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Reg

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Reg last won the day on August 22 2015

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  1. JasonG, Do you repair your ML coils or just toss them? I suspect some can be repaired. Reg
  2. You shouldn't have the detector automatically balance out gold with the GM4b. That usually happens with a detector that has an automatic ground balance system. However, if you ground balance over very small gold, it might happen. So, be careful on the ground balancing. Now, if the ground balance is not set correctly even by the slightest amount, you can easily miss very small gold in areas with a lot of black sand or even under some rocks having magnetite in them. You might experiment with this to see what I mean. Take some black sand and lay a small nugget in it and see if you can detect it. If you get even the slightest negative response from the black sand as you pass the coil over it, most likely you will miss the nugget. Get the ground balance right on the money or even with a very slight positive signal from the sand and they you should get a signal from the small gold you put in the sand. The ground balance thing is touchy when trying to hunt around black sand and does take time to master. Watch the videos for the GMT made by Jimmy Sierra. He points this black sand and gold problem out in one of them. Reg
  3. Ed in SoDak gave the best generic response. What he also said was very critical and that is, ideal sweep speed is detector dependent. Some VLF's work better when they are moved faster and the only way to know for sure is to some serious testing. The best approach is to use a very small target, preferably a non ferrous one. Next, bury the target. Yes, you can get an idea in an air test, but the in ground test also takes in other factors that are not easy to explain. PI's are different. Because an extra amount of filtering is used on a PI, the sweep speed is more critical for more reasons than one. Also, on PI's such as the newer ML's, the programs change factors than can influence that sweep speed, so again, the best technique is to do a little experimenting. The TDI is also very speed dependent and again, the ideal target is a very small piece of gold or other non ferrous object. Sweep too fast and small gold will be missed. The reason is actually reasons. One, the filtering is such that it has a peak at a certain speed. This varies a little between the TDI and the TDI pro because of a slight filter difference. The second has to do with the circuitry that eliminates half of the wee-woo response. Remember, on the TDI, the audio is either a wee or a woo. The corresponding second part of the wee-woo or the woo-wee is eliminated and filtering is involved. Sweep too fast and this filtering becomes an issue. Since most people use a Mono type coil on the TDI, the determination of the ideal sweep speed is quite constant. However, switching or using a DD coil does alter this ideal sweep speed. As for the "cone" theory on a mono, you might be surprised if you actually try to determine any front to back width between a mono and a DD. If you think about it, why would the transmit signal strength differ between the DD and the mono in terms of the theoretical field structure. Now, side to side or width of detection does change between a mono and a DD. This width difference also has a large effect on the ideal sweep speed. Experiment with it and you will see for yourself. One last note, too fast of a sweep speed has another serious problem on the ML. Swing over a shallow piece of iron trash and see how long the target signal lingers. While it is lingering, the ground covered is basically not detected for weaker signals since the stronger iron signal is still dominating. The two basic factors to determine the ideal sweep speed is to experiment and using common sense. Slow and fast are relative terms. A good example is fast to a nascar driver is not the same it is to the 75 year old neighbor driver. BTW, slow isn't the same for the two drivers mentioned. Both types of drivers require practice and experience if they are going to do the best they can. The same holds true for people using detectors. Reg
  4. Just for the record, the foldback design is something I designed a few years ago. It was my answer to the dual field design White's had that wouldn't step on the patent. Information of that design can be found on the Geotech1 forum, for those interested. I posted the basics as well as how to build one. The folded 8 as I called it allowed for one to have two different size coils in the same housing by using a figure 8 design where the top half of the 8 was folded back into the bottom half. Making the 8 lopsided would provide two different size coils, thus, better sensitivity to small gold because the smaller part of the winding would enhance the signal. The instructions on how to build coils as well as the original foldback design and even the materials used to build the first coil made by this guy were supplied by me. Fortunately, I still have some of the emails from that era providing proof for those who might believe otherwise. In fact, his first attempt didn't work because the wire I sent him was something I had not tried but recently purchased. It was Teflon coated wire that contained a strand of steel wire, something I didn't know even existed. Once I figured out what might be wrong, I sent him a different roll of wire, that did work. Here is a link to that post on the Geotech1 forum. http://www.geotech1....dual field coil Just drop down and read my posts pertaining to the figure 8 fold back design. I even have a pic showing the steps to make one. This was posted back in 2009. Now, with that said, don't expect coils built for the ML to act just like those built for the TDI. The TDI is very forgiving and will work with a wide range of designs, while the ML will not do the same. ML requires a coil have very stringent parameters to work properly. In other words, in simple terms, if you can count, solder and have a little common sense, you can build a coil that will work on the TDI. That is the beauty of this detector. Now, with that said, the reason I posted this is to just let people know building a coil for the TDI is easy while it is much more difficult to build properly working one for the ML. Reg
