@AlienGrey I'll tell you as much as I know. In retrospect I really should have taken precise measurements of every coil so I could use them to improve the calculator, but alas these meetups become quite busy and hectic.
The setup you posted is Eric+Aaron's Cosmic Induction Generator style setup.
* It is a 'concatenated extra', so the white and copper coils both serve as one half of an Extra coil. The left half is one extra coil, the right half is the other extra coil.
* The copper coil is the current coil and is slightly wider than 1:1 height-width ratio. The white coil is the potential coil and it is slightly taller than 1:1 height-width ratio.
* Coils are wound in opposition (one wound CW, the other CCW). Each coil 'half' is wound the same direction.
* The current coils by themselves resonate around 7000-9000 kc depending on spacing with a magnification factor (q factor) of around 370.
* The coils together resonate around 5600kc with a magnification factor around 520 (!!).
* The coil impedance combined is around 200-400 ohm, so they are driven with a matching/coupling transformer/balun to match to the HF transmitter.
* The end rings serve to help balance/distribute the dielectric field in each section. Not required but they slightly improve stability.
If you're trying to wind a coil yourself,
Use my coil calculator here:
https://hakasays.com/DollardTeslaCoilCalculatorGeneral build style/dimensions here:
https://hakasays.com/blog/tesla-highvoltage/build-a-tesla-coil-design-and-construction/* Play with the values and try to get wire spacing as close to 'ideal wire spacing' as practical for peak efficiency.
* Try to keep the height-diameter ratio around 1:1 or a little taller.
* For peak efficiency coils I would use RG316 cable for everything now (using the outer jacket as the conductor). It's silver plated, has a crazy low resistance, effective wire gauge of 10awg, and is widely available many different places. If not, be sure to use 20awg or thicker as the coil depends on high surface area for both resistance and the dielectric interaction.
With the above and a good open frame you should easily be able to get Q factor of 150+ in a single coil, or 250+ in 'cosmic induction' style.
I don't maintain a Skype presence, but I am on Discord quite often @ Hakasays#7694 if you want to chat sometime
I'm always happy to help others get up-to-speed.
"An overly-skeptical scientist might hastily conclude by scooping and analyzing a thousand buckets of ocean water that the ocean has no fish in it."