Radio jamming
Encyclopedia
Radio jamming is the transmission of radio
signals that disrupt communications
by decreasing the signal to noise ratio. Unintentional jamming occurs when an operator transmits on a busy frequency
without first checking whether it is in use, or without being able to hear stations using the frequency. Another form of unintentional jamming occurs when equipment accidentally radiates
a signal, such as a cable TV plant that accidentally emits on an aircraft
emergency frequency.
The concept can be used in wireless data network
s to disrupt information flow. It is a common form of censorship in totalitarian countries, in order to prevent foreign radio stations in border areas from reaching the country.
.
signals to disrupt control of a battle. A transmitter
, tuned to the same frequency as the opponents' receiving equipment and with the same type of modulation
, can, with enough power, override
any signal at the receiver
.
The most common types of this form of signal jamming are random noise, random pulse, stepped tones, warbler, random keyed modulated CW
, tone, rotary, pulse, spark, recorded sounds, gulls, and sweep-through. These can be divided into two groups – obvious and subtle.
Obvious jamming is easy to detect because it can be heard on the receiving equipment. It usually is some type of noise such as stepped tones (bagpipes), random-keyed code, pulses, music (often distorted), erratically warbling tones, highly distorted speech, random noise (hiss) and recorded sounds. Various combinations of these methods may be used often accompanied by regular morse
identification signal to enable individual transmitters to be identified in order to assess their effectiveness. For example, China, which used jamming extensively and still does, plays a loop of traditional Chinese music while it is jamming channels (c.f. Attempted jamming of number stations).
The purpose of this type of jamming is to block out reception of transmitted signals and to cause a nuisance to the receiving operator. One early Soviet attempt at jamming western broadcasters used the noise from the diesel generator that was powering the jamming transmitter.
Subtle jamming is jamming during which no sound is heard on the receiving equipment. The radio does not receive incoming signals yet everything seems superficially normal to the operator. These are often technical attacks on modern equipment, such as "squelch capture". Thanks to FM capture effect
, Frequency Modulated broadcasts may be jammed, unnoticed, by a simple unmodulated carrier.
ground radio operators would attempt to mislead pilots by false instructions in their own language, in what was more precisely a spoofing attack
than jamming. Radar jamming is also important to disrupt use of radar
used to guide an enemy's missiles or aircraft. Modern secure communication techniques use such methods as spread spectrum
modulation to resist the deleterious effects of jamming.
Jamming of foreign radio broadcast
stations has often been used in wartime (and during periods of tense international relations) to prevent or deter citizens from listening to broadcasts from enemy countries. However such jamming is usually of limited effectiveness because the affected stations usually change frequencies, put on additional frequencies and/or increase transmission power.
Jamming has also occasionally been used by the Governments of Germany
(during WW2), Israel
, Cuba
, Iraq
, Iran
(Iraq and Iran war, 1980–1988), China
, North and South Korea
and several Latin American countries, as well as by Ireland
against pirate radio
stations such as Radio Nova
. http://www.radiowaves.fm/history5.shtml The United Kingdom
government used two coordinated, separately located transmitters to jam the offshore radio
ship, Radio North Sea International
off the coast of Britain in 1970.
and other allied stations. Along with increasing transmitter
power and adding extra frequencies, attempts were made to counteract the jamming by dropping leaflets
over cities instructing listeners to construct a directional loop aerial
that would enable them to hear the stations through the jamming. In the Netherlands such aerials were nicknamed "moffenzeef" (English: "kraut sieve" )
Soviet (and Eastern Bloc) jamming of some Western broadcasters led to a "power race" in which broadcasters and jammers alike repeatedly increased their transmission power, utilised highly directional
antennas and added extra frequencies to the already heavily overcrowded shortwave
bands to such an extent that many broadcasters not directly targeted by the jammers (including pro-Soviet stations) suffered from the rising levels of noise and interference.
A further method used was operating transmitters for domestic radio stations on the same or nearby frequencies. For example, for many years East Germany operated at Wiederau
a transmitter on the same mediumwave frequency (575 kHz) that Mühlacker radio transmitter used with an output power of 100 kW, which made it difficult to receive the AFN
Mühlacker radio transmitter in much of the East Germany.
Radio Free Europe
and its sister service Radio Liberty were the main target of Soviet jammers followed by Voice of America
and the BBC World Service
.
Other stations targeted by the Soviet jammers (but not to the same extent as RFE/RL/VOA/BBC) included Deutsche Welle
and occasionally Radio Vaticana, Kol Yisrael
and Radio Canada International
. The jamming usually only took place during programming in languages widely spoken in Eastern Bloc countries (e.g., Russian
, Polish
, Czech
, Lithuanian
, etc.). Programmes in English
or other major Western languages were rarely (if ever) jammed intentionally.
