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Szczepan Białek wrote:
Now you have to decide what your half wave antenna is going to do. Charge up only and let the power leak away or radiate without having any power! A 1/2WL dipole is a standing-wave antenna. Believe it or not, ~80% of the steady-state energy on a 1/2WL dipole is not radiated, i.e. as far as total energy is concerned, radiation is a secondary effect. Energy is traveling in both directions at the same time on a standing-wave antenna. At the tip of the antenna, the two energy flows are equal. At the feedpoint, the reflected wave is only ~20% down in energy level from the forward wave - the reflected voltage and current are only ~10% down from the forward voltage and current. The feedpoint impedance of a 1/2WL dipole is the result of superposition of the forward and reflected waves. The Z0 of a 1/2WL dipole using #14 wire at a height of 30 feet is very close to 600 ohms. -- 73, Cecil, IEEE, OOTC, http://www.w5dxp.com |
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