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'.
In contemporary usage, the term longwave is not defined precisely, and its intended meaning varies. It may be used for radio wavelengths longer than 1,000 m i.e. frequencies up to 300 kilohertz (kHz), including the International Telecommunication Union's (ITU's) low frequency (LF, 30–300 kHz) and very low frequency (VLF, 3–30 kHz) bands. Sometimes the upper limit is taken to be higher than 300 kHz, but not above the start of the medium wave broadcast band at 520 kHz.
In Europe, Africa, and large parts of Asia (International Telecommunication Union Region 1), where a range of frequencies between 148.5 and 283.5 kHz is used for AM broadcasting in addition to the medium-wave band, the term longwave usually refers specifically to this broadcasting band, which falls wholly within the low frequency band of the radio spectrum (30–300 kHz). The "Longwave Club of America" (United States) is interested in "frequencies below the AM broadcast band" (i.e., all frequencies below 520 kHz).
Because of their long wavelength, radio waves in this frequency range can diffract over obstacles like mountain ranges and travel beyond the horizon, following the contour of the Earth. This mode of propagation, called ground wave , is the main mode in the longwave band. 2,000 kilometres (1,200 mi) from the transmitting antenna. Very low frequency waves below 30 kHz can be used to communicate at transcontinental distances, and can penetrate saltwater to depths of hundreds of feet, and is used by the military to communicate with submerged submarines.The attenuation of signal strength with distance by absorption in the ground is lower than at higher frequencies, and falls with frequency. Low frequency ground waves can be received up to
Low frequency waves can also occasionally travel long distances by reflecting from the ionosphere (the actual mechanism is one of refraction), although this method, called skywave or "skip" propagation, is not as common as at higher frequencies. Reflection occurs at the ionospheric E layer or F layers. Skywave signals can be detected at distances exceeding 300 kilometres (190 mi) from the transmitting antenna.
Non-directional beacons transmit continuously for the benefit of radio direction finders in marine and aeronautical navigation. They identify themselves by a callsign in Morse code. They can occupy any frequency in the range 190–1750 kHz. In North America, they occupy 190–535 kHz. In ITU Region 1 the lower limit is 280 kHz.
There are institutional broadcast stations in the range that transmit coded time signals to radio clocks. For example:
Radio-controlled clocks receive their time calibration signals with built-in long-wave receivers. They use long-wave, rather than short-wave or medium-wave, because long-wave signals from the transmitter to the receiver always travel along the same direct path across the surface of the Earth, so the time delay correction for the signal travel time from the transmitting station to the receiver is always the same for any one receiving location.
Longwaves travel by groundwaves that hug the surface of the earth, unlike mediumwaves and shortwaves. Those higher-frequency signals do not follow the surface of the Earth beyond a few kilometers, but can travel as skywaves, ‘bouncing’ off different layers of the ionosphere at different times of day. These different propagation paths can make the time lag different for every signal received. The delay between when the long-wave signal was sent from the transmitter (when the coded time was correct) and when the signal is received by the clock (when the coded time is slightly late) depends on the overland distance between the clock and the transmitter and the speed of light through the air, which is also very nearly constant. Since the time lag is essentially the same, a single constant shift forward from the time coded in the signal can compensate for all long-wave signals received at any one location from the same time signal station.
The militaries of the United Kingdom, Russian Federation, United States, Germany, India and Sweden use frequencies below 50 kHz to communicate with submerged submarines.
In North America during the 1970s, the frequencies 167, 179 and 191 kHz were assigned to the short-lived Public Emergency Radio of the United States. Nowadays, in the United States, Part 15 of FCC regulations allows unlicensed use of 136 kHz and the 160–190 kHz band at output power up to 1 watt with up to a 15-meter antenna. This is called Low Frequency Experimental Radio (LowFER). The 190–435 kHz band is used for navigational beacons.
