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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 Signal Corps Laboratories, 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 invented 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, Signal Corps Laboratories (SCL) at Fort Monmouth, New Jersey, which l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chatsworth, Illinois
Chatsworth is an Incorporated town#Illinois, incorporated town in Livingston County, Illinois, Livingston County, Illinois, United States. The population was 1,332 at the 2020 census. Geography Chatsworth is located in southeastern Livingston County in northern Chatsworth Township, Livingston County, Illinois, Chatsworth Township, with a small salient (geography), panhandle extending north into Charlotte Township, Livingston County, Illinois, 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, Illinois, Gilman and west to Interstate 55 at Chenoa, Illinois, 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 (state) ... [...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. 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 (Segen). The rank of (קצין מקצועי אקדמאי (קמ"א (''katsín miktsoí akademai'' or "kama"), a professional academic officer (that is, a medical, dental or veterinary ... [...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 ... [...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 liberation of German-occupied Western Europe during World War II. The operation was launched on 6 June 1944 ( D-Day) with the Normandy landings (Operation Neptune). 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 cross-channel landings in 1944 was made at the Trident Conference in Washington in May 1943. American General Dwight D. Eisenhower was appointed commander of Supreme Headquarters Allied Expeditionary Force, and British General Bernard Montgomery was named commander of the 21st Army Group, which comprised all the land forces involved in the operation. The Normandy coast in northwestern France was chosen as the site of the landings, with the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pacific War
The Pacific War, sometimes called the Asia–Pacific War or the Pacific Theatre, was the Theater (warfare), theatre of World War II fought between the Empire of Japan and the Allies of World War II, Allies in East Asia, East and Southeast Asia, the Pacific Ocean, Pacific and Indian Oceans, and Oceania. It was geographically the largest theatre of the war, including the Pacific Ocean theater of World War II, Pacific Ocean theatre, the South West Pacific theater of World War II, South West Pacific theatre, the Second Sino-Japanese War, and the brief Soviet–Japanese War, and included some of the Largest naval battle in history, largest naval battles in history. War between Japan and the Republic of China (1912–1949), Republic of China had begun in 1937, with hostilities dating back to Japanese invasion of Manchuria, Japan's invasion of Manchuria in 1931, but the Pacific War is more widely accepted to have started in 1941, when the United States and United Kingdom entered the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vacuum Tube
A vacuum tube, electron tube, thermionic 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. It takes the form of an evacuated tubular envelope of glass or sometimes metal containing electrodes connected to external connection pins. The type known as a thermionic tube or thermionic valve utilizes thermionic emission of electrons from a hot cathode for fundamental Electronics, electronic functions such as signal amplifier, amplification and current Rectifier, rectification. Non-thermionic types such as vacuum phototubes achieve electron emission through the photoelectric effect, and are used for such purposes as the detection of light and measurement of its intensity. In both types the electrons are accelerated from the cathode to the anode by the electric field in the tube. The first, and simplest, vacuum tube, the diode or Flem ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
World War II
World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the world's countries participated, with many nations mobilising all resources in pursuit of total war. Tanks in World War II, Tanks and Air warfare of World War II, aircraft played major roles, enabling the strategic bombing of cities and delivery of the Atomic bombings of Hiroshima and Nagasaki, first and only nuclear weapons ever used in war. World War II is the List of wars by death toll, deadliest conflict in history, causing World War II casualties, the death of 70 to 85 million people, more than half of whom were civilians. Millions died in genocides, including the Holocaust, and by massacres, starvation, and disease. After the Allied victory, Allied-occupied Germany, Germany, Allied-occupied Austria, Austria, Occupation of Japan, Japan, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SCR-270
The SCR-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 7 December 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 radar concepts as early as the l ... [...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 whi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SCR-268
The SCR-268 (for ''Signal Corps Radio no. 268'') was the United States Army's first radar system. Introduced in 1940, it was developed to provide accurate aiming information for antiaircraft artillery and was also used for gun laying systems and directing searchlights against aircraft. The radar was widely utilized by both Army and United States Marine Corps, Marine Corps air defense and early warning units during World War II. By the end of World War II the system was already considered out of date, having been replaced by the much smaller and more accurate SCR-584 microwave-based system. Development The Signal Corps (United States Army), Signal Corps had been experimenting with some radar concepts as early as the late 1920s, under the direction of Colonel William R. Blair, director of the Signal Corps Laboratories at Fort Monmouth, New Jersey. While most of the Corps' efforts revolved around infra-red detection systems (a popular idea at the time), as well as a newer genera ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermal Detector
A thermal column (or thermal) is a rising mass of buoyant air, a convective current in the atmosphere, that transfers heat energy vertically. Thermals are created by the uneven heating of Earth's surface from solar radiation, and are an example of convection, specifically atmospheric convection. Thermals on Earth The Sun warms the ground, which in turn warms the air directly above. The warm air near the surface expands, becoming less dense than the surrounding air. The lighter air rises and cools due to its expansion in the lower pressure at higher altitudes. It stops rising when it has cooled to the same temperature, thus density, as the surrounding air. Associated with a thermal is a downward flow surrounding the thermal column. The downward-moving exterior is caused by colder air being displaced at the top of the thermal. The size and strength of thermals are influenced by the properties of the lower atmosphere (the ''troposphere''). When the air is cold, bubbles of warm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermal Radiation
Thermal radiation is electromagnetic radiation emitted by the thermal motion of particles in matter. All matter with a temperature greater than absolute zero emits thermal radiation. The emission of energy arises from a combination of electronic, molecular, and lattice oscillations in a material. Kinetic energy is converted to electromagnetism due to charge-acceleration or dipole oscillation. At room temperature, most of the emission is in the infrared (IR) spectrum, though above around 525 °C (977 °F) enough of it becomes visible for the matter to visibly glow. This visible glow is called incandescence. Thermal radiation is one of the fundamental mechanisms of heat transfer, along with conduction and convection. The primary method by which the Sun transfers heat to the Earth is thermal radiation. This energy is partially absorbed and scattered in the atmosphere, the latter process being the reason why the sky is visibly blue. Much of the Sun's radiation tra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
