BipolarAfter seeing many of this design, I thought i would have a go at building one, It's much the same as building a conventional coil, but the primary is in the middle, I wasn't too bothered about getting it perfect, so I guessed the amount of turns for the primary, though based it on what Teslamap suggested.
14" winding height
Current toploads are 2" tree baubles covered in foil.
For the primary tuning I started with a rough coil of wire, tuned the coil, then made a neater one with the spacer
bars and supports, there's about 10 turns.
The secondary is supported on 2 insulated posts with metal posts above the coil, the ends of the coil have discs for support with bolts for connection to the posts.
If I had to make this again, I would probably add a centre tap on the secondary for RF earth, the wire would pass between the windings of the secondary, this is the only coil (so far) that has booted a nearby computer that was shut down.
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