Furuno FSV-30, Operator'S Manual

Page: 87 / 190

3. VERTICAL MODE
3-7
3.7 Eliminating Weak Echoes
Echoes from targets such as bottom and fish return to the transducer in order of
distance to them, and when we compare their intensities at the transducer face,
those from nearer targets are generally stronger when their reflecting properties
are nearly equal. The sonar operator will be quite inconvenienced if these
echoes are directly displayed on the screen, since he can not judge the actual
size of the target from the size of echoes displayed on the screen. To overcome
use the TVG function. It 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
irrespective of the ranges to them.
The FSV-30 has three TVG functions, NEAR, MEDIUM and FAR, and they
mainly compensate for propagation loss on short, middle and long ranges
respectively, centered at the ranges as shown in the figure at the bottom of page
2-11. The higher the TVG setting the greater the amplification of echoes.
The TVG is also used to suppress unwanted echoes and noise which appear in
a certain range area on the screen such as sea surface reflections and cruising
noise. To set TVG properly, do the following:
1. Press the [MENU] key to open the main menu.
MENU QUIT
H-SCAN SETTING...
V-SCAN SETTING...
OTHERS...
TX PULSE LENGTH-H : 9
TX POWER-H
: 9
TVG-NEAR-H : 0
TVG-MEDIUM-H : 0
TVG-FAR-H : 0
AGC-H : 0
2ND AGC-H : 0
ECHO AVERAGE-H : 0
COLOR-H : COLOR 1
COLOR RESPONSE-H : COLOR CURVE 3
Main Menu
2. Select V-SCAN SETTING and press the [MENU] key.