Boeing 737-300 Series User manual

MAINTENANCE MANUAL – ATC SYSTEM
for
Boeing 737-300 Series Aircraft
Notice: This is confidential and proprietary information of General Aerospace and may not be used or disclosed by the recipient
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GENERAL AEROSPACE
932 Ponce de Leon Blvd.
Coral Gables, FL 33134
ENGINEER
O. Obando
CHECKED
J. Carballo
APPROVED
M. Flores
Maintenance Manual – ATC System
Boeing 737-300,Series Aircraft
SCALE:
SIZE:
CAGE CODE:
DRAWING NO:
Rev: I/R
NONE
A
0LL89
GA-BC17-ATC-MM
Page: CP-1

GENERAL AEROSPACE
Boeing 737-300
MAINTENANCE MANUAL
EFFECTIVITY
PW245
DRAWING # GA-KD28-ATC-MM
Page LR-1
Use and disclosure shall be in accordance with the proprietary legend located on the cover of this document Aug 15/10
LOG OF REVISIONS
Revision No.
Description
Pages Revised
Approved by
Date
I/R
Initial Release
All
MFC
08/15/10

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EFFECTIVE PAGES
Cover page
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ATC SYSTEM
TABLE OF CONTENTS
Chapter
Section
Subject Subject Page
ATC System 34-53-00
Description and Operation 34-53-00
1. General 1
2. ATC Control Panel 1
3. ATC Transponder 3
4. ATC antenna 3
5. Operation 3
Troubleshooting 34-53-00
1. General 101
2. References 101
3. Prepare for Troubleshooting 101
Adjustment /Test 34-53-00
1. General 501
2. Operational Test – ATC System 501
3. System Test - ATC System (With the IFR ATC-601 Test Set) 502
4. System Test - ATC System (With the TIC T-48 or T-49 Test Set) 506
Air Traffic Control (ATC) Antenna 34-53-11
Removal / Installation 401
Air Traffic Control (ATC) Transponder 34-53-21
Removal / Installation 401
Air Traffic Control (ATC) Control Panel 34-53-31
Removal / Installation 401
Air Traffic Control (ATC) Antenna Switch 34-53-41
Removal / Installation 401

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ATC – DESCRIPTION AND OPERATION
1. General (Figure. 1)
A. The Air Traffic Control Radar Beacon System (ATCRBS or ATC), provides airplane tracking, altitude and
identification information to an ATC ground station. The ATC transponder responds to an interrogation
from an ATC ground station. The ATC system responds to ground station interrogations in one of three
different modes: mode-A, mode-C and mode-S. Mode-A and Mode-C provide identification and altitude
information. Mode-S provides selective airplane identification and data link capabilities. After a ground
station interrogation, the transponder automatically transmits a pulse coded reply signal in one of the above
modes. The mode of reply is determined by the mode of interrogation.
B. Two ATC systems are installed on the aircraft, each with its own transponder. Only one transponder
operates at a time. A dual ATC Control Panel provides independent and isolated control for both systems.
Control information is sent to either transponder by discrete signals and an ARINC 429, 572, 718, or 730
bus.
C. ATC antennas:
The bottom antenna is shared by the transponder 2 (Mode C) and transponder 1 (Mode S). A RF relay for
bottom antenna switches between transponders 1 or 2.
The top antenna is used by Transponder 1.
D. Each transponder receives altitude data from Air Data Computer 1 (ADC-1).
E. The ATC, TCAS and DME systems operate in the same L-band frequency range. A suppression circuit is
connected between the TCAS Computer, ATC transponders and the DME interrogators to prevent
simultaneous transmissions.
F. The ATC system operates in three different modes: Mode-A, mode-C and mode-S. The mode of operation
is determined by the mode of interrogation from a ground station and the current configuration of the
altitude reporting function.
G. The ATC-1 system receives 115VAC 400Hz, power from the electronics power bus No. 1. Power is
supplied through the ATC-1 circuit breaker located on the left load control center circuit breaker panel P18.
H. The ATC-2 system receives 115 volt, 400Hz ac power from the electronics power No. 2 bus. Power is
supplied through the ATC No. 2 circuit breaker located on the right load control center circuit breaker
panel P6.
2. ATC Control Panel (Fig. 1)
A. The ATC Control Panel is located on the aft electronic control panel (P8). The Control Panel contains
switches and controls which provide reply codes and mode selection for two ATC transponders. The
Control Panel is divided into two operational systems No. 1 and No. 2. Each system. Each system provides
its respective transponder with tuning and control signals for system operation.
(1) ATC Control Panel
The controls and indicators operate in the following manner:
(a) The ATC keypad select the 4-digit identification code which is displayed in the ATC code
display window.
(b) The transponder select switch activates the left or right transponder, as selected. Both
transponders are off with the switch in the STBY position.
(c) The altitude reporting switch enables the transponder to reply with coded altitude information
supplied by left and right ADCs.
(d) The identification switch causes the transponder to transmit a special pulse with each ATC code
reply generated. This is used to identify the airplane on the ground station scope.

