Mediumwave
Encyclopedia
Medium wave is the part of the medium frequency
(MF) radio band used mainly for AM radio broadcasting
. For Europe
the MW band ranges from 526.5 kHz to 1606.5 kHz
and in North America
an extended MW broadcast band
goes from 535 kHz to 1705 kHz.
at night (skywave
). This makes this frequency band ideal for both local and continent-wide service, depending on the time of day. For example, during the day a radio receiver in the state of Colorado
is able to receive reliable but weak signals from high-power stations such as 770KKOB
, or 610KNML
500 miles away from their towers in Albuquerque, New Mexico
, due to groundwave propagation. The effectiveness of groundwave signals largely depends on ground conductivity
and higher conductivity results in better propagation. At night, the same receiver may pick up signals as far away as 1110KFAB in Nebraska
reliably, depending on atmospheric noise and man-made interference.
Some experiments and trials are planned or under way for a digital modulation such as Digital Radio Mondiale
(DRM).
In 1923, the Commerce Department realized that as more and more stations were applying for commercial licenses, it was not practical to have every station broadcast on the same three wavelengths. On May 15, 1923, Commerce Secretary Hoover announced a new bandplan which set aside 81 frequencies, in 10 kHz steps, from 550 kHz to 1350 kHz (extended to 1500, then 1600 and ultimately 1700 kHz in later years). Each station would be assigned one frequency (albeit usually shared with stations in other parts of the country and/or abroad), no longer having to broadcast weather and government reports on a different frequency than entertainment. Class A and B stations were segregated into sub-bands.
Nowadays in most of the Americas
, mediumwave broadcast stations are separated by 10 kHz and have two sideband
s of up to ± 5 kHz in theory, although in practice stations transmit audio of up to 10 kHz. In the rest of the world, the separation is 9 kHz, with sidebands of ± 4.5 kHz. Both provide adequate audio quality for voice
, but are insufficient for high-fidelity broadcasting, which is common on the VHF
FM
bands. In the US and Canada the maximum transmitter power is restricted to 50 kilowatts, while in Europe
there are medium wave stations with transmitter power up to 2 megawatts daytime.
Most United States AM radio stations are required by the Federal Communications Commission
(FCC) to shut down, reduce power or employ a directional antenna array at night in order to avoid interference with each other due to night-time only long-distance skywave propagation ("skip"). Those stations which shut down completely at night are often known as "daytimers". Similar regulations are in force for Canadian stations, administered by Industry Canada
.
and a higher one for directional
radiation with minima in certain directions. The power limit can also be depending on daytime and it is possible, that a station may not work at nighttime, because it would then produce too much interference. Other countries may only operate low-powered transmitters on the same frequency, again subject to agreement. For example, Russia
operates a high-powered transmitter, located in its Kaliningrad
exclave and used for external broadcasting, on 1386 kHz. The same frequency is also used by low-powered local radio stations in the United Kingdom
, which has approximately 250 medium-wave transmitters of 1 kW and over; other parts of the United Kingdom can still receive the Russian broadcast. International mediumwave broadcasting in Europe has decreased markedly with the end of the Cold War
and the increased availability of satellite and Internet TV and radio, although the cross-border reception of neighbouring countries' broadcasts by expatriates and other interested listeners still takes place.
Due to the high demand for frequencies in Europe, many countries operate single frequency networks; in Britain, BBC Radio Five Live
broadcasts from various transmitters on either 693 or 909 kHz. These transmitters are carefully synchronized to minimize interference from more distant transmitters on the same frequency.
Overcrowding on the Medium wave band is a serious problem in parts of Europe contributing to the early adoption of VHF
FM broadcasting
by many stations (particularly in Germany). However in recent years several European countries (Including Ireland
, Poland
and, to a lesser extent Switzerland
) have started moving away from Medium wave altogether with most/all services moving exclusively to other bands (usually VHF).
with C-QUAM
being the most common in the United States as well as other countries, and receivers that implement the technologies are relatively rare.
