Minelab CTX 3030 Detecting Forum

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hunting in trash
Posted by: sube
Date: March 15, 2014 09:02PM This only works in ferrous coin ,can be ground coin, beach,high trash , low thrash , and so forth but ferrous coin has to be selected . This is a coin with no audio ,since target trace is independent of the audio it shows up on the screen .The eye opener here is the half no audio but it's there plain as day but you will not here it if it's east and west .North and south it should ring clear as a bell but if it is mast the other way you won't here it. It does not have to be a nail any iron object will mast the coin except very small iron objects .The smaller the iron the more depth you will get .This is a stacked iron object on top of a good coin or touching , only ferrous coin will work .I work very heavy trash and when I mean slow that Means baby steps forward swing speed does not matter over lapping is what counts .This will open up areas you though were finished you won't get them all but you will get a lot that are mast and are silent hits . If someone has a e-trac let me know what it says in this situation , my explore nulls on this and I think the e-trac will to .AS far as north and south any mode will pick this up but you can't swing both ways when you hunt .My trash is very dense when I go to north and south I will hit another nail which will kill the signal from the opposite way .So if your hunting by sound your leaving coins behind watch that target trace it's another disc circuit you been running all the time and probably didn't understand . sube

Re: hunting in trash
Posted by: parkgt
Date: March 15, 2014 09:30PM
Another interesting video with more food for thought!

Thanks again.

Time for another software update...
Posted by: Chris(SoCenWI)
Date: March 15, 2014 10:05PM

I did some of the same experiments and posted them quite awhile back. I did find that with using the target trace too many of pure iron falsing hits gave diggable signals. But looking at the video he shows them being much somewhat higher numbers. I didn't notice/remember this. Will have to try again. But the fact that the machine can "see" a coin under iron on an east-west swing is something very enticing. To get an coin/iron audio signal with the CTX or any signal with the older explorers pretty much had to be dead on aligned in the north-south. Even a couple degrees of would be a null.

But... If they can show an east-west hit on the screen they can also make it have an audio component. And this would all be more informative if they would trash the 12 ferrous line. Suspect this is strictly an software issue and could be changed.


Re: hunting in trash
Posted by: sube
Date: March 15, 2014 10:16PM
Chris in the field where I hunt most of my falses come in at 40 or 41 easy to eliminate by going north and south . But the point here is the degraded signal of say a dime which hits 12.44 will be drawn en down to 12.37 or less the key is seeing the iron in the right corner telling you it's with iron .also I still like the 12 line because that's where minlab decided to put non-ferrous items instead of all over the screen just easier to see it's non-ferrous .As far as giving a audio east west don't think it well happen target trace is independent of audio and I think the audio sees the nail and nulls but the target trace sees both objects and places them both on the screen. sube

Edited 1 time(s). Last edit at 03/15/2014 10:23PM by sube.

Re: hunting in trash
Posted by: Bayoubug
Date: March 15, 2014 10:17PM
That's some great information to know. What if you have a discrimination pattern running instead of a clean screen. Do you get any different results? I don't hunt with a white screen that much right now... The places that I've been hunting have a lot of trash and iron and I just can't stand listening to the machine gun. Thanks for the video too.

Re: hunting in trash
Posted by: sube
Date: March 15, 2014 10:26PM
Bayoubug yes works with as much disc as you want .It' not audio it's target trace which is independent of audio . sube

Re: hunting in trash
Posted by: rsarge1
Date: March 16, 2014 09:38AM
well that just opened my eyes I've been hunting good sound hits only, great video showing how great this machine can be, now I will be changing how I hunt and give it a try, awesome video I have learned so much from the videos here thanks


Happy Hunting All


Re: hunting in trash
Posted by: Snakeriver
Date: March 16, 2014 11:09AM
I really find your videos informative! Thanks for taking the time to make them Sube, much appreciated!

Re: hunting in trash
Posted by: smittyman1956
Date: March 16, 2014 05:40PM
Keep up the good work Sube! I may get the hang of this thing yet!

Re: hunting in trash
Posted by: sube
Date: March 17, 2014 12:54PM
(Quote) I did find that with using the target trace too many of pure iron falsing hits gave diggable signals. But looking at the video he shows them being much somewhat higher numbers. I didn't notice/remember this. Will have to try again. Chris my falses come in at 40 to 41 I call it the wheat penny false because that's where they hit for me .As to many pure falses (What you will have to remember is the coin without audio is always going to be downgraded such as the half going from 12.46 to 12.37 same with dime quarter and penny) .A coin that has iron with it but is not totally mast will give audio and give a harder hit and more color in the cursor also the #s well be higher. Again my falses happen at 12.40 to 12.41 there either pure falses or wheat Penny's all you have to do is sweep the opposite way and make sure it pinpoints where the good sound is coming from .Another thing I have found is the false is a hard hit because it is concentrated on the point of the nail very small concentrated hit if it going in and out on the same sweep or you move a tiny bit from your original sweep it go's away . Then chances are you have a nail false a coin on the other hand being a bigger target dose not display this character the coil can be moved a lot more off center and still retain the cursor hope that helps. Round iron objects display similar to the coin hit and are harder to eliminate but most iron that falses usually are jagged and have some type of point on them giving a nail like false . Washers and round items well I guess you will just have to dig . sube

Edited 2 time(s). Last edit at 03/17/2014 01:16PM by sube.

