How Fish Finders Work

Fish finders are an essential tool in any fisherman's arsenal. They help you probe the depths of a lake bed or look out into shallow waters to reveal the best fishing spots. Today's versatile electronics offer an overwhelming array of features and specs so to help you make sense of it all here are some basic facts to help you choose.

Fish finders operate under water to map contours, identify objects, including fish, and create a picture on the display of everything they find. These are not cameras so the resulting display is not like looking at a video or a photo of the underwater scene. Rather they identify objects using sonar technology and then interpret the scene using a graphical representation. Using sonar, (sound waves) they send signals out in the water. When the signal hits an object it bounces back to the fish finder. Using specialized signal processing computations and by analyzing the return signal, this helpful piece of marine electronics can give you a lot of information about encountered objects.

Primary Components
A fish finder is made up of two primary components, the display and the transducer. The transducer is the power source that sends a beam into the water, processes the returning signal and sends it to the display screen. The transducer can be mounted directly on the outside hull of the boat – called a transom mount, or through a hole in the hull of the boat looking directly down into the water under the boat.

Understanding the Specs

Cone Angle refers to the size of the beam that spreads out under the water to provide coverage. Angles are represented in degrees and only objects in the cone angle can be identified. A long narrow cone focuses down in deep waters whereas a wide short cone identifies fish over a wider area in shallow waters. Beams can vary from about 60 degrees to 120 degrees. Multi-beam Fish Finders use more than one beam set at different angles to cover the water at shallow and deeper depths at once. Frequency is the strength of the sonar signal measured in KHz. It works together with the cone angle to determine whether the beam will be focused on deep water or shallow water. Lower frequencies can penetrate the water more deeply than higher frequencies (50 KHz is low frequency whereas 192 or 200 KHz is high frequency)

Display Screens
Look for high resolution, sunlight viewable displays so that it is easy to distinguish features in strong sunlight. Some fish finders have color displays while others have black and white. Remember these are not photos but rather representations so sometimes it is easier to see contrast in black and white, though color can be used effectively to distinguish different targets such as fish, rocks, etc.

Integrated Fish Finders
Most people want different marine electronics components for a variety of different purposes. It can be cost effective to buy a fish finder that is combined with a GPS or a chart plotter. In addition to saving you money such integrated instrument has the added benefit of taking up less real estate on your boat's dash.