  5. Hi Tom, I use the TDI as well as the SL and like them both. No, they are not ML's but that isn't a bad thing. No, the TDI series will not go as deep as many ML's which is the big thing always mentioned. What the TDI has going for it is its ability to handle noise, hotrocks, black sand and be able to actually ignore a lot of the iron junk while detecting the size of nuggets most often found. This makes cherry picking targets quite easy in the worst kind of environments. In my opinion, most TDI's sold by owners are done so by people who have actually not used the PI long enough to fully understand or appreciate it. The longer one owns this detector and uses it often will find why so many people who have taken time to learn them actually prefer to use them. They work well and with experience will allow a person to hunt even trashy areas quite effectively. Better yet, they really do work well when trying to hunt old sites for silver and copper coins. To work best, the TDI needs to be operated slowly when compared to what a person usually runs a VLF. Sweep too fast and one can miss very small gold quite easily. Also, there is no need to operate or try to operate at maximum sensitivity. Learning how to adjust the GB to reduce noise and/or set the level of iron junk rejected is one important characteristic of this detector. Master this feature and you have come a long way in mastering the detector. Reg
  6. Hi Frank, I had forgotten about the post that was on another forum pertaining to coil current and battery life, but even though that post is a few years old, the fundamentals still stand. ML detectors are very finicky about what coil will work on them, so as a general rule, the inductance and resistance remain the same regardless of coil size. As mentioned in the other post, there can be some variation between the DD's and the Mono type coils but this can occur because on a DD, the receive winding is the winding that plays an important part as to whether the coil will work or not. In the case of a DD, one can vary the inductance a little more and still get the detector to work ok. This was pointed out by Robby H. on the post on the other forum. However, even as he stated, the change is very little. One other interesting post on that other forum indicated the ML average current draw to be about 0.8 amps with variations of up to about 0.1amp. So, in very simple terms, the current draw is over 3/4 amp and usually less than 1 amp per hour. Now, with all that gobbly-gook out of the way, the basic rules still apply and that means because coils have basically the same resistance and inductance regardless of their shape and size, the results will be the same current useage. We have a tendency to try to think in common sense terms and not so much in technical terms, especially if the technical training is not there. This is what makes us human and always trying to find an answer to a problem needing technical training to better understand. As a perfect example, if you run a battery down froma full charge does it weigh less? Think about it, something changed, right? Well, that is off the subject a little, but when you read all the different posts on this thread, there are some good answers relating to battery life to keep in mind. One good one has to do with external amplifiers. If that amplifier has its own battery then the detector battery useage is or should be minimal. As mentioned before, some typical battery currents of a ML PI were in the .80 amp range. Now, if a person uses a 7800 ma battery which is the same as saying it is a 7.8A battery, will the battery last almost 10 hours? The simple answer is no and that is based upon the fact that most batteries are rated based upon an ideal current draw. Change the amount of current used and the battery life can diminish quite dramatically. Actual battery life at heavy current drains can reduce to half time or so and in doing so, the internal battery resistance can become a problem resulting in detector stability. So, in simple terms, a 7800ma battery may only last 4 to 5 hours continual use and still be be in good or at least usual shape. Just so you know, the typical current output of a Li Ion 18650 cell is about 2600 ma or 2.6A at 3.6V. So, for a 7.2V battery we have two cells in series. Now,, if you want a 7800 ma battery rated at 7.2V, there will be three battery stacks in parallel (where a stack consists of two cells in series). thus, there will be 6 batteries that could fail. What makes things worse is the ease of buying lower priced batteries with claims of having the same battery life as a quality made battery. A cheap chinese knockoff, as a general rule will not last as long or work as well as a quality made battery from a different source. All of this is compounded by the fact that when a battery pack fails, it usually is because of one weak battery giving up. Since the batteries are usually in series, then one weak one renders the entire pack useless that is made up of only one series stack. In the case of multiple batteries in parallel, one dead battery drops the effectiveness signficantly, thus one will experience a shorter run time. Finally, if battery life is something one is trying to increase, then when you stop detecting, turn the machine off, even if it only for a few minutes at a time. You would be surprised at how much battery drain can happen if this simple rule isn't followed. JasonG pointed out something to keep in mind and that is, the edge of a large coil allows a person to detect small gold quite well. No, you won't get dramatic depth but a few inches is better than trying to detect that same nugget by using the center of the coil. Try it and you will see what I mean. Now, knowing the edge of the coil can be the detection zone for very small nuggets, can anyone now better understand how one can dig a deep hole before finding the nugget? The bottom line is the nugget isn't where we think it is. Now, for those of you who still want to check for themselves on this coil size and battery current, I strongly recommend you use non contact test equipment. In this case, a simple clamp on ammeter that uses an inductive pickup works quite well and is reasonably accurate. Here is a link to what I mean. http://www.ebay.com/...