PimentoUK

The short extension at the elbow-cup is light, it's three-piece construction - the tube is 50 thou ( 1.25mm ) wall-thickness, the joiner is short and large-bore, the end-cap is thin and hollowed-out. There's no plastic plug, obviously. The middle-rod extender is somewhat over-engineered. The walls are 2mm thick at the insertion sections, meaning they're 3mm thick over the central 33mm length. So I could've bored it to 1.5mm, and had shorter insertion overlaps. The 33mm length could've been 8mm shorter if I'd simply moved the spring-pip 12mm, but aesthetically the under-inserted rod would look ugly. Being at the top end of the rod means the weight's not felt as much as weight lower down, closer to the coil. The shortened lower rod is of course lighter, but only by 13 grams. So overall, it is a bit heavier. But I never use the coil cover, which weighs 65 grams ( for the 11" coil ). In practice the weight gain is easily ignored. The new upper rod is tricky to make due to the thin-wall ( 1mm / 40 thou ) tubing ML use. I can only get 48 / 50 / 56 thou, so I'm going to be boring out some 50 thou over a 65mm length, before I bend it, drill it etc, to make it match the middle rod. Edit: I have no plans for a folding/removeable control box, as the 10.5" coil is the limiting factor in that direction. It would've been nice if the handgrip/control-box assembly was 10-15mm ( 0.5" ) shorter, but it is what it is.

On the current Eqx, the pip-locating holes on the middle shaft are spaced 40mm apart, which I think is too far, and a spacing of about 30mm would be better if the new machines share this shaft style. Unrelated: Some people obviously like the XP GMP / Deus style of audio, which I understand has also been 'replicated' on other machines, possibly the DeepTech Vista? . A sort of all-metal with rolling tone-ID changes, leaving the user to make the decisions re: dig/no-dig. It would be worth ML considering this as an audio option on future machines. I'm certain it's achievable in single-freq mode, but in 'Multi', I've no idea.

In the thread about possible design improvements for the Equinox series, I said the breakdown of the three-piece shaft could be improved. It currently has two reasonably short upper parts, and one excessively long lower rod. To improve packing, the upper rods need to be a bit longer, and the lower rod shortened. Having done this exercise on my Fisher F75 shaft, I turned my design ideas to the Eqx. The upper rod obviously has the 'height', due to the control pod and lower stand, and this limits the compactness to 28cm / 11" in that direction. This is slightly larger than the coil, which measures 10.5" on its shortest diameter. The middle rod will pack diagonally, meaning it can be about 7cm / 2.5" longer than the upper rod. I also decided that the insertion overlaps of the lower rod, and the middle rod, could be reduced by a total of about 2.5cm / 1". So my design ended up with the upper shaft 2.5cm / 1" longer; the middle rod 2.5cm / 1" longer with 12mm / 0.5" less insertion; and the lower rod shortened by 80mm / 3.1" , with 12mm less insertion. Practically speaking, the upper rod was extended at the rear end with a bit of lathe work, with two new holes for the elbow-cup. The handgrip was moved back 2.5cm / 1", needing one new hole drilling. The middle rod was a bit more complex. I machined an extender piece that adds 33mm to the top end of the rod, trimmed 8mm off the insertion section, and moved the pip location hole 5mm towards the rod end. This makes the rod effectively 38mm longer, but only physically 25mm longer. Trimming 80mm off the carbon rod and making the new pip-hole 12mm closer to the end completes that job. The end result is the detector will pack in a 47cm x 28cm ( 18.5" x 11" ) space, see pic below. Individual rod lengths are: Upper = 47cm ; Lower & middle = 53.5cm ( 18.5" & 21" ) I ultimately intend making a new upper rod, with a bend below the handgrip, offsetting the coil and lower rod sections, which will deal with the twisting issue that's been previously discussed here and elsewhere.

"A question: When I see guys using their machines, they have to be swinging in order to get a signal, is this the case with most VLF detectors? Can you guys give me a quick rundown on some of the machines and how they detect?" Nearly all commercially available VLF machines are 'motion mode' in operation, except when in 'pinpoint mode'. A few have a 'permanent pinpoint mode' as a feature, such as the Fisher F75. One manufacturer that still makes a range of true non-motion machines is C-Scope in the United Kingdom, the CS1220XD is the flagship of the models: https://www.csmetaldetectors.com/shop/category/non-motion-metal-detectors

Geotech1 seem to get spammer problems, but their security methods to tackle it made it tougher to register for everyone else. There is this page that may help: https://www.geotech1.com/forums/showthread.php?24472

@Longbow62: Should we assume you're using the stock 11" coil ? Do you have the large coil ? Have you considered buying one?

