Interesting that you note the extra coil to be 1/2 wavelength long vs 1/4 wavelength. I guess together that would produce a 3/4 wavelength system that would still have a voltage maximum at the top. In Richard Hull's Guide to the CO Springs Notebook, he states the primary and secondary can be a huge range....the important thing he notes is that the primary secondary can be highly coupled and acts as a high power signal generator. He feeds his primary and secondary into a 1/4 wavelength coil.
Really excited to see your results following the 1/4 -1/2 wavelength secondary and extra coil. Makes sense. Ive primarily used Richard Hull's advice and gone with a highly coupled primary & secondary to increase power into the system, but perhaps this type of system is missing something.....
Looking forward to the results!
I have always worked with 1/4 + 1/2 because that is what Tesla writes. It is easier if you follow Richard Hull's guide, but not better. If you have 1/4 wave in your extra coil, that means it has a high voltage on one end and a high current on the other end. Having a high current on the lower end of your extra coil means that you can not have 1/4 wave in your secondary coil. Thus you can not create a resonance rise in your secondary, and it will act as a normal transformer giving an output voltage based on the windings ratio. Therefore his setup is less effective in creating very high voltages, but it is a lot easier and it allows you to use a cheaper capacitor bank.
In a 1/4 - 1/2 setup you also have a tightly coupled primary-secondary which requires very precise tuning in order to get good results.