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ART 13 Transmitter
The AN/ART-13 was a radio transmitter manufactured by Collins Radio that found widespread use during and after World War II in military aircraft. History US Navy (T-47/ART-13 Radio Transmitter) training on board the USS Nereus, circa. 1952 In 1940 the Collins Radio Company designed a new radio transmitter for the US Navy. The transmitter, Navy designation ATC, was later re-designated under the Joint Army-Navy (JAN) system as T-47/ART-13. The Army Air Force adopted a slightly improved version as the T-47A/ART-13, most made by Stewart-Warner. The USAAF matched the AN/ART-13A with the BC-348 receiver, whose -R and -Q models were known under the JAN system as the AN/ARR-11. The resulting communications system was known as the AN/ARC-8 and was the liaison radio set on many larger USAAF aircraft beginning late in World War II. Some were still in service in the early 1970s. The earlier AN/ART-13 was widely used in post-World War II Navy aircraft, being paired up post-World War ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radio Transmitter
In electronics and telecommunications, a radio transmitter or just transmitter is an electronic device which produces radio waves with an antenna. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. When excited by this alternating current, the antenna radiates radio waves. Transmitters are necessary component parts of all electronic devices that communicate by radio, such as radio and television broadcasting stations, cell phones, walkie-talkies, wireless computer networks, Bluetooth enabled devices, garage door openers, two-way radios in aircraft, ships, spacecraft, radar sets and navigational beacons. The term ''transmitter'' is usually limited to equipment that generates radio waves for communication purposes; or radiolocation, such as radar and navigational transmitters. Generators of radio waves for heating or industrial purposes, such as microwave ovens or diathermy equipment, are not usually called transmitters, e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
B-29 Superfortress
The Boeing B-29 Superfortress is an American four-engined propeller-driven heavy bomber, designed by Boeing and flown primarily by the United States during World War II and the Korean War. Named in allusion to its predecessor, the B-17 Flying Fortress, the Superfortress was designed for high-altitude strategic bombing, but also excelled in low-altitude night incendiary bombing, and in dropping naval mines to blockade Japan. B-29s dropped the atomic bombs on Hiroshima and Nagasaki, the only aircraft ever to drop nuclear weapons in combat. One of the largest aircraft of World War II, the B-29 was designed with state-of-the-art technology, which included a pressurized cabin, dual-wheeled tricycle landing gear, and an analog computer-controlled fire-control system that allowed one gunner and a fire-control officer to direct four remote machine gun turrets. The $3 billion cost of design and production (equivalent to $ billion today), far exceeding the $1.9 b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Frequencies
Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is equal to one event per second. The period is the interval of time between events, so the period is the reciprocal of the frequency. For example, if a heart beats at a frequency of 120 times a minute (2 hertz), the period, —the interval at which the beats repeat—is half a second (60 seconds divided by 120 beats). 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. Definitions and units For cyclical phenomena such as oscillations, waves, or for examples of simple harmonic motion, the term ''frequency'' is defined as the number of cycles or vibrations per unit of time. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
High Frequency
High frequency (HF) is the ITU designation for the range of radio frequency electromagnetic waves (radio waves) between 3 and 30 megahertz (MHz). It is also known as the decameter band or decameter wave as its wavelengths range from one to ten decameters (ten to one hundred meters). Frequencies immediately below HF are denoted medium frequency (MF), while the next band of higher frequencies is known as the very high frequency (VHF) band. The HF band is a major part of the shortwave band of frequencies, so communication at these frequencies is often called shortwave radio. Because radio waves in this band can be reflected back to Earth by the ionosphere layer in the atmosphere – a method known as "skip" or " skywave" propagation – these frequencies are suitable for long-distance communication across intercontinental distances and for mountainous terrains which prevent line-of-sight communications. The band is used by international shortwave broadcasting stations ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Medium Frequency
Medium frequency (MF) is the ITU designation for radio frequencies (RF) in the range of 300 kilohertz (kHz) to 3 megahertz (MHz). Part of this band is the medium wave (MW) AM broadcast band. The MF band is also known as the hectometer band as the wavelengths range from ten to one hectometer (1000 to 100 m). Frequencies immediately below MF are denoted low frequency (LF), while the first band of higher frequencies is known as high frequency (HF). MF is mostly used for AM radio broadcasting, navigational radio beacons, maritime ship-to-shore communication, and transoceanic air traffic control. Propagation Radio waves at MF wavelengths propagate via ground waves and reflection from the ionosphere (called skywaves). Ground waves follow the curvature of Earth. At these wavelengths they can bend (diffract) over hills, and travel beyond the visual horizon, although they may be blocked by mountain ranges. Typical MF radio stations can cover a radius of several hun ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Low Frequency
Low frequency (LF) is the ITU designation for radio frequencies (RF) in the range of 30–300 kHz. Since its wavelengths range from 10–1 km, respectively, it is also known as the kilometre band or kilometre wave. LF radio waves exhibit low signal attenuation, making them suitable for long-distance communications. In Europe and areas of Northern Africa and Asia, part of the LF spectrum is used for AM broadcasting as the "longwave" band. In the western hemisphere, its main use is for aircraft beacon, navigation (LORAN), information, and weather systems. A number of time signal broadcasts also use this band. Propagation Because of their long wavelength, low frequency radio waves can diffract over obstacles like mountain ranges and travel beyond the horizon, following the contour of the Earth. This mode of propagation, called ''ground wave'', is the main mode in the LF band. Ground waves must be vertically polarized (the electric field is vertical while the magnet ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amplitude Modulation