=item1e6641e475 There are lots of clamp on meters but most do not read DC current, so be careful when buying one if that is your purpose in buying one. Personally, I like the DC current clamp on because I can even read the battery current draw of a vehicle without taking a battery lead off. Just clamp the jaws around one of the leads coming from the battery and read the current. This is about the safest test one can do and should be accurate enough for what you are wanting to know regardless if you are checking a detector or your car. On the detector, use an old lead acid battery hookup for the easiest access to a battery lead and clamp around one of the battery leads and you should get an idea of the current drawn. Change coils and you should see little to no difference. Reg
  7. There used to be a pinned discussion about what the tones tell you but I can't find it now, so I will post something here instead. The tones are just part of what happens in a PI, whether it be a TDI or a ML. Filtering is another big issue that can cause strange things. Combine the two and one would be amazed at just what can happen to a perfectly good signal from a target. On the Video in this thread, you heard one way signals. Now, at first glance you might think that one way response was telling you about the signal itself. In some cases that may be true but in this case, it isn't and similar responses occur on other detectors. To prove my point, if you ever built the bucket that Patrick built that sort of simulated what was being done in the video, you can verify what I am saying now. That is, in the video present, the one way signal isn't because of a weak signal. If it was, then moving to the other side of the box and pushing the target through wouldn't cause a response until it was pulled back. Well, in the video the target was always inserted from the closest side you need to watch again very carefully. I mentioned once the person slowed down the movement of the nugget it could be heard both ways. Also, he hesitated before he slowed down and left the nugget on the back side just a little longer before pulling it back. When he did this at about 3:42 or close to it, you will notice the signal wasn't there when he pushed the nugget in, but was there when he pulled the nugget back. Then the helper slowed down his movement and the nugget was heard both directions. BTW, how many people noticed what I said in the last paragraph? The fact that the nugget was ignored even going in tells me something else is going on, especially when the target is generating a reasonably strong response. So, why does it matter what is going on? Simple, the target response is strong enough it shouldn't simply disappear and it certainly can't be caused by not being over the target, so what is happening? Well, on the TDI there is a blanking circuit that eliminates half the signal once it goes through a filter. The blanking circuit is eliminated half of a wee/woo or a woo/wee signal, leaving only the wee or woo, depending which happens first. Now, what happens is the blanking circuit doesn't shut off perfectly and on strong enough signals can cause odd things to happen. SLoooooooooow down and the blanking circuit has the ability to settle down. Just as important is the fact that this blanking circuit can be triggered by noise. If that happens, brief signals which can happen especially on very weak targets could be missed. On a ML, something somewhat similar can happen but it isn't the same. In this case, go over a visible piece of trash and you get a strong signal that can last for a very long time. Try it and you will see what I mean. Anyway, the strong response from the trash overwhelms a filter and the audio response can linger long enough that another deeper target can be missed because the stronger rsponse is still lingering. The signal on a ML lingers much longer than that found on the TDI because of the filter design and associated circuitry. Now, on the later model ML's, there are different modes, timings, or whatever you want to call the different setting and in some cases the filtering is altered such that the recovery speed is made faster. The point I am trying to make is one should listen very carefully to any and all changes even on the ML and I suspect you will be able to figure out a lot more about your detector than you know now. On the TDI one can ignore iron if it is large enough if the proper adjustments are made. I strongly suspect something similar could be done once a person fully understands the different settings at their disposal. Anyway, it is something to think about and maybe try. If I get my hands on one of the later models of ML I will try a few things with it, but because I don't know if I will ever hunt in AZ again and where I hunt in CO, the gold is usually too small for a PI, I probably will not buy even a used one just to see. Unfortunately, it takes time to figure out just what is happening or what might happen when settings change. Doing your best to take the time to try to see and listen what is happening just might help you with your selection of adjustments in the long run. Now, for TDI owners, most never really take