ARRL

Propagation

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

October 2014

East Coast

Midwest

West Coast

Alaska/Hawaii

These predictions are for a solar flux of 141.

 

September 2014

East Coast

Midwest

West Coast

Alaska/Hawaii

These predictions are for a solar flux of 125.

August 2014

East Coast

Midwest

West Coast

Alaska/Hawaii

These predictions are for a solar flux of 144.

July 2014

East Coast

Midwest

West Coast

Alaska/Hawaii

These predictions are for a solar flux of 144.

June 2014

East Coast

Midwest

West Coast

Alaska/Hawaii

These predictions are for a solar flux of 144.

 

May 2014

East Coast

Midwest

West Coast

Alaska/Hawaii

These predictions are for a solar flux of 142.

April 2014

East Coast

Midwest

West Coast

Alaska/Hawaii

These predictions are for a solar flux of 145.

March 2014

East Coast

Midwest

West Coast

Alaska/Hawaii

These predictions are for a solar flux of 146.

February 2014

East Coast

Midwest

West Coast

Alaska/Hawaii

These predictions are for a solar flux of 146.

January 2014

East Coast

Midwest

West Coast

Alaska/Hawaii

These predictions are for a solar flux of 152.

December 2013

East Coast

Midwest

West Coast

Alaska/Hawaii

These predictions are for a solar flux of 126.

November 2013

East Coast

Midwest

West Coast

Alaska/Hawaii

These predictions are for a solar flux of 129.

October 2013

East Coast

Midwest

West Coast

Alaska/Hawaii

These predictions are for a solar flux of 123.

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

East Coast

Midwest

West Coast

Alaska/Hawaii

These predictions are for a solar flux of 123.

June 2013

East Coast

Midwest

West Coast

Alaska/Hawaii

These predictions are for a solar flux of 130.

May 2013

East Coast

Midwest

West Coast

Alaska/Hawaii

These predictions are for a solar flux of 118.

April 2013

East Coast

Midwest

West Coast

Alaska/Hawaii

These predictions are for a solar flux of 115.

March 2013

East Coast

Midwest

West Coast

Alaska Hawaii

These predictions are for a solar flux of 119.