Geotech

The peer-to-peer comms was done via the same wireless link used for headphones, and also for the wireless USB dongle. The code to support peer-to-peer and dongle comms was physically removed (not just bypassed) to satisfy the Minelab settlement. But you don't need any of this to "hack" the system. As anyone knows, extracting micro code from products is a $300 endeavor, courtesy of China. And with the V3, it's even easier than that (though I won't say how). When you're done, what you will have is the biggest incomprehensible mess of assembly code imaginable. V3 was written in C/C++, and to do anything with it that's the code you need to work with. But I would argue you need even more than that, you need a Jeff who understands the code and can actually do something with it. Jeffs are hard to come by, and even White's will struggle to do anything with it without a Jeff.

Yes, same exact unit, just whether you like red or green. Sunray had a nice thing going for a while. The good news is that in the world of wireless it won't be long before everyone has wireless pinpointers that mimic the Sunray mode of operation. The TRX was designed to do that (has space for a wireless module) but never got there. The Fisher/Tek models will eventually get wireless.

I signed off on final paperwork just now. First shipment may go on the truck today. Again, this is Tek only, not Fisher.

Production began today on the Tek version. Don't know if any shipped. Fisher next week. The delay was two-fold. First, when units from the pilot run were water-tested a few failed at 10 feet. We determined that the Gore membrane isn't reliable to 10 feet, so we backed off to a 6 foot rating. Second, the overmolded plastic was difficult to get right, and to make that job worse the molder (USA, not China) shut down for Christmas. But what I saw today was really nice and worth the extra wait.

Electrically, gold, silver, & copper are all "good conductors." But, while good, gold is a lower conductor. In detector-land, "conductance" has become a bit of a misnomer to describe the phase (or decay) response of different targets. The size, shape, and thickness of the target often dominates the response, although the alloy also plays a role. In PI detectors, the decay time is measured instead of phase. Gold has a faster decay because, as a lower "conductor," it has more electrical resistance which acts to kill off the eddy currents quicker. Silver has less resistance, and the eddy currents last longer resulting in a longer response time. This is an over-simplified explanation that really requires a book, or at least a chapter in a book.

When I was thinking of the cover, there was no doubt I wanted a detector wide open on the bench with all the guts exposed, and all that crap laying around it. The question was, which detector? I decided on the Red Baron because it represented such an enormous shift in hobby detectors. In the background, there is also a Tesoro (modified Bandido), White's (XL-Pro), and Minelab (Sovereign), plus a couple of home-brews. BTW, that was my real work bench at White's, and that's how it usually looked. Or worse.

Good example. In this case it's not being used as a traditional pinpointer, but as a very small metal detector. I recall someone once sawed down a Tesoro to just the handle, the uMax box, and a 4" coil. Seems that would be an ideal hut/pit detector. Tesoro Pinpointer Conversion

As you know, Mark Rowan got a patent on zero-motion disc but it requires 3 frequencies. Probably won't show up in a pinpointer any time soon. Since a PP has to run in static mode, motion disc methods are out, and you are left with old-fashioned TR-disc methods that are prone to have problems. I think that's the issue in the video.

Steve, how much iron ends up in the bedrock crevices? Is it mostly shards from old logging/dredging cables and the like? A potential problem with this is that the smaller gold is already right at the threshold of the ferrous/non-ferrous break point, so there is a decent likelihood of a wrong ID, and that goes up if the bedrock includes decent mineralization. My thought remains: if the pinpointer indicates there is something in the crevice, it is probably worth a look.

Basically it's just battery life. The F75 will actually run on 2-AA batteries, but with (a little less than) half the run time. Newer detector designs use switching regulators that can boost the battery voltage to whatever is needed. You can literally run a detector on a single AA battery. Everything internal is the same regardless of the input voltage, so a bigger battery pack doesn't offer any more depth. PI detectors can be more voltage sensitive as the TX circuit often runs directly off the battery.

I was wondering why the guy from White's posted a review of the Pro-Find. Now I know. I've never quite understood why people want a pinpointer that discriminates. When you're detecting and made the decision to dig, you want to extract whatever is in the ground. If it's clearly a good signal and the pinpointer finds iron (esp small iron), you want to pull the iron and re-scan. If it's an iffy signal, then you should already expect that there may be good and bad targets in the same hole. Pinpointing ain't the time to discriminate and, as the video demonstrates, a non-motion pinpointer will never be as competent at target disc as the main detector. All that said, I will probably eventually design a VLF pinpointer that does target ID. Gotta give the people what they want, even if it makes no sense.

Mid-Jan for the pinpointers is what I heard.

Air hots are pretty good (nickel @ 3+" @ med sens) and should be the same in ground. It has a frequency offset adjust (16 levels) so you can minimize interference.

