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Found 195 results

  1. I was reading the Australian Electronic Gold Prospecting Forum today and noticed a post about detector depth. I was wondering what others think about today's detectors compared to what was available 25 years ago. I read somewhere that (Woody) the guy that does mods to detectors thinks that for outright depth the sd2000 still goes the deepest. I wouldn't know as I've never owned a sd2000 or a gpz7000. Anyway, i found the comments at AEGPF interesting and wonder if anyone here has actually done a depth comparison between the zed and sd2000. Heres the snippet from AEGPF Quote from AEGPF: "The deepest Pi detector ever developed in my opinion was a prototype SD2000 that BC modified for the late Jim Stewart.BC slowed down the clock speed to give a very long pulse and made some other unknown changes to the circuit to cope with higher currents etc. At the time the SD2000 came out BC stated that it was at about 95% of the maximum potential depth that any handheld PI could ever achieve (and still pass emission standards). However, the deepest PI that has ever been made for gold was Corybns detector which detected a nugget of around 10oz? at 3 feet in depth in WA. Somewhere on the forum is a reference to it and I will try and find the link when I have time. "What is interesting is that the deepest nuggets ever detected by a Pi was by a detector used in the early 1980's in WA-Corbyn's wheeled detector! Pictures of it and the depths of some of nuggets he found with it can be seen in Mike Wattones book: Quest for gold.NO Pi detector today could match the depths Corby got on at least one nugget! (4cm nugget at over 36" in mineralized ground)"
  2. Editors Note: this thread split from http://www.detectorprospector.com/forum/topic/4335-the-reg-wilson-gold-album/ Nice stuff again... I'm having cardiac palpitations seeing all this gold....lol I wonder if you could tell us how your sled was rigged up. That looks nice for some open ground. Keep it coming....
  3. Jonathan Porter

    QED Review

    So far there has been no real “direct” reviews of the QED, in effect just innuendo clouded by politics, which is not helpful. With the help of a friend I've just finished some testing of the QED and want to share our impressions here in the hopes of getting the ball rolling for some quality discussions (but maybe this is being too optimistic?) We hope and believe our tests were rigorously objective, the QED was used for general gold hunting and also comprehensively tested on buried real gold pieces of various sizes in a variety of soils, considerable care was taken to ensure no placebo/bias.* We deliberately tested on only frequently detected but historically very productive public fields, not private property in which it can be relatively easy to find gold using any technology due to only ever seeing a few detectorists. First and foremost, important details of the QED's method of operation that are different to other detectors which needs to be clearly understood: Unlike Minelab detectors, the QED has a “dead zone” that can be varied using the Volume control. The threshold is set using the Bias control and has 2 different audio threshold settings, an upper and a lower value. When the Bias is turned down in number below the threshold lower value, OR, turned up in number above the upper threshold value, the “Threshold” audio increases as per usual. Suppose for example, the lower audio threshold bias value of the Bias control happens to be 50 and the upper threshold bias number happens to be 60. Then if the Bias is turned down below 50 OR turned up above 60, the audio “threshold” level increases as per usual. For these threshold examples, 50 and 60, small gold (fast time constant targets) “in effect” produce signals less than 55 (half way between 50 and 60), and larger gold “in effect” produce signals more than 55. If the Bias is set at the lower threshold limit, 50 for example, then the detection of small gold will give the usual INCREASE in audio level response, and larger gold will give a BELOW threshold level response, OR If Bias is set at the higher threshold limit, 60 for example, then the detection of larger gold will give the usual INCREASE in audio level response, and smaller gold will give a BELOW audio threshold level response. Similarly with ground noise; some ground noise will in effect produce signals below 55, so that if the Bias is set at 50, this ground noise will give an increase in audio sound, but if the Bias is set at 60, this ground noise will give a below threshold audio response. Conversely, if the ground noise is in effect above 55, then if the Bias is set at 50, this ground noise will give a below threshold audio, but if Bias is set at 60, this ground noise will give an increase in audio level. Signals in effect BETWEEN 50 and 60 are in the “dead-zone,” for which the audio is below threshold. Signals in effect below 50 OR above 60 give an increase in audio. So if threshold is set at the lower threshold of 50, then faint signals from small gold will give an above threshold audio, and large targets a below threshold audio. Whereas its the opposite for the upper threshold of 60, faint signals from large gold will give an above threshold audio, and small targets below threshold audio. So for shallow small gold select the lower threshold limit, for big deeper gold select the upper threshold limit. Bigger target signals will produce above threshold