A shortwave radio receiver is a radio receiver that can receive one or more shortwave bands, between 1.6 and 30 MHz. A shortwave radio receiver often receives other broadcast bands, such as FM radio, Longwave and Mediumwave. Shortwave radio receivers are often used by dedicated hobbyists called shortwave listeners.
While home built shortwave receivers had been used by amateur radio operators and radio experimenters prior to World War I, [1] [2] the first time shortwave radio reception was available to the general public was through the use of shortwave frequency converters sold as accessories to broadcast-band radio sets during the mid 1920s. Such converters were generally found unsatisfactory in performance, and so dedicated shortwave receiving sets soon appeared on the market. National Radio Company introduced the SW-2 "Thrill box" shortwave regenerative receiver in 1927, and later offered improved models, such as the highly regarded SW-3. Other notable early shortwave receivers included Pilot Radio's "Super Wasp" line of regenerative receivers. [3]
E.H. Scott Radio Laboratories offered its superheterodyne "World's Record" shortwave receiver kit in the late 1920s, [4] [3] and In 1931 Hammarlund introduced the "Comet Pro", the first fully assembled commercial shortwave superheterodyne receiver. [5] Hallicrafters introduced the "Super Skyrider" in 1935, a superheterodyne shortwave receiver available in several different models that covered the broadcast band up to 30 MHz. [3] In 1936, Hammarlund introduced their "Super-Pro" superheterodyne shortwave receiver. [6]
Superheterodyne receiver circuits soon essentially replaced all previous receiver designs, and radio manufacturers such as RCA, Zenith, Philco, Emerson, and Stromberg-Carlson offered consumers table or console model "all wave" sets that could receive both mediumwave and shortwave bands. By 1936 it was estimated that 100 percent of console models and 65 percent of table model radios were able to receive shortwave broadcasts. [3]
Following development of several prototypes between 1939 and 1941, Zenith introduced the Model 7G605 Trans-Oceanic 'Clipper' in 1942, an early portable shortwave receiver marketed to consumers. [7] [8] Shortwave receiver designs had traditionally employed vacuum tubes, but solid state circuit designs began to emerge in the 1950s. The Magnavox model AW-100 was introduced in 1957 and was among the first commercial fully transistorized shortwave radio receivers, [9] along with the Trans-Oceanic Royal 1000 (1957) [10] [11] [12] and Trans-World Portable T-9 Code 126 (1958). [13]
As shortwave receivers evolved, they gained a number of improvements over their early counterparts. Direct digital tuning eliminated the guesswork and imprecision inherent in analog tuners. Solid state components minimized frequency drift. Synchronous detection improved audio fidelity and stability. And miniaturization of components along with integrated circuits enabled the manufacture of small, portable shortwave receivers with adequate sensitivity to deliver satisfactory shortwave reception. [14]
Modern battery-operated portable shortwave radio receivers often called world radio or world band receivers are marketed primarily to those wishing to receive international broadcasts, and are offered in a range of compact "travel size" to smaller "pocket size" units. [15]
Shortwave receivers known as communications receivers are typically larger table top sets used in amateur radio, commercial, and military installations, and by serious hobbyists. They typically include features that enable increased sensitivity and selectivity. [16]
Radios for shortwave reception generally have higher performance than those intended for the local mediumwave, longwave or FM broadcast band, since dependable reception of shortwave signals requires a radio with increased sensitivity, selectivity, dynamic range and frequency stability. Modern shortwave radio receivers are relatively inexpensive and easily accessible, and many hobbyists use portable "world band" receivers and built-in telescopic antennas. Serious hobbyists may use communications receivers and outdoor antenna located away from electrical noise sources, such as a dipole made from wire and insulators.
The typical shortwave radio receiver design is a superheterodyne receiver. Software-defined radios replace one or more stages of a superheterodyne receiver with digital signal processing for filtering, demodulation or other processing.
A well equipped shortwave radio receiver can receive CW and SSB modes in addition to the AM mode traditionally used by broadcasters. Some modern shortwave radio receivers can receive digital radio signals.
Some receivers only tune within frequency bands allocated by international agreement. This may be necessary in some countries where restrictive laws prevent persons from listening to non-broadcast stations. Others offer continuous tuning over the whole shortwave frequency range, allowing the user to listen to amateur radio, marine, air, and utility stations as well as broadcasters.
