Diffraction Parameters

Select Configure - Options - Program Options - Diffraction - Diffraction Parameters. Alternately click the frequency box on the status bar.

Diffraction Algorithm

Select the default diffraction method

Tropospheric Scatter Loss

Tropospheric scatter loss can be calculated using either of the following relationships:

30 * log10(Frequency)

36 + 20 * log10(Frequency)

The latter relationship effectively removes the frequency dependence in tropospheric scatter loss. The cross over frequencies of these two definitions is 3981 MHz. If the scatter loss method is set to Auto, then the program will use the correct method, based on the specified frequency.

If the NSMA automatic diffraction algorithm is selected, then the 36 + 20·log(f) relationship will always be used.

Climatic Region

The climatic region determines the time variability of the combined diffraction and tropospheric scatter loss. This is used in an OHLOSS calculation.

Polarization

This is the design polarization and is global to all modules in the program. With the exception of the two ray optics algorithm, polarization does not significantly affect the diffraction loss calculations.

Frequency

This is the design frequency and is global to all modules in the program.

Divergence

Divergence is the scattering of a reflected wave due to the curvature of the earth. This applies to the two ray optics algorithm only. The option is global and its primary use is in the Multipath - Reflections module.

Tree type

This option applies to single trees and ranges of trees, which have been manually entered on the profile. The basic tree types are: bare trees, full leaf trees, evergreen trees and rain forest. Each of these types are classed as either wet or dry foliage. Tree loss on a path profile is calculated as the smaller of the losses calculated as a knife edge and the loss calculated as a lateral wave along the tree tops. The lateral wave loss calculation depends on the type of tree and the wet or dry classification.

Default Clutter Category

The clutter category selection only applies to clutter databases which contain the clutter heights but no description. In a description only clutter database, the actual clutter category is used. The Wet foliage - Dry foliage options applies to all clutter databases.