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The USA, Cuba, the USSR, N. Korea (DPRK), S. Korea (ROK), People's Republic of China (PRC) and the  E. Germany (GDR) all regularly blocked rival nations programs with jamming devices. Most nations have jammed some stations at some time in their history. 

The Americans launched the station Radio Free Europe while Western broadcasts were launched in the Eastern bloc with the start of the Cold War. The Soviets became alarmed and the radio jamming war would later develop in to a major Cold War issue.

The USSR made heavy use of radio jamming to prevent its citizens from listening to political dangerous broadcasts from the British Broadcasting Corporation (BBC) and the Voice of America (VOA) and other western broadcasters. By 1952, there were approximately 200 jamming stations with a total of between 3 and 4 megawatts of output power, which expanded to about 1,700 transmitters with a combined 45 megawatts of output power by the early 1960's. The total electricity consumed along with the site construction and personnel costs was enormous.

The conceptEdit

Radio jamming is achieved by deliberately transmitting the radio signals of one's own station's transmissions or man made interference from a jamming device on the same frequency as the intended target station with enough strength as to smother their transmissions and stop it from being heard by listeners in the jamming zone.

The operating transmitters for domestic radio stations on the same or nearby frequencies was a routine thing in the GDR (E. Germany). For example, for many years East Germany operated at Wiederau a transmitter on the same medium wave frequency (575 kHz) that Mühlacker radio transmitter used with an output power of 100kW, which made it difficult to receive the AFN Mühlacker radio transmitter in much of the East Germany.

Techniques used to jam signals via a jamming device also included smothering rival services' frequency in a maliciously generated signal containing things like loud hissing noises, music or the playing of domestic broadcast tapes backwards on reel-to-reel recorders in to a powerfull trasmitting unit.

The use of formal and informal and informal jamming techniques lead to a so called transmission "power race" in which broadcasters and jammers alike repeatedly increased their transmission power, utilised highly directional antennas and/or added extra frequencies (known as "barrage" or "frequency diversity" broadcasting) to the already heavily overcrowded shortwave frequency spectrum. This was happening 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 western stations or Soviet jamming devices spilling in to there frequency zone.

Unfortunately some Radio France International, Raidió Teilifís Éireann, RAI — Radiotelevisione italiana S.p.A. and Radio Polonia (called the Polish Radio External Service after January 2007) signals in both East and West Germany were all victims of the collateral damage caused by the jamming of other stations in the closing stages of the Cold War.


Radio Moscow began issuing  its broadcasts in 1922 and had its Italian language medium-wave service was specifically was jammed on the orders of Italian dictator Benito Mussolini during the late 1930s.

The Cold War led to increased international broadcasting, most of which contained either news, sport, music or propaganda disguised as news; as Communist and anti-Communist states attempted to influence each other's domestic population.

The Voice of America, the BBC World Service, the (then covertly) CIA-backed Radio Free Europe/Radio Liberty, Radio Havana Cuba international, Radio Moscow and Radio Peking all jostled for the attention and political loyalty of the global public.

W. Germany (the FRG) resumed regular shortwave broadcasts using Deutsche Welle on May 3, 1953. RDW's Julich transmitter site began operation in 1956, with 11 100-kW Telefunken transmitters and the later Wertachtal opened in 1972 and began operating with 4 500-kW transmitters.

Meanwhile, East Germany's Nauen site began transmitting Radio DDR, which later Radio Berlin International, on October 15, 1959.

The USA began jamming Radio Havana Cuba international from the mid-1960s to the mid-1980s.

From the early 1970s, satellites generating frequency swinging carrier signals were used to even better at interfering with rival nation's broadcasts. Nevertheless, the oppressed people continued (or attempted) to listen to Western broadcasts. The Soviets stopped jamming foreign broadcasts, excluding Radio Free Europe, from 1963 to 1968 and from 1973 to 1980. The jamming ended in 1988, except for Radio Free Europe was, which had to wait until the August of 1991.

By 1989, there were 15 RDW transmitters in W. Germany, 4 of which relayed the Voice of America.

Targeted stationsEdit

Soviet targetsEdit

  • Radio Free Europe (obsessively).
  • Radio Liberty (obsessively).
  • Voice of America.
  • BBC World Service.
  • Deutsche Welle.
  • Raadio vabadus Eesti- ja Liivimaal (A Swedish individual of ethnically Estonian origins and a couple of his Sweedish friends who were briefly operative in southern Finland during 1947 and 1948 on a narrow amiture S.W. frequency).
  • Radio Beijing International/China Radio International (occasionally).
  • Radio Tirana (occasionally).
  • Radio Vaticana (occasionally).
  • Kol Yisrael  (occasionally).
  • Radio Canada International (occasionally).

The jamming usually only took place during programming in languages widely spoken in Eastern Bloc countries (e.g., Russian, Polish, Czech, German, Lithuanian, etc.). Programmes in English or other major Western languages, such as French, Italia, Jaanese, etc; other than German; were rarely (if ever) jammed intentionally.

Russia balalaika music, choral Russia folk music and hissing noises were used as jamming signals.

East German targetsEdit

  • Radio Free Europe (obsessively)
  • Radio Liberty (obsessively)
  • Voice of America
  • BBC World Service
  • Deutsche Welle

German, Russian and occasionally English language broadcasts were jammed.

