A Simultaneous Radiotelephone and Visual Range Beacon for the Airways

Abstract

Increased use of the airway radio services by transport operators has resulted in a demand for continuous range beacon service. At the same time the weather broadcast information has increased in importance and the interruptions to the beacon service have become more frequent. To eliminate difficulties arising from this conflict, a transmitting system has been developed which provides simultaneous transmission of visual range beacon and radiotelephone signals. This system is designed to employ existing equipment so far as possible. By combining two transmitting sets into one the cost of buildings and antenna equipment is reduced. Continuous check on the operation of both systems can be obtained with less personnel than required at present. The transmitting set consists of a two-kilowatt radiotelephone transmitter operating into a nondirective antenna system and an additional set of amplifier branches supplying power through a goniometer into two loop antennas. The two antenna systems are symmetrically disposed with respect to each other and coupling effects are balanced out to prevent distortion of the space pattern. The phase of the currents in the different antenna systems is controlled by a phase-shift unit and means for checking the adjustment of this phase relationship continuously is provided. The equipment on the airplane to receive this service is changed only by the addition of a small filter unit which keeps the low-frequency reed voltages from reaching the head telephones and the voice frequencies from the reed indicator.