Changing The Range; Determining Actual Radar Range - Raymarine SL70M Owner's Handbook Manual

Chapter 3: Standard Radar Operations

Changing the Range

RANGE
Figure 3-1:
➤ Each time you press the RANGE key, the range changes to the next available
setting. The system will beep three times if no further range scale is available.
➤ To change the range quickly, press and hold the required arrow on the RANGE
key.
The range scale and range ring interval indicators, at the left-hand end of the
status bar, are updated whenever you change the range.

Determining Actual Radar Range

The actual maximum radar range is essentially line-of-sight, and is limited by
the height of the scanner and the height of the target as shown in Figure 3-1.
Table 3-2 lists some range examples:
Figure 3-2:
Table 3-2:
Antenna Height (m)
3
3
5
5
Note: The ranges shown in the table are theoretical maximum ranges. The ra-
dar horizon is greater than the optical horizon, but the radar can only detect
targets if a large enough target is above the radar horizon.
Increases
the range scale
Decreases
the range scale
Changing the Radar Range
a
1
Radar
R max = 2.23 (
R max maximum radar range
h radar antenna height
H target height
R max = radar horizon of antenna (
Determining Radar Range
Radar Range
Target Height (m)
3
10
3
10
Selected Range ring
range scale spacing
6nm
Status Bar
R max
a
2
Earth
h + H )
in nautical miles
in metres
in metres
a
) + radar horizon of target (
1
Maximum Range (nm)
7.8
10.9
8.9
12.0
3-3
343°T
D3939_1
Cliff
a
)
2
D1643-2