Longwave radio frequencies are those below 500 kHz, which correspond to wavelengths longer than 600 meters. They have the property of following the curvature of the earth, making them ideal for continuous, continental communications. Unlike shortwave radio, longwave signals do not reflect or refract using the ionosphere, so there are fewer phase-caused fadeouts.

The earliest radio transmitters, including the Alexanderson alternator, were all longwave transmitters.

In Europe, North Africa and Asia, longwave radio frequencies between 153 and 279 kHz are used for domestic and international broadcasting. In the Americas, frequencies between 200 and 430 kHz are used for non-directional beacons (NDBs), and do not necessarily follow the same 9 kHz spacing that other areas do.

The frequency of 60 kHz is used by several nations, such as the USA, UK, and Japan, for extremely accurate time and precision frequency signals. (77.5 kHz is used in Germany.) Many commercial appliances (such as self-setting clocks) sold since approximately 2000 have a VLF receiver capable of receiving these signals, which penetrate indoors more effectively than mediumwave or shortwave signals.

Radio signals below 50 kHz are capable of penetrating ocean depths to approximately 200 meters. The United States, Russian, British, Swedish, and Indian navies communicate with submarines on these frequencies.

In addition, Royal Navy nuclear submarines carrying ballistic missiles are allegedly under standing orders to monitor the BBC Radio 4 transmission on 198 kHz in waters near the U.K. It is rumoured that they are to construe a sudden halt in transmission as an indicator that the U.K. is under attack, whereafter their sealed orders take effect.

In North America there is a special amateur radio in the longwave range called LowFER.

As aerials are usually used: mast antennas which are fed at the bottom and which are insulated against ground, mast antennas fed by the guy ropes (such masts are usually grounded), T-aerials, L-aerials and long wire aerials. In future the use of crossed field antenna is to be expected, if claims for their efficiency is proven.

T-aerials and L-aerials are depending on the requirements mounted on as well grounded as insulated masts or towers.

The height of aerials differ from usage: for NDBs the height is just around 10 metres, while for more powerful navigation transmitters as DECCA masts with a height around 100 metres are used. T-aerials have a height between 50 and 200 metres, while mast aerials are usually taller than 150 metres.

The height of mast aerials for LORAN-C is around 190 metres for such with radiation powers below 500 kW and around 400 metres for such with powers more than 1000 kilowatts. The first type of LORAN-C aerials is insulated against ground.

Longwave broadcasting stations use mast antennas with heights of more than 150 metres or T-aerials. The mast antennas can be ground-fed insulated masts or upper-fed grounded masts. It is also possible to use cage aerials on grounded masts.

Nearly all longwave aerials are not as high as the quater of the radiated wavelength. The only longwave transmission aerial realized with a height corresponding to the half of the radiated wavelength was Warszaw Radio Mast.

For broadcasting stations often directional aerials are required. They consist of multiple masts, which need not to be from the same height. Some longwave aerials consist of multiple mast antennas arranged in a circle with or without a mast antenna in the centre. Such aerials focus the transmitted power toward ground and gave a large zone of fading free reception. Because they are very expensive, they are barely used. One aerial of this kind was used by transmitter Orlunda in Sweden.

Longwave transmitting antennas take up large amounts of space, and have been the cause of controversy in the United States and Europe due to fears over proximity to high-power radio waves.

List of longwave broadcasting transmitters

List of the most important longwave broadcasting transmitters (Source: http://de.wikipedia.org/wiki/Langwelle ).

