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  1. Here’s a topic for all you “Rocket Scientists” out there (and anyone else who’d like to chime in). I was having a discussion with another dealer. He felt that single frequency worked better because there’s a certain amount of performance loss with Multi. I was always of the opinion that Multi-Frequency was the best for most types of Metal Detecting. It allows you to hit ALL the targets that react better to certain kHz. Here’s an example from another hobby of mine (most of us have more than one). I shoot muzzle loading guns. The “Round Ball” type projectile that was used for hundreds of years performs best when shot out of a rifled barrel with a slow twist. Twist refers to the how many inches of flight it (the projectile) takes to make one revolution. The conical bullet came out during the Civil War and requires a faster twist. For modern muzzle loading rifles a slow twist would be 1 turn in 56, 60, 66, 70, etc. inches. For conicals, 32, 28, 24, etc. inches. In the 70s, one company came up with the idea of a “Compromise” twist; 1 tun in 48”. That way you only have to buy one gun. You can use Round Balls for Target shooting and Conicals for hunting. It shoots both “well”. Having said all that, does the Single Frequency work better than the Multi? Is there any kind of lack of performance or trade off having them (kHz) work simultaneously? Thanks! Walt
  2. A pretty fascinating set of photos posted over at http://md-hunter.com/homemade-metal-detector-amazing-photos/
  3. I tripped over this at the Minelab website: This posting, together with the label, also provides an indication of which Minelab products are protected under the Patents Act of various other countries. Product(s) US Patent Number Australian Patent Number GPZ 7000 6636044 783737 7310586 8106770 2011200515 D686924 342365 (Design) 2009262370 2012101855 9547065 2013201330 GPX 4500, GPX 4800, GPX 5000 2011200516 8106770 2011200515 6636044 783737 SDC 2300 2011200516 8106770 2011200515 6636044 783737 D652330 9829598 2014274608 9547065 2013201330 Gold Monster 1000 7432715 2005276953 CTX 3030 7310586 D686924 342365 (Design) 8854043 2013201248 9239400 2013200451 E-TRAC 7310586 X-TERRA 305, X-TERRA 505, X-TERRA 705, X-TERRA 705 Gold Pack, X-TERRA 705 Dual Pack 7432715 2005276953 EQUINOX 600, EQUINOX 800 7432715 2005276953 7579839 9366779 2014218372 Vanquish 340, Vanquish 440, Vanquish 540, Vanquish 540 Pro-Pack 7432715 2005276953 7579839 9366779 2014218372 GO-FIND 20, GO-FIND 40, GO-FIND 60 GO-FIND 22, GO-FIND 44, GO-FIND 66 7432715 2005276953 D756247 360432 (Design) 9557390 7310586 National Geographic Pro Series Metal Detector 7432715 2005276953 D756247 360432 (Design) 9557390 7310586 AN/PSS-14 6636044 783737 F3, F3 L, FE S, F3 LS, F3 UXO, F3 Compact 7310586 6636044 783737 F3 Compact D652330 F3Ci 7432715 2005276953 D652330 STMR Array 6636044 783737 7310586 MDS-10 7432715 2005276953 7579839 9366779 2014218372 Other patents that may apply to the above products 7474102 7652477 7791345 8063777 8237560 8614576 2007272230 9250348 9348053 2017279664 9429674 2014218370 10078148 2014268189
  4. Most of the sites I hunt have very mild ground. I typically leave my GB at 0 most of the time. When I do take the time to Ground Balance, I usually get single digits with occasional numbers in the teens. Do the GB numbers reflect the levels of mineralization in the soil? Do soils with high mineralization have higher numbers? The manual says nothing about it.
  5. Most people act like it’s all about depth. This machine versus that machine.... which is deeper? In my experience for some things max depth does matter. Like gold prospecting. Get a GPX 5000 or GPZ 7000 and dig. Or beach detecting or relic detecting with PI detectors. If depth really was all that mattered, everyone would use a PI. But we do not. Not even the gold prospectors and beach hunter. To state the obvious, not everyone can afford a GPZ 7000 or has access to ground where it will pay off. For some people, a Gold Bug 2 makes more sense. And not all of us are physically capable of digging deep holes for junk all day... we need to narrow the odds. Even if that means giving up depth. VLF tends to be about discrimination, but again all it seems we hear about is depth. But what kind of depth? Depth with good discrimination? How good? I am very cognizant when running a VLF that I’m not running a detector that gets max depth. That being the case, ergonomics and audio matter a lot to me. How it feels on my arm, and sounds to my ear. If I hate the sounds a detector makes I’m not going to enjoy things as much. Frankly, I can make up for a little less depth by just finding better sites or hunting longer hours, if that means having a detector I enjoy using. I say depth is not everything when it comes to VLF detectors. Important, yes, but it perhaps it should not be the sole criteria for most people. What say you?
