Xtrem Hunter

[Carl-NC]

We have plenty of large iron junk in our old farmland. Mostly plough blade parts and related items like harrow tines. Also plenty of iron sheet metal. So all my hoard hunting ends up locating endless quantities of that junk, in some places a piece every 2 metres. So some non-motion discrimination, that is accurate at determining large iron is 'IRON' would be pretty handy.

Same is true in the US. A lot of the big iron pieces will often ID as non-ferrous because the eddy response is stronger than the magnetic response. To better ID iron, you need to analyze the signal through the whole sweep, or use multifrequency.

Many sites that are pasture land, and have been left uncultivated for 100+ years seem to show noticeable variations in ground signal from one spot to another. So using a single-freq machine in non-motion mode gives you the problem of continuously sensing just ground-signal changes ( and of course NOT sensing weakening ground signal, which ultimately reduces sensitivity to wanted targets.) So ... reducing sensitivity to the ground is a desireable feature.
One obvious 'solution' should be the use of multi-frequency ( two is enough, I would think ).

You can solve this either with a ground-grab feature or with slow motion operation (not quite no-motion). With 3 frequencies you can theoretically make a zero-motion detector that cancels ground and discriminates iron.

Another would be the use of search-coil arrangements that inherently cancel ( partially, at least ) the ground signal. So, just as the 'Bigfoot' coil has a figure-8 Rx coil ( and mono Tx ) , a two-box 'equivalent' could be : a three-box. A middle Rx coil, and two Tx coils either side, in anti-phase. Like an existing two-box, but with another Tx the other side of the Rx. The Rx is in induction balance with each Tx individually, but the anti-phase wiring of Tx's means lower sensitivity to the ground ... provided the detector is held level. Multi-freq or single freq should both be compatible with this coil arrangement.

You probably want a [ RX- | TX | RX+ ] configuration instead, as having 2 out-of-phase TX coils produces a far-field null that limits depth. The DOD coil used on the GPZ is an example, and the 19" might even be a good size. I would probably prefer a coplanar coil to an orthogonal coil because it's something you can swing and cover ground faster. Probably the only way I would use a 2-box is with data logging and a mapping program. White's sold a boatload of TM808s to cache hunters, and I thought it was a fairly poor choice for this. My 808 was unable to detect my cache (220 silver quarters) buried 60cm deep.

And I think Audio presentation is important for this kind of machine. It seems that use of stereo audio could bring benefits.
The three-box setup will presumably have 'Bigfoot' behaviour -( different response to targets under the 'heel' and the 'toe' ) , stereo audio may be helpful in picking out the different responses ?

My preference is to use stereo to put AM in one ear and Disc in the other. Even when you want to discriminate iron, it's still very helpful to hear everything in the ground. The AM signal lets you distinguish very close targets.

Also - the choice of operating frequency is worth some thought. It seems there is a concensus that a low-ish freq, like 5 to 8 kHz is the smart choice, presumably making some assumptions that the target is moderately high in conductivity. This may not in fact be the case, and my hunch is that a higher freq may yield better results ... perhaps 12 - 18 kHz range for single freq operation, and (12 plus 36 or 48 ) if going multi-f ( 12/36 or 13/39 for a 3:1 ratio, a la Fisher CZ-series, or 12/48 for a 4:1 BBS system ... or something like Park2 / Field2 on the Equinox, with 18.2kHz as the 'dominant' and 8.2 / 39k as ground rejection additional freqs. ( if I ever found time to make the beast, my 3-box would be on my Fisher F75, 13kHz single-freq. ... I think making such a contraption for my Equinox would be too ambitious )

In the US most hoards will be high conductor coins, like silver dollars or halves. For these, you want a low frequency, even down to 1-2 kHz. The hoards I've seen in the British Museum are mostly small thin coins so a higher frequency (15-20 kHz) will work better. The technology that might work well is that given in US11022712. It could be set up as a 3 frequency TX (say, 1/5/25 kHz) with the weighting shifted low or high depending on what you are searching for.

