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  2. High frequency - Wikipedia

    en.wikipedia.org/wiki/High_frequency

    HF's position in the electromagnetic spectrum.. High frequency (HF) is the ITU designation [1] [2] for the band of radio waves with frequency between 3 and 30 megahertz (MHz). It is also known as the decameter band or decameter wave as its wavelengths range from one to ten decameters (ten to one hundred meters).

  3. Electromagnetic spectrum - Wikipedia

    en.wikipedia.org/wiki/Electromagnetic_spectrum

    The spectrum is divided into separate bands, with different names for the electromagnetic waves within each band. From low to high frequency these are: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. The electromagnetic waves in each of these bands have different characteristics, such as how they are ...

  4. Radio atmospheric signal - Wikipedia

    en.wikipedia.org/wiki/Radio_atmospheric_signal

    A frequency vs. time plot (spectrogram) showing several whistler signals amidst a background of sferics as received at Palmer Station, Antarctica on August 24, 2005.A radio atmospheric signal or sferic (sometimes also spelled "spheric") is a broadband electromagnetic impulse that occurs as a result of natural atmospheric lightning discharges.

  5. Atmospheric wave - Wikipedia

    en.wikipedia.org/wiki/Atmospheric_wave

    Atmospheric waves, associated with a small dust storm of north western Africa on 23 September 2011. An atmospheric wave is a periodic disturbance in the fields of atmospheric variables (like surface pressure or geopotential height, temperature, or wind velocity) which may either propagate (traveling wave) or be stationary (standing wave).

  6. Ionosphere - Wikipedia

    en.wikipedia.org/wiki/Ionosphere

    Eventually, a frequency is reached that enables the wave to penetrate the layer without being reflected. For ordinary mode waves, this occurs when the transmitted frequency just exceeds the peak plasma, or critical, frequency of the layer. Tracings of the reflected high frequency radio pulses are known as ionograms.

  7. Radio spectrum - Wikipedia

    en.wikipedia.org/wiki/Radio_spectrum

    High frequency [18] VHF: 0.03 to 0.3 GHz: Very high frequency [18] UHF: 0.3 to 1 GHz: Ultra-high frequency [18] L: 1 to 2 GHz: Long wave S: 2 to 4 GHz: Short wave C: 4 to 8 GHz: Compromise between S and X X: 8 to 12 GHz: Used in World War II for fire control, X for cross (as in crosshair). Exotic. [19] K u: 12 to 18 GHz: Kurz-under K: 18 to 27 ...

  8. Infragravity wave - Wikipedia

    en.wikipedia.org/wiki/Infragravity_wave

    Namely, the mean sea level oscillates with a wavelength that is equal to the length of the group, with a low level where the wind waves are highest and a high level where these waves are lowest. This oscillation of the sea surface is proportional to the square of the short wave amplitude and becomes very large when the group speed approaches ...

  9. Frequency - Wikipedia

    en.wikipedia.org/wiki/Frequency

    Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio signals , radio waves, and light. For example, if a heart beats at a frequency of 120 times per minute (2 hertz), the period—the time interval between beats—is half a second (60 ...