Garmin GTX 320 ATC User Manual
GTX 320 ATC TRANSPONDER
MAINTENANCE MANUAL
190-00133-02 (Rev B)
®
GARMIN
1200 E. 151st Street
Olathe, KS 66062 USA
16 March 1999
®
This publication is the property of GARMIN. It may not be reproduced or transmitted in any form whether printed
or electronic, without the expressed written consent of GARMIN International.
GARMIN
1200 E. 151st Street
Olathe, KS 66062 USA
Telephone: 913-397-8200 or 1-800-800-1020
www.garmin.com
REVISION RECORD
NOISIVERETADNOITPIRCSEDOCE
A89/42/40ESAELERLAITINI------
B99/61/30ETIRWERDNAESIVER04601
©Copyright 1999, by GARMIN Corporation. All rights reserved.
190-00133-02 Rev B A
TABLE OF CONTENTS
SECTION 1
DESCRIPTION AND OPERATION
P ARAGRAPH PAGE
1.1 INTRODUCTION ............................................................................................................... 1-1
1.2 GENERAL DESCRIPTION ................................................................................................ 1-1
1.3 TECHNICAL SPECIFICA TIONS........................................................................................ 1-1
1-4 EQUIPMENT DESCRIPTION............................................................................................ 1-2
1-5 SCOPE OF MAINTENANCE............................................................................................. 1-3
SECTION 2
SPECIAL TEST EQUIPMENT
2.1 INTRODUCTION ............................................................................................................... 2-1
2.2 SPECIAL TOOLS AND TEST EQUIPMENT...................................................................... 2-1
SECTION 3
ALIGNMENT AND TESTING
3.1 INTRODUCTION ............................................................................................................... 3-1
3.2 ALIGNMENT...................................................................................................................... 3-1
3.3 TESTING ........................................................................................................................... 3-5
SECTION 4
DISASSEMBL Y AND REASSEMBL Y
4.1 INTRODUCTION ............................................................................................................... 4-1
4.2 INSPECTION..................................................................................................................... 4-1
4.3 FRONT SUBASSEMBL Y................................................................................................... 4-1
4.4 CLEANING ........................................................................................................................ 4-2
190-00133-02 Rev B i
SECTION 1
DESCRIPTION AND OPERATION
1.1 INTRODUCTION
This manual provides all of the procedures, principles of operation, and information necessary to repair and
maintain the GARMIN GTX 320 ATC Transponder. Refer to GARMIN Installation Manual P/N 190-00133-01
for installation and operating information.
1.2 GENERAL DESCRIPTION
The GARMIN GTX 320 Transponder is an integral part of the Air Traffic Secondary Radar Beacon System
(ATCRBS, Figure 1-1), which consists of the following components:
INTERROGATORIn the ATCRBS, the interrogator, a ground-based radar beacon transmitter/receiver, scans
in synchronization with the primary surveillance radar (PSR) and transmits ground radar interrogation signals on a
carrier frequency of 1030 ± 2 MHz, which repeatedly requests all transponders on the mode being used, to reply.
The replies that are received are mixed with the primary surveillance radar returns and both are displayed on the
same radarscope.
TRANSPONDERThe GTX 320 Transponder is an airborne radar transceiver. It automatically receives
interrogations from the ATCRBS and selectively replies with a specific pulse group (code) only to those interrogations being received on the mode to which it is set, Mode A (no altitude information) or Mode C (automatic
altitude information).
These replies are independent of, and much stronger than a primary radar return. The GTX 320 replies to both
Mode A and Mode C interrogations on a carrier frequency of 1090 ± 3 MHz, with a rated power of 176 watts
minimum at the antenna port. The GTX 320 is also equipped with IDENT capability which activates the Special
Position Identification Pulse (SPI) for approximately 20 seconds, identifying that transponder return from other
aircraft on the ATC scope.
RADARSCOPEThe radarscope used by the controller displays returns from both the primary surveillance
radar system and the ATCRBS. These returns, called targets, are what the controller refers to in the control and
separation of traffic.
1.3 TECHNICAL SPECIFICATIONS
Refer to the GTX 320 Installation and Operation Manual (P/N 190-00133-01) for technical specifications.
190-00133-02 Rev B 1-1
Figure 1-1. ATCRBS System
1.4 EQUIPMENT DESCRIPTION
The GTX 320 consists of two major assemblies, the Main PCB Assembly and the Front Subassembly.
1.4.1 Main PCB Assembly (Not Field Repairable)
The Main PCB Assembly contains the following circuits:
IF Amplifier and Pulse Discriminator
Local Oscillator and Mixer
Power Supply
Programmable Logic Device
Light Dimming Circuitry
Modulator and Transmitter
1.4.2 Front Subassembly (Field Replaceable)
The Front Subassembly consists of the following:
Reply Code Switches and Mode Function Selector
Front Display and Knobs
Backlighting Circuitry
Front PCB Assembly
190-00133-02 Rev B 1-2
1.5 SCOPE OF MAINTENANCE
Due to the overall complexity of the unit, GARMIN recommends limiting field maintenance to the following:
Removal and Replacement of the Front Subassembly
Transmitter Frequency Adjustment
Transmitter Power Output Peaking Adjustment
190-00133-02 Rev B 1-3
SECTION 2
SPECIAL TEST EQUIPMENT
2.1 INTRODUCTION
This section identifies the special tools and test equipment essential to repair the GTX 320. Standard equipment is
not listed. For any questions regarding special tools and test equipment contact the GARMIN Customer Service
Department at the address listed on Page A.
2.2 SPECIAL TOOLS AND TEST EQUIPMENT
Test HarnessLocally Fabricated
Test PanelLocally Fabricated
Alignment ToolLocally Fabricated
Antenna Test Cable ConnectorLocally Fabricated
2.3.1 Test Panel and T est Harness
A Test Panel must be fabricated by the shop which meets the typical test setup criteria given Figure 2-3. Additionally, a corresponding test harness must be fabricated which allows for the necessary connections between J102 and
the Test Panel. Use Figure 2-3 as an aid in fabricating the test harness.
2.3.2 Alignment Tool
The alignment tool is used to adjust the transmitter frequency (C620) and the transmitter power output (C635).
Figure 2-1. Alignment Tool
190-00133-02 Rev B 2-1
2.3.3 Antenna Test Cable Connector
The antenna test cable incorporates a BNC connector at the test fixture antenna and a male BNC blindmate connector (GARMIN P/N 330-00198-00) at the transponder. Figure 2-2 shows the connector. Follow accepted industry
practices when installing the BNC connector. Use the following instructions when installing the blindmate BNC.
1. Trim coax outer insulation back ½ inch.
2. Trim braid (not center conductor or insulation) back ¼ inch.
3. Strip insulation back 0.120.
NOTE
If the outside diameter of the coax braid is smaller than the inside diameter of the
center connector sidewall opening, place the ferrule over the coax braid, flush against
the coax outer insulation before performing the next step.
4. Insert cable (center conductor, dielectric and shield braid) through the sidewall of the connector and solder the
center conductor to the center pin of the connector.
NOTE
When using low-loss cable, it may be necessary to flatten the solid wire center
conductor slightly so it can fit the slot on the RF connector center pin. When soldering, avoid applying excess heat to the connector body, and center conductor insulator.
5. Heat the outside of the connector sleeve and, at the same time, apply solder between the braid and the sleeve.
6. Continue to apply heat until the solder flows evenly.
7. Install 50 ohm match.
8. Insert connector cap and tack solder in two places.
Figure 2-2. Blindmate Antenna Connector
190-00133-02 Rev B 2-2
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