18 posts in this topic
By Steve Herschbach
Here is a subject you will rarely see. What makes for a good looking metal detector? There are many I have swung over the years that were downright embarrassing. Maybe that is why I try to make sure I detect when nobody can see me! These days though there are some good looking detectors out there, kind of like the sports cars of the genre. My favorite - the F75 Special Edition, also called the Limited Edition. Fisher can't make up its mind.
By Steve Herschbach
I do what I can to foster competition that develops alternatives to the all too common single frequency VLF detector. There are plenty of options out there, but in my opinion they all weigh too much or cost too much. Usually both. I envision people out there with a popular VLF prospecting machine like the Gold Bug Pro, GMT, AT Gold, X-Terra 705, etc. These machines all sell for around $700 and weigh 2.5 - 3.9 lbs. They would like to add a ground balancing PI (GBPI) to what they have. I think that for "normal people" with normal budgets a machine under $2K and under four pounds just makes sense. It would be more than twice what they spent for their VLF, and in this day and age there is no reason why a decent PI should weigh over 4 lbs. To clarify what I am talking about here, I should say that for many people a $700 single frequency detector is a great place to start and in many cases is all a person ever needs. However, there are places where extreme ground mineralization and mineralized rocks (hot rocks) severely impede the performance and use of single frequency detectors. Alternative technology to deal with these conditions has been developed, by far the most familiar being the Minelab ground balancing PI (GBPI) detectors. These differ from common PI detectors by having the ability to ground balance. Other brands have offered the Garrett Infinium and ATX and the White's TDI models. These detectors are used not just for prospecting but also by relic hunters, beach detectorists, and others who face challenges regarding ground mineralization and single frequency detectors. Frankly, in my opinion GBPI technology is largely maxed out. The main room for improvement comes now in better ergonomics at lower prices. This challenge therefore limits detectors to those that weigh under 4 pounds with battery included, and which sell brand new with warranty after discounts for under US$2000. Detectors need not be ground balancing PI models, but must offer similar ability to ignore mineralized ground and hot rocks that trouble single frequency detectors. I am going to rate detectors as to their relative performance using what I call the "Minelab Rating Scale. Details here.
1. Minelab SD 2000 - crude first version, very poor on small gold, excellent on large deep gold
2. Minelab SD 2100 - vastly refined version of SD 2000
3. Minelab SD 2200 (all versions) - adds crude iron disc, ground tracking
4. Minelab GP Extreme - adds greatly improved sensitivity to small gold, overall performance boost.
5. Minelab GP 3000 - Refined GP Extreme
6. Minelab GP 3500 - Greatly refined GP 3000, last and best of analog models
7. Minelab GPX 4000 - First digital interface, rock solid threshold
8. Minelab GPX 4500 - Refined GPX 4000, solid performer
9. Minelab GPX 4800 - Released at same time as GPX 5000 as watered down version
10. Minelab GPX 5000 - Culmination of the series, current pinnacle of GBPI prospecting machine technology.
All Minelab models leverage an existing base of over 100 coil options from tiny to huge.
I am a very practical person when it comes to prospecting. I know all the existing models and options by all brands very well, perhaps better than almost anyone. This is the way I look at it is this. If I personally were to spend a lot of money to go to Australia for one month, and needed a GBPI detector, considering machines past and present, what would I take and in what order of choice? Put aside concerns of age, warranty, etc. just assume functioning detectors.
Here is the issue in a nutshell. On the Minelab scale of one to ten as listed above, I would be generous in rating the White's TDI SL as a 2. Same with the Garrett Infinium which I will mention in passing as it is no longer being made. If I was going to spend a month of my time and a lot of money going on a prospecting trip to Australia, I would choose a TDI in any version over the SD 2000. I might go with a TDI Pro over a SD 2100 but I would have to think real hard about that, and when push comes to shove I would go SD 2100 were it not for the realities of age I said to ignore. A newer TDI Pro might be a better bet than a very old SD 2100 from a reliability standpoint, but again, this would be a tough choice. The TDI SL not really. In my opinion I would be shooting myself in the foot to go on this hypothetical trip with a TDI SL instead of a SD 2100.
