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When a famous Hollywood actress encountered an avant-garde composer during the World War II, they invented a radio technology that, as all experts of today would say, revolutionized tele- communications. Their invention is used increasingly today by more than a billion people around the world, in cordless phones, cellular phones, wireless internet, or in transmitting data. It is not only secure against interference, it also uses the broadcast spectrum more efficiently than other techniques.
- Where did it begin?
The first story begins with Hedy's first husband, Fritz Mandl, an Austrian who operated an exceptionally unscrupulous business selling weapons after the first world war. While accompanying her husband to see the reviewing films of various field tests on torpedo systems, Hedy had already formed in her mind some ways of circumventing the jamming that helped protect the signals from being snoopped. However, the idea of frequency hopping popped up one day during a conversation with Antheil and she said: "Hey, look, we're talking to each other and we're changing frequencies all the time." So they started working on Hedy's idea right away.
- About Hedy's ideas.
What Hedy wanted more than anything was to help her adopted country against the Nazis. The problem that most intrigued her was the one that had come up at Mandl's dinner meeting: how to use radio to steer a torpedo while protecting the signals from enemy jamming? A simple radio signal sent to control a torpedo was too easy to block. But what if the signal hopped from frequency to frequency at split-second intervals? If so, despite jamming, the signals would arrive at the receiver mostly intact. If you try to listen it would only hear random noise. But if both the sender and the receiver hop frequency in sync, they both can hear everything clearly (this also was figured out at one party when Hedy and George tried to talk to each other in vain because people made too much big noise. Then Hedy suggested they both sing something together, and when they sang they could clearly hear each other's words. That is because by singing the same tune, they were hopping together at the same frequency). The idea of preventing jamming by using a frequency hopping mechanism turned out to be quite effective. If one can divide the signals into small packets and send those packets out across a broad spectrum of frequencies, the chances are excellent that they will elude any jammer tuned to block any given frequency.
- The help of George Antheil.
What was missing in Hedy's idea was a method of synchronizing the transmitter and the receiver. But Antheil had a solution for that. He had already encountered a similar problem and did find the solution for it: how could he keep the 16 player pianos used in his most famous work - Ballet Mecanique - in time as they played together? Back then he attempted to synchronize them using punched tape. Perhaps the transmitter and receiver of a torpedo control system could be similarly coupled.
- Applicability
At the time their patent was awarded in 1942, this idea of preventing jamming by using frequency hopping was so new and ahead of its time that there was no mechanical technology advanced enough to make it practical. Thus they needed something smaller than a player piano to fit into a torpedo. And their patent was stored in the military's secret files, gathering dust. Technology continued to advance. In 1957, engineers at Sylvania reused the basic idea, but rather than employing paper rolls to provide the synchronization, they used electronic circuitry. It was first put to real use in the blockade of Cuba in 1962, about three years after the patent had expired. Although this meant that Hedy Lamarr and George Antheil did not receive any money for their idea, subsequent patents have usually referred to the Lamarr-Antheil patent as the basis of their work. In this way they at least have some recognition for their ground breaking work. Now the concept is used as the basis of many military communications schemes where the hopping is used to prevent jamming. It is also used in cellular systems including GSM to reduce the effects of interference and in some wireless systems for the same reason.
- Patent no.2292387.
The two applied for the patent. Patent number 2,292,387 was granted on 11th August 1941 under her married name Hedy Kiesler Markey, along with co-inventor George Antheil, as a "Secret Communication System". The name Markey was that of the second of six of Hedy Lamarr's husbands. The patent also specified that a high-altitude observation plane could be used to steer a torpedo. This invention was the first instance of spread-spectrum communication based on frequency-hopping techniques.
- She made it.
- Drafts.
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