Digital electronic commutator for radio direction finding system

In a radio direction finder system having an azimuthal array of directional antennas, receiver means, a source of slewing direction command signals, and cathode ray tube display means, electronic commutator means comprising:

• a plurality of RF gates and each connecting at least one of said antennas to said receiver means;
• ring counter means having a plurality of stages each corresponding to at least one of said RF gates and operative to enable said RF gates to sample radio reception by said antennas sequentially as said ring counter stages are triggered;
• a source of signals at a predetermined first frequency;
• first digital logic means for deriving signals of a second predetermined frequency from said first frequency signals and applying them as trigger signals to said ring counter means;
• second digital logic means for deriving sync signals and sine and cosine signals of a predetermined frequency from said first frequency signals and applying them to said display means whereby sweep of the cathode ray tube thereof is synchronous with operation of said ring counter so that a pattern representative of radio signals about the azimuth is displayed;
• and
• Schmidt trigger means responsive to one of said sync signals to provide signals to said display means for generation of a strobe line as a bearing indicator each sweep of said cathode ray tube.