Coaxial Cable ("coax" for short) has long been used to transmit data and video signals. It is one of the first media to support 10BASE2 and 10BASE5 Ethernet, which can achieve 10 Mb/s up to 185 meters or 500 meters, respectively. s transmission. The term "coaxial" means that the central conductor of the cable and its shield have the same axis or center point. Some coaxial cables may have multiple shielding layers, such as a four-shielded coaxial cable, which contains two layers of shielding, and each layer of shielding is composed of aluminum foil wrapped with wire mesh. The shielding characteristics of coaxial cable make it have strong anti-electromagnetic interference ability and can transmit high-frequency signals over long distances.
Although we usually think that coaxial cable is only used in broadband video and cable television (CATV) home applications, in the business enterprise environment, from closed circuit television (CCTV), audio and video to RF antennas, and even some network connections, you can find Its figure. Therefore, it is very necessary to understand this cable medium and how to test it.
There are many different types of coaxial cables that support a wide range of professional applications, such as satellite communications, industrial, military, and marine applications. The three most common types of non-industrial Coaxial cables are RG6, RG11 and RG59, of which RG6 is most commonly used as CCTV Cable and CATV Cable in corporate environments. The center conductor of RG11 is thicker than RG6, which means that its insertion loss is lower and the signal transmission distance is longer. However, thicker RG11 cables are more costly and very difficult to bend, which makes them unsuitable for deployment in indoor applications, but more suitable for long-distance outdoor installations or straight backbone links. RG59 is more flexible than RG6, but its loss is higher. It is rarely used in other applications except for low-bandwidth, low-frequency analog video applications (rear-view cameras in automobiles) with short distances and limited wiring space.
The digital signal 3 (DS3) signal used in the central office (also called T3 line) transmission service also uses Coaxial cables, including 75 Ω 735 type and 734 type. The 735 type cable has a coverage distance of 69 meters, while the 734 type cable has a coverage distance of 137 meters. RG6 cable can also be used to transmit DS3 signals, but the coverage distance is shorter.