As an electronics engineer, I have to say your project is very neat and well planned. Are you a member of Carl & George's "Geotech1 Forum" ? It's a useful resource, if nothing else, and there's always the angry Lithuanian/Bulgarian/ etc guys to keep the place entertaining. Re: the coil. I would advise designing your machine to work with a known good commercial coil, then when you're confident it's working OK, consider making your own coil. Your chances of success are much improved that way.

Here's the BBC's version of the story: https://www.bbc.co.uk/news/uk-wales-46179570 Every one of those old-time miners is named Dai ...[humour] It is possible to pan the rivers for gold, but I'm sure it's just flecks, not detectable stuff. But even that can land you in trouble: https://www.theguardian.com/uk-news/2018/may/10/police-investigate-gold-panning-welsh-river

I assume there's three 18650's in parallel, so if the best available types with 3400 mAh capacity are used, that's 10200 mAh , which is about double the nominal 5000 mAh capacity of the 26650 size. Even if more modest 2400 mAh cells were used, that's still 7200 mAh, with estimated 19 hours run-time.

I would leave it 'original-looking' if it was mine, just stick to internal tinkering. Isn't there a mod that adds 20 batteries to boost TX output? That one sounds like a good use for modern Lithium cells.

I assume that's Sven in the red top? I notice that machine has 3 additional pots on it. Do you have any plans to modify and improve your machine ?

An interesting question, BigSky Guy. The 8-pin coil connector only uses 7 pins, there's a spare. And the 0 Volt/ground of the USB port appears to be connected to one of the coil pins ( transmit cold ). So in principle, the spare pin could connect to the 5 Volt of the USB port. That then allows you to charge the battery through the coil connector. However, it's worth noting he's used an 8-pin connector for the audio output, even though it only needs 3 pins .... so perhaps he's simply wired all 4 USB pins to that connector ( and just leaving one spare pin )

Quote: "I think (could be wrong...) a rough rule-of-thumb is that an opening in a conductive shield should be smaller than the wavelength of the incident wave in order to be effective. A 2.4 GHz EM wave has a wavelength of 125 mm." Unfortunately not. The rule-of-thumb I use is to keep the aperture size below 0.1 wavelength, but the experts seem to prefer even smaller sizes. There's a reason microwave ovens have very small holes in the window screen. Here's one online guide, (though they are manufacturers of screening products, so are naturally going to encourage people to be thorough ) https://leadertechinc.com/blog/how-apertures-affect-emi-shielding/ So your shielding would have to be pretty good to seriously block the 2.4GHz Blutooth etc radio links, but they are pretty low power short-range links, so any attenuation may cause problems. I'm not sure using wired headphones is going to be a better option, either. The headphone cable is an antenna, that can couple RF signals directly into the control box. There's almost certainly some RF filtering on those wires inside the box, plus you could fit a ferrite filter on the headphone cable close to the plug. Using the internal loudspeaker would be the option worth trying in bad EMI.

My test location was going to be near a radio tower, that's bristling with directional microwave antennae, probably 5 GHz and up, but may well have lower freq cellphone gear on it, 800 MHz & up. It drives my Fisher F75 mad, I found that positioning myself so my body was between the tower and the control-box, made a significant improvement. The sight of me walking backwards across the field would no doubt have left observant onlookers puzzled. But they would probably assume I'm wierd simply for metal detecting ... so it may just be dismissed as 'fruitcake behaviour' . Adding a foil 'hat' to my detector would just confirm this. The Eqx still gets some EMI in this location ( plus probable hidden EMI ), and the body-block technique still works on it, so I think it would be a good test site for foil hats etc. I shall try and do some experiments in the next week or so.

Quote: "First Texas used EMI paint on the T2/F75 connected to ground to help although there are far better technologies now where they can incorporate conductive fibres when moulding the part. T2/F75 etc coils are moulded from conductive plastic. But there's shielding and there's shielding. A terrific shield is not desirable on a coil, as it stops it picking up metal objects. On the control box, anything from solid metal to low-resistance graphite is useful. The huge weak point in the T2 control-box shield is the massive hole in one side where the LCD is. There are ways of making a see-through screened panel, but it would be cost-prohibitive on a consumer metal detector. Edit: one possible 'see-through' screen material is the perforated sheet that's inside the glass window of microwave ovens. Next time I see a dumped oven, I may have to do some salvaging. I suppose I should point out that kitchen foil shields ( and metal boxes ) are not that compatible with 2.4 GHz radio headphone links. For info, the antenna is at the top edge of the control box, running horizontally.

