Garmin GTX 320, GTX 320A INSTALLATION MANUAL
GTX 320/320A
TRANSPONDER
INSTALLATION
MANUAL
(GTX 320 Shown)
GARMIN International, Inc.
1200 E. 151
Olathe, KS 66062 USA
190-00133-01 Revision L
st
June 2001
Street
££££
© Copyright 1999-2002
GARMIN Ltd. or its subsidiaries
All Rights Reserved
Except as expressly provided herein, no part of this manual may be reproduced, copied, transmitted,
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written consent of GARMIN. GARMIN hereby grants permission to download a single copy of this
manual and of any revision to this manual onto a hard drive or other electronic storage medium to be
viewed and to print one copy of this manual or of any revision hereto, provided that such electronic or
printed copy of this manual or revision must contain the complete text of this copyright notice and provided
further that any unauthorized commercial distribution of this manual or any revision hereto is strictly
prohibited.
Information in this document is subject to change without notice. GARMIN reserves the right to change or
improve its products and to make changes in the content without obligation to notify any person or
organization of such changes or improvements.
GARMIN International, Inc.
1200 E. 151
Olathe, KS 66062 USA
Telephone: 913-397-8200
Dealer Line: 1-800-800-1420
Web Site Address: www.garmin.com
st
Street
INFORMATION SUBJECT TO EXPORT CONTROL LAWS
This document may contain information which is subject to the Export Administration Regulations
(“EAR”) issued by the United States Department of Commerce (15 CFR, Chapter VII, Subchapter C) and
which may not be exported, released, or disclosed to foreign nationals inside or outside of the United States
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RECORD OF REVISIONS
Revision Revision
Date
A
B
C
D
E
F
G
H
J
K
L
02/10/97 Initial Rel --05/30/97 Clarify Antenna Requirements 7096
07/08/97 Lengthens Mount Screws, Add Notes 7344
08/21/97 Depth Behind Panel 7539
09/18/97 Wiring Diagram Corrections 7673
01/23/98 Add Spring Washer 8310
06/05/98 Correct reference to 50 ohm match bushing 8808
05/14/99 Updates and Corrections 10985
09/25/00 Redraw 14199
11/05/01 Updates and Clarifications 16878
06/06/02 Updated unit and accessory part numbers 18314
Description ECO #
Page A GTX 320/320A Installation Manual
Rev. L 190-00133-01
TABLE OF CONTENTS
PARAGRAPH PAGE
1 GENERAL DESCRIPTION .................................................................................................................1
1.1 INTRODUCTION.................................................................................................................................1
1.2 EQUIPMENT DESCRIPTION.............................................................................................................1
1.3 TECHNICAL SPECIFICATIONS........................................................................................................1
1.3.1 Transponder Specifications .......................................................................................................1
1.3.2 Physical Characteristics-GTX 320 ............................................................................................2
1.3.3 Physical Characteristics-GTX 320A..........................................................................................2
1.4 EQUIPMENT AVAILABLE................................................................................................................2
1.4.1 Configurations Available...........................................................................................................2
1.4.2 Installation Accessories .............................................................................................................3
1.5 ADDITIONAL EQUIPMENT REQUIRED.........................................................................................3
1.6 INSTALLATION APPROVAL............................................................................................................3
1.7 ATC TRANSPONDER TESTS AND INSPECTIONS ........................................................................4
1.8 LIMITED WARRANTY ......................................................................................................................4
2. INSTALLATION ..................................................................................................................................5
2.1 INTRODUCTION.................................................................................................................................5
2.2 UNPACKING AND INSPECTING EQUIPMENT..............................................................................5
2.3 ANTENNA INSTALLATION..............................................................................................................5
2.3.1 Location Considerations ............................................................................................................5
2.3.2 Antenna Installation...................................................................................................................5
2.3.3 Installation Approval Considerations for Pressurized Aircraft .................................................6
2.3.4 Antenna Cable Installation ........................................................................................................7
2.3.5 Antenna Cable Connectors ........................................................................................................7
2.4 GTX 320/320A INSTALLATION........................................................................................................9
