Reg

Here is a link to the ebay listing. i bought one and just finished charging it. Now, I have to wait until it quits raining to try it. http://www.ebay.com/itm/TDI-SL-metal-detector-battery-charger-/221741088697?pt=LH_DefaultDomain_0&hash=item33a0cc7fb9 Reg

Hey, what about sugar batteries? They seem to be on the horizon also. Just google sugar batteries to learn more. Reg

Hi Steve, I am not the one who can give you the truly technical answers to your questions, since I work more on trial and error than trying to calculate things out. Most people work using my technique anyway. Now, as for ML's claim of 6000 feet of wire, well Litz wire is made up of multiple strands and they may be using a type that has 45 strands , so each foot of wire will be 45 feet of strands. If they are using more strands per foot, then the number of feet adds up quickly. Now, lets say they are aiming for 450 uh or so tx, then that will be maybe well over 100 feet of primary wire, or 4500 feet just for the TX. Personally I feel they are using more strands in their litz than I mentioned. Now, I have no idea just what they are doing for the receive. A typical PI DD coil will have maybe 450 uh winding, but a VLF can have 4 to 8 mh. I have no idea just what the sq wave pulse will use. As I mentioned in a different post, the coil action is similar to an air core transformer, so one needs to know more calculations than the average person would understand to calculate that out. So, wind one with extreme number of receive windings (actually a pair, one for each side) and see how it works. Since the coils are mounted so they oppose each other, the result is going to respond as a total near zero. I suspect the greater number of windings in each receive winding will increase the importance of a better balance, but I haven't tried much of anything yet. What I do know is my "balance" technique in trying to make each side identical is a joke and is embarrassing to look at. I put the coil together so crudely and quickly, I wasn't even sure it would work, but it did surprisingly well. Now, there are lots of different coil designs out there. Yes, Garrett used a stacked coaxial design in some of their coils back in the late 70's and 80's. Jack Gifford used the coax in some of his designs also in some of his pre Tesoro days. One that most people do not know about is Eric Foster used a Garrett stacked coax housing and built a coil for his PPD1, which was a discriminating PI. by sampling during the on time, he could easily tell iron junk from non ferrous objects. Coaxial coils worked extremely well close to fences, but they didn't ground balance that well. At least, the ones I used didn't. Yes, there was a discriminating PI built back in the 80's. I understand it worked quite well on a saltwater beach, but sucked on dry land, since there was no ground balancing built in this detector. Getting back to my design of the dual D, well it was built the way I built it because it was fast and very convenient. I didn't have to wind anything. I just used what I had already made. Reg

I was curious just how a dual D coil would work on a TDI and this is what I found but first, I need to say my Dual D differs a little from ML's or Minelab's design a little. The reason is simple, I wanted to use what I already had made and just modify the mounting. My main TX coil looks basically the same is those in the posts of the dual D coil, but my RX coil is a little different. Instead, my two D coils are part of one large winding shaped into two D's, with a half twist in the leads passing through the center of the TX winding A simple half twist puts one winding out of phase with the other RX winding, so cancellation is the same. Ok, here are the results. First, the coil is quite sensitive, very quiet, and requires no ground balance signal at all. At least, it doesn't at my house. The detector is so quiet with or without the GB on, it is clear that I could increase the gain and, thus, the depth when using this coil. The coil housing I used is a 12" by 9" so it is smaller than the factory 12". However, the sensitivity is close to the same I am also betting I can increase the windings in the receive with little to no major noise effect,and possibly a little gain. I also have an idea to increase the gain another way. Right now, I see a depth increase on the TDI since I can run with the GB off just fine even over really bad ground, but I feel I can do much better with a few other tricks. So, it is possible even the old detectors have life left. Reg

There is another guy who is making batteries for the TDI and the SL. So for a person owning a TDI or a SL and doesn't want to build up their own pack, this guy might help. He is building up 18V battery packs for the TDI and 14.8V packs for the SL among others. Right now he is at the DIV hunt and will be back home Sunday. He is using Panasonic 3400mah batteries in his packs. Here is a link to his post. http://www.mytreasurespot.com/main/list.php?7 Just drop down the post about special TDI batteries by Reidman. Reg

