Geotech

It's a custom made display, you can only get it from Nokta.

I have little practical time with this coil but I did take a prototype to the coast to try it in the surf. I found that it slices through water better than any other coil I've ever tried. Unfortunate that there is no MF detector to bolt it to.

8 hours ago, mcjtom said:

Could you describe the 'double ring' of iron at depth (as opposed to nonferrous single ring as iron at depth)?  Near-surface ferrous targets could double (or triple) ring for different reasons - does it sound different than the 'double ferrous ring' at depth?

 

p.s. A question probably for @Geotech: does it make sense to explain the 'double ring' of iron target at depth as:

1) the Tx magnetic field magnetizing the ferromagnetic target by induction and the target returning the signal immediately, in phase,

2) the same alternating Tx field inducing eddy currents in the target which in turn produce Rx magnetic field, but this time the return is delayed.

The delay between the two returns changes the way how a target sounds?

I don't know how it sounds on the Equinox (and possibly on Vanquish by association), but I tried to imagine why deep iron should 'double beep' but deep nonferrous could show like iron but not 'double beep'...

It's the same issue as described here. A shallow iron target will double-beep even with a brisk sweep but with deep iron the two beeps blend together (due to the geometry of depth vs coil size) unless you slow down the sweep rate.

Deep non-ferrous can start to look ferrous because the ground response (with is almost purely positive-reactive) overwhelms the now-tiny negative-reactive portion of the non-ferrous, so that the target's reactive signal ends up looking ferrous. This is more likely to happen with low conductors than with Big Silver Coins. It also depends on the quality of the ground filters. Less likely to happen with the old 4-filter designs, which no one makes any more (AFAIK).

Shallow non-ferrous can double-beep because as you get really close to the RX coil the edge of the coil becomes more sensitive than the center. Gold prospectors use this to "edge-detect" really small nuggets with PI mono loops.

I need to make some pattern measurements on a Cleansweep coil for my book. If anyone has one (either 4pin or 5pin, doesn't matter) and willing to loan it, I'll pay shipping both ways. I have a Cleansweep which has been sitting in a box for 10 years, I pulled it out and the null has shifted so badly it is unusable.

21 hours ago, phrunt said:

Why has it taken so long for other detectors to do the same?

Dunno, I proposed this at White's and again at FTP, no interest.

1 hour ago, markinswpa said:

The way I see it SMF is 6 year old technology and most agree  that its peaked.

SMF is either 23 or 33 years old, depending on your definition of SMF. And I would not be so sure it's peaked.

That confirms what I've heard: high-end multifrequency with color display. From what I know they started work on this 12-13 years ago. It'll be interesting to see if they borrowed anything from the V3.

Apparently Republic is the gold capital of Washington State. 8 million ounces and still going. But few places for prospecting, it's all deep hard rock stuff. Almost ended up in White Salmon, gorgeous area.

Where abouts in Washington?

I posted a reply to Woody's video. The ferrites shield the solder connections so they don't light up with sudden changes in ground mineralization. Woody mentions this late in the video but doesn't seem to think that's what they're for.

The core purposes of VFlex were (1) to transmit coil parametrics (like "this is a 10" DD coil optimized for 18kHz") to the control box and (2) to use a security check to limit 3d party coils. Whether or not #2 was an afterthought I don't know, but I suspect it was planned and deliberate, as it was for printer cartridges. A great way to limit competition. Otherwise, a simple resistor in the coil could be used to ID the coil type.

The inclusion of a preamp in the coil might be considered part of VFlex, but in reality it has nothing to do with the micro that is the at core of VFlex. That is, you can do VFlex without the preamp in the coil, and you can put a preamp in the coil without the micro. But if there is no micro in the coil, then there is no VFlex. I don't recall that the original Go-Finds used VFlex, but the newer models apparently do.

11 hours ago, Aureous said:

Good to see that the designer is given credit right on the front...eh @Geotech??? 😉 

LMAO, I like that the coil appears to have a metallic housing. I would design it with vibranium, besides being durable it does not support eddy currents so is not detected.

Placing the preamp in the coil improves noise immunity because the RX signal from the coil to the control box is now driven by a low impedance and has also been gained up. Minelab started this with the original X-Terras (30/50/70) and I assume all their detectors are now designed this way. I'm not sure if Garrett or Nokta do this, and XP obviously does.

