Coaxial cable from the inside out is divided into four layers: the central copper (single strand of solid or stranded strand), plastic insulator, mesh conductive layer and wire sheath. The central copper wire and the mesh conductive layer form a current loop. Because the central copper wire and mesh conductive layer for the coaxial relationship named.
Coaxial cable conduction AC rather than direct current, that is, every second there will be several times the direction of the current reversal.
If a high-frequency current is transmitted using a general wire, the wire will correspond to an antenna that emits radio outwards, which dissipates the power of the signal and reduces the received signal strength.
Coaxial cable is designed to solve this problem. The radio from the center wire is isolated by the mesh-like conductive layer, and the mesh-shaped conductive layer can control the emitted radio by grounding.
Coaxial cable also has a problem, that is, if a cable over a large extrusion or twisting deformation, then the central wire and the mesh between the conductive layer is not always the same distance, which will cause the internal radio waves will be Reflected back to the signal source. This effect reduces the available signal power. In order to overcome this problem, the center wire and the mesh-like conductive layer are joined by a layer of plastic insulator to ensure that the distance between them is always the same. This also causes the cable to be stiff and not easy to bend.
SYV cable full name solid polyethylene insulated RF coaxial cable, coaxial cable in a.
SYV-75-5: SYV stands for video cable, 75 represents impedance of 75 ohms, and 5 represents wire thickness.
SYV 75-5-1 (A, B, C)
S: RF Y: Polyethylene insulation V: Polyvinyl chloride sheath A: 64 B: 96 C: 128
75:75 ohm 5: wire diameter 5MM 1: on behalf of a single core
SYV cable role: monitoring commonly used video lines are mainly SYV75-3 and SYV75-5 two. If you want to transmit video signals within 200 meters can be used SYV75-3, if the range of 350 meters can be used SYV75-5.
SYV cable use environment: equipment bracket connection, CCTV (CCTV), shared antenna system (MATV) and color or monochrome radio frequency monitor transfer. These applications do not require the selection of precision video coaxial cable with exceptionally stringent electrical tolerances. Video coaxial cable characteristic resistance is 75 ohms, this value is not free to choose. The physics proves that the attenuation characteristics of the video signal are optimized at 77 ohms. In low power applications, the material and design determines the optimal impedance of the cable is 75 ohms.