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Roy, W7EL wrote:
"If the wavelength is 1m, the voltage induced in the center of an open-circuited 1m dipole by a 1V/m field is 0.5 volt, not 1 volt." An open-circuited dipole (has a small gap in its middle) is mot resonnant at a wavelength of 2 meters, but its individual pieces are resonant at a wavelength of 1 meter. At 2 meters, not a wavelength 1m, each 0.5 m piece of the half-wavelength, 1 meter long dipole has a high reactance because 0.5 m is too short at a wavelength of 2 meters to be resonant. At longer wavelengths, the reactance rises.. High reactance does not oppose non-existing current in an open-circuit. I agree the voltage induced in 1/2-meter of wire properly placed within a 1V/m uniform field is 0.5 volt, not 1 volt. The induced voltage in a wire within a uniform field sweeping the wire rises uniformly along the wire. It can be assumed to be the summation of tiny increments of voltage all along the wire. The voltages of the too-short dipole halves add just as two cells in some flashlights add. Their vectors are head to tail. But, current will be limited by radiation and loss resistances of the wires. It will also be limited by reactance in the wires. Open-circuit, 0.5 V + 0.5 V = 1V. Best regards, Richard Harrison, KB5WZI |
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