[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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