Cylinder Coils?

[Tinkerer]

Tinkerer, absolutely, i would be really interested in the whole process, of course to simplify it, a large mono coil for a Minelab would be the go, like i said i have a large coil but i have seen a vid of someone who had built a 1metre mono and that coil could easily pick up this 10c size in the middle and at about 2ft height, so i would say that my coil is not made right.
AMX?, what the hell is that if you don't mind me asking, has this design/platform got the potential for large increases in depth?

The Minelab coils have quite tight specs. There is not a whole lot that can be improved within the specs. Woody (detector mods) has probably experimented every which way. I can do no better and don't have a Minelab to compare with.

AMX is a very advanced platform in the making. Look for the AMX project on this forum. Many of the usual limits of traditional PI have been overcome. There is great potential for very high sensitivity and extraordinary depth.

[Carl-NC]

And large coils, i have a 1metre coil that someone made for me, i made the housing for it, i used it in Victoria for a couple of hours, didn't find anything with it, but i know that it won't pick up 10 cents in the middle of the coil (Australian 10 cents is about the size of large marble, it is sensitive to small ****e close to the windings but won't hit this 10cents in the middle.

This is normal, and any size coil will do this if the target is small enough relative to the coil. Prospectors commonly use coil-edge detection on small bits or to pinpoint. The problem is that the coil is just too large to efficiently detect the target's field, most of the target field is canceled by reverse-field effects. One solution is to place a much smaller RX coil concentrically. Tesoro did this on their VLF coils.

Of the detectors I've tried, the GPZ wins hands-down on detecting big chunks deeper. Part of that is the big stock coil, but a bigger part is the CCPI operation. AMX also uses CCPI. As Tinkerer says, there is much to explore here. I would like to see an 18-inch concentric with a 4-6 inch RX.

AMX Project

[Nova]

Thanks Tinkerer for your contribution to this thread, i will have to look into this platform, sounds very interesting.
You might be right Carl about this large coil, the size of the object is maybe just a fraction too small to be picked up, i would challenge you on the GPZ being the deepest, as many have done tests and i recall someone did a test on a 10 oz nugget and it was the SD2200d that got it the deepest, maybe it was just on this shaped nugget that the 7000 couldn't hit, but on average if we were to test 10 different shaped nugget of equal weight maybe the 7 would win on 70% of them, Testing, testing and testing, i think we could do with a clone each, to do the testing for us LOL, there just isn't enough time to do it all damn!!!!
So Carl, this AMX project, is there a future prospect of a detector coming to market by yourself using this new platform or is this like an "open" project for users to make themselves, mostly those on this forum?, if that's the case that will exclude a lot of us, who don't have electronics knowledge, can you tell me the direction you think this platform will go?

[Nova]

I forgot to mention, this large coil can hit the bottom of a coke can at around 4ft in an air test, so it is "working", i probably should look at this coil as being the ideal coil for chasing those large slugs at depth, as it won't signal on bullets or other similar sized objects buried at the 5-12inch mark, yep, i've just convinced myself to do proper testing, like this you are always wondering and never sure, test and surety will follow!!!!! - an old Chinese proverb by a not so Chinese Nova!!!

[Tinkerer]

This is normal, and any size coil will do this if the target is small enough relative to the coil. Prospectors commonly use coil-edge detection on small bits or to pinpoint. The problem is that the coil is just too large to efficiently detect the target's field, most of the target field is canceled by reverse-field effects. One solution is to place a much smaller RX coil concentrically. Tesoro did this on their VLF coils.

Of the detectors I've tried, the GPZ wins hands-down on detecting big chunks deeper. Part of that is the big stock coil, but a bigger part is the CCPI operation. AMX also uses CCPI. As Tinkerer says, there is much to explore here. I would like to see an 18-inch concentric with a 4-6 inch RX.

