By Joe D.
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!👍👍
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.
Note that a challenger has a half pound of weight they can add to the TDI SL and still make the 4 lb mark, and retail can be almost double the $1049 of the TDI SL and still come in at the 2K mark. I therefore do not think my challenge is outright crazy.
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. Maybe?
White's Electronics TSI SL metal detector
I'm new on this forum and like Alexandre Tartar, I live in north of France.
I was a young prospector in the 90's and asked my father (electronic engineer with good knowledge in magnetic field theory) to build a PI to hunt the beaches. So we have made, in a few months, an home-made PI metal detector 25 years ago, based on the technology of the old White's Surfmaster PI (mono coil). I remember the use of FETs (Field Effects Transistors to make 200 volts pulses). It worked, but unfortunately, my father was afraid by a so powerful magnetic fields and has continued his research on VLF detectors, until today !
After this short presentation, here's my question :
Is the Impulse AQ a bipolar detector ?
Le Jag has explained us on the french forum "detecteur.net" this technology developped by Alexandre :
Positive and Negative pulse are alternatively sent.
The positive one light the gold ring but magnetize the soil.
The negative one demagnetize the soil.
What about it ?
By Steve Herschbach
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:
By Steve Herschbach
Steve's Law of Target Depletion - All good locations with high value targets will be detected with progressively more aggressive means until no metal can be found. When any location contains items of great perceived value, detector technology will normally be applied in reverse order of aggressiveness. First will be VLF discrimination "cherry picking". This will be followed by varying degrees of "turning down the discrimination" to dig iffy targets and then on to using the barest of ferrous/non-ferrous discrimination. This will finally be followed by "all metal" detecting to remove masking effects with either VLF or PI detectors. If the location is considered good enough all targets will eventually over time be completely removed until no detector is able to acquire a target. At this point a site may be considered "hunted out" until a new technology arrives allowing for more depth or ground separation capability, when a few more remaining metal items will be removed. The key concept is that since discrimination is unreliable, all metal items must be removed from high value locations in order to rest assured nothing has been overlooked.
Nugget hunters and beach hunters get right with the program. If a nugget "patch" is located it will be relentlessly pounded until no metal remains. Beaches survive to some degree by being a renewable resource but even on beaches the richer, older deposits of jewelry are worked out over time. Good relic locations can and will be subjected to the same attention given to nugget patches, detected relentlessly until no metal remains. The rule is that as long as you can find a piece of metal hope remains that good items can be found. If not you, somebody else can and will return until no metal remains. I have promoted PI detectors for all uses for this very reason for over 15 years now - see that last few paragraphs at www.losttreasure.com from 2005.
Most people consider depth to be problem number one, but for many areas target masking is by far the more serious issue. Until detectors can actually see through trash instead of blocking it out, even the smallest surface trash can and will block deeper adjacent items from being detected. Superb discrimination only gets you so far and ultimately the only solution is to remove the surface trash to see what lurks below. The only real limitation we face in this regard is in areas sensitive to digging holes of any sort, like a well groomed park. Even there, slow careful extraction of surface trash over time can reveal old coins missed by others for decades.
Beneath The Mask by Thomas Dankowski