Harmonic generation and mixing in the 8∼80 GHz region has been studied in point‐contact junctions made with sharply tipped tungsten whisker and sintered polycrystalline YBa2Cu3O7−yor single‐crystal Bi2Sr2CaCu2Oxat room temperature. The signal‐to‐noise ratio (SNR) of beat notes as a function of harmonic numbernis observed up to the tenth order and decreases with a slope ofn−5.6for even harmonic numbers. The dependence of the SNR of the beat note on a dc bias voltage and the current‐voltage characteristics have been measured simultaneously and theoretically analyzed using the current‐dependent mixing characteristics. The potential barrier and the insulating thickness for YBa2Cu3O7−yare estimated.