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Thread: Minnkota's universal sonar

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    Default Minnkota's universal sonar

    I was doing some research and ran across this:http://www.minnkotamotors.com/suppor....asp#ConeAngle

    I had always assumed (there I go again) that they used a standard 20 deg cone. But apparently I am wrong. If I read this right, its only 14 deg. 20 is narrow enough considering the shallow water I fish, but 14. That sux!
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    Quote Originally Posted by IBNFSHN
    I was doing some research and ran across this:http://www.minnkotamotors.com/suppor....asp#ConeAngle

    I had always assumed (there I go again) that they used a standard 20 deg cone. But apparently I am wrong. If I read this right, its only 14 deg. 20 is narrow enough considering the shallow water I fish, but 14. That sux!
    When comparing cone angles, make sure they are measured at the same signal strength. Most manufactures use -3Db and some use -10Db. The lower outer edge signal strength when using the same centerline signal strength as a reference results in a larger specified cone angle.
    Last edited by PanMan_VA; 11-03-2005 at 08:54 PM. Reason: clarification of statement
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    Quote Originally Posted by PanMan_VA
    When comparing cone angles, make sure they are measured at the same signal strength. Most manufactures use -3Db and some use -10Db. The lower signal strength results in a larger cone angle.
    According to that article that 14 is measured at -3db. I may look into mouting the xducer that came with it on the bottom of the TM. See if it makes that much difference.
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    Quote Originally Posted by IBNFSHN
    I was doing some research and ran across this:http://www.minnkotamotors.com/suppor....asp#ConeAngle

    I had always assumed (there I go again) that they used a standard 20 deg cone. But apparently I am wrong. If I read this right, its only 14 deg. 20 is narrow enough considering the shallow water I fish, but 14. That sux!
    ----------------------------------------------------------------------------------------------------
    I am a Lowrance/Eagle owner and as I understand their website
    Cone Angle
    A transducer's cone angle determines its coverage area of the underwater world. The wider the cone angle, the greater the area that's covered. We offer a variety of 192 kHz transducers with either a wide (20) or narrow (8) cone angle. We also offer a variety of 200 kHz transducers with either a wide (20) or narrow (12) cone angle. The 50 kHz transducers come with a 35 cone angle. And the dual frequency transducers come with both a narrow (12) 200 kHz and a 50 kHz cone angles.

    Generally, use a wide cone angle for fishing shallow to medium depths. The narrow cone penetrates to deeper depths, but shows less fish and structure due to its narrow beam.

    Minn Kota says:

    How does the Universal Sonar work on both 192 kHz and 200 kHz fish locators?
    UNIVERSAL SONAR FREQUENCY In the simplest terms, sonar manufacturers utilize transducers that operate within a + or - range of ~ 2 kHz of their products frequency, so a 192 kHz depth finder transducer will have a range from ~ 190 kHz to 194 kHz and a 200 kHz depth finder transducer will have a range from ~ 198 kHz to 202 kHz. Minn Kota has designed and utilizes a 196 kHz transducer that operates within a + or - range of ~ 6 kHz (190 kHz - 202 kHz) effectively covering the frequency range without sacrificing performance. Minn Kota also say's The Universal Sonar transducer has a single beam cone that measures 14 degrees at -3dB.
    That means speed and temp will not work neither will multi beam depth finders.
    I believe you are correct IBNFSHN the 14 degree cone angle will decrease the viewing area of a 192/200 khz transducer by 30%. The MinnKota page you mentioned shows coverage of 5ft. in 20 ft. of water. With a 20 degree cone I believe that coverage is 8ft.
    I appreciate you bringing this up. A major down side to the autopilot is that transducer cable flapping in the water. I don't think they have solved the problem to my satisfaction with the universal sonar.