signals regardless of whether they are small or larger targets. However the Volume control controls the dead-zone width; the gap between the upper and lower threshold Bias settings, that is, the dead zone gap is increased by turning the Volume down, or decreased by turning the Volume up. In fact the QED can be set to operate with NO dead-zone (like the usual Minelab PI audio). To do this: a. Vary the Bias between the upper and lower threshold. Note the gap. b. Increase volume a bit. c. Re-do a. and note the decrease in the gap. d. Continue to repeat a, b, c until there is no gap. (This will allow some feel for true ground noise etc.) However the QED audio has a very low level signal EVEN if below threshold, This below threshold faint audio signal is just the pitch signal only, and detects all signals, ground noise, target signals, whether long time constant or short, and EMI. But this below threshold pitch sensitivity is not as acute as the audio set at threshold per point 2 below, and it is very soft. Yet even further, if a target or ground noise (or EMI) does drive the audio below threshold, the nature of the audio is that it has the usual “re-bound” response once the coil has moved over and past the target or ground noise. I refer to the lower pitch audio following the initial target higher pitch audio (“high-low”) or the opposite; the higher pitch audio following the initial target lower pitch audio (“low-high”) effect known from Minelab PI's. So for moderately weak target signals that cause the audio to dip below threshold once the coil moves beyond the target and the audio then rebounds above threshold. To recap; for these targets, as the coil passes over the target the audio goes first below threshold THEN above the threshold. However for the fainter of these target signals (the important signals one listens for in thrashed ground), this rebound signal is hard to discern compared to the same signal that would occur if the Bias had been set at the alternative threshold setting for which the audio signal then would have given an initial increase in threshold as the coil passes over it and then a below threshold rebound. Therefore, it is important to understand that you EITHER need to set the Bias to chase the faint small targets in shallow ground (Bias at the lower number setting), but lose out a bit on the faint large target signals OR set the Bias to chase the faint larger targets in deeper ground (Bias at the higher number threshold setting) but lose out a bit on the smaller targets. The QED has a “motion” audio response; meaning the coil has to be moved to hear a signal. It can be operated both quickly, and also, remarkably slowly. If the coil is moved “remarkably” slowly it is possible to hear the average audio detect a very faint target above the audio “background random chatter”, considerably more readily than if the coil was moved at a typical realistic operational speed. When depth testing and when you know where the target is, beware that you do not slow down the coil swing to an artificial unnatural swing speed to enable the detection of a deep target at its known location.* Important recommendations: 1. It's very important to get the threshold (Bias) spot on for optimal results, If the threshold level is too high, then faint signals get drowned out, but if the audio threshold level is too low then only the residual very faint pitch signal remains, but this faint pitch only signal is less sensitive to target signals than the audio set optimally as per point 2 immediately following. 2. The threshold must be set so that it is just audible; in effect just immediately below the “real” audio threshold signal, so that what you are hearing is just between only the pitch signal and actual above threshold audio. 3. Note that the effective principal threshold control (Bias) is temperature dependent and requires reasonably frequent adjustment over time as the ambient temperature changes to get best results. Therefore there is NO actual specific optimal Bias number setting, rather it entirely depends on temperature. It can be as high as 70 in very hot conditions 4. Once 2. and 3. are optimally achieved, you will find that the GB setting has to be spot on for best results. If you find that it is not critical, you really need to re-address points 2. and 3. 5. The QED does produce ground noise that sounds on occasion like a target. If you aren't digging some ground noise you do not have it set up properly, especially in variable soils. With ANY detector (automatic GB or Manual) altering the GB setting slightly to eliminate a faint “deep target-like signal” will result in eliminating the faint signal whether it is ground noise OR in fact a deep real metal target. 