Furuno FCV-30 Operator's Manual page 88

3. CHANGING SETTINGS
Tx pulse length (Manual): Operative when TX pulse length is set to Manual. The pulse
length range is 0.2-5(ms). The smaller the figure, the better the resolution, however the
detection range is shorter. Conversely the larger the figure, the better the detection but the
lower the resolution.
ETR Compensation dialog box
Draft: To get depth from the sea surface (rather than the transducer), enter ship's draft.
Setting range: -15.0-60.0(m).
Sound velocity: Adjust the sound velocity of the Tx pulse if the depth indication is incorrect.
Setting range: 200-2000(m/s).
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