Amplitude modulation (AM) is a modulation technique used in electronic communication, most commonly for transmitting messages with a radio wave. In amplitude modulation, the amplitude (signal strength) of the wave is varied in proportion to that of the message signal, such as an audio signal. This technique contrasts with angle modulation, in which either the frequency of the carrier wave is varied, as in frequency modulation, or its phase, as in phase modulation. AM was the earliest modulation method used for transmitting audio in radio broadcasting. It was developed during the first quarter of the 20th century beginning with Roberto Landell de Moura and Reginald Fessenden's radiotelephone experiments in 1900. This original form of AM is sometimes called double-sideband amplitude modulation (DSBAM), because the standard method produces sidebands on either side of the carrier frequency. Single-sideband modulation uses bandpass filters to eliminate one of the sidebands and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Modulated Continuous Wave
Modulated continuous wave (MCW) is Morse code telegraphy, transmitted using an audio tone to modulate a carrier wave. The Federal Communications Commission defines modulated continuous wave in 47 CFR §97.3(c)(4) as "Tone-modulated international Morse code telegraphy emissions having designators with A, C, D, F, G, H or R as the first symbol; 2 as the second symbol; A or B as the third symbol." See Types of radio emissions for a general explanation of these symbols. Types of Morse code radio transmissions (CW and MCW) discussed in this article include: * A1A and A2A — Double-sideband amplitude modulation (AM); One channel containing digital information, no subcarrier (A1A) or using a subcarrier (A2A); Aural telegraphy (intended to be decoded by ear) * F2A — Frequency modulation (FM); One channel containing digital information, using a subcarrier; Aural telegraphy * J2A and J2B — Single-sideband with suppressed carrier; One channel containing digital information, using a subc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Continuous Wave
A continuous wave or continuous waveform (CW) is an electromagnetic wave of constant amplitude and frequency, typically a sine wave, that for mathematical analysis is considered to be of infinite duration. It may refer to e.g. a laser or particle accelerator having a continuous output, as opposed to a pulsed output. Continuous wave is also the name given to an early method of radio transmission, in which a sinusoidal carrier wave is switched on and off. Information is carried in the varying duration of the on and off periods of the signal, for example by Morse code in early radio. In early wireless telegraphy radio transmission, CW waves were also known as "undamped waves", to distinguish this method from damped wave signals produced by earlier ''spark gap'' type transmitters. Radio Transmissions before CW Very early radio transmitters used a spark gap to produce radio-frequency oscillations in the transmitting antenna. The signals produced by these spark-gap transmitters c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vintage Amateur Radio
Vintage amateur radio is a subset of amateur radio hobby where enthusiasts collect, restore, preserve, build, and operate amateur radio equipment from bygone years, such as those using vacuum tube technology. Popular modes of operation include speaking over amplitude modulation (AM), and communicating using Morse code through continuous wave (CW) radiotelegraphy. Some enthusiasts have interest in owning, restoring and operating vintage military and commercial radio equipment such as those from 1940s to 1960s. Some undertake to construct their own gear, known in ham slang as homebrewing, using vintage parts and designs. A number of amateur radio clubs and organizations sponsor contests, events, and swap meets that cater to this specialized aspect of the hobby. Appeal Vintage radio enthusiasts contend that the precise digital frequency displays and state-of-the-art, microprocessor-based features of modern amateur equipment lacks the aesthetic appeal and "soul" of amateur electroni ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Empire Of Japan
The also known as the Japanese Empire or Imperial Japan, was a historical nation-state and great power that existed from the Meiji Restoration in 1868 until the enactment of the post-World War II 1947 constitution and subsequent formation of modern Japan. It encompassed the Japanese archipelago and several colonies, protectorates, mandates, and other territories. Under the slogans of and following the Boshin War and restoration of power to the Emperor from the Shogun, Japan underwent a period of industrialization and militarization, the Meiji Restoration, which is often regarded as the fastest modernisation of any country to date. All of these aspects contributed to Japan's emergence as a great power and the establishment of a colonial empire following the First Sino-Japanese War, the Boxer Rebellion, the Russo-Japanese War, and World War I. Economic and political turmoil in the 1920s, including the Great Depression, led to the rise of militarism, nationa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hiroshima, Hiroshima
is the capital of Hiroshima Prefecture in Japan. , the city had an estimated population of 1,199,391. The gross domestic product (GDP) in Greater Hiroshima, Hiroshima Urban Employment Area, was US$61.3 billion as of 2010. Kazumi Matsui has been the city's mayor since April 2011. Hiroshima was founded in 1589 as a castle town on the Ōta River delta. Following the Meiji Restoration in 1868, Hiroshima rapidly transformed into a major urban center and industrial hub. In 1889, Hiroshima officially gained city status. The city was a center of military activities during the imperial era, playing significant roles such as in the First Sino-Japanese War, the Russo-Japanese War, and the two world wars. Hiroshima was the first military target of a nuclear weapon in human history. This occurred on August 6, 1945, at 8:15 a.m., when the United States Army Air Forces (USAAF) dropped the atomic bomb "Little Boy" on the city. Most of Hiroshima was destroyed, and by the end of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