There were also periods when China
and the USSR jammed each other's programmes. The USSR also jammed Albanian programmes at times.
Some parts of the world were more impacted by these broadcasting practices than others
Meanwhile some listeners in the Soviet union and Eastern bloc
devised ingenious methods (such as homemade directional loop antennas) to hear the Western stations through the noise. Because radio signal radio propagation
on shortwave
can be difficult to predict reliably listeners sometimes found that there were days/times when the jamming was particularly ineffective because radio fading (due to atmospheric conditions
) was affecting the jamming signals but favouring the broadcasts. On other days of course the reverse was the case. There were also times when jamming transmitters were (temporarily) off air due to breakdowns or maintenance. The Soviets (and most of their Eastern bloc allies) used two types of jamming transmitter. Skywave
jamming covered a large area but for the reasons described was of limited effectiveness. Groundwave jamming was more effective but only over a small area and was thus only used in/near major cities throughout the Eastern bloc
. Both types of jamming were less effective on higher shortwave frequencies (above 15 MHz) however many radios in the USSR didn't cover the higher bands. Skywave jamming was usually accompanied by morse
signals in order to enable (coded) identification of the jamming station in order that Soviet monitoring posts could assess the effectiveness of each station.
In 1987 after decades of generally refusing to acknowledge that such jamming was even taking place the Soviets finally stopped jamming western broadcasts with the exception of RFE/RL
which continued to be jammed for several months into 1988. Previously there had been periods when some individual Eastern bloc countries refrained from jamming Western broadcasts but this varied widely by time and country. In general outside of the USSR itself Bulgaria was one of the most prolific operators of jamming transmitters in the Eastern bloc with East Germany the least.
While western governments may have occasionally considered jamming broadcasts from Eastern Bloc
stations, it was generally accepted that doing so would be a pointless exercise. Ownership of shortwave
radios was less common in western countries than in the USSR where due to the vast physical size of the country many domestic stations
were relayed on shortwave as it was the only practical way to cover remote areas. Additionally western governments were generally less afraid of intellectual competition from the communist bloc.
However in Latin America
there were instances of communist radio stations such as Radio Venceremos
being jammed, allegedly by the CIA
, while there were short lived instances where Britain
jammed some Egypt
ian (during the Suez crisis
), Greek (Prior to Cyprus
gaining independence) and Rhodesia
n stations.
acquired standard short-wave radio-broadcasting equipment designed for general public radio-broadcasting and technical support from Thales Broadcast Multimedia, a former subsidiary of the French
state-owned company Thales Group
.
has frequently used jamming of satellite TV (as well as filtering the Internet and restricting Internet connectivity speed and other methods) as a strategy to prevent the consequences of freedom of expression in the last decade. Most of the jamming took place in the year 2009 after the controversial presidential election in Iran to control the flow of information and updates about the protests. Although most of the jamming is done on news channels or political ones, another famous series of jamming started around July 2010 on a non-political, Persian language satellite TV channel called "Farsi1" which airs Persian-dubbed popular TV series.
Radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...
signals that disrupt communications
Telecommunication
Telecommunication is the transmission of information over significant distances to communicate. In earlier times, telecommunications involved the use of visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, and optical heliographs, or audio messages via coded...
by decreasing the signal to noise ratio. Unintentional jamming occurs when an operator transmits on a busy frequency
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
without first checking whether it is in use, or without being able to hear stations using the frequency. Another form of unintentional jamming occurs when equipment accidentally radiates
Radiation
In physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing...
a signal, such as a cable TV plant that accidentally emits on an aircraft
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...
emergency frequency.
The concept can be used in wireless data network
Wireless network
Wireless network refers to any type of computer network that is not connected by cables of any kind. It is a method by which homes, telecommunications networks and enterprise installations avoid the costly process of introducing cables into a building, or as a connection between various equipment...
s to disrupt information flow. It is a common form of censorship in totalitarian countries, in order to prevent foreign radio stations in border areas from reaching the country.
Distinction between "jamming" and "interference"
Originally the terms were used interchangeably but nowadays most radio users use the term "jamming" to describe the deliberate use of radio noise or signals in an attempt to disrupt communications (or prevent listening to broadcasts) whereas the term "interference" is used to describe unintentional forms of disruption (which are far more common). However the distinction is still not universally applied. For inadvertent disruptions, see electromagnetic compatibilityElectromagnetic compatibility
Electromagnetic compatibility is the branch of electrical sciences which studies the unintentional generation, propagation and reception of electromagnetic energy with reference to the unwanted effects that such energy may induce...
