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Utility Station
The term utility station is used to describe fixed radio broadcasters disseminating signals that are not intended for reception by the general public (but such members are not actively prohibited from receiving). Utility stations, as the name suggests, do broadcast signals that have an immediate practical use, by means of analog or usually digital modes; most often utility transmissions are of a "point-to-point" nature, intended for a specific receiving station. Utility stations are most prevalent on shortwave frequencies, though they are not restricted to the shortwave frequencies. Examples of utility station and modes One common use of utility stations is disseminating weather information. Weather information is often broadcast using RTTY and sending synoptic codes, or weather charts are sent using radiofax, which are used by mariners and others. Airports make voice weather broadcasts on HF, known as VOLMET. Some examples include New York Radio, which broadcasts weather info ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radioteletype
Radioteletype (RTTY) is a telecommunications system consisting originally of two or more electromechanical teleprinters in different locations connected by radio rather than a wired link. Radioteletype evolved from earlier landline teleprinter operations that began in the mid-1800s. The US Navy Department successfully tested printing telegraphy between an airplane and ground radio station in 1922. Later that year, the Radio Corporation of America successfully tested printing telegraphy via their Chatham, Massachusetts, radio station to the R.M.S. Majestic. Commercial RTTY systems were in active service between San Francisco and Honolulu as early as April 1932 and between San Francisco and New York City by 1934. The US military used radioteletype in the 1930s and expanded this usage during World War II. From the 1980s, teleprinters were replaced by personal computers (PCs) running software to emulate teleprinters. The term radioteletype is used to describe both the original radi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Synoptic Code
SYNOP (surface synoptic observations) is a numerical code (called FM-12 by WMO) used for reporting weather observations made by manned and automated weather stations. SYNOP reports are typically sent every six hours by Deutscher Wetterdienst on shortwave and low frequency using RTTY. A report consists of groups of numbers (and slashes where data is not available) describing general weather information, such as the temperature, barometric pressure and visibility at a weather station. It can be decoded by open-source software such as seaTTY, metaf2xml or Fldigi. SYNOP information is collected by more than 7600 manned and unmanned meteorological stations and more than 2500 mobile stations around the world and is used for weather forecasting and climatic statistics. The format of the original messages is abbreviated, some items are coded. Message format Following is the general structure of a SYNOP message. The message consists of a sequence of numeric ''groups'', which may also con ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Weather Chart
A weather map, also known as synoptic weather chart, displays various meteorological features across a particular area at a particular point in time and has various symbols which all have specific meanings. Such maps have been in use since the mid-19th century and are used for research and weather forecasting purposes. Maps using isotherms show temperature gradients, which can help locate weather fronts. Isotach maps, analyzing lines of equal wind speed, on a constant pressure surface of 300 or 250 hPa show where the jet stream is located. Use of constant pressure charts at the 700 and 500 hPa level can indicate tropical cyclone motion. Two-dimensional streamlines based on wind speeds at various levels show areas of convergence and divergence in the wind field, which are helpful in determining the location of features within the wind pattern. A popular type of surface weather map is the surface weather analysis, which plots isobars to depict areas of high pressure and l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radiofax
Radiofacsimile, radiofax or HF fax is an analog signal, analogue mode for transmitting monochrome images via high frequency (HF) radio waves. It was the predecessor to slow-scan television (SSTV). It was the primary method of sending photographs from remote sites (especially islands) from the 1930s to the early 1970s. It is still in limited use for transmitting weather charts and information to ships at sea. History Richard H. Ranger, an electrical engineer working at RCA, Radio Corporation of America (RCA), invented a method for sending photographs through radio transmissions. He called his system the wireless photoradiogram, in contrast to the fifty-year-old Fax, telefacsimile devices which used first telegraphic wires, and then later was adapted to use the newer telephone wires. On 29 November 1924, Ranger's system was used to send a photograph from New York City to London. It was an image of President Calvin Coolidge and was the first transoceanic radio transmission of a pho ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
High Frequency
High frequency (HF) is the ITU designation for the range of radio frequency electromagnetic waves (radio 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 (ten to one hundred meters). 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
VOLMET
{{Use dmy dates, date=December 2021 VOLMET (French origin ''vol'' (flight) and ''météo'' (weather report)), or meteorological information for aircraft in flight, is a worldwide network of radio stations that broadcast TAF, SIGMET and METAR reports on shortwave frequencies, and in some countries on VHF too. Reports are sent in upper sideband mode, using automated voice transmissions. Pilots on international routes, such as North Atlantic Tracks, use these transmissions to avoid storms and turbulence, and to determine which procedures to use for descent, approach, and landing. The VOLMET network divides the world into specific regions, and individual VOLMET stations in each region broadcast weather reports for specific groups of air terminals in their region at specific times, coordinating their transmission schedules so as not to interfere with one another. Schedules are determined in intervals of five minutes, with one VOLMET station in each region broadcasting reports ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SITOR
