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Cablul coaxial nu poate fi ignorat

2021-03-05

Cablu coaxialpoate sasă nu fie ignorat

 

Pentru testarea cablurilor de cupru, am discutat multe despre conținutul legat de cabluri de cupru echilibrate cu perechi torsadate, cum ar fi categoria 6 (CAT 6), categoria 6 (CAT 6A) și categoria 8 (CAT 8). Deși acest tip de cablare este utilizat pe scară largă pentru a susține transmiterea Ethernet a vocii, datelor și a videoclipurilor, nu înseamnă că este singurul tip de cablare din cupru pe care îl puteți întâlni.

Cablu 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 poate sa 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 cablu coaxials may have multiple shielding layers, such as a four-shielded cablu 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 cablu coaxial make it have strong anti-electromagnetic interference ability and poate sa transmit high-frequency signals over long distances.

Although we usually think that cablu 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 poate sa find Its figure. Therefore, it is very necessary to understand this cable medium and how to test it.

Tipul principal

There are many different types of cablu 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 cablu 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.

 

Cablu coaxialsau, de asemenea, impedanțe diferite - de obicei 50, 75 și 93Ω. 50Ω cablu 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 poate sa 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 cablu coaxial was used in IBM mainframe networks in the 1970s and early 1980s, with very few applications and expensive. Although the 75 Ω cablu coaxial impedance is most commonly encountered in most applications today, it should be noted that all components in the cablu 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 cablu 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 poate sa also be used to transmit DS3 signals, but the coverage distance is shorter.

For any cablu 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 cablu coaxial supports the intended application.