Understanding how a fish finder works will help you to understand how to use it. Fish finders work using sonar. It’s a technology that uses sound waves to display underwater objects. The fish finder produces the sound wave and with the transducer sends it through the water. Penetrating the water deeper, the sound wave starts to spread in the form of a cone (commonly called a beam). As the wave encounters objects within this beam, it sends the signal back to the transducer.
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Commercial fishermen also make use of these characteristics. They conduct a search by low frequency (i.e., 15 kHz) beams first to grasp the general locations of fish schools around the boat. Subsequently, they narrow the search area for a fish school, using high frequency beams (200 kHz), to detect the exact location of the fish school and operate the boat to be directly above the targeted fish school.
These units are battery operated and the signal is transmitted back to the receiver. So, don't expect a lot of range or HD resolution. But, if you simply want to know how deep the water is ahead of you so that you can make better choices, this is it. For me, I would need to cast it with a rod/reel loaded with heavy braid. The areas I'd likely cast to would hopefully hold big snook and in the spring they love this color. I don't want the "dog ate my homework" story to become the "snook ate my transducer" story.
Transducers: Fishfinders operate using a single frequency transducer, dual frequencies, multiple frequencies or a broadband CHIRP system. In general, higher frequencies give the finest detail resolution, the least background noise on your screen and the best view from a fast-moving boat, but don’t penetrate as deeply as lower frequencies. Shallow-water inland anglers generally choose higher frequencies of 200kHz, 455kHz or 800kHz. For maximum depth, use lower frequencies. We recommend 200kHz or higher (up to 800kHz) for water depths up to 200' and 80kHz or 50kHz for deeper waters.
However, fish finders for professional use, i.e., those used by commercial fishermen, can make use of other frequencies. Such frequencies include 15, 22, 28, 38, 45, 50, 68, 75, 88, 107, 150 and 200 kHz. There are some special fish finders that utilize the frequency of 400 kHz, but it is quite a rare case. As you can see, there is an extensive range of configurable frequencies available for fish finders for fishery vessels, and a fish finder generally makes use of a combination of two frequencies (high and low frequencies). The selection of the frequencies depends upon the intended purposes of the fish finder, which include, inter alia, finding specific fish species; grasping the seabed condition; conducting a wide-area-search with the search angle of 90 degrees at one go; conducting detailed search for fish schools; detecting fish schools that give weak echo returns; avoiding interference/conflict with other fish finders used nearby. The searchable range (depth) and search area are dependent upon the frequency used. On the one hand, high frequency ultrasound is suitable for a detailed search, although it cannot be used for search in deep water. Low frequency ultrasound, on the other hand, is suited for general searches in a wider area as well as searching in deep water.

A GPS is a must have for many fishers and having it in one unit with a fish detector is economical, space saving and convenient. Having the addition of a GPS gives you many benefits. It will give you the ability to mark hot fishing spots and easily return to them in the future, as you can mark the spot on the GPS and then track your way back to it later. These spots are called waypoints and on most units you will be able to mark hundreds or even thousands of them.
When checking the transducer, the most important feature is the cone angle. For a bigger perspective of the verges underneath, choose a bigger degree on the cone. The wider beam gives more coverage of the under water and allows locating more fish within it. However, its drawback is the quick loss of strength. Due to this, it cannot penetrate the water as deep as the narrow cone. The narrow one can go really deep even in shallow waters and can also give information on the composition of the bottom.
When checking the transducer, the most important feature is the cone angle. For a bigger perspective of the verges underneath, choose a bigger degree on the cone. The wider beam gives more coverage of the under water and allows locating more fish within it. However, its drawback is the quick loss of strength. Due to this, it cannot penetrate the water as deep as the narrow cone. The narrow one can go really deep even in shallow waters and can also give information on the composition of the bottom.
It’s often been said that the act of fishing isn’t actually about catching a fish. Rather, it’s about a quiet moment with nature and a chance to sit, think and relax, whether on your bass fishing boat or on the banks of a river. Of course, if you’re a sport fisherman reeling in that prize monster on a white-capped ocean, there isn’t much relaxation to be had. If you prefer ice fishing or fly fishing, shop eBay for everything you need for a day on the water. We have the right gear for you, regardless of whether your allegiance lies with Orvis, Shimano or Abu Garcia.
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