My Primary Radio Interest
Extreme long range VHF and UHF communications is my primary interest in Amateur Radio. Specifically, I am focusing on tropospheric ducting paths exceeding 3,000km. A large percentage of my web page focuses on this aspect of the hobby.


Overview
Tropospheric ducting spanning long trans-oceanic paths has not been fully explored. Several regions are already well proven. Some of these have been worked for more than 5 decades, while others are more recently “discovered”. These established paths are:

• California to Hawaii
• The Australian Bight
• West coast of Europe down West coast of North Africa
• Reunion Island to South Africa

Other trans-oceanic ducts have long been suspected. Occasional reports of DX reception over very long oceanic paths have been reported over several paths.  Probably the main reason these paths have not been worked yet is the lack of operators interested in and equipped to work these paths in the optimum locations.  Some of the paths yet to be worked include:

• North Atlantic     
  
• North America to West Africa
• North America to Europe
• South Atlantic    
  
• Southern Africa to South America
• Southern Africa to St. Helena and Ascension Islands
  
• South Indian Ocean   
  
• Reunion/ Mauritius to Australia
• South Africa to Australia
• North Indian Ocean  
  
•  Africa to India or Indonesia

Propagation Mechanism
The primary propagation mechanism for trans-oceanic ducting is the subsidence temperature inversion. There is a lot of detail available on the Internet on this propagation mode, and will not be repeated here. The reader is encouraged to review the following articles on the web.

• DF5AI has several excellent pages on tropospheric trans-oceanic ducting.
  
• Australian National VHF DX Group
  
• Atmospheric Refraction: How Electromagnetic Waves Bend in the Atmosphere and Why it Matters provides a good synopsis if inversions.
  
• Thermodynamic Structures of Subsidence Inversions is a good white paper on the climatology of subsidence inversions.

Additional Data Sources

• Hepburn maps           
  
• Weather Charts, isobaric         
  
• Weather charts, Sea Surface Temperature
  
• Radiosonde data
  
• FM Scan web page