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Voltage Induced in a Half-Wave Dipole

May 25th Fact-of-the-Day

A half-wave dipole collects RF energy from a broadside wavefront area of 0.1305 square wavelength. The RF resistance of free space is 377 ohms. P = E2 / R watts. Therefore, if a receiving antenna in free space has no losses and is orientated optimally with respect to an incoming electromagnetic wavefront it will intercept (0.1305 wavelength2 x E2) / 377 watts, where E is the field-strength of the wave in volts-per-meter. A simple half-wave dipole transforms the 377 ohm resistance of free space to 72 ohms at its center terminals. E = square-root (P * R) volts. Therefore, the RF voltage across receiving half-wave dipole center terminals is square-root (P * 72) volts, where P is the induced power result from the previous calculation. ©2005 Martek International All rights reserved.

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