Did Hedy Lamarr really invent frequency-hopping, or spread spectrum switching?
Ok..I guess the first question that comes to mind is: What is frequency hopping, or spread spectrum switching. I’ll get to the Hedy Lamarr aspect presently.
Our story starts way back in the early 1940’s, after the outbreak of World War II. The British navy (and the U.S. navy, after America joined the war effort), were using a radio control system to guide torpedoes from their ships to destroy the German battleships and submarines. The technology of the day used a fixed radio broadcast frequency to communicate to a receiver in the torpedoes. The problem was that the transmitted signal, being a steady tone, was easily picked up by the German radio equipment, allowing them to ‘jam’ or interfere with the signal, and steer the torpedo off course.
What was needed was a different broadcast method, making it fairly impossible to lock onto the signal. This is where the story takes a rather odd turn…
We now take you to Hollywood, California…
Hedy Lamarr was one of many glamorous Hollywood actresses of the 1940’s, along with Katherine Hepburn, Ingrid Bergman, etc. While she may be less well-known today, she was well-regarded in her day for her acting abilities and striking good looks. She was no dumb, glamorous air-head though. She was one smart cookie, as they say.
In 1933 in her native Austria, she married an industrialist, Fritz Mandal, who specialized in munitions and weapons control systems. He was very protective (perhaps jealous) of his beautiful wife, so she accompanied him wherever he went. She was privy to some detailed discussions with colleagues about weapons control systems. She wasn’t just sitting around looking pretty either, she was taking it all in. She started getting some ideas on how to solve the problem of tracking and guiding torpedoes.
Eventually, she divorced her husband, then moved to England and America to pursue her acting career. In the early 1940’s, while making a name for herself on the silver screen, she met with a composer and writer by the name of George Anthiel. They ended up discussing all kinds of things, including the ongoing World War II.
Hedy Lamarr's ingenious invention...
Hedy Lamarr came up with an idea for tracking torpedoes that used a method that rapidly switched the transmitted frequencies (referred to as ‘frequency hopping’) such that the enemy wouldn’t be able to pick up and interfere with the transmission. George Anthiel’s idea was to use a punched-paper mechanism, similar to the paper roll of a player-piano, to switch frequencies. The trick was co-ordinating the signals between the control ship, and the torpedo. Once that problem was more or less solved, they applied for a patent on the process, which they were awarded in 1942.
Unfortunately, the U.S. navy, though they realized the idea had merit, felt the idea was too impractical, and considering that the [inventors] were first and foremost..entertainers, and that neither of them had any scientific or practical training, they dismissed the idea, and didn’t pursue it further.
However, in the late 50’s, with the advent of the transistor, the concept was resurrected, further developed and put to use by the navy. Although their patent had expired by this time, the Lamarr-Anthiel patent was cited as the basis for the navy’s torpedo control systems. Ultimately it was employed as part of the naval blockade off Cuba in 1962.
The story doesn’t end there, however…
Modern day use of frequency hopping – spread spectrum
Military organizations throughout the world have been using a similar system for a few decades. It has several advantages over a single transmission frequency.
- Superior immunity from adjacent channels and external interference
- Intercepting transmissions by outside receivers is much more difficult
- More efficient use of the available bandwidth
- Many users can share the same transmission bandwidth without stepping on each other’s toes
Flash forward to the 1980’s, with the introduction of mobile phones. Unlike standard, land line telephones, which have a dedicated line for each user, mobile phones, and cellphones share a wide-bandwidth carrier channel. This channel (depending on the size) can handle anywhere from a few dozen to many thousands of discrete transmissions.
Each wireless phone transmission contains a pseudo-random code, and the equipment at the receiving end knows how to decipher the code and figure out which bits are for your wireless phone only..then pass on the data message it contains. The amazing thing is that your message is being rapidly switched along this channel, thousands of times per second. This is what makes it relatively immune to interference while walking around, or driving past many tall buildings and other structures.
Wireless networks for the home or business, cordless phones, and radio-controlled planes and models use this same technology. Wireless networks use special protocols to send and receive data messages. In all of these systems, it is possible to also use data encryption. This adds an extra layer of security, just in case the transmission code and the method is deciphered, it would take a great deal more effort to crack the encryption, and unravel the original message.
However, rather than get into a detailed technical explanation of how spread spectrum or frequency hopping works, all you really need to know is that the technology that makes it possible, works quietly and efficiently in the background. Plus, the technology is getting better and more efficient and cost-effective all the time.
Now all we need is smaller fingers, and magnifying glasses to use these ever-shrinking devices.
Recognition for lasting contributions…at last
By the way, even though Hedy Lamarr and George Anthiel never really received the recognition they deserved at the time, in 1997 Hedy Lamarr (and George Anthiel, in absentia – he died in 1959) were given the Electronic Frontier Foundation (EFF) Pioneer Award. Hedy Lamarr was also the first female to be given the BULBIE Gnass Spirit of Achievement Bronze Award given to inventors who have made a lasting contribution to society through science, business and the arts.
So, the next time you pick up that cell phone and make or receive a call, you can quietly thank Hedy Lamarr and George Anthiel for planting the seed that made it all possible.
This article ©2011 by timorous+