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Fishfinder for shallow water

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  • Fishfinder for shallow water

    What kind of performance differences could I expect between a 20 beam and a 60 beam fishfinder? It seems that I would have better shallow water performance with a 60 beam, or dual 20/60 beams. I was looking at the PiranhaMAX 240 with triple beam 90 (35/20/35) coverage, but that model is being discontinued (I can get the last one, the display model, at my Bass Pro for 10% off).

    I'll probly never fish in water deeper than 25'-30' here in south Louisiana, most likely I'll stay in 3'-15' of water. And very rarely in shallow salt water.

    Advice?


  • #2
    Re: Fishfinder for shallow water

    iboght the hummingbbird 565 dual beam bout two year ago and it works great. i use mine mostly for depth, structure, and bait (gotta have them shad).

    just read the book and set it up for your kind of fishing.

    i want one of the 3-d models but the wife says NOOO.

    the 20 beam is kind of narrow in my opinion, but any one is better than none.

    good luck and happy fishing.
    give a man a fish and he will eat for a day...........teach him how to fish and he will sit in a boat and drink beer all day.



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    • #3
      Re: Fishfinder for shallow water

      Originally posted by LSUfan71 View Post
      What kind of performance differences could I expect between a 20 beam and a 60 beam fishfinder? It seems that I would have better shallow water performance with a 60 beam, or dual 20/60 beams. I was looking at the PiranhaMAX 240 with triple beam 90 (35/20/35) coverage, but that model is being discontinued (I can get the last one, the display model, at my Bass Pro for 10% off).

      I'll probly never fish in water deeper than 25'-30' here in south Louisiana, most likely I'll stay in 3'-15' of water. And very rarely in shallow salt water.

      Advice?
      Check out this graph by Vexilar; http://www.vexilar.com/pages/product...s_lc-507c.html

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      • #4
        Re: Fishfinder for shallow water

        Well, after readin some online reviews I ran down to the Bass Pro in Denham Springs and got the PiranhaMAX 240. Couldn't find any negative comments about it. And the only unit with a 90 cone, it looks like it would be the best in shallow water.

        Should be able to get it on the boat sometime in the next decade, I'll let you guys know how it performs.

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        • #5
          Re: Fishfinder for shallow water

          I have a Humminbird 565 and it is a great unit except for very shallow water. The unit displays a digital reading from 1 to 4 feet when in water 3 feet and under. I understand the 60 degree beam is only active when using the "Fish ID" feature. I may be selling mine to get a unit that displays shallow water less then 3 feet a little more accurate.

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          • #6
            Re: Fishfinder for shallow water

            Speaking of cone angles, here is some good information on how they measure cone angles. When selecting your unit make sure your comparing apple to apples when comparing cone angles. Some manufactures stretch the truth a bit in their advertising.

            Between the varying cone angles and the sensitvitiy setting on the unit you may be seeing far less than you think you are.

            Transducer Cone Angles:

            The transducer concentrates the sound into a beam. When a pulse of sound is transmitted from the transducer, it covers a wider area the deeper it travels. If you were to plot this on a piece of graph paper, you would find that it creates a cone shaped pattern, hence the term "cone angle." The sound is strongest along the center line or axis of the cone and gradually diminishes as you move away from the center.
            In order to measure the transducer's cone angle, the power is first measured at the center or axis of the cone and then compared to the power as you move away from the center. When the power drops to half (or -3db[decibels] in electronic terms), the angle from that center axis is measured. The total angle from the -3db point on one side of the axis to the -3db point on the other side of the axis is called the cone angle.

            This half power point (-3db) is a standard for the electronics industry and most manufacturers measure cone angle in this way, but a few use the -10db point where the power is 1/10 of the center axis power. This gives a greater angle, as you are measuring a point further away from the center axis. Nothing is different in transducer performance; only the system of measurement has changed. For example, a transducer that has an 8 degree cone angle at -3db would have a 16 degree cone angle at -10db.

            Lowrance offers transducers with a variety of cone angles. Wide cone angles will show you more of the underwater world, at the expense of depth capability, since it spreads the transmitter's power out. Narrow cone angle transducers won't show you as much of what's around you, but will penetrate deeper than the wide cone. The narrow cone transducer concentrates the transmitter's power into a smaller area. A bottom signal on the sonar unit's display will be wider on a wide cone angle transducer than on a narrow one because you are seeing more of the bottom. The wide cone's area is much larger than the narrow cone.

            High frequency (192 - 200 kHz) transducers come in either a narrow or wide cone angle. The wide cone angle should be used for most freshwater applications and the narrow cone angle should be used for all saltwater applications. Low frequency (50 kHz) sonar transducers are typically in the 30 to 45 degree range. Although a transducer is most sensitive inside its specified cone angle, you can also see echoes outside this cone; they just aren't as strong. The effective cone angle is the area within the specified cone where you can see echoes on the display. If a fish is suspended inside the transducer's cone, but the sensitivity is not turned up high enough to see it, then you have a narrow effective cone angle. You can vary the effective cone angle of the transducer by varying the receiver's sensitivity. With low sensitivity settings, the effective cone angle is narrow, showing only targets immediately beneath the transducer and a shallow bottom. Turning the sensitivity control up increases the effective cone angle, letting you see targets farther out to the sides.


