Gia 63W Related Alerts And Problems - Garmin G1000 Maintenance Manual

__________________________________________________________________
5.6

GIA 63W RELATED ALERTS AND PROBLEMS

5.6.1 COM
Symptom
Weak COM transmit power
Weak COM receiver or
COM squelch opens
intermittently
No COM sidetone
COM Bleedover
5.6.1.1 COM Adjustment Procedure
The COM Calibration Procedure is not a required procedure and is not generally performed
during installation or maintenance. This procedure may be used to adjust COM receiver
25kHz/8.33kHz squelch settings if needed. If the COM squelch opens after performing this
procedure, the aircraft's electrical system may be noisy causing the COM squelch to open. Find
the source of electrical system noise and correct (electrical motors are a common source of
interference). Desensitizing the COM squelch to prevent it from opening due to electrical
system noise may reduce the receiving range of the COM.
To set COM squelch threshold:
1. Connect a ground power unit to the aircraft.
2. Disconnect GIA COM antenna connector at the back of the GIA rack and connect an RF
generator.
a. For 25kHz frequency spacing; set the RF generator to 5.0μV hard, modulated
30% at 1000Hz.
b. For 8.33kHz frequency spacing; set the RF generator to 3.0μV hard, modulated
30% at 1000Hz.
3. Turn on the Perspective system and allow to initialize in normal mode.
4. Turn off the PFD and MFD by pulling their circuit breakers.
5. Restart the PFD and MFD in Configuration Mode.
6. On the PFD, turn to the COM SETUP page.
G1000 System Maintenance Manual
190-00907-00
Recommended Action
•
Switch GIA1 and GIA2, to verify location of problem:
•
If problem follows unit, replace GIA.
•
If problem does not follow unit, check COM antenna and
cabling for faults.
•
Switch GIA1 and GIA2, to verify location of problem:
•
If problem follows unit, perform GIA COM Procedure per
Section 5.6.1.1.
−
Replace GIA if COM adjustment does not achieve
desired results.
•
If problem does not follow unit, check COM antenna and
cabling for faults.
•
Switch GIA1 and GIA2, to verify location of problem:
•
If problem follows unit, replace GIA.
•
If problem persists, replace 1347.
•
Verify on the GMA CONFIGURATION page that "MUTE AUDIO
ON TX" has a green box. Due to the closeness of the COM
antennas and high power of the COM transceivers, normal Split
COM operation is not approved. If the box is black, highlight
"MUTE AUDIO ON TX" with the cursor and press the ENT key to
turn the box green.
Page 5-43
Rev. B