
Garmin G1000 Cockpit Reference Guide for the DA42
190-00406-05 Rev. B
10-12
SECTION 10 – HAZARD
AVOIDANCE
10.7 AIRBORNE COLOR WEATHER RADAR
(OPTIONAL)
Weather Radar Basics
Antenna Beam Illumination
It is important to understand the concept of the
antenna beam illumination. The radar beam is much like
the beam of a spotlight. The farther the beam travels, the
wider it gets. The radar is only capable of “seeing” what is
inside the boundaries of the beam.
80
Altitude (x1000 ft.)
Range (nautical miles)
Antenna at Zero Tilt
Half Power at Bea
m Sidelobes
18,000 ft.
18,000 ft.
Max Power at Beam Center
9°
0
300
45
60 75
90
15
Figure 10-19 Radar Beam from 10 inch Antenna
Figure 10-20 Radar Beam in Relation to the Curvature of the Earth
Figure 10-19 depicts a radar beam’s characteristics.
The figure illustrates vertical dimensions of the radar
beam, although the same holds true for the horizontal
dimensions. In other words, the beam will be as wide
as it is tall. Note that it is possible not to see areas of
precipitation on the radar display because of the antenna
tilt setting. With the antenna tilt set to zero in this
illustration, the beam overshoots the precipitation at 15
nautical miles. The curvature of the earth can also be a
factor, especially at range settings of 150 nautical miles or
more ( Figure 10-20).
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