Doppler DFer

• Designed by WA2EBY, plans published in QST Magazine, May 1999.

• 4-antenna array simulates a single spinning antenna

• As the antenna “spins” it moves towards and away from the transmitter a cyclical Doppler shift is imparted to the FM signal.

• The FM receiver demodulates the shift as a 500Hz sine wave.

• The DFer measures the phase difference between the spinning antenna and the received signal.