time to see what will or can happen. In many cases, they see something on a video or hear of a setting that worked for someone and they mimic it while not knowing fully why or what is happening. The TDI is a simple machine to use but in some ways it is complicated to set up for the absolute best setting. Actually, complicated isn't the right word but because it takes time and understanding to better understand what is happening, it is the best word I can think of. Actually, no detector is perfect or easy to use if one wants to get the most out of it. When in doubt stick with the recommended settings or the base settings, which ever works best for you. Don't expect the detector to teach you. Instead, you have to learn the detector and what it is telling you and why. Regardless of the field of endeavor, those that become experts do so though extensive training, practice and hard work. Quite often failures are part of that learning experience. So, in very simple language, learn your detector and practice a lot. Don't get fancy until you fully understand the basics. Well, I hope I haven't bored you too much. Reg
  8. I have decided to add a little bit more about the chirp and how one can make one detector look worse or better than another. I will also offer a suggestion when making comparisons that I think will make sense for those interested. Now, if you watch the video you will see that the TDI also chirps but not as much as the SL. This chirp is more apparent when the operator was moving the coil up and down more and/or faster. Fortunately, or unfortunately, the chirp isn't nearly as strong on the SL. Now, can a person take the same target and make one detector look worse than another? Yep it can be done, especially if the test target isn't a perfect shape. To prove this, you can test nuggets by changing the orientation with respect to the coil. In other words, on a flat nugget that has irregular contours front and back, it is possible to see a small difference simply by turning the nugget over. Better yet, take a flat nugget and turn it a little so the surface is not perfectly parallel to the coil and signals can change. Take a flat nugget and turn it edgewise and see what happens. To alleviate this problem, one can purchase relatively cheap brass bearings or round balls and use them for test target. Brass does a really good job of mimicking gold targets. No matter how you turn a ball, the detector sees the same approximate surface area. Next, try different sweep speeds when trying real world testing, where you bury a target and see what you can do to detect it. This sweep speed thing is important but is more obvious on the real small targets. One thing not shown on the video listed but discussed on another forum was the SL appeared to fail when testing a certain coil. What happened was the detector seemed to whine forever and simply didn't work like it should. Well, if you read this or see a video about it, you will see it isn't a factory coil. What is happening is the SL doesn't work the same as the TDI (imagine that) and doesn't act the same when a coil is marginal for the delay setting. Had the person who made this issue experimented just a little, he probably would have stumbled into the simple fix and that is turn the delay up just a little. Build a coil too large or one with too much inductance and there is a good chance it won't work right at the shortest delay. Again, just how the detector reacts to such a coil differs between the TDI and the SL. Relic hunters often alter the delay to try to eliminate small junk. So, such a change in the delay eliminates any possible problem just mentioned. So, my suggestion is this, if you own the SL or the TDI for that matter and you decide to purchase a larger coil, and that coil doesn't seem to act right or not work at all, try advancing the delay from the minimum 10 usec to maybe 15 usec and see if that helps. The not acting right takes a little experimenting to better understand because a coil may work but be noisy or generate odd signals if stopped quickly simply because of this problem. So, keep in mind a large coil that is just marginal can do some strange things that may act like the coil is bad. When in doubt, try turning the delay up at least 3 usec and see what happens. Both the TDI and the SL can detect gold and ignore most nails and other larger trash, providing the gold is about 1/4 oz or less on the high purity gold. On the lesser purity, the size can increase a lot before gold will be ignored like the nails. In fact, I combined three 1/2oz nuggets by putting them in a plastic container and the three together still responded such that they sounded off with a high tone. This high tone normally indicates a smaller nugget and not the larger ones. However, in this case, the nuggets were rough and the gold purity was lower, so, the combination allowed one to ignore nails or other larger iron junk while still getting good signals on the larger gold objects. The ferrous objects that will be detected will be pieces of nails or short pieces of wire, maybe boot tacks, or small pieces of tin cans to name a few. Now, keep in mind that there will always be exceptions, so one might get a signal or two from some larger object such as an odd nail that one might think should be ignored. To ignore these nails requires the operator select the low conductor single tone mode. When this selection is made, any object that creates a low tone will be ignored. Now, one can reverse the process and only try to detect very large pure gold and ignore a lot of the trash. This can be done by adjusting the GB and using the high conductor mode. Nuggets above maybe 3/8 oz or larger will usually give a reliable signal, providing the nugget is solid and the gold has high purity. The nuggets in the 1/4 oz to 3/8 oz can go either way, depending upon the nugget itself and the adjustment of the GB control. Ghost town hunters or coin hunters can use