GA 35, GA 36, and GA 37 Antenna Installation Instructions
Page 2-5
190-00848-00
Revision A
2.3
Antenna Grounding
Antenna grounding is necessary for optimum antenna performance. The antenna performance is also
dependent on the size of the ground plane. The aircraft skin provides the appropriate ground plane in
metallic aircraft for antenna performance and lightning protection. Additional guidance is provided
below.
2.3.1
Ground Plane
For optimum antenna performance, a metallic ground plane or skin sized at least 7.5 inches beyond the
perimeter of the antenna is recommended. If ground plane is added to the aircraft, round its edges to be as
circular as practical for best performance.
2.3.2
Electrical Bonding
It is important that the antenna baseplate is electrically bonded to the aircraft ground plane. 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 structure local to
where the equipment is mounted. Measure the electrical bonding resistance using a calibrated milliohm
meter. An equivalent OEM procedure may also be substituted.
Typically it is not necessary to remove paint under the footprint of the antenna on the metal skin of the
aircraft to achieve a good electrical bond. The painted surface prevents corrosion and should be left intact
if possible. If paint removal is necessary for bonding, be careful to avoid excessive chipping or cracking
beyond the antenna baseplate, to prevent corrosion. The resistance of 2.5 milliohms can usually be
achieved through the antenna mounting screws which attach to the antenna doubler.
To measure the antenna bonding resistance, perform the following steps:
1.
Disconnect coaxial cable(s) from the antenna connector(s).
2.
Measure the resistance between the antenna connector body and a nearby exposed portion of
conductive aircraft structure (e.g. a nearby exposed rivet on fuselage stringer).
3.
The measured resistance should be equal to or less than 2.5 milliohms.
Summary of Contents for GA 35
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