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  1. I know there's already a bunch of stuff written on iron masking. But there might be some new readers that could benefit. Over on Monte's forum I started a discussion on iron masking didn't get a lot of response but Monte did write some very informative responses if you want to visit the topic on his site it's under the relic/old site hunting section. Here's the video. Would love any additional comments on the subject if anyone would like to interject. I'm no expert and certainly don't know everything about every metal detector out there so I'm open to any constructive criticism or comments.
  2. I am a big fan of the White's SignaGraph display. A version 1.0 was originally developed for the Eagle Spectrum. The Eagle Spectrum underwent a complete hardware revamp, and was renamed the Spectrum XLT. A more refined version 1.1 of the software was matched up in the XLT with a much better LCD display. The SignaGraph was also used on the DFX, and was largely the same as on the XLT, with the addition of multifrequency options. The SignaGraph was later greatly enhanced on the V models (Vision, V3, V3i, VX3) and renamed the SpectraGraph. The genius of the SignaGraph/SpectraGraph is the ability to display multiple target id numbers at the same time, and even to choose how the target id number is determined. Here is the SignaGraph explained by its designer, engineer Mark Rowan. More details can be gleaned from the White's XLT User Guide. Spectrum XLT Engineering Note The SignaGraph™ "Phase Spectrum Analyzer" by Mark Rowan Some time ago, I had a conversation with an avid treasure hunter whose instrument of choice was White's Eagle II SL 90. He described to me a technique with which he could discern pull tabs from rings, nickels, and other desirable targets by listening for some subtlety in the audio response. Then he asked me, "If I can do this, why can't you program the Eagle's microprocessor to do it?" My response was, "If you can do it yourself, why would you want the microprocessor to do it for you?" I mention this as a means of illustrating what I consider to be the metal detector designer's fundamental dilemma, which is, as Prince Hamlet might have phrased it, "To beep or not to beep". More specifically, if you're faced with a target at some depth in badly mineralized ground and the detector has a hard time getting a solid reading on it, what do you do? If you design your detector to ignore the target, and then someone comes along with their El Cheapo brand detector and digs the target, which just happens to be a $10 gold piece -- you're in big trouble. If, on the other hand, your customers find that they're spending most of their time chiseling through eight inches of hardpan and finding bent nails and wads of aluminum foil, you're not much better off. The point I was trying to make with the gentleman who had devised the clever pull tab discriminating scheme was, that if you put too much of that kind of "intelligence" into your metal detector, there are always going to be those targets that you miss because the machine got fooled. Which brings me, of course, to the newest White's model, the Spectrum XLT. The Spectrum XLT has all of the features, performance, and flexibility of previous members of the Eagle series, plus a new display which makes the instrument remarkably easy to use. It also makes use of a new way of displaying information about targets -- the "SignaGraph™ or "Phase Spectrum Analyzer" -- which shows the operator everything that we currently know how to display about the characteristics of metallic objects in the ground. In this way, we have gone a long way towards addressing the dilemma I mentioned earlier. The Spectrum XLT is a very "smart" detector, but it is also an "honest" one. Having done the best it can to determine the probable identity of a target, the Spectrum XLT gives you all of the information you need to make your own decision (human beings are, despite what you might have heard, still a whole lot smarter than computers) to dig, or not to dig. Before I begin to describe in some detail what the SignaGraph™ is and how it works, I should emphasize that you don't need to know how it works in order to use it effectively, and that the best way to learn how to use it.... is in the field. In a very short time you will begin to recognize certain display patterns as being characteristic of certain types of targets. I should also point out that even if you ignore the SignaGraph™ altogether, this instrument still has the audio discriminator, V.D.I. number, that its predecessors had, plus the icons, and some significant improvements in terms of weight, physical size, and ease of operation. White's SignaGraph display For many years, White's has built detectors which identify targets based on a V.D.I. number (V.D.I. stands for Visual Discrimination Indicator) which characterizes metallic objects according to their size, shape, and composition. The V.D.I. scale on the Spectrum XLT runs from -95 to +95. Large positive numbers typically indicate objects which are good electrical conductors; for example, silver dollars will come in at 92. Smaller positive numbers usually indicate objects which, because of their size, shape, or composition, are not as conductive; nickels will read about 20 and aluminum foil may come in near 5. Large negative numbers are typical of targets which are readily magnetized, but which conduct electricity poorly or not at all. Some sands or soils which have a high concentration of ferromagnetic minerals may read -93. Metals containing iron have both magnetic and conductive properties, which causes them to spread over a wide area of the scale, although most typically iron objects will fall in the range -30 to -75. The V.D.I. reading is an excellent way to determine the identity of most commonly occurring targets, although I might mention in passing that the only 100% reliable discriminator is called a shovel. However, as a famous metal detector engineer once said, "Life is grossly unfair" (actually, there is no such thing as a famous metal detector engineer, and life really is fair, it just doesn't want anybody to know). For one thing, the signal which a detector receives back from even moderately mineralized ground is typically much stronger than the signal it receives from the targets buried in it. This makes determining an accurate V.D.I. number for a target at any substantial depth a very challenging business indeed. Furthermore, some targets will cause an abrupt change in V.D.I. response during the course of a single pass under the loop; the most notorious of these are the dreaded bottlecap and the dreaded small piece of foil near the surface in bad ground. Enter, as they say, the Spectrum XLT. The SignaGraph™ is very similar in some respects to the familiar analog V.D.I. meter. The display is calibrated from left to right in V.D.I. units, from -95 to +95. When the loop is passed over a target, a V.D.I. determination is made, and a vertical bar is placed at the appropriate place on the scale; near the right end of the scale, say, for a reading of 78. So far, this is just what an analog V.D.I. meter would do. At this point, the similarity ends. An analog meter can indicate only one value at a time; with the SignaGraph™, up to 30 readings can be displayed simultaneously. Also, the vertical height of the bars in the display has significance; the height can either be used to indicate signal strength or a running total of the number of readings at that point on the scale ( the operator may choose which of these two indications is to be used). The advantage of this