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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. Radio broadcasting - Wikipedia

    en.wikipedia.org/wiki/Radio_broadcasting

    AM transmissions cannot be ionospheric propagated during the day due to strong absorption in the D-layer of the ionosphere. In a crowded channel environment, this means that the power of regional channels which share a frequency must be reduced at night or directionally beamed in order to avoid interference, which reduces the potential ...

  4. Skywave - Wikipedia

    en.wikipedia.org/wiki/Skywave

    Radio waves (black) reflecting off the ionosphere (red) during skywave propagation. Line altitude in this image is significantly exaggerated and not to scale. In radio communication, skywave or skip refers to the propagation of radio waves reflected or refracted back toward Earth from the ionosphere, an electrically charged layer of the upper atmosphere.

  5. List of musical symbols - Wikipedia

    en.wikipedia.org/wiki/List_of_musical_symbols

    Musical symbols are marks and symbols in musical notation that indicate various aspects of how a piece of music is to be performed. There are symbols to communicate information about many musical elements, including pitch, duration, dynamics, or articulation of musical notes; tempo, metre, form (e.g., whether sections are repeated), and details about specific playing techniques (e.g., which ...

  6. Extremely low frequency - Wikipedia

    en.wikipedia.org/wiki/Extremely_low_frequency

    ELF and VLF waves propagate long distances by an Earth–ionosphere waveguide mechanism. [5] [18] The Earth is surrounded by a layer of charged particles (ions and electrons) in the atmosphere at an altitude of about 60 km (37 mi) at the bottom of the ionosphere, called the D layer, which reflects ELF waves.

  7. Very low frequency - Wikipedia

    en.wikipedia.org/wiki/Very_low_frequency

    The conductive ionosphere and the conductive Earth form a horizontal "duct" a few VLF wavelengths high, which acts as a waveguide confining the waves so they don't escape into space. The waves travel in a zig-zag path around the Earth, reflected alternately by the Earth and the ionosphere, in transverse magnetic (TM) mode.

  8. Ionospheric sounding - Wikipedia

    en.wikipedia.org/wiki/Ionospheric_sounding

    In telecommunications and radio science, an ionospheric sounding is a technique that provides real-time data on high-frequency ionospheric-dependent radio propagation, using a basic system consisting of a synchronized transmitter and receiver.

  9. Music industry - Wikipedia

    en.wikipedia.org/wiki/Music_industry

    Musicians working in a recording studio An audience watching a concert. The music industry refers to the individuals and organizations that earn money by writing songs and musical compositions, creating and selling recorded music and sheet music, presenting concerts, as well as the organizations that aid, train, represent and supply music creators.