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Harold A. Zahl
Harold Adelbert Zahl (August 24, 1904 – March 11, 1973) was an American physicist who had a 35-year career with the U.S. Army Signal Corps Laboratories, where he served as the director of research at Fort Monmouth and made major contributions to radar development. He is perhaps most famous for inventing the GA-4 Transmitter-Receiver Tube and the VT-158, which became known as the Zahl tube. Early life Harold Zahl was born in Chatsworth, Illinois, the son of an Evangelical minister. While still in high school, he became an amateur radio operator (call letters 6BHI). He graduated in physics and mathematics from North Central College in Naperville, Illinois, in 1927, and then attended the University of Iowa where he earned an M.A. degree in 1929 and a Ph.D. degree in 1931, both in solid-state physics. Signal Corps Laboratories Upon completing his doctorate, Zahl joined the staff of the Signal Corps Laboratories (SCL) at Fort Monmouth, New Jersey, which later became part of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chatsworth, Illinois
Chatsworth is an incorporated town in Livingston County, Illinois, United States. The population was 1,332 at the 2020 census. Geography Chatsworth is located in southeastern Livingston County at (40.754256, -88.293023). The town is in northern Chatsworth Township, with a small panhandle extending north into Charlotte Township. The town limits also extend south from the town center and include a large undeveloped area in central Chatsworth Township. U.S. Route 24 runs through the town south of the town center, leading east to Interstate 57 at Gilman and west to Interstate 55 at Chenoa. According to the 2020 census, Chatsworth has a total area of , all land. History Founding Chatsworth was laid out by Zeno Secor (1809 – 1875) and Cornelia Gilman on June 8, 1859. Both founders were from New York. Secor was a member of the Board of Directors of the company that was building the Peoria and Oquawka Railroad. He was a noted civil engineer and marine engine designer, who wa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
First Lieutenant
First lieutenant is a commissioned officer military rank in many armed forces; in some forces, it is an appointment. The rank of lieutenant has different meanings in different military formations, but in most forces it is sub-divided into a senior (first lieutenant) and junior (second lieutenant) rank. The NATO equivalent rank for land force officers is OF-1 rank. In navies, while certain rank insignia may carry the name lieutenant, the term may also be used to relate to a particular post or duty, rather than a rank. Indonesia In Indonesia, "first lieutenant" is known as ''Letnan Satu'' (''Lettu''), Indonesian National Armed Forces uses this rank across all three of its services. It is just above the rank of second lieutenant and just below the rank of captain. Israel In the Israel Defense Forces, the rank above second lieutenant is simply lieutenant. The rank of (קצין מקצועי אקדמאי (קמ"א (''katsín miktsoí akademai'' or "kama"), a professional aca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radiation Laboratory
The Radiation Laboratory, commonly called the Rad Lab, was a microwave and radar research laboratory located at the Massachusetts Institute of Technology (MIT) in Cambridge, Massachusetts. It was first created in October 1940 and operated until 31 December 1945 when its functions were dispersed to industry, other departments within MIT, and in 1951, the newly formed MIT Lincoln Laboratory. The use of microwaves for various radio and radar uses was highly desired before the war, but existing microwave devices like the klystron were far too low powered to be useful. Alfred Lee Loomis, a millionaire and physicist who headed his own private laboratory, organized the Microwave Committee to consider these devices and look for improvements. In early 1940, Winston Churchill organized what became the Tizard Mission to introduce U.S. researchers to several new technologies the UK had been developing. Among these was the cavity magnetron, a leap forward in the creation of microwaves that made ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Invasion Of Normandy
Operation Overlord was the codename for the Battle of Normandy, the Allied operation that launched the successful invasion of German-occupied Western Europe during World War II. The operation was launched on 6 June 1944 (D-Day) with the Normandy landings. A 1,200-plane airborne assault preceded an amphibious assault involving more than 5,000 vessels. Nearly 160,000 troops crossed the English Channel on 6 June, and more than two million Allied troops were in France by the end of August. The decision to undertake a cross-channel invasion in 1944 was taken at the Trident Conference in Washington in May 1943. General Dwight D. Eisenhower was appointed commander of Supreme Headquarters Allied Expeditionary Force, and General Bernard Montgomery was named commander of the 21st Army Group, which comprised all the land forces involved in the invasion. The coast of Normandy of northwestern France was chosen as the site of the invasion, with the Americans assigned to land at sectors ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pacific War
The Pacific War, sometimes called the Asia–Pacific War, was the theater of World War II that was fought in Asia, the Pacific Ocean, the Indian Ocean, and Oceania. It was geographically the largest theater of the war, including the vast Pacific Ocean theater, the South West Pacific theater, the Second Sino-Japanese War, and the Soviet–Japanese War. The Second Sino-Japanese War between the Empire of Japan and the Republic of China had been in progress since 7 July 1937, with hostilities dating back as far as 19 September 1931 with the Japanese invasion of Manchuria. However, it is more widely accepted that the Pacific War itself began on 7 December (8 December Japanese time) 1941, when the Japanese simultaneously invaded Thailand, attacked the British colonies of Malaya, Singapore, and Hong Kong as well as the United States military and naval bases in Hawaii, Wake Island, Guam, and the Philippines. The Pacific War saw the Allies pitted against Japan, the latter ai ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vacuum Tube
