Every attempt has been made to keep this site as simple as possible with a minimum of technical jargon. I figure that complex, obfuscated and obtuse writing is unlikely to attract new listeners!

It is hoped that those with an insatiable appetite for learning may find the following resources useful in explaining the underlying concepts and principles of FM DX. Enjoy!

What does the term DX mean?

A simple explanation by an unknown author  

A simple explanation by Belgian club DX Antwerp 

A simple explanation by Girard M. Westerberg

What is Tropo? 

A simple explanation by Glenn Hauser

What is Sporadic E? 

A simple explanation by Glenn Hauser 

A simple explanation by Universal Radio

A simple explanation by Herman, Amateur S57ONW

A simple explanation by Dave, Amateur G8TTI 

A simple explanation by Emil, Amateur W3EP

How do these two forms of propagation likely occur? Why?

A comprehensive explanation by Girard M. Westerberg

What information can I obtain from the ionograms? Will this allow me to make inferences about current Es paths which support the FM or 2 metre band? In simple terms, what does the established research to date suggest? What are Spread Es?

Please read section 7 & the case studies.

What are the likely characteristics of blanketing Sporadic E?  What is the E layer (also referred to as the Es layer) of the ionosphere? What are Es hops?

Please read pages 8-9. 

A comprehensive explanation by Australian space weather agency IPS

What are geomagnetic disturbances of the ionosphere? What are Coronal Holes? How might these disturbances affect Sporadic E conditions? 

Please read pages 3-4.

A comprehensive explanation by Andrew McDonald, PhD of IPS 

What is an ionogram? What are intense Es that may cause blanketing? 

A simple explanation by Chris J. Davis of the UK's Rutherford Appleton Laboratory 

Of the variables that can be identified from ionograms, which are important in assessing real-time Sporadic E conditions? 

A simple explanation by the US NOAA - National Geophysical Data Center

What do blanketing Es commonly look like on Australasian ionograms? What should I be looking out for on the ionograms? How do I identify the foEs variable from ionograms?

Please familiarize yourself with the diagrams on pages 11 & 22 only. 

A comprehensive explanation by the US NOAA - World Data Centre A for Solar-Terrestrial Physics 

What do blanketing Es look like on ionograms? How can I estimate an approximate Maximum Useable Frequency using the Secant Law and the foEs variable reading? 

A simple explanation by Pat J. Dyer, Amateur WA5IYX 

Is it possible for thunderstorms to precipitate Sporadic E? What are gravity waves? How might gravity waves form in the troposphere and stratosphere? What is one possible relationship between gravity waves, wind shear & the formation of Sporadic E? Is there only limited data available to researchers? If so, why might this limit the investigation of all proposed theories linking thunderstorms to the formation of Sporadic E? 

A comprehensive explanation by German Amateurs V. Grassmann et. al.

How strong is the correlation between intense meteor shower activity and the formation of multiple layers of Sporadic E? Are there ambiguities in the research undertaken? If so, why? 

A comprehensive explanation by Indian Researchers H. Chandra et. al.

Small icons by Dry Icons.  The theories behind FM DX radio propagation are rarely "black and white" or to put it another way, precisely defined. Both beginners and active enthusiasts are encouraged to read widely. Above all, have fun learning and keep a generous open mind to alternative perspectives. To quote Socrates... "True wisdom comes to each of us when we realize how little we understand about life, ourselves, and the world around us."