Interesting, I had some tinkering ideas along these lines myself. I think it could work better if the shield (foil) was electrically connected to the zero volts / power ground of the electronics. This is accessible in two places, the M12 coil connector, pin 2 ( Transmit cold ) and more conveniently, the USB port. As you look at the rear of the control pod, it's the bottom-right contact. If you carefully cut a piece of PVC electrical insulating tape so it covered the other 3 contacts, leaving just the one exposed, it would make the experiment safer. As an electronics guy, I have some small sprung-loaded contacts ( similar to those used on the XP Deus coil charging clip), and was going to use one to make the connection, but there's lots of improvised ways to do it. I had the idea of having a short length of 3mm threaded stud sticking out. The foil would be fitted over this, punching a small hole in it, then a nut screwed on top to clamp the foil, and make the electrical connection. I do have some special solder that is for aluminium, and works OK on kitchen foil, that I could attach a small brass washer to the foil for a higher calibre bodge.

I agree with Mike H's opinion that this test has the major flaw that you're increasing air-gap to mimic a deeper coin. Problem number one is that it's not realistic, as you don't normally sweep your coil 6 inches off the ground. Problem number two is you're not being consistent - you've got one coil 6 inches above the ground, one close to it, so you've made multiple differences between tests, making a comparison almost impossible. And problem number 3 is the real flaw: adding air-depth plus coin depth together, and assuming this is equivalent to a deeper-buried coin, when it's not. When you hold a coil 6 inches above the ground, not only are you reducing the target signal, you're also reducing the ground signal. Your target signal may be reduced 20-fold, but your ground signal is reduced 5-fold as well. So you are proportionally-speaking making it easier for your detector. The ground signal a detector picks up is significant, and finding a deep coin can involve finding a target that's one-fiftieth the strength of the ground it's buried in. Seperating these two signals is what differentiates a 'deep' machine from a poor one. Tests that involve the same piece of undisturbed ground, and targets that are inserted through PVC tubes etc to varying depths, are fairly realistic. Obviously a properly-buried target is best, but that then means multiple coins at multiple depths in a test-garden. The subject of search-coil size vs performance on the F75 does interest me, as I have an F75. I saw no shortage of forum chat about how some larger coils worked well on the Tek T2, but those for the F75 always seemed disappointing. Eventually, I bought a Mars Tiger at a sensible price secondhand off eBay, so could evaluate one for myself. I was deeply unimpressed. No noticeable depth improvement over stock, and no tolerance to a small air-gap, either. So on any rough grass areas it was worse than stock. It very soon went back on eBay. ( it seemed well made and solid, with good strain-relief on the coil connector, and a little rubber boot to protect it )

Built like a brick shithouse is a quaint British expression. It refers to the days when the lavatory was not indoors, but a seperate building at the end of your garden. They were often crude wooden constructions, but better quality ones were made of bricks. A brick shithouse. And being 2m tall may have implications on your detector fit. You may want a longer shaft ... but don't forget the limited length of cable that's standard on the coil. Another reason for an extension-cable, even if it is only 4 inches long.

"They turn on but do not detect any metal. Is it the electrolytic capacitor, the flat pack The IC or is it in the coil itself that is the problem? Is that long rod a radio frequency coil?" I only have experience of the standard ProPointer, so can't comment specifically about the AT. But ... It's not the big electrolytic, it's not the microprocessor, it's not the coil. Most problems are related to the environmental factors. It's got water ingress. It's got condensation inside. It's got dirt inside. The physical beating it takes has caused a fault, such as a broken wire to the coil. I presume you've opened it up ? Look for corrosion, dirt, water staining. I would expect it to have conformal coating ( a varnish like laquer) on most of the PCB, but it's not applied everywhere. Clean it with a brush, a wet Q-tip etc, put it somewhere warm for a day to dry out. Inspect it under a lens/loupe/magnifying glass.

Here's an example of cracking on the weak point in the moulding, this one from a UK beach hunter. The uppermost of the two cracks will be the moulding flaw, I think.