Tuners on analog receivers may include a bandspread control to allow accurate tuning of closely spaced frequencies. Receivers with digital tuning usually allow direct entry of frequencies with sufficient accuracy and precision so as not to require additional fine-tuning adjustment.
A number of specialized features are typically found in shortwave receivers. [17]
Additional for superheterodyne receivers:
Additional for software-defined radio / digital baseband receivers:
A feature coming into wide use in modern shortwave receivers is DSP technology, short for digital signal processing. DSP is the use of digital means to process signals, and a primary benefit in shortwave receivers is the ability to tailor the bandwidth of the receiver to current reception conditions and to the type of signal being listened to. A typical analogue-only receiver may have a limited number of fixed bandwidths, or only one, but a DSP receiver may have 40 or more individually selectable filters. [19]
Another important trend in modern shortwave listening is the use of "PC radios", or radios that are designed to be controlled by a standard personal computer.[ citation needed ] These radios as the name suggests are controlled by specialized PC software using a (serial) port connected to the radio. A PC radio may not have a front-panel at all, and may be designed exclusively for computer control, which reduces cost. In pure software-defined radios, all filtering, modulation and signal manipulation is done in software, usually by a PC soundcard or by a dedicated piece of DSP hardware. [20]
Older vacuum tube-based communications receivers are affectionately known as boatanchors for their large size and weight. Such receivers include the Collins R-390 and R-390A, the RCA AR-88, the Racal RA-17L and the Marconi Elettra. However, even modern solid-state receivers can be very large and heavy, such as the Plessey PR2250, the Redifon R551 or the Rohde & Schwarz EK070. [21]
In radio communications, single-sideband modulation (SSB) or single-sideband suppressed-carrier modulation (SSB-SC) is a type of modulation used to transmit information, such as an audio signal, by radio waves. A refinement of amplitude modulation, it uses transmitter power and bandwidth more efficiently. Amplitude modulation produces an output signal the bandwidth of which is twice the maximum frequency of the original baseband signal. Single-sideband modulation avoids this bandwidth increase, and the power wasted on a carrier, at the cost of increased device complexity and more difficult tuning at the receiver.
A superheterodyne receiver, often shortened to superhet, is a type of radio receiver that uses frequency mixing to convert a received signal to a fixed intermediate frequency (IF) which can be more conveniently processed than the original carrier frequency. It was long believed to have been invented by US engineer Edwin Armstrong, but after some controversy the earliest patent for the invention is now credited to French radio engineer and radio manufacturer Lucien Lévy. Virtually all modern radio receivers use the superheterodyne principle; except software-defined radios, which use direct sampling.
Shortwave radio is radio transmission using shortwave (SW) radio frequencies. There is no official definition of the band, but the range always includes all of the high frequency band (HF), which extends from 3 to 30 MHz ; above the medium frequency band (MF), to the bottom of the VHF band.
In communications and electronic engineering, an intermediate frequency (IF) is a frequency to which a carrier wave is shifted as an intermediate step in transmission or reception. The intermediate frequency is created by mixing the carrier signal with a local oscillator signal in a process called heterodyning, resulting in a signal at the difference or beat frequency. Intermediate frequencies are used in superheterodyne radio receivers, in which an incoming signal is shifted to an IF for amplification before final detection is done.
Radio broadcasting is the broadcasting of audio (sound), sometimes with related metadata, by radio waves to radio receivers belonging to a public audience. In terrestrial radio broadcasting the radio waves are broadcast by a land-based radio station, while in satellite radio the radio waves are broadcast by a satellite in Earth orbit. To receive the content the listener must have a broadcast radio receiver (radio). Stations are often affiliated with a radio network that provides content in a common radio format, either in broadcast syndication or simulcast, or both. Radio stations broadcast with several different types of modulation: AM radio stations transmit in AM, FM radio stations transmit in FM, which are older analog audio standards, while newer digital radio stations transmit in several digital audio standards: DAB, HD radio, DRM. Television broadcasting is a separate service that also uses radio frequencies to broadcast television (video) signals.
