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Tdi Pro Coil Comparison On The Goldfields


karelian

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On 9/21/2019 at 10:33 PM, karelian said:

The duel field coils do well in low to moderate mineralization, but when the soil is hot in Australia they transmit more ground noise and are more difficult to ground balance than mono coils;  in my experience. This is particularly true for the larger coils and less so for the small ones. I only have experience with the White's 12" duel field and the Jimmy duel field coils. Most of the mono coils beat the duel field Jimmy  in Australian soils. The Sadie was the best of the small coils and the Detech equals it. Slight advantage to the Sadie on small gold and slight advantage to the Detech on larger deeper targets. 

If the Jimmy coil is equal to the  7.5" White's duel field then I can say the Detech 8"  which is near identical to the Sadie mono, will have a clear advantage in hot ground encountered in Australia. This would be  reflected in the coil chart results between the Jimmy and Sadie.  Hard won life lessons, plus an army drill instructor have pointed out that behind every stuff up there is an assumption. The above opinion is based on at least one assumption... since I've never seen or used the White's 7.5" duel field coil, only the Jimmy. Also White's didn't promote the duel field coils in Australia, instead providing the mono versions on local machines. Jim In Idaho has posted a video comparing the White's 7.5" duel field and Sadie in the USA, probably more useful than my Australian experiences. Seems that in the US soils,  the performance is very close.. Type of ground and levels of mineralization seem to be the determining factor in Australia and probably also in hot US ground.  Hope this is not a confusing or contradictory answer and is useful to some degree. 

All the best, Karelian

 

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Hi Karelian, thanks for this, I recently bought a 6" Detech mono for my pops tdi SL Special edition, after reading yours and others post on the detech 8" for small gold. I haven't tried it yet, a week old. But I am starting to second guess not getting the sadie. Should I be? thinking about returning it and getting the sadie.

In CA where i go in gold country its highly mineralized with lots of iron obviously. I did a quick air test of a .4g piece and wasn't too impressed, but i know that means nothing, it was much much better than the standard MJ coil in the same scenario.

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Nuggets the 6" Detech mono is a great choice for the Tdi Sl, it should make for easier ground balancing in hot ground, smoother operation with less ground noises than the standard coil while running higher gain.  Makes for a light weight and well balanced rig that is user friendly. For some reason Tdi machines love the Sadie coil, that being said the Detech coils are more sturdy, well built solid coils with better water proofing. I run the Detech 8" mono on my Tdi Pro, but for the Tdi SL I suspect the 6" mono is a better choice. Smaller lighter coil and a fraction easier to ground balance.

The Tdi Sl needs the battery boost to give that little bit extra depth. Yes sadly the stock SL with stock battery is not that impressive in regards to depth.  If you are running the standard battery voltage, try some lithium batteries as an experiment to see what performance edge they provide. Lithiums usually run at 14.8 volts in the battery tray, should give you an idea of what a higher output battery pack can do to the Tdi Sl.  All the best for 2021.

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  • 2 years later...

Has anyone tried the Nugget Finder 8x12 evolution coil on the tdi sl? with the ion batteries? Curious to see the difference between the evo and the sadie for gold.

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I have. Lots more sensitive and deeper. I have been out only once with it. I will be selling my TDI stuff, since I have the Axiom now.

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  • 1 month later...

Not sure if this thread is still active, but I recently picked up a first model White's TDI because here in AZ there is enough mineralization and hot rocks where I go that I wanted to try PI, but as a hobbyist buying a SDC2300 (that I understand is probably the next step up) was just more than I could justify. I knew going in that the TDI is "old technology" and is much less capable, but I figured it had to be better than my VLF machines in some circumstances, and I must say that it is a real step up with regard to locating targets that are then refined with the VLF (I have a MXT w/ a 4X6, a Legend, and my detecting buddy uses a GB 2). Most of our detecting is in washes where big coils are impractical, and of course less responsive to small gold anyway.

The TDI came with the usual Jimmy Dual Field Mono 5.5"X10, which is OK (I have no real basis for comparison), but is not that hot for small gold (sub-gram down to 3 grains), and the nose of the coil is not useful for pinpointing. I know the TDI was never a great small gold finder, but figure a better coil could make up for some of that limitation.

