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Interview with George Colby - 11/19/00

Summary: Had to design a waveform that was compatible with ATCRBS. Discrete addressing would cut down on traffic. Knew that Lincoln Lab had to build a cheap transponder for the general aviation community.

  • In 1970, Lincoln Laboratory decided to pursue research work with the FAA. They took one of the divisions run by Herb Weiss. Under him was Paul Drouilhet, who was told to build a group. George Colby was the 8th person to join that group. Unless most people, he came from industry rather than from Lincoln Lab.

  • His first effort was to do a characterization of ATCRBS transponders. They built an airborne measurement facility (AMF) that one could fly around and map signals. They visited different local airports and issued a report. Then the development turned to collision avoidance systems.

  • One of the considerations was the design of an appropriate waveform, since it had to be compatable with the ATCRBS waveforms. "At that time the projection for air traffic was growing exponentially and there was a fear that the air traffic control system would just become simply overloaded." They felt that discrete addressing would "cut down on the traffic."

  • His specialty was in hardware design. He designed and built the transponder. His group knew that any system had to be affordable to general aviation. There were already quite inexpensive conventional ATCRBS transponders, but "there semeed to be a very strong correlation between cost and consistency of the transponder....the cheaper were all over the place in terms of frequency and stability."

  • "As I recall, personal concern of mine was to keep power consumption down...just a matter of efficient circuit design so that we didn't get a huge battery drain." The problem didn't quite matter nearly much to commercial airlines, but battery drain was a big deal for general aviation.



  • The Story of Mode S: An Air Traffic Control Data Link Technology last modified: 12.06.2000