type of display format becomes evident when the loop is passed over a bottlecap or some other flat, thin iron object. Although the instrument may respond with a loud, clear audio output, and the V.D.I. readout may register a value near the upper end, the SignaGraph™ will tend to "smear out"; numerous segments will appear throughout the display, many or most of them in the negative (typically iron) range. Try the same things with a coin, and you won't see the "smear"; typically you will see 1-3 bars grouped closely together near the top end of the scale. If any smearing does occur, as it might on a deep coin in bad ground, the more accurate readings will stand taller in the display and will tend to persist from sweep to sweep. Another unique advantage of the Spectrum XLT is the ability to make use of information gathered during the course of multiple sweeps of the loop. For years, clever detectorists have realized that by passing the loop over the target repeatedly and mentally keeping track of the range over which readings appear, and the most frequently occurring numbers within that range, they can achieve the highest possible accuracy on really tough targets. The Spectrum XLT performs this operation automatically. The standard mode of operation is the so-called "Graph Averaging" mode, in which a continuous count is kept of the number of readings that fall into a particular slot in the graph. This might also be a good time to mention that more than one V.D.I. determination is made during the course of a sweep; sometimes as many as 6 or 8 readings will be taken during a single pass, so it only takes a couple of sweeps for the effect of averaging to become significant. What you will see in the field will be a single bar on the display which will "grow" until it stands out prominently above the other bars on the display. Although it is not necessary to adjust them, there are a number of controls that allow you to customize the way that the graph is displayed. It can be set up to clear itself on each sweep of the loop, if you find that too much information is persisting in the display for too long. Or, you can configure it to let the vertical bars fade slowly out of view. Even the rate at which this fading takes place is adjustable. If you don't want to be bothered with any of that, then don't be. The factory preset settings should work just fine for almost anyone. For those of you who want to know an explanation of Accumulate, Average, and Fade, one is included in this Guide. If all of this sounds confusing or mysterious to you, allow me to put your mind at ease. The Spectrum XLT is one of the simplest-to-operate detectors you will ever use. I shall describe just how and why it is so easy to use momentarily; but before I finish talking about the SignaGraph™, I want to say it one more time-- you don't need to be a Nobel Prize candidate to figure out what the display is telling you. The usual response from somebody seeing it for the first time is something like: "Okay, I get it now. Now leave me alone and let me hunt!" What is it that makes the Spectrum XLT so easy to use? The key is something that is known in the software business as a "menu-driven interface". To implement that, we have used what is known in the display business as "A True Graphics Display". What all of this means to you, the user, is that all of the controls and options are listed clearly in plain English on the display. A flashing arrow appears on the screen next to one of those options; you can move the arrow up or down with the two "arrow" keys on the 5-key touchpad. When the arrow is next to the control you are interested in, you push the ENTER key. That is everything you need to know to run this machine. If you are like me and you hate reading instruction manuals, I believe I can safely guarantee that you will be able to operate the Spectrum XLT successfully your first time out without ever having to open the cover -- although the manual should be extremely helpful if you want to fine-tune the performance of your detector by adjusting any or all of a rather lengthy list of professional options. Incidentally, another name for this method of running a machine is the "point-and-shoot" method; you point at what you want, then "shoot" with the ENTER key to make it happen. Finally, for those in a hurry, there are a number of "shortcuts" designed to make accessing commonly used features as fast as possible. What makes the Spectrum XLT even easier to use are the factory preset programs (like those in previous Eagles) which you can load with just a few simple keystrokes, following the prompts in the display. These programs configure the machine automatically so that the beginner or casual treasure hunter can expect a great deal of success over a broad range of conditions. Any attempt on my part to detail all of the advanced features and controls which the Spectrum XLT has to offer would probably leave me with blisters on both of my typing fingers. Suffice it to say that all of the features we have had in previous state-of-the-art detectors are here in this one, plus several new ones. Most of the features are there because somebody asked for them -- the moral of the story being, keep those cards and letters coming, and we will continue trying our best to give you the kind of detector you really want. Mark Rowan was a Senior Engineer for White's Electronics, Inc. Mark holds degrees in General Science, and Electronics Engineering Technology, and is a graduate of the University of Oregon. His background includes satellite communications and RF test and measurement instrumentation. White's SignaGraph examples from Spectrum XLT manual
  3. Prompted by one of Abenson's recent posts (including link and discussions on Monte's site) I decided to BYO and do some testing myself. Here's my build: Template on the left. That came from Monte's .pdf. I'm pretty sure my printer got the scale correct. I will point out that 20d nails (the big ones) have a length tolerance of +/- 3/32" (+/- 2.4 mm) and Monte's appear to be on the low tolerance end with mine on the high end, but hopefully that doesn't matter much if at all. My board is 1/2" plywood and the two coin recesses have USA small cent diameter. Nails are epoxied in place, slightly (~1 mm) recessed. I've read Monte's document 3 times and still have some questions/uncertainties which have led to this post. My first question probably has an obvious answer given that (from his document) he created this test based upon an actual ghost town site discovery with these locations of nails and an Indian Head Penny at coin location #1 (center). My question is: how close to the board are you supposed to swing the coil? I took the board outside for my first test -- no coins at all to get a baseline. Minelab Equinox 800, 11" coil, EMI canceled, ground balanced, Park 1 custom 5 tones, Recovery Speed = 5, Iron Bias F2 = 0, sensitivity/gain = 17, no discrimination (i.e. no channels notched out). Swinging as close to the board as I could get I heard non-ferrous signals from one or two directions. I could 'cheat' and look at digital TID's, but from what I've read this is supposed to be an audio only test. So how do I proceed and determine (once I put a coin on the board) if I'm hearing the coin or the falsing nail signals? I don't think simply creating a threshold to eliminate the nail falsing is a reasonable solution in this case (as you would do for an analog detector such as an early Tesoro, from what I understand). I could be wrong on that, of course. Again, I didn't look at the digital TID, but my lowest channel (including ferrous) ends at +5 and it was above that.