I found a used Razorback 8.5X11 I got to to try, and can buy for $100, and it seems considerably hotter than the Jimmy, and pinpoints on the front edge considerably better, but I can find no real information about it online from any users. 

I've read that THE optimal smaller coil for the TDI is the 6X8 Nugget Finder Sadie coil that can be had (new) from Australia for about $225 delivered in ebay.

My question is whether  the 6X8 Sadie is likely better enough to justify the additional $125 bucks for one without trying one? I know that's a tough question given I haven't seen anyone mentioning using the 8.5X11 Razorback coil. I understand that Miner John now makes and markets the old Razorback line of coils, so maybe he still makes the 8,5X11 under the "Miner John" that someone may be using and could comment.

Now that most everyone has moved-on from the TDI it seems that information is hard to come buy, but I am hoping someone here might offer an educated opinion.

Thanks,

Bob

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36 minutes ago, bobinyelm said:

I understand that Miner John now makes and markets the old Razorback line of coils, so maybe he still makes the 8,5X11 under the "Miner John" that someone may be using and could comment.

I wasn't aware that brand coil is still being made.  Seems they got wiped out a couple years back from one of the many California weather disasters (possibly a forest fire).

There's a 4"x6" coil for the TDI which you might be able to find either here (post a Wanted To Buy Ad in the classifieds) or on Ebay and sometimes a used Sadie can be found, too -- I did.  (Ditto the WTB ad suggestion.)

Before buying any more coils for the TDI I recommend this excellent, detailed review (multiple posts in this thread) by karelian who is also a member here:

https://www.prospectingaustralia.com/threads/coiltek-6-mono-tdi-coil-first-impressions-small-coil-comparisons.21209/

 

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Yes, I read that Thread and it's very thorough!

I am amazed at he information volunteered here and the other MDing Forums, and much appreciate it!

In some cases, it's difficult to make direct comparisons as there are SO MANY different variation of coils. Korelian mentions a 'Razorback Longreach 10X6 Mono, which I haven't found anywhere, while I found a Razorback 8.5X11 Mono TDI  locally, which is close size wize, but could be different electrically and perform very differently perhaps.

SO many Coils, so little time (and money).

I just figure since I am using a "2nd Class machine*," I would need a 1st Class Coil" to get the most out of it to maximize results. I kinda' figure it's like tires on high performance cars- Best tires on a lesser vehicle can trump a superior car with on tires.

*Compared to an ATX or Minelab PI

Bob

PS Based on many recommendations on the Forums, I did the other night purchase a new Sadie 6X8 directly from Australia. I'll be eager to see how it performs when I get it. I can borrow the Razorback 8.5X11 TDI coil to compare, and always sell the Sadia if it isn't as good (Miner John mentioned in an email that the Sadie 6X8 was GREAT on Minelab but not so much on the TDI, but of course there are many variables (soil, mineralization, etc) so I will compare them on he ground here.

But thanks and I appreciate your suggestions very much.

Bob

Korelian Data:

0.5 grain gold coin. Winner is Razorback Longreach 10 x 6 mono at 27cm, second goes to Nugget Finder Sadie at 26cm.

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9 hours ago, bobinyelm said:

 

Korelian Data:

0.5 grain gold coin. Winner is Razorback Longreach 10 x 6 mono at 27cm, second goes to Nugget Finder Sadie at 26cm.

I'd be willing to bet sizeable money that Mike meant to type .5gram, and not .5 grain when he did that test result. The chance of any TDI seeing any gold as small as .5 grain at 10" is somewhere between slim and zero...LOL

Jim

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4 hours ago, Jim in Idaho said:

 The chance of any TDI seeing any gold as small as .5 grain at 10" is somewhere between slim and zero...LOL

Jim

I don't have any experience with the TDI yet, so I am sure you're correct.

In reality, the ability to see 0.5gr targets just would demonstrate extreme sensitivity, though practically, looking for pieces that small, other than indicating the presence of gold in the area, worth about $2 each would be economically unproductive. 

In spreadsheet presentation of Korelian's data, it's obvious you are on the money with your statement.

 

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When choosing test targets I make sure everything could be replicated, so no nuggets where used. I should have included images of the 1 grain ingot and half gram gold coin. Pictures make things clearer. 

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