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Use and disclosure shall be in accordance with the proprietary legend located on the cover of this document AUG 15/10
ATC System Component Location
Figure 1
TCAS/ATC Control Panel
Detail B. Transponder
Detail B. RF Switch

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MAINTENANCE MANUAL
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3. ATC Transponders (Figure. 1)
A. The transponders are located on the E2 electronic equipment rack on E2-2 shelf.
B. The active ATC transponder transmits a coded reply when it is interrogated by an ATC ground station.
C. This aircraft is equipped with two Mode-S transponders.
D. Transponders Mode-S:
This transponder has the following switches and indicators:
(1) An LRU STATUS indicator light which turns green when a transponder self-test is successful and
turns red when a transponder self-test detects a failure.
(2) A red ANTENNA TOP FAIL indicator light which comes during self-test when the upper antenna
impedance is incorrect.
(3) A red ANTENNA BOT FAIL indicator light which comes during self-test when the lower antenna
impedance is incorrect.
(4) A red ALTITUDE FAIL indicator light which comes on when the altitude input source indicates a
barometric altitude failure.
(5) A red CONTROL FAIL indicator light which comes on when there is a failure of the control input.
(a) A TEST switch which starts a transponder self-test.
4. ATC Antennas
A. The antennas are installed on the top and the bottom of the airplane. The top antenna and bottom antenna
are connected to the Mode-S transponders. Two RF switching relays connect the bottom antenna and top
antenna to the active transponder. The top antenna is located on the centerline of the fuselage at station
430.25. The bottom antenna is located on the centerline of the fuselage at station 355. The antennas are
omni-directional L-blade type antennas. Each antenna can transmit and receive signals for the active
transponder. When active the Mode-S transponder automatically uses the antenna with the greatest signal
strength.
5. Operation
A. Basic ATC Transponder Principles
(1) The transponder is an integral part of the Air Traffic Control Radar Beacon System (ATCRBS). In the
airplane, its function is to transmit a coded response to a coded interrogation transmitted by the air
traffic control ground station.
(2) There are two types of radar at each ATC ground station. The first, called the Primary Surveillance
Radar (PSR), operates on the normal radar principles of receiving energy reflected from the airplane
under surveillance. The second, called the Secondary Surveillance Radar (SSR), operates on the coded
reply from the airborne transponder. Both radars are used in conjunction to develop the total air traffic
situation and to display it on a single radar scope.
(3) The SSR interrogates the transponder in one of two modes. These are referred to as mode A, or mode
C interrogations. The type of interrogation is determined by the spacing between two pulses (P1 and
P3) transmitted by the SSR on a carrier of 1030 ± 2 MHz. Each interrogation contains a third pulse at
the same frequency which is not transmitted by the SSR but by an omni directional antenna which is
located at the ground radar station. This pulse is transmitted 2 µsec after the P1 pulse and is referred to
as P2. Mode A and mode C interrogation characteristics are shown in Fig. 2.
(4) The purpose of P2 is to allow the airborne transponder to determine whether the interrogation come
from the main beam or a side lobe of the SSR. If the transponder has been interrogated by a side lobe,
no reply is generated. A reply to a side lobe interrogation would give the ground radar operator an
erroneous position reading of the airplane carrying the transponder. The transponder determines by an
amplitude comparison between P1 and P2 if the interrogation is by a side lobe. If P1 is larger than P2,
the interrogation is a valid main beam interrogation. If P2 is equal to or larger than P1, the
interrogation is from the side lobe of the SSR.
(5) The transponder replies to mode A and mode C interrogations with a coded pulse group on a carrier
frequency of 1090 ± 3 MHz. The transmitted message consists of four octal digits (0-7) which gives
the transponder the capability of 4096 different identification numbers and altitude data from -1000 to
+128,000 ft. In a mode A reply the coding of the pulses represents an identification number of the

