Instruct: Given a question, retrieve documents that can help answer the question.
Query: Who developed the first VHF-band radar system?
Germany has a long heritage of using electromagnetic waves for detecting objects. In 1888, Heinrich Hertz, who first demonstrated the existence of these waves, also noted that they, like light, were reflected by metal surfaces. In 1904, Christian Hülsmeyer obtained German and foreign patents for an apparatus, the "Telemobilskop", using a "spark gap transmitter" that could detect ships and prevent collisions; this is often cited as the first radar, but, without directly providing range, it does not qualify for this classification. With the advent of the radio tube and electronics, other detection-only systems were developed, but all used continuous waves and could not measure distance.
In 1933, physicist Rudolf Kühnhold, Scientific Director at the "Kriegsmarine" (German Navy) "Nachrichtenmittel-Versuchsanstalt" (NVA—Experimental Institute of Communication Systems) in Kiel, initiated experiments in the microwave region to measure the distance to a target. For the transmitter, he obtained assistance from two radio amateur operators, Paul-Günther Erbslöh and Hans-Karl Freiherr von Willisen. In January 1934, they formed at Berlin-Oberschöneweide the company "Gesellschaft für Elektroakustische und Mechanische Apparate" (GEMA) for this work.
The first person to use resonant circuits in a radio application was Nikola Tesla, who invented the resonant transformer in 1891. At a March 1893 St. Louis lecture he had demonstrated a wireless system that, although it was intended for wireless power transmission, had many of the elements of later radio communication systems. A grounded capacitance-loaded spark-excited resonant transformer (his "Tesla coil") attached to an elevated wire monopole antenna transmitted radio waves, which were received across the room by a similar wire antenna attached to a receiver consisting of a second grounded resonant transformer tuned to the transmitter's frequency, which lighted a Geissler tube. This system, patented by Tesla 2 September 1897, 4 months after Lodge's "syntonic" patent, was in effect an inductively coupled radio transmitter and receiver, the first use of the "four circuit" system claimed by Marconi in his 1900 patent "(below)". However, Tesla was mainly interested in wireless power and never developed a practical radio "communication" system.
In 1947, Raytheon built the "Radarange", the first commercially available microwave oven. It was almost tall, weighed and cost about US$5,000 ($ in dollars) each. It consumed 3 kilowatts, about three times as much as today's microwave ovens, and was water-cooled. The name was the winning entry in an employee contest. An early Radarange was installed (and remains) in the galley of the nuclear-powered passenger/cargo ship NS "Savannah". An early commercial model introduced in 1954 consumed 1.6 kilowatts and sold for US$2,000 to US$3,000 ($ to $ in dollars). Raytheon licensed its technology to the Tappan Stove company of Mansfield, Ohio in 1952. They tried to market a large 220 volt wall unit as a home microwave oven in 1955 for a price of US$1,295 ($ in dollars), but it did not sell well.
In 1874, German scientist Karl Ferdinand Braun discovered the "unilateral conduction" across a contact between a metal and a mineral. Indian scientist Jagadish Chandra Bose was the first to use a crystal for detecting radio waves in 1894. The crystal detector was developed into a practical device for wireless telegraphy by Greenleaf Whittier Pickard, who invented a silicon crystal detector in 1903 and received a patent for it on November 20, 1906. Other experimenters tried a variety of other minerals as detectors. Semiconductor principles were unknown to the developers of these early rectifiers. During the 1930s understanding of physics advanced and in the mid 1930s researchers at Bell Telephone Laboratories recognized the potential of the crystal detector for application in microwave technology. Researchers at Bell Labs, Western Electric, MIT, Purdue and in the UK intensively developed point-contact diodes ("crystal rectifiers" or "crystal diodes") during World War II for application in radar. After World War II, AT&T used these in their microwave towers that criss-crossed the United States, and many radar sets use them even in the 21st century. In 1946, Sylvania began offering the 1N34 crystal diode. During the early 1950s, junction diodes were developed.