  4. The Accumulate, Average, and Fade controls exist on several White's models, having first been introduced on the White's Eagle Spectrum. The functions govern how the SignaGraph™ and SpectraGraph™ displays show targets and so are unique to White's detectors. These display controls are also used on the DFX and V models. This note appended to the Engineers Guide to the Spectrum XLT offers a basic explanation of what these controls are doing. The display controls are also covered on pages 45-46 of the XLT Users Guide (excerpted below). Spectrum XLT Engineering Note Using Spectrum XLT Modes: Accumulate, Average, and Fade by Mark Rowan Although the SignaGraph™ display format has been well received, there seems to be some confusion regarding the option (average accumulate, and fade) and how to use them. Perhaps a more detailed explanation is called for. The default (preset) condition is Accumulate/Average/Fade, the fade rate being fairly slow. With each sweep over the target, several attempts are made to assign it a V.D.I. number. Each reading (There may be only one or two, or as many as six or eight readings per sweep) is reported to the user as a vertical bar on the SignaGraph™. (NOTE: If all eight readings are the same, the user will only see one bar). In Accumulate mode, these bars are not "cleared out or "blanked" on subsequent sweeps, but continue to "build up" in the display so that the user sees the entire history of multiple passes over the target. Squeezing the trigger will clear the display if it gets too cluttered, or if the user chooses to move to a different target with those of the second one. However, continually having to squeeze the trigger can be a nuisance -- this is where Fade comes in. If a certain period of time elapses with no new target responses, the vertical bars will be shortened by one increment. Eventually, they will disappear from the display. Notice, however, that if a new response comes along quickly enough, the Fade timer is reset (this is necessary to prevent readings from beginning to fade before the user has even had time to see them). Thus, if the Fade rate is slow and the user is sweeping the loop fairly quickly, no fading will occur until he stops swinging the loop or moves away from the target If he is working a trashy area or has his sensitivity cranked up to the noise threshold, the Fade out may be disabled entirely. This is the justification for the Fade Rate control. If the fade rate is increased, the user can find a level at which Fading will reliably occur, but which is not too fast for his personal taste or his style of hunting. If the Accumulate control is turned off the instrument is in the "single sweep" mode. Each sweep of the loop causes the display to be cleared, and only those readings made during the current pass over the target to be shown. The primary advantage of this is that it reduces the chance for readings from two different targets to be confused with each other. If the Fade rate is set to 0, fading is disabled and display bars will remain indefinitely. Average mode is entirely different than either the Accumulate or "single-sweep" mode of operation. When Averaging is turned off (the default in all preset programs have Averaging on) the vertical height of the display bar is an indication of the strength of the signal when that reading was taken. With Averaging, however, the height of the bar represents a running total of the number of readings that have occurred at that point on the display. For example, if you pass the loop several times over a gold ring and get readings of 1, 10, 40, 10, 10, -20, and 10, the display will show a tall bar at the place corresponding to 10 on the display, and very short bars at the positions corresponding to -10, 0, and 40. If the count exceeds the vertical resolution of the display, the bar remains at its maximum height and all other bars in the display are reduced by one increment, eventually disappearing from the display. The usefulness of this is that if the error in the V.D.I. readings is random (such as that caused by electromagnetic interference or irregular loop motion), it will eventually average out and the display will "lock on", showing a single prominent segment at the correct point on the display. Unfortunately, there is a catch. Iron and foil targets which mimic coins will also appear to "lock on"; the smearing one would normally expect will be suppressed somewhat. However, in the hands of a skilled user this should be a very useful feature. Mark Rowan was a Senior Engineer for White's Electronics, Inc. Mark holds degrees in General Science, and Electronics Engineering Technology, and is a graduate of the University of Oregon. His background includes satellite communications and RF test and measurement instrumentation.
