Radio wave

radio wavesradioradio signalairwavesradio emissionradiowaveradio signalsHertzian waveRadio scienceradio wavelengths
Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light.wikipedia
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Electromagnetic spectrum

spectrumspectraspectral
Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light.
This frequency range is divided into separate bands, and the electromagnetic waves within each frequency band are called by different names; beginning at the low frequency (long wavelength) end of the spectrum these are: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays at the high-frequency (short wavelength) end.

Radio receiver

receiverreceiversRadios
Radio waves are generated artificially by transmitters and received by radio receivers, using antennas.
In radio communications, a radio receiver, also known as a receiver, wireless or simply radio is an electronic device that receives radio waves and converts the information carried by them to a usable form.

Antenna (radio)

antennaantennasradio antenna
Radio waves are generated artificially by transmitters and received by radio receivers, using antennas.
In radio engineering, an antenna is the interface between radio waves propagating through space and electric currents moving in metal conductors, used with a transmitter or receiver.

Radio

radio communicationradio communicationswireless
Radio waves are very widely used in modern technology for fixed and mobile radio communication, broadcasting, radar and radio navigation systems, communications satellites, wireless computer networks and many other applications.
Radio is the technology of signaling and communicating using radio waves.

Radar

radar stationradarsradar system
Radio waves are very widely used in modern technology for fixed and mobile radio communication, broadcasting, radar and radio navigation systems, communications satellites, wireless computer networks and many other applications.
Radar is a detection system that uses radio waves to determine the range, angle, or velocity of objects.

Infrared

IRnear-infraredinfra-red
Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light.

Broadcasting

broadcastbroadcasterbroadcasters
Radio waves are very widely used in modern technology for fixed and mobile radio communication, broadcasting, radar and radio navigation systems, communications satellites, wireless computer networks and many other applications.
Broadcasting is the distribution of audio or video content to a dispersed audience via any electronic mass communications medium, but typically one using the electromagnetic spectrum (radio waves), in a one-to-many model.

Communications satellite

satellite communicationssatellitecommunication satellite
Radio waves are very widely used in modern technology for fixed and mobile radio communication, broadcasting, radar and radio navigation systems, communications satellites, wireless computer networks and many other applications.
The high frequency radio waves used for telecommunications links travel by line of sight and so are obstructed by the curve of the Earth.

Skywave

ionospheric reflectionsky waveionospheric propagation
Different frequencies of radio waves have different propagation characteristics in the Earth's atmosphere; long waves can diffract around obstacles like mountains and follow the contour of the earth (ground waves), shorter waves can reflect off the ionosphere and return to earth beyond the horizon (skywaves), while much shorter wavelengths bend or diffract very little and travel on a line of sight, so their propagation distances are limited to the visual horizon.
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.

Electromagnetic radiation

electromagnetic waveelectromagnetic waveselectromagnetic
Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light. His mathematical theory, now called Maxwell's equations, predicted that a coupled electric and magnetic field could travel through space as an "electromagnetic wave".
It includes radio waves, microwaves, infrared, (visible) light, ultraviolet, X-rays, and gamma rays.

Radio spectrum

bandradio bandspectrum
The radio spectrum is divided into a number of radio bands on the basis of frequency, allocated to different uses.
Electromagnetic waves in this frequency range, called radio waves, are widely used in modern technology, particularly in telecommunication.

Diffraction

diffraction patterndiffractdiffracted
Different frequencies of radio waves have different propagation characteristics in the Earth's atmosphere; long waves can diffract around obstacles like mountains and follow the contour of the earth (ground waves), shorter waves can reflect off the ionosphere and return to earth beyond the horizon (skywaves), while much shorter wavelengths bend or diffract very little and travel on a line of sight, so their propagation distances are limited to the visual horizon. In 1887, German physicist Heinrich Hertz demonstrated the reality of Maxwell's electromagnetic waves by experimentally generating radio waves in his laboratory, showing that they exhibited the same wave properties as light: standing waves, refraction, diffraction, and polarization.
These effects also occur when a light wave travels through a medium with a varying refractive index, or when a sound wave travels through a medium with varying acoustic impedance – all waves diffract, including gravitational waves, water waves, and other electromagnetic waves such as X-rays and radio waves.

