Steve Herschbach

I don't want to give the impression Minelab compatible coils won't work on a TDI. Nearly all will, though you may have to advance the pulse delay to get them to operate without overload. The vast majority will work just fine. But some won't.

A new written review... http://www.dankowskidetectors.com/discussions/read.php?2,125359,125496#msg-125496

OK Chuck, I just got my May issue of ICMJ's Prospecting & Mining Journal, and there, on pages 16 and 17, is a full color two page ad for the GM1000. With absolutely no new information that you did not already know. Well, unless they have not mentioned it uses a 24-bit signal processor. I don't recall seeing that before. But hey, it is a print ad!

I hate to bring this up but this all gets complicated by the fact that not all TDI detectors are the same, nor are all Minelab compatible coils the same. If you make a detector it has to pass within certain tolerances but there are variations. The same with coils. And as long as a coil is made for a specific detector you can be sure those two sets of tolerances align. Yet as manufacturers can tell you just building coils for a certain detector results in many rejects right off the production line. It is hard to do even for a machine you are planning on. Now take coils with tolerances assumed for one detector and put it on another. Frankly, you just don't know. If the tolerances both swing the right way you are probably going to be ok. If the tolerances go in opposite directions you may have a problem. One guy may report a certain Coiltek coil made for the Minelab GPX (or GP or SD) works just great on his TDI, and you get the same coil and put it on your TDI and it is very poor. The chances are very high that every combination of TDI and non-standard coil is going to vary quite a bit. And don't go expecting refunds for bad performance when you buy a coil made for one machine and put it on something else. I am not trying to be a bummer here, just being realistic and warning people that putting coils made for one machine on another is an experimental thing. It is best done with coils had cheap so you are not out much if it does not work out. I have put coils made for Fisher 13 kHz machines on Fisher 19 kHz machines and they seemed to work ok. What is not a great idea with PI detectors is usually a worse idea with VLF detectors. Here is what Dave Johnson (the designer) had to say on that subject.

In 2014 I posted a review of a detector by a company almost nobody here had ever heard of: http://www.detectorprospector.com/forum/topic/352-detailed-review-of-the-nokta-fors-gold-nugget-detector/ If you look at that review of the Nokta FORS Gold you will see I had made several comments about things I think needed improving on the machine. Yes, I do that sort of thing. What amazed me is Nokta fixed every one of them, and in record time - I made a special note in the review about it later. It made a serious impression on me. What then followed was a quick succession of machines by Nokta and Makro, the sister company. Nothing earth shattering per se but top flight performance at aggressive prices and a willingness to try new ideas and listen to feedback. Frankly, it came on so quickly it actually turned some people off, and I saw complaints about too many machines too fast! The entire time that we are seeing this rapid succession of machines most of us are waiting on this or that manufacturer to deliver just one new machine. October 2014 to now, and I am looking at a machine in the Nokta Impact that frankly has no exact equivalent from many of the old school top tier manufacturers. Maybe you guys see no merit in being able to select frequencies but I am highly focused on replacing all my various VLF machines with just one detector, and it is most likely going to be a selectable frequency model that wins that competition. If Nok/Mak can get from FORS CoRe to Impact in three years the "Big 5" manufacturers had better get serious and quick about picking up the pace. The listen and bend over backwards to please attitude alone is getting a lot of fans willing to forgive in other areas. Next up we will no doubt be seeing PI models and multi frequency.... and who knows what else. People can and will argue the relative merits of the Impact versus the other top-of-the-line models, but just the fact the Impact is getting compared to the very best anyone else can make says something about how far this company has come. Anyway, I have my own ideas about the Nokta Impact and what I will be doing with it, and most revolve around the large coil. The main thing I wanted to note here is what an accomplishment this is a for a company almost none of us heard of less than three years ago, and what it means for where they will be three years from now. Congratulations to the Nokta and Makro team and most especially to Dilek Gönülay for an impressive job well done.

