X-Terras & Bottlecaps

[Smudge]

One thing I always loved about Tesoros was their ability to give you a scratchy signal on most bottlecaps, even with low discrimination.

I am looking at the X-Terras and have to wonder how they handle these pesky things. I would image the higher frequency coils would tend to make bottlecaps look like good targets, just as lower frequency coils would be better at identifying them as junk.

Likewise, I would think the DD coils would do a worse job on bottlecaps than a concentric coil would.

I only ask because bottlecaps are the one junk target I HATE to dig.

Has anyone worked on this issue?

 

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[Longhair]

Well....I can tell you that you're pretty much on the mark, except for the part about DD coils doing a worse job.

I can also tell you the reasons that the HF coil is the worst for discriminating crown caps. It has to do with the target bin widths being narrower at the top of the scale with the HF coils, coupled with the difference in target response between the three freq's. The MF coils actually have the most uniform bin segment widths providing the most honest/accurate TID's, and the LF coils have the widest bins at the high end. What this means is that it's easier for high conductors to bleed over into adjacent bins with the HF, whereas the opposite is true with the LF. When you factor in the targets response to the fequency selected, understanding that rusty iron is basicly at the very bottom of the scale, you'll find that often what causes it to register as a high conductor is what's known to be a "wrap-around effect", which boils down to it producing a harmonic that causes it to be placed in a high value bin.

Here's an illustration that shows the difference in bin widths between the three frequencies.

What I've found to work well for dramatically reducing the number of those pesky things is, I knock out -8 and 48.
Another thing to do, is to learn to listen for a harmonic second tone mixed with the stronger good sounding tone. It's hardest with the HF coils (nearly impossible with my destroyed hearing), but some say that it is present.

Personally, for coin shooting I prefer the MF or LF coils. Unless I'm hunting at the beach for jewelry, or reasonably clean fields for relics, the HF coils stay home.
FWIW, the new Coiltek LF coils are HOT! And as such they tend to make bottlecaps very distinguishable by scratchy, broken, or faint tones. There is very little "iffy" about these coils, and the only down-side is that they aren't reliable nickel seekers, due to the lower conductor properties of nickels.