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Av. Kit Install. Manual
190-00067-02 Rev. J
Page 10
If a COMM antenna is found to be the problem, a 1.57542 GHz notch filter (GPN 330-
00067-00) may be installed in the VHF COMM coax, as close to the COMM as possible.
This filter (GPN 330-00067-00) is required for the GNC 300 transmitter).
If a COMM is found to be radiating, the following can be done:
1) Replace or clean VHF COMM rack connector to assure good coax ground.
2) Place a grounding brace between the GNC 300, VHF COMM, and ground.
3) Shield the VHF COMM wiring harness.
2.1.6 COMM ANTENNA INSTALLATION INSTRUCTIONS
The COMM antenna should be installed according to the manufacturer's
recommendations.
2.2 RACK CONSIDERATIONS
2.2.1 ACCESSIBILITY
Plan a location which gives the pilot complete and comfortable access to the entire
keypad and which is plainly visible from the pilots perspective. Check that there is
adequate depth for the rack in the instrument panel. A location away from heating
vents or other sources of heat generation is optimal. Figure 2-2 illustrates a typical
aviation rack installation.
2.3 CABLING AND WIRING
The recommended antenna cable type for both antennas is M17/155-0001 (RG-58A/
U) per MIL-C-17. Maximum allowable length for the GPS antenna using this cable
type is 40 feet. Other cable types with 50 ohms nominal impedance and longer lengths
can be used for the GPS antenna, provided the installer insures that the attenuation
does not exceed 10dB at 1.5 GHz for the specific installation. Check that there is
ample space for the cabling and mating connectors. Avoid sharp bends in cabling,
particularly the COMM antenna cable, and routing near aircraft control cables.
Cabling for the GNC 300 should not be routed near components or cabling which are
sources of electrical noise.
Do not route the COMM antenna cable near any ADF antenna cables.
Route the GPS antenna cable as far as possible away from all COMMs and COMM
antenna cable.
2.4 COOLING AIR
Cooling air is not required for the GNC 300 but is highly recommended because, as
with any electronic equipment, reduced operating temperature can contribute to
increased reliability. Additionally, location of the GNC 300 in a stack of other power