  6. I hope this topic hasn't already been covered and I'm not writing it in the wrong place. Recently, based on my lack of knowledge in this sector, I have however noticed large differences in actual life, not only because of battery chemistry ... I mean something about the use of power itself in using the tool. Thinking of a mobile phone, the standby time is merely relative to the battery capacity, as is the duration in call or video call, much less long ... So every time a detector is used in an area where there are several signals and we are busy digging or at least hearing many of them, the battery duration is more affected and reduced... This for me, as an inexperienced, means not being able to have a clear measure of the actual duration of the battery pack ... You can never know regardless of how many signals will pass below the coil ... So I then discovered the natural drop in voltage, added to that of absorption in the most arduous use ... And what about threshold instability and false signals if, for example, a pulse is not properly regulated and a too low delay makes it continuously sound for nothing by activating the retuning? At this point I have the impression that even with higher capacities, the voltage drop is the most difficult factor to defeat, even before the capacity .... I am facing the insertion of bms modules in these days and in the future I could add step up or step down modules if necessary, but first I would like to understand to what extent it is possible to delay the cut off, if not eliminating some form of protection that these boards cut away leaving a lot of useful voltage. Unprotected batteries can have a bad end if it is lithium, so there is a compromise between safety and durability ... I repeat again ... I am not an expert and anyone who can add his knowledge on the subject, do it without brakes because I am well open to constructive technical comments, or even comic and bad ...
  7. Of all the different types of metal detectors, the two box is the oldest(?) but also one of the least used. Defintitely a detector for special situations, but with a couple possible exceptions, for the proper situation it's the best choice for the job. I'm aware of two standalone models still available new -- Fisher Gemini-3 and White's TM808. Garrett's Treasure Hound (see P. 43 of their latest catalog) and apparently a new kid on the block are attachments for specific standard (control unit + shaft + single coil housing) detectors. In particular what has me wondering (and confused) is the fact that the Gemini-3, operating at 81.92 kHz doesn't appear to have a gound balancing adjustment but the TM808 (6.5 kHz) does. I was under the (naive?) impression that low frequencies are less susceptible to ground mineralization but here it seems in practice, it's just the opposite. Any thoughts/explanations?
  8. Hi, I am new to the forum. Anyone have any experience with this brand of detectors ? https://uigdetectors.com/en/gold-and-metal-detectors I am thinking of buying a Minelab SDC 2300, but in my internet search last night, I came across this brand I have never heard of called UIG detectors. Looks like they have some interesting looking detector technology. Before I drop money on an SDC 2300, I want to make sure I consider the competition as there may be other reliable and fun technology to experiment with.
  9. First time I think I have seen this. https://patents.google.com/patent/US20190353818A1/en
  10. Just wondering if anyone has tried any 3D Ground Scanning metal Detector? Also, what's the best 3D Ground Scanning metal Detector in the market? Can anybody share their experience.
  11. Those impressive video results of the Fisher Impulse AQ with its 12.5” mono coil on the 10K Gold ring at 17”-18” and 14K Gold ring at 19”-20” as did a 22K Gold ring drove my curiousity to air test two Gold rings using a QED in its Beach Mode-11 operating at its pulse delay of 7.5uS with a NF 12” Advantage mono coil. For my test, the QED’s settings were Threshold-B at 5 below Null and Factory Default for Threshold-A at 30 and Gain at 1. (Threshold-A settings range from a 1 up to 90 and the Gain settings range from 1 up to 10} The results for a clear response on a 3.04-gram 9K 21mm diameter Gold ring was 17” and on a 2.05-gram 18K 19mm diameter Gold ring was 16”. I have no idea how a QED using its Beach Mode would operate within a Beach environment and my intention is not to compare in anyway the QED to the Fisher Impulse AQ only results using a pulse delay of 7.5uS.
  12. Hand held backscatter xray. I want one. https://www.dael.com/assets/files/Documenten/hbi-viken-sec2.pdf HH Mike
  13. The latest issue of the ICMJ is out, and I have an article in it titled Selectable Frequency vs Multi Frequency Detectors. Those of you with a digital subscription can read it online. The ICMJ has a policy against mentioning brand names in articles so I wanted to post this as a supplement to the article. Most metal detectors process a single frequency. Low frequencies, that is single digit frequencies under 10 kHz, react well to high conductive targets, like coins, or large items, even if those items are of low conductivity. If you look at this typical metal detector target scale below you will note that non-ferrous items read higher not just based on conductivity but size also. Low frequency detectors also do not "light up" the ground or hot rocks as much as detectors operating at higher frequencies. Many do not even offer ground balance controls because a factory preset level works well enough for some uses. Low frequency machines under 10 khz therefore tend to be aimed at the coin detecting market. There are too many models to list but most people have heard of the 6.5 khz Garrett Ace 250 as a perfect example. High frequencies 30 khz and over have extreme sensitivity to low conductive and small items, but also struggle more with ground penetration and hot rocks. Their extreme sensitivity to tiny trash items like aluminum bits do not make them very practical for any detecting except gold prospecting. Machines 30 khz and higher tend to be dedicated prospecting machines. Examples would be the 48 khz White's GMT, 71 kHz Fisher Gold Bug 2, 56 kHz Makro Gold Racer, and 45 khz Minelab Gold Monster 1000. In 2002 White's introduced the White's MXT at 14 kHz, and it is a perfect example of how detectors running in the "teens" make excellent "do-it-all" detectors. Since then everyone and their brother has jumped on that bandwagon, and there are too many machines running in the 10 kHz - 20 khz region to mention. Prospectors in particular would recognize the 19 khz Fisher Gold Bug Pro, but few know it is also sold in slightly different versions as the Teknetics G2, Fisher F19, and Teknetics G2+, all 19 kHz detectors sold to the general coin and relic market. Garrett has the 15 kHz AT Pro and 18 khz AT Gold to name a couple more popular metal detectors. Here is some information for those of you who are more technically minded. George Payne was one of the engineers who patented many of the basic concepts used in VLF detectors to this day. Here is an excerpt from his article at http://jb-ms.com/Baron/payne.htm (2002): "The r