Frequency	Name of transmitter	Country	Location	Kind of aerial	Power	Remarks
153 kHz	Deutschlandfunk	Germany	Donebach	directional aerial, two guyed steel framework masts, 363 m high, fed at the top	500 kW	night 250 kW
	Radio Romania	Romania	Brasov		1200 kW
	NRK Finnmark	Norway	Ingoy	omnidirectional aerial, guyed steel framework mast of 362 m height	100 kW
162 kHz	France Inter	France	Allouis	two guyed steel framework masts, height 350 m, fed on the top	2000 kW
171 kHz	Radio Medi	Morocco	Nador		1200 kW
	Radio Rossiya	Russia	Kaliningrad		1200 kW
177 kHz	DeutschlandRadio Berlin	Germany	Zehlendorf near Oranienburg	cage aerial mounted on 359.7 m high guyed mast, triangle aerial on 3 150 m high guyed steel framework masts	500 kW
183 kHz	Europe 1	Germany	Felsberg	directional aerial, 4 insulated guyed steel framework masts, heights: 282 m, 280 m, 26 m and 270 m	2000 kW	French Program
189 kHz	RUV	Iceland	Hellissandur	omnidirectional aerial, guyed steel framework mast, height 412 m	300 kW
189 kHz	RAI	Italia	Caltanissetta	omnidirectional aerial, guyed steel framework mast, height 282 m	10 kW	inactive since August 2004
198 kHz	BBC Radio 4	United Kingdom	Droitwich	T-aerial on 2 guyed steel framework masts with a height of 213 metre	500 kW	BBC World Service
	BBC Radio 4	United Kingdom	Burghead	Guyed steel framework mast	50 kW
	BBC Radio 4	United Kingdom	Westerglen	Guyed steel framework mast, height 152 m	50 kW
	Radio Polonia	Poland	Raszyn	Guyed insulated mast, 335 m high	500 kW	only active at daytime
207 kHz	Deutschlandfunk	Germany	Aholming	directional aerial, two guyed steel framework masts, 265 m high, fed at the top	500 kW	night 250 kW
216 kHz	Radio Monte Carlo	France	Roumoules	directional aerial, 3 300 metre high guyed steel framework masts, 330 metre high guyed steel framework mast as backup aerial	1200 kW	Transmitter site exterritorial, exclave of Monaco
225 kHz	Radio Polonia	Poland	Solec Kujawski	2 guyed radio masts fed on the top, heights 330 m and 289 m	1000 kW	Earlier tranmitter site Konstantynow
234 kHz	RTL	Luxemburg	Beidweiler	directional aerial, 3 guyed grounded steel framework masts, 290 m high, with vertikal cage aerials	2000 kW	Spare transmitter site Junglinster
243 kHz	Danmarks Radio	Danmark	Kalundborg	Alexanderson aerial, carried from 2 118 Meter high freestanding steel framework towers	300 kW
252 kHz	RTA Algier	Algeria	Tipaza		1500 kW	French programme; during nighttime half transmitter-power
	RTÉ Radio 1	Ireland	Clarkestown	Guyed steel framework mast, insulated against ground, height 248 m	500 kW	Earlier used by Atlantic 252 and TeamTalk 252
261 kHz	Transmitter Burg	Germany	Burg	Cage aerial on 324 m high guyed steel framework mast, 210 m high steel tube mast, insulated against ground, omnidirectional radiation	200 kW	inactive at the moment
	Radio Rossiya	Russia	Taldom		2500 kW	Most powerful transmitter in the world
270 kHz	ČRO 1 - Radiožurnál	Czech Republic	Topolna	two grounded guyed steel framework mast with cage aerials, height 257 m, directional radiation with maximum of radiation in East-West direction	500 kW
279 kHz	Musicmann279	Isle of Man	± 5 km off Ramsey	Crossed field antenna	500 kW	Tests planned to begin in early 2005 pending a summer 2005 launch
	BR1	Belarus	Minsk		500 kW

See also

• Electromagnetic spectrum: Shortwave, Low frequency, Groundwave, Skywave
  • Radio: AM radio, BBC Radio 4, BBC Light Programme, Radio clock, Office de Radiodiffusion Télévision Française, Warsaw radio mast, Digital Radio Mondiale, International broadcasting,
  • Shipping: Satellite navigation system, Navigation, Shipping Forecast
• Lists: List of music videos by year, List of wave topics
• Other: 1 E3 m, National Institute of Standards and Technology, Fail-Safe

External links

• "Longwave Club of America".