G900X/G950 Installation and Maintenance Manual – G900X/G950 Installation Overview
Page 1-31
190-00719-00
Revision D
1.6.9
VHF COM/GPS Interference
On some installation VHF COM transceivers, Emergency Locator Transmitter (ELT) antennas, and
Direction Finder (DF) receiver antennas can re-radiate through the GPS antenna. The GIA 63(W) COM
does not interfere with its own GPS section. However, placement of the GPS antenna relative to a COM
transceiver and COM antenna (including the GIA 63W COM antenna), ELT antenna, and DF receiver
antenna is critical.
Use the following guidelines, in addition to others in this document, when locating the GIA 63W and its
antennas.
•
GPS Antenna—Locate as far as possible from all COM antennas and all COM transceivers
(including the GIA 63W COM), ELT antennas, and DF antennas. The GPS antenna is less
susceptible to harmonic interference if a 1.57542 GHz notch filter is installed on the COM
transceiver antenna output.
•
Locate the GIA 63W as far as possible from all COM antennas.
If a COM antenna is found to be the problem, a 1.57542 GHz notch filter (Garmin P/N 330-00067-00)
may be installed in the VHF COM coax, as close to the COM as possible. This filter is not required for
the GIA 63(W) transmitter.
If a COM is found to be radiating, the following can be done:
1.
Replace or clean the VHF COM rack connector to ensure good coax ground.
2.
Place grounding straps between the GIA 63(W) unit, VHF COM and a good ground.
3.
Shield the VHF COM wiring harness.
1.7 Instructions for Continued Airworthiness
Instructions for Continued Airworthiness (ICA) for each individual LRU of the G900X/G950 system are
contained in the associated LRU section of this document. It should be noted that these instructions are
applicable for each individual LRU but are not intended as an aircraft level ICA requirement.