Best coil design for surf PI

[Eddy71]

Printed circuit board - inductance coil?



(photo from here)https://pcbstator.com/news/selecting...vs-perfect-fit

[mermelado]

Printed circuit board - inductance coil?

[ATTACH]55944[/ATTACH]

(photo from here)https://pcbstator.com/news/selecting...vs-perfect-fit

But this is not for metal detectors. Somewhere I read that they did not give good results. Has anyone tried something like this? Of course for a coil of an IB, it must be impossible to balance it, unless two plates are made and overlapped. Also a large coil would be very expensive. I would like to test coils with aluminum wire, because it weighs much less, the problem is that its electrical resistance is much higher.

[James]

The best coil I made an preformed very well was a basket weave using Litz wire. I still use it today after all these years. Stay safe an healthy. Jim

[Koala]

Best coil design for surf PI

depends what you are looking for

a sub gram gold or a buried bus

most people will be looking for coin or ring size objects with the surf PI

I doubt there is much / anything to be gained over a standard coil for these targets

[mermelado]

With the Mirage I have a 7", 8.5", 9.5" and 10.5" Coil. All are 300UH and 1.4 Ohms. That's with the cable included as it is a continuation of the coil. All my coil cables are 1m long. I mainly use the 7" coil over all the other coils as on the Mirage it gives me the same depth as the 10.5" but more sharper on small targets. I use a 350UH Coil for the Pickini 4 and it is an 8" Coil. My 8" coil works best on the Pickini over all the coils I've tried wth it. I always use the same wire with my 3DSS Builds which is 0.5mmx16 strands/PTFE Coated/600v. I've tried tons of different gauge/stranded/enamelled wire but this wire has given me the best performance and results overall. Regards, Marty.

The 16 wires of the cable are enameled?. I have seen something similar on Aliexpress, but they do not seem enameled, so I do not see much sense not to use it rigid. The Litz wire that I know, its wires are insulated from each other.
In case of not being insulated, wouldn't you get similar results using common electric cable?

[MartyJ1963]

Hiya. No, the 16 strands of wire are not individually enamelled. The 3DSS Coil uses a lot more wire than when building a normal 'Bundle wrap coil to get the same inductance because of all the angles and spaces created by the geometry of 3DSS. But, all the spaces etc, create less capacitance which makes for a faster coil. The down side to the 3DSS, to me, is the coil will weigh a lot more than a bundle wrap/spiral coil etc. The extra weight of the coil has never bothered me but a lot of people obviously prefer the lightest coil possible. @Akhnoth,,,,I have never built a 3DSS Coil to specifically use in water/river hunting/the ocean etc. If I were to build one, I.E:- a 'heavy 'Weighted' 3DSS, I would apply one coat of Fibreglass to 2 x surgical bandage layers I applied over the 2 x layers of Medical paper tape that enclose the wire windings. Then,,,if the structure was solid enough as not to distort or mishape and move the wires etc, I would apply layers of Plaster of paris or paint layers of resin over that last coat of fibreglass I applied. When the required weight is achieved I would then apply 2-3 more coats of Fibreglass to seal it all. The last thing you want to do is flood your 3DSS wire windings with resin/Plaster etc and ruin the geometry/self shielding of a fast coil and make it slow. Regards, Marty.

[mermelado]

Hiya. No, the 16 strands of wire are not individually enamelled. The 3DSS Coil uses a lot more wire than when building a normal 'Bundle wrap coil to get the same inductance because of all the angles and spaces created by the geometry of 3DSS. But, all the spaces etc, create less capacitance which makes for a faster coil. The down side to the 3DSS, to me, is the coil will weigh a lot more than a bundle wrap/spiral coil etc. The extra weight of the coil has never bothered me but a lot of people obviously prefer the lightest coil possible. @Akhnoth,,,,I have never built a 3DSS Coil to specifically use in water/river hunting/the ocean etc. If I were to build one, I.E:- a 'heavy 'Weighted' 3DSS, I would apply one coat of Fibreglass to 2 x surgical bandage layers I applied over the 2 x layers of Medical paper tape that enclose the wire windings. Then,,,if the structure was solid enough as not to distort or mishape and move the wires etc, I would apply layers of Plaster of paris or paint layers of resin over that last coat of fibreglass I applied. When the required weight is achieved I would then apply 2-3 more coats of Fibreglass to seal it all. The last thing you want to do is flood your 3DSS wire windings with resin/Plaster etc and ruin the geometry/self shielding of a fast coil and make it slow. Regards, Marty.

So I suppose that the fact that it is multi-core is secondary and that the real objective is for it to have a thicker sleeve than a simple varnish, to give more separation between layers and for said sleeve to be as less conductive / capacitive as possible. It is not clear to me why you want a submersible coil to be heavy, it is true that it will be heavier by its nature, but adding weight with plaster of paris I do not understand why. It would also be perhaps interesting to use polyurethane foam. In any case, the part that I consider the most difficult remains, which is the outlet for the cable, which can be a waterway and use a water-resistant cable. Since you use the same coil wire and that shows that it does not need to be shielded, a submersible cable similar to those used by water bonbas could be used.

[Akhnoth]

... @Akhnoth,,,,I have never built a 3DSS Coil to specifically use in water/river hunting/the ocean etc. If I were to build one, I.E:- a 'heavy 'Weighted' 3DSS, I would apply one coat of Fibreglass to 2 x surgical bandage layers I applied over the 2 x layers of Medical paper tape that enclose the wire windings. Then,,,if the structure was solid enough as not to distort or mishape and move the wires etc, I would apply layers of Plaster of paris or paint layers of resin over that last coat of fibreglass I applied. When the required weight is achieved I would then apply 2-3 more coats of Fibreglass to seal it all. The last thing you want to do is flood your 3DSS wire windings with resin/Plaster etc and ruin the geometry/self shielding of a fast coil and make it slow. Regards, Marty.

Hello Marty,

thanks for your informations. I have already read that if the windings are flodded with resin the coil will be slow and efforts will be in vain.
If I use carbon fibre instead of fiberglass is it possible without reducing the performance of the coil ?
Regards, Akhnoth

[MartyJ1963]

Hi Akhnoth. I have never used Carbon fibre so I can't really help you with that, sorry. The only way I have ever covered my own 3dss coils is using fibreglass. Regards, Marty.

[mermelado]

Hello Marty,

thanks for your informations. I have already read that if the windings are flodded with resin the coil will be slow and efforts will be in vain.
If I use carbon fibre instead of fiberglass is it possible without reducing the performance of the coil ?
Regards, Akhnoth

I insist on the possibility of using polyurethane foam, in theory it is watertight and light, it is necessary to know its capacitive properties.