The standard ground plane antenna consists of a vertical radiator
which is insulated and centered between 4 horizontal surrounding
radials which extend out from the base of the antenna. Each radial
is evenly spaced 90 degrees or so from each other around the vertical
element.

Gain is -0.29 dB less than dipole. Angle of radiation is 27 degrees.

Enter the formula for the antenna calculation (normally 234/f):

divided by
Freq. MHZ

The vertical length is
feet.

The 4 radials are each
feet.