Kelly McSweeney

Aug 2nd 2017

Not Just a Movie Star: Wi-Fi, Bluetooth Go Back to Hedy Lamarr Invention


Frequency hopping, a Hedy Lamarr invention, paved the way for Wi-Fi, Bluetooth and more, but she is better known as a beautiful actress. During her film career in the 1930s and 1940s she starred alongside the likes of Clark Gable, Spencer Tracy, Judy Garland and Lana Turner. Frequently typecast as a temptress, Lamarr grew bored with the uncomplicated roles, so when she wasn’t on set, she challenged herself by inventing new traffic signals and improving tissue box designs. She was a “maker” ahead of her time.

Hedy Lamarr in The Heavenly Body (1944)

Hedy Lamarr: Self-Taught Inventor

Born Hedwig Eva Maria Kiesler to a non-practicing Jewish family in Austria in 1914, she married an Austrian weapons manufacturer when she was still a teenager with a budding acting career. He was 14 years older than her, and known for being controlling and possessive. She frequently accompanied her husband at business meetings where fascists and Nazis discussed military technology such as remote-controlled weapons. While hosting extravagant parties that were attended by Mussolini, Hitler and their associates, Lamarr heard the men discussing how they would detect and jam the radio signals that American aircraft and weapons used to communicate.

Years later, Lamarr used this dinner party intelligence as the foundation for a secret communication system to help defeat the Nazis in World War II. After divorcing her first husband and moving to the United States to pursue acting, she invented frequency hopping encryption, a radio-guidance system for torpedoes that prevented jamming and detection.

Lamarr partnered with composer George Antheil to develop a method that used a piano roll to switch between 88 frequencies. While conventional communication could easily be intercepted, frequency hopping makes jamming much harder, because both the transmitter and receiver “hop” to different frequencies. Since the sequence of frequencies is known by the transmitter and receiver ahead of time, it would seem random to any eavesdroppers.

In 1942, she and Antheil were granted a patent for their invention. The patent explains:

“Briefly, our system as adapted for radio control of a remote craft, employs a pair of synchronous records, one at the transmitting station and one at the receiving station, which change the tuning of the transmitting and receiving apparatus from time to time, so that without knowledge of the records an enemy would be unable to determine at what frequency a controlling impulse would be sent.”

The Fate of Frequency Hopping

Lamarr’s goal was to contribute to the war effort, but the Navy didn’t take her piano-based invention seriously at the time. Instead, they advised her to focus her efforts on using her fame to sell war bonds (which she did — quite successfully). Two decades later, the Navy debuted a similar frequency hopping device during the Cuban Missile Crisis. Frequency hopping devices are still used by today’s governments.

Although the technology was originally designed for military use, frequency hopping led to the commercialization of the electromagnetic spectrum. Lamarr never profited from her invention because her patent expired decades before wireless communication proliferated. Her idea is the foundation for today’s wireless communication such as Wi-Fi, Bluetooth and CDMA (code division multiple access) communications.

In fact, frequency-hopping spread spectrum transmission will be even more important in the future, as demand for wireless communication increases and the electromagnetic spectrum remains finite. The technique prevents intentional jamming, but it also helps minimize any unintentional interference caused by an overcrowded spectrum.

Radios that integrate all radio-frequency functions will be essential for wireless communication. Now that nearly any device can be connected to the internet, jamming and wireless hacking are a looming concern. Electronic warfare — the use of the electromagnetic spectrum or directed energy to control the spectrum — could be the next military crisis. This could range from hacking and cyberattacks to high-power microwave attacks.

To prepare, Northrop Grumman is developing solutions such as SIGINT (signals intelligence), which involves gathering intelligence by intercepting electronic signals. Now that radar techniques have improved, even stealth aircraft can be detected, and radar frequencies will be overcome by serious competitors. Air survivability in these situations will have to come from other approaches, such as electronic defense against incoming missiles. Pilots will have to learn to trust people who are not in the raid with them to perform mission-critical functions from remote desktops.

Today and in the future, popular consumer gadgets as well as defense technology will continue to depend on this Hedy Lamarr invention. Although she didn’t receive the recognition she deserved for her innovations in techology in her lifetime, Hedy Lamarr was inducted to the National Inventors Hall of Fame in 2014.