(d)
The ground return signal from the receive antenna is coupled through the receive circulator to the stripline mixer. A sample of the transmitted signal is also applied to the mixer. The mixer processes the instantaneous transmit and receive signal frequencies to produce an output difference frequency which is proportional to airplane altitude above the terrain. This signal is applied to the preamplifier and tracking filter circuits.
(e)
The preamplifier and tracking filter adjusts the signal gain and filters the signal to improve the systems signal tracking capabilities. The output is applied to the pointer stow circuit which provides an on scale altitude signal to the time domain filter. This filter processes the signal to remove double bounce signals and provides signal tracking.
(f)
The output from the time domain filter is applied to the dual frequency counter and operational amplifier circuits. Pulse outputs from the frequency counters are converted to dc altitude signals by the operational amplifiers. The amplifiers provide the dc altitude signals used to drive the height indicator and to provide altitude data to other systems on the airplane. The autopilot/flight director system uses the altitude signal to facilitate gain programming of the glide slope and localizer deviation signals during approach modes. The auto throttle system uses the altitude signal to enable speed control during the low altitude flare maneuver.
(g)
The dc altitude signals are also applied to the receiver-transmitter altitude fixed trip circuits. Each altitude trip circuit consists of an adjustment potentiometer, altitude detector, dc amplifier, and a switch which drives a relay. The dc altitude input voltage is compared to a reference voltage (altitude trip setting). If the input voltage exceeds the reference voltage, the trip relay remains de-energized. When the input voltage is less than the reference voltage, the trip relay is energized. The output from each altitude trip circuit is a ground signal to using equipment.
(2) Altitude Indication (Collins 339H-1 HI)
EFFECTIVITY AZ ALL; IB 406-499
CONFIG 03 Page 5 Aug 25/88
34-33-00
RECEIVER TRANSMITTER
LRRA 1 or 2 System Schematic
Figure 3 (Sheet 1)
EFFECTIVITY AZ ALL; IB 406-407;
CONFIG 1 LESS IB APLS INCORP 799 Page 6SB 34-2155
34-33-00
Apr 25/88
LRRA 1 or 2 System Simplified Schematic
Figure 3 (Sheet 2)
EFFECTIVITY
CONFIG 1 AZ ALL; IB 406,407, LESS IB
799 Page 7APLS INCORP SB 34-2155 Apr 25/88
34-33-00
RECEIVER TRANSMITTER
LRRA 3 System Schematic
Figure 3 (Sheet 3)
EFFECTIVITY
CONFIG 1 IB 408-499 PLUS IB APLS
799 Page 8INCORP SB 34-2155 Apr 25/88
34-33-00
ADI
INCOP OF SB 34-220
LRRA 1 or 2 System Schematic
Figure 3 (Sheet 4)
EFFECTIVITY
CONFIG 1 IB 408,409 PLUS IB APLS
799 Page 9INCORP SB 34-2155 Apr 25/88
34-33-00
RECEIVER TRANSMITTER (860F-4)
LRRA 3 System Schematic
Figure 3 (Sheet 5)
EFFECTIVITY CONFIG 1AZ ALL; IB 406-499
799 Page 10
34-33-00
Apr 25/88
LRRA 3 System Schematic
Figure 3 (Sheet 6)
EFFECTIVITY CONFIG 1AZ ALL; IB 406-499
799 Page 11
34-33-00
Apr 25/88
636305
(a)
In the height indicator, the positive dc altitude voltage from the receiver-transmitter and a dc feedback voltage from the isolation amplifier are applied to the differential preamplifier. The dc feedback voltage represents the position of the altitude pointer, and the dc altitude voltage represents airplane altitude.
(b)
When the two voltages applied to the differential preamplifier are not equal in value, a difference voltage is produced and applied to the servo-amplifier. The servo-amplifier drives the motor which repositions the feedback potentiometer (and altitude pointer) until the voltages are equal. When the two voltages are equal, the altitude pointer indicates the correct airplane altitude.
(c)
The DH control knob is mechanically coupled to the DH index and to two contacts of the DH switch. Adjustment of the DH control knob positions the DH index to the selected altitude and positions the contacts of the DH switch. The DH switch contacts are connected to an ON coil and an OFF coil in the DH relay. The opposite sides of both coils are connected to the power supply positive flag supply. When the DH index is set to an altitude greater than the airplane altitude, the power supply negative flag supply is applied through the DH switch to the ON coil closing the relay contacts to turn on the DH light(s). When the DH index is set to an altitude less than the airplane altitude, the DH switch closes in the opposite direction and the power supply negative flag supply is applied to the OFF coil. The DH relay is a latching relay and remains in one position until the opposite coil is energized.
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本文链接地址：747飞机维护手册AMM CHAPTER 34 - NAVIGATION 第34章导航2(59)