I just posted a long screed on the "more depth" thing on another forum and decided to copy it here as applicable.... Des D Wrote: ------------------------------------------------------- > "Steve, > > May the 6th, Garrett are promising 'More Depth!', > from what appears to be the existing platform AT, > VLF tech?" You know the score Des. Any of us that have been around do. I have not seen "more depth" on a coin since my Compass Gold Scanner Pro with 12" coil. PI etc for gold nuggets is a different matter - progress seen there. People confuse the issues and marketers work the gray area. To most people more depth means the absolute maximum depth coins can be detected and accurately identified at. Right off the bat I can tell you that max depth here in Reno is approximately half what Tom sees in Florida due to the difference in mineralization. His accurate id on a dime at 10" is my accurate id on the same dime with the same machine at 5". That one fact alone makes nearly all online comparison tests of detectors completely worthless to me. It accounts for the vast majority of online debates, arguments, and accusations of bias, etc. Mineralization rules this game, and what works in mild ground does not necessarily work well in highly mineralized ground. What works well in magnetite laden ground does not necessarily work well in maghemite laden ground, and vice versa. Even more serious are depth limitations from masking due to adjacent trash targets. We hit max accurate id depth for clear coin type targets in milder ground ages ago. However, manufacturers are filling in the gaps for performance in highly mineralized ground and in dense trash and we therefore get more "apparent depth" If I have a coin at two inches with a nail to each side, and detector A cannot see the coin because it is masked, and detector B can see that same coin because it has a faster recovery speed, is not detector B "going deeper" than detector A? It can detect a coin at two inches that the other detector can not. By this standard the Deus "goes deeper" than many detectors, but it still won't hit Tom's dime any deeper. Or a manufacturer uses a different frequency and a better designed coil to find a coin in my Reno ground a bit deeper. Let's say we are looking for a nickel. The previous model has a concentric coil and ran at 8 kHz. Great for silver in mild ground, not good for nickels in bad ground. So we get new model running at 15 kHz with DD coil. Much better depth on nickel in bad ground. More depth! Maybe not quite as good on silver as it used to be, but let's just not worry about that, hmmm? Bottom line no better depth on Tom's dime in Florida, but the ad can claim "better depth". Previous model did not ground balance to salt range. Poor depth on beach. Now ground balances to salt range, "more depth" on beach. But no better depth on Tom's dime in Florida. More depth where, on what, under what conditions, and with what trade offs made? Gaining depth in one area often imposes new limitations somewhere else. They never mention those in the ads. Minelab's new GPZ has technology that allows it to pick up certain spongy, wire gold type specimens that a GPX 5000 cannot detect when sitting on the coil. If a detector cannot detect something, and another detector can find it at 5", how much deeper is that? 100%? 500%? I have personally found targets with my GPZ at depths 200% to 300% deeper than my GPX 5000 can find those specific wire gold specimens. Minelab largely pulled a number out of a hat and was very conservative, claiming "up to 35% greater depth" than the GPX 5000. People hear what they want to hear. People consistently read "up to 35%" and interpret that to mean "35% across the board". The GPZ will not detect a nice, solid, round nugget any deeper than a GPX. The advantage is on specific gold types. So people get up in arms, much gnashing of teeth and pulling of hair ensues, tantrums thrown, all because people chose to ignore what the words "up to" mean. It means once somewhere, someplace, under some conditions, but true and verifiable. It is a true statement. "Up to" can also mean "same as" under most circumstances. I get all this. I made my living in marketing and sales. I see right through this stuff but at the same time I do not get angry because I understand it. An advantage is being had, just not for all people under all circumstances. And almost never, under any circumstances, will it mean any more depth on Tom's dime. People who ask on the internet "will it go deeper" are just engaging in an entertaining game we like to play on forums that keeps forum owners like me happy by stirring up discussions. Are machines going deeper on a dime in the clear in mild ground? No. But are they getting better, by using better coils or better recovery or better discrimination/ground rejection techniques at eking out finds from the ground, very often finds at shallower depths? Absolutely! And are they easier to handle, more forgiving while doing so, making it easier for novices to get expert results? For sure. We are getting machines that are getting more more finds in places other machines failed, and the machine that finds the coin the other machine missed does "go deeper". But please everyone quit with the nonsense and hearing what you want to hear and reading "more depth" to mean more absolute depth on a dime in mild ground. That is almost impossible without that new patent. I love the new machines, I love what they do and how they do it, and playing around with them brings joy to my otherwise boring life. There are indeed advantages to be had by knowledgeable people leveraging a new coil or a new frequency or recovery speed - or combination of them all - to make finds previously missed. I am personally seeking a machine that runs really well at a low frequency on silver coins, and can then be switched to a high frequency to work well on gold. And satisfies my personal tastes for sound, feel on arm, menu structure, etc. Toss in the ability to also run in true multi frequency mode, for beaches, and we are getting close to the perfect detector. The V3i in theory did it but it has its limitations also. The Impact delivers much of what the V3i offers in a more traditional package and operating system, the only thing really lacking being the multi frequency operation. So will the new Garrett deliver more depth? I am sure it will on some target under some circumstance in some place. But will it go deeper than existing VLF machines on a dime in the clear? Not if it is a VLF without a new patent number attached. The reality for most of us is I expect an AT Pro with wireless headphone capability built in and hopefully a more readable display for old eyes. Make a great machine a bit better. More depth? Yeah, whatever. How To Make Yourself Crazy!

