Furuno GP-1850WDF, GP-1850WF manual 11-10, Echo Offset 200kHz, Echo Offset 50kHz, TVG concept

11. CUSTOMIZING YOUR UNIT

SYSTEM SETUP menu description

FISH ALM LVL: Sets the fish alarm sensitivity; namely, which echo strength will trigger the alarm. HIGH, only the strong echoes (red and reddish brown) trigger the alarm; NORMAL, echoes from strong to medium strength (greater than yellow) trigger the alarm, LOW, any echo (greater than light-blue) triggers the alarm.

TX POWER: Turns TX power on/off.

TVG 200kHz, TVG 50kHz: TVG (Time Varied Gain) compensates for propagation attenuation of the ultrasonic waves. It does this by equalizing echo presentation so that fish schools of the same size appear in the same density in both shallow and deep waters. In addition, it reduces surface noise. Note that if the TVG level is set too high short range echoes may not be displayed.

Fish school A

Fish school B

TVG concept

ECHO OFFSET 200kHz, ECHO OFFSET 50kHz:

If the on-screen echo level appears to be too weak or too strong and the level cannot be adjusted satisfactorily with the gain control, adjust echo offset to compensate for too weak or too strong echoes.

SEABED LVL 200kHz, SEABED LVL 50kHz:

If the depth indication is unstable in automatic operation or the bottom echo cannot be displayed in reddish-brown by adjusting the gain control in manual operation, you may adjust the bottom echo level detection circuit, for both 50 kHz and 200 kHz, to stabilize the indication. Note that if the level is set too low bottom echoes cannot be acquired and if set too high regards the fish school as the bottom, so the depth indication will not be fixed. The default setting for both 200 kHz and 50 kHz is 80.

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