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• Propagation is best on frequencies having multiple
   horizontal reflecting layers.
   
• A layer above 350 km indicates weaker propagation
   than a layer at a lower altitude.
   
• A thick E layer (below 150 km) can produce
   excellent propagation when there is no F2 layer.
   
• Vertical "rain" indicates a weak reflecting layer
   with increased atmospheric noise.
   
• Vertical artifacts below 150 km are foreign or
   domestic broadcast stations.

Ionogram provided by UML Space Science Lab