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The ionosphere and its effect on radio



Author: Ivo Ivanov Rumen Pankov

Area DXers 03/20/1911

The atmosphere has three layers. Farthest from the Earth's surface is called the ionosphere. It lies at an altitude of 50 to 350 kilometers and is subdivided into three sub-layers, designated by the letters D, E and F.
During the day, the higher short wave frequencies above 15 megahertz, are reflected in the ionosphere and reach remote areas on earth.
In the afternoon, overnight and at dawn, almost the same thing happens with short-wave frequencies less high with long wave and medium wave.
ultrashort waves in the ionosphere are reflected rarely and in special circumstances. In it the air is saturated with different elementary particles. For radio the most important are the ions. Their quantity and concentration substantially affect the quality of radio wave propagation.
The formation and disappearance of ions is called ionization. It occurs under the effect of several factors, most of them sporadic, such as for example the fragments of meteorites or satellites that are burning in the atmosphere. The largest and strongest influence in this direction is exercised the sun with its activity.
When solar activity is weak, so is the ionization in the atmosphere and the radio waves are reflected with difficulty, which has the effect of a reception worse. In such circumstances the ideal time to listen are the hours at dusk and dawn, at frequencies from 6 to 10 megahertz. Such has been the situation over the past three years.
stronger solar activity produces a higher ionization in the ionosphere and creates better conditions for the reception of distant signals in all types of radio waves, even the ultra. However, the activity of the sun at times causes disturbance in the magnetic field and ionosphere. In such cases it is not reflected but rather absorbed the airwaves. In such periods the radio signals may disappear.
Usually this occurs between 8 AM and 2 PM local time, at frequencies between 3 and 13 megahertz. You can also occur in longer and more frequent, but rarely. Unfortunately for now
science has failed to create a method to predict the magnetic anomalies and destabilization in the ionosphere under the influence of solar activity. Nevertheless, the destabilization may be provided with two or three days in advance through the system of satellites placed into orbit around land at high altitude.
These satellites are mounted telescopes and sophisticated apparatus for the continuous observation of the sun and the processes that run on it.
After explosions, volcanic eruptions and other phenomena that make the solar corona issued particle flows can be determined that, after 36 or more hours, there will be disruptions in radio communications and other areas of life.
With the help of some basic and general knowledge of physics and astronomy, tracking of submissions made by the organizations and agencies dedicated to observing and analyzing solar activity, also the plain listeners could An estimate of the conditions for listening on the following days.


English version by Raina Petkova