In September 2002, the United States Federal Communications Commission
approved the proprietary iBiquity
in-band on-channel
(IBOC) HD Radio
system of digital audio broadcasting
, which is meant to improve the audio quality of signals. The Digital Radio Mondiale
(DRM) IBOC system has been approved by the ITU
for use outside North America
and U.S. territories
.
s are most commonly used. Stations broadcasting with low power can use masts with heights of a quarter-wavelength
, while high power stations mostly use half-wavelength. The usage of masts longer than 5/8 of radiated wavelength gives a bad radiation pattern. Usually mast antennas are insulated against ground and show a high voltage against ground during transmission, which complicates maintenance, installation of air safety warning lights or using the mast as a tower for UHF/VHF-radio, but there are several ways to use grounded masts or towers.
If grounded masts or towers are required, then cage aerial
s or long-wire aerials are used. Another possibility consists of feeding the mast or the tower by cables running from the tuning unit to the guys or crossbars in a certain height. Directional aerials consist of multiple masts
, which need not to be from the same height. It is also possible to realize directional aerials for mediumwave with cage aerials where some parts of the cage are fed with a certain phase difference.
For medium-wave (AM) broadcasting, quarter-wave masts are between 153 ft and 463 ft high, depending on the frequency. Because quarter-wave masts are so large they can be unnecessarily costly and uneconomic, and other types are more commonly used on medium wave for local broadcast stations of under 5 kW, examples being T- and L-antennas. The design of these smaller antennas uses the technique commonly used on Long Wave
to allow smaller masts to be used. In this method the mast size is reduced, producing less radiation resistance
and increased reactance
, and wires are added, supported by the same mast or masts, to compensate these deficiencies adequately. The details depend on the requirement for grounded or insulated towers and masts. The dimensions can and must be calculated accurately to meet the required specifications in bandwidth, power handling and radiation efficiency.
A popular choice for lower-powered stations is the umbrella antenna
, which needs only one mast one tenth wavelength or less in height. This antenna uses a single mast insulated from ground and fed at the lower end against ground. In that sense it is a simple monopole, but at the top of the mast extra wires are connected (usually about six) which slope downwards at an angle of 40-45 degrees as far as about one-third of the total height, where they are terminated in insulators and thence outwards to ground anchors. Thus the umbrella antenna can use the guy wires as part of the antenna.
In some rare cases dipole antenna
s are used, which are slung between two masts or towers. Such antennas are intended to radiate a skywave
. The medium-wave transmitter at Berlin-Britz
for transmitting RIAS used a cross dipole mounted on five 30.5 metre high guyed masts to transmit the skywave to the ionosphere at nighttime.
Europe's largest antenna park is placed in Northern Jutland, Denmark. The well-known German DX'er Wilhelm Herbst has constructed and built the antennas. DXers are welcome to use the facilities.
For low-noise reception at frequencies below 1.6 MHz, which includes long and medium waves, loop antennas are popular because of their ability to reject locally generated noise. This class of antennas includes the ferrite-rod antenna, also known as a loopstick antenna, which is by far the most common antenna in use for broadcast reception throughout the world. Transistor radios contain a loopstick as the receiving antenna.
Medium frequency
Medium frequency refers to radio frequencies in the range of 300 kHz to 3 MHz. Part of this band is the medium wave AM broadcast band. The MF band is also known as the hectometer band or hectometer wave as the wavelengths range from ten down to one hectometers...
(MF) radio band used mainly for AM radio broadcasting
AM broadcasting
AM broadcasting is the process of radio broadcasting using amplitude modulation. AM was the first method of impressing sound on a radio signal and is still widely used today. Commercial and public AM broadcasting is carried out in the medium wave band world wide, and on long wave and short wave...
. For Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
the MW band ranges from 526.5 kHz to 1606.5 kHz
and in North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
an extended MW broadcast band
Extended AM broadcast band
The extended mediumwave broadcast band, commonly known as the [AM] expanded band, is a broadcast frequency allocation which moved the upper limit of the AM bandplan from 1610 to 1700 kHz.- History :...
goes from 535 kHz to 1705 kHz.
