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All Tdi's Are Not Equal


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Having bought both The TDI SL and then the TDI Pro it was only matter of time before I started comparing one against the other and what I found was quite disturbing, With the SL you get a nice light weight package and on the surface it's only down fall appears to the limited power supply and after a short time I managed to increase the burn time by just over an extra 50%,

With the TDI Pro word soon got around that if a person was to turn the Ground Balance off  then the depth would be greatly improved IE with the GB ON testing it using a US Quarter the TDI Pro would see the coin at a distance of 12 to 14 inches, But by turning the GB off the Pro can see the Quarter at about 18 to 20 inches +/-, But with turning the GB off the TDI then goes in to what I call a Smoothing mode where it adjust the GB slightly and as long as a person maintains a level sweep height the TDI will remain quiet as long as there are no sudden movements up or down in height, So all that was said about the TDI Pro stands True, SEE the video below, 

So Armed with what most folks knew about the TDI / TDI Pro's, It would be very easy to assume the same could be said for the TDI SL, Sadly this is not True and the results could not be worse, With the Ground balance on Both machines are equal on small targets with the Ground Balance ON ?, but once the targets start to get bigger than a large coin then the Pro starts to get ahead and with the GB off on a target that is 6" Across/round then the Pro will see it at distances that can be measured in FEET further than it does with the GB ON.

Knowing this and doing the same tests with the SL with the GB ON all is equal to the Pro on targets about the size of a Quarter or less, But REMEMBER that smoothing effect that the Pro does with the GB OFF, well the SL does it when the GB is ON now this has a serious effect on the SL because once the Item goes in front of the Coil it gives a faint woo sound at 15" to 16" then after about 2 maybe 3 passes in front of the coil the distance then drops to about 12 and a half inches, Now remember that smoothing effect again, Well what is going on here is that the machine is actually tracking out the Item to a degree and I am sure that many would agree that that is a bad thing, and the only way to make the machine see the Quarter again at 15 to 16 inches is to bring the coin up to the coil and almost overload the signal which resets the smoothing effect and then it will see the coin at full depth again, but in the real world you cant do that so if you do here a faint target Do Not keep sweeping the coil over it or it will be Smoothed or GB'd out and if that happens then you need to sweep the coil over another patch of ground and then sweep the target area again, Once you get within the normal detection range you can proceed as normal.  

Now once you turn the GB OFF this is where it all goes wrong again Because for One you loose that smoothing effect because it no longer does it PERIOD, And Two the distance that it can see the Quarter very faintly is now 11 and a half inches using the same 12" DF Mono and for some reason that overloading trick now has NO effect so that 11 and a half inches is all you will ever get,

Steve once posted that the TDI SL felt like it lacked the Horse power of the TDI Pro and in a way that is true ?? AND if this is the case when you consider that in the GB off position it should be running at Full power and that it is running like the GB is ON and with the GB ON it is Smoothing out everything which should only happen in the GB off Position is causing a depth loss which is already running in a mode that is limited It appears that it has the same features as the Pro but it is wired back to front. If you get my meaning. And I am sure that this is why the MXT with the factory 12" can out run the TDI SL.

This now brings us to the Coils, we all know that a small coils can see those tiny bits, But the 12 DF is One 12" coil and One 6" coil, yeah ? And that the 7.5" DF is One 7 and a half inch coil and One 3" coil ,Well this is where All Coils are Equal because the 7.5 has the same depth as the 12" DF on small Items and both of them Struggle to see Items smaller than 0.17 grams which is quite small really where as the Average normal VLF will see bits down to 0.02 to 0.03 grams even my 15" MXT Max coil can see them, Where the DF Coils excel is on things about half the size of an Airgun Pellet and bigger, On coins like Tiny Roman Minims these coils are Awesome but just don't expect too much from them in prospecting venues,

Please watch this Video to see the Smoothing effect in action, And Note the depth he gets on that Nickel with the GB turned Off.

Thank you,,, John

 

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The TDI Pro of course has a more powerful battery than a stock TDI SL and this matters a great deal with ground balance off. People do need to be aware ground balance exists for a reason. If you have a Pro and can get it to operate smoothly with ground balance off it is an extremely powerful unit second perhaps to only the Eric Foster Deepstar as a beach detector. However, if the ground is severely mineralized or hot rocks abound, there comes a point where the ground balance on mode provides better depth and smooth operation.

