auminesweeper

So how is it working out for you Chuck ? john

hello Jim, it is always a great day when you turn up, and thank you for your constructive views, I started this thread because I have seen so many people trying to look for an answer to testing coils etc So I found a list I kept about the Conductivity and Resistance of metals so then I tried to match Gold with the closest set of numbers and that did not work because if the conductivity was close then the Resistance was wrong so then I tried to match them by weight and that did not work either, and where people had said that lead signals louder than Gold when using bits that are the same weight, That did not work because the equal weights ended up in the lead piece being bigger. So the Conductivity was wrong then the Resistance was wrong and then the weight was wrong, So the only way for it to work successfully is to go by mass, As in the same physical size and the only way to do that is to multiply or divide one metal or the other by 1.6992 , The problem is because nuggets are not like coins or Items etc, So I was trying to create a base line So I would have and Idea of what a Coils limits are, I even went as far as buying Black Sand so it would give me real minerals to put in the ground to deal with, Along with using highly magnetic signs that Ground Balance around the 86 on the GND meter. With health being less than Ideal I have not had a chance to get out there to put my theories in to action, But the things I have done have worked well enough to be close to the real world. Which is why I started this thread, But I can not put it together like you did your Silver Thread, because this is more of a Beep or No Beep type of research, Good to see you Jim, take care, john

Well my SL does have those features because when I set the GB to 7 and turn the Gain to 10 and if I wave a coin in front of it, the first time it will see at 15" and by the 2nd or 3rd sweep it will not signal the coin past 11 or 12 inches and when you turn the GB off it sees the coin at about 11 and a half inches and unlike the TDI Pro it suffers a depth loss unless it sees Copper, I Appreciate what you are saying but this is what happens, and these things do not happen with the Pro, I have owned this machine for about 18 months and it has always had these features / Problems, Sorry But the TDI Pro has the smoothing effect when the GB is turned OFF, and you only have to watch that video to see it in action and my SL does it when the Ground balance is turned On and it has ZERO Depth Increase when the GB is turned off, Even in Air Tests or in the Ground, Sorry Reg I respect the fact that you are a Wizard when it comes to Building and operating these machines, But please do not try and tell me what my machine is NOT doing or as you put it does not have these features, because I am here and so is the Machine and as a side Note there is another member on the forum who has seen both of my machines in Action, john

I love Army surplus gear all my optics are DOD, But I don't want to melt what little gold I get.

I found this elsewhere and thought it might be useful. http://chemelec.com/Projects/Metal-1a/Understanding-the-PI-Detector.htm

jumping on a plane is not practical at the moment, and testing things in the garden is a lot cheaper than driving out to the gold fields even if I was back home, The whole idea of this thread was to highlight the pitfalls of substituting lead for gold during testing and it is more for people who want to know more about their machines than people who only use one when they go prospecting, Coming from an engineering back ground I really like using detectors but I also like to know what makes them tick, and many people still don't know how to test machines beyond Air Tests. If it is of little use or interest then just Deteat the whole thread. And Delete my profile at the same Time.

I agree, I told junior 2 weeks ago I'd had enough and I wanted to go back home well that did not work out to well,

Yeah that's right, And of course we do not know how that person treats his machines, it's very easy to bag a company but if the owner is less than respectful towards that machine then the sky's the limit as to what can go wrong with it. My machines always look like the day I bought them even 3, 4, 5 years down the track, after two years of owning my last GMT A Dealer gave me 90 dollars less than what I paid for it New, But I guess most folks are not like me. john

I someone on another forum has had to send their Pro back 6 times due to many issues and it has cost him more in shipping etc than it cost him to buy the machine when it was new and he is not happy about the quality of the repairs either. john

I would but seeing as this is about using substitutes as test pieces it makes it a little awkward lol

Your such a Tease, lol.

No Steve neither have I, It was because some one posted that lead was louder and the fact that I always weigh the test bits that I use and then I realized that I had Adjust the weights because by going on weight alone I was ending up with bits that were physically bigger so I found that I had to Divide one or multiply the other by 1.6992 to make the result more accurate, and that figure comes from one cubic cm of Gold weighing 19.32grams and divide it by the weight of one cubic cm of lead being 11.37grams which equals 1.69920, and that figure relates to the size or weight of only these two metals in relation to each other, For testing purposes only. John

