Aircraft Scatter Elevation Angles
One question often asked during discussions around aircraft scatter is to do with what elevation angle required for antennas when working aircraft scatter?
For the most part this only become an issue on the higher microwave bands where beamwidths start to under illuminate scatter regions.
A better question concerns the distance than can be worked on this mode. Unfortunately it is not easy to make accurate calculations as the refractive index is not known along the entire path. Many calculations incorrectly apply the 4/3 Earth radius rule resulting in overly optimistic predictions. The calculations have to take into account that the path through the troposphere and the refractive index will change for differenet elevation angles and path lengths.
Rather than rely on complex and variable calculations, experience has shown the simple table below (which contains height and distance to arrive at the elevation angle) is more than adequate.
The table has been in use for a few years in Europe and has been verified for use up to 10 GHz.
|QRB||Reflection Height – 8km||Reflection Height – 10km||Reflection Height – 12km||Reflection Height – 14km|
|Elevation Angle (deg)||Elevation Angle (deg)||Elevation Angle (deg)||Elevation Angle (deg)|