In free space, how does the gain of two three-element, horizontally polarized Yagi antennas spaced vertically 1/2 wavelength apart typically compare to the gain of a single three-element Yagi?
AnswerApproximately 3 dB higher
Stacking two identical Yagis vertically by about one-half wavelength typically provides about 3 dB more gain than a single antenna.