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 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, medium-wave, and short-wave 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, including the International Telecommunication Union's low frequency and very low frequency 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, 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. The "Longwave Club of America" is interested in "frequencies below the AM broadcast band".

Propagation

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. 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 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.
Low frequency waves can also occasionally travel long distances by reflecting from the ionosphere, 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 from the transmitting antenna.

Non-broadcast use

Non-directional beacons

s 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.

Time signals

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 and when the signal is received by the clock 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.

Submarine communication

The militaries of the United Kingdom, Russian Federation, United States, Germany, India and Sweden use frequencies below 50 kHz to communicate with submerged submarines.

LowFER

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. The 190–435 kHz band is used for navigational beacons.

Historic

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.

Broadcasting

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.

Carrier 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.
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.

Long-distance reception

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 have been verified.

List of long-wave broadcasting transmitters

List of stations currently operating

Freq.
Station
name		LanguageCountryLocationAerial
type		Power
CoordinatesNotes
153Radio Antena SatelorRomanianBrașovT-aerial on 2 guyed steel lattice masts, height: 200
Fifth state-owned radio station in Romania
162ANFR FrenchAllouisTwo guyed lattice steel masts, height: fed on the top1000
/
2000
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.
164MNB Radio 1MongolianUlaanbaatar tall cable-stayed steel truss mast500Broadcasts from 21:00 to 14:00 UTC
171Médi 1Arabic and FrenchNadorDirectional aerial consisting of three guyed steel lattice masts, tall1600
Private and commercial Moroccan radio network
189RÚV Rás 1/RÚV Rás 2IcelandicGufuskalar near HellissandurSlight 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: 300Iceland's national public service broadcaster
198BBC Radio 4/BBC World ServiceEnglishDroitwich T-aerial on two guyed steel lattice masts insulated against ground with a height of 500
All four transmitters carry Radio teleswitch PSK data; Droitwich relays BBC World Service from 01:00 to 05:20 UTC
198BBC Radio 4/BBC World ServiceEnglishBurghead Omnidirectional aerial, guyed steel lattice mast, height 50All four transmitters carry Radio teleswitch PSK data; Droitwich relays BBC World Service from 01:00 to 05:20 UTC
198BBC Radio 4/BBC World ServiceEnglishWesterglen Omnidirectional aerial, guyed steel lattice mast, height 50All four transmitters carry Radio teleswitch PSK data; Droitwich relays BBC World Service from 01:00 to 05:20 UTC
198BBC Radio 4/BBC World ServiceEnglishDartford Tunnel 0.004-All four transmitters carry Radio teleswitch PSK data; Droitwich relays BBC World Service from 01:00 to 05:20 UTC
207RÚV Rás 1/RÚV Rás 2IcelandicEiðar near EgilsstaðirOmnidirectional aerial, steel lattice mast insulated against ground, height 100Iceland's national public service broadcaster
209MNB Radio 1MongolianChoibalsanCable-stayed steel truss mast, height: 75Broadcasts from 21:00 to 14:00 UTC
209MNB Radio 1MongolianDalanzadgadCable-stayed steel truss mast, height: 75Broadcasts from 21:00 to 14:00 UTC
209MNB Radio 1MongolianOlgiiOmnidirectional antenna, high guyed mast30Broadcasts from 21:00 to 14:00 UTC
225Polish Radio Programme OnePolishSolec KujawskiDirectional aerial, two guyed radio masts fed on the top, heights and 1000
Earlier Konstantynów was used
227MNB Radio 1MongolianAltaiCable-stayed steel truss mast75Broadcasts from 21:00 to 14:00 UTC
234RTLFrenchBeidweilerDirectional aerial, three guyed grounded steel lattice masts, high, with vertical cage aerials1500
/
2000
Spare transmitter site Junglinster
243DR LangbølgeDanishKalundborgSemi-directional Alexanderson antenna 153/333 degrees, two grounded steel lattice radiating towers with interconnecting top wire capacitance50
Transmitting in time slots only
252Radio Algeria
Chaîne 3		ArabicTipazaOmnidirectional aerial, single guyed lattice steel mast, height 750
/
1500		Half transmitter power during night
252RTÉ Radio 1English and IrishClarkstownOmnidirectional aerial, guyed steel lattice mast, insulated against ground, height 150
/
300		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.
270ČRo RadiožurnálCzechTopolnáDirectional aerial, two grounded high guyed steel lattice mast with cage aerials50
Broadcasting from Monday to Friday 05:00–24:00 CET and 06:00–24:00 CET at weekends

