Coaxial cable introduction

Introduce

Coaxial cable is divided into thin cable: RG-58 and thick cable RG-11. And use very few semi-rigid coaxial cables and feed tubes.

Thin cable

The thin cable has a diameter of 0.26 cm and a maximum transmission distance of 185 meters. When used, it is connected to a 50 Ω termination resistor, T-connector, BNC connector and a network card. The wire price and connector cost are relatively low, and no equipment such as a hub is required. It is suitable for setting up a small Ethernet network with concentrated terminal equipment. The total cable length should not exceed 185 meters, otherwise the signal will be severely attenuated. The impedance of the thin cable is 50Ω.

Thick cable

The thick cable (RG-11) has a diameter of 1.27 cm and a maximum transmission distance of 500 meters. Due to its relatively large diameter, it is less flexible and is not suitable for installation in a narrow indoor environment. The production method of RG-11 connector is also relatively complicated and cannot be directly connected to a computer. It needs to be passed through a switch. Turn the device into an AUI connector and then connect it to your computer. Due to the strength of the thick cable, the maximum transmission distance is also longer than the thin cable, so the main purpose of the thick cable is to play the role of the backbone of the network to connect several networks formed by thin cables. The thick cable has an impedance of 75Ω.

Semi-rigid coaxial cable

This type of cable is used infrequently and is usually used for the connection of modules inside communication transmitters. Since the transmission loss of this line is small, there are also some disadvantages such as high hardness and difficulty in bending. In addition, most of the transmission frequency of such cables can reach 30Ghz. Model CXJ--50--3 The typical structure of this type of cable is shown in the following table. Structure Material Diameter (mm) 1. Inner conductor silver plated copper wire 0.932. Insulator Polytetrafluoroethylene (PTFE) 3.003. Outer conductor

1 seamlessly annealed copper tube 3.58

2 tin (alloy) seamless copper tube

3 silver-plated seamless copper tube

At present, the technology is gradually improving, and there are also some such wire rods with large bending amplitudes. However, the author recommends that such copper wire should be used as much as possible in places where flexibility is not required to ensure stability.

Basic Information

English abbreviation SYV, often have 75-7, 75-5, 75-3, 75-1 and other models, the characteristic impedance is 75 ohms, in order to adapt to different transmission distances. It is the main medium for transmitting video signals in asymmetric baseband mode.

The main application area

The main application areas are: bracket connection of equipment, closed circuit television (CCTV), shared antenna system (MATV), and transfer of color or monochrome RF monitors. These applications do not require the selection of precision video coaxial cables with particularly strict electrical tolerances. The characteristic resistance of the video coaxial cable is 75 ohms. This value is not optional. Physics has demonstrated that the attenuation characteristic optimized for video signals occurs at 77 ohms. In low power applications, the material and design determine the optimal impedance of the cable to be 75 ohms.

Standard video coaxial cables have both solid and multi-strand conductor designs. It is recommended to use a multi-strand conductor design in applications where the cable is to be bent, such as the internal connection of a CCTV camera to the tray and bracket assembly, or the transmission cable of a remote camera.