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Varying Height And Azimuth?

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While experimenting with my Gold Racer, I think I saw more stable VIDs by raising the coil and scanning perpendicular to magnetic north. There seemed to be a height that was most stable, and scanning perpendicular to magnetic north tended to eliminate oscillation between very low and very high values.  It wasn't perfect, but it was suggestive.  I'm wondering if anyone else has anything to offer about this.

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Minelab pulse induction detectors in particular are susceptible to directional swing issues but it is not something normally encountered with a VLF. There is a scientific basis for what you are experiencing however.

Metal Detector Basics & Theory by Bruce Candy

See pages 12 and 13 and in particular the section on atmospheric sources of interference.

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    • By Jonathan Porter
      A common subject that has come up recently with all the coil discussions is X signal and what it portrays. This thread is to put some clarity on what X means to the GPZ 7000 end user and why you should use your Ferrite.
      When the 7000 was released its software was designed to automatically calibrate for a component in the ground called X signal, there is no need for me to go into the scientific aspects of what X is and nor am I qualified to do so however, in the case of the GPZ, it is NECESSARY that the Ferrite be used and operators, no matter what or where the ground is they are working, should make it part of their daily detecting regime even if they can’t discern or understand the need for it.
      The GPZ has the ability to ‘balance’ out X signals, to do this you need to activate the Quick-Trak button on the front of the handle. When you press the button you are also activating the regular ground balance that any high end gold specific metal detector uses, initially when the button is triggered tracking is forced or sped up briefly, this also means the GPZ 7000 is doing two things at once when the QT button is triggered. On the first release software the Auto Ground Balance mode was trying to actively cancel out X signals as well as G signals running in parallel with each other, to some extent the G balance will also try to balance out some X signal if the X signal is loud enough but overall the detector requires X balance to cancel out X signals effectively. The issue with the release software was the X balance was too lively and was being too easily dragged away from accuracy by Salt signals and Saturation signals of which WA and Victoria are well know for (most gold fields suffer from these signals).
      Minelab then released the Ferrite to help operators to let the detector ‘SEE’  what X signal really was in Salty and Saturable ground, during the release WA and Victoria had suffered a long and extended rain event so the ground was water logged, Salt is conductive so therefore is exacerbated by moisture. Because of the water logged ground during this time it caused lots of early complaints from GPZ users. Not long after this Minelab also developed a software update to slow the Ferrite balance down so it would not be so readily dragged away by those pesky signals, this helped a lot but I was still advocating using the GPZ in Fixed GB mode. At a later stage another software release was provided that allowed the user to use a SEMI AUTO mode where once the Ferrite Balance was completed the X balance would be FIXED whilst allowing the G balance to continue to actively track the regular ground balance, this is my preferred and advised mode.
      X signal in the ground is not like G signal, it is in varying subtle degrees but is not as VARIABLE as regular ground G signal, the reason a GPZ makes a signal on X is because since the last calibration the temperature of the electronics has shifted or if in Auto GB mode other signals in the ground have confused or altered the X balance calibration. The only real way to tell if your calibration is OUT or WRONG is to use the Ferrite to confirm if this is so, which is why it is so vital you make it part of your daily routine.
      NOISE:
      Noise is any sort of audio signal that should not be there, noise competes with targets plain and simple. The less noise you have the more obvious targets will sound and the deeper your detector will run or more accurately the deeper you’ll be able to discern a target (assuming you are also using the optimised Ground type and Gold modes for the ground you are searching and the size of nuggets targeted), all targets under the coil are being energised by the Tx evenly at all times relative to coil position, however user choice of settings, calibrations and coil control have a huge impact on the outcome. If the ferrite balance is out then a signal off any X in the ground is going to join the audio and potentially compete with you being able to discern a target signal.
      X SIGNALS and X COILS
      The GPZ 7000 is a very versatile metal detector, if can be used even if the Ferrite calibration is WAY OFF as is evidenced by users who refuse to update their detectors or who refuse to use the Ferrite (or both), or if users are using X coils that make a signal on the Ferrite regardless of doing a Ferrite balance. I am a purist so will always check my Ferrite balance because even 0.1% less noise in the audio is an advantage in my opinion. 
