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  1. 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.
  2. 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
  3. 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.
  4. 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?????????
  5. 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.
  6. 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
  7. 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
  8. 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?
  9. 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
  10. 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!
  11. I often see posts on various forums where people use high GB phase numbers as examples of hot, mineralized ground. I thought that GB phase numbers are only indicative of the TYPE of ground(rock,soil,clay,salt). Rock, soil, and clay can actually be pretty benign or very mineralized. Isn't the determining factor for hot ground that affects metal detectors the amount of Fe3 in the soil? A phase reading of 89 may be mild soil if the amount of IRON in the soil is low. Conversely a phase reading of 65 may be very hot ground if the ground consists of clays with high iron content. Some VLF detectors now have Fe3 meters on them and the higher the reading is on that meter the more the ground will affect your detection depth and the accuracy of the VDI number(if supplied). It seems like many people are confused by this. I think it is important info that can affect your coil selection(size and type), the amount of discrimination you may choose to use, and the mode(all-metal or discriminate) that we run in. We need somebody that knows their stuff to give us a definitive answer!
  12. 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?
  13. 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......
  14. 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
  15. 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?
  16. 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
  17. 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.
  18. 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?
  19. 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
  20. I know this topic has appeared off and on over the years, but I'd like to better understanding on the theory and principle of using one over the other, ie. depth, and target id and what compromises do I induce. The reason I ask is the new V4 for XP Deus has the ability to set a minus discrimination. It kills the ability to use the "horseshoe" screen for ferrous target ID, but VID numbers are tolerable. What theoretically happens if I set a negative discrimination, but use Notch to handle ordinary ferrous trash?
  21. Can you guys help me to compile a list of all current VLF detectors on the market that will run in a true ALL METAL no/non motion setting as a user defined base mode, not a hold trigger or pinpoint button held type option but a base mode of operation. Much like what the original M Scope Fisher Gold Bug 19 khz unit operated as. I am seeking a VLF unit with least amount of or no discrimination that operates in all metal no motion, ability to turn up gain and sens as well as GB preferred and has ability to add large format aftermarket coil. I believe that the Tesoro Outlaw has all metal no motion mode.
  22. For over a decade I've ask for one small feature to a good detector. Say for instance on the Fisher F75 detector or another machine of comparable abilities. Add a two tone function in the motion all metal mode. Nothing fancy, just one tone for ferrous and another for non-ferrous. Being a computer programmer for several years I can't imagine this would be very difficult. Now on the F75, while in motion all metal mode the machine gives better depth and also gives an ID for detected metal objects. So since nothing is really needed except assigning a tone to the ID number scheme why is it so hard to acquire a unit with that feature. I know the V3i has a feature similar, but it lacks the depth capability of the F75 in my ground. Now I've ask again. I'll check back in another decade.
  23. On subject of coils and systems... I was out working some areas for relics with a couple others and one guy was killing it with an very vintage 70s Garrett Master Hunter BFO unit with a large home made looking square coil of pvc looking material. After looking into I found that BFO is Beat Frequency Oscillator and was popular before T/R VLF format machines. BFO was not good for small coin shooting and nugget hunting and lacked ability for quality discrimination from what I read but excelled in depth ability, especially on large ferrous cache targets as well as finding mineral deposits like drifts of black sands or veins of ore. So are there currently any units that still use a BFO mode or format? I can find vintage BFO type units available very reasonably priced, is there any information out there on how to bring them up to current on a battery system and build large coils suitable for this type of cache detecting?
  24. Detector coils are not antenna. They are part of a highly tuned inductive coupling system.
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