# Voltage Induced in a Half-Wave Dipole

May 25th Fact-of-the-DayA 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 = E^{2} /
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 wavelength^{2} x E^{2})
/ 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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