Medium wave propagation characteristics
Medium wave signals have the property of following the curvature of the earth (the groundwave) at all times, and also refracting off the ionosphereIonosphere
The ionosphere is a part of the upper atmosphere, comprising portions of the mesosphere, thermosphere and exosphere, distinguished because it is ionized by solar radiation. It plays an important part in atmospheric electricity and forms the inner edge of the magnetosphere...
at night (skywave
Skywave
Skywave is the propagation of electromagnetic waves bent back to the Earth's surface by the ionosphere. As a result of skywave propagation, a broadcast signal from a distant AM broadcasting station at night, or from a shortwave radio station can sometimes be heard as clearly as local...
). This makes this frequency band ideal for both local and continent-wide service, depending on the time of day. For example, during the day a radio receiver in the state of Colorado
Colorado
Colorado is a U.S. state that encompasses much of the Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains...
is able to receive reliable but weak signals from high-power stations such as 770KKOB
KKOB
KKOB is an AM radio station operating out of Albuquerque, New Mexico, the oldest in the state. It operates on 770 kHz with 50,000 Watts of power and is owned by Cumulus Media. The station's format is talk radio. Its brand is "News Radio 770 KKOB."...
, or 610KNML
KNML
KNML is an American radio station in Albuquerque, New Mexico. It is owned by Cumulus Media and has a sports talk format called "The Sports Animal"...
500 miles away from their towers in Albuquerque, New Mexico
Albuquerque, New Mexico
Albuquerque is the largest city in the state of New Mexico, United States. It is the county seat of Bernalillo County and is situated in the central part of the state, straddling the Rio Grande. The city population was 545,852 as of the 2010 Census and ranks as the 32nd-largest city in the U.S. As...
, due to groundwave propagation. The effectiveness of groundwave signals largely depends on ground conductivity
Ground conductivity
Ground conductivity refers to the electrical conductivity of the subsurface of the earth.-Radio propagation:Ground conductivity is an extremely important factor in determining the field strength and propagation of surface wave radio transmissions...
and higher conductivity results in better propagation. At night, the same receiver may pick up signals as far away as 1110KFAB in Nebraska
KFAB
KFAB is a 50,000 watt clear channel news and talk radio station licensed to Omaha, Nebraska. The station is owned by Clear Channel Communications. It provides a strong signal to most of eastern Nebraska during the day, and at least grade B coverage as far as Kansas City, Topeka, Sioux City and Des...
reliably, depending on atmospheric noise and man-made interference.
Some experiments and trials are planned or under way for a digital modulation such as Digital Radio Mondiale
Digital Radio Mondiale
Digital Radio Mondiale is a set of digital audio broadcasting technologies designed to work over the bands currently used for AM broadcasting, particularly shortwave...
(DRM).
Medium wave in the Americas
Initially Broadcasting in the United states was restricted to two wavelengths: "entertainment" was broadcast at 360 meters (833 kHz), with stations required to switch to 485 meters (619 kHz) when broadcasting weather forecasts, crop price reports and other government reports. This arrangement had numerous practical difficulties. Early transmitters were technically crude and virtually impossible to set accurately on their intended frequency and if (as frequently happened) two (or more) stations in the same part of the country broadcast simultaneously the resultant interference meant that usually neither could be heard clearly. The Commerce Department rarely intervened in such cases but left it up to stations to enter into voluntary timesharing agreements amongst themselves. The addition of a third "entertainment" wavelength, 400 meters, did little to solve this overcrowding.In 1923, the Commerce Department realized that as more and more stations were applying for commercial licenses, it was not practical to have every station broadcast on the same three wavelengths. On May 15, 1923, Commerce Secretary Hoover announced a new bandplan which set aside 81 frequencies, in 10 kHz steps, from 550 kHz to 1350 kHz (extended to 1500, then 1600 and ultimately 1700 kHz in later years). Each station would be assigned one frequency (albeit usually shared with stations in other parts of the country and/or abroad), no longer having to broadcast weather and government reports on a different frequency than entertainment. Class A and B stations were segregated into sub-bands.
