mcjtom

Would depth be the third variable, omitted in this chart, which would correlate with lowering the VIDs for any of those rings?

Would at least these general statements be roughly correct? Whether measuring the response phase change in a single frequency or comparing the responses in different frequencies in MF (and also disregarding how such GB scale and its 'zero' or default are implemented in a particular detector), the ground balance objective is to filter out (ignore) the slow-changing responses caused by moving the coil over the ground minerals devoid of valid, smaller/weaker, targets. Rather than targeting all slow-changing signals, the filter tries to decrease only those on the ferrous-conductive 'ID' scale that the particular mixture of minerals in the ground is likely to produce (i.e. preventing unnecessary removal of slow-changing signals in the range outside of the minerals-mixture), but it needs to be shown (set to) what range it should be. Pumping (or even sweeping) the coil over given soil simulates such slow-changing responses and allows the machine to detect the ferrous/conductive nature of the signal due to the ground in order to subsequently aim the filter (automatically or manually) at the most consequential slow-changing signal range to be decreased by the filter and thus best quiet the machine on this ground type. If the ground signal increases when moving the coil towards the ground, the machine GB (the particular range of 'IDs' for slow-changing signals set to be filtered) is off and the filter range is incorrectly set too much towards removing slow-changing ground signals in the ferrous range, best represented by magnetite (at the expense of insufficiently filtering the true ground response which may be in the more conductive range, i.e. towards the salt). If the coil 'sings' when being moved away from the ground, it indicates that the machine GB is also not set optimally, but this time it is trying to filter the higher conductive range (closer to salt) whereas the actual soil response may be in the magnetite range and remain unfiltered (thus producing the false signal caused by spacial changes in soil composition or changing the coil-to-ground distance).

Would my understanding of this be correct then: if pushing the coil towards the ground produces signal, it means that the GB value is set too high for this ground (on Fisher's scale) and too low on Minelab's scale (and when pulling the coil up, the reverse is true)?

It looks like this may be the answer as in 'yes', if Minelab uses similar metaphor:

I made a 1.23 g bead That's probably close in size to a sphere 11 mm in diameter? - JB Weld density is some 1.93 g/cm^3 (from MSDS).

Tom Dankowski seems to suggest that any metal near the coil can disturb the balanced magnetic field around it and create blind spots even if not moving wrt the coil. But then the cable connecting the coil with the control box should influence it too. Maybe the mas of metal wires in it is not significant enough or perhaps being off centre makes it less influential? Anyhow, it looks like one may be better of using an epoxy without steel filling when working around the coil, just in case... I guess the question is: is it worth to reinforcing the ears at all - do they really break off easily? One reason I have for it is that I remove coil from the shaft to make the machine more compact and be able to fit the parts in a duffle bag I use on the motorcycle - so maybe it makes sense to make it stronger before it's too late?

The Vanquish evidently does something useful with sorting out the changing ground signal strength and type (at least on the beach). A question for those that used both machines: does it behave as if the ground balance was fixed (e.g. similar to zero in Beach 1 mode on the Nox) or more as if there was a Tracking ground balance in action?

In the photography world, Fujifilm got itself a lot of fans and good will (and thus sales I imagine) by promoting Kaizen - updating firmware of cameras long discontinued and replaced with newer models. Fuji X-E2 is a great example - the last firmware update made it into a totally different and better camera. Fuji didn't have to do it.

A bit off topic of building coils, but I was thinking of buying this detector vs. Nokta Pulsedive for snorkeling and light diving. Have anybody tried both and could offer some comments on what to expect and which one would be a better idea?

The coil is Vanquish 10x7". JB Weld original. It is detectable if the bead is large enough.

I was considering reinforcing the coil ears with some fiberglass and epoxy (on the outside). Two questions: a) does it make sense to do that at all? b) I'm partial to JB Weld for the epoxy part, which is non-conductive (the steel powder is fine and the particles isolated by the epoxy matrix), but it is relatively ferromagnetic. Even though the ears don't move with respect to the coil, would it have a potential of disturbing the magnetic field so close to the coil, as I understand some metal lower rods and bolts did in older detectors designs?

