Geotech

To clarify on Aureous' post, I modified a TDI to test out an idea I had, it was a lot easier than trying to mod an Impulse. To do this I had to write new micro code from scratch. The idea worked but needs more effort. The code includes a switch to exactly replicate the original TDI timing and I sent a few chips to someone with a bunch of dead TDIs but he says the chips were acting squirrely so, again, needs more work.

Nothing White's had while I was there.

The TekPoint & F-Pulse are identical except for color.

The "New & Improved" is a matter of opinion. I made some minor tweaks to the circuitry to improve consistency but was also asked to remove some features and change the interface to make it simpler to use. Personally, I don't think it's any simpler and I particularly liked the Turbo modes that are no more. Also can't do audio-only any more. Otherwise, it performs the same as before.

For your purpose the Gemini has 2 major drawbacks. First, it's a classic TR design (not VLF-ground balancing) so it is more affected by soil mineralization. Second, it runs at 82kHz which is even more sensitive to mineralization. So it may have problems inside a cave. Probably a better choice (if you really want to use a 2-box style) is the TM808 which is a VLF-GB design running at 6.6kHz.

Yep, the missing components were for a bipolar version. Alexandre was convinced that this was the best approach but I convinced him to consider an H-bridge drive which is what he is now playing with. There is a way to use a twin-coil drive to cancel salt but I don't think that was his intent. Rather, it naturally cancels EFE and allows you to run a higher pulse rate.

Battery is 76WHrs, so it's 330mA@14.4V or 660mA@7.2V.

From Brent's exploded view it looks rain resistant but not waterproof. Doesn't look like anything White's was working on. Looks like it uses a 4-pin microphone-style connector. This means it's not compatible with older Minelab coils but on the bright side it means the coil isn't chipped.

Any rumors on pricing?

JP is right. The TDI-SL was specifically designed as a $1000 detector for the African market. Lightweight, cheap, and ran on AA's but fell a bit short in sensitivity. When we pitched it to various people in Africa the only question we ever heard was, "Does it go as deep as Minelab?" It did not, so we then sent a bunch of free detectors to Africa in the hope that some people would find gold and it would kick-start sales. Never happened.

Yeah, I agree, I think the TDI is at the end of the road. I had designed it with some hooks for ground tracking & performance upgrades but the ATX is a better platform. To Tom's post, one day I would like to see half-sine make it at least to field testing. I think it has a lot of potential. Yup, agreed.

And a Garrett coil. This thing sells for $850 on Ali Express, can't imagine there are too many people willing to pay that much for very questionable performance.

I think it began with the Lobo ST. The Cortes, deLeon, Golden, Tejon, Vaquero, Cibola, and Sandshark all have digital audio. Not sure about the Tiger Shark or Silver, never had one. Compadre was likely still all-analog.

All the last-generation Tesoro designs had digital audio.

I can't speak to what coils might be available. The only ones mentioned so far are the 8" (stock, I assume) and a 12", both solid disc style. There is nothing to prevent aftermarket coils but they are difficult to make and with a much smaller market share we'll see if anyone jumps in. But right now we need to finish the design and then see if FTP can manufacture it.

No,we will at least build out the remaining 40 or so we have parts for and then decide where to go with it.

The beach version is what Alexandre had focused on and was ready first. It did not have the small sensitivity of the (e.g.) SDC2300 and we didn't know how tough that would be to solve. Turns out dropping delay from 7us to 3us wasn't as hard as I feared, although it remains to be seen if FTP can manufacture it.

It is light and a breeze to swing. No idea on the price, that hasn't been decided yet. I've lobbied for $2k. No discrimination, it happily finds those rotten can flakes. In most places I did not find the manual GB to be an issue. But in one locale the ground varied by the meter and I found myself tweaking the GB every few swings. Once I swap the locations of the fine/coarse knobs then it will be fairly easy to use the thumb to tweak the GB control on-the-fly. As I recall, the QED has to be placed in a particular mode to adjust GB which makes it difficult & tedious. Impulse GB works in any mode.

It's strictly manual, no grab. GPX coils might work (I haven't tried it yet) but you won't get the minimum delay of 3us using them.

It's my understanding that the AQ will resume in the next 1-2 months. It will not have the drop-in batteries but will still have the clip-on NiMH pack. I finally got the green light to take the Impulse/Gold out for a field test, did so a few weeks ago in N. California. No gold but numerous small lead and quite a bit of rotted tin can flakes. Found some rough edges that need polishing but overall it performed very well. Very light & balanced, a pleasure to swing for hours. It does have the tube batteries, per Joe's photo above, and 8" solid coil. Small gold sensitivity is pretty much tied with the SDC2300, Impulse may go a little deeper on gram+ nuggets. Biggest drawback is the Impulse is currently manual GB only. Question is whether to finish what we have & release, or develop ground tracking for it.

I lived in Greensboro for many years and walked the tracks in the McLeansville area. Quite a bit of the trackside property is wooded so you're not gonna drag a PI mat around very well, and all of it is private land. But the biggest obstacle to finding this treasure is that the story itself is fake. There was no Civil War gold train and there are no pots of gold. The story originated in 1969 in True Treasure magazine which published mostly fabricated treasure stories. People like Jameson repeat those stories for the purpose of selling books.

It's a souvenir shop ring, off one of those carousels that have a couple hundred common names. Next to the keychain carousel and fridge magnet carousel.

No idea, I don't have one.

Please don't tell anyone (we're trying to keep it under wraps) but that spiffy new coil is available on Amazon: https://www.amazon.com/Fisher-inch-Coil-Triangulated-Bi-Axial/dp/B09SNVRXHC Apparently only at Amazon, as far as I can tell. Limit 2 per person. If anyone can purchase, on the open market, the new Fisher MF detector in 2022 I will send them one of my paychecks. Offer good for the first person who can show proof-of-purchase. I'm not sure why we keep aiming for the foot and pulling the trigger but it sure makes for sore feet and a red face.

I still like lead shot for a target standard though it certainly has more variation than I expected. I recently made another batch of test paddles and measured the pieces to find close-to-nominal weights, ferinstance 0.75gr for #9. Lead shot does have a few percent antimony so, no, it's not pure. BTW, lead shot is made by dropping molten lead inside a tall "shot tower." Making tiny solder spheres by hand is durn near impossible. And you'd still have to make a whole bunch and weigh them all to find the perfect size you're looking for, assuming a standard gets established. Copper wire bits will also work for test targets. Alloy and diameter are nicely consistent but length may not be, especially for very short pieces. As a piece gets longer, orientation can make a difference and orientation effect can differ with mono, concentric, and DD coils. I also use aluminum foil pieces, 25x25mm squares stacked to various thicknesses, plus 10x10mm and 5x5mm for "tiny" targets. To compare results with someone in, say, New Zealand would require that our household aluminum foil has the same thickness. Not sure that is so. All-in-all, coming up with a perfect target standard ain't easy. Everything has pros & cons.