Re-hashing the PI/VLF Hybrid Discussion

I had a debate with myself last night over the feasibility of/use for a hybrid PI/VLF detector. Before you go off thinking I'm nuts for doing so consider that as both an insomniac and a former engineer I'm forced to have such conversations with myself as most sane people are asleep when these ideas hit me and, as a matter of fact, no they can't just wait until the next morning.

I searched for previous threads on the subject and found then read one from about a year and a half ago. The two main things I remember from that thread are:
1.) The majority of the arguments against a detector of this type had something to do with the fact that the VLF's disc circuit won't work at PI depths so what's the point.
and
2.) Geotech (Carl) has already designed and built a true hybrid of this type that ran as both a PI and a VLF simultaneously.

What I don't remember anyone bringing up in that thread is the one thing that, in my mind, would make this detector worth it's weight in gold especially to relic hunters and/or prospectors that work in tailing piles. I believe that's what they're called but I'm not a prospector. That one thing is dual mode (in this case triple mode) audio similar to what the Nautilus machines and some of the White's detectors are equipped with.

I haved loved the mixed mode audio of a Nautilus running all metal in one ear and disc in the other since I first used the DMC-2b. Once you get proficient with it the lag, or lack thereof, between the two channels actually helps suss out ferrous targets from non-ferrous targets. Another huge benefit of it is that when you get a signal, especially a weak one, from the all metal side but no report at all from the disc side, even with no disc dialed in, you know it's a DEEP target and you need to start digging.

Now, imagine a hybrid PI/VLF machine running much the same way with the combined disc and all metal audio from the VLF circuit in one ear and the audio of the PI circuit in the other.

1.) Shallow targets that aren't disc'ed out on the VLF side will sound off with signals from all three circuits. The audio from the all metal and disc circuits of the VLF side will be combined in one ear while the audio from the PI will sound off in the other.

2.) Targets too deep for the disc circuit of the VLF side but still in range of it's all metal circuit will give an all metal report in one ear while the PI circuit sounds off in the other.

3.) Lastly, and to me this is the good part, targets that are too deep for both the all metal and disc circuits of the VLF side but still in range of the PI circuit will sound off in the PI ear only. In which case you need to start digging.

If you guys can come up with a reason for not wanting a detector with the functionality described above, especially if the individual circuits could be switched on and off independently, you've got me beat. According to Carl the design work is complete so now all we've just gotta talk them into building and marketing it.

Quote:"If you guys can come up with a reason for not wanting a detector with the functionality described above ... you've got me beat."
I never understood this "if it's deep it's gotta be dug" concept. It seems to imply that a small range of targets that are in a specific range of detectability are "desirable", when that is not the case. They're just as likely to be rusty crap as any other target. And why do you say that such targets have to be DEEEP. They could just as easily be simply very small, and at quite modest depth?

I've heard people say the same thing about the UK-made Arado 120, popular in the 1980's. This was a sensitive non-motion machine, with a moving-coil meter disc readout. The notion was that "if there's audio, but the meter doesn't move, dig it". Inevitably some of these weak targets were good, so users thought the Arado was a great machine. In truth, it's the excessive hole-digging that's the cause of the success.

Aren't most nuggets found in 'difficult' dirt, where a PI will easily out-do VLF ? So there's going to be a lot of these fringe-depth targets to hack out the ground.
And in milder dirt, the frequency of the VLF is important. A high frequency machine ( 50kHz, say) will out-gun the PI on tiny nuggets.

I think you are correct in wanting a stereo detector, even if it's just rudimentary X in one ear, Y in the other.
Your proposed machine should also have options such as PI in one ear, VLF all-metal in the other, with VLF target ID on the display.
And 'best-of' all-metal in one ear, disc VLF in the other might be easier to work with.



Edited 1 time(s). Last edit at 12/02/2018 01:51PM by Pimento.

My guess is they believe/know some targets change the deeper they are...... but that could be a low percentage unless you get some kind of audio that tells you check it out ... which normally means taking a little dirt/sand off at least. They also believe because they arent finding targets the site is hunted out..... but in most cases a lot of targets are masked or even on edge. Wonder what the percentage of those are? I do find it odd as a beach hunter..... many choose NOT to want to dig foil/small gold targets or want a machine that really gets a few more inches on those targets. For me ...... id just like a PI that gives me promising audio..... like reverse hunting with the Xcal. But as an ole dirt kicker....... i also recognize beach hunting isnt nearly as complicated to wiggle those target tones out.

Here we go again........
This topic keeps popping up, I think its worth discussion. I've previously suggested the same in the past with regards to utilizing both PI and VLF as a super hybrid. I agree with the concept but......