A vacuum tube, electron tube, valve (British usage), or tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to which an electric voltage, potential difference has been applied. The type known as a thermionic tube or thermionic valve utilizes thermionic emission of electrons from a hot cathode for fundamental electronic functions such as signal amplifier, amplification and current rectifier, rectification. Non-thermionic types such as a vacuum phototube, however, achieve electron emission through the photoelectric effect, and are used for such purposes as the detection of light intensities. In both types, the electrons are accelerated from the cathode to the anode by the electric field in the tube. The simplest vacuum tube, the diode (i.e. Fleming valve), invented in 1904 by John Ambrose Fleming, contains only a heated electron-emitting cathode and an anode. Electrons can only flow in one direction through the device—fro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
World War II
World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposing military alliances: the Allies and the Axis powers. World War II was a total war that directly involved more than 100 million personnel from more than 30 countries. The major participants in the war threw their entire economic, industrial, and scientific capabilities behind the war effort, blurring the distinction between civilian and military resources. Aircraft played a major role in the conflict, enabling the strategic bombing of population centres and deploying the only two nuclear weapons ever used in war. World War II was by far the deadliest conflict in human history; it resulted in 70 to 85 million fatalities, mostly among civilians. Tens of millions died due to genocides (including the Holocaust), starvation, ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SCR-270
The SCR-270 (Set Complete Radio model 270) was one of the first operational early-warning radars. It was the U.S. Army's primary long-distance radar throughout World War II and was deployed around the world. It is also known as the Pearl Harbor Radar, since it was an SCR-270 set that detected the incoming raid about 45 minutes before the December 7, 1941, attack on Pearl Harbor commenced. Two versions were produced, the mobile SCR-270, and the fixed SCR-271 which used the same electronics but used an antenna with somewhat greater resolution. An upgraded version, the SCR-289, was also produced, but saw little use. The -270 versions were eventually replaced by newer microwave units based on cavity magnetron that was introduced to the US during the Tizard Mission. The only early warning system of the sort to see action in World War II was the AN/CPS-1, which was available in mid-1944, in time for D-day. Building of the radar The Signal Corps had been experimenting with some rad ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Duplexer
A duplexer is an electronic device that allows bi-directional ( duplex) communication over a single path. In radar and radio communications systems, it isolates the receiver from the transmitter while permitting them to share a common antenna. Most radio repeater systems include a duplexer. Duplexers can be based on frequency (often a waveguide filter), polarization (such as an orthomode transducer), or timing (as is typical in radar). Types Transmit-receive switch In radar, a transmit/receive (TR) switch alternately connects the transmitter and receiver to a shared antenna. In the simplest arrangement, the switch consists of a gas-discharge tube across the input terminals of the receiver. When the transmitter is active, the resulting high voltage causes the tube to conduct, shorting together the receiver terminals to protect it, while its complementary, the anti-transmit/receive (ATR) switch, is a similar discharge tube which decouples the transmitter from the antenna while no ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermal Detector
A bolometer is a device for measuring radiant heat by means of a material having a temperature-dependent electrical resistance. It was invented in 1878 by the American astronomer Samuel Pierpont Langley. Principle of operation A bolometer consists of an absorptive element, such as a thin layer of metal, connected to a thermal reservoir (a body of constant temperature) through a thermal link. The result is that any radiation impinging on the absorptive element raises its temperature above that of the reservoir – the greater the absorbed power, the higher the temperature. The intrinsic thermal time constant, which sets the speed of the detector, is equal to the ratio of the heat capacity of the absorptive element to the thermal conductance between the absorptive element and the reservoir. The temperature change can be measured directly with an attached resistive thermometer, or the resistance of the absorptive element itself can be used as a thermometer. Metal bolometers us ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermal Radiation
Thermal radiation is electromagnetic radiation generated by the thermal motion of particles in matter. Thermal radiation is generated when heat from the movement of charges in the material (electrons and protons in common forms of matter) is converted to electromagnetic radiation. All matter with a temperature greater than absolute zero emits thermal radiation. At room temperature, most of the emission is in the infrared (IR) spectrum. Particle motion results in charge-acceleration or dipole oscillation which produces electromagnetic radiation. Infrared radiation emitted by animals (detectable with an infrared camera) and cosmic microwave background radiation are examples of thermal radiation. If a radiation object meets the physical characteristics of a black body in thermodynamic equilibrium, the radiation is called blackbody radiation. Planck's law describes the spectrum of blackbody radiation, which depends solely on the object's temperature. Wien's displacement law de ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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