TM 11-6625-2575-14
The resultant drive signal is coupled to varactor
(3) SWEEP RATE switch S103, a front
panel control, is used to select the desired mode
of operation. In the LINE position, the 60-Hz
line-sync signal drives the Schmitt trigger at a
60-Hz rate. In the 5- to 60-Hz and 0.05- to 5-Hz
(fig. FO-3)
a. Bandswitch. The rf sections of bandswitch
free-running. The SWEEP RATE may be con-
S601 consist of coaxial switches S601-1A and
tinuously adjusted by R120B R120C, the front
S601-1B. In the HIGH band position, the vari-
panel vernier control. In each case, the respective
able oscillator is direct-coupled to R602, and
rc time constants (R118, R120B, and C102 for
Z603 to RF OUT connector J611. In the LOW
the 5-to 60-Hz rate; and R117, R120C, C102, and
band position, the variable oscillator signal is
C103 for the 0.05- to 5-Hz rate) determine the
coupled to the mixer where it mixes with the
sweep rate.
fixed 700-MHz oscillator signal. Lowpass filter
(4) In the MANUAL and EXT modes, the
FL551 couples the mixer difference frequency to
the video amplifier where the signal is amplified.
MANUAL mode, the sweep drive and the hori-
From the video amplifier, the signal is coupled
to the output. Bandswitch S601 includes sections
by the position of R120A in voltage divider net-
2A, 2B, 2C, 2D, 3B, 3C, and 3D in addition to
work R123, R120A, and R127. Resistor R120A
the rf sections. These additional sections couple
is ganged to R120B and R120C, the front panel
or uncouple B + and rf blanking voltages to the
vernier adjustment. In the EXT position, an ex-
respective high and low band circuits.
ternal generator is used in place of the internal
b. High Frequency Band. The variable uhf os-
rate circuit.
cillator uses a mechanically tunable line to tube
b. Linearity Circuit. The linearity circuit am-
the range of 300 MHz to 1200 MHz. Adjustable
plifies and reshapes the input triangular wave. It
resistor R509 is ganged to the shaft of the tuned-
is required to provide a linear frequency-versus-
lined control to provide a nearly constant output
voltage characteristic in the rf output display at
over the tuning range. In the WIDE and NAR-
all SWEEP WIDTH settings, and in both the
ROW sweep modes, varactor CV501 is electroni-
LOW and HIGH frequency bands.
cally varied by the reshaped sweep drive signal
to provide a linear frequency-versus-voltage
(1) The triangular wave from the rate gen-
characteristic. In the cw mode, the varactor drive
erator is coupled to emitter follower Q105. Three
outputs are coupled from separate voltage divid-
ers in the emitter circuit of Q105. One output is
oscillator output at connector J501 is coupled
the SCOPE HORIZ drive, a triangular signal.
from a grounded loop network of resistors, R500,
(2) The other two outputs are coupled to
R501, and R507. In the high frequency range,
the variable oscillator output is coupled through
fier Q106 and nonlinear amplifier Q107. The non-
filter FL501, bandswitch S601, the monitor, and
linear amplifier characteristics are controlled by
attenuator Z603 to RF OUT connector J611. The
the diode break circuit consisting of resistors
R136 through R146, diodes CR104 through
resistive pi pads which provide 0 to 70 dB of out-
CR113, and resistors R148 through R157. As a
positive-going signal is coupled to the emitter of
Q107, the individual diodes are reverse-biased;
c. Low Frequency Band. In LOW BAND opera-
but as the collector voltage increases, individual
tion, the variable-oscillator signal is mixed with
diodes conduct in sequence, and the output signal
the 700-MHz, fixed-oscillator signal. The low-
is reshaped by the nonlinear, diode break cir-
level output is couped through FL551 to the
cuit.
video amplifier. The video amplifier output is
(3) The outputs of the linear and nonlinear
coupled to coaxial switch section S601-1B and
to the monitor. The amplified signal is coupled
WIDTH switch and potentiometer combination
to the attenuator and to RF OUT connector
S101, R146A, and R146B. The two combined
J611. The sweep signal is generated in the vari-
signals maintain rf output sweep linearity under