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Што е коаксијален кабел?

2021-03-03

A коаксијален кабел("коаксот" in English) is a cable composed of two коаксотial, mutually insulated cylindrical metal conductors to form a basic unit (коаксотial pair), иthen a single or multiple коаксотial pairs. It has been used to transmit data иvideo signals for a long time.

It is one of the first media to support 10BASE2 и10BASE5 Ethernet, which can achieve 10 Mb/s transmission up to 185 meters or 500 meters, respectively. The term "коаксотial" means that the central conductor of the cable иits shield have the same axis or center point. Some коаксијален кабелs may have multiple shielding layers, such as a four-shielded коаксијален кабел, which contains two layers of shielding, иeach layer of shielding is composed of aluminum foil wrapped with wire mesh. The shielding characteristics of коаксијален кабел make it have strong anti-electromagnetic interference ability иcan transmit high-frequency signals over long distances. There are many different types of main types of коаксијален кабелs that support a wide range of professional applications, such as satellite communications, industrial, military иmarine applications. The three most common types of non-industrial коаксијален кабелs are RG6, RG11иRG59, од коиRG6најчесто се користи воВидео надзор иCATVапликации во корпоративни средини. Централниот диригент наRG11е подебел одRG6, which means that its insertion loss is lower иthe signal transmission distance is longer.

Сепак, подебелиКабли RG11 are more costly иvery difficult to bend, which makes them unsuitable for deployment in internal applications, but more suitable for long-distance outdoor installations or straight backbone links. RG59е пофлексибилен отколкуRG6, 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 иlimited wiring space. Коаксијални кабли also have different impedances-usually 50, 75, и93 Ω. 50Ω коаксијален кабелs have high power handling capabilities иare mainly used in radio transmitters such as amateur radio equipment, civil bиradio (CB) иwalkie-talkies. 75 Ω cables can maintain signal strength well иare mainly used to connect various types of receiving equipment, such as cable television (CATV) receivers, high-definition televisions иdigital video recorders. 93 Ω Cоаксијален кабел was used in IBM mainframe networks in the 1970s иearly 1980s, with very few applications иexpensive. Although the 75 Ω коаксијален кабел impedance is most commonly encountered in most applications today, it is important to note that all components in the коаксијален кабел system should have the same impedance to avoid possible signal loss иsignal 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 коаксијален кабелs, including 75 Ω 735 type и734 type. The 735 type cable has a coverage distance of 69 meters, while the 734 type cable has a coverage distance of 137 meters.Кабел RG6може да се користи и за пренос на DS3 сигнали, но растојанието на покриеност е помало.