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Boeing 737-300
MAINTENANCE MANUAL
EFFECTIVITY
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DRAWING # GA-BC17-ATC-MM
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airplane carrying the transponder. The coding of a mode A reply can consist of up to fifteen pulses.
Twelve of these pulses carry the identification number. Two others, called framing pulses, come before
and after the twelve information pulses. The last is a special identification pulse to aid the radar
operator. The mode C reply is basically the same as a mode A reply; however, in a mode C reply, the
coding of the pulses represents altitude data. The data to be transmitted is inserted in the transponder
on the appropriate input lines on the main connector and originate at the altitude digitizer. The special
identification numbers and the reply coding characteristics for the full 15 pulse reply are shown in Fig.
2.

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MAINTENANCE MANUAL
EFFECTIVITY
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Transponder Reply Pulses
Figure 2

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Boeing 737-300
MAINTENANCE MANUAL
EFFECTIVITY
PW245
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DRAWING # GA-BC17-ATC-MM
Page 6
Use and disclosure shall be in accordance with the proprietary legend located on the cover of this document AUG 15/10
B. Functional Description
(1) Receiver
(a) Received signals from the antenna are routed through the Diplexer/Low Pass Filter and applied to
the Pre-selector/Mixer. In the Pre-selector the signal is passed through a bandpass filter tuned to
1030 MHz. The filter output is applied to the mixer diode and mixed with the 970-MHz local
oscillator (LO) signal. The LO signal is filtered in the pre-selector, by a 2-pole bandpass filter
prior to mixing. The 60-MHz IF signal from the mixer is applied to the IF amplifier/detector
module where it is amplified and detected. The output of the IF amplifier/detector is applied to the
video processor where it is amplified, pulse shaped, cleaned up by a noise suppression circuit, and
elimination of P2 pulse is performed if the received signal is from the ATC ground station main
lobe. The signal is then sent to the decoder/encoder circuitry.
(2) Decoder/Encoder
(a) The video processor output is applied to the decoder/encoder along with the 2.7586 MHz 2-phase
clock from the decoder/encoder (D/E) oscillator. The decoder/encoder then decodes the received
message, determines whether mode A or mode C data is requested and then develops the
appropriate serial data output to be applied to the transmitter.
(3) Transmitter
(a) The modulator accepts the decoder/encoder serial data outputs, adjusts the amplitude and width of
the pulses and supplies the proper signals to the transmitter modulator circuit. The modulation
signal modulates the transmitter oscillator which is a 1090-MHz cavity controlled pulsed
oscillator. The output of the transmitter oscillator is approximately 1.5 watts peak RF power. The
pulse RF signal is applied to the exciter module where the signal is amplified to 150 watts peak
RF power. This 150 watt signal is then used to drive the power amplifier module where the RF
signal is amplified to 500 watts peak RF power. The power amplifier output is then sent to the
Diplexer to be routed to ATC transponder antenna.
(4) Functional Test
(a) Upon manual activation of the test switch, either on the unit front panel or Control Panel, the
functional test module will generate an RF pulsed signal. This signal is then applied to the local
oscillator module where 60-MHz sidebands are generated on the local oscillator signal. These
sidebands are a pulsed pair which is properly spaced to represent a valid mode interrogation. The
LO signal with the 60-MHz sidebands is applied to mixer and a 60-MHz If signal is generated.
From this point on the signal is processed as a valid interrogation and the monitor/reply indicator
as well as the light on the front panel will come on. The front panel light will go out immediately
when the front panel switch is released; however, the control panel reply indicator will remain on
for the prescribed 15 seconds after the last reply.
(5) Monitor
(a) On transponders with fault indicators, the R/T monitor circuits check the transponder for proper
output power, frequency, mode decoding, clock frequency, and shift register fill-up. The monitor
circuit supplies signals to these to provide an indication of the operational status of the
transponder. The ANT monitor circuits check the dc resistance of the antenna and coaxial cable. If
the circuits detect a dc resistance greater than 200 ohms, the ANT fault indicator will be activated.
The ANT fault indicator is reset by depressing the RESET switch on the transponder front panel.
The R/T fault indicator is reset from inside the transponder.
(b) On all transponders when eight consecutive replies are completed, the reply indicator (transponder
and Control Panel) are energized.
C. Mode-A and Mode-C Operation
(1) There is no power switch on the ATC Control Panel. Power is applied to the system when the ATC-1
and ATC-2 circuit breakers on the P6 and P18 panels are closed.
(2) Altitude Reporting.
(a) The desired altitude reporting condition is set with the altitude reporting switch. The '1' position
causes the altitude reporting function to come on and sets the altitude data source to ADC 1. The
'2' position is not installed. The OFF position disables the altitude reporting function of the ATC
system.

