Furuno FR-2105-B - Manual (Page 15)

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Category of Equipment Units
Display unit (Monitor, Processor unit, Control unit)
To be installed in a Protected area
Power supply unit To be installed in a Protected area
RF Transceiver unit To be installed in a Protected area
Antenna unit To be installed in an Exposed area
Performance Monitor To be installed in an Exposed area
Precautions for high speed targets
! Assume your ship is making 40 kt and a target ship is approaching at 40 kt right toward you.
Then the relative speed is 80 kt. With the antenna revolving at 42 rpm, the target blip
appears jumping to a new location 59 m nearer. This jump corresponds to 19 mm on the
300 mm display using the 0.25 nm range scale. On such a short range you may lose the
track of target in the midst of sea clutter, random noise or other targets. Use one step larger
range scale.
! ARPA can fail to track a target when the relative speed exceeds 100 kt.