[time-nuts] Building a mains frequency monitor

Tom Van Baak tvb at LeapSecond.com
Thu Apr 7 14:44:07 UTC 2016


Mark,

Start with:

https://en.wikipedia.org/wiki/Electrical_network_frequency_analysis

and then spend some time searching. There's hundreds of technical papers and interesting details. Definitely time nut material.

/tvb


----- Original Message ----- 
From: "Mark Sims" <holrum at hotmail.com>
To: <time-nuts at febo.com>
Sent: Wednesday, April 06, 2016 10:27 PM
Subject: [time-nuts] Building a mains frequency monitor


> And that can be very interesting...  a while back I read some stories on how the NSA, police, etc could find out where an audio recording was made by correlating AC hum in the recording with logs that they had of the power grids.  Apparently logging AC mains is rather popular among the spooky / law enforcement types around the world (Britain appears to be rather fond of it).
> I did an experiment where I logged the AC mains at a few places around town along with some audio recordings made in the same areas.  I used some simple correlation software and could easily determine where and when the recordings were made.
> -----------------
>> Phase noise? The line frequency shifts phase every time a major
> electrical load is added or dropped from the power line.
> 
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