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Non se pode ignorar o cable coaxial

2021-03-05

Cable coaxialpodenon ser ignorado

 

Para probas de cables de cobre, discutimos moito sobre o contido relacionado co cableado de par trenzado equilibrado, como a categoría 6 (CAT 6), a categoría 6 (CAT 6A) e a categoría 8 (CAT 8). Aínda que este tipo de cableado é amplamente utilizado para soportar a transmisión de voz, datos e vídeo por Ethernet, non significa que sexa o único tipo de cableado de cobre que poida atopar.

Cable coaxial ("coax" in English) has long been used to transmit data and video signals. It is one of the first media to support 10BASE2 and 10BASE5 Ethernet, which pode achieve 10 Mb up to 185 meters or 500 meters, respectively. /s transfer. The term "coaxial" means that the central conductor of the cable and its shield have the same axis or center point. Some cable coaxials may have multiple shielding layers, such as a four-shielded cable coaxial. The cable contains two layers of shielding, and each layer of shielding is composed of aluminum foil wrapped with wire mesh. The shielding characteristics of cable coaxial make it have strong anti-electromagnetic interference ability and pode transmit high-frequency signals over long distances.

Although we usually think that cable coaxial is only used in broadband video and cable television (CATV) home applications, but in the commercial enterprise environment, from closed circuit television (CCTV), audio and video to radio frequency antennas, and even some network connections, you pode find Its figure. Therefore, it is very necessary to understand this cable medium and how to test it.

Tipo principal

There are many different types of cable coaxials 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 cable coaxials are RG6, RG11, and RG59, of which RG6 is most commonly used in applications such as CCTV and CATV 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.

 

Cable coaxialstamén teñen diferentes impedancias, normalmente 50, 75 e 93Ω. 50Ω cable coaxials have high power handling capabilities and are mainly used in radio transmitters such as amateur radio equipment, civil band radio (CB) and walkie-talkies. 75 Ω cables pode maintain signal strength well and are mainly used to connect various types of receiving equipment, such as cable television (CATV) receivers, high-definition televisions and digital video recorders. 93 Ω cable coaxial was used in IBM mainframe networks in the 1970s and early 1980s, with very few applications and expensive. Although the 75 Ω cable coaxial impedance is most commonly encountered in most applications today, it should be noted that all components in the cable coaxial system should have the same impedance to avoid signal loss and signal loss at the connection point. Internal reflections that reduce video quality.

The digital signal 3 (DS3) signal used in the central office (also known as T3 line) transmission service also uses cable coaxials, including 75 Ω 735 type and 734 type. The 735 type cable has a coverage distance of up to 69 meters, while the 734 type cable has a coverage distance of up to 137 meters. RG6 cable pode also be used to transmit DS3 signals, but the coverage distance is shorter.

For any cable coaxial, successful installation depends on the use of high-quality components and correct installation techniques, especially the installation of connectors. Insertion loss is affected by the total length of the installed link and is the main parameter to ensure that the cable coaxial supports the intended application.