Extraterrestrial Communications

Extraterrestrial Communications: Extraterrestrial Communications : The most recent, and by far the fastest-growing, field of communications involves the use of various satellite relays, of which the first was launched in 1957,-12 years after the practicability and orbital positioning of stationary satellites were first described and calculated. The field may be subdivided into three parts, each […]

Space Waves

Space Waves: Space waves generally behave with merciful simplicity. They travel in (more or less) straight lines! However, since they depend on line-of-sight conditions, space waves are limited in their propagation by the curvature of the earth, except in very unusual circumstances. Thus they propagate very much like electromagnetic waves in free space. Such a […]

Sky Wave Propagation

Sky Wave Propagation – The Ionosphere : The Sky Wave Propagation- the  ionosphere is the upper portion of the atmosphere, which absorbs large quantities of radiant energy from the sun, becoming heated and ionised. There are variations in the physical properties of the atmosphere, such as temperature, density and composition. Because of this and the different types […]

Electromagnetic Spectrum

Electromagnetic Spectrum: In an earth environment, electromagnetic waves propagate in ways that depend not only on their own properties but also on those of the environment itself; some of this was seen in the preceding section. Since the various methods of propagation depend largely on frequency, the complete electromagnetic spectrum is now shown for reference […]