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Hi All,
I have posted some info about this subject on the 3 to 1 ratio posting but will add a little more here. Originally, I built up a 3 1/2" by 12" coil and tried it. I was impressed with the results as a mono coil design. However, the housing is a little small for a DD design so that was not tried at this time.
Now, one new request I have made to Bill Hays is to build a larger rectangular form that is 5 1/2" by 18" long. This size lends itself to making several different type coils. The reason for such a design is it will work very well for several types of coils that can be used for various reasons. The elongated shape works extremely well for a couple of new coil projects. So, lets discuss just what can be done.
First, a simple mono coil could be built. Nothing new here except the odd shape of a coil that is about 5 1/2" by 18". Expect great depth and a lot of ground coverage.
Next, one can build a DD coil. Again, nothing really new here, just two coils that are wound and positioned correctly. One would really want the overlap zone to extend along the long side so the detection zone is about the length of the coil. Again, the coil should work very well.
Next, one could build an odd figure 8 mono coil. In this case, a coil a little larger than the housing is built and this coil is twisted one half turn in the center (middle of the lengthwise side) into a figure 8 type shape. Now, half of the "face" of the coil is facing down and the other half would be facing up. This type of coil would be noise canceling and would be a great choice in very noisy areas. The down side is there is some depth loss when compared to a full mono coil and there will be a null point in the center of the coil. Since half the coil is facing up and the other half is facing down, then any noise will generate opposite signals in the halves, and as such, the noise will cancel.
Ok, now for another odd design, the modified dual coil design. In this case, a full size mono coil is built and a full size odd figure 8 type mono coil is also built. However, the figure 8 coil will now be used as a separate receive coil much like the receive coil on a DD design. Such a design is not only noise canceling but also a naturally ground canceling design. Such a design should work great in about any environment since it minimizes any externally caused noise and reduces the ground response dramatically. The key to minizing the ground signal is to keep the coil level over the ground.
One odd feature of this design is the signals one would receive. One half of the receive coil would generate a positive response from a non ferrous object while the other half a negative response. In other words, lets say you connected the receive coil such that the front half produced a nice positive response on a nickel, then the back half of the coil would produce a negative response.
This is not a new design but is basically the design of the White's Bigfoot. At least, that is what I am told.
Anyway, I thought some of you might enjoy trying out some of these coil projects. I have built all of them in the past, but didn't have the ideal housing. Hopefully, that will change here shortly once Bill H. gets them done.
Reg
I have posted some info about this subject on the 3 to 1 ratio posting but will add a little more here. Originally, I built up a 3 1/2" by 12" coil and tried it. I was impressed with the results as a mono coil design. However, the housing is a little small for a DD design so that was not tried at this time.
Now, one new request I have made to Bill Hays is to build a larger rectangular form that is 5 1/2" by 18" long. This size lends itself to making several different type coils. The reason for such a design is it will work very well for several types of coils that can be used for various reasons. The elongated shape works extremely well for a couple of new coil projects. So, lets discuss just what can be done.
First, a simple mono coil could be built. Nothing new here except the odd shape of a coil that is about 5 1/2" by 18". Expect great depth and a lot of ground coverage.
Next, one can build a DD coil. Again, nothing really new here, just two coils that are wound and positioned correctly. One would really want the overlap zone to extend along the long side so the detection zone is about the length of the coil. Again, the coil should work very well.
Next, one could build an odd figure 8 mono coil. In this case, a coil a little larger than the housing is built and this coil is twisted one half turn in the center (middle of the lengthwise side) into a figure 8 type shape. Now, half of the "face" of the coil is facing down and the other half would be facing up. This type of coil would be noise canceling and would be a great choice in very noisy areas. The down side is there is some depth loss when compared to a full mono coil and there will be a null point in the center of the coil. Since half the coil is facing up and the other half is facing down, then any noise will generate opposite signals in the halves, and as such, the noise will cancel.
Ok, now for another odd design, the modified dual coil design. In this case, a full size mono coil is built and a full size odd figure 8 type mono coil is also built. However, the figure 8 coil will now be used as a separate receive coil much like the receive coil on a DD design. Such a design is not only noise canceling but also a naturally ground canceling design. Such a design should work great in about any environment since it minimizes any externally caused noise and reduces the ground response dramatically. The key to minizing the ground signal is to keep the coil level over the ground.
One odd feature of this design is the signals one would receive. One half of the receive coil would generate a positive response from a non ferrous object while the other half a negative response. In other words, lets say you connected the receive coil such that the front half produced a nice positive response on a nickel, then the back half of the coil would produce a negative response.
This is not a new design but is basically the design of the White's Bigfoot. At least, that is what I am told.
Anyway, I thought some of you might enjoy trying out some of these coil projects. I have built all of them in the past, but didn't have the ideal housing. Hopefully, that will change here shortly once Bill H. gets them done.
Reg
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