190-01182-02
GTR 225/GNC 255 TSO Installation Manual
Rev. F
Page 6-20
6.6.4
VHF COM
6.6.4.1
Antenna Check
If desired, the antenna VSWR can be checked using an inline wattmeter in the antenna coaxial using
frequencies near both ends of the band. The VSWR should be less than 2:1. A VSWR of 2:1 will cause a
drop in output power of approximately 12%.
6.6.4.2
Receiver/Transmitter Check
1. Tune the unit to a local VHF frequency
2. Verify the receiver output produces a clear and understandable audio output.
3. Verify the transmitter functions properly by contacting another station and getting a report of
reliable communications.
6.6.4.3
Aux Audio Input Check
This check is only required for installations with an AUX audio source connected to pin P2001-3 and pin
P2001-19.
1. Connect an audio source to the AUX Audio input (P2001-3 and P2001-19).
2. Verify that AUX audio is heard over the pilot headset position.
6.6.4.4
Database Check
Check the frequency database to ensure it is current. The database information is displayed during the unit
display start-up sequence. To check the database:
1. Cycle power on the GTR/GNC and let the start-up sequence complete.
2. Press
FUNC
.
3. Turn the outer knob to SYS CONFIGURATION.
4. Turn the inner knob to DATABASE INFO.
5. Press
ENT
.
6. Verify the frequency database effectivity (EFCTV) date has not lapsed.
6.6.4.5
RS-232 Serial Interface Checks
The interfaces to RS-232 equipment such as the GTN 6XX/7XX or GNS 400W/500W series GPS sources
should be checked as follows.
1. Operate the connected GPS source and the GTR/GNC in normal mode.
2. Ensure the aircraft has a clear view of the sky for this check. This check should not be performed
in a hangar.
3. Verify the connected GPS source has a valid GPS satellite fix.
4. Press
FUNC
.
5. Turn the inner knob to NEAREST APT.
6. Press
ENT
.
7. Verify the wiring between the GPS source and the GTR/GNC if the GTR/GNC displays “NO
GPS.”
The interfaces to RS-232 equipment such as the G500/G600 or other serial interface should be checked as
follows.
1. Operate the connected serial remote tune source and the GTR/GNC in normal mode.
2. Ensure the remote source is able to display data from the GTR/GNC.
Содержание GNC 255A
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