VOACAP Information

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HF Propagation Prediction and Ionospheric Communications Analysis

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Radio propagation is the behavior of radio waves when they are transmitted, or propagated from one point on the Earth to another, or into various parts of the atmosphere. Radio propagation is affected by the daily changes of water vapor in the troposphere and ionization in the upper atmosphere, due to the Sun. There is a correlation between sunspots and propagation conditions. Sunspots are dark regions on the surface of the Sun. There are more sunspots when the Sun is more active, and produces more radiation, which can affect the Earth’s ionosphere. The sunspots appear in cycles of 11 years. Due to the sun’s radiation and flux values, we can expect different propagation during dark respectively light hours.

HamSphere 4.0 is based on real shortwave propagation including sunspots and solar flux values. As a shortwave listener or a shortwave Ham operator you are already fully aware of these conditions and you carefully plan your antennas, transceivers, QRV times and locations for these phenomenons. Voice of America’s transmitter technicians and planners have used a sophisticated area coverage analysis program called VOACAP for years. This program is now available to the public and can be used as an online service.

This is a good opportunity for you to explore these propagations hands-on. Just follow this link to the VOACAP Online system and start exploring it.

The VOACAP Online prediction system is the most accurate system on the market with over 50 years of radio propagation experience built in. Thanks to: Jari Perkiömäki, OH6BG/OG6G who avidly keep this “work-in-progress guide” alive.

You basically drag and drop the QTH for Transmitter and Receiver and the predicted radio propagation is displayed as a colored “pie-chart” with probability calculations for all bands over 24 hours. You can also experiment with different antennas, transmitter power and sun spot numbers.

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Solar-Terrestrial Data

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