What type of radiation pattern is created by two 1/4-wavelength vertical antennas spaced 1/4-wavelength apart and fed 90 degrees out of phase?
Cardioid✓Respuesta correcta
A figure-eight end-fire along the axis of the array
A figure-eight broadside to the axis of the array
Omni-directional
Explicación
Quarter-wave spacing adds 90 degrees of path difference, which exactly cancels the 90-degree feed difference in one direction along the axis and doubles it to 180 degrees in the other. Reinforcement one way and a deep null the other gives the heart-shaped cardioid.