this feature to ignore iron trash with a very high reliably while still detecting silver and copper coins. What is nice is the TDI family of detectors can actually see through some of this iron junk (such as nails and wire) and detect nuggets under or nearby some types of trash. Just how well this can be done can vary because of the GB setting and/or the iron junk involved. As an example, nails may be ignored, but a full tin can won't be and can cause good objects near or under it to be ignored also. So, fully understanding just how the TDI or SL works and how signals can be manipulated can make a big difference between success and failure. Finally, there is a price differnce between the SL and the TDI, so one shouldn't expect the SL to react the same as the TDI. On the plus side, the SL costs less, is lighter, and quieter. These factors alone make a big difference to me. One last note that has to do with the SL and something you might find on a video or a post on a different forum and that is the SL threshold is very smooth but seems to have a deadband, meaning there seems to be a dead space where a target can't be detected and this includes faint target signals. Well, remember what I said about setting the frequency control to minimize the noise? The worse the noise, the bigger this deadband can be. This deadband is telling you the noise is bad and being ignored. With practice you will be able to determine the deadband. Minimize the noise and you will minimize the deadband. Well, that is enough for now. Reg
  9. Mariposa... I don't put any stock in the video you posted. Why??? Well, the TDI and SL are two different detectors. One of the things I have harped about was the difference between the TDI and the SL. Well, the guy in the video and those on his forum have gone out of their way to call me about every name in the book because they feel they should be the same and when they find a difference they whine like children. So, I don't agree with their tactics or their logic, or lack thereof. Now, with that said, if you watch a very small portion of the video you will see two perfect examples of what I am talking about. First, I need to explain something and state again that the TDI and the SL are two different detectors. There are a lot of similarities but there are a couple of fundamental designs differences also. This means, you can't set the two detectors identical and expect them to perform the same. The problem with many on a particular website is they get upset when they can't run the SL detector the way they want or think is should work, rather than the way it should be run. Now, the video does point this out for those watching closely, you will notice something on the video when they test the SL with the 1 gram nugget. They claim they can only hear the target in one direction, right? Listen closely at the end of that test and notice they can hear the target much better and in both directions. Why? Simple, the the target was moved at a slightly different speed. I have harped that when using the SL, the proper technique is to operate the detector very slowly and smoothly. Now, in the video, they are testing backwards, meaning they have the coil stationary and moving the "world with its targets", right? Wrong, but that is another story. What can't be seen easily is the actual sweep speed a person might be using to obtain the results they do. What can be seen is when the guy moved the nugget just a little slower, they could suddenly hear the nugget in both directions. Operate the detector at a nice slow deliberate pace and it gets even better, but rather than do that, certain people want to operate the detector however they want and demand the detector perform the way they want. When it doesn't comply, they scream foul and complain something is wrong with the detector. Next, which I probably should have placed first is to discuss the bounce signal the guy complained about when he tried to ground balance the detector. Had he not been bouncing the coil but moving it up and down slowly like is done by digger bob in his videos, that "bounce" signal would not exist. Now, I found that bounce signal to have some unique advantage, but because of the complaints, a simple mod which was nothing more than adding one resistor eliminated that signal. So, that bounce signal is no longer audible. However, that doesn't change the filter characteristics also related to the bounce and the one way signal will still exist if the coil is swept too fast. Again, slow down the sweep speed and the signal becomes a two way signal and the depth increases accordingly. I figured out a little more about what the bounce is happening but that isn't for debate or discussion for that matter. What should be pointed out is on the newer units, the bounce signal shouldn't exist or be very minimal at the most. Just as important is the fact that if a person has one of the very first, they might want to check with the factory and have the mod installed on their detector. It does make operating too fast much more pleasant. Now, one truly stupid thing done in the video is to arbitrarily set the the frequency control. Why have it if one isn't going to use it properly, right? What the decision to set the frequency control at mid position and leave it there is simply showing that the guy doesn't know squat about the detector. To sort of explain this frequency control, I will relate something similar that is part of the setup of the SD2200 and that is to reduce the effects of noise. To do this, one has a time consuming procedure of holding a button, raising the coil and moving the coil to find the loudest noise. Then one has to wait until the detector beeps letting the operator know, the detector has found the best frequency the detector should run at to have the least noise. It is this setting on the SD or any PI for that matter, that will allow one to hear the weakest signals. So, on the SL and TDI, the