Installation Instructions

Beam width

A beam width is defined as the width of the main lobe at an angle where the radi-

ated power is halved as measured from the position from which the strongest radio

wave is radiated.

2.2 Characteristics of Radar Wave

Radio waves from the radar propagate while bending slightly along the terrestrial sur-

face. This characteristic varies dependent on the density of the atmospheric air. The sight

distance D of a radar generally is said to be approximately 6% longer than the optical sight

distance and is calculated using the equation below :

D (NM) = 2.22 ( h1 + h2 ) where, h1= antenna height in meters

h2= target height in meters

Fig.2-3 Radar wave

Targets difficult to display on screen

The intensity of the reflected wave from a target depends on the distance, height,

and size of the target, as well as its material and shape. Targets constructed with

FRP, wood, or other low-reflectance materials or those that have a small incident angle

are difficult to display on a screen. Therefore, FRP and wooden ships, sandy beaches,

and sandy or muddy shallows all are difficult to catch and require attention when

monitoring on the screen. Especially, coast lines on the radar image appear to be pre-

sent more apart from the ship than they are actually located. Therefore, it is important

not to misinterpret the available data.

Shadow zones of radar

Radar waves are characteristic in that they propagate straight ahead. Therefore,

if the ship's smokestack or mast is located near the antenna or there is a tall ship or

mountain at the side of the ship, such an object generates a shadow behind it. In this

Apparent coastline

Actual(invisible)

coastline

Invisible

Visible

Fig.2-4 Targets difficult to display on screen

h1 h2

Line of sight

Radar Radio

Wave

Earth