This paper describes an analysis of the close to carrier phase noise characteristics of the Colpitts and Butler oscillator circuits. It is shown that the quality factor can be improved by introducing two or more crystal resonators in the oscillation circuits. Based on the Leeson's model, the near carrier phase noise is estimated using the calculated quality-factor obtained by the analysis of the frequency slope in the output impedance. As a result, it was shown by using plural crystal resonators in the phase noise close to carrier frequencies are improved.