Furuno FR-8251 Manual De Usuario

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

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.

 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.

  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.

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.

Echo stretch 2 is not available with the

short pulse.

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.

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.

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.