Toni wrote:
Ok, so trying to summarize your answers, it seems that

- Electric and Magnetic fields, effectively, go together, but
their ratio may vary, especially at the antenna's near field.

- Cecil Moore says in free space this ratio is the 377 ohms
characteristic impedance. I don't know how to mathematically
check this, but seems reasonable to me.

SNIP

Zo = SQRT[u/e]

where u = permeability of free space
where e = permittivity of free space