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Cable according to the different parts of the conductor, there are two main, one is pure copper material, one is copper clad aluminum material. Copper clad aluminum in English is: Copper clad aluminum, so copper clad aluminum conductor is also commonly known as: CCA conductor. Copper clad aluminum composite wire was first introduced by Germany in the last century in the 30 's, then in the United Kingdom, the United States, France and other countries to promote, widely used in various fields. America's CATV cable started experimenting with copper clad aluminum wire as early as 1968, consuming up to 30,000 tonnes per year. Now the Americas have used copper clad aluminum (steel) cables instead of pure copper cables. In recent years, China's copper clad aluminum CATV cable has also begun to be used heavily. The country in 2000 established the industry standard--sj/t11223-2000, vigorously promote the use of copper clad aluminum cable.
At present, Shanghai, Guangzhou, Zhejiang, Liaoning and other land cable television stations have been widely used copper clad aluminum cable, good response. The copper clad aluminum is in the aluminum or the aluminum/steel alloy core material surface concentric cladding copper layer, pulls out and becomes, the copper layer thickness is above 0.55mm.
Because the high frequency signal transmits on the conductor has the skin effect characteristic, the cable television signal transmits in the copper layer surface above 0.008mm, the copper clad aluminum inner conductor can satisfy the signal transmission request completely, its signal transmission characteristic and the same diameter line copper body is consistent.
Copper clad aluminum and pure copper can be compared in the following three ways:
Mechanical characteristics: The strength and elongation of pure copper conductor is larger than that of copper clad aluminum conductor, which means that pure copper is better than copper clad aluminum in mechanical properties. From the point of view of cable design, pure copper conductor has better mechanical strength than copper clad aluminum conductor, which is not necessary in the practical application process. Copper clad aluminum conductor lighter than pure copper, so the copper clad aluminum cable in the overall weight than pure copper conductor cable to light, which will give cable transport and cable erection and construction of convenience.
In addition, copper clad aluminum is softer than pure copper, the cable produced by copper clad aluminum conductor is better than pure copper cable in softness.
Electrical properties: Because the electrical conductivity of aluminum is worse than that of copper, the DC resistance of the copper clad aluminum conductor is larger than that of the pure copper conductor, and this has no effect. The main 2014 mid-term exam sprint comprehensive review guide Beijing area test questions in Jiangsu area test questions to see if the cable will be powered, such as to provide power to the amplifier, if it is used for power, Copper clad aluminum conductor will lead to additional power consumption and lower voltage. When the frequency exceeds 5MHz, there is no obvious difference between the two different conductors at this time. Of course, this is mainly because of the skin effect of high-frequency currents, the higher the frequency, the flow of the current is closer to the conductor surface, in the copper clad aluminum conductor surface is actually pure copper material, when the frequency is high to a certain time, the entire current plating in the copper material flow. In 5MHz cases, the current flows in about 0.025 mm thickness near the surface, while the copper clad aluminum conductor is about one times thicker than this thickness. For coaxial cable, because the transmission signal is above 5MHz, so the copper clad aluminum conductor and pure copper conductor transmission effect is the same.
The attenuation of the actual test cable can prove this.
Copper clad aluminum than pure copper conductor soft, in the production process is easy to straighten treatment, so to a certain extent, it can be said that copper clad aluminum cable than with pure copper conductor of the cable return loss index.
Economy: Copper clad aluminum conductors are sold by weight, and pure copper conductors are sold by weight, and copper clad aluminum conductors are more expensive than pure copper conductors of the same weight. But the same weight of copper clad aluminum is much longer than the pure copper conductor length, and the cable is calculated by length. The same weight copper clad aluminum wire is 2.5 times times the length of copper wire, the price is only hundreds of yuan per ton. Combined, copper clad aluminum has an advantage.
As the copper clad aluminum cable is lighter, the transportation cost of cable, installation and erection cost will be reduced, will bring some convenience to the construction.
Ease of maintenance: The use of copper clad aluminum can reduce network failures, avoid network personnel in the maintenance of "winter shear core, Summer shear" (Aluminum belt longitudinal package or aluminum tube products). Because the copper inner conductor of the cable differs greatly from the thermal expansion coefficient of the aluminum outer conductor, in the hot summer, the outer conductor of aluminum is larger, the copper inner conductor is relatively shrinking, and can not fully contact with the elastic contacts in the F Head seat; In the winter, the aluminum outer conductor shrinkage is large, so that the shielding layer off.
When the coaxial cable adopts the copper clad aluminum inner conductor, it differs from the thermal expansion coefficient of the aluminum outer conductor slightly, the fault of the cable core is greatly reduced and the transmission quality of the network is improved.
Generally speaking, the overall performance of copper clad aluminum conductor is better than pure copper conductor, it will save the cost of users. Industry insiders believe that the wire and cable industry to adopt copper clad aluminum wire is also a relief of the current enterprise pressure a good way. Aluminum wire outside a layer of copper through the pull system of bimetal wire, due to the small proportion, good transmission performance, especially for RF coaxial cable in the inner conductor, compared with pure copper wire, its density of 40% or so. The transmission characteristic is superior to pure copper wire, and is the ideal conductor of RF coaxial cable branch line.