Refractivity behaviour must be taken into account in propagation prediction methods used in service planning. Two examples are given:
Rec. P.[BLM] – is to be a replacement of the well-known Rec. P.370 used for broadcasting in the VHF and UHF bands. The new Rec provides a method for point-to-area services, also using curves as a basis, and covers % times for planning the wanted service (e.g. 50%) and also for evaluating interference signals at % times down to 1%. At these low %s, it is super-refractivity that is considered the dominant propagation mechanism.
Similarly Rec. P.452 attempts to cover all propagation mechanisms that can occur between two points on the surface of the Earth. It is used particularly at microwave frequencies and for the detailed evaluation of potentially interfering signals when services share frequencies. The mechanisms of super-refraction and ducting are modelled in the Rec. An example of the use of this Rec is given later.