The development of microwave technology during World War 2, such as the klystron and magnetron tubes and parabolic antennas made radiative (far-field) methods practical for the first time, and the first long-distance wireless power transmission was achieved in the 1960s by William C. Brown. In 1964 Brown invented the rectenna which could efficiently convert microwaves to DC power, and in 1964 demonstrated it with the first wireless-powered aircraft, a model helicopter powered by microwaves beamed from the ground. A major motivation for microwave research in the 1970s and 80s was to develop a solar power satellite. Conceived in 1968 by Peter Glaser, this would harvest energy from sunlight using solar cells and beam it down to Earth as microwaves to huge rectennas, which would convert it to electrical energy on the electric power grid. In landmark 1975 experiments as technical director of a JPL/Raytheon program, Brown demonstrated long-range transmission by beaming 475 W of microwave power to a rectenna a mile away, with a microwave to DC conversion efficiency of 54%. At NASA's Jet Propulsion Laboratory he and Robert Dickinson transmitted 30 kW DC output power across 1.5 km with 2.38 GHz microwaves from a 26 m dish to a 7.3 x 3.5 m rectenna array. The incident-RF to DC conversion efficiency of the rectenna was 80%. In 1983 Japan launched MINIX (Microwave Ionosphere Nonlinear Interaction Experiment), a rocket experiment to test transmission of high power microwaves through the ionosphere.
Raytheon's research on the magnetron tube revealed the potential of microwaves to cook food. In 1945, Raytheon's Percy Spencer invented the microwave oven by discovering that the magnetron could rapidly heat food. In 1947, the company demonstrated the Radarange microwave oven for commercial use.
Lee de Forest (August 26, 1873 – June 30, 1961) was an American inventor, self-described "Father of Radio", and a pioneer in the development of sound-on-film recording used for motion pictures. He had over 180 patents, but also a tumultuous career—he boasted that he made, then lost, four fortunes. He was also involved in several major patent lawsuits, spent a substantial part of his income on legal bills, and was even tried (and acquitted) for mail fraud. His most famous invention, in 1906, was the three-element "Audion" (triode) vacuum tube, the first practical amplification device. Although De Forest had only a limited understanding of how it worked, it was the foundation of the field of electronics, making possible radio broadcasting, long distance telephone lines, and talking motion pictures, among countless other applications.
The process was invented in Hanau, Germany in 1917. Heraeus Vacuumschmelze and Dr. Wilhelm Rohn applied for a patent on vacuum melting on 12 January 1918 and were granted a German patent DE 345161. E.F. Northrup built the first prototype of a vacuum induction furnace in the United States of America in 1920. Medium frequency furnaces were seen soon afterwards in England and Sweden in 1927. The process was initially developed to refine certain special metals such as cobalt and nickel. As these metals and alloys became more common, the process of VIM became more widely used. VIM now helps to melt a variety of metals for aircraft and nuclear applications.
In the early 1920s, Drs. Walter H. Schottky and Erwin Gerlach co-invented the first ribbon microphone. By turning the ribbon circuit in the opposite direction, they also invented the first ribbon loudspeaker. A few years later, Dr. Harry F. Olson of RCA started developing ribbon microphones using field coils and permanent magnets. The RCA Photophone Type PB-31 was commercially manufactured in 1931, greatly impacting the audio recording and broadcasting industries. Condenser microphones at the time could not compare to its frequency response. Radio City Music Hall employed PB-31s in 1932. The following year, the 44A came on the scene. Its tone and pattern control helped reduce reverberation. Many RCA ribbon models are still in use and valued by audio engineers.
She was named in honor of Reginald Aubrey Fessenden, born in Brome County, Quebec, Canada, 6 October 1866. He served as head chemist with Thomas Edison's East Orange, New Jersey, laboratories. In 1890 he began concentrating on electrical engineering, and through the next years made many important inventions and improvements in existing devices. His great contributions in the field of radio (particularly the invention of radio-telephony were of marked benefit not only to the Navy but to all seamen. He died 22 July 1932, at his home on Bermuda.
Reginald A. Fessenden was born Quebec in 1866, and entered Bishop's University as a precocious young mathematical prodigy, but left in 1884 without graduating. In 1886, he took a position at the Edison Machine Works, working for inventor Thomas Edison. During an academic period teaching at Purdue University and at the University of Pittsburgh, Fessenden engaged in research on the nascent subject of wireless telegraphy. Much of the rest of his life he was employed in industry, either directly or as a consultant, but was often living near poverty, and produced a stream of inventions. In 1904 he invented the rotary spark-gap transmitter, and in 1906 he built a large transmitter in Massachusetts from which he successfully made a voice transmission. He also discovered the means to recombine separate frequencies to form a coherent audible sound. At his death he was described by inventor and businessman Elihu Thomson as "the greatest wireless inventor of the age, greater than Marconi."