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(b) The desired ATC system is set with the transponder select switch. The '1' position causes the
Control Panel to send an 'ON' discrete to transponder No. 1 if the AIR/GND RELAY is in AIR
mode and the mode switch is set to XPDR. The '2' position causes the Control Panel to send an
'ON' discrete to transponder No. 2 if the AIR/GND RELAY is in AIR mode and the mode switch
is set to XPDR.
(3) If the altitude reporting function is on, then the ATC system will reply to mode-A and mode-C ground
station interrogations. If the altitude reporting function is off, then system will reply only to mode-A
interrogations. Mode-S replies are not affected by the condition of the mode switch.
(4) The identity code and mode configuration information is sent to the transponders through ARINC
busses and discrete. The 4-digit code identifies the airplane to the ground station for mode-A and
mode-C interrogations.
(5) When the airplane leaves the ground, the AIR/GND relay is set to AIR. This sends a discrete signal to
the Control Panel. The Control Panel then sends an 'ON' discrete to the selected transponder. At this
point, the system will respond to ground station interrogations.
D. Mode-S Operation
(1) Mode-S functions operate when the mode-S programming plug is configured with a unique mode-S
address. If all the programming pins are grounded (they have a bit value of one), then there is no
unique address and the mode-S functions do not operate. The mode-S code is hard wired on mode-S.
The identity code set on the ATC Control Panel has no effect on the mode-S address code of the
airplane. Mode-S functions in the airplane are automatic and are not configured by the pilot.
E. Self-Test Operation
(1) Both ATC transponders have Built-In Test Equipment (BITE). A BITE test can be started if the
transponder to be tested has power. The BITE test is started when the TEST switch on the transponder
face is pushed. The BITE test does the following:
(a) Does a checksum of internal ROM contents.
(b) Tests the transponder RAM.
(c) Simulates noise sources and monitors the results.
(d) Tests the antenna impedance.
(e) Simulates a Mode-S All-Call interrogation and reply (Mode-S transponder only).
(f) Samples the internal power supply monitor.
(g) Checks the operation of the serial busses connected to the transponder
(2) Mode-S Transponders:
The green LRU STATUS indicator light will come on if no errors were detected during the BITE test.
It will illuminate red if any part of the BITE test fails.
(3) The BITE monitor continuously tests transponder functions while the ATC system operates normally
(not in test mode). If a failure is detected, the red CTL indicator light will come on and a
TRANSPONDER FAIL DISCRETE will be sent to the Control Panel. If the altitude input from the
ADC is in error, the red ALT indicator light will come on.

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ATC SYSTEM - TROUBLE SHOOTING
1. General
A. The troubleshooting procedures make use of the self-test features of the ATC transponder and ATC system
tests to isolate problems. These procedures are in a tree-type format.
B. If the procedure does not correct the problem examine and repair if necessary, the circuit between the
equipment.
C. The troubleshooting procedures are applicable to ATC system No.1 (Figure 101) and ATC system No.2
(Figure 102).
2. References
A. 24-22-00/201, Manual Control
B. 34-53-02/501, ATC System - Adjustment/Test
C. 34-53-11/201, ATC Antenna - Removal/Installation
D. 34-53-21/201, ATC Transponder - Removal/Installation
E. 34-53-31/201, ATC Control Panel - Removal/Installation
3. Prepare for Troubleshooting
A. Supply the electrical power (Ref 24-22-00).
B. Make sure the ATC, interphone and air data system circuit breakers on P18 and P6 panels are closed.
C. On the ATC Control Panel, set the ATC select switch to the transponder to be tested (No.1 or No.2).
NOTE: Let the transponder warm-up for at least one minute.
D. Do the operational or system test (Ref. 34-53-00/501).