Hi Russ, Sorry to hear about your health problems. Hopefully, that is all behind you now. Just take it easy until you are up to full speed. Glad to see you can still get out and find that gold. You have always been talented that way. I still remember the hunts we had together. Thanks for taking me to those special places. Hope they produce a bunch more gold for you. Reg

Eldorado, A metal detector coil isn't an "antenna" even though many people refer to it as such. Here is an interesting link to the basics of a detector coil in simple terms. http://www.geotech1.com/pages/metdet/info/coils.pdf Here is an interesting bit of history. http://www.deeptech-bg.com/search_coils.pdf As for the rest of the rest, well, Mrs. Brown has a perfect response she learned in elocution lessons and that is, "That's Nice". Reg

Hotrock, Please learn the difference between a coil of wire used as a transmit or a receive winding and an antenna. The windings in a coil act much like a transformer, which can have different polarities on the secondary. In the case of a metal detector coil, the tx winding is the primary and the receive winding(s) are the secondary. This idea is not the same as a set of bunny floppers you used to use on TV's. Changing the output polarity of any receive winding on a DD coil or the DOD design can be reversed by simply flipping the secondary winding. It works no matter how hard you try to convince the unknowing it doesn't. Now, I have wasted enough time on this trivial issue. Reg

Hotrock, "Flipping the receiver antenna coils or connection wires does nothing to change this. The polarity of the received signal wave or field determines the receiver instantaneous antenna polarity regardless of antenna configuration or orientation." OH!!! Really????? How do you reverse the phase of a winding? You really should build one and try it before making such statements. BTW, I have built dozens of DD coils and used the simple technique of flipping the windings when the polarity is wrong. Worked every time. Reg

Changing polarity on a receive winding is simple. Lift the receive winding up and flip it over. So, if you look at the pic above, then lift the top blue winding up and simply flip the receive winding so the right side of the winding is now on the left side and visa versa. We could call this a half twist also. The result is the top of the winding becomes the bottom, but fits the same. On a conventional DD coil, you could make a coil with inverted signals. This works on some PI's but not all. The TDI may not work or work right with this coil. Reg

Jason, Here is the pic mikebg posted in 2011. This idea can be traced back to 2008 when mikebg posted something almost identical. Depending upon the polarity of the to receive windings, they could be both ground and noise canceling. On level ground, this could allow the gain to be increased dramatically with the limit almost dependent upon internal noise. Reg

Jasong, FYI, the super DD coil was originally called the DOD coil when proposed by a guy in 2011 who went by the handle mikebg. A pic of the coil in jpeg can be seen on the geotech1 forum. Here is a link to it. http://www.geotech1.com/forums/showthread.php?18469-Hammerhead-modded-vs-sd2000-series&highlight=mikebg+dod+coil Just drop down to mikebg's post and click on the DOD jpg pic. Reg

Tom, Meteors are what fly by or seen falling before they hit the earth or moon. Meteorites are ones that have landed. Gold Basin meteorites generally are the stony type, which are commonly missing the typical black crust. What does show are black dots or bumps that when rubbed on a leg of jeans pants will display a silvery shiny dot. This will be the nickel in the meteorite. Most meteorites found today are the stony type. When cut and polished, the Gold Basin meteorites are quite beautiful with a chocolate brown color with bright shiny silvery dots or blotches. Unfortunately, I don't have a pic of one right now. Gold Basin meteorites don't bring much money these days but earlier they were worth over $2.00 per gram. Years back, it wasn't that uncommon to find one worth over $500. I don't know the going price today, but I have heard they often sell for maybe one fourth of that amount today. There are actually several different meteorites found at gold basin with some giving a stronger signal than others. Most if not all are considered "finds" and not "falls". A find is a meteorite found that was not tracked in the sky and later found. A fall is the one tracked and later found. On a detector, the stony meteorites often sound much like a piece of basalt. If you have no basalt in your area to test, then you might search through old red turn of the century bricks used in houses, etc. You should be able to find several that sound off, with some louder than others on a detector. Reg

