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Quasi-Doppler-Shift Radio Direction Finders

March 12th Fact-of-the-Day

Servo Corporation of America patented Quasi-Doppler-Shift Radio Direction Finders in the 1940's. Their method eliminates the need for the mechanically rotating dipole required by the standard Doppler-Shift method by rapidly commutating a receiving feed-line to a number of fixed vertical dipoles arranged in a ring to simulate the rotation of a single dipole. The result is a fixed antenna structure and a direction finding system that has exceptional performance characteristics under adverse conditions. Three or more fixed dipoles can be used. However, professional systems generally use at least eight and higher-performance systems generally use sixteen. The reliability and performance is so good compared to other methods that Quasi-Doppler-Shift Direction Finders have been installed by the Federal Aviation Administration at more than 350 airports in the United States. ©2005 Martek, International. All rights reserved.


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