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Institute for Telecommunication Sciences / Resources / Radio Propagation Software / IF77 / IF-77 Electromagnetic Wave Propagation Model (Gierhart-Johnson)

IF-77 Electromagnetic Wave Propagation Model (Gierhart-Johnson)

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, which is applicable to air/air, air/ground, air/satellite, ground/ground, and ground/satellite paths. The IF-77 was incorporated into a number of FORTRAN programs that are useful in estimating the service coverage of radio systems. These programs may be used to obtain a wide variety of computer-generated microfilm plots.

The IF-77 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.

The work was performed under contract to the U.S. Department of Transportation (DOT), contract number DTFA01-82-Y-10539 and published in the report:

The IF-77 software is available for download as a "zip" file. The download contains software developed by NTIA. NTIA does not make any warranty of any kind, express, implied or statutory, including, without limitation, the implied warranty of merchantability, fitness for a particular purpose, non-infringement and data accuracy. NTIA does not warrant or make any representations regarding the use of the software or the results thereof, including but not limited to the correctness, accuracy, reliability or usefulness of the software or the results. You can use, copy, modify, and redistribute the NTIA-developed software upon your acceptance of these terms and conditions and upon your express agreement to provide appropriate acknowledgments of NTIA's ownership of and development of the software by keeping this exact text present in any copied or derivative works. By clicking this link to download the software, you acknowledge that you have read the above disclaimer.

The zip package contains:

  • ata.exe: An executable file for ATA that runs on a PC under DOS
  • Sample input file for ATA. Run with: ata < > atoa.out
  • atoa.out: Sample output file for ATA.
  • cards.txt: Text description of data input cards.
  • Source file for ata.for
  • Source file for aalos.for
  • Source file for amsc.for
  • Source file for asorp.for
  • if77_intel.exe: In response to changing times, this executable was developed to run on a Windows 7, 64-bit machine. It has been tested at ITS, but due to the many different ways in which Windows 7 can be configured, we cannot warrant that it will run on all Windows 7 computers in all environments. Source code is not provided for this executable.

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 following publications provide additional information:

For assistance with downloads, contact For technical questions about IF-77, contact Paul McKenna, (303) 497-3474,