.
Method
Intentional communications jamming is usually aimed at radioRadio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...
signals to disrupt control of a battle. A transmitter
Transmitter
In electronics and telecommunications a transmitter or radio transmitter is an electronic device which, with the aid of an antenna, produces radio waves. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. When excited by this alternating...
, tuned to the same frequency as the opponents' receiving equipment and with the same type of modulation
Modulation
In electronics and telecommunications, modulation is the process of varying one or more properties of a high-frequency periodic waveform, called the carrier signal, with a modulating signal which typically contains information to be transmitted...
, can, with enough power, override
Override
Override may refer to:* Override * OverRide * Overriders, an insurance term* Overriding * Manual override, a function where an automated system is placed under manual control...
any signal at the receiver
Receiver (radio)
A radio receiver converts signals from a radio antenna to a usable form. It uses electronic filters to separate a wanted radio frequency signal from all other signals, the electronic amplifier increases the level suitable for further processing, and finally recovers the desired information through...
.
The most common types of this form of signal jamming are random noise, random pulse, stepped tones, warbler, random keyed modulated CW
Continuous wave
A continuous wave or continuous waveform is an electromagnetic wave of constant amplitude and frequency; and in mathematical analysis, of infinite duration. Continuous wave is also the name given to an early method of radio transmission, in which a carrier wave is switched on and off...
, tone, rotary, pulse, spark, recorded sounds, gulls, and sweep-through. These can be divided into two groups – obvious and subtle.
Obvious jamming is easy to detect because it can be heard on the receiving equipment. It usually is some type of noise such as stepped tones (bagpipes), random-keyed code, pulses, music (often distorted), erratically warbling tones, highly distorted speech, random noise (hiss) and recorded sounds. Various combinations of these methods may be used often accompanied by regular morse
Morse code
Morse code is a method of transmitting textual information as a series of on-off tones, lights, or clicks that can be directly understood by a skilled listener or observer without special equipment...
identification signal to enable individual transmitters to be identified in order to assess their effectiveness. For example, China, which used jamming extensively and still does, plays a loop of traditional Chinese music while it is jamming channels (c.f. Attempted jamming of number stations).
The purpose of this type of jamming is to block out reception of transmitted signals and to cause a nuisance to the receiving operator. One early Soviet attempt at jamming western broadcasters used the noise from the diesel generator that was powering the jamming transmitter.
Subtle jamming is jamming during which no sound is heard on the receiving equipment. The radio does not receive incoming signals yet everything seems superficially normal to the operator. These are often technical attacks on modern equipment, such as "squelch capture". Thanks to FM capture effect
Capture effect
In telecommunication, the capture effect, or FM capture effect, is a phenomenon associated with FM reception in which only the stronger of two signals at, or near, the same frequency will be demodulated....
, Frequency Modulated broadcasts may be jammed, unnoticed, by a simple unmodulated carrier.
History
During World War IIWorld War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
ground radio operators would attempt to mislead pilots by false instructions in their own language, in what was more precisely a spoofing attack
Spoofing attack
In the context of network security, a spoofing attack is a situation in which one person or program successfully masquerades as another by falsifying data and thereby gaining an illegitimate advantage.- Spoofing and TCP/IP :...
than jamming. Radar jamming is also important to disrupt use of radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
used to guide an enemy's missiles or aircraft. Modern secure communication techniques use such methods as spread spectrum
Spread spectrum
Spread-spectrum techniques are methods by which a signal generated in a particular bandwidth is deliberately spread in the frequency domain, resulting in a signal with a wider bandwidth...
modulation to resist the deleterious effects of jamming.
Jamming of foreign radio broadcast
Broadcasting
Broadcasting is the distribution of audio and video content to a dispersed audience via any audio visual medium. Receiving parties may include the general public or a relatively large subset of thereof...
stations has often been used in wartime (and during periods of tense international relations) to prevent or deter citizens from listening to broadcasts from enemy countries. However such jamming is usually of limited effectiveness because the affected stations usually change frequencies, put on additional frequencies and/or increase transmission power.
Jamming has also occasionally been used by the Governments of Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
(during WW2), Israel
Israel
The State of Israel is a parliamentary republic located in the Middle East, along the eastern shore of the Mediterranean Sea...
, Cuba
Cuba
The Republic of Cuba is an island nation in the Caribbean. The nation of Cuba consists of the main island of Cuba, the Isla de la Juventud, and several archipelagos. Havana is the largest city in Cuba and the country's capital. Santiago de Cuba is the second largest city...