Most work well. Some will not, or with limitations. Previous thread here....

Well Mike, I am extremely interested in hearing what you have to say. First, you just described the ground conditions here in Reno to a tee. Dimes start to read ferrous at 5-6" with most machines. Too many forums are based back east and focus on detecting milder ground. People who talk about 10" dimes are living in a different world than people in the western states in particular. That, and you are one of the few people I pay serious attention to when you post because you know your stuff, especially as regards jewelry detecting. You catch me when I post something wrong - I love that! So please, yes, let's hear your views as they are vitally needed by those who live where the detecting is not easy. These people are underserved and think they are doing something wrong or that their machines are broken because they do not get the depths people talk about on other forums. It is important to get the word out it is not like that everywhere. You will find most people on this forum are working in areas like you are in yourself. That is the norm on this forum, not the exception.

Just posted April 26 - regular users are getting their hands on the Impact now. Some nice finds plus some lessons in what not to do....

OK, what follows is not a recommendation. It is simply what I tend to do. Others have other ideas. More often than not when park hunting for jewelry I focus first on deciding on a good site. For me that means anywhere hands are in action making tossing, pushing, or flinging motions. Soccer fields and children's swings are classic examples. If I think the site is good, I simply dig all non-ferrous targets. However, if time is limited and my patience thinner than normal I might do two other things. If I really am just hot to chase gold I may very well just knock out the entire high end coin range except for quarters. Seems like lots of quarters out there these days and they add up fast. You might question the dollar area but that is normally large junk. Dollar.....................RejectQuarter..................AcceptPenny/Dime...........RejectIH Penny................RejectZinc Penny.............RejectScrew Cap.............AcceptLarge Men's Ring...AcceptMen's Ring.............AcceptLarge Tab...............AcceptSmall Tab...............AcceptNickel.....................AcceptWomens Ring.........AcceptSm Womens Ring...Accept Foil..........................AcceptWire........................RejectNails........................RejectHot Rock.................Reject Again, it is normally just dig all non-ferrous targets. But if cherry picking I may skip most coins, especially zinc pennies. Yes, rings could appear there, but you have to call your shots as you please. So with that in mind if my time is really limited and I really have no patience, I may go to my final cherry pick mode. Skip the quarters also, and the screw caps, and the very light foil. There can be lots of light foil out there and the gold you might find there will be tiny stuff, like ear rings or thin chains. Dollar.....................RejectQuarter..................RejectPenny/Dime...........RejectIH Penny................RejectZinc Penny.............RejectScrew Cap.............RejectLarge Men's Ring...AcceptMen's Ring.............AcceptLarge Tab...............AcceptSmall Tab...............AcceptNickel.....................AcceptWomens Ring.........AcceptSm Womens Ring...Accept Foil..........................RejectWire........................RejectNails........................RejectHot Rock.................Reject That zone is where you are going to find the majority of gold jewelry items by weight. If in an area where men's rings are a big factor, then opening up the screw cap and even zinc penny range makes sense. Where women's jewelry is prevalent keeping that light foil area open makes sense. Conversely, if you get into a place where one certain type of pull tab is driving you crazy, you may want to knock it out. There are no clear answers here. It is all about time, patience, and calling the odds based on your experience. There are other strategies, like just digging nice, clean, solid sounding signals. I tend to always stick with shallow targets that require nothing more than a pinpointer and screwdriver to recover, as plugging takes too much time. Recovering huge volumes of targets matters, and plugging causes too much damage if done every foot. My standard procedure is just pop out any non-ferrous target my pinpointer can hit. If my pinpointer can't detect it it is too deep and so I move on to the next target. And as noted above I may vary my disc settings to suit my mood or circumstances. Great books to help you out from Clive Clynick at http://www.clivesgoldpage.com/

