A coaxial cable consists of two concentric conductors, an inner conductor and a tubular outer conductor, which is used simultaneously for the return of the signal. This is called an unbalanced line.
The distance between outer conductor (sheath) and inner conductor is kept constant by a solid insulation (dielectric) made of high polymer plastics. Due to the shielding effect of the outer sheath, the coaxial cable does not emit the frequency (signal) to be transmitted to the environment. The same applies to the irradiation of disturbances from the environment. The attenuation of environmental influences on the signal line is given as attenuation measure. The losses of the skin effect at high frequencies are kept low by the good conductive surface of the inner conductor.
The specification of the characteristic impedance is an important parameter for the selection of the right cable. Areas of application for coaxial cables are video technology, electrical measuring technology and applications in which radio signals
A coaxial cable consists of two concentric conductors, which are seperated by a dielectric and by a screen. Fields of applocation for coaxial cables are video technology, electrical measurement as well as applications, where radio signals have to be transferred without loss.
A double screened coaxial cable is presented here
Structure of a double screened coaxial cable:
1 = inner conductor - solid wire or stranded wires (1b)
2 = dielectric / isolation
3a = braid or foil
3b = braid or foil
4 = outer sheath
more information about the structure of such cables: Structure coaxial cable
The wave impedance is only depending on the outer diameter of the inner conductor, the inner diameter of the outer conductor and the dielectric constant of the intermediate dielectric. A vacuum is the best dielectric.
Question: Which is the right cable for my application?
For applications up to 1GHz we recommend the RG174, for applications up to 2.5GHz we recommend the RG179, RG188, RG187 or RG316. For applications above 2.5Ghz we recommend the use of low loss cable such as SS405, Multiflex_86 or CLF100. Due to the used materials and the cable structure, those cables are suitable for high frequencies (see illustration „Attenuation“).
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