Geotech

6 hours ago, Chase Goldman said:

Actually, according to Billy's reference (using X-R components), it's the frequency at which the resistive R component of the target signal that is greatest which also corresponds to the reactive X component being at it's half power (-3dB) point.

This is correct. As you go up in frequency the R response increases, then decreases. The X response always increases. And the composite vector response always increases.

The reason the R response matters is because in VLF detectors the R response is what we look at to determine when a target is under the coil. When the detector is ground balanced the R channel has no ground signal at all but the X channel does. A target shows up in both the R channel and the X channel but it is the R channel that is target-only.

High conductors tend to have a fairly weak R signal at higher frequencies but a very strong X signal. If you have really good differentiators then you can probably get enough ground suppression in the X channel to separate out big silver. Back when VLF was first introduced there was only one demodulator. In TR-Disc mode you would tune the demod phase to discriminate. In VLF mode you would tune it to ground balance. There was no separate X channel which is why the early VLFs ran at such low frequencies: 1-3kHz. It was the only way to get the R response of silver out of the mud.

The waveforms look the same but there is quite a bit of difference between them. The Deus2 actually looks a lot more like the DFX than the Equinox. It's always better to look at the coil current when figuring out MF waveforms. That can be done with a pick-up coil if you know how to do it.

If you've ever had your luggage "swabbed" in airport security they are doing the same thing. It would be amusing if TSA used rats instead.

As far as I know, the 5 changes have been done. I haven't seen any of it except for the 8" coil. The batteries are supposed to drop into the arm rest tube a la Tarsacci. This eliminates the battery pack & cable which is good. But IMO the pod also needs an overhaul and my recommendation is we don't continue without that.

I read the Kellyco page, OMG that's awful. I'll see if I can get it removed.

That's exactly how I measure the responses of various coils. I take the demod outputs straight to an oscope and measure real signal strength. That would not work for measuring the overall response of a real detector because it bypasses all the filtering & DSP, but you could take the signal off the headphone jack and put it on some kind of meter.

R9 is one of the limitations to earlier sampling. If you want to kill 2 cats with 1 stone then raise the value of R9 to, say, 2.2k or maybe 3.3k. This will lower the power dissipation and speed up the diode clamp recovery. The trade-off is it also raises the thermal noise but the SL already runs pretty quiet so it may be acceptable. Unfortunately the SL sample delay is set by firmware so you would also need a solution for that.

Dimed, I use a metronome app on my phone sand and just listen to the ticks, it's pretty easy to synchronize the sweep reversals on the ticks and still listen to the target responses.

Steve, you are right that a mechanical sweeper would be best but that's quite a project. I use a much simpler jig made of 2x4's:

I make it ~6 feet long and glide the coil right on the top board to the beat of the metronome. Targets are placed on the 3" tier* (nail-quarter-nail) which is marked in 1/2" spacings** so now I have precisely repeatable depth, target spacing, and sweep speed. There is also a 6" tier so I can do a deeper test or a staggered-depth test. I can also place Monte's nail board on a tier and test that.

I don't think it's necessary to take the audio out of the equation and, in fact, it could be really tricky to do that. I'm listening for 3 distinct audio responses and as the targets get really close together this becomes a very rapid-fire sound that might be tough to "meter." With everything else tightly controlled, it's not too hard to hear when those responses start to blend.

I came up with this back at White's and did a bunch of testing on all sorts of detectors, new & old. At that time the Garrett AT-Gold was the best at about 1-1/2" minimum spacing and the Tejon was second at 2". Most all other detectors were around 4" including the Deus which had 1st-gen firmware before they got serious with recovery speed. The old analog XL-Pro was around 8".

* not 3-1/2" as I said in the prior post

** I cut shallow v-notches for the nails so they don't roll around

While the components can handle the higher voltage, Tony makes a good point in the other thread: be mindful of the extra heat generated. A lot of people have successfully run the SL at 14.4V but any higher than that requires some careful diagnostics before you call it done. Otherwise you could end up cooking the circuit.

3 hours ago, Jeff McClendon said:

In real world, bed of nails situations there is absolutely no way that I would ever swing my coil in such a fast and haphazard way as the tester in the video you referenced. The same goes for many other testers that I have seen lately who think that swinging a coil really fast over nails and coins is a true representation of what these detectors can actually achieve in real world situations or that the one that can be swung fastest is the best for all ferrous/non-ferrous situations. I certainly will swing fairly quickly in tiny 1 to 3" swings when I have isolated a non-ferrous target in a high iron or high aluminum trashed site to zero in and center the target under the coil. I would never do that while walking a site to try and find a quality non-ferrous target in a densely trashed area which Monte's Nail Board test recreates.

Jeff, you have exactly nailed my biggest 'peeve' concerning all these separation tests: they simply don't reflect a realistic hunting style. I mentioned this in a video Calabash did showing coin/bottle cap separation. Using super-fast super-short sweeps he showed that the Deus II would ignore the BC and detect the coin. But right at the end of the video he inadvertently did a couple of normal sweeps over the combination and the Deus barely made a chirp. If, using normal hunt sweep, you don't get a good enough response to say, "Hey, what was that?" then it's a fail.