So the big question John - does running a TDI SL with a battery as powerful as that in the TDI Pro bring back the missing depth in ground balance off mode?

Except for not being submersible the original TDI and TDI Pro variant are very powerful beach machines and with the old Eric Foster units facing issues that come with age probably the best option currently available for those wanting to hunt the beach with a PI. It is truly a shame that White's never got it into a waterproof submersible design despite that being requested from day one by users - my very first TDI review asked for it! I waited and waited and waited - and now I have a Garrett ATX. You can't just turn the ground balance off with it as you can the TDI but you can get close as this video by the same guy illustrate. The TDI is shown again in this one also.

 

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Nice write up John and thanks for sharing. I have two SL's and my experience with this detector is extensive but limited to nugget hunting; Here are some of my observations with the SL;

  This machine works best with small mono coils; 7.5" Mono Aussi,, 4x6 TDI Mono Shooter, and 5.5x9.5 Miner John. The SL just seems to lack the power for depth and stability for the larger mono / duel frequency series of loops.

Running these small coils often allows me to run the gain maxed and even at times turn the GB off .

The SL's lite weight and great ergonomics(with small coils) make it easy to swing all day. I actually removed the control box from one of the units and belt mounted it. This has really helped prospect for shallow residual / eluvial placer bleeding off epithermal deposits on the steep mountain sides out in the desert.

This IS NOT the machine to nugget shoot washes and arroyo's where over-burden can be a factor and depth capability is key

Even though not waterproof (or very water resistant) it can take one heck of a beating.

The unit has been very effective for me finding small "picker" size nuggets in some very shallow yet nasty mineralized soil. I would suppose the SDC2300 is probably a better choice for the same  applications these days. However for me, the TDI SL (and GB2) are the right tools for specific tasks that I know very well and can work effectively. I think about  getting a 2300 and Gold Racer some day............but not yet

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The ergonomics of the TDI SL are the best thing going in a ground balancing PI. It is a pleasure to swing and does not fall over when placed on the ground like nearly all other machines made these days. I sure would like to have the SDC 2300 guts stuffed in the TDI SL box!

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Great write-up John, thanks! I use an RNB 3100 LI-iON in my TDI SL. It runs at a higher voltage (just over 12.5v) than the standard rechargeable pack and that helps to smooth things out with the GB off. I believe there are also some higher voltage packs available, on the forums, that fit the SL and are around 14v. Although, I haven't personally tried one of those.

The thing I disliked most about my SL was the stock S-Rod setup that's also shared with the GMZ... The angle bothered my wrist and the grip was too thin for my liking. I had White's swap out the original S-Rod for a straight shaft (with a pistol grip like the one on the TDI Pro). My SL is now perfectly balanced, even with the 14x8 Digger coil (Dan Geyer version) attached. I can now swing it in comfort for 7+ hours without having to change battery packs.

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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 :ohmy: 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     

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Great post John, lots of info there. I can only comment that I have handled quite a few TDI SL detectors and I do not recall any losing depth with ground balance shut off. It is possible that your machine has an issue there so maybe have somebody else who has one do check the two modes and see what happens. And hopefully report.

But in all honesty that was not something I examined a lot as I always used GB on so I could be wrong. If ground is mild enough to run GB off than a good VLF in all metal mode will do as well as the TDI SL and weigh less plus have discrimination available as an option. Hot rocks are the TDI's main reason for existing when it comes to prospecting. Otherwise your MXT makes as much or more sense. In my opinion at least

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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 

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The last TDI SL that I had I tested against a Gold Bug Pro, X-Terra 705, and MXT. All those units could do as well as the TDI SL in medium mineralized ground when operated in their respective all metal prospect modes. The SPP that I got recently is as you know just a stripped down TDI SL and similar testing against VLF machines at Rye Patch had the same result. My conclusion was that the sole reason to own a TDI SL or SPP would be to handle extreme ground or hot rocks that those machines could not handle. Lacking those conditions a good VLF would be my preference.

You could say the same about the Garrett Infinium, but in its case at least it was waterproof and so found its niche more as a beach machine than a prospecting machine.

I am sure what most people hoped when White's made the TDI was that it would result in a progression of more powerful detectors that would end up giving Minelab a serious run for the money. Instead White's dumbed down the machine to make it lighter and more affordable. Who knew that for all intents and purposes the original TDI was going to be as good as it got? Not I, that's for sure.

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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.

 

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