Enter your Transmitter Antenna Height, Receiver Antenna Height, Height Units, and K-Factor into the Line of Sight Calculator to find your Line of Sight Distance, Radio Horizon for both antennas, and the First Fresnel Zone Radius — everything you need to check whether your signal can actually make it from point A to point B.
Line of Sight Distance
--
Line of Sight Distance
--
Radio Horizon
--
Radio Horizon
--
First Fresnel Zone Radius
--
Line of sight distance is the maximum theoretical distance between two antennas where radio waves can travel in a straight line without obstruction from the Earth's curvature or terrain features.
Line of sight is the geometric distance based on antenna heights and Earth's curvature. Radio horizon extends further due to atmospheric refraction, which bends radio waves slightly beyond the geometric horizon.
The K-factor accounts for atmospheric refraction effects on radio waves. A standard value of 1.33 represents typical atmospheric conditions where radio waves bend slightly, extending the effective range beyond geometric line of sight.
Higher antennas provide greater line of sight distance. The relationship follows a square root function - doubling antenna height increases range by about 41%, not double.
Line of sight calculations are primarily used for VHF, UHF, and microwave frequencies (30 MHz and above) where radio waves behave more like light rays and don't bend significantly around obstacles.
The First Fresnel Zone is an elliptical area around the line of sight path that must be kept clear of obstacles for optimal signal transmission. Typically 60% clearance is required for good signal quality.
Yes, mountains, hills, buildings, and other obstacles can significantly reduce actual transmission range below the calculated line of sight distance. This calculator provides the theoretical maximum range.
You can enter antenna heights in either meters or feet. The calculator automatically converts between units and provides results in both kilometers and miles for distance measurements.