Size discrimination with Pulse Induction machines?

[motherlode77]

Hey guys, I've been cache hunting for some time now, I had bought a Bulgarian PI that I have since gotten rid of, it would sound off loud on every nail and small piece, no good for my purpose. My question is, will a Pulse Induction machine discriminate out the small trash if you put a bigger coil on it? Say a 40x40" square? Am I better off getting a 2 box Whites or Discovery? Target would be gallon paint can size likely, between 1-3 feet deep (I seriously doubt any deeper than 3). Any input is appreciated, though it would be excellent if someone with a PI and large coil could weigh in or perhaps test their unit with a large coil, so see if it overlooks small trash

 

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[signal_line]

Clive Clynick has a book on pulse induction machines "Pulsepower".

 

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[Tom_in_CA]

.... I first took a Fisher 2 box out, but it was all over the place....

Here's a thought : If you know your target is a paint-can-sized object, at XX deep, then just: Get yourself some lunch-box sized sample targets. Go bury them in some sandy beach dune scenario, and pass hither and yonder or your target. To familiarize yourself with your objective.

And better yet: Some sort of farm yard where oodles of habitation/work-zone junkage exists. And then bury several paint can sized objects within the mess, to test the relative signals between-targets. Walking back and forth over all of them multiple times, from multiple angles. And try different compositions. Eg.: paint cans are iron. But try conductive objects of similar size in your test bed.

 

[signal_line]

Yeah, and put a marker when you bury them so you can find them again. LOL

 

[hispania]

A good example of the depth of a high-end detector and the ability to discriminate that does not offer a pi. The metal plates are used to simulate the treasures buried in Central and South America.

 

[motherlode77]

Tom, signal line, and Terry, thank you. Yes I have buried a paint can, and a copper target, at 3.5 feet, for testing, so far the only machine that finds it consistently and strongly is the TM-800, so this thing does what it says it does. The Bulgarian did find it, but as I said, it also "found" every nail and tack and piece of garbage with equal signal strength. TM-800 is taking a trip with me, we'll see what she finds

 

[signal_line]

Just so you know, my experience has been the two-box is less than worthless. You think you went over the ground but go back over it with the pulse. Get Clive's book first so you know how to use one. Obviously wasting my time here. Two box is nowhere near what a pulse can do. Something not right. 10 - 1 says you need to learn how to use one, learn what it is telling you.

 

[Carl-NC]

ML77, the cave mode on the older TM800 was a plain TR mode that was actually very useful in looking for ground anomalies, if you knew how to use it. Sure, it still detects metal. Unfortunately, White's redesigned the TM808 around the XL-Pro circuit and got rid of cave mode. If you try for a repair, call White's first and specifically ask to talk to Todd in Service... ask him if he can fix it. Usually they just swap out boards, and the '800 is so old they may not have boards for it. It might also be the rotary selection switch, they are known to go bad. There is no repairing it or replacing it, the company long ago quit making those. It is possible, but not easy, to kludge in a fix.

Once upon a time I buried a test target of 220 silver quarters (3 lbs) in a plastic container (no other metal); exactly 24" deep. No detector could locate it; not the TF900, TM808, Gemini, or any PI machine I had. I happen to be between having my 104B stolen and buying the SSP, so I didn't have a large coil PI. I did wind a 24" coil for a TDI but it wasn't shielded and was too noisy, but I suspect (from air tests) it would have worked. The point is, if your cache is in a glass canning jar with a wire-bail lid, you're in for a tough time. If it has a zinc lid or is in a metal paint can, maybe not so bad. But if it's a paint can, the can will be your dominant target, so you don't want to disc out ferrous.

SAT is an auto-retune feature and is usually designed for the speed of a swingin' detector. When you put a 1m coil on a PI you can't swing it, you just walk it, so the SAT is now too fast and targets disappear. The SAT needs to be slowed by a factor of 10 or more. Usually an easy swap of a resistor or a capacitor.

