Check the shielding layer netting: check whether the braiding number is enough, braid the copper material, check the solderability, scrape the tinned copper wire to see if it is copper wire, and the hardness of aluminum magnesium alloy wire is significantly higher than that of copper wire; The poor cables are those with sparse netting, uneven distribution and not tightly wrapped with the insulating layer.

Check the core wire: the diameter is 0.78 to 0.8mm for SYV cable and 1.0mm for SYWV cable; Recently, a cable with syv75-5 core diameter of 1.0mm has emerged. The characteristic impedance of this cable is certainly not 75 ohm and is not applied to 75 ohm transmission system.

Check the adhesive force between the core wire and the insulating layer: cut the insulating layer obliquely, pull the core wire according to the stripping direction, and see if there are bonding process materials between the core wire and the insulating layer; Good cables have large adhesion, but poor cables have no adhesion.

Longitudinal tensile test: take one meter of cable, peel off the core wire in layers, and leave 10 cm long for the insulation layer, shielding layer and outer sheath.