48-732: Kalundborg Radio was a major transmission facility for long - and mediumwave at the harbour of Kalundborg in Denmark . Longwave broadcasts on 243 kHz began on 27 August 1927 and ceased on 31 December 2023. Mediumwave broadcasts on 1062 kHz began on 1 October 1951 and ceased in June 2011. The transmitter site was inaugurated on 27 August 1927 and started broadcasting the first channel of Danish radio on 243 kHz longwave (LW) with 300 kW . On 1 October 1951, mediumwave (MW) broadcasts of DR P2 commenced on 1062 kHz (282 m wavelength) with 250 kW. These two transmitters had
96-472: A 2.8 kHz sliver of spectrum from 71.6 kHz to 74.4 kHz beginning in April ;1996 to UK amateurs who applied for a Notice of Variation to use the band on a noninterference basis with a maximum output power of 1 Watt ERP . This was withdrawn on 30 June 2003 after a number of extensions in favor of the cross-European standard 136 kHz band. Very slow Morse Code from G3AQC in
144-463: A built-in pre-amplifier . Due to the long wavelengths in the band, nearly all LF antennas are electrically short , shorter than one quarter of the radiated wavelength, so their low radiation resistance makes them inefficient, requiring very low resistance grounds and conductors to avoid dissipating transmitter power. These electrically short antennas need loading coils at the base of the antenna to bring them into resonance. Many antenna types, such as
192-577: A common reserve transmitter. On 15 February 2007 at 00:05, LW transmissions from Kalundborg were suspended after 80 years of service. They resumed in Digital Radio Mondiale (DRM) mode at reduced power (200 W) on 3 October 2008 after substantial modifications to the aerial earlier that year. During 16-31 October 2009, the old MW and LW reserve transmitter served in place of the regular MW and LW DRM transmitters. Until mid-June 2011, broadcasts on 1062 kHz at 250 kW continued on
240-619: A height around 100 meters are used. T-antennas have a height between 50–200 meters, while mast aerials are usually taller than 150 meters. The height of mast antennas for LORAN-C is around 190 meters for transmitters with radiated power below 500 kW, and around 400 meters for transmitters greater than 1 000 kilowatts. The main type of LORAN-C antenna is insulated from ground. LF (longwave) broadcasting stations use mast antennas with heights of more than 150 meters or T-aerials . The mast antennas can be ground-fed insulated masts or upper-fed grounded masts. It
288-572: A lack of LW on new consumer receivers, increasing interference levels, the energy inefficiency of AM and high electricity costs at transmitters. In 2014 and 2015 Russia closed all of its LW broadcast transmitters. As of 2024 more than half of LW frequencies are unoccupied and some of the remaining services are scheduled for closure. BBC Radio 4 (UK) announced that it will stop distinct programming for LW broadcasts in 2024 in an effort to transition listeners to other means of listening. A closure date for LW broadcasts has not yet been announced. With
336-640: A maritime wire, frame, or active antenna, reception improved up to 1,500 km of range. Every year on 4 May, Danmarks Radio rebroadcast the "message of liberation," from the Kalundborg transmitter in an hour-long memorial broadcast that began after the news at 20:00. On 4 May 1945, the Danish service of the BBC broadcast the original "message of liberation," marking the end of WWII in Denmark: "At this moment, it
384-421: A number of frequencies, varying by country, between 120–148 kHz. Some radio frequency identification ( RFID ) tags utilize LF. These tags are commonly known as LFIDs or LowFIDs (low frequency identification). The LF RFID tags are near-field devices, interacting with the inductive near field , rather than with radiated waves (radio waves) that are the only part of the electromagnetic field that persists into
432-571: A restricted time schedule. After that, the MW transmitter was taken out of service. A new 50 kW LW transmitter replaced the MW service. During 6-12 September 2012, the transmitter also broadcast BBC programmes with 10 kW of power in DRM mode outside DR's broadcast blocks in connection with the international broadcasting exhibition IBC 2012 in Amsterdam . Shipping Forecast bulletins produced by
480-439: Is also possible to use cage antennas on grounded masts. For broadcasting stations, directional antennas are often required. They consist of multiple masts, which often have the same height. Some longwave antennas consist of multiple mast antennas arranged in a circle with or without a mast antenna in the center. Such antennas focus the transmitted power toward ground and give a large zone of fade-free reception. This type of antenna
528-620: Is also referred to as the 1 750 meter band. Requirements include: Many experimenters in this band are amateur radio operators. A regular service transmitting RTTY marine meteorological information in SYNOP code on LF is the German Meteorological Service ( Deutscher Wetterdienst or DWD ). The DWD operates station DDH47 on 147.3 kHz using standard ITA-2 alphabet with a transmission speed of 50 baud and FSK modulation with 85 Hz shift. In parts of
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#1732783454146576-539: Is announced that Montgomery has stated that the German troops in Holland, Northwest Germany, and Denmark have surrendered." The LW antenna was an Alexanderson aerial with two grounded 118 m steel lattice radiating towers connected by top capacitance wires. The northern tower was fed from the transmitter through a top coil, with the top coil of the southern slave tower being fed via the capacitance wires. The MW aerial
