During the so-called Cold War, totalitarian regimes sought to block radio or TV broadcasts, except the ones they controlled. The Cold War is over, but those jamming efforts continue in some parts of the world. VOA Correspondent Gary Thomas reports from Washington on the 21st century battle of the airwaves.
Authoritarian governments still try to silence criticism and unfavorable news coverage in their countries by the age-old expedient of throwing critics in jail and shutting down their publications. But what does today's autocrat do about broadcasts being beamed into his country from sources outside his reach?
Simple. He jams them.
A longtime researcher on international broadcasting at the Voice of America, Kim Elliott, says the methods of jamming radio broadcasts are still much the same as they have been, even with new technologies.
"It is simply a matter of putting a noxious signal on the same frequency as the broadcaster that is trying to get into the country. And it was that way during World War II, it was that way during the Cold War, and it is still that way. If you tune across your short-wave radio, you will hear a raucous noise on one frequency, and you will hear the hapless international radio broadcaster in the background trying to get into the country," he said.
The result is rather like being in a crowded room watching a sporting event, with the cheering so loud that it is almost impossible to hear the person sitting right next to you.
Free speech advocates have always condemned jamming as an attempt to cut off the uninterrupted flow of information. Kenneth Tomlinson, the chairman of the U.S. government's Broadcasting Board of Governors that oversees VOA, Radio Free Asia, and other government-sponsored broadcast entities, has said it is illegal, and interferes with the free and open flow of international transmissions.
Experts say that, ironically, newer broadcast technologies, such as television, are actually easier to jam than old-fashioned short-wave radio, simply because radio can air on so many different frequencies at once.
Broadcast researcher Kim Elliott says jamming TV signals, especially from satellites, is relatively simple.
"Of all the media available to international broadcasting, short-wave is the most difficult to interdict. And that is because of the physics of transmission at short-wave frequencies," he said. "Signals from more distant transmitters come through better than signals from transmitters closer up. Television transmissions travel much shorter distances, and so those are much easier to jam. Or, if they are from a satellite, they are easy to jam because it only requires a few watts [of power]. And it does not have that kind of immunity [from jamming] that short-wave has."
Asia specialist Vincent Brossel, with the French media research group Reporters Without Borders, says radio still remains the main source of information for many people around the world.
"The radio is something like the most democratized and the most popular media in the world, due to the fact that many people cannot read, or do not have any access to Internet," he said. "The only way to touch millions, or billions of people around the world is radio."
Analysts say this is why China has become the biggest practitioner of international radio jamming in the post-Cold War world.
Mr. Brossel says Western firms, such as the French firm Thales', have sold broadcast equipment to China that also can be used for jamming.
"What is very interesting is that some Western companies are selling technology to the Chinese, and Chinese are selling technology for jamming to some Third World countries," he said. "So, it means that, just for business reasons, foreign companies like Thales' are helping the Chinese government to prevent millions, or billions of listeners from getting some free and independent radio programs."
Thales' officials have declined to comment on the company's sales. An American firm, Continental Electronics, also has sold transmission equipment to China, and to VOA, Radio Free Asia, and Taiwan, as well.
Experts say the term "jamming equipment" is really a misnomer, since a transmitter is something of a two-edged sword that can not only be used to broadcast, but can be easily converted to jam broadcasts.
Although Iran's theocratic government officially bans satellite television and has jammed foreign broadcasts, including those of exile Persian-language stations, the jamming has been sporadic, and is usually conducted during elections and other political events. Azadeh Moaveni, an Iranian-American journalist, who has reported from Iran, says the reality is different than official policy.
"Satellite television is technically banned," she said. "It is implicitly tolerated. And you could, I think, say comfortably that the majority of the country has access to satellite news."
Sometimes political jamming is tried as well.
Eutelsat, a European satellite operator, earlier this said it would not renew its contract to carry the signal of a new language broadcast outlet called New Tang Dynasty TV, or NTDTV Its links to the Falun Gong group, which is banned in China, earned it official Chinese displeasure. Mr. Brossel of Reporters Without Borders said Eutelsat was under what he called "tremendous pressure" from China to cancel the NTDTV contract. But last month Eutelsat agreed to renew it.