2.5 ELECTRICAL CONNECTIONS .......................................................................................................10
2.6 CHECK EXISTING COAX AND ANTENNA..................................................................................12
2.7 INSTALLATION USING EXISTING NARCO AT 150 INSTALLATION RACK .........................12
2.8 INSTALLATION USING EXISTING BENDIX/KING 76A/78A INSTALLATION RACK...........13
3. POST INSTALLATION CONFIGURATION & CHECKOUT PROCEDURE................................14
3.1 AIRCRAFT STATION LICENSING REQUIREMENTS .................................................................14
3.2 OPERATION ......................................................................................................................................14
3.2.1 Function Selection Switches....................................................................................................15
3.2.2 Code Selection .........................................................................................................................15
3.2.3 IDENT Button..........................................................................................................................16
3.2.4 Reply Light ..............................................................................................................................16
GTX 320/320A Installation Manual Page i
190-00133-01 Rev L
PARAGRAPH PAGE
APPENDIX A. CERTIFICATION DOCUMENTS....................................................................................17
A.1 CONTINUED AIRWORTHINESS ....................................................................................................17
A.2 ENVIRONMENTAL QUALIFICATION FORM - (GTX 320).........................................................20
A.3 ENVIRONMENTAL QUALIFICATION FORM - (GTX 320A)......................................................22
APPENDIX B. ASSEMBLY AND INSTALLATION DRAWINGS ........................................................24
APPENDIX C. STC PERMISSION-GTX 320 ...........................................................................................39
LIST OF ILLUSTRATIONS
FIGURE PAGE
2-1 DB-25 Pin-Out Definitions .................................................................................................................11
3-1 Transponder Front Panel.....................................................................................................................14
B1 GTX 320/320A Outline Drawing........................................................................................................25
B2 GTX 320/320A Connector/Rack Kit Assembly Drawing ..................................................................27
B3 GTX 320/320A Recommended Panel Cutout Dimensions.................................................................29
B4 GTX 320/320A Interconnect Wiring Diagram ...................................................................................31
B5 Dual Transponder Interconnect Wiring Diagram ...............................................................................33
B6 NARCO AT 150 Installation Adapter Assembly Drawing.................................................................35
B7 KING KT 76A/78A Installation Adapter Assembly Drawing............................................................37
Page ii GTX 320/320A Installation Manual
Rev L 190-00133-01
1. GENERAL DESCRIPTION
1.1 INTRODUCTION
This manual provides the installation and operating instructions for the GARMIN GTX 320 and the GTX 320A
Transponders. Information pertaining to the maintenance, alignment, and procurement of replacement parts is
found in the GTX 320 Maintenance Manual, P/N 190-00133-02 and the GTX 320A Maintenance Manual, P/N
190-00133-08. After installation of the GTX 320/ GTX 320A, FAA Form 337 must be completed by an
appropriately certificated agency and ATC transponder tests required by 14 CFR, Part 91.413 must be completed
to return the aircraft to service.
1.2 EQUIPMENT DESCRIPTION
The GARMIN GTX 320/320A Transponder is a radio transmitter and receiver that operates on radar frequencies.
Receiving ground radar interrogations at 1030 MHz, it transmits a coded response of pulses to ground-based
radar on a frequency of 1090 MHz.
As with other Mode A/Mode C transponders, the GTX 320/320A replies with any one of 4,096 codes, which
differ in the position and number of pulses transmitted. By “replying” to ground transmissions, your
GTX 320/320A enables ATC computers to display aircraft identification, altitude and ground speed on ATC
radar screens. The GTX 320/320A is equipped with IDENT capability that activates the Special Position
Identification Pulse (SPI) for approximately 20 seconds (18 seconds for the GTX 320A) identifying your
transponder return from other aircraft on the controller’s scope.
1.3 TECHNICAL SPECIFICATIONS
1.3.1 Transponder Specifications
SPECIFICATION CHARACTERISTIC
TSO, JTSO TSO C74c Class 1A, JSTO C74C Class 1A
TSO ENV CAT (A1D1)-CA(BMN)XXXXXXZBABAUZXXXXXX
Applicable Documents
Temperature Range
Power Requirements
Humidity
Altitude 50,000 Feet
Transmitter Frequency 1090 MHz
Transmitter Power
Receiver Frequency 1030 MHz
Receiver Sensitivity
Mode A Capability 4096 Identification Codes
Mode C Capability 100 Foot Increments from -1000 to 63,000 Feet
External Suppression Input
GTX 320: FAA TSO C74c; RTCA DO-160C, JTSO C74c
GTX 320A: FAA TSO C74c; RTCA DO-160D, JTSO C74c
-20°C to +55°C (Continuous Operation)
GTX 320: +11.0 to +33.0 VDC: 12 Watts Max.