, Iraq
Iraq
Iraq ; officially the Republic of Iraq is a country in Western Asia spanning most of the northwestern end of the Zagros mountain range, the eastern part of the Syrian Desert and the northern part of the Arabian Desert....
, Iran
Iran
Iran , officially the Islamic Republic of Iran , is a country in Southern and Western Asia. The name "Iran" has been in use natively since the Sassanian era and came into use internationally in 1935, before which the country was known to the Western world as Persia...
(Iraq and Iran war, 1980–1988), China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
, North and South Korea
Korea
Korea ) is an East Asian geographic region that is currently divided into two separate sovereign states — North Korea and South Korea. Located on the Korean Peninsula, Korea is bordered by the People's Republic of China to the northwest, Russia to the northeast, and is separated from Japan to the...
and several Latin American countries, as well as by Ireland
Ireland
Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...
against pirate radio
Pirate radio
Pirate radio is illegal or unregulated radio transmission. The term is most commonly used to describe illegal broadcasting for entertainment or political purposes, but is also sometimes used for illegal two-way radio operation...
stations such as Radio Nova
Radio Nova (Ireland)
Radio Nova was a pirate radio station broadcasting from Dublin, Ireland. Owned and operated by the UK pirate radio veteran Chris Cary, the station’s first broadcasts were during the summer of 1981 on 88.5mhz FM and 819khz AM.-Early history:...
. http://www.radiowaves.fm/history5.shtml 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...
government used two coordinated, separately located transmitters to jam the offshore radio
Offshore radio
Offshore radio is radio broadcasting from ships or fixed maritime structures, usually in international waters. The claimed first wireless broadcast of music and speech for the purpose of entertainment was transmitted from a Royal Naval craft, the HMS Andromeda, in 1907...
ship, Radio North Sea International
Radio North Sea International
Radio North Sea International also known as Radio Nordsee International in German and Radio Noordzee Internationaal in Dutch, was a European offshore radio station, run by the Swiss firm Mebo Telecommunications, jointly owned by Swiss engineer, Edwin Bollier, and his business partner, Erwin Meister...
off the coast of Britain in 1970.
World War II
In occupied Europe the Nazis attempted to jam broadcasts to the continent from the BBCBBC World Service
The BBC World Service is the world's largest international broadcaster, broadcasting in 27 languages to many parts of the world via analogue and digital shortwave, internet streaming and podcasting, satellite, FM and MW relays...
and other allied stations. Along with increasing transmitter
Transmitter
In electronics and telecommunications a transmitter or radio transmitter is an electronic device which, with the aid of an antenna, produces radio waves. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. When excited by this alternating...
power and adding extra frequencies, attempts were made to counteract the jamming by dropping leaflets
Airborne leaflet propaganda
Airborne leaflet propaganda is a form of psychological warfare in which leaflets are scattered in the air. Military forces have used aircraft to drop leaflets to alter the behavior of people in enemy-controlled territory, sometimes in conjunction with air strikes...
over cities instructing listeners to construct a directional loop aerial
Loop antenna
A loop antenna is a radio antenna consisting of a loop of wire, tubing, or other electrical conductor with its ends connected to a balanced transmission line...
that would enable them to hear the stations through the jamming. In the Netherlands such aerials were nicknamed "moffenzeef" (English: "kraut sieve" )
Cold War era
During much of the Cold WarCold 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...
Soviet (and Eastern Bloc) jamming of some Western broadcasters led to a "power race" in which broadcasters and jammers alike repeatedly increased their transmission power, utilised highly directional
HRS type antennas
HRS type antennas are more or less the standard antenna used for long distance high power shortwave broadcasting .- History of HRS design :...
antennas and added extra frequencies to the already heavily overcrowded shortwave
Shortwave
Shortwave 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...
bands to such an extent that many broadcasters not directly targeted by the jammers (including pro-Soviet stations) suffered from the rising levels of noise and interference.
A further method used was operating transmitters for domestic radio stations on the same or nearby frequencies. For example, for many years East Germany operated at Wiederau
Wiederau transmitter
The Wiederau transmitter is the oldest broadcasting facility in Saxony. It is located near Wiederau, a village which is part of the municipality of Pegau, and is used for medium-wave, FM and Television broadcasting....
a transmitter on the same mediumwave frequency (575 kHz) that Mühlacker radio transmitter used with an output power of 100 kW, which made it difficult to receive the AFN
American Forces Network
The American Forces Network is the brand name used by the United States Armed Forces American Forces Radio and Television Service for its entertainment and command internal information networks worldwide...
Mühlacker radio transmitter in much of the East Germany.