I have the greatest respect for the F75 Ltd but I suspect the Patriot is the wolf in sheep's clothing here. Not sure what to make of the switch from concentric coil on F70 to DD coil on Patriot as I am rather fond of concentric coils but DD is all the rage these days so probably the better way to sell it. There is a DD variant of the F70 available also for $50 more but the concentric has normally been the stock coil. Click on picture for larger view.

The machines generate quite a bit of internal heat so it would not surprise me. Rob, what do you mean rained all day? In Alaska it is only of note if you say "all week" or "all month". Nothing like days on end in rain gear and a mosquito head net - oh, I miss that so much! Rob Allison, first visit to Moore Creek, Alaska, August 2005 - Found 14 nuggets totalling 3.76 ounces

Wilma, Doug the Minelab dealer from Alaska in center, and Jim the undercover geologist on left. At my old Moore Creek property in Alaska. I am guessing I have spent more days in the rain with a Minelab PI than most people. Nice to not be concerned about that anymore with the GPZ.

Really great info on lower price FTP machines which which I have no familiarity at all. I use the 13 kHz and 19 kHz models which tend to cost more. It explains why they had to keep the price so low on the F44. Really appreciated. What are your thoughts on the new Tek Patriot /F70 variant as a value proposition at only $399? Seems like a heck of a lot of detector for the price. Tempting.....

Just another note to help the thought processes. There are two types of detector sensitivity controls. By far the most common is just an ability to adjust the sensivity on the receiver side. If you get too much electrical interference, the first thing to do is lower the sensitivity. Lowering sensitivity usually reduces EMI effects far faster than it reduces the attainable depth on targets. Changing coils can also have a huge impact as the coil is the main route into the detector for EMI. Smaller coils almost always are better behaved around EMI. Special figure 8 wound "anti interference" coils can eliminate it entirely. The BigFoot coil is EMI immune as far as a coil can be. Some detectors like the V3i and DEUS, for example, allow you to increase the transmit power (TX Boost). This can add depth in mild ground of help compensate for depth differences seen at different operating frequencies. Low frequencies like more power. However, this extra power eats batteries faster. It can also result in less depth in bad in bad ground as the extra power just lights up the ground minerals more, to the point where the coils overload and shut down. In mild ground a trick to reduce EMI is to reduce the receiver sensitivity, which also reduces the EMI. Increasing the TX however adds no EMI but can add back the depth lost by reducing the receiver sensitivity. But again ,this only really works in mild ground. In my mind I like a detector that has a receiver sensitivity setting such that, when turned up all the way, the detector misbehaves and gets "too sensitive". This indicates to me the engineers are pushing the limits, and so backing off from full settings is needed to ge best results. Unfortunately, too many novices fall prey to max setting syndrome. The detector then acts as if it is defective. Many complaints result. Engineers throw in towel, make sure next detector always behaves well at max sensitivity setting. Honestly, if the detector gets squirrelly at max sensitivity settings, don't complain! That really is a feature in my book. If a detector always runs well at max sensitivity I can't help but feel a little performance has been left on the table.

Look at the F75. Super sensitive receiver, but near unusable in many urban areas. So Fisher adds digital filtering (DST) and now the detector works far better in urban areas. But lost its edge in remote EMI free locations. That upsets some people because they hate anything that makes it sound like a detector is less powerful. But if the circuit is so over sensitive you have to back all the settings down to get it to work at all you end up in the same place or worse. To me the F75 with DST is a far better detector because it will work most anywhere now but you will now see people seeking out the old versions because they perceive the F75 DST as being neutered. And for all metal use in remote areas it may be the old versions work better for some people. Some detectors never show any audio side effects from EMI but the interference can act to silently kill performance without you even knowing about it. THis is not uncommon on silent search type units in particular. The interference is there, you just can't hear it, but you are running at sub par performance. If engineers could design detectors knowing for a fact they would always be operated in areas free of EMI you would see an immediate increase in detector performance. Most detectors are dumbed down to one degree or another due to EMI mitigation necessities. There really is no magic easy answer here. Keep it in perspective however. The number one problem is not EMI but interference from induced ground signals. The main goal in new tech is to figure out how to best induce detectable signals into the desired targets while not "lighting up" the ground at the same time. Bad ground has far more impact on detector performance than EMI in most situations.

