This paper describes a frequency synthesizer which enables any frequency that is harmonically related to a sub-multiple of a standard frequency to be generated by means of a decade system involving a synthesis process. The adjacent harmonic interference is substantially independent of the order of the harmonic and can be extremely small.The paper is divided into two Parts. The limitations of the present technique as applied to frequency measurements and the means of overcoming them are given in Part 1, while Part 2 outlines the principles of the frequency synthesizer and gives a detailed description of a typical example with some applications of its uses as a source.