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4. ECHO SOUNDER MODE
4-7
4.9 Range Marker
The range marker functions to measure the range to a target echo (fish school, bottom, etc.)
1. Operate the Omnipad to place the cursor on the location desired.
2. Press the R/B key to display the range marker. The range marker appears along with
range indication.
3. To erase the range marker, press the R/B key again, or place the cursor on the range
marker and press the R/B key.
Range
NAV
DATA
or
A-SCOPE
DISPLAY
Depth, Water Temp. Display
67
Range marker
Range marker
4.10 Adjusting the Picture
4.10.1 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 appears 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 ES menu.