jasong

I have quite number of posts in the past talking about doing similar things myself, both with the GPZ and the 4500 (Salt Coarse achieves a similar effect). It's not as useful as it sounds in theory though because the technique means you miss a lot of normal size (normal for the US anyways) gold since Extra Deep flat out misses entirely a ton of what I'd call my bread and butter gold - at any depth. I tested it on a range of nuggets when the GPZ first came out. To me it's a last resort technique, at least here in the US where the type of gold it misses is a majority of my finds. What I'm talking about here is something potentially more useful for every day prospecting, being able to keep the detector running hot using normal timings, or something close to it since there is usually some loss of sensitivity associated with discrimination. But with enough CPU power I'm not even sure that would be the case since you could could have the computer/Geosense do something like only turn on discrim temporarily after a target has already been detected, or every 4th cycle or something along those lines, in order to stay in normal timings and maximize sensitivity.

Is there anything to be gained with regards to accuracy via a hybrid discrimination - ie looking at how a target affects both the time constant and the phase shift combined? Does one potentially give useful info the other doesn't give in some cases? Reason I ask is because as detectors get more sensitive, those little bits of tin cans and wire that are like 0-4 inches deep become a higher and higher percentage of dug targets. Being able to discrim just those shallow targets out would save a lot of time, even if accepting a certain amount of gold loss for 1st/2nd passes during the general prospecting phase. In some places it'd allow me to literally 2x the amount of ground I could cover. Anything deeper than 6-8 inches probably all needs dug anyways even when just prospecting. So just having some fairly decent shallow discrimination on a prospecting machine would be pretty useful in many cases and save a lot of time just being able to concentrate on digging the targets that are higher probability of being gold, especially in cases where the gold is usually always deeper than 6" or so and the trash is usually always shallower. In that sense - accurate depth discrimination would be an extremely useful tool in the prospecting realm.

Ok cool, think I have the basics straight in my head. The main question I have is since the TX wave is continuous, why can't they also sample and measure the phase offset of the RX wave relative to the TX, similar to a VLF? And if that's technically possible, then isn't discrimination possible with ZVT too? In my head it seems just a matter of having enough CPU power to multitask and look at things both in time and frequency domains. Edit: or maybe it's the phase offset of the same TX when it passes over a target? I can't remember now how it all works. But just in general, possible with ZVT too?

Thanks, I knew you'd have already looked at this on a scope. So unless I'm misunderstanding something, it's basically similar to what I diagrammed out on the previous page? Just with a real world square-like waveform that has ringing and finite sloped rise/fall edges due to real world impedence factors instead of the perfect ideal square wave I drew, right? If so, then I have 2 more questions. But I want to make sure I have this part clear in my head first.

Another thought occurs to me too regarding hybrids - the fact that there are 2 RX loops could provide for some interesting sampling techniques vis a vis a little from column a, a little from column b, plus the ability to run in a mode similar to a gradiometer, not looking at RX strengths but instead analyzing the difference between two RX fields of any strength, or how a single field changes in time domain. A hugely important capability in experimental physics. Or maybe already does and that's why they use a DOD for the GPZ. Accurate depth discrim should technically be one possibility along that line. Also, if running as PI, there is technically no reason why the GPZ couldn't just use the TX loop as an RX as well to give you effectively 2 different size coils in the same coil (a DOD and a smaller mono). Or for that matter, a true mono mode switch on the detector to run normal (aka lightweight) standalone mono coils, which would probably be better since the loop could be wound optimized for both TX and RX unlike a DOD TX loop. Just some thoughts here pertaining to potential future developments. One thing I'm almost certain of though is discrimination is a possibility, somehow. Or maybe already is.

Not sure where that quoted paragraph came from - but that's pretty much the point I was making. "Zero voltage transmission" is sorta a non sensical term, scientifically speaking. The only time it makes sense is if the mag field is stable, which means there is no transmission occuring. EM waves by very defintion are changing, not stable, and stable EM fields don't transmit. I might have my sampling on the diagram I drew 90 degrees off though. Dunno, and no desire to go read ML patents again to find out.