Thanks for the feedback. I think the important points are

• Ability to handle dynamic ground conditions
• Really good iron ID, especially with big iron
• Super slo-mo or zero motion
• Depth depth depth

On the last point, a TX that can put out an enormous signal would help. Maybe even a harness-mounted battery like the older GPX. You'll have to deal with the channel offsets due to the coil null but that's manageable.

[Skippy]

"A question : why is there no such detector on the market so far?"br> It's a VERY niche part of the hobby, that almost no-one does. So there's few products made for such hunting.
I once asked for advice on hoard-hunting techniques over on the Dankowski Detectors forum ( this was back when it was quite active ) . And I got absolutely Zero Zip Nada responses, not a sausage. Thanks, guys.
When XP released info about the ( new D2-based ) two-box, someone posted about it on a very popular U.K forum. Nearly all replies were insults or jokes. "does it pick up satellite TV signals?"; "How much? My car is worth less than that" ; "Who is going to drag that thing around for hours on end, Mr Universe?"; " who wants to dig 5 metre deep holes?". Moderators deleted nearly every post, those that remained didn't seem to be from potential customers, itching to get their hands on one.
Perhaps it would be a good Geotech1 project, seeing as commercial manufacturers are not that interested.

[ivconic]

Apart from the remarks on ergonomics (with which I agree), the rest of the remarks are of a purely technical nature and can be discussed further.
But that wasn't my point. When you asked about the detector for hoards, I suggested that model because I worked with it and it performed very well.
As long as the detector is doing a good job; I am not at all interested in the technical side and what is "under the hood".
The ML Relic Hawk will remain high on my list of the best I've owned and used.

[Riss]

I disagree!
I had 2 of those during the years.
Excellent relic and hoard hunter, and I mean it, no jokes at all.
What bothered me all the time was the large enclosure and lack of speaker, I don't like to use headphones.
In fact; recntly I redrawn and refined the pcb desing and intend to order 5pcs pcb at JLPcb, intend to diy few of those.
Just for my own pleasure.
ML Relic Hawk and ML Musketeer are the one and the very same machine with few small differences.
Relic Hawk is having 3 switchable modes for the "recovery speed" while Musketeer don't.
Musketeer is having the speaker while Relic Hawk don't.
And that's about all for differences.
I had fantastic deep finds with Relic Hawk, some incredibly deep Roman coins.
So I am pretty confused with your claims upon it.
But.. as they say: tastes and choices are not discussed.

However, I disagree with your disagreement …

1. ergonomics for village idiots training to lift weights -garbage garbagе
2. oscillator – garbage
3. circuit engineering to integrators – garbage
4. double differentiation schematics ( second order Butterworth High Pass filter ) - garbage
5. sensitivity to leaks and moist air ( 10 Megaohm rezistors ) - garbage
6. the circuit board and box design - heavy, bulky , ext. – garbage

I don't want to go on anymore, that's enough
For several months my problems with the Internet are constantly growing - to write this took me 1 hour and 15 minutes !!!

[Riss]

Skippy - I enjoyed reading your posts .A question : why is there no such detector on the market so far? -what do you think are the reason(s) ?

[Skippy]

Also - the choice of operating frequency is worth some thought. It seems there is a concensus that a low-ish freq, like 5 to 8 kHz is the smart choice, presumably making some assumptions that the target is moderately high in conductivity. This may not in fact be the case, and my hunch is that a higher freq may yield better results ... perhaps 12 - 18 kHz range for single freq operation, and (12 plus 36 or 48 ) if going multi-f ( 12/36 or 13/39 for a 3:1 ratio, a la Fisher CZ-series, or 12/48 for a 4:1 BBS system ... or something like Park2 / Field2 on the Equinox, with 18.2kHz as the 'dominant' and 8.2 / 39k as ground rejection additional freqs. ( if I ever found time to make the beast, my 3-box would be on my Fisher F75, 13kHz single-freq. ... I think making such a contraption for my Equinox would be too ambitious )

[Skippy]

Quote:"What would make a good hoard detector design?"
I was also wondering what he had in mind ....
As I've done some 'hoard hunting' in European conditions, I do have some thoughts about what would be desireable features.