One of the stumbling blocks is that as the soil becomes heavier in mineralization, the VLF side of the machine is less capable of accurate target i.d., there is a loss of depth and the sensitivity must be adjusted to cope with the minerialized ground.

Add EMI to the equation and the VLF exponentially loses its abilities to i.d. at a depth compared to the PI side of the machine's detection depth capabilities.

In some scenarios where black sand / heavy concentrations of magnetite or similar iron oxides are extreme.... the VLF becomes inoperable and only the PI side would be functional.

In a perfect world with no EMI and neutral ground, we could have the best of both worlds in one machine.

Nasa-Tom has chimed in on these previous discussions with his vast knowledge..... maybe he'll jump in on this one again.

Up to my ____ in Pulltabs, Grant

maybe this could help you understand =)

[www.ideaconnection.com]

This thought-process is plausible and fairly sound; yet/however, as Pimento points out...….. there is indeed nearly the same ratio of good-to-bad targets at depth. Unless you are a Archaeologist …… it is not (time) cost-effective to dig every deep target. Have you ever hunted/experienced a demo site whereby ….. say...…. 10" of top soil had been removed/scraped-off...…. and ………. you learned that: there are just as many target hits in the dirt ….. as there was before the topsoil was removed. The ratio of bad targets to good targets remains about the same. Yes...… the modern aluminum trash may be reduced..... or even zeroized; yet/however; the iron nails content has linearly increased.... whereby..... the 'ratio' of good-to-bad targets …. remains about the same. Then...….. as Pimento points out again...…,,,,,,,,, what about small targets that read 9" deep; yet, in actuality...… are only 2" deep.

I'm TRYING to find the time to write/start a thread titled: ADVANCED TRAINING.

You guys......wow you really know how to mess up a bowl of Cheerios. All I want is a machine that finds gold too.

Looking forward to your new thread Tom.

Then there's the complexity of the coil.
If you choose a DD, you're going to have to use the TX and RX coils for both PI and VLF, I think. So your PI is not going to be getting the same depth as a round mono coil the same size. I'm unfamiliar with DD's on PI machines, so I don't know if the gain can be made up in some way. Your alternative, using the TX coil as the receive for the PI is viable, but doesn't sound simple. The sweet-spot of the PI coil will be in a different place to that of the VLF, for one thing. So some clever processing involving time-delays would be called for.

If you use a concentric coil, using the TX and RX for both modes makes more sense, but if you did use the TX as receive for PI mode, it would at least match up the sweet-spot with the VLF side of things.
You could get complicated, and have a triple-D coil, one TX in the middle, and dedicated RX's either side, that would make your arm stronger.

so you guy's dont read ... well you should start and it will probably answer your question on the patent i linked...

2004 patent. If it had much promise, you would think somebody would have licensed it.

Whites has a hybrid patent as well and Carl Moreland was working on it before he left.

20110316541

Rick Kempf
Gold Canyon AZ- where there is no gold

Pimento, the "if it's deep its gotta be dug" concept makes perfect sense to me. Digging only targets that the detector gives a good positive ID on does two things. First, it ensures that we're leaving a lot of good targets in the ground. Second, it nullifies the need for an all metal circuit on any detector.

Even with the best modern detectors equipped with the most advanced discrimination circuits available to date there's no guarantee that targets at any depth are going to be good just because the detector said so. Disc circuits can be fooled by any number of factors and the deeper you go the more those factors, especially mineralization, come into play.

I get excited when a target sounds off in all metal yet can't be heard in disc. Think about it this way, suppose someone lost a handful of change and their wedding band at the same time and place and all the items were laying flat. Which sunk into the soil faster and will be deeper when I swing my coil over them years later? The coins may be easy picking for my disc circuit while the ring may be just out of it's range but still be detectable in all metal. Give the items a few more years and the PI circuit may be the only one that still hits on the ring.

Adding a PI circuit to the mix just gives me an even deeper all metal circuit. Again, there's no guarantee that the target won't be junk but without the PI circuit you won't even know the target is there.....and it just may be a diamond engagement ring.
Also, those targets that read as if they're 9" deep but turn out to be small targets only 2" deep are a problem for all detectors not just this hybrid.

As far as the complexity of the coil goes, I already pointed out that Carl has already made a working prototype of this type of hybrid detector.

If the sites where someone has found good stuff were systematically dug to a depth of 18” and every metal target identified, i wonder what the result would be.

My bet, what Tom D. And multitudes of archaeologists have documented - namely that current metal detectors, relying on discrimination - miss most targets (they are supposed to after all - discrimination) and among those missed targets there are VERY many which would be of interest to US.

