Signal Acquisition Check; Vhf Com Interference Check - Garmin GPS 400W Installation Manual

5.5.2

Signal Acquisition Check

All other avionics should be turned off at the start of this test. Turn on the 400W Series
unit.
Upon acknowledgement of the Instrument Panel Self-Test Page, the Satellite Status Page is displayed. If
the unit is unable to acquire satellites, relocate the aircraft away from obstructions which might be
shading GPS reception. If the situation does not improve, check the GPS antenna installation.
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 Position Page, verify that the lat/lon agree with a known reference position.
2. While monitoring the Satellite 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 400W Series unit and is functioning properly.
5.5.3

VHF COM Interference Check

The interference check must be completed on all IFR installations.
It is known that certain non-aviation radios, including marine transceivers, can interfere
with civil aviation navigation and surveillance equipment including the 400W Series unit.
When installing 400W Series equipment, it is the responsibility of the installer to ensure
that the 400W Series unit modification is compatible with all previous aircraft
modifications. Garmin recommends that whenever a 400W Series unit 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 400W Series
unit. Special care should also be taken to ensure that there is no interference with the
400W Series unit if non-aviation radios are installed in an aircraft after a 400W Series
unit 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 400W Series unit.
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.
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GNS 400W Series Installation Manual
190-00356-08