      The X coils do actually balance out the Ferrite over the receive winding part of the coil (not as cleanly as a ML coil but acceptable), but they do manifest a LOUD signal in another location that any savvy X coil user will soon identify unless a mod is done during manufacture (I am unsure of coils made in the last month or so but it is easy to tell). The manufacturer was unwilling to do the mod due to feedback from customers not complaining, the resistance was based around the mod adding a lot of weight to the coil (gets the coils up into Minelab coil weight territory, isn’t that interesting?). I am unsure how he went about removing the Ferrite signal or the mod required to do so and am not at liberty to discuss why a ferrite signal happens in the first place. The reason I was pushing so hard for the mod was to try and get the X coils across the line for PERFORMANCE parity with ML coils in the hopes of accessing the dongle, the X coils showed potential but needed to be refined, in the end the current option was decided upon and I was no longer needed.
      As it currently stands any coil that makes a noise on the Ferrite (especially a LOUD noise) will by default make an unacceptable signal off X signal in the ground, operators will not really notice this signal as it will blend in with general ground noise responses, believe me it is there and it is COSTING you depth!!
      I do not use the X coils in Clermont because of these main reasons, our ground is saturable and the X coils saturate much more readily than the Minelab coils, most of my coils have the mod so X signal is not such a problem but a couple of them do not so they don’t get used either, with the larger coils I always use GENERAL/DIFFICULT and every X coil I have used makes touch and knock noises, some are acceptable (The Spiral wound ones seem best) but in most cases General/Difficult is out thereby negating the advantage of using a larger coil for larger deeper nuggets. 
      To fully appreciate the differences in the coils I am going to include the settings I use so GPZ operators can benchmark what I am experiencing with their own settings.
      SETTINGS
      Audio Smoothing: OFF
      Ground Smoothing: OFF
      Sensitivity: 9
      Threshold: 27
      Gold Type: HIGH YIELD (To experience Knock and rub noise use GENERAL/DIFFICULT)
      Ground Type: DIFFICULT
      Volume: 6 to 8 for Headphones (either through a B&Z booster or GPZ direct), 12 for WM12
      Ground Balance: SEMI-AUTO
      Conclusions and Suggestions:
      At no stage have I said the X coils are unusable just user beware. In quiet ground they should be OK and in variable ground, like I operate in here, they are usable but twitchy. I have found gold with them but choose not to use them full time in my areas due to the above issues and my being fussy about noise. I did during supervised testing (under duress I might add for the very reasons that have been borne out online) find gold in ground I frequent, I expressed that I was impressed that I was able to find gold with them in such a flogged area and that they showed potential which was borne out by my continued involvement till I was no longer needed.  I have since been back to that area with customers on training and as always have found gold over the same ground as is typical of Clermont thanks to its high variablity ground.
      My favourite X coils are the flat wound ones because they seem to handle our ground better and have less touch sensitivity, however they are a LOT heavier. In essence they are what they are and did not meet required standards to be officially recognised, which is a shame because I too desperately want to see more coil options for the GPZ.
      JP
    • By Skookum
      Good evening,
      I’m venturing into the spotlight here with my first post to ask what likely amounts to a novice’s question.  
      It stems from an experience I had about a year ago with finding my largest nugget. The location was in a small creek bed, which had been conveniently cleared of cobbles and overburden down to a small patch of bedrock surrounded by smooth, silty clay by a dredger.
      Using a GM 1000, I had detected out several small nuggets from within the bedrock cracks that had been exposed, but not properly crevassed by the prior prospector.  However, the thick clay surrounding the exposed bedrock had pockets of varying degrees of moisture.
      This was providing me a bit of challenge since the wetter spots seemed to be behaving just like hot spots. After an extended wrestling match with the wetter signals and the available settings, I gave up.  
      However, by the time the next weekend came around, I just couldn’t get those wet spots out of my mind.  With the heat of the summer and record drought conditions, I guessed those spots may have dried just enough to deserve one final pass.
      Within minutes of returning, I had found a solid, repeatable, 2 bar non-ferrous signal in the deepest clay pocket on the upstream side of the rock. (This exact spot had seemed masked the week before.)  Digging 4-5 inches down into the smooth clay I found a “rock” that made my detector sing.  Cleaning it off revealed a beautiful 1/3 ozt. nugget. Call it beginner’s luck—because I do. 
      Now for my question. Were those wet spots of clay giving me fits because of greater relative mineralization, heterogeneity of moisture, or VLF technology?  Perhaps it was some of each?  
      Part of my curiosity stems from never having used a PI detector.  For those of you with plenty of PI experience, do you also struggle with wet spots or mud spots for lack of a better term?  And, if so, are certain PI detectors more resistant to the struggle?
      Thanks for any input you might spare.
    • By Dan Fox
      I believe there is not much more they can squeeze out of VLF technology, even multiple frequency has it's limits and is really only 2 frequencies.
      Are manufactures better off concentrating on coil design rather than just tweaking an existing design adding a letter or two to the name?
       