Willis Haviland Carrier (November 26, 1876 – October 7, 1950) was an American engineer, best known for inventing modern air conditioning. Carrier invented the first electrical air conditioning unit in 1902. In 1915, he founded Carrier Corporation, a company specializing in the manufacture and distribution of heating, ventilation, and air conditioning (HVAC) systems.
The Canadian inventor Reginald Fessenden was the first to conceive of using reflected seismic waves to infer geology. His work was initially on the propagation of acoustic waves in water, motivated by the sinking of the Titanic by an iceberg in 1912. He also worked on methods of detecting submarines during World War I. He applied for the first patent on a seismic exploration method in 1914, which was issued in 1917. Due to the war, he was unable to follow up on the idea. John Clarence Karcher discovered seismic reflections independently while working for the United States Bureau of Standards (now the National Institute of Standards and Technology) on methods of sound ranging to detect artillery. In discussion with colleagues, the idea developed that these reflections could aid in exploration for petroleum. With several others, many affiliated with the University of Oklahoma, Karcher helped to form the Geological Engineering Company, incorporated in Oklahoma in April, 1920. The first field tests were conducted near Oklahoma City, Oklahoma in 1921.
The development of thermionic valves starting around 1902, provided an entirely electronic method of amplifying signals. The first practical version of such devices was the Audion triode, invented in 1906 by Lee De Forest, which led to the first amplifiers around 1912. Since the only previous device which was widely used to strengthen a signal was the relay used in telegraph systems, the amplifying vacuum tube was first called an "electron relay". The terms "amplifier" and "amplification", derived from the Latin "amplificare", ("to enlarge or expand"), were first used for this new capability around 1915 when triodes became widespread.
The Cooke and Wheatstone telegraph was an early electrical telegraph system dating from the 1830s invented by English inventor William Fothergill Cooke and English scientist Charles Wheatstone. It was the first telegraph system to be put into commercial service. The receiver consisted of a number of needles which could be moved by electromagnetic coils to point to letters on a board. This feature was liked by early users who were unwilling to learn codes, and employers who did not want to invest in staff training.
The Nippon Hōsō Kyōkai (NHK, the Japan Broadcasting Corporation) began conducting research to "unlock the fundamental mechanism of video and sound interactions with the five human senses" in 1964, after the Tokyo Olympics. NHK set out to create an HDTV system that ended up scoring much higher in subjective tests than NTSC's previously dubbed "HDTV". This new system, NHK Color, created in 1972, included 1125 lines, a 5:3 aspect ratio and 60 Hz refresh rate. The Society of Motion Picture and Television Engineers (SMPTE), headed by Charles Ginsburg, became the testing and study authority for HDTV technology in the international theater. SMPTE would test HDTV systems from different companies from every conceivable perspective, but the problem of combining the different formats plagued the technology for many years.
Listening habits changed in the 1960s due to the introduction of the revolutionary transistor radio, which made possible by the invention of the transistor in 1946. Their compact size — small enough to fit in a shirt pocket — and lower power requirements, compared to vacuum tubes, meant that for the first time radio receivers were readily portable. The transistor radio became the most widely used communication device in history, with billions manufactured by the 1970s. Radio became a ubiquitous "companion medium" which people could take with them anywhere they went.
About 20 years later, John Ambrose Fleming (scientific adviser to the Marconi Company
and former Edison employee) realized that the Edison effect could be used as a radio detector. Fleming patented the first true thermionic diode, the Fleming valve, in Britain on November 16, 1904 (followed by in November 1905).
The first microphone that enabled proper voice telephony was the (loose-contact) carbon microphone (then called transmitter). This was independently developed around 1878 by David Edward Hughes in England and Emile Berliner and Thomas Edison in the US. Although Edison was awarded the first patent in mid-1877, Hughes had demonstrated his working device in front of many witnesses some years earlier, and most historians credit him with its invention.
