Metal Detector Discrimination Really Sucks

I am primarily a prospector but have also been coin and jewelry detecting since 1972. Like most people when in parks I use discrimination to pick targets but when prospecting I usually dig it all. Not always though, sometimes I am tired or an area is just too trashy so I crank in a little VLF discrimination to sort things out.

The problem is when prospecting I have seen some pretty scary things. It is one thing to walk away from a dime because your detector called it a nail. Think about walking away from a solid multi ounce chunk of gold because your detectir called it a nail. Not likely, you say? Far too likely, I am afraid. I and others dig big nuggets other people leave behind on a regular basis, and I know I have missed some very big ones myself in the past. It gets your attention to realize you may have walked away from $40,000.00.

I have this pile of detectors headed my way to check out. One, the Nokta Fors Gold, showed up yesterday. Good first impression out of the box, but that is another story. The main thing is today I got it out along with a Gold Bug 2, Gold Bug Pro, F75, White's GMT, and CTX 3030. I rounded up a 1 gram gold nugget and a collection of nails and hot rocks and did a little playing around this afternoon.

I am still waiting for the XP Deus to show up and a V3i so this was more about coming up with some methodology more than anything. My interests run more towards hot rocks and magnetite sand than would be the case with most people. So the particulars do not matter at the moment, except this.

Discrimination sucks! You fire these babies up in all metal and they are all powerful detectors that do the job, with some amazing depth for VLF units (not counting the CTX which lacks a true all metal mode). It is pretty easy to compare units as it really just boils down to depth and how well they handle hot rocks, which is mostly a function of frequency and ground balance. EMI is a big factor in urban areas also but much less so when prospecting.

So then I put the detectors in disc mode and I just cut the legs out from under them. Bam, instant lost depth. Also, target masking or so-called reactivity is usually a non-issue in pure all metal modes. Not so at all in disc modes, and disc modes that lack true zero discrimination settings mask targets immediately even when set to zero.

Anyway, all I can say is playing around for awhile with these units and my pile of hot rocks and little nails was rather disheartening. It was just so darn easy to get that little nugget to bang out loud in all metal, then disappear entirely in disc modes. Or get detected but called ferrous. Or get masked by a nearby hot rock or nail. It just hammered home with me once again the huge difference in raw power between something like a GPX 5000 and even the best VLF detectors in all metal mode, and how that huge difference becomes an almost impossibly large gulf once you turn to disc modes. When you just go detecting in a park you do not see what you are missing. But in my case it was all to visible and really kind of bummed me out seeing just how far we have to go when it comes to metal detector discrimination.

The only icing on this cake is, as Tom has often tried to remind people, a huge amount of fantastic stuff in the ground, and not deep at all. It is there, quite shallow, just under or near that thing you discriminated out. If we could see through discriminated items rather than be blocked by them an amazing amount of stuff would come to light.

Beneath The Mask by Thomas Dankowski

The Painful Truth by Thomas Dankowski



Edited 2 time(s). Last edit at 09/18/2014 02:00AM by Steve Herschbach.

Prompted............ and worth re-mentioning:

How do you know what you are missing............ if you don't know it even exists.


I discovered a stunning phenomenon a few years ago.... whilst archaeological site recovery/pit digging (with rare Earth magnets)............ and am desperately seeking to find time to disseminate/educate.

Bravo to you Steve for saying what needs to be said. We always get impressed by the discrimination abilities of our detectors never realizing what we are leaving behind. Since we do not know, we think we are doing great.

We often use the excuse that we have too little time to detect so discrimination helps us cover more territory and find more good targets? Why do we believe we have to cover a large area when we hunt?

Once I covered a small area in a park using discrimination. Then I went over it again in all metal. More good targets were found. I am certain if I did it again and again, more and more targets would be found.

It has certainly been an eye opener for me!

What we need is a 3D ground scanner This is when I will spend $2600 on a coin shooter.

The v3i keeps me guessing if I have it at its optimum performance and that's my only gripe though I am still learning it.

The v3i though here in Australia I think is a great machine for detecting silvers and coins without digging aluminium screw caps. Here is why.

Just dig targets that fall in the low and high frequency range as aluminium screw caps fall in the mid range frequency. Large rings though
may fall in the middle frequency as well and you may miss one or 2 though need to do more tests around this. Best policy though is to dig it
all which takes me back to Vaquero and how much I did find with it hence why I wanted to try a Deus because its the same type of beep and
dig machine with many more features rather than relying on a screen.

