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Thread: Sounder fundamentals for the guys who wanted it

  1. #76

    Re: Sounder fundamentals for the guys who wanted it

    I’m Brian! !!
    So’s my wife

  2. #77

    Re: Sounder fundamentals for the guys who wanted it

    Simple and basic (I hope) explanations about sounder frequencies, power and target separation for different depth users.

    Attachment 121658

    I don't know how to delete an attachment so I'm stuck with 2. The one below this is the one I want to delete if some kind soul can assist please.

  3. #78

    Re: Sounder fundamentals for the guys who wanted it

    Tall tales but true. Chapter 2.

    Clear as mud or any queries?


    Attachment 121670

  4. #79

    Re: Sounder fundamentals for the guys who wanted it

    Now that we’ve all had plenty of time to think about sounder basics, it’s probably time to reflect on the most significant development to occur in fish-finding circles in many many years.

    That was the introduction of CHIRP technology and what it brought to the sounder table was a truly remarkable feature.

    Up until then the only way to obtain accurate deep views (1000ft +) was to use low frequency channels 50 khz, 83 khz or 200khz simply because low frequency channels travel further in water.

    If we wanted to obtain more depth than 1000ft then we simply used more power. That meant making the pulse/ping longer.

    We’ve all seen the submarine movie “Hunt for Red October” and how pulse/pings were used to communicate. One single ping lasted for a long time (apparently).

    With fish-finding sounders, pings are actually pre-set as very, very short and are repeated continually many times per second.

    The longer the pulse/ping, the more power is fed into the water and the greater the range attained.

    Sounds great but the real problem associated with longer/more powerful pings is that target separation (range resolution) suffers badly. Target separation/range resolution is the ability to distinguish between targets close together. With a normal pulse sounder, that distance could easily be up to 1.65m.

    So if 2 fish are 1.65metres or less apart, then they’ll show up as 1 single blob.

    A fish 1.65m or less from the bottom will show up as a lump/blob attached to the bottom.

    That might seem OK in 1000ft + of water but hopeless in shallow water.

    CHIRP technology changed that by getting rid of the pulse/ping length as the determining factor for target separation/range resolution.

    It was replaced by sweeping a frequency band across our designated “channel” and that SWEEP range then became the determining factor.

    Our ability to distinguish between target separation/range resolution magically became independent of sounder power and depth and INCREASED dramatically. Suddenly we could see targets individually that were only 16mm apart. Fish near the bottom became individual fish unless they were 16mm or less from the bottom (˝ inch).

    From 1.65 metres to 16mm for a sweep of 50. The greater the sweep, the better the target separation/range resolution. A sweep of 100 gives us 8mm separation.

    And THAT increased target separation/range resolution was independent of the channel used AND also independent of the depth of water.


    Attachment 121972
    Conventional pulse sounder


    Attachment 121973
    Same image CHIRP

    And THAT folks is what CHIRP technology brings to the fish finder table.

    So the question then changes from “ What is CHIRP and should I change?” and becomes “ Why am I NOT using CHIRP?”

  5. #80

    Re: Sounder fundamentals for the guys who wanted it

    Sent a PM to you

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