Introduction
Radio waves, like light waves and all other forms of electromagnetic radiation, normally travel in straight lines. Obviously this does not happen all the time, because long - distance communication depends on radio waves traveling beyond the horizon. How radio waves propagate in other than straight-line paths is a complicated subject, but one that need not be a mystery. This page provides basic understanding of the principles of electromagnetic radiation, the structure of the Earth's atmosphere and solar-terrestrial interactions necessary for a working knowledge of radio propagation. More detailed discussions and the underlying mathematics of radio propagation physics can be found in the references listed under additional resources.
The Sun, being the largest engine in our solar system, has a great effect on propagation as its "exhaust" interacts with our Earth's magnetic field. A rudimentary knowledge of sunspots, solar flares and mass ejections will help the amateur take advantage of these effects to enhance his pleasure, or understand his plight. A good basic understanding of this can be had by reading the article "The Sun, the Earth, the Ionosphere." See also the list of other articles on propagation.
You can get custom professional-grade high-frequency (3-30 MHz) propagation predictions online.
Where can I find solar data?
Mark Downing, WM7D, has graphs of solar data on his web site.
Current HF Propagation Charts
March 2014
February 2014
January 2014
December 2013
November 2013
October 2013
September 2013
East Coast
Midwest
West Coast
Alaska/Hawaii
These predictions are for a solar flux of 128.
August 2013
East Coast
Midwest
West Coast
Alaska/Hawaii
These predictions are for a solar flux of 126
July 2013
June 2013
May 2013
April 2013
March 2013
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