Radio jamming is the (usually deliberate) 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 checking that it is in use first, or without being able to hear distant stations on the same 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. In information theory, a signal is the sequence of states of a communications channel that encodes a message. ... Copy of the original phone of Alexander Graham Bell at the Musée des Arts et Métiers in Paris Telecommunication is the transmission of signals over a distance for the purpose of communication. ... The phrase signal-to-noise ratio, often abbreviated SNR or S/N, is an engineering term for the ratio between the magnitude of a signal (meaningful information) and the magnitude of background noise. ... The term Jamming can refer to several things: Jamming as an electronic warfare (EW) - a technique to limit the effectiveness of an opponents communications and/or detection equipment, like Radio Jamming and Radar Jamming E-Mail Jamming- used by electronic political activists or hackers to disable e-mail systems... FreQuency is a music video game developed by Harmonix and published by SCEI. It was released in November 2001. ... Radiation as used in physics, is energy in the form of waves or moving subatomic particles. ... Cable television or Community Antenna Television (CATV) (and often shortened to cable) is a system of providing television, FM radio programming and other services to consumers via radio waves transmitted directly to people’s televisions through fixed coaxial cables as opposed to the over-the-air method used in... Look up aircraft in Wiktionary, the free dictionary. ...

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.

How it is done

Intentional communications jamming is usually aimed at radio 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. Antenna tower of Crystal Palace transmitter, London A transmitter (sometimes abbreviated XMTR) is an electronic device which with the aid of an antenna propagates an electromagnetic signal such as radio, television, or other telecommunications. ... In telecommunications, modulation is the process of varying a periodic waveform, i. ... In radio terminology, a receiver is an electronic circuit that receives a radio signal from an antenna and decodes the signal for use as sound, pictures, navigational-position information, etc. ...

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. In science, and especially in physics and telecommunication, noise is fluctuations in and the addition of external factors to the stream of target information (signal) being received at a detector. ... A continuous wave (CW) is an electromagnetic wave of constant amplitude and frequency. ...

Obvious jamming is easy to detect as it can be heard on the receiving equipment. It usually is some type of noise such as stepped tones (bagpipes), random-keyed code, pulses, erratically warbling tones, random noise (hiss) and recorded sounds.

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 that 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".

History of Jamming

During World War II a variation of radio jamming was used where ground operators would attempt to mislead pilots by false instructions in their own language. 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. Combatants Allied powers: China France Great Britain Soviet Union United States and others Axis powers: Germany Italy Japan and others Commanders Chiang Kai-shek Charles de Gaulle Winston Churchill Joseph Stalin Franklin Roosevelt Adolf Hitler Benito Mussolini Hideki Tōjō Casualties Military dead: 17,000,000 Civilian dead: 33,000... Radar jamming is the intentional emission of radio frequency signals to interfere with the operation of a radar by saturating its receiver with false information. ... This long range radar antenna, known as ALTAIR, is used to detect and track space objects in conjunction with ABM testing at the Ronald Reagan Test Site on the Kwajalein atoll. ... Spread-spectrum telecommunications is a technique in which a signal is transmitted in a bandwidth considerably greater than the frequency content of the original information. ...

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. Broadcasting is the distribution of audio and/or video signals which transmit programs to an audience. ...

During the Cold War Soviet jamming of 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. For other uses, see Cold War (disambiguation). ... // What are HRS type antennas The curtain antenna is a dipole array, consisting of rows and columns of dipoles. ... A solid-state, analog shortwave receiver Shortwave radio operates between the frequencies of 3,000 kHz and 30 MHz (30,000 kHz) [1] and came to be referred to as such in the early days of radio because the wavelengths associated with this frequency range were shorter than those commonly... Soviet redirects here. ...

Jamming has also occasionally been used by the Governments of Germany (during WW2), Cuba, Iraq, Iran (Iraq and Iran war, 1980-1988), China, North and South Korea and several Latin American countries. as well as by the authorities in several countries against pirate radio stations including Radio Nova in Ireland and Radio Northsea International off the coast of Britain. Korea (Korean: 한국 or 조선, see below) is a geographic area, civilization, and former state situated on the Korean Peninsula in East Asia. ... Latin America consists of the countries of South America and some of North America (including Central America and some the islands of the Caribbean) whose inhabitants mostly speak Romance languages, although Native American languages are also spoken. ... The term pirate radio usually refers to illegal or unregulated radio broadcasting. ... Radio Nova was a pirate radio station broadcasting from Dublin, Ireland. ... Lockerbie bombing suspect Edwin Bollier Edwin Bollier and his partner, Erwin Meister, founded the Meister/Bollier (Mebo) electronics firm in Zürich, Switzerland. ...

Cold War era

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 Cover of Radio Liberty booklet The Most Important Job in the World Radio Free Europe/Radio Liberty (RFE/RL) is a radio and communications organization which is funded by the United States Congress. ... Radio Free Europe/Radio Liberty (RFE/RL) is a radio and communications organization which is funded by the United States Congress. ... The Voice of America (VOA) is the official international broadcasting service of the Government of the United States. ... The BBC World Service is one of the most widely recognised international broadcasters of radio programming, transmitting in 33 languages to many parts of the world. ...

