|
SRF-39
The SRF-39 is a portable AM/ FM radio introduced in approximately 1992 by Sony. It uses a single AA battery, as its analog electronics draw very little current. It was one of the first radios to use the CXA1129 30-pin integrated circuit, which later was responsible for the SRF-39's sensitive and selective performance.T. Okanobu, H. Tomiyama and H. Arimoto"Advanced low voltage single chip radio IC" IEEE Transactions on Consumer Electronics, vol. 38, no. 3, pp. 465-475, Aug. 1992, doi: 10.1109/30.156724. A variant of the SRF-39, the SRF-39FP, has a transparent case, designed to thwart contraband concealment. The radio often appears on the commissary lists of U.S. federal prisons, hence the "FP" suffix. The SRF-39 was followed by the SRF-49 in 1997, the PSY-03 in 1999, and the SRF-59 in 2001. These radios are popular in the DXing community due to their sensitivity, selectivity and ferrite antennas. See also *History of radio The early history of radio is the history of techno ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
AM Broadcasting
AM broadcasting is radio broadcasting using amplitude modulation (AM) transmissions. It was the first method developed for making audio radio transmissions, and is still used worldwide, primarily for medium wave (also known as "AM band") transmissions, but also on the longwave and shortwave radio bands. The earliest experimental AM transmissions began in the early 1900s. However, widespread AM broadcasting was not established until the 1920s, following the development of vacuum tube receivers and transmitters. AM radio remained the dominant method of broadcasting for the next 30 years, a period called the "Golden Age of Radio", until television broadcasting became widespread in the 1950s and received most of the programming previously carried by radio. Subsequently, AM radio's audiences have also greatly shrunk due to competition from FM (FM broadcasting, frequency modulation) radio, Digital audio broadcasting, Digital Audio Broadcasting (DAB), satellite radio, HD Radio, HD (digi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Federal Prison
A federal prison is operated under the jurisdiction of a federal government as opposed to a state or provincial body. Federal prisons are used for convicts who violated federal law (U.S., Mexico), inmates considered dangerous (Brazil), or those sentenced to longer terms of imprisonment (Canada). Not all federated countries have a legal concept of "federal prison". Australia The Australian federal government does not directly control most prisons or detention facilities. There are a relatively small number of federal detention facilities, consisting of military detention facilities (such as the Defence Force Correctional Establishment), immigration detention facilities, and holding cells in Australian Federal Police stations in some territories. The vast majority of criminal prosecutions in Australia take place within state or territory court systems under state or territory law, however a relatively small number of prosecutions in state and federal courts occur under federal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
History Of Radio
The early history of radio is the history of technology that produces and uses radio equipment, radio instruments that use radio waves. Within the timeline of radio, many people contributed theory and inventions in what became radio. Radio development began as "wireless telegraphy". Later radio history increasingly involves matters of broadcasting. Discovery In an 1864 presentation, published in 1865, James Clerk Maxwell proposed theories of electromagnetism, with mathematical proofs, that showed that light and predicted that radio and x-rays were all types of electromagnetic waves propagating through free space. Between 1886 and 1888 Heinrich Rudolf Hertz published the results of experiments wherein he was able to transmit electromagnetic waves (radio waves) through the air, proving Maxwell's electromagnetic theory. [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Loop Antenna
A loop antenna is a radio antenna consisting of a loop or coil of wire, tubing, or other electrical conductor, that is usually fed by a balanced source or feeding a balanced load. Within this physical description there are two (possibly three) distinct types: * Large loop antennas (or ''self-resonant loop antennas'') have a perimeter close to one or more whole wavelengths at the operating frequency, which makes them self-resonant at that frequency. They are the most efficient of all antenna types for both transmission and reception. Large loop antennas have a two-lobe radiation pattern at their first, full-wave resonance, peaking in both directions ''perpendicular'' to the plane of the loop. * Halo antennas are shortened dipoles that have been bent into a circular loop, with the ends not quite touching. Some writers prefer to exclude them from loop antennas, since they can be well-understood as bent dipoles, others make halos an intermediate category between large and small loo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Selectivity (radio)
Selectivity is a measure of the performance of a radio receiver to respond only to the radio signal it is tuned to (such as a radio station) and reject other signals nearby in frequency, such as another broadcast on an adjacent channel. Selectivity is usually measured as a ratio in decibels (dB), comparing the signal strength received against that of a similar signal on another frequency. If the signal is at the adjacent channel of the selected signal, this measurement is also known as adjacent-channel rejection ratio (ACRR). Selectivity also provides some immunity to blanketing interference. LC circuits are often used as filters; the Q ("Quality" factor) determines the bandwidth of each LC tuned circuit in the radio. The L/C ratio, in turn, determines their Q and so their selectivity, because the rest of the circuit - the aerial or amplifier feeding the tuned circuit for example - will contain present resistance. For a series resonant circuit, the higher the inductance and the l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sensitivity (electronics)
