On Wednesday, July 25, 2012 3:11:31 AM UTC-5, Szczepan Bialek wrote:
So "enters in = radiates from"?

To the extent that RF energy penetrates to a skin effect depth, the conductor is not perfect and dissipates some of the power. All real-world antennas dissipate some of the RF power in I^2*R (and possibly dielectric) losses. In an efficient antenna, most of the system energy is "lost" in space as coherent radiation.

When the free electrons in a conductor are acting as a bucket brigade for the RF fields/waves/photons, they are essentially vibrating in place because of their very slow drift velocity. Those I^2*R losses in the wire are due to coherent RF photons that are absorbed by electrons and not re-emitted as coherent RF photons but are instead converted to heat energy, the price that Mother Nature requires be paid for all that vibration. In an antenna that is 90% efficient, 10% of the coherent RF energy is converted into non-coherent heat energy. That's the energy that Poynting was talking about.
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73, Cecil, w5dxp.com