Figure 66. High-Level Modulator With
3. So you see, when reflections occur because of impedance mismatch, the
voltage on the PFN does not remain constant and the applied voltage to the
Also, if the PFN voltage is not constant from
pulse to pulse, the applied voltage to the magnetron is not constant either.
Likewise, magnetron power output varies, causing frequency modulation.
Therefore, the PFN voltage must be held constant from pulse to pulse. This
is the job of the reverse-current diode.
Learning Event 8:
1. Part B of Figure 66 shows the action of the reverse-current diode, V4.
pulse transformer primary because of impedance mismatch.
pulse makes V4 conduct and a reverse current flows from ground, through the