SONAR stands for Sound Navigation Ranging. Whether you’re a beginner or an expert fisherman, you’ve possibly heard about fish finders or perhaps even used one in before. Even so, there are many people that use these devices don’t really know how they work. Using a fish finder to discover fish below the waterline is not tough nor complicated and it only take some practice and fundamentals to understand how they function.
Essentially, these nice fishing gadgets are made up of two elements – a screen that is positioned in the boat if you have a portable one, which then shows potential fish and their depth location, and a transducer, that features an underwater sensor that transmits data back up to the screen. The screen is just that – a monitor with computing power enough so it takes the raw data from the transducer and provides it in a simply understandable means. Basically the transducer is the component doing all the work.
A boat with a depth finder system has one or more transducers fitted to the hull or there are models that can send signals through the hull as well.
The transducer sends sonar waves (or pings) down into the water. When the sonar wave hits something, either fish, plants, rocks or bottom, it guesses the size and depth of the item, and sends that information back to the screen for the fisherman to interpret. The time between these short pings will vary depending on the device, but always have to be adequate enough to let the returning ping to get back from the deepest bottom spectrum for which the unit is meant for. Some models can handle a number of depth ranges, meaning they can change the timing of their sound pulses for each depth range as necessary.
Sound moves quite fast in water, around a mile per second, so it doesn’t take too much time for a signal to get back so that the device can send out another signal. The short surges or spikes of sound last for only a little period of time, and are indicated in terms of milliseconds. The time between signals, known as the sounding rate, must not only be long enough to let the ping sounds to return from each signal, but must also be timed accurately to match precisely with the speed of a turning wheel, in the scenario of a graph or recorder unit. A regular sounding rate for older type more wallet friendly flasher units may be 24 times a second, while for a more advanced LCD unit it can be as slow as once every couple of seconds.
The sound that is sent out under the water varies in frequency, with the most common being 50 and 200 KHz. New high definition image transducers like the ones from Lowrance can manage with multiple frequencies from around 400 KHz to way up to 800 KHz.
Modern transducers can in fact separate between a fish, a strand of seaweed, rocks and the river bottom. Fish are displayed by little fish icons on the display, weeds are showed by little weeds and so on.
Read more about fishing sonars – http://www.fishfinderadvisor.com/