TM 11-6625-1633-45
selected by the DEVIATION METER RANGE selector
order to maintain the required phase between the oscil-
switch and applied to the grid of amplifier A1V3. The
lations, as the frequency is changed by varying the posi-
output of amplifier A1V3 is applied through coupling
tion of the shorting plunger, klystron tracking potenti-
capacitor AlC1 to the full-wave rectifier bridge, con-
ometer A4R20 is mechanically gauged to the move-
sisting of diodes A1CR5 through A1CR8. The rectified
ments of the shorting plunger.
output, in parallel with deviation meter adjustment po-
tentiometer AlR1, is applied across deviation meter M1.
e. When MODULATION selector switch S2 is in the
Deviation meter M1 indicates a signal level proportional
INT SINE position, the modulation signal from cathode
to the sine wave modulation signal amplitude and,
follower A1V2 is applied to the reflector of the klystron.
therefore, proportional to the kilohertz deviation ((1)
The reflector voltage is thereby sinusoidally varied to
above ) .
produce a frequency modulated output. The frequency of
the modulating signal is selected by the position of IN-
TERNAL MODULATION FREQUENCY selector
2-5. Analysis of Klystron Oscillator Circuit
switch S1. The available frequencies are 1,000 Hz,
1,600 Hz, 20 KHz, 68 KHz, and 108 KHz.
f. In the EXT SINE position of MODULATION se-
oscillator, a cavity assembly, and a mechanical tracking
lector switch S2, and with an external sine wave modu-
system. The operating range of the klystron oscillator is
lating signal applied, the operation of the klystron is
from 600 MHz to 1,850 MHz.
identical as in the INT SINE position of the MODULA-
TION selector switch (e above). The external modulat-
b. The operation of the klystron oscillator is con-
ing signal frequency can vary over the range of 250 Hz
trolled by the position of MODULATION selector
to 108 KHz.
switch S2. With MODULATION selector switch S2 in
the OFF position, klystron oscillator A4V1 is cut off and
g. In the EXT PULSE position, the operation is
the power monitor bridge circuit may be balanced using
similar to the INT SINE position (e above) except that
ZERO SET potentiometers R51 and R52.
with an external pulse applied, the klystron will produce
an fm signal instantaneously varied at the same repeti-
c. When MODULATION selector switch S2 is in the
tion rate as the modulating pulse. In between pulses, the
CW position, the klystron tube operates as a velocity
carrier center frequency is obtained as an output. When
modulated oscillator. The external cavity, in the form of
the pulse is present, the output frequency is shifted
a coaxial transmission line, consists of two concentric
above or below the center frequency by an amount pro-
cylinders. The klystron tube is inserted at one end of this
portional to the amplitude of the pulse. The modulation
line so that the outer cylinder makes contact with the
pulse repetition frequency (prf ) can be approximately
first interaction grid (the one closer to the cathode), and
300 to 380,000 pulses per second ( pps ) .
the inner cylinder makes contact with the second inter-
action grid. At the other end of the line, the circuit is
h. The function of two of the four tubes projecting
completed by a movable shorting plunger. The position
from the cavity (c above) is to couple the rf signal by
of the plunger determines the resonant frequency of the
means of attenuator probes to RF OUTPUT jack J5.. The
cavity. Four tubes, protecting from the sides of the cav-
attenuators consist of circular waveguides operated be-
ity, permit the coupling of rf energy to the output at-
low cutoff. Electromagnetic energy injected into the
tenuator and the power monitor bridge.
waveguides is attenuated exponentially with the distance
from the cavity. The rf power is coupled out by two vari-
d. The cathode of klystron tube A4V1 is fixed at -325
able-position probes within the waveguide tubes. Probe
volts by the beam power supply, while the reflector volt-
Z1 is used for frequencies below 825 MHz and probe Z2
age of the tube is varied with the position of klystron
for frequencies above 825 MHz. Coaxial relay K4 func-
tracking potentiometer A4R20. The maximum negative
tions as an rf switch. It connects the proper attenuator
reflector voltage is limited by the reflector power supply
probe to the RF OUTPUT jack as a function of the cen-
voltage (-650 volts) and the setting of 1850 MC potenti-
ter frequency selector handwheel position.
ometer A4R19; the minimum reflector voltage is deter-
mined by the setting of 600 MC potentiometer A4R3. In
2-3
