ITU-R P618-8 Rain Model

This ITU rain model is included for backwards compatibility and is superseded by ITU-R P618-12.

Parameter	Description
Surface Temperature	The surface temperature used by the model.
Enable Cross Polarization Loss	Models depolarization of a communications link due to rain.

Tropospheric Scintillation

Parameter	Description
Compute Deep Fade	Select to model strong destructive interference.
Surface Temperature	Enter the surface temperature value.
Tropo Fade Outage	Enter the Tropospheric Fade Outage as a percentage. STK will compute the loss in dB that will occur for the percentage time not exceeding the specified limit.
Percent Time Refractivity Gradient < -100 N	The percentage of time that the reflectivity gradient in the lowest 100 meters of the atmosphere is less than -100 N units/km.

The Tropospheric Scintillation model is based on modeling RF energy in a beam with a certain beam width. Since Dipole antennas are omni-directional and do not provide a beam width, a standard dish antenna with 1.0 meter diameter and 70% efficiency is assumed for computing scintillation loss only. This does not impact link budget computations, which are still carried out for a dipole antenna selected as the system model.