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Prepare the ATC system for
troubleshooting as described in
paragraph 3. On the
transponder’s front panel push
and hold the TEST switch. Do
ALL the LED indicators come
on for 1 second?
NO
Replace the ATC transponder (Ref 34-53-21/401) and do the required
test.
YES
If the red TPR-FAIL LED indicator comes on, replace the ATC
transponder (Ref 34-53-21/401) and do the required test.
If the red CTL LED indicator comes on, replace the ATC Control Panel
(Ref 34-53-31/401) and do the required test.
YES
Replace the top ATC antenna
(Ref 34-53-11/401) and do the
required test.
If the red UPPER ANT LED
indicator comes on, examine
the top antenna cable. Is the
cable OK and the ATC
transponder installed
properly?
NO
Repair or replace the antenna
cable or install the ATC
transponder properly (Ref 34-
53-31/201)
YES
Replace the bottom ATC
antenna (Ref 34-53-11/401)
and do the required test.
If the red LOWER ANT LED
indicator comes on, examine
the bottom antenna cable. Is
the cable OK and the ATC
transponder installed
properly?
NO
Repair or replace the antenna
cable or install the ATC
transponder properly (Ref 34-
53-31/201)
After 1 second, do ALL LED
indicators go off and the green
TPR-PASS LED indicator
comes back on and stays on for
10 seconds?
NO
If the red ALT LED indicator comes on, make sure the air data computer
system is operational (Ref 34-12-01) and do the transponder test again. If
the red ALT LED indicator comes on, replace the ATC transponder (Ref
34-53-21/401) and do the required test.
YES
Had the system malfunctioned
in flight?
NO
System is operational
YES
Next page
Trouble shooting diagram for ATC Transponder No.1
Figure 101 (Sheet 1).

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From previous page
YES
System is operational
If the system test failed REC
SENS, TRANSPONDER
FREQ, or SLS test, replace the
transponder (Ref 34-53-
21/401) and do the system test
again. Is the test OK?
NO
Examine the ATC antenna
cable. Repair or replace as
necessary (Ref 34-53-11/401)
YES
System is operational
If the system test failed CODE
test, replace the transponder
(Ref 34-53-21/401) and do the
system test again. Is the test
OK?
NO
Replace the ATC Control
Panel (Ref 34-53-31/401)
YES
System is operational
Do the system test (Ref 34-53-
02 Adjustment/Test).
If the system test failed ALT
RPTG test, make sure air data
computer(s) is (are)
operational (Ref 34-12-01/501)
and do the ALT RPTG test
again. Is the test OK?
NO
Replace the ATC transponder
(Ref 34-53-21/401) and do the
required test.
Trouble shooting diagram for ATC Transponder No.1
Figure 101 (Sheet 2).

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Prepare the ATC system for
troubleshooting as described in
paragraph 3. On the
transponder’s front panel push
and hold the TEST switch. Do
ALL the LED indicators come
on for 1 second?
NO
Replace the ATC transponder (Ref 34-53-21/401) and do the required
test.
YES
If the R/T light indicator comes on, replace the ATC transponder (Ref
34-53-21/401) and do the required test.
YES
Replace the top ATC antenna
(Ref 34-53-11/401) and do the
required test.
If the ANT light indicator
comes on, examine the top
antenna cable. Is the cable OK
and the ATC transponder
installed properly?
NO
Repair or replace the antenna
cable or install the ATC
transponder properly (Ref 34-
53-31/201)
YES
Replace the bottom ATC
antenna (Ref 34-53-11/401)
and do the required test.
If the ANT light indicator
comes on, examine the bottom
antenna cable. Is the cable OK
and the ATC transponder
installed properly?
NO
Repair or replace the antenna
cable or install the ATC
transponder properly (Ref 34-
53-31/201)
Do all indicators lights go off?
NO
YES
Had the system malfunctioned
in flight?
NO
System is operational
YES
Next page
Trouble shooting diagram for ATC Transponder No.2
Figure 102 (Sheet 1).

