Fish finders are based on technology that was first developed by the US navy. Called SONAR (SOund NAvigation and Radar) the technology was used to find enemy submarines in the depths of our seas and oceans during wartime. Modern day fish finders uses the same active sonar to detect fish and ‘the sea bottom’ and displays them on a graphical display device, generally a LCD or CRT screen.
Sonar works by bouncing sound waves off the sea floor. It’s really just a combination of a speaker, a microphone and a stopwatch. As the sound bounces off the sea floor and returns to the sonar receiver, the distance can be measured. This is because we know the rate by which sound travels through water and the time it takes for the sound to return. The speed of sound in water depends on the temperature, salinity and ambient pressure (depth).
The development of sonar evolved over time, becoming more sophisticated and accurate. Someone then discovered that SONAR could be used to find fish!
Modern day fishfinders use these sound waves to find and identify underwater structures, the bottom of the sea and its contours. It can even tell if the sea floor is hard and rocky or soft and sandy. The depth of the water directly below the transducer can also be measured.
So, how do fishfinders do this? Fishfinders send a sound wave signal into the water below and work out the distance or depth by measuring the time between the transmission of the sound wave and when the sound wave is reflected off of an object back to the fishfinder. The fishfinder is able to use the reflected signal to interpret the location, the size and composition of an object.
SONAR is very fast. A sound wave can travel from the surface to a depth of 240 feet and back again in less than 1/4 of a second ! Sonar uses “precision sound pulses” or “pings” that are sent into the water in a cone-like or tear-shaped beam. The sound pulses “echo” back from objects in the water such as the bottom, fish and other submerged objects like tree branches. These returned echos are displayed on the fishfinder screen. Each time a new echo is received, the old echoes are moved across the screen creating a scrolling effect on the screen.
The scrolling effect shows all the recent echoes side by side on the screen. This gives you a great view of what lies beneath you, including the bottom and fish that are there and any submerged structure.
These sound pulses can be transmitted at various frequencies. Very high frequencies are used for high definition applications but they are not much good in deep water as they cannot penetrate very deeply. High frequency sonar (around 200 kHz) is used in most fishfinders as this is a good compromise between resolution and depth requirements. Low frequencies (83kHz) are used to achieve the depth requirements. Typically fishfinders use a combination of high frequency and low frequency sound pulses to give you a great overall picture of the depths below.
Another important part of your fishfinder is its power output. Greater power output allows the sonar signal to penetrate through weeds and thermoclines, reach deeper depths and operate more effectively in “noisey” environments such as when the boat is running at high speed. More power allows you to see those smaller targets at greater distances and to see deeper into the water.
Most modern fishfinders use a combination of high and low frequency pulses that overlap on each other. For example, DualBeam Plus from Humminbird uses a 200/83 kHz combination. The low frequency 83 kHz beam sends out a wide 60 deg cone shaped beam to get large area coverage at great depths. The area of coverage with this beam is equal to your depth. Within this low frequency cone shaped beam, a high frequency, 200kHz central beam is sent out in a narrow 20deg cone shape to give you great detail directly beneath the boat. It is this combination of the high and low frequency that gives you great images of the fish and structure beneath you.
Fishfinders that use a combination of high and low frequency SONAR are suitable for a very wide range of environmental conditions. You can use them in shallow or very deep water or in fresh or salt water. How deep your fishfinder will work depends a lot on the water conditions, how fast your boat is going, how hard the bottom is and also how your transducer has been installed. Having your transducer installed correctly is critical to good performance so consider having it done professionally or at least follow the installation instructions as best you can.
Why use a fish finder?
Because they work! End of Story. Load up your boat with your supplies head out on the water, flick the fish finder on, find the fish, catch the fish. It is that simple !
There is a wide range of Fish Finder technology currently available. The secret is to define your needs and match them to the appropriate fish finder. There are handheld models that can be used river or lake side, models that attach to your rod and reel, models that fit on your wrist, models that can be mounted on a kayak all the way up to the fully feature packed models.
The greatest advance to the electronic fish finder has been the introduction of the GPS fish finder, which allows the fisherman to navigate unknown waters with the aid of Global Positioning Systems. Very cool technology!
At Fishfinderking.com, you are able to select the most appropriate fish finder for your needs from a wide range of fishfinders. We are sure that we have the model for you. We have the best prices and the best customer service. If you have a question, email us via our contact page and you will get a response within 24hours.
Here at FishFinderking.com we carry fish finders from all the major manufacturers.