NEW TDI maybe??

[dewcon4414]

Im on a couple of Forums and we have been talking sensitivity to small targets in salt water. The subject went to the TDI and it being the only PI currently being produced with a 10uS... most are 15 or higher. During this we were lucky to have Carl from Whites come on and provide this:

"TDI runs as low as 10us. Mass-producing 10us coils is not too difficult. Mass-producing 8us (or even 6us) coils is not difficult, either, but requires a change in the coil design. One reason TDI is limited to 10us is because a design goal was compatibility with ML/Coiltek coils.

Reducing the sample delay increases target response pretty much for ALL targets. It's most noticeable for small gold but everything benefits. Ground response increases as well, and operation in wet salt becomes impossible. For the same reason a salt-mode VLF can't detect small gold, a PI that can ignore wet salt also can't detect small gold. Same physics.

It's no secret that White's is working on a waterproof TDI. Actually, it's my personal project. All-new case, all-new circuit. Goal is 6us, so it might not run Coiltek coils."

I had been looking at the TDIs getting some good information on PIs from Bill Crabtree. While reading up on the TDI i noticed KelleyCo no longer had them on their web site for sale. We thought at fist it was because Whites might have felt people needed in house training on the machine to preclude returns. Im hoping this is a sooner than later project for Carl. But his comment also seems to say .....here it is but its going to be difficult to use in salt water. Hey ill take that chance. Anyone using the TDI? Doesnt it sort of have a hi-lo tones like the Inf. LS?

Dew

 

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[Terry Soloman]

I have been in a lot of arguments over pulse delay. On the beach, going down to a 10us delay is only possible in the wet sand, and on most beaches 10us is going to be very noisey. In many cases it will not be stable enough to hear the small targets you are trying to hear. That's why the Dual Field only goes down to 15us. Once you actually get in the saltwater at five-feet or more in depth, you'll need to increase the delay to at least 20us to get a smooth threshold. The TDI, in my opinion, is overpriced and overrated. I used one in the goldfields for 300-hours and was completely underwhelmed. A whole lot of hype.

 

[bigscoop]

First, I think we need to define, "small gold". Big difference between raw/pure small gold and the small 10k, 14k, 18k gold earring backs typically found on the beaches. This statement bothers me, "For the same reason a salt-mode VLF can't detect small gold, a PI that can ignore wet salt also can't detect small gold. Same physics." Just how small and what purity of gold is he referencing?

 

[bigscoop]

Dew, after battling with the deep sand and small gold issue/testing all summer long, that the following presented the best answer VS a PI machine.


Once we factor everything in, if we can find ways to make the smaller coil hunt deeper then are we better off?

 

[dewcon4414]

BS.... to me headphones and COILS have been the greatest advancement in the past years. I think physics may come into play with that tiny coil getting big coil depth. Improved processors to filter the amount of information might be a better improvement. Yes..... there is only going to be so much of that power you can use IN salt water and its going to affect sensitivity to small gold targets. But thats not just PIs but mult freqs VLF are affected as well. But they are thinking outside the box..... i like that and yes id buy one. Single freqs do a better job with sensitivity to these target, but we get that and we loose depth. Im guessing the relic ... and even some of the gold field hunters... will like this machine. Not the depth of a ML because of the power to the coil from those huge batteries, but it may have decent depth with better sensitivity. BS... you are also right a PI does have better sensitivity to smaller raw gold than it does to gold jewelry.

 

[bigscoop]

TH brings up a good point when he ask "how many of these smaller items does it take to equal one average size gold ring?" And of course, is there enough of these smaller gold items out there to justify going after them? Personally, I'm just trying to settle on a setup that allows me equal access to both without having to dig everything.

 

[dewcon4414]

I am to BS. I believe there are a lot more think. Like i said its not about deep digging... several of these targets DONT exceed our VLFs depth.... they just arent seen. As always its a different style of hunting... time consuming... maybe. Here in Fl we have a lot of depositors... all the time so cant say TH is wrong in his thinking. The problem is how much sensitivity can we put to use, if just a couple uS less that most PIs using 15uS then it may not be worth your hard earned money. This salt issue is the limiter..... not depth. Depth wise we are still missing a lot of gold with say an Xcal. When we talk small gold.... at what depth. gold tends to become a null at depth.... size and K come into play as well. Interesting NASA Tom did a test with a CZ on various K, white/yellow and size 5 ring. The size 5 18K ring was the deepest hit surprisingly ..... at 6.3 inches... yes 6.3 inches. 14 white gold .... was 5.1 inches. I know someone is going to say..... ive dug them at 18", but again to me depth out there is a guess at best. Id say we are missing gold wouldnt you?

Dew

 

[bigscoop]

Dew, Let's say 17" is the practical max performance limit of our machine. As we both know, sensitivity is lost the deeper we penetrate the salt environment, and it is further lost as we increase the size of the coil/footprint. On the other hand, as we decrease the size of the coil we gain not only sensitivity, but also, "performance stability". Now the interesting thing that I've noticed is this, as we modify our machine to allow it to hunt deeper with the small coil we don't lose this stability, which allows us to hunt with a higher degree of sensitivity at increasing depths. And the real surprise, in most cases these smaller coils were actually hunting "a lot" deeper then I first realized. The problem is that the supporting machine features simply aren't sensitive enough to support the entire depths that are actually being scanned. But if we can squeeze the entire scope out all of this performance then what might we have in the end? This is what I've been playing with in recent months and I really believe it can be done with very significant results. But, only time will truly tell just how much can actually be gained?

 

[ivanll]

TDI-Pro works fine for gold detecting, be it on our gold fields or beaches.

It does have a high and low tone for target conductivity ID but it does not sound the same as an Infinium LS


ivanll