List of stations that have closed or are otherwise inactive

Freq.
Station
name		CountryLocationAerial
type		Power
CoordinatesNotes
153-------
153DeutschlandfunkDonebachDirectional aerial, two guyed steel lattice masts, 363 m high, fed at the top500 ; closed
153Radio MayakAshgabat650closed
153YuFMTaldom transmitterOmnidirectional aerial, guyed steel lattice mast of 257 m height300closed
153NRK P1/P2IngøyOmnidirectional aerial, guyed steel lattice mast tall, fed at the top, ex-Omega equipment100closed
153Radio RossiiPopova near Komsomolsk-na-Amure1200closed
153Radio Algerie
Chaîne 1		KénadsaThree tall guyed masts500inactive
162TRT Radyo 4AgriTwo guyed lattice steel masts, height 250 m1000 ; inactive
162Kanal UzbekistanTashkent150closed
162Radio RossiiNorilskOmnidirectional antenna, 205 m high antenna150 ?closed
162Radio Yuldash, Radio RossiiUfa150closed
171-------
171NPO Radio 1Lopik500closed
171Radio-1Lapichi?500/1000closed
171Voice of RussiaOktyabrsky257 m metres tall antenna.1200closed
171Radio RossiiBolshakovo near KaliningradOmnidirectional antenna, 257 m high guyed lattice steel mast with cage antenna 600closed
171Radio Ukraine 1Krasne near LvivOmnidirectional antenna, 259 m high guyed lattice steel mast with cage antenna 150/75inactive
171Radio RossiiRadugaOmnidirectional antenna, 255 m high guyed lattice steel mast with cage antenna 250closed
171Radio 1MurmanskOmnidirectional antenna, 257 m high guyed lattice steel mast with cage antenna 150closed
171Radio 1NoginskOmnidirectional antenna, 242 m high guyed lattice steel mast with cage antenna 150closed
171Radio 1Ezhva near SyktyvkarOmnidirectional antenna, 257 m high guyed lattice steel mast with cage antenna 150closed
171Radio RossiiTulagino near YakutskOmnidirectional antenna, circle antenna with 1 central and 6 ring masts150 ; ; ; ; ; ; closed
177-------
177Deutschlandradio KulturZehlendorf near OranienburgOmnidirectional aerial, cage aerial mounted on 359.7 m high guyed mast, triangle aerial on 3 150 m high guyed steel lattice masts500closed
180TRT Radyo 1PolatliOmnidirectional antenna, 250 m high guyed latice steel mast1200inactive
180Radio RossiiYelizovo near Petropavlovsk-KamchatskiyOmnidirectional antenna, 255 m high guyed lattice steel mast150closed
180Radio MayakKruchina near ChitaOmnidirectional antenna, 200 m high guyed lattice steel mast150inactive
180Kazakh Radio 1Alma-Ata250closed
180Kazakh Radio 1Aktyubinsk150closed
180Kazakh Radio 1Chimkent50closed
183-------
183Europe 1Felsberg-BerusDirectional aerial, four ground insulated steel lattice masts,, and tall; spare aerial: two ground insulated steel lattice masts, height: 750Main antenna:


Spare antenna:
closed
189-------
189Rai Radio 1CaltanissettaOmnidirectional aerial, guyed steel lattice mast, height 282 m10closed
189Sveriges Radio P1Orlunda, near Motala300closed
189Radio RossiiKostantinogradovka near BlagoveshchenskOmnidirectional aerial, 257 m high guyed lattice steel mast with cage antenna 1200closed
189Sakartvelos RadioDusheti250inactive
198-------
198Polskie Radio Parlament/Radio PoloniaRaszynOmnidirectional aerial, guyed steel lattice mast insulated against ground, 335 m high200closed
198Chaine 1Berkaoui2000closed
198Radio MayakSaint Petersburg – OlginoOmnidirectional aerial, 205 m high guyed steel lattice mast150inactive
198Radio MayakAngarskBefore 2001: T-antenna spun between 2 205 m tall guyed steel lattice mast250, possibly closed
198Radio MayakAvsyuninoOmnidirectional antenna, 257 m high guyed lattice steel mast with cage antenna 150inactive
198Radio MayakUfa150closed
198Radio 1Krasnaya Rechka near Bishkek150closed
207-------
207RNE Radio 5LogroñoDirectional antenna, 300 metres tall.>100closed
207Radio Ukraine 1BrovaryOmnidirectional antenna, 259.6 m high guyed lattice steel mast with cage antenna 600closed
207Radio al-UrdunniyaAl Karanah? ; closed
207Radio MayakTyndaOmnidirectional aerial, steel lattice mast insulated against ground, height 244 m150closed
207DeutschlandfunkAholmingDirectional aerial, two guyed steel lattice masts, 265 m high, fed at the top500 ; closed
207SNRT Al Idaâ Al-WataniaAzilal Demnate tall guyed mast400inactive
209-------
209Radio MayakTynda150closed
216-------
216NRK P1Lambertseter near Oslo200closed
216Radio Monte Carlo InfoRoumoulesDirectional aerial, three high guyed steel lattice masts, high guyed steel lattice mast as backup aerial700
/
1400