procedure is different. On them, one should adjust the frequency control SLOWLY (YES I AM SHOUTING) while listening carefully for the setting that has the least amount of noise. On the SL, this adjustment should probably be done with the gain at maximum simply because the noise reduction circuitry makes it difficult to hear the noise. Now, here is the obvious reason once a person understands what is happening. On any PI, excessive noise or chatter makes it impossible to hear the very weak signals buried in that chatter. Eliminate or minimize the chatter and one can easily gain inches in depth of detection. On the SL, this is very important because the special noise reduction circuitry is trying to eliminate that chatter, but in the process any very weak signal buried in that chatter is eliminated also. This elimination is the only way it can be done since the noise or chatter is a variable signal that can last for some time. So, to obtain the best depth on any PI, the detector should be adjusted to eliminate as much chatter as possible. Are you getting the picture of why I say don't put much stock in the video? Well, a lot more mis information can be found on the website associated with the video, so be careful of believing what you read. So far I have given you some information that is important to know when operating the TDI or SL. Now, I will give you a little more but it requires you know a little more about the difference in the detectors. The TDI is built about the original GS 5 design which uses a 14 volt Li Ion battery that shuts off when the voltage gets down to about 12V or actually a little less. This particular battery actually charges up to about 16V. So, a fully charged TDI battery can be 16V or very close to it. To cut down on the weight of the SL and make purchasing batteries cheaper and easier for the operator, the power supply design was altered so the detector could operate satisfactorily on 8 AA rechargeable batteries. With the nominal voltage of 1.2V for the rechargeable battery, the operating voltage becomes less than 10V much of the time. Keep in mind I say nominal because the fully charged battery will be higher than the 1.2V. Actually, the SL is designed to operate at or down to about 8.5V before the battery alarm begins to tell the operator it is time to change. Now, even if the circuitry of the two detectors are the same, do you see a difference? A fully charged TDI has almost twice the voltage applied as a nearly fully discharged SL. Will that make a difference? You bet it will. However, the depth difference normally won't be as much as displayed if one is using factory coils. Use a smaller coil such as the elliptical Jimmy DF coil and this petential depth difference becomes even less. So, compound any serious battery difference along with improper setting of the frequency control and then toss in a larger coil and anything can happen. Furthere compound this with trying to operate the detector way too fast for its design and you can make a really good detector look bad. This can be further compounded by not knowing anything about the ground balance (GB) and how its adjustment can alter the depth of detection of various objects including certain sizes of gold and it only gets worse. This is why I harp on people to learn their detector and all its quirks. Now, just for the record, this recommendation doesn't just apply to the TDI or the SL, but also applies to the ML's. Yes, sweep speed is very important on the ML's, especially when in trashy areas. Again, this is a subject for discussion on a different post. The point of all of what I have written is there is a whole lot of bad info out there posted by people who are legends in their own mind because they have owned a detector for a while. So, it is not just a good idea to believe something because someone owns a detector and they make a video or worse yet, believe that the video is going to tell you something you should know. If you don't believe me, that is fine, but just look at drivers out there on the streets and freeways. Most don't know the laws and many don't even care because they have been driving long enough that the world is theirs. Here in Colorado, I swear half of the drivers don't know they can turn right on a red light. Those that do know they can turn don't know or don't care that they are supposed to stop first. Would you want those experts teaching you or your kids to drive?????? This same mindset should hold true for using a detector. The only big difference is with a detector you will simply not find much if you follow or use bad habits, while with a vehicle, making mistakes or using bad habits could be a matter of life or death. Getting back to the TDI and the SL, what works for the TDI may not work that way, with the SL or any other detector for that matter. The truth is, there is an ideal sweep speed for every design that works best and once a person gets in the groove of that sweep speed, one will have better success. Also, the battery voltage is more critical on the SL and should be checked more often. Using recargeables works fine on the SL but should be swapped out more often and not wait until the light comes on. Personally, I am using Li ion batteries on my SL and swap packs every few hours. I also use nothing larger than a factory coil and because most gold found now is small, I use the smaller coil to make it easier to get closer to the ground plus will detect smaller gold better. The SL, or the TDI for that matter, is not a ML so don't try to mimic what ML owners do. The design of the TDI family, including the SL is such that going to a larger coil may not get the results you think it would. A larger coil may work well for relic hunters looking for large objects, but one could easily begin to miss small gold. Well, I hope this helps clear things up. Now, I probably should duck because I am sure some weekend warrior (one of the so called 3 day old experts) will try to wreak havoc on what I have just posted. Reg
