Garmin GRA 5500 Installation Manual page 20

8. Relative Antenna Spacing (Single System): The two antennas must be spaced apart a minimum
distance of 20 inches (center to center). They must be spaced a maximum distance apart of not
more than their equivalent distance to the ground while parked, taxiing, or at aircraft touchdown
(whichever is less). The absolute maximum spacing is 6 feet (regardless of touchdown, taxiing, or
parked height). For example, if the antenna distance to the ground at touchdown is 36 inches and
when parked is 30 inches, then the antenna spacing must not be more than 30 inches. Ideally, the
antennas would be spaced halfway between the given minimum and maximum constraints for the
aircraft.
9. Dual System Additional Guidance: Each individual system within a dual system installation must
first conform to the constraints of a single system. In addition, a dual system installation must
conform to an end-to-end configuration (as shown in
configuration (as shown in
center) minimum spacing between systems with no limit on maximum spacing. The side-by-side
configuration requires 5 inches (center to center) minimum spacing between systems with
maximum spacing limited by the 35° angle as shown. For example, if the spacing between TX1
and RX1 is 30 inches, then the spacing between RX2 and RX1 must not be more than 30 inches
multiplied by the tangent of 35° (approximately 21 inches). The angular limit is necessary because
unwanted signal leakage between TX to RX increases rapidly as the end-to-end antenna
orientation transitions toward a pseudo side-to-side orientation (TX to TX and RX to RX antenna
spacings are not vulnerable to this leakage). It is essential that functional antenna numbering
assignments (e.g. – TX1, RX2, etc.) are used during planning and installation in order to avoid
confusion.
10. Triple System Additional Guidance: Each individual system within a triple system installation
must first conform to the constraints of a single system. In addition, a triple system installation
must conform to an end-to-end configuration (as shown in
side configuration (as shown in
The end-to-end configuration requires 5 inches (center to center) minimum spacing between
systems with no limit on maximum spacing. The side-by-side configuration requires 5 inches
(center to center) minimum spacing between systems with maximum spacing limited by the
overall 35° angle as shown. The hybrid configuration requires the minimum distances and
maximum angles shown. It is essential that functional antenna numbering assignments (e.g. –
TX1, RX2, etc.) are used during planning and installation in order to avoid confusion.
190-01277-00
Rev. A
Figure 2-3). The end-to-end configuration requires 5 inches (center to
Figure 2-3), or a hybrid configuration (as shown in
Figure 2-1 or Figure 2-2)
Figure 2-1 or Figure
GRA 5500 Installation Manual
or a side-by-side
2-2), a side-by-
Figure 2-4).
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