JRC JMA-3400 Series, Instruction Manual, Page: 61 / 314

Chapter 1 INSTALLATION
13
„
ELECTRICAL SELECTION CRITERIA
z
The installation height of the scanner relates to the maximum detection distance.
The higher, the better. However, if it is too high, radio wave energy greatly attenuates
above the scanner's vertical beam width (the point -3 dB from the peak of the main-lobe).
As a result, it is difficult to detect a close-in target. Sea clutter also increases.
Determine the installation height by taking into consideration the weight, maximum
length of the cable, and maintenance after installation. If the installation height of the
scanner is low, it is difficult to detect a long distance target. The ship's mast, derrick,
and chimney interfere with radiating beam causing the range that cannot be viewed
on the radar display to increase.
1.3.2 LOWEST SCANNER INSTALLATION HEIGHT
Generally, the lowest scanner installation position is supposed to be on the A-B line shown in Fig. 1-3-2.
In the case of the JMA-3400 series radar, 2
ș
equals 20°.
Specifically, the scanner position is normally elevated so that the chimney and the shrine-gate type mast do
not interfere with radiating beam.
JMA-3400 :
ș
= 10 ° (2
ș
= 20 °)
Fig. 1-3-2