Radio Free Europe
Radio Free Europe
Radio Free Europe/Radio Liberty is a broadcaster funded by the U.S. Congress that provides news, information, and analysis to countries in Eastern Europe, Central Asia, and the Middle East "where the free flow of information is either banned by government authorities or not fully developed"...
and its sister service Radio Liberty were the main target of Soviet jammers followed by Voice of America
Voice of America
Voice of America is the official external broadcast institution of the United States federal government. It is one of five civilian U.S. international broadcasters working under the umbrella of the Broadcasting Board of Governors . VOA provides a wide range of programming for broadcast on radio...
and the BBC World Service
BBC World Service
The BBC World Service is the world's largest international broadcaster, broadcasting in 27 languages to many parts of the world via analogue and digital shortwave, internet streaming and podcasting, satellite, FM and MW relays...
.
Other stations targeted by the Soviet jammers (but not to the same extent as RFE/RL/VOA/BBC) included Deutsche Welle
Deutsche Welle
Deutsche Welle or DW, is Germany's international broadcaster. The service is aimed at the overseas market. It broadcasts news and information on shortwave, Internet and satellite radio on 98.7 DZFE in 30 languages . It has a satellite television service , that is available in four languages, and...
and occasionally Radio Vaticana, Kol Yisrael
Kol Yisrael
Kol Yisrael is Israel's public domestic and international radio service, operated as a division of the Israel Broadcasting Authority.-History:...
and Radio Canada International
Radio Canada International
Radio Canada International is the international broadcasting service of the Canadian Broadcasting Corporation . Until 1970, it was known as the CBC International Service and was sometimes referred to as the "Voice of Canada" in its early years.- The early years :The idea for creating an...
. The jamming usually only took place during programming in languages widely spoken in Eastern Bloc countries (e.g., Russian
Russian language
Russian is a Slavic language used primarily in Russia, Belarus, Uzbekistan, Kazakhstan, Tajikistan and Kyrgyzstan. It is an unofficial but widely spoken language in Ukraine, Moldova, Latvia, Turkmenistan and Estonia and, to a lesser extent, the other countries that were once constituent republics...
, Polish
Polish language
Polish is a language of the Lechitic subgroup of West Slavic languages, used throughout Poland and by Polish minorities in other countries...
, Czech
Czech language
Czech is a West Slavic language with about 12 million native speakers; it is the majority language in the Czech Republic and spoken by Czechs worldwide. The language was known as Bohemian in English until the late 19th century...
, Lithuanian
Lithuanian language
Lithuanian is the official state language of Lithuania and is recognized as one of the official languages of the European Union. There are about 2.96 million native Lithuanian speakers in Lithuania and about 170,000 abroad. Lithuanian is a Baltic language, closely related to Latvian, although they...
, etc.). Programmes in English
English language
English is a West Germanic language that arose in the Anglo-Saxon kingdoms of England and spread into what was to become south-east Scotland under the influence of the Anglian medieval kingdom of Northumbria...
or other major Western languages were rarely (if ever) jammed intentionally.
There were also periods when China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
and the USSR jammed each other's programmes. The USSR also jammed Albanian programmes at times.
Some parts of the world were more impacted by these broadcasting practices than others
- EurasiaEurasiaEurasia is a continent or supercontinent comprising the traditional continents of Europe and Asia ; covering about 52,990,000 km2 or about 10.6% of the Earth's surface located primarily in the eastern and northern hemispheres...
(worst affected, including mediumwaveMediumwaveMedium wave is the part of the medium frequency radio band used mainly for AM radio broadcasting. For Europe the MW band ranges from 526.5 kHz to 1606.5 kHz...
frequencies particularly 720 kHz used by RFE) - North AsiaNorth AsiaNorth Asia or Northern Asia is a subregion of Asia, consisting of the Asian portion of Russia.The Phillips Illustrated Atlas of the World 1988 defines it as being most of the former USSR, the part that is to the east of the Ural Mountains...
, AmericasAmericasThe 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...
and Sub-Saharan AfricaAfricaAfrica is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
(partly affected) - AustralasiaAustralasiaAustralasia is a region of Oceania comprising Australia, New Zealand, the island of New Guinea, and neighbouring islands in the Pacific Ocean. The term was coined by Charles de Brosses in Histoire des navigations aux terres australes...
