Quarter Wave Ground Plane Antenna

The Quarter Wave Ground Plane Antenna is a special case of a vertical dipole antenna, where the lower half is a mirror image of the top half. The mirror image is created by a reflecting ground plane. In this case the ground plane is created by 3 to 6 radial elements. Their length is 12% longer than the quarter wave dipole element. All elements are scaled by 95% to cancel a small inductive reactance. The radials are bent downward by approximately 42 degrees to adjust the feedpoint impedance to 50 ohms (for an ideal infinite horzontal ground plane the impedance would be 36 ohms).