component acts differently. It is maximum at one particular frequency and decreases if you go up or down in frequency. We call the special frequency at which the r signal is maximum, the target’s “-3db” frequency. It also turns out that at the -3db frequency the x signal is one-half of its maximum value. This special frequency is unique to each target and is different for different target. The higher the conductivity of the target the higher will be the targets -3db frequency. Conversely, the lower the conductivity the lower the -3db frequency. The -3db frequency of the high conductivity target will also make the r signal peak at a high frequency, normally well above the operating frequency of the VLF detector. This will make the high conductivity target have lower sensitivity on the VLF detector because the r signal amplitude drops if we are significantly below the -3db frequency. Simply put, maximum sensitivity on a VLF detector would be if we position the operating frequency directly at the target’s -3db frequency. For example, a dime and penny have a -3db frequency of about 2.7KHz. This is where their r signal peaks and would be the best frequency for picking them up using a VLF detector. However, a silver dollar has a -3db frequency of 800Hz. Nickels, on the other hand, have a -3db frequency, where its r peaks, at about 17KHz. Targets like thin rings and fine gold are higher still. Clearly there is no one frequency that is best for all these targets. The best you can do is have an operating frequency that is a compromise." Well, if low frequencies are good for coins and high frequencies good for gold, why not make machines that can do both? Or both at once? Instead of picking a compromise frequency? Selectable frequency refers to machines that can select from one of several possible frequencies, but process the signal from only one frequency at a time. The key is not what a detector transmits so much as what it processes. These may also be referred to as switchable frequency detectors. Multiple or multi frequency detectors process the signal from two or more frequencies at once. In theory this multifrequency analysis can be done simultaneously or sequentially at a very high speed. The end resultant is the same - the results from two or more frequencies are compared to derive information that cannot be had by analyzing a single frequency alone. Multiple frequency detectors usually have a fundamental frequency, and then other "harmonic" or secondary frequencies they also use, but the power (amplitude) fades with distance from the primary frequency. From page 9 of Minelab's Metal Detecting Terminology: You can find more information on harmonic frequencies at http://www.ni.com/white-paper/3359/en/ and here also. Coils normally must be wound specifically to make use of any given frequency or set of harmonic frequencies. A coil will usually work best at the given fundamental frequency making it difficult to get the best possible performance at all frequencies using one coil. The Minelab X-Terra series specifically requires a coil change to achieve a frequency change for this very reason. People who own them know 3 kHz coils weigh more than 18.75 kHz coils. Why? Because heavier windings are used at 3 khz for optimum performance at that frequency. Here is what is probably an incomplete list of selectable frequency detectors and year of release: 1989 Minelab Eureka Ace Dual 8 kHz 19.5 kHz 1993 Minelab XT 17000 6.4 kHz 32 kHz 1994 Compass X-200 6 kHz 14 khz 1997 Minelab XT 18000 6.4 kHz 20 kHz 60 kHz 1999 Minelab Golden Hawk 6.4 kHz 20 kHz 60 kHz 2002 Minelab Eureka Gold 6.4 kHz 20 kHz 60 kHz 2005 Minelab X-TERRA 50 7.5 kHz 18.75 kHz 2006 Minelab X-TERRA 70 3 kHz 7.5 kHz 18.75 kHz 2009 Minelab X-TERRA 305 7.5 kHz 18.75 kHz 2009 Minelab X-TERRA 505 3 kHz 7.5 kHz 18.75 kHz 2009 Minelab X-TERRA 705 3 kHz 7.5 kHz 18.75 kHz 2009 XP DEUS 4 kHz 8 kHz 12 kHz 18 kHz 2016 Rutus Alter 71 Variable 4 - 18 kHz 2017 XP DEUS V5 Additional 14 kHz 30 khz 55 khz 80 khz options 2017 Nokta Impact 5 kHz 14 kHz 20 kHz 2017 Makro Multi Kruzer 5 kHz 14 kHz 19 kHz 2018 Nokta Anfibio 5 kHz 14 kHz 20 kHz Multiple frequency or multi frequency machines have become very confusing, as a lot of marketing material has focused on the number of frequencies transmitted. What really matters is what frequencies a detector receives, and how the information is compared and processed for results. Some commentary here. Many people look at the marketing material and assume that a machine processing multiple frequencies is somehow working across the board to deliver the best possible results at all frequencies. However, the two issues outlined above do apply. The machines are employing harmonic frequencies, and so cannot compete with a machine optimized at a single frequency as opposed to one of the distant harmonics running at less amplitude. Second, making one coil run perfectly at all frequencies is extremely difficult, again giving the dedicated machine an edge. I highly recommend people not go down the technical rabbit hole but instead focus on what the machines do, on how they act. Two things are very apparent. First, the big market for a long time was coin detectors, and the goal always was to identify coins as deep as possible while ignoring trash as well as possible. Processing two or more frequencies simultaneously gives the detector engineer more information to work with. All the focus was on developing great coin detectors and guess what, the multi frequency machines for all intents and purposes act just like very good lower frequency coin detecting machines. Good ground rejection, and great discrimination on coins for as deep as it can be achieved. The multi frequency machines don't really go deeper than single frequency coin detectors, they just do a better job delivering clean discrimination results to depth. Here is a list of introductory models of multi frequency detectors and year of introduction. I am not listing all the derivative models to reduce clutter. I will post that later. 1991 Fisher CZ-6 5 & 15 kHz 1991 Minelab Sovereign BBS 1999 Minelab Explorer S/XS FBS 2001 White's DFX 3 kHz & 15 kHz (Simulates single frequency by ignoring half the dual frequency signal) 2012 Minelab CTX 3030 FBS2 2020 Minelab Vanquish Multi-IQ Second, single frequency detectors have a ground balance problem. They can ground balance to mineralized soil, OR they can ground balance to salt water. Multi frequency machines can reduce signals from both mineralized beaches and salt water simultaneously, making them ideal for saltwater use. 1993 Minelab Excalibur BBS (Sovereign in waterproof housing) 1995 Fisher CZ-20 5 & 15 kHz (CZ-6 in waterproof housing) 2001 White's Beach Hunter ID 3 & 15 kHz (DFX in waterproof housing) There is a third class of machine that can run either as selectable frequency OR multi frequency detectors. Quite rare at this time. 2009 White's Spectra Vision 2.5 Khz or 7.5 kHz or 22.5 kHz or all three at once 2018 Minelab Equinox 5 kHz or 10 kHz or 15 kHz or 20 kHz or 40 kHz plus multi frequency options 2020 Garrett Ace Apex 5 kHz or 10 kHz or 15 kHz or 20 kHz plus multi frequency options In my opinion multi frequency has delivered