This calculator allows you to estimate the interior and exterior radii of an antenna’s coverage based on its height, its electrical inclination (downtilt) and the vertical beamwidth. It helps define the useful range of the signal and adjust the orientation for uniform coverage.
It is particularly useful for network engineers, cell site designers, and technicians who plan base station coverage and want to limit cell-to-cell interference.
Formulas
Interior radius = H / ( tan(A + BW/2) × 5280 )
Exterior radius = H / ( tan(A – BW/2) × 5280 )
Where H is the antenna height (in feet), A is the tilt angle (in degrees), and BW is the vertical beamwidth (in degrees). Radii are obtained in miles (convertible to kilometers or meters).
Explanation of formulas
- The inner radius is the minimum distance where the main signal hits the ground.
- The outer radius represents the maximum useful range distance of the beam.
- Tangent functions are used to relate the tilt angle to the beam geometry.
- These calculations are essential to avoid gray areas and excessive overlap.
Calculating the coverage radius of a 100 foot antenna with a 5° downtilt
Inlet : H = 100 ft, A = 5°, BW = 10°
Output : Inner radius ≈ 0.96 miles, Outer radius ≈ 1.92 miles
Benefits and uses
- Optimizes coverage of cellular and radio antennas.
- Reduces interference between neighboring sites.
- Facilitates planning of mobile and wireless networks.
- Practical tool for RF engineers and antenna installers.