Swedish station SAQ, located at the Varberg Radio Station facility in Grimeton, is the last remaining operational Alexanderson alternator long-wave transmitter. Although the station ended regular service in 1996, it has been maintained as a World Heritage Site, and makes at least two demonstration transmissions yearly, on 17.2 kHz.
Longwave is used for broadcasting only within ITU Region 1. The long-wave broadcasters are located in western, northern, central, and southeastern Europe, the former Soviet Union, Mongolia, Algeria, and Morocco.
Typically, a larger geographic area can be covered by a long-wave broadcast transmitter compared to a medium-wave one. This is because ground-wave propagation suffers less attenuation due to limited ground conductivity at lower frequencies.
Long-wave carrier frequencies are exact multiples of 9 kHz; ranging from 153 to 279 kHz, except for a French-language station, Europe No. 1 in Germany. This station kept correctly spaced channels spacing for 4 months—only 7 years ago, and all Mongolian transmitters are 2 kHz above the internationally recognized channels.[ clarification needed ]
Until the 1970s, some long-wave stations in northern and eastern Europe and the Soviet Union operated on frequencies as high as 433 kHz.
Some radio broadcasters, for instance Droitwich transmitting station in the UK, derive their carrier frequencies from an atomic clock, allowing their use as frequency standards. Droitwich also broadcasts a low bit-rate data channel, using narrow-shift phase-shift keying of the carrier, for Radio Teleswitch Services.
In 2014 and 2015 Russia closed all of its LW broadcast transmitters.
Because long-wave signals can travel very long distances, some radio amateurs and shortwave listeners engage in an activity called DXing. DXers attempt to listen in to far away transmissions, and they will often send a reception report to the sending station to let them know where they were heard. After receiving a report, the sending station may mail the listener a QSL card to acknowledge this reception.
Reception of long-wave signals at distances in excess of 17,000 kilometres (11,000 mi) have been verified.
|153||Radio Antena Satelor||Romanian||Brașov||T-aerial on 2 guyed steel lattice masts, height: 250 metres (820 ft)||200||Fifth state-owned radio station in Romania|
|162||ANFR (TDF time signal, previously France Inter)||French||Allouis||Two guyed lattice steel masts, height: 350 metres (1,150 ft) fed on the top||1000|
|Time signal phase-modulated; the frequency broadcast France Inter until the end of 2016. Now only the time signal for public clocks is transmitted. The ANFR is in charge of this.|
|164||MNB Radio 1||Mongolian||Ulaanbaatar||259 metres (850 ft) tall cable-stayed steel truss mast||500||Broadcasts from 21:00 to 14:00 UTC|
|171||Médi 1||Arabic and French||Nador||Directional aerial consisting of three guyed steel lattice masts, 380 metres (1,250 ft) tall||1600||Private and commercial Moroccan radio network|
|189||RÚV Rás 1/RÚV Rás 2||Icelandic||Gufuskalar near Hellissandur||Slight oval bi-directivity aerial, top loaded parallel connected triangular loops, mast as a common member, all guys insulated except two radiating diametrically opposed grounded top guys, loops closed by copper straps in the ground from two conducting guy grounding points to base of the guyed steel lattice mast insulated against ground, height: 412 metres (1,352 ft)||300||Iceland's national public service broadcaster|