Nowadays in most of the Americas
Americas
The Americas, or America , are lands in the Western hemisphere, also known as the New World. In English, the plural form the Americas is often used to refer to the landmasses of North America and South America with their associated islands and regions, while the singular form America is primarily...
, mediumwave broadcast stations are separated by 10 kHz and have two sideband
Sideband
In radio communications, a sideband is a band of frequencies higher than or lower than the carrier frequency, containing power as a result of the modulation process. The sidebands consist of all the Fourier components of the modulated signal except the carrier...
s of up to ± 5 kHz in theory, although in practice stations transmit audio of up to 10 kHz. In the rest of the world, the separation is 9 kHz, with sidebands of ± 4.5 kHz. Both provide adequate audio quality for voice
Human voice
The human voice consists of sound made by a human being using the vocal folds for talking, singing, laughing, crying, screaming, etc. Its frequency ranges from about 60 to 7000 Hz. The human voice is specifically that part of human sound production in which the vocal folds are the primary...
, but are insufficient for high-fidelity broadcasting, which is common on the VHF
Very high frequency
Very high frequency is the radio frequency range from 30 MHz to 300 MHz. Frequencies immediately below VHF are denoted High frequency , and the next higher frequencies are known as Ultra high frequency...
FM
Frequency modulation
In telecommunications and signal processing, frequency modulation conveys information over a carrier wave by varying its instantaneous frequency. This contrasts with amplitude modulation, in which the amplitude of the carrier is varied while its frequency remains constant...
bands. In the US and Canada the maximum transmitter power is restricted to 50 kilowatts, while in Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
there are medium wave stations with transmitter power up to 2 megawatts daytime.
Most United States AM radio stations are required by the Federal Communications Commission
Federal Communications Commission
The Federal Communications Commission is an independent agency of the United States government, created, Congressional statute , and with the majority of its commissioners appointed by the current President. The FCC works towards six goals in the areas of broadband, competition, the spectrum, the...
(FCC) to shut down, reduce power or employ a directional antenna array at night in order to avoid interference with each other due to night-time only long-distance skywave propagation ("skip"). Those stations which shut down completely at night are often known as "daytimers". Similar regulations are in force for Canadian stations, administered by Industry Canada
Industry Canada
Industry Canada is the department of the Government of Canada with responsibility for regional economic development, investment, and innovation/research and development. The department employs 6104 FTEs across Canada....
.
Medium wave in Europe
In Europe, each country is allocated a number of frequencies on which high power (up to 2 MW) can be used; the maximum power is also subject to international agreement by the International Telecommunication Union ITU . In most cases there are two power limits: a lower one for omnidirectionalOmnidirectional antenna
In radio communication, an omnidirectional antenna is an antenna which radiates radio wave power uniformly in all directions in one plane, with the radiated power decreasing with elevation angle above or below the plane, dropping to zero on the antenna's axis. This radiation pattern is often...
and a higher one for directional
Directional antenna
A directional antenna or beam antenna is an antenna which radiates greater power in one or more directions allowing for increased performance on transmit and receive and reduced interference from unwanted sources....
radiation with minima in certain directions. The power limit can also be depending on daytime and it is possible, that a station may not work at nighttime, because it would then produce too much interference. Other countries may only operate low-powered transmitters on the same frequency, again subject to agreement. For example, Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
operates a high-powered transmitter, located in its Kaliningrad
Kaliningrad
Kaliningrad is a seaport and the administrative center of Kaliningrad Oblast, the Russian exclave between Poland and Lithuania on the Baltic Sea...
exclave and used for external broadcasting, on 1386 kHz. The same frequency is also used by low-powered local radio stations in the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
, which has approximately 250 medium-wave transmitters of 1 kW and over; other parts of the United Kingdom can still receive the Russian broadcast. International mediumwave broadcasting in Europe has decreased markedly with the end of the Cold War
Cold War
The Cold War was the continuing state from roughly 1946 to 1991 of political conflict, military tension, proxy wars, and economic competition between the Communist World—primarily the Soviet Union and its satellite states and allies—and the powers of the Western world, primarily the United States...
and the increased availability of satellite and Internet TV and radio, although the cross-border reception of neighbouring countries' broadcasts by expatriates and other interested listeners still takes place.