6. You need to listen to the soft “subliminal” threshold of the QED very carefully, quality headphones are a must. 7. “Gain” acts as a sensitivity control as you would expect. I suggest that the QED is best used as a specialist very fine (Small) gold detector. It produced a reasonably clear but quiet response to the extreme small gold (of the order of 0.1 g), we managed to find 5 tiny pieces in well-worked ground in all totaling 1 gram, although the SDC would have picked 5 of the 5, but not so well in one location due to power line noise (This could be remedied somewhat by lowering the Gain of the SDC and using minimal threshold). However, we purposely went over exactly the same ground with the SDC with the SDC set at a lower threshold and 3 on the gain, and then found 3 more pieces of gold; we are 100% sure we had already passed the QED exactly over the target locations so we put this down to QED ground noise masking targets. The QED struggles compared to the SDC in the more mineralised soils, however the QED does seem superior to the ATX. To get the most out of the QED, use a small coil such as an 8” Commander mono, and set the Mode as low as possible so long as the ground signals do not become too intrusive. Usually 1 or 2 is OK for Minelab coils, but some other coils may produce too much ground noise at this setting so you may need to increase the Mode to 3 or above dependent on the ground. Further, we got some very thin aluminium foil and very gradually trimmed it down until the SDC could no longer detect it. This represents particularly fast time constant targets (“extremely” small gold), and found that the QED did still detect it, but only within several mm of the coil surface, not further. But this does mean that the QED will detect extremely small shallow pieces that the SDC will not. Alternatively we suggest the QED is also a suitable lightweight low-cost patch hunter when used with a large coil with the Mode turned up so that there is less ground noise. For the sake of completion, to answer questions posed of the QED depth for an Australian 5 cent piece compared to the Zed both using the same sized coils. We measured this carefully and we are not prepared to give exact figures to avoid any trivial arguments, other than to say that the QED detected between 60% to 2/3rd of the depth of the Z. The QED susceptibility to EMI in areas remote from mains compared to the 5k on EMI noisy days? In one word: “Good. The QED susceptibility to mains in urban areas compared to the SDC or Zed? In two words: “Typically Bad.” The QED’s main strength is its cost, light weight, ergonomics, and simplicity of use, and yes it IS definitely simple to use, but a bit “fiddly.” It has no “magic settings” once you understand exactly how it operates as described above. Going back to the SDC really highlighted the difference a light weight detector can have on general comfort and enjoyment of detecting, and our experiences with the QED underscored Minelab's poor ergonomics. In our opinion the QED fits a market where people are looking for a cheap detector capable of finding small gold in thrashed areas, and are wanting more coil choices without the specialised "one size fits all" approach of the SDC. Good value for money. Its main weakness is its underlying ground noise, which although having the advantage of being “hidden” in the dead zone, nevertheless limits depth compared to lower ground noise capable detectors, for targets other than the very fast time constant targets. In summary it works relatively best in the less mineralised soils for small gold. Beyond the scope of the above suggested prospecting (very small gold & patch hunting mainly in relatively unmineralised soils), I choose not to comment further, other than we will not be using the QED for purposes other than secondary activities, and still intend to use other well-known detectors for primary prospecting activities because of their other advantages. No doubt others with QED's will disagree with us. We welcome this, and would be happy to be proved wrong. Ultimately, time tells the truth by substantial gold finds or lack thereof in well-worked ground. *Note: because of the subtle audio, it is easy to imagine you are “hearing” a target above the general background ground noise when you know where it is. We endeavoured to avoid this tendency.
  4. I am going through one of those periods where I load up a bit on new detectors and let it all sort out. Darwin's Survival Of The Fittest Detectors! This winter a number will not survive and will be looking for new home. This is the only way I have found that works for me. Detectors that serve a good purpose for me get used, others end up sitting. If they sit long enough, they are no longer needed. I have my nugget detecting fairly well sorted out. The GPZ 7000 gets used 90% of the time. I might pull out a VLF for a really trashy place, or for where the gold is smaller than the GPZ can hit (really small!). I do keep a Garrett ATX around to handle salt ground or oddball hot rocks the GPZ has trouble with but those situations have proven quite rare so far. So the GPZ is an obvious keeper. The ATX does double duty as my favorite water hunting machine so there is another. In the land of VLF however it is more complicated. I have this idea that a good selectable frequency detector might really do the trick in replacing two or more other models. The key there however is what I am going to go ahead and call "frequency spread" for lack of a better term. What do I mean by frequency spread? Simply put, the number of kHz between the lowest and highest frequency the detector can operate at. The lowest frequency is basically the "large item" frequency that more easily handles bad ground, and the high frequency is the "small item" frequency that tends to have more issues with mineralized ground or hot rocks. The high frequency option is critical for a person like me who nugget hunts. To really be able to replace machines like the 45 kHz Minelab Gold Monster 1000, 48 kHz White's GMT, 56 kHz Makro Gold Racer, or 71 kHz Fisher Gold Bug 2, the highest frequency option of the detector needs to be 30 kHz or higher or as close to that as is possible. Low frequencies in the single digits are great for