I agree it's probably closer to PI than VLF. But I really think it's sort of a hybrid. A PI basically works by doing a pulse, then being quiet (at 0 volts) and listening during a sample period. Then just repeats this pulse - sample period over and over. But really it's still a cyclic square wave maybe with variable duty cycle, it's just the lower cycle ends up at zero volts, but it's still basically a square wave with a 0v (aka ground) reference and no negative reference. Like this: Whereas ZVT I believe is somewhat of a misnomer. I don't think there is any "zero volt transmission", in fact it's kind of a non-sensical term because transmission implies voltage - an electric field cannot exist without some voltage to begin with, that's literally the defintion of the electric field - volts/distance. Every changing magnetic field has an electric field associated with it, and vice versa. I think what ZVT does is use a PI-like TX wave, but changes the voltage reference so that each part of the wave has both a positive and negative component. And then, the sample occurs when the magnetic field switches polarity due to the voltage switching polarity. So, in the white circled areas here: That's the best I can make out of it from their weird patent language. If this is somewhat along the lines of what ZVT is then it's basically a hybrid between PI and VLF. It samples somewhat like a PI (aka, decay time (time domain) not phase offset (frequency domain)) but uses a continuous wave. And it also means you can take the benefits from both (ground immunity and discrimination) selectively by sampling like a PI once cycle and like a VLF the next cycle. Or actually, you could probably sample both ways simultaneously if this is really the way it works. I'm curious if Carl or Chet or someone can comment further, I'm sure they've looked at the TX waveform on an actual scope. I could be misunderstanding something, the language is so weird and hard to decipher. That's a simplification, an actual wave could have variable duty cycles or anything else and needn't be a perfect square wave either. For instance, something like this is still a continuous wave, but it'll sound like a "pulse" on a radio for instance. This duty cycle and pulse spacing likely what comprises the "timings" like Normal/Difficult, etc.

A big problem I see is that Minelab has done a great job effectively pricing a lot of younger people out of the gold machines. I started as the youngest person on the US forums in my early 20's and now in my early 40's I feel like I'm still one of the youngest people posting on the US sites, which is ridiculous to say as a middle aged man with graying hair and wrinkles. There seem to be more younger people doing it in Australia where you can reasonably expect to pay your expensive detector off still. But I would think there might be a cold winter coming in a decade for US gold specific detector dealers because most the people I've met in the field are 65+ years old, many are getting past 75 or 80. Combine that with nugget depletion and the future doesn't look too incredibly profitable to me. Also clearly the dealer margins have shrunk significantly on the 6000 because trying to get a good deal on one was harder than any detector prior, and they'll probably shrink even more with the next release because just like Ford now getting rid of dealers for EV's - the next step to saving money is slowly eliminating middle men in most other industries too. Minelab continues to basically entirely ignore the very people who made coin/relics so popular and kept Garrett in the game too, which is a huge mistake on their part. Those people being content creators, primarily Youtube, who can give them millions of views which equates to more advertising value than they could ever pay for on their own. Putting detectors in the hands of people that essentially promote them endlessly for free is also more effective than ads because it reaches a demographic that doesn't consume normal ads, and in a way they trust rather than view with suspicion since it's not actually ads but just people showing them doing things they like doing with products they choose to use on their own. I've told them this multiple times, they don't care and seem to think they can do it better themselves. If they want to have any hope of keeping a good market in the US then they need their good prospecting machines at $2500 or under and they need to start putting them in the hands of younger people that will go out and use them daily and post about it. Otherwise I think the US gold-specific detector market is probably on a long, slow road to eventual death by attrition even if there were more nuggets here to find.

I just hope we don't enter another era of marginally eeking out small tech gains with each new $10k detector, sorta like we saw when I first started paying attention to detectors around the time the 3500 was king. The 4000 was...eh. The 4500 was enough to convince me to buy an expensive machine and start playing the PI game (I had a GMT only at the time) but it wasn't that much better than the 3500's people I knew were using, honestly. The 5000 left me ho-hum and I went back to the 4500 since I didn't need Fine Gold and I didn't see a lot of stability improvement to make the price tag worth holding. I get the feeling that's kinda what they are looking at doing with ZVT, and if that's the case, I'm losing interest in the game. I'd take a lightweight 7000 equivalent, sell my 6 and 7, and probably call it good there. Everything I've read leads me to believe that discrim is entirely possible on hybrid type machines. That we've had to wait and wait and wait makes me wonder if I'm either wrong (very likely), or ML is just playing a game milking tech improvements out again like with the old GPX game. 7 years since the Z release...? That's an eon in the tech world. Either way, I feel my excitement for new machines sapping and going away lately compared to how I felt about seeing what the future might hold after the Z first came out. I'm saying this all as a guy sitting squarely in the USA though. I'm guessing in Australia and other places in the world where nuggets are still more numerous, people might not look at it the same way.

