[This document is part of the help files integrated into the ITS HFBC software package.]

REC533 is a PC/Windows based implementation of the International Telecommunication Union's (ITU) propagation model Recommendation ITU-R PI.533. It 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 REC533, running on a PC under Windows, was developed and is maintained by the United States Department of Commerce, National Telecommunications and Information Administration, Institute for Telecommunication Sciences (NTIA/ITS) located in Boulder, Colorado. It incorporates a colorful, user-friendly interface to easily modify input variables and produce the desired results.

Two implementations of REC533 are provided:

• REC533 - produces point-to-point predictions. Tabular output or contours of any output variable on a 24-hour by 30-MHz graph.
• RECAREA - 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).

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Background

This propagation prediction method for use in the estimation of reliability and compatibility between frequencies of about 3 MHz and 30 MHz derives from a method first proposed in 1983 by CCIR Interim Working Party 6/12 with later refinements following considerations by WARCs for HF broadcasting, the CCIR, broadcasting and other organizations. The procedure applies a ray-path analysis for path lengths up to 7000 km, composite mode empirical formulations from the fit to measured data beyond 9000 km, and a smooth transition between these approaches over the 7000 - 9000 km distance range.

Monthly median basic MUF, incident sky-wave field strength, and available receiver power from a lossless receiving antenna of given gain are determined. Signal strengths are standardized against a CCIR measurement data bank. The method requires the determination of a number of ionospheric characteristics and propagation parameters at specified "control points".

The propagation program was made available to the ITU in July 1993 by Working Party 6A (WP6A). Information on the availability of that program is found in Resolution 63. This implementation was simultaneously developed by the U.S. Department of Commerce NTIA/ITS in Boulder, Colorado under contract from the Voice of America. It includes the point-to-point and area coverage models.