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2.3.4 Antenna Installation Considerations
The following guidelines should be observed when implementing the antenna installation:
1. Antenna and airframe surfaces should be prepared and bonded according to guidance given in
Section 2.4.
2. A visual inspection should be performed to verify that all coaxial cables are connected properly
before attempting to operate the equipment.
3. Always refer to the antenna manufacturer's provided installation material for any additional
installation guidance specific to the antenna type being used.
2.4 Electrical Bonding
All electrical equipment, supporting brackets, racks, and antennas should be electrically bonded to the
aircraft's main structure. Refer to SAE ARP 1870 Section 5 when surface preparation is required to
achieve electrical bond. The electrical bond should achieve direct current (DC) resistance less than or
equal to 2.5 milliohms to the local structure to where the equipment is mounted. Compliance should be
verified by inspection using a calibrated milliohm meter. An equivalent OEM procedure may also be
substituted. There may be OEM specific reasons for electrically isolating equipment or having a higher
bond resistance. These reasons should be rationalized upon installation approval. In general, Garmin
recommends that all GRA 5500 equipment be electrically bonded.
2.5 Cabling and Wiring
Refer to the interconnect examples in
and installation methods that are compliant with governing aviation regulations and standards.
Any bend radius applied to a cable must not exceed the minimum bend radius specification as prescribed
by the cable manufacturer for the specific cable type. It is recommended that the bend radius applied to a
coaxial cable is minimized when in close proximity to the connector ferrule or compression housing in
order to decrease side loading of the cable at the crimp or compression area. Whenever possible, it is
recommended that no clearly visible bending exists within 1/2 inch of each coaxial cable assembly
connector ferrule or compression housing. All cables should be secured in a manner that minimizes any
potential back and forth side loading of the cable at the connector crimp or compression area. When
routing the wire and cable, the installing agency should observe the following important precautions:
•
Route all wiring and coaxial cables in a manner that maintains a minimal length of cable needed to
complete the required connections, while avoiding, (as much as possible) routing near noisy
environments such as power sources and circuits that carry or generate heavy current, 400 Hz
generators, trim motors, pulse transmitting equipment, or fluorescent lighting power sources.
•
For all wiring and coaxial cables, do not exceed the specified minimum bend radius and eliminate
any potential of sharp bends that exceed the minimum bend radius (refer to preceding paragraph
for additional cable recommendations).
•
Ensure that all wiring and coaxial cables are properly secured while avoiding the potential of
deteriorating the integrity of the insulation and jackets because of rubbing against the aircraft
structure, other installed equipment, or excessively tight cable ties.
•
Prior to connecting the fabricated wiring harness to the GRA 5500, verify correct routing of
aircraft power and aircraft power ground to the assigned pins and verify that aircraft power is
available at the assigned pins after routing verification.
GRA 5500 Installation Manual
Page 2-10
Appendix C
for wire gauge guidance. Use only wire, coaxial cable,
190-01277-00
Rev. A
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