[time-nuts] Re Another reason to monitor line frequency

[dschuecker]

Hi,

here in Germany police is recording line frequency since 2010, just as I 
do :).

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

https://de.wikipedia.org/wiki/Netzfrequenz_als_Grundlage_f%C3%BCr_forensische_Analysen

Don't know if they brought someone to jail with this.

With newer audio equipment you should get lower hum levels. I do not 
think that you find any harmonics of 50Hz or 60Hz for, say the audio 
track of a youtube video, I never tried, though. For my audio tape 
recorder of the 1970s you will surely get a hum signature.

Maybe there is also a chance to find the hum in the brightness of the 
video signal.

There are other strange aspects on grid frequency: for the first 15min 
of some hours of the day grid frequency is systematic high or low. This 
has to do with the spot market trade period of 15 min and a systematic 
over/underestimate of the demand/production. A too high demand brings 
grid frequency down and vice versa.

Cheers

Detlef

Am 19.01.2022 um 12:31 schrieb Hal Murray:
> The hidden background noise that can catch criminals
> https://www.youtube.com/watch?v=e0elNU0iOMY
> 5 1/2 minutes.
>
> He's good in a geeky sort of way. Time sink warning.
>
> Why European Clocks are Running Slow, and British Clocks Aren't
> https://www.youtube.com/watch?v=bij-JjzCa7o
> 4 minutes
>
> Here is his rant on time zones. :)
>
> The Problem with Time & Timezones - Computerphile
> https://www.youtube.com/watch?v=-5wpm-gesOY
> 10 minutes.
>
>
>