Topic: Radio

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A History of the World in 100 Objects (2010)

British Museum Radio BBC Radio/UK Radio

A History of the World in 100 Objects was a joint project of BBC Radio 4 and the British Museum, comprising a 100-part radio series written and presented by British Museum director Neil MacGregor. In 15-minute presentations broadcast on weekdays on Radio 4, MacGregor used objects of ancient art, industry, technology and arms, all of which are in the British Museum's collections, as an introduction to parts of human history. The series, four years in planning, began on 18 January 2010 and was broadcast over 20 weeks. A book to accompany the series, A History of the World in 100 Objects by Neil MacGregor, was published by Allen Lane on 28 October 2010. The entire series is also available for download along with an audio version of the book for purchase. The British Museum won the 2011 Art Fund Prize for its role in hosting the project.

In 2016, a touring exhibition of several items depicted on the radio program, also titled A History of the World in 100 Objects, travelled to various destinations, including Abu Dhabi (Manarat Al Saadiyat), Taiwan (National Palace Museum in Taipei), Japan (Tokyo Metropolitan Art Museum in Tokyo, Kyushu National Museum in Daizafu, and Kobe City Museum in Kobe), Australia (Western Australian Museum in Perth and National Museum of Australia in Canberra), and China (National Museum of China in Beijing and Shanghai Museum in Shanghai).

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Arecibo message

History Telecommunications Radio Astronomy

The Arecibo message is a 1974 interstellar radio message carrying basic information about humanity and Earth sent to globular star cluster M13. It was meant as a demonstration of human technological achievement, rather than a real attempt to enter into a conversation with extraterrestrials.

The message was broadcast into space a single time via frequency modulated radio waves at a ceremony to mark the remodeling of the Arecibo radio telescope in Puerto Rico on 16 November 1974. The message was aimed at the current location of M13 some 25,000 light years away because M13 was a large and close collection of stars that was available in the sky at the time and place of the ceremony. The message forms the image shown here when translated into graphics, characters, and spaces.

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Comfort Noise

Telecommunications Radio

Comfort noise (or comfort tone) is synthetic background noise used in radio and wireless communications to fill the artificial silence in a transmission resulting from voice activity detection or from the audio clarity of modern digital lines.

Some modern telephone systems (such as wireless and VoIP) use voice activity detection (VAD), a form of squelching where low volume levels are ignored by the transmitting device. In digital audio transmissions, this saves bandwidth of the communications channel by transmitting nothing when the source volume is under a certain threshold, leaving only louder sounds (such as the speaker's voice) to be sent. However, improvements in background noise reduction technologies can occasionally result in the complete removal of all noise. Although maximizing call quality is of primary importance, exhaustive removal of noise may not properly simulate the typical behavior of terminals on the PSTN system.

The result of receiving total silence, especially for a prolonged period, has a number of unwanted effects on the listener, including the following:

  • the listener may believe that the transmission has been lost, and therefore hang up prematurely.
  • the speech may sound "choppy" (see noise gate) and difficult to understand.
  • the sudden change in sound level can be jarring to the listener.

To counteract these effects, comfort noise is added, usually on the receiving end in wireless or VoIP systems, to fill in the silent portions of transmissions with artificial noise. The noise generated is at a low but audible volume level, and can vary based on the average volume level of received signals to minimize jarring transitions.

In many VoIP products, users may control how VAD and comfort noise are configured, or disable the feature entirely.

As part of the RTP audio video profile, RFC 3389 defines a standard for distributing comfort noise information in VoIP systems.

A similar concept is that of sidetone, the effect of sound that is picked up by a telephone's mouthpiece and introduced (at low level) into the earpiece of the same handset, acting as feedback.

During the siege of Leningrad, the beat of a metronome was used as comfort noise on the Leningrad radio network, indicating that the network was still functioning.

Many radio stations broadcast birdsong, city-traffic or other atmospheric comfort noise during periods of deliberate silence. For example, in the UK, silence is observed on Remembrance Sunday, and London's quiet city ambiance is used. This is to reassure the listener that the station is on-air, but primarily to prevent silence detection systems at transmitters from automatically starting backup tapes of music (designed to be broadcast in the case of transmission link failure).

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Evolved antenna

Telecommunications Radio Electronics Engineering

In radio communications, an evolved antenna is an antenna designed fully or substantially by an automatic computer design program that uses an evolutionary algorithm that mimics Darwinian evolution. This procedure has been used in recent years to design a few antennas for mission-critical applications involving stringent, conflicting, or unusual design requirements, such as unusual radiation patterns, for which none of the many existing antenna types are adequate.

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Plasma Antenna

Telecommunications Radio Electronics Engineering

A plasma antenna is a type of radio antenna currently in development in which plasma is used instead of the metal elements of a traditional antenna. A plasma antenna can be used for both transmission and reception. Although plasma antennas have only become practical in recent years, the idea is not new; a patent for an antenna using the concept was granted to J. Hettinger in 1919.