  5. I’m sure I read somewhere that all of these common connectors (typically for headphones) such as the 8 pin style have a limited amount of mating cycles. Connector integrity cannot be assured after this. I guess there is a small amount of wear and tear on the male/female metal contact points as well as the plastic/rubber moulding that keeps water out. Any views on this? Thanks Tony
  6. The cell phone is now a common day device owned by most people. It was inevitable that a metal detector designer would mimic the look and feel of a cell phone in an attempt to modernize how metal detectors are perceived. As far as I know it was Quest (back when they were named Deteknix) that first came up with this design. Or at lest they were the first to really market something like this in 2015. Then we next got the Minelab Equinox in 2018. And now the Nokta/Makro Simplex+ in 2019. Some might call this copycat designing but form follows function to a certain degree and all items copy others in some ways. All T-shirts have a head hole and two arm holes. Still, I think Deteknix/Quest gets the credit here for first popularizing this design. I'll be surprised if more are not to follow. Quest metal detector Minelab Equinox metal detector Nokta/Makro Simplex+ metal detector Quest metal detector controls & display Minelab Equinox metal detector controls & display Nokta/Makro Simplex+ metal detector controls & display
  7. Out with the Minelab Equinox yesterday and getting frustrated with the difficulty of switching to the user 'profile' (plenty of complaints on that since its release) but then wondering why we have only one memory slot. Sure, many detectors have zero.... Are there detectors on the market (or even from the past -- no longer manufacturered) that have more than one user memory slot? It's hard to believe in 2020 with gigabytes of memory in so many small packages/products that we can't have 2 or (am I asking for too much?) 4 places to put user custom set search modes.
  8. I had a guy approach me at the lake today who lost a 14K college class ring size 11. I told him I would spend time looking for it and get it back to him if I happen to recover it. I have a 10K college class ring I found this year(unable to locate owner) but, it's a 10K. On the Simplex, it reads 64-65, the Nox hits at 20-21 I'm wondering how much of a difference the 14K will read. Any help would be appreciated. Thanks.
  9. Might be a silly question, but I can't find the answer. Seems like all the lower end detectors are always around 5-8 khz. I was always under the impression that the sweet spot for the biggest target range was around 12-18 khz. Are the lower frequencies cheaper to implement, or is there another reason?
  10. Here’s a topic for all you “Rocket Scientists” out there (and anyone else who’d like to chime in). I was having a discussion with another dealer. He felt that single frequency worked better because there’s a certain amount of performance loss with Multi. I was always of the opinion that Multi-Frequency was the best for most types of Metal Detecting. It allows you to hit ALL the targets that react better to certain kHz. Here’s an example from another hobby of mine (most of us have more than one). I shoot muzzle loading guns. The “Round Ball” type projectile that was used for hundreds of years performs best when shot out of a rifled barrel with a slow twist. Twist refers to the how many inches of flight it (the projectile) takes to make one revolution. The conical bullet came out during the Civil War and requires a faster twist. For modern muzzle loading rifles a slow twist would be 1 turn in 56, 60, 66, 70, etc. inches. For conicals, 32, 28, 24, etc. inches. In the 70s, one company came up with the idea of a “Compromise” twist; 1 tun in 48”. That way you only have to buy one gun. You can use Round Balls for Target shooting and Conicals for hunting. It shoots both “well”. Having said all that, does the Single Frequency work better than the Multi? Is there any kind of lack of performance or trade off having them (kHz) work simultaneously? Thanks! Walt
  11. A pretty fascinating set of photos posted over at http://md-hunter.com/homemade-metal-detector-amazing-photos/
  12. I tripped over this at the Minelab website: This posting, together with the label, also provides an indication of which Minelab products are protected under the Patents Act of various other countries. Product(s) US Patent Number Australian Patent Number GPZ 7000 6636044 783737 7310586 8106770 2011200515 D686924 342365 (Design) 2009262370 2012101855 9547065 2013201330 GPX 4500, GPX 4800, GPX 5000 2011200516 8106770 2011200515 6636044 783737 SDC 2300 2011200516 8106770 2011200515 6636044 783737 D652330 9829598 2014274608 9547065 2013201330 Gold Monster 1000 7432715 2005276953 CTX 3030 7310586 D686924 342365 (Design) 8854043 2013201248 9239400 2013200451 E-TRAC 7310586 X-TERRA 305, X-TERRA 505, X-TERRA 705, X-TERRA 705 Gold Pack, X-TERRA 705 Dual Pack 7432715 2005276953 EQUINOX 600, EQUINOX 800 7432715 2005276953 7579839 9366779 2014218372 Vanquish 340, Vanquish 440, Vanquish 540, Vanquish 540 Pro-Pack 7432715 2005276953 7579839 9366779 2014218372 GO-FIND 20, GO-FIND 40, GO-FIND 60 GO-FIND 22, GO-FIND 44, GO-FIND 66 7432715 2005276953 D756247 360432 (Design) 9557390 7310586 National Geographic Pro Series Metal Detector 7432715 2005276953 D756247 360432 (Design) 9557390 7310586 AN/PSS-14 6636044 783737 F3, F3 L, FE S, F3 LS, F3 UXO, F3 Compact 7310586 6636044 783737 F3 Compact D652330 F3Ci 7432715 2005276953 D652330 STMR Array 6636044 783737 7310586 MDS-10 7432715 2005276953 7579839 9366779 2014218372 Other patents that may apply to the above products 7474102 7652477 7791345 8063777 8237560 8614576 2007272230 9250348 9348053 2017279664 9429674 2014218370 10078148 2014268189
  13. Most of the sites I hunt have very mild ground. I typically leave my GB at 0 most of the time. When I do take the time to Ground Balance, I usually get single digits with occasional numbers in the teens. Do the GB numbers reflect the levels of mineralization in the soil? Do soils with high mineralization have higher numbers? The manual says nothing about it.
