Page 5-22
GTN 725/750 TSO Installation Manual
Rev. A
190-01007-02
5.6.2 Signal
Acquisition
Check
NOTE
All other avionics should be turned off at the start of this test, with the GTN powered on.
Ensure the GTN is able to acquire sufficient satellites to compute a GPS position. From the Home page,
touch the AUX button and then touch the GPS Status button. Under ‘Status’, ensure that a 3D Fix, or 3D
Diff Fix is obtained. If the unit is unable to acquire satellites, move the aircraft away from obstructions
which might be shading GPS reception. If the situation does not improve, check the GPS antenna
installation.
NOTE
After installation, the initial acquisition of position can take up to 20 minutes.
Subsequent acquisitions will not take that long.
Once GPS position information is available, perform the following steps:
1.
On the GPS Status Page, verify that the LAT/LON agree with a known reference position.
2.
While monitoring the GPS Status Page, turn on other avionics one at a time and check the GPS
signal reception to make sure it is not affected (no significant signal degradation).
3.
Before proceeding with the VHF COM interference check, ensure that any connected equipment
is transmitting and/or receiving data from the GTN and is functioning properly.
5.6.3
VHF COM Interference Check
NOTE
The interference check must be completed on all IFR installations.
NOTE
It is known that certain non-aviation radios, including marine transceivers, can interfere
with civil aviation navigation and surveillance equipment including the Garmin GTN.
When installing GTN equipment, it is the responsibility of the installer to ensure that the
GTN modification is compatible with all previous aircraft modifications. Garmin
recommends that whenever a GTN is installed in an aircraft that has been modified with
non-aviation radios, particular care should be exercised to verify that these do not
interfere with proper function of the GTN. Special care should also be taken to ensure
that there is no interference with the GTN if non-aviation radios are installed in an
aircraft after a GTN has been installed. If interference is found, it can be addressed by
relocating antennas, rerouting cables, using filters to attenuate unintentional harmonic
frequency transmissions, or using various other techniques for elimination of the
interference. It may be necessary to remove or replace the interfering radio with a model
that does not interfere with the proper functioning of the GTN.
If you are testing a transmitter from a non-aviation device, each frequency must be
verified by transmitting for at least 30 seconds on each channel.
Summary of Contents for GTN 725
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