Monday, February 13, 2012

Cold War Radio Jamming

SW jamming antenna array
Radio jamming is the deliberate broadcast of an interference signal to prevent the reception of a radio transmission. When talking about radio jamming during the Cold War, we generally think about the disruption of enemy military radio communications and weapon systems signals, a small part of what is known as electronic warfare or EW.

However, radio jamming was also used extensively for non-military purposes during the Cold War. Although the Iron Curtain divided the world physically between East and West, no barbed wire, high fence or border guard could stop radio signals from travelling across borders. During the Cold War, propaganda was a powerful weapon in politics and the battle between ideologies. Winning the hearts of the enemy's civilian population was just as important as depicting the enemy as a tyrannic aggressor.

Both East and West excelled in doing so, but probably the best known examples are the extensive jamming of the powerful shortwave and medium wave stations of Radio Free Europe (RFE) and the Voice of America (VOA). Both these stations have broadcast for decades in various languages, mostly towards eastern-block and Latin American countries, to bypass the censored press in those countries.

Many Soviet citizens listened - often illegally - to these stations to catch a glimpse of what was happening in the West. Of course, these stations not only scheduled the usual international news and entertainment, but also propaganda, directed against the Soviet regime. Sometimes they even inserted covert messages for dissidents or intelligence personnel, operating inside the Soviet Union. It was hardly a secret that RFE initially was a CIA funded station, set up specifically to fight the Cold War by political and propaganda means.

As eager the Western policy makers and intelligence services were to get their broadcast across, into the Eastern-Bloc countries, so eager were the Soviets to prevent these signals from arriving to their citizens' radios. To counter this threat by the West, many very powerful jamming transmitters operated in Russia, Czechoslovakia, East Germany, Poland, Romania, Hungary and Bulgaria, to name a few. It was often a cat and mouse game between the radio stations, slightly changing the frequency to enable their listeners to tune in clearly, and the jamming station operator tuning his jamming signal right onto the broadcast frequency.

To disrupt the reception of powerful shortwave radio stations, they used even more powerful jamming transmitters, up to 500 Kilowatt (that's a massive 500.000 Watt) with various interference signals such as noise, non-stop music or even recorded voices played backwards. These high-power jamming stations were often located near densely populated areas to increase their effectiveness. Radiation and health apparently were not an issue in those days.

Although the Cold War has ended more than two decades ago, the practice of jamming radio stations still continues in several countries. Amoung them are North Korea, China, Iran and Cuba. Radio jamming is a popular technique for some regimes to (try to) keep their citizens ignorant by extensive censorship.

To get an idea of the jamming equipment and methods they used, I can recommend a visit to Rimantas Pleikys' Radio Jamming website with detailed information, images and sound samples of former East European jamming transmitters. You can also read his excellent paper Radio Jamming in the Soviet Union, Poland and other East European Countries (pdf). He also wrote a book on this subject which is apparently no longer available (maybe you can catch it second-hand).

UPDATE: An excellent video documentary (in English) about radio jamming can be view on Polskieradio.

Rimantas Pleikys is an amateur radio operator, founder of several radio stations and former Minister of Communications and Informatics of Lithuania.

More about the Cold War battle over radio waves is found on my website.

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