Chapter 8: Using the Radar (Digital)
187
8.4 Radar range and image quality
Radar operates by transmitting radio pulses, then detecting the reflections as the
pulses bounce back from objects within radar range. The reflections are processed
and displayed on-screen as ‘echoes’.
Range
Radar range is limited by the height of your scanner and the height of the target, as
illustrated below:
The table below gives the approximate range for various antenna and target
heights.
Image quality
Not all radar echoes are produced by valid targets. Spurious echoes may be caused
by:
• Side lobes
• Indirect echoes
• Multiple echoes
• Blind sectors
• Sea, rain or snow clutter
• Interference
Through observation, practice, and experience, you can generally detect these
conditions very quickly and use the radar controls to minimize them.
Antenna height
(m)
Object height
(m)
Range
(nm)
3
3
7.7
3
10
10.9
5
3
8.8
5
10
12
a
1
a
2
Earth
h
H
Cliff
Radar
D1643-3
Rmax
Rmax = 2.23 ( h + H )
Rmax
h
H
maximum radar range
radar antenna height
target height
in nautical miles
in metres
in metres
Rmax = radar horizon of antenna (
a
1
) + radar horizon of target (
a
2
)
81244_4.book Page 187 Thursday, January 31, 2008 1:53 PM