well on its promise. The Minelab BBS and FBS machines are renowned for their ability to discriminate trash and detect coins due to their sophisticated processing. Again, focus on what they do. Not even Minelab in their marketing tells anyone these are prospecting detectors. Second, the Fisher CZ-20/21 and various Minelab Excalibur models are without a doubt the most popular and successful non-PI saltwater beach detectors made. I have a White's DFX and I think it is a fantastic jewelry machine in particular. A good coin machine but lacks a bit of punch. The Vision/V3i upped the ante but while amazing on paper suffers from interface overload. The Minelab units are simple by comparison and a lesson on how people in general just want the detector to get the job done. Feature overload is not a plus. However, I think White's has the right idea. The ability to run either separate frequencies or multiple frequencies at once is very compelling. I just think nobody has really done it right yet in a properly configured package. The V3i has the ingredients, but needs to be stuffed in something like an MX Sport with a simplified interface and improved ground balance system. (2018 note - Minelab Equinox released). It really never did beat the White's MXT in some ways and many people when "upgrading" to the V3i end up going back to the MXT. Selectable frequency has yet to really deliver on its promise in my opinion. So far it has been difficult to produce a selectable frequency machine that truly performs at all frequencies on par with a dedicated single frequency machine. The Minelab Eureka Gold at 60 kHz just never gets mentioned in the same breath as the White's Goldmasters/GMT or Fisher Gold Bug 2. Also, most selectable frequency machines in the past have been very feature limited prospecting machines, restricting their overall market appeal. I personally think we have seen enough variations of single frequency detectors. I do not believe much can be done to exceed the performance of the dedicated single frequency VLF type machines we currently have. What can obviously be done is a better job of packaging machines that deliver true punch at different frequencies, or multi frequency machines that bring across the board performance closer to what is expected of PI detectors. I do think we are seeing this happen now. The new Nokta Impact and the new DEUS V4 update are expanding the available options in selectable frequency in more usable packages. The Minelab GPZ and other hybrid platforms blur the line between what is traditionally considered PI and VLF and simply need the addition of discrimination to go to the next level. There is still a lot of potential to deliver machines that might reduce the number of machines many of us feel compelled to own by delivering more across the board performance in a single machine that would now take several detectors. Exciting days ahead. For those who want to try and get their head around selectable frequency and multi frequency technology, Minelab and White's have a gold mine of information in a few of their references. Dig into the following for some great explanations and diagrams. Minelab - Metal Detector Basics and Theory Minelab - Understanding Your X-Terra White's - Spectra V3i Owners Guide White's - V3i Advanced Users Guide Better yet are the last three parts of the DFX instructional video by White's featuring engineer Mark Rowan explaining frequency and multi frequency methods:
  14. What do you make of this description on KellyCo? It seems to suggest the IPTU sensor would work with machines other than the Invenio. Does anyone know if that is true and how that would work? "One of the biggest issues that people run into when metal detecting is difficulty with accuracy. The IPTU Sensor (Invenio) is going to help increase your accuracy and help you find more items and be sure what they are and where they are better. This is an easy to install sensor and is going to make a world of difference when it comes to your overall success when metal detecting. This sensor works with Invenio detectors and is a great addition to any metal detector." https://www.kellycodetectors.com/catalog/iptu-sensor-for-invenio
  15. The original 1985 Fisher Impulse metal detector A note on saltwater. On dry land and in freshwater pulse induction (PI) detectors can be run to max limits. Not so in saltwater. There is an inherent limiting factor in saltwater that tends to flatten top end performance on all PI detectors, or even VLF detectors for that matter. The problem is simple - saltwater is conductive and so is visible to electromagnetic devices like metal detectors. Pulse induction detectors saw their earliest use as beach detectors because of the pulse delay control. Lower pulse delays expose items with a shorter time constant, and this usually means low conductive and/or small items. As the pulse delay increases a PI loses overall sensitivity. Early beach PI detectors all came with a preset, relatively high pulse delay that made saltwater invisible to the detector. In general somewhere around a pulse delay of 10 uS saltwater becomes visible to a PI detector. The number varies for several reasons, First, salinity varies greatly around the world, everything from salt free fresh water, all the way to the Great Salt Lake, which is water supersaturated with salt. Oceans and bays vary, and especially bays that have large river inflows, and therefore lower salinity levels. Large, shallow, enclosed bays with no rivers may act as evaporation dishes, and have abnormally high salinity levels. Further, this effect is accentuated the deeper you take a detector, and so detectors used for true SCUBA diving must be run at higher delay levels at depth. You can't just pick a number like 10 uS and say that is the magic number for dealing with saltwater. 9 uS may work well, or it may take 12 uS to eliminate feedback from the saltwater in your location. The coil detects like a globe in all directions, and so it is not just the water under the coil, but all around the coil that is affecting it. This large ball of saltwater is like a giant target. Many hunters riding the edge of sensitivity can tell you a detector can pick up waves as they pass over, making the water deeper. This long winded explanation is to make people realize that you can't just magically make the detector itself more powerful and get "more depth" or "more sensitivity." The salt range overlaps the tiny gold range, and so if you make a detector able to detect fine gold chains and tiny gold ear rings, it will detect the saltwater. If your set the pulse delay to eliminate the salt signal, you lose the tiny gold items. This is an inherent wall on both PI and VLF small gold performance in saltwater. We have had detectors for decades that can detect tiny gold that people say they want to detect in saltwater, the Fisher Gold Bug 2 for instance. The problem is the Gold Bug 2 will not work in a saltwater environment. The water is just a huge signal to a Gold Bug 2. I have gone round and round with people for the last twenty years trying to explain why you can't detect certain fine gold chains, small ear rings, small platinum, etc. in saltwater. The