|198||BBC Radio 4/BBC World Service||English||Droitwich (SFN)||T-aerial on two guyed steel lattice masts insulated against ground with a height of 213 metres (699 ft)||500||All four transmitters carry Radio teleswitch PSK data; Droitwich relays BBC World Service from 01:00 to 05:20 UTC|
|Burghead (SFN)||Omnidirectional aerial, guyed steel lattice mast, height 154 metres (505 ft)||50|
|Westerglen (SFN)||Omnidirectional aerial, guyed steel lattice mast, height 152 metres (499 ft)|
|Dartford Tunnel (SFN)||0.004|
|207||RÚV Rás 1/RÚV Rás 2||Icelandic||Eiðar near Egilsstaðir||Omnidirectional aerial, steel lattice mast insulated against ground, height 221 metres (725 ft)||100||Iceland's national public service broadcaster|
|209||MNB Radio 1||Mongolian||Choibalsan||Cable-stayed steel truss mast, height: 275.84 metres (905.0 ft)||75||Broadcasts from 21:00 to 14:00 UTC|
|Dalanzadgad||Broadcasts from 21:00 to 14:00 UTC|
|Olgii||Omnidirectional antenna, 352.5 metres (1,156 ft) high guyed mast||30||Broadcasts from 21:00 to 14:00 UTC|
|225||Polish Radio Programme One||Polish||Solec Kujawski||Directional aerial, two guyed radio masts fed on the top, heights 330 metres (1,080 ft) and 289 metres (948 ft)||1000||Earlier Konstantynów was used ( )|
|227||MNB Radio 1||Mongolian||Altai||Cable-stayed steel truss mast||75||Broadcasts from 21:00 to 14:00 UTC|
|234||RTL||French||Beidweiler||Directional aerial, three guyed grounded steel lattice masts, 290 metres (950 ft) high, with vertical cage aerials||1500|
|Spare transmitter site Junglinster ( , , )|
|243||DR Langbølge||Danish||Kalundborg||Semi-directional Alexanderson antenna 153/333 degrees, two grounded 118 metres (387 ft) steel lattice radiating towers with interconnecting top wire capacitance||50||Transmitting in time slots only|
|252|| Radio Algeria |
|Arabic||Tipaza||Omnidirectional aerial, single guyed lattice steel mast, height 355 metres (1,165 ft)||750|
|Half transmitter power during night|
|RTÉ Radio 1||English and Irish||Clarkstown||Omnidirectional aerial, guyed steel lattice mast, insulated against ground, height 248 metres (814 ft)||150|
|The only AM transmitter for RTÉ Radio 1, power is decreased at night to 100 kW, it was scheduled to cease broadcasting in June 2019 In April 2019 it announced an antenna upgrade and the closure was postponed.|
|270||ČRo Radiožurnál||Czech||Topolná||Directional aerial (maximum of radiation in east–west direction), two grounded 257 metres (843 ft) high guyed steel lattice mast with cage aerials||50||Broadcasting from Monday to Friday 05:00–24:00 CET and 06:00–24:00 CET at weekends|
|Deutschlandfunk||Donebach||Directional aerial, two guyed steel lattice masts, 363 m high, fed at the top||500||;||closed|
|YuFM||Taldom transmitter||Omnidirectional aerial, guyed steel lattice mast of 257 m height||300||closed|
|NRK P1/P2||Ingøy||Omnidirectional aerial, guyed steel lattice mast 352 metres (1,155 ft) tall, fed at the top, ex-Omega equipment||100||closed|
|Radio Rossii||Popova near Komsomolsk-na-Amure||1200||closed|
| Radio Algerie |
|Kénadsa||Three 357 metres (1,171 ft) tall guyed masts||500||inactive|
|162||TRT Radyo 4||Agri||Two guyed lattice steel masts, height 250 m||1000||;||inactive|
|Radio Rossii||Norilsk||Omnidirectional antenna, 205 m high antenna||150||?||closed|
|Radio Yuldash, Radio Rossii||Ufa||closed|
|NPO Radio 1||Lopik||500||closed|
|Voice of Russia||Oktyabrsky||257 m metres tall antenna.||1200||closed|
|Radio Rossii||Bolshakovo near Kaliningrad||Omnidirectional antenna, 257 m high guyed lattice steel mast with cage antenna ( ARRT-antenna)||600||closed|
|Radio Ukraine 1||Krasne near Lviv||Omnidirectional antenna, 259 m high guyed lattice steel mast with cage antenna ( ARRT-antenna)||150/75||inactive|
