Extra coils - XT 70, 3 kHz deeper on silver coins, etc.?

[David]

It comes with the (10" x 5" DD 18.75 kHz and) 9" Concentric 7.5 kHz. For the XT 70, the extra 9" Concentric 3 kHz is suppose to be deeper on silver coins. How much deeper and it worth the money to purchase this if I am hunting after about 90% silver coins ?? Is the extra depth on silver coins of the 3 kHz very small, something like 1 inch or less and not worth it or alot more and worth it ??

Any other help with the 10" DD round is appreciated, in 7.5 and 18.75 kHz for gold prospecting.

Also for the 6" Concentric 7.5 kHz and 6" DD 18.75 kHz (waterproof). Is the 6" DD 18.75 the only coil that is waterproof or they all are waterproof ?? Do the Concentric coils have more accurate pinpointing and also "improved target identification" over DD coils do you find in the real world ?? Thanks, David!

 

[Digger]

I can only speak from my own experience. But I don't think there is any appreciable difference in depth between the 9-inch concentric at 7.5 kHz and the 9-inch concentric at 3 khz. You can even toss in the 9-inch concentric at 18.75, for that matter. All achieve the same depth in my neck of the woods. But there are reasons other than "equal depth" that I like the 3 kHz. Due to lower frequencies being more "in-tune" with higher conductive targets (such as silver and copper), it is LESS "in-tune" with lower conductive targets (such as iron and aluminum can slaw). Running the 3 kHz coil in all metal, with multiple tones, is the combination I use on old farmsites and open areas that allow the larger coils. It may not hunt any deeper than the other two frequencies. But it provides a very distinct audio tone on deep iron and other ferrous targets "bordering on" a high conductive reading.

Regardless of the size or shape of the coil, my recommendation for prospecting would be the 18.75 kHz coils in the DD design. Again, higher frequency coils are more "in-tune" with the lower conductive gold. And DD coils are designed to compensate for higher levels of mineralzation, which is frequently encountered at gold bearing sites.

All of the X-Terra coils are waterproof except the 6 X 10 Elliptical coil. It is categorized as being "water resistant". Some have reported good results making their elliptical coil waterproof by adding a bead of silicon around the seam where the coil cover meets the coil. And dabbing a bit around where the coil cable enters the coil.

Theoretically, concenteric coils offer a higher degree of accuracy in target ID. With the X-Terra coil options, both concentric and DD coils provide accurate TID. I will say that I beleive concentrics will lock on to targets better, when approaching from a multitude of directions. But in trashy areas, the small DD coil seems to separate targets better than the small concentric. However, the DD will sometimes provide more of a "flute" sound when isolating a good target. Although the pinpointing technique is different with DD coils than concentric, with a little practice, pinpointing is a snap with either. JMHO HH Randy

 

[David]

Thanks alot Randy. I wish a (fourteen) 14 inch round DD (and maybe also a Concentric) for the XT -70 will be made for fast ground coverage for all three, prospecting and coins and relics.

I also wish the XT-70 had more notches than 28 in steps of 2. Something like 100 or 200 notches for more accuracy. I would like to knock our new pennies and only find old ones here in Canada. David!