, South AmericaSouth AmericaSouth America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
(rarely affected)
Meanwhile some listeners in the Soviet union and Eastern bloc
Eastern bloc
The term Eastern Bloc or Communist Bloc refers to the former communist states of Eastern and Central Europe, generally the Soviet Union and the countries of the Warsaw Pact...
devised ingenious methods (such as homemade directional loop antennas) to hear the Western stations through the noise. Because radio signal radio propagation
Radio propagation
Radio propagation is the behavior of radio waves when they are transmitted, or propagated from one point on the Earth to another, or into various parts of the atmosphere...
on shortwave
Shortwave
Shortwave 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...
can be difficult to predict reliably listeners sometimes found that there were days/times when the jamming was particularly ineffective because radio fading (due to atmospheric conditions
Ionosphere
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...
) was affecting the jamming signals but favouring the broadcasts. On other days of course the reverse was the case. There were also times when jamming transmitters were (temporarily) off air due to breakdowns or maintenance. The Soviets (and most of their Eastern bloc allies) used two types of jamming transmitter. 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...
jamming covered a large area but for the reasons described was of limited effectiveness. Groundwave jamming was more effective but only over a small area and was thus only used in/near major cities throughout the Eastern bloc
Eastern bloc
The term Eastern Bloc or Communist Bloc refers to the former communist states of Eastern and Central Europe, generally the Soviet Union and the countries of the Warsaw Pact...
. Both types of jamming were less effective on higher shortwave frequencies (above 15 MHz) however many radios in the USSR didn't cover the higher bands. Skywave jamming was usually accompanied by morse
Morse code
Morse code is a method of transmitting textual information as a series of on-off tones, lights, or clicks that can be directly understood by a skilled listener or observer without special equipment...
signals in order to enable (coded) identification of the jamming station in order that Soviet monitoring posts could assess the effectiveness of each station.
In 1987 after decades of generally refusing to acknowledge that such jamming was even taking place the Soviets finally stopped jamming western broadcasts with the exception of RFE/RL
Radio Free Europe
Radio Free Europe/Radio Liberty is a broadcaster funded by the U.S. Congress that provides news, information, and analysis to countries in Eastern Europe, Central Asia, and the Middle East "where the free flow of information is either banned by government authorities or not fully developed"...
which continued to be jammed for several months into 1988. Previously there had been periods when some individual Eastern bloc countries refrained from jamming Western broadcasts but this varied widely by time and country. In general outside of the USSR itself Bulgaria was one of the most prolific operators of jamming transmitters in the Eastern bloc with East Germany the least.
While western governments may have occasionally considered jamming broadcasts from Eastern Bloc
Warsaw Pact
The Warsaw Treaty Organization of Friendship, Cooperation, and Mutual Assistance , or more commonly referred to as the Warsaw Pact, was a mutual defense treaty subscribed to by eight communist states in Eastern Europe...
stations, it was generally accepted that doing so would be a pointless exercise. Ownership of shortwave
Shortwave
Shortwave 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...
radios was less common in western countries than in the USSR where due to the vast physical size of the country many domestic stations
Broadcasting in the Soviet Union
Broadcasting in the Soviet Union was owned by the state, and was under its tight control and Soviet censorship.Broadcasting's governing body in the Soviet Union was the "USSR State Committee for Television and Radio Broadcasting", or USSR Gosteleradio , which was in charge both of Soviet TV and...
were relayed on shortwave as it was the only practical way to cover remote areas. Additionally western governments were generally less afraid of intellectual competition from the communist bloc.
However in Latin America
Latin America
Latin America is a region of the Americas where Romance languages – particularly Spanish and Portuguese, and variably French – are primarily spoken. Latin America has an area of approximately 21,069,500 km² , almost 3.9% of the Earth's surface or 14.1% of its land surface area...
there were instances of communist radio stations such as Radio Venceremos
Radio Venceremos
Radio Venceremos was an 'underground' radio network of the anti-government Farabundo Martí National Liberation Front during the Salvadoran Civil War. Despite the end of the war in 1992, the network continues to broadcast...
being jammed, allegedly by the CIA
Central Intelligence Agency
The Central Intelligence Agency is a civilian intelligence agency of the United States government. It is an executive agency and reports directly to the Director of National Intelligence, responsible for providing national security intelligence assessment to senior United States policymakers...
, while there were short lived instances where Britain
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...
jammed some Egypt
Egypt
Egypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...
ian (during the Suez crisis
Suez Crisis
The Suez Crisis, also referred to as the Tripartite Aggression, Suez War was an offensive war fought by France, the United Kingdom, and Israel against Egypt beginning on 29 October 1956. Less than a day after Israel invaded Egypt, Britain and France issued a joint ultimatum to Egypt and Israel,...
