Case #10171

The VHF/UHF Propagation Prediction Program, otherwise known as CRC-PREDICT^®, is used for estimating radio signal strengths on terrestrial paths at VHF and UHF, given a transmitter location, power, and a receiver location(s). Since transmission paths are often obstructed by terrain, CRC-PREDICT operates concurrently with a machine-readable Canadian topographic database consisting of elevation and surface codes; recorded at 500-metre intervals. CRC-PREDICT can also be used without such database, either by manually entering path profiles, which is an effective but time-consuming task, or by using a general description of the terrain.

When a path profile is present, the main calculation is that of diffraction attenuation due to terrain obstacles. These obstacles are primarily hills, or the curvature of the earth, but can also include trees and/or buildings. The presence and particular location of trees and buildings are considered in the calculation; however, their height and structure are not considered. If the user is aware of a particular obstacle consisting of trees or buildings that are not present in the terrain data, an additional loss estimate can be included. The diffraction calculation is done by starting at the transmitting antenna and finding the radio field at progressively greater distances. At each step, the field at a point is found by a numerical integration over the field values found in the previous step. For long paths, tropospheric scatter becomes important. CRC-Predict combines the tropospheric scatter signal with the diffraction signal.

The calculation can be done for different percentages of time, locations, or probability (time and locations combined).

FEATURES

The new Version 3.1 is a significant upgrade over the previous Version 2.08 (which is no longer being maintained). The new features are:

• the source code is now written in C language, facilitating a modern user interface
• the program now uses Windows for insertion of input parameters
• the program uses the following graphical output plots:
  • a real-time area plot complete with a background map which shows rivers, lakes, roads, towns, place names and urban areas
  • a stand-alone version of the area plot which will plot existing CRC PREDICT output files
  • a height/distance plot for radial and point-to-point calculations
  • a 32-bit Windows stand-alone height/distance plot (hd_plot) which will plot existing CRC PREDICT output files, including single radials extracted from area coverage files
• a new driver for DTED elevation data has been added
• the accuracy of prediction has been improved in the upper UHF range
• the Users Guide has been up-dated and converted to HTML

POTENTIAL APPLICATIONS

• land mobile planning (i.e. radio system design);
• broadcasting;
• point-to-point relays;
• interference studies.

DELIVERABLES

Version 3.1 will be delivered in machine-readable (object 1) code only on CD ROM for suitable PCs running on DOS Windows and Windows 95. The software will only be released upon execution of a single computer user license.

PROTECTION

Copyright
Know-how

CONTACTS

Dave Rogers
Research Program Manager
Radio Propagation Research
Tel: (613) 998-5174
Fax: (613) 998-4077
E-mail: dave.rogers@crc.gc.ca

Jeet Hothi
Director, Technology Transfer Office
Tel: (613) 990-2089
Fax: (613) 990-7671
E-mail: jeet.hothi@crc.gc.ca