AMX Project

I could make an 18" concentric, Induction Balanced coil for the AMX. I also have a TX to run it on.
We can use this coil as an example to walk through the design and build process.
As this coil is designed for the AMX platform, I suggest we discuss this coil build on the AMX Coil thread.

[Tinkerer]

Thanks Tinkerer for your contribution to this thread, i will have to look into this platform, sounds very interesting.
You might be right Carl about this large coil, the size of the object is maybe just a fraction too small to be picked up, i would challenge you on the GPZ being the deepest, as many have done tests and i recall someone did a test on a 10 oz nugget and it was the SD2200d that got it the deepest, maybe it was just on this shaped nugget that the 7000 couldn't hit, but on average if we were to test 10 different shaped nugget of equal weight maybe the 7 would win on 70% of them, Testing, testing and testing, i think we could do with a clone each, to do the testing for us LOL, there just isn't enough time to do it all damn!!!!
So Carl, this AMX project, is there a future prospect of a detector coming to market by yourself using this new platform or is this like an "open" project for users to make themselves, mostly those on this forum?, if that's the case that will exclude a lot of us, who don't have electronics knowledge, can you tell me the direction you think this platform will go?

I have often heard that the SD2200d was the deepest detector for large nuggets. So I suggest we use the specifications of the SD2200 for comparison.
The SD2200 is a traditional Pi platform and is therefore limited to around 300uH coil inductance. about 300uH is the "brick wall" limit of the traditional PI.
If you increase the inductance, you increase the delay to the first sample.
This brick wall limit means that you have to use fewer and fewer turns of wire as you increase the diameter of the coils.
The depth of detection is directly related to the diameter of the coil.
Since on the traditional PI you can not increase the number of turns, you increase the current Amps. This makes a stronger field, but entails many other problems.

The AMX platform has demolished several of the "brick wall" limits. It is closer related to the GPZ 7000, but not the same. I would say it is the most modern or advanced PI platform in the making.

[Nova]

Ok Tinkerer, lets hope were still around to see this come to fruition, the Globalists seem hellbent on getting WW3 going, so for the moment it's wait and see!!

[Smirnov-Arta]

Good morning,
A cylindrical coil doesn't make sense...It has already happened.
Once...Theoretically, it was considered that a cylindrical coil is capable of reducing the level of field tension/impact on the first/upper layers of the soil (0-10 cm)...the theory has not been confirmed by practice. Therefore, I do not recommend repeating this, although if you want, then try it. The "ideal operation" of the coil, ... the creation of a uniform electromagnetic field, etc., is created by a flat coil, with a pitch (distance between turns) of winding equal to the diameter of the wire. This is implemented in some MD's...
(sorry for the Google translation)

[Tinkerer]

Good morning,
A cylindrical coil doesn't make sense...It has already happened.
Once...Theoretically, it was considered that a cylindrical coil is capable of reducing the level of field tension/impact on the first/upper layers of the soil (0-10 cm)...the theory has not been confirmed by practice. Therefore, I do not recommend repeating this, although if you want, then try it. The "ideal operation" of the coil, ... the creation of a uniform electromagnetic field, etc., is created by a flat coil, with a pitch (distance between turns) of winding equal to the diameter of the wire. This is implemented in some MD's...
(sorry for the Google translation)

Thank you for your feedback, Smirnov,

How do you build the flat TX coil with 300uH inductance, 0.4 Ohm and 300mm outer diameter?

[Smirnov-Arta]

...

And what is the difficulty? If the diameter of the coil TX is 300mm, then the length of the coil is 940 mm. In order to get 300 uH, only 19 turns are needed. I leave the choice of the wire diameter to you. The technology of winding any flat coil will not be difficult for you to find on the Internet. It is possible technologically with templates pre-made on 3D printers. But, if for 1 sample, it is possible, with the help of ordinary thick paper / cardboard and glue, to make 19 turns. The first turn (internal) is more difficult to make, the rest will lie next to it easier. Believe me, it's nothing complicated. It will take no more than 1 hour)...maybe faster when you practice). Try it, there's nothing complicated!

