Sorry, Fireguy, I was overly sarcastic there.
If you just want to wind a coil for the heck of it, the only way you'll know if it works or not is to hook it up to the detector it was designed for. You can pick up a BH Junior brand new for typically about $60, that way you have both a detector and the searchcoil that goes with it. This model is particularly easy to wind searchcoils for because there is no tuning capacitor or other circuitry inside the searchcoil, and the transmitter and receiver windings are approximately the same inductance. The standard searchcoil is concentric but for experimental purposes you'll find a DD easier to get right.
People who are unfamiliar with metal detectors often get the idea that the "antenna" on a metal detector is pretty much like a ham radio antenna. It isn't. A better model is air core transformer in a condition of induction balance. And, nonmetallic electrostatic shielding is almost always necessary.
There's a technical forum where people from all over the world grapple with searchcoil issues, the name of the forum begins with a G. (Sorry, don't know if admins permit links to that particular noncommercial forum.)
Have fun!
--Dave J.
