The calculator app is designed to give the vertical height of a particular antenna, for the frequency and wavelength chosen. This does NOT take into consideration the type or size of horizontal reflectors, of even if there is a need for them. Enter the desired frequency and select the wavelength. Click on Calculate and the optimum length for that combination will be displayed in feet,inches and fractions of inches, and in meters. To optimize the antenna for a frequency RANGE, do the calculations twice, once for the low end of the range and once for the high end; then average the two and plan to adjust the VSWR on both ends of the range as needed.