Coaxial cable is used as a transmission line for radio frequency signals. Its applications include feedlines connecting radio transmitters and receivers with their antennas, computer network (Internet) connections, digital audio (S/PDIF), and distributing cable television signals. One advantage of coaxial over other types of radio transmission cable is that in an ideal coaxial cable the electromagnetic field carrying the signal exists only in the space between the inner and outer conductors. This allows coaxial cable runs to be installed next to metal objects such as gutters without the power losses that occur in other types of transmission lines. Coaxial cable also provides protection of the signal from external electromagnetic interference.
Coaxial cable conducts electrical signal using an inner conductor (usually a solid copper, stranded copper or copper plated steel wire) surrounded by an insulating layer and all enclosed by a shield, typically one to four layers of woven metallic braid and metallic tape. The cable is protected by an outer insulating jacket. Normally, the shield is kept at ground potential and a signal carrying voltage is applied to the center conductor. The advantage of coaxial design is that electric and magnetic fields are restricted to the dielectric with little leakage outside the shield. Conversely, electric and magnetic fields outside the cable are largely kept from interfering with signals inside the cable. Larger diameter cables and cables with multiple shields have less leakage. This property makes coaxial cable a good choice for carrying weak signals that cannot tolerate interference from the environment or for stronger electrical signals that must not be allowed to radiate or couple into adjacent structures or circuits.
Common applications of coaxial cable include video and CATV distribution, RF and microwave transmission, and computer and instrumentation data connections.
The characteristic impedance of the cable is determined by the dielectric constant of the inner insulator and the radii of the inner and outer conductors. A controlled cable characteristic impedance is important because the source and load impedance should be matched to ensure maximum power transfer and minimum standing wave ratio. Other important properties of coaxial cable include attenuation as a function of frequency, voltage handling capability, and shield quality.
Coaxial cable design choices affect physical size, frequency performance, attenuation, power handling capabilities, flexibility, strength, and cost. The inner conductor might be solid or stranded; stranded is more flexible. To get better high-frequency performance, the inner conductor may be silver-plated. Copper-plated steel wire is often used as an inner conductor for cable used in the cable TV industry.
|Conductor||Solid copper or Tinned Copper|
|Shield||Tinned copper or Bonded aluminium polyethylene terephthalate|
|Outersheath||Flame-retardant-polyvinyl chloride (FR-PVC) or Low Smoke Zero Halogen (LSZH)|
|Cable CT Coaxial Cable||Suitable for professional TV and CCTV system installations, including digital, satellite, terrestrial and cable TV.|
|RG Coaxial Cable URM Coaxial Cable||50 or 75 Ohm, suitable for a broad range of applications including low power video, video signal, and broadband signals. Available in Duct Grade or with a LSZH sheath|
|Coaxial BT3002 16 Way / 8 Way Cable Coaxial RA7000 Equivalent Cable||Manufactured to BT Specifications.|