Geotech

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