We have plenty of large iron junk in our old farmland. Mostly plough blade parts and related items like harrow tines. Also plenty of iron sheet metal. So all my hoard hunting ends up locating endless quantities of that junk, in some places a piece every 2 metres. So some non-motion discrimination, that is accurate at determining large iron is 'IRON' would be pretty handy.
My general feeling is the 'standard' two-box implementations are TOO big, and what is needed is something inbetween a large conventional coil, and the usual two-box size.
Many sites that are pasture land, and have been left uncultivated for 100+ years seem to show noticeable variations in ground signal from one spot to another. So using a single-freq machine in non-motion mode gives you the problem of continuously sensing just ground-signal changes ( and of course NOT sensing weakening ground signal, which ultimately reduces sensitivity to wanted targets.) So ... reducing sensitivity to the ground is a desireable feature.
One obvious 'solution' should be the use of multi-frequency ( two is enough, I would think ).
Another would be the use of search-coil arrangements that inherently cancel ( partially, at least ) the ground signal. So, just as the 'Bigfoot' coil has a figure-8 Rx coil ( and mono Tx ) , a two-box 'equivalent' could be : a three-box. A middle Rx coil, and two Tx coils either side, in anti-phase. Like an existing two-box, but with another Tx the other side of the Rx. The Rx is in induction balance with each Tx individually, but the anti-phase wiring of Tx's means lower sensitivity to the ground ... provided the detector is held level. Multi-freq or single freq should both be compatible with this coil arrangement.
And I think Audio presentation is important for this kind of machine. It seems that use of stereo audio could bring benefits.
The three-box setup will presumably have 'Bigfoot' behaviour -( different response to targets under the 'heel' and the 'toe' ) , stereo audio may be helpful in picking out the different responses ?

[ivconic]

...Karl, come to Bulgaria and you will understand ...When a class engineer gets acquainted with Roman settlements , and digs up a few cubic meters, then his insight comes to visit …

I agree with this. Over the years I have noticed on the forum that "western" engineers lack the experience of such sites and soils as we have here.
I guess it's a good idea for Carl to visit you in Bulgaria. Unfortunately, I do not think the same for Serbia and me personally, because I am not in a position to organize such a thing.

[ivconic]

Sorry , but Minelab Relic Hawk is complete garbage . I have repaired 2 pieces , I've had his schematic for about 20 years . Karl, come to Bulgaria and you will understand . Just kidding , but also on the territory of Serbia you can answer the question yourself . The requirements are many -sensor system type , current through a transmission coil , ext . This is all discussed here . When a class engineer gets acquainted with Roman settlements , and digs up a few cubic meters, then his insight comes to visit …

I disagree!
I had 2 of those during the years.
Excellent relic and hoard hunter, and I mean it, no jokes at all.
What bothered me all the time was the large enclosure and lack of speaker, I don't like to use headphones.
In fact; recntly I redrawn and refined the pcb desing and intend to order 5pcs pcb at JLPcb, intend to diy few of those.
Just for my own pleasure.
ML Relic Hawk and ML Musketeer are the one and the very same machine with few small differences.
Relic Hawk is having 3 switchable modes for the "recovery speed" while Musketeer don't.
Musketeer is having the speaker while Relic Hawk don't.
And that's about all for differences.
I had fantastic deep finds with Relic Hawk, some incredibly deep Roman coins.
So I am pretty confused with your claims upon it.
But.. as they say: tastes and choices are not discussed.

[Riss]

Minelab Relic Hawk with 39cm coil was quite a hoard hunter at the time.
You can make it by yourself, we have the complete documentation posted on the forum.



Simpler the better.
I gave an example above.

