X Terra frequency and depth

[atomicscott]

I was reading Randy's review of the 3 WOT 15" coils and was noticing that the depth on the air tests of both the 3 khz AND 18.75 khz coils was a good bit better than the depth of the 7.5 khz coil, on pretty much every target tested in the article. I realize these are only air tests, but my question is: Is the increase of depth on the LF and HF coils due solely to the frequency of the coils, or is it something that is particular to the WOT coils? Hypothetically, would the 6" DD 3khz (Digger) coil and the 6" 18.75 kHz DD coil BOTH be deeper than a 6" DD 7.5 khz coil (if one were indeed available)? Are 3 kHz and 18.75 kHz frequencies just deeper?

 

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[Longhair]

Generally speaking, low frequencies penetrate the ground deeper than higher frequencies.

Having said that, there are distinct differences between the ability of concentric coils and DD coils of any given frequency in various soil conditions. In mild ground, a concentric will cover more ground thoroughly and see deeper at the coil center than the DD. But in hot ground a DD often has an advantage, because it does not have as much total volume of minerals in the detection field to compensate for.

 

[atomicscott]

Generally speaking, low frequencies penetrate the ground deeper than higher frequencies.

Having said that, there are distinct differences between the ability of concentric coils and DD coils of any given frequency in various soil conditions. In mild ground, a concentric will cover more ground thoroughly and see deeper at the coil center than the DD. But in hot ground a DD often has an advantage, because it does not have as much total volume of minerals in the detection field to compensate for.

Thanks LH, Im well aware of the differences between dd and concentric coils. I had heard that generally, lower frequencies were deeper. My question was why then, is the higher frequency dd coil deeper than the mid frequency coil in Randy's W&E treasures air tests. I know that there is no 6" 7.5 khz dd coil to compare, but if it were available, would it still have the least depth when compared to the other 2 aforementioned coils? The 15" LF and HF coils were deeper than the MF coil on every target tested other than the clad/silver dimes

 

[Longhair]

OK, first of all, you already said it....they're air tests.
Aside from that, in the case of the 15" coils, you'll notice that his sensitivity was only 26 on the MF coil, 28 on the HF coil, and 30 on the LF coil.

So the bottom line is more that the response from the different target metals is the biggest difference between the coils. One frequency over another will not see significantly deeper under all but extreme circumstances.

 

[atomicscott]

I did notice that he was only able to run the MF coil at 26. Now that also makes me wonder, does the MF coil not run as stable requiring the sensitivity to be backed down thereby losing perceptible depth? Thanks for your responses Longhair, but this was also puzzling me. I am interested in purchasing the 18.75 6" DD for hunting for jewelry and natural gold (as well as the better separation in trash). I have the MF 6" concentric, and was wondering if I could expect similar depth with the 6" HF DD.

 

[Longhair]

OK....if you notice, all three coils also chose different noise cancel channels as well, so it is entirely possible that EMI harmonics effected the 7.5kHz coil enough more that it had stability issues requiring less sensitivity. I'm guessing....but it's a pretty educated guess.

And it's quite likely that the 6" HF DD will see at least as deep as the 6" MF CC, due largely to it's having less mineralized ground to deal with in the detection field.

 

[atomicscott]

OK....if you notice, all three coils also chose different noise cancel channels as well, so it is entirely possible that EMI harmonics effected the 7.5kHz coil enough more that it had stability issues requiring less sensitivity. I'm guessing....but it's a pretty educated guess.

And it's quite likely that the 6" HF DD will see at least as deep as the 6" MF CC, due largely to it's having less mineralized ground to deal with in the detection field.

Thank you Longhair, it all makes more sense to me when you factor in all the variables. I'm going to grab an HF 6" dd coil, I think it would be a great addition to the arsenal. I will report back after Ive had a chance to try both the coils back to back. Thanks again for the info!

 

[Bart@Big Boys Hobbies]

Thanks again Longhair!

He already covered it but again. Air tests aren't much help really and do NOT represent a coin that is been buried awhile. Test you see with freshly buried coins or air tests are far from accurate.

When long Hair speak... listen! Great knowledge he has!

 

[atomicscott]

Thanks again Longhair!

He already covered it but again. Air tests aren't much help really and do NOT represent a coin that is been buried awhile. Test you see with freshly buried coins or air tests are far from accurate.

When long Hair speak... listen! Great knowledge he has!

True, but for strictly comparative reasons air tests can be helpful.

 

[issombeituni]

I have the 18.75 and the 3 . The 18.75 is amazing on nickels and the 3 is amazing on coins an silver. I will tell u first hand the 3 is deeper with the right settings

 

[atomicscott]

I have the 18.75 and the 3 . The 18.75 is amazing on nickels and the 3 is amazing on coins an silver. I will tell u first hand the 3 is deeper with the right settings

Hey thanks for the info! I was more interested in the 18.75 for the better separation over the concentric and finding gold jewelry (beaches, lakes and parks) as well as occasional nugget shooting. I have read in some older reviews that a guy was getting about 8-10" average on coins with the 18.75 6". I know I have found a lot of clad dimes/quarters in the 8-9" range (in good ground) with the 6" 7.5 concentric coil.