 

[Tom_in_CA]

Just so you know, my experience has been the two-box is less than worthless. You think you went over the ground but go back over it with the pulse. Get Clive's book first so you know how to use one. Obviously wasting my time here. Two box is nowhere near what a pulse can do. Something not right. 10 - 1 says you need to learn how to use one, learn what it is telling you.

Uhhh, I don't know how a 2-box can be "useless". They find stuff just fine. So what do you mean ? Do you mean as in Depth attained ? If so, then I'll admit that ... yes... various standard pulse machines DO go deeper than 2-box units on large items. Sure. BUT THE DEVIL IS IN THE DETAILS : If you start finding diddly little stuff, that forever bogs you down checking/digging small items, then .... what good is that ?

 

[Tom_in_CA]

ML77, the cave mode on the older TM800 was a plain TR mode that was actually very useful in looking for ground anomalies,....

I remember my old 66TR could do that. In theory anyhow. But didn't see much use for it. I was looking for metal (coins etc...) not voids in the earth.

 

[motherlode77]

Just so you know, my experience has been the two-box is less than worthless. You think you went over the ground but go back over it with the pulse. Get Clive's book first so you know how to use one. Obviously wasting my time here. Two box is nowhere near what a pulse can do. Something not right. 10 - 1 says you need to learn how to use one, learn what it is telling you.

Just so you know, my experience has been the two-box is less than worthless. You think you went over the ground but go back over it with the pulse. Get Clive's book first so you know how to use one. Obviously wasting my time here. Two box is nowhere near what a pulse can do. Something not right. 10 - 1 says you need to learn how to use one, learn what it is telling you.

Signal, out of all the machines tested, the TM 800 2 box performed the strongest, while discriminating out small trash. I don't see how it's less than worthless. The only PI I had out there was a Bulgarian, and as I said, signal intensity was the same for a nail 1" deep as it was for my target range size at the probable depth. Is there a PI machine you recommend? As for the TM 800, I just bought it, it is testing well, so I'm taking it out to location and seeing what it finds, at least if I do dig junk targets with that, they'll be larger items and much fewer of them, discriminating out nails and small junk helps massively at this location

 

[Carl-NC]

I remember my old 66TR could do that. In theory anyhow. But didn't see much use for it. I was looking for metal (coins etc...) not voids in the earth.

Not just voids, but ground disturbances and soil compaction. Tim Williams makes an add-on called the Arc-Geo Logger that can map the ground response and plot it in 2D, but requires the TR (cave) mode.

 

[signal_line]

Less than worthless means you might think it is working but it's not picking up the target. Not even what i would call highly mineralized ground.

 

[motherlode77]

Less than worthless means you might think it is working but it's not picking up the target. Not even what i would call highly mineralized ground.

Signal, I see what you mean now. My hope is still that I will find it with this unit, as it WAS picking up my buried test targets really well. But of course, if I go over the ground with this thoroughly and don't find it, then I will be disappointed in its abilities, as I am 90% certain of this cache still being there, and 100% on the location. Someone had said to expect less depth on actual gold targets vs. copper tests, is this true, and if so why? Also, something I noted was that iron was giving a stronger signal that aluminum or copper. Seeing as aluminum and copper are more conductive by far, why would this be the case?

 

[erte]

i know with my gpx and stock dd coil a large piece of iron like my shovel gives a great booming sound with iron reject on, since you still need a detector that won't completely discriminate iron since you said the object is a steel pot, if i were you i would borrow a gpx with dd coil to test out your situation. i would get a few iron and steel pots and bury them from 2-4 feet down and on top of the soil to 5 inches down sprinkle on some nails and rusted bits or the small bothersome metals you have already found. Then test the gpx in iron reject mode, i would also test the detech ultimate 15'' dd as i heard it might discriminate a little better- don't know but just test a gpx with different dd coils, i think coiltek has a 20*40'' dd coil for gpx, might even test out a garrett atx with dd coil with iron reject- don't know, guess you should borrow and try different detectors... i could probably test out my gpx 4800 with its stock dd coil for you by making a similar situation in my yard ... post here or pm me the general size/dimensions of the steel pot object, i'll find a similar one in my garage and bury it down 3 ft and send a picture of the bad metal pieces you already found, or i could just throw on top some nails and small rusted metals then go over it with gpx in different iron settings to see if it works...