|Radio Rossii||Raduga||Omnidirectional antenna, 255 m high guyed lattice steel mast with cage antenna ( ARRT-antenna)||250||closed|
|Radio 1||Murmansk||Omnidirectional antenna, 257 m high guyed lattice steel mast with cage antenna ( ARRT-antenna)||150||closed|
|Radio 1||Noginsk||Omnidirectional antenna, 242 m high guyed lattice steel mast with cage antenna ( ARRT-antenna)||150||closed|
|Radio 1||Ezhva near Syktyvkar||Omnidirectional antenna, 257 m high guyed lattice steel mast with cage antenna ( ARRT-antenna)||150||closed|
|Radio Rossii||Tulagino near Yakutsk||Omnidirectional antenna, circle antenna with 1 central and 6 ring masts||150||; ; ; ; ; ;||closed|
|Deutschlandradio Kultur||Zehlendorf near Oranienburg||Omnidirectional aerial, cage aerial mounted on 359.7 m high guyed mast, triangle aerial on 3 150 m high guyed steel lattice masts||500||closed|
|180||TRT Radyo 1||Polatli||Omnidirectional antenna, 250 m high guyed latice steel mast||1200||inactive|
|Radio Rossii||Yelizovo near Petropavlovsk-Kamchatskiy||Omnidirectional antenna, 255 m high guyed lattice steel mast||150||closed|
|Radio Mayak||Kruchina near Chita||Omnidirectional antenna, 200 m high guyed lattice steel mast||150||inactive|
|Kazakh Radio 1||Alma-Ata||250||closed|
|Kazakh Radio 1||Aktyubinsk||150||closed|
|Kazakh Radio 1||Chimkent||50||closed|
|Europe 1||Felsberg-Berus||Directional aerial, four ground insulated steel lattice masts 270 metres (890 ft), 276 metres (906 ft), 280 metres (920 ft) and 282 metres (925 ft) tall; spare aerial: two ground insulated steel lattice masts, height: 234 metres (768 ft)||750||Main antenna:|
|Rai Radio 1||Caltanissetta||Omnidirectional aerial, guyed steel lattice mast, height 282 m||10||closed|
|Sveriges Radio P1||Orlunda, near Motala||300||closed|
|Radio Rossii||Kostantinogradovka near Blagoveshchensk||Omnidirectional aerial, 257 m high guyed lattice steel mast with cage antenna ( ARRT-antenna)||1200||closed|
|Polskie Radio Parlament/Radio Polonia||Raszyn||Omnidirectional aerial, guyed steel lattice mast insulated against ground, 335 m high||200||closed|
|Radio Mayak||Saint Petersburg – Olgino||Omnidirectional aerial, 205 m high guyed steel lattice mast||150||inactive|
|Radio Mayak||Angarsk||Before 2001: T-antenna spun between 2 205 m tall guyed steel lattice mast||250||, possibly||closed|
|Radio Mayak||Avsyunino||Omnidirectional antenna, 257 m high guyed lattice steel mast with cage antenna ( ARRT-antenna)||150||inactive|
|Radio 1||Krasnaya Rechka near Bishkek||150||closed|
|RNE Radio 5||Logroño||Directional antenna, 300 metres tall.||>100||closed|
|Radio Ukraine 1||Brovary||Omnidirectional antenna, 259.6 m high guyed lattice steel mast with cage antenna ( ARRT-antenna)||600||closed|
|Radio al-Urdunniya||Al Karanah||?||;||closed|
|Radio Mayak||Tynda||Omnidirectional aerial, steel lattice mast insulated against ground, height 244 m||150||closed|
|Deutschlandfunk||Aholming||Directional aerial, two guyed steel lattice masts, 265 m high, fed at the top||500||;||closed|
|SNRT Al Idaâ Al-Watania||Azilal Demnate||304.8 metres (1,000 ft) tall guyed mast||400||inactive|
|NRK P1||Lambertseter near Oslo||200||closed|
|Radio Monte Carlo Info||Roumoules||Directional aerial, three 300 metres (980 ft) high guyed steel lattice masts, 330 metres (1,080 ft) high guyed steel lattice mast as backup aerial||700|
|Radio Rossii||Krasnoyarsk||Omnidirectional antenna, guyed lattice steel mast, 210 m tall||150||closed|
|Radio Rossii||Atamanovka||Directional antenna||150||closed|
|Radio Rossii||Birobidzhan||2 guyed masts, 260 m high||30||;||closed|
