Furuno CH-250 manual Vert menu

3.11 Adjusting the Picture

3.11.1 Displaying weak echoes clearly

Echoes from targets (such as the bottom or a fish) return to the transducer in order of the distance to them, and when their intensities are compared 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 he won’t be able to judge the actual size of the target from the size of echoes displayed on the screen. To overcome this inconvenience, use the TVG function. It compensates for propagation loss of sound in water: amplification of echoes on short range is suppressed and gradually increased as range increases, so that similar targets are displayed in similar intensities irrespective of the ranges to them.

The TVG also functions to suppress unwanted echoes and noise which appears in a certain range area on the screen.

To adjust TVG:

1.Press the [MENU] key to open the menu.

2.Press to select MENU and then press or to select the VERT menu.

MENU	COM1 COM2 HORZ	VERT	ES PRESET SYS
TVG LEVEL	4.0
TVG DISTANCE	4.0
GAIN ADJUST	0
RES. COLOR	LOG
CLUTTER	0
HORZ RANGE	x1

: SELECT : CHANGE MENU: END

Figure 3-13 VERT menu

3. Press or to select TVG DISTANCE and press to show the following dialog box.

TVG DISTANCE		4.0
GAIN
Hi
Lo	200m

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