James Clerk Maxwell

MaxwellJ. C. MaxwellJames Maxwell
Radio waves were first predicted by mathematical work done in 1867 by British mathematical physicist James Clerk Maxwell.
The unification of light and electrical phenomena led his prediction of the existence of radio waves.

Electric current

currentelectrical currentcurrents
They are generated by electric charges undergoing acceleration, such as time varying electric currents.
When oscillating electric currents flow at the correct voltages within radio antennas, radio waves are generated.

Frequency

frequenciesperiodperiodic
Radio waves have frequencies as high as 300 gigahertz (GHz) to as low as 30 hertz (Hz).
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 (sound), radio waves, and light.

Maxwell's equations

Maxwell equationsMaxwell equationMaxwell’s equations
His mathematical theory, now called Maxwell's equations, predicted that a coupled electric and magnetic field could travel through space as an "electromagnetic wave".
Known as electromagnetic radiation, these waves may occur at various wavelengths to produce a spectrum of light from radio waves to γ-rays.

Line-of-sight propagation

line of sightline-of-sightradio horizon
Different frequencies of radio waves have different propagation characteristics in the Earth's atmosphere; long waves can diffract around obstacles like mountains and follow the contour of the earth (ground waves), shorter waves can reflect off the ionosphere and return to earth beyond the horizon (skywaves), while much shorter wavelengths bend or diffract very little and travel on a line of sight, so their propagation distances are limited to the visual horizon.
In contrast to line-of-sight propagation, at low frequency (below approximately 3 MHz) due to diffraction, radio waves can travel as ground waves, which follow the contour of the Earth.

Lightning

lightning boltlightning strikelightning strikes
Naturally occurring radio waves are emitted by lightning and astronomical objects.
Huge quantities of extremely low frequency (ELF) and very low frequency (VLF) radio waves are also generated.

Transmitter

radio transmittertransmittersradio transmitters
Radio waves are generated artificially by transmitters and received by radio receivers, using antennas.
In electronics and telecommunications a transmitter or radio transmitter is an electronic device which produces radio waves with an antenna.

Radio propagation

propagationpropagation moderadio wave propagation
Radio propagation is the behavior of radio waves as they travel, or are propagated, from one point to another, or into various parts of the atmosphere.

Ionosphere

ionosphericD layerionospheric physics
Different frequencies of radio waves have different propagation characteristics in the Earth's atmosphere; long waves can diffract around obstacles like mountains and follow the contour of the earth (ground waves), shorter waves can reflect off the ionosphere and return to earth beyond the horizon (skywaves), while much shorter wavelengths bend or diffract very little and travel on a line of sight, so their propagation distances are limited to the visual horizon.
Medium frequency (MF) and lower high frequency (HF) radio waves are significantly attenuated within the D layer, as the passing radio waves cause electrons to move, which then collide with the neutral molecules, giving up their energy.

Parabolic antenna

dish antennaparabolicparabolic dish antenna
A parabolic antenna is an antenna that uses a parabolic reflector, a curved surface with the cross-sectional shape of a parabola, to direct the radio waves.

Guglielmo Marconi

MarconiMarconi WirelessMarconi's Wireless Telegraph Company
Italian inventor Guglielmo Marconi developed the first practical radio transmitters and receivers around 1894-1895.
At the time, this radiation was commonly called "Hertzian" waves, and is now generally referred to as radio waves.

Heinrich Hertz

Heinrich Rudolf HertzHertzHeinrich Rudolph Hertz
In 1887, German physicist Heinrich Hertz demonstrated the reality of Maxwell's electromagnetic waves by experimentally generating radio waves in his laboratory, showing that they exhibited the same wave properties as light: standing waves, refraction, diffraction, and polarization.
This experiment produced and received what are now called radio waves in the very high frequency range.

Magnetic field

magnetic fieldsmagneticmagnetic flux density
His mathematical theory, now called Maxwell's equations, predicted that a coupled electric and magnetic field could travel through space as an "electromagnetic wave".
For instance, electrons spiraling around a field line produce synchrotron radiation that is detectable in radio waves.