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The table below shows typical maximum radar ranges for various
radar antenna heights and target heights. Remember that although
the radar horizon is greater than the optical horizon, the radar
can only detect targets if a large enough target is above the radar
horizon.
Antenna height
(meters) Target height
(meters) Maximum range
(Nautical miles)
3 3 7.7
3 10 10.9
5 3 8.8
5 10 12
Radar image quality
A number of factors can affect the quality of a radar image, including
echoes, sea clutter, and other interference.
Not all radar echoes are produced by valid targets. Spurious or
missing 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.
Side Lobes
Side lobe patterns are produced by small amounts of energy from
the transmitted pulses that are radiated outside the narrow main
beam. The effects of side lobes are most noticeable with targets at
short ranges (normally below 3 nm), and in particular with larger
objects. Side lobe echoes form either arcs on the radar screen
similar to range rings, or a series of echoes forming a broken arc.
D1638-5
1
2 2
3
4
5
6
6
Item Description
1 Main lobe
2
Side lobes
3 Antenna
4 Arc
5 True echo
6 Side echoes
138 e7 / e7D — User reference