JRC JMA-5104, Инструкция по эксплуатации, Страница: 139 / 242

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Take the following into consideration when selecting the installation location:
(1) Consider the weight of the scanner unit and decide what height it can be raised for
installation in the ship.
(2) Height at which the scanner unit is installed has to do with the maximum detectable range,
the higher its position is the better. On the other hand, however, if raised too high, at a point
beyond the beam width (-3 dB position) along the vertical direction radio wave energy will be
affected noticeably, making it difficult to spot targets lying very near.
When installing the unit, consider its weight, longest permissible cable length, and the
requirements during future maintenance.
Refer to 4.1, "Height of and the Distance to the Target" for the relation between the height of
the scanner unit and maximum detectable range.
(3) If the width of the radiated beam is 2 θ (most energy is concentrated within this width), then
the energy reduces considerably in directions outside the 2 θ range. Thus, if the scanner unit
is raised too high it will be difficult to spot targets lying very close-by. If, on the other hand,
the scanner unit is installed low, it will be obvious to miss distance targets, and the ship's
mast derrick, funnel, etc. will intercept the radiated beams, making most of your targets
unobservable. In general, the lowest position of the scanner unit should be as shown by the
line AB in the following figure. For example, angle 2
θ is 20 ˚ for the radar of JMA-5110.
Normally, when deciding the height of the scanner, it is necessary to make sure that the
ship's mast does not obstruct the beams.
B
A
2 : Vertical beam width
=12.5°
Lowest Position of Scanner Unit
(4) When selecting the position of the scanner along the length of the ship, make sure that the
shading caused by the ship's mast on the radio waves does not coincide with the ship's center
line. If the ship has no large obstruction towards front, normally the scanner is placed on
top of the steering room along the ship's center line.
(5) Avoid placing DF (direction finder) of VHF (communications) antenna near the scanner as
these will interfere with the radiated waves.
(6) Soiling of the radiating surface of the scanner by the smoke from funnel affects radar
performance, clean the radiating surface form time to time. To facilitate maintenance, place
the scanner in the right position and use mast and tower of the right structure.
(7) Note that, if placed near ship's flag or rope may cause by wind to wrap or coil around the
radiator and damage it.
(8) Do not select the derrick post as the location for scanner installation. The derrick post is
subject to large vibrations.