I was recently listening to one of my favorite Podcasts… The Way I Heard It with Mike Rowe. I’ve been working my way back through the archives of this show and got to Episode 1: The Million Dollar Kiss. He was telling the story of a young woman, who escaped from a life she didn’t want to take part in, only to become famous for her face in Hollywood, but was also a savvy inventor. During WWII, she patented a machine that would alter technology forever. This woman was, of course, Hedy Lamarr.
I’m obviously a little behind on learning about her, but most of the media available about her talks about how she was mostly recognized for her beauty and it took many decades for her to be recognized for her contribution to modern day communications… Notably, WiFi. The most interesting part for me is the invention itself.
Hedy Lamar sat down in 1942 with the intention of developing an idea to help out the navy. She disliked Nazis and wanted to be apart of the retaliation effort. So she started by thinking about torpedos. And how we communicate with torpedos to keep them on track. And why that wasn’t working. She discovered that the Germans were discovering the radio frequency on which we were communicating to the torpedos, and then sending out opposing messages on the same frequency in order to push the torpedo off track.
She postulated that frequencies could be changed intermittently and for incongruent amounts of time but still carry the necessary data to guide the torpedo. She began to develop this idea and enlisted the help of her composer friend, George Antheil in order to implement this idea. George was a master at synchronizing player pianos in order to compose symphonies. He and Hedy surmised that they could use a miniaturized version of a player piano scroll in order to synchronize the transmitter (“Mother Ship”) and receiver (torpedo). To be able to send and receive on the same hopping frequencies.
She invented channels, and labeled them A-H. But to add a level of complexity only allowed the receiver (torpedo) to receive on channels D, E, F, and G. She did this so that the radio operator at the transmitter could send out spoof signals on a frequency that was not actually received in order to confuse the enemy operators. The radio operator at the transmitter would get a warning indicator when an unusable channel was being used and could still send across that channel, but know that it wouldn’t be received by the torpedo.
The data being sent from transmitter to receiver was not terribly complex. Very simply it was an R Key (Right) and an L Key (Left) for rudder control. It’s easy to see how this was easily adapted into 1s and 0s in the first implementations of WiFi.
Her entire invention is purely mechanical in nature. It works using the miniaturized piano scroll along with mechanical oscillators, modulators, and amplifiers and runs on a battery.
The idea of frequency hopping and RF modulation is a fairly complicated one in modern times. I’m blown away by it’s ingenious implementation so long ago.
You can find the text and diagram of the original patent here. It’s a good read.