General information on the VOACAP propagation prediction model
[This document is part of the help files integrated into the ITS HFBC software package.]
The Ionospheric Communications Enhanced Profile Analysis and Circuit Prediction Program (ICEPAC) 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 ICEPAC (a descendent of IONCAP), 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 ICEPAC are provided:
- ICEPAC - produces point-to-point predictions. Tabular output or contours of any output variable on a 24-hour by 30-MHz graph.
- ICEAREA - 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 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).
For many years, numerous organizations have been employing the HF spectrum to communicate over long distances. It was recognized in the late 1930's that these communication systems were subject to marked variations in performance. The effective operation of long-distance HF systems increased in proportion to the ability to predict variations in the ionosphere, since such an ability permitted the selection of optimum frequencies, antennas, and other circuit parameters. Research demonstrated that most variations in HF system performance were directly related to changes in the ionosphere, which in turn are affected in a complex manner by solar activity, seasonal and diurnal variations, as well as latitude and longitude. Various organizations developed computer models to analyze HF circuit performance.
The Ionospheric Communications Analysis and Prediction Program (IONCAP) developed by ITS and its predecessor organizations, became one of the more accepted and widely used models for HF propagation predictions. However, IONCAP demonstrated poor performance in the polar region and used some of the older electron density profile structures. To correct these problems, IONCAP was transformed into ICEPAC by adding the Ionospheric Conductivity and Electron Density (ICED) profile model described in Tascione (1987). The ICED profile model is a statistical model of the large-scale features of the northern hemisphere. The model recognizes the different physical processes that exist in the different regions of the ionosphere. It contains distinct algorithms for the sub-auroral trough, auroral zone, and polar cap.
Tascione, T.F., K.W. Kroehl, and B.A. Hausman, A technical description of the ionospheric conductivity and electron density profile model (ICED, version 196-II), Syst. Doc Vol. VII, Air Weather Serv., U.S. Air Force, Scott Air Force Base, Ill., 1987.
NTIA/ITS version of ICEPAC for Point-to-Point predictions
The name ICEPAC used here represents the implementation of NTIA/ITS's ICEPAC propagation prediction program in the Point-to-Point mode. This is to differentiate it from ICEAREA which represents ICEPAC 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 ICEPAC for complete information on operation.
NTIA/ITS version of ICEPAC for Area coverage predictions
The name ICEAREA used here represents the implementation of NTIA/ITS's ICEPAC propagation prediction program in the Area Coverage mode. This is to differentiate it from ICEPAC which represents ICEPAC 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 ICEAREA for complete information on operation.