|225||TRT GAP||Van||Omnidirectional antenna, 250 m high guyed lattice steel mast||600||inactive|
|Radio Rossii||Surgut||Omnidirectional antenna, 257 m high guyed lattice steel mast with cage antenna ( ARRT-antenna)||1000||closed|
|Radio Jamahiriya||Yafran near Tripoli||1000||closed|
|Radio 1||Krasny Bor transmitter near Sankt-Peterburg||Omnidirectional aerial, 271.5 metres tall guyed mast with cage antenna||1200||closed|
|Public Armenian Radio||Kamo||?||500||?||closed|
|Radio Rossii||Koskovo near Murmansk||Omnidirectional aerial, 210 m tall guyed mast||250||inactive|
|Radio 1||Novosemeykino near Samara||Four 205 metres tall towers insulated against ground arranged in a square||2000||; ; ;||closed|
|Radio Rossii||Raduzhnyy near Magadan||Omnidirectional aerial, 259 m high guyed lattice steel mast with cage antenna ( ARRT-antenna)||1000||closed|
|Radio Rossii||Odinsk near Irkutsk||Omnidirectional aerial, 259 m high guyed lattice steel mast with cage antenna ( ARRT-antenna)||500||closed|
|Radio 1||Koskovo near Arkhangelsk||Omnidirectional aerial, 257 m high guyed lattice steel mast with cage antenna ( ARRT-antenna)||500||closed|
|243||TRT Radyo 4||Erzurum||Omnidirectional antenna, 185 m high guyed lattice steel mast||200||inactive|
|Radio Rossii||Razdolnoye near Ussuriysk||Omnidirectional antenna, 259 m high guyed lattice steel mast with cage antenna ( ARRT-antenna)||1000||closed|
|Kazakh Radio 2 Shalkar||Karaganda||Omnidirectional aerial, guyed steel lattice mast of 254 m height||1000||closed|
|Kazakh Radio 2 Shalkar||Alma-Ata||1000||closed|
|Armenian Radio 1||Kamo||150||?||closed|
|Yle Radio 1||Lahti||200||,||closed|
|Radio Rossii||Kazan||Omnidirectional aerial, 152 m high guyed lattice steel mast with cage antenna ( ARRT-antenna)||100||closed (9 January 2014)|
|Radioropa Info||Burg||Omnidirectional aerial, cage aerial on 324 m high guyed, grounded steel lattice mast, 210 m high steel tube mast, insulated against ground||200||closed|
|Radio Rossii||Taldom||Omnidirectional antenna, circle antenna with 1 central and 5 ring masts, height of central mast 275 m||2500||; ; ; ; ;||closed|
|Radio Rossii||Kruchina near Chita||Omnidirectional antenna, guyed lattice steel mast, 260 m high||150||closed|
|Radio Rossii||Tyumen||Omnidirectional antenna, guyed lattice steel mast, 220 m high||150||closed|
|Radio Rossii||Vorkuta||Omnidirectional antenna, guyed lattice steel mast, 220 m high||50||closed|
|Radio Horizont||Vakarel||One of the few Blaw-Knox Towers in Europe, 215 m high||75||closed|
|Radio Rossii||Orenburg||Omnidirectional aerial, guyed steel lattice mast of 137 m height||25||closed|
|Radio 1||Khabarovsk||2 guyed steel lattice masts, height: 164 m||150||;||closed|
|Radio Rossii||Gorno-Altaisk||Omnidirectional antenna, 143m high guyed lattice steel mast||50||closed|
|Radio Rossii||Selenginsk||Omnidirectional aerial, 260 m high guyed lattice steel mast with cage antenna (ARRT-antenna)||150||closed|
|Radio Rossii||Vestochka near Yuzhno-Sakhalinsk||Omnidirectional antenna, guyed lattice steel mast, 258 m high||1000||closed|
|Radio Rossii||Yekaterinburg||Omnidirectional aerial, guyed steel lattice mast of 256 m height, fed at the top||150||closed|
|BR Pershy Kanal/BR Radyjo Stalitsa||Sasnovy||353.5 metres tall guyed mast||500||closed|
|TR1 Watan Radio||Ashgabat||Cable-stayed steel truss mast||150||inactive|
|MusicMann 279||Isle of Man||Crossed field||never launched|
Shortwave radio is radio transmission using shortwave 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 3–30 MHz ; above the medium frequency band (MF), to the bottom of the VHF band.
Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light. Radio waves have frequencies as high as 300 gigahertz (GHz) to as low as 30 hertz (Hz). At 300 GHz, the corresponding wavelength is 1 mm, and at 30 Hz is 10,000 km. The wavelength of a radio wave can be anywhere from shorter than a grain of rice to longer than the radius of the Earth. Like all other electromagnetic waves, radio waves travel at the speed of light in vacuum. They are generated by electric charges undergoing acceleration, such as time varying electric currents. Naturally occurring radio waves are emitted by lightning and astronomical objects.
Medium wave (MW) is the part of the medium frequency (MF) radio band used mainly for AM radio broadcasting. The spectrum provides about 120 channels with limited sound quality. During daytime, only local stations can be received. Propagation in the night allows strong signals within a range of about 2000 km. This can cause massive interference because on most channels, about 20 to 50 transmitters operate simultaneously worldwide. In addition to that, amplitude modulation (AM) is prone to interference by all sorts of electronic devices, especially power supplies and computers. Strong transmitters cover larger areas than on the FM broadcast band but require more energy. Digital modes are possible but have not reached the momentum yet.
Very low frequency or VLF is the ITU designation for radio frequencies (RF) in the range of 3–30 kHz, corresponding to wavelengths from 100 to 10 km, respectively. The band is also known as the myriameter band or myriameter wave as the wavelengths range from one to ten myriameters. Due to its limited bandwidth, audio (voice) transmission is highly impractical in this band, and therefore only low data rate coded signals are used. The VLF band is used for a few radio navigation services, government time radio stations and for secure military communication. Since VLF waves can penetrate at least 40 meters (120 ft) into saltwater, they are used for military communication with submarines.
Low frequency (LF) is the ITU designation for radio frequencies (RF) in the range of 30–300 kHz. Since its wavelengths range from 10–1 km, respectively, it is also known as the kilometre band or kilometre wave.
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 hectometer. 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.
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 (2.31–25.82 MHz), aviation communication, government time stations, weather stations, amateur radio and citizens band services, among other uses.
Radio propagation is the behavior of radio waves as they travel, or are propagated, from one point to another, or into various parts of the atmosphere. As a form of electromagnetic radiation, like light waves, radio waves are affected by the phenomena of reflection, refraction, diffraction, absorption, polarization, and scattering. Understanding the effects of varying conditions on radio propagation has many practical applications, from choosing frequencies for international shortwave broadcasters, to designing reliable mobile telephone systems, to radio navigation, to operation of radar systems.
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.
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.
CHU is the call sign of a shortwave time signal radio station operated by the Institute for National Measurement Standards of the National Research Council of Canada.
A non-directional (radio) beacon (NDB) is a radio transmitter at a known location, used as an aviation or marine navigational aid. As the name implies, the signal transmitted does not include inherent directional information, in contrast to other navigational aids such as low frequency radio range, VHF omnidirectional range (VOR) and TACAN. NDB signals follow the curvature of the Earth, so they can be received at much greater distances at lower altitudes, a major advantage over VOR. However, NDB signals are also affected more by atmospheric conditions, mountainous terrain, coastal refraction and electrical storms, particularly at long range.
