[time-nuts] Mains as time-reference

Magnus Danielson magnus at rubidium.dyndns.org
Wed Dec 29 18:45:58 UTC 2010


Fellow time-nuts,

Just for fun I have been looking at the mains as a time-reference.

I've used an OSA 8600 as reference and divided down to PPS by a TADD-2. 
While not absolute time reference, it is way quieter than the mains so I 
think it is good enough to have some fun at least. Just to illustrate 
the issue.

I use a HP5335A to measure the time from PPS to rising edge of 50 Hz as 
being accessible through a transformer.

The ADEV has a peak at 30 s measuring 2,3E-4 and another at 6000 s 
measuring 4,3E-4.

The phase changes over -0.11923 to +10,979 so a time difference 
peak-to-peak of 11,098 seconds.

While I could refine my measurements to ensure trigger jitter is not 
causing any major issues, the ADEV slope from 1 s is rising rather than 
lowering, so it rather seems like source behaviour dominates.

While this attempt is a hack, I hope it inspires people to fiddle around 
a little. :)

Cheers,
Magnus




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