Excellent Mike. Good resource and thanks for the link.
I compared results and they are very close to simulation.
Next, I am using old school DUBILIER caps as padders in the
load cap slot. They are rated at 2.5 kV and 5 kV test. The ESR
at low frequencies is quite low, need to see what I have at say
40 meters and if the RMS current x ESR or cap dissipation is excessive.
I am trying to chase down an efficiency issue.
73' Alan
Are you talking about the 8XX series doorknob caps?
The lower value ones are NP0, but most of them are N750 or even more, so if they heat up, your loading will drift.
Some guys put a second air dielectric variable in parallel with their main loading cap and switch it in. There are some nice 1000 volt rated variables on Ebay now from old HP generators.
A more modern, compact and elegant approach is to use some of the ATC100E porcelain MLCC caps available on EBAY now. They come in 2500volt ratings and some have silver plated tabs. They can handle 15-18 RF amps each at a wide frequency range. They are widely used in Class E transmitters.
Here is a shot from the data sheet:
https://datasheets.avx.com/100E.pdf