      After market coils quite often improve a detectors performance, so shouldn't manufactures be looking in this area rather than using the same coil designed years ago?
      Would like your thoughts
    • By Steve Herschbach
      I do what I can to foster competition that develops alternatives to the all too common 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 metal detector for beach, relic, or gold detecting. These machines all sell for around $700 and weigh 2.5 - 3.9 lbs. Perhaps 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 VLF 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 VLF 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 (discontinued) plus Garrett ATX and the White's TDI models.   These detectors are used not just for gold prospecting but also by relic hunters, beach detectorists, and others who face challenges regarding ground mineralization and VLF 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 VLF 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 detecting. 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 gold prospecting for one month, and needed a GBPI detector, considering machines past and present, what would I get 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, 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 way over 4 lbs and sells for slightly over $2000. The price is close enough really but the 7 lb weight is way off.
      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 Minelabs. 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 $1049. 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.

    • By Steve Herschbach
      Which metal detectors have the most reliable target ID numbers?
      Target ID is a function of depth - the deeper the target, the more difficult it is to get a clean target ID as the ground signal interferes. Other items directly adjacent to the desired target can also cause inaccurate numbers. The more conductive the item, the higher the resulting ID number, but also the larger the item the higher the number. Silver is more conductive than gold, so a gold item will give a lower number than the same size silver item. But a very large gold item can give a higher number than a small silver item, so numbers do not identify types of metal. Gold and aluminum read the same and vary in size so to dig one you dig the other. Only mass produced items like coins produce numbers that are more or less the same over the years but a zinc penny will read lower than a copper penny due to the change in composition.
      In general iron or ferrous targets produce negative numbers or low numbers. Aluminum, gold, and US nickels produce mid-range numbers. And most other US coins produce high numbers. Other countries coins, like Canadian coins with ferrous content, can read all over the place.
      The scale applied varies according to manufacturer so the number produced by each detector will vary according to the scale used. The 0-100 range for non-ferrous targets is most common but there are others. Minelab employs a dual number system on a 2D scale with thousands of possible numbers, but they are now normalizing the results produced to conform more closely to the linear scale used by other manufacturers.

      Increasing ground mineralization has a huge effect on the ability to get a good target ID. Ground mineralization is nearly always from iron mineralization, and this tends to make weak targets, whether very small targets or very deep targets, misidentify. The target numbers get dragged lower, and many non-ferrous targets will eventually be identified as iron if buried deep enough. Small non-ferrous readings and iron readings actually overlap. That is why any discrimination at all is particularly risky for gold nugget hunters.
      If you want target ID numbers to settle down, lower sensitivity and practice consistent coil control. The target number will often vary depending on how well the target is centered and how fast the coil moves.
      Higher sensitivity settings lead to jumpier numbers as the detectors become less stable at higher levels. The interference from the ground signal increases and interference from outside electrical sources also increases, leading to less stable numbers.
      Higher frequency detectors are inherently more sensitive and are jumpier. So lean lower frequency for more solid results. Multi frequency detectors act like low frequency detectors and tend to have more solid target numbers due to the ability to analyze a target with different frequencies.
      Another issue is the number of target categories, or ID segments, or VDIs, or notches, or bins (all names for the same thing) that a detector offers.
      For instance here are the number of possible target id categories or segments each detector below offers:
      Fisher CZ-3D = 7
      Garrett Ace 250 = 12
      Minelab X-Terra 305 = 12
      Minelab X-Terra 505 = 19
      Minelab X-Terra 705 = 28
      Minelab Equinox = 50
      Fisher F75 (and many other models) = 99
      White's MXT (and many other models) = 190
      Minelab CTX 3030 = 1750
      Fewer target categories means more possible items get lumped together under a single reading, but that the reading is more stable. Many detectors will tell you the difference between a dime and a quarter. The Fisher CZ assumes you want to dig both so puts them under one segment along with most other coins.
      People who use detectors with many target numbers usually just watch the numbers jump around and mentally average the results. Some high end detectors can actually do this averaging for you! But I think there is something to be said for owning a detector that simplifies things and offers less possible numbers to start with. The old Fisher CZ method still appeals to me, especially for coin detecting. So do detectors like the Garrett Ace 250 or Minelab X-Terra 505 for the same reason.
      The problem is that as people strive to dig deeper targets or smaller targets the numbers will always get less reliable. But if you want to have a quiet performing metal detecting with solid, reliable target numbers look more for coin type detectors running at lower frequencies under 10 kHz or at multiple frequencies and possibly consider getting a detector with fewer possible target segments. And with any detector no matter what just back that sensitivity setting off and you will get more reliable target numbers.
      ads by Amazon...
      Detectors often use tones to identify targets and often use far fewer tones than indicated by the possible visual target id numbers. The X-Terra 705 for instance can use 28 tones, one for each segment. However, most people find this too busy, and so simple tone schemes of two, three, or four tones may be selected. I think it is instructive that many people often end up ignoring screen readings and hunting by ear, using just a few tones. This ends up just being an ultra basic target id system much like the simpler units offer. Reality is that most people do not need or care about huge numbers of target numbers. For many just three ranges suffice, low tone for iron, mid tone for most gold items, and high tone for most US coins. The meter could do the same thing, but for marketing purposes more is better and so we get sold on detectors with hundreds of possible target ID numbers. Perhaps this is a digital representation of an old analog meter with its nearly infinite range of response but the reality is we do not need that level of differentiation to make a simple dig or no dig decision.
      Finally, a picture often says it all. Below we have a shot of the White's M6 meter. I like it because the decal below illustrates a lot. You see the possible numerical range of -95 to 95 laid out in the middle. Over it is the simplified iron/gold/silver range. Note the slants where they overlap to indicate the readings really do overlap. Then you get the probable target icons. -95 is noted as "hot rock" because many do read there.