            Courtesy of Lowrance electronics
            Grady White 226
            200 Evinrude Ocean Pro
            Evinrude Renegade Offshore Prop

            Furuno FCV 587 Sounder
            Garmin 4208 Multifunction Display
            ICOM M504A VHF
            Shakespeare Galaxy 5225-XT Antennas

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            • #7
              Re: Fishfinder for shallow water

              General rule of thumb.... High frequency for shallower water.. A few years back someone was producing a 455kHz unit... I think it may have been Hummingbird.
              At that frequency it wouldn't be any good for anything more than about 100-150 feet, but fantastic in the shallower stuff. And I would stay with a narrower beam.

              Chris.............
              The world takes on a whole new perspective when viewed from 100' below...



              1972 Bertram 'Bahia Mar' 20
              2006 Mercruiser 4.3MPI (0W617679) w/Alpha 1 Gen II (0W829301)
              **
              Please don't send service questions in private messages. That's what the forum is for. Messages of thanks, always accepted.
              **
              Member of the month - April 2013. http://www.iboats.com/blog/achris-member-of-the-month/

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              • #8
                Re: Fishfinder for shallow water

                Accordin to Humminbird my unit has these numbers, not that I know what it means but it seems to be a nice set-up:

                200 kHz / 20˚ @ -10db
                455 kHz / (2) 35˚ @ -10db

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                • #9
                  Re: Fishfinder for shallow water

                  Originally posted by LSUfan71 View Post
                  Accordin to Humminbird my unit has these numbers, not that I know what it means but it seems to be a nice set-up:




                  Had Hummingbird used the industry standard -3 db instead of 90˚ coverage your unit would have only been rated to 45˚ coverage.

                  200 kHz / 10˚ @ -3db
                  455 kHz / (2) 15.5˚ @ -3db
                  Grady White 226
                  200 Evinrude Ocean Pro
                  Evinrude Renegade Offshore Prop

                  Furuno FCV 587 Sounder
                  Garmin 4208 Multifunction Display
                  ICOM M504A VHF
                  Shakespeare Galaxy 5225-XT Antennas

                  Comment



                  • #10
                    Re: Fishfinder for shallow water

                    Originally posted by dingbat View Post
                    Had Hummingbird used the industry standard -3 db instead of 90˚ coverage your unit would have only been rated to 45˚ coverage.

                    200 kHz / 10˚ @ -3db
                    455 kHz / (2) 15.5˚ @ -3db
                    So I can reason that this is fine because I'll always be fishing shallow water, right?

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                    • #11
                      Re: Fishfinder for shallow water

                      Originally posted by LSUfan71 View Post
                      So I can reason that this is fine because I'll always be fishing shallow water, right?
                      You're fine. You're just not looking at as much bottom as Hummingbird's marketing hype would lead you to believe
                      Grady White 226
                      200 Evinrude Ocean Pro
                      Evinrude Renegade Offshore Prop

                      Furuno FCV 587 Sounder
                      Garmin 4208 Multifunction Display
                      ICOM M504A VHF
                      Shakespeare Galaxy 5225-XT Antennas

                      Comment



                      • #12
                        Re: Fishfinder for shallow water

                        The designated cone angle is (usually) specified at -3db. That's the point where the signal strength is half power. It does not mean the signal goes no further... It indicates the rate, from off centre, at which the signal strength decreases.

                        So, what does that mean in real world terms. It means that if you are over a hard bottom that has good reflective properties, such as a reef, then more of the weaker part of the signal, the side-lobes, will be reflected. And because those side-lobes are further from the transducer, they will take longer to get back.... What you will see is a thicker bottom line. Conversely in soft bottoms, like mud, the signal is absorbed and not reflected so easily, you'll see a very thin bottom line.

                        Have fun,

                        Chris.......
                        The world takes on a whole new perspective when viewed from 100' below...



                        1972 Bertram 'Bahia Mar' 20
                        2006 Mercruiser 4.3MPI (0W617679) w/Alpha 1 Gen II (0W829301)
                        **
                        Please don't send service questions in private messages. That's what the forum is for. Messages of thanks, always accepted.
                        **
                        Member of the month - April 2013. http://www.iboats.com/blog/achris-member-of-the-month/

                        Comment



                        • #13
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                          Re: Fishfinder for shallow water

                          You need to read your manual and understand how the multiple beams are used and displayed on the screen. Humminbird has done this differently on different units. Early 3-beam units used the down looking sonar for bottom and fish, and side for fish only. On more recent units, like quadrabeam, the screen can be split to show three bottom profiles, and you can determine some idea of how the structure is running.

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