  14. Most people act like it’s all about depth. This machine versus that machine.... which is deeper? In my experience for some things max depth does matter. Like gold prospecting. Get a GPX 5000 or GPZ 7000 and dig. Or beach detecting or relic detecting with PI detectors. If depth really was all that mattered, everyone would use a PI. But we do not. Not even the gold prospectors and beach hunter. To state the obvious, not everyone can afford a GPZ 7000 or has access to ground where it will pay off. For some people, a Gold Bug 2 makes more sense. And not all of us are physically capable of digging deep holes for junk all day... we need to narrow the odds. Even if that means giving up depth. VLF tends to be about discrimination, but again all it seems we hear about is depth. But what kind of depth? Depth with good discrimination? How good? I am very cognizant when running a VLF that I’m not running a detector that gets max depth. That being the case, ergonomics and audio matter a lot to me. How it feels on my arm, and sounds to my ear. If I hate the sounds a detector makes I’m not going to enjoy things as much. Frankly, I can make up for a little less depth by just finding better sites or hunting longer hours, if that means having a detector I enjoy using. I say depth is not everything when it comes to VLF detectors. Important, yes, but it perhaps it should not be the sole criteria for most people. What say you?
  15. I hope this topic hasn't already been covered and I'm not writing it in the wrong place. Recently, based on my lack of knowledge in this sector, I have however noticed large differences in actual life, not only because of battery chemistry ... I mean something about the use of power itself in using the tool. Thinking of a mobile phone, the standby time is merely relative to the battery capacity, as is the duration in call or video call, much less long ... So every time a detector is used in an area where there are several signals and we are busy digging or at least hearing many of them, the battery duration is more affected and reduced... This for me, as an inexperienced, means not being able to have a clear measure of the actual duration of the battery pack ... You can never know regardless of how many signals will pass below the coil ... So I then discovered the natural drop in voltage, added to that of absorption in the most arduous use ... And what about threshold instability and false signals if, for example, a pulse is not properly regulated and a too low delay makes it continuously sound for nothing by activating the retuning? At this point I have the impression that even with higher capacities, the voltage drop is the most difficult factor to defeat, even before the capacity .... I am facing the insertion of bms modules in these days and in the future I could add step up or step down modules if necessary, but first I would like to understand to what extent it is possible to delay the cut off, if not eliminating some form of protection that these boards cut away leaving a lot of useful voltage. Unprotected batteries can have a bad end if it is lithium, so there is a compromise between safety and durability ... I repeat again ... I am not an expert and anyone who can add his knowledge on the subject, do it without brakes because I am well open to constructive technical comments, or even comic and bad ...
  16. Of all the different types of metal detectors, the two box is the oldest(?) but also one of the least used. Defintitely a detector for special situations, but with a couple possible exceptions, for the proper situation it's the best choice for the job. I'm aware of two standalone models still available new -- Fisher Gemini-3 and White's TM808. Garrett's Treasure Hound (see P. 43 of their latest catalog) and apparently a new kid on the block are attachments for specific standard (control unit + shaft + single coil housing) detectors. In particular what has me wondering (and confused) is the fact that the Gemini-3, operating at 81.92 kHz doesn't appear to have a gound balancing adjustment but the TM808 (6.5 kHz) does. I was under the (naive?) impression that low frequencies are less susceptible to ground mineralization but here it seems in practice, it's just the opposite. Any thoughts/explanations?
  17. Hi, I am new to the forum. Anyone have any experience with this brand of detectors ? https://uigdetectors.com/en/gold-and-metal-detectors I am thinking of buying a Minelab SDC 2300, but in my internet search last night, I came across this brand I have never heard of called UIG detectors. Looks like they have some interesting looking detector technology. Before I drop money on an SDC 2300, I want to make sure I consider the competition as there may be other reliable and fun technology to experiment with.
  18. First time I think I have seen this. https://patents.google.com/patent/US20190353818A1/en
  19. Just wondering if anyone has tried any 3D Ground Scanning metal Detector? Also, what's the best 3D Ground Scanning metal Detector in the market? Can anybody share their experience.
  20. Those impressive video results of the Fisher Impulse AQ with its 12.5” mono coil on the 10K Gold ring at 17”-18” and 14K Gold ring at 19”-20” as did a 22K Gold ring drove my curiousity to air test two Gold rings using a QED in its Beach Mode-11 operating at its pulse delay of 7.5uS with a NF 12” Advantage mono coil. For my test, the QED’s settings were Threshold-B at 5 below Null and Factory Default for Threshold-A at 30 and Gain at 1. (Threshold-A settings range from a 1 up to 90 and the Gain settings range from 1 up to 10} The results for a clear response on a 3.04-gram 9K 21mm diameter Gold ring was 17” and on a 2.05-gram 18K 19mm diameter Gold ring was 16”. I have no idea how a QED using its Beach Mode would operate within a Beach environment and my intention is not to compare in anyway the QED to the Fisher Impulse AQ only results using a pulse delay of 7.5uS.
