Furuno 1833C Manuel D’Utilisation

2. RADAR OPERATION 
 
 

 

The minimum range is defined by the shortest distance at which, using a scale of 
1.5 or 0.75 nm, a target having an echoing area of 10 m

2

 is still shown separate 

from the point representing the antenna position. It is mainly dependent on the 
pulselength, antenna height, and signal processing such as main bang 
suppression and digital quantization. It is best to use the shortest possible range 
as long as the clarity and definition of the picture remain good. 
 
Maximum range 

The maximum detecting range of the radar, Rmax, varies considerably 
depending on several factors such as the height of the antenna above the 
waterline, the height of the target above the sea, the size, shape and material of 
the target, and atmospheric conditions. 
 
Under normal atmospheric conditions, the maximum range is equal to the radar 
horizon or a little shorter. The radar horizon is longer than the optical one by 
about 6% because of the diffraction property of the radar signal. Rmax is given 
in the following equation. 

R

max

= 2.2 x ( h1  +  h2  )

 

where       

Rmax:  radar horizon (nautical miles) 

 

        h1: 

antenna height (m) 

                          h2: 

target height (m) 

Radar horizon

Optical horizon

For example, if the height of the antenna above the waterline is 9 meters and the 
height of the target is 16 meters, the maximum radar range is; 

R

max

= 2.2 x ( 9 + 16  ) = 2.2 x (3 + 4) = 15.4 nm

 

 
It should be noted that the detection range is reduced by precipitation (which 
absorbs the radar signal).