coin hunting or very large gold nuggets in bad ground. Frequencies in the teens are a great compromise. Some examples: Nokta Impact 5 kHz, 14 kHz, and 20 kHz (15 kHz lowest to highest) XP DEUS Low Frequency Coil 4 kHz, 8 kHz, 12 kHz, and 18 kHz (14 kHz lowest to highest) Rutus Alter 4.4 kHz to 18 kHz in 0.2 kHz steps (13.6 kHz lowest to highest) White's V3i 2.5 kHz, 7.5 kHz, 22.5 kHz (20 kHz lowest to highest - bonus - runs in multifrequency mode) I am still waiting on the XP DEUS High Frequency Elliptical Coil 14 kHz, 30 kHz, and 81 kHz (67 khz lowest to highest). The XP HF 9" round running at 14 kHz, 30 khz, and 59 khz (45 kHz lowest to highest) is currently available. In theory the White's V3i is a real winner here but I have just never really taken to the V3i as a prospecting detector. I have to be honest and say that so far the Impact floats my boat more in that regard due to its more traditional approach to a detector interface, all metal modes, and ground balancing. The problem with all of them though is they just don't reach high enough to be used both as coin and jewelry machines and yet still be capable of retiring the high frequency nugget detectors. And that is why I am still patiently waiting for that XP Deus V4 high frequency elliptical coil. At 81 kHz (or 59 kHz in 9" round version) the Deus HF coils on paper at least could in theory make the high frequency nugget detectors redundant. I have to admit I still have doubts however. So far dedicated specifically tuned single frequency detectors have always won the day. For a lot of people however, a selectable frequency machine might prove to be "good enough". The downside with the Deus is that to get the deeper seeking lower frequency large coil option you have to wrap up quite a bit of money into two coils. The 9.5" elliptical is just not going to reach real deep due to its small size. I have the 11" round low frequency coil which can run as low as 4 kHz, so together the two coils make a pretty formidable package. The other machines however can run both much smaller and much larger coils, and at considerably less cost than what DEUS coils cost due to each one being a self contained metal detector. It may be that the XP HF 9" round running at 14 kHz, 30 khz, and 59 khz (45 kHz lowest to highest) is the better compromise option for most people than the 5.5" x 9.5" elliptical. The Impact does suit me as far as the way it functions and I like the excellent inexpensive coil selection. It is a shame it weighs twice as much as the DEUS, but that may actually be a benefit when it comes to balancing large coils. Overall at the moment I am really liking the Impact - I just wish the frequency had topped out higher. I really wanted more like 5 - 15 - 30 kHz. Going from 14 kHz to 20 kHz is not quite providing the extra "pop" on tiny gold I would like to see.
  5. I've been comparing numerous detectors as of late. I wonder about iron audio. I've been thinking about this,,based on what I see with some of my detectors,,,and am wondering if there would be some benefits. Iron volume as far as it being ON,,,does give distinct audio when the coil passes over detected ferrous material,,,but the being able to hear the iron volume tone(s) seems is tied to disc setting(s). Meaning run too high a disc setting,,,no iron tone whatsoever (with it selected). Could this be changed,,,where iron audio would be provided no matter the disc setting if a user wanted?? I could see at least some application,,where it might come in handy. For example hunting in a site with gobs of maybe lower conductive materials,,,just turn up the disc and hunt,,,,but operator might want to know if any areas seemed to be maybe moreso afflicted with iron and nails,,,,to maybe want to hunt this particualr area,,,using different strategy, detector settings,,,or even another coil or detector. I may be off base here,,,but would like to hear some folks thoughts on this. BTW,I do realize maybe notch could be used along with lower disc and do maybe the same thing.
  6. Here it is folks. Loaded with tuning tips! http://www.minelab.com/__files/f/254716/KBA%2024-1%20Basics%20of%20the%20GPZ%207000%20Technology%20Zero%20Voltage%20Transmission%20(ZVT).pdf "A significant technical achievement of GPZ 7000 ZVT technology was in creating the ultra‐stable transmitted magnetic field during the receive period, to ensure that the large reactive component of the soil signal, X, is not detected, in the same way that it is not detected in PI." Figure 2 shows a comparison between the ZVT VRM soil signal and the nearest equivalent PI soil VRM signal; both transmitted magnetic signals being bi‐polar, with the same fundamental frequency and same rapid change of magnetic field period. It should be noted that the PI receive period is half that of the ZVT period, because the PI system shown in figure 2 transmits for half the time and receives for the other half of the time, unlike ZVT that transmits and receives simultaneously just about all of the time. The important difference in the VRM signals is that the PI signal decays away substantially faster than the ZVT system. This indicates that the receive signal for PI is less sensitive to longer Time Constant (TC) components compared to shorter TC targets than ZVT, and this is one of the main reasons why ZVT technology is better at detecting large nuggets compared to PI; another main reason being from the double length receive period in ZVT compared to PI for the same fundamental frequency.
