Coaxial cable: device and principle of operation, characteristics of thin and thick wire

A coaxial cable is an electrical conductor with a central core and shield, located coaxially and separated by insulation or an air gap. Such a conductor design was invented at the end of the 19th century by the English physicist O. Heaviside. Unlike shielded wire, it is used to transmit electrical signals in the radio frequency range. The cable is used in television antennas, computer networks, etc.

Device and principle of operation

The coaxial cable should provide good signal transmission with minimal interference. In an area with strong interference, a wire is used, which has 4 protective screens. The cable device includes:

• The inner conductor is a single straight or twisted conductor. Sometimes made of copper tubing or stranded wire. In addition to copper, the material can be copper alloy, copper-plated aluminum, silver-plated copper, etc.
• Insulation - solid material is polyethylene, fluoroplastic or tape made from it. Sometimes filled with other substances that do not conduct current and ensure the alignment of the inner and outer conductors.
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• The outer conductor is a braid made of thin copper wire, foil or a film covered with a layer of aluminum. It is located between the outer cover and the inner insulation.
• Sheath is the last layer of the cable, which serves to insulate and protect the conductor from the effects of sunlight. It is made of materials that are resistant to ultraviolet radiation.

Cable types may differ in the presence of additional protection against external interference. In addition, some coaxial wires have a metal mesh on the outside that absorbs external electromagnetic signals.

This allows data transmission to be carried out without distortion. The main signals are transmitted along the center conductor, and the metal braid acts as a grounding function, protecting the transmission from electrical and crosstalk.

Interference appears from the impact on the cable of nearby wires. The insulation between the core and the sheath is of great importance, which protects the wire from short circuits. The outer braid can be rubber, plastic or Teflon.

Areas of use

Coaxial cable has recently been used in a variety of applications, providing high-speed data transmission with reliable protection against interference. In some qualities, it is significantly ahead of the twisted pair.

But twisted pair is gradually replacing coaxial wire, since its installation is much easier and faster. Coaxial cable is used in local computer networksx, especially where a bus configuration is used. Energy absorbers, which computer experts call terminators, are installed at each end of the line.

These elements protect the cable from internal signal reflections and provide the required data transfer rate. In addition to buses, coaxial wire is used in star and passive star network configurations to transmit signals in various electronic and electrical systems.

Types of cables

All cables are classified according to the RG (Radio Guide) scale. Depending on the design features and functional purposes, each element has its own marking. There are two main types:

1. Thin coaxial cable - the wire diameter does not exceed 6 mm, therefore it is highly flexible. It is used for short distances, since the signal attenuates faster in it. It is considered the most acceptable form for mounting local networks and connecting to each computer. For ease of installation and connection, special connectors are used.
2. Thick wire is a classic element with a diameter of about 10 mm. It features a more powerful and rigid design, which requires special devices for installation and adjustment. It is considered a more expensive product, therefore it is used only when necessary. Some thick cables come with two shields and extra insulation between them. This provides better protection against external influences and better listening ability.

There is another type of cable that is used in electrical networks. Its design is no different from other types of coaxial products. It consists of an internal single-core wire and a multi-core braid, between which there is an insulation layer.

Outside, it is protected by a dielectric shell made of plastic and supplemented with armoring reinforcement. The disadvantage of this design is considered to be a rather large weight, which does not allow its use in overhead lines.

Characteristics of wires

All types of coaxial wires are characterized by common indicators. The most important parameter is considered the resistance of the medium to wave propagation, which determines the quality of the signal.. This indicator is influenced by the material of the central core and its properties:

• the dielectric constant;
• capacity;
• inductance;
• resistivity.

In addition, the material of the inner core affects the attenuation of the signal transmission, which depends on the distance of the line. Coaxial cable is also characterized by factors such as linear capacitance and inductance.

Capacitance describes the ability of a wire to store charge, and inductance describes the ability of a wire to create a magnetic field. The geometric dimensions of the important elements of the wire are taken into account when determining the methods of its installation in order to ensure the further efficient operation of the entire line.