Given that Vanquish has been described as a simplified Nox, and that its settings (fixed or somewhat adjustable) can be approximately related to those on the Nox (e.g. the overall mode probably similar to Beach 1, high iron balance likely about 8, three different recovery speeds within recovery speed range on the Nox - but I'm not sure where), could someone comment on what ground balance mode on the Nox resembles what the Vanquish may have been set to do in this department?

What platform does the forums use?

Was that resolved? I have no idea, but something tells me that at high iron-bias the the non-ferrous signal is replaced by the ferrous one, if below threshold...

Does it mean that if I’m finding lots of pull tabs on a beach I should be happy that the machine works, but I’m in the wrong spot, more or less? 🙂

To recover such deep targets from wet sand, are you using a scoop, and if so a big or a small one? I'm set on a small, round, SS scoop, but I can only imagine how useful it may be on the wet beach...

Not a plot and a random source, but it seems that adding copper to silver lowers the conductivity of the alloy in similar fashion to gold-silver/copper alloys, below the conductivity of either pure metal. fichesthesscopag2 (3).pdf

CooB has an interesting 'beach shovel'. Would anyone have any experience using it (or something like it) on the beach (or elsewhere)? http://scoopbycoob.com/?product=new-model-stainless-steel-2-0mm-shovel-for-digging10mm-hexahedron-holes

Many thanks for all these! What would be the minimum useful thickness of a stainless steel plate (excluding rod socket reinforcement) of which the scoop is made? Would 1.5 mm be the magic number, balancing the weight and sturdiness?

I got myself a cheap poly-carbonate sand scoop. It's kind of sturdy, but I already found that it doesn't work particularly well, especially in wet sand, for at least three reasons: it's not as sturdy as stainless steel and digging the gravel is not easy, the holes are not big enough for the wet sand to fall through easily (I think I need a mesh at the bottom somehow), and, for compactness, my scoop doesn't have a long handle, which makes it pretty difficult to dig quickly and often... I was hoping that somebody could point me out to a better scoop that I could either buy online (Amazon, Lazada - the latter is better as there are no import duties in Thailand) or that could inspire me to ask someone here to make for me. The ideal one would be: small in size with the mesh that allows the wet sand to fall through (but, which would also allow or the scoop to be pushed into the sand with one's foot) with a longer handle, possibly removable (but not the full length as it won't be portable enough the way I do it - motorcycling...) cheap... (I know, but one has to start somewhere...). Cheers!

https://www.theguardian.com/world/2022/jan/12/landmine-hunting-hero-rat-dies-in-cambodia-after-stellar-career?CMP=Share_iOSApp_Other

This has been said many times, but there is nothing like seeing it. I can’t tell the difference between those particular two, in any orientation, either by sound or ID (on Vanquish 440). Are there any tricks of the trade to increase the chance of differentiating the right-size gold ring from a modern beer can pull tab?

Not a review, but a chart of the Vanquish 440 correlation between the target IDs, tone breaks, and the notch bars - which I believe is correct and helpful, but missing from the manual - before the original post is buried deep. The target ID scale on this detector is non-linear, with the middle range between 0 and 20 stretched and both ends compressed. The break points between tones, except for one case of Low-Med in Jewelry Mode (at VID 0|1) do not correspond to break-points between notch segments. The yellow values, below the target identification guide graphics, represent the standard response (+/-1) for modern (Rama IX/X, 2008+) Thai Baht coins, when the target signal is strong. After the Factory Reset (press the Power button for 7 seconds when starting), the Custom mode reverts to the Coin mode (and its recovery speed and the low/medium tone break at the VID 2|3), with a particular notching: only VIDs 11-13 and 21-40 ranges are notched in. The accepted notches correspond to the ranges of modern US coins signals.

Cheers for that! The question was really about the particular choice of Minelab's default notching in the Custom mode, not how to change it. I think I might have figured out the answer: the notching-in corresponds to all modern US (but not Australian) coins with the nickel at around 13 and the rest at 21+.

There is an interesting factory preset for custom mode: based on Coin mode with its fast recovery time and low/medium tone break at ID 2/3 but only ID 11-13 and 21-40 ranges notched in. What may be the intended purpose of it?