Best coil design for surf PI

[mermelado]

Hi:
In the link thats is published above, regarding the construction of a basket coil, it is said that it is necessary to connect a 30k resistor, so that the Koshchei-5l/lM detector recognizes it. I wonder if for our home detectors, Surf PI, etc. is it necessary to also use some kind of resistance in the coil?

Another question:
Do you think that this type of coil offers benefits in Pickini 4, since its topology is diferent from most of the detectors?
Thanks you.

[MartyJ1963]

Hiya Martin. Thanks for the Tufnol descripton, I'll have to look it up and maybe try it out.
My partner and I are waiting for our 2nd jab too and like you, we haven't ventured out yet only to shop for necessities etc.
I'll let you know how I go with that Farm permission and when things have safely calmed down a bit you're welcome to come through and hunt the land with us,,,see what the future holds for us all.
Regards, Marty.

[MartinB]

Sorry, forgot to answer your question
Tufnol is basically resin bonded paper very similar to Formica.
It is light weight and easy to cut, but like Formica it is a little brittle.
I would suggest using a Dremel or similar to cut it rather than a hand saw or jig saw

[MartinB]

Thanks Marty
I will look them up tomorrow.
Yes, it would be good to meet up when things get better. I am waiting for my second jab before I start to circulate a little more.
Been working on the basket coil tonight but not finished yet.
Regards
Martin

[MartyJ1963]

Hi Martin, I took some pics of that new full reel cos' it still had the details on. It's from a company called 'Lynder'. See attached photos. Regards, Marty.

[MartyJ1963]

Hi Martin, Sound! If I can can permission on that Farm then maybe we could meet up and detect it sometime when all this Covid crap is under control!,,Lol. Exchange a few ideas too! What is the Tufnol you mentioned? Is it the coating on the wire or for Vacuum forming? Yes, I noticed your (safety warnings! I always take heed to people who know what they're talking about! I've done all sorts in my time, I'm a joiner and disaster recovery technician by trade, but I make my living as a professional vocalist. I did a 3 year stint in the R.A.F in the 80's and I teach Wingchun and Jeet Kune Do classes (Unpaid) just because it's a big part of my life and I love it. I used to have a main hobby before Detector building, which was breeding and training Birds of Prey but I don't have the space for it now,,,just Gung fu and Detectors!,,Lol. I've not found that link for you yet but I'll keep searching for you. If you're ever up this neck of Yorkshire I have a spare reel of the wire I use (brand new) if you ever want to call in for it,,,free of course,,a new friend gift. I know we're still under restrictions with the Covid but you're welcome to a reel of it if you want. Regards, Marty.

[MartinB]

Hi Marty
Thanks for the information. Last night I found a supplier of Tufnol sheet out in Gainsborough; Trent Plastics. Tufnol is light, has excellent electrical properties and is not affected by moisture. I didn't realise is was still manufactured so I am quite pleased that I found it. My background is electrical engineering and safety as you may have guessed from some of my previous posts. I have only been building detectors for a year or so since I retired and just becoming familiar with how the circuits work. To date, I have not had any sparkling success which is why I need to change my approach to coil building. This is a great international forum so I was really surprised to see that you lived so close. I am just south of M1 J29. There are lots of fields around here but sadly most have been open-cast mined, or belong to either Chatsworth or the National Trust, neither of which allow detecting, which forces me to go further afield.
Kind regards
Martin

[MartyJ1963]

