Introduction to coaxial cable

Coaxial cable (abbreviated as "COAX") is a cable composed of two coaxial, mutually insulated cylindrical metal conductors to form the basic unit (coaxial pair), and then composed of single or multiple coaxial pairs.

Long used to transmit data and video signals, it was one of the first media to support 10BASE2 and 10BASE5 Ethernet, enabling 10 Mb/s transmission up to 185 meters or 500 meters, respectively. The term "coaxial" means that the axis or center point of the center conductor of the cable and its shield is the same. Some coaxial cables may have multiple shields, such as four-shielded coaxial cables, which contain two shields, each shielded consisting of an aluminum foil wrapped wire mesh. This shielding characteristic of coaxial cable makes it have strong anti-electromagnetic interference ability and can transmit high-frequency signals over long distances.

Main type

There are many different types of coaxial cables that support a wide range of specialized applications, such as satellite communications, industrial, military, and marine applications. The three most common types of non-industrial coaxial cable are RG6, RG11, and RG59, with RG6 most commonly used in applications such as CCTV and CATV in enterprise environments. The RG11 has a thicker center conductor than the RG6, which means lower insertion loss and longer signal distances. However, thicker RG11 cables are more expensive and very bendable, making them unsuitable for deployment in internal applications and more suitable for long-distance outdoor installations or straight backbone links. The RG59 is more flexible than the RG6, but its losses are high and are rarely used in applications other than low-bandwidth, low-frequency analog video applications (rearview cameras in cars) where short distances and trunking space are limited.

Coaxial cables also vary in impedance – typically 50, 75 and 93 Ω. 50 Ω coaxial cables have high power handling capabilities and are mainly used for radio transmitters such as amateur radio equipment, civil band radio stations (CBs) and walkie-talkies. 75 Ω cable maintains signal strength well and is primarily used to connect various types of receiving equipment, such as cable television (CATV) receivers, high-definition televisions, and digital video recorders. 93 Ω coaxial cable was used in IBM mainframe networks in the 70s and early 80s of the 20th century, with very few applications and expensive. While a coaxial cable impedance of 75 Ω is most commonly encountered in most applications today, it is important to note that all components in a coaxial cable system should have the same impedance to avoid internal reflections at the connection point that can cause signal loss and degrade video quality.

Digital Signal 3 (DS3) signals used for central office (also known as T3 lines) transmission services also use coaxial cable, including Type 75 Ω 735 and Type 734. Type 735 cables cover up to 69 meters, while Type 734 cables cover up to 137 meters. RG6 cables can also be used to transmit DS3 signals, but over shorter distances