I believe radio and television broadcasting makes use of accurate time in
studio and the wider transmission network.

I've worked in quite a few data centres where there's been a local NTP
server that was synced to GPS or, prior to the availability of GPS, the
"local" broadcast time signal.

On Tue, 29 Nov 2022, 09:29 Dr. David Kirkby via time-nuts, <
time-nuts@lists.febo.com> wrote:

I believe the electricity distribution network uses real time to measure
phase.
It used to be  done by modulating an RF carrier and sending over the grid
superimposed on HV, but the ability to get nanosecond real time precision
removes the need to do that - they can just measure the AC waveform
directly at the point of measurement.  They also use fibre optic as an
alternative.

Andy
www.g4jnt.com

On Tue, 29 Nov 2022 at 09:31, Dr. David Kirkby via time-nuts <
time-nuts@lists.febo.com> wrote:

Definitely navigation and positioning in real-time.

The better the time factor the better the position and with that navigation

On Tue, Nov 29, 2022, 11:30 AM Dr. David Kirkby via time-nuts <
time-nuts@lists.febo.com> wrote:

On 11/28/2022 8:45 PM, Dr. David Kirkby via time-nuts wrote:

Greetings David,

As a Time-Nut of the lowest order myself (Junior Time Nut?  Apprentice Time Nut?) I probably should wait for the answers of more senior Time-Nuts...but other than GPS/cellular...I think you've got two other sources that the non-Nut public uses:

--> WWVB / 60 kHz.  Many "atomic" clocks can sync to the 60 kHz signals sent by WWV.  Above my right monitor I've got the Time-Nuts variant of one of these clocks, a kit from Universal Solder in Canada:

https://universal-solder.ca/product/canaduino-application-development-kit-with-everset-es100-mod-wwvb-bpsk-atomic-clock-receiver-module/

(there are other sources outside the USA that I can't recall on different frequencies)

One of the really nice things about this kit is that if you know basic Arduino, you can tweak it's code (maybe open-source?) to your liking.  I've been meaning to modify the Arduino code on mine so that it constantly syncs to WWVB rather than once a day now.

-->  NTP.  While I can't remember where I saw it, I did see a clock kit (maybe with Nixie tubes?) that synced to NTP.  My bedside table has a little ESP32 "weather station" that's got a time display that comes from NTP and it's always spot dead on compared to the cell phone.  Truth be told, most people sitting at a computer will use the time from their computer clock, and if it's synced via NTP, that's likely way more precise than anyone will ever need.

You could also listen manually to WWV on 5, 10, 15, and 20 MHz shortwave, and call in to the time phone number that I can't recall, but not sure how many people do this these days?  I do use WWV as a test signal when I work on shortwave radios.  I do recall growing up (now 40 years ago almost - eeek!) my father would call the time number, set his watch, then set all the other clocks in the house to his watch that was the "standard."  :)

Past those sources, the common quartz-movement wall clock is probably much better today than anything from years ago.  As long as it's set right once, it's probably close enough for anything a human would need?

Just my thoughts!
-ben

PTP is used in digital radio and TV studios and in the distribution of studio programming to transmitter sites.

Sent from my iPhone

Hi,

I'm sure others can speak in more depth than I, but birtually all major
cloud providers and/or services that make use of large datacentres
(think Facebook, Instagram, Linkedin etc. if you want publicly aware
examples) - will run their own NTP servers or other similar time
standards to ensure their geographically dispersed systems have a shared
understanding of what the time is.

This is crucial for things as mundane as consistent end user experience
(who posted first?) to ensuring network security.

Cheers,
Hugh

On 29/11/2022 08:15, Dr. David Kirkby via time-nuts wrote:

At least when I did VLBI for geodesy, we used GPS to do the initial rough synchronization so we could get fringes.  After that the offset between the local masers is part of the solution.  You needed masers, though that could be considered syntonization rather has synchronization.  And since Earth rotation is defined in terms of atomic time, you obviously need a tie to UTC.

On 11/28/22 20:45, Dr. David Kirkby via time-nuts wrote:

• Navigation
• Anything that requires precise frequency
• Anything that requires time synchronization

Radio communications systems that require synchronization to keep the
transmitter and receiver "in step" use GNSS for synchronization. Also
systems that do radio direction finding by time difference of arrival
(TDOA) need precise synchronization of all the receivers.

With the advent of GNSS we have high accuracy time and frequency
standards nearly anywhere on the earth with very simple equipment. It
has opened up whole new industries.

One interesting one is an autopilot that sports a "land this airplane"
button. The AP looks up the nearest suitable airport from a database and
then navigates to it and lands the airplane. This is a natural result of
high-accuracy position information, which itself is a result of
high-accuracy timing.

Those of us who mess about with navigation see time and space as
opposite sides of the same coin.

--

*Brian Lloyd *
WB5BL - J79BL - NNA6BL
706 Flightline
Spring Branch, TX 78070
brian@heaviside-hf.com mailto://brian@heaviside-hf.com
+1.210.620.0011