), Greek (Prior to Cyprus
Cyprus
Cyprus , officially the Republic of Cyprus , is a Eurasian island country, member of the European Union, in the Eastern Mediterranean, east of Greece, south of Turkey, west of Syria and north of Egypt. It is the third largest island in the Mediterranean Sea.The earliest known human activity on the...
gaining independence) and Rhodesia
Rhodesia
Rhodesia , officially the Republic of Rhodesia from 1970, was an unrecognised state located in southern Africa that existed between 1965 and 1979 following its Unilateral Declaration of Independence from the United Kingdom on 11 November 1965...
n stations.
People's Republic of China
In 2002, ChinaPeople's Republic of China
China , officially the People's Republic of China , is the most populous country in the world, with over 1.3 billion citizens. Located in East Asia, the country covers approximately 9.6 million square kilometres...
acquired standard short-wave radio-broadcasting equipment designed for general public radio-broadcasting and technical support from Thales Broadcast Multimedia, a former subsidiary of the French
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
state-owned company Thales Group
Thales Group
The Thales Group is a French electronics company delivering information systems and services for the aerospace, defense, transportation and security markets...
.
- It is assumed that China is using ALLISSALLISSALLISS is a fully rotatable antenna system for high power shortwave radio broadcasting in the 6 MHz to 26 MHz range. An ALLISS module is a self contained shortwave relay station that is used for international broadcasting.- FAQ :...
technology for jamming foreign radio stations broadcasting into China. - Thales jamming technology only operates at power levels below 500 kW (for its shortwave jamming products).
- Adele Milna (BSEE) of Continental Electronics (in an audio file held at shortwave.org) claims that China has duplicated his companies 100 kW, 250 kW shortwave transmitters. It is unclear if these products were indeed duplicated or if broadcast jamming (as opposed to future product sales) were a reason for the duplication.
Iran
The country of IranIran
Iran , officially the Islamic Republic of Iran , is a country in Southern and Western Asia. The name "Iran" has been in use natively since the Sassanian era and came into use internationally in 1935, before which the country was known to the Western world as Persia...
has frequently used jamming of satellite TV (as well as filtering the Internet and restricting Internet connectivity speed and other methods) as a strategy to prevent the consequences of freedom of expression in the last decade. Most of the jamming took place in the year 2009 after the controversial presidential election in Iran to control the flow of information and updates about the protests. Although most of the jamming is done on news channels or political ones, another famous series of jamming started around July 2010 on a non-political, Persian language satellite TV channel called "Farsi1" which airs Persian-dubbed popular TV series.
Other Countries
- Since the early 1960s, the practice of radio jamming has been very common in CubaCubaThe Republic of Cuba is an island nation in the Caribbean. The nation of Cuba consists of the main island of Cuba, the Isla de la Juventud, and several archipelagos. Havana is the largest city in Cuba and the country's capital. Santiago de Cuba is the second largest city...
, blocking not only American government funded radio stations (such as VOAVoice of AmericaVoice of America is the official external broadcast institution of the United States federal government. It is one of five civilian U.S. international broadcasters working under the umbrella of the Broadcasting Board of Governors . VOA provides a wide range of programming for broadcast on radio...
) but also radio stations owned and/or operated by (or selling airtime to) Cuban exileCuban exileThe term "Cuban exile" refers to the many Cubans who have sought alternative political or economic conditions outside the island, dating back to the Ten Years' War and the struggle for Cuban independence during the 19th century...
groups transmitting from Miami, FloridaMiami, FloridaMiami is a city located on the Atlantic coast in southeastern Florida and the county seat of Miami-Dade County, the most populous county in Florida and the eighth-most populous county in the United States with a population of 2,500,625...
, such as La Cubanisima, Radio Mambi, WWFEWWFEWWFE , known as "La Poderosa", is a commercial radio station in Miami, Florida, broadcasting to the Miami-Fort Lauderdale area. WWFE's format is Spanish, with an emphasis on Cuban news and music.-External links:*...
La Poderosa and Cadena Azul. The same practice has been applied to Radio MartiRadio MartíRadio y Televisión Martí is a radio and television broadcaster based in Miami, Florida, financed by the United States government , which transmits Spanish radio broadcasts to Cuba...
and TV MartiTV MartíTV Martí was created by the US government to provide news and current affairs programming to Cuba. It is named after Cuban independence leader José Martí, and is the television equivalent to Radio Marti.-History:...