Although he was the man responsible for its technology, Farnsworth appeared only once on a television program. On July 3, 1957, he was a mystery guest ("Doctor X") on the CBS quiz show "I've Got A Secret". He fielded questions from the panel as they unsuccessfully tried to guess his secret ("I invented electronic television."). For stumping the panel, he received $80 and a carton of Winston cigarettes. Host Garry Moore then spent a few minutes discussing with Farnsworth his research on such projects as high-definition television, flat-screen receivers, and fusion power. Farnsworth said, "There had been attempts to devise a television system using mechanical disks and rotating mirrors and vibrating mirrors—all mechanical. My contribution was to take out the moving parts and make the thing entirely electronic, and that was the concept that I had when I was just a freshman in high school in the Spring of 1921 at age 14." When Moore asked about others' contributions, Farnsworth agreed, "There are literally thousands of inventions important to television. I hold something in excess of 165 American patents." The host then asked about his current research, and the inventor replied, "In television, we're attempting first to make better utilization of the bandwidth, because we think we can eventually get in excess of 2,000 lines instead of 525 ... and do it on an even narrower channel ... which will make for a much sharper picture. We believe in the picture-frame type of a picture, where the visual display will be just a screen. And we hope for a memory, so that the picture will be just as though it's pasted on there."
Shortly after the invention of the telephone attempts were made to adapt the technology for military use. Telephones were already being used to support military campaigns in British India and in British colonies in Africa in the late 1870s and early 1880s. In the United States telephone lines connected fortresses with each other and with army headquarters. They were also used for fire control at fixed coastal defence installations. The first telephone for use in the field was developed in the United States in 1889 but it was too expensive for mass production. Subsequent developments in several countries made the field telephone more practicable. The wire material was changed from iron to copper, devices for laying wire in the field were developed and systems with both battery-operated sets for command posts and hand generator sets for use in the field were developed. The first purposely-designed field telephones were used by the British in the Second Boer War. They were used more extensively in the Russo-Japanese War, where all infantry regiments and artillery divisions on both sides were equipped with telephone sets. By the First World War the use of field telephones was widespread.
The Lichtenstein radar was among the earliest airborne radars available to the Luftwaffe in World War II and the first one used exclusively for air interception. Developed by Telefunken, it was available in at least four major revisions, called FuG 202 Lichtenstein B/C, FuG 212 Lichtenstein C-1, FuG 220 Lichtenstein SN-2 and the very rarely used FuG 228 Lichtenstein SN-3. (FuG is short for "Funk-Gerät", radio set). The Lichtenstein series remained the only widely deployed airborne interception radar used by the Germans on their night fighters during the war — the competing FuG 216 through 218 "Neptun" mid-VHF band radar systems were meant as a potentially more versatile stopgap system through 1944, until the microwave-based FuG 240 "Berlin" could be mass-produced; the "Berlin" system was still being tested when the war ended.
Early FuG 202 Lichtenstein B/C units were not deployed until 1942. They operated at a maximum RF output power of 1.5 kW, on the 61 cm wavelength (490 MHz, or low UHF band), requiring complex "Matratze" (mattress) antennas, consisting of thirty-two dipole elements, mounted in four groups of eight, each at the forward end of one of four forward-projecting masts.
The Nizhny Novgorod Research Institute of Radio Engineering (Russian acronym: NNIIRT) has since 1948 developed a number of radars. These were mainly radars in the VHF-band, and many of which featured developments in technology that represented "first offs" in the Soviet Union. Innovations include the first Soviet air surveillance radar with a circular scan: the P-8 Volga (NATO: KNIFE REST A) in 1950, the first 3D radar: the 5N69 Salute (NATO: BIG BACK) in 1975, and in 1982 the first VHF-band 3D-radar: the 55Zh6 Nebo (NATO: TALL RACK). Other innovations were radars with frequency hopping; the P-10 Volga A (NATO: KNIFE REST B) in 1953, radars with transmitter signal coherency and special features like moving target indicator (MTI); the P-12 Yenisei (NATO: SPOON REST) in 1955 as well as the P-70 Lena-M with chirp signal modulation in 1968 or the widely used P-18 Terek (NATO: SPOON REST D) in 1970.
Beginning in 1975, NNIIRT developed the first VHF 3D radar capable of measuring height, range, and azimuth to a target. This effort produced the 55Zh6 'Nebo' VHF surveillance radar, which passed acceptance trials in 1982.
In August 1940, the Army issued a specification for a new GL radar that combined a VHF set like the Mk. II with a microwave-frequency tracking system with high accuracy. It required:P. E. Pollard of the Air Defence Research and Development Establishment in Christchurch, Dorset had been one of the first people to consider radar as early as 1930, and had been working with the "Army Cell" at the Air Ministry Experimental Station for some time before joining other Army researchers at Christchurch, Dorset. They selected British Thomson-Houston (BTH), who built the earlier 5 m GL sets, to build a prototype. Pollard moved to BTH's plants in Rugby, Warwickshire to work on the new system.