W. German targetsEdit

German language broadcast were targeted.

Chinese targetsEdit

  • Voice of America
  • BBC World Service
  • Radio Free Asia
  • All Taiwanese services
  • Radio Moscow (occasionally)

Drumming, Chinese folk music and hissing noises were used as jamming signals.

USA targetsEdit

UK targetsEdit

  • Radio Pyongyang.
  • Radio Moscow (occasionally)
  • Radio Beijing International/China Radio International (occasionally)

The usual jamming signals were buzzing, chugging, bubbling, clicking, whisteling, wiring and hissing noises.

Cuban targetsEdit

N. Korean targetsEdit

  • KBS Radio 1 (obsessively)
  • KBS Radio 2 (obsessively)
  • KBS 2FM 89.1 (obsessively)
  • KBS Radio 3 (obsessively)
  • KBS Radio Social Education (obsessively)
  • Korean Forces Network
  • KBS World Radio (obsessively)
  • South Korea's clandestine shortwave broadcast, Echo of Hope (obsessively)
  • Voice of America
  • Free North Korea Radio (which originates from US transmitters in Guam) (obsessively)
  • Radio Free Asia
  • NHK
  • BBC World Service
  • The British run Lincolnshire Poacher covert numbers station is smothered out in N. Korea by Radio Pyongyang operating on exactly the same frequency.

Before the inter-Korean treaty of 2000 KBS Radio 1 used to deliver certain programmes (merged with then KBS Radio Social Education) which condemned the North Korean regime at midnight each day.

The type of the jamming North Korea uses on shortwave is a 'Jet Plane Noise', which makes it very hard to hear the radio broadcasts. North Korea also jams. The coastal parts of Gyeonggi Province, Incheon, Chungcheong, and sometimes Jeolla regions has KBS Radio 1 Seoul (711 kHz) broadcasts intermittently jammed by strange beeping sounds, which seem to be jamming signals issued by the DPRK. Jamming is only used against Korean language services.

It is still illegal for North Koreans to listen to anything other than state-run radio all all radios sold by state shops in North Korea are pre-tuned to only government stations. Some illegal radios capable of receiving foreign broadcasts can be bought on the black market, but the penalty for being caught was and still is at best several years of misery in a gulag, if not in many cases, an arbitrary execution with in a few day of arrest.

Because of electricity shortages in North Korea, the radio jamming and broadcasting activities are not always consistent and are sometimes interrupted by power failures.

S. Korean targetsEdit

  • Radio Pyongyang (obsessively)
  • PBS Pyongyang (obsessively)
  • KCBS Wiwon (obsessively)
  • KCBS Pyongyang (obsessively)
  • KCBS Haeju (obsessively)
  • NHK (obsessively)
  • All other Japanese services

The South Korean government broadcasts several bizarre-sounding jamming sounds which are usually warbling or chugging noises. Jamming is crappy due to 20-50MW S. Korean jammers fighting against a roughly 500MW Radio Pyongyang signal.

In Seoul, Incheon and Gyeonggi Province or near the DMZ has these strange signals on several MW frequencies, mixing with the stronger members of the North Korean radio broadcasts.

According to the National Security Act in South Korea, it was and still is technically illegal to tune into or publish frequencies of North Korean and Japanese broadcasts since they obsessively hate both nations. It is known people cannot be easily caught and/or punished for just listening to those broadcasts individually in a private place. However, the public listening and distribution of recordings of the programs are a prosecutable criminal offences.

Technical note on jammingEdit

Shortwave receivers are capable of receiving shortwave transmissions (2,000 to 30,000 kHz or 2 to 30 MHz). Depending on time of day, season of year, solar weather and Earth's geomagnetic field, a signal might reach around the world.

This sort of map is used by radio engineers to determine the best frequencies to reach international audiences on shortwave bands. In this case, a transmitter is sited in the Southern Vancouver Island, using a frequency of 12095 kHz and transmitting at the 500 kW power level. The picture shows a good signal over the Southern Pacific. The signal fades out as it approaches the East Coast of Australia.

In previous decades shortwave (and sometimes high-powered mediumwave) transmission was regarded as the main (and often the only) way in which broadcasters could reach an international audience. In recent years the proliferation of technologies such as satellite broadcasting, the Internet, and rebroadcasts of programming on AM and FM within target nations has meant that this is no longer necessarily the case.

Transmitter output power has increased since 1920. Higher transmitter powers do guarantee better reception in the target area. Higher transmitter power in most cases counteracts the lesser effects of jamming.

1950s : 100 kW
1960s : 200 kW, early 1960s (2 x 100 kW 'twinned')
1970s : 300 kW, but many 250 kW transmitters sold
1980s : 500 kW sometimes transmitters were "doubled up" to produce 1000 kW output
1980s-present: 600 kW single, 1200 kW from twinned transmitters.

International stations generally use special directional antennas to aim the signal toward the intended audience and increase the effective power in that direction. Use of such antennas for international broadcasting began in the mid-1930s and became prominent by the 1950s. By using antennas which focus most of their energy in one direction, a modern station may achieve the equivalent, in that direction, of tens of millions of watts of radio power.

Also seeEdit


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