High frequency (HF) is the ITU designation for the range of radio frequency electromagnetic 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. 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 (3.95–25.82 MHz), aviation communication, government time stations, weather stations, amateur radio and citizens band services, among other uses.
Digital Radio Mondiale is a set of digital audio broadcasting technologies designed to work over the bands currently used for analogue radio broadcasting including AM broadcasting—particularly shortwave—and FM broadcasting. DRM is more spectrally efficient than AM and FM, allowing more stations, at higher quality, into a given amount of bandwidth, using xHE-AAC audio coding format. Various other MPEG-4 and Opus codecs are also compatible, but the standard now specifies xHE-AAC.
A regenerative circuit is an amplifier circuit that employs positive feedback. Some of the output of the amplifying device is applied back to its input so as to add to the input signal, increasing the amplification. One example is the Schmitt trigger, but the most common use of the term is in RF amplifiers, and especially regenerative receivers, to greatly increase the gain of a single amplifier stage.
In radio communications, a radio receiver, also known as a receiver, a wireless, or simply a radio, is an electronic device that receives radio waves and converts the information carried by them to a usable form. It is used with an antenna. The antenna intercepts radio waves and converts them to tiny alternating currents which are applied to the receiver, and the receiver extracts the desired information. The receiver uses electronic filters to separate the desired radio frequency signal from all the other signals picked up by the antenna, an electronic amplifier to increase the power of the signal for further processing, and finally recovers the desired information through demodulation.
A cordless telephone or portable telephone has a portable telephone handset that connects by radio to a base station connected to the public telephone network. The operational range is limited, usually to the same building or within some short distance from the base station.
A tuner is a subsystem that receives radio frequency (RF) transmissions, such as FM broadcasting, and converts the selected carrier frequency and its associated bandwidth into a fixed frequency that is suitable for further processing, usually because a lower frequency is used on the output. Broadcast FM/AM transmissions usually feed this intermediate frequency (IF) directly into a demodulator that converts the radio signal into audio-frequency signals that can be fed into an amplifier to drive a loudspeaker.
Shortwave listening, or SWLing, is the hobby of listening to shortwave radio broadcasts located on frequencies between 1700 kHz and 30 MHz. Listeners range from casual users seeking international news and entertainment programming, to hobbyists immersed in the technical aspects of radio reception and collecting official confirmations that document their reception of distant broadcasts (DXing). In some developing countries, shortwave listening enables remote communities to obtain regional programming traditionally provided by local medium wave AM broadcasters. In 2002, the number of households that were capable of shortwave listening was estimated to be in the hundreds of millions.
The Hallicrafters Company manufactured, marketed, and sold radio equipment, and to a lesser extent televisions and phonographs, beginning in 1932. The company was founded by William J. Halligan and based in Chicago, Illinois, United States.
DXing is the hobby of receiving and identifying distant radio or television signals, or making two-way radio contact with distant stations in amateur radio, citizens' band radio or other two-way radio communications. Many DXers also attempt to obtain written verifications of reception or contact, sometimes referred to as "QSLs" or "veries". The name of the hobby comes from DX, telegraphic shorthand for "distance" or "distant".
In a radio receiver circuit, the RF front end, short for radio frequency front end, is a generic term for all the circuitry between a receiver's antenna input up to and including the mixer stage. It consists of all the components in the receiver that process the signal at the original incoming radio frequency (RF), before it is converted to a lower intermediate frequency (IF). In microwave and satellite receivers it is often called the low-noise block downconverter (LNB) and is often located at the antenna, so that the signal from the antenna can be transferred to the rest of the receiver at the more easily handled intermediate frequency.
The Trans-Oceanic was a brand of portable radios produced from 1941 to 1981 by Zenith Radio. They were characterized by heavy-duty, high-quality construction and their performance as shortwave receivers.
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, including 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.
Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 3 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitter connected to an antenna which radiates the waves, and received by another antenna connected to a radio receiver. Radio is widely used in modern technology, in radio communication, radar, radio navigation, remote control, remote sensing, and other applications.
R-311 "Omega" is a Soviet era shortwave radio receiver designed for military use. It was manufactured from 1954 until the mid-1970s.
R-350M "Eagle" is a Soviet portable short-wave radio transceiver designed for covert operations.
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