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Notch Discrimination on the X-TERRA - Ever wonder what you're missing? Part 2

October 06, 2010 11:34am

Randy Horton
Randy Digger Horton

Part One of this blog post described how the X-TERRA categorizes targets, based on their conductive values. In Part Two, learn how to increase your opportunity to detect jewelry and old coins by modifying the preset Patterns.

Now that I've outlined how the ferrous vs. conductive properties are represented by the visual and audio TID, let’s evaluate some targets. If you turn your X-TERRA 70 or 705 to the Coin/Treasure Mode, and set it to hunt in factory preset Pattern 2, you will be rejecting notch segments -8, -6, -4, -2, +2, +4, +6, +14, +16, +18, +20, +22, +24, +26 and +48. You will be accepting notch segments 8, 10, 12, 28, 30, 32, 34, 36, 38, 40, 42, 44 and 46. Those of you who have performed target ID tests with your X-TERRA know that this setting will accept U.S. pennies, nickels, dimes, quarters, half dollars and dollar coins. A Coin hunters dream? Not necessarily. Although repeated tests indicate that modern US coins will TID within the ranges set by Pattern 2, there are many variables that can affect the target ID information provided to the user. Some of these variables include coins on edge, adjacent trash that distorts the information sent to the processor, multiple coins in close proximity, target depth, soil conditions, ground balance settings etc. There are simply too many variables to guarantee that one TID number will always represent a specific target for every site. Coins wear thin; jewelry can be of many different metallic compositions, shapes and sizes. And, the mineralization of the site can fluctuate dramatically. Hopefully, what I am about to share with you will help you find more treasures. You will likely have to dig more trash while finding it. But if you understand what your discrimination setting is doing for you (or to you), you're bound to find more good stuff!

X-TERRA metal detector scale X-TERRA 705 pattern 2

To get a better idea of what you might be passing over as trash, let’s check out the conductive properties of various items some might "skip over" while detecting. Again, these numbers are based on the X-TERRA 70 and 705 TID, using the parameters of factory preset Pattern 2. Remember, as I mentioned above, TID numbers are not cast in stone.

If you are passing over targets represented by the X-TERRA 70 and the 705 with a numeric TID of +2, +4 and +6, you risk missing rose gold rings, platinum rings, white gold rings and some foreign coins.

If you are passing over targets represented with a TID of +6, +8 and +10, you risk missing more white gold rings, more platinum rings, thin yellow gold rings, lead and brass shells and the US nickel 3-cent piece.

If you set your detector to reject TID numbers +14 and +16, you will risk missing very thin silver coins, the $1.00 US Gold coin, thin yellow gold rings, Shield nickels, Liberty V nickels, 40% silver War nickels, many wedding bands, 10kt class rings, tokens and more foreign coins.

If you set your notches to reject +16, +18 and +20, you will risk missing gold rings, tokens, various gold jewelry, 14kt rings, brass, the US $2.50 Gold piece, Indian Head cents, Flying Eagle cents, more foreign coins and even large 10kt class rings.

If you rejected notch segments +20, +22, +24 and +26, you risk missing more Indian Head pennies, the US silver 3-cent piece, the US $5 Gold piece, large gold rings, small silver pieces, gold jewelry and medallions, and still more old tokens.

So there you have it. A few of the items that some of you might be passing over, in an attempt to not dig foil, pull tabs and other "trash" items. I realize that each of us has our own preferences for setting the discrimination on our detectors. I suppose you could say we are all creatures of habit. But the next time you hit that old park or picnic ground, you might want to ask yourself if you're rejecting notch segments that include targets that you wouldn’t mind digging.

Enjoy the Hunt!

Randy Horton (Digger)
You'll never know for sure......unless you dig it!


Another dynamite article! You convinced me earlier about hunting in all metal since on my next hunt, I found a 14K gold ring. Thanks again for sharing your expertise.
Posted By: chuckciao on October 07, 2010 10:05pm
Thanks for the kudos Chuck. And congrats on finding the 14K gold ring. Learning to use All Metal or zero discriminate (along with multiple tones) will allow much of your hunting to be done "by ear". Learning the subtle sound harmonics provided by deeply buried iron can save you lots of frustration while hunting old farm sites as well. HH Randy
Posted By: Digger on October 13, 2010 08:30am
Hi, I read this article two weeks ago, so I change my detecting mode to All Metal, this is very helpful for me because sometimes I´m searching for relics in battle fields for research purposes, so bullets, buttons and other stuff are important evidences to me.

