Raymarine E120W, Reference Manual

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142 E-Series Networked Display Reference Manual
Maximum radar range
Maximum radar range is essentially line-of-sight, so is limited by the height of the
scanner and the height of the target as illustrated below:
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.
Factors impairing a radar picture
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) Target height (m) Maximum range (nm)
3 3 7.7
3 10 10.9
5 3 8.8
5 10 12.0
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
)