Instability of quartz crystal oscillator frequencies

Abstract

1) From the above relation of the oscillator frequency instability to the measuring time intervals it follows that the short-term frequency instability rises with a decreasing time interval smaller than one minute. For an interval of 1.9 sec it amounts to 14·10−10 (Fig. 1, surface oscillators Nos. 2 and 4). The minimum value of the frequency instability of underground and surface oscillators lies in the limits of 1–4 minutes and is equal approximately to (2–3)·10−10. For time intervals above that value the frequency instability increases again and for a 24-hour frequency instability amounts to (4.8–7.8)·10−10 for surface and to 7.4·10−10 for underground oscillators. 2. The frequency instability of underground oscillators differs but little from that of surface oscillators. 3. The distribution of the frequency instability variations of quartz oscillators has a random nature and follows in the main the normal distribution law. This applies not only to the short-term, but also to the 24-hour frequency instability of oscillators which have steady stabilized supplies and temperature over long periods of time.