problem is not the detectors - it is the saltwater. The same problem exists to some degree on trying to detect larger items. You can make a very powerful detector, but you have to inhibit the detection of saltwater, and this tends to put a ceiling on the maximum attainable performance in saltwater. No matter the machine you use, once you hit the saltwater you can only advance the pulse delay and sensitivity controls to a certain point before the detector starts to protest. The exact settings where this occurs will vary by location. This all assumes "no mineral" sand. Add magnetic soil content to the beach or bottom being hunted, and you have yet another limiting factor to contend with. Add this all up and do not expect to run the Impulse AQ Limited at a pulse delay of 7 Us and maximum sensitivity in a typical saltwater environment. You will likely have to lower one or the other or both settings to get stable performance, and this requirement tends to be a limiting factor on all PI performance in saltwater. It is this knowledge that keeps me from ever expecting miracles to occur when I try new detectors in saltwater environment. The problem is not the detectors - it is the saltwater. The original 1985 Fisher Impulse metal detector
  16. 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.
  17. I have seen it said a few times now that the new Fisher Impulse AQ has "no holes". This started as a very specific mention on the part of the designer, and now has been expanded into a range of assumptions that do not match how I view the subject. First, what is a "hole?" The classic definition originated around ground balancing pulse induction metal detectors. The first and most simple ground balance method is a basic subtraction. Determine where the ground is reading with the detector, then provide a control to subtract that signal. Many people do not realize that ground signals and gold nugget signals within normal range are basically infinite and overlap 100%. This is due to the nature of natural gold nuggets, which occur in endless variety as far as size, shape, and composition. When added to the ground, they mix and blend with the ground signal, and in one way can be considered a naturally occurring component of a ground signal. There is one simple rule you must keep in mind that makes all discussions of a "hole" simple. For every potential ground signal that exists, there is also a corresponding gold signal. The ground balance control is just a special discrimination control. When you eliminate any one type of ground signal or hot rock, you automatically eliminate any gold signals that are identical to those ground and hot rock signals. The nature of the electronics involved is not 100% in that the ground balance rejection point is not perfectly sharp edged, but covers a small range. Within this rejected ground range, you have the most intense rejection effect at the setting itself. However, items that fall close to the setting, while not eliminated, are weakened, and deliver less than normal depth. The effect is similar to that seen when black holes are diagrammed, and targets that are unintentionally eliminated because they fall into this range are said to "fall into the hole." The classic metal detector ground balance "hole" This can also be seen with many VLF detectors. Take a detector with a manual ground balance control, and grab a coin. Air test the coin depth, while running the ground balance control to both extremes. Depending on the coin or target you test, like a gold ring, you will usually find that the depth varies with the ground balance setting. On a simple ground balance detector with a single ground balance "channel" the effect is quite pronounced. On the White's TDI the ground balance setting is normally around 8. This also corresponds with nuggets weighing approximately 1/4 ounce, though again, because of the natural variation of gold nuggets, the range is actually very large, and based on the time constant of the nugget, not any particular weight. Any nugget that reads at the setting of 8 is essentially eliminated. Nuggets that fall near to the setting have greatly weakened responses. Minelab first addressed this issue with detectors that have two ground balance "channels". Channels have historically referred to detectors that have two separate ground balance "channels" but people are now misusing the term to refer to detectors that are returning dual audio results that can be separated into "channels." This is not the same thing. A dual channel PI has two ground balance sample points that are being compared. The Minelab SD 2100 has a switch that lets one chose one or the other or both ground balance channels. One favors long time constant targets (large nuggets) and the other short time constant targets (small nuggets). The ground result is roughly the same on either channel. By comparing and combining results from the two channels, emphasizing the one with the strongest nugget signal, the "hole" is largely eliminated. This was the major advance and secret to Minelab PI MPS "multi-period sensing" detector technology. The "timings" developed over time were progressively sophisticated comparisons of multiple channel results intended to address specific ground and hot rock situations. No matter what though, the hole never goes away entirely. If you eliminate a certain hot rock, you lose gold that reads like that hot rock. People who set for and are willing to dig what others consider ground and hot rock noises, find targets with PI detectors that others miss. It's one of the secrets of the pros. At a minimum, on Minelab detectors, hunting with a different timing will reveal gold missed with another timing. To sum up, a hole in metal detector terms is what occurs when a good item is unintentionally rejected when some undesired item is rejected or discriminated. This usually refers to good items lost due to the ground balance setting, but can include any items accidentally rejected due to a detector eliminating some undesired target or range of targets. And that brings us to the new Fisher Impulse AQ and the claim of "no holes." As in all marketing claims, yes.... and no. Alexandre Tartar has be quite firm since day one in emphasizing that the AQ is specifically designed to find gold ring range targets to the exclusion of everything else. In his early writings he says that the AQ does focus on this range, and that in that defined gold ring range there are no holes. This is true. Unfortunately that statement has been extrapolated beyond the original intent. It all depends on how you want to define things. I am going with the definition above "a hole in metal detector terms is what occurs when a good item is unintentionally rejected when some undesired item is rejected or discriminated." Under that definition the Impulse AQ has two holes. They have simply been redefined as not being holes, but being something else. The ground balance control has been hijacked on the AQ and is employed as a discrimination control. Instead of being set to reject a certain ground signal, it is being used to reject a certain target range, specifically many ferrous targets. In the process, most U.S. coins