Find's Treasure Forums
Welcome to Find's Treasure Forums, Guests!
You are viewing this forums as a guest which limits you to read only status.
Only registered members may post stories, questions, classifieds, reply to other posts, contact other members using built in messaging and use many other features found on these forums.
Why not register and join us today? It's free! (We don't share your email addresses with anyone.) We keep email addresses of our users to protect them and others from bad people posting things they shouldn't.
Click here to register!
Need Support Help?
Cannot log in?, click here to have new password emailed to you
Changed email? Forgot to update your account with new email address? Need assistance with something else?, click here to go to Find's Support Form and fill out the form.
X-Terra 705 Coil Selection
- Thread starter mapper65
- Start date
You make a good point about mineralization. Barnacle Bill made an excellent post regarding this matter, and how to determine what your mineralization is, some time back. This is the link to his post, as found in the FAQFAQ section. http://www.findmall.com/read.php?55,574329,574329#msg-574329
Strictly my opinion....... and keeping in mind that the ground phase reading does not necessarily reflect the true mineralization of a particular site. I have moderatley mineralized soil conditions. I know this by performing the function Barnacle Bill described in the link above. And due to my detecting this part of the Country (with lots of different detectors) since 1972. As such, I've found concentric coils will achieve greater depth of detection than a comparibly sized DD coil. However, Minelab's X-TERRA coils are not "comparible" in size. Thus, it is difficult to determine whether or not the 10.5 inch DD will hunt deeper than the 9-inch concentric, at the same frequency. But, since you indicated that your ground phase readings typically run in the 17 - 25 range, I'd suggest you will obtain better results with the DD coils. My rule of thumb has been a ground phase reading of 28, on the X-70 and 705. By that I mean, if you are able to properly ground balance your X-70 or 705 at a ground phase reading of 28 or higher (= less mineralization), then a concentric coil will be your best bet. By best, keep in mind that although the concentrics do require a bit more overlap when sweeping, they provide a more accurate TID and depth is not compromised at lower mineralization. If you require a ground balance setting of less than 28 (= more mineralization), I'm convinced (through extensive comparison testing) that the DD coil will provide better results than a concentric coil. It just plain operates with more stability. So, my recommendation for your particular application (with higher levels of mineralization) would be to consider using a DD coil.
As to a smaller coil........ I hunt for old coins at old sites. Since my ground is moderately mineralized, the concentric coils do a great job for me. And for most of my hunting in wide open areas, I opt for the 9-inch concentric at 3kHz. I believe the lower frequency not only is better suited for the copper and silver coins I seek. But I also find that the subtle sounds provided by deeply buried iron targets allows me to avoid most of them. I've made several posts concerning those sounds. For sites with multiple adjacent targets, (nasty - trashy areas) a smaller coil is a plus. And for target separation, the "narrow" detecting pattern of a DD coil is a vast improvement over the wider detection pattern of a concentric. I have found that any of the three frequencies will detect gold, silver, coppper etc. I know that the lower frequencies are better suited for higher conductive targets. And the higher frequencies are better suited for lower conductive targets. But honeslty, the difference between 3 khz - 7.5 kHz and 18.75 kHz is not a huge difference. Not when you consider the VLF's built primarily for gold are running upward of 60kHz. So for me, in those areas with lots of adjacent targets, it's the size and design, not the frequency. I am willing to use ANY of the three frequencies for finding coins and jewelry. Since I want a smaller coil for less of a footprint, and the DD design separates targets better, I use the 6-inch DD at 18.75 khz. Granted, I may think I dig more can slaw than I might with the same size and design at 3 kHz. (due to a more pronounced harmonic audio response of ferrous targets) But that is just speculation on my part, as the only frequency at this configuration is 18.75 kHz. If there is any trade off here, it would be trading the 7.5 kHz frequency provided by the 6-inch concentric, for the 6-inch DD at 18.75 kHz. I believe I get more benefits with the better separation than I would ever lose due to the higher frequency.
As to pinpointing....... some report the DD coil to be more difficult to pinpoint with than a concentric. I don't think it is more difficult. Just different. To pinpoint with the small DD coil, you can still X over the target and dig where the loudest audio is directly below where the rod fastens to the coil. OR, you can X back and forth over the target, while slowly dragging the coil back away from the target. Just as you indicated, the sound will drop off as the target leaves the detection field. In the case of the small DD, that location is just under the front tip of the coil, when you are dragging it back toward you.
