3. VERTICAL MODE

When a fish school is located on a long-range setting (about 800 meters) and is approaching own ship do as follows:

Adjust the tilt to keep the fish school in the center of the sonar beam, namely, fish school is displayed in strongest colors possible. Confirm that the fish echo is displayed in the same color as it approaches. If the color suddenly changes to weaker colors as the fish enters MEDIUM and NEAR areas, the TVG is improperly set. Adjust the TVG. If this again produces sea surface reflections and noise try to remove them with AGC and NL controls.

Note: If the above procedure does not produce satisfactory results, the TVG curve can be changed on the V-SCAN SETTING menu. Also refer to section 3.8.4 “Adjust Near AGC”.

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Furuno FSV-84 manual Vertical Mode