Getting Started > Understanding the Fishfinder and Sonar

Understanding the Fishfinder and Sonar

The Fishfinder 340C is a fully automatic, color sonar unit that allows you to go out on the water and find fish without having to configure a lot of settings. However, you can customize each setting as you prefer.

If you have used a Fishfinder before, you might already know how to interpret the sonar information on the screen, so you can skip this section. If you have not used a Fishfinder before, you might want to learn a bit about sonar: what it is, how it works, and what you might see on the Fishfinder 340C screen. This manual provides a general understanding of those things that you need to know about sonar that can help you interpret the screen and find the fish.

Understanding Sonar

During installation, you connect your Fishfinder 340C to a transducer. The transducer uses sound to determine information about what is in the water beneath your boat. Then the transducer sends the information to your Fishfinder to be shown on the screen for you to view and interpret.

The transducer sends sound waves down into the water in a cone shape, similar to a flashlight beam (covering a smaller circular area at the top and angling out to a larger circular area at the bottom). These sound waves reflect off of any object that they hit, and then the waves travel back up to the transducer. These objects could be fish, branches, the bottom, or any other object that has density that is different from the water. The transducer receives the sound wave information, and then sends the information to the Fishfinder. The Fishfinder shows the information on the screen for you to see and interpret. The type of transducer and settings that you choose determine how the information appears on the screen.

Using Dual Frequency

Dual frequency works best for deep water (for example, off-shore) applications. The 200 kHz frequency allows you access to great detail about what is underneath your boat. The 50 kHz frequency provides less detailed information, but penetrates to greater depths with the same power. You can choose either or both frequencies to get the information that you want. If you choose dual frequency, the transducer alternates between the 50 kHz and 200 kHz signals. This capability allows you to see the best picture available at any depth.



Fishfinder 340C Owner’s Manual