Raymarine Pathfinder Radar RL70C PLUS User Manual
Chapter 3: Standard Radar Operations
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Identifying False Echo Returns
Not all echoes are direct returns to the radar antenna. Occasionally signals
appear at positions where there is no actual target. These are called false
echoes, and may be caused by side lobes, ghost images, indirect echoes or
multiple echoes.
appear at positions where there is no actual target. These are called false
echoes, and may be caused by side lobes, ghost images, indirect echoes or
multiple echoes.
This section briefly describes the echo patterns that can be produced by false
echoes and the likely cause. It should be noted that the radar operator, through
observation, practice, and experience, can generally detect these conditions
very quickly. These effects can usually be minimized using the radar controls.
echoes and the likely cause. It should be noted that the radar operator, through
observation, practice, and experience, can generally detect these conditions
very quickly. These effects can usually be minimized using the radar controls.
Side Lobes
A small part of the RF energy from each transmitted pulse is radiated outside
the single narrow beam. This produces side lobe patterns, shown in
Figure 3-3.
the single narrow beam. This produces side lobe patterns, shown in
Figure 3-3.
Side lobes have no effect on distant or small surface objects. However, the
echo from a large object at short range may produce an arc on the radar screen
similar to a range ring or a series of echoes forming a broken arc. Side-lobe
echoes normally occur at ranges below 3nm, and can be reduced by adjusting
the SEA control.
echo from a large object at short range may produce an arc on the radar screen
similar to a range ring or a series of echoes forming a broken arc. Side-lobe
echoes normally occur at ranges below 3nm, and can be reduced by adjusting
the SEA control.
Figure 3-3:
Side Lobes
Table 3-3:
Controls to Adjust the Radar Picture
Control
Option
Function
Default Setting
GAIN
GAIN
SEA
RAIN
FTC
SEA
RAIN
FTC
Controls the strength of the target returns
Reduces sea returns
Reduces close rain or snow returns
Reduces distant rain or snow returns
Reduces sea returns
Reduces close rain or snow returns
Reduces distant rain or snow returns
AUTO
AUTO-HARBOUR
OFF
OFF
AUTO-HARBOUR
OFF
OFF
MULTI
TUNE
Fine tunes the receive
AUTO
TARGETS
Soft Key
Soft Key
INT REJ
EXPANSION
WAKES
EXPANSION
WAKES
Turns interference rejection on/off
Turns target expansion on/off
Turns wakes on/off and selects wakes length
Turns target expansion on/off
Turns wakes on/off and selects wakes length
ON
OFF
OFF
True echo
Side echoes
Main lobe
Antenna
Arc
Side lobe
Side lobe
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