No need to be sorry mate, I was doing some testing today and I used some tiny bits of lead and one bit was so tiny and one of my machines could not see it so I squashed it flat and BANG there it was, thinner than a piece of paper but loud as all heck, So I then made some more bits around 0.012 grams without squashing them and my machine was seeing them at about an inch and a half so then I got to thinking about people saying about using lead as a substitute for testing a coils nugget hunting ability and then the Cogs got going so I did a search on lead and Gold and I saw the weights of the 2 compared to their size and one thing led to another and this is where I ended up at. I had read on other forum that people were saying that lead sounds louder than gold when they posted the weights So then I got to thinking and worked out why, Because that test piece that is lead weighing 0.012 grams or 0.2 grains, If it was Gold and equal in Size would weigh 0.022 grams which it was seeing and about an inch and a half, which is not bad for a VLF. Remembering that there are 480 grains to an Ounce and it is seeing 0.2 grains. john

What I am saying is because detectors respond to physical mass, Because if I had a 0.3 gm Gold nugget and a piece of lead that was the same physical size then they would both respond similar but if I had an 0.3gm Gold Nugget and a 0.3gm Lead nugget the signal would be stronger on the 0.3 Lead nugget because it is Physically bigger, Yes ?? john

Ya know thinking about it even back then ML made monos for the 3000 and the 35 so I can't see them making them if they did not work because it would be just dead money, but like all machine whether it is a PI or a VLF a person should change the coils to suit the ground conditions So really it is more about matching the machine / coil to the conditions, even on a VLF if the ground is too hot we go from a Concentric to a DD and the same rules must apply to certain PI's Aye. John

Well I already know the TDI will see a cut half at 12 inches +/- and if they are celtic bronze/copper coins then you can add a bit more to that and seeing as Celtic Gold Staters contain a lot of copper then you can maybe add an inch possibly 2 inches, But it will see them a bit further than the cut halfs Ok See I didn't leave you out of it, I wouldn't forget my Mate, I am not that mean, john

I have often wondered about the difference in these to metals because we often use lead to test machines or coils and it seems that the Two are quite far apart, It works out that lead is 41% lighter than Gold when compared to A 1 cubic foot Block of Gold to a cubic foot of lead, So if a person uses a 0.05 gram piece of lead to test the depth of a coil it would be 41% larger than an equal size in weight in Gold . Giving you a false example of real world testing This topic has come up before on other forums where people have just compared the two signals saying that lead hits louder but that is not the case because after doing the maths the reason it is louder is because it is that much bigger as in 1.6992 times heavier because one cubic cm of lead weighs 11.37 grams and one cubic cm of Gold weighs 19.32, So when you find an 0.03 gram piece of Gold and you want to simulate finding such a small piece then the piece of lead you need should weigh 0.0176 grams and an 0.05 gm of Gold is equal in size to 0.0294 gram piece of Lead or rounded off at (0.03 grams). Adding to this a cube of Gold that measure 14" square would weigh about One Ton Cubic foot of 24c pure Gold=1204 lbs/cf > (1) Cubic foot of Rolled Lead= 711 lbs/cf A difference of 493 pounds in a 12 inch x 12 inch x 12 inch cube. Anyway this is just something to bare in mind when a person is trying to test out machines and coils when you do not have access to tiny nuggets. John

I Agree, The first thing I noticed was how sleepy the SL is when it comes to small nuggets, I tried them from 0.08 to 0.12 and then 0.17 grams and it seems that 0.17 is the point where it starts to wake up seeing them at about an inch or so, As to how much the MJ coils do for the SL I am not sure, But I see guys with the TDI pro and ML PI's and they are finding really tiny nuggets, But the SL can see the those tiny Roman Minims that measure less than 1/4" of an inch across at huge depth, but the thing that concerns me most is the fact that it prefers copper over Gold and that copper is the only metal that has the boost effect with the GB off IE On a 39mm Morgan Dollar it see's it at 12 to 13 inches, But on a 31mm very thin copper Victorian penny it will see it at 16 to 17 inches, Which is about 25 to 30% increase, These pennies are 95% copper 4% Tin and 1% Zinc where as the Morgan is .900 Silver and a lot bigger and because of that smoothing effect the differences are variable with the GB On, with the distance on the Morgan starting off at around 14" maybe ? 15 inches and fades to about 12" within 2 sweeps of the coil, I think you summed it up best about using it in the hot rock Gardens where Nuggets grow.

You will do fine with either of them for sure, Tesoro's are great in junk filled site when you get the hang of them and throughout the EU where there is thousands of years of man made junk they can still find the good gear. john

Good Info Mark, but you should try it using a Quarter with the GB on and sweep slowly because the SL is a Low and slow machine Slow than using an FBS machine in an Iron filled site, at first you will notice that it will signal between 14 to 15 inches and then it will track out the coin and then see it at about 11 and a half inches, when it does that then bring the coin up to the coil where it almost makes the overload sound and take it away quickly and then sweep it in front of the coil again and it should make a soft noise at about 15" plus and then after a couple more sweeps it will track it back out to below the 12 inch mark, Ok See here, john