  21. Hand held backscatter xray. I want one. https://www.dael.com/assets/files/Documenten/hbi-viken-sec2.pdf HH Mike
  22. The latest issue of the ICMJ is out, and I have an article in it titled Selectable Frequency vs Multi Frequency Detectors. Those of you with a digital subscription can read it online. The ICMJ has a policy against mentioning brand names in articles so I wanted to post this as a supplement to the article. Most metal detectors process a single frequency. Low frequencies, that is single digit frequencies under 10 kHz, react well to high conductive targets, like coins, or large items, even if those items are of low conductivity. If you look at this typical metal detector target scale below you will note that non-ferrous items read higher not just based on conductivity but size also. Low frequency detectors also do not "light up" the ground or hot rocks as much as detectors operating at higher frequencies. Many do not even offer ground balance controls because a factory preset level works well enough for some uses. Low frequency machines under 10 khz therefore tend to be aimed at the coin detecting market. There are too many models to list but most people have heard of the 6.5 khz Garrett Ace 250 as a perfect example. High frequencies 30 khz and over have extreme sensitivity to low conductive and small items, but also struggle more with ground penetration and hot rocks. Their extreme sensitivity to tiny trash items like aluminum bits do not make them very practical for any detecting except gold prospecting. Machines 30 khz and higher tend to be dedicated prospecting machines. Examples would be the 48 khz White's GMT, 71 kHz Fisher Gold Bug 2, 56 kHz Makro Gold Racer, and 45 khz Minelab Gold Monster 1000. In 2002 White's introduced the White's MXT at 14 kHz, and it is a perfect example of how detectors running in the "teens" make excellent "do-it-all" detectors. Since then everyone and their brother has jumped on that bandwagon, and there are too many machines running in the 10 kHz - 20 khz region to mention. Prospectors in particular would recognize the 19 khz Fisher Gold Bug Pro, but few know it is also sold in slightly different versions as the Teknetics G2, Fisher F19, and Teknetics G2+, all 19 kHz detectors sold to the general coin and relic market. Garrett has the 15 kHz AT Pro and 18 khz AT Gold to name a couple more popular metal detectors. Here is some information for those of you who are more technically minded. George Payne was one of the engineers who patented many of the basic concepts used in VLF detectors to this day. Here is an excerpt from his article at http://jb-ms.com/Baron/payne.htm (2002): "The r component acts differently. It is maximum at one particular frequency and decreases if you go up or down in frequency. We call the special frequency at which the r signal is maximum, the target’s “-3db” frequency. It also turns out that at the -3db frequency the x signal is one-half of its maximum value. This special frequency is unique to each target and is different for different target. The higher the conductivity of the target the higher will be the targets -3db frequency. Conversely, the lower the conductivity the lower the -3db frequency. The -3db frequency of the high conductivity target will also make the r signal peak at a high frequency, normally well above the operating frequency of the VLF detector. This will make the high conductivity target have lower sensitivity on the VLF detector because the r signal amplitude drops if we are significantly below the -3db frequency. Simply put, maximum sensitivity on a VLF detector would be if we position the operating frequency directly at the target’s -3db frequency. For example, a dime and penny have a -3db frequency of about 2.7KHz. This is where their r signal peaks and would be the best frequency for picking them up using a VLF detector. However, a silver dollar has a -3db frequency of 800Hz. Nickels, on the other hand, have a -3db frequency, where its r peaks, at about 17KHz. Targets like thin rings and fine gold are higher still. Clearly there is no one frequency that is best for all these targets. The best you can do is have an operating frequency that is a compromise." Well, if low frequencies are good for coins and high frequencies good for gold, why not make machines that can do both? Or both at once? Instead of picking a compromise frequency? Selectable frequency refers to machines that can select from one of several possible frequencies, but process the signal from only one frequency at a time. The key is not what a detector transmits so much as what it processes. These may also be referred to as switchable frequency detectors. Multiple or multi frequency detectors process the signal from two or more frequencies at once. In theory this multifrequency analysis can be done simultaneously or sequentially at a very high speed. The end resultant is the same - the results from two or more frequencies are compared to derive information that cannot be had by analyzing a single frequency alone. Multiple frequency detectors usually have a fundamental frequency, and then other "harmonic" or secondary frequencies they also use, but the power (amplitude) fades with distance from the primary frequency. From page 9 of Minelab's Metal Detecting Terminology: You can find more information on harmonic frequencies at http://www.ni.com/white-paper/3359/en/ and here also. Coils normally must be wound specifically to make use of any given frequency or set of harmonic frequencies. A coil will usually work best at the given fundamental frequency making it difficult to get the best possible performance at all frequencies using one coil. The Minelab X-Terra series specifically requires a coil change to achieve a frequency change for this very reason. People who own them know 3 kHz coils weigh more than 18.75 kHz coils. Why? Because heavier windings are used at 3 khz for optimum performance at that frequency. Here is what is probably an incomplete list of selectable frequency detectors and year of release: 1989 Minelab Eureka Ace Dual 8 kHz 19.5 kHz 1993 Minelab XT 17000 