Figure 16.

Measuring Standing Waves of Current.

28. The impedance varies along a mismatched line.

a. The impedance at any point on a transmission line is the ratio of

the voltage to the current at that point.

Figure 16 shows that the

impedance varies along a shorted line.

This happens because the waves

reflected by the short cause the voltage and current to vary.

Part A of

Figure 17 shows the standing waves of voltage and current along a line which

is one wavelength long. The voltage is minimum and the current maximum at

the shorted end.

The impedance at the shorted end is zero.

One-quarter

wavelength back from the short toward the generator, the impedance is

maximum because of the maximum voltage and minimum current at that point. A

half wavelength back from the short, the impedance is minimum again.

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