Steve and Rick, PI's are different animals that are very dependent upon the target decay curve as to whether the object is heard or not. If the minimum delay is 10usec and the decay of a target is done by 9.5usec, then you won't hear a peep. What you experienced with the TDI is what ML owners experienced several years ago when I was using a low powered PI with a shorter delay. My detector would give a nice strong signal on a couple of "invisible nuggets" and the ML owners couldn't get a peep on any PI model out at that time. Now, the TDI wasn't specifically made to find small gold like the 2300 is, and the fact the design is quite old now. So, one shouldn't be surprised at the results. Dankowski has complained about the lack of being able to find small gold for years. Now, if the old TDI is adjusted back to 8 usec or even close to that setting, then I would suspect you will get some signal from the small sponge gold. Also, after looking at the video made by a guy in OZ, a modified TDI Pro comes awfully close to the sensitivity of a 2300, so I would think it would come close to the 2300 on the sponge gold. Remember, the test in the video was done with a later model TDI Pro with a few mods, which included a quieter preamp, a special noise reduction board and an additional addition that further enhanced small gold signals. The later TDI and the Pro only differ by a couple of changes and additions. The mod package only costs about $140 max which makes this mod quite reasonable when you think it reduced the warble to almost nothing when in the LOW mode and dramatically less warble in the ALL mode, plus gets a better response on small gold. So, there is or can be more life in the old TDI. Reg

Rick, You don't need to worry about going back. Simply advance the delay a little to do the same thing. As for coils, I strongly recommend Miner John's coils. The reason is, they are patterned after Eric Foster's coils designed to work the best on the TDI. The MJ coils draw less current and thus will work at shorter delays than a coil made to work on a Minelab. Some GS 5's had a constant current to limit the ramp time on a coil. That was not added to the TDI because White's coils are much closer in design to the Eric Foster design, at least coil current wise. I don't recommend dual field coils to be used with shorter delays. This type of design doesn't ground balance that well to begin with.Shorten the delay time and it only gets worse. Instead, use MJ folded mono coils to enhance small gold signals. The folded mono was something I designed to do the same thing as the dual field and that is, enhance small gold signals. My design is in public domain and can be built by anyone. Now, if small gold is the primary objective, then I also recommend shortening the pulse on time to maybe 50 usec. This will help with ability to sample properly at 8 usec Reg

Steve pointed out how to attach a file and I wasn't smart enough to look at the bottom of the screen and use the attach files option. Well, got it figured out so here is the pic of the GS 5 board and the control to adjust to reduce the delay. The TDI board is basically the same so figuring out which pot to adjust should be easy. Reg

Hi DP, The through the hole TDI can be adjusted to something like 8 usec with a simple turn of a pot. However, when you do this, most larger coils will not work right. By larger coils I mean anything greater that maybe 10" diameter. So, the minimum delay works on something like an 8" mono coil just fine but could be marginal with a 8" by 11" or larger. I don't see a way to post a pic from my computer, so email me and I will send you a pic of a GS 5 board showing the proper pot to turn. The technique is somewhat like you said, turn the pot ccw (counter clockwise). It will only turn about 1/8 of a turn. My email address is rgsniff@comcast.net . As always, any mod(s) or adjustment(s) by the owner is done at their own expense and are solely responsible for the results. One word of caution and that is, do not turn any other internal pots. All other pots require test equipment to recalibrate the unit and that is a pain to do. I gave this info to a guy and he was determined to find a pot to turn on the surface mount units. Since those are microprocessor controlled, there is no pot that will reduce the delay. Now, on the later surface mount units, I came up with a different mod that works quite well even with a 12" coil. This mod is part of a combination to reduce the noise warble common to the TDI. I don't do any mods anymore but friend of mine who is very qualified does them. Since soldering and other techniques are required, I decided to not make it a do it yourself change. Here is a link showing the TDI and the ML2300 on a test of buried targets in bad OZ ground. The TDI has the mods. Getting back to the 8 usec mod on the early TDI's, it is a pain taking the TDI apart to make the adjustment.so be careful. Reg

