The subject of radio wave propagation has fascinated me sense I first started to understand the phenomenon almost 60 years ago. It is extremely important to us as ham radio operators to understand radio propagation and why some frequencies respond in a way very different then other frequencies if we are going to most effectively use radio propagation to communicate.
With the advent of satellites being used for long range radio communications and the popularity of repeaters, cell sites, and microwave links assisting with more localized radio communications needs VHF, UHF and above now dominates the government and commercial radio frequency communications needs. HF is a lot less appealing to professional communications then it was in the past.
But if, as far as I am concerned it is not if but when, these other system suffer a major catastrophe and thus no longer function amateur radio operators are the ones who will still have the knowledge of how to use natural radio propagation phenomenons to maintain communications.
If you are having a little difficulty understanding the aspects of how HF propagation and the ionosphere work together watch this video. Tyler N7FP has done an excellent job of explaining the subject and though he says it is probably not for Technician Class hams I believe it is good information for all hams.
For video [CLICK HERE]