I find it virtually impossible to understand ML's patents and other technical writing. It's like it's intentionally obfuscated and confusing in a way. The way I understand ZVT is as a semi-hybrid. ZVT uses a continuous wave very much like a VLF (but not necessarily a nice sine wave), but it still samples like a PI - ie, looking at target signal decay and not signal phase offsets like a VLF. But it samples during the transition from positive to negative instead of only having positive pulses and then periods of "silence" with no pulse where the machine does nothing but listen to signal decay like a pure PI does. If that's the case then it seems like you could selectively choose which mode to sample with on a ZVT machine - more PI like for raw depth and ground immunity, or more VLF like for some level of discrim and ultra-sensitivity to speci stuff. Again, if that's also the case, then with enough processing power to control mode switching, you might be able to effectively operate both types of detectors simultaneously and have the computer filter the bad parts of each mode out while only giving the operator the good parts of each mode. At least, that's my hope with something like the 8000, with regards to adding some usable discrim.

Hard to ID rocks from photos but if I had to guess based on the looks of it and the fact you said it's "very very heavy", my initial guess would be BIF. AKA - banded iron formation. It has a huge variety of appearances though so it's not always recognizable just from a photo. There is however a ton of it in the Canadian Shield area, from memory. Try to stick a strong magnet to it. Some is more magnetic than others but I'm guessing most has enough iron in it to be at least somewhat magnetic. If not magnetic then try scratching with a knife, it could be something like shale. Petrified wood will not scratch usually since it's silicified, but it doesn't look like petrified to me anyways.

I'd call the 6000 the jack of all trades. 7000 is the undisputed heavyweight king, and I do mean heavy. I'm pretty well convinced now that if there is going to continue to be a market for high dollar, high end detectors then some new idea needs to come out soon. Maybe it's just me, but I think I only got one more high dollar detector left in me and then there just won't be enough scraps left over under the table to spend that kind of money pursuing anymore after an 8000, or whatever it may be. A lightweight 8000 that goes as deep or deeper than the 7000 will be the new king by default. But they really need something completely new and different after that to keep a good number of people buying these machines in this price range, IMO.

The Reebok soles got weaker after Converse stopped making them, it's a shame because they were the gold standard detecting boot for years. I keep a pair around as backups while I try other boots because they are comfortable though. I am currently using pull on waterproof Chaco boots similar style like TBoykin posted. This style is nice for detecting, the soles are built way burly. But mine don't have composite toes, they are more like water resistant than water proof, and they don't go up quite high enough and let stuff in the tops occasionally. So I'll probably try something else next season, but they are my new favorite style for general use boots right now. Some cowboy style boots are close to perfect for detecting, can be waterproof, but they have no way to tighten the calves up and I don't know how that doesn't drive people crazy with them flopping around on the shins. Bates and 5-11 both give me similar sole problems as the Reeboks with the soles wearing down quick. Tactical Research boots came apart at stitching for me. I was going to try these Timberland True Grits next - side zip, composite toe, waterproof, high tops. But I can't find them for sale in person to see if eyelets are metal and the reviews state they are massive boots and heavy, so I'm waiting to see if some store stocks them so I can try on first.

I don't understand how capturing a nugget in the bottom of the scoop saves time? Is the idea to discard the top portion of dirt unchecked? That seems like a way to lose even more nuggets out of a scoop than simply halving the dirt until the nugget is visible. I guess I've never personally had a nugget just fall out of the scoop before, but maybe it's a common problem others have and this is what the scoop is for, and not for saving time? Just curious what the use case is.

Interesting. Thanks for the tests and posts El Nino, I learned something new today...

Or maybe it doesn't have a concentric? It's confusing...looks like one. But they are calling it a DD. That's one oddly designed DD if so.

My recall was it lacked outright depth on the bigger stuff, but I don't remember exactly. If so, some of that could be coil related too. Garrett might still want to consider making it as light as the 6000 and then looking into proper concentrics - or having them be made for them. A lightweight PI for less than half the cost of a 6000, but with equal performance on small stuff and better performance on the bigger, deeper stuff would put a US manufacturer right back into the game again. I'm actually pretty surprised they never did, especially as you mention Simon, how much Steve posted about something similar very early on. Almost makes me want to see if Garrett wants to sell the ATX patents/design cheap if they have no plans for it. Minelab is kinda setting themselves up for stray competition to enter the game lately IMO and someone with a decent sense of business saavy, customer interaction, and a hunger for competition could probably find a way to take some decent market share away now if there is seriously just a machine out there floating around that could be fairly easily modified to equal or outperform the 6000 for half the price. Edit: or maybe it already has a concentric? Looking at a photo of the machine stock. Admittedly, I don't know much about this one.

