A CRYSTAL CONTROLLED ADF (AUTOMATIC DIRECTION FINDER) UTILIZES A STABILIZED MASTER OSCILLATOR (SMO) AND A SINGLE REFERENCE CRYSTAL TO PROVIDE DIGITAL FREQUENCY SELECTION IN PRESELECTED INCREMENTS OF ANY DESIRED FREQUENCY WITHIN THE TUNING RANGE OF THE ADF. A REFERENCE FREQUENCY IS DERIVED FORM THE SINGLE REFERENCE CRYSTAL AND IS USED AS A COMPARISON FOR A NEWLY SELECTED FREQUENCLY. A VOLTAGE CONTROLLED OSCILLATOR (VCO) IS TUNED BY A CARACTOR DIODE FROM A PORTION OF THE SMO CIRCUIT. THE OUTPUT OF THE VCO IS FED TO A VARIABLE FREQUENCY DIVIDER WHICH DIVIDES THE VCO FREQUENCY. A FREQUENCY DISCRIMINATOR BRINGS THE VCO FREQUENCY CLOSE TO THE REFERENCE FREQUENCY AND A PHASE DETECTOR PROVIDES THE ADDITIONAL FINE CONTROL THAT BRINGS THE VCO TO THE EXACT SELECTED FREQUENCY WITHIN THE LIMITS OF THE CRYSTAL REFERENCE.