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.

• The Sun, the Earth, the Ionosphere:
  What the Numbers Mean, and Propagation Predictions--a brief introduction to propagation and the major factors affecting it. By Carl Luetzelschwab, K9LA
• An Introduction to Gray-Line DXing 
  QST November 1992, pp. 80-82
  The transitions from darkness to daylight and daylight to darkness cause drastic changes in the ionosphere. Use this to your DX advantage.
• Catch a Falling Star 
  QST October 1997, pp. 63-67
  A Beginner's guide to meteor-scatter communication.
• Sporadic E--A Mystery Solved? Part 1
  QST October 1997, pp. 39-41
  One of the world's leading ionospheric scientists explains the physics of sporadic E.
• Sporadic E--A Mystery Solved? Part 2
  QST November 1997, pp. 38-42
• HF Propagation: The Basics
  QST December 1983, pp. 11-15
  Say it's 10 P.M. in Savannah, and you'd like to reach out and QSO someone in southern Europe. A solid knowledge of how signals travel will help you decide if you've got a fighting chance.
• Radio Waves And Communications Distance
  QST, January 1985, pp. 31-33
• Here Comes the Sun
  QST, Lab Notes, October 1996, pp. 74-75
• Radio Waves and the Ionosphere
  QST, November 1999, pp. 62-64
• Propagation Broadcasts and Forecasts Demystified
  QST November 1991, pp. 20-25
• ARLP029: Propagation de K7VVV
  W1AW broadcasts a weekly Propagation Bulletin. In this one Tad Cook, K7RA, formerly K7VVV,  gives a summary of what the numbers in a propagation forecast mean and how they are compiled.
• The Brendan Trophies: Insights for the New Millennium
  QST August 2002, pp. 36-39
  Can amateurs cross the Atlantic on 144 MHz without satellites or moonbounce?
• Understanding Solar Indices
  QST September, 2002, pp. 38-40
  When someone tells you that the flux is up to 200 and the K is 3, do you know what they are talking about? You will after you read this article!
• What is VOACAP Trying to Tell Me?
  A Presentation to The Yankee Clipper Contest Club Feb. 1, 2003, Milford, CT, by Dean Straw, N6BV, Senior Assistant Technical Editor, ARRL
• Why We Stack ‘Em! Covering All the Angles
  A Presentation to The Yankee Clipper Contest Club, Feb. 1, 2003, Milford, CT, by Dean Straw, N6BV, Senior Assistant Technical Editor, ARRL
• Microwave Propagation in the Upper Troposphere
  QEX July/August, 2003
  Amateur microwave work need not be restricted to operation
• Propagation Planning for DXpeditions 
  6 Steps for a More Successful Trip by Carl Luetzelschwab K9LA
• Propagation Planning for Contests
  Using Propagation Predictions to Develop a Band Plan by Carl Luetzelschwab K9LA
• Practical Radio Aurora
  QST March 1990, pp 20-25.  While solar events such as coronal mass ejections can seriously disturb HF propagation, the same events can also enhance VHF propagation.

• An Introductory Tutorial to W6ELProp (96,641 bytes, PDF file)
  A Guide to Running Your Own Propagation Predictions, by Carl Luetzelschwab, K9LA. W6ELProp is named after the amateur call sign held by Sheldon C Shallon.
• An Introductory Tutorial to VOACAP (92,076 bytes, PDF file)
  A Guide to Running Your Own Propagation Predictions, by Carl Luetzelschwab, K9LA
• Electronics Technician Volume 7—Antennas and Wave  Propagation NAVEDTRA 14092 Large 3.11MB download.

• Steve Nichols G0KYA and Alan Melia G3NYK wrote a series of propagation articles for the RSGB that is now an ebook.  It can be downloaded from Steve Nichols’ blog.

• Radio Signal Propagation
  Many articles on how radio signals travel great distances at different frequencies. Topics include sporadic E, sunspots, troposcatter, meteor scatter, sudden ionospheric disturbances, and ground wave propagation.
• hfradio.org propagation
  This page is dynamically created from many sources using automation, and the information contained is as fresh as possible. This page will reload every 15 minutes, which will refresh any content that has changed since last viewing.
• W1AW Propagation Bulletins W1AW, the Hiram Percy Maxim Memorial Station provides informational bulletins to Amateur Radio Operators.
• DX-Listeners' Club Solar Terrestrial Activity Report
  The Solar Terrestrial Activity Report is generally updated once a day. The report contains a graphical view of the last 2 months' solar flux values, sunspot count and planetary A index. In addition there is information on recent solar events as well as predictions for the next days. Charts of all sunspot cycles from cycle 1 are available as well as comparisons of the most recent cycle with previous cycles
• D-Region Absorption Prediction
  Presented by the NOAA/Space Environment Center
• Today's Space Weather
• Welcome to The Aurora Page
  Information, forecasts, links and images about the "Northern Lights".
• VHF / UHF Tropospheric Ducting Forecast
• Paul Kelley N1BUG maintains Aurora Sentry, a page with satellite maps that show auroral activity
• VOACAP.com Monthly point to point and coverage area predictions for HF propagation.

• G3USF's Worldwide List of HF Beacons Martin Harrison G3USF maintains a list of HF beacons.
• G3USF's Worldwide List Of 50MHz Beacons Martin Harrison G3USF maintains a list of 50MHz beacons.

• VHF/UHF BEACONS by WZ1V Ron Klimas WZ1V maintains a list of VHF/UHF beacons.

• Ham CAP 1.5
  HF propagation prediction tool for Amateur Radio.  Freeware by Alex Shovkoplyas, VE3NEA.
• HF Propagation Models from NTIA/ITS
  U.S. Department of Commerce NTIA/ITS Institute for Telecommunication Sciences High Frequency Propagation Models. The package includes ICEPAC, VOACAP, and REC533. Freeware.  
• Radio Mobile Freeware by VE2DBE
  This software by Roger Coude VE2DBE predicts the performance of VHF and UHF radio systems.
• PropView
  PropView uses the included IonCap propagation prediction engine to forecast the minimum and maximum useable frequencies between two locations over a specified 24 hour period.
• ACE-HF Professional Propagation Software for HF Radio Operators
  QST Product Review, November 2002 $200 program with 30 day trial (2022).
• DX Atlas by VE3NEA (Afreet Software, Inc.)
  Alex Shovkoplyas VE3NEA provides this software program. $30 program with 30 day trial (2022).