WIFI Vertical Sector Antenna Tilt Angle Calculator
Antenna beam footprints and Antenna Gain
But this is only one part of what we need to do to. We now need to look at some antenna specification sheets to see what gain they achieve and what their horizontal and vertical beam footprint looks like. So we start with these horizontal and vertical beam footprint diagrams below.
Antenna Beam Footprints
The diagrams show the relative signal strength of a typical sector antenna. What these diagrams show is how the relative signal changes with angular position. Lets take the horizontal pattern. We see the reference point marked as 0 on the right on the centre line. It is here we can expect a maximum signal level from the antenna. If we then measure the signal level at different points of the compass moving round in a circle we can plot points at different power levels thus creating the red line representing the antenna footprint. On the centre line at a point marked as (-3) is a circle which intersects the red line above and below the centre line.
The half power point used for Gain measurement
In the diagram the (-3) point intersects the red line at compass points 60 degrees either side of the centre line ensuring that the half power point indicated by the (-3) meaning minus 3 dB ensures that in this sector all points can expect to receive half the maximum power achieved at the reference point (0). By convention the antenna gain is measured at these end points.
Calculating the Vertical Sector Antenna Tilt Angle
From this antenna image notice the antenna has an adjustable mounting bracket for changing the vertical tilt of the antenna which will be required to maximise the signal propagation in the target zone for none point to point applications. Note that in a point to point application between antennas there would be no need to calculate a tilt angle if the antennas were at the same height. If they are not at the same height we would calculate a tilt angle but this time change the calculation slightly to ensure the maximum signal was carried directly on the line of sight between the antennas.