624-542: 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 the ITU Radio Regulations
672-532: Is often considered a medium wave sub-band. 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
720-525: 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 s. LF radio waves exhibit low signal attenuation , making them suitable for long-distance communications. In Europe and areas of Northern Africa and Asia, part of the LF spectrum is used for AM broadcasting as
768-469: Is the main mode in the longwave band. 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 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, can penetrate saltwater to depths of hundreds of feet, and are used by
816-573: Is used for broadcasting only within ITU Region 1. The long-wave broadcasters are located in Europe, North Africa and Mongolia . 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 ground conductivity at lower frequencies. Many countries have stopped using LW for broadcasting because of low audience figures,
864-536: Is vertical while the magnetic field is horizontal), so vertical monopole antennas are used for transmitting. The transmission distance is limited by the absorption of ground waves in the Earth. The attenuation of signal strength with distance is lower than at higher frequencies. Low frequency ground waves can be received up to 2,000 kilometres (1,200 mi) from the transmitting antenna. Low frequency waves can also occasionally travel long distances by reflecting from
912-482: The 2 200 meter band (135.7–137.9 kHz) is available to amateur radio operators in several countries in Europe, New Zealand, Canada, US, and French overseas dependencies. The world record distance for a two-way contact is over 10,000 km from near Vladivostok to New Zealand . As well as conventional Morse code many operators use very slow computer-controlled Morse code (so-called "QRSS" ) or specialized digital communications modes. The UK allocated
960-611: The BBC Radio 4 transmission on 198 kHz in waters near the UK. It is rumoured that they are to construe a sudden halt in transmission, particularly of the morning news programme Today , as an indicator that the UK is under attack, whereafter their sealed orders take effect. The United States has four LF stations maintaining contact with its submarine force: Aguada, Puerto Rico , Keflavik, Iceland , Awase, Okinawa , and Sigonella, Italy , using AN/FRT-95 solid state transmitters. In
1008-533: The Danish Meteorological Institute ( Danmarks Meteorologiske Institut ) ceased on 1 November 2023 ahead of full closure of the longwave service on 31 December 2023. It was possible to receive the LW signal of the Kalundborg transmitter outdoors over a distance of 800-1,000 km on a standard transistor radio or a longwave-compatible car radio. By connecting the receiver to a stationary or
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#17327834541461056-547: 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. AM broadcasting is authorized in the longwave band on frequencies between 148.5 and 283.5 kHz in Europe and parts of Asia. In Europe and Japan, many low-cost consumer devices have since
1104-496: The umbrella antenna and L- and T-antenna, use capacitive top-loading (a "top hat"), in the form of a network of horizontal wires attached to the top of the vertical radiator. The capacitance improves the efficiency of the antenna by increasing the current, without increasing its height. The height of antennas differ by usage. For some non-directional beacons (NDBs) the height can be as low as 10 meters, while for more powerful navigation transmitters such as DECCA , masts with
1152-434: The " longwave " band. In the western hemisphere, its main use is for aircraft beacons, navigation ( LORAN , mostly defunct), information, and weather systems. A number of time signal broadcasts also use this band. The main mode of transmission used in this band is ground waves , in which LF radio waves travel just above the Earth's surface, following the terrain. LF ground waves can travel over hills, and can travel far beyond
1200-436: The 160–190 kHz band a transmitter / amplifier output power to the antenna of at most 1 watt, with an antenna at most 15 meters (49 feet) high; this is called Low Frequency Experimental Radio (LowFER). The 190–435 kHz band is used for navigational beacons . Frequencies from 472–479 kHz are available to licensed amateurs as the new 630 m band , part of the now-defunct maritime band , but this
1248-480: 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
1296-537: The U.S., the Ground Wave Emergency Network or GWEN operated between 150 and 175 kHz, until replaced by satellite communications systems in 1999. GWEN was a land based military radio communications system which could survive and continue to operate even in the case of a nuclear attack. The 2007 World Radiocommunication Conference (WRC-07) made a worldwide amateur radio allocation in this band. An international 2.1 kHz allocation,
1344-737: The UK was received 3,275 miles (5,271 km) away, across the Atlantic Ocean , by W1TAG in the US on 21-22 November 2001 on 72.401 kHz. In the United States, there is an exemption within FCC Part ;15 regulations permitting unlicensed transmissions in the frequency range of 160–190 kHz. Longwave radio hobbyists refer to this as the ' LowFER ' band, and experimenters, and their transmitters are called ' LowFERs '. This frequency range between 160 kHz and 190 kHz
