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Xterra 705 Coils
- Thread starter Reddog777
- Start date
That depends on your soil mineralization levels. If your ground is moderately mineralized, concentric coils will provide more depth than a DD coil of the same size. However, in highly mineralized soil, the DD coil will hunt deeper than a similarly sized concentric. The unofficial "rule of thumb" that I use is a ground phase setting of 28........ if I can properly set the ground phase of my 705 with a ground balance number of 28 or larger, I consider the ground to be moderately mineralized and prefer the concentric coils. If the ground balance number is smaller than 28, then I get better performance out of the DD coils.
In a nutshell, larger coils hunt deeper. Smaller coils separate targets better. DD coils separate targets better than concentric coils. Lower frequency coils will detect higher conductive targets (copper, silver etc) better than higher frequency coils. Higher frequency coils are better with lower conductive targets such as gold and iron, than lower frequency coils. Lower frequency coils will detect larger objects at greater depths than higher frequency coils of the same size. Higher frequency coils will detect smaller targets at greater depths than a lower frequency coil. With all that in consideration, know that ALL three frequencies will detect all metals. Some frequencies just do better with certain conductive properties (as mentioned above).
In my moderately mineralized soil, I like the 3 kHz concentric for those "wide open" spaces. I don't see much difference in the target response generated by coins. But I can hear a much clearer "low tone" on deeply buried iron. And I like the 6-inch DD at 18.75 for the trashy sites. Nothing better for target separation and sensitivity to small targets. JMHO HH Randy
In a nutshell, larger coils hunt deeper. Smaller coils separate targets better. DD coils separate targets better than concentric coils. Lower frequency coils will detect higher conductive targets (copper, silver etc) better than higher frequency coils. Higher frequency coils are better with lower conductive targets such as gold and iron, than lower frequency coils. Lower frequency coils will detect larger objects at greater depths than higher frequency coils of the same size. Higher frequency coils will detect smaller targets at greater depths than a lower frequency coil. With all that in consideration, know that ALL three frequencies will detect all metals. Some frequencies just do better with certain conductive properties (as mentioned above).
In my moderately mineralized soil, I like the 3 kHz concentric for those "wide open" spaces. I don't see much difference in the target response generated by coins. But I can hear a much clearer "low tone" on deeply buried iron. And I like the 6-inch DD at 18.75 for the trashy sites. Nothing better for target separation and sensitivity to small targets. JMHO HH Randy
Thanks Digger. Your explanation of the coil frequencies actually made sense to me. For a while now I have been trying to understand the real difference between the coils.
I think what I can sum up from all that is - use different coils at a same site. For example if I have been hitting a park using the 5x10 DD only then if I go back there with the 10.5 MF then in theory I might find other things that the 5x10 HF missed and vice-versa.
One question though: You wrote "Higher frequency coils will detect smaller targets at greater depths than a lower frequency coil". Can you roughly define what a "small target" is? If I believe there are some deep small silvers in a park, I'm talking Aussie Threepences that are I think about the same size as your dimes; and when I say deep probably around 8inches on average, would the 5x10HF be more suited to the task than the 10.5 MF? MF is better for silvers, but HF is better for small stuff. So what if it's small and silver?
As I wrote before though I think the simplest for me would be to go back to sites that I have hunted a lot and use the 10.5 MF which I just recently got.
Cheers
Snoopy
I think what I can sum up from all that is - use different coils at a same site. For example if I have been hitting a park using the 5x10 DD only then if I go back there with the 10.5 MF then in theory I might find other things that the 5x10 HF missed and vice-versa.
One question though: You wrote "Higher frequency coils will detect smaller targets at greater depths than a lower frequency coil". Can you roughly define what a "small target" is? If I believe there are some deep small silvers in a park, I'm talking Aussie Threepences that are I think about the same size as your dimes; and when I say deep probably around 8inches on average, would the 5x10HF be more suited to the task than the 10.5 MF? MF is better for silvers, but HF is better for small stuff. So what if it's small and silver?
As I wrote before though I think the simplest for me would be to go back to sites that I have hunted a lot and use the 10.5 MF which I just recently got.
Cheers
Snoopy
To me a small target is something less than 14mm in diameter. Things like small childs rings, ear-rings or other smaller pieces of jewelry. The reason I use 14mm for a number is because that is the size of an old US Silver 3-cent piece, the smallest coin I've found. US dimes are nearly 18mm in diameter (17.9 if I recall) I found the silver 3-cent piece using the 6-inch DD, which is 18.75 kHz. I'm convinced I didn't find it due to the frequency of the coil....... but due to the small coil's superior separation capabilites. If they made a 3kHz coil in that size, I'd be using it instead. But honestly, I think any of the coil frequencies will find dime sized (and larger) items equally as well as another. Now coil design......that's something different. Between the two coils you mentioned, I'd opt for the larger round DD as I've found it hunts deeper than the elliptical in my neck of the woods. But that is just my opinion, based on my findings at my site conditions. HH Randy
Mick in Dubbo
New member
I've personally found that the high frequency DD coils give a significantly more stable TID to the other coils. They don't seem to be affected by EMI issues like the other coils. Don't know why, it just is. I also much prefer the sensitivity of the high frequency coils.
Mick Evans.
Mick Evans.