JMA-9100 Instruction Manual > 6.TRUE AND FALSE ECHOES ON DISPLAY > 6.4 FALSE ECHOES
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For instance, assuming that the pulse length is MP3 (on the repetition frequency
of 1400 Hz), the first pulse is reflected from a target at about 58 NM or more and
received during the next pulse repetition time. In this case, a false echo (second
time echo) appears at a position that is about 58 NM shorter than the actual
distance. If the false echo appears at 5 NM on the radar display, the true distance
of the target is 5+58=63 NM. On the pulse length is SP1 (on the repetition
frequency of 2250 Hz), a false echo may appear at a position that is about 36 NM
shorter than the actual distance.
This type of false echo can be discriminated by changing over the range scale (the
repetition frequency), because the distance of the target changes accordingly.
If second time echo is appeared, the use of Economy mode in PRF menu is
effective. Otherwise, Stagger Trigger menu set to on. (See Section 3.8.3 "Set
Scanner Unit (TXRX Setting)").
f. Radar Interference
When another radar equipment using the same frequency band as that on own ship
is near own ship, a radar interference pattern may appear on the radar display.
This interference pattern consists of a number of spots which appear in various
forms. In many cases, these spots do not always appear at the same places, so that
they can be discriminated from the target echoes. (See Fig 6-9)
Fig 6-9: Radar interference
If radar equipment causing an interference pattern and this radar are of the same
model, their transmitting repetition frequency is nearly the same. As a result,
interference patterns may be displayed concentrically.
In this case, the interference patterns cannot be eliminated by using only the
interference reflector function, so ine-tune the transmitting repetition
frequency.(See Section 3.8.3 "Set Scanner Unit (TXRX Setting)")
An interference suppressing effect can be heightened by applying a different
transmitting repetition frequency to the interference pattern source radar and this
radar.
HL HL
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