4. ECHO SOUNDER MODE
4-4
4.6 How to Adjust the Picture
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.
If these echoes are displayed directly on the screen, the size of the displayed 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 function. It compensates for propaga-
tion 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 appears in a
certain range area on the screen.
4.6.1 How to adjust the TVG for echo sounder mode
1. Press the MENU key to open the menu.
2. Press S to select the menu bar.
3. Press X or W to select [ES].
4. To reduce reflections from the sea surface or plankton, press T to select [TVG
Level] ([TVG Level-LF]/[TVG Level-HF] on CH-600), then press X to show the
[TVG Level] settings.
5. Press X or W to adjust the TVG level. Ideally, a setting between 2.0 and 5.0
should be sufficient. A larger setting reduces the gain over distance.
As the setting is adjusted, the current setting is shown in a dashed line and the
level indication changes to show the new setting.
200m
TVG Level
Gain
Hi
Lo
4. 0
Current setting
New setting
TVG Level
indication
changes to
show the
new setting.
200m
TVG Level
Gain
Hi
Lo
4. 0
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