SITOR (SImplex Teletype Over Radio) is a system for transmitting text messages. It was developed in the 1960s by Koninklijke TNT Post as an improvement over radioteletype (RTTY). Although it uses the same frequency-shift keying (FSK) modulation used by regular RTTY, SITOR uses error detection, redundancy, and/or retransmission to improve reliability. There are two SITOR modes: * SITOR-A is used for point to point links. SITOR-A uses automatic repeat request (ARQ) to gain reliability. If the receiver detects an error, it requests a retransmission. * SITOR-B is used for broadcast links. SITOR-B transmits each character in a message twice to gain reliability. If the receiver detects an error in the first character, it uses the copy. If both characters are garbled, the receiver won't know what was sent. * SITOR-B by definition uses forward error correction (FEC), versus ARQ for SITOR-A. SITOR sends 7-bit characters as a bit stream at 100 baud (which, in this case, is 100 bits per sec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ANDVT
The Advanced Narrowband Digital Voice Terminal (ANDVT) is a secure voice terminal for low bandwidth secure voice communications throughout the U.S. Department of Defense. Devices in the ANDVT family include the AN/USC-43 Tactical Terminal (TACTERM), the KY-99A Miniaturized Terminal (MINTERM), and the KY-100 Airborne Terminal (AIRTERM). ANDVT uses LPC-10 voice compression. The functions of the MINTERM are similar to those of the TACTERM; its updated design includes an improved modular architecture, and it has been reduced in size. The MINTERM is lightweight, low-power, single channel, half-duplex, narrowband/wideband/wireline terminal providing secure voice and data communications with full key distribution and remote rekey capabilities. The MINTERM is certified to secure traffic up to TOP SECRET. The MINTERM improvements include the following: *Concurrent voice and data modes enable the users to connect both data equipment and voice handsets. *VINSON (KY-57/58) mode of operation a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Link-11
TADIL-A/Link 11 is a secure half-duplex tactical data link used by NATO to exchange digital data. It was originally developed by a joint committee including members from the Canadian Navy, US Navy and Royal Navy to pass accurate targeting information between ships. The final standard was signed in Ottawa in November 1957, where the British proposed the name "TIDE" for "Tactical International Data Exchange". It was later made part of the NATO STANAG standardization process. The system operates on two frequencies, one in the high frequency (HF) range for over-the-horizon (OTH) communications, and another in the ultra high frequency (UHF) range that uses much smaller antennas and is suitable for smaller ships but lacks the OTH performance. The system broadcasts packets of 30 bits length, with 6 bits of error correction and 24 bits of payload data. The payload is encrypted. Link 14 was adopted at the same time as a low-end counterpart to Link 11. Link 14 is essentially a digital te ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Automatic Link Establishment
Automatic Link Establishment, commonly known as ALE, is the worldwide de facto standard for digitally initiating and sustaining HF radio communications. ALE is a feature in an HF communications radio transceiver system that enables the radio station to make contact, or initiate a circuit, between itself and another HF radio station or network of stations. The purpose is to provide a reliable rapid method of calling and connecting during constantly changing HF ionospheric propagation, reception interference, and shared spectrum use of busy or congested HF channels. Mechanism A standalone ALE radio combines an HF SSB radio transceiver with an internal microprocessor and MFSK modem. It is programmed with a unique ALE address, similar to a phone number (or on newer generations, a username). When not actively in contact with another station, the HF SSB transceiver constantly scans through a list of HF frequencies called ''channels'', listening for any ALE signals transmitted by oth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NOAA Weather Radio
NOAA Weather Radio NWR; also known as NOAA Weather Radio All Hazards is an automated 24-hour network of VHF FM weather radio stations in the United States (U.S.) that broadcast weather information directly from a nearby National Weather Service office. The routine programming cycle includes local or regional weather forecasts, synopsis, climate summaries or zone/lake/coastal waters forecasts (when applicable). During severe conditions the cycle is shortened into: hazardous weather outlooks, short-term forecasts, special weather statements or tropical weather summaries (the first two aren't normally broadcast in most offices). It occasionally broadcasts other non-weather related events such as national security statements, natural disaster information, environmental and public safety statements (such as an AMBER Alert), civil emergencies, fires, evacuation orders, and other hazards sourced from the Federal Communications Commission's (FCC) Emergency Alert System. NOAA Weather R ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Traveler Information Station
A travelers' information station (TIS), also called highway advisory radio (HAR) by the United States Department of Transportation, is a licensed low-powered non-commercial radio station, used to broadcast information to the general public, including for motorists regarding travel, destinations of interest, and situations of imminent danger and emergencies. They are commonly operated by transportation departments, national and local parks departments and historic sites, airport authorities, local governments, federal agencies, colleges and universities, hospitals and health agencies, and for special events and destinations. United States Current regulations and applications In the United States, most Travelers Information Stations (TIS) are licensed by the Federal Communications Commission (FCC), although stations operated by U.S. national parks and others under U.S. federal government jurisdiction are licensed by the National Telecommunications and Information Administration ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
