Winding a coil for a White's TDI

[glabelle]

I've just picked up a TDI on eBay. It comes with the stock coil. I'd like to try an 8" size coil for coinshooting, but $249 for the accessory coil? Yikes!

Anyone know the characteristics required for a TDI coil. Inductance? Any parallel capacitance? Is there one coil or 2 required? Pinout on the cable?

Thanks,
George
Aloha, Oregon

[Daedalus]

Glabelle there are some videos online showing how to wind a PI coil , I have watched them but do not have the links . Do a search on google and you will find quite a few , and there were two that did a great job of showing how to do this.

You might give this a try .

[Reg]

Glabelle,

You can find a lot of info on windingTDI coils on another forum. So, you might google making a TDI coil or maybe a 40" by 40" TDI coil. Once you are on the right forum, then you can search and find lots of info on making TDI and other coils.

Now, with that said, making a TDI coil is really not difficult, especially if you only want to make one for coin hunting. Also, the smaller the diameter the coil, the easier it is to make one that will work at the minimum delay.

So, making an 8" coil shouldn't be hard.

As for the inductance, shoot for 300 uh. Use a quality coax with a stranded center and preferably with a served shielding. I like the Mogami coax for this purpose. Use decent stranded wire for the coil. The best wire is Teflon coated wire to minimize the capacitance, but that won't be that critical when making an 8" coil.

The TDI works well with a simple mono coil and doesn't need to be complicated with multiple windings. In fact, the simple mono actually is the best, in my opinion.

Coil housings are also available for those not wanting to try to build one. Again you can google what you want. I am not sure if posting other sites such as one that sells coil housings under their parts list is ok, but it should be.

Reg