While Antheil was besieging Washington with glandular criminology between sessions at the drafting board with Hedy Lamarr, Hedy was filming Ziegfeld Girl, choreographed by Busby Berkeley, co-starring Judy Garland, Lana Turner, James Stewart, and Tony Martin. Shooting began in September 1940 and lasted until January 1941, coterminous with the conception of frequency hopping. The jeweled peacock-feather headdress Hedy wore in the film, one of her biographers writes, “became her trademark.” It was an Adrian concoction, high camp, and one of his last; he left MGM in September 1941 to start his own business. Hedy, after filming Ziegfeld Girl by day and inventing by night, flew off to the Riviera early in the new year for a midwinter vacation. The British foreign secretary, Anthony Eden, was there; at his request, she briefed him on the state of European public opinion.
Hedy legally changed her name that winter, from Hedwig Kiesler to Hedy Lamarr. Her mother was now living with friends in London, and Hedy continued to pursue arranging her immigration. She also hired the Los Angeles legal firm of Lyon & Lyon to develop the Lamarr-Antheil patent application, which involved searching the records for possible prior knowledge and helping craft the most encompassing possible language.
Between 23 December 1940, when the two inventors submitted their first rough ideas to the National Inventors Council, and 10 June 1941, when they filed their patent application not merely for a radio-controlled torpedo but for a much broader, pioneering, and fundamental “Secret Communication System,” Hedy and George constructively reduced their invention to practice. Doing so was necessary to win a patent, because a patent requires that novel ideas be embodied in a mechanism that works. But again crucially: the particular mechanism described in the patent application need be only illustrative, one of a number of possible embodiments. Hedy and George chose to embody their idea in a player-piano-like mechanism because they knew how to design such a mechanism, not because it was the only possible system that their idea would support.
“Langner seems to be deeply interested,” Antheil wrote to Bullitt late in this second phase of invention development. “He promises to promote the matter with all possible vigor; he believes that it will work.” Langner had arranged the connection with Samuel Stuart Mackeown, professor of electrical engineering at Caltech in Pasadena. “He requested Mackeown to get in touch with me and work out some additional details,” Antheil wrote. “This was done, and Dr. Mackeown is now as enthusiastic about the torpedo anti-jam device as is anyone. He states positively that it will work.”
[NINE]
Red-Hot Apparatus
In the proposal that Hedy Lamarr and George Antheil sent to the National Inventors Council in December 1940, there is an important final paragraph that hints at the next stage of development of the ideas they described:
We are, at present, working upon a method of sending the radio signal from the sender-ship to torpedo which will incline to make it even more silent and undetectable than now, due to the actual sender-apparatus itself.
Around this time, Antheil carefully sketched and noted their “method” on two sides of an ordinary No. 10 office envelope. Their invention, he wrote, now consisted of “two sister system[s],” which he lists as “(1) Synchronized alternating radio wavelength devices for both sending ship and receiving torpedo” and “(2) Minimum broadcast time length device to double ensure torpedo against jamming.” Number 2 was the system Hedy and George had presented to the National Inventors Council on 23 December that depended on limiting the transmissions to brief bursts between stretches of radio silence to limit enemy jamming. Number 1 was the new system they were working on in the winter and spring of 1941, which Antheil listed as “synchronized alternating”—that is, the transmitter and the receiver frequency-hopped together in synchrony.
Now, however, in his literally back-of-the-envelope diagram, Antheil added a crucial new concept: “ribbons” perforated with instructions to the torpedo about both the minimum-time sequence and the frequency-hopping sequence:
(a) The ribbon wavelength synchronizer runs its perforations continuously, allowing sender to broadcast at any time deemed necessary—and as often.
(b) The ribbon wavelength alternator synchronizer has a predetermined pattern—impossible to guess at by the enemy—since it insures a two-way lock against such possible jamming.
So the signal that passed between the ship and its torpedo would now not only be extremely brief but also hop from frequency to frequency. And the hopping would be not manually controlled but controlled by “ribbons,” the general term Hedy and George were using here for a control device such as a player piano’s scrolling roll of paper. Once again, their notations make it clear that they were thinking beyond the specific mechanism of the player piano to a more universal concept of analog control programmed with punched tape.
Antheil had faced a similar control problem when he attempted to synchronize player pianos, and the mechanism he now proposed for his and Hedy’s invention was similar: using matching player-piano-like rolls of paper in transmitter and receiver with slots cut into the paper to encode the changes in frequency. As the slots rolled over a control head, they would actuate a vacuum mechanism similar to the mechanism in a player piano, except that instead of the operation culminating in a pushrod moving the piano action, it would culminate in pushrods closing a series of switches. The switches would be arrayed below the pushrods. Closing a specific switch would connect one of several differently tuned condensers—devices that store electric charge—to an oscillator. An oscillator is an electronic circuit that generates a regularly changing radio signal, called a carrier wave:
Each different condenser would impose a different frequency on the carrier wave—more cycles per second or fewer:
Antheil waggishly affirmed a range of up to eighty-eight frequency hops for the system, the number of keys on a piano—a musician’s sly autograph.
With a signal hopping all over the radio spectrum, and doing so not regularly but arbitrarily, more or less at random, the transmission would be impossible to jam because an enemy would be unable to follow it. He might accidentally jam one frequency if the signal happened to hop there, but with a potential for hundreds of hops per minute, the transmission would lose very little information from such minor interference. Anyone listening on a single frequency would not even realize a signal was being transmitted, since he would hear, at most, only an occasional brief blip.
To make jamming even more difficult, George and Hedy proposed using seven tuning condensers on the transmitter but only four on the receiver. Three of the transmitter channels would thus send a false signal, one with no operating function, further complicating any effort to determine which transmissions to jam. Antheil’s hobby of inventing and breaking codes, which he had shared with his deceased brother, Henry, found application in this feature.
How much of the electronics of their invention Hedy and George designed themselves isn’t clear from the available record. Obviously, the player-piano-like system was George’s contribution. He also knew more than a little about radio electronics from his Hollywood experience recording his music for reproduction on sound film. “It’s my daily work,” he reminded Bill Bullitt once, “here in the studios, to know everything about microphones and sound-recording.” Hedy’s knowledge would have been whatever she had picked up during her years at the Mandl dinner table; as Antheil wrote to Bullitt, “Hedy was once married to a big Austrian munitions manufacturer and knows her munitions upside down.” (In the same letter Antheil noted of their torpedo that it “can be guided over twenty miles by radio,” which may have overestimated a torpedo’s fuel capacity.)