GTX 320A: +11.0 to +33.0 VDC: 20 Watts Max.
95% @ +55°C for 16 Hours; 85% @ +38°C for 32 Hours
125 Watts minimum, 150 Watts nominal at the antenna with 1.5
coaxial cable loss at 1090 MHz
GTX 320: -72 dBm Nominal for 90% replies
GTX 320A: -74 dBm Nominal for 90% replies
Low ≤ 0.5 V; High ≥ 8 V
dB
GTX 320/320A Installation Manual Page 1
190-00133-01 Rev L
1.3.2 Physical Characteristics-GTX 320
Bezel Height 1.63 inches (41 mm)
Bezel Width 6.25 inches (159 mm)
Rack Height (Dimple to Dimple) 1.71 inches (43 mm)
Rack Width 6.30 inches (160 mm)
Depth Behind Panel with
Connectors (measured from face of
aircraft panel to rear of connector
backshells)
Weight (Unit Only) 1.7 lbs. (0.8 kg)
Weight (Installed with rack and
connectors)
1.3.3 Physical Characteristics-GTX 320A
Bezel Height 1.63 inches (41 mm)
Bezel Width 6.25 inches (159 mm)
Rack Height (Dimple to Dimple) 1.71 inches (43 mm)
Rack Width 6.30 inches (160 mm)
Depth Behind Panel with
Connectors (measured from face of
aircraft panel to rear of connector
backshells)
Weight (Unit Only) 2.3 lbs. (1.1 kg)
Weight (Installed with rack and
connectors)
8.78 inches (223 mm)
2.3 lbs. (1.1 kg)
8.78 inches (223 mm)
2.9 lbs. (1.3 kg)
1.4 EQUIPMENT AVAILABLE
1.4.1 Configurations Available
ITEM GARMIN P/N
GARMIN GTX 320 Transponder 010-00135-00
GARMIN GTX 320A Transponder 010-00247-00
GARMIN GTX 320 Transponder includes GARMIN installation kit, P/N 010-10161-00 010-00135-03
GARMIN GTX 320A Transponder includes GARMIN installation kit, P/N 010-10161-01 010-00247-02
Page 2 GTX 320/320A Installation Manual
Rev L 190-00133-01
1.4.2 Installation Accessories
ITEM GARMIN P/N
Mounting Rack 115-00285-00
Connector Kit 011-00651-01
Rear Backplate 011-00677-01
Mounting Rack, Rear Backplate and Connector Kit
(Includes 115-00285-00, 011-00677-01 and 011-00651-01)
GARMIN GTX 320/320A Narco Adapter 010-10158-00
GARMIN GTX 320/320A KT76A Adapter 010-10159-00
GARMIN GTX 320/320A Antenna kit* 010-10160-00
010-10161-01
* Note: A transponder antenna approved to TSO C66( ) or C74( ) that has been installed to meet the
requirements of this manual may be approved for use with the GTX 320/320A.
1. 5 ADDITIONAL EQUIPMENT REQUIRED
• Antenna Sealant - Use antenna manufacturer’s instructions, install according to FAA
AC 43.13-2A.
• Cables - The installer will supply all system cables. Cable requirements and fabrication is
detailed in Section 2 of this manual.
• Hardware - #6 Flat Head Screw (6 ea.) and #6-32 Self Locking Nut (6 ea.). Hardware required to
mount installation rack is not provided.
1.6 INSTALLATION APPROVAL
The conditions and tests required for TSO approval of the GTX 320/320A Transponder and antenna are
minimum performance standards. It is the responsibility of those desiring to install this transponder and antenna
either on or within a specific type or class of aircraft to determine that the aircraft installation standards are
within the TSO standards. The GTX 320/320A and antenna may be installed only if further evaluation by the
applicant documents an acceptable installation and is approved by the administrator. For GTX 320/320A TSO
compliance, see Appendix A. For antenna TSO compliance, refer to antenna manufacturer’s literature.
1.7 ATC TRANSPONDER TESTS AND INSPECTIONS
The ATC transponder tests required by 14 CFR, Part 91.413 may be conducted using a bench check or portable
test equipment and must meet the requirements prescribed in Part 43 Appendix F.