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From previous page
YES
System is operational
If the system test failed REC
SENS, TRANSPONDER
FREQ, or SLS test, replace the
transponder (Ref 34-53-
21/401) and do the system test
again. Is the test OK?
NO
Examine the ATC antenna
cable. Repair or replace as
necessary (Ref 34-53-11/401)
YES
System is operational
If the system test failed CODE
test, replace the transponder
(Ref 34-53-21/401) and do the
system test again. Is the test
OK?
NO
Replace the ATC Control
Panel (Ref 34-53-31/401)
YES
System is operational
Do the system test (Ref 34-53-
02 Adjustment/Test).
If the system test failed ALT
RPTG test, make sure air data
computer is operational (Ref
34-12-01/501) and do the ALT
RPTG test again. Is the test
OK?
NO
Replace the ATC transponder
(Ref 34-53-21/401) and do the
required test.
Trouble shooting diagram for ATC Transponder No.2
Figure 102 (Sheet 2).

GENERAL AEROSPACE
Boeing 737-300
MAINTENANCE MANUAL
EFFECTIVITY
PW245
34-53-00GA
DRAWING # GA-BC17-ATC-MM
Page 501
Use and disclosure shall be in accordance with the proprietary legend located on the cover of this document AUG 15/10
ATC SYSTEM - ADJUSTMENT/TEST
1. General
A. The ATC system adjustment/test procedure contains two tasks. One is an operational test; the other is a
system test. The operational test is a fast check of the ATC system and no test equipment is needed. The
system test first does the operational test. Then it uses test equipment to examine the ATC code reception,
altitude reporting, transponder sensitivity, side lobe suppression and transmitter frequency.
B. The system test uses the Instrument Flight Research 601 ATC ramp test sets or the TIC T-48 or T-49 ramp
test set. Because the ATC transponder responds to signals from the antenna with the strongest signal
strength, it is necessary to put the test set antenna close to the airplanes antenna to do a proper test. The test
set antenna should be put near the bottom ATC antenna on the airplane to examine the bottom transponder
circuitry and the same for the top ATC antenna.
2. Operational Test - ATC System
A. General
(1) The operational test is a fast check of the ATC system. It uses only the system's BITE function. No
special test or ground equipment is necessary.
(2) The ATC transponder internal BITE circuitry does a self-test on all internal circuitry. This includes the
injection of Mode S signals into the receiver unit to examine if the signals are processed properly. If
the Mode S function fails, the red TPR FAIL LED indicator comes on.
B. References
(1) AMM 24-22-00/201, Manual Control
C. Access
(1) Location Zones
101/102 Flight Compartment
205 Electronic Compartment
(2) Access Panel
1201 Electronics Equipment Access Door
D. Prepare for the Operation Test
(1) Supply electrical power (AMM 24-22-00/201).
(2) Close these circuit breakers.
(a) P18 Load Control Center - Left
1) ATC 1
2) ADC 1
3) ALTM CAPTAIN
(b) P6 Load Control Center - Right
1) ATC 2
E. Procedure (Mode-S Transponder)
(1) On the ATC Control Panel, set the transponder select switch 1.
(a) Start the self test on the front of the transponder.
(b) Airplane with Collins ATC transponder;
Make sure the LED’s sequence that follows occurs:
1) All LED’s comes on for about one second
2) All red LED’s go off
3) The green LED stay on
(c) Release the TEST switch.
(2) Set the ATC system to STBY.

