VHF Omnirange accuracy improvements

The paper covers some of the most important advances in accuracy improvements of the VHF Omnirange made over the last 14 years. The development of the conventional VOR transmitting antenna is described. By means of a universal ground calibration technique the omnibearing error has been minimized and made essentially uniform from station to station at the VOR facilities. The problems of siting VOR stations are described. The developments of the Doppler VOR and the muitilobe precision VOR have been conducted to minimize siting errors. The area of tower VOR facilities is introduced as a possible solution to siting errors, particularly siting errors not amenable to Doppler VOR and muitilobe precision VOR techniques. The reduction of the parasitic currents of the Doppler VOR antenna system is outlined. Advances in the simulation of Doppler VOR antenna rotation results in less spurious sideband components. A short discussion is presented on single-sideband vs. double-sideband Doppler VOR operation.