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190-00133-02 Rev B                                                                                                                                                                                     1-1

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:

•  

INTERROGATOR

—In 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.

•  

TRANSPONDER

—The 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 interroga-

tions 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.

•  

RADARSCOPE

—The 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.

Содержание GTX 320 ATC

Страница 1: ...GTX 320 ATC TRANSPONDER MAINTENANCE MANUAL 190 00133 02 Rev B GARMIN 1200 E 151st Street Olathe KS 66062 USA 16 March 1999...

Страница 2: ...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 Copyright 1999 by GARMIN Corporation All...

Страница 3: ...S 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 INTR...

Страница 4: ...scope TRANSPONDER The 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 tho...

Страница 5: ...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 Tran...

Страница 6: ...NTENANCE 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 Trans...

Страница 7: ...ated Test Panel Locally Fabricated Alignment Tool Locally Fabricated Antenna Test Cable Connector Locally Fabricated 2 3 1 Test Panel and Test Harness A Test Panel must be fabricated by the shop which...

Страница 8: ...all 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 sidewa...

Страница 9: ...190 00133 02 Rev B 2 3 Figure 2 3 Test Setup Test Harness J102...

Страница 10: ...lowing equipment or suitable substitute is used to adjust the transmitter frequency 1 Transponder DME Test Set IFR Systems ATC 1400A 2 Power Supply Topward 2000 3 Digital Oscilloscope Tek TDS 320 or s...

Страница 11: ...VEL 50 dBm SLS ECHO OFF FREQUENCY POWER TOGGLE SWITCH F1 P1 ______ OK 3 Set the GTX320 transponder mode select control knob to the ON position ______ OK NOTE Allow the unit to warm up for approximatel...

Страница 12: ...190 00133 02 Rev B 3 3 Figure 3 1 C620 and C635 Location...

Страница 13: ...Time 50 nS to 200 nS Pulse Width 350 nS to 550 nS 5 Adjust C635 for maximum power output as read from the ATC1400A test set The power must be greater than 125 watts ______ 125 Watts 6 Verify that the...

Страница 14: ...approximate 5 second delay before the unit transmits ______ OK 5 Rotate the mode select switch on the GTX320 to the ALT position The GTX320 shall continue to reply to valid interrogations ______ OK 6...

Страница 15: ...om the MTL in Mode A 6 Increase the RF level to 50 dB above MTL The reply rate displayed on the ATC 1400A shall be at least 90 ________ 90 Reply Rate 3 3 3 5 Reply Pulse Characteristics 1 Set the osci...

Страница 16: ...MTL a value of 21 dBm assuming an MTL of 71 dBm The percent reply shall be at least 90 as indicated on the ATC 1400A ______ Reply 3 3 3 7 Automatic Overload Control AOC 1 Set the SLS ECHO toggle swit...

Страница 17: ...8 0 volts The unit must suppress the replies to any interrogations received during the time of the suppression pulse ______ OK 3 3 3 10 External Altittude Encoder Inputs 1 Set the digital oscilloscop...

Страница 18: ...etween the P1 and P3 pulses as viewed on the oscilloscope and shown in Figure 3 4 ______ OK 7 Verify that the unit is correctly encoding the altitude by observing the XPDR CODE digital display on the...

Страница 19: ...l appear next to the P3 pulse on the oscilloscope See Figure 3 5 5 Rotate the mode select switch to the SBY position 6 Press the IDENT button on the transponder The reply light shall turn on for appro...

Страница 20: ...de select switch to the ALT position The ALT nomenclature and the four reply code digits shall be illuminated with a higher intensity than the OFF SBY ON and TST nomenclature ______ OK 3 3 3 16 TST Te...

Страница 21: ...so that it returns to the ALT position The reply light shall remain on ______ OK 3 3 3 18 Numerical Reply Code Switches 1 Rotate the XPDR MODE switch on the ATC 1400A to position A 2 With the transpon...

Страница 22: ...190 00133 02 Rev B 3 13 Figure 3 6 ATC 1400A Test Settings...

Страница 23: ...for bent or broken pins on the 25 pin connector 4 Inspect for damage to the BNC connector 4 3 FRONT SUBASSEMBLY P N 011 00263 00 1 Remove power to the unit 2 Remove the bottom cover 5 screws to expose...

Страница 24: ...Rev B 4 2 Figure 4 1 Front Subassembly Installation 4 4 CLEANING After reassembly clean the external surface of the transponder when inspection shows dirt smudges etc Wipe with a damp lint free stati...

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