Hello Tony,

As long as your wire with D=4mm is not close to other structures (say
0.25...0.5m), you will not exceed 1 kVp/mm when the wire itself is carrying
12kVp. You still have some margin before getting close to 3 kV/mm.

At ground level, influence of HF frequency on dielectric breakdown voltage of
air is negligible. If the wire is coated, the diameter increases, hence
reducing the E-field at the plastic-air interface.

When VSWR doesn't, change (with increasing power), the loss due to corona
discharge will be minimal. Of course when you lose 10W from 2kW, you will not
notice this probably. However if you get a discharge between metal and plastic
insulation, the plastic will fail in the end (due to spark erosion).

conducting Droplets (rain) do reduce the breakdown voltage as it distorts the
field. This introduces 'hot spots'. Unfortunately I don't have data on this.

I could imagine that moisture/water layer on the wire would introduces some
loss (as you get a current through the moisture layer). But this is not due to
corona effect.

It can be calculated, as you know the voltage and you can calculate the
capacitance to ground (so you know the capacitive current that "leaves" the
wire.


--
Wim
PA3DJS

Thanks for info. When things go down to the physics level, it is not so easy to
understand phaenomena, unless one has specific knowledge on them.

73

Tony I0JX