  10. Rim, I am not sure why you think you can't find larger gold with a VLF. Just because someone didn't find any larger gold before they changed detectors doesn't mean the previous detector wouldn't find the large stuff. Personally, I have found several nuggets 1/4 oz and larger with VLFs and I only hunt on a very limited basis, maybe a couple weeks a year, but did so over many years. The truth is, you have to be able to get the coil over a large piece of gold before you can detect it. Remember, the longer you hunt for gold, the more experience you get and that opens up new places. Now, one thing I will say is it is easier to miss larger gold on a VLF because of the hunting conditions. Rocks that are ignored by a PI will cause a VLF to ignore targets below them if the detector is set up wrong. That is easy to display. However, once a person realizes this and knows how to set the detector to minimize the masking effect, the less of a problem such rocks become. I have a ML PI, a couple of TDI's but I still use a VLF when the situation warrants it. In fact that was the case a couple of weeks ago when I was down nugget hunting in New Mexico. The gold found where we were hunting was too small for a PI to reliably detect, so out came the VLF. Unfortunately, I didn't find any gold, but I don't blame that on the detector. Gold in the 1 grain or less in size is difficult to find regardless and then the gold has to be close enough to the coil. This means keepng the coil very low and going slow. Now, knowing the area helps and after giving some very serious thought to the area after a few days of hunting and knowing the size of gold that was being found with dry washers, I would have changed my hunting strategy. If I go back there, that is what I will do. Half the battle in any search is not only the location but the strategy one uses and why. The knowledge one learns over the years will allow for changes and in many cases all for the right reasons. So, the detector is just a part of the puzzle if you hope to be successful. As a point, my dad and I found several large nuggets that could have been found by any type or brand of detector that works because they were so shallow. Now, these nuggets were found within yards of where a lot of very serious nugget hunters had hunted before. The common location most nugget hunters were hunting was an area well known for gold but hunted to death. Thus a hunter could search for hours where everyone was hunting and not even find one piece of scrap or junk, let alone any nuggets. Cross the road and even a 1 oz nugget was found within 10 yards of where we parked. Several other large nuggets (1/4 oz or larger) were found within a 30 yard radius of that 1 oz find. Get this, I helped a young boy (maybe 9 years old or so) find his first nugget when I helped him use one of my VLF's to hunt the area. That nugget was about a 1/4 oz piece of the yellow stuff, buried maybe 3" in a dry wash. His parents couldn't believe someone would do that for their son and allow the boy to keep the nugget. The kid promised he would hang on to that nugget and sell it to help with his college education. Reg
  11. Hi Jack, I never tried to use an ohmmeter to check the gold content, so I can't say for sure. However, my best guess woule be no, meaning one can't tell with any real accuracy the gold content. However, if done right, it might indicate some generallities. One might use a TID (Target ID) type metal detector and then you would have to have a baseline from which to work. On a coin machine with TID, the readout indicators already display that two objects with identical chemistries will have different readings. This is displayed by noting that silver coins vary in conductivity indication by their size. The same would hold true for gold nuggets. So, one might get an idea of the difference between nuggets from different areas that are very close to the same in size. Thus, what one can determine would be general concepts such as a small gold nugget will normally read less on the meter than a larger piece of gold from the same vein or location. Thee is no doubt that the chemistry or purity will also do the same. Remember, size, shape, purity, surface characteristics and contiguous connections in the case of specimens all will factor in on how a gold nugget will respond. On a VLF with metering capabilities, this means how it will read on a digital or analog readout. On a PI, it also means how the nugget will respond with a high/low or low/high tone, or in the case of the TDI rather the nugget will indicate a high tone or a low tone. Now, on the ML's, the settings or program selected can also alter the indications, so this isn't quite as forward as one might think. Even the tone indications can change by simply altering the delay or the ground balance setting. So, the TDI sort of shows you something as to what might really be happening on the ML if one were to analyze a target or two and compare the results by going through all the timings, etc, on the ML and then comparing similar results to what one gets with a TDI at different settings. Since the ground balance technique is limited on a PI, meaning one can vary cerain factors, other factors have to be fundamentally the same. What this means is when changing programs, one is changing one or more of the following, pulse length, delay setting, relationship between the main sample and the secondary sample, and finally, the other filtering that has an influence. What is important to remember is not so much what is changed, but how a certain timing or program setting affects the target response across a band of targets. This will show how some targets are high/low tones and others are low/high tones and how they change with a different setting. Knowing this will help the operator better understand what the target might be. Unfortunately, the gold characteristics