That is what’s left to do in hobbiest metal detector design. Get the stuff others have missed.

Everything else is just repetition of what has come before - with a new wrinikle here, a new wrinkle there.

Rick Kempf
Gold Canyon AZ- where there is no gold

My thoughts were that it would more productive time-wise to dig 100 new targets that gave a reasonable indication that they were 'good' ( non-iron, to me) rather than struggle to dig 100 probably-deep-ish targets that are completely unknown and 75% likely to be iron rubbish.

I have some practical insight into this, detecting land that was last cultivated 350-400 years ago. My F75 is more than capable of finding targets several inches deeper than it can ID them, just in Disc mode. Using the strategy of digging targets that are clearly there, but beyond ID distance, resulted in approx 1 non-ferrous target to 10 iron targets. And some of the iron was fairly large - big nails, broken bits of horseshoe, and so correspondingly deep. Some holes were 16 inches deep. That's a lot of digging for a piece of scrap.

And regarding "... the need for an all metal circuit on any detector"
I personally would mainly use all-metal in locations where I know that the level of iron rubbish is low, so a dig-all policy is likely to give an acceptable return on the digging effort. Such places are usually woodland. I'm not that skilled in the use of all-metal mode, to be honest, I prefer to simply use the F75 in DE (default) mode, with Disc=1. This hits on just about all metal targets, giving an 'Iron' ID on weak targets. As I'm most familiar with this mode, I'm able to match the all-metal mode peformance, that I'm inexperienced with.
And those among us that intentionally dig iron targets will also use all-metal, I presume ? The F75 ( and T2) has the neat feature of giving target ID on the screen while using all-metal mode audio, which is what prompted me to suggest a 'mode' for your dream detector that had the two all-metals in both ears, and the screen for disc ID info.

Re: the complexity, I realise it's achievable , and has been done. Mrand has made production-ready machines, they've been mentioned over on Geotech1, and in a thread on here:
[www.dankowskidetectors.com]

L'lytle78 Wrote:
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> 2004 patent. If it had much promise, you would th
> ink somebody would have licensed it.
>
> Whites has a hybrid patent as well and Carl Morela
> nd was working on it before he left.
>
> 20110316541


Im pretty sure it is but not for civilian (soon to been with the mdt) as it the case for most new tech anyway.
Btw why should we discuss something that has been well documented already, like we are creating something that dont exist yet, theory crafting...
Discuss about existing patents should be more interesting ?! Dont you all think ?
I suspect some brand like white will push their new secret hybrid machine to distrupt the launch of fisher aq for exemple.



Edited 1 time(s). Last edit at 12/03/2018 12:29AM by youdig.

youdig Wrote:
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> I suspect some brand like white will push their n
> ew secret hybrid machine to distrupt the launch of
> fisher aq for exemple.


Whites has no new secret machines. If they had the ability to bring their idea to fruition and market it, they would have already.

youdig Wrote:
-------------------------------------------------------
> maybe this could help you understand =)
>
> [www.ideaconnection.com]

I like a lot of the work Carl Nelson has done at John Hopkins, but this patent isn't one of them. It's a very clunky approach to a hybrid system.

In the 1960's Tony Barringer pioneered (AFAIK) half-sine systems. This is the most sensible way to approach a hybrid system. In fact, I have it working in a security walk-thru detector I'm designing. At White's I had it working in a ground beeper.

Geotech Wrote:
-------------------------------------------------------
> youdig Wrote:
> --------------------------------------------------
> -----
> > maybe this could help you understand =)
> >
> > [www.ideaconnection.com]
> ltaneous-Time-domain-and-Frequency-domain-Metal-D.
> html
>
> I like a lot of the work Carl Nelson has done at J
> ohn Hopkins, but this patent isn't one of them. It
> 's a very clunky approach to a hybrid system.
>
> In the 1960's Tony Barringer pioneered (AFAIK) hal
> f-sine systems. This is the most sensible way to a
> pproach a hybrid system. In fact, I have it workin
> g in a security walk-thru detector I'm designing.
> At White's I had it working in a ground beeper.

do you have the patent number ? thank you.

the whites TM808 found the jersey hoard of bronze coins and gold .half a ton of finds .but its too dated package wise

youdig Wrote:
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> do you have the patent number ? thank you.

Try 3020471 and 4157579. Probably others, do a search on Anthony Barringer.

Mrand has a Hybrid hes built..I think he sells them on a build to order basis..??



I have info on this website somewhere about it.

Keith

“I don't care that they stole my idea . . I care that they don't have any of their own”
-Nikola Tesla