Operator's Manual

7-1
7. FISH FINDER
This chapter describes the functions of the fish finder, which requires the Bottom Dis-
crimination Sounder BBDS1, Network Sounder DFF series, ETR-6/10N or ETR-30N,
or Color LCD Sounder FCV-1150.
Many procedures in this chapter require you to open the “fish finder source menu.”
This menu has the name [DFF1/BBDS1/DFF1-UHD], [DFF3/FCV], [ETR-6/10N] or
[ETR-30N], depending on your system. Instead of writing all menu names, we write
"fish finder source." For example, “Open the [Fish Finder-fish finder source] menu.”
7.1 How the Fish Finder Operates
The fish finder determines the distance between its transducer and underwater ob-
jects such as fish, lake bottom or seabed and displays the results in different colors or
shades of gray according to echo strength.
Ultrasonic waves transmitted through water travel at a nearly constant speed of 4800
feet (1500 meters) per second. When a sound wave strikes an underwater object such
as fish or sea bottom, part of the sound wave is reflected back toward the source. Thus
by calculating the time difference between the transmission of a sound wave and the
reception of the reflected sound wave, the depth to the object can be determined.
The picture displayed by the fish finder contains a series of vertical scan lines. Each
line is a "picture" of the objects under the boat. The series of pictures are put side-by-
side across the screen to show the contours of the bottom and echoes from fish. The
amount of history of objects that have moved under the boat can be less than a minute
to more than one minute depending on the picture advance speed.