I think I´ll always choose the AM mode and start training my hearing to identify targets and check the numeric ID.

Remember... In doubt, dig.

Greetings from Mexico.
M.P.C. Ignacio Moreno
Posted By: guruainur on November 07, 2010 04:15am
Thanks for your previous input on "threshold" Randy.

Here's another situation I hope you can help with.

I was recently hunting a home lawn and found a
'44 mercury dime apparently by accident; I wasn't confident in digging for it because it gave me a -8 on the ID with very intermitant 28-32 pops on the ID. I was in all metal mode and
the coin was only about 3" deep. after Retreiving it, I was frustrated because of how
many times this has happened and I chose not to
dig a -8 range ID. So I put the coin back in the ground and covered it up, swept the area again and it still came up -8 range with interminant pops of 28-32. When I put the coin on its side,it wouldn't ID even intermitantly good. Also, when pinpointing the coin's known position, it's off about 3". This seems to be the case on all my silver coin finds.

I can't stopped thinking about all the -8's I haven't dug. Am I doing something wrong?

Thanks for any help,

Posted By: SpenCo on November 09, 2010 10:22am
SpenCo, Something doesn't sound right. From what you've told me so far, I see three different possibilities for the -8 TID. The TID of targets buried in the ground are dependent on a properly adjusted detector (primarily NC, GB, Sens, Threshold), possible adjacent targets and the "angle" the target is, in relationship to the coil.

If you got a TID of -8 on the Mercury dime, and your detector is properly adjusted, I'd question that you may have actually been getting the TID of a larger, adjacent piece of ferrous metal. Not the dime. The "pop" sounds you mentioned, along with the 28 - 32 TID, indicate to me that you were getting "mixed" signals. If you put the coin back in the same hole it came out of, you were likely getting the TID of that adjacent target again. A metal detector will process the information from all the metal targets under the coil, at any one time. Larger targets "take priority" over smaller targets due to the strength of the signal they send back to the receive circuitry. When a larger target over-rides a smaller target, we call that target masking. Slower sweep speed and a DD coil will aid in reducing target masking.
When a metal detector sends an electrical signal into the ground via the transmit portion of the coil (similar to an electromagnetic field) that signal energizes metallic objects. In turn, those metallic objects generate their own eddy currents. These eddy currents are "picked up" by the receive portion of the coil. The detector analyzes various attributes of that electrical signal produced by the target and assigns a value to it, based on the software. This target value is then relayed to the user via audio response and visual TID. In the case of your Mercury dime, if the flat surface of the coin is parallel to the coil, the transmit signal will saturate the entire surface area of that coin. The signal sent back to the receive windings are based on that flat coin. The TID will represent the value of those signals, as processed by the software. Typically a Merc is around a 36 - 38. If, however, the coin is on edge, the surface receiving the electronic transmitted signal is very small and will not generate the same response as when it is flat. Coins on edge will not generally provide the same TID as those same coins when flat. They are usually lower in reading, and shallow ones may even "double beep". The deeper the coin on edge, the more variance there will be. A good excercise might be to air test some coins at various angles and at different distances from the coil, to better understand how that angle and depth will effect the response of the detector.
In direct response to your ignoring the -8 signals, wondering now if they were silver coins, I don't think that is the case. The notch segment of -8 and +48 are much "narrower" notch segments than the other notches. This was done in an effort to reduce the wrap around effect of highly ferrous targets, into the conductive range. Rejecting -8 or +48 should not have an effect on your detector's ability to detect US coins.

In summary, my suggestions on the -8 readings for the Mercury dime would include assuring you have properly set the NC, GB, Threshold and Sensitivity. Slow down your sweep speed in an effort to isolate individual targets. And recognize that a small Double-D coil is the ultimate weapon in separating targets. And again, perform some airtests and learn how the angle and depth of the target will effect the TID and audio response.

As to your pinpoint question.......are you using a DD coil or a concentric? Which Pinpoint mode are you using? And where do you set the coil when you press the Pinpoint button?

Hang in there. We'll get this figured out! HH Randy
Posted By: Digger on November 12, 2010 09:43am
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