Abstract: A proportional digital control system for radio frequency synthesizers using binary coded decimal control to a frequency synthesizer tunable in contiguous small interval increasing or decreasing steps throughout the frequency bandwidth range of operation. A fine tune dial switch circuit generates a two signal output with one a step count signal and the other an up-down control signal generated only upon rotation of the fine tuning dial and with the signal pulse rates thereof a direct function of the rate of fine tune dial turning. The up-down control signal is an up or down signal input to up-down pulse counting to BCD output circuits as determined by phase relation thereof to the step count signal and with the phase determined by direction of fine tune dial turning clockwise for up count and counterclockwise for down count.