  7. Hi, Regarding the VLF detectors.Can someone answer for me what constitutes a VLF with good discrimination?.I feel to discriminate that speed is a factor as well.Otherwise no matter how good,if a target is next to iron it will read off a good hit. The Deus has fast reactivity,so is this now a good discriminator.Between ferrous and non ferrous?. How does this compare to say the Nokta Impact for speed discrimination. Thanks in advance Ash
  8. The more I learn (by reading and experience) the more I realize that unmasking is the holy grail future of induction balance (IB) detectors. Dankowski has been emphasizing the issue for years (as your link to a 2000 article shows Dankowski - Beneath The Mask). The sites I hunt are visciously peppered with iron, small and large. That goes for old homesites here in the Midwest and out West, at old abondoned mines, placer sites, and ghost towns. As bad as littering is today, at least we have trash barrels, recycling, refuse collection, and advertising pleas to keep the world a beautiful place. I get the impression that back in the 19th century the thought didn't even occur to them. People can still cherry pick (using strict discrimination) to avoid the trash. If all you're after is recent drops (clad, zinc, and maybe a few pieces of silver jewelry) then go for it. I want old stuff and, as you note, that means dealing with lots of trash. But even careful hunting today is hampered severely by masking. As Tom D.'s report shows, not only don't you hear the good target, sometimes you don't even here the bad ones! How do you know there might be good target being masked if your detector responds as if there is no metal at all within its search field?! It's my impression that masking is just as big of a problem for nugget hunters. Does it just get less attention because most nugget hunting is done with pulse induction (PI) and zero volt transmission (ZVT) technology, which (AFAIK) doesn't offer much discrimination anyway. If you're really going to dig-it-all, including iron, then eventually you're going to find just about every piece of detectable metal within range.
  9. http://md-hunter.com/new-xp-q-mond-machine-novelty-2018-look-at-that/ Is this for real, why not go with the smart phone?????????
  10. Hello, Does the coal or carbon block the EM signals? For example if the metal object buried and covered by shield of carbon or coal. Does the metal detector able to penetrate this type of materials.
  11. I think I could show more interest in any of Garrett detectors but in my opinion they try to put too much info in such a small area. They could take a lesson from White's and let it pop up on the screen on what you detected. This looks like what Minelab is doing the same as White's with a big and better display so all has no trouble to see. I don't see myself buying anything from Garrett until they do. White's has some for the same reason I wouldn't buy either. The young will buy the small screen but with a large one the younger and older will buy. So detector companies you want your sales to go up then come out with a larger display. Chuck
  12. I was wondering about this new machine to hit the market and do believe other manufactures are also releasing soon, the same or very similar type of technology.I dont belive it s new.Can we obtain a list of the main players who will be releasing something similar so i may do a comparison.I think Fisher has one but dont think the At Max coming soon is the same.I m asking this as im not 100% tech savy but dont believe Minelab is the first here or by any means the best.In saying that ,this machine looks very sweet indeed.Also last point.In regard to reactivity speed ,where does the AT Max come in.Thanks in advance. Ash
  13. So Steve or somebody explain to me, putting aside higher frequency is more sensitive to tiny objects like gold nuggets. I realize that. Does higher or lower frequencies go deeper? is there any difference for general coin or relic hunting? Would one or the other pick up or let me hear better a deeper fainter signal?
  14. I always have one question in mind which is the best frequency for silver and gold jwellary or treassure hord at the same time i know 7 to 15 khz is for silver relics tressure 15khz to upper is for gold suppose if i find a cannal full of silver and gold jwellary which frequency is best suited for it
  15. Looks funny but there is not far between this video and a decent beach detector at least. Just need the digger scoop arm on the back. Kind of like turning a Roomba loose on the beach!
  16. Steve, your a great source for unbiased information. I trust your opinion greatly. Don't fret over what just happened. Many many people view you as a great resource. As you know I have been metal detecting for 30 years. I still consider myself a newbie. However, it is with the same old machine. Back when I purchased my machine we were told it will detect everything, it's a do all machine. I new of prospecting machines, but never knew the difference or seen the demand until I came to this forum. So if you have time, please answer these question. I am going to throw these out as I don't really know how to ask the correct question. What if the difference in a gold machine vs a regular machine? What makes them stand out? I know there is a frequency difference, but what make them stand on when looking for gold? Are they just not tuned for gold?
