I'm working on a 144 MHz antenna using a gamma match. The best result (resonance 50+j0 at 144.400 MHz) I reached is a 10 mm diameter gamma rod, 15 cm long and a capacity of 10 pF.
I thought to obtain the 10 pF with a 4 mm rod inside the gamma rod (internal diameter 8 mm). The dielectric is air.
Since I will use 1 kW I wonder if this configuration (dielectric air, spacing 2 mm) is sufficient for the power I'll use or I have to find a different configuration (having more spacing at the dielectric).
More in general, how can I esteem the maximum power of a gamma match with air dielectric? Is there a rule to decide the minimum better dielectric spacing in function of the power to use?