How To Suppress Unwanted Echoes; How To Suppress Bottom And Sea Surface Reflections In Shallow Waters - Furuno FSV-25S Operator's Manual

2. HORIZONTAL MODE
2.7.3

How to suppress unwanted echoes

This sonar's noise suppressor removes weak echoes such as sea surface reflections
and echoes from plankton. Because the noise suppressor does not work against
strong echoes it is useful for detecting schools of fish.
1. Press the MENU/ESC key to show the main menu.
2. Click [Gain Setting].
3. Press the H/V/S key to select the [H1] or [H2].
4. Click [Noise Suppress] to show the setting box.
5. Click
The higher the setting, the higher the degree of suppression.
6. Click [Quit] to close the box.
7. Long-push the MENU/ESC key to close all menus.
2.8 How to Suppress Bottom and Sea Surface
Reflections in Shallow Waters
In shallow fishing grounds with hard or rocky bottom, bottom reflections often interfere
with wanted fish echoes and they can not be eliminated sufficiently with the aforemen-
tioned near gain and AGC functions, especially when the Tilt is set to a larger angle in
order to track schools of fish approaching within 400 m. In such cases try to reduce
the output power by adjusting the Tx power instead of turning down the gain. The pic-
ture becomes clearer when the output power is reduced rather than when the gain is
decreased as illustrated below.
INCORRECT
METHOD
CORRECT
METHOD
1. Press the MENU/ESC key to show the main menu.
2. Click [TX/RX Setting].
3. Press the H/V/S key to select the [H1] or [H2] tab.
4. Click [TX Power]
2-12
or to change the setting.
Fish echo
Near Gain and AGC
adjusted with
TX POWER kept high
Reduce TX POWER
with Near Gain AGC
kept constant
Quit
Cancel
2
(0.0~10.0)
Fish echo
weakened
Fish echo