Due to the high demand for frequencies in Europe, many countries operate single frequency networks; in Britain, BBC Radio Five Live
BBC Radio Five Live
BBC Radio 5 Live is the BBC's national radio service that specialises in live BBC News, phone-ins, and sports commentaries...
broadcasts from various transmitters on either 693 or 909 kHz. These transmitters are carefully synchronized to minimize interference from more distant transmitters on the same frequency.
Overcrowding on the Medium wave band is a serious problem in parts of Europe contributing to the early adoption of VHF
Very high frequency
Very high frequency is the radio frequency range from 30 MHz to 300 MHz. Frequencies immediately below VHF are denoted High frequency , and the next higher frequencies are known as Ultra high frequency...
FM broadcasting
FM broadcasting
FM broadcasting is a broadcasting technology pioneered by Edwin Howard Armstrong which uses frequency modulation to provide high-fidelity sound over broadcast radio. The term "FM band" describes the "frequency band in which FM is used for broadcasting"...
by many stations (particularly in Germany). However in recent years several European countries (Including Ireland
Republic of Ireland
Ireland , described as the Republic of Ireland , is a sovereign state in Europe occupying approximately five-sixths of the island of the same name. Its capital is Dublin. Ireland, which had a population of 4.58 million in 2011, is a constitutional republic governed as a parliamentary democracy,...
, Poland
Poland
Poland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north...
and, to a lesser extent Switzerland
Switzerland
Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....
) have started moving away from Medium wave altogether with most/all services moving exclusively to other bands (usually VHF).
Stereo and digital radio transmissions on medium wave
Stereo transmission is possible and offered by some stations in the U.S., Canada, Mexico, the Dominican Republic, Paraguay, Australia, The Philippines, Japan, South Korea, South Africa, and France. However, there are multiple standards for AM stereoAM stereo
AM stereo is a term given to a series of mutually incompatible techniques for wireless radio broadcasting stereo audio in the AM band in a manner that is compatible with standard AM receivers...
with C-QUAM
C-QUAM
C-QUAM is the method of AM stereo broadcasting used in Canada, the United States and most other countries. It was invented in 1977 by Norman Parker, Francis Hilbert, and Yoshio Sakaie, and published in an IEEE journal....
being the most common in the United States as well as other countries, and receivers that implement the technologies are relatively rare.
In September 2002, the United States Federal Communications Commission
Federal Communications Commission
The Federal Communications Commission is an independent agency of the United States government, created, Congressional statute , and with the majority of its commissioners appointed by the current President. The FCC works towards six goals in the areas of broadband, competition, the spectrum, the...
approved the proprietary iBiquity
IBiquity
iBiquity Digital Corporation is a company formed by the merger of USA Digital Radio and Lucent Digital Radio, with the goal of creating an in-band on-channel digital radio system for the United States and around the world...
in-band on-channel
In-band on-channel
In-band on-channel is a hybrid method of transmitting digital radio and analog radio broadcast signals simultaneously on the same frequency....
(IBOC) HD Radio
HD Radio
HD Radio, which originally stood for "Hybrid Digital", is the trademark for iBiquity's in-band on-channel digital radio technology used by AM and FM radio stations to transmit audio and data via a digital signal in conjunction with their analog signals...
system of digital audio broadcasting
Digital audio broadcasting
Digital Audio Broadcasting is a digital radio technology for broadcasting radio stations, used in several countries, particularly in Europe. As of 2006, approximately 1,000 stations worldwide broadcast in the DAB format....
, which is meant to improve the audio quality of signals. The Digital Radio Mondiale
Digital Radio Mondiale
Digital Radio Mondiale is a set of digital audio broadcasting technologies designed to work over the bands currently used for AM broadcasting, particularly shortwave...
(DRM) IBOC system has been approved by the ITU
International Telecommunication Union
The International Telecommunication Union is the specialized agency of the United Nations which is responsible for information and communication technologies...
for use outside North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
and U.S. territories
United States territory
United States territory is any extent of region under the jurisdiction of the federal government of the United States, including all waters including all U.S. Naval carriers. The United States has traditionally proclaimed the sovereign rights for exploring, exploiting, conserving, and managing its...
