A common guideline is that you'll will need the turning level with the crystal to generally be ten°C increased when compared to the upper operating temperature in the OCXO oscillator circuit. They required even more enhancements in temperature stability, electric power use, and period sound relative to additional Sophisticated oscillators. https://temperature-compensated-c93715.verybigblog.com/30461297/the-greatest-guide-to-tcxo-oscillators