This coil was one of Tesla's later designs, and is said to have spooky anti-gravity effects when pumped with the correct frequencies and voltages. I won't be working in that high-power range with this un-powered crystal radio !
The core of the Tesla Football Antenna is made with four 2 inch paper cones glued and taped together. The paper cones were doubled up, two on each side, for strength and smoothness.
The 30 gauge wire conical coils are wound laboriously by hand. The thick 10 gage copper wire was carefully bent to conform to the football coil without disturbing the coils of the coil. (Note to self...don't try this again without coating the wires with a resin or glue first, because the coils will start unravelling...)
After this small coil-winding feat, two snazzy Banana Plug ends are put on. These ones were found at an electronics store.
Here's a link to a similar coil that puts out sparks!