5. Conclusions

Quartz resonators have been constantly evolving since their introduction in the 1930s. Progress has been made towards ever wider frequency coverage and ever higher stability. In the 1970s, the best stability was around 10 ^-12 for an Allan variance calculated at 10 s. Today, the best published results are around 6 · 10 ^-14 . In 1970, an oscillator with thermal stability of the order of 10 ^-8 was a very large peak object (> 3dm ³ ). In 1997, the best OCXOs offer a stability of less than 10 ^-10 , while large production volumes of 36 x 26 x 17 mm ³ or 40 x 30 x 20 m ³ are all...