2. HORIZONTAL MODE
2-9
2.6
How to Eliminate Weak Echoes
Echoes from targets such as bottom and fish return to the transducer in order of dis-
tance to them, and when we compare their intensities at the transducer face, those
from nearer targets are generally stronger due to little propagation attenuation and lit-
tle absorption. If these echoes are displayed directly on the screen, the size of the dis-
played echo from the same school of fish may change with distance, making it difficult
to judge the actual size of the school of fish. To overcome this inconvenience use the
TVG curve function. This function compensates for propagation loss of sound in water;
amplification of echoes on short range is suppressed and gradually increased as
range increases so that similar targets are displayed in the similar intensities irrespec-
tive of the ranges to them.
2.6.1
Change sensitivity of TVG curve
Four TVG curves are available and they vary the gain from large to small.
1. Press the
MENU/ESC
key to open the main menu.
2. Click [Gain Setting].
3. Press the
H/V/S
key to select the [H1] or [H2] tab.
4. Select [TVG Curve].
5. Click
S
or
T
to select a suitable Log value.
The smaller the number, the gentler the gain changes over
distance.
6. Click [Quit] on the setting box to close the box.
7. Long-push the
MENU/ESC
key to close all menus.
The TVG is also used to suppress unwanted echoes (sea surface
reflections, cruising noise, etc.) on near ranges. If the selected
curve does not provide satisfactory results, see section 2.6.2 for how to adjust the
near gain and far gain.
Gain Setting
Quit
H1 P1
H2 P1
V P1
TVG Curve
: 15Log
Near Gain
: 5.0
Near Gain Distance
: 400m
Far Gain
: 5.0
Far Gain Distance
: 400m
AGC Near
: 4.0
AGC Far
: 4.0
AGC Distance
: 20m
Noise Suppress
: 2.0
Noise Supp. (SHIP)
: 0.0
Quit
Cancel
(0~40Log)
15Log
Summary of Contents for FSV-2S
Page 1: ...COLOR SCANNING SONAR FSV 25 FSV 25S OPERATOR S MANUAL www furuno com Model ...
Page 14: ...SYSTEM CONFIGURATION xii This page is intentionally left blank ...
Page 74: ...2 HORIZONTAL MODE 2 44 This page is intentionally left blank ...
Page 92: ...4 NUMERIC GRAPHIC DATA DISPLAY 4 4 This page is intentionally left blank ...