same voltage and current ratio. To take an example, a 50 ohm feeder with 100 watts entering will have a voltage of 70.7 volts and a current of 1.414 amps. A 25 ohm load would require a voltage of 50 volts and a current of 2 amps to dissipate the same current. To resolve this discontinuity, power is reflected and standing waves are generated. When the load resistance is lower than the feeder impedance, voltage and current magnitudes like that shown in Figure 4.10 are set up. Here the total current at the load point is higher than that of the perfectly matched line, whereas the voltage is less. The values of current and voltage along the feeder vary as shown along the feeder. For small values of reflected power the waveform is almost sinusoidal, but for larger values it becomes more like a full wave rectified sine wave. This waveform consists of voltage and current from the forward power plus voltage and current from the reflected power. At a Total current (If + /R) Total voltage (V4 + VR) Position Distance along of load feeder (a) Load resistance is lower than feeder impedance Total voltage (Vf + VR) Total current (If + 1/R Position Distance along of load feeder (b) Load resistance is higher than feeder impedance Figure 4.10 Voltage and current magnitudes for a mismatched line 88 Newnes Guide to Radio and Communications Technology distance a quarter of a wavelength from the load the combined voltages reach a maximum value while the current is at a minimum. At a distance half a wavelength from the load the voltage and current are the same as at the load. A similar situation occurs when the load resistance is greater than the feeder impedance; however, this time the total voltage at the load is higher than the value of the perfectly matched line. The voltage reaches a minimum at a distance a quarter of a wavelength from the load and the current is at a maximum. However, at a distance of a half wavelength from the load the voltage and current are the same as at the load. It is often necessary to have a measure of the