The Introduction of Coaxial Cables
Introduction :   Coaxial Cable Catalog >>
  • A coaxial cable is one that consists of two conductors that share a common axis. The inner conductor is typically a straight wire, either solid or stranded and the outer conductor is typically a shield that might be braided or a foil.
  • Coaxial cable is a cable type used to carry radio signals, video signals, measurement signals and data signals. Coaxial cables exist because we can't run open-wire line near metallic objects (such as ducting) or bury it. We trade signal loss for convenience and flexibility. Coaxial cable consists of an insulated center conductor which is covered with a shield. The signal is carried between the cable shield and the center conductor. This arrangement give quite good shielding against noise from outside cable, keeps the signal well inside the cable and keeps cable characteristics stable.
  • Coaxial cables and systems connected to them are not ideal. There is always some signal radiating from coaxial cable. Hence, the outer conductor also functions as a shield to reduce coupling of the signal into adjacent wiring. More shield coverage means less radiation of energy (but it does not necessarily mean less signal attenuation).
  • Here is a quick overview of common coaxial cable impedances and their main uses:

50 Ohms :

  • 50 ohms coaxial cable is very widely used with radio transmitter applications. It is used here because it matches nicely to many common transmitter antenna types, can quite easily handle high transmitter power and is traditionally used in this type of applications (transmitters are generally matched to 50 ohms impedance). In addition to this 50 ohm coaxial cable can be found on coaxial Ethernet networks, electronics laboratory interconnection (for example high frequency oscilloscope probe cables) and high frequency digital applications (for example ECL and PECL logic matches nicely to 50 ohms cable). Commonly used 50 Ohm constructions include RG-8 and RG-58.

75 Ohms :

  • The characteristic impedance 75 ohms is an international standard, based on optimizing the design of long distance coaxial cables. 75 ohms video cable is the coaxial cable type widely used in video, audio and telecommunications applications. Generally all baseband video applications that use coaxial cable (both analogue and digital) are matched for 75 ohm impedance cable. Also RF video signal systems like antenna signal distribution networks in houses and cable TV systems are built from 75 ohms coaxial cable (those applications use very low loss cable types). In audio world digital audio (S/PDIF and coaxial AES/EBU) uses 75 ohms coaxial cable, as well as radio receiver connections at home and in car. In addition to this some telecom applications (for example some E1 links) use 75 ohms coaxial cable. 75 Ohms is the telecommunications standard, because in a dielectric filled line, somewhere around 77 Ohms gives the lowest loss. For 75 Ohm use common cables are RG-6, RG-11 and RG-59.

Typical coaxial cable constructions are:


RG Coaxial Cables :

  • RG Coaxial Cables are used as a connection cable in the high signal sequences of wireless and data communication systems where lower attenuation required, RF and microwave transmission, data transmission and instrumentation control. Some of these cables are based upon MIL-Spec designs and are often referred to by their RG type number.MIL-C-17 is the government specification document used to standardize coaxial cables. Other impedance cables are used for data transmission and instrumentation control. 50 ohms coaxial cables are used in most radio frequency and microwave transmission, local Area Network (LAN), computer and many instrumentation /control applications.

Braided Coaxial Cable :

  • Braided Coaxial Cable is by far the most common type of closed transmission line because of its flexibility. It is a coaxial cable, meaning that both the signal and the ground conductors are on the same center axis. The outer conductor is made from fine braided wire, hence the name "braided coaxial cable". This type of cable is used in practically all applications requiring complete shielding of the center conductor. The effectiveness of the shielding depends upon the weave of the braid and the number of braid layers. One of the draw-backs of braided cable is that the shielding is not 100% effective, especially at higher frequencies. This is because the braided construction can permit small amounts of short wavelength (high frequency) energy to radiate. Normally this does not present a problem; however, if a higher degree of shielding is required, semirigid coaxial cable is recommended. In some high frequency flexible coaxial cables the outer shield consists if normal braids and an extra aluminium foil shield to give better high frequency shielding.

Semi-rigid and Semi-flexible Coaxial Cable :

  • Semi-rigid and Semi-flexible Coaxial Cable uses a solid tubular outer conductor, so that all the RF energy is contained within the cable, are used in wireless communication, broadcast and military equipments for transmission of radio frequency signals. For applications using frequencies higher than 30 GHz a miniature semirigid cable is recommended.

Leaky Coaxial Cables :

  • Leaky Coaxial Cables allow radio, cellular and Wi-Fi communication in areas where free space electromagnetic radiation typically can’t reach. These cables are used in tunnels, mines, large buildings or building complexes, alongside rail lines and in underground malls to facilitate greater wireless network coverage.

50 Ohm RF Coaxial Cables :

  • 50 Ohm RF Coaxial Cables are transmission coaxial cables for GSM antennas, and the halogen-free cables are suitable for laid on hooks, and pulled through walls or through technical ducts.

Trunk Cables :

  • Trunk Cables are used used in CATV-community antenna television, CCTV-closed-circuit television, and DBS-direct broadcasting satelite.

BT3002 Coaxial Cable :

  • BT3002 Coaxial Cables are mainly used for indoor installation in the transmission equipments for the digital telephone exchange system. Due to their miniature size, they can also be used for other applications where high performance is essential.