Looks like H.K "Blue" Garland. A guide to panning, mining and detecting in Australasia. ( click on the image, it's actually much larger )

Oh, cool, I now have the missing 'source' button to toggle between plain text and html. And if I shrink down the page once, the sub & superscript buttons appear... though not in the 'edit post' mode, I have to shrink twice to get them then ?? But with html editing available, I think I can sort out all the trickier things. And Goldseeker's tip re: colours seems to work. Cut some text, paste it into the post as black. Then select it all, then choose a new colour, and the whole lot changes colour. A little test: Susceptibility = 250 x 10-6 units (cgs) Steve said: "I just jiggered the toolbars." ..which is OK in the privacy of your own home. HeHe. Time to try and edit some of my non-functional posts then...

Is this the icon that appears as <> and says 'code' when you hover over it? I get that one appear when I shrink things down once. It's not the same icon as Steve marked in red, the piece of paper with 'source' next to it. It gives me a blank screen, though? Shouldn't it show my text etc? I'll have to read up on that, and experiment. Years ago, eBay listings had that feature, you could just tab between plain text and html, I used it to put urls of externally-hosted images in my listings. That was when you only got 1 small image for free. But eBay dropped the feature, as clumsy html would mess up the page. They enclosed it in an i-frame for a while, to isolate it from all the other garbage they splatter all over your listing, but it still didn't work. They're too greedy. When people look at my listing, I want them to see my listing, not thousands of links to other peoples items. eBay was OK 15 years ago, not now.

I've looked at the release notes for V 4.5, released in September 2020, and it states: "Deprecated: BBCode parsing support - upgrading users will be asked during upgrade if they wish to retain BBCode parsing support." That was when there were a lot of cosmetic changes, like the 'Edit Post' moving to a drop-down menu, and evidently you chose not to retain BB code support. There's no sign of the 'switch to html' button when I post, no matter how many times I "ctrl&-" to zoom out. Likewise, I can't get the 'subscript' and 'superscript' options which CKeditor's website implies are standard options. I can't even work out how to change that line I pasted from Invisions website into blue text, so it's clear it's not my writing. I chose 'blue', then pasted the text and it pasted black. I tried deleting the first D of deprecated, changing to 'blue', typing D in the anticipation the rest would change to blue.. but it didn't, just the first D was blue, the rest stayed black. Sigh.

My proposed scale(s) actually are logarithmic, there is a fixed ratio between every value on the scale, so a mathematical formula absolutely exists that converts from one to the other. And it's surprisingly simple. Notice how I chose '40' to represent 10000 ? Well log (base 10) of 10000 = 4. Multiply that by 10 and that's the displayed value. So a susceptibility value of 40 (x 10-6) displays as 10 log (40) = '16'. And to convert back: Susceptibility = 10 ^ ( display_value/10 ) hence a display of '34' = 10 ^ 3.4 = 2512 ( x 10-6 ) units (cgs metric) And with a bit of practice and a memory mnemonic, it's not hard to learn the conversion. The decade displayed values 20, 30, 40 etc are the round-numbers 100, 1000, 10000 , and the mnemonic that "30 has 3 zeroes" "20 has two zeroes" etc. defines which is which. Having sorted out the basic decades, the 4 'fill-in' numbers 16, 25, 40, 64, well, they can be 'fudged' to 15, 25, 40, 65 with no practical loss, that makes them a bit more memorable. So.. you've got a reading of '28' ? You know '30' is 1 and 3 zero's = 1000. 28 is one reading lower, so it's the "65" value, which means it will be 650 as that's the next value below 1000. so: 650 x 10-6 susceptibility (cgs) ... or 650 ppm magnetite concentration if you're using that scale. A better way is to have an '888' display. Even if it's not used for much else on the machine, it would be great for a Fe3O4 meter. Just use the 3-band resistor code, as mentioned previously. '161' = 160 x 10-6 units. '103' = 10000 x 10-6 units. (It would be a good battery voltmeter, too. '391' = 3.91 Volts) As far as 99% of people won't use it, you're probably right .... however Tom D has observed that since Fisher/Tek started putting Fe3O4 meters on their machines, people have been mentioning their readings. I think if a decent capability meter was available, the uses for it would encourage more uptake. Tom D would actually be able to measure his sandy Florida dirt. You could probably use it to locate fire pits. I think old tracks in woodland have different mineralisation/iron levels to the surrounding land. A good meter may give evidence of this, even when other evidence, like a depression in the ground, are not visible. US park hunters often talk about 'fill dirt' , it's possible a good meter may indicate older vs.newer areas, thus enabling you to hunt more intelligently. I've noticed fields change their 'character' as you move across them. The reason being that old hedgerows have been removed. When the hedge was present, there was more activity on one side than the other. Now it's gone, this historic difference may show up in ground strength.