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    Quote Originally Posted by PanMan_VA
    When comparing cone angles, make sure they are measured at the same signal strength. Most manufactures use -3Db and some use -10Db. The lower signal strength results in a larger cone angle.
    PanMan, I think you may have it backward.
    To clear up this angle and signal stuff:
    Consider two transducers, each rated at 20 degrees, but one at -3dB, the other at -10dB;
    The -3dB model has a higher signal strength at 10 degrees away from centerline than the -10dB model. That would imply that the -3dB job has a wider beam than the -10dB.
    For you normal people:
    -3db means 1/2 the power of the centerline of the beam.
    -10dB means 1/10 the power of the centerline of the beam.
    It's a logarithmic expression. Don't worry about it.
    The farther away you go from the centerline of any beam (0 degrees), the lower the power.
    That means that when you go away from the centerline (at increasing angles) you come to an angle where the power has dropped to half. Go farther away, and the power has dropped to one tenth. Don't get confused. At a given angle, the -3dB job has dropped to 1/2. The -10dB job has dropped to 1/10.
    The 10 degrees I refer to would actually be stated as 20 degrees by the mfr because they rate at the total cone angle, 10 degrees away in each direction.
    It makes it very confusing, even for me, when they use different measurement standards. What if you had one rated at 20 deg at -3dB and another rated 25 deg at -10dB? You could only figure it out if you knew more about each beams power dispersion characteristics. And who has time for that, even if you know how?
    In my opinion, the -3dB rating is much more realistic.
    Also, stick with the wider angles for Crappie fishing.
    I have never seen anyone rate their xducer angle at -10dB. Who does that?
    Last edited by Pomoxis 2; 11-03-2005 at 06:03 PM.
    Sorry for my Crappie attitude.

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    I have a Minn-Kota with the universal sonar. I put my transducer on it because the universal transducer will not show temperature. Plus I get a better reading on my depth finder with the transducer that came with the unit. They have a good idea, but need to put better transducers in their trolling motors.
    Have a crappie day!:D [email protected]

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    Quote Originally Posted by Pomoxis
    PanMan, I think you may have it backward.
    To clear up this angle and signal stuff:
    Consider two transducers, each rated at 20 degrees, but one at -3dB, the other at -10dB;
    The -3dB model has a higher signal strength at 10 degrees away from centerline than the -10dB model. That would imply that the -3dB job has a wider beam than the -10dB.
    For you normal people:
    -3db means 1/2 the power of the centerline of the beam.
    -10dB means 1/10 the power of the centerline of the beam.
    It's a logarithmic expression. Don't worry about it.
    The farther away you go from the centerline of any beam (0 degrees), the lower the power.
    That means that when you go away from the centerline (at increasing angles) you come to an angle where the power has dropped to half. Go farther away, and the power has dropped to one tenth. Don't get confused. At a given angle, the -3dB job has dropped to 1/2. The -10dB job has dropped to 1/10.
    The 10 degrees I refer to would actually be stated as 20 degrees by the mfr because they rate at the total cone angle, 10 degrees away in each direction.
    It makes it very confusing, even for me, when they use different measurement standards. What if you had one rated at 20 deg at -3dB and another rated 25 deg at -10dB? You could only figure it out if you knew more about each beams power dispersion characteristics. And who has time for that, even if you know how?
    In my opinion, the -3dB rating is much more realistic.
    Also, stick with the wider angles for Crappie fishing.
    I have never seen anyone rate their xducer angle at -10dB. Who does that?
    Forgive me if I sound a little like Moose here.

    The Humminbird Legend series depth finders specified their cone angles at -10dB. Go to the Humminbird website and look at the specifications in the online manual for one of the 900 series sidescan models. Their cone angles are specified @ -10db. Most other companies specify their cone angles at -3dB.

    http://www.humminbird.com/products.asp?ID=512

    Now let's tackle the cone angle part. You misinterpreted what I meant.

    Take a transducer that has a cone angle of 20 degrees @ -3dB. The same transducer may have a cone angle of 35 degrees @ -10dB. What I ws trying to say in as few words as possible is a transducer will have a wider cone angle specified when it is measured at a lower power level for the return signal. That is why the reference signal strength is important when talking cone angles.

    The Lowrance web site has a good tutorial on transducer cone angles for anyone that is interested in learning more.

    http://www.lowrance.com/Tutorials/So...utorial_06.asp
    Last edited by PanMan_VA; 11-04-2005 at 04:26 PM.
    Keith
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    The bottom line here is that the Universal sonar SUX. Good idea, but needs improved a whole lot.
    Fair Winds and Following Seas

    Bill H. PTC USN Ret
    Chesapeake, Va


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    Default interesting stuff

    I am not sure, but i would think that the sonar unit processors algorythms would filter out anything beyond the -3db range. Usually the -3db range is considered the outer edge of the cone and anything beyond this is undesirable. I don't know about this -10db stuff, but I think it is hype....I could be wrong...Ultrasound has a very narrow angle of coincidence, be it in or out of water...IBNFSHN right on here.
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    Quote Originally Posted by IBNFSHN
    The bottom line here is that the Universal sonar SUX. Good idea, but needs improved a whole lot.
    Agreed. IMHO, the best approach is to mount the transducer that came with the depth finder to the trolling motor rather than use the US. Special mounts are made for this purpose. MK PowerDrives need special attention when securing the transducer cable that allows the motor shaft to slide up and down in the trolling motor mount.
    Keith
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