A fish finder is a sonar instrument that is designed for the specific purpose of detecting fish underwater. It does so by detecting reflected impulses of sounds energy. All the electronic impulses that are reflected off fish are converted into information that is then display in graphic rendition on the screen of the fish finder. In addition to locating fish, these units also measure the depth of the water, locating underwater debris, and bottom structure. The image on the screen of the fish finder can represent just one fish in the form of a small icon or with a series of arches.

How to choose a fish finder? There are so many fish finder brands and models of fish locators available that it can be quite difficult to figure out which one would best meet your needs and your individual fishing style. Moreover, it’s also easy to get lost in transducers, echoes, sonar, flashers and transom mounts. The most important thing to keep in mind when choosing a good fish finder is the question: will it help you to catch more fish? To make this choosing process less complicated and so you can understand more about fish detector features we have compiled this buying guide. Using this information will help you to make the best choice.

For just around 600 you can get this Raymarine Dragonfly fish finder that offers features that are usually found on much pricier models. It uses next-gen CHIRP technology that gives photo-like imagery with high resolution structure. The CHIRP technology transmits a wide spectrum of frequencies and the result is a much higher resolution. The generous size (5.7 inches) of the display gives an easy read of the underwater details and the 1600 nits gives clear viewing even in bright daylight.


In operation, an electrical impulse from a transmitter is converted into a sound wave by an underwater transducer, called a hydrophone, and sent into the water.[3] When the wave strikes something such as a fish, it is reflected back and displays size, composition, and shape of the object. The exact extent of what can be discerned depends on the frequency and power of the pulse transmitted. Knowing the speed of the wave in the water, the distance to the object that reflected the wave can be determined. The speed of sound through the water column depends on the temperature, salinity and pressure (depth). This is approximately c = 1404.85 + 4.618T - 0.0523T2 + 1.25S + 0.017D (where c = sound speed (m/s), T = temperature (degrees Celsius), S = salinity (per mille) and D = depth).[4] Typical values used by commercial fish finders are 4921 ft/s (1500 m/s) in seawater and 4800 ft/s (1463 m/s) in freshwater.
Early sporting fathometers for recreational boating used a rotating light at the edge of a circle which flashed in sync with the received echo, which in turn corresponded to depth. These also gave a small flickering flash for echos off of fish. Like today's low-end digital fathometers, they kept no record of the depth over time and provided no information about bottom structure. They had poor accuracy, especially in rough water, and were hard to read in bright light. Despite the limitations, they were still usable for rough estimates of depth, such as for verifying that the boat had not drifted into an unsafe area.

The sound wave spreads as it gets further from the transducer. The wider the cone, the larger the coverage area, but the as the cone angle spreads, sensitivity diminishes. A 20-degree cone is considered a versatile angle for fishers who frequent different water depths. More advanced devices come with double and triple beams, ideal for scanning deep water depths.
THE LIMBO: How low can you go? Or, how low do you need to go? This is an important question you need to answer. If you don't need to see what's 1000 feet below you, they you can certainly save yourself some money. You did save the gift receipts for those much_appreciated_but_unwanted Christmas gifts, didn't you? Before we take the drill off the charger, let's ponder some options and then work backwards to determine what your needs/wants/limitations are.
If I'm scouting a new area I won't know anything about what sort of structure is ahead until I paddle over it, blowing out any fish that may have been there. With this little guy, I could cast it to the spot, get a read on what's below and proceed. And, you have the luxury of retrieving it slowly to see bottom contours between you and that fishy spot. There have been a number of occasions when I've made numerous casts at a fishy looking location (without any luck), only to paddle over there and discover that it was 10" deep, nobody home.
In operation, an electrical impulse from a transmitter is converted into a sound wave by an underwater transducer, called a hydrophone, and sent into the water.[3] When the wave strikes something such as a fish, it is reflected back and displays size, composition, and shape of the object. The exact extent of what can be discerned depends on the frequency and power of the pulse transmitted. Knowing the speed of the wave in the water, the distance to the object that reflected the wave can be determined. The speed of sound through the water column depends on the temperature, salinity and pressure (depth). This is approximately c = 1404.85 + 4.618T - 0.0523T2 + 1.25S + 0.017D (where c = sound speed (m/s), T = temperature (degrees Celsius), S = salinity (per mille) and D = depth).[4] Typical values used by commercial fish finders are 4921 ft/s (1500 m/s) in seawater and 4800 ft/s (1463 m/s) in freshwater.
The display is all about pixels. With more pixels you will be able to see more details, so it’s also an important factor to consider. More pixels also means higher price of the fish detector. We would suggest going minimum 240(v) x 160(h) pixels of the screen. However, this screen will give a pretty blocky image. To have a sharper image and better resolution, you will need to invest more.
BUT DOES A FISHFINDER REALLY FIND FISH? Does a woodchuck really chuck wood? Sorry jackwagon, I had to go there. A fishfinder works on the same theory as deep space telescopes identifying distant stars. It doesn't see "fish" but it does see things that don't look like water. Once the data is processed, the resulting image is therefore labeled fish. Therefore, these units absolutely process the data and tell you if fish are in the beam. But alas, they don't know what they're eating, or if they're even in the mood to eat. But, I do believe that fish will almost always eat if given the right offering. But, you have to find them first.
The term tackle, with the meaning "apparatus for fishing", has been in use from 1398 AD.[1] Fishing tackle is also called fishing gear. However the term fishing gear is more usually used in the context of commercial fishing, whereas fishing tackle is more often used in the context of recreational fishing. This article covers equipment used by recreational anglers.
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