From time to time I try my hand at writing fiction. It is advisable, they say, to create convincing characters, to describe real people doing plausible things. Hollywood actress Hedy Lamarr, and composer George Antheil, seem to have taken that rule and stamped on it, and these two are real life characters.
Hedy subsequently became the trophy wife of a wealthy European arms manufacturer, Friedrich Mandl, who counted Hitler and Mussolini among his chums. Mandl wanted to control Hedy’s life, he tried to buy up all existing prints of Ecstasy and destroy them. Hedy says she hid out from Mandl in a brothel and ended up having to ‘entertain’ one of the clients in order to maintain her cover. The marriage didn't last, she met Louis B. Mayer and moved to Hollywood.
Ballet Mécanique which was to be performed by an orchestra of some 16 player pianos, see Essential Music. In the era before electronic amplification Antheil wanted to achieve very high volume levels, rock concert levels, and using 16 player pianos was how he chose to do it.
George turned up in Hollywood in 1938, then tried his hand at novel writing, he wrote an advice column for Esquire, and eventually wrote the musical scores for a number of Hollywood movies. He also authored a number of books of male interest including one called "The Glandbook for the Questing Male" which was intended to give men an insight into identifying the sexual availability of women. Hedy contacted him when she was looking for a non-surgical means to increase her breast size.
So, in 1940 George and Hedy met and the conversation turned, somehow, to the radio control of torpedoes! Most popular accounts say that Hedy brought, from her time married to her first husband, knowledge of the potential control problems of torpedoes. George brought a knowledge of player piano technology.
At the time torpedoes were mainly free running devices and homing systems were still a little way in the future. When Hedy and George were getting their heads together radio control had been tried. They knew that a radio control system would be subject to jamming, (transmissions on the same frequency which would scrabble the control signals) They decided that in order for radio control to be viable the control system would need to hop quickly between different frequencies. The idea was that the controlling transmitter would constantly change frequency and that the receiver in the torpedo would change its frequency, to follow that of the transmitter.
The diagram, from the patent, shows the transmitter and receiver. Hedy has signed it 'Hedy Hiesler Markey', which was her married name at the time.
The system is controlling the rudder of a torpedo and a tone corresponding to 100 Hz will drive the rudder left and 50 Hz will drive it to the right. At the same time, the transmission frequency, which on a conventional broadcast transmitter is fixed, is made to change under the control of a player piano type roll. A motor is driving the piano roll, and as the piano roll perforations pass over switches different capacitors are switched into the master oscillator circuit of the transmitter.
The switched capacitors change the frequency of the transmitter, if you were listening to the transmitter on a radio you’d need to constantly re-tune, as to a different station. If you were trying to jam the system, you’d need to retune your transmitter as well. Of course, in order to maintain control, the receiver in the torpedo has to switch to the new frequency automatically. It also has a piano roll, punched identically to that in the transmitter, this would retune the receiver so that it stays in tune with the transmitter.
The transmitter and receiver need to stay synchronized in order for continuity of communications to be maintained. George had already encountered synchronization problems with his work Ballet Mécanique and those 16 player pianos. Lack of synchronization between the instruments had turned the first attempts into a cacophony and the 16 pianos had been reduced to four. The patent recognizes the synchronisation problem and although they do not illustrate a synchronization method they suggest it is prior art, and already in use in telegraphy and television.
The US Navy did not persevere with Hedy and George’s invention. Radio control of torpedoes was quite a difficult trick, and most torpedoes were straight runners, with simple autopilots to control direction and depth, or were controlled by wires. Eventually Germany introduced homing torpedoes which went for the acoustic noise of the propellers of the target.
However, the 50Hz, 100Hz modulators could easily have been replaced by a speech modulator, and this would have given secure voice communications much like the Havequick radios currently in use by the British Armed forces. In the Havequick the transmitter frequency comes from a pseudo-random algorithm which can be seeded by the current date and time. The sequence of the pseudo-random number is highly classified and knowing it would be like having a copy of one of George and Hedy’s player piano rolls. – It would permit an outside agency to know the sequence of frequencies which would still allow jamming or interception the transmission.
The mechanical system doomed the practicality of the system. The player piano roll needed a source of vacuum for the reader switches and the synchronisation system would have tricky to impliment. Although the principle described is sound, as with Babbages mechanical computer, proper electronics is much better. Hedy and George, like Charles Babbage before them, had a good idea that was just a little ahead of its time. They had to use mechanical methods, methods which were not totally impractical but would be better achieved using electronic switching techniques.
Hedy Lamarr, from nude scenes in Ecstasy to Time Domain Frequency Multiplexing. If you put her in a short story they’d laugh at you. Incredible characters, don’t you just love them?