Choosing the right Coaxial Cable Impedance


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Choosing the right coaxial cable impedance is important for ensuring maximum performance from the signal being carried over the cable. How do we select the correct impedance parameter for your project?

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To optimize signal transfer and minimize reflection issues, the coaxial cable should be matched to the load impedance. In general, coaxial cables have two main standards - 50Ω and 75Ω. The 50Ω coaxial cable is used for professional and commercial applications. The 75Ω standard is used for most domestic TV and VHF FM applications. In some cases, a custom impedance value may be required for a specific application; you can derive this impedance with the below equation. Please note that the impedance of coaxial cable is dependent on the dielectric constant of the cable and the diameter of the inner and outer conductors.

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    where:
    Zo: Characteristics impedance in Ω
    D: Inner diameter of the outer conductor
    d: Diameter of inner conductor
    єr: Relative permeability of the dielectric