c. Now, look at the discharge cycle in Part A.
At the instant the
switch closes (thyratron fires), Cst is short-circuited through the load.
The discharge of Cst develops a negative rectangular pulse of 6KV. Charging
choke and nonconducting diode isolate the power supply from the short-
circuited switch.
Figure 62.
DC Resonant Charging Circuit With Holding Diode.
d. Part B of Figure 62 shows the waveform analysis of the DC resonant
charging circuit.
Compare these waveforms with those shown in Figure 61.
Notice, now, the PFN does not discharge exactly at the instant the voltage
oscillation reaches its peak. Instead, the discharge of the PFN is delayed,
resulting in a lower PRF. So, you see, the charging diode allows more than
one PRF to be used in a radar set. Note, too, in Part B, that every time
the switch fires, a negative pulse is developed across the load.
This
negative pulse is the modulator output which is coupled to the magnetron by
a pulse transformer.
78
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