Rubidium vs OCXO — Which Frequency Reference Do You Need?

Both rubidium frequency standards and OCXOs are used where quartz alone isn't accurate or stable enough — but they sit at different points on the performance and cost spectrum, and understanding the difference helps you avoid over- or under-specifying your system.

What is an OCXO?

An OCXO is a quartz crystal held at a constant temperature inside a small oven, giving it excellent short-term stability and low phase noise. Read our full guide to what an OCXO is for more detail.

What is a rubidium frequency standard?

A rubidium frequency standard uses the resonance of rubidium atoms as its reference instead of a quartz crystal. This gives it a fundamentally different — and generally superior — long-term accuracy and stability, since atomic transitions don't drift the way a mechanical quartz resonator can over months and years.

Comparing the two

• Long-term accuracy: Rubidium significantly outperforms OCXO over weeks, months, and years — quartz inevitably ages and drifts, atomic references do not in the same way.
• Short-term stability and phase noise: A good OCXO can actually match or exceed rubidium here, which is why the two are often combined (a rubidium-disciplined OCXO, for example).
• Holdover: Rubidium holds accurate timing for far longer during a reference outage.
• Size and power: OCXOs are smaller and consume less power.
• Cost: OCXOs are considerably more affordable.
• Warm-up: Both need a warm-up period, but rubidium standards typically take longer to reach full specification.

Which one do you need?

If your application needs excellent short-term stability and low phase noise at a reasonable cost and size — RF systems, telecom infrastructure, general test equipment — an OCXO is usually the right choice. If you need the best possible long-term accuracy and holdover — metrology labs, GNSS timing infrastructure, network synchronisation masters — a rubidium standard is worth the extra size, power, and cost.

Vikronix supplies both

Browse our OCXO range or our Frequency Standards range (including rubidium references via Quartzlock), or get in touch if you're not sure which fits your application.