Thanks to Dick PA0SE for doing further tests. Replacing the antenna with a
increased capacitance from a vacuum variable has lower losses than the
circuit" but it is a reasonable approximation for gathering measured data.
What about replacing the antenna by a capacitor in series with a resistor,
would't that be a better simulation ?
For low power tests (as Dick did) a short piece of coax can be used as low
loss capacitor. Most 50 Ohm coax is 101pF/m, so a 1 to 3 meter length will
be sufficient. The coax cal be rolled up to get things compact, an
alternative is a number of short pieces in parallel. Cheap and flexible
coax such as RG174 will withstand up to 1.5kV (according to specifications
that tend to be rather conservative), RG58 even up to 2.5kV.
For those interested in high power testing : RG8 and RG213 are specified at
5kV, RG218 at 11kV.
73, Rik ON7YD