentric conducting shield, with the two separated by a dielectric (non-conducting) material. The term "coaxial" refers to the inner conductor and the outer shield sharing a geometric axis. Coaxial cable was invented by English engineer and mathematician Oliver Heaviside, who patented the design in 1880.

Design and Construction

The basic construction of a coaxial cable includes four layers:

1. The inner conductor which carries the majority of the electric current. This can be made of solid or stranded copper or aluminum.
2. An insulating layer or dielectric surrounds the inner conductor. Common materials used include polyethylene (PE), polyvinyl chloride (PVC), or fluorinated ethylene propylene (FEP). This layer provides electrical insulation between the inner conductor and the outer layers.
3. The outer conductor or shield, which may be made of braided aluminum, copper, or another metal, serves as a ground and protects the inner conductor from electromagnetic interference (EMI) from external sources.
4. The outermost layer is a plastic sheath that protects the cable from physical damage and also acts as an additional insulation layer.

Types of Coaxial Cable

Coaxial cables come in various sizes, identified by RG (Radio Guide) numbers, which relate to the cable dimensions and characteristics. Common types include:

• RG-6: Widely used in residential and commercial settings for television signals, Internet connectivity, and digital video.
• RG-11: Offers lower attenuation compared to RG-6, making it suitable for longer distances. It is often used for the same applications as RG-6 but for larger buildings or longer runs.
• RG-58: A thinner cable that is commonly used for radio communications and thin Ethernet networks.

Applications

Coaxial cable is used in a wide range of applications due to its ability to shield signals from external electromagnetic interference, making it ideal for carrying high-frequency electrical signals with minimal loss. Key applications include:

• Television distribution networks, including cable television.
• Internet service delivery, especially broadband Internet.
• Closed-circuit television (CCTV) and security camera installations.
• Radio frequency (RF) connections, including antennas and radio equipment.

Advantages and Disadvantages

Advantages:

• High bandwidth, capable of supporting large amounts of data transmission.
• Good resistance to interference from external electromagnetic sources.
• Can be used over relatively long distances with minimal signal loss.

Disadvantages:

• More expensive and less flexible than simpler wires like twisted pair cables.
• The installation can be more complex, requiring special connectors and tools.
• Signal loss (attenuation) increases with distance and frequency, requiring the use of repeaters or amplifiers for long-distance or high-frequency applications.

Maintenance and Troubleshooting

Maintaining coaxial cable involves regular inspections for physical damage, ensuring connectors are properly secured and protected from the elements, and testing for signal loss. Troubleshooting common issues may include checking for loose connections, replacing damaged sections of cable, and using signal amplifiers to overcome attenuation.

Coaxial cable Resources
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