A lot can be said about propagation…
The very first thing I noticed when I got interested with propagation was a vast number of websites displaying charts and grids related to HF propagation conditions, but I didn’t really understand them at first. There are more types of measurements about the Sun’s activities than most care to understand, but there are a few ones that are very important to learn if you want to be able to understand a propagation report.Richard Corbeil VE2XIP
High frequency (HF) radio signals, which are signals in the frequency range of 3-30 MHz, have several unique propagation properties that make them useful for certain types of communication.
One of the key properties of HF radio signals is that they can be reflected by the ionosphere, a layer of the Earth's upper atmosphere that is ionized by solar radiation. This allows HF signals to be propagated over long distances, sometimes even around the globe, by bouncing off the ionosphere. This type of propagation is known as skywave propagation. The ionosphere also provides a degree of protection against interference and jamming, making it a popular choice for military and other secure communications.
Another important property of HF radio signals is that they can also be absorbed by the ionosphere. This can happen when the signal is propagating at a frequency that is not reflected effectively by the ionosphere, or when the ionosphere is particularly dense or disturbed. Absorption can limit the distance that an HF signal can travel and can also cause fading, which can make the signal difficult to receive.
HF radio signals can also be propagated via the ground wave. This is the direct wave that travels along the surface of the Earth and is affected by the electrical conductivity of the Earth's surface. The ground wave can provide reliable communications over distances up to a few hundred kilometers, but its usefulness is limited by terrain, which can block or reflect the signal.
In conclusion, HF radio signals have unique properties that make them useful for long-distance communications. The ionosphere allows them to be reflected and propagated over long distances, but also has the ability to absorb them. Ground wave propagation can provide communications over shorter distances, but is limited by terrain. These properties make HF radio signals useful for certain types of communication, such as HAM radio, military and other secure communications, but also have certain limitations that need to be considered.
On the propagation subpages I will mainly mention my experiences with radio propagation.