If portable test equipment with appropriate coupling to the aircraft antenna system is used, operate the test
equipment for ATCRBS transponders at a nominal rate of 235 interrogations per second to avoid possible
ATCRBS interference. An additional 3 dB loss is allowed to compensate for antenna coupling errors during
receiver sensitivity measurements conducted in accordance with Part 43 Appendix F, Paragraph (c)(1) when
using portable test equipment.
GTX 320/320A Installation Manual Page 3
190-00133-01 Rev L
1.8 LIMITED WARRANTY
GARMIN warrants this product to be free from defects in materials and manufacture for one year from the date
of purchase. GARMIN will, at its sole option, repair or replace any components that fail in normal use. Such
repairs or replacement will be made at no charge to the customer for parts or labor. The customer is, however,
responsible for any transportation costs. This warranty does not cover failures due to abuse, misuse, accident or
unauthorized alteration or repairs.
THE WARRANTIES AND REMEDIES CONTAINED HEREIN ARE EXCLUSIVE AND IN LIEU OF ALL
OTHER WARRANTIES EXPRESS OR IMPLIED OR STATUTORY, INCLUDING ANY LIABILITY
ARISING UNDER ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR
PURPOSE, STATUTORY OR OTHERWISE. THIS WARRANTY GIVES YOU SPECIFIC LEGAL RIGHTS,
WHICH MAY VARY FROM STATE TO STATE.
IN NO EVENT SHALL GARMIN BE LIABLE FOR ANY INCIDENTAL, SPECIAL, INDIRECT OR
CONSEQUENTIAL DAMAGES, WHETHER RESULTING FROM THE USE, MISUSE, OR INABILITY TO
USE THIS PRODUCT OR FROM DEFECTS IN THE PRODUCT. SOME STATES DO NOT ALLOW THE
EXCLUSION OF INCIDENTAL OR CONSEQUENTIAL DAMAGES, SO THE ABOVE LIMITATIONS MAY
NOT APPLY TO YOU.
To obtain warranty service, call the GARMIN Customer Service department (913-397-8200) for a returned
merchandise tracking number. The unit should be securely packaged with the tracking number clearly marked on
the outside of the package and sent freight prepaid and insured to a GARMIN warranty service station. A copy
of the original sales receipt is required as the proof of purchase for warranty repairs. GARMIN retains the
exclusive right to repair or replace the unit or software or offer a full refund of the purchase price at its sole
discretion. SUCH REMEDY SHALL BE YOUR SOLE AND EXCLUSIVE REMEDY FOR ANY BREACH OF
WARRANTY.
Page 4 GTX 320/320A Installation Manual
Rev L 190-00133-01
2. INSTALLATION
2.1 INTRODUCTION
This section provides the necessary information for installing the GTX 320/320A Transponders, and where
required, optional accessories. Installation of the GTX 320/320A will differ according to equipment location and
other factors. Cabling will be fabricated by the installing agency to fit these various requirements. This section
contains interconnect diagrams, mounting dimensions, and information pertaining to installation. Each
installation shall be accomplished to meet the requirements of FAA AC 43.13-2A.
2.2 UNPACKING AND INSPECTING EQUIPMENT
Carefully unpack the equipment and make a visual inspection of the unit for evidence of damage incurred during
shipment. If the unit is damaged, notify the carrier and file a claim. To justify a claim, save the original shipping
container and all packing materials. Do not return the unit to GARMIN until the carrier has authorized the claim.
Retain the original shipping containers for storage. If the original containers are not available, a separate
cardboard container should be prepared that is large enough to accommodate sufficient packing material to
prevent movement.
2.3 ANTENNA INSTALLATION
2.3.1 Location Considerations
A. The antenna (GARMIN P/N 010-10160-00) should be well removed from any major protrusions, the
engine(s), propeller(s), and antenna masts. It should also be as far removed as practical from
landing gear doors, access doors, or other openings that could alter its radiation pattern.
B. The antenna should be mounted on the underside of the aircraft and in a vertical position when the
aircraft is in level flight.
C. Avoid mounting the antenna within three feet of the ADF sense antenna or any other
communication antenna and six feet from the DME antenna.
D. To prevent RF interference, the antenna must be physically mounted a minimum distance of three
feet from the GTX 320/320A.
