General information on the VOACAP propagation prediction model
[This document is part of the help files integrated into the ITS HFBC software package.]
The Voice of America Coverage Analysis Program (VOACAP) predicts the expected performance of high frequency (HF) broadcast systems, and in doing so is useful in the planning and operation of HF transmissions for the four seasons, different sunspot activities, hours of the day, and geographic location.
This current version of VOACAP running on a PC under Windows, incorporates a colorful, user-friendly interface to easily modify input variables and produce the desired results.
Two implementations of VOACAP are provided:
- VOACAP - produces point-to-point predictions. Tabular output or contours of any output variable on a 24-hour by 30-MHz graph.
- VOAAREA - produces area coverage predictions. Contours of any output variable on world maps.
See the appropriate HELP file for more details of each model.
The information provided within this program via the HELP windows, as well as in the quick reference guide is concise and practical, written with the assumption that anyone executing these programs has a basic understanding of HF radio broadcasting, the propagation prediction model, and Windows (3.1 or newer).
In 1985, the Voice of America (VOA) adopted the Ionospheric Communications Analysis and Prediction Program [Teters et al.,1983] as the approved engineering model to be used for broadcast relay station design and antenna specification. As the program was modified for these purposes, the name was changed to the Voice of America Coverage Analysis Program (VOACAP) to distinguish it from the official National Telecommunications and Information Administration (NTIA) IONCAP program. The development of VOACAP was accomplished for VOA by the Naval Research Laboratory and the Institute for Telecommunication Sciences (Department of Commerce, NTIA).
Teters, L.R., J.L. Lloyd, G.W. Haydon and D.L. Lucas, Estimating the Performance of Telecommunication Systems Using the Ionospheric Transmission Channel, Institute for Telecommunication Sciences NTIA Report 83-127, July 1983.
VOACAP - VOA version of IONCAP for Point-to-Point predictions
The name VOACAP used here represents the implementation of VOA's VOACAP propagation prediction program in the Point-to-Point mode. This is to differentiate it from VOAAREA which represents VOACAP in the Area Coverage mode.
Point-to-Point means that the propagation for a path from a transmitter to a receiver is calculated. Output may be either tabular (line printer style reports), or graphical (contours of parameters on a Frequency versus Time plot).
See the HELP topics under VOACAP for complete information on operation.
VOAAREA - VOA version of IONCAP for Area coverage predictions
The name VOAAREA used here represents the implementation of VOA's VOACAP propagation prediction program in the Area Coverage mode. This is to differentiate it from VOACAP which represents VOACAP in the Point-to-Point mode.
Area Coverage means that the propagation for a path from a transmitter to a GRID of receivers is calculated. All parameters (20) are saved and may be plotted when requested. Results consist of contours of any parameter plotted on world political boundaries. Plots are created with an Azimuthal-Equidistant projection. The user specifies the projection center and the area of interest relative to that projection center.
The following layers of data may be included:
- Latitude/Longitude lines
- CIRAF zones
- World political boundaries
- User defined CITIES file
- Antenna main beam direction
- Contours of any propagation parameter
See the HELP topics under VOAAREA for complete information on operation.