6.4 kHz 32 kHz 1994 Compass X-200 6 kHz 14 khz 1997 Minelab XT 18000 6.4 kHz 20 kHz 60 kHz 1999 Minelab Golden Hawk 6.4 kHz 20 kHz 60 kHz 2002 Minelab Eureka Gold 6.4 kHz 20 kHz 60 kHz 2005 Minelab X-TERRA 50 7.5 kHz 18.75 kHz 2006 Minelab X-TERRA 70 3 kHz 7.5 kHz 18.75 kHz 2009 Minelab X-TERRA 305 7.5 kHz 18.75 kHz 2009 Minelab X-TERRA 505 3 kHz 7.5 kHz 18.75 kHz 2009 Minelab X-TERRA 705 3 kHz 7.5 kHz 18.75 kHz 2009 XP DEUS 4 kHz 8 kHz 12 kHz 18 kHz 2016 Rutus Alter 71 Variable 4 - 18 kHz 2017 XP DEUS V5 Additional 14 kHz 30 khz 55 khz 80 khz options 2017 Nokta Impact 5 kHz 14 kHz 20 kHz 2017 Makro Multi Kruzer 5 kHz 14 kHz 19 kHz 2018 Nokta Anfibio 5 kHz 14 kHz 20 kHz Multiple frequency or multi frequency machines have become very confusing, as a lot of marketing material has focused on the number of frequencies transmitted. What really matters is what frequencies a detector receives, and how the information is compared and processed for results. Some commentary here. Many people look at the marketing material and assume that a machine processing multiple frequencies is somehow working across the board to deliver the best possible results at all frequencies. However, the two issues outlined above do apply. The machines are employing harmonic frequencies, and so cannot compete with a machine optimized at a single frequency as opposed to one of the distant harmonics running at less amplitude. Second, making one coil run perfectly at all frequencies is extremely difficult, again giving the dedicated machine an edge. I highly recommend people not go down the technical rabbit hole but instead focus on what the machines do, on how they act. Two things are very apparent. First, the big market for a long time was coin detectors, and the goal always was to identify coins as deep as possible while ignoring trash as well as possible. Processing two or more frequencies simultaneously gives the detector engineer more information to work with. All the focus was on developing great coin detectors and guess what, the multi frequency machines for all intents and purposes act just like very good lower frequency coin detecting machines. Good ground rejection, and great discrimination on coins for as deep as it can be achieved. The multi frequency machines don't really go deeper than single frequency coin detectors, they just do a better job delivering clean discrimination results to depth. Here is a list of introductory models of multi frequency detectors and year of introduction. I am not listing all the derivative models to reduce clutter. I will post that later. 1991 Fisher CZ-6 5 & 15 kHz 1991 Minelab Sovereign BBS 1999 Minelab Explorer S/XS FBS 2001 White's DFX 3 kHz & 15 kHz (Simulates single frequency by ignoring half the dual frequency signal) 2012 Minelab CTX 3030 FBS2 2020 Minelab Vanquish Multi-IQ Second, single frequency detectors have a ground balance problem. They can ground balance to mineralized soil, OR they can ground balance to salt water. Multi frequency machines can reduce signals from both mineralized beaches and salt water simultaneously, making them ideal for saltwater use. 1993 Minelab Excalibur BBS (Sovereign in waterproof housing) 1995 Fisher CZ-20 5 & 15 kHz (CZ-6 in waterproof housing) 2001 White's Beach Hunter ID 3 & 15 kHz (DFX in waterproof housing) There is a third class of machine that can run either as selectable frequency OR multi frequency detectors. Quite rare at this time. 2009 White's Spectra Vision 2.5 Khz or 7.5 kHz or 22.5 kHz or all three at once 2018 Minelab Equinox 5 kHz or 10 kHz or 15 kHz or 20 kHz or 40 kHz plus multi frequency options 2020 Garrett Ace Apex 5 kHz or 10 kHz or 15 kHz or 20 kHz plus multi frequency options In my opinion multi frequency has delivered well on its promise. The Minelab BBS and FBS machines are renowned for their ability to discriminate trash and detect coins due to their sophisticated processing. Again, focus on what they do. Not even Minelab in their marketing tells anyone these are prospecting detectors. Second, the Fisher CZ-20/21 and various Minelab Excalibur models are without a doubt the most popular and successful non-PI saltwater beach detectors made. I have a White's DFX and I think it is a fantastic jewelry machine in particular. A good coin machine but lacks a bit of punch. The Vision/V3i upped the ante but while amazing on paper suffers from interface overload. The Minelab units are simple by comparison and a lesson on how people in general just want the detector to get the job done. Feature overload is not a plus. However, I think White's has the right idea. The ability to run either separate frequencies or multiple frequencies at once is very compelling. I just think nobody has really done it right yet in a properly configured package. The V3i has the ingredients, but needs to be stuffed in something like an MX Sport with a simplified interface and improved ground balance system. (2018 note - Minelab Equinox released). It really never did beat the White's MXT in some ways and many people when "upgrading" to the V3i end up going back to the MXT. Selectable frequency has yet to really deliver on its promise in my opinion. So far it has been difficult to produce a selectable frequency machine that truly performs at all frequencies on par with a dedicated single frequency machine. The Minelab Eureka Gold at 60 kHz just never gets mentioned in the same breath as the White's Goldmasters/GMT or Fisher Gold Bug 2. Also, most selectable frequency machines in the past have been very feature limited prospecting machines, restricting their overall market appeal. I personally think we have seen enough variations of single frequency detectors. I do not believe much can be done to exceed the performance of the dedicated single frequency VLF type machines we currently have. What can obviously be done is a better job of packaging machines that deliver true punch at different frequencies, or multi frequency machines that bring across the board performance closer to what is expected of PI detectors. I do think we are seeing this happen now. The new Nokta Impact and the new DEUS V4 