Effects on ionosphere |
||||
| By Tymon Hytem-5496 | ||||
Sporadic E layer effects are when radio waves are returned are returned to earth by the E layer at frequencies considerably greater than the critical frequency of the layer. These are believed to be caused by partial reflections from sharp boundaries to stratified ionization. Further the ionizing effects of the minute meteors continuously received by the earth may at least partially account for the ionization that remains in the ionosphere at night time. Irregularities in electron distribution in the ionosphere causes scattered reflections of radio waves. These reflected signals are generally weak, irregular and diffused and may be caused in any of the layers. Further these reflected signals some times become quite complex because of the interaction between layers. The vertical heights of scattered reflections depend upon the type of scattering and may lie between ninety to about fifteen hundred kilometers. Scatter reflections are also caused when an ionosphere wave on refraction from the ionosphere strikes the earth. The scattered energy then propagates away from the point of scatter refraction in the same general way as that from a transmitting antenna. How ever the signals so produced are some forty decibels weaker than the main signals. Scattering of radio waves may be radiated usefully utilized in the following waves that is scatter signal may be radiated within the skip region and with highly directional transmitting antenna, a receiving antenna lying appreciably to one side of the path of the main beam may also adequately receive the signal as caused by scattered wave traveling at right angles to the main beam. The effect produced by the ionosphere on a radio wave is not linear, that is, not proportional to the magnitude of the wave, hence two strong radio waves passing through the ionosphere concurrently may interact to produce cross modulation products. The magnitude of such a cross modulation may in some cases be large enough to produce appreciable effect. First such interference reported involved radio Luxemburg. Hence the effect is termed as Luxemburg effect. But the Luxemburg effect has not been generally observed with even most powerful transmitters. Hence there is a possibility that the effect might have been produced by external cross modulation instead of cross modulation in the ionosphere. |
||||
| Article Source: http://articlejam.co.za | ||||
|
||||
|
||||
| © 2010 articlejam.co.za |