If that ATX is detecting 0.027 gram nuggets at all then color me surprised... I have to admit I never really gave the ATX a 2nd glance at all due to it's weight, but if it's hitting 0.027 grammers at 2cm then it probably has something going for it in the underappreciated performance category. Makes me wonder why they never redesigned it into a lighter machine? The 6000 is generally hitting down to 0.03g for me in the field, might go smaller in a testing setup but no idea since I haven't done tests. But either way, Garrett could have had a 6000 years before the 6000 came out with a lighter weight ATX if your tests are accurate, El Nino?

I wouldn't buy any expensive detector on the basis of just a 2 nugget patch unless you have a good reason to think there is quite a lot more gold left deeper there, or you have some other areas to work in addition. If time is of the essence due to surgery and the people with 6000's aren't coming until next year, might see if any shops or dealers in AZ rent a 6000 or 7000 for a day. Back in the early 2000's there were a couple that rented GPX's, not sure about now. If you are mostly after deep, larger stuff though, the cheapest way to do that would have been with that 5000 with a 16" or 18" coil. Larger coils on an older GPX also have the benefit of ignoring some of the smaller trash, and you can ignore it further by running settings like Salt Coarse. A 6000 is going to hit every piece of tiny surface trash.

Usually that kind of stuff is railroad clinker/ballast, kid picked it up from a track somewhere and then later discarded it. I used to be one such kid.

Most excellent.

Not sure, I hadn't noticed them before so I decided to click on them out of curiosity, got lucky that a place I was looking was one with really high resolution imagery, and I was like..."wait a second, this is actually LIDAR, awesome!". In some places it appears to be 1m resolution (or less?), and you can see stuff aerial imagery don't show. In other places the resolution isn't enough to be really useful yet though. Also noticed when I was browsing Google Maps or something (I can't remember exactly which app) that the base layer before they render the maps on top, when terrain is enabled, is also LIDAR. It was a few months ago, I noticed by accident on a slow 3g connection that wasn't rendering the top layer very fast. Whatever the app was, I couldn't force it to just display the LIDAR layer though so I never posted it. You know maybe it was like Zillow or something like that...can't remember. So anyways, seems like the data sets are getting distributed better now. It was a serious pain in the butt to track each individual snapshot down and stitch them, etc until recently.

Found this map of availability and progress. Looks like most of the Sierras (crosshatched) are planned to be completed by the end of the fiscal year so those in CA should have some interesting imagery to work with by next year I'm guessing. Lots of the Mohave Desert is for some reason just not a priority to acquire imagery on though yet unfortunately. White is no imagery and no plans to acquire it yet. Most areas on the East Coast seem to available though, or almost complete.

It may have been up for a while and old news, but new to me, I just browsed through some stuff and noticed that what they are calling "3DEP" is in fact LIDAR imagery. It's not available everywhere yet, but it's easy to view it in the places it is now - before this you had to import imagery into GIS or other similar programs and now you can just browse it like you would Google Earth. Some places have extremely high resolution LIDAR while others are lower resolution and not as useful. Arizona unfortunately is one of the places lacking in sufficient coverage. https://apps.nationalmap.gov/viewer/ Go there, open the layers list (3rd icon from the left), and select a 3DEP layer. I find the "Elevation Tinted Hillshade" to be easiest to see details on. Here is an example - as you can see - there are foundations plainly visible and things like stream channels are also visible through vegetation, old roads, etc. LIDAR is more useful than aerials in cases like these and probably are useful for relic/coin detectorists as well.

One was the first post you made here, and the other was the first post you made in another thread that I was actively posting in where you called us bitchers, among other things IIRC. To be clear, what I told you was that you came in hot telling us our opinions were like an ass, which is after all what a "backside" is. I was just trying to communicate to you that it's not a great way to join an already existing conversation, before any attempt is made to share information, evidence, or anything else that might change people's minds or move the topic of discussion forward in a productive manner. And you are right - in a lot of cases I've seen you get some responses you don't deserve at all, but in cases like this the response I gave you was suitable. This is my post, about concentrics. I'm just sharing my experience and thoughts about concentrics in general or anything on the subject, on both machines, and venturing to imagine what the potential of the coils might be in other applications and welcoming other people would join in with whatever thoughts, ideas, or experience they have. I appreciate the apology though. None of it is a big deal, it's all been moved well past already. Your more constructive input on topics is understood by almost everyone to be a unique and appreciated view. We are all passionate here about the things we talk about, or we wouldn't be here talking about them. And most people including myself do understand that you have extra passion towards machines that you were personally involved in the development of, so that's definitely understandable. I'd feel the same way if I saw something I felt was a misrepresentation of work I had done and poured my heart and soul into too. No worries, We are at like 11 pages at this point so there is already a variety of things being discussed. And I'm out of field reports to post about the X Coil concentrics anyways now so was drifting off topic myself too into things which this topic set my mind wandering into.