4. SLANT MODE
4-7
4.7 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. It compensates for propagation loss of sound in water; amplifica-
tion of echoes on short range is suppressed and gradually increased as range increas-
es so that similar targets are displayed in the similar intensities irrespective of the
ranges to them.
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. Select [Gain Setting] then push the left-click button.
3. Press the H/V/S key to select the [S] tab.
4. Select [Sel. TVG Curve] then push the left-click button.
5. Select a curve then push the left-click button.
The smaller the number, the gentler the gain change over distance.
6. Select [Quit] on the setting window then push the left-click button to close the box.
7. Long-press 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 satis-
factory results, try to adjust [TVG-Near], [TVG-Medium] or [TVG-Far], as shown
below.
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