Air-Wave Battle

From a quiet office in Manhattan, Engineer George Q. Herrick, of the Voice of America, was fighting a furious electronic battle last week for Russia's radio audience. His weapons were powerful transmitters spotted through the northern hemisphere. His projectiles were radio waves. Herrick chalked up a victory whenever the Voice's broadcasts broke through Soviet jamming to reach Russian ears.

Soviet transmitters began jamming the Voice's Russian-language programs in February 1948. They were not too successful then, but last month a mighty barrage of jamming broke out. It practically obliterated the Russian-language programs of both the Voice of America and the British Broadcasting Corp. Directional receivers proved that the Russians had put 150 transmitters on the job.

After the first few days of defeat, the Voice and BBC rallied. They called up reinforcements (more transmitters) and settled down to a long, subtle contest. Soviet jamming proved that Voice programs were being heard by the Russian people and were feared by the Kremlin. Now all the Voice's Russian-language programs carry a punch line: "Obviously somebody considers it dangerous to permit the Soviet people to listen to truthful information from a free radio."

Strategic Error. The Voice's opportunity was originally of Russian making. To reach its own people over vast Russian distances, the Soviet government built many short-wave (6,000 to 21,000-kilo-cycle) transmitters and distributed about 5,000,000 short-wave receivers to listeners. This proved a strategic mistake. Under good conditions, short-wave listeners could also hear programs from as far away as the U.S. and Manila.

The news-starved Russian people took quick advantage. Voicemen believe that about 8,000,000 Russians listen regularly to bootlegged news from the West. The reports then flash by grapevine all over the Soviet Union. The Kremlin's answer was jamming. But, says Voiceman Herrick, "jamming is like a chess game." First you make a move. Your opponent makes a move; then you make a countermove.

The simplest kind of jamming, says Herrick, is to compete with the opponent on the same wave length. This is not very effective, for the human ear can hear a human voice through noise of greater intensity. A better technique is to broadcast on a wavelength slightly different from the opponent's. The two waves react on one another. The result of this collaboration is a squealing "beat," part of whose ear-whacking energy comes from each wave. Still better is the technique of varying the frequency of the jamming wave so that it straddles the opponent's. This produces a loud, pulsating whistle. The Russians superimpose unpleasant noises (i.e., bagpipe squeals and ducks' quacking) on their jamming waves.

One way to counter jamming is to use so many frequencies that the opponent cannot obliterate them all. The Voice now uses 36 stations and the BBC 25. They change their frequencies suddenly and often, instructing the Russian listeners to "search all short-wave bands." This keeps the jammers on the jump. It takes them about twelve seconds on the average to find and jam a dodging program. In the unjammed interval, an alert Russian listener may sometimes pick up a tidbit of news.

Clipped Voice. An effective anti-jamming device is a "de-emphasizing and pre-emphasizing clipper" developed by Herrick and his crew. It distorts the voice a little but at the same time makes it more intelligible and harder to obliterate.

Monitoring stations report that about 20% of the programs are getting through entirely unjammed; 35% are jammed but still intelligible. Since the news is repeated over & over 24 hours a day, the Russians are undoubtedly still getting much news from the outside world. So far they have not been forbidden to listen to the Voice. As one escaped Russian airman put it: "To listen is not forbidden but it is not recommended."

Voiceman Herrick is confident that superior U.S. and British technology can lick the Soviet jammers. In this sort of warfare the offensive generally has the advantage. It is almost impossible to drive all unauthorized words out of a nation's air. During World War II, the Nazis used massive jamming equipment and also made it a capital crime to listen to Allied broadcasts. But the news still got through.

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