Garmin GTX 320/320A TRANSPONDER INSTALLATION MANUAL
Brand: Garmin, Pages: 37
Page 11 from 37
GTX 320/320A Installation Manual Page 7
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
12.5 M17/112 RG304
17.0 311601 M17/127 RG393
Supplier InformationVendor: Electronic
5300 W. Franklin Drive
Franklin, WI 53132
Fax: 414-421-5301MIL-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).
Page 12 from 37
Page 8 GTX 320/320A Installation Manual
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".
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.
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 13 from 37
GTX 320/320A Installation Manual Page 9
2.4 GTX 320/320A INSTALLATION
Avoid installing the unit near heat sources. If this is not possible, ensure that additional cooling is
provided. Allow adequate space for installation of cables and connectors. The installer will supply
and fabricate all of the cables. All wiring must be in accordance with FAA AC 43.13-2A.
GTX 320 units that are at Mod Level 1 must use the Mod Level 1 Rack Assembly. After Mod
Level 1, GTX 320 installations are 0.170" (4.31 mm) deeper in the panel.
A. Assemble the connector/rack kit according to figure B2. Install the rack assembly according to the
dimensions given in figures B1. Mounting brackets are not supplied due to the wide range of
mounting configurations available. Suitable mounting brackets may be fabricated from sheet metal
or angle stock. To ensure a sturdy mount, rear support for the unit should be provided.
B. Do not insert screws through the rear plate of the mounting tray, into the transponder. These holes
are only for use with the adapter described in paragraph 2.8.
C. Looking at the bottom of the transponder, make sure the front lobe of the locking mechanism is in a
vertical position. This can be accomplished by using a 3/32" Allen wrench through the face plate.
D. Slide the unit into the rack until the front lobe of the unit touches the rack. Guide pins on the back
plate will help in the proper alignment of the unit in the rack.
E. Turn the Allen wrench clockwise until unit is secured in the rack. Continue turning until tight. Do
not overtighten the screw.
F. To remove the unit from the rack, turn the 3/32" Allen wrench counterclockwise until it disengages
from the rack.
Page 14 from 37
Page 10 GTX 320/320A Installation Manual
2.5 ELECTRICAL CONNECTIONS
All electrical connections, except for the antenna, are made through a single, 25 pin, D subminiature connector.
Figure 2-1 defines the electrical characteristics of all input and output signals and identifies the cable
requirements for each signal. Required connector and associated hardware are supplied in the installation kit
(P/N 010-10160-00). See figures B4 and B5 for interconnect wiring diagrams.
Larger pins are supplied for the connector to provide power and ground at pins 13, 14, 15, and 25 when required.
Refer to Figure B4, Note 3.
Pin Contact Part Numbers
25 pin connector (P102)
Wire Gauge 18 AWG 20-24 AWG
GARMIN P/N 336-00023-00 336-00022-00
Military P/N N/A M39029/63-368
AMP N/A 205090-1
Positronic FC6018D M39029/63-368
ITT Cannon See Note 3 031-1007-042
Recommended Crimp Tools
Wire Gauge18 AWG 20-24 AWG
Extraction ToolPositioner Insertion/
Military P/N M22520/2-01 N/A M81969/1-02 M22520/2-08 M81969/1-02Positronic 9507 9502-11 M81969/1-02 9502-5 M81969/1-02ITT Cannon 995-0001-584 N/A N/A 995-0001-604 980-2000-426AMP 601966-1 N/A N/A 601966-5 91067-2Daniels AFM8 K774 M24308/1-02 K13-1 M24308/1-02Astro 615717 N/A M81969/1-02 615724 M81969/1-02
1. Insertion/extraction tools from ITT Cannon are all plastic; others are plastic with metal tip.
2. Non-GARMIN part numbers shown are not maintained by GARMIN and consequently are subject to
change without notice.
3. Alternate contacts for 18 AWG wire: As an alternative to the Positronic contacts listed (and provided
in the installation kit), the installer may use contacts made by ITT Cannon under P/N 031-1007-001.
These contacts require the use of a different crimp tool positioner than shown in the table, with the part
numbers as follows: Daniels P/N K250, Astro P/N 616245, or ITT Cannon P/N 980-0005-722.
4. All wires must be passed through the backshell before being assembled to connector.
5. In aircraft equipped with a dropping resistor for +28 VDC buss voltage, make sure the dropping
resistor is bypassed.
Page 15 from 37
GTX 320/320A Installation Manual Page 11
1 Not Used
2 Do Not Connect
3 Altitude A1
4 Altitude C2
5 Altitude A2
6 Altitude A4
7 Altitude C4
8 External Ident
9 Altitude B1
10 Altitude C1
11 Altitude B2
12 Altitude B4
14 Switched Power Output
15 Aircraft Power (+11 to +33 VDC)
16 External Standby
17 External Suppression (Suppress I/O-GTX 320A)
18 Altitude D4
19 Not Used
20 Not Used
21 Not Used
22 Not Used
23 28 V Lighting
24 14 V Lighting
Figure 2-1. DB-25 Pin-Out Definitions