Furuno FR-8111 - Manual (Page 41)

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1.32 Echo Stretch
On long ranges target echoes tend to shrink in
the bearing direction, making them difficult to
see. On short and medium ranges such as 1.5, 3
and 6 nm range scales, the same sized targets get
smaller on screen as they approach own ship.
These are due to the inherent property of the ra-
diation pattern produced by the antenna. To en-
hance target video, use the echo stretch feature.
+
If a distant target
is hard to see,
use ES 2.
Enlarged in range
direction by ES 2
ECHO STRETCH 2
Forstretching echoes near
perimeter of CRT ECHO STRETCH 1
For stretching echoes
near own ship
+
If a target becomes
smaller as it approaches
own ship, use ES 1.
Enlarged by ES 1
Figure 1-27 Echo stretch
1) Press the MENU key.
2) Select the ECHO SIG menu and press the
ENTER/SELECT key.
3) Select STRETCH and press the ENTER/SE-
LECT key.
4) Select 1 2, or OFF.
5) Press the ENTER/SELECT key followed by
the MENU key.
Note 1: Echo stretch magnifies not only small
target pips but also returns from sea surface, rain
and radar interference. For this reason, make sure
that these types of interference have been suffi-
ciently suppressed before activating the echo
stretch feature.
Note 2: If the 1.5 nm range is preset for
pulselength SP (0.08
µ
s) or M2 (0.3
µ
s), and the
3 nm scale for M1 (0.3
µ
s), the echo stretch fea-
ture is not available on these range scales.
Note 3: Suppress sea clutter and noise before
activating echo stretch, since the echo stretch cir-
cuit stretches not only target echoes but also sea
clutter and noise.
Note 4: Echo stretch 2 is not available with the
short pulse.
1.33 Noise Rejection
White noise can be suppressed by turning on N
REJ on the ECHO SIG menu.
1) Press the MENU key.
2) Select the ECHO SIG menu.
3) Press the ENTER/SELECT key.
4) Select N REJ and press the ENTER/SELECT
key.
5) Select ON.
6) Press the ENTER/SELECT key.
7) Press the MENU key.
1.34 Selecting Pulselength
Pulselength can be selected on the ranges between
0.75 and 24 nautical miles, on the menu.
Pulselengths available are a short pulse, two me-
dium pulses, and a long pulse.
Presetting pulselength
Two sets of pulselengths can be preset on the
ECHO SIG menu: P/L SET 1 and P/L SET 2.
1) Press the MENU key.
2) Select the ECHO SIG menu.
3) Press the ENTER/SELECT key.
4) Select P/L SET 1 (or P/L SET 2) and press the
ENTER/SELECT key.
5) Select pulselength and press the ENTER/SE-
LECT key.
6) Select P/L SET 2 (or P/L SET 1) and press the
ENTER/SELECT key.