Ameri-King AK-451-ELT - Manual (Page 34)

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Each of the above listed antennas requires a ground plane. On aircraft constructed
with non-conductive materials, such as composite or fiberglass, a ground plane must
be added. Ideally, the ground plane should extend out from the antenna mounting
point at least 24 inches in every direction. Many times this is not possible, but an
effective plane can be constructed as follow:
A 'doubler' layer of sheet metal, such as aluminum, can be mounted under the aircraft
skin. Alternatively, four or more 'radials' fastened to the underside of the fuselage
skin can be used to fashion a ground plane. Each radial can metallic type, 22 AWG
wire, etc. Tape should be at least 1 inch wide and each radial 24", minimum. The
ground plane connects to the shield of the RF antenna connector. Resistance between
the ground plane and shield connection should be maintained at 0.003Ω maximum. A
star washer should be used between the antenna connector housing and ground plane.
Take precautions to guard against corrosion, loosening, etc.
Ground Plane
On fabric-covered aircraft or aircraft with other types of nonmetallic skin, the
manufacturer’s recommendations should be followed in order to provide the
necessary ground plane. An acceptable method of accomplishing this is by providing
a number of metal foil strips in a radial position from the antenna base and secured
under the fabric or wood skin of the aircraft See diagram below:
Figure 5: - Antenna ground plane for nonmetallic aircraft
Note: THE LENGTH OF EACH FOIL RADIAL SHOULD BE AT LEAST
EQUAL TO THE ANTENNA LENGTH.
An effective, light-weight, ground plane formed from radial strips of copper foil. A
doubler may be required to reinforce the installation for resistance to impact,
vibration, ice, washing, etc. and can serve as connection points for the radials.
Specific antenna installation instructions follow. Also, AC 43.13-2B, paragraph 310
provides additional guidance for antenna installations.