A transmission medium is a system or substance that can mediate the propagation of signals for the purposes of telecommunication. Signals are typically imposed on a wave of some kind suitable for the chosen medium. For example, data can modulate sound, and a transmission medium for sounds may be air, but solids and liquids may also act as the transmission medium. Vacuum or air constitutes a good transmission medium for electromagnetic waves such as light and radio waves. While material substance is not required for electromagnetic waves to propagate, such waves are usually affected by the transmission media they pass through, for instance, by absorption or reflection or refraction at the interfaces between media. Technical devices can therefore be employed to transmit or guide waves. Thus, an optical fiber or a copper cable is used as transmission media.
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.
Medium frequency (MF) is the ITU designation for radio frequencies (RF) in the range of 300 kilohertz (kHz) to 3 megahertz (MHz). Part of this band is the medium wave (MW) AM broadcast band. The MF band is also known as the hectometer band as the wavelengths range from ten to one hectometers. Frequencies immediately below MF are denoted low frequency (LF), while the first band of higher frequencies is known as high frequency (HF). MF is mostly used for AM radio broadcasting, navigational radio beacons, maritime ship-to-shore communication, and transoceanic air traffic control.
In radio, longwave, long wave or long-wave, and commonly abbreviated LW, refers to parts of the radio spectrum with wavelengths longer than what was originally called the medium-wave broadcasting band. The term is historic, dating from the early 20th century, when the radio spectrum was considered to consist of longwave (LW), medium-wave (MW), and short-wave (SW) radio bands. Most modern radio systems and devices use wavelengths which would then have been considered 'ultra-short'.
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.
A radiotelephone, abbreviated RT, is a radio communication system for conducting a conversation; radiotelephony means telephony by radio. It is in contrast to radiotelegraphy, which is radio transmission of telegrams (messages), or television, transmission of moving pictures and sound. The term is related to radio broadcasting, which transmit audio one way to listeners. Radiotelephony refers specifically to two-way radio systems for bidirectional person-to-person voice communication between separated users, such as CB radio or marine radio. In spite of the name, radiotelephony systems are not necessarily connected to or have anything to do with the telephone network, and in some radio services, including GMRS, interconnection is prohibited.
In radio communication, skywave or skip refers to the propagation of radio waves reflected or refracted back toward Earth from the ionosphere, an electrically charged layer of the upper atmosphere. Since it is not limited by the curvature of the Earth, skywave propagation can be used to communicate beyond the horizon, at intercontinental distances. It is mostly used in the shortwave frequency bands.
The Tilted Terminated Folded Dipole or Balanced Termination, Folded Dipole (BTFD) - also known as W3HH antenna - is a general-purpose shortwave antenna developed in the late 1940s by the United States Navy. It performs reasonably well over a broad frequency range, without marked dead spots in terms of either frequency, direction, or angle of radiation above the horizon.
Sveriges Radio AB is Sweden's national publicly funded radio broadcaster. Sveriges Radio is a public limited company, owned by an independent foundation, previously funded through a licensing fee, the level of which is decided by the Swedish Riksdag. As of 1 January 2019, the funds stem from standard taxation. No advertising is permitted. Its legal status could be described as that of a quasi-autonomous non-governmental organization.
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.
Bodenseesender was a radio transmission facility of VoA, US SWR near Meßkirch-Rohrdorf in Southern Germany for medium wave established in 1964. It shut down on January 8, 2012, and one month later, on February 7, 2012, the last mast was demolished.
Vatican Radio is the official broadcasting service of Vatican City.
Shortwave bands are frequency allocations for use within the shortwave radio spectrum. Radio waves in these frequency ranges can be used for very long distance (transcontinental) communication because they can reflect off layers of charged particles in the ionosphere and return to Earth beyond the horizon, a mechanism called skywave or “skip” propagation. They are allocated by the ITU for radio services such as maritime communications, international shortwave broadcasting and worldwide amateur radio. The bands are conventionally named by their wavelength in metres, for example the ‘20 meter band’. Radio propagation and possible communication distances vary depending on the time of day, the season and the level of solar activity.
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".
Sitkūnai Radio Station is a large facility for medium wave and shortwave broadcasting at Sitkūnai, Lithuania. The decision to build a new transmitting centre near the village of Sitkunai, about 17 km (11 mi) north of Kaunas was made by the Government of Lithuania in 1937. The building works started in 1939, and after completion, a 120 kW medium wave transmitter from Standard Telephones and Cables in the United Kingdom was ordered. However, the outbreak of World War II stopped the shipment. The empty transmitter buildings in Sitkunai survived the war with almost no damage and were used as a military compound by the German army in 1941–1944, and later as a primary school. Because the Soviet Lithuania was badly covered by radio signals, the Soviet authorities decided to continue the building work at Sitkunai and turn the site into a main shortwave and medium wave transmitting centre. During 1951 and 1952 two 50 kW shortwave transmitters, dismantled from an East German utility site as war reparations were installed in Sitkūnai. Several curtain antennas were erected and one 150 kW mediumwave transmitter was installed (665 kHz). During the January Events in 1991, Sitkūnai Radio Station was among those transmitting sites broadcasting to the world about the Soviet military actions in Vilnius when 14 civilians were killed and more than 600 injured.
Superrock KYOI was a short-wave US radio station located at Saipan island in the Pacific region from 1982 to 1989. The aim was to deliver broadcast rock and pop music to Japan, but due to short-wave distribution features it was also well-heard in the USSR, China, Australia, New Zealand, and some Pacific countries, where it became legendary.
A QSL card is a written confirmation of either a two-way radiocommunication between two amateur radio or citizens band stations; a one-way reception of a signal from an AM radio, FM radio, television or shortwave broadcasting station; or the reception of a two-way radiocommunication by a third party listener. A typical QSL card is the same size and made from the same material as a typical postcard, and most are sent through the mail as such.
The Federal Radio Corporation of Nigeria (FRCN) is Nigeria's state radio broadcasting organization. Its subsidiary is the domestic radio network known as Radio Nigeria, with FM stations across the 36 states and Zonal station in the 6 geopolitical zones that broadcast on the SW. According to FRCN, it is the largest broadcasting organization in Africa.
The Grigoriopol transmitter, officially the Transnistrian Radio and Television Center, is a very large broadcasting facility situated near Maiac, an urban settlement 11 km northeast of Grigoriopol, Transnistria (Moldova).
The Suomen Radioamatööriliitto (SRAL) is a national non-profit organization for amateur radio enthusiasts in Finland. SRAL was founded in 1921 and has approximately 3,500 members. SRAL supports amateur radio operators in Finland by sponsoring amateur radio operating awards and radio contests. SRAL was one of the sponsor organizations for the 2002 World Radiosport Team Championships held near Helsinki. The SRAL also represents the interests of Finnish amateur radio operators and shortwave listeners before Finnish and international telecommunications regulatory authorities. SRAL is the national member society representing Finland in both Nordic Radio Amateur Union and International Amateur Radio Union.
