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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.
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.
GARMIN ECHOMAP 73SV FISH FINDER LIKE NEW CONDITION. Condition is Used. comes with everything in the box as new except the mounting screws for transducer, I only used this for about 1 year, then went to a garmin echo plus chirp unit, everything works like new , has original box, I know the transducer alone will sell for $200-249 alone when new any questions feel free to email me!
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.

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Fishfinders allow anglers to see a graphic representation of what is beneath their boats so they can identify fish. To choose a fishfinder, consider the type of unit—whether it includes GPS and is part of a boatwide network, size of the fishfinder’s footprint, resolution of the display, how much transmitting power you need, and what frequencies will work best in the inland, coastal or deep-water environment where you fish.
Referred to as a fishfinder, graph, sounder or recreational sonar, these products provide anglers with the ability to locate and target open-water baitfish, game fish and cover. This underwater-viewing advantage helped launch sportfishing markets like never before, as anglers were able to better understand depth contours, bottom composition and structure location, plus how fish related to this environment.
Points are more gradual than drop offs, but spotting them is just as easy (see the screen shot below). Make sure you maintain a steady speed when trolling or reeling so you get an accurate reading on how steep the incline is. You should scan with a narrow sonar beam to get the clearest reading, and to ensure you see any shelfs or humps which wider beam scanning might not pick up (our page onhow sonars workexplains why this is).
CHIRP fishfinders transmit less peak power than a conventional fishfinder, but their wide-band, frequency modulated pulses (130-210kHz, for example) can be very long in duration and put 10-50 times more energy into the water. Using digital pattern matching and signal processing, CHIRP devices achieve unprecedented resolution and target detection. Your ability to resolve individual fish, or separate fish from bottom structure, is now a matter of inches, instead of several feet with traditional fishfinders. See individual fish in groups, instead of a single mass.
To get the most of the both there’s the dual beam type of transducers. It’s also called dual frequency and which combines both features in one unit. Other types of transducers are more specialized. They include multiple beams (can be 4 or more). These cover a larger area of the underwater and can even give a 3D image on the display. One more option is the side beam transducer. These units shoot their signals to the sides, which increases the search area for fish.
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.
Raymarine has a few units that come with a built in GPS. The Dragonfly 4Pro, Dragonfly 5Pro, and Dragonfly 7Pro all have built in GPS. Pay close attention to the unit you are buying, because if you are looking for built in GPS the standard Dragonfly 4 and Dragonfly 5DVS do not have that feature built in. You absolutely have to go Pro to make sure you get the GPS you’re looking for.
Ultrasound frequency used by a fish finder generally ranges from 15 kHz to 200 kHz. However, the majority of the conventional fish finders oriented for recreational craft utilize 50 kHz and 200 kHz. Such fish finders available in the market incorporate electronic circuitry that can transmit and receive ultrasound in these two frequencies. Also, a transducer mounted on the bottom of the craft is configured to handle these two frequencies.
Simrad’s GO9 XSE Combination GPS/ Fishfinder offers a networkable 9” Touchscreen unit at an affordable price point. An Internal 10Hz GPS Receiver quickly and accurately locates position on the included C-Map Pro Charting while the included TotalScan Transom Mount Transducer provides detailed underwater images. Compatible with detailed mapping from C-MAP MAX-N, Navionics, Insight, Insight Genesis, and NV Digital Charts.
The Axiom 9RV from Raymarine is a top of the line 9” Multi-Function Display with RealVision Sonar and comes packed with an RV-100 Transom Mount Transducer. The included RV transducer will provide CHIRP DownVision, CHIRP SideVision, High Frequency CHIRP and RealVision 3D all in one. Detailed U.S and Canadian Mapping for Coastal and Lake water is also included with Navionics+ Mapping.
The swivel sinker is similar to the plain one, except that instead of loops, there are swivels on each end to attach the line. This is a decided improvement, as it prevents the line from twisting and tangling. In trolling, swivel sinkers are indispensable. The slide sinker, for bottom fishing, is a leaden tube which allows the line to slip through it, when the fish bites. This is an excellent arrangement, as the angler can feel the smallest bite, whereas in the other case the fish must first move the sinker before the angler feels him.