 

[erte]

an idea popped into mind i just went and air tested my tesoro vaquero with stock 8*9 coil on a hollow steel cooking pot size 5*8 inches, put the sens to max and disc at 3 o clock position and tested a variety of small metal objects. About 90 percent were disc'd out and the hollow pot was coming in at 25 inches in the air, who knows maybe all you need for the job is a tesoro?

 

[signal_line]

Signal, I see what you mean now. My hope is still that I will find it with this unit, as it WAS picking up my buried test targets really well. But of course, if I go over the ground with this thoroughly and don't find it, then I will be disappointed in its abilities, as I am 90% certain of this cache still being there, and 100% on the location. Someone had said to expect less depth on actual gold targets vs. copper tests, is this true, and if so why? Also, something I noted was that iron was giving a stronger signal that aluminum or copper. Seeing as aluminum and copper are more conductive by far, why would this be the case?

I used to know but my memory is failing. If I tried to answer I'd probably be wrong and i don't feel like going and looking it up. If you are really interested there are articles on the internet about metal detector technology. Or Carl has a book on detectors. I don't know, for some reason people refuse to read as much as they can about it. That's not how you get ahead. I guess they think the knowledge will just come to them through the air. I'm not telling you what Clive has in his books.

 

[motherlode77]

I used to know but my memory is failing. If I tried to answer I'd probably be wrong and i don't feel like going and looking it up. If you are really interested there are articles on the internet about metal detector technology. Or Carl has a book on detectors. I don't know, for some reason people refuse to read as much as they can about it. That's not how you get ahead. I guess they think the knowledge will just come to them through the air. I'm not telling you what Clive has in his books.

For the sake of keeping this forum clean, I'm not going to reply as I am inclined to, but will remain civil.

I have been doing little but reading up on metal detectors and geophysical equipment in my spare time the last couple years or so, it just so happens that finding information about such things is pretty closely guarded, or just so niche that it is rare. I didn't know that Carl had a book, how would I know that, osmosis? As for Clive 's books, you've just suggested that to me about a day ago, so that's not enough time to even ship it to me, let alone get into it. Add to that the fact his book is geared specifically for beach hunting, which is far different from what I am doing, and that's why I haven't bought it yet. I have no idea why you are insinuating I refuse to do research.

 

[motherlode77]

Less than worthless means you might think it is working but it's not picking up the target. Not even what i would call highly mineralized ground.

Signal, Clyde's "Pulse power" book, I know you said you won't tell me what's in it, but can you give me some reasons for buying it? I'm not hunting beaches, how would it be relevant to my search?

 

[signal_line]

Ah, save your money.

 

[erte]

if each bottle holds smaller nuggets(don't know)...maybe applies similar to gold chain theory, then maybe a higher frequency vlf with bigger coil for depth with some discrimination would work. maybe read more into tesoro lobo, maybe even equinox 800 would work the best?

Why Can’t My Detector Detect A Gold Chain?
Gold chains are very difficult to detect, particularly very fine chains. Each link of a chain can be very small and the detector sees each link as a separate target, so it can easily be missed. You are more likely to detect the actual clasp or any pendants that may still be on the chain as these are much larger than the individual chain links. High frequency detectors such as the Eureka Gold, or an X-TERRA 705 with an 18.75 kHz coil in prospecting mode, will often pick up fine chains better than most coin detectors.

https://www.minelab.com/knowledge-base/frequently-asked-questions