Antenna Downtilt & Coverage Calculator Chart

An Antenna Downtilt and Coverage Calculator, or Antenna Tilt Calculator, aids the user by providing an approximate downward angle at which to install a directional antenna to reach desired signal strength and coverage between a transmitter and receiver at different heights and some distance away. An example use case is when a cell-tower directional transceiver is located at the top of a tower mast and a user is trying to figure out the best downtilt angle for that directional antenna to provide optimal service to an antenna at the top of a building, possible for the purpose of feeding a distributed antenna system (DAS) that provides cellular service coverage within the building.

The previous equation is an approximation approach to determining the appropriate downtilt angle from the 0-degree horizon from the antenna’s perspective given the height of the tower from the ground(Ht), height of the target from the ground (Hr), and the distance between the two antennas. The inner and outer radius of the primary antenna beam (coverage) can also be determined once the downtilt angle (Adt), in degrees,  is found as long as the antenna beamwidth (in degrees) is known (Abw).

In many cases, the primary antenna is declared the “transmitter” where the secondary, or target, antenna is declared the “receiver”. In this description the “transmitter” is the directional antenna where the receiver is assumed to be an omnidirectional antenna with adequate azimuthal beamwidth to efficiently capture the “transmitter”. In another case where both the “transmitter” and “receiver” antennas are directional, then the uptilt angle of the “receiver” antenna is simply 90 degrees minus the downtilt angle of the “transmitter” antenna.

It is important to note that all of the inputs into the Antenna Downtilt & Coverage Calculator should be in the linear units either inches, feet, yards, miles, centimeters, meters, or kilometers. If performing the calculation by hand, then linear units need to all be the same. The online calculator provided by Pasternack is able to handle inputs in different linear units.

This calculation is meant to provide a first order approximation only and will not necessarily provide optimal signal strength between the two nodes. It is likely that using an RF Power Meter at the adjustable node while driving the other antenna and finding a point at which the maximum signal energy is coupled, will result in the best installation.