If the antenna is being installed on a composite aircraft, ground planes must sometimes be added.
Conductive wire mesh, radials, or thin aluminum sheets embedded in the composite material provide
the proper ground plane allowing the antenna pattern (gain) to be maximized for optimum
transponder performance.
2.3.2 Antenna Installation
Install the antenna according to the antenna manufacturer’s instructions and FAA AC 43.13-2A.
NOTE
GTX 320/320A Installation Manual Page 5
190-00133-01 Rev L
2.3.3 Installation Approval Considerations for Pressurized Aircraft
Antenna and cable installations on pressurized cabin aircraft require FAA approved installation design and
engineering substantiation data whenever such installations incorporate alteration (penetration) of the cabin
pressure vessel by connector holes and/or mounting arrangements.
For needed engineering support pertaining to the design and approval of such pressurized aircraft antenna
installations, it is recommended that the installer proceed according to any of the following listed alternatives:
1. Obtain approved antenna installation design data from the aircraft manufacturer.
2. Obtain an FAA approved Supplemental Type Certificate (STC) pertaining to and valid for the subject
antenna installation.
3. Contact the FAA Aircraft Certification Office in the appropriate Region and request identification of FAA
Designated Engineering Representatives (DERs) who are authorized to prepare and approve the required
antenna installation engineering data.
4. Obtain FAA Advisory Circular AC-183C and select (and contact) a DER from the roster of individuals
identified there under.
Contact an aviation industry organization such as the Aircraft Electronics Association and request their
assistance.
Page 6 GTX 320/320A Installation Manual
Rev L 190-00133-01
2.3.4 Antenna Cable Installation
When routing antenna cables, observe the following precautions:
• All cable routing should be kept as short as possible and as direct as possible.
• Avoid sharp bends.
• Avoid routing cables near power sources (e.g., 400 Hz generators, trim motors, etc.) or near
power for fluorescent lighting.
• Avoid routing cable near ADF antenna cable (allow at least a 12-inch separation).
The table below lists the recommended 50 ohm double shielded coax antenna cable vendor and the type to be
used for specific lengths of cable. Adherence to this table will ensure that the coax installation will not exceed
the maximum allowable 1.5 dB attenuation at the transmitter operating frequency of 1090 MHz.
Max. Length (feet) ECS Type MIL-C-17 Type RG Type
8.8 M17/128 RG400
10.0 3C142B
12.5 M17/112 RG304
17.0 311601 M17/127 RG393
21.0 311501
27.0 311201
41.0 310801
Supplier Information
Vendor: Electronic
Cable Specialists
5300 W. Franklin Drive
Franklin, WI 53132
Tel: 800-327-9473
414-421-5300
Fax: 414-421-5301
MIL-C-17 types: See
current issue of
Qualified Products List
QPL-17.
RG types: See current
issue of Qualified
Products List QPL-17.
2.3.5 Antenna Cable Connectors
One of two rack connectors is provided (item 6 or 12 in the installation drawing, figure B2). RF Adapter item 12
(P/N 330-00326-00) requires the cable to be terminated to an appropriate type BNC plug (provided by installer),
which is then attached to item 12. Any 50 ohm, double shielded cable may be used, provided it introduces less
than 1.5 dB attenuation at 1 GHz including the connector.
Connector item 6 (P/N 330-00198-00) requires the cable to be terminated directly to it and can accommodate
only M17/128 (RG-400) cable. The completed cable including connectors must introduce no more than 1.5
attenuation at 1 GHz. Instructions for installing the item 6 are shown below (steps A-G).
GTX 320/320A Installation Manual Page 7
190-00133-01 Rev L
dB
A. Trim coax outer insulation back 0.50".
B. Trim braid (not center conductor or insulation) back 0.25".
C. Strip Insulation back 0.120".
NOTE
Place the ferrule over the coax braid, flush against the coax outer insulation before performing the
next step if the outside diameter of the coax braid is smaller than the inside diameter of the center
connector sidewall opening.
D. 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.
E. Heat the outside of the connector sleeve and at the same time apply solder between the braid and the
sleeve. Continue to apply heat until the solder flows evenly.
F. Install 50 1 Matching Bushing.
G. Insert connector cap and tack solder in two places.
Page 8 GTX 320/320A Installation Manual
Rev L 190-00133-01
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