Steve, The truth is, the SPP fell on its face in OZ and needed a fix to work well. Not much was written about it but the SPP had a bad "hiccup" as it was called. That sound was very annoying and caused several people to take the SPP back. I know, I was asked to see if I could help fix the problem. With the help of a guy named Luke Lindsay, we managed to solve the problem and greatly improve the stability of the SPP (also the SL series). Today, SPP owners who add the single tone feature can scan the ground for small gold so easily it isn't funny even in the worst of ground in OZ. I need to get Luke to upload some of his videos so you can appreciate what I mean. Reg

Rick, All ground balancing PI's have holes. It is a known fact the TDI has one because I have spent a lot of time trying to get people to recognize it. I also have offered advice on how to minimize the problem. Check Bearkat's you tubes and you will see the GPX 5000 has holes as does the new 2300. I am confident the ATX has a hole or holes if it has two tones for targets. You can't go from a high tone to a low tone without having a "0" or no tone and is where the hole exists. In most cases, including the TDI, this is often a dip in the depth of detection rather than a true hole but it exists. As for the TDI I am sure a simple add on option could minimize the hole as it exists today. Reg

Hi Rick, Yes, I will be working on adding the noise reduction mod to the TDI and Pro that is found on the SL series. Also, when time permits, I will add it to my through the hole unit and on all TDI's I will make it switchable so you can have the noise reduction or switch it out. I also have replaced the preamp and that makes a difference. On the through the hole unit, it is a little more difficult to change the preamp but can be done. Now, here is a link to a video made in OZ where the guy has only one noise reduction mod and not the main one installed and he can detect a .03gram nugget with the TDI. Once he gets the other noise reduction mod, it will run as smooth as the SL. Actually, it will run smoother. Right now, he has the detector at full gain and the warble is quite a bit lower then most TDI's because of a different noise reduction mod that reduces the warble. but doesn't eliminate it like on the SL. Reg

I believe all ground balancing PI's made today have holes. It doesn't matter if it does, if one knows how and why exist and are created, so they can work around them. Now, fortunately I don't know of any PI that will have a hole that will cause this puppy to be missed. Here is something else interesting, a home made non ground balancing detector could be made that wold work fine via a long delay and it would detect this nugget just fine. As far as Alan's assessment of the Minelab 2300 or the ATX, I can't say just what is true or not, but I am confident something similar could be done with the ATX that would show weaknesses. That is why I try to see people are made aware of them regardless of the detector used. I still use the TDI and yes, the TDI has the problems mentioned, but with a few tricks, they can be circumvented and any gold lost in a hole can be detected with a few minor adjustments. No, the depth capability won't be equal to what would be on other nuggets, but they will be detected. Another interesting situation is the "hole" may not be for all depths or it may. So, a nugget might be detected at 5" but not at 3" or in the worst case, not at all. Shift the delay if it is possible and the hole changes or if the delay is advanced far enough and the GB turned off, the hole is gone and minimal or no ground signal to deal with. As for making the hole and issue in an article, well, it would take a book to fully describe it. One last note, I have been working with a few guys in OZ and now I am trying to convince them to try a little trick that will allow them to walk over some of the worst ground and have a nearly perfectly smooth threshold almost silent detector while still detecting gold at very respectable depths. In fact, the nugget displayed in Alan's video should be detected quite easily while using my technique while at the depth it was buried. Reg

Hi Rick, Is what you asked for actually feasible? The answer is yes. Been there, done that several years ago. There are a lot of tricks needed to overcome the various limitations associated with sampling at such a short delay and more and more tricks are being found every day. As an example, I suspect that the new ML has only one size coil because that is most likely what was needed to work at the shorter delays reliably and have the sensitivity people want. Make the coil such that it is not changeable and one problem is overcome. Carl was right, it was/is possible to sample at 8 usec on the TDI. He is also right that to do so required the right coil for it to work. So, to modify a TDI one would have to make the unit only work on the right coil at the shorter delay and advance the delay when the coil required it. Could this be done automatically? My guess it could but I haven't done it....yet. As an example, if you use the 12" mono coil, then the 10 usec would most likely be the norm, but change to the smaller 7 1/2" mono and it is quite possible an 8 usec sample could work. Use a DD coil and things get easier to early sample. Adjust the pulse width and/or pulse power and again, changes can be done to the minimal sampling time. So, there is always room for improvement and this means I will have to get back to programming micro's to make it easier. Reg