      The M6 can generate 7 tones depending on the target category. I have added red lines to the image to show where these tones sit in relation to the scale. It breaks down as follows:
      -95 = 57 Hz (Very Low) Hot Rock
      -94 to -6 = 128 Hz (Low) Iron Junk
      -5 to 7 = 145 Hz (Med Low) Gold Earrings, Chains - Foil
      8 to 26 = 182 Hz (Medium) Women's Gold Rings/Nickel - Small Pull Tabs
      27 to 49 = 259 Hz (Med Hi) Men's Gold Rings - Large Pull Tabs
      50 to 70 = 411 Hz (High) Zinc Penny/Indian Head Penny - Screw Caps
      71 to 95 = 900 Hz (Very High) Copper Penny/Dime/Quarter/Dollar
      Note that the screen reading of +14 is noted as being a nickel or ring but it can also be the "beaver tail" part of an aluminum pull tab or the aluminum ring that holds an eraser on a pencil, among other things.
      The best book ever written on the subject of discrimination is "Taking A Closer Look At Metal Detector Discrimination" by Robert C. Brockett. It is out of print but if you find a copy grab it, assuming the topic interests you.
      Always remember - when in doubt, dig it out! Your eyes are the best target ID method available.


    • By Steve Herschbach
      High Frequency Gold Nugget Detector Roundup
      Our cup runneth over!
      Just a few years ago the market for "over 30 kHz nugget detectors" was quite limited. For a long time there were only a few options:
      Fisher Gold Bug 2 (71 kHz) $764 with one coil
      Minelab Eureka Gold (6.4, 20, & 60 kHz) Discontinued $1049 when new with one coil
      White's GMZ (50 kHz) Discontinued $499 when new with one coil
      White's GMT (48 khz) $729 with one coil
      Things were that way for over a decade. Then in 2015 Makro introduced the Gold Racer (56 kHz) $599 with one coil. Sister company Nokta released the AU Gold Finder (56 kHz) $799 with two coils
      Then in 2017 we see the Minelab Gold Monster 1000 (45 khz) at $799 with two coils. And although not a dedicated nugget detector, the Deus high frequency coil options (up to 80 kHz) were also released, $1520 for complete detector with one HF coil.
      Now in 2018 we get another general purpose machine, the Equinox 800, that can hit 40 khz, $899 with one coil. And just announced...
      the Makro Gold Kruzer (61 kHz) $749 with two coils and
      the White's Goldmaster 24K (48 khz) $729 with one coil
      These last two announcements have made barely a ripple in the prospecting world, or at least going by other forums that seems to be the case. There are various reason for that (forums not being prospecting oriented or being Minelab centric) but still the lack of buzz is interesting. I do believe people are both burned out by all the new introductions and that the market is saturated with high frequency models. Leaving out the general purpose machines to sum up the current options it looks like the current "sweet spot" for pricing is a high frequency model at $749 with two coils. The Gold Bug 2 saw a price reduction to $699.
      Makro Gold Racer 56 kHz - $599 one coil
      Fisher Gold Bug 2 71 kHz - $699 one coil
      White's Goldmaster 24K 48 kHz - $729 one coil
      White's GMT 48 khz - $729 one coil
      Makro Gold Kruzer 61 kHz - $749 two coils
      Minelab Gold Monster 1000 45 kHz - $799 two coils
      Nokta AU Gold Finder 56 kHz - $799 two coils
      Added 1/2019 XP ORX up to 81 kHz - $899 one coil

      High frequency nugget detectors compared

      White's Goldmaster 24K, Minelab Equinox 800, Gold Monster 1000, Makro Gold Kruzer

      Minelab Gold Monster, Fisher Gold Bug 2, Makro Gold Racer, Nokta Impact
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