2. Do not use the wrong characteristic impedance. Characteristic impedance is an important technical parameter of coaxial cable. There are several kinds of commonly used 75Ω, 50Ω, etc. There are many impedance mismatches in use, such as the signal-to-noise ratio of the transmitted signal decreases, the image produces ghosting or coarse and coarse texture. Interference, deteriorating the frequency characteristics of the system, causing an increase in the data error rate in the data transmission system.
3. Prevent the inner and outer conductors from being separated when connecting. Coaxial cable is a special structure transmission line. The inner and outer conductors have specific structural relationships and functions. The circuit connections also have their own specific connection. The inner and outer conductors cannot be interchanged at will, otherwise the signal will be affected normally. Transmission, can not get satisfactory results.
4. Improve the installation quality of cable ends and cable connectors. When the end of the coaxial cable is connected to the terminal box, amplifier, etc., the connection quality of the outer conductor (mainly the woven mesh) cannot be ignored. If the connection is loose or disconnected, the signal level will be greatly reduced. In the middle of the TV screen, there is usually an obvious horizontal black belt, and the vertical direction has a slow left shifting interference band. The system is also very susceptible to interference from nearby power frequency and radio frequency; when the outer conductor and the joint contact resistance is too large ( If the outer conductor is oxidized, there is rust on the joint, etc., the reverse attenuation characteristics will occur, and the attenuation of the low frequency band will be greater; the coaxial cable assembly at the joint and the connection point of the cable may not be standardized. The characteristic impedance changes greatly, resulting in reflections that form standing wave interference.
5. Prevent the coaxial cable from being interfered with the power line in parallel. Transmission lines, power transformers, electric motors, industrial electrical equipment, various household appliances, etc. are all strong sources of electromagnetic pollution. Coaxial cables cannot be paralleled with power lines during wiring, and are preferably kept away from electrical equipment. And its lines, so that it can avoid the above interference to a certain extent, and can also be protected from leakage caused by power line leakage, overheating and fire.
6. Strengthen moisture-proof and waterproof measures. In open air and visible water, equipment such as amplifiers and branch distributors must be equipped with waterproof boxes; the joints of coaxial cables should be fabricated at the near end with a waterproof bend (curved path of arc downwards) to prevent water droplets from flowing along the cable. In the joint parts and other circuits, the cable end (joint) should be coated with sealant waterproof; the main way of moisture and water vapor intrusion into the cable is the cable head and sheath, so the inspection and maintenance of the sheath can not be ignored. If the sheath is damaged, it should be wrapped in time.
7, the line reservation can not be too much. The attenuation of the signal in the cable increases with the increase of the cable length. Generally, the cable is attenuated by 2dB per 10m cable. Therefore, it is desirable that the cable path is as short as possible, and there is no need to reserve too much during wiring. Some people are neat and beautiful. The coiled cable is rolled into a small disk and then fastened with wires. As a result, the signal attenuation is increased, and the frequency characteristics of the system are changed, resulting in deterioration of the high frequency performance of the signal.
8, the impact on high temperature can not be ignored. According to the temperature characteristics of the coaxial cable, the metal (inner and outer conductor) loss and dielectric loss of the cable will increase when the ambient temperature rises, and the attenuation of the coaxial cable will increase by about 0.2% for every 1 °C increase in temperature. Therefore, when wiring, keep the coaxial cable away from high-temperature heat sources and high-temperature environment. When the temperature rises excessively, the signal quality may be degraded and the stability of the system may be damaged.