3. Amateur radio activities

Listening is a radio amateur's main activity. Many factors influence the reception of radio signals. Wave propagation fluctuates greatly with the seasons, the time of day, the state of the atmospheric and ionospheric layers, and the sun. The longest variation cycle is that due to the sun, which has a period of eleven years. Propagation peaked in 1991. Then come the seasons, with circuits lengthening in spring and narrowing in autumn above 10 MHz. Night makes it easier to reach waves below 10 MHz, while restricting those above. In THF, the ionosphere acts on the range via the sporadic E layer, allowing openings of several thousand kilometers for a few minutes to several days. The phenomenon of atmospheric temperature inversion produces the same results in spring and autumn. Diligent listening to the beacons enables us to detect these phenomena and take advantage of this good propagation for...