Furuno FR-1710, Operator'S Manual

Page: 24 / 78

1-10
1.13 Pulselength, Echo Stretch
The ECHO control selects pulselength, and
echo stretch when it is not turned on with a
user key ([F1], [F2], [F3]). The pulselength in
use is displayed at the upper-left position of
the screen using the abbreviations (suffixed
with “P”) shown in the table on the next page.
Echo stretch level (ES1, ES2) in use appears
at the bottom left position, using the indica-
tion ES1 or ES2.
Appropriate pulselengths are preset to indi-
vidual range scales and function keys. There-
fore, you are not usually required to select
them. If you are not satisfied with the current
pulselength settings, however, it is possible
to change them by the ECHO control. The
ECHO control settings which can select the
echo stretch are shown in the table below.
The legend and pulselengths are shown in
below.
5 2 7 1 / 0 1 7 1 - R F S D 0 6 7 1 - R F
s µ 7 0 . 0 : P 1 S s µ 8 0 . 0 : P S
s µ 5 1 . 0 : P 2 S s µ 3 . 0 : P 1 M
s µ 3 . 0 : P 1 M s µ 6 . 0 : P 2 M
s µ 5 . 0 : P 2 M s µ 2 . 1 : P L
s µ 7 . 0 : P 3 M
s µ 2 . 1 : P L
On long ranges target echoes tend to shrink
in the bearing direction, making them diffi-
cult to see. On short and medium ranges such
as 1.5, 3 and 6 nm scales, the same size
targets get smaller on screen as they ap-
proach the own ship. These are due to the
inherent property of the radiation pattern of
the antenna. To enhance target video, use
the echo stretch function. There are two
types: echo stretch 1 (ES1) to enlarge in bear-
ing direction for long range detection, and
echo stretch 2 (ES2) to enlarge in range di-
rection.
Note: The echo stretch magnifies not only
small target pips but also returns (clutter) from
sea surface, rain and radar interference. For
this reason make sure these types of inter-
ference have been sufficiently suppressed
before activating this function.
+
If a distant target
is hard to see,
use ES 1.
+
If a target becomes
smaller as it approaches
own ship, use ES 2.
Enlarged with ES2
Enlarged in bearing
(circumferential)
direction with ES1
Figure 1-10 Echo stretch