Ground plane antenna
The ground plane antenna consists of a vertical rod lifted by four radials. The ground plane antenna is designed for unbalanced feed cables, like a coaxial cable. The driven element is often 1/4 λ long and the frequency is often between 10 and 512 MHz.
l is the symbol for length and is measured in meter (m).
f is the frequency in megahertz (MHz).
f v is the velocity factor.