A 12-Course Radio Range for Guiding Aircraft with Tuned-Reed Visual Indication

This paper describes a directive radiobeacon (or radio range) of the visual indicating type, which has been developed by the Bureau of Standards to provide radio-marked courses at air terminals where more than four airways converge. The radio range is similar in design to the double-modulation type, with the addition of a third amplifier train and accompanying modulation frequency. It provides twelve equisignal zones which may be oriented within rather wide limits and made to coincide with the converging airways. In order to prevent coupling between amplifier branches special means are employed to supply them successively rather than simultaneously. These methods are described in detail. Three-phase radio-frequency supply is used to excite the amplifier trains, which is received from a single-phase oscillator of conventional type by means of a phase divider. This prevents possible trouble due to the employment of a three-phase oscillator with three tuned oscillating circuits. To transfer the energy to the antenna system a goniometer with three primary coils is employed. These are displaced 120 deg. from each other and coupled to the two crossed loop antennas through two secondary coils whose displacement is 90 dog. This permits the use of two antennas to establish a space pattern from three amplifier branches. Means for aligning this resultant space pattern with the airways are also discussed and several examples are given. Satisfactory tests have been made at distances of more than 100 miles.