[Tinkerer]

And what is the difficulty? If the diameter of the coil TX is 300mm, then the length of the coil is 940 mm. In order to get 300 uH, only 19 turns are needed. I leave the choice of the wire diameter to you. The technology of winding any flat coil will not be difficult for you to find on the Internet. It is possible technologically with templates pre-made on 3D printers. But, if for 1 sample, it is possible, with the help of ordinary thick paper / cardboard and glue, to make 19 turns. The first turn (internal) is more difficult to make, the rest will lie next to it easier. Believe me, it's nothing complicated. It will take no more than 1 hour)...maybe faster when you practice). Try it, there's nothing complicated!

Smirnov, thank you for your feedback. I appreciate your help.

I have no problem building the actual coil, but first I want to get the numbers right.
To compare the bipolar TX with the monopolar TX of a traditional PI, We need to have comparable parameters.
The Minelab mono coils are well known. This is why I want to use a known Minelab coil for comparison.
The Minelab coils are quite specific in their parameters, This is where the numbers: 300uH, 0.4Ohm 300mm diameter, come from.

[Smirnov-Arta]

....

There's nothing wrong with that if it doesn't work out the first time). This is normal! Make 1 test run for 20 turns. Measure the data...and you will understand what needs to be changed. More or less turns. With regard to 300uH...this is a conventional conventional meaning...if there are small deviations plus/ minus...It won't matter. With regard to the resistance of the coil itself. It's not that simple. Yes, of course, it is desirable that it tends to zero (ideal). BUT! As a result, we need to create a field... That is, you need to take into account the power supply of the circuit...6/9/12V. I mean, you can make more coil resistance, but then you need more power. The field will end up being almost the same. The choice is yours).

[Carl-NC]

The spiral coil calculators will probably get you close enough. For 1mm wire, I find that N=23 is just slightly low and N=24 is slightly high. I would go high and then remove an inner winding if needed.

From the table in post #6 you can see that magnet wire is plenty good for SRF and even has a low R(100kHz). However, with 1mm wire this might have higher self-eddy losses so you may need to consider litz.

The best way to wind a spiral is to print a plastic holder. You can spray adhesive on a disc, but I found that it's not tacky enough and dries out before I get done winding. So instead, I sprayed adhesive on a disc and then laid duct tape adhesive-side-up on the disc. The duct tape is very tacky. For a starting inner diameter I used a plywood disc purchased from here. In fact, I bought a bunch of their discs and made bobbins for winding coils 3" up to 12".

[ozgold]

I have often heard that the SD2200d was the deepest detector for large nuggets. So I suggest we use the specifications of the SD2200 for comparison.
The SD2200 is a traditional Pi platform and is therefore limited to around 300uH coil inductance. about 300uH is the "brick wall" limit of the traditional PI.
If you increase the inductance, you increase the delay to the first sample.
This brick wall limit means that you have to use fewer and fewer turns of wire as you increase the diameter of the coils.
The depth of detection is directly related to the diameter of the coil.
Since on the traditional PI you can not increase the number of turns, you increase the current Amps. This makes a stronger field, but entails many other problems.

The AMX platform has demolished several of the "brick wall" limits. It is closer related to the GPZ 7000, but not the same. I would say it is the most modern or advanced PI platform in the making.

Hi Tinkerer.

Been experimenting with M/Lab coils for years, the ultimate inductance for medium to large deep nuggets is 325uH. If this increases the delay, no matter, you are not chasing tiny gold.

ozgold.

[Smirnov-Arta]

Dear colleagues. I ask you to pay attention again. It makes no sense to talk about an abstract coil, without a circuit and software (if there is one) one or another MD. Physics is the same for everyone. Magnetic flux, voltage, etc. the characteristics of the coil, approximated by the area of the coil, will depend on the power supply of the coil (V)... etc. Therefore, it is necessary to consider some theoretically ideal coil in relation to the circuit and in no other way.