After Jim died Jimmy Normandi bought all his Bigfoot inventory and had Roy Van Epps building them in the old defunct Discovery factory. I went there to visit Roy one day, what an eerie place, like a ghost factory. Roy and a helper were building Bigfeet that day, he said only about half of what he built would work right. Health problems forced him to stop, no idea who got all the left over stuff. There was also a big batch of stuff stored at Whites for building coaxial Eliminator coils (also Karbowski). Like the Bigfoot, those were also unique and useful.

I've been up to the Aho mines and the ruins of their cabin, very similar mine tunnels. Forestry has been installing bat grates on most of the tunnels to keep people out, but someone has come behind them and cut holes in the grates to crawl in. They're quite dangerous, the last time I was in Aho #1 a big slab of ceiling was cleaving off. When it falls, it'll crush anyone under it.

The D2 is epoxy-potted, but not completely filled. So weight can vary a lot depending on how much epoxy was used. And that can vary a lot depending on who is running the epoxy machine, it's all a manual process.

At PriorJob is found out that all official communications between the company and dealers had to be done via snail-mail because many of them didn't own a computer. I asked, do they all own a telephone? Should we play it safe and use the telegraph instead? I suggested that we require all dealers to have a computer and to understand and use email, but that didn't happen. Not necessarily. While many dealers are detectorists, some are not (inherited the business, or just a side-line), and many of the dealers are old-timers who prefer simple machines. Hand them a modern LCD-and-button interface and they don't know what to do. These are the ones most likely to still be using the telegraph, see above. As detectors get more and newer features and have graphical displays with menus, the dealers have no idea how to run them, so they're less likely to try and sell those models.

A little late on the topic... I've known and worked with a whole lot of engineers. The cliches are largely true, and Dilbert paints a fairly accurate picture of the engineering mind. When I tell people that I'm an engineer, I often see that sad look in their eyes that says, "Oh, bless your heart." My partner had that look when I first told her; now she says, "Ya know, for an engineer, you're pretty self-aware." Right out of college I worked at NASA-KSC. Only for 5 months, but ever since then my resume says "Rocket Scientist -- NASA" as a joke. Another engineer got annoyed at my joke because he thought I was trying to be a braggart. He didn't get it. Engineers often don't.

There are several ways to do a simultaneous VLF/PI. The method I did at White's is called truncated half-sine, I got a patent on it if you want the details. There are other time-domain TX waveforms that will give similar results. And there are other waveforms that are neither VLF nor PI, but perform as if they were both. At some point, we'll have to come up with new terminology for this. Probably someone's marketing dept will kindly step in and do that for us. Modulating a sine wave on a pulse would make for a difficult TX circuit design but I'm sure it could be figured out. It reminded me that I was loosely involved with a third VLF/PI effort, a design that my book co-author had conjured up. He sent me a prototype (I still have it) and it worked, but had flaws. He figured out how to fix the flaws, but then never got the time to implement the fixes. I should call him.

BFO detectors were popular in the 60's & 70's as the detecting hobby emerged. They were super-easy & cheap to build, a simple design can be made with only 3 transistors. Anyone could become a detector manufacturer. Garrett probably had the best designs, and they were about the last to continue making them, up til the early 80's. BFO is not good on depth, in any category. That's why no one makes them any more. The only thing BFO did that was semi-unique was respond well to mineralization, something you normally don't want, unless you are tracking black sand deposits. But you can actually do that with some VLF models, if you know how. Besides having the best BFO, Garrett also made the best assortment of coils. Here's an old photo of my vintage collection, in the middle is a Garrett BFO with the 24x24" square coil. It's easy to build a custom coil, it's just a single coil of wire, I think the inductance is around 500uH. Shielding is important because it's very sensitive to ground capacitance.

Yes, in radar impedance matching is critical. There are no opamps to make life easy!

Impedance matching is done on RF systems where circuits are difficult to design with low/high impedances, so they are normally designed around 50 or 200 ohm impedances. At sub-MHz, it's easy to design around opamps which don't need impedance matching. For the RX coil, the incoming magnetic field induces a voltage on the coil, so all we need to do is slap it on a non-inverting opamp. For the TX coil, yeah, you can stick it on a 3904. But usually it's resonated with a capacitor at the desired frequency. This creates a sinusoid, plus recycles energy. Not for impedance matching.

And metal detectors don't radiate electromagnetic energy by design, too. Only a local magnetic field, just like a transformer. We do our best to suppress the electric field with shielding.

That's just it, they don't. A detector coil is no more an antenna than the transformer hanging on a power pole.

Detector coils are not antennae, they are designed as a transformer. There is no EM propagation, only a local magnetic field. The coils don't have to be impedance-matched to anything. Most RX coils are just connected to a high-impedance preamp, with some token load resistor (typically 10k). Some designs throw in a few extra components to reduce EMI.