VOACAP is a radio propagation model

Radio propagation model

A radio propagation model, also known as the Radio Wave Propagation Model or the Radio Frequency Propagation Model, is an empirical mathematical formulation for the characterization of radio wave propagation as a function of frequency, distance and other conditions...

 that uses empirical data to predict the point-to-point path loss

Path loss

Path loss is the reduction in power density of an electromagnetic wave as it propagates through space. Path loss is a major component in the analysis and design of the link budget of a telecommunication system....

 if given as inputs: two antennae (configuration and position), solar weather, and time/date.

It was originally designed for Voice of America

Voice of America

Voice of America is the official external broadcast institution of the United States federal government. It is one of five civilian U.S. international broadcasters working under the umbrella of the Broadcasting Board of Governors . VOA provides a wide range of programming for broadcast on radio...

.

It is coded in Fortran. The program was eventually ported to Windows, then ported to Linux (voacapl). The program has I/O

I/O

I/O may refer to:* Input/output, a system of communication for information processing systems* Input-output model, an economic model of flow prediction between sectors...

 in the form of text files, but wrappers now exist in Python part of the GPL pythonProp project.

Official link: http://www.voacap.com/