1, PVC jacket: the surface can be seen inside the compilation of a regular "uneven", indicating that the processing technology is good, will not produce a relative sliding, is a good cable; smooth appearance, do not see the compaction of the " Roughness ", pinch the jacket with loose feeling, is poor cable.
2, check the shield layering: the number is enough, copper mesh, check the solderability, tinned copper scraping to see inside is not copper, aluminum-magnesium alloy line hardness was significantly greater than copper; Uneven distribution, and the insulation layer is not tight, such as poor cable.
3, check the core: diameter --- SYV cable 0.78 to 0.8mm, SYWV cable is 1.0mm; Recently there has been a SYV75-5 core diameter is 1.0mm cable, the characteristic impedance of this cable, certainly not 75 ohms, not to the 75 ohm transmission system.
4, check the core and the insulation of the adhesive force: oblique cut insulation layer, according to the direction of pulling off the core line to see the core and insulation layer there is no bonding process materials; good cable has a greater adhesion, poor cable No glue.
Longitudinal tensile test: take one meter cable, layered stripping core, insulation, shielding, outer jacket, the remaining 10 cm long.
Method is: two hands, respectively, the cable adjacent to the two layers, in the opposite direction to pull; good cable general force can not move, poor cable can be easily pulled out.