except nickels are also rejected. So we have called the ground balance a disc control, and are attempting to eliminate ferrous items. The unintentional side effect is that many high conductors including most U.S. coins are rejected. Note that if this setting is high enough, heavy large gold rings can be eliminated. The ground balance hole is there, and in a big way. We are going to define it out of existence however by calling it a discrimination control. The Volcanic Mode, by eliminating intense beach mineralization, will have an adverse effect on most targets. It has to. You can't eliminate a ground signal that severe without an unintended adverse effect. The Impulse AQ is also locked into salt rejection mode at all times, even in "all metal" mode. Well, almost all metal mode - I wish there was a switch to shut off the salt rejection. There is still a filter engaged, so this is not a pure pulse mode. The machine is always set to eliminate salt signal. This means that small gold items like thin gold chains, small ear rings, aluminum foil, and small gold nuggets, are also going to be unintentionally eliminated. You catching the drift here? Unintended side effects, trade offs deemed necessary to get a desired end deemed more important. Welcome to metal detecting. So we have another hole in the extreme low end, but we have redefined it as being a preset salt rejection mode. So does the Fisher Impulse AQ have "holes" in the detection pattern? It simply depends how you want to look at it. If you define the only genuine desired range of the detector as being a narrow range focused on gold rings, there are indeed no holes in that particular range. But if you consider the entire range of possible targets that can be found with a metal detector, the AQ is explicitly said to reject at least two target ranges of concern to some detectorists depending on the settings. It always is in salt rejection mode, and so will always miss low conductor targets. Engaging the disc mode will also lose many targets of interest to coin hunters. So are those holes or are they not? You decide. Fisher does not define the term anywhere to my knowledge. It can mean whatever they want it to mean. Leaving it undefined means people just plug in their own assumptions. Frankly, none of this should come as a shock or a surprise to people who have been paying attention. I in fact have already written a long article, the Fisher Impulse AQ Discrimination Explanation, that has put all this out there for anyone with ears to listen. I have concerns that the marketing folks seize on simple catchword phrases, that make nice blurbs for people who don't really understand the technology and the limitations. People read what they want into such statements, and this in turn creates unrealistic expectations. This inevitably blows back when disappointed customers feel they were mislead. Frankly, I have always believed in underselling a product and letting it prove itself. Setting up unrealistic expectations is a setup for failure in my opinion. Keeping expectations realistic results in pleasant surprises and better long term outcomes. My goal here is therefore not to knock the Impulse AQ, but to educate people into having realistic expectations. Will you buy this detector and just go dig rings while digging no junk? No, that is not going to happen. Read the article at the link above. Are there items that the AQ will not detect as an unintentional side effect of eliminating undesired signals. Absolutely. Finally, let's talk the upcoming Fisher Impulse Gold model. The Impulse AQ fails as a gold prospecting detector because the ground balance control is being employed as a discrimination control, and because the detector is locked in salt rejection mode. Obviously the salt rejection needs an ability to be turned off. I'd prefer this as a control so salt mode can be engaged on salt alkali ground in the desert, or for some hot rock rejection. It would be a shame to eliminate it entirely, but that may be their solution. If we had a switch for that on the AQ it would have been nice also for dry beach and fresh water use. In any event, salt rejection must be gone or optional on the Impulse Gold, or all that small gold the machine is designed to find is lost. The disc control has to go back to being a ground balance control. Discrimination capability outside of perhaps a dual tone effect common on ground balancing PI detectors will therefore be unlikely on the Impulse Gold. What also will happen with an adjustable ground balance will be the inevitable hole that follows with such a control, Fisher can minimize the hole as much as possible, but again, you can't reject a certain hot rock without losing the nugget that has the exact same time constant. The ultimate constraint on the kind of gold a PI detector can find has never been pulse delay. There are commercial PI detectors designed to find pin-sized targets. For gold prospecting the constraint is always the ground. If you make a detector with a 1 uS pulse delay, all it will do is light up the ground like the largest target ever found. The key is the ground balance technology employed, and how efficient it is at eliminating ground and hot rocks, plus alkali effects in some areas, while losing as few gold nuggets as possible. There is a point where making the pulse delay short enough basically duplicates what a high frequency VLF does, and it creates all the same problems with ground and hot rocks you get with a high frequency VLF. Short pulse delays and air testing is totally meaningless. The Impulse Gold will have to ground balance effectively, and doing that will bring its performance parameters into line at best, in my opinion, with the limits we have already seen explored for those who are familiar with and have used current available technology. The main low hanging fruit waiting to be picked here is high performance in a light weight, ergonomic, and affordable package. Anyone expecting massive improvements in existing gold prospecting technology probably does not understand the constraints involved, and is likely to be disappointed. My advice? Be realistic and look for a new benchmark for what a gold prospecting detector can do without breaking your wallet or your back, and you are going to be happy with the new Fisher Impulse Gold. That is how all this works folks, time constants. PI detectors know nothing about ground or gold or ferrous or non-ferrous. Conductivity is loosely involved if at all. You can accept targets and reject targets or ground based on their time constant, and for every good target there is a bad target that has an identical time constant, and vice versa. That is the reality of the technology, and getting your head around it is the key to knowing what these detectors can and cannot do. Does the Impulse AQ exhibit any detection “holes?” My answer is define first exactly what you mean when using the term, then apply that to the AQ to get your own answer. UNDERSTANDING THE PI METAL DETECTOR by Reg Sniff For anyone who wants to dispute any of the above, please provide an exact definition of what a “detection hole” is, and how it does or does not apply to the Fisher Impulse AQ.
