Radar System Engineering

SEL!. 13.19] THE RANGE-HEIGHT INDICATOR 547
C03 e = 1 are sufficiently good approximations. In Fig. 13.52, information
for the vertical sweep is derived by modulating a high-frequency
oscillation by a variable condenser, using the voltage-dividing circuit of
Fig. 13.7. This is peak-detected by the cathode follower Vl, whose
cathode circuit has a time constant that is long compared with the
period of oscillation. The cathode and grid of VI are so biased that
the former is at ground potential in the absence of signal. The demodulated
voltage controls a sawtooth generator of the ordinary type, thus
providing sawteeth modulated in proportion to the elevation angle.
These are passed through a phase splitter and a push-pull amplifier to
the vertical deflecting coils. Since the sweep is always in the same
From
mechamcal
Differential
gear
repeater —-
Potentiometer
—
Sawtooth
generator
J_
Sector control
lk’
Delay
Flip.flop
circuit
1 30
CRT
—
Flip.flop
—
Sawtooth
generator
— Amplifier
FIG. 1353.-V-beam height indicator,
direction, d-c restorers provide adequate clamping on the output stages.
The horizontal sweep, of constant amplitude, is generated in the ordinary
way and amplified as was the vertical one. Off-centering is provided
by proper biasing of the driver tubes. A delay can be used in the
horizontal circuit to allow a distant range interval to be examined in
detail. (If this is not a requirement, the same flip-flop can be used for
both sawtooth generators. ) A controllable height marker can be
derived, if desired, by applying the modulated sawtooth to a biased-diode
delay circuit, as explained in Sec. 13.12.
V-beam Height Indicator.—In the V-beam height indicator (Fig.
13.53), a linear potentiometer turned by a mechanical repeater provides
the azimuth data, a differential gear allowing control of the sector
displayed. The vertical deflection is obtained by adding, in the driving
amplifiers, a slowly varying voltage proportional to the azimuth angle
measured from the edge of the sector chosen and a range sweep modulated