Path Profile Data Entry Form - Vigants Barnett
The first portion of this data entry form is common to all multipath fade probability algorithms.
The Vigants Barnett method uses a C factor to calculate propagation reliability. If the path center coordinates are available, the C factor can be obtained with its calculate button. The following guidelines are given for direct entry of the C factor:
| C = 0.25 | good propagation conditions in mountainous and dry climates |
| C = 1 | average propagation conditions for average terrain and climatic conditions |
| C = 4 to 6 | difficult propagation conditions over water and in gulf coastal areas |
Maps showing C Factors are also available.
Alternately, the C factor can be calculated from the terrain roughness and a climatic factor. This is the preferred method. If the path center coordinates are available, the climatic factor can be obtained with its calculate button. The following guidelines are used for the climatic factor
| cf = 0.5 | good propagation conditions in mountainous and dry climates |
| cf = 1 | average propagation conditions for average terrain and climatic conditions |
| cf = 2 | difficult propagation conditions over water paths and in gulf coastal areas |
Terrain roughness can be entered directly in the range 6 to 42 meters (20 to 140 feet) or graphically calculated by clicking its calculate button. More on the Terrain Roughness Calculation.
An option to use Path Inclination is included. Path inclination is not normally used in the Vigants - Barnett multipath fade algorithm. A modification taken from ITU-R P.530-8 is available to account for path inclination. Click the blue arrow in the Path Inclination field to access the Path Inclination window. A summary of the calculation is displayed along with the option to include it in the current calculation.