Furuno 1834C-BB User Manual

4. VIDEO SOUNDER OPERATION 

The zero line (sometimes referred to as the transmission line) represents the transducer’s 
position, and moves off the screen when a deep phased range is used. 

Zero line

Shift

Echoes from the bottom are normally the strongest and are displayed in reddish-brown, but 
the color and width will vary with bottom composition, water depth, frequency, sensitivity, 
etc. 
 
In a comparatively shallow depth, a high gain setting will cause a second or sometimes a 
third or a fourth echo to be displayed at the same interval between them below the first 
echo trace. This is because the echo travels between the bottom and the surface twice or 
more in shallow depths. 
 
The color of the bottom echo can be used to help determine the density of the bottom 
materials (soft or hard). The harder the bottom, the wider the trace. If the gain is set to show 
only a single bottom echo on mud, a rocky bottom will show a second or third bottom return. 
The range should be chosen so the first and second bottom echoes are displayed when 
bottom hardness is being determined. 

Intensity difference
in water depth

Second bottom
echo

Rock base

Mud and sand