  18. A post I made 11 years ago.... https://www.findmall.com/threads/whites-official-audio-volume-fix.127081/post-802630
  19. A common misperception among those new to metal detecting is that metal detectors can identify one metal from another. How much we wish that were true. The reality is that for all practical purposes the common metal detector target id scale is based on a combination of the conductive or ferrous properties of the item multiplied by the size and shape of the item. There are two common terms in use for this scale. The Target ID or TID scale is the most generic. White's also popularized the use of Visual Discrimination Indicator or VDI numbers. You will see references to both TID and VDI numbers and both refer to the same thing. The problem when you use Google is that TID also refers to Terminal ID number, which is for credit card machines. VDI gets far better results as the preferred term and so is what I will use from now on. The VDI scale is almost always arranged the same way by common convention although in theory it can be rearranged any way you want. The common scale has ferrous items on the low end and non-ferrous items on the high end. Ferrous items are like mirror images of non-ferrous items and so the most common arrangement of the VDI scale is with small items in the middle with ferrous getting larger in one direction and non-ferrous getting larger in the other direction. The ferrous and non-ferrous ranges actually overlap in the middle. Large Non-Ferrous Medium Non-Ferrous Small Non-Ferrous Tiny Ferrous/Non-Ferrous Overlap Small Ferrous Medium Ferrous Large Ferrous We can assign a numeric range to this basic VDI scale any way we want. Many early machines went with a 0 - 100 scale, with the ferrous compressed into the low end of the scale: 100 Large Non-Ferrous 50 Medium Non-Ferrous 20 Small Non-Ferrous 5 Tiny Ferrous/Non-Ferrous Overlap 3 Small Ferrous 1 Medium Ferrous 0 Large Ferrous The idea of ferrous as negative numbers made sense due to the mirror imaging in size between ferrous and non-ferrous. A very common White's scale runs from -95 to 0 to +95 95 Large Non-Ferrous 50 Medium Non-Ferrous 15 Small Non-Ferrous 0 Tiny Ferrous/Non-Ferrous Overlap -15 Small Ferrous - 20 Medium Ferrous - 40 Large Ferrous The "positive only" 0 - 100 VDI scale seems most popular these days with other manufacturers, but the scheme varies. Two very common setups are 0-40 ferrous and 41-99 non-ferrous OR 0-10 ferrous and 11-99 non-ferrous. But as I noted you can set this up any way you want and so other scales do exist. When we look at just the non-ferrous part of the scale, what is important is how the detector "sees" the target. In very simple terms conductive targets are either very weak or very strong or somewhere in between. Small items are weak targets. Low conductive metals are weak targets. Large items are strong targets. High conductive metals are strong targets. The shape matters. Irregular shapes or thin items are weak targets. Rounded and thick items are strong targets. On a conductive scale of 0 to 100: 0 = very small targets 100 = very large targets 0 = very thin targets 100 = very thick targets 0 = very low conductive metals 100 = very high conductive metals 0 = very irregular shaped targets 100 = very rounded targets, especially is a hole in the middle Add this all up and small gold items are low on the VDI scale and large gold items high on the scale. Silver being a better conductor than gold, a silver item will read higher on the scale than the identical size and shape gold item. In general silver will read higher than gold. However, a very large gold item can read higher than a very small silver item. Chasing thin hammered silver coins in the U.K., especially the cut varieties, is not that different than hunting gold nuggets. What you rapidly figure out is the metal detector VDI scale can only get repeatable results on certain man made items that are the same every time, like a U.S. nickel or a U.S. dime. And even these signals degrade when deep in the ground or in proximity to other items under the search coil at the same time. Given all the limitations, it is a wonder we get any degree of accuracy at all with detector discrimination systems. With that, I give you a standardized White's VDI scale taken directly from the control box of my White's DFX. This -95 to 0 to +95 scale is common on many modern White's detectors. Nearly all other detectors have the same relative positioning of items just with different numeric scales, an exception of note being the Fisher CZ detectors, which use a rearranged scale. This DFX scale is helpful because it includes gold coins. The main thing I want you to focus on here is the relative positioning of items on the scale. As a detectorist operating in the United States, I always pay attention to just three things 1. where do the ferrous numbers start? 