Looking for an 8x9 and 10x12 that will run on the 10/12 kHz models. Might also consider 17kHz coils.

I've never seen a screen cover "go bad." However, the display might. It's not clear when you say "the face don't light up very well" whether you mean the backlight isn't working well or the display itself is faded. But both can happen. Also, indoors it can be hard to read without the backlight. So first, I would take it outside or make sure the backlight is on. Next, I would pop off the pod faceplate (it snaps on) and look at the screen without the screen cover.

5 hours ago, Steve Herschbach said:

But maybe we are just talking semantics. What you think of as a hole and I think of may be different things. To me a hole occurs when a detector will not pick up a nugget it should pick up due to whatever ground canceling method is in use also knocking out the gold target.

In a detector with only a single GB channel (like the TDI), it is possible to find a small range of conductivities at the conductivity transition point that are severely suppressed. When I air test the SDC with a continuous array of conductive targets, I can easily find the two transition points between the three regions. I could not find any range of suppressed targets with the SDC, target detection through both transition points was quite good. This tells me that the mathematical target holes are filled in.

Again, that's in air. If particular targets are then lost in particular ground, then that could be due to the way the tracking algorithm is working, rather than the mathematical target hole. I suspect the same thing would happen in a multiperiod detector. In other words, you can eliminate the mathematical target hole with either multi-TX or multi-RX, but you will likely still face the same issues with certain targets in certain ground. I can see calling that a "target hole" but it may be a completely different issue.

This was linked from another recent thread, and I don't recall reading it before. So another better-late-than-never reply.

Quote

From Brent Weaver:
"but if they are a single pulse detector, they are going to have a hole in their detection, period."

This is not necessarily true. The SDC2300 is a single pulse detector and it has no target hole.

The reason for a target hole is that eddy responses have an exponential curve and viscous ground responses have a power law curve. A "single channel" GB detector takes 2 samples of the response curve, and 2 samples (basically a straight line) are not enough to distinguish the two types of curves. Therefore, there will always be a 2-point eddy response that matches the 2-point ground response, and this gives you a target hole.

The target hole can be moved around in a number of ways. Changing the TX pulse width will do it, but so will changing the sample timing or even the bandwidth response of the preamp. So, as Brent says, you can create a detector that transmits 2 different pulse widths, with their own RX channels, and they will have target holes at different places so that, when combined, there is no overall target hole.

But you can do the exact same thing with a single pulse detector, by creating 2 RX channels that place the target holes in different places. Again, this can be done by using different preamps, or by simply creating 2 channels with different sample timings. Normally, each channel takes 2 samples but they can be combined. Above I said that 2 samples are not enough to distinguish the two types of curves... but 3 samples are. You can create a first channel that takes Sample1 and Sample2 and this will give you a target hole, call it Hole1. Then you take Sample1 and Sample3 and this gives you a different target hole, call it Hole2. Combine the 2 results and there is no hole.

You can actually hear this result in the SDC as it gives a wee-woo response for very low conductors (below Hole1), a woo-wee response for medium conductors (between Hole1 & Hole2), and a wee-woo response again for very high conductors (above Hole2). All with a single TX pulse width.

Offhand, I can't think of a PI design that will be damaged by turning it on without a coil connected. In fact, it would be engineering malpractice to release such a design. In designing and building PI circuits, I hot-swap the coil all the time and don't think twice about it. That said, I suggest following the manufacturer's recommendation.

I just checked out the new forum. There are 6 threads, and 3 of them are spammers. If you're gonna run a forum, you gotta stay on top of it. Not only being vigilant with spammers, but also by stimulating conversations and keeping the personal sniping under control. I enjoyed Dankowski's forum in the past but it's really lost the plot and everyone seems to have left. I doubt a new forum script will fix that.

@Aureous is correct. At White's the coil housings and skid plates were made with an ABS/polycarbonate blend, don't recall the ratio but maybe 50/50. ABS alone wears quickly, PC alone wears well but is brittle.

Can you post photos of the control panels? MW might be "modulated waveform," makes a different sound in the receiver.