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mcjtom

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  1. Out of curiosity: is this coin different from 'the US copper penny'? Which one is the modern, copper-coloured 1 cent coin?
  2. Did anybody publish some approximate ML VIDs for modern bullets and their brass shells? I imagine that if they are not badly deformed, they should have pretty standard VIDs, similar to coins? For example, uncorroded .22 brass shells read around 9-10 on Vanquish - a 9 mm shells at about 17.
  3. Would it be safe to assume that the GB adjustments on MF detector such as the Nox would mostly adjust the location of the ferrous ground type hi-pass filter, as opposed to adjusting the range of the the other filter trying to ignore the non-ferrous salt water ground response, in general? I guess my logic is that, depending on the composition of the ferromagnetic minerals in the ground, the location of their 'time-constant' changes, but the wet salty ground signal time constant is relatively stable - just the intensity differs?
  4. It looks like there are two VID clusters for those rings too (at least in air or if the signal is strong), somewhat blurrily demarcated by an imaginary 'nickel' (or maybe a pull tab in my case) of around 13 to 15. The low karatage of most of the rings didn't seem to make much difference (or actually could contribute to increasing the VIDs due to relatively higher conductivity of low-grade 9K alloy - see the gold alloys conductivity chart above).
  5. What would be the range of possible GB type signal elimination on Nox ID scale? Somewhere within low negative to slightly positive IDs?
  6. Cheers! Would the Relic mode be the worst in your area (which I imagine has the ground leaning toward the magnetite type?), as the Relic GB is probably set more away from it (toward more conductive salty type) than the other two? But then, the Relic mode has the slowest recovery time, which may make it more susceptible to ground noise of any type... All I'm trying to figure out is if the apparent difference in GB settings between Vanquish modes can be used to ones advantage, given different ground types (for instance, would the Relic mode that seems to have GB closer to conductive wet salt, be of an advantage on the beach, as opposed to the other two, which may be closer to the right GB on the iron-mineralised ground?). It may seem trivial, given the Vanquish adjustment limitations (which may be a good thing as fiddling is limited 🙂), but I'm trying to understand my machine...
  7. Would knowing which direction the ground balance is fixed in different Vanquish modes help you any in different grounds?
  8. Yes, cheers! But I'm just wondering what the wet salt beach itself (with no black sand and without any targets), would show as falsing on the Nox (as opposed to magnetite mineralised ground). Would it be in low positive VIDs or still in low negative ones?
  9. If the Nox is not well ground-balanced on ferromagnetic ground, it falses (due to ground) in low negative VIDs, I understand? What VIDs are likely if the ground blance is off on the wet salt beach (or surf)?
  10. It appears that while GB on Vanquish may be 'fixed', it is not fixed equally between modes: in addition to other differences between Vanquish modes (recovery time, default notching, and low/mid tone break), in the Coin and Jewelry modes the GB seems to be set more towards reducing more ferrous type of ground signal (toward magnetite) and in Relic mode the GB seems to be set more towards eliminating more conductive ground signal (toward salt). If the actual ground type differ from the one assumed in a Mode, insufficiently reduced ground signal may creep in when the coil is moved over mounds and depressions or when the ground type changes over short distances, I gather. While I'm still working on convincing myself that the above is the case (to perhaps take an advantage of it once I understand it better), perhaps playing with the Vanquish modes in different ground types could quiet the machine (if the GB is the culprit)?
  11. This is probably nothing new, but often the composition/karatage of the gold alloys is reported along with the size/shape of the item on test VID vs. Target charts. It looks to me that there should be v. little difference in the conductivity of gold alloys between some 12 to 20 karat (50% - 83% of gold), so the VID differences are probably driven by mass, shape, orientation (and depth/ground type) of the object, and not so much by the gold alloy 'karatage' when it comes to jewelry?
  12. Would depth be the third variable, omitted in this chart, which would correlate with lowering the VIDs for any of those rings?
  13. 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).
  14. 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)?
  15. It looks like this may be the answer as in 'yes', if Minelab uses similar metaphor:
  16. 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).
  17. 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?
  18. 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?
  19. 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.
  20. 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?
  21. The coil is Vanquish 10x7". JB Weld original. It is detectable if the bead is large enough.
  22. 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?
  23. 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?
  24. 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...
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