Coaxial Cables


Coaxial Cables are an electrical cable with an inner conductor surrounded by a tubular insulating layer typically of a flexible material with a high dielectric constant, all of which are surrounded by a conductive layer (typically of fine woven wire for flexibility, or of a thin metallic foil), and finally covered with a thin insulating layer on the outside. The term coaxial comes from the inner conductor and the outer shield sharing the same geometric axis. Coaxial cable was invented by English engineer and mathematician Oliver Heaviside, who first patented the design in 1880.

Coaxial cable is used as a transmission line for radio frequency signals, in applications such as connecting radio transmitters and receivers with their antennas, computer network (Internet) connections, and distributing cable television signals. One advantage of coax over other types of transmission line 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 transmission lines, and provides protection of the signal from external electromagnetic interference.

Coaxial cable should not be confused with other shielded cable used for carrying lower frequency signals such as audio signals. Shielded cable is similar in that it consists of a central wire or wires surrounded by a tubular shield conductor, but it is not constructed with the precise conductor spacing needed to function efficiently as a radio frequency transmission line.

Constructional specification
RF and Video Co-axial Cables are transmitting video signals with solid Copper centre conductor of different sizes, foamed polythene insulated and further sealed Alluminium foil tapped and Alluminium wire braided with 60% coverage and PVC sheathed Cables.

RF Cable type RG 59 RG 6 RG 11
Conductor dia mm 0.71 0.91 1.63
Di- electric 3.75 4.60 7.15
Alluminium myler tape

overall dia

3.95 4.80 7.35
Alluminium wire braid

Coverage

60% 60% 60%
PVC sheath OD 6.10 7.15 10.10


Electrical parameter
Nominal D.C. resistance

Ohms / Km

44.83 27.30 8.50
Nominal Capacitance pF/ft. 16.20 16.20 16.20
Impedence in Ohms 75 Ohms 75 Ohms 75 Ohms
Attenuation at 1000 MHZ

dB/100 meter

27.10 21.70 14.10
Applications
Co-axial Cable are used in TV sets, Radios, Ethernets and other video equipments.

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