Maser Analysis: Short Term and Phase Noise Performance

This page reports the results of short-term (from 0.001 second to a few days) stability of the Morehead VLG-10-1 P2 maser versus a selection of quiet oscillators. However, more properly this is reporting the stability performance of those oscillators as, except at averaging times of a few seconds or less, the maser is more stable than any of the references.

The maser's phase noise was also measured. However, this measurement was made at the 10 MHz output and it is not known how this data correlates with the maser 100 MHz output.

The first reference against which the maser was tested is an Oscilloquartz 8607 option 008 BVA oven-controlled quartz oscillator ("OCXO"). The BVA with the 008 option is the lowest ADEV quartz oscillator that is commercially available. It is specified to have an ADEV of 8x10-14 from averaging periods ("tau") of three to thirty seconds. In fact, the BVA is frequently used as the "flywheel" oscillator in masers.

Now, the maser should be better than the BVA for tau greater than 10 seconds or so -- one currently available maser, the MicroSemi MHM-2010 is specified for ADEV of 2x10e-14 for tau of 10 seconds, improving to 5x10-15 at 100 seconds.) But if nothing else, this is a way to see how well the BVA performs!

An issue with any quartz oscillator is that it drifts -- its frequency changes, hopefully in a predictable way, over time. The standard ADEV calculation is influenced by this drift. To minimize its effects, we don't want to collect data much longer than we have to. So, I did two measurements of the BVA against the maser: one for 30 minutes, taking 1000 samples per second to yield ADEV down to 0.001 second, and a second for 12 hours at one sample per second to yield ADEV out to about 10K seconds. Here are the results, presented with error bars to give a sense of how reliable the values are (the more samples, the greater the confidence).