Effective Protection Of Network Connection In Adverse Environment

- May 11, 2018 -

There are usually two kinds of network connector inlet water. One is that the connection inlet water leads to partial influent of cable, which causes the dielectric coefficient of intermediate insulation layer to change, and cable attenuation increases, especially for high frequency signal, which is reflected as high end signal at the user end. The snowflake becomes more and more, and on the main line the amplifier output level slope is small or negative (if the output is tilted); another is that the connection is oxidized by the inlet of the connector, especially on the line fed by the common cable. As a result, the power supply malfunction affects the normal operation of the whole downstream amplifier, and the slope becomes larger and the signal quality deteriorates.

The existing cables are generally copper internal conductors, external conductors are aluminum magnesium alloy wire or aluminum shell. Both inner and outer conductors are oxidized in the air, especially in aqueous environments. Copper can be oxidized at room temperature and high temperature to form black copper oxide and basic copper carbonate, commonly known as copper-green, but the basic copper carbonate can be decomposed into copper oxide at high temperature. These two oxidation products are both insulators and insoluble in water, which have great influence on the feed and signal transmission of CATV transmission system.

The aeruginosa formed at room temperature can be regarded as an equivalent capacitance to form an oxide film insulating layer between the inner conductor and the joint. The high frequency current is easier to pass through than the low frequency current, which shows that both the high and low end signals are attenuated, but the low end attenuation is more serious. At the user end for low level, there may be a variety of interference mesh. At the same time, because of the existence of oxide layer, the conductivity of inner conductor is greatly reduced, the voltage drop of the cable in this section is increased, the voltage of the lower stage is insufficient, and the lower amplifier may work unusually or not.

If the cable joint is damp or influent, the inner conductor and the outer conductor will discharge easily when the power supply cable is transmitted, and a large amount of heat energy will be produced, and the inner conductor will undergo a violent oxidation reaction to form black copper oxide. The density of copper oxide is higher than that of copper green, the attenuation of low frequency signal is greater, the conductivity of inner conductor is weaker, and the influence on the circuit is greater. Moreover, due to the existence of the oxide layer outside the inner conductor, the dielectric constant and inner conductor radius change. Cable impedance may be severely mismatched, and right-hand double-shadow may occur in the back-stage line.

The outer conductor is usually made of aluminum - magnesium alloy wire , aluminum - magnesium is a metal with relatively active chemical properties , and once the joint water inlet and outer conductor discharge , a large amount of heat is generated , which can accelerate the corrosion of the outer conductor . Once the corrosion of the outer conductor is serious , the signal attenuation becomes large , and the conducting capacity of the outer conductor is greatly reduced , and the power supply voltage of the rear stage is low , and the amplifier is not working normally or not .

The common way to reduce the network malfunction caused by the inlet water is to adopt the waterproof joint. Because the construction process of waterproof joints is more complicated, the products of various manufacturers are intermingled, the level of construction personnel is uneven, and the use of waterproof joints is inconvenient for future maintenance and maintenance, so in some places waterproofing joints are not used. Instead, it uses an ordinary RF head. Because of the poor waterproof performance of the common radio frequency head, even if the waterproof tape is used, the water inlet of the joint is inevitable, which is a potential major hidden danger for the cable television system fed by the common cable. In some places, a simple method is adopted: installing a rain shield, which, although relatively primitive, is effective in solving the problem of inlet water to some extent, but at the same time bringing about the problem of heat dissipation. Because the radome is not in close contact with the amplifier, it reduces the convection of the air in the outer layer of the heat sink of the amplifier, and the operating temperature of the amplifier will increase, and various performance indexes will inevitably decrease.

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