mentioned before can change any standard results one might run on a series of nuggets from different locations. Thus, this idea as a form of tecting can get complicated in a hurry. Actually, it isn't as complicated as it might appear once a person realizes that knowing more about the gold from a location has an effect and what that effect might be. For me, this is a simple but very important principal. As an example, in one location here in Colorado, a large nugget will normally read as a high tone on my TDI even if it is an ounce or more, while a similar size nugget found at or near Rich Hill will read a strong low tone. So, I can change my settings accordingly to maximize my ability to find the gold by size if I know what to expect. This is further a benefit because ferrous objects also have a level of predictablility, meaning I can separate the gold from the iron junk, thus reducing the targets I need to dig. I suspect this can be also done with the ML once a person has a good handle on target responses of both gold and ferrous junk in the various modes, programs, or timings. Reg
  12. Rim, I am curious where you read that statement. Now, one might mix things up a little and that just might be what happened by meaning it is possible to use lead as a suitable target for gold and when testing with lead, one will learn there will be hotrocks that will cause a lead target to be ignored. This condition happens easily on any VLF. Simply ground balance to typical normal ground and take a piece of magnetite maybe the size of a golf ball and place a piece of lead such as a lead bullet or even a gold nugget up to a half oz next to or under the magnetite rock and you will see how easily the magnetite causes the gold to be missed. The reason is simple, the signal from the magnetite is a multitude times stronger than the signal from gold, thus even a large piece of gold can be ignored. Fortunately, the GB 2 doesn't suffer nearly as bad from this condition as most other nuggethunting VLF detectors. BTW, I used to use this demo when discussing why ground balancing is very important. My test object was a half oz nugget I found at Rich Hill and the magnetite was a golf ball size black hotrock I picked up years before here in Colorado. I would take the nugget and display how well I could detect it. I then would take a bag of plain dirt and ground balance the detector to the dirt. I then took the nugget and the dirt and displayed how I could detect the nugget through the dirt. At this ground balance setting all VLF's tested failed to detect the nugget when I combined with the rock and passed them by the coil The VLF's tested included the GB 2, plus a bunch of other gold detectors such as the XT18000, the Lobo, A Whites Goldmaster, and a few other detectors I had at the time. A while back I demonstrated to a GB 2 owner how easily a simple granite rock with some magnetite in it could easily cause a small nugget to be ignored. All I had to do was to have the rock produce a slight but obvious negative response when passed over with the coil. This can be easily done by adjusting the ground balance. At this setting, a small nugget placed next to under the rock would easily cause the nugget to be ignored. Anyway, it is something to test. One final note and that is, lead can be substituted for gold, but brass is a little more accurate in mimicking gold. Usually, lead is much less conductive than gold, but when the chemistry is right, meaning the gold is alloyed with a higher silver or copper content, it is possible that the gold will have a reduced conductance that is closer to gold. How wide of a range does the gold vary? Well, a half oz nugget found at Rich Hill was very conductive because of the high purity. Another nugget found a few miles from Rich HIll displayed quite a different response and reacted like a much lower conductive metal. Near pure gold can be mimicked by using something like an aluminum ingot. For those interested, here is a link to a site that displays how the conductivity of gold can vary. If you look at the chart at this site, one column is conductivity and you will notice that pure gold has a rating of 77 while gold heavily alloyed with silver can have a conductivity rating as low as 10. http://www.deringern...dGoldAlloys.asp Another chart at this website displays most metals and their conductivity. http://www.eddy-curr...com/condres.htm There are some variations as to exact conductivities of each metal but the variations are minor with copper being the baseline of 100 and all other metals displayed as they relate to it. Sorry to be so long winded, but when I get started, it is hard to quit. Fortunately, readers have the option to quit reading if it becomes boring. Reg
  13. Didn't know S.E. Michigan had any gold outside of rings and such, except for the gold sent to one of the refineries like the one at Waterford. N.W. MI (Upper Peninsula) has copper nuggets, though. Have you tried hunting any of those? Reg
  14. RH, I suspect the model your friend has is the GTAX 350 which uses two battery holders. Unfortunately, I don't think Radio Shack carries the particular holder you need, but you can get them on ebay. Here is a link to the ones I believe you will need. Double check with your friend to make sure this holder matches the one he has. http://www.ebay.com/...-All-Categories Hope this helps. Reg
  15. I have a standard coil somewhere but they are scarcer than hen's teeth. What do you have to trade? Hate to let an old (not used) coil go for nothing considering their rarity. Also, I might have one of the small elliptical's somewhere if I can find it. BTW, I have an original Lobo in AZ I need to get back. Tony Pancake has it. Hope it still works since it is modified dramatically and worked extremely well, much better than original. The disc feature is enhanced and one of the best anywhere even on very tiny gold. Reg
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