A device for generating a spectrally pure waveform of a desired frequency including an oven controlled crystal oscillator (122) for generating a reference frequency signal, a waveform memory (116) containing data on the waveform, a segment determination circuit (120) coupled to the waveform memory (116) for creating segments of the waveform in the waveform memory (116) based on the reference frequency signal and the desired frequency, a programmable memory (124) coupled to the segment determination circuit (120) for receiving and storing the segments of the waveform in dedicated address memories, a digital-to-analog converter (126) coupled to the programmable memory (124) for downloading the address memories of the programmable memory (124) and forming analog signals, and a filtering component (128) for filtering the analog signals to obtain the waveform of the desired frequency.