Hi Carl, I suspected you were taking time getting up to speed on your new job. Glad you seem to like it. Take your time and no need to rush getting back to me. I have plenty of other projects I need to work on. Reg

Hi Steve, I see you resurrected a couple of my posts. Yes, the original TDI's could operate at close to 8 usec and that did allow them to find smaller gold. Unfortunately, it could cause problems for the owners if they didn't know what they were doing since large coils may act like they are working correctly but really are not. Ultimately, failure to operate properly could cause problems for White's so I was quite careful as to who received the info on how to adjust the detector. The 8 usec adjustment works with smaller coils that are properly built. Miner John who is the new owner of Razorback coils is doing things right. The key on the original 200 TDI's is to keep the coil size down if you want it to work right at the 8 usec and even then, the ground signal is extremely strong and can cause problems. Eric used to make a 10" coil he used on some of his non ground balancing high power PI's and that was about the biggest size coil I knew of that worked consistently at the shorter delay. I certainly don't recommend trying anything bigger. Now, getting back to the old posts, one guy really did called me a liar and went on to say I never hunted but all I did was I spouted off about detectors. I still have his email on my old computer. I do need to get that old computer set up again so I can retrieve a lot of valuable info. No, that email is NOT part of that valuable info. I thought I had copied the info onto a usb drive but for some reason that info wasn't on the drive once I moved over to my new computer I got to avoid problems that might arise because of lack of support for my old favorite XP system. The truth is, what I advocated was a TDI could use a DD coil to help an owner recognize ferrous objects if those objects were close enough to the coil. What would happen would be the iron signal would cause a transition to a low tone if it was close enough. Now, what I didn't tell the "wizard with all the answers" was if the iron signal was already a low tone, it couldn't make the transition because it was already there. DUH!!! The key is to set the GB setting such that ferrous objects generate a high tone. This is usually around 4 on the GB of a TDI. With the GB off, all signals are high tones. Now, when using a DD coil, close iron generally would give a low tone. Raise the coil and it will revert to a high tone. I used this ferrous signal transition for years on my low powered PI and it worked well. Reg

Hi Carl, When you get a chance, drop me an email. I am hearing the project you mentioned has sort of been resurrected. Also, I have some software questions. BTW, how in the heck are things going for you now? Hope all is well and everything is working out.. On a different note, the PI I mentioned was considered a low powered unit and that is part of why it could go down to a shorter delay. Also, one big trick was to use a DD coil . With that combination, I could hit the 8 usec delay well and pretty well match the big boys on a typical 1 gram nugget for depth and clearly beat them on the smaller stuff while using AA batteries that would last a couple of days of hunting. The cute part of this non production model was the fact that a DD would alter the signal from reasonably large iron relatively close to the coil, so it could be ignored. The really small iron such as bits of tin cans or shavings off the blade of a cat would give an abrupt response that was easy to recognize. Gold responses were always smooth and clear. I even had a couple of LEDs, one blue and one red to let me know the probability of the metal. The part of the design did need some improvement but it worked. Unfortunately, I was using an extremely compact housing and had no room for further modification. I remember one trip to the 24K club where I got there about a week after one of their pushes. I swear the entire push area was stomped down with footprints, leaving no spot that hadn't been hunted hard. Well, i was using something new and never seen on a PI before, a 12" by 3" rectangular coil that I could slip into the mild trenches left by the cat during the push. To shorten the story, within an hour I picked out a half gram nugget from the worked out area out of one of those trenches. As for the long narrow rectangular coil design, I had Bill Hays make the initial housings for me and today, they are quite popular. One more thing, a couple of things mentioned recently gave me some ideas to try that just might allow a means of detecting smaller gold on the TDI. Now, I need to work on that project. Reg