Near real-time information about the solar terrestrial environment and HF propagation with BTX

HF propagation shows considerable day-to-day variation, caused mainly by the influence of variations in solar radiation. In order to maintain HF communications under changing propagation conditions it is necessary to adapt the frequencies in use to the real-time situation. Forecasts required for this purpose suffer from time lag between the observations of the propagation environment and the arrival of the prediction information. The author describes what kind of data is available from various sources in near real-time. following is a description of Bildschirmtext (BTX), which is the German Videotex service. This system carries a considerable amount of solar-terrestrial information free of charge