Help needed to make a PI coil

Hello to all,
I would want to make a coil for a small PI detector (brand: " MP20 ", made several years ago by the German firm "TB metal Detectors").
I am interested by targets buried at depths from 1 to 2 meters.
Please, could you indicate me the size and number of turns for this coil?
Thanks to all.

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http://www.thunting.com/smf/index.php/topic,62658.msg309985.html#msg309985

Thank you for your answer, Homefire.

After reading of documents, we were prospecting of 2 small golden boxes buried in the same ground but in different locations, here in Belgium in year1792.
One of the small boxes was found at +- 50 cms in 2014 by using a CTX3030.
The second box stay untraceable. But we wonder maybe it's buried in a part of the property where the ground which the level changed by the contribution of new lands.
This is the way we wanted to use the MP20 in our ownership, but we lost the coil a model of which we would want to make.

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I have been watching this topic and see that since Xavier is no longer with us, we have lost our best expert on coil design. I worked with him so long and he was so inquisitive that he actually became the expert he was. Now, to my advice.

You said you lost the coil? Do you have another machine of the same model to test yours? Before you begin you must insure that your machine is working properly. Then you must use an LCR meter and read your coil to record the impedance, inductance, capacitance and resistance of the coil. Most PI machines use a single coil. Once you do that, you have to develop a pattern chart known as a Smith Chart of the coil field shape and size. After that, we may be able to advise you on how to build a replacement coil. This is not going to be easy or cheap. You won't be saving any money, believe me. You might want to look on eBay to see if there are any used ones for sale or even a larger coil designed for your box.

Posted on: March 06, 2016, 08:46:09 am

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You could also go to the TB Electronics web site and look for a dealer who may just have a second hand coil you can buy.

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Hi all. Good advice from Golddigger. But if it were me, I would just make a 1Msq. out of Cat5 networking cable. Strands seriesed, as per the Sniffer XR71 design. It will either work, or it won't. I realise that too little resistance can make things run hot, but coils really aren't rocket science. I have half a dozen home-made PI coils of varying shapes and materials- 26 and 22 AWG speaker wire, .25mm enamelled, and Cat5 cable, that I experiment with on SurfPro, Sniffer, Pirate, Newhobby NH-5. All but the extreme parameters will work on most to some degree, with the Sniffer and the Pirate being at either extreme. The 6 inch Cat5, 3 twisted winds, ends seriesed, coil I made for the Pirate (450uH) can ping 1.8g of flour gold at 5 inches on my SurfPro!! The 50x30 square,Cat5, 3 flat winds, ends seriesed, but circuited 3 strands before the end(still joined though) to get 450 uH, I made for the Sniffer, but that also works better on the SurfPo. The 19 winds 8 inch 26AWG, 350uH, I made for the SurfPro actually works better on the Sniffer.
 My whole reasoning behind self-build is learning and bypassing corporatism wherever possible.
My advice would be invest $9AUD in a 15M roll of cat5 networking cable. Make a 1Msq. single(8 strands end seriesed). A 70x40 (2 winds,strands seriesed, circuited with experiment), and a 50x30 (3 winds, strands seriesed, circuited with experiment).
But I am a bush mechanic, so what would I know?
 I just had a gawk at it- Low power. Pre-set...Maaate...Dunno if you will ever make that a deepseeker with any coil......Maybe rather than sourcing and buying a coil for it you should just get an XR71 kit, a control box and a broomstick for the same or less money??

Maybe being low power you should try 50x30 max. 2 winds Cat5, circuited with experiment??

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wow.
what type/brand is your Green detector?
been able to adjust 7 control pots its a treasure on itself.
Good work Timc

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