I tested the AT Gold on iron infested ground and sold it after playing with it for 3 hours.

I tested a G2 and that was not bad but you can hear the hot rocks and by watching the meter spike.

The Deus will be the last vlf I will be testing out in the Goldfields though.

My Deus arrived 2 days ago. Just need to find some time to take it out to test.

Put the Deus in Full tone and use no disc or very little. Let your ears help you decide.

I think you will be surprised how well the Nugget responds in mineral with the DEUS..

like in the other topic...the ground bal handles/looks the ground different..It allows for see though...

Youve got to not think of the DEUS like other VLFs..even if disc mode if you turn the silencer off and couple that with the see through ground mineral it has you will rethink Disc limitations...Not perfect or foolproof but noteworth all the same...The DEUS in disc mode does not do a lot of filtering...

its hard to talk about it till you get it and run then you will get a grasp of what can be advantageous......

Keith



Edited 1 time(s). Last edit at 09/18/2014 03:09AM by Keith Southern.

fsdigital12 Wrote:
-------------------------------------------------------
> Put the Deus in Full tone and use no disc or very
> little. Let your ears help you decide.

Does not matter. If you are running tones you are running in disc mode. All you are doing is employing a method that helps to a small degree. Just like faster recovery helps, but it can't do anything about the majority of masked targets.

Very good write up Steve. Please keep posting your findings in this thread ,if you have the time. Ray

Quote:
" with some amazing depth for VLF units (not counting the CTX which lacks a true all metal mode). "

Steve, I'm sure you're probably already aware of this, but there's a tricky way to put the CTX into an all metal mode;
1. Set the pinpoint to sizing.
2. Turn on pinpoint lock.

Now when you'd like to hunt an area in all-metal, just tap the pinpoint button and there you go. A perfectly functional all-metal mode.
(Tap the pinpoint again to switch back to the normal, discriminate screens and audio.)

Sometimes it's better to listen to the unprocessed signal to determine the size, shape, and depth of an object...especially in clutter.

mike



Edited 1 time(s). Last edit at 09/18/2014 03:31AM by Mike in CO.

You know Mike, I was aware of that but had forgot about it. Thanks for reminding me because now I want to see if it is functionally identical to normal all metal modes.

I hear you Keith and I have no doubt about what you say. But something tells me I am going to be happy to get back to my PI units again when I wrap this little adventure in VLF land up!

That's the way I run the CTX at the beach.
Look at it this way with the pinpoint method. You are taking an instant value of the ground signal and then comparing your sweep to it.
It often needs to be retuned, but goes awfull deep!

Often you'll get signals not registering in the disc mode, now and again I had a silver ring just snow up the display with target trace on.
Like static on a TV,... older TV's :-)
Those are the targets I really like to dig!! Take a decent scoop with you, it will give you a workout.

I was really hoping to hear some beautifull things about small gold and chains on the beach with the SDC2300. But it seems nobody has bothered yet.
Price wise it is a bit of a big investment to try, haven't even got the time at the moment!!

There is a Deus hype going on at the moment,... I spent 3 days playing with the latest software in my test garden. When it's trying to sniff out targets in a complex target situation,...
It isn't a lot better than any decent single frequency VLF out there and the all metal tones drive your brain in overload!
People don't loose jewelry at a Roman site in the middle of a field!
People loose jewelry anywhere there is drink, fun and lot's going on. With all the modern day trash as well!
A lot of guys have said the Deus is HOT on gold,... frequency wise Yes,... reporting it Yes,... reporting it in a mixed target situation NO,... You are better off with an X-terra 705 with the 10x5 HF coil and a pattern set to knock out high conductors and running a threshold. The nulling tells you to Slooooooowwwww down.
The audio discrimination picks out tiny fragments of the signal and signals them.
Hit the button and check if the signal is a coin or not.
Try hitting buttons on a Deus to change anything when it's cold and rainy.
XP guys,.... WE NEED BIGGER BUTTONS,... maybe they'll listen if you shout. Doubt it :-)

Discrimination is indeed the biggest problem in our hobby.
Fascinating isn't it :-)

HH
Johnb

Hey John theres better machines for sure when working through modern trash...

