How work a DVOR?

Answer 1

The Doppler VOR DVOR is the second generation VOR, providing improved signal quality and accuracy. The REF signal of the DVOR is amplitude modulated, while the VAR signal is frequency modulated. This means that the modulations are opposite as compared to the conventional VORs. The frequency modulated signal is less subject to interference than the amplitude modulated signal and therefore the received signals provide a more accurate bearing determination.

The Doppler effect is created by letting the VAR signal be «electronically rotated», on the circular placed aerials, at a speed of 30 revolutions per second. With a diameter of the circle of 13.4 meters, the radial velocity of the VAR signal will be 1264 m/s. This will create a Doppler shift, causing the frequency to increase as the signal is rotated towards the observer and reduce as it rotates away with 30 full cycles of frequency variation per second. This results in an effective FM of 30 Hz. A receiver situated at some distance in the radiation field continuously monitors the transmitter. When certain prescribed deviations are exceeded, either the IDENT is taken off, or the complete transmitter is taken off the air.