I'm not picking on Calabash, it seems that everyone is doing these tests like this. But nobody does normal hunting with a 3" sweep at a blistering speed. Yes, it might be used for zeroing in on a suspected target, and for that these test results are useful, but you need the normal hunt results first.

When I test separation I use a 1 meter sweep at 1m/s set by a metronome. My preferred target arrangement is a silver quarter placed between 2 transverse-oriented 16p nails, all at a 3-1/2" depth. I reduce spacing until the detector can no longer issue 3 distinct target responses. A lot of people test by placing the nails longitudenally but this becomes a test for a co-located composite response instead of a separation response. If you understand why nails give a double-beep when swept longitudenally then you will understand the mechanics of this test.

They probably have a better PI design in the ATX, but it's overweight and desperately needs a new body. The V3 was a marvel of software development but the hardware was sub-par. I doubt anyone will be able to take the existing design and do much with it.

The only detectors that White's made that are worth continuing are the MXT-based designs (GM-24k, MX-Sport, MX5, etc), the TRX pinpointer, and the TM808. Garrett is making the GM-24k and I expect they will not make any other MX models. I think they will never make the TRX because it adds nothing to their already-dominant position. The TM808 would be a good addition, maybe they'll eventually add that one. Otherwise, I'm at a loss as to why Garrett bought them in the first place.

The TDI-Pro-Oz is identical to the TDI-Pro except it has a normal mono coil instead of a dual field coil. The DF coil has some lift-off issues on severe ground.

I designed the TDI-SL and deliberately made the PCB to fit either the metal case or the Beachhunter case. I had the factory build 3 prototypes, they tested fine but mgmt wasn't interested. A few years after I left they finally released it.

There are some mods that people have done to the SL which slightly improve it for nugget hunting. I doubt the BH would benefit as much. The bigger battery is probably the best upgrade.

The TDI Beachhunter uses the TDI SL board which I designed to take 20V, even more if you swap out a few caps. My prototype has fewer controls, I don't remember exactly and I'll need to dig it out to see.

I have an original prototype I built at Whites, it's a little different than what finally got released years later. I haven't thought about selling it but might consider it.

I know this is an old thread but I would not recommend using the TDI Beachhunter underwater. Both the coil and the case are notorious for developing stress cracks and leaking. I would consider it splash proof at best.

On Sundays the place is usually deserted. When I used to visit I was often the only one there on weekends. When the factory is running on Saturdays they all park off the left side of the photo. My office is the first window to the right of the main entrance. Haven't seen it in 2 years.

I've moved from Oregon to Republic, WA and am looking for anyone familiar with prospecting in this area. Ferry County has produced somewhere around 4 million ounces of gold and still has active gold mining going on. In particular, I'm looking for places that would be good test grounds for metal detectors. Feel free to respond on the forum, or via PM if you prefer.

Thanks,
Carl

Wish I could say what's going on but I have no idea. I'm as much in the dark as everyone else.

There are two "balance points" to consider: the angle balance point, and the sweep balance point. The angle balance point is what most people are considering, and the ideal location is at the top of the handle. When you grab the handle the detector should have a rest position of about 45°.

The most perfect point for sweep balance is right where the elbow ends up. That's where most people pivot their swing. Any net weight forward of the elbow creates a moment of inertia that must be overcome by torque. Even a detector that has good angle balance but is heavy (like the CTX) still requires a lot of torque at the reversal of each sweep because there is considerable mass forward of the pivot point. A detector like the Deus has practically all its weight at the far end of the rod so it feels nose-heavy (poor angle balance) but still requires less torque (better sweep balance).

Showing a detector balanced on a pole halfway down the shaft says "poor angle balance" and suggests that the sweep balance may also be poor, unless the overall weight is exceptionally low. I suspect that an XP GoldMaxx with the box mounted under the elbow would have better angle balance and sweep balance than any of these newer models.

It's my understanding that for u/w you have to run a clip-on antenna from the pod to the coil, same as with Deus 1. The bone-phones either do the same or simply plug in to the M12 connector on the back. Underwater Scuba comms and model submarine remotes use the lower VLF band which probably doesn't have the bandwidth the Deus needs. I suspect they continue to use the 2.4GHz ISM band which only travels inches in seawater, ergo the need for wires.

The plug on the bottom is likely a vent plug. For diving it obviously needs to be sealed, for weatherproof it can be unsealed for breathing. This is important for altitude changes, especially on flights.

😢 *Sigh*

I read that Kellyco spiel and just shook my head in disbelief. Sadly, it appears to have been written by someone here at FTP. I honestly don't know what to say, other than I feel like I owe everyone an apology.

I'm 100% with Steve on this. I don't care for wireless coils for the exact same reasons. For every coil I want to buy, I'm actually buying another detector. Also don't care for a cable inside the shaft, creates more problems than it solves. Yeah, those clean shafts look cool but that ain't enough to make metal detecting look any less uncool than it is.

Those are the pics I've seen.