Radio Wave


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radio wave

[′rād·ē·ō ‚wāv]
(electromagnetism)
An electromagnetic wave produced by reversal of current in a conductor at a frequency in the range from about 10 kilohertz to about 300,000 megahertz.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Radio Wave

 

an electromagnetic wave of wavelength greater than 500 micrometers (μm) or of frequency less than 6 × 1012 hertz (Hz). Radio waves have many applications, including radio broadcasting, radiotelephone communications, television, radar, and radio meteorology. In these cases radio waves are a means of wireless transmission of information, which may be in the form of speech, telegraph signals, or images. Radio waves are used to determine the direction and, in range only radar, the distance to various objects. Their other uses include the obtaining of information about the structure of the upper atmospheric layers, the sun, and the planets.

Table 1. Subdivisions of radio spectrum
Subdivision1Wavelength range (m)Frequency range (Hz)
1These subdivisions are discussed in individual articles of the encyclopedia
Superlong waves ......greater than 104less than 3 × 104
Long waves..........104–10333 × 104–3 × 105
Medium waves........103–1023 × 105–3 × 106
Short waves..........102–103 × 106–3 × 107
Meter waves .........10–13 × 107–3 × 108
Decimeter waves ......1–0.13 × 108–3 × 109
Centimeter waves......0.1–0.013 × 109–3 × 1010
Millimeter waves......0.01–0.0013 × 1010–3 × 1011
Submillimeter waves ......103–5 × 10–53 × 1011–6 × 1012

The first experimental transmissions of signals by means of radio waves were carried out by A. S. Popov between 1895 and 1899. Popov used wavelengths of 200 to 500 m—that is, frequencies of 1.5 × 106 to 0.6 × 106 Hz. The subsequent development of radio engineering resulted in the employment of a wider spectrum of electromagnetic waves. The lower limit for the spectrum of radio waves radiated by radio-transmitting devices is of the order of 103–104 Hz.

Many sources of radio waves exist in nature. Examples are the stars, including the sun, the galaxies, the metagalaxy, and the planets. Radio astronomy’s investigation of radio waves from extraterrestrial sources has permitted us to broaden our knowledge of the universe. Some processes that occur within the earth’s atmosphere are also accompanied by the generation of radio waves. For example, radio waves result from lightning discharges (seeATMOSPHERICS) and from the excitation of oscillations in the ionospheric plasma. Such processes can cause the excitation of radio waves of frequencies as low as fractions of a hertz.

Since radio waves of different frequencies propagate differently within the limits of the earth and in outer space, they find different applications in radio communications and in scientific investigations. On the basis of the characteristics of progaga-tion, generation, and—to some extent—processes, the radio spectrum is commonly divided into a number of subdivisions, which are given in Table 1. The basic classification of radio waves into bands for radio communications purposes has been established by the international Radio Regulations. Bands 4 through 11 in Table 2 are used by the various radio services; the designations of the other bands listed are standard Soviet usage.

M. B. VINOGRADOVA

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

RF

(Radio Frequency) The range of electromagnetic frequencies above the audio range and below infrared light (from 10 kHz to 300 GHz). RF transmission includes AM and FM radio, analog and digital TV, satellite communications, cordless phones, cellular and Wi-Fi. Signals can be focused in one direction (directional), or they can transmit in all directions (omnidirectional).

Frequency and Power
The range of frequencies and power output determine how well RF signals can penetrate objects. Signals up to 5 GHz can generally transmit through wooden and plaster walls in their path, but the higher the frequency, the more an unobstructed view from transmitter to receiver is required. See line of sight, RF modulation, RF shielding, RF remote control, RFI, microwave and ISM band.


RF Ports
Radio frequency ports (right) are typically coaxial cable connectors for antennas and TVs. See coaxial cable.
Copyright © 1981-2019 by The Computer Language Company Inc. All Rights reserved. THIS DEFINITION IS FOR PERSONAL USE ONLY. All other reproduction is strictly prohibited without permission from the publisher.
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