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IF-77 Air-to-Ground Propagation Model (Gierhart-Johnson)

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IF-77 Air-to-Ground Propagation Model (Gierhart-Johnson)

Applicability of the Propagation Model

The IF-77 radio wave propagation model is applicable to air/ground, air/air, ground/satellite, and air/satellite paths. It can also be used for ground/ground paths that are line-of-sight or smooth earth. Model applications are restricted to telecommunication systems operating at radio frequencies from about 0.1 to 20 GHz with antenna heights greater than 0.5 m. In addition, radio-horizon elevations must be less than the elevation of the higher antenna. The radio horizon for the higher antenna is taken either as a common horizon with the lower antenna or as a smooth earth horizon with the same elevation as the lower antenna effective reflecting plane.

History of the Software Implementation

In 1973, ITS released the IF-73 (ITS-FAA-1973) air/ground propagation model developed for the Federal Aviation Administration (FAA). IF-73 evolved into the IF-77 (ITS-FAA-1977) model. The IF-77 was incorporated into a number of FORTRAN programs that are useful in estimating the service coverage of radio systems. These programs were used to obtain a wide variety of computer-generated microfilm plots. Extensive comparisons of IF-77 predictions with measured data were made, and an atlas of basic transmission loss predictions was generated using the model. The work was performed under contract to the U.S. Department of Transportation (DOT), contract number DTFA01-82-Y-10539 and published in 1983.

Releases

A list of all available software releases can be viewed here. The original IF-77 software written by NTIA is Release v1.0. The release package contains:

  • ata.exe: An executable file for ATA that runs on a PC (tested on Windows 7)
  • atoa.in: Sample input file for ATA. Run with: ata.exe < atoa.in > atoa.out
  • atoa.out: Sample output file for ATA.
  • cards.txt: Text description of data input cards.

References

Contact

For technical questions about IF-77, contact Paul McKenna, [email protected].