TM 11-5840-281-35/1
c. Glidepath Control Circuit (fig. 7-13 and 757).
and height-finder control circuits, and an E (voltage)
reference supply.
The cursor control section also
The configuration of the glidepath control circuit (fig. 7-
contains a calibrated angle data simulating circuit
13), which controls the cursor and fill-in sawtooth
(artificial angle voltage circuit) for alignment of the cursor
generators, sawtooth slopes, differs from the courseline
generator.
control circuit in several aspects.
b. Courseline Control Circuit (fig. 7-13 and 7-
(1) The antenna angle data and glidepath
58). The courseline cursor angle information which
reference voltages are summed in an amplifier and
controls the slope of the cursor sawtooth, is the sum of
applied to the sawtooth generators as the cursor angle
two sources of information.
no. 1 and fill-in angle no. 1 inputs.
(1) One source is the az-el angle volts
The cursor angle no. 2 and fill-in angle no. 2 inputs to
which causes the slope of the cursor sawtooth to track
the sawtooth generators are grounded.
the changing azimuth scan angle (Antenna AS-
(2) The amplifier in which the summing
1292/TPN-8). The other source is from one of two
occurs has a variable gain feature. The amplifier gain
COURSELINE controls, R1126 or R1127, which
(glidepath amplifier) is inversely proportional to the
determines the slope the cursor sawtooth will have for
particular glidepath selected; that is, for a low-angle
any instantaneous azimuth antenna scan angle. One
glidepath, the amplifier gain will be relatively high, and
COURSELINE control is for left-of-runway and the other
vice-versa. This characteristic is necessary when a
is for right-of-runway coverage. For left-of runway
cursor must be produced corresponding to a low
coverage, the cursor must curve downward on the
glidepath with a close touchdown point. In producing a
display with increasing range.
For right-of-runway
low-angle glidepath, the elevation antenna works through
operation, the cursor curves upward with increasing
a small angle to scan the complete glidepath. This
range; the runway parallell line blip will be above the
would result in a small change in angle volts which would
cursor; therefore, the antenna angle data supplied to the
be insufficient to develop a complete glidepath cursor
cursor generating circuits must be inverted when
without amplification.
changing from left-of-runway to right-of runway. For left-
(3) The glidepath amplifier consists of
of-runway coverage, the angle data (az-el angle volts) is
emitter-follower transistor Q9701, amplifier transistor
applied to the cursor sawtooth generator as the cursor
Q9702, and emitter-follower transistor Q9703 on the
angle no. 1 input and to the fill-in sawtooth generator as
cursor control subassembly. The az-el angle volts at the
the fill-in angle no. 1 input. Courseline reference
emitter of transistor Q9705 is applied to the base of
voltage, established by COURSELINE 1 control R1126
transistor Q9701 through resistor R9703. The glidepath
and inverted by angle voltage inverter stages Q9707,
control voltage from GLIDEPATH 1 control R1128A is
Q9708, Q9709, and Q9713 on the cursor control
also applied to the base of control Q9701 via CURSOR
subassembly, is applied to the cursor and fill-in sawtooth
switch S1104B. The sum of the az-el angle volts and the
generators as the cursor angle no. 2 and fill-in angle no.
glidepath volts at the emitter of transistor Q9701 is
2 inputs. For right-of-runway coverage, the angle data
amplified and inverted by transistor Q9702 and coupled
and courseline reference voltages are reversed.
through transistor Q9703 to the output of the circuit. A
(2) The angle data is applied through angle
portion of the output of emitterfollower transistor Q9703
voltage inverter transistors Q9707, Q9708, Q9709, and
is applied to the base of emitter-follower transistor
Q9713 on the cursor control subassembly and applied to
Q9702 as negative feedback via CURSOR switch S1104
the cursor and fill-in sawtooth generators as cursor angle
and GLIDEPATH 1 control R1128B. GLIDEPATH 1
no. 2 and fill-in angle no. 2 inputs. The courseline
control R1128B (on the same shaft as R1128A) is so
reference voltage is established by COURSELINE 2
wired that as the glidepath angle is reduced by control
control R1127 and applied to the cursor and fill-in
R1128A, the series resistance of control R1128B is
sawtooth generators as the cursor angle no. 1 and fill-in
increased, and less negative feedback is delivered to the
angle no. 1 inputs. OFFSET 1 control R1121 supplies a
base of emitter-follower transistor Q9701.
courseline reference voltage. These controls are used to
(4) The output of the glidepath amplifier is
provide compensation for the distance between the
applied to the cursor sawtooth generator subassembly
runway centerline and Radar Set AN/ TPN-18 by
as the cursor angle no. 1 input. Glidepath data is
establishing a dc reference level for the cursor trigger
applied across a resistor network consist-
generator sawtooth baseline
2-46
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