![]() ![]() However the Solar Flux provides a good first order approximation, particularly for the F region that is responsible for most long distance ionospheric radio communications propagation. There is a statistical relationship rather than a direct one because the level of radio noise received at 2800 MHz is about a million times less in intensity than that of the radiation that creates the ionisation in the ionosphere. ![]() The level of ionising radiation that is received from the Sun is approximately proportional to the Solar Flux. Thus these figures are of great interest for ionospheric radio propagation prediction. To overcome this, the standard is taken as the reading from the Penticton Radio Observatory in British Columbia, Canada. Even when correction factors have been applied it is not easy to be able to provide a consist series of figures. The level of solar radiation varies around the globe. An SFU has the units 10 -22 Watts per metre 2 per Hz. The index is quoted in terms of Solar Flux Units (SFU). This solar index is measured by detecting the level of radio noise emitted at a frequency of 2800 MHz (10.7 cms). It provides an indication of the level of radiation that is being received from the Sun. One of the major indicators of solar activity used for radio propagation prediction is known as the solar flux and it has a major impact on radio communications propagation conditions. These take the various indices into account along with the position on the globe, time of day, season, and the position in the sunspot cycle. ![]() However there several packages of radio propagation prediction software that are available. Using these it is possible to manually deduce what conditions may be like. ![]() The main solar indices are the solar flux and the geomagnetic indices known as the A and K indices. However it is indicators of the level of solar radiation and geomagnetic activity that give the best clues to the possible state of radio communications propagation conditions via the ionosphere. There are many indicators that enable the HF radio propagation conditions to be predicted. Image Coutesy NASA Radio propagation prediction In this way radio communications users who require propagation via the ionosphere can choose the best times and frequencies in which to establish their radio communications. For example for broadcasting as well as for users of two way radio communications links that utilise the HF bands as well as mobile radio communications, maritime radio communications, and many other point to point radio users, a knowledge of the propagation patterns that will be in existence at a particular time are almost essential. However for many applications radio propagation prediction is necessary. Ionospheric radio propagation is notoriously changeable. These interactions cause the radio signals to change direction, and to reach areas which would not be possible if the radio signals travelled in a direct line. As they do this the radio signals can be reflected, refracted or diffracted. Ionospheric propagation Ionosphere Ionospheric layers Skywaves & skip Critical frequency, MUF, LUF & OWF How to use ionospheric propagation Multiple reflections & hops Ionospheric absorption Signal fading Solar indices Propagation software NVIS Transequatorial propagation Grey line propagation Sporadic E Spread FĪs electromagnetic waves, and in this case, radio signals travel, they interact with objects and the media in which they travel. Ionospheric propagation tutorial includes. Solar Indices: Solar Flux A K Kp Index As the radiation from the Sun is the major influence on the ionosphere, solar indices including the solar flux, A index, Ap index, K index and the Kp index are all important in predicting the state of the ionosphere and HF ionospheric radio propagation. ![]()
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