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 GNS 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 Garmin GNS
400W Series. When installing GNS 400W Series equipment in accordance with the
appropriate STC, it is the responsibility of the installer to ensure that the GNS 400W
Series unit modification is compatible with all previous aircraft modifications. Garmin
recommends that whenever a GNS 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 GNS 400W Series unit. Special care
should also be taken to ensure that there is no interference with the GNS 400W Series
unit if non-aviation radios are installed in an aircraft after a GNS 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 GNS 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.
400W Series Installation Manual
190-00356-02
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Page 5-29
Rev. G