Thanks sube, I'll have to try it again once the ground thaws.. Pretty soon now.N/T
Posted by: Chris(SoCenWI)
Date: March 18, 2014 12:45AM

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Re: hunting in trash
Posted by: DigginVt
Date: March 18, 2014 04:53PM
Nice videos Sube, should be helpful, lots of good info. Must still be frozen for you too if you're detecting in your living room :thumbup:

Dad always said "half ass means doing it twice"

Re: hunting in trash
Posted by: sube
Date: March 18, 2014 05:13PM
It's frozen all right but it's the foot and a half snow that bothers mean .Next week for a couple of days back to -3 to -5 for a few days lots of time to play around with the detector . Would like to make a video on falsing because a lot of people have problems with this but I can't do it because I have to do it in the field . sube

Re: hunting in trash
Posted by: Johnnyanglo
Date: March 18, 2014 11:38PM
Elongated iron when swept along its length will null whatever else is under the coil - no audio. Try placing a quarter on the ground and sweep lengthwise down a nail 3" from the coin - you won't hear a thing with the 11" DD. So, you'll need a smaller coil and to work from various angles in iron junk soil if you hope to uncover non-ferrous targets. Elongated iron swept parallel (not lengthwise) will not mask the coin.

Why? The magnetic field lines do two things (in all detectors): 1) they are repelled by non-ferrous 2) tend to flow through ferrous. The nail acts as a conduit that effectively bends the field lines along its length and away from the coin. Non-ferrous when illuminated by the primary field will set up a voltage across the coin surface, causing electrons to flow, which induces a secondary magnetic field that opposes /cancels the primary. Thus, the field lines are somewhat bent around the coin (which alters the IB at the receive coil and generates a voltage in the receive coil). Iron has the opposite effect, bringing in field lines through the iron metal (like lightning to a flag pole). The difference between the positive and negative response from ferrous and non-ferrous allows detectors to differentiate between these metals. Soil minerals, like mag-hematite and magnetite, are also culprits (especially when in layers within the ground) at truncating primary field penetration.

The soil matrix loaded with iron nails is creating a complex distortion that is 1) turning the field lines toward the horizontal (most nails lay flat and therefore channel coil energy into the horizontal) 2) greatly decreasing detectable depth of non-ferrous. Interestingly enough, the iron has a much stronger affect on the receive coil than the tiny secondary magnetic field generated in the non-ferrous coin. Thus, the iron nail can be detected to great depths (12-14") while the coin is lost beyond half that (5-6").

The nail has tiny domains (electron level) which are turned by the magnetic field from the transmit coil and align temporarily along the field lines. The patches of unbalanced domains (ferromagnetic) only stay aligned until the illumination passes - then they scramble again. The aligning and unaligning of the nail's polarity produces a secondary field that disturbs the receive coil's balance, generating a signal. The more ferromagnetic the target the greater this effect and the stronger / deeper the target can be detected.

Usually you can tell it is a nail - unfortunately the sharp pointy parts also produced a non-ferrous like signal (eddies) that combined with the strong ferrous response can fool most detectors that the object has non-ferrous properties (usually the display jumps from 35Fe to 12Fe. You may think there is a nail next to a coin. But, a coin has only the eddy current and usually gives a tight response within one small zone of the display while the deeper nail will drift around the 12Fe line. This is because as you make your small coil sweeps the nail head/tip/bends are being hit at different angles and are generating weaker/stronger non-ferrous eddy responses. Thus, the Co value is less stable - moving back and forth between 30Co and 45Co. It looks somewhat like a penny/dime - but too jittery. With the CTX you should also see the nail's ferromagnetic response (from the iron shaft) too - down at the bottom of the screen 28 - 35Fe values.

You will also notice the the coin's audio will be rounder and longer while the nail's non-ferrous response from the tip/head/bends will be chirpy and short. Check the depth meter - it'll often jump about from 4-5" deep to 10-12" deep as the nail responds to the varying sweep angles. Sweep angles don't bother a round non-ferrous target - the depth will usually be stable (assuming you keep the sweep centered over the target and don't change the sweep speed).

Altogether, the chirpy tone, the fluttering Co value along the 12Fe line, the obvious iron response at the bottom of the screen, and sometimes the off-center pinpointing (you switch to pinpoint and all of a sudden the target seems to have moved), are tell-tale signs you've got a nail masquerading as a non-ferrous target. It'll still effectively mask any non-ferrous target around it - so you'd have to clear the field of nails before you really start to find the deeper buried coins. Failing that, the next best thing is to search slowly and sweep in short sweep lengths while changing sweep angles as you go. Listen for that fairly repeatable round tone (ignore the chirps) or the fairly isolated TID that isn't jumping about (ignore the rest).

Occasionally dig a jumpy, chirpy signal to reinforce the lesson and find that nail at 10" laying horizontal in the ground. Also, don't use much discrimination or you'll never even get the coin's strangled round tone to sound off in a bed of nails. Disc reduces effective depth and sensitivity - use it very carefully.


Re: hunting in trash
Posted by: sube
Date: March 19, 2014 08:14AM
Johnnyanglo Thanks for the great explanation on iron falses with nails and iron as usually you have a great way with words and the technical aspect of what's going on . If you would be so kind to explain how target trace is seeing the coin running east and west but not giving audio and displaying this on the 12 line I would very much appreciate this . Such as the half in the video where it's solid at 12.37 instead of 12.46 but giving no audio and clearly showing on target trace .I know the coin will hit north south and display a great cursor but we can't hunt east and west and north and south at the same time . So my ? is what is target trace doing that audio is not . I value your opinion from the technical view . sube

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