Measured vs. volume model-predicted flicker-of-frequency instability in VHF quartz crystal resonators

Both passive, in-bridge and in-oscillator measurements for AT, SC, and BT-cut, overtone-mode resonators operating at 40, 80, 100, and 160 MHz have been performed. Measurements were made using four-crystal oscillators as low-noise reference signal generators. The data indicate poor agreement between measured and mode-predicted resonator stability, especially for fifth-overtone AT and SC-cut resonators operating at 40 and 160 MHz. Measured data were also compared to predictions using an alternative model proposed by T. Parker (1985). Using the Parker model, relatively poor agreement was found for the case of BT-cut resonators. The data suggest that further refinement of resonator short-term stability models is necessary