TM 9-4931-294-15/2
for each diode is progressively lower than the +22.5volt
output.
When operating voltage is applied, Miller
input. Since the output from the beta network is applied
integrator Q501, Q502 and Q516 generates a negative
to the parallel connected anodes of the diodes, triggering
going sweep voltage. The slope of this sweep voltage is
of each diode becomes a function of the beta input. At a
determined by the position of SWEEP RATE FREQ
low level beta output, all diodes are back biased and the
RANGECPS switch S106 and SWEEP RATE ADJ
beta input appears solely across resistor R1301. As the
control R114. The output of the Miller integrator is
beta amplitude increases, the number of diodes which
applied to comparator Q504 which generates a pulse
conduct increases, placing more and more resistors in
when the sweep voltage reaches a dc reference voltage
parallel with resistor R1301. Thus, as the beta amplitude
obtained from voltage divider R501, R506 and R507.
increases, the shaper resistance is decreased. By
This pulse triggers oneshot multivibrator Q505 and
careful selection of shaper network components, the
Q506, which generates a positive going, 10millisecond
voltage feedback assumes an inverse exponential form.
wide pulse. The multivibrator output is applied through
(4) Regulator error amplifier. In CW operation the
emitter followers Q522 and Q507 to gate diode CR506,
which causes CR506 to conduct and the Miller integrator
regulator error amplifier (figure 2-12) senses any voltage
to return to its quiescent state. After 10 milliseconds the
difference that exists when combining the positive
multivibrator returns to its steady state condition; the gate
voltage level input from the shaper network and the
diode is cut off, and the Miller integrator generates the
negative voltage level preset by FREQUENCYMC control
next sweep voltage, repeating the process. The result is
R1502. For A F, internal, or external sweep modes of
a sawtooth waveform train with a 10millisecond delay
operation, the circuit senses the difference that exists
between sweeps. This sawtooth train is applied through
when combining the positive shaper network input and
emitter follower Q503 to SWEEP WIDTH control R111, ∆
the
negative
voltage
level
preset
by
the
FREQUENCYMC control and the sweep voltage. The
F% control R108, and sweep output amplifier Q710.
difference of the combined voltage inputs is applied
The SWEEP WIDTH control adjusts the sweep voltage
through emitter follower Q515 to amplifier Q513. The
applied to the regulator error amplifier, when MODE
amplified difference voltage is applied through emitter
switch S103 is positioned for INT SWEEP operation.
The ∆ F% control adjusts the sweep voltage applied to
follower Q511 to dc amplifier Q509. Voltage limit
difference amplifierQ519 and Q520 controls the gain of
the regulator error amplifier over a smaller range when
dc amplifier Q509.
When the output from the
MODE switch S103 is positioned for A F operation. The
highvoltage circuits increases above the reference level
amplified output of Q710 is available at SWP OUT
set by highvoltage limit potentiometer R1403 in the rf
connector J105. The oneshot multivibrator output is also
head, an output from Q712 in the highvoltage monitor is
applied to blanking pulse generator Q517 where it is
applied to Q520. The resulting output from the voltage
amplified and applied to BLANKING connector J106.
limit difference amplifier decreases the gain of dc
(6) Anode voltage supply and square wave
amplifier Q509, thus limiting the highvoltage output to the
generator.
level set by highvoltage limit potentiometer R1403. The
(a)The ac input voltage for the anode voltage
signal output from Q509 is then applied through emitter
supply (figure 2-14) is applied from the secondary winding
followers Q508 and Q703 to pass transistors Q701 and
of transformer T704 to bridge rectifier CR204CR207.
Q702 and controls their collector to emitter resistance.
The output of the bridge rectifier is filtered by capacitor
(5) Sweep generator.
Basically, the sweep
C205 and applied to pass transistor Q205. Difference
generator (figure 2-13) operates by continuously
amplifier Q201 and Q202 senses the difference between
triggering a Miller integrator circuit each time this circuit
a reference level set by RF LEVELLEVEL ADJ control
reaches a certain voltage level in its linear sweep
R102 and the input to the LEVEL IN connector when
external signal source leveling is used.
2-14