Early practical examples of the technology used discharge tubes to contain the plasma and are referred to as ionized gas plasma antennas. Ionized gas plasma antennas can be turned on and off and are good for stealth and resistance to electronic warfare and cyber attacks. Ionized gas plasma antennas can be nested such that the higher frequency plasma antennas are placed inside lower frequency plasma antennas. Higher frequency ionized gas plasma antenna arrays can transmit and receive through lower frequency ionized gas plasma antenna arrays. This means that the ionized gas plasma antennas can be co-located and ionized gas plasma antenna arrays can be stacked. Ionized gas plasma antennas can eliminate or reduce co-site interference. Smart ionized gas plasma antennas use plasma physics to shape and steer the antenna beams without the need of phased arrays. Satellite signals can be steered or focused in the reflective or refractive modes using banks of plasma tubes making unique ionized gas satellite plasma antennas. The thermal noise of ionized gas plasma antennas is less than in the corresponding metal antennas at the higher frequencies. Solid state plasma antennas (also known as plasma silicon antennas) with steerable directional functionality that can be manufactured using standard silicon chip fabrication techniques are now also in development. Plasma silicon antennas are candidates for use in WiGig (the planned enhancement to Wi-Fi), and have other potential applications, for example in reducing the cost of vehicle-mounted radar collision avoidance systems.

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The Machine Stops

Novels Radio Novels/Science fiction Novels/Short story

"The Machine Stops" is a science fiction short story (12,300 words) by E. M. Forster. After initial publication in The Oxford and Cambridge Review (November 1909), the story was republished in Forster's The Eternal Moment and Other Stories in 1928. After being voted one of the best novellas up to 1965, it was included that same year in the populist anthology Modern Short Stories. In 1973 it was also included in The Science Fiction Hall of Fame, Volume Two.

The story, set in a world where humanity lives underground and relies on a giant machine to provide its needs, predicted technologies similar to instant messaging and the Internet.

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Wartime Broadcasting Service

Radio BBC Radio/UK Radio

The Wartime Broadcasting Service is a service of the BBC that is intended to broadcast in the United Kingdom either after a nuclear attack or if conventional bombing destroyed regular BBC facilities in a conventional war.

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Terahertz Gap

Technology Physics Radio Astronomy Engineering

In engineering, the terahertz gap is a frequency band in the terahertz region of the electromagnetic spectrum between radio waves and infrared light for which practical technologies for generating and detecting the radiation do not exist. It is defined as 0.1 to 10 THz (wavelengths of 3 mm to 30 µm). Currently, at frequencies within this range, useful power generation and receiver technologies are inefficient and unfeasible.

Mass production of devices in this range and operation at room temperature (at which energy k·T is equal to the energy of a photon with a frequency of 6.2 THz) are mostly impractical. This leaves a gap between mature microwave technologies in the highest frequencies of the radio spectrum and the well developed optical engineering of infrared detectors in their lowest frequencies. This radiation is mostly used in small-scale, specialized applications such as submillimetre astronomy. Research that attempts to resolve this issue has been conducted since the late 20th century.

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Whistler (Radio)

Physics Meteorology Radio

A whistler is a very low frequency or VLF electromagnetic (radio) wave generated by lightning. Frequencies of terrestrial whistlers are 1 kHz to 30 kHz, with a maximum amplitude usually at 3 kHz to 5 kHz. Although they are electromagnetic waves, they occur at audio frequencies, and can be converted to audio using a suitable receiver. They are produced by lightning strikes (mostly intracloud and return-path) where the impulse travels along the Earth's magnetic field lines from one hemisphere to the other. They undergo dispersion of several kHz due to the slower velocity of the lower frequencies through the plasma environments of the ionosphere and magnetosphere. Thus they are perceived as a descending tone which can last for a few seconds. The study of whistlers categorizes them into Pure Note, Diffuse, 2-Hop, and Echo Train types.

Voyager 1 and 2 spacecraft detected whistler-like activity in the vicinity of Jupiter known as "Jovian Whistlers", implying the presence of lightning there.

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Brinkley Act: Bans US broadcasters from being connected to a Mexico transmitter

United States Law Radio

The Brinkley Act is the popular name given to 47 U.S.C. § 325(c) (originally section 325(b) of the Communications Act of 1934). This provision was enacted by the United States Congress to prohibit broadcasting studios in the U.S. from being connected by live telephone line or other means to a transmitter located in Mexico.

Prior to World War II, Dr. John R. Brinkley controlled a high-power radio station, XERA, located in Ciudad Acuña, Coahuila (Acuna City), on the U.S.-Mexican border, across the Rio Grande from Del Rio, Texas. The programs on Brinkley's stations originated from studios in the US, which were connected to his transmitters via international telephone lines. Brinkley ran a popular but controversial program offering questionable medical advice to his listeners. Since Brinkley's transmitters were licensed in Mexico, which at the time had very limited regulation of broadcast content, his broadcasting licenses could not be directly threatened by the US government.

Dr. Brinkley's activities at his studio were thought to be a local matter, outside Congress's regulatory powers. However, the communications between the studio and his transmitters clearly involved international commerce and were therefore within Congress's power to regulate under the Commerce Clause. The operative language is as follows:

No person shall be permitted to locate, use, or maintain a radio broadcast studio or other place or apparatus from which or whereby sound waves are converted into electrical energy, or mechanical or physical reproduction of sound waves produced, and caused to be transmitted or delivered to a radio station in a foreign country for the purpose of being broadcast from any radio station there having a power output of sufficient intensity and/or being so located geographically that its emissions may be received consistently in the United States, without first obtaining a permit from the Commission upon proper application therefor.

The law goes on (47 U.S.C. § 325(d)) to state that the legal process for requesting such a permit is the same as that for requesting or renewing a license for a domestic station.

Although the original purpose of the Brinkley Act was to shut down a broadcaster, such applications are today granted as a matter of course, and a number of US broadcasters are permitted to program Mexican stations from their US studios in communities such as San Diego, California and Brownsville, Texas, where as many as a third of the stations in each radio market are licensed in Mexico. In recent years the law has returned to prominence, as its provisions have been used to extend US ownership limits to Mexican stations leased by US broadcasters.