Original poster: "D.C. Cox" <resonance@xxxxxxxxxx>Off a standard toroid of 30 x 7 or 34 x 8.5, discharging to a 7 inch ground terminal, or most any terminal of reasonable size discharging to a well rounded ground terminal of 25-30% of the size of the main terminal, it works out to approx 26.5 kV/cm. This is a single spark discharge (once per 10-20 second spacing) from a Tesla coil or Van de Graaff generator.
It's a reasonably accurate way to measure true TC output (peak discharge potential in single pulse mode).
Use a 50 kV diode string and approx 6-10 megOhm resistance on the primary side to set the firing rate. This way the spark will not "grow" as it does at high rep rates and accurate measurements can be taken.
Dr. Resonance
The 30 kV/cm figure for initial breakdown is valid for at least 300 MHz. (At least, this is what my "Reference Data for Radio Engineers" says.) Antonio Carlos M. de Queiroz"Never noticed that; it's one of my standard references (have several editions starting with #1, but never looked up breakdown voltage).Ed