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    • Coaxial Cables

    		 Any 50 Ohm coax will work for attaching external antennas on wireless
    network equipment for 2.4Ghz and 5,8Ghz equipment. However there are a number
    of factors that affect performance due to rf leakage and attenuation due
    to materials and shielding used by manufacturers. These factors become more
    important the higher the frequency and lower the power level used. Both
    apply to wireless network equipment and so it is important to use higher
    quality coaxial cables or keep lengths to a minimum.

    This translates into a 50 Ohm coax cable with a non-foam dielectric eg
    Teflon, PTFE or polyethylene and double screened shielding with less than
    1.5db per metre at a frequency greater than 2 GHz.

    But remember a loss of 3db means a 50% reduction in power…

    Examples are:

    Semi-Rigid RG402U or RG405U suitable for hard wiring and fixed pigtails

    LMR195 suitable for making Pigtails max 3 Meters

    CFD200 or CNT200 suitable for making Pigtails max 5 Meters

    CNT400, CFD400 or LMR400 suitable for Antenna runs up to 10 Meters

    LDF4-50A (Heliax) suitable for Antenna runs up to 20 Meters

    The impedance of a coaxial cable that has a round center conductor
    and a round outer conductor is as follows:

    Zo = 138 Log (D/d)

    Log is always to base 10, (ln is natural log).

    Zo is the surge impedance, generally 50 ohms,

    D = inside diameter of the outer conductor,

    d = outside diameter of the inter conductor.

    Any dielectric other than air requires that the constant 138 be modified
    by dividing it by the square root of the dielectric constant of the insulating
    material.