  17. On his forum at http://www.dankowskidetectors.com/discussions/read.php?2,121626 This gives a very rare, in fact as far as I know, never before seen inside look at the prototyping process and field test reporting. Thomas Dankowski is a true "engineer nerd" (I say that as a compliment) and so goes to extreme lengths and detail beyond what would normally be seen. His extremely lengthy and copious notes also provide many insights about what to possibly expect from the new Nokta Impact. Keep in mind things changed from the early reports to the final product so things Tom talks about early on change at later dates. Quoting from his thread out of context could cause a lot of misperceptions to arise. The thread well illustrates something I have observed for some time. When it comes to max depth, standard single frequency induction balance detecting technology is tapped out. Look at the struggle to obtain not another inch but even just another 0.1 inch of depth. The main advantages have come as of late in recovery speed and the ability to separate closely spaced targets. Max depth however is at a standstill. Tom's testing just confirms what I have been seeing for years. It is near impossible to discern more than hair splitting differences for max depth between most top of the line VLF detectors these days. And now a Report on the Nokta Impact from Keith Southern And a Report From Ziggy Report from Lawrenzo - Low-Boy/LCPM Report from tnsharpshooter Report from goodmore Report from Sven1
  18. Steve, Every since you posted that you lose depth when you ground balance, It is in the back of my mind........ "Ground balancing is a filter and not all that different that the way the discrimination system works. The ground signal or salt signal (or both) are identified and then tuned out. The ground effect is still there, but the detector subtracts it from the overall signal. The key word there is "subtracts". Ground balance methods work by subtracting part of the signal, and all subtractive methods create depth losses of some sort the closer any detected item gets to the "hole" created by subtracting the ground or salt signal. Signals are not perfect but spread over a small range, and so eliminating any signal usually means taking out a small range of signals. " I have always tried to keep my detectors ground balanced while using them.... Now I wonder if I should? Can you put my mind at ease......
  19. I got my first metal detector in 1986. It was a White's Coin Master 6000 DI Pro. I bought it because I live near the beach and a friend of mine had a friend who was selling them. I didn't know much about detectors and I used it on the beach in the dry sand only for about 3 years before life happened and I put it away. I didn't get another detector until 2010 and it was a ML 5000. Now that I had it I had to start learning about the desert and more about metal detectors. One of the first things that I 'noticed' about a detector is that you don't have to be directly over a target to hear it. You get a sense for a target by coming close. You get a bigger sense for an aluminum can than you do a quarter for instance. I've searched and searched over the years for a way to describe this near to target sense which is much greater in the 5000 (PI) and the 7000 (ZVT) than with the Coin Master (VLF). Today I was reading an email from Kellyco who is the company that services most Minelabs in the United States. They also sell most other detectors and give advice to their customers. The email that I received led me to a reprint of an article: How Metal Detectors Work Reprinted with permission from Modern Metal Detectors. The full article is here: https://www.kellycodetectors.com/catalog/how-metal-detectors-work#more In that article it uses the term Fringe Area Detection and that gave definition to what I had been trying to describe for years. I had tried to say a coil is like a Nerf ball with many targets off the search area and you are drawn to a target like a moth to a flame. As it turns out this is just 'fringe area detection' which lets us push our detectors to much greater finds. I think you will see how many times we have discussed this part of metal detecting without using this term. The fringe area on my 7000 is larger than the illustration shown. Here is what the article says about fringe area detection: Fringe Area Detection Fringe area detection is a phenomenon of detection, the understanding of which will result in your being able to discover metal targets to the maximum depth capability of any instrument. The detection pattern for a coin may extend, say, one foot below the search coil. The detection pattern for a small jar of coins may extend, perhaps, two feet below the search coil as illustrated in the drawing on the facing page. Within the area of the detection pattern, an unmistakable detector signal is produced. This illustration shows the location and approximate proportional size of the fringe detection area in which faint target signals from around the outer edges of a normal detection pattern can be heard. What about outside the detection pattern? Does detection take place? Yes, but the signals are too weak to be discerned by the operator except in the fringe area around the outer edges of the detection pattern as shown in the drawing above. A good set of headphones is a must, if you desire to hear fringe area signals. The next more important thing, is training in the art of discerning the faint whispers of sound that occur in the fringe area. Skill in fringe area detection can be developed with practice, training, concentration and faith in your ability. Develop fringe area detection ability to a fine art and you are on your way to some great discoveries that many detector operators will miss. The ability to hear fringe area signals results in greatly improved metal detection efficiency and success. Mitchel
  20. If somebody has offered you at option: 1. to reduce the weight of your favourite detector by half 2. to increase its depth by 10% What would you choose?