JMHO HH Randy
Strictly my opinion....... and keeping in mind that the ground phase reading does not necessarily reflect the true mineralization of a particular site. I have moderatley mineralized soil conditions. I know this by performing the function Barnacle Bill described in the link above. And due to my detecting this part of the Country (with lots of different detectors) since 1972. As such, I've found concentric coils will achieve greater depth of detection than a comparibly sized DD coil. However, Minelab's X-TERRA coils are not "comparible" in size. Thus, it is difficult to determine whether or not the 10.5 inch DD will hunt deeper than the 9-inch concentric, at the same frequency. But, since you indicated that your ground phase readings typically run in the 17 - 25 range, I'd suggest you will obtain better results with the DD coils. My rule of thumb has been a ground phase reading of 28, on the X-70 and 705. By that I mean, if you are able to properly ground balance your X-70 or 705 at a ground phase reading of 28 or higher (= less mineralization), then a concentric coil will be your best bet. By best, keep in mind that although the concentrics do require a bit more overlap when sweeping, they provide a more accurate TID and depth is not compromised at lower mineralization. If you require a ground balance setting of less than 28 (= more mineralization), I'm convinced (through extensive comparison testing) that the DD coil will provide better results than a concentric coil. It just plain operates with more stability. So, my recommendation for your particular application (with higher levels of mineralization) would be to consider using a DD coil.
As to a smaller coil........ I hunt for old coins at old sites. Since my ground is moderately mineralized, the concentric coils do a great job for me. And for most of my hunting in wide open areas, I opt for the 9-inch concentric at 3kHz. I believe the lower frequency not only is better suited for the copper and silver coins I seek. But I also find that the subtle sounds provided by deeply buried iron targets allows me to avoid most of them. I've made several posts concerning those sounds. For sites with multiple adjacent targets, (nasty - trashy areas) a smaller coil is a plus. And for target separation, the "narrow" detecting pattern of a DD coil is a vast improvement over the wider detection pattern of a concentric. I have found that any of the three frequencies will detect gold, silver, coppper etc. I know that the lower frequencies are better suited for higher conductive targets. And the higher frequencies are better suited for lower conductive targets. But honeslty, the difference between 3 khz - 7.5 kHz and 18.75 kHz is not a huge difference. Not when you consider the VLF's built primarily for gold are running upward of 60kHz. So for me, in those areas with lots of adjacent targets, it's the size and design, not the frequency. I am willing to use ANY of the three frequencies for finding coins and jewelry. Since I want a smaller coil for less of a footprint, and the DD design separates targets better, I use the 6-inch DD at 18.75 khz. Granted, I may think I dig more can slaw than I might with the same size and design at 3 kHz. (due to a more pronounced harmonic audio response of ferrous targets) But that is just speculation on my part, as the only frequency at this configuration is 18.75 kHz. If there is any trade off here, it would be trading the 7.5 kHz frequency provided by the 6-inch concentric, for the 6-inch DD at 18.75 kHz. I believe I get more benefits with the better separation than I would ever lose due to the higher frequency.
As to pinpointing....... some report the DD coil to be more difficult to pinpoint with than a concentric. I don't think it is more difficult. Just different. To pinpoint with the small DD coil, you can still X over the target and dig where the loudest audio is directly below where the rod fastens to the coil. OR, you can X back and forth over the target, while slowly dragging the coil back away from the target. Just as you indicated, the sound will drop off as the target leaves the detection field. In the case of the small DD, that location is just under the front tip of the coil, when you are dragging it back toward you.
JMHO HH Randy
7centsworth
Well-known member
I have never used many coils , but I can tell you I really like my 6 inch dd coil. I have found alot of coins my stock coil has missd.
Gday mapper,
I went through the same stuff.
To me, pinpointing with a DD coil is easier than with a concentric, using the wiggle and pull back method as Digger describes.