Thanks for posting that Steve, see even that ATX does the smoothing effect when you turn the GB Off but my SL does it when the GB is On and again when it is off there is a large depth loss so using the SL like this Guy does is a bad Idea. BUT due to the type of metal if you turn off the GB the SL comes alive on Copper and the next metal it like is flat lead, But 9 karat Gold and US Quarters cause a depth loss when the GB is Off, As I have said before my mate dug a Victorian half penny at 13 and a half inches That I measured as it was dug using an MXT with the 12 inch coil with the Gain on about 6.7, So if he had turn the MXT right up and used the Prospecting mode then I am sure he would have found it if it had been 2 - 3 maybe 4 inches deeper and so the MXT has already gone deeper than what the SL Air tests at and deeper than what it see's in the ground but with the SL because of that smoothing effect the distance drops from 15" to about 12" at best, but because the SL loves Copper when you turn off the GB it comes back to life at 15"to almost 17" again but that seems to be the only metal that the SL will see deeper with the GB Off, Lead is 50/50 ? and that's questionable but every other metal I tried shows a depth loss with the GB off. Having owned both the Pro and the SL, I have had to think long and hard as where the SL fits in to the Prospecting world and I am still not convinced about It as to where it fits within the Prospecting Periodic Table, Because where I see the MXT as The Stepping Stone in to the prospecting world which then ventures in to the Mid frequency machines and then to Hi power Pulse machines and then the king of Detectors the GPZ. Although with the GB on the SL matches the Pro on small stuff with the 2 to 16 inch range I am at a total loss because in lesser ground my MXT will smoke it when fitted with matching coil sizes So I tend to try and justify or invent a reason to pick the MXT over the SL and for the reasons you have pointed out I tend to go with the MXT 99% of the time because to me the SL is more of a Red headed step child, To me this is the only detector that does not fit under any particular heading, Because if I need a hoard hunter I would buy a Two Box, for fine Gold then the mid frequency machines come to mind and If a PI is needed then the ATX, The GPX and the TDI Pro are the standard, But the SL is an Orphan and the only real use's that I can invent for it is either chest mount it with a 6x10 or a 7"or 8"X12 MJ folded mono and use it for exploring the high country because remember it does have that small Gold depth as per the Pro and when you are just poking around you don't need mega battery life so the lightness of the whole setup works well for that purpose , Baring in mind that the SDC is a very compact unit but the down fall is when you compare prices of the two But having that 12" coil might give the SL an edge on larger deeper targets, and another reason to buy the SL is if you are one of those people who may need a PI once in a blue moon or a person who is on a tight budget but there again because we are passionate about this hobby we will do what ever we can and work our way up to the machine we want so that's is not a good enough reason, Another good thing is that the Battery fits most of the E and V series machines and the battery has a bit more gas in the tank than the standard V3i Battery so if you need a PI once in a while then that works, But if not then it is cheaper just to buy the battery for your other machines. Even though I own the machine I still can not honestly justify my reason/s for owning it and the best Idea that I can come up with for it is to chest mount it with one of MJ's elliptical coils as above so it will see smaller Gold and keep it for high country exploration. john PS, If someone with a standard SL with the factory 12" DF could test their SL using a US Quarter By setting the GB to 7 and max the Gain out with the Con switch in ALL or High, and lay a tape measure down in front of the coil and then sweep the Quarter in front of the coil and if it does not pict it up at say 13 to 14 inches or make a faint woo at 15 inches then bring the coin up to the coil quickly and over load the coil so the smoothing effect resets it's self and then try it at 15" and sweep slowly and the first or 2nd time it will make a very soft woo sound at that distance, and then turn the GB off and try it, because it should see it at 11 and a half inches and also note that the overload trick will make no difference when the GB is off and that smoothing effect is non existent, and it will no longer make any report at 14 to 15 inches, thank you, John

Yeah I was wondering about mono coils on the 3500 because some folks reckon that the 35 does not like them in hot ground, I only used DD's on mine and in the DD mode as I had no reason to use the mono mode, but now I have another one I have got to go through the coil thing all over again because technology and coil designs have really moved on where as the detectors have come to a stand still for a while. john