The Warsaw Radio Mast was a telecommunications tower located near the town of Gąbin, central Poland, and the world's tallest structure at 646.38 metres (2,120.7 ft) from 1974 until its collapse on 8 August 1991. It was the second tallest structure ever built, being surpassed as the tallest by the Burj Khalifa tower in the United Arab Emirates, completed in 2009.
RTÉ Radio 1 is the principal radio channel of Irish public-service broadcaster Raidió Teilifís Éireann and is the direct descendant of Dublin radio station 2RN, which began broadcasting on a regular basis on 1 January 1926. The station is a rare modern example of a mixed radio channel, offering a wide spectrum of programming which is mainly speech-based but also includes a fair amount of music.
The Roumoules transmitter is the main broadcasting facility for longwave and mediumwave broadcasting of Radio Monte Carlo near Roumoules, France and is owned by Monaco Media Diffusion. The 1000 and 2000kW transmitters installed are among the most powerful in the world and can be received well at nighttime throughout Europe.
The Droitwich transmitting station is a large broadcasting facility for long-wave and medium-wave transmissions, established in 1934 in the civil parish of Dodderhill, just outside the village of Wychbold, near Droitwich in Worcestershire, England. The site is the location of the British Broadcasting Corporation's most powerful long-wave transmitter, which together with the two Scottish long-wave transmitters at Burghead and Westerglen forms a network broadcasting on the same frequency. The masts can be seen to the east from the M5 motorway, between Droitwich and Bromsgrove, as well as to the west from the Herefordshire/Worcestershire border. At night, the two sets of aircraft warning lights are visible from a long distance. Due to the bright red lights illuminated at night, some locals have renamed the site "the devil horns of Wychbold". The station is owned and operated by Arqiva.
Grimeton Radio Station in southern Sweden, close to Varberg in Halland, is an early longwave transatlantic wireless telegraphy station built in 1922-1924, that has been preserved as a historical site. From the 1920s through the 1940s it was used to transmit telegram traffic by Morse code to North America and other countries, and during World War 2 was Sweden's only telecommunication link with the rest of the world. It is the only remaining example of an early pre-electronic radio transmitter technology called an Alexanderson alternator. It was added to the UNESCO World Heritage List in 2004, with the statement: "Grimeton Radio Station, Varberg is an outstanding monument representing the process of development of communication technology in the period following the First World War." The radio station is also an anchor site for the European Route of Industrial Heritage. The transmitter is still in operational condition, and each year on a day called Alexanderson Day is started up and transmits brief Morse code test transmissions, which can be received all over Europe.
The Mainflingen mediumwave transmitter is a mediumwave transmission facility south of the A3 motorway near Mainflingen, Hesse, Germany. Mainflingen was the first mediumwave transmitter for the radio station Deutschlandfunk. It went into service in 1962 with a transmission power of 50 kW, on a frequency of 1538 kHz, at the upper end of the mediumwave band. This frequency has a bad groundwave propagation and therefore a low range at daytime, but an excellent skywave propagation with a long range at night.
Near vertical incidence skywave, or NVIS, is a skywave radio-wave propagation path that provides usable signals in the distances range — usually 0–650 km (0–400 miles). It is used for military and paramilitary communications, broadcasting, especially in the tropics, and by radio amateurs for nearby contacts circumventing line-of-sight barriers. The radio waves travel near-vertically upwards into the ionosphere, where they are refracted back down and can be received within a circular region up to 650 km from the transmitter. If the frequency is too high, refraction fails to occur and if it is too low, absorption in the ionospheric D layer may reduce the signal strength.
MW DX, short for mediumwave DXing, is the hobby of receiving distant mediumwave radio stations. MW DX is similar to TV and FM DX in that broadcast band (BCB) stations are the reception targets. However, the nature of the lower frequencies used by mediumwave radio stations is very much different from that of the VHF and UHF bands used by FM and TV broadcast stations, and therefore involves different receiving equipment, signal propagation, and reception techniques.