The 10.5 " DD coil is the largest available to date but is quite heavy which can put some people (me included) off them.
it is a fact that lower frequency coils are more sensitive to silver...however
I hunt 90% for coins and use the beaut 5x10" DD 18.75khz coil mostly - I have picked up some deep silver getting nice high tones no problems whatsoever.
I dont want to put a concentric back on after using a DD for a while, it seperates close together coins (or other targets or junk) like no concentric could.
IMHO the blade like pattern must scan more deep ground than a concentric.
Happy swinging mate.
T59
I went through the same stuff.
To me, pinpointing with a DD coil is easier than with a concentric, using the wiggle and pull back method as Digger describes.
The 10.5 " DD coil is the largest available to date but is quite heavy which can put some people (me included) off them.
it is a fact that lower frequency coils are more sensitive to silver...however
I hunt 90% for coins and use the beaut 5x10" DD 18.75khz coil mostly - I have picked up some deep silver getting nice high tones no problems whatsoever.
I dont want to put a concentric back on after using a DD for a while, it seperates close together coins (or other targets or junk) like no concentric could.
IMHO the blade like pattern must scan more deep ground than a concentric.
Happy swinging mate.
T59
TURNMASTER
Active member
"I get the impression that pin pointing is possible but just not as accurate as we can do with a concentric coil." No, I do not think so. With a bit of practice you should be very accurate. I find center to the coil "draw a line" turn 90 deg repeat and X marks the spot. I do use the Pinpoint function also and it works just fine. I do run into problems when there are multiple targets and I am trying to pick out a dime, seems like nails push the signal around a bit (?).
The 5X10 DD and 6" DD seperate real well and for extreem trash the 6" DD is great. So far most of my good coins came from these 2 coils. I also have the 10.5" DD in 7.5khz and I dig much less iron, but do not use it in many of the yards I hunt due to trash.
Of the coils I have the order of seperation is;
6" HF DD
5X10 HF DD
10.5 MF DD
8" MF CC
HOWEVER I hardly use the 8" stocker anymore and do not have a ton of time on the 10.5" DD yet, 40 hours maybe more. I think they may be roughly equivelent in seperation, based on math the 10.5" wins. A lot of the soil I hunt justifies the DD coils. The 10.5 DD covers ground much faster and I believe its every bit as deep as the 8" MF CC, maybe deeper.
Oldest finds with the Xterra go to the 10.5" DD and the 5X10 DD. Tie at 1898. First silver with the Xterra is the 6"dd.
Good luck,
Jeff
The 5X10 DD and 6" DD seperate real well and for extreem trash the 6" DD is great. So far most of my good coins came from these 2 coils. I also have the 10.5" DD in 7.5khz and I dig much less iron, but do not use it in many of the yards I hunt due to trash.
Of the coils I have the order of seperation is;
6" HF DD
5X10 HF DD
10.5 MF DD
8" MF CC
HOWEVER I hardly use the 8" stocker anymore and do not have a ton of time on the 10.5" DD yet, 40 hours maybe more. I think they may be roughly equivelent in seperation, based on math the 10.5" wins. A lot of the soil I hunt justifies the DD coils. The 10.5 DD covers ground much faster and I believe its every bit as deep as the 8" MF CC, maybe deeper.
Oldest finds with the Xterra go to the 10.5" DD and the 5X10 DD. Tie at 1898. First silver with the Xterra is the 6"dd.
Good luck,
Jeff
TURNMASTER
Active member
I have heard that 6" MF CC is a HOT little coil with some real good depth.
mapper65
Member
Even though I originally posted that I was buying the 6 inch and 10.5 inch 7.5 kHz coils, I decided to also buy one of the 10.5 inch 18.75 kHz coils which arrived today ahead of the other two. I mainly bought it for when I goto the beach a few times a year but couldn't resist trying it out. Tonight I went to a grove in local park where I had previously spent about 3 hours with the stock coil. On the day that I was there with the stock coil, I found a sterling silver ring, a dime and a George Bush Sunoco token. Tonight I found 15 coins! I was very surprised to find 3 nickels since nickels have not came easy for me with the stock coil. The 6 inch and 10.5 inch 7.5 kHz coils will arrive tomorrow. On Saturday I plan on going back to the spot where I recently found an 1834 Half Dime and 1941 Mercury dime. I'm excited about the chance of possibly finding more with the new coils