Again the DEUS is first and foremost a ferrus non ferrous seperator....Its strongest point so far for me is it sees buttons in iron better than the competition...even some of the best on the market at the moment for working iron and setup with the sleuthiest of unmasking settings just cant signal on some of the Civil war period buttons intermingled in iron as easy or at times cant do it period like DEUS or GMP...

The DEUS is great at seeing though Mineral and telling you if its iron or not and is also great at hearing small low conductors in iron on an advanced level...

Nothings perfect as in anything...But I like to stress to use it for what it does best and you will be pleased with your purchase...It's world calss in what it does best and that can be the difference between the find of a lifetime or going home empty handed...especially on hunted hard old/ancient sites...

Use a hammer to drive a nail ....Use a screwdriver to drive a screw....

Keith

Steve,

I found I like my Pi more than most VLF's I have tried after finding out what you have found out.
Found one VLF I really liked for my hunting style and conditions and it likes gold, goes deep and very pleasant to use.
It's the AKA Berkut. It's unlike any VLF I have ever used and think it will be the last one I buy. Unless Tesoros Cazador when ever that comes out,
turns out to be a good machine, then I will have an excuse to buy one more, mainly for the wife. For her Tesoros seem to be a good match.
You might want to take a good look at the AKA Sorex and the wide selection of search coils.

DeepTech Vista X with 3 search coils.
Works for me

If it was easy everyone and their brother would be swinging on the weekend. The day that metal detectors leave all the aluminum and foil in the ground and pull out all the gold is the day that you will never get on another property.

Yep ! I have worked on archaeological sites , [ Indian Wars, Civil War , etc. ] & several of us detected an area til we knew [ thought ] there were not any metal objects left at all. Then, we dug & sifted test pits & found lead buck & balls, uniform & tack items , etc., etc. in most every test pit ! It always makes me think what I may be leaving behind every time I go detecting.

Now that the weather is starting to cool off, I am going back to an old picnic grove that has been hunted for decades, and run some of my units in all metal and dig everything and see what possibly others (including me), left in the ground. Lots of iron and small foil at this site,, but after reading this post, it peeks my interest to see what an all metal hunt at this location will produce.

Old silver coins, up to this day, have been taken from this site, so I imagine it's worth it to pursue an all metal hunt.

It certainly has its place in trashy parks where I would never get off my knees, however in your case I can understand your frustration just from reading as all we have in Pa. are coal nuggets...
Certainly if I lived in gold country would buy a good gold machine and go from there...

Discrimination has certain signal amplification thresholds that have to be reached before a signal can be analyzed and put in a bucket. Couple that with everyone's desire to have reliable discrimination......well, you see which direction that threshold level might have a tendancy to travel.....

Adding discrimination to the all metal mode, whither it be tone, visual, or what have you, is still subject to the same limitations.

That doesn't include the issues around the bucketizing process itself.

HH
Mike

You cant add discrimitatiopn to an all metal mode...its not all metal anymore..

Any type disc info you get while in all metal threshold based modes is taken from the disc circuit...

This is where the Nautilus can excell ...it runs both modes att the same time in audio unison....the deepies wont report on the disc side till some dirt is removed..or you get that faint fluttry hit right at the edge of the disc depth....

Now either one by themselves arent worth much ,,,a deep faint all metal hit or a fuzzy weak or surely not there disc hit is not informational...

Combine them in unison...and the earth comes alive...and also in the way the all metal reports with the disc....in scenarios like wide loud allmetal hit wiht scratchy disc hits is surley a large piece of iron....a report that starts opn the allmetal side a bit before the disc side and ends a bit after the disc report is a low conductor....A report that starts right before the all metal report and ends right after it is a Mid conductor....a rpeort that is in almsot perfect unison wiht the disc and all metal the same time is a good high conductor...

Plus you know a weak all metal hit that does not report in disc is worth digging dirt out of the wat till it does report...

This is where all the other manufacturers missed the boat....like whiles with the Mixed modes...they did not match the Nautilus pure audio ....the Nautilus is a very advanced instrument even to this day in the way it operates...two machines using one coil more or less...not so with the whites mixed processing mode...

Nothing in the VLF world is as deep as a all metal threshold based ground balancing system..But nauiltus Knew this and did what was available to enhance the disc mode....Unison reports..

If a person has never ran a Nautilus they have missed some of the best quality audio and depth that a vlf has offered even till today...

