Geotech

Tom, I'm in the valley every month, I live in Junction City. I even do field testing up Quartzville Creek, so I drive right by White's on the way. Next time I'm out that way I'll give you a yell.

" Quod Erat Demonstrandum" "That which was to be shown" or "Thus it has been shown"

I've always been a big supporter of the independent developer, both through Geotech and my jobs with White's and FTP. The QED coulda been released years ago through White's, and probably as a better incarnation than what's about to hit the street. But I gave Howard a choice: you can either continue to throw rocks at Minelab, or you can let us build QEDs. Can't do both. Unfortunately, he picked up another pile of rocks. It'll be interesting to see how well the QED performs. Despite the way things wound up at White's, I wish him well.

I have a soft spot for the TDI-SL since it was my baby. Originally I had plans for taking it further, and if you look closely at the PCB you will see those plans. But the reality is, that platform has pretty much reached its limit, which is why I was spending all my efforts developing a whole new platform. Unfortunately, White's made some choices that killed the whole thing. Reducing the delay to 8us is easy-peasy. Getting it to work is not. Getting it to work in a way that's manufacturable is even worse. If you measure carefully, you will even notice that the 10us setting on the TDI is actually closer to 11us. If a lower delay was easily doable on the SL, it woulda been done. The reality is that the SL is fast approaching its EOL. There are new competitors on the horizon that will absolutely run rings around the TDI. If not the QED (and I'm as big a skeptic as anyone) then there are others. In the end, the only way to keep it alive will be to lower the price to $599, with free shipping. All this said, I whole-heartily encourage you to spend a lot of time & effort trying to improve the SL.

Garrett had a TM on the name "Treasure Vision" which refers to their GTI display. However, a Chinese detector called the "Treasure Vision" was already being sold in the US and Garrett was not enforcing their TM in that case. And, unlike patents, if you don't enforce a trademark ALL THE TIME you lose the right to enforce it at all. So White's could have dismissed their complaint, but chose to avoid a conflict.

The patent in question is US7310586, which covers wired and wireless data transfer (no, I'm not speculating, yes, I have the docket). It's the same patent they sued White's over when I was working there. I found prior art that would invalidate the patent but White's decided to settle instead.

Here's what I have: Pin2: Orange Pin3: Orange-shield (also connected to strain relief) Pin4: Green Pin5: Green-shield Pin1: no connect

I haven't looked at this patent so I have no opinion on it one way or the other, but I'd bet heavily that it gets approved. The US Patent Office, and the patent process in general, is widely recognized as thoroughly and utterly broken. USPTO is so overwhelmed and understaffed that most applications get only a few hours of examination; approval doesn't mean the patent has merit, and I'd guess that over half of all patents have little or no merit. Minelab is well-known to have patents on already-existing techniques, such as Litz coils and Eric Foster's ground subtraction method. They're gaming a broken system.

Karbowski was literally making them in his barn. When he died, Jimmy Normandi got all the remnants and had Roy Van Epps (the last surviving entity of the old Discovery Electronics) building them at the Discovery Ghost Factory. Roy made enough off Bigfeet to occasionally buy dinner.

Here's a little back-of-the-envelope figuring... Let's say the Bigfoot in active production can't justify a $500 price tag. Maybe $375 MSRP for a typical $300 street price. Let's say the manufacturer sells wholesale at 60% MSRP, that's $225 which would give a dealer $75 mark-up to street. The manufacturing costs for this coil will push $100, so the manufacturer makes $125 per coil. They average 10/month, so this comes up to $15,000 per year. Not really worth the effort to develop and tool up for such a coil. Now you'll say, "I'll bet the market is a lot higher than 10/month!" Maybe, maybe not. I knew the last guy who was hand-building Bigfoot coils, and 10/month was about right. And, to make matters worse, half of those he built didn't work, so he built 20 to sell 10. This would be an opportunity for an entrepreneur to step in and develop a family of Bigfeet coils, not just for White's but Tesoro, Fisher, Garrett, etc. Then your market really opens up, and makes sunk development costs more palatable. But it would still be a one-man band, not enough money to be made to hire any help.

There are 2 interference mechanisms that people are mixing in to the discussion. One is operational interference, where the active signal created by the PP couples into the main detector. Same issue people have when trying to run detectors in close proximity. It doesn't matter what the nominal frequencies are. A 12kHz PP can interfere with a 56kHz Racer. Harmonics can couple directly in and intermods can get generated that fall in-band. But because of variations in both the PP and the detector operating frequencies, along with the narrow bandwidth of the detector's baseband (typically 10-20 Hz), it will happen with some people but not others. Most of the time, the odds are in your favor. The second problem is that of inductive ringing, whereby bringing a closed coil of wire close to a detector coil will cause the detector to couple with the coil. This isn't so noticeable in a VLF detector, but in a PI detector it causes the flyback to ring. Even when a pinpointer is turned off the coil usually has a cap across it, so it can still ring (even more so, because it's resonated). The Minelab PP disconnects (opens) the coil at turn-off so it won't do this.