GENERAL AEROSPACE
Boeing 737-300
MAINTENANCE MANUAL
EFFECTIVITY
PW245
34-53-00GA
DRAWING # GA-BC17-ATC-MM
Page 502
Use and disclosure shall be in accordance with the proprietary legend located on the cover of this document AUG 15/10
Procedure (Mode-C Transponder)
(3) On the ATC Control Panel, set the transponder select switch 2.
(a) Start the self test on the front of the transponder.
(b) Airplane with Collins ATC transponder;
Make sure the SELF TEST light illuminates
(c) Release the TEST switch.
(d) Press RESET for ATC Transponder 2.
(4) Set the ATC system to STBY.
3. System Test - ATC System (With the IFR ATC-601 Test Set)
A. General
(1) This system test is a more complete check of the ATC system. The system test first does the ATC-
Operational Test. Then it uses ground test equipment to examine the left and right ATC systems.
(2) The IFR ATC-601 test set is used to test the functionality of the mode S transponder. All twenty tests
can be run automatically in the AUTO mode or individually in single test mode. Results from the last
test are shown on each test page. The PASSED/FAILED indication is shown on top of the page. To do
a single test, use the select keys to get to the desired test and push the RUN/STOP key.
B. Special Tools and Equipment
(1) ATC Transponder Ramp Test Set IFR ATC-601
C. References
(1) AMM 24-22-00/201, Manual Control
(2) AMM 34-12-01/501, Air Data Computer System
D. Access
(1) Location Zones
101/102 Flight Compartment
205 Electronic Compartment
E. Prepare for the System Test
CAUTION: Do not place the remote test set antenna closer than 15 inches (0.40 meters) to the aircraft
antenna with the test set on. This will cause damage to the test set.
(1) Put the test set antenna approximately 30 feet from the ATC antenna for the related system.
NOTE: The test set antenna must be within the line of sight of the ATC antenna.
(2) Put the test set antenna in position towards the aircraft antenna.
(3) Connect the coax cable from the remote test set antenna to the test set.
(4) Close these circuit breakers:
(a) P18 Load Control Center - Left
1) ATC 1
2) DADC 1
(b) P6 Load Control Center - Right
1) ATC 2
(5) Do the ATC Operational Test.
(6) Set the PWR switch on the Test Set to the ON position.
NOTE: The test set is a source of interference for radio and L-band radar equipment operating on the
airplane and located near the test set. Turn the test set off as soon as the test is completed or
when you must perform other radio checks on the airplane.
(7) Push the SETUP key to enter the SETUP menu.

GENERAL AEROSPACE
Boeing 737-300
MAINTENANCE MANUAL
EFFECTIVITY
PW245
34-53-00GA
DRAWING # GA-BC17-ATC-MM
Page 503
Use and disclosure shall be in accordance with the proprietary legend located on the cover of this document AUG 15/10
NOTE: For information regarding the battery test, timing and recharging refer to the operation section
of the test set operators manual.
(8) Push the SELF TEST key on the Test Set.
(9) Push the RUN/STOP key to start the self test.
(a) Make sure the test set display shows PASSED.
(10) Push the SETUP key to enter the SETUP menu.
(11) Enter 30 feet in the RANGE field for the TOP and BOTTOM antenna.
(12) Enter 17 feet for the HEIGHT field for the TOP antenna and 3 feet for the BOTTOM antenna.
(13) Choose the bottom antenna on the SELECTED field.
(a) Use the SLEW keys to change the values.
(b) Use the SELECT keys to change the items.
(c) Use the SELECT keys to select the antenna which you must test.
(14) Enter the gain listed on the test set antenna into the GAIN_1030 and GAIN_1090 field.
(15) Enter the cable loss listed on the cable in the LOSS field.
(16) Open this circuit breaker.
(a) P6 Circuit breaker Panel
1) AIR/GND and LTS
(17) Set the captain's altimeter to 29.92 inches of mercury.
F. ATC System Test
CAUTION: Do not use codes 7500, 7600-7677, and 7700-7777. These are emergency codes.
(1) Set the code switches on the ATC Control Panel to a desired ATC ID code.
(2) Set the transponder select switch on the ATC Control Panel to the No. 1 system.
(3) On the ATC Control Panel do the steps that follow:
(a) Set the mode switch on the ATC Control Panel on the XPDR position.
(b) Set the altitude source switch on the ATC Control Panel to the 1 (2) position.
(4) Push the AUTO TEST key on the Test Set.
(5) Use the RUN/STOP key to start or stop individual test.
(6) Use the SELECT key to select each individual test.
(7) Do a check of the REPLY DELAY TEST.
(a) Make sure the reply delay is 128.00µs (±0.25µs) for mode S and ITM.
(b) Make sure the reply delay is 3.00µs (±0.50µs) for ATC A and C.
(8) Do a check of the REPLY JITTER TEST.
(a) Make sure the reply jitter is ≤0.05µs for mode S.
(b) Make sure the reply jitter is ≤0.06µs for ITM A and C.
(c) Make sure the reply jitter is ≤0.1µs for ATC A and C.
(9) Do a check of the ATCRBS REPLY TEST.
(a) Make sure the spacing of the F1 to F2 pulse is 20.3µs (±0.10µs).
(b) Make sure the duration of the F1, F2 pulse is 0.45µs (±0.10µs).
(10) Do a check of the SLS LEVEL TEST.
(a) Make sure the reply is received when the SLS pulse is -9dB and no reply is received when the SLS
pulse is 0dB.
NOTE: Run the SLS level test in less than 95 feet (28.96 meters) of the UUT antenna.
(11) Do a check of the ATC ONLY ALL-CALL TEST. (Mode-S transponder Only)
(a) Make sure the mode S transponder did not reply to the interrogation (PASSED TEST).

