Reference Manual Part 2

131 Chapter 11: Radar
Radar status
The following table summarizes the various scanner states and
associated status icons.
11.3 Radar range and image quality
Radar operates by transmitting radio pulses, then detecting the
reflections as the pulses bounce back from objects within radar
range. The reflections are processed and displayed on-screen as
‘echoes’.
Range
Radar range is limited by the height of your scanner and the height
of the target, as illustrated below:
The table below gives the approximate range for various antenna
and target heights.
Image quality
Not all radar echoes are produced by valid targets. Spurious ech-
oes may be caused by:
Status Icon Description
Transmit
(TX)
Scanner on and transmitting.
This is the usual mode of operation.
Standby
(STDBY)
Scanner powered on but not transmit-
ting; antenna not rotating.
This is a power-save mode used when
radar is not needed for short periods.
When you return to transmit mode, the
magnetron does not need to warm up.
This is the default mode.
Off Scanner powered off.
When radar is not required.
Timed
transmit
Scanner switches between on/trans-
mitting & standby mode.
Power save mode when constant use of
radar not required. To set up this option,
see page 131
D7440-1
(Rotating icon)
D6894-2
(static icon)
D7441-1
(grayed-out icon)
D7442-1
(rotating/static icon)
Antenna height
(m)
Object height
(m)
Range
(nm)
3 3 7.7
3 10 10.9
5 3 8.8
5 10 12
a
1
a
2
Earth
h
H
Cliff
Radar
D1643-3
R
max
R
max
= 2.23 ( h + H )
R
max
h
H
maximum radar range
radar antenna height
target height
in nautical miles
in metres
in metres
R
max
= radar horizon of antenna (
a
1
) + radar horizon of target (a
2
)