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DIY Bigfoot coil?

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  • #1

    DIY Bigfoot coil?

    I surprised this hasn't come up before - either something everyone knows but me or some kind of taboo...
    Please describe details about the Bigfoot coil - winding details, how to make your own, how to customize to your particular detector.
    I got the chance to try one today with an XLT. I can see why it is used for contests but I would expect a coil with such dimensions to act as it did.
    The only weird thing was how it pinpointed at one end and supposedly it should be ground balanced using the same tip.
    I passed on the opportunity to buy it as I typically dig things deeper than it will sense.
    I can see though why this is a popular coil for detecting contests.
    What is the history here - why no longer made if it satisfies this purpose?

    Barry
    Tags: bigfoot coil xlt
  • #2
    The Bigfoot is difficult to make. It does not lend itself to automated equipment and is very labor-intensive and expensive. I once looked at putting it into production but for the low sales number there was no way it made sense.

    It is made with a full-size transmit coil and a figure-8 receive coil. One problem is that White's historically has used very high inductance RX coils which makes the figure-8 tough to make. A Bigfoot for Explorer/ETrac would probably be a lot easier to make.

    Another place for the Bigfoot is hunting large sports fields for recent jewelry drops.

    - Carl
    • Likes 1

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    • #3
      I don't understand what makes it difficult to make. The Tx is simple but the RX is many turns in a figure 8... Can't you just make a loop and twist it to the figure 8 config?
      Is the adjustment of matching +/- halves the issue? Would two separate but end to end RX coils be the same thing or different?

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      • #4
        Originally posted by bklein View Post
        I don't understand what makes it difficult to make. The Tx is simple but the RX is many turns in a figure 8... Can't you just make a loop and twist it to the figure 8 config?
        Is the adjustment of matching +/- halves the issue? Would two separate but end to end RX coils be the same thing or different?
        These are questions you could answer relatively easily by trying to build one.

        However, I can see why the major beeper manufacturers might not be interested. It's labour intensive to manufacture, and has a low volume of sales. Basically not worth the effort involved.

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        • #5
          I DO want to make one - just want a better description of what to do as I've never seen the guts of one. Is the RX coil made as a single and twisted, single and crosswound, or two separate but joined coils? Or maybe any of these work - to your point - if done right?

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          • #6
            Barry, have you a book ITMD?

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            • #7
              There is a brief discription on GeoTech: Coil Basics by Carl Moreland: http://www.geotech1.com/pages/metdet/info/coils.pdf

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              • #8
                That is a good write-up. Here's another discussion - I'm thinking he has RX/TX backwards though?
                http://www.findmall.com/read.php?31,1294729
                KT315 - is the Delta pulse schematics comment related to this coil or?
                (I have the book but have not checked it for a coil discussion. I have a ~3foot stack of MD literature/copies/printouts. Unfortunately my memory isn't the greatest.)
                Usually in this forum, guys get to the detail - I used this wire, measured for this inductance, used this epoxy, tweaked this or that.

                How important is the ground balance benefit from the split8 config when the coil is used in parks for contests etc.? Seems the ID capability of the detector is messed with - at least with the one I tried it didn't work even if I change TX frequency.

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                • #9
                  Originally posted by bklein View Post
                  I DO want to make one - just want a better description of what to do as I've never seen the guts of one. Is the RX coil made as a single and twisted, single and crosswound, or two separate but joined coils? Or maybe any of these work - to your point - if done right?
                  Offhand I don't recall. I have a Bigfoot that I split open but it's in storage in one of 50 boxes marked "Misc".

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                  • #10
                    KT315 - is the Delta pulse schematics comment related to this coil or?

                    this is a signature. no related. the author of that is fredrico alias his post #10 http://www.geotech1.com/forums/showt...t=Vandal+Pulse

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                    • #11
                      Field Test: http://www.jimmysierra.com/BFTest.html

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                      • #12
                        would a bigfoot type coil work on a surf pi that has been configured for a dd coil?

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                        • #13
                          I think it would respond only on half the coil, the other half would null over targets.

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                          • #14
                            Would another option be to make two overlapping rectangles similar to a "DD"? I think Tesoro makes their Bigfoot look-alikes that way.

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                            • #15
                              Yup, that's what Tesoro does. There are trade-offs.

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