The pros and cons of cable television joint has a close relationship with the construction difficulty, the stability of the system quality and waterproofness, etc. Therefore, the necessity of improving identification ability and exchanging identification experience is evident. Here, the author writes some preliminary experiences for peer’s references.

1. There must be hollow-out grooves in the internal thread inside of F-head lock sleeve.
F-head lock sleeve is a kind of non throughout internal thread, the thread inside closed to the base must produce a circle of hollow-out grooves. Therefore, the threads can be attacked through, the joints of splitter and distributor can be spined to end. No loose of cable clamping sleeve can keep the permanent good contact
Some inferior F heads produced by some manufacturers have no hollow-out groove. It is often difficult to spin the joint of splitter and distributor to the end and can't press cable sleeve. As time goes by, it may cause poor contact fault and become extremely difficult to find out. Or in order to joint spin in place, more strength is given on it, therefore often can create branch distributor joint thread damages. Especially the aluminum thread. Because the hollow-out groove is at the bottom of the inside part of F-head lock sleeve, it is often neglected by quality inspection personnel and users.  

2. F-head contact pins should stationarily fit with insulating plates and joint shells.
Common -9 -12 F-head usually has contact pins. The pins can be divided into two parts, that is, the front pins and the back cable core thread. These two parts require to be stationary fits with insulating barriers, that is, sticking with a little force and cannot be loose and swing. In addition, pay attention to central bore centrality of insulating plate and there cannot be eccentric phenomenon.
There is better one groove or two grooves in the cable core sleeve behind F-head pins. No groove (Garden tubular)or four grooves will bring inconvenience to construction and loose clamp of cable core. （Inconvenience also produced if you heat the welding wire with a wind-proof lighter).
Insulating plates should stationarily fit with connector shell and too big gap is not allowed.
Some inferior F heads produced by some manufacturers have wide fit clearance, which are loose and swaying. Some even have obvious insulation board center hole which is not at the point of the middle, thus causing eccentric pin, influencing electric parameter. Therefore, this kind of product should not be used.

3. Cable waterproof function of water joint should be checked carefully.
The sleeve end inside where a water joint finally tightens usually settles a cable waterproof rubber pad which is about 10mm wide. When the sleeve is gradually tightened, the length of settled waterproof rubber pad is gradually shrinking. Then the inner diameter of waterproof rubber pad is forced to shrink and holds down the outer sheath of cable tightly to take waterproof effect. Sometimes the water joints produced by some manufacturers are not good quality, when tightening the sleeves, the inner diameter of waterproof rubber pad will not shrink or shrink not enough, then has no waterproof effect. Therefore testing the cable waterproof effect must regarded as a very important quality control program. There is an easy way, that is to use a water joint to tighten the sleeve gradually, if the inner diameter of waterproof rubber pad can reduce into half of the original one, the waterproof effect of the water joint is fine. Of course, it is best to make a joint by cable to test and confirm it. In addition, the quality of waterproof rubber pad is crucial. Waterproof rubber pad with superior qualities is made up of silicone rubber, usually translucent, with soft handfeel, easy to compress, flexible and not easy to aging metamorphism.