Coaxial cables transmit high-frequency electrical signals such as radio frequency signals or telecommunications signals.They are used in audio and video for high-quality transmission.">

Coaxial cable - Everything you need to know !

Coaxial cables transmit high-frequency electrical signals.
Coaxial cables transmit high-frequency electrical signals.

Coaxial Socket

A coaxial cable is a type of cable used to transmit high-frequency electrical signals, such as RF (radio frequency) signals or telecommunications signals.

Its structure consists of two concentric conductors : a central conductor and an external shield.

The central conductor, usually made of copper or aluminum, is surrounded by an insulating sheath, often made of plastic or Teflon. This insulating sheath provides electrical insulation between the center conductor and the outer shield, protecting the signal from external electromagnetic interference.

The outer shield is a metal layer that surrounds the insulating jacket. It acts as an electromagnetic barrier, protecting the signal from external interference and preventing signal leakage.

The combination of these elements allows the coaxial cable to provide reliable and robust signal transmission, even in environments subject to electromagnetic disturbances or interference.

Coaxial cables are widely used in a variety of applications, including telecommunications, computer networks, audio and video equipment, security systems, surveillance systems, and more.

They are valued for their ability to transmit high-frequency signals over long distances with little signal loss and good immunity to electromagnetic interference, making them a popular choice for many data transmission and communication applications.

Wall Coaxial Outlet

The wall coaxial socket is very common in domestic installations.

What are the different types of coaxial cables ?

There are several types of coaxial cables, each suitable for specific applications based on factors such as signal frequency, power, usage environment, and performance requirements. Here are some of the main types of coaxial cables :

  • 50 ohm coaxial cables :
    These cables are widely used in RF (radio frequency) applications where an impedance of 50 ohms is required, such as telecommunications equipment, measurement and test equipment, radio antennas, broadcast equipment, etc. RG-58, RG-174, and LMR-195 coaxial cables are common examples of 50 ohm coaxial cables.

  • 75 ohm coaxial cables :
    These cables are mainly used in video and audio applications, such as cable TV, video broadcasting systems, professional audio equipment, and TV antenna connections. RG-6 and RG-59 coaxial cables are most commonly used in residential and commercial applications.

  • Semi-rigid coaxial cables :
    These cables are used in applications where superior mechanical stability and electrical performance are required. They are used in high-frequency communication systems, test and measurement equipment, aerospace and military applications, and more.

  • Low-loss coaxial cables :
    These cables are designed to minimize signal losses over long distances and at high frequencies. They are used in applications that require low-attenuation signal transmission, such as long-distance links, cellular networks, satellite links, etc. The LMR-400 and LMR-600 coaxial cables are examples of commonly used low-loss cables.

  • Shielded coaxial cables :
    These cables have additional shielding for enhanced protection against external electromagnetic interference. They are used in environments with high electromagnetic interference, such as industrial plants, military equipment, defense applications, etc.


The different parts of a coaxial cable
The different parts of a coaxial cable

Technical principles

The central core, which can be single-stranded or multi-stranded in copper or tinned / silver-plated copper, or even copper-plated steel, is surrounded by a dielectric, insulating material.

The dielectric can be surrounded by a single or double conductive braid, under which a coiled copper or aluminium strip / tape or a tube made of bare copper, corrugated copper, tinned copper or tinned aluminium can be presented, and on the other hand, an insulating and protective outer sheath.
For coaxial cables with an external shield in the form of a metal tube, the term semi-rigid cable is generally used.

Its specific shape makes it possible not to generate or capture any external disturbing flow. This type of cable is used for the cable distribution of high or low frequency digital or analogue signals as well as for radiating cables associated with a transmitter, in particular used to carry radio waves in tunnels or underground passages.

The two conductors of opposite poles of a coaxial cable are of different natures (on a two-wire line, made up of two parallel conductors separated by a dielectric, they are undifferentiated) : the core, which is the central copper conductor, is surrounded by an insulating material, then by a shield which is the second conductor, usually made of copper braids.
The specific characteristic of this type of cable is that the central axes of symmetry of the two conductors merge : the consequence is that they are subject to the same disturbances induced by the surrounding electromagnetic fields.
The shielding also prevents the conductors from causing disturbances to the external environment. It works on the principle of the Faraday cage.

The wanted signal is equal to the voltage difference between the two conductors.
In theory, when the axes are perfectly merged, the external magnetic fields create the same potential gain (or loss) on both parts of the cable.
The induced voltage (created by the disturbing fields) is therefore zero, and the signal is transmitted without disturbance.
Coaxial cables are used to transmit high-quality audio and video signals.
Coaxial cables are used to transmit high-quality audio and video signals.

Uses

Coaxial cables are used in a multitude of applications due to their high-frequency signal transmission characteristics and ability to resist electromagnetic interference. Here are some of the most common uses of these cables :

  • Telecommunications : Coaxial cables are widely used in telecommunications networks to transmit RF signals, such as telephone signals, broadband internet signals (modem cable), cable television signals, and digital broadcast signals.

  • Computer networks : Although less common than twisted-pair cables (such as Ethernet cable), coaxial cables have been used in the past for computer local area networks (LANs), especially in 10BASE2 and 10BASE5 coaxial networks.

  • Audio and video equipment : Coaxial cables are used to transmit high-quality audio and video signals, such as those used in home theater systems, professional sound systems, broadcast equipment, and surveillance cameras.

  • Measurement and test equipment : Coaxial cables are widely used in measurement and test equipment, such as oscilloscopes, signal generators, spectrum analyzers, and RF measurement instruments, due to their ability to transmit accurate and reliable signals.

  • Military and aerospace applications : Coaxial cables are used in various military and aerospace equipment, such as radars, communication systems, navigation systems, and surveillance systems, due to their reliability and resistance to extreme environmental conditions.

  • Security and surveillance systems : LCoaxial cables are used in security and surveillance systems, such as CCTV (Closed Circuit Television) video surveillance systems, to transmit high-quality video signals over long distances with little signal loss.

  • Medical Applications : Coaxial cables are used in some medical equipment, such as medical scanner
    scanner by flight time
    This scanner can be used to scan buildings Scanner by flight time
    s and diagnostic systems, to transmit electrical and RF signals accurately and reliably.


Facilities

From the end of the twentieth century, coaxial cable was gradually replaced by optical fibre for long-distance use (more than one kilometre) as well as for IP links intended for businesses or individuals, in particular with the FTTH standard.

The coaxial cable can be installed along walls, gutters or buried because the presence of objects does not influence the propagation of the signal in the line as long as it is not applied too much bending or curvature that affects its impedance.
The energy loss in a coaxial cable increases with frequency or distance (length of the link) and is affected by the characteristics of the dielectric.

The connection to the coaxial cable must be made by using coaxial connectors that are suitable for the cable and mounted in accordance with the instructions provided in order to maintain the desired transmission quality characteristics of the whole (see for example the BNC connector).
For Digital Terrestrial TV, IEC 60169-22 plugs are recommended, while for satellite TV it is the F plugs to be screwed, although they are mounted on the same type of "consumer" cable.

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