Steve regarding the power supply I tried it with the standard HD 2200 mah pack @ 11.6 volts then I tried the 8 cell dry pack @ 13.04 volt and the best results were using the 8 energizer lithium batteries that gave me 14.64 volts, It ran for well over 10 hours and made the signals a little sharper but because of that smoothing effect it is almost impossible to measure any depth increase without having to do that overload trick, So the higher voltage does have an effect but not enough to stand out, Side by side both machines with the GB On both machines are equal on small nugget type targets, but then that smoothing effect on the SL makes it hard to test it, when the target is In the ground it is less noticeable because it actually focusses on the ground But it does go deep on bigger targets As for depth on the SL I did manage to find the supports of a subway tunnel at about 5 to 6 feet down with the GB On, The thing that concerns me is why there is such a huge depth loss of about 33% when you turn the GB off where as the Pro gains about 25% by turning the GB off On large items with the SL there seems to be no depth advantage whether the GB is on or off, And the one thing that has shown a constant variation in depth is where you have the frequency control Anywhere from 13 minutes to the hour to the 12 O'clock position seems to be the power area but going after the 12 O'clock position shows a depth loss as In inches between the 12 and 3 O'clock positions and the closer to the 3 you go the worse it gets, When you consider that this control is for tuning out EMI, This is more noticeable on the SL for the simple reason it runs so quiet in almost any position with just a slight warble or pulse Churp sound so you can adjust it to see the responses This tends to be more noticeable on small targets. Here's my take on it as I see It, 1) For prospecting with the GB On, on common sized nuggets it is equal to the Pro for depth and sensitivity with factory coils 2) Forget about using it with the GB off like in the video for beach hunting because even in the Air it will not see a Quarter beyond 11 and a half inches with the GB OFF, so the sand is not going to give you a depth boost, 3) Always try to keep the frequency control between the Mid area between 9 and 12 O'clock position, CLOSER to the 11 the better for a good average. 4) On Large targets lets say the size of a Zippo lighter the GB On is still deeper where as the SL see's it at 22" +/- than in the Off position, But Now the TDI Pro now leaps ahead by a good 5 to 6 inches maybe more with the GB On, once the targets get really big it makes no difference on depth with the SL whether the GB is On or Off and what the SL can see at 4 to 4 and a half feet the Pro is now see them at 5 to 6 feet Final Thoughts.... So for searching small ish nuggets the SL is equal to the PRO but if you want to find nuggets that are closer to VLF territory then buy MinerJohns coils because neither machine will do it without them. The SL's power supply is the one thing that will always be hurting sales because every Prospector knows about it whether they are part timers or Hard Core 49er's, The best times I got using my modded pack was 6 hours 37 minute and If I use 8 of those lithium Energizer throw away batteries then that time is stretched to 12 to 14 hours But they are not cheap but you do get the thrill of running it at 14.64 volts which gives you that happy feeling knowing that you now have that legendary TDI Pro Power. Where this machine excels is when it comes to Basalt rocks and Serpentine, I love em, because where other machines Yodel away the SL will work In / On them and if they still give you a tough time if you increase the Pulse delay to 12 or 13 they will vanish ? NOW WAIT UP, some of you are Now thinking that if I move my delay higher than 10 then I am going to miss Small Gold Well NO your not because when it comes to the standard Coils they are as blind as a bat when it comes to those Tiny Nuggets that fall within the 10us delay setting, and with the factory coils you can run the Delay to about 12 and a half to 13 before you will see any effect as to what machine can actually see, So that's a good thing, Yes ?? The SL is great if you want a PI to go and checkout some new locations because of the weight etc and in those places where you need the GB it is equal to the Pro on small Gold, side by side testing I would go as far to say that on a couple of targets the SL saw them deeper as in an inch or less, Remembering that Both machines were Maxed out not running the Pro at say 6 because my Pro ran very very smooth indeed even in the city. Under normal detecting/prospecting situations where you need the GB you are not being short changed but on bigger deeper targets as in beyond 2 to 3 feet what will be a whisper or a faint "Woo" on the SL, On the Pro will be more noticeable and once those targets get above say 2 to 3 inches square/Round then the Pro gets ahead. John

Lol, Geez you Guys are a tough audience, But your right because I would of expected the VDI's to jump around once the depths got up around the 7 or 8" mark and get progressively worse. john

Nenad, I think that the larger DD coils are Blind to surface junk and even more so when you hold them about 6 inches or more off the ground, So to me large DD's just cant see targets as small as a concentric can, IE like when I changed the Twin D coil on my GMT to The Long scan of equal size, But the 8x14 Comcentric is about as sensitive as the 6x10 Twin D coil maybe less to the point of it being more like a normal VLF with a DD. The coils I use are 12" and bigger concentrics and they can see just about as good as a 6x10 DD Down to 0.02 to 0.03 grams and there is about a 20% drop in the ground balance reading / setting So they do have some hidden talents So my soil reading of 57 to 64 ish would read 69 to 76 if I was to use a DD, as to why this is happening I am not sure but it is something that I noticed during testing. , On my first 3500 it came with an 11" DD and it was no way near as sensitive as the 15" CON on my VLF, But the 11" DD commander coil did allow the 35 to ignore/ ID some trash in the top 6 inches, after that the rest was down to fate, As for the GPX series I don't know much about how they deal in the above situations,