rooftop television yagi-uda antennas these used @ vhf , uhf frequencies. the amount of signal received distant transmission source geometric in nature due inverse-square law, , leads concept of effective area. measures performance of antenna comparing amount of power generates amount of power in original signal, measured in terms of signal s power density in watts per square metre. half-wave dipole has effective area of 0.13 λ {\displaystyle \lambda } . if more performance needed, 1 cannot make antenna larger. although intercept more energy signal, due considerations above, decrease output due moving away resonant length. in roles higher performance needed, designers use multiple elements combined together. returning basic concept of current flows in conductor, consider happens if half-wave dipole not connected feed point, instead shorted out. electrically forms single ⁄2-wavelength element. overall current pattern same; current 0 @ 2 en...
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