Abstract: A full-octave direct frequency synthesizer which can switch in under one microsecond and whose control frequencies are all harmonics of a single precision clock. Each stage generates a frequency in the 50-100 MHz range; the generated frequency is the sum of one-tenth of the input frequency plus an added increment within the full octave 50-100 MHz range. Each stage includes a first section for operating on the input frequency and the control frequencies for deriving a selected one of five possible frequencies, and a second section for deriving two possible frequencies from each of the five derivable by the first section. The final stage generates a frequency in the 500-1,000 MHz range, in steps of 0.5 Hz.