GENERAL AEROSPACE
Boeing 737-300
MAINTENANCE MANUAL
EFFECTIVITY
PW245
34-53-00GA
DRAWING # GA-BC17-ATC-MM
Page 504
Use and disclosure shall be in accordance with the proprietary legend located on the cover of this document AUG 15/10
(12) Do a check of the MODE S ALL CALL TEST. (Mode-S transponder Only)
(a) Make sure the test set shows PASSED and the airplane's mode S address.
(13) Do a check of the INVALID MODE S ADDRESS TEST. (Mode-S transponder Only)
(a) Make sure the mode S transponder did not reply (PASSED TEST).
(14) Do a check of the SPR ON/OFF TEST. (Mode-S transponder Only)
(a) Make sure a reply is received when SPR is ON and no reply is received when SPR is OFF.
(15) Do a check of the MODE S UF0 TEST. (Mode-S transponder Only)
(a) Make sure (Downlink format) DF=0, AC=(airplane's altitude) and ADDRESS=(airplane's mode S
address) (WDM 34-53-12).
NOTE: Make sure the reported altitude is within | 125 feet of the local field elevation altitude
shown on captain's altimeter (applicable for all altitude reporting check).
(16) Do a check of the MODE S UF4 TEST. (Mode-S transponder Only)
(a) Make sure DF=4, AC=(airplane's altitude) and ADDRESS=(airplane's mode address).
(17) Do a check of the MODE S UF5 TEST . (Mode-S transponder Only)
(a) Make sure DF=5, ID=(selected ATC ID code on the ATC Control Panel) and
ADDRESS=(airplane's mode S address).
(18) Do a check of the MODE S UF11 TEST. (Mode-S transponder Only)
(a) Make sure DF=11 and AA=(airplane's address).
(19) Do a check of the MODE S UF16 TEST. (Mode-S transponder Only)
(a) Make sure DF=16, AC=(airplane's altitude) and ADDRESS=(airplane's mode S address).
NOTE: No reply to the UF16 test is not a failure of the ATC system.
(20) Do a check of the MODE S UF20 TEST. (Mode-S transponder Only)
(a) Make sure DF= 20, AC= (airplane's altitude) and ADDRESS= (airplane's mode S address).
NOTE: No reply to the UF20 test is not a failure of the ATC system.
(21) Do a check of the MODE S UF21 TEST. (Mode-S transponder Only)
(a) Make sure DF= 21, ID= (selected ATC ID code on the ATC Control Panel) and ADDRESS=
(airplane's mode S address).
NOTE: No reply to the UF21 test is not a failure of the ATC system.
(22) Do a check of the SQUITTER TEST. (Mode-S transponder Only)
(a) Make sure the squitter's period is between 0.8 to 1.2 seconds.
(23) Do a check of the FREQUENCY TEST.
(a) Make sure the reply frequency of the transponder Mode S is 1090 MHz ±1MHz or 1090±3 for
ATCRBS Transponder type.
(24) Move the test set to less than 50 feet from the top ATC antenna.
NOTE: Make sure the top ATC antenna is not in the line of sight of the test set antenna. Follow the
test set operator's guide to reduce multi-path errors. Do the test several times with the test set
at different locations until you get valid results.
(25) Push the SETUP key on the test set and enter the appropriate range for the top and bottom antenna.
(26) Do a check of the DIVERSITY TEST. (Mode-S transponder Only)
(a) Make sure the power level difference is ≥20dB between 'on' antenna squitters and 'off' antenna
squitters.