I think it ought to be required to learn to detect with a nautilus.. it will make you learn so much about target behavior and dirt signal distortions...

Keith

I would guess when Mike said this: "add discrimination to the all-metal mode" he meant as done on machines like the GMP, Deus. That's how I interpreted it. The advantage of adding disc to an all-metal mode is it lets you hear the whole picture, all through the sweep, rather than just when the machine decides it's a peak-point in the signal. But it's harder on the ear/brain, so takes some learning.

Sven1 Wrote:
-------------------------------------------------------
> Steve,
>
> I found I like my Pi more than most VLF's I have
> tried after finding out what you have found out.
> Found one VLF I really liked for my hunting style
> and conditions and it likes gold, goes deep and
> very pleasant to use.
> It's the AKA Berkut. It's unlike any VLF I have
> ever used and think it will be the last one I buy.
> Unless Tesoros Cazador when ever that comes out,
> turns out to be a good machine, then I will have
> an excuse to buy one more, mainly for the wife.
> For her Tesoros seem to be a good match.
> You might want to take a good look at the AKA
> Sorex and the wide selection of search coils.


And yet more interesting detectors. It appears the Europeans are going to put some real heat on the US manufacturers. More competition can do nothing but benefit us all. Thanks for the tip Sven, and best of luck to you on your future hunts.

Im pretty sure what hes talking about Pimento is the way detectors add say Visual I.D. while in the all metal mode....its not part of the all emtla mode but sampled form the phase shift circuit and displayed or even heard while in the all metal mode...

The DEUS does have a true all metal mode in the prospecting mode only.......But the iron I.d. and visual I.D. is brought over from the phase shifted side used for disc in that mode......

Even if say the DEUS is set to zero disc ALL metal accept it is getting that through a disc circuit..not a single channel raw all metal mode...The DEUS uses a full report disc mode like a 1266 used to you hear it all,,,,, its still phase shifted to say a target is a small piece of iron or large piece of silver and thats a disc circuity doing it......

This is where the disc limitations are coming from....the way I was talking about the Nautilus running is a way one maverick desinger found to combat disc ineffectiveness...give a raw signal feed and a phase shifted single feed in unison...

Keith

Now if Nautilus got out of the 70's era and updated the lunchbox machines with a smaller circuit board to fit into a compact box the size of a Tejon and battery box under the armcuff...........

DeepTech Vista X with 3 search coils.
Works for me

Quote: "I'm pretty sure what he's talking about is the way detectors add say Visual I.D. while in the all-metal mode....it's not part of the all-metal mode but sampled form the phase shift circuit and displayed, or even heard, while in the all metal mode"

Perhaps Mike could elaborate on what he was meaning, there's certainly a few ways of attacking the disc / all-metal problem.
But the fundamental problem is this: You need more, better-quality information from a target in order to determine a target ID. Working out if something is there or not [ie. conventional all-metal] is not that hard. But trying to measure the target phase shift, when the signal is barely there, and is dwarfed by ground signal (which is also wobbling around, in amplitude and phase), is just not practical. If you increased the 'sensitivity', you would just get nonsense ID's that jumped about, and told you nothing. The only way to get better quality ID's is to have a stronger target signal, ie. a shallower target.

What about the Whites MXT that has prospect mode, and tells the iron %. Can,t that be used to tell if a target is less iron. I know everythings else will read a less % of iron and you if you want to dig or not.

Flintstone Wrote:
-------------------------------------------------------
> What about the Whites MXT that has prospect mode,
> and tells the iron %. Can,t that be used to tell
> if a target is less iron. I know everythings else
> will read a less % of iron and you if you want to
> dig or not.

The MXT will hit a target deeper than it can get an accurate iron reading for all the reasons stated above. Worse, the more mineralized the ground is, and the more fringe the target, the more likely the MXT is to misidentify the gold nugget as ferrous. This is not the fault of the MXT - it is just the way discrimination works. One thing I really like though, no matter what, the MXT will never give you a better than 90% indication an item is ferrous. It always reminds you there is a 10% chance it is gold. Would you dig 10 holes for a gold nugget?



Edited 1 time(s). Last edit at 09/19/2014 10:00PM by Steve Herschbach.

Years ago (on this forum) I posted/challenged folks to dig/recover just 12 fairly deep mid-tone (medium/low) conductors each/every time they hunt. If you are a relic hunter....... you already know why.

