Furuno FMD-8010 - Manual (Page 28)

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The interference rejector circuit is a kind of sig-
nal correlation circuit. It compares the received
signals over successive transmissions and sup-
presses randomly occurring signals. There are
three levels of interference rejection depending
on the number of transmissions that are corre-
lated. These are indicated by the legends IR1, IR2
and IR3 at the bottom right-hand position of the
screen.
To turn on or off the interference rejector circuit;
1) Press the MENU key.
2) Select ECHO SIG and press the ENTER/SE-
LECT key.
3) Select INTRF and press the ENTER/SELECT
key.
4) Select level of suppression desired (higher the
number the greater the suppression) and press
the ENTER/SELECT key.
5) Press the MENU key.
Figure 1-19 Radar interference
1.25 Echo Trails
Echo trails are simulated afterglow of target ech-
oes that represent their movements relative to own
ship or true movements with respect to land, in a
single tone or gradual shading depending on the
setting on the TRAIL menu.
True or relative trails
You may display echo trails in true or relative
motion. Relative trails show relative movements
between targets and own ship. In the true mo-
tion, the moving targets have trails according to
their speeds, but stationary targets stay still.
True motion trails require a gyrocompass signal
and own ship speed input to cancel out own ship's
movement and present true target movements in
accordance with their over-the-ground speeds and
courses (not heading). Refer to the automatic and
manual speed input procedures for entering own
ship's speed information.
True trails Relative trails
Figure 1-20 True and relative echo trails
Note: If the true trail is selected on the stabilized
RM (CU, NU), targets whose extensions hit own
ship are not always on a collision course.
Starting echo trail
Press the ECHO TRAIL key to start the echo trail
function. “REL (or TRU) TRAIL”, the echo trail
time selected (on the TRAIL menu) and elapsed
time appear at the top right-hand corner of the
display. Then, afterglow starts extending from all
targets.
Canceling echo trail
Press the ECHO TRAIL key to erase echo trails
and echo trail indications.
Trail time
Trail time can be selected on the TRAIL menu.
1) Press the MENU key.
2) Select the TRAIL menu.
3) Press the ENTER/SELECT key.
4) Select TIME and press the ENTER/SELECT
key.
5) Select trail time among 15 seconds, 30 sec-
onds, 1, 3, 6, 15, 30 min, or continuous (99
minutes 59 seconds).