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Communications Receiver
A communications receiver is a type of radio receiver used as a component of a radio communication link. This is in contrast to a ''broadcast receiver'' which is used to receive radio broadcasts. A communication receiver receives parts of the radio spectrum not used for broadcasting, that includes amateur, military, aircraft, marine, and other bands. They are often used with a radio transmitter as part of a two-way radio link for shortwave radio or amateur radio communication, although they are also used for shortwave listening. Features Commercial communications receivers are characterized by high stability and reliability of performance, and are generally adapted for remote control and monitoring. For marketing purposes, many hobby-type receivers are advertised as "communications receivers" although none are suited for heavy-duty, reliable 24-hour use as the primary form of communication for an isolated station. Typically, a communications receiver is of the superheterody ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
National HRO Shortwave Communications Receiver
National may refer to: Common uses * Nation or country ** Nationality – a ''national'' is a person who is subject to a nation, regardless of whether the person has full rights as a citizen Places in the United States * National, Maryland, census-designated place * National, Nevada, ghost town * National, Utah, ghost town * National, West Virginia, unincorporated community Commerce * National (brand), a brand name of electronic goods from Panasonic * National Benzole (or simply known as National), former petrol station chain in the UK, merged with BP * National Car Rental, an American rental car company * National Energy Systems, a former name of Eco Marine Power * National Entertainment Commission, a former name of the Media Rating Council * National Motor Vehicle Company, Indianapolis, Indiana, USA 1900-1924 * National Supermarkets, a defunct American grocery store chain * National String Instrument Corporation, a guitar company formed to manufacture the first resonator g ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Intermodulation
Intermodulation (IM) or intermodulation distortion (IMD) is the amplitude modulation of signals containing two or more different frequencies, caused by nonlinearities or time variance in a system. The intermodulation between frequency components will form additional components at frequencies that are not just at harmonic frequencies (integer multiples) of either, like harmonic distortion, but also at the sum and difference frequencies of the original frequencies and at sums and differences of multiples of those frequencies. Intermodulation is caused by non-linear behaviour of the signal processing (physical equipment or even algorithms) being used. The theoretical outcome of these non-linearities can be calculated by generating a Volterra series of the characteristic, or more approximately by a Taylor series. Practically all audio equipment has some non-linearity, so it will exhibit some amount of IMD, which however may be low enough to be imperceptible by humans. Due to t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rohde & Schwarz
Rohde & Schwarz GmbH & Co KG (, ) is an international electronics group specializing in the fields of electronic test equipment, broadcast & media, cybersecurity, radiomonitoring and radiolocation, and radiocommunication. The company provides products for the wireless communications, broadcast & media, cybersecurity and electronics industry, aerospace and defense, homeland security and critical infrastructures. In addition to the Munich headquarters, there are regional headquarters in the United States (Columbia, Maryland) and in Asia (Singapore). About 7,700 of the company's employees work in Germany. Worldwide the company has a total of around 13,000 employees in over 70 countries. Exports account for around 85 percent of revenues. History The company was founded by Lothar Rohde and Hermann Schwarz who met while studying physics in Jena. They built their first T&M instrument in 1932, and in August 1933, the ''Physikalisch-Technisches Entwicklungslabor Dr. Rohde & Dr. Sch ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plessey
The Plessey Company plc was a British electronics, defence and telecommunications company. It originated in 1917, growing and diversifying into electronics. It expanded after World War II by acquisition of companies and formed overseas companies. It was listed on the London Stock Exchange and was a constituent of the FTSE 100 Index. In 1989, it was taken over by a consortium formed by GEC and Siemens which split the assets of the Plessey group. The majority of Plessey's defence assets were amalgamated into BAE Systems in 1999 when British Aerospace merged with the defence arm of GEC, Marconi Electronic Systems (MES). A small portion of the defence market, mostly embedded electronic systems and circuitcards remained with GE, formerly GE Fanuc and GE Intelligent Platforms (GE-IP) and now Abaco Systems based in Huntsville, Alabama, and in Towcester, Northamptonshire. The bulk of Plessey's telecommunications assets were acquired by Ericsson through its 2005 acquisition of Marconi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Marconi Company
The Marconi Company was a British telecommunications and engineering company that did business under that name from 1963 to 1987. Its roots were in the Wireless Telegraph & Signal Company founded by Italian inventor Guglielmo Marconi in 1897, which underwent several changes in name after mergers and acquisitions. The company was a pioneer of wireless long distance communication and mass media broadcasting, eventually becoming one of the UK's most successful manufacturing companies. In 1999, its defence equipment manufacturing division, Marconi Electronic Systems, merged with British Aerospace (BAe) to form BAE Systems. In 2006, financial difficulties led to the collapse of the remaining company, with the bulk of the business acquired by the Swedish telecommunications company, Ericsson. History Naming history *1897–1900: The Wireless Telegraph & Signal Company *1900–1963: Marconi's Wireless Telegraph Company *1963–1987: Marconi Company Ltd *1987–1998: GEC-Marconi Ltd ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Racal