The problem is mostly in the detector though adding wireless does just add another interference source that has to be dealt with. This can be seen in the Minelab WM10 and WM12 wireless modules and the fact that the CTX and GPZ versions ended up different due to interference issues. Anyone designing a wireless system, be it Bluetooth, etc has to deal with the interference issue. And look at the problems we face with pinpointers and detectors interfering with each other. It just keeps getting worse.

It actually is very simple. Metal detectors have a transmit circuit (TX) and a receiver circuit (RX). You see marketing focus all about what the detectors transmit, but that is actually kind of beside the point. VLFs are transmitting usually on a primary frequency plus all kinds of harmonic frequencies. PI detectors are like frequency shotguns, just blasting all over the place. Just ask any VLF operator trying to work near a PI. Detectors are transmitting on far more frequencies than are actually used, except for marketing purposes. More is better, right? Well, not really. Seen from another perspective throwing frequencies off all over the place is a waste of energy and focusing all the power into a single frequency gets the most punch. And if you get really technical about it metal detectors are not actually intentionally transmitting anything except an electromagnetic field. So forget all that. What really matter most is that the detector is tuned to receive and process only certain frequencies. The electromagnetic field generated by a metal detector coil induces eddy currents into conductive targets, that in turn can be sensed by the metal detector. The signals deep in the ground from tiny targets are like NASA trying to hear the Voyager spacecraft in interstellar space. Most of the work in a detector goes into trying to build a sensitive receiver that wants to pick up everything in the world, and then tuning and filtering it to remove the vast amount of interference from EMI, the ground, and trash targets. Part of that effort may include receiving and comparing two or more frequencies. Minelab PI detectors have incredibly sensitive receivers and do actually have to compensate for the constant lighting strikes around the world (sferics) and the earths magnetic field. My first metal detector was actually just a little square printed circuit board with a few components and a 9V battery plugged into it. The coil was printed on the board. The receiver was any AM radio you had. You just set the radio at the right frequency, and it heard what the little board was doing. See, the DEUS is not as revolutionary as people think - my very first detector in the 1970s was wireless. So forget all the transmitting stuff and just think in terms of ultra sensitive radio receiving devices and you can easily see where the problems arise. In a nutshell, how to pick up the signal generated by a current induced into a 1 grain gold nugget buried in mineralized soil with power lines nearby while I am carrying a cell phone and a lightning storm looms in the distance! The basics of the transmitter end are generally old school. Induction balance VLF type detectors, or pulse induction detectors, with simple or modified pulse trains. Where most of the action has been going on as of late is in the area of signal processing and how detectors sort out the good stuff from the bad using microprocessors and sophisticated algorithms all acting all the receiving side of things. Typical, I started out intending to give a simple answer and then made it complex by loading up on details......

The best reason I can come up with for the Scuba Tector is as a very low cost shallow water snorkeling detector for lakes and beaches, especially for places where you might want to be less than obvious. I have worked at times in very shallow surf on my knees where that little unit may have been a lot handier than trying to use a full size detector while on my knees. But in the end it is just too small to make an effective replacement for a full size detector, and rather bulky for a pinpointer. Kind of a classic tool looking for a job!

Yeah Mike, I wish White's would ditch all the old molds and start over. They need to look at the 7" concentric shipping with the new Tesoro Mojave to see how coils should be made. White's old thick foam filled coils hark back to the 1970's and are actually kind of embarrassing at this point. I think some of the performance edge some detectors enjoy these days has less to do with the detector and more to do with properly designed high performance coils that have been mated to them. White's hooking up with DeTech was not a bad move in that regard, in an least jump starting a supply of modern coils for their machines. The main reason people like the 5.3 is only because it is the only small concentric option available, which is why I have mine. But it sure is not because it is a great design compared to other small concentrics out there. Great point and well worth White's hearing it. Thanks Mike. Seriously, I though about grabbing a Mojave just to get the coil, as the detector with coil costs less than many coils on the market these days!

