190-01182-02 GTR 225/GNC 255 TSO Installation Manual
Rev. F Page 3-1
3 INSTALLATION OVERVIEW
3.1 Introduction
Always follow acceptable avionics installation practices per AC 43.13-1B, AC 43.13-2B, or later FAA
approved revisions of these documents. The communications installation instructions have been prepared
to meet the guidance material defined by AC 20-67B, Airborne VHF Communications Equipment
Installations.
3.2 Antenna Considerations
Considerations for the mounting location of the antennas required for the GTR/GNC is provided in this
section. For mounting the COM and NAV antennas, refer to the aircraft manufacturer’s data.
3.2.1 COM Antenna Location
The GTR/GNC COM antenna should be installed away from all projections, engines and propellers. The
ground plane surface directly below the antenna should be a flat plane over as large an area as possible
(18" square, minimum). The antenna should be mounted a minimum of six feet from any DME or other
COM antennas, and four feet from any ADF sense antennas. The COM antenna should also be mounted as
far apart as practical from the ELT antenna. Some ELTs have exhibited re-radiation problems that cause
interference with other radios, including GPS. This can happen when the COM (GTR/GNC or any other
COM) is transmitting on certain frequencies such as 121.15 or 121.175 MHz, which may cause the ELT
output circuit to oscillate from the signal coming in on the ELT antenna coax.
If simultaneous use of two COM transceivers is desired (split-COM or simul-COM), the COM antennas
should be spaced for maximum isolation. A configuration of one topside antenna and one bottom side
antenna is recommended. The GTR/GNC does not require a transmit interlock, but other COM radios such
as the GNS 530W may require it for split-COM operations.
Canadian installations are required to meet Industry Canada specifications for maximum
radiation as documented in Radio Specifications Standard 102 (RSS-102). For more
information about RF exposure and related Canadian regulatory compliance, contact:
Manager, Radio Equipment Standards
Industry Canada
365 Laurier Avenue
Ottawa, Ontario
K1A 0C8
In accordance with Canadian Radio Specifications Standard 102 (RSS 102), RF field strength
exposure to persons from an antenna connected to this device should be limited to 60V/m for
controlled environment and 28 V/m for uncontrolled environment.
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