Text: > Ever heard of "Spread Spectrum" ? One example of this technology is the use of a single channel by many transmitters at the same time, essentially the concept behind CDMA in mobile phones. Frequency Hopping may be more familiar to you and which works like this..... Assume a transmitter is able to transmit on any one discrete frequency between F1 and F100. We now force the equipment to transmit on each frequency for 1 second, but in a random fashion. Should some form of interference occur on one of say 3 of these frequencies, the system will still have achieved 97% reliability. This approach is particularly attractive where a system is required to operate under severe interference such as jamming. > > OK, now back to Hedy Lamaar, whom it turns out conceived the idea of Spread Spectrum along with a Musician friend George Antheil. They were both sitting together at a piano and Antheil was hitting random keys and Lamar was following him further down the piano, a fraction later. "Look", she said, "We're talking to each other, and yet we're changing all the time". They saw the concept of using the various patterns to create a Radio signal sequence which might by used to bypass missile jammers all set up on a paper piano roll. > > Their US patent for a "Secret Communication System" was granted in 1942 however the Navy felt that the piano roll mechanism was too cumbersome, and apparently missed the real concept anyway. Some 20 years after their Patent expired however the possible worth of "Spread Spectrum" transmissions was realized in the current Missile technology etc. > > Hedy Lamaar was later given an Electronics award in 1997. > > Check out Spread Spectrum technology for yourselves, the ARRL Handbook has a section on it, it's fairly heavy going but interesting. Unfortunately you won't find any reference to the film star and her musician friend, cruel things patents. > > Hedy's last years were ignominious to say the least, being arrested for shoplifting in L.A. in 1991. > > So there we are, Hedy Lamaar was more than just another Hollywood pretty face. > > Excerpted from The Herald Sun 21/01/00 - Assoc. Press

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