I'm the "Carl" half of Geotech... the Sea Hunter coil would probably work just fine. I use a Garrett XL500 PI coil on my Hammerhead design and it does nicely in the water.

Pinpointer interference is hit-or-miss. All detectors, including pinpointers, have manufacturing variance in their operating frequencies. In your experience the Minelab interfered with the Racer; someone else would say they work just fine together. The short of it is, you're unlikely to get a correct answer.

GB, on a whim I tried the Garrett BFO coil on my TDI. It's a dual 5+12, the 12" reads 120uH and the 5" reads 140uH. Each coil can be run individually as long as the idle coil is dampened to keep it from ringing. Sensitivity is poor, 4-5 inches on a nickel, but I did not re-dampen the active coil, and I'm sure it's overdamped and reducing the sensitivity. Furthermore, the ~3 ohms of coil resistance is limiting the turn-on current; the TDI has an internal 2 ohm series R that could be shorted to compensate for this, but the SL has no such resistor. So the short of it is, yes, it will work. And with some tweaking, it may work OK. But those tweaks will likely make the stock coils not work, unless you add a way to switch the damping R. Also, running the Garrett coils in series could also work, but would require each coil to be dampened to get to an overall good decay. And then, the 6 ohms of coil resistance will be a problem you can't solve.

The TDI should be just fine driving 180uH. If you want to play it safe, put a few ohms in series with it to start with. And, as I said, it'll need a different damping resistor, the TDI has 680 ohms which will probably end up too low.

I also looked at this many years ago when I did the Hammerhead design, I wanted a dirt-cheap coil that's easy to get, and there are a billion of those old Garrett BFOs still around. From my notes, the Garrett BFO coils have about 120uH inductance and 3 ohms of resistance. The TDI prefers 300uH and less resistance, maybe an ohm or so. I decided not to use the Garrett coil for Hammerhead but don't remember why, it woulda/coulda worked. It also would probably work on the TDI, in that the likelihood of damage is pretty nil, but I have no idea how it would work. Certainly the damping resistor would need modification. Lower inductance will increase the TX field but weaken the RX sensitivity, and higher R will weaken the TX field. Addendum: As I think about this some more, it seems like I may have stuck that huge 24" square Garrett BFO coil on a TDI. I was looking for a way to find my silver test cache. I must have been disappointed in the results because I wound my own 24" coil.

Jimmy contacted me a few weeks ago, said White's was terminating their distributorship. I assume it's now a done deal.

The GMT came first, MXT followed. The MXT Pro originally had 5 buttons, management said it was too complicated so I had to go with 3 and use pictures instead of words.

White's is an interesting history of missed opportunities.

Hi Steve, no apology necessary! Even though I'm on the inside, I enjoy the speculation as well.

I really wish I could reply to this thread and address several points, but unfortunately I can't. At some point things will speak for themselves, for both companies.

I'm guessing the new ML has a fixed loop because it uses a recycled military package which may have had no provision for a loop connector. I would consider this to be a severe drawback, esp at this price point. I'm also guessing that Garrett isn't using a multi-period approach to solve the target hole problem (if they did solve it, I haven't tested an ATX), ergo there is no issue with the MPS patent. I know how to do it patent-free in the TDI but it adds a lot of analog circuitry. I know better ways to do it sans TDI.

Hi everyone, thanks for the kind words. FTP is shaping up to be an interesting job. Way more horsepower and openness to new ideas, plus I get to work with Dave. Always wanted to work with Dave. Yes, you can take a TDI and force it to sample at 8us, and it may or may not work. It's certainly not mass-producible. A mass production 6-8us sampler is a different design. I've done it, but in deference to my previous employer I can't say what I done. I can say that I believe I can do it again in a way that doesn't infringe on my past, but I can't say when that might happen, as my plate is already full, overflowing, and spilling all over the floor. FTP will keep me hopping for a long time. Reg, I still owe you a call. Maybe next week when I'm back in El Paso. Meanwhile, feel free to email me. - Carl

Yikes, I wish it were so easy. The TDI running at 10us is pushing the absolute lower limit of that circuit. It won't go lower, that requires a new design. I got beat up on a pretty regular basis by certain people who wanted iron ID added to the TDI. As in, "Just take the TDI and add iron ID to it!" Yup, that's all you gotta do Ironically, I was working on a new design that went down to 6us, and had iron ID, and ground balance with no target hole. I suspect that is a Dead Horse now. - Carl