.
Antennas
For transmission, mast radiatorMast radiator
A mast radiator is a radio mast or tower in which the whole structure itself functions as an antenna. This design is commonly used for transmitting antennas operating at low frequencies, in the VLF, LF and MF ranges, in particular those used for AM broadcasting. The metal mast is electrically...
s are most commonly used. Stations broadcasting with low power can use masts with heights of a quarter-wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
, while high power stations mostly use half-wavelength. The usage of masts longer than 5/8 of radiated wavelength gives a bad radiation pattern. Usually mast antennas are insulated against ground and show a high voltage against ground during transmission, which complicates maintenance, installation of air safety warning lights or using the mast as a tower for UHF/VHF-radio, but there are several ways to use grounded masts or towers.
If grounded masts or towers are required, then cage aerial
Cage aerial
A Cage aerial is a radio antenna, which consists of the top portion of a tower or mast and of several parallel wires, which are radially arranged around the lower part of the mast. one advantage of the cage aerial is that the supporting tower can be grounded, allowing it to be used for other radio...
s or long-wire aerials are used. Another possibility consists of feeding the mast or the tower by cables running from the tuning unit to the guys or crossbars in a certain height. Directional aerials consist of multiple masts
Tower array
A tower array is an arrangement of multiple radio towers which are mast radiators in a phased array. Tower arrays can consist of free-standing or guyed towers or a mix of them....
, which need not to be from the same height. It is also possible to realize directional aerials for mediumwave with cage aerials where some parts of the cage are fed with a certain phase difference.
For medium-wave (AM) broadcasting, quarter-wave masts are between 153 ft and 463 ft high, depending on the frequency. Because quarter-wave masts are so large they can be unnecessarily costly and uneconomic, and other types are more commonly used on medium wave for local broadcast stations of under 5 kW, examples being T- and L-antennas. The design of these smaller antennas uses the technique commonly used on Long Wave
Longwave
In radio, longwave refers to parts of radio spectrum with relatively long wavelengths. The term is a historic one dating from the early 20th century, when the radio spectrum was considered to consist of long, medium and short wavelengths...
to allow smaller masts to be used. In this method the mast size is reduced, producing less radiation resistance
Radiation resistance
Radiation resistance is that part of an antenna's feedpoint resistance that is caused by the radiation of electromagnetic waves from the antenna. The radiation resistance is determined by the geometry of the antenna, not by the materials of which it is made...
and increased reactance
Reactance
Reactance is the opposition of a circuit element to a change of electric current or voltage, due to that element's capacitance or inductance. A built-up electric field resists the change of voltage on the element, while a magnetic field resists the change of current...
, and wires are added, supported by the same mast or masts, to compensate these deficiencies adequately. The details depend on the requirement for grounded or insulated towers and masts. The dimensions can and must be calculated accurately to meet the required specifications in bandwidth, power handling and radiation efficiency.
A popular choice for lower-powered stations is the umbrella antenna
Umbrella antenna
An umbrella antenna is a top-loaded electrically lengthened monopole antenna, consisting in most cases of a mast fed against ground, to which six or more wires are connected at the top, sloping downwards...
, which needs only one mast one tenth wavelength or less in height. This antenna uses a single mast insulated from ground and fed at the lower end against ground. In that sense it is a simple monopole, but at the top of the mast extra wires are connected (usually about six) which slope downwards at an angle of 40-45 degrees as far as about one-third of the total height, where they are terminated in insulators and thence outwards to ground anchors. Thus the umbrella antenna can use the guy wires as part of the antenna.
In some rare cases dipole antenna
Dipole antenna
A dipole antenna is a radio antenna that can be made of a simple wire, with a center-fed driven element. It consists of two metal conductors of rod or wire, oriented parallel and collinear with each other , with a small space between them. The radio frequency voltage is applied to the antenna at...
s are used, which are slung between two masts or towers. Such antennas are intended to radiate a skywave
Skywave
Skywave is the propagation of electromagnetic waves bent back to the Earth's surface by the ionosphere. As a result of skywave propagation, a broadcast signal from a distant AM broadcasting station at night, or from a shortwave radio station can sometimes be heard as clearly as local...