update are expanding the available options in selectable frequency in more usable packages. The Minelab GPZ and other hybrid platforms blur the line between what is traditionally considered PI and VLF and simply need the addition of discrimination to go to the next level. There is still a lot of potential to deliver machines that might reduce the number of machines many of us feel compelled to own by delivering more across the board performance in a single machine that would now take several detectors. Exciting days ahead. For those who want to try and get their head around selectable frequency and multi frequency technology, Minelab and White's have a gold mine of information in a few of their references. Dig into the following for some great explanations and diagrams. Minelab - Metal Detector Basics and Theory Minelab - Understanding Your X-Terra White's - Spectra V3i Owners Guide White's - V3i Advanced Users Guide Better yet are the last three parts of the DFX instructional video by White's featuring engineer Mark Rowan explaining frequency and multi frequency methods:
  23. What do you make of this description on KellyCo? It seems to suggest the IPTU sensor would work with machines other than the Invenio. Does anyone know if that is true and how that would work? "One of the biggest issues that people run into when metal detecting is difficulty with accuracy. The IPTU Sensor (Invenio) is going to help increase your accuracy and help you find more items and be sure what they are and where they are better. This is an easy to install sensor and is going to make a world of difference when it comes to your overall success when metal detecting. This sensor works with Invenio detectors and is a great addition to any metal detector." https://www.kellycodetectors.com/catalog/iptu-sensor-for-invenio
  24. The original 1985 Fisher Impulse metal detector A note on saltwater. On dry land and in freshwater pulse induction (PI) detectors can be run to max limits. Not so in saltwater. There is an inherent limiting factor in saltwater that tends to flatten top end performance on all PI detectors, or even VLF detectors for that matter. The problem is simple - saltwater is conductive and so is visible to electromagnetic devices like metal detectors. Pulse induction detectors saw their earliest use as beach detectors because of the pulse delay control. Lower pulse delays expose items with a shorter time constant, and this usually means low conductive and/or small items. As the pulse delay increases a PI loses overall sensitivity. Early beach PI detectors all came with a preset, relatively high pulse delay that made saltwater invisible to the detector. In general somewhere around a pulse delay of 10 uS saltwater becomes visible to a PI detector. The number varies for several reasons, First, salinity varies greatly around the world, everything from salt free fresh water, all the way to the Great Salt Lake, which is water supersaturated with salt. Oceans and bays vary, and especially bays that have large river inflows, and therefore lower salinity levels. Large, shallow, enclosed bays with no rivers may act as evaporation dishes, and have abnormally high salinity levels. Further, this effect is accentuated the deeper you take a detector, and so detectors used for true SCUBA diving must be run at higher delay levels at depth. You can't just pick a number like 10 uS and say that is the magic number for dealing with saltwater. 9 uS may work well, or it may take 12 uS to eliminate feedback from the saltwater in your location. The coil detects like a globe in all directions, and so it is not just the water under the coil, but all around the coil that is affecting it. This large ball of saltwater is like a giant target. Many hunters riding the edge of sensitivity can tell you a detector can pick up waves as they pass over, making the water deeper. This long winded explanation is to make people realize that you can't just magically make the detector itself more powerful and get "more depth" or "more sensitivity." The salt range overlaps the tiny gold range, and so if you make a detector able to detect fine gold chains and tiny gold ear rings, it will detect the saltwater. If your set the pulse delay to eliminate the salt signal, you lose the tiny gold items. This is an inherent wall on both PI and VLF small gold performance in saltwater. We have had detectors for decades that can detect tiny gold that people say they want to detect in saltwater, the Fisher Gold Bug 2 for instance. The problem is the Gold Bug 2 will not work in a saltwater environment. The water is just a huge signal to a Gold Bug 2. I have gone round and round with people for the last twenty years trying to explain why you can't detect certain fine gold chains, small ear rings, small platinum, etc. in saltwater. The problem is not the detectors - it is the saltwater. The same problem exists to some degree on trying to detect larger items. You can make a very powerful detector, but you have to inhibit the detection of saltwater, and this tends to put a ceiling on the maximum attainable performance in saltwater. No matter the machine you use, once you hit the saltwater you can only advance the pulse delay and sensitivity controls to a certain point before the detector starts to protest. The exact settings where this occurs will vary by location. This all assumes "no mineral" sand. Add magnetic soil content to the beach or bottom being hunted, and you have yet another limiting factor to contend with. Add this all up and do not expect to run the Impulse AQ Limited at a pulse delay of 7 Us and maximum sensitivity in a typical saltwater environment. You will likely have to lower one or the other or both settings to get stable performance, and this requirement tends to be a limiting factor on all PI performance in saltwater. It is this knowledge that keeps me from ever expecting miracles to occur when I try new detectors in saltwater environment. The problem is not the detectors - it is the saltwater. The original 1985 Fisher Impulse metal detector
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