747飞机维护手册AMM CHAPTER 34 - NAVIGATION 第34章导航4(59)

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 B.  The ATC system is comprised of two independent ATC transponders located in the main equipment center. (See figure 1.) Each transponder is connected to an ATC antenna located forward on the lower side of the airplane. A common ATC control module provides pilots' controls for both transponders.
 C.  ATC 1 transponder receives +28-volt dc power from the essential radio bus via the ATC 1 DC circuit breaker. (See figure 2.) The operating power for ATC 2 transponder is derived from radio bus No. 2 via the ATC 2 DC circuit breaker.
 XA NOTE:____Provisions for 115V AC power supply are made for ATC No. 1 and XA 2 respectively from the essential radio bus and radio bus No. 2.
 D.  Interface between the ATC system and other systems on the airplane is as shown on figure 2. Since the ATC and DME systems are both pulse coded and operate in the same frequency range, a signal suppression system is connected between the two systems to prevent interference.
 2.  ATC Control Module
__________________
 A.  The ATC control module is common to both ATC 1 and ATC 2 transponders. The control module contains controls, switches, and indicators to permit the pilot to operate and monitor the ATC system.
 B.  The position of the function selector switch determines the operational status (off, standby, or on in mode A or B) of the ATC transponder selected by the ATC switch. The ATC switch also determines whether CADC 1 or CADC 2 supplies altitude data to the ATC system.
 C.  The control module also houses identification coding switches, a test button, an identification button, and a monitor light.
 3.  ATC Transponder
_______________
 A.  The ATC transponders, located on shelf E3-6 in the main equipment center are housed in a standard 1/2 ATR long case. Electrical connections are made to the unit through a connector on the rear of the case and to two BNC connectors on the front. A SELF TEST button and MONITOR light are mounted on the front panel of the unit.
 4.  Antenna
_______
 A.  The two ATC antenna are conventional blade-type units connected to the transponders by coaxial cable. Each antenna performs the transmitting and receiving functions for its respective transponder.
 5.  Operation_________(See figure 3.)
 A.  Functional Description
 EFFECTIVITY

 AF 101-151 with AEB 34-587  CONFIG and AEB 34-607  01 Page 1  Apr 25/96

34-53-00
SEE A
NO. 2 ATC ANTENNA NO. 1 ATC ANTENNA 
ATC TRANSPONDERS 
FUNCTION SELECTOR 
OFF STBY  A  B  CODE 00.00  g MONITOR OFF ALT REPORT 
1  ATC  2  IDENT  TEST r 
CODING SWITCHES IDENTIFICATION 
ATC CONTROL MODULE A 

Air Traffic Control System Component Location
Figure 1

EFFECTIVITY

 CONFIG 2 AF 101-151704 Page 2
34-53-00
 Jan 25/77

P7 ELECTRONIC CIRCUIT 
BREAKER PANEL  ATC System Interface 
Figure 2 
EFFECTIVITY
AF 101-151 T35249  34-53-00  704  CONFIG 2 Page 3 Apr 25/80 

 (1)  
The 1030-MHz coded interrogation signal, received by the ATC system, is applied from the ATC antenna through the rf diplexer to the first preselector cavity. A total of four successively-coupled preselector cavities are used. The 1030-MHz signal present in the fourth preselector cavity is coupled to the diode mixer in the mixer injection cavity. The 1,090-MHz local oscillator injection signal is developed in the local oscillator injection cavity, and is coupled to the diode mixer where it is combined with the preselector output signal. Mixer output, at 60 MHz, is applied to the IF/detector module.

 (2)  
The IF/detector module operates at 60 MHz and employs seven broad-band amplifier stages followed by a video amplifier and an emitter-follower. Output in volts, versus input in db, is linear over the operating range of 50 db. The detected video pulse output is applied to the decoder.

 (3)  
The decoder serves to decode pulse pairs corresponding to predetermined ranges of pulse spacing, pulse width, and pulse amplitude, and to produce trigger pulses to the encoder only if these conditions are properly met. The decoder receives suppression pulses from the DME system in the airplane which disable the decoder while the other equipment is transmitting. The decoder supplies suppression pulses to the DME equipment to disable it while the ATC system is transmitting.

 (4)  
When an output signal is obtained from the decoder circuits, as a result of proper interrogation, the encoder circuits are triggered to initiate the transponder reply train as determined by the setting of the identification coding switches on the ATC control module which is applied to the modulator.
　
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