Furuno CSH-5L/CSH-8L Fine Tuning The Sonar Picture, Eliminating Unwanted Echoes, How TVG works

2.FINE TUNING THE SONAR PICTURE

2.1Eliminating Unwanted Echoes

Echoes from targets such as bottom and fish return to the transducer in order of distance to them, and when we compare their intensities 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 the actual size of the target cannot be judged from the size of echoes displayed on the screen. To overcome this inconvenience, the TVG function is incorporated. It compensates for propagation loss of sound in water; amplification of echoes on short rang is suppressed and gradually increased as range increases so that similar targets are displayed in the similar intensities irrespective of the ranges to them.

The CSH-5L/CSH-8L incorporates two TVG functions, NEAR and FAR, and they mainly compensate for propagation loss on short and long ranges respectively, centered at the ranges shown below.

NEAR
300	m

FAR

How TVG works

The TVG is also used to suppress unwanted echoes and noise which appear in a certain range area on the screen such as sea surface reflections and cruising noise. To obtain the proper TVG setting, follow the procedure below.

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 TVG NEAR.

5.Use the [GAIN] control to adjust gain.

6.Use the [RANGE] control to choose TVG FAR.

7.Use the [GAIN] control to adjust TVG FAR (setting range: 0-10).

8.When sea surface reflections or plankton layers disturb the picture, adjust TVG NEAR to eliminate them. They will be eliminated by decreasing the setting by “1” or “2.”

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