2. where does a U.S. nickel read? and 3. where does a U.S. dime read? If I know those three things, I can adjust almost instantly to any detector scale in existence, because I know how everything else reads in relation to those three points on the scale. Standard White's VDI scale Looking at the scale you can use gold coins as a rough guide to where large gold nuggets will read, although coins being pure gold and round will read much better than gold nuggets of the same size. It might take a one pound gold nugget to read the same as a one ounce $20 gold coin, which in turn reads very close to the U.S. silver quarter reading. On the other end, tiny gold, tiny ferrous, and salt water, being a low conductive target, all overlap. This is why if you tune out salt water on the beach, you also tune out single post gold ear rings and thin gold chains, which read like small gold nuggets. If a prospector tunes out salt alkali readings on a salt lake, there go the small gold readings. And the chart shows that if you get too aggressive in rejecting all ferrous items, good items can be lost also. When I say small it is important to note what we are really talking about is small/weak readings. A large gold item buried very deep in mineralized ground will have a very weak reading and appear as a small target to the detector. This means a very deep large items can appear just like a very small gold item and be lost for the very same reasons as those small items. Again, think weak targets and strong targets to get a better feel for how things react in the field. To sum up, gold and platinum are low conductive metals, and when also small in size read very low on the VDI scale, even dipping into the ferrous range. The foil range is the sweet spot for ear rings, thin gold chains, small womens rings, and platinum items. In general women's gold rings will read below a U.S. nickel and men's gold rings will fall above a U.S. nickel on the VDI scale. Nearly all gold nuggets found by most people are going to read nickel and lower just because nearly all gold nuggets are small. However, as this photo I made using my DFX and some gold nuggets shows, gold nuggets can read all over the place due to their shape and purity. Surprisingly, if you add silver to gold the conductivity drops as alloys are less conductive than pure metals. This makes many gold jewelry items and gold nuggets far harder to detect than would be the case were they pure gold. See this article for details on this nugget photo Some Gold Nugget VDI Numbers Target id numbers for naturally occurring gold nuggets You can get some great spreadsheets for jewelry VDI numbers for White's and Minelab detectors here. There are no doubt many people who have read this who are just shaking their head and thinking "this is why I just dig everything". I absolutely agree, when at all possible, that is the best solution. Unfortunately it simply is not possible in some locations where trash targets outnumber the good by thousands to one. This is where knowing the VDI scale and how it works can pay off. 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.
  20. I am new here so there may be a better forum to ask this question so redirect me if needed. I have a Teknetics Delta 4000. I need to probe a fiberglass tube 2 inches in diameter to see if I can detect a copper beryllium strip which should be inside. Unfortunate I cannot get closer than 16 ft to the tube. I have found a 25 foot 5 pin DIN cable that would extend the cable that is on the 4000. I could then detach the pickup coil and mount that on a 16 ft PVC rod leaving the electronics and readout with me. I only need to know if there is something there or not there. The rod is 100 ft off the ground and 16 ft out from my closest reach. Anyone ever tried to extend the cable?. I know it is not a perfect situation but I would save me a lot of money if I can detect the metal strip. Regards Mike
  21. Hello, I'm looking for detector that can detect up to 4 meters (~13 ft) with > 10 grams of gold on orchard ground I've bought "BR gold step" but it was useless now I'm looking on "minelab GPZ 7000" but I wanted to ask here if there it will be good one for my case or there is another choice my budget is 10,000$ PS: can I use GPZ 7000 with my gold step to get more accurate reads ?
  22. Hello all, I was reading Steve's post on "Best detector values under $500 dollars"! And noticed something! I noticed that MineLab is the only manufacturer that listed the operation temperature, and storage temperature of their equipment! Being a Native of South Florida with its oppressive heat, humidity, and salt air, most of the year! I have experienced first hand what happens to electronics, plastics, adhesives, etc... that many of you in certain States, and Country's, have also experienced! Suffice it to say to the uninitiated, that it is a bad idea to leave these items in an enclosed vehicle for an extended period of time!♨️ The last couple of weeks, i have been trying to figure out if coil or detector color, can adversely affect function and longevity, in these types of conditions! (not just inside vehicles)! Proof has been hard to find, without the advantages that the designers, and bench testers, have at their disposal! I know "most" electronics have overload protection built in; from energy spikes , as well as heat! That would be an obvious "failure"! But short of this "failure", will detection depth, or circuit function be appreciably reduced based solely on the surface, and internal temps of the parts themselves? Especially the copper windings of the coil! Are PI detectors more likely to suffer, due to the added power output? And is this a cumulative, or situational effect that goes unnoticed? ( loss of depth with hot coil, or circuit function)! Just wanted to get that out there for any input you all have!! Based on the huge knowledge base on this forum!👍👍
  23. I am somewhat new to metal detecting and was recently told, by a veteran detector, that all machines are multi frequency. I was also told to not buy into the multi frequency hype and that machines advertised as ones, is a marketing ploy. Please help! Is he right?
  24. Is this detector able to detect diamond? I am trying to find a diamond from a ring that fell out a number of years ago in my garden. My friend Aberal Molzesman said in his blog tha it is possible.
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