X-terra 705 coil

[fever87]

After hunting the highly mineralized soil of Culpeper County VA with the stock coil on the 705 I am looking at trying to mitigate the soil issues I encountered. Does anyone have any recommendations about a new coil to use to help beat that soil? I am not looking to invest in a PI machine (yet) so I am looking at a lower investment such as a DD coil if that is the way to go for now.
Can anyone with more experience speak to the advantages of a different coil over the stock concentric coil? Thanks.

 

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[Bart@Big Boys Hobbies]

With hot ground a single freq is always gonna suffer there. A DD coil will help some depending on the ground.

 

[fever87]

Thanks Bart. Does it matter what freq to get a DD in? I understand the concept that a DD works on but not sure if getting a new coil in a higher or lower freq would have any affect on performance for, as you stated, its a still a single freq and that has difficulty in hot ground.

 

[Bart@Big Boys Hobbies]

Lower frequency is better for coins and big objects. Higher frequency is better for lower conductors (gold) and small targets. Hope that helps.

 

[fever87]

Lower frequency is better for coins and big objects. Higher frequency is better for lower conductors (gold) and small targets. Hope that helps.

That does help - was unaware of the advantage of the freq difference. Thanks!

 

[Longhair]

Another thing to consider, is that lower frequencies penetrate the ground better(deeper) than higher frequencies, so if you have high mineral content in the ground, lower frequency will see more of it. A DD coil will always do better in mineralized soil, and a small DD will do best.

If you're hunting silver coins in mineralized conditions, the best that you can do is a compromise between frequency, coil size, and search pattern configuration.

BarnacleBill on another forum wrote up the procedure for measuring ground minerization with the Xterra. This procedure will only work correctly if the MF (7.5kHz) stock concentric coil is used.

Procedure in Normal GB mode with GB Tracking "OFF" and Sens=20:

A. Auto-noise cancel in the area you will hunting with the coil held 3 feet above the ground and parallel to it.

B. Locate a target free area of soil.

C. Engage Normal GB & remain in the GB screen.

D. Place coil on the soil. Do not press the coil against the ground! This will distort the coil shape and give an inaccurate result. Simply allow the weight of the machine to lightly keep it against the ground.

E. Press the Auto GB button and raise coil about two feet above the ground before Auto GB has completed. If by the time you reach the apex of pulling the coil up to two feet it doesn't complete, then pump up and down from just above the ground to two feet high as accurately as possible. Recall that Auto GB signals with a tone when completed.

F. While still in GB mode press and hold Patterns button to get the numbers. The numbers are six digits in length but read out in three groups of two that will repeat if the Patterns button is held down. Therefore 99 99 99(almost a million) is the largest number possible and 0(00 00 00) is the smallest. Forty-six thousand would appear as the following sequence, 04--60--00. Make a note of the numbers which we will call the "IRON NUMBER"(Magnetite...Black-Sand).

G. As a reference, numbers in the thousands are mild ground, medium grounds tens of thousands , and hot hundreds of thousands. For clarity:
1. 0(zero) >> 10K mild ground.
2. 10K >> 100K medium ground.
3. 100K >> 1M hot to scorching.

Procedure in Beach GB mode with GB Tracking "OFF":

The same as above in normal GB except that your are measuring conductivity. Great for Ocean beaches, salt flats, & dried up lake beds etc. I would also take three samples in the exact same spot and average them to get an average number, using either of the above procedures.

Hope this helps!

 

[GioTheGreek]

I thought I knew a bit about my Xterra 70... until I read that Barnacle Bill quote. I have a lot to learn. Thanks for the tips.

 

[BuffaloBob]

After hunting the highly mineralized soil of Culpeper County VA with the stock coil on the 705 I am looking at trying to mitigate the soil issues I encountered. Does anyone have any recommendations about a new coil to use to help beat that soil? I am not looking to invest in a PI machine (yet) so I am looking at a lower investment such as a DD coil if that is the way to go for now.
Can anyone with more experience speak to the advantages of a different coil over the stock concentric coil? Thanks.

Colorado gold prospecting means black sand and hot rocks. I us a 6" DD High Frequency waterproof with my best success. Not as much trash signals and very sensitive. Also I like my 5x10 DD HF eliptical for guiding through heavy brush. The 6" are pretty economical and I use a lot for coin shooting too.
BB

 

[Longhair]

As I said, a DD will always do better than a concentric in highly mineralized soil conditions. A DD looks at a narrower slice of ground, so the accumulative effect of the minerals is less, regardless of frequency. So a smaller DD will be seeing an even smaller amount of the minerals.

It's a shame that MineLab hasn't produced a lower frequency DD coil, or allowed anyone else to. For most of my hunting I use either the MF DD or the LF concentric. An LF DD of any size will deffinately be my favorite when one becomes available.
For as much as I use my HF DD I probably ought to sell it. It is the least useful to me.

 

[BuffaloBob]

As I said, a DD will always do better than a concentric in highly mineralized soil conditions. A DD looks at a narrower slice of ground, so the accumulative effect of the minerals is less, regardless of frequency. So a smaller DD will be seeing an even smaller amount of the minerals.

It's a shame that MineLab hasn't produced a lower frequency DD coil, or allowed anyone else to. For most of my hunting I use either the MF DD or the LF concentric. An LF DD of any size will deffinately be my favorite when one becomes available.
For as much as I use my HF DD I probably ought to sell it. It is the least useful to me.

Also depends a lot on where you are detecting. Colorado for example may have some olde Spanish coins but for the most part our pulltabs are usually less than 8" deep. Many finds are just below surface. So my 705 has to be "de-tuned" to fit those type ground conditions.

My 705 will get signals deeper than I care to dig. If you are lucky to detect areas back east or CW era sites, then that would be a different story. IMHO.

Figure out what you are searching for, take into consideration the terrain and take a shot at what you feel is best. I believe that about any detector will locate great stuff. It's not the gear as much as how you do it.

I have seen detecting buddies find the greatest stuff without Minelab equipment! Don't know how they do it. I'm saving for the big 15" Coiltec jobbo. Always another coil....
BB

 

[BILL R]

highly mineralized soil x-terra 705

With hot ground a single freq is always gonna suffer there. A DD coil will help some depending on the ground.

check out randy Horton free e-book at minelab on the 705