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 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.^{[citation needed]} State motto (Russian): Пролетарии всех стран, соединяйтесь! (Transliterated: Proletarii vsekh stran, soedinyaytes!) (Translated: Workers of the world, unite!) Capital Moscow Official language None; Russian (de facto) Government Federation of Soviet republics Area  - Total  - % water 1st before collapse 22,402,200 km² Approx. ... This article is about the German international broadcaster. ... Administration building and radio masts at Vatican City Radio Vaticana (Vatican Radio) is the official broadcasting service of the Vatican. ... Radio Canada International (RCI) is the international broadcasting service of the Canadian Broadcasting Corporation (CBC). ... The English language is a West Germanic language that originates in England. ...

There were also periods when China and the USSR jammed each other's programmes.

Some parts of the world were more impacted by these broadcasting practices than others

• Eurasia (worst affected, including mediumwave frequencies)
• North Asia (partly affected)
• Americas (partly affected)
• Sub-saharan Africa (partly affected)
• Australasia, South America (rarely affected)

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 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 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. Eurasia African-Eurasian aspect of Earth Eurasia is the Earths largest landmass covering about 21215121321km² compared with the Americas (approximately 42,000,000 km²), Africa (approximately 30,000,000 km²), and Antarctica (approximately 13,000,000 km²). Eurasia comprises the traditional continents of Europe and Asia. ... Mediumwave radio transmissions serves as the most common band for broadcasting. ... Regions of Asia:  Northern Asia  Central Asia  Western Asia  Southern Asia  Eastern Asia  Southeastern Asia North Asia or Northern Asia is a subregion of Asia. ... World map showing the Americas CIA political map of the Americas The Americas are the lands of the Western hemisphere or New World consisting of the continents of North America[1] and South America with their associated islands and regions. ... A world map showing the continent of Africa Africa is the worlds second-largest and second most-populous continent, after Asia. ... Australasia Australasia is a term variably used to describe a region of Oceania: Australia, New Zealand, and neighbouring islands in the Pacific Ocean. ... South America South America is a continent crossed by the equator, with most of its area in the Southern Hemisphere. ... A map of the Eastern Bloc. ... In biology, antenna (plural: antennae) refers to the sensing organs of several arthropods. ... The word propagation can mean: Multiplication or increase, as by natural reproduction. ... A solid-state, analog shortwave receiver Shortwave radio operates between the frequencies of 3,000 kHz and 30 MHz (30,000 kHz) [1] and came to be referred to as such in the early days of radio because the wavelengths associated with this frequency range were shorter than those commonly... Relationship of the atmosphere and ionosphere The ionosphere is the part of the atmosphere that is ionized by solar radiation. ... It has been suggested that this article or section be merged with Ionosphere. ... Groundwave is the propagation of radio waves close to the surface of the Earth. ...

In 1987 after decades of 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. Cover of Radio Liberty booklet The Most Important Job in the World Radio Free Europe/Radio Liberty (RFE/RL) is a radio and communications organization which is funded by the United States Congress. ...

While western governments may have occasionally considered jamming broadcasts from Eastern Bloc stations it was generally accepted that to do so would be a pointless exercise as in most western countries ownership of shortwave radios was not particularly widespread unlike in the USSR where due to the vast physical size of the country some domestic stations were relayed on shortwave (as it was the only practical way for them to cover remote areas). NATO 2002 Summit in Prague. ... Unofficial Seal of the Warsaw Pact Distinguish from the Warsaw Convention, which is an agreement about airlines financial liability and the Treaty of Warsaw (1970) between West Germany and the Peoples Republic of Poland. ... A solid-state, analog shortwave receiver Shortwave radio operates between the frequencies of 3,000 kHz and 30 MHz (30,000 kHz) [1] and came to be referred to as such in the early days of radio because the wavelengths associated with this frequency range were shorter than those commonly...

However in Latin America there were instances of communist radio stations such as Radio Venceremos being jammed -allegedly by the CIA. Latin America consists of the countries of South America and some of North America (including Central America and some the islands of the Caribbean) whose inhabitants mostly speak Romance languages, although Native American languages are also spoken. ... Radio Venceremos (Spanish; in English, We Shall Overcome Radio) was an underground radio network of the anti-government Farabundo Martí National Liberation Front (FMLN) during the Salvadoran Civil War. ... The Central Intelligence Agency (CIA) is an intelligence agency of the United States government. ...

Post Cold War (1989 -- Present)

In 2004, China acquired radio jamming technology and technical support from French state-owned company, Thales Group. shelby was here 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... The Thales Group (Euronext: HO) is a global electronics company serving aerospace, defence, and information technology markets worldwide. ...

• It is assumed that China is using ALLISS technology for jamming foreign radio stations broadcasting into China.
• Thales jamming technology only operates at power levels below 50kw (for it shortwave jamming products).
• Adele Milna (BSEE) of Continental Electronics (in an audio file held at shortwave.org) claims that China has duplicated his companies 100kw, 250kw 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.

This article may be too technical for most readers to understand. ...

External links

• SESP Group (jammer manufacturer)
• H.P. Marketing & Consulting Wüst GmbH
• An article on Soviet jammers
• Another article on Soviet jammers
• Vesuvius Marsivia
• Radio Jamming Module