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The other types of electromagnetic waves besides radio waves, infrared, visible light, ultraviolet, X-rays and gamma rays, can also carry information and be used for communication. The wide use of radio waves for telecommunication is mainly due to their desirable propagation properties stemming from their longer wavelength. [24]
Because of the difficulty of building antennas that can radiate such long waves, ELF have been used in only a very few human-made communication systems. ELF waves can penetrate seawater, which makes them useful in communication with submarines, and a few nations have built military ELF transmitters to transmit signals to their submerged ...
2182 kHz is a medium-wave frequency still used for marine emergency communication. Marine VHF radio is used in coastal waters and relatively short-range communication between vessels and to shore stations. Radios are channelized, with different channels used for different purposes; marine Channel 16 is used for calling and emergencies.
Radio waves are more widely used for communication than other electromagnetic waves mainly because of their desirable propagation properties, stemming from their large wavelength. [12] Radio waves have the ability to pass through the atmosphere in any weather, foliage, and through most building materials.
The radio waves carry the information across space to a receiver, where they are received by an antenna and the information extracted by demodulation in the receiver. Radio waves are also used for navigation in systems like Global Positioning System (GPS) and navigational beacons, and locating distant objects in radiolocation and radar.
The worldwide Omega system used frequencies from 10 to 14 kHz, as did Russia's Alpha. VLF was also used for standard time and frequency broadcasts. In the US, the time signal station WWVL began transmitting a 500 W signal on 20 kHz in August 1963. It used frequency-shift keying to send data, shifting between 20 kHz and 26 kHz. The WWVL service ...
The purpose of the carrier is usually either to transmit the information through space as an electromagnetic wave (as in radio communication), or to allow several carriers at different frequencies to share a common physical transmission medium by frequency division multiplexing (as in a cable television system).
In addition, use of millimeter wave bands for vehicular communication is also emerging as an attractive solution to support (semi-)autonomous vehicular communications. [ 15 ] Shorter wavelengths in this band permit the use of smaller antennas to achieve the same high directivity and high gain as larger ones in lower bands.