How Fishfinders Work?

Fishfinders are helpful instruments that can show a fisherman a number of things about the environment around him. These things can include: the typography, the depth of the water, fish, boat speed, and the temperature of the water. The readings or images on the screen can either be set to black and white or color. They can also be set to different sensitivities as well as zoom in to different locations.

The fishfinder is attached to the hull of the boat and emits a sonar signal, or sound wave, into the surrounding water. The sound wave starts narrow but broadens out in a cone-like shape as it goes deeper. These sound waves continue, until they hit something, and then bounce back to the fishfinder. The fishfinder then measures the time between the different waves that bounce back and calculates the distance. Most fishfinders will be able to accurately measure distances within a difference of two to three inches. Once this calculation is done, it projects its findings on the screen in picture form.

The fishfinder will be able to read the typography of the ground by how strongly the signal bounced back. The softer the material the bottom is composed of, such as mud and hydrophyte, the weaker the signal will be when it returns. This is because the softer materials tend to absorb some of the sound wave; while harder material, like rocks, will reflect it.

The different sound waves projected will also produce different results. The cone-like sound waves can be projected out at different angles. This makes the area it covers vary in width. For example, a 60 degree beam will show a wider area around the boat than a 20 degree beam. Some fishfinders, like Humminbird, will also send out multiple beams at once. These beams can vary from two up to six simultaneously. This also makes the area covered vary; because more beams projected means more area being analyzed. More beams also increase the accuracy at which the surroundings are being detected. Another difference is the frequency of the sound being emitted. The higher the frequency the better the picture will be. However, the lower the frequency is, the deeper the sonar will be able to go. There are a few fishfinders that will be able to emit a dual frequency to get deeper and still have a sharper image.

Water conditions also have an effect on fishfinders. If the water is choppy, it can create bubbles that will disrupt the sonar signal. Particles or biologics floating in the water will also botch the signal as they'll absorb the sound energy.

Fish can be shown on the screen as either an arch or a fish symbol. To have a fish symbol displayed, the fishfinder analyzes the sonar return for specific data points. Once these have been established, the fish finder will exhibit a fish image on the screen. For an arch to be displayed, the fish must pass directly through the sound wave. Because fish rarely pass directly under the transmitter, only partial arches are usually shown.