[time-nuts] Recording mains frequency/phase [WAS: No GPS satellites]
Mark Sims
holrum at hotmail.com
Sat Feb 28 22:20:41 UTC 2015
When I first came across that article on theregister.com, I thought that it was a rather cute idea and decided to give it a try. I set up a couple of data recorders that logged AC zero crossings to an SD card (with 64 Mhz clock resolution). They were set up around 8 miles apart. I also recorded a sound file at each location from a sound card (92 kHz sample rate). None of the recordings were time-synced and the recording time-bases were simple crystal oscillators. I cut a random sections out of the sound recordings and fed them into what amounts to a correlator program and ran it against the zero-crossing logs. It had very few problems finding a best-fit of the sound snippets to the appropriate zero crossing data files.
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