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On Sep 22, 3:34*am, Szczepan Białek wrote:
Up to now the acoustic analogy is fully applicable. Not if one understands the physics of radiation. But it is experimentally proved. Stationary charge - electric field, Moving charge - magnetic field. Untrue, and I challenge you to cite any credible experimental data that you think proves your belief. Far-field EM radiation is produced only by the current flow on the antenna, and that radiation contains BOTH the electric and the magnetic fields. You may have missed the accurate description posted by Chris, and pasted below. "The acceleration of charge in an antenna results almost entirely from the applied potential difference at its terminals. The radiated fields result from the alternating current effectively passing through the radiation resistance, and all the other, reactive, fields have no direct effect on the radiation resistance, or the component of the current that passes through it in phase with the voltage that is developed across it, which together, of course, represent the radiated power. The reactive fields affect the terminal impedance and a large imaginary part can upset the device trying to send power into the antenna, but that is more of a system issue. The alternating current that passes through the radiation resistance is composed of charge that moves in time with each RF cycle, accelerating and decelerating accordingly. The electrostatic field developed between the ends of a half-wave dipole reaches its maximum value a quarter of a cycle later than the voltage at the drive point so any effect it has on the charge in the antenna elements during each cycle must be reactive, and it doesn't affect the radiation resistance or the radiated wave." RF |
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