A Harmonic Method of Intercomparing the Oscillators of the National Standard of Radio Frequency

A method of precisely measuring the frequency difference between two frequency standards which have nominally the same fundamental frequency is outlined. The application of this method to the continuous intercomparison of the piezo oscillators in the primary frequency standard maintained by the National Bureau of Standards is described. The customary method of measuring the frequency difference between two piezo oscillators utilizes the beat frequency between the two standards at the fundamental frequency or one of the harmonics. The method described utilizes the frequency produced by heterodyning two consecutive harmonics to obtain any desired precision of frequency comparison without necessitating the operation of any circuits at exceedingly high frequencies.