400W Series Installation Manual Page 5-29190-00356-02 Rev. G5.5.2 Signal Acquisition CheckNOTEAll other avionics should be turned off at the start of this test. Turn on the GNS 400WSeries unit.Upon acknowledgement of the Instrument Panel Self-Test Page, the Satellite Status Page is displayed. Ifthe unit is unable to acquire satellites, relocate the aircraft away from obstructions which might beshading GPS reception. If the situation does not improve, check the GPS antenna installation.NOTEAfter 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 theGPS 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 equipmentis transmitting and/or receiving data from the 400W Series unit and is functioning properly.5.5.3 VHF COM Interference CheckNOTEThe interference check must be completed on all IFR installations.NOTEIt is known that certain non-aviation radios, including marine transceivers, can interferewith civil aviation navigation and surveillance equipment including the Garmin GNS400W Series. When installing GNS 400W Series equipment in accordance with theappropriate STC, it is the responsibility of the installer to ensure that the GNS 400WSeries unit modification is compatible with all previous aircraft modifications. Garminrecommends that whenever a GNS 400W Series unit is installed in an aircraft that hasbeen modified with non-aviation radios, particular care should be exercised to verify thatthese do not interfere with proper function of the GNS 400W Series unit. Special careshould also be taken to ensure that there is no interference with the GNS 400W Seriesunit if non-aviation radios are installed in an aircraft after a GNS 400W Series unit hasbeen installed. If interference is found, it can be addressed by relocating antennas,rerouting cables, using filters to attenuate unintentional harmonic frequencytransmissions, or using various other techniques for elimination of the interference. Itmay be necessary to remove or replace the interfering radio with a model that does notinterfere with the proper functioning of the GNS 400W Series unit.If you are testing a transmitter from a non-aviation device, each frequency must beverified by transmitting for at least 30 seconds on each channel.