1392-565: The adoption of the Geneva Frequency Plan of 1975 , long-wave carrier frequencies are exact multiples of 9 kHz; ranging from 153 to 279 kHz. One exception was a French-language station, Europe 1 in Germany, which retained its prior channel spacing until the long-wave service was terminated in 2019. Other exceptions are all Mongolian transmitters, which are 2 kHz above the internationally recognized channels. Until
1440-438: The band 135.7–137.8 kHz is allocated (on a secondary basis) to Amateur radio worldwide, subject to a power limit of 1 watt EIRP. Many countries' regulators license amateurs to use it. 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 allow unlicensed use of
1488-408: The carrier, for Radio Teleswitch Services . 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
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1536-484: The exact same frequency, and has a similar timecode . Radio signals below 50 kHz are capable of penetrating ocean depths to approximately 200 metres (660 ft); the longer the wavelength, the deeper they go. The British, German, Indian, Russian, Swedish, United States, and possibly other navies communicate with submarines on these frequencies. In addition, Royal Navy nuclear submarines carrying ballistic missiles are allegedly under standing orders to monitor
1584-569: The far field. As such, they are technically not radio devices nor radio antennas, even though they do operate at radio frequencies, and are called "antennas" in the RFID trade, but not in radio engineering . It is more proper, and technically more informative to think of them as secondary coils of very loosely coupled transformers . Since the ground waves used in this band require vertical polarization , vertical antennas are used for transmission. Mast radiators are most common, either insulated from
1632-727: The ground and fed at the bottom, or occasionally fed through guy-wires. T-antennas and inverted L-antennas are used when antenna height is an issue. LF transmitting antennas for high power transmitters require large amounts of space, and have been the cause of controversy in Europe and the United States, due to concerns about possible health hazards associated with human exposure to radio waves . Antenna requirements for LF reception are much more modest than for transmission. Although non-resonant long wire antennas are sometimes used, ferrite loop antennas are far more popular because of their small size. Amateur radio operators have achieved good LF reception using active antennas : A short whip with
1680-400: The horizon, up to several hundred kilometers from the transmitter. Because of their long wavelength , low frequency radio waves 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 LF band. Ground waves must be vertically polarized (the electric field
1728-444: The late 1980s contained radio clocks with an LF receiver for these signals. Since these frequencies propagate by ground wave only, the precision of time signals is not affected by varying propagation paths between the transmitter, the ionosphere, and the receiver. In the United States, such devices became feasible for the mass market only after the output power of WWVB was increased in 1997 and 1999. JJY transmitting broadcast on
1776-822: 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. ELF 3 Hz/100 Mm 30 Hz/10 Mm SLF 30 Hz/10 Mm 300 Hz/1 Mm ULF 300 Hz/1 Mm 3 kHz/100 km VLF 3 kHz/100 km 30 kHz/10 km LF 30 kHz/10 km 300 kHz/1 km MF 300 kHz/1 km 3 MHz/100 m HF 3 MHz/100 m 30 MHz/10 m VHF 30 MHz/10 m 300 MHz/1 m UHF 300 MHz/1 m 3 GHz/100 mm SHF 3 GHz/100 mm 30 GHz/10 mm EHF 30 GHz/10 mm 300 GHz/1 mm THF 300 GHz/1 mm 3 THz/0.1 mm Low frequency Low frequency ( LF )
1824-464: The military to communicate with submerged submarines . 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
1872-482: 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 ,
1920-460: 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
1968-482: 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
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2016-423: 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
2064-525: 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
2112-411: 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
2160-480: 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
2208-719: The world where there is no longwave broadcasting service, Non-directional beacons used for aeronavigation operate on 190–300 kHz (and beyond into the MW band). In Europe, Asia and Africa, the NDB allocation starts on 283.5 kHz. The LORAN -C radio navigation system operated on 100 kHz. In the past, the Decca Navigator System operated between 70 kHz and 129 kHz. The last Decca chains were closed down in 2000. Differential GPS telemetry transmitters operate between 283.5 and 325 kHz. The commercial " Datatrak " radio navigation system operates on
2256-487: Was an insulated guyed steel lattice mast with a height of 147 metres. All masts virtually stood in the sea on the narrow Gisseløre peninsula, providing excellent radiation efficiency. Times given in Central European Time . Source: Longwave In radio, longwave , long wave or long-wave , and commonly abbreviated LW , refers to parts of the radio spectrum with wavelengths longer than what
2304-406: 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' (i.e. VHF , UHF , and microwave ). In contemporary usage,
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