Furuno CSH-5L/CSH-8L manual Displaying Surface Fish Clearly, Suppressing Bottom Tail, 2.3.1 AGC

2.FINE TUNING THE SONAR PICTURE

8.On a long range, locate a fish school which is approaching own ship. Note that the tilt should be kept adjusted so that the fish school is always placed in the center of the sonar beam, i.e., so that the fish school is displayed in strongest colors possible. Check that the fish echo is displayed in the same color while it approaches. If the color changes suddenly to weaker colors as the fish echo enters FAR and NEAR areas, the TVG is improperly set. Adjust the TVG to correct it. If this again produces sea surface reflections and noise, try to remove them with the AGC and noise limiter as described later on.

9.Press the [MENU] key to close the menu.

2.2Displaying Surface Fish Clearly

When you are searching for surface fish with the tilt set to a narrow angle, sea surface reflections may disturb or mask wanted fish echoes. In this case, in addition to the TVG adjustment described earlier, adjust AGC on the SONAR menu. Normally set it between “0” and “3.”

2.3Suppressing Bottom Tail

As noted earlier, fish schools (echoes) located near the bottom are sometimes difficult to detect because you have to discriminate them from the bottom reflections. AGC, PULSE LENGTH and 2ND AGC in the SONAR menu, if used properly, decrease the tail of bottom reflections, making it easier to discriminate bottom fish.

2.3.1AGC

The AGC functions to automatically reduce the receiver gain only against strong echoes such as the bottom or a large fish school. Since weak echoes remain unaffected, a small fish school becomes easier to detect. Adjust the AGC so it works only on bottom reflections.

1.Press the MENU key.

2.Use the [RANGE] control to choose [MENU MODE] at the top of the screen.

3.Use the [GAIN] control to choose SONAR to display the SONAR menu.

4.Use the [RANGE] control to choose AGC.

5.Use the [GAIN] control to set AGC value. The setting range is 0-10 and the higher the setting the stronger the AGC effect.

6.Press the [MENU] key to close the menu.

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