You see the problem now?
The Garrett ATX fares better. I would rate it a 3, roughly analogous to the SD 2200 variants. Still an agonizing choice really and the ATX being new versus SD 2200 being old might again be the tipping point, but from a pure prospecting options perspective the case can be made that the SD 2200 might be the better way to go. The problem for this challenge is the ATX weighs over 4 lbs and sells for over $2000
That's it folks. That is reality. The best of the best that the competition can offer can only go solidly up against models Minelab has not made in years. I am not saying that to be mean or as some kind of Minelab toadie, that is my pure unvarnished opinion as a guy who is pretty well versed on the subject.
Let's bring it all home. This person with the $700 machine really, really wants that under 4 lb, under $2K GBPI machine, but if they do their homework they discover that truthfully, they would be better off shopping for a used Minelab than what the competition offers new. With the TDI SL rated as a 2 the ATX in a much lighter box at under $2K is a solid win as a 3. A well designed ATX with standard dry land coils would look very enticing as compared to the GP series Minelab's and with a stronger battery system might rate 4 to 6 on my comparative scale. But Garrett refuses to budge!
White's can certainly do something, anything to improve the TDI SL. A battery that lasts all day would be a good start. In the end they are limited by the basic single channel design of the machine. The SD 2000 dual channel design was literally the answer to and the improvement on the single channel technology used in the TDI, the basics of which predate the SD 2000. Still, White's currently owns the under 4 lb under $2K GBPI category so they have the first out of the starting gate advantage. Anything they do would at the very least just show they have not given up.
The Minelab MPS patent that formed the basis of the SD series has expired. Not sure about DVT, which formed the basis of the GP series. Where is the competition? What the heck is going on here? Much gnashing of teeth and pulling of hair is going on here, that's what!!!
That is my challenge to the manufacturers. Under 4 lbs, under $2K, on the 1-10 scale I am offering, what is the best you can do?
The TDI SL as a 2? Really? Yes, really, that is currently the best of the best in the brand new ground balancing PI, full warranty, under 4 lb, under $2k category. You can pick up a 3.5 lb TDI SL right now brand new for $1089. The White's TDI SL takes the crown.
Hopefully we will see more competition in this wide open category soon. I have been beating this drum for years to no avail, but I do have reason to believe we are finally going to see more alternatives soon. I hope.
On subject of coils and systems... I was out working some areas for relics with a couple others and one guy was killing it with an very vintage 70s Garrett Master Hunter BFO unit with a large home made looking square coil of pvc looking material. After looking into I found that BFO is Beat Frequency Oscillator and was popular before T/R VLF format machines. BFO was not good for small coin shooting and nugget hunting and lacked ability for quality discrimination from what I read but excelled in depth ability, especially on large ferrous cache targets as well as finding mineral deposits like drifts of black sands or veins of ore.
So are there currently any units that still use a BFO mode or format? I can find vintage BFO type units available very reasonably priced, is there any information out there on how to bring them up to current on a battery system and build large coils suitable for this type of cache detecting?
By Steve Herschbach
Everyone needs to watch this video.
We talk all the time how lower frequencies ignore ground better and penetrate deeper on larger targets, but how high frequencies are better at getting small targets to respond. This video does a superb job of illustrating how high frequencies do a better job at "lighting up" a small gold target. The key is we are using one detector and coil with all the settings just the same - the only thing that changes is the frequency. This eliminates other extraneous factors that usually play into comparisons of this sort.
What this video does not show is how higher frequencies not only "light up" the target but also mineralized ground, creating difficulty with penetrating deeply in that ground. One of the great lessons in metal detecting is that there is no free lunch, and very often improving one thing comes at a cost somewhere else.
You can skip right to "the good part" at 2:45