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SMR-3600
50
5. Basic knowledge in observation
5-1. Scanning range and target
•
The maximum range to targets that can be scanned by radar is influenced by the
transmission output power, antenna beam width, receiving sensitivity and its performance
as well as by other factors as follows;
•
The height of targets, the distance to targets and the height of radar antenna have an
influence on the maximum scanning ranges, too.
This is because the electric wave that is launched from radar goes straight without almost
zero influence by the curve of the earth.
For example, if the antenna is 3 meters high away from the sea surface, 10 meters high-
islands that are located 10 miles away from the position are displayed on the screen but 5
meters high islands are not displayed at the same distance. These values are the
theoretical values, not consistent depending on the conditions such as weather.
Theoretically, more than 7.6 meters’ height is required for targets that are 10 miles away
but targets that are lower than that are not displayed on the screen. So pay sufficient
attention.
The actual maximum scanning range of radar is related to straight sight.
The following formular shows the limitations of scanning distance, depending on the
height of radar antenna and the height of targets.
R
max
(Max.Scan Range)= 2.23(
√
h +
√
H)
h = Antenna height
H = Target height
•
Reflection from targets
As the strength of reflection from targets are related to the sizes of targets and to the
elements and images of the targets, we cannot say that only the reflection from big targets
is strong. If the coastal lines are flat, only the mountains or bays of the inland may be seen
on the image screen, depending on the geographical conditions of the coastal lines.
Therefore, the image should be used to measure the distance to the coastal lines.
•
Wave route status
Sometimes it is impossible to scan the targets behind as the wave is blocked by mountain,
rain and snow being on the wave route.
Summary of Contents for SMR-3600
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