Radar Range And Image Quality - Raymarine a67 Wi-Fi Installation And Operation Instructions Manual

2. Select Power up Radar to turn the radar on, or Power down
Radar to turn the radar off.
3. Select Radar: Tx to start the radar transmitting, or Radar:
Stdby to stop the radar transmitting.
162

16.4 Radar range and image quality

Maximum radar range
The usable range of the radar is limited by factors such as the
height of the scanner, and height of the target.
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:
a
1
1
R ma x = 2.23 (
Item
1
2
3
a
1
a
2
R
max
h
H
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 Target height
(meters) (meters)
3 3
3 10
5
3
5 10
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.
R ma x
a
2
2
h + H )
Description
Radar equipped vessel.
Curvature of the earth.
Target (Cliff).
Radar horizon of antenna.
Radar horizon of target.
Maximum radar range in nautical
miles.
R = a + a
max 1 2
Radar antenna height in metres.
Target height in metres.
Maximum range
(Nautical miles)
7.7
10.9
8.8
12
New a Series / New c Series / New e Series
3
D1643-4