,
Backup antenna:
closed
216Azerbaijan RadioBaku500closed
216Radio RossiiKrasnoyarskOmnidirectional antenna, guyed lattice steel mast, 210 m tall150closed
216Radio RossiiAtamanovkaDirectional antenna150closed
216Radio RossiiBirobidzhan2 guyed masts, 260 m high30 ; closed
225TRT GAPVanOmnidirectional antenna, 250 m high guyed lattice steel mast600inactive
225Radio RossiiSurgutOmnidirectional antenna, 257 m high guyed lattice steel mast with cage antenna 1000closed
234-------
234Radio MoldovaGrigoriopol1000closed
234Radio JamahiriyaYafran near Tripoli1000closed
234Radio 1Krasny Bor transmitter near Sankt-PeterburgOmnidirectional aerial, 271.5 metres tall guyed mast with cage antenna1200closed
234Public Armenian RadioKamo?500?closed
234Radio RossiiKoskovo near MurmanskOmnidirectional aerial, 210 m tall guyed mast250inactive
234Radio 1Novosemeykino near SamaraFour 205 metres tall towers insulated against ground arranged in a square2000 ; ; ; closed
234Radio RossiiRaduzhnyy near MagadanOmnidirectional aerial, 259 m high guyed lattice steel mast with cage antenna 1000closed
234Radio RossiiOdinsk near IrkutskOmnidirectional aerial, 259 m high guyed lattice steel mast with cage antenna 500closed
234Radio 1Koskovo near ArkhangelskOmnidirectional aerial, 257 m high guyed lattice steel mast with cage antenna 500closed
243TRT Radyo 4ErzurumOmnidirectional antenna, 185 m high guyed lattice steel mast200inactive
243Radio RossiiRazdolnoye near UssuriyskOmnidirectional antenna, 259 m high guyed lattice steel mast with cage antenna 1000closed
243Kazakh Radio 2 ShalkarKaragandaOmnidirectional aerial, guyed steel lattice mast of 254 m height1000closed
243Kazakh Radio 2 ShalkarAlma-Ata1000closed
252-------
252Armenian Radio 1Kamo150?closed
252Yle Radio 1Lahti200, closed
252Radio TojikstonDushanbe150closed
252Radio RossiiKazanOmnidirectional aerial, 152 m high guyed lattice steel mast with cage antenna 100closed
261-------
261Radioropa InfoBurgOmnidirectional aerial, cage aerial on 324 m high guyed, grounded steel lattice mast, 210 m high steel tube mast, insulated against ground200closed
261Radio RossiiTaldomOmnidirectional antenna, circle antenna with 1 central and 5 ring masts, height of central mast 275 m2500 ; ; ; ; ; closed
261Radio RossiiKruchina near ChitaOmnidirectional antenna, guyed lattice steel mast, 260 m high150closed
261Radio RossiiTyumenOmnidirectional antenna, guyed lattice steel mast, 220 m high150closed
261Radio RossiiVorkutaOmnidirectional antenna, guyed lattice steel mast, 220 m high50closed
261Radio HorizontVakarelOne of the few Blaw-Knox Towers in Europe, 215 m high75closed
270-------
270Radio RossiiOrenburgOmnidirectional aerial, guyed steel lattice mast of 137 m height25closed
270Radio 1Khabarovsk2 guyed steel lattice masts, height: 164 m150 ; closed
270Radio SlovoNovosibirsk?150?closed
279-------
279Radio RossiiGorno-AltaiskOmnidirectional antenna, 143m high guyed lattice steel mast50closed
279Radio RossiiSelenginskOmnidirectional aerial, 260 m high guyed lattice steel mast with cage antenna 150closed
279Radio RossiiVestochka near Yuzhno-SakhalinskOmnidirectional antenna, guyed lattice steel mast, 258 m high1000closed
279Radio RossiiYekaterinburgOmnidirectional aerial, guyed steel lattice mast of 256 m height, fed at the top150closed
279BR Pershy Kanal/BR Radyjo StalitsaSasnovy353.5 metres tall guyed mast500closed
279TR1 Watan RadioAshgabatCable-stayed steel truss mast150inactive
279MusicMann 279Isle of ManCrossed fieldnever launched