Deep Targets, Target ID and Hype

[Anonymous]

Guys,
I'm an admitted newbie. I've only been in this hobby since the start of the summer. However, I've spent a LOT of time detecting, read everything I could get my hands on about detectors, talked to a lot of experienced folks and done quite a bit of "controlled" tests. I own both a DFX and a Minelab ExpII and numerous coils. My question is about target id related to depth. Now keep in mind, I have no real questions about tones, VDI numbers, Smart graph results or those types of metrics with sub-six inch targets. My question relates to DEEP targets, where "deep" is defined as greater than 8 inches. Here's the deal -- my tests show that a deep target, more often than not, will id incorrectly. That is, given ANY detector, the detector will not necessarily produce metrics (tones, etc) that indicate the correct conductivity and/or inductance of the target as expected. I believe this is verified by the fact that experienced users of EVERY detector I've researched claim that the depth of the detector increases by reducing the discrimination of the detector, with the BEST depth obtained with NO discrimination. Could it be that the detector "magically" increases its power as discrimination decreases? I can't find any evidence that this is true. The only explanation I can come up with is that depth increases as discrimination decreases because the "correct" target id is WRONG at greater depths. Could someone please correct the error in my logic. I really, really want to understand this concept.
Thanks!

 

[Anonymous]

Your question indicates a high degree of perception and intelligence! I believe that your explanation that "depth increases as discrimination decreases because the "correct" ID is wrong at greater depths" certainly makes a lot of sense, and those of us who have been detecting for a number of years (I have been detecting for over 20 years) with different detectors will wholeheartedly agree with your conclusion! I have been detecting with my Explorer XS for approximately nine months and have encountered many variables. For example, I have at times dug deep items that have not had "repeating signals" but still recovered silver coins at 8+ inches. I think it all boils down to this: if you have the inclination, dig any "questionable" signals. I always tell the story of my uncle and I--we both had a Whites 6000D coinmaster and he always found more coins and interesting items than I. One day I asked him why he found so much more than I, considering that we both had the same machines, and he simply said "I set the machine on discrimination, and then I dig everything, no matter what the meter says!" So, there you have it--go your own way, if you have the inclination to dig those "unusual" signals, whether they be visual or tonal, you will probably find more "valuable" items than you would otherwise. The only compromise is that you will have to do more work in that you will have to spend more time digging! If you're not lazy, I guarantee that you will find more than the average detectorist will find! Good Luck!! ~Larry~

 

[Anonymous]

Hey Futzman,
I agree that the screen is not to be used for deep coins. But I do not agree that the tones cannot be used. I think they can be used. I have found pennies and a silver dime at 9 to 9.5 inches with my 7.5" coil. When I found them, the crosshairs were worthless, but the tone made me dig them. The tones had pitches that were in the coin ranges (high enough), and the tones were a broken warbling sound.
On the other hand, I think that if my coins were next to 5 inch deep rusty nails that were producing false coin hits, I would have never dug those coins because the rusty nails' areas of influence would have covered up the coins. So I think trash presence makes a big difference with respect to depth potential.
As for discrimination, I agree that a deep coin that puts off questionable signals will cause nulling when you have a bunch of discrimination being used. Although I have seen my buddies pull 8-inch-deep coins out when they were using a bunch of discrimination (indian head and standing liberty quarter 8 and 8.5 inches measured depth--I measured the depth myself while the coins were still in place).
Mike

 

[Anonymous]

This is hypothetical as well:
Could it be that the more you disc out the less frequencies enter the ground and thus less depth occurs?
Say you only have silver opened up. I don't know what frequency is best for silver but I'm sure it is different for nickel/gold.
With a single freq. or dual freq. detector, this may blow my whole theory though since you can disc out many things and still have a single freq. enter the ground.
So what causes greater depth with less disc.?
Maybe it is all in the receptor part of the detector and not the sender coil?
Maybe it is picking up only part of the signal sent back and thus less depth?
Maybe we should ask (or "axe" [ebonics] <img src="/metal/html/grin.gif" border=0 width=15 height=15 alt=":grin"> ) a physicist?
Tony

 

[Anonymous]

Hey Tony,
I suspect that the machine puts out all the frequencies at all times. I also think that the machine detects all the usual targets whether you have them discriminated out or not. But I think the difference is that if you have a target discriminated out, the machine detects it anyway, but gives you a null instead of the sound signature of that signal.
So for example if you have a pulltab discriminated out and you go over a pulltab, the machine detects the pulltab with no problem. But instead of making the sound of a pulltab, you get silence--loss of threshold.
I think the depth issue is that if you have a deep coin, the detector detects it with no problem. But the signals being given off by that deep coin are distorted into iron or aluminum signals. If you have iron or aluminum discriminated out, you will hear a null most of the time. If you lower your discrimination, those distorted signals from the deep coin come in and you hear them and thus "get better depth".
Mike

 

[Anonymous]

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[Anonymous]

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[Anonymous]

Mike,
Thanks for the explanation. I guess I should have clarified my statement about the Minelab tones and deep targets. I meant to say that in ferrous tone mode the sounds are mostly wrong. However, the conduct tones appear to be pretty consistent on deep coins (at least in my coin garden). I suppose that with a lot of earth overhead it's certainly possible the inductance (ferrous) readings would be skewed.
Now with the DFX, the tones AND the VDI readings are skewed. I've done testing with the DFX with deep, silver coins in my coin garden and the only way I can get the DFX to respond is running with no discrimination. Even then, there's no way I would interpret its responses as "coins". In this regard, the Minelab is the way better for deeper coins in my books. Then again, I'm a newbie so what do I know <img src="/metal/html/lol.gif" border=0 width=15 height=15 alt=":lol">

 

[Anonymous]

The clue to what is really is happening is given to us by those detectors that report an ID number associated with each target. One will quickly notice IN ONE'S TEST GARDEN, the ID number will decrease as the depth of the target increases, also,the Id number will decrease in value as the black magnitite mineralization increases, but will increase as the red hematite/Alumninum Oxide mineralization increases. What this means: if any level of discrimination or notches are used, chances are good all deep items in mineralized ground will fall in a discriminated zone and not be detected, where as if it were more shallow, it would be correctly ID'ed while running in the discriminating mode. Further, if the nonferrous target is lying beside or under a piece of iron, it only makes the goody recoverable using all metal mode. In iron ridden sites that is not practical so that is why the old timers like Larry and myself run at the verge of total iron rejection or even better- a little less so regardless how low the ID number may fall due to this situation, it will barely be detected!! Many of my grestest finds have read as foil or nickle, and turned out to be very deep lead, brass, bronze, copper, gold and even silver goodies!! Make that test garden using soil from many areas in your neck of the woods and see how the Explorer responds. I do not have an Explorer but the book by Andy Sabisch (at the top of page 8 and else where) states custom discrimination patterns can be made in the air at home as the design of the FBS circuits are not affected by mineralization and therefore those patterns will work properly in the field. I am starting to believe that is not a 100% accurate statement but may work pretty decently as advertised up to moderatly mineralized areas. Good luck --JD

 

[Anonymous]

Guys, all I can say after reading all this is -- thank god I have my Periscope! Sounds like I'm going to have to start evaluating all those deep, questionable targets...