[time-nuts] Rb vs.Crystal OCXO

[Tom Van Baak]

> Hi Everyone,
> I'm newer to this forum but I really enjoy reading the discussions. I have
> a pretty basic question.
> I'm wondering why one would chose an Rb Oscillator over a traditional OCXO?
> It does not immediately appear there is a phase noise advantage in the Rb..
> Thanks,
> ~Shane

Welcome to time-nuts. Good question.

In some applications the exceptional long-term frequency accuracy and stability you get with Rb is more important than the better phase noise, smaller size, lower power, better short-term stability, longer lifetime, or cheaper price that you get with an OCXO.

When you buy a new OCXO, it might be accurate to 4 or 5 or 6 digits, out-of-the-box. You have to mechanically (screw) or electronically (EFC) calibrate it to get closer. If you want, say, 9 digits of accuracy, then you may have to re-calibrate it every day or at least once a week.

When you buy a new Rb, it might be accurate to 9 or 10 or 11 digits, out-of-the-box. If you want, say, 9 digits of accuracy, then you may have to calibrate it every couple of years.

/tvb