Blind And Shadow Sectors; Target Resolution - Icom MR-1000RII Instruction Manual

■ Blind and Shadow sectors

Blind or Shadow sectors may exist because of obstruc-
tions such as masts, derricks or other metal objects.
An obstruction may throw either a complete or partial
shadow as shown in the diagram below. If a target is
in a shadow sector, target echoes may not appear on
the screen.
Shadow sector
Mast or
similar
obstruction

■ Target resolution

Target resolution is determined by the horizontal beam
width and transmit pulse width. Sometimes it is difficult
to detect two targets which are separated by short dis-
tances or which are in the same direction.
D Distance resolution
When two targets are separated by more than the
pulse width, they appear as two echoes.
When two targets are not separated by more than
the pulse width, they appear as 1 echo.
Target 2
Target 1
Transmit Echoes
pulse
Target 1,2
Transmit Echo
pulse
When tall and massive targets such as a large island
are located at close range also shadowed without pro-
ducing any echoes. This phenomenon is called blind
sector. It is very important to know the bearings and
widths of all shadow sectors caused by your own
ship's obstructions.
Blind sector
Your ship
D Direction resolution
When two targets are separated by more than the
horizontal beam width, they appear as two echoes.
When two targets are not separated by more than
the horizontal beam width, they appear as one
echo.
Target 1
Scanner
Target 2
Scanner
Target 1, 2
BASIC RADAR THEORY
Large
Small
island island
Target 1
Target 1
Target 2
Target 2
Target 1
Target 2
Target 1, 2
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