There are two main types of cables, one is pure copper material and the other is copper-clad aluminum material. The English name of copper clad aluminum is: Cooper Clad Aluminum, so copper clad aluminum conductors are also often called: CCA conductors. Copper-clad aluminum composite wire was first introduced in Germany in the 1930s, and was subsequently promoted in the United Kingdom, the United States, France and other countries, and was widely used in various fields. CATV cables in the United States began to try copper-clad aluminum wires as early as 1968, and the consumption amounted to 30,000 tons per year. Now American countries have replaced pure copper cables with copper-clad aluminum (steel) cables.

Copper-clad aluminum is made by concentrically clad copper layer on the surface of aluminum or aluminum-steel alloy core material, and the thickness of the copper layer is more than 0.55mm. Because the transmission of high-frequency signals on the conductor has the characteristics of skin effect, the cable TV signal is transmitted on the surface of the copper layer above 0.008mm, and the copper-clad aluminum inner conductor can fully meet the signal transmission requirements. body consistent.

We can compare copper-clad aluminum and pure copper in the following three aspects:

Mechanical properties

The strength and elongation of pure copper conductors are greater than that of copper-clad aluminum conductors, which means that pure copper is better than copper-clad aluminum in mechanical properties. From the point of view of cable design, pure copper conductors have the advantages of better mechanical strength than copper-clad aluminum conductors, which are not necessarily required in practical application. The copper-clad aluminum conductor is much lighter than pure copper, so the overall weight of the copper-clad aluminum cable is lighter than that of the pure copper conductor cable, which will bring convenience to the transportation of the cable and the construction of the cable. In addition, copper-clad aluminum is softer than pure copper, and cables produced with copper-clad aluminum conductors are better than pure copper cables in terms of flexibility.

Electrical properties

Because the conductivity of aluminum is worse than that of copper, the DC resistance of copper-clad aluminum conductors is larger than that of pure copper conductors. Whether this affects the power mainly depends on whether the cable will be used for power supply, such as power supply for amplifiers, if it is used for power supply , the copper clad aluminum conductor will cause additional power consumption and the voltage will drop more. When the frequency exceeds 5MHz, the AC resistance attenuation at this time has no obvious difference under these two different conductors. Of course, this is mainly due to the skin effect of high-frequency current. The higher the frequency, the closer the current flows to the surface of the conductor. The surface of the copper-clad aluminum conductor is actually pure copper material. When the frequency reaches a certain level, the entire current is plated. It flows in the copper material. At 5MHz, the current flows in a thickness of about 0.025 mm near the surface, and the copper layer of the copper clad aluminum conductor is about twice as thick. For coaxial cables, because the transmitted signal is above 5MHz, the transmission effect of copper-clad aluminum conductors and pure copper conductors is the same. This can be proved by the attenuation of the actual test cable. Copper-clad aluminum is softer than pure copper conductors, and it is easy to straighten in the production process. Therefore, to a certain extent, it can be said that the return loss index of cables using copper-clad aluminum is better than that of cables using pure copper conductors.

economy

Copper-clad aluminum conductors are sold by weight, and pure copper conductors are also sold by weight. The price of copper-clad aluminum conductors is more expensive than that of pure copper conductors of the same weight. But the copper-clad aluminum of the same weight is much longer than the pure copper conductor, and the cable is calculated by length. The same weight, copper-clad aluminum wire is 2.5 times the length of copper wire, and the price is only a few hundred yuan per ton. Taken together, copper clad aluminum is very advantageous. Because the copper-clad aluminum cable is relatively light, the transportation cost and installation cost of the cable will be reduced, which will bring certain convenience to the construction.

Ease of maintenance

The use of copper-clad aluminum can reduce network failures and prevent network personnel from “cutting the core in the winter and cutting the skin in the summer” (aluminum strip or aluminum tube products) during maintenance. Due to the large difference in thermal expansion coefficient between the copper inner conductor and the aluminum outer conductor of the cable, in the hot summer, the aluminum outer conductor stretches greatly, and the copper inner conductor retracts relatively, so it cannot fully contact the elastic contact piece in the F head seat; in severe cold In winter, the aluminum outer conductor shrinks greatly, causing the shielding layer to fall off. When the coaxial cable adopts the copper-clad aluminum inner conductor, the thermal expansion coefficient difference between it and the aluminum outer conductor is small. When the temperature changes, the fault of the cable core pulling is greatly reduced, and the transmission quality of the network is improved.

In general, the overall performance of copper-clad aluminum conductors is better than that of pure copper conductors, which will save users’ costs.

The use of copper-clad aluminum wire in the wire and cable industry is also a good way to relieve the current pressure on enterprises. The aluminum wire is coated with a layer of copper and drawn from a bimetallic wire. Because of its small specific gravity and good transmission performance, it is especially suitable for the inner conductor of the radio frequency coaxial cable. Compared with pure copper wire, its density is Pure copper is about 40%. And the transmission characteristic is better than pure copper wire, it is the most ideal inner conductor of RF coaxial cable branch line.