Years ago every relic hunter that I hunted with had a Nautilus and I had a CZ 6a (and I still own and use it). We often compared weaker signals on both machines and never did one find a signal that the other would not also recognize as a good signal. So does that mean that the Nautilus also has the same masking problems in iron as the CZ 6a? I always worked my machine in zero descrimination so all iron would report, but we all know as the signal of a good target gets deeper the signal strength weakens until it falls into the iron range, and then fails to report at all as it is too deep or weak of a return signal for the detector to report a target at all. Many of the older hunters that are still alive swear by their Nautilus detectors in my N.C. And Va. soil. I understand how the Nautilus works with discriminate in one side of the earphones and all metal in the other. Great setup. But does it have a leg up on the CZ? Both are deep. Both are good. You may talk me into buying a Nautilus yet. Steve, Keith, and Nasa Tom, I would really like to hear your opinions and thoughts on this. I know they are old technology, but I feel they are still great detectors although I have to admit that I never used a Nautilus for more than a few minutes and never liked the idea of sending a detector in to get the coil tuned every couple of years as the Nautilus required and the fact that it ate batteries like a kid eats candy.
This is a great thread that makes many of us look hard at descrimination issues and question our own thinking as to what targets are worth digging. We hear time and again how descrimination is a function of how lazy we are. Something to save time and dig only the good targets with a minimum of trash targets, but now we see why so many relic hunters have started useing PI detectors to find many good targets in bad ground that were missed for years useing VLF detectors in descrimination modes. Kind of drives home the point that even in good ground a VLF detector in all metal will find many great targets that have been missed for years all because of descrimination.
Hope my questions on CZ and Nautilus comparisons does not interfere with the direction of this discussion...Stuart

The nautilus strong poitn is nt unmasking in iron... actually when you use a nautilus for elic hunting ..you usually have a npothe rmachien to pick in iron with..

The Nautilus is for Camp site retrieval not thick house site hunt's...Oh it does as well as alot of units in iron but its not stellar...it works best in depth...and finding the iron concentrations to work on..pur relci unit.. wlak thorugh the woods and slow down when the iron starts...Its very very hot on brass....not a fast machine but a sensitive powerful machine...

like you stated whatever the CZ heard in iron the Nautilus heard and Vice versa..

Now where the Naultius would out do a mass market assembly line consumer grade unit is in pure raw depth when the dirt is not mineralized...the power of the nautilus even to this day is very very deep...I have many times pulled past a foot flying eagles/indian heads....15+ inch 3 ringers...this is where the depth gets crazy deep...its the all metal report you have to analyze...then scrape the dirt back till the target is close enough to let the discriminator work...

I still see the nauitlus in good dirt even in the disc side as one fo the deepest brass diggers ever made...you can understand the dpeth till you see it do it...eagle coats at past a foot no problem...

but the dirt has to be non mineralized to se the full effect..

in alot of my dirt I get alot of all metal blow back from the nautilus...you have to rememebr the nautilus is running 44 volts to the coil its a very powerful machine.. will eat through 4 9 volts in about 9 hours...

I at this point would not reccomend a Nautilus to anyone... the owner of the company past away...and the doors are closed...does not look good.

and the coils need to be recalibrated about every year or two....they are hard to keep in tune past that...just going form sun to shade till the temp stabilizes makes them noisy...Its not because there poor built but because they are running on the extreme edge of power that a commerical made assembly line machine cant run because of failure and cost to build....Nauitlus used only the Highest components and suplied on the control box the ability to tune the coil to the box as temps changed and as the coil aged...called R&C controls...they had to be exactly tuned or the coil falsed badly...

they used a extremely clean disc circuit...with some awesome audio modualtion....but Im afraid they are now a thing of the past for servicability..theres still new ones out there but as the coils go out of tune theres only maybe a couple of people that know how to align them...but it would not be the factory doing it...never hear much of component failure...look inside one and youll know why....QUALITY....they are old school...they need to warm up awhile to run the best... and get one that is balancing the coil at 12 oclock on the R&C control and get in some good dirt and you have never seen depth like you will see...Crazy depth...Depth manufacturers right now cant achieve Smoothly...

I just wish someone would build a light weight Nautilus DMC....But they would nto have the power Im afraid...

I dont recommend buying one.. the last one I had was out of tune so I let it go cheap...

keith

Thanks for your comments Keith. Much appreciated.