I just got an X-Terra 70 and it came with a 6 inch HF DD coil as part of the package deal. I do not plan on prospecting with it but do occasionally hunt places that are pretty trashy and around playground equipment. I hunt a lot in open areas around parks or schools. Would I be better off trading the 6 inch for a 10.5 DD 7.5khz coil instead of the 6 inch or is there not really much depth difference to gain with the 10.5 coil over the standard coil. Thanks.
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Which coil for X-Terra 70?
- Thread starter Bill_S
- Start date
I know that there have been several posts concerning the "benefits" of the 10-inch DD coils. And, I agree that they are excellent coils. But whether or not they are the "best" coil for you will depend on the sites you hunt and the mineralization in your soil. I live in a part of the USA that has moderate to lightly mineralized soil. Through extensive testing, I've proven to myself that the 9-inch concentric coils will detect just as deep as the 10-inch DD coils. I realize that this may not be the same results that others have. But it all depends on the soil conditions where you are hunting. The 10-inch DD coil covers more ground with each sweep. And the DD design is "hot" from front tip to the rear. The detection pattern of the concentric coils is not "straight up and down", so I make an effort to overlap my swaths more carefully. I don't have a magic formula for when a DD coil is required. But again, through testing, I've determined that having a GB number of 28 is kind of a breaking point for me. In other words, if I can GB my concentric coil with a numeric indication of 28 or higher, the concentric stays on for the hunt. On the other hand, if the mineralization is such that the number is lower than 28, I find I have better results (and more stability) if I switch to a DD coil. Again, nothing magic. Just an observation I've made in my neck of the woods.
As to the 6-inch coil..... keep it. It is an excellent coil for target separation in trashy locations. If I am hunting in a yard or open field, (and the soil mineralization allows it) I will likely use one of my 9-inch concentrics. If I encounter an abundance of trash, I put on the 6-inch and work around them. With that said, I will point out that the 6-inch DD at 18.75 kHz goes against my thoughts on coil frequency and design. As I mentioned, I like the concentric coils for this part of the Country. And for silver and copper targets, the 3 kHz is my favorite coil. (the 7.5 kHz is a close second) The high frequency coils are more "receptive" to lower conductive targets. For a coin shooter like me, that means I dig more iron, foil and aluminum can slaw with the HF coils than the Lower 3 kHz or the Mid-Range 7.5 kHz. However, Minelab does not currently make a small DD coil in any frequency than the 18.75. And, I believe I get better target separation with the DD, as compared to the 6-inch concentric at 7.5 kHz. So, there are trade-offs. I would rather have the additional separation characteristics of the 6-inch DD, and dig some extra trash, as compared to using the 6-inch concentric and not feel as if I have done an adequate job of target separation. But as I've said several times before, if you took the tags off of each of my 6-inch coils, I probably couldn't tell them apart. Both provide great sensitivity and amazing depth of detection.
The "rules" of thumb I use are..... smaller coils separate better. Larger coils detect deeper. Concentric coils are best suited for moderately mineralized soil. DD coils are best suited for highly mineralized soil. Lower frequencies are best for high conductive targets such as copper and silver. Higher frequencies are best suited for lower conductive targets, such as gold. Lower frequencies detect larger targets deeper. And higher frequencies are better at finding small targets (at shallower depths). Regardless of the frequency, coil size, shape or design (concentric or DD), rest assured that each of them will do a great job of detecting US coins. JMHO HH Randy
As to the 6-inch coil..... keep it. It is an excellent coil for target separation in trashy locations. If I am hunting in a yard or open field, (and the soil mineralization allows it) I will likely use one of my 9-inch concentrics. If I encounter an abundance of trash, I put on the 6-inch and work around them. With that said, I will point out that the 6-inch DD at 18.75 kHz goes against my thoughts on coil frequency and design. As I mentioned, I like the concentric coils for this part of the Country. And for silver and copper targets, the 3 kHz is my favorite coil. (the 7.5 kHz is a close second) The high frequency coils are more "receptive" to lower conductive targets. For a coin shooter like me, that means I dig more iron, foil and aluminum can slaw with the HF coils than the Lower 3 kHz or the Mid-Range 7.5 kHz. However, Minelab does not currently make a small DD coil in any frequency than the 18.75. And, I believe I get better target separation with the DD, as compared to the 6-inch concentric at 7.5 kHz. So, there are trade-offs. I would rather have the additional separation characteristics of the 6-inch DD, and dig some extra trash, as compared to using the 6-inch concentric and not feel as if I have done an adequate job of target separation. But as I've said several times before, if you took the tags off of each of my 6-inch coils, I probably couldn't tell them apart. Both provide great sensitivity and amazing depth of detection.
The "rules" of thumb I use are..... smaller coils separate better. Larger coils detect deeper. Concentric coils are best suited for moderately mineralized soil. DD coils are best suited for highly mineralized soil. Lower frequencies are best for high conductive targets such as copper and silver. Higher frequencies are best suited for lower conductive targets, such as gold. Lower frequencies detect larger targets deeper. And higher frequencies are better at finding small targets (at shallower depths). Regardless of the frequency, coil size, shape or design (concentric or DD), rest assured that each of them will do a great job of detecting US coins. JMHO HH Randy
