ITSHF  Propagation Analysis Package                       Date: 7 Feb 1997

REC_GEN   General information on the REC533 propagation prediction model

REC533 is a PC/DOS 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 30MHz 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 written
with the assumption that anyone executing these programs has a basic understanding
of HF radio broadcasting, the propagation prediction model, and the Windows
operating system Version 3.x, 95, or NT.

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* BACKGROUND *
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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.
It is available by contacting NTIA/ITS at:
	Chris Behm (303)497-3375
		  E-mail: cbehm@its.bldrdoc.gov
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