[time-nuts] The 5MHz Sweet Spot

[Tom Knox]

A while ago I mentioned 5MHz oscillators were used in most metrology applications compared to the more commonly available 10MHz because 5MHz was a sweet spot for quartz. At the time I didn't know why. I finally had a chance to ask the person I learned this from why. The main reason is simply physical size. The larger crystal lattice allows many manufacturing advantages that allow for a higher Q. He also explained I was wrong in an earlier statement, metal/quartz migration on quartz oscillator was not a major problem even after decades, but could become more of a factor if driven hard. That does not mean the deposition and lead bonding has no negative effect. The BVA solves this by capacitive coupling the quartz rather then direct metal deposition. 

Thomas Knox