Basket coils don't need shields?

[mermelado]

Hello Marty,
I plan to build a 3DSS coil but I have a question regarding the thickness of the cardboard. Is it important to have a cardboard thicker or a thinner one ?
I can choose 3mm cardboard (tufnol) or 5mm or 10mm. What is the best thickness of cardboard that gives a stronger magnetic field ?
Thanks, Regards, Akhnoth

If you have a 3D printer, I have a form ready to print.

[Akhnoth]

Hello Marty and Mermelado,

Mermeado : I have no 3D printer, I always build things manually. Thanks for your proposal

Marty : Yes of course, the thinner material is lighter. I will take the 1/8" of plywood as you. Have you some information to share of your open cell foam ? Have you a commercial name and the company that sells it ? Can you send some pictures of your building process. And I wonder how the foam will sink when the wire is passing over it ?
Thanks for your support

Akhnoth

[MartyJ1963]

Hiya Akhnoth. I'm sorry I don't have any phot's of the way I build my coils. I have 2 coils to make soon so I will try to take photo's for you. The 'Open cell foam' is similar to Polystyrene foam but is made from plastic. It is usually what companies use for packing around electrical items etc for shipping. The wire sinks into the plastic as you wind your coil but it helps n raising the centre of the coil to give it a more 'Oval' or 'Round shape and helps space the wire better for less capacitance. I have noticed less capacitance in the coils I have built with the 'Foam' addition than without. It also strengthens the plywood a little better too. When my coils are finished and tested I wrap the coil with 2 coats of medical paper tape then 2 wrappings of surgical fabric bandage. Then I give one coat of Fibreglass and leave 24 hours to dry. I lightly sand the first coat of fibreglass then wipe clean and add a second layer of fibreglass. Then sand again. I make a separate piece for the centre of the coil on which receives the Clevis etc. I stitch the centre piece on with waxed cotton (used in tent making) and then apply a 3rd coat of fibreglass to the coil to protect the 'Stitches' etc. Hopefully soon I will document my next 2 coil builds and post them here. Hope this helps. Regards, Marty.

[Akhnoth]

Hiya Akhnoth. I'm sorry I don't have any phot's of the way I build my coils. I have 2 coils to make soon so I will try to take photo's for you. The 'Open cell foam' is similar to Polystyrene foam but is made from plastic. It is usually what companies use for packing around electrical items etc for shipping. The wire sinks into the plastic as you wind your coil but it helps n raising the centre of the coil to give it a more 'Oval' or 'Round shape and helps space the wire better for less capacitance. I have noticed less capacitance in the coils I have built with the 'Foam' addition than without. It also strengthens the plywood a little better too. When my coils are finished and tested I wrap the coil with 2 coats of medical paper tape then 2 wrappings of surgical fabric bandage. Then I give one coat of Fibreglass and leave 24 hours to dry. I lightly sand the first coat of fibreglass then wipe clean and add a second layer of fibreglass. Then sand again. I make a separate piece for the centre of the coil on which receives the Clevis etc. I stitch the centre piece on with waxed cotton (used in tent making) and then apply a 3rd coat of fibreglass to the coil to protect the 'Stitches' etc. Hopefully soon I will document my next 2 coil builds and post them here. Hope this helps. Regards, Marty.

Hello Marty, your explanations are very clear. Thanks for your informations. I can wait for your futur post with photos. I had the same idea to add something to help having more "rounded" shape of the wire windings.
For the "open cell foam" you are refering to, I have seen that it's made of low density polyethylen. Am I right ?
For the protection with fiberglass I don't have any experience. But I want to learn about it, so if you have also some information of this process. I will be happy to read it. carefully.
I have a question of the coil weight after the fiberglass process ?
And as there is some air inside the enclosure when the coil is used underwater it will be less weighted ?

Thanks a lot Marty

Akhnoth

[mermelado]

Hi Marty,
I see that you are a coil expert and I would like to ask you about the type of cable you use to attach your basket coil to your Pickini4 detector. It turns out that in my initial tests connecting the coil directly to the detector, I am almost certain that I have obtained a certain sensitivity to gold, enough to experiment on the beaches, but when I finished the project and joined it with RG174, that sensitivity has been lost, I do not know if it is chance or if the cable is at fault. Please note that the tests were done with small gold plated chains, as I do not have any nuggets. For other types of objectives, such as coins, I have not noticed changes.

[mermelado]

Hi Marty,
I see that you are a coil expert and I would like to ask you about the type of cable you use to attach your basket coil to your Pickini4 detector. It turns out that in my initial tests connecting the coil directly to the detector, I am almost certain that I have obtained a certain sensitivity to gold, enough to experiment on the beaches, but when I finished the project and joined it with RG174, that sensitivity has been lost, I do not know if it is chance or if the cable is at fault. Please note that the tests were done with small gold plated chains, as I do not have any nuggets. For other types of objectives, such as coins, I have not noticed changes.

Forget this:
I would also like to know the approximate length of your cable and the firmware version you use
Thanks

[MartyJ1963]

Hiya Mermelado. Believe me, I am no coil expert,,,Lol. I'm still struggling to learn how to tune VLF Coils and use my Oscilloscope properly. I think I just have more luck with 3DSS Coils because have experimented wth them mostly. The length of cable I use is about 1 metre. Ths cable is just a continuation of the coil winding. I first measure 39 inches of wire then start winding my coil. When I have achieved 6 full revolutions of the former I measure the end wire and, before cutting, I peel back some wre insulation and check the induction. For the Mirage I try to achieve exactly 300uh. For the pickini4 I use 350uh. This is including the coil windings and cable together. The firmware I use for the Pickini4, I think, is the last firmware posted by Bernard. I always use a continuation of the wire for my cable with 3DSS builds and only use a separate cable with my VLF coils. Regards, Marty.

[mermelado]

Hiya Mermelado. Believe me, I am no coil expert,,,Lol. I'm still struggling to learn how to tune VLF Coils and use my Oscilloscope properly. I think I just have more luck with 3DSS Coils because have experimented wth them mostly. The length of cable I use is about 1 metre. Ths cable is just a continuation of the coil winding. I first measure 39 inches of wire then start winding my coil. When I have achieved 6 full revolutions of the former I measure the end wire and, before cutting, I peel back some wre insulation and check the induction. For the Mirage I try to achieve exactly 300uh. For the pickini4 I use 350uh. This is including the coil windings and cable together. The firmware I use for the Pickini4, I think, is the last firmware posted by Bernard. I always use a continuation of the wire for my cable with 3DSS builds and only use a separate cable with my VLF coils. Regards, Marty.

VLF coils in IB detectors are another story. I have made one until now and I thought it was going well, but I also did a TGSL at the same time and now everything is going quite bad, the problem is that if you don't have a coil that you know is going well or a Tested Treasure, there is always the He doubts whether the fault is in the chicken or the egg. Regarding your method, I am curious to know how that thread from the coil reaches the detector, maybe you use a heat shrinkable macaron? because I don't think the cables are lurching loose. Maybe you have a photo to share with us? Thanks, Martin.

Extra question:
Are those 50uh difference between the two coils noticeable? that is, have you tried exchanging them between the two detectors and have you noticed differences?