Sorry , but Minelab Relic Hawk is complete garbage . I have repaired 2 pieces , I've had his schematic for about 20 years . Karl, come to Bulgaria and you will understand . Just kidding , but also on the territory of Serbia you can answer the question yourself . The requirements are many -sensor system type , current through a transmission coil , ext . This is all discussed here . When a class engineer gets acquainted with Roman settlements , and digs up a few cubic meters, then his insight comes to visit …

[ivconic]

Over 100 years have passed since the invention of the first metal detectors , but there is no detector on the market with features I want ( detector for hoards ) . I know it can be done , i know how to do it . Unlikely ever to be on the market …

Minelab Relic Hawk with 39cm coil was quite a hoard hunter at the time.
You can make it by yourself, we have the complete documentation posted on the forum.

What would make a good hoard detector design?

Simpler the better.
I gave an example above.

[Carl-NC]

What would make a good hoard detector design?

[Riss]

Over 100 years have passed since the invention of the first metal detectors , but there is no detector on the market with features I want ( detector for hoards ) . I know it can be done , i know how to do it . Unlikely ever to be on the market …

[ivconic]

If the question applies to the 2box coils; the answer is NO!
If the question applies to Deus II itself; the answer is MAYBE, I'm waiting to see a lot more positive results before I decide to spend that money on a new toy.
Because times are hard, the search is slowly losing its meaning, the fields are totally explored... Deus 1 is a sufficient toy for now and everything else is a luxury.
I'm working on Depth Doubler, I have good test results, there's no reason to build a collection of expensive toys that bring me almost no profit.
I'm not that rich and I don't have that much space in my house to build a toy store.
It's a game only for the rich.
But what caught my attention and prompted me to comment is what can be seen in the first video.
And that's the 2box coils and its capabilities, at least what's shown in the video, and they think it's something worth advertising.
Ha,ha,ha!
A target of 1x1 meter, at a depth of 2.5 meters... forgive me, but this is not a sensational achievement or a breakthrough in performance!
About 20 years ago with my first Garrett GTI 2500 and ~30cm Scorcher coil I successfully detected a SMALLER object at 2 meters depth on
the test site in All Metal mode.
It was a silver tray with a diameter of about 32 cm. Back then, there were no cheap cameras or cell phones like today, so I didn't record any of that.
And in those years I tried the same with White's Spectrum Eagle, Spectrum XLT and a little later the DFX; all three successfully detected the same target in All Metal mode.
At 2 meters deep.
Of course, it was a broad, medium-quiet and vague target response.
If I didn't know where and what the target was; I would rather interpret it as a response of some mineralization.
Later, many detectors were tested on the same training ground.
Delta Pulse, Pulse Star II, Pulse Star II Pro... FelezJoo Pi.. ALL more or less successfully detected the same target.
The differences are only in the clarity of the response.
And will the detectorist in natural conditions, when he does not know what to expect; decide to dig there or not.
The best response was definitely the Pulse Star II with a 45cm coil and even better with a 1x1m coil.
That's was the response which 99% of detectorists would choose to dig and check.
And if the target was 1x1 meter like in the video; I am 100% sure that the response of all detectors would be much clearer and better.
So the video is ridiculous, pointless, shows no progress and gives no meaningful reason for a person to decide to buy it.
And when it comes to ferromagnetic targets, metals and objects with good magnetic properties; there than the magnetometer is inviolable!
I have already mentioned somewhere the example of the detection of a rusty iron "beak" from a Roman galley, at a depth of 17.3 meters at sea.
It's about my Euromag 3D and the customer who bought it from me and immediately started searching with it while diving and researching marine finds.
They managed to get a clear signal from the rubber boat with the device at that depth.
And from other customers I received reports about depths of 4-6 meters on the soil.
So the example of a 1x1 meter target at a depth of 2.5 meters is something quite expected, nothing special, not a good enough argument to sell the product.

[Xtrem]

NO, because they has stolen my nickname