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  2. Ionosphere - Wikipedia

    en.wikipedia.org/wiki/Ionosphere

    Relationship of the atmosphere and ionosphere. The ionosphere (/ aɪ ˈ ɒ n ə ˌ s f ɪər /) [1] [2] is the ionized part of the upper atmosphere of Earth, from about 48 km (30 mi) to 965 km (600 mi) above sea level, [3] a region that includes the thermosphere and parts of the mesosphere and exosphere. The ionosphere is ionized by solar ...

  3. File:Very-low-frequency radio propagation in the ionosphere ...

    en.wikipedia.org/wiki/File:Very-low-frequency...

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  4. Ionosonde - Wikipedia

    en.wikipedia.org/wiki/Ionosonde

    An ionosonde, or chirpsounder, is a special radar for the examination of the ionosphere. The basic ionosonde technology was invented in 1925 by Gregory Breit and Merle A. Tuve [ 1 ] and further developed in the late 1920s by a number of prominent physicists, including Edward Victor Appleton .

  5. File:Stratification in the lower ionosphere (IA ...

    en.wikipedia.org/wiki/File:Stratification_in_the...

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  6. Sporadic E propagation - Wikipedia

    en.wikipedia.org/wiki/Sporadic_E_propagation

    Sporadic E (abbreviated E s or SpE) is an uncommon form of radio propagation using a low level of the Earth's ionosphere that normally does not refract radio waves above about 15 MHz. Sporadic E propagation reflects signals off relatively small ionization patches in the lower E region located at altitudes of about 95–120 km (50–75 miles).

  7. Non-line-of-sight propagation - Wikipedia

    en.wikipedia.org/wiki/Non-line-of-sight_propagation

    The ionosphere is a region of the atmosphere from about 60 to 500 km (37 to 311 mi) that contains layers of charged particles which can refract a radio wave back toward the Earth. A radio wave directed at an angle into the sky can be reflected back to Earth beyond the horizon by these layers, allowing long-distance radio transmission.

  8. Radio broadcasting - Wikipedia

    en.wikipedia.org/wiki/Radio_broadcasting

    The earliest radio stations were radiotelegraphy systems and did not carry audio. For audio broadcasts to be possible, electronic detection and amplification devices had to be incorporated. The thermionic valve, a kind of vacuum tube, was invented in 1904 by the English physicist John Ambrose Fleming. He developed a device that he called an ...

  9. Ionospheric pierce point - Wikipedia

    en.wikipedia.org/wiki/Ionospheric_pierce_point

    Here R is the mean Earth radius, H is the mean height of the ionosphere shell. The IPP or Ionospheric Pierce Point is the altitude in the ionosphere where electron density is greatest. [1] These points can change based on factors like time of day, solar activity, and geographical location, which all influence ionospheric conditions. [2]