**Stability** of the GPSDO (part 0091-000) as expressed by the Allan Deviation has been independently checked by Tom van Baak :

**http://www.nist.gov/pml/div688/grp40/glossary.cfm#Accuracy** *σ(τ) is a stability metric which shows the RMS frequency change you can expect over a τ second interval. Frequency deviations measured at 10 MHz relative to an atomic frequency standard using a TSC 5110A time interval analyser. More.*

**Phase Noise** of the GPSDO has been independently checked by Tom van Baak :

Phase Noise *is the short term (say 1s or less) fluctuations in*
*the phase of a waveform, and is typically the noise you could "hear" around a carrier signal on a radio. This plot was made
using a TSC 5120A Phase Noise Test Set and a Wenzel 5 MHz Ultra-Low-Noise reference oscillator. The solidus is the instrumentation floor. More.*

**Accuracy:** From a practical viewpoint, if you measure the GPSDO frequency over a short period, the spread in readings is a useful indication of accuracy:

**Histogram** *of GPSDO frequency deviation measured over 10s intervals using using an HP53131A Universal Counter and Rubidium reference oscillator. The standard deviation is 10 ^{-11} which implies that 99% of measurements will fall within ±3x10^{-11 } or ±0.0003 Hz*

**Harmonics:** On a spectrum analyser, the GPSDO output signal level is 13 dBm (1V rms). The 2nd harmonic is -46 dB down and the remainder are below -60 dB.

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Last updated: 2020 Jul 05