The Role of SYV Coaxial Cable in CATV System

Coaxial cable is the main medium used to transmit radio frequency signals in cable television system. It is a conductor composed of a core wire and a shield mesh tube. Because the axes of these two conductors are coincident, they are called coaxial cables. Coaxial line.

Coaxial cable structure

The RF coaxial cable is composed of an inner conductor, an insulating medium, an outer conductor (shielding layer) and a sheath 4 part.

Inner conductor

The inner conductor is usually made up of a solid conductor. By using the skin effect of high-frequency signals, an empty copper tube or copper-coated aluminum rod can be used. Copper-clad steel wire is used for the user network that does not require power supply. Copper or aluminum wire is recommended for the network or trunk line. This can not only guarantee the transmission performance of the cable, but also meet the requirements of power supply and mechanical performance, reduce the weight of the cable, and reduce the cost of the power cable.

Insulating medium

Insulating media can be made of polyethylene, polypropylene, polyvinyl chloride (PVC) and fluoroplastics. The commonly used insulating media is polyethylene with low loss and good process performance.

Outer conductor

The outer conductor of the coaxial cable has a double role. It serves as a conductor of the transmission circuit and also has a shielding effect. The outer conductor usually has three structures.

(1) Metal tubular. This structure is made of copper or aluminum tape longitudinal welding, or seamless copper tube extrusion drawing, this type of structure is the best shielding performance, but poor flexibility, commonly used in trunk cable.

(2) Aluminum plastic composite tape vertical bag lap. This kind of structure has a good shielding effect, and the manufacturing cost is low, but because the outer conductor is a circular tube with a longitudinal seam, electromagnetic waves will leak out through the gap and should be used with caution.

(3) Combination of woven mesh and aluminum-plastic composite tape longitudinal package. This is developed from a single braided mesh structure. It has characteristics such as good flexibility, light weight, and reliable joints. Experiments have shown that the use of a reasonable composite structure greatly improves the shielding performance. At present, this structural form is greatly improved. use.

jacket

Black cables with excellent weather characteristics should be used for outdoor cables, and light-colored polyethylene should be used for indoor user cables.