TM11-6625 -2948 -14+P
whose frequency is determined by 1A3C17, 1A3R34,
In order to obtain other levels of power, the ATTENUA-
TOR control is adjusted so that the desired level is under
by varying 1A3R36. The oscillator output (pin 3) is fed to
the hairline of the attenuator dial. This adjustment varies
the D-type flip-flop 1A3U3 (pin 11). The output frequency
the position of the attenuator probe in its waveguide-
of 1A3U3 is 1/2 that of the output of 1A3U4 as character-
ized by the flip-flop. The output of 1A3U3 (pin 13) is
pipe follows a rigid physical law and is extremely accurate,
applied to the Schmitt trigger 1A3U2 through the MODU-
thus the rate of attenuation is transcribed into the dial.
L A T I O N SELECTOR switch only in the INT SQ WAVE
position. The bias supplies for 1A3U3 and 1A3U4 are
(Fig. 5-2 and 5-2.1 )
tapped from the 40V supply in the same manner as for
The Schmitt trigger 1A3U2 is a gate with fast rise and
decay times. The positive voltage to 1A3U2 is held at
when the INT SQ WAVE mode of operation is not used.
+12 volts and the negative supply at ground using dropping
resistor 1A3R13 and zener diode 1A3CR1. The ground is
referenced
at
-1280V.
Diodes
1A3CR2
and
1A3CR3
act
The six-position MODULATION SELECTOR switch 1A3S1
as protective diodes for 1A3U2 and 1A3C15 is a speed up
selects the proper mode of operation for the various func-
capacitor to handle fast pulses. The input to the gate
tions. The klystron grid is biased so that it is held positive
(pin 1) is held at +12V in the CW, INT FM and EXT FM
(approximately 10V) with respect to the cathode in CW,
positions and at ground (-1280 volts) in the RF OFF, INT
I N T FM ~, and EXT FM positions and is held to cut-off
SQ WAVE and EXT
positions via the MODULA-
(approximately -30 volts with respect to the cathode) in
the RF OFF and EXT
positions. In the INT SQ
details). The output of the gate (pin 2) is amplified by
WAVE position it is switched between +10 and -30 volts.
transistor 1A3Q1 to a suitable level so that the grid of the
The grid voltage is determined by the adjustment of 1A5R5
klystron is biased properly for different modes of opera-
tion. In the amplifier circuit 1A3CR5 is a protective diode
The circuit operation in each positions of the MODULA-
for
1A3Q1,
and
1A3C14
is
a
speed
up
capacitor.
The
T I O N SELECTOR which is described in paragraphs a.
amplifier itself acts as an inverter, and the gate 1A3U2 also
through f.
acts as an inverter; therefore, the logic output of 1A3Q1
is the same as the input of the gate 1A3U2.
a. RF OFF Position (Fig. 2-2). In the RF OFF position,
the voltage at the input to the Schmitt trigger gate is
returned to ground through the MODULATION SELEC-
TOR switch. The output of the amplifier 1A3Q1 is, there-
There is a time delay of approximately 60 seconds when
fore, at ground potential (-1280 ref grid) and the grid is
the set is turned on before the beam, repeller and control
thus placed at a negative potential sufficient to drive the
supply voltages are turned on. This delay is necessary in
klystron into cut-off and thus inhibiting oscillation.
order that the klystron tube not be damaged. The time
delay is accomplished by utilizing integrated circuit 1A4U1.
b. CW Position ( Fig. 2-2). In the CW position, the voltage
Pin 3 of 1A4U1 is held high (approximately 12 volts) for
at the input to the Schmitt trigger gate (pin 1 of 1A3U2)
a period determined by the RC time constant of 1A4R13
is held at +12V (with respect to -1280v as referenced
and 1A4C7. When 1A4C7 charges to a high enough level,
ground). The output of the amplifier is thus +40V and the
the timer 1A4U1 changes its state at pin 3 from 12 volts
grid is thus placed at a potential that permits the klystron
to ground, which in turn, changes the output of voltage
to oscillate.
regulator 1A4U3 so that the oscillations start and all the
c. INT SQ WAVE Position (Fig. 2-2). In the INT SQ
supplies (-1250, -1850, and 40 V) turn on (see para-
WAVE position the input to the Schmitt trigger is fed
graph 3-22 for more details). Zener diode 1A4CR4 and
from the output of flip-flop 1A3U3. The square wave out-
r e s i s t o r 1A4R14 are used to supply a bias voltage of
put of the flip-flop moves the Schmitt trigger gate up and
12 volts to integrated circuit 1A4U1.
down at the same rate. The grid driven by the amplifier,
therefore,
modulates the klystron oscillations, producing
a square
wave modulation of output. The rate itself, is
(Fig. 5-2 and 5-2.1 )
Square waves, variable from 950-1050 Hz, are generated
controlled
by the setting of 1A3R36 which changes the
using 1A3U3 and 1A3U4. 1A3U4 is utilized as an oscillator
frequency
of the basic oscillator 1A3U4.