, operated by the U.S. Information AgencyUnited States Information AgencyThe United States Information Agency , which existed from 1953 to 1999, was a United States agency devoted to "public diplomacy". In 1999, USIA's broadcasting functions were moved to the newly created Broadcasting Board of Governors, and its exchange and non-broadcasting information functions were...
since 1985. - North KoreaNorth KoreaThe Democratic People’s Republic of Korea , , is a country in East Asia, occupying the northern half of the Korean Peninsula. Its capital and largest city is Pyongyang. The Korean Demilitarized Zone serves as the buffer zone between North Korea and South Korea...
and South KoreaSouth KoreaThe Republic of Korea , , is a sovereign state in East Asia, located on the southern portion of the Korean Peninsula. It is neighbored by the People's Republic of China to the west, Japan to the east, North Korea to the north, and the East China Sea and Republic of China to the south...
still regularly jam some of each other's radio (and sometimes television) stations. (See: Radio jamming in KoreaRadio jamming in KoreaRadio jamming on the Korean Peninsula makes the border region one of the world's busiest places for radio signals. Medium wave jamming is dominant in the area including Seoul and the DMZ...
) - Several middle eastern countries (particularly IranIranIran , officially the Islamic Republic of Iran , is a country in Southern and Western Asia. The name "Iran" has been in use natively since the Sassanian era and came into use internationally in 1935, before which the country was known to the Western world as Persia...
) jam shortwave broadcasts (and even occasionally attempt to jam satellite TV signals) targeted at their countries. - Pakistan has recently stated its intention to begin jamming clandestine radio stations operated by the Taliban
- Ethiopia has jammed the DWDWDW may refer to:* DW Stadium, formerly known as the JJB Stadium and where Wigan Athletic play football* Deadweight tonnage, a ship measurement for capacity, tonnage* Deutsche Welle, a German international broadcasting organization...
and VOA transmissions as well as ESAT Ethiopian Satellite Television - In ArgentinaArgentinaArgentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
, aerial TV channel Canal 13Canal 13 (Argentina)El Trece is an Argentine television network and the flagship station of the same network, located in the capital of Argentina, Buenos Aires.- Foundation :...
, cable TV news channel Todo NoticiasTodo NoticiasTodo Noticias is an Argentine news cable channel. It is owned by the Group Clarín. TN began broadcasting on Tuesday, June 1, 1993, at 07:00...
and AM radio Radio Mitre were jammed by an unidentified source coming from South AmericaSouth AmericaSouth America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
. All of these stations belong to the Artear media company, which belongs to Grupo ClarínGrupo ClarínGrupo Clarín is the largest media conglomerate of Argentina.-Overview:Established as such in 1999, it includes the Clarín newspaper , Papel Prensa , the Artear media company, and numerous other media outlets.Rooted in the successful, 1945 launch of the centrist daily,...
. This media corporation gained international notoriety for their ongoing confrontation with the Argentine Government which started during the 2008 Argentine government conflict with the agricultural sector2008 Argentine government conflict with the agricultural sectorThe 2008 Argentine government conflict with the agricultural sector started in March 2008, which then extended into a prolonged period of turbulent politics...
.
See also
- Radio jamming in ChinaRadio jamming in ChinaRadio jamming in the People's Republic of China is a form of media censorship that involves deliberate attempts by state or Communist Party organs to interfere with radio broadcasts...
- Radio jamming in KoreaRadio jamming in KoreaRadio jamming on the Korean Peninsula makes the border region one of the world's busiest places for radio signals. Medium wave jamming is dominant in the area including Seoul and the DMZ...
- Mobile phone jammer
- Association of Old CrowsAssociation of Old CrowsThe Association of Old Crows is an international professional organization specializing in electronic warfare, tactical information operations, and associated disciplines headquartered in Alexandria, Virginia...
- Wireless signal jammerWireless signal jammerWireless signal jammers are devices used to disrupt radio signals. The low cost of manufacture of wireless signal jammers and their damaging effects have added to their popularity and frequent use.-Use for denial of service:...
- Electronic warfareElectronic warfareElectronic warfare refers to any action involving the use of the electromagnetic spectrum or directed energy to control the spectrum, attack an enemy, or impede enemy assaults via the spectrum. The purpose of electronic warfare is to deny the opponent the advantage of, and ensure friendly...
- Eastern Bloc information disseminationEastern Bloc information disseminationEastern Bloc information dissemination was controlled directly by each country's Communist party, which controlled the state media, censorship and propaganda organs...
- Culture jammingCulture jammingCulture jamming, coined in 1984, denotes a tactic used by many anti-consumerist social movements to disrupt or subvert mainstream cultural institutions, including corporate advertising. Guerrilla semiotics and night discourse are sometimes used synonymously with the term culture jamming.Culture...
External links
- Various articles on Soviet jammers 1 2 3 4
- extensive site on radio jamming
- Article on recent jammers with audio samples
- Audio sample of jamming (c1982) at start of BBC World service (Russian) programme includes jamming station morse ID
- Ethopia jams VOA (2010)
- Ultra Fast Folloow Jammer Description (2007)