Coaxial cable

Coaxial cable is a kind of wire and signal transmission line, which is generally made of four layers of materials: the innermost layer is a conductive copper wire, the outer layer of the wire is surrounded by a layer of plastic (for insulator and dielectric), and the outer layer of the insulator is a thin mesh conductor (generally copper or alloy), and then the outer layer of the conductor is the outermost insulating material as the outer skin.

Use of coaxial cable

Coaxial cable can be used for the transmission of analog and digital signals, and is suitable for a variety of applications, including television transmission, long-distance telephone transmission, short-distance connection between computer systems, and LAN. Coaxial cable and broadband coaxial cable (i.e. network coaxial cable and video coaxial cable) are more expensive than twisted pair, but their anti-interference performance is better than twisted pair. Coaxial cable can be selected when many devices need to be connected and the communication capacity is quite large. As a means of transmitting TV signals to thousands of households, coaxial cable has developed rapidly, which is cable TV. A cable TV system can load dozens or even hundreds of TV channels, and its transmission range can reach tens of kilometers.

Advantages and disadvantages of coaxial cable

The advantages of coaxial cable are that it can support high-bandwidth communication on relatively long lines without repeaters, but its disadvantages are also obvious: first, it is large in size, and the diameter of the thin cable is 3/8 inch thick, which takes up a lot of space in the cable duct; The second is that it cannot bear entanglement, pressure and serious bending, which will damage the cable structure and prevent signal transmission; Finally, the cost is high, and all these shortcomings can be overcome by twisted pair. Therefore, in the current LAN environment, it has been basically replaced by the Ethernet physical layer specification based on twisted pair.

Coaxial cable application

In cable TV transmission, coaxial cable is widely used in medium and small transmission systems due to its low cost and easy construction. Especially in the "last 1km" transmission of HFC (Hybrid Fiber-Coaxial) network, other cables cannot be replaced. Many passive devices, active devices and users need to be connected by cable. All devices connected by coaxial cable need to achieve impedance matching. If there is no match, the signal will be reflected between the components and cables, increasing the impact of noise and ghost on the transmitted image. The quality of cables of the same specification produced by different manufacturers sold on the market varies greatly. However, as long as cables produced by regular manufacturers are selected (the price is on the high side), their raw materials, electrical performance and production process can be guaranteed, and their quality is also trustworthy.