Hi Martin. For the formerI mainly use MDF@1/4" of an inch thick or sometimes plywood. The finished coil is a little heavier because until I've built a satisfactory Vacuum former (a 'still' on going project), to build lighter ones, I have always fibreglassed them. The weight, when swinging, has never bothered me. The wire is just plain uncoated copper stranded. I get the same performance with 400v wire as the 600v and it's lighter too. Where abouts south are you from me? I've made quite a few friends on Geotech but never had the privelige to meet anyone yet. I can only go local to detect as I've never driven and the nearest coastline to me is Grimsby,,Lol. A few days ago I remembered a local Farmer who gave me a ton of fertile chicken eggs to incubate way back in 2000,,,really nice polite guy and didn't know him from Adam,,I knocked on his door and asked him to sell me some fertile eggs. He kindly gave them to me for nothing so I offered to him that if he ever ever needed any help with repairs around his Farm I would them for him for nothing (I'm qualified 1st/2nd/3rd fix Carpenter/Joiner) and left him my number. He never called me but thinking about him now I may knock on his door again and ask for permission to detect his land. The Farm is about a 30 minute walk from mine. I've only ever been out detecting about 5-6 times in the 4-5 years I've been building detectors,,Lol. Hopefully he's still around as it was 20 years ago! Plenty of Woods though! So I've been 'Google Earthing' it all looking for ancient walkways and paths. I found a woods, about an hours walk from mine, that adjoins a Farmers field, and where it joins and meets the woods is an old Roman site. The paths in the Woods go straght over the top of it. There's a story to that area as well,,,in the 15th century young couples about to be married would hide a piece of Silver beneath a big rock for good luck. Several have been found over the last fifty years,,,all beneath big boulder type rocks in that particular woods. When the weather decides to 'Stay' warmer longer I'll be checking out that woods. I'll try to find a link for you for that wire. Regards, Marty.

[MartinB]

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.

Hi Marty
Some really good stuff here. Like you, I have tried lots of different types of wire but have not achieved the performance I am looking for, therefore I think my next step will be to try a 3Dss coil. What material do you use for the former? and just to be nosey, where do you purchase your PTFE cable from and is it plain copper or silver plated? Just noticed that you live only a few miles north of me.
Regards
Martin

[MartyJ1963]

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.

[6666]

Hi Marty, sounds like you have been having good success with the 3Dss, that ring is a bonus !, what diameter was that P4 coil ?
One day I will test one on our goldfields, it will be interesting to see how it handles our ground

[MartyJ1963]

The first P.I I ever made was the 'Surf' and I use a 257UH 3DSS with that. I use 300UH 3DSS with my 'Mirage'. I use a 350UH 3DSS with my 'Minipulse Rev D and E'. I use a 350UH 3DSS with the 'Barracuda'. I use a 350UH with my 'Pickini 4' (Which found me a diamond encrusted 18ct gold ring at over 12") and a 350UH 3DSS with my 'Felezjoo' (Which I'm still experimenting with). I made a 3DSS for my 'Gold-Max P.I' (Elliot) but haven't worked out yet why I'm having shielding issues with that no matter what coil I try. I hope that helps somewhat? I bind them with thin medical gauze bandage and just fibreglass them afterwards though I'm still in the process of building my updated Vacuum former so I can form proper shells for them. Regards, Marty.

[6666]

A 3DSS Coil does not require shielding,,It 'Self-shields' due to its geometry,,,I use them on all my P.I's and I have never had any issues,,until something better comes along I won't use anything else. They're easy to build, a little time consuming, and require more wire than a bundle wrap etc, but a lot less capacitance that makes for a faster coil that you don't have to shield. Check out the 'Chance P.I Build' thread if you have never built one,,great reference for the 3DSS. Regards, Marty.

Hi Marty which PI have you been using ?

[MartyJ1963]

A 3DSS Coil does not require shielding,,It 'Self-shields' due to its geometry,,,I use them on all my P.I's and I have never had any issues,,until something better comes along I won't use anything else. They're easy to build, a little time consuming, and require more wire than a bundle wrap etc, but a lot less capacitance that makes for a faster coil that you don't have to shield. Check out the 'Chance P.I Build' thread if you have never built one,,great reference for the 3DSS. Regards, Marty.

[Emersonpaz]

Hello guys analyzing the datasheets of the operatives a great quality replacement would be the Burn Brown OPA637