Longwave

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:

• WWVB in Colorado, United States, on 60 kHz
• DCF77 in Frankfurt, Germany, on 77.5 kHz
• JJY in Japan, on 40 & 60 kHz
• 66.66 kHz in Taldom transmitter, Russia
• BPC in Lintong, China, 68.5 kHz
• MSF time and 60 kHz frequency standard transmitted from Anthorn in the UK.
• TDF from Allouis, France, on 162 kHz

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.

Licensed operators in the U.S. may transmit on the newly-allocated 2200 m band from 136–139 kHz at maximum equivalent power radiated from the antenna of 1 watt (EIRP); most nations in Europe already have adopted the new band, along with many others worldwide.

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 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 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.[9]

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.[11]

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.[12]

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.[13]

[14] [15] [16] [17]

Freq. (kHz)	Station name	Language	Country	Location	Aerial type	Power (kW)	Coordinates	Notes
153	Radio Algerie Chaine 1	Arabic and French	Algeria	Kenadsa	Three 357 metres (1,171 ft) tall guyed masts	500
	Radio Antena Satelor	Romanian	Romania	Brașov	T-aerial on 2 guyed steel lattice masts, height: 250 metres (820 ft)	200	45°45′22.27″N 25°36′26.77″E 45°45′13.16″N 25°36′25.15″E	Fifth state-owned radio station in Romania
164	MNB Radio 1	Mongolian	Mongolia	Ulaanbaatar	259 metres (850 ft) tall cable-stayed steel truss mast[18]	500	47°47′54.67″N 107°11′14.7″E	Broadcasts from 21:00 to 14:00 UTC
171	Médi 1	Arabic and French	Morocco	Nador	Directional aerial consisting of three guyed steel lattice masts, 380 metres (1,250 ft) tall	1600	35°02′50.65″N 2°55′22.81″W 35°02′30.27″N 2°55′16.16″W 35°02′9.89″N 2°55′9.52″W	Private and commercial Moroccan radio network
189	RÚV Rás 1/RÚV Rás 2	Icelandic	Iceland	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	64°54′26″N 23°55′19.5″W	Iceland's national public service broadcaster
198	Cnaine 1	Arabic and French	Algeria	Berkaoui		2000
	BBC Radio 4	English	United Kingdom	Droitwich (SFN)	T-aerial on two guyed steel lattice masts insulated against ground with a height of 213 metres (699 ft)	500	52°17′46.9″N 2°6′24.32″W 52°17′40.4″N 2°6′20.62″W	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	57°41′57.9″N 3°28′4.78″W
				Westerglen (SFN)	Omnidirectional aerial, guyed steel lattice mast, height 152 metres (499 ft)		55°58′33″N 3°48′58.8″W
				Dartford Tunnel (SFN)		0.004
207	SNRT Al-Idaa Al-Watania	Moroccan	Morocco	Azilal Demnate	304.8 metres (1,000 ft) tall guyed mast	400
	RÚV Rás 1/RÚV Rás 2	Icelandic	Iceland	Eiðar near Egilsstaðir	Omnidirectional aerial, steel lattice mast insulated against ground, height 221 metres (725 ft)	100	65°22′22.93″N 14°20′27.29″W	Iceland's national public service broadcaster
209	MNB Radio 1	Mongolian	Mongolia	Choibalsan	Cable-stayed steel truss mast, height: 275.84 metres (905.0 ft)	75	48°00′17.27″N 114°27′17.6″E	Broadcasts from 21:00 to 14:00 UTC
				Dalanzadgad			43°31′54.43″N 104°24′41.4″E	Broadcasts from 21:00 to 14:00 UTC
				Olgii	Omnidirectional antenna, 352.5 metres (1,156 ft) high guyed mast	30	48°57′24.52″N 89°58′13.15″E	Broadcasts from 21:00 to 14:00 UTC
225	Polskie Radio Program I/Polskae Radyjo	Polish	Poland	Solec Kujawski	Directional aerial, two guyed radio masts fed on the top, heights 330 metres (1,080 ft) and 289 metres (948 ft)	1000	53°1′21.01″N 18°15′32.63″E 53°1′12.83″N 18°15′44.06″E	Earlier Konstantynów was used (52°22′3.91″N 19°48′7.04″E). 3-minutes news bulletins by Belarusian service Polish radio aired every day in 6:40, 12:20 (12:10 in Sunday) and 22:20 (22:05 in Sunday) (Warsaw time).[19]
227	MNB Radio 1	Mongolian	Mongolia	Altai	Cable-stayed steel truss mast	75	46°19′25.52″N 96°15′31.2″E	Broadcasts from 21:00 to 14:00 UTC
234	RTL	French	Luxembourg	Beidweiler	Directional aerial, three guyed grounded steel lattice masts, 290 metres (950 ft) high, with vertical cage aerials	1500 / 2000	49°43′42.57″N 6°19′4.29″E 49°43′49.2″N 6°19′15.02″E 49°43′55.81″N 6°19′25.67″E	Spare transmitter site Junglinster (49°43′0.35″N 6°15′28.9″E, 49°43′6.56″N 6°15′40.27″E, 49°43′12.75″N 6°15′51.44″E)
243	DR P1	Danish	Denmark	Kalundborg	Semi-directional Alexanderson antenna 153/333 degrees, two grounded 118 metres (387 ft) steel lattice radiating towers with interconnecting top wire capacitance	50	55°40′39.27″N 11°4′8.6″E 55°40′32.91″N 11°4′14.33″E	Transmitting in time slots only
252	Radio Algeria Chaîne 3	Arabic	Algeria	Tipaza	Omnidirectional aerial, single guyed lattice steel mast, height 355 metres (1,165 ft)	750 / 1500	36°33′58.14″N 2°28′50.3″E	Half transmitter power during night
	RTÉ Radio 1	English and Irish	Ireland	Clarkstown	Omnidirectional aerial, guyed steel lattice mast, insulated against ground, height 248 metres (814 ft)	150 / 300	53°27′46″N 6°40′39″W	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.[20] In April 2019 it announced an antenna upgrade and the closure was postponed.[21]
270	ČRo Radiožurnál	Czech	Czech Republic	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	49°7′32.88″N 17°30′45.97″E 49°7′18.85″N 17°30′41.78″E	Broadcasting from Monday to Friday 05:00–24:00 CET and 06:00–24:00 CET at weekends. Will be ceased broadcast in 31 December 2021.
279	TR1 Watan Radio	Turkmenian	Turkmenistan	Ashgabat	Cable-stayed steel truss mast	150	37|51|14.89|N|58|21|57.99|E|type:landmark	name=Ashgabat transmitter