. The medium-wave transmitter at Berlin-Britz
Transmitter Berlin-Britz
Transmitter Berlin-Britz is a broadcasting facility for medium wave, shortwave and FM on the site of a former tree nursery in Berlin-Britz. It was established in 1946 and until 1993 it was the most important transmitter of RIAS. It is now used by Deutschlandradio.The Berlin-Britz transmitter...
for transmitting RIAS used a cross dipole mounted on five 30.5 metre high guyed masts to transmit the skywave to the ionosphere at nighttime.
Europe's largest antenna park is placed in Northern Jutland, Denmark. The well-known German DX'er Wilhelm Herbst has constructed and built the antennas. DXers are welcome to use the facilities.
For low-noise reception at frequencies below 1.6 MHz, which includes long and medium waves, loop antennas are popular because of their ability to reject locally generated noise. This class of antennas includes the ferrite-rod antenna, also known as a loopstick antenna, which is by far the most common antenna in use for broadcast reception throughout the world. Transistor radios contain a loopstick as the receiving antenna.
See also
- Medium frequencyMedium frequencyMedium frequency refers to radio frequencies in the range of 300 kHz to 3 MHz. Part of this band is the medium wave AM broadcast band. The MF band is also known as the hectometer band or hectometer wave as the wavelengths range from ten down to one hectometers...
band, of which the medium wave band forms a part. - AM radioAM broadcastingAM broadcasting is the process of radio broadcasting using amplitude modulation. AM was the first method of impressing sound on a radio signal and is still widely used today. Commercial and public AM broadcasting is carried out in the medium wave band world wide, and on long wave and short wave...
- LongwaveLongwaveIn radio, longwave refers to parts of radio spectrum with relatively long wavelengths. The term is a historic one dating from the early 20th century, when the radio spectrum was considered to consist of long, medium and short wavelengths...
- MW DXMW DXMW DX, short for mediumwave DXing, is the hobby of receiving the reception of distant mediumwave radio stations. MW DX is similar to TV and FM DX in that broadcast band stations are the reception targets...
- ShortwaveShortwaveShortwave radio refers to the upper MF and all of the HF portion of the radio spectrum, between 1,800–30,000 kHz. Shortwave radio received its name because the wavelengths in this band are shorter than 200 m which marked the original upper limit of the medium frequency band first used...
- FM radioFM broadcastingFM broadcasting is a broadcasting technology pioneered by Edwin Howard Armstrong which uses frequency modulation to provide high-fidelity sound over broadcast radio. The term "FM band" describes the "frequency band in which FM is used for broadcasting"...
- Satellite radioSatellite radioSatellite radio is an analogue or digital radio signal that is relayed through one or more satellites and thus can be received in a much wider geographical area than terrestrial FM radio stations...
- List of European medium wave transmitters
- Wave plan of GenevaWave plan of GenevaThe Geneva Frequency Plan of 1975 is the internationally agreed frequency plan which was drawn up to implement the provisions of the Final Acts of the Regional Administrative LF/MF Broadcasting Conference held in Geneva, Switzerland, in...
External links
- "Building the Broadcast Band" the development of the 520-1700 kHz MW (AM) band
- M3 Map of Effective Ground Conductivity in the USA
- MWLIST worldwide database of MW and LW stations
- www.mwcircle.org The Mediumwave Circle. A UK-based club for Mediumwave DXDX-In science and medicine:* Diagnosis, medical shorthand symbol generally written as Dx or Dx* The DX molecule or motif, used in DNA nanotechnology* Digital radiography, an abbreviation used in the DICOM standard-In technology and the Internet:...
'ers and enthusiasts. - http://www.mwlist.org/mwlist_quick_and_easy.php?area=1&kHz=153 - List of long- and mediumwave transmitters with GoogleMap-Links to transmission sites