The sensitivity of an electronic device, such as a communications system receiver, or detection device, such as a PIN diode, is the minimum magnitude of input signal required to produce a specified output signal having a specified signal-to-noise ratio, or other specified criteria. Sensitivity is sometimes improperly used as a synonym for ''responsivity''. Electroacoustics The sensitivity of a microphone is usually expressed as the sound field strength in decibels (dB) relative to 1 V/ Pa (Pa = N/ m2) or as the transfer factor in millivolts per pascal (mV/Pa) into an open circuit or into a 1 kiloohm load. The sensitivity of a loudspeaker is usually expressed as dB / 2.83 VRMS at 1 metre. This is not the same as the electrical efficiency; see Efficiency vs sensitivity. The sensitivity of a hydrophone is usually expressed as dB re 1 V/μPa. Receivers Sensitivity in a receiver, such a radio receiver, indicates its capability to extract information from a weak signal, quantifi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DXing
DXing is the hobby of receiving and identifying distant radio or television signals, or making two-way radio contact with distant stations in amateur radio, citizens' band radio or other two-way radio communications. Many DXers also attempt to obtain written verifications of reception or contact, sometimes referred to as " QSLs" or "veries". The name of the hobby comes from DX, telegraphic shorthand for "distance" or "distant". The practice of DXing arose during the early days of radio broadcasting. Listeners would mail "reception reports" to radio broadcasting stations in hopes of getting a written acknowledgement or a QSL card that served to officially verify they had heard a distant station. Collecting these cards became popular with radio listeners in the 1920s and 1930s, and reception reports were often used by early broadcasters to gauge the effectiveness of their transmissions. Although international shortwave broadcasts are on the decline, DXing remains popular among de ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
The New Yorker
''The New Yorker'' is an American weekly magazine featuring journalism, commentary, criticism, essays, fiction, satire, cartoons, and poetry. Founded as a weekly in 1925, the magazine is published 47 times annually, with five of these issues covering two-week spans. Although its reviews and events listings often focus on the Culture of New York City, cultural life of New York City, ''The New Yorker'' has a wide audience outside New York and is read internationally. It is well known for its illustrated and often topical covers, its commentaries on popular culture and eccentric American culture, its attention to modern fiction by the inclusion of Short story, short stories and literary reviews, its rigorous Fact-checking, fact checking and copy editing, its journalism on politics and social issues, and its single-panel cartoons sprinkled throughout each issue. Overview and history ''The New Yorker'' was founded by Harold Ross and his wife Jane Grant, a ''The New York Times, N ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Commissary
A commissary is a government official charged with oversight or an ecclesiastical official who exercises in special circumstances the jurisdiction of a bishop. In many countries, the term is used as an administrative or police title. It often corresponds to the command of a police station, which is then known as a " commissariat". In some armed forces, commissaries are officials charged with overseeing the purchase and delivery of supplies, and they have powers of administrative and financial oversight. Then, the " commissariat" is the organization associated with the corps of commissaries. By extension, the term "commissary" came to be used for the building where supplies were disbursed. In some countries, both roles are used; for example, France uses " police commissaries" (''commissaires de police'') in the French National Police and "armed forces commissaries" (''commissaires des armées'') in the French armed forces. The equivalent terms are ''commissaire'' in French, ''c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
FM Broadcasting
FM broadcasting is a method of radio broadcasting using frequency modulation (FM). Invented in 1933 by American engineer Edwin Armstrong, wide-band FM is used worldwide to provide high fidelity sound over broadcast radio. FM broadcasting is capable of higher fidelity—that is, more accurate reproduction of the original program sound—than other broadcasting technologies, such as AM broadcasting. It is also less susceptible to common forms of interference, reducing static and popping sounds often heard on AM. Therefore, FM is used for most broadcasts of music or general audio (in the audio spectrum). FM radio stations use the very high frequency range of radio frequencies. Broadcast bands Throughout the world, the FM broadcast band falls within the VHF part of the radio spectrum. Usually 87.5 to 108.0 MHz is used, or some portion thereof, with few exceptions: * In the former Soviet republics, and some former Eastern Bloc countries, the older 65.8–74 MHz band ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Integrated Circuit
An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Large numbers of tiny MOSFETs (metal–oxide–semiconductor field-effect transistors) integrate into a small chip. This results in circuits that are orders of magnitude smaller, faster, and less expensive than those constructed of discrete electronic components. The IC's mass production capability, reliability, and building-block approach to integrated circuit design has ensured the rapid adoption of standardized ICs in place of designs using discrete transistors. ICs are now used in virtually all electronic equipment and have revolutionized the world of electronics. Computers, mobile phones and other home appliances are now inextricable parts of the structure of modern societies, made possible by the small size and low cost of ICs such as modern computer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
.jpg "Click for more on -> Integrated Circuit")