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Joined: 31 October 2018
Posts: 26
15 October 2019 02:55 pm


in my area i can t get coiltec tdi or other s search coil which working fine so i wont to try
to using them in my tdi spp but with little change in hard ware to make the search coil harmonic
with my tdi spp.
i have 12 inch tdi coil . but i want to make larger coil for more depth in gold . o i miss some
informathion to start make new search coil or changing some any minilab coil for my spp
i want to make 18inch concentrec coil or mono.



Joined: 31 October 2018
Posts: 26
16 October 2019 02:27 am

This the imformation about minilab serch coils . now we need some one give us whites tdi sl serch coils information
DD Coil Measurements.

Minelab 11"DD GPX coil. Coiltek 430 x 280 DD Pro. SEF 21" x 17" DD.

TX pins 5-4 Inductance = 294 uh. 249 uh. 293 uh.
" " " Resistance = 0.4 ohms. 0.5 ohms. 0.46 ohms.

RX pins 1-2 Inductance = 368 uh. 524 uh. 416 uh.
" " " Resistance + 17.1 ohms. 7.2 ohms. 8.21 ohms.

Inductance between pins 2-4. 590 uh. 775 uh. 712 uh.
Resistance between " " " 17.5 ohms. 7.7 ohms. 8.5 ohms.

SRF TX 492 kHz 509 kHz 356 kHz
SRF RX 496 kHz 570 kHz 356 kHz
rx 148pf

Remembering pins 1-5 are shorted in the coil plug.
Pins 3-4 are shorted in the coil plug.

Two additions but only inductance's and resistances as I do not now have the coils and this is all I logged.

11" SD series DD TX inductance 314 uh resistance .4 ohms. RX inductance 402 uh resistance 14.4 ohms.

11" GP series DD TX inductance 304 uh resistance .4 ohms. RX inductance 348 uh resistance 14.6 ohms.


Joined: 28 July 2014
Posts: 274
16 October 2019 10:41 am

What area are you from. Concentric coils have not been known to work well in Australia. That's why when the TDI Pro was imported it was fitted with a mono coil. Don't you have access to any large coils?? Any coil that works on a minelab will work on the TDI. Coiltek do make large coils specifically for the TDI. Should be plenty for sale on the net. Don't see that its worth making your own. Plenty of choices out there. big_smile

Oh Well!...It's not the end of the world.....That'll probably happen tomorrow!


From: Central West NSW
Joined: 27 January 2015
Posts: 4,107
16 October 2019 10:56 am

This thread might be of some help to you … diy-coils/
As said most Minelab compatible coils will work with the Whites TDI series detectors but you may struggle with larger Minelab coils on the SPP. Some have reported having to use a higher pulse delay with larger coils on the TDI but the SPP is somewhat limited being set at 10us delay. Would require some trial & error.
Obviously Whites TDI specifically made coils should work better. There is some info on what the difference is in the above post (& why not to use TDI specific coils on Minelabs).
As well as the Coiltek TDI range you could look for Miner Johns coils … mono-coil/
Jimmy Sierra also used to sell some larger sizes - 14x18 BigShot & 20" Sierra Grande you could try to source.

Everything we use comes from mining or farming.


Joined: 31 October 2018
Posts: 26
16 October 2019 03:12 pm

thank u mr mbasko for your help .

i think the main point there pulse defrent . .... the resestance .& inductance

in minilab search coil resestance les les tham 0.5 ohm and in tdi sl 1.6 to 2 ohm
in minilab we can say rx cap middle (145 -150)pf in white tdi sl (????????????)pf
in minilab inductance tx (from 249 to 363)uh in whites tdi sl (????????????) uh
in minilab inductance rx (from 416 to 775 )uh in whites tdi sl (????????????) uh


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