It is readily understood that a piece of wire has an inherent inductance. What’s in a name? Co-axial means that both conductors in the cable share the same axis, i.e: if you cut a piece of coaxial cable and look at the cut end, the radius of the both inner and outer conductors can be measured from the center line of the inner conductor. The ratio of the amplitudes of the voltage and current of a single wave, propagating down the line.Ī single wave meaning a wave traveling in one direction, with no reflected waves or other anomalies. Properly defined, the characteristic impedance is: In the simplest terms, the characteristic impedance is calculated by the formula on the right, taking the square root of the distributed inductance (nH per meter, for example) divided by the distributed capacitance (pF per meter, for example). If you want to know why 50 ohms was arrived at as a sort of standard for radio applications, you can read this post. Most coaxial cables have a characteristic impedance of 50 or 75 ohms. The RF world is full of esoteric terminology, and not least of these is characteristic impedance, or Z 0.

Multisim 12 impedance meter