Racal Electronics plc was a British electronics company that was founded in 1950. Listed on the London Stock Exchange and once a constituent of the FTSE 100 Index, Racal was a diversified company, offering products including voice loggers and data recorders, point of sale terminals, laboratory instruments and military electronics, including radio and radar. At its height it was the third largest British electronics firm; it operated throughout 110 countries worldwide and employed over 30,000 people. It was the parent company of Vodafone, before the mobile telephony provider was sold in 1991. Racal was purchased by Thomson-CSF (now Thales Group) in 2000, thereby giving the French firm access to the UK defence and armaments market. In 2001, Racal Instruments, Inc. became an independent company after a leveraged buyout from Thales. In 2004, Racal Instruments, Inc. was acquired by EADS North America Defense and Test Services, Inc., which was then acquired by Astronics Corporati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
R-390A
The R-390A /URR is a general coverage HF radio communications receiver designed by Collins Radio Company for the United States Armed Forces. History The R-390A military shortwave radio receiver was the result of a project undertaken by the United States Army Signal Corps in 1954 to replace the existing R-390 receiver then in use. The R-390 had done its job so well that the Corps decided continued use of this type of receiver necessitated an improved, reduced-cost version. There are many references to the R390A in the open literature during this period; a picture of the receiver appeared in the May 1959 issue of ''QST''. The total production of the R-390A (as determined by the high serial numbers noted) is over 55,000 units. Initial production started in 1955 and ran through approximately 1970, and then was restarted in 1984 by Fowler Industries for Avondale Shipyards. Manufacturers and their approximate production numbers are: Companies which made spare modules, but not whole s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Collins Radio Company
Rockwell Collins was a multinational corporation headquartered in Cedar Rapids, Iowa, providing avionics and information technology systems and services to government agencies and aircraft manufacturers. It was formed when the Collins Radio Company, facing financial difficulties, was purchased by Rockwell International in 1973. In 2001, the avionics division of Rockwell International was spun off to form the current Rockwell Collins, Inc, retaining its name. The company was acquired by United Technologies Corporation on November 27, 2018, and now operates as part of Collins Aerospace, a subsidiary of Raytheon Technologies. History Arthur A. Collins founded Collins Radio Company in 1933 in Cedar Rapids, Iowa. It designed and produced both shortwave radio equipment and equipment for the burgeoning AM radio broadcast industry. Collins was solicited by the military, the scientific community, and the larger AM radio stations for special equipment. Collins supplied the equipment t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Boat Anchor (computer Science)
In amateur radio and computing, a boat anchor or boatanchor is something obsolete, useless, and cumbersome – so-called because metaphorically its only productive use is to be thrown into the water as a boat mooring. Terms such as brick, doorstop, and paperweight are similar. Amateur radio In amateur radio, a ''boat anchor'' or ''boatanchor'' is an old piece of radio equipment. It is usually used in reference to large, heavy radio equipment of earlier decades that used tubes. In this context ''boat anchors'' are often prized by their owners and their strengths (e.g. immunity to EMP) emphasised, even if newer equipment is more capable. An early use of the term appeared in a 1956 issue of ''CQ Amateur Radio Magazine''. The magazine published a letter from a reader seeking "schematics or conversion data" for a war surplus Wireless Set No. 19 MK II transceiver in order to modify it for use on the amateur bands. The editor added this reply: The editor's use of the term gene ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electromagnetic Shielding
In electrical engineering, electromagnetic shielding is the practice of reducing or blocking the electromagnetic field (EMF) in a space with barriers made of conductive or magnetic materials. It is typically applied to enclosures, for isolating electrical devices from their surroundings, and to cables to isolate wires from the environment through which the cable runs (). Electromagnetic shielding that blocks radio frequency (RF) electromagnetic radiation is also known as RF shielding. EMF shielding serves to minimize electromagnetic interference. The shielding can reduce the coupling of radio waves, electromagnetic fields, and electrostatic fields. A conductive enclosure used to block electrostatic fields is also known as a '' Faraday cage''. The amount of reduction depends very much upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of holes in a shield to an incident electromagn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bandspread
In a radio receiver, a bandspread control is a secondary tuning control that allows accurate tuning of closely spaced frequencies of a radio band. With a main tuning control that covered a wide range of frequencies, for example 10-14 megahertz in a few turns of the tuning knob, a very small motion might change the tuning by tens of kilohertz and would make accurate tuning to any particular frequency difficult. A calibrated bandspread tuning control allows the main tuning to be set to a predefined spot on the control, and the bandspread allows tuning of a particular frequency within some restricted range of the main tuning control. One method of adding a bandspread control was to put a relatively small value variable tuning capacitor and dial directly in parallel with the main tuning variable capacitor ( or connected to a tap on the coil of the tuned circuit). The smaller capacitor would have much less effect on the resonant frequency than the main capacitor, allowing fine discrimina ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Q Multiplier
In electronics, a Q multiplier is a circuit added to a radio receiver to improve its selectivity and sensitivity. It is a regenerative amplifier adjusted to provide positive feedback within the receiver. This has the effect of narrowing the receiver's bandwidth, as if the Q factor of its tuned circuits had been increased. The Q multiplier was a common accessory in shortwave receivers of the vacuum tube era as either a factory installation or an add-on device. In use, the Q multiplier had to be adjusted to a point just short of oscillation to provide maximum sensitivity and rejection of interfering signals. A Q multiplier could also be adjusted to act as a notch filter, useful for reducing the interfering effect of signals on frequencies near to the desired signal. In some receiver designs, the Q multiplier was made to also serve as a beat frequency oscillator by adjusting it to oscillate. This could be used for reception of single sideband or Morse radiotelegraphy, but in that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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