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Negalima ignoruoti koaksialinio kabelio

2021-03-05

Koaksialinis kabelisgalinegalima ignoruoti

 

Bandydami varinius kabelius, daug diskutavome apie subalansuotą vytos poros varinių kabelių turinį, pvz., 6 kategoriją (CAT 6), 6 kategoriją (CAT 6A) ir 8 kategoriją (CAT 8). Nors tokio tipo kabeliai plačiai naudojami balso, duomenų ir vaizdo perdavimui per Ethernet, tai dar nereiškia, kad tai yra vienintelis varinių kabelių tipas, su kuriuo galite susidurti.

Koaksialinis kabelis ("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 gali 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 bendraašis kabeliss may have multiple shielding layers, such as a four-shielded bendraašis kabelis. 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 bendraašis kabelis make it have strong anti-electromagnetic interference ability and gali transmit high-frequency signals over long distances.

Although we usually think that bendraašis kabelis 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 gali find Its figure. Therefore, it is very necessary to understand this cable medium and how to test it.

Pagrindinis tipas

There are many different types of bendraašis kabeliss 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 bendraašis kabeliss 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.

 

Koaksialinis kabelisstaip pat turi skirtingas varžas - paprastai 50, 75 ir 93Ω. 50Ω bendraašis kabeliss 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 gali 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 bendraašis kabelis was used in IBM mainframe networks in the 1970s and early 1980s, with very few applications and expensive. Although the 75 Ω bendraašis kabelis impedance is most commonly encountered in most applications today, it should be noted that all components in the bendraašis kabelis 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 bendraašis kabeliss, 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 gali also be used to transmit DS3 signals, but the coverage distance is shorter.

For any bendraašis kabelis, 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 bendraašis kabelis supports the intended application.