Furuno CH-270 - Manual (Page 66)

3. VERTICAL SCAN MODE
3-12
3.11 Adjusting the Picture
3.11.1 Displaying weak echoes clearly
Echoes from targets (such as the bottom or a fish) return to the transducer in order of the
distance to them, and when their intensities are compared 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 won’t be able to judge the actual size of the target from the size of
echoes displayed on the screen. To overcome this inconvenience, 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 similar intensities irrespective of the ranges to them.
The TVG also functions to suppress unwanted echoes and noise which appear in a certain
range area on the screen.
To adjust TVG:
1. Press the [MENU] key to open the menu.
2. Press ▲ to choose MENU and then press ◄ or ► to choose the VERT menu.
TVG LEVEL 4.0
TVG DISTANCE 4.0
GAIN ADJUST 0
RES. COLOR LOG
CLUTTER 0
HORZ RANGE x1
: SELECT : CHANGE MENU: END
MENU COM1 VERT ES PRESET SYS COM2 HORZ
VERT menu
3. Press ▲ or ▼ to choose TVG DISTANCE and then press ► to show the following
dialog box.
4.0
200m
TVG DISTANCE
Hi
Lo
GAIN