Raytheon Pathfinder 1200 Instruction Manual page 77

Circuit components:
L201 Charging Choke
CD203 SCR Switch
T201 Pulse Transformer
and the PFN consists of L202, C204, C205, C206.
K201 is the pulse selection relay which is controlled by RANGE switches in the
display unit.
-',
By setting the OPERATE switch on the control panel to "ON" position, the
modulator trigger pulse is fed to the base of TR 1 from the transmitter trigger generator
circuit in the display unit.
The MOD-MH of 330 V de is fed to the PFN capacitors C204, C205 and C206
via L201. Because of the resonant charging action of L201, the PFN reaches almost
twice the voltage of the input. Since the charging efficiency is approximately 90
%.
the PFN voltage reaches nearly +600 V.
On receiving a positive pulse at the gate of CD203 from the emitter follower
TR201 via R205, the SCR switch begins to conduct and the voltage which is charged
across the PFN capacitor is discharged via CD203 and T201.
Consequently, the pulse determined by the PFN appears on the primary windings
of the pulse transformer T201 and this pulse is stepped up to the cathode of the
magnetron via T201 (approximately 1 : 13).
The peak voltage of the pulse on the pulse transformer primary windings is
-260V, and the magnetron cathode voltage is -3.6 kV. On short ranges, the pulse
length is 0.12 usee. On longer ranges when the K201 operates, the output pulse length
is 0.5 usee. (K201 is controlled by RANGE switches in-the display unit.)
As a result:
Range
Pulse Length Pulse Repetition Frequencies
0.25 nm
0.12JJ.sec
920 Hz
0.5 nm
0.12 usee 920 Hz
1 nm
0.12JJ.sec 920 Hz
2 nm
0.12JJ.sec
920 Hz
4 nm
0.5 JJ.sec 920Hz
8
nm
0.5 JJ.sec 920 Hz
12 nm 0.5 JJ.sec
920Hz
2)
Magnetron Transmitter
While the high voltage pulse is fed to the cathode of the magnetron, the magne-
tron generates high energy oscillations in the region of 9445 MHz for the duration of
the input pulse.
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