Szczepan Bia³ek wrote:
It seems that EM is useless for antennas. I do not know what is in
space. May be that there EM is usefull.

EM (photonic) waves travel at the speed of light in the medium.
EM (photonic) waves do not travel inside conductors. EM (photonic)
waves travel in space near to the surface of a conductor. For an
HF wire antenna, the photonic waves travel in the space surrounding
the wire and some is radiated. For a wire transmission line, the
fields of the photonic waves tend to cancel and not much is radiated.
For a wave guide, the photonic waves travel in the space on the
inside of the wave guide and very little energy escapes the conductive
sides of the wave guide.

The purpose of using a conductor with free electrons is that the
free electrons are capable of emitting EM waves in the form of
photons.

1. Without the photons, there would be no radiation.

2. Without the free electrons, there would be no photons.

3. Without the metal conductor, there would be no free electrons.

It is a very simple cause and effect chain from the aluminum or
copper antenna to the release of photons as radiation. I think
my 12 year old grandson could understand the principles involved.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com