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190-00133-02 Rev B 3-1
SECTION 3
ALIGNMENT AND TESTING
3.1 INTRODUCTION
This section of the manual consists of alignment and test procedures. Perform the following procedures to iden-
tify failed units (troubleshooting) and after completing any repairs. The procedures assume familiarity with the
setup and operation of the special test equipment listed in Section 2. Units failing any part of alignment or testing
must be returned to GARMIN for repair except for the front subassembly which may be field replaced.
3.2 ALIGNMENT
Field alignment of the GTX 320 is limited to adjusting the transmitter frequency. No other attempt at alignment
should be made. Adjust the transmitter frequency before testing the unit.
3.2.1 Alignment Equipment
The following 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 suitable equivalent
4. Voltmeter Fluke 79
5. 50 Ohm Load ITT Pomona Model 3840-50
6. Transmitter Adjustment Tool Locally Made (see Figure 2-1)
7. Rack-Mount BNC to BNC Cable (RG-58/U having a total cable loss of 1.5 dB at 1090 MHz)
3.2.2 Alignment Setup
Figure 2-3 shows a typical alignment and test setup based on the I/O of the 25 pin connector (J102) and the rear
antenna connector (J103). Use the +28 VDC input during alignment.
3.2.3 Alignment Procedure
CAUTION
Use extreme care when adjusting C620, so that the transmitter is NOT allowed to
oscillate at frequencies below 1080 MHz, and risk damaging the mixer. A failed
mixer cannot be replaced in the field, the unit must be returned to GARMIN for
repair. A failed mixer will degrade MTL by several dB.