  21. No, I'm not talking about politics and being a Moveon.org trainer. I'm talking about resistivity detecting. Electrical resistivity tomography From Wikipedia, the free encyclopedia Electrical resistivity tomography (ERT) or electrical resistivity imaging (ERI) is a geophysical technique for imaging sub-surface structures from electrical resistivity measurements made at the surface, or by electrodes in one or more boreholes. If the electrodes are suspended in the boreholes, deeper sections can be investigated. It is closely related to the medical imaging technique electrical impedance tomography (EIT), and mathematically is the same inverse problem. In contrast to medical EIT however ERT is essentially a direct current method. A related geophysical method, induced polarization, measures the transient response. The technique evolved from techniques of electrical prospecting that predate digital computers, where layers or anomalies were sought rather than images. Early work on the mathematical problem in the 1930s assumed a layered medium (see for example Langer, Slichter). Andrey Nikolayevich Tikhonov who is best known for his work on regularization of inverse problems also worked on this problem. He explains in detail how to solve the ERT problem in a simple case of 2-layered medium. During the 1940s he collaborated with geophysicists and without the aid of computers they discovered large deposits of copper. As a result, they were awarded a State Prize of Soviet Union. Andrey Nikolayevich Tikhonov, the "father of ERT" When adequate computers became widely available the inverse problem of ERT could be solved numerically, and the work of Loke and Barker at Birmingham University was among the first such solution, and their approach is still widely used. With the advancement in the field of Electrical Resistivity Tomography (ERT) from 1D to 2D and now-a- days 3D, ERT has explored many fields. The applications of ERT include fault investigation, ground water table investigation, soil moisture content determination and many others. In industrial process imaging ERT can be used in a similar fashion to medical EIT, to image the distribution of conductivity in mixing vessels and pipes. In this context it is usually called Electrical Resistance Tomography, emphasising the quantity that is measured rather than imaged. https://en.wikipedia.org/wiki/Electrical_resistivity_tomography Here is one unit being offered by Kellyco. https://www.kellycodetectors.com/blog/find-gold-resistivity?utm_source=email&utm_medium=BlogBUTTON&utm_content=BlogGoldResistivity&utm_campaign=MSTRBlogGoldResistivity20170624&utm_term=Lead_SuperBowlGiveaway2016 Mitchel
  22. As a rule do the lower vlf frequencies punch deeper than the higher ones, say 4.8 verses 14khz? But what is the trade off? Are some frequencies better for silver coins? How does iron enter into this? Need to understand how this all fits together! Thanks for any and all answers.
  23. A lot of detectors let you notch out (silence) a target identification (TID) band but are there any that let you choose which tone (audio frequency) to assign to a band?
  24. I do what I can to foster competition that develops alternatives to the all too common single frequency VLF detector. There are plenty of options out there, but in my opinion they all weigh too much or cost too much. Usually both. I envision people out there with a popular VLF prospecting machine like the Gold Bug Pro, GMT, AT Gold, X-Terra 705, etc. These machines all sell for around $700 and weigh 2.5 - 3.9 lbs. They would like to add a ground balancing PI (GBPI) to what they have. I think that for "normal people" with normal budgets a machine under $2K and under four pounds just makes sense. It would be more than twice what they spent for their VLF, and in this day and age there is no reason why a decent PI should weigh over 4 lbs. To clarify what I am talking about here, I should say that for many people a $700 single frequency detector is a great place to start and in many cases is all a person ever needs. However, there are places where extreme ground mineralization and mineralized rocks (hot rocks) severely impede the performance and use of single frequency detectors. Alternative technology to deal with these conditions has been developed, by far the most familiar being the Minelab ground balancing PI (GBPI) detectors. These differ from common PI detectors by having the ability to ground balance. Other brands have offered the Garrett Infinium and ATX and the White's TDI models. These detectors are used not just for prospecting but also by relic hunters, beach detectorists, and others who face challenges regarding ground mineralization and single frequency detectors. Frankly, in my opinion GBPI technology is largely maxed out. The main room for improvement comes now in better ergonomics at lower prices. This challenge therefore limits detectors to those that weigh under 4 pounds with battery included, and which sell brand new with warranty after discounts for under US$2000. Detectors need not be ground balancing PI models, but must offer similar ability to ignore mineralized ground and hot rocks that trouble single frequency detectors. I am going to rate detectors as to their relative performance using what I call the "Minelab Rating Scale. Details here. 1. Minelab SD 2000 - crude first version, very poor on small gold, excellent on large deep gold 2. Minelab SD 2100 - vastly refined version of SD 2000 3. Minelab SD 2200 (all versions) - adds crude iron disc, ground tracking 4. Minelab GP Extreme - adds greatly improved sensitivity to small gold, overall performance boost. 