Production of the SD 2200D commenced in May 1998 http://www.minelab.com/customer-care/product-notices/discontinued-products/sd-2200d Owners Manual Minelab SD 2200D An updated version of the green SD 2200D was produced from 2002 - 2009, the blue SD2200v2 In all the SD 2200 had a ten year production run, and as a value option was missed by many when it was discontinued. Not surprising the batteries are bad. The sealed lead acid batteries were not exactly long life units and if not well cared for went lame. Storing without a charge or overcharging both were bad for the batteries. Coiltek made a good aftermarket Li-Ion setup for them that were quite popular, the "Pocket Rocket", that used common Sony batteries with an adapter. I don't think they are sold new anymore but you might track one down. The lead acid batteries are easily replaced. The detector looks brand new otherwise - very generous of your friend. The genuine lead acid replacement is Minelab part # 3011-0212. It is also possible to carefully pry the dome top of your battery and glue it onto a new replacement aftermarket battery that usually cost much less. Minelab does not make the actual battery, just the dome top. Tip - the Minelab AC charger supplied with the SD pumps current continuously and will overcharge the battery if left on too long. Bad design; it is way too easy to forget and leave a battery on charge too long, and no way to monitor charging progress. I always used the 12v charger myself, which is regulated and has a little led light to tell you when battery is fully charged. If need be buy a mains to 12V converter and then hook the 12V charger to that.

I don't think anyone is claiming this unit would equal a 16HP run 6" dredge for power. My Keene 6" dredge ran just fine with twin Keene 6HP pumps, for 12HP total. The unit in question is underpowered but should work fine at shallow depths. Truthfully, we are all just offering best guesses however, and you may be right - it could just be too underpowered to work well. If the price is right then selling the 9HP and re powering to a 13HP would be no big deal but I would be sure the price I paid took that possibility into account.

For background on electrical interference in VLF detectors here is a great essay on electrical interference by Dave Johnson of First Texas Products. You can also find a more detailed discussion that includes PI detectors in section 2.1 of this Minelab document by Bruce Candy. OK, so I am bench testing my new Teknetics G2 at home recently. The 19 kHz models are renowned for being immune to EMI (ElectroMagnetic Interference). No electrical interference ever (well, almost never) even at highest gain levels. As a rule, the lower the frequency, the more issues you have with EMI. It is especially bad under 10 kHz. DEUS owners may see significant EMI at 4 kHz, only a little at 8 kHz, and none at 12 and 18 kHz. Another reason why manufacturers favor mid frequency over low frequency detectors these days. I have been bench testing detectors in my house for years so think I know the EMI levels. No issues with previous 19 kHz units like the Gold Bug Pro and F19. Yet this new G2 chatters like crazy! I fire off an email to First Texas asking if some change I was unaware of. Nope. And could not be a bad coil because both coils I have did it. Then on another go I noticed the EMI was bad on one end of house but not the other. I walk around and the detector leads me to a new LED bulb I installed recently. This thing is pumping out 19 kHz EMI like crazy! Not long ago I installed a number of these cheap LED bulbs in my house. https://www.amazon.com/Feit-Electric-Replacement-CEOM60-927/dp/B01BJ0Y1MC Looks like my mission to upgade my house to all LED just ran into a snag! More on LED bulb interference - https://www.google.com/search?num=30&q=led+bulb+electrical+interference&oq=led+bulb+electrical+interference Just shows how more and more we are surrounded by new forms of electrical interference to make life harder for detector engineers.

My doing nothing is not a judgement of the merit or lack of merit of the product. The forum exists to present information that might be helpful to people. Maybe this product would be helpful for somebody, and I am sure people can judge for themselves. I don't like spammers mainly because they are sneaky third party types trying to pull one over on the forum. But I have no problem with straight up "hey, I made this cool gizmo if somebody wants to buy one" though the Classifieds is the more appropriate venue for advertising. That said, welcome to the forum Bootyhunter. There are also forums here for coin & relics, jewelry, etc. so maybe you can hang around and post a tale or a find or two.

Nice - thanks for posting Rob!