Furuno CSH-23 - Manual (Page 28)

3-2
4. When sea surface reflections or plankton layers disturb the
picture, decrease appropriate TVG option by one or two steps
by pressing – (minus) key.
5. When fish school is located on a long range setting (about
800 meters) which is approaching own ship.
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 ar-
eas, 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 re-
sults, the TVG curve can be changed on the SYSTEM menu.
The 30 log setting is normal. The 25 log setting is useful for
searching fish schools near shorelines or shallow waters. The 35
log or 40 log setting raises the gain on a long range and is suit-
able for searching tuna, bonito, etc., which are usually searched
with high gain setting.