Coaxial Cable refers to one cable with two concentric conductors but for the conductor and shielding layer which shares the same axis.The most common coaxial cable consists of a copper conductor isolated by an insulating material, with another ring conductor and its insulator outside the inner layer, and then the whole cable is covered by a sheath of PVC or teflon
Coaxial cable can be used for analog and digital signal transmission which is suitable for a variety of applications, the most important of which are television transmission, long distance telephone transmission, short distance connection between computer systems and local area network.Coaxial cable is growing rapidly as a means of transmitting TELEVISION signals to millions of homes: cable TELEVISION.A cable TV system can carry dozens or even hundreds of TV channels, with a range of tens of kilometers.Coaxial cable has long been an important part of long-distance telephone network.Today, it faces increasing competition from fiber optics, ground-based microwaves and satellites.
Coaxial cables can be divided into two basic types: baseband coaxial cables and broadband coaxial cables .
Baseband coaxial cable
Baseband coaxial cable shielding layer is usually made of copper mesh structure, its characteristic impedance for 50 Ω.The cable is used to transmit digital signals. Commonly used models are RG-8(thick cable) and RG-58(thin cable).The most obvious difference between thick cable and thin cable is the cable diameter.Thick cable is suitable for large local network with long standard distance and high reliability.However, the rough cable network must install transceiver and transceiver cable, which is difficult to install, so the overall cost is high.On the contrary, thin cable is simpler and cheaper.However, the cable should be cut off in the process of installation, so it is easy to have the hidden trouble of bad contact when the joint is too large.
Whether the network is connected with a thick cable or a thin cable, the fault point often affects all the machines on the entire cable, making fault diagnosis and repair difficult.Therefore, the baseband coaxial cable has been gradually replaced by unshielded twisted pair or optical cable .
Wide-band coaxial cable
Broadband coaxial cable shielding layer is usually use aluminum stamping, and its characteristic impedance for 75 Ω.This cable is commonly used to transmit analog signals, commonly known as RG-59. It is the standard transmission cable used in cable television networks and can transmit multiple TV signals simultaneously on one cable.Broadband coaxial cable can also be used as a transmission medium in some computer networks.