Basic Knowledge Of Coaxial Cable And Twisted Pair Cable

- Mar 13, 2018-

The coaxial cable can be divided into baseband coaxial cable and broadband coaxial cable (ie, network coaxial cable and video coaxial cable) for the purpose of use. Coaxial cable is divided into 50Ω baseband cable and 75Ω broadband cable. The baseband cable is subdivided into thin coaxial cable and coarse coaxial cable. Baseband cable for digital transmission only, data rates up to 10Mbps.

Coaxial cables can transmit signals over a wider frequency range (100 kHz to 500 MHz) than twisted pair cables. Frequently used in the network is the RG-58 coaxial cable.

The network coaxial cable is a cable composed of coaxial conductors insulated from each other: the inner conductor is a copper wire, and the outer conductor is a copper tube or a net. The electromagnetic field is enclosed between the inner and outer conductors, so the radiation loss is small and the influence of external interference is small. It is commonly used to transmit multiple telephones and televisions.

The name of the coaxial cable is related to its structure. Coaxial cable is also one of the most common transmission media in LANs. The pair of conductors is used to transmit information and based on a cylindrical outer conductor sheathing the outer surface of the inner conductor. The two conductors are isolated from each other by an insulating material. The center of the outer conductor and the center axis are in the same center.  so-called coaxial cable, coaxial cable is designed to do so, but also to prevent the transmission of external electromagnetic interference signals.

Classification method:

According to the diameter of the coaxial cable can be divided into thick coaxial cable and thin coaxial cable. Thick coaxial cable is suitable for relatively large local networks. It has a long standard distance and high reliability. Because it does not need to cut off the cable during installation, it can flexibly adjust the network access position of the computer as required. However, the network must be installed with a transceiver cable. It's more difficult to install, so the overall cost is high. On the contrary, the thin cable installation is relatively simple and the cost is low. Since the cable is cut during the installation process, both ends must be equipped with a basic network connector (BNC) and then be connected to both ends of the T connector. This is one of the most common failures that occur in Ethernet networks that are currently in operation.

Whether it is a thick cable or a thin cable, which is a bus topology, that single cable is connected to multiple machines. This topology is suitable for a dense machine environment, but when a contact fails, the fault will affect the entire cable in series of all the machines. The diagnosis and repair of faults are troublesome and will be gradually replaced by unshielded twisted-pair or fiber optic cables.

Pros and Cons:

The advantage of coaxial cable is that it can support high-bandwidth communications over relatively long repeater-less lines, and its disadvantages are also obvious: First, the bulky, thin cable diameter is 3/8 inch thick, and it takes up a lot of space in the pipeline; the second is that it cannot withstand tangles, stress, and severe bending. These can damage the cable structure and prevent the transmission of signals. Finally, the cost is high, and all these disadvantages are exactly what the twisted pair can overcome. So now The LAN environment has basically been replaced by the twisted-pair Ethernet physical layer specification.