The Civil Aeronautics Administration VHF Omnirange

This report describes the development of a vhf-omnirange system, operating in the frequency band of 112 and 118 mc. The range furnishes magnetic-bearing information with respect to the range station, and provides definite track guidance between the station and any point within its service area. The omnirange produces two 30-cps signals: one is constant in phase and independent of the aircraft's position, and the other varies in relative phase directly in accordance with the magnetic bearing of the aircraft from the station. A phase-measuring device in the receiver enables the pilot to determine his magnetic bearing with respect to the station, and to select and fly a range course on any desired magnetic bearing. The accuracy of the system, including the receiver plus ground equipment, in operation at the Civil Aeronautics Administration Experimental Station, Indianapolis, Indiana, is approximately 1.5 degrees. The ground equipment has been in continuous operation for more than 3 years. The vhf omnirange has been selected as part of the common Civil-Military System, Transition Program, as recommended by the Radio Technical Commission for Aeronautics.