5. Minelab GP 3000 - Refined GP Extreme 6. Minelab GP 3500 - Greatly refined GP 3000, last and best of analog models 7. Minelab GPX 4000 - First digital interface, rock solid threshold 8. Minelab GPX 4500 - Refined GPX 4000, solid performer 9. Minelab GPX 4800 - Released at same time as GPX 5000 as watered down version 10. Minelab GPX 5000 - Culmination of the series, current pinnacle of GBPI prospecting machine technology. All Minelab models leverage an existing base of over 100 coil options from tiny to huge. I am a very practical person when it comes to prospecting. I know all the existing models and options by all brands very well, perhaps better than almost anyone. This is the way I look at it is this. If I personally were to spend a lot of money to go to Australia for one month, and needed a GBPI detector, considering machines past and present, what would I take and in what order of choice? Put aside concerns of age, warranty, etc. just assume functioning detectors. Here is the issue in a nutshell. On the Minelab scale of one to ten as listed above, I would be generous in rating the White's TDI SL as a 2. Same with the Garrett Infinium which I will mention in passing as it is no longer being made. If I was going to spend a month of my time and a lot of money going on a prospecting trip to Australia, I would choose a TDI in any version over the SD 2000. I might go with a TDI Pro over a SD 2100 but I would have to think real hard about that, and when push comes to shove I would go SD 2100 were it not for the realities of age I said to ignore. A newer TDI Pro might be a better bet than a very old SD 2100 from a reliability standpoint, but again, this would be a tough choice. The TDI SL not really. In my opinion I would be shooting myself in the foot to go on this hypothetical trip with a TDI SL instead of a SD 2100. You see the problem now? The Garrett ATX fares better. I would rate it a 3, roughly analogous to the SD 2200 variants. Still an agonizing choice really and the ATX being new versus SD 2200 being old might again be the tipping point, but from a pure prospecting options perspective the case can be made that the SD 2200 might be the better way to go. The problem for this challenge is the ATX weighs over 4 lbs and sells for over $2000 That's it folks. That is reality. The best of the best that the competition can offer can only go solidly up against models Minelab has not made in years. I am not saying that to be mean or as some kind of Minelab toadie, that is my pure unvarnished opinion as a guy who is pretty well versed on the subject. Let's bring it all home. This person with the $700 machine really, really wants that under 4 lb, under $2K GBPI machine, but if they do their homework they discover that truthfully, they would be better off shopping for a used Minelab than what the competition offers new. With the TDI SL rated as a 2 the ATX in a much lighter box at under $2K is a solid win as a 3. A well designed ATX with standard dry land coils would look very enticing as compared to the GP series Minelab's and with a stronger battery system might rate 4 to 6 on my comparative scale. But Garrett refuses to budge! White's can certainly do something, anything to improve the TDI SL. A battery that lasts all day would be a good start. In the end they are limited by the basic single channel design of the machine. The SD 2000 dual channel design was literally the answer to and the improvement on the single channel technology used in the TDI, the basics of which predate the SD 2000. Still, White's currently owns the under 4 lb under $2K GBPI category so they have the first out of the starting gate advantage. Anything they do would at the very least just show they have not given up. The Minelab MPS patent that formed the basis of the SD series has expired. Not sure about DVT, which formed the basis of the GP series. Where is the competition? What the heck is going on here? Much gnashing of teeth and pulling of hair is going on here, that's what!!! That is my challenge to the manufacturers. Under 4 lbs, under $2K, on the 1-10 scale I am offering, what is the best you can do? The TDI SL as a 2? Really? Yes, really, that is currently the best of the best in the brand new ground balancing PI, full warranty, under 4 lb, under $2k category. You can pick up a 3.5 lb TDI SL right now brand new for $1089. The White's TDI SL takes the crown. Hopefully we will see more competition in this wide open category soon. I have been beating this drum for years to no avail, but I do have reason to believe we are finally going to see more alternatives soon. I hope.
  25. Can someone please explain the differences in a PI machine and a VLF machine in layman's terms or point me in a direction on the site if it has already been posted up some where just trying to learn
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