Description Of Radar; General; Minimum And Maximum Ranges - Furuno 1835 Operator's Manual

2.

DESCRIPTION OF RADAR

2.1

General

2.1.1

Minimum and maximum ranges

Minimum range
The minimum range is defined by the shortest distance at which, using a scale of
0.0625 or 0.125 nm, a target having an echoing area of 10 m
the point representing the antenna position.
The minimum range depends on the pulselength, antenna height, and signal process-
ing (like main bang suppression and digital quantization). Use a shorter range scale
as far as it gives favorable definition or clarity of picture. This MODEL 1835 series
meets the requirements of IEC 62252 5.14.1 (Class A).
Maximum range
The maximum detection range, Rmax, varies depending on the height of the antenna,
the height of the target above the sea, the size, shape and material of the target, and
the atmospheric conditions.
Under normal atmospheric conditions, the maximum range is equal or a little shorter
than the optical horizon. The radar horizon is longer than the optical one by approxi-
mately 6% because of the diffraction property of the radar signal. The Rmax is shown
in the following formula.
R = 2.2 x ( h1 + h2)
max
where R
max
h1: antenna height (m)
h2: target height (m)
If the height of the antenna is 9 m and the height of the target is 16 m, the maximum
radar range is;
R = 2.2 x ( 9 + 16) = 2.2 x (3 + 4) = 15.4 nm
max
Note: The detection range is reduced by precipitation (which absorbs the radar sig-
nal).
: radar horizon (nautical miles)
2
Radar horizon
Optical horizon
is shown separate from
2-1