That is cool. I use a gps NTP server on my home network and live with sub-millisecond time sync. I’d go PTP but the equipment is a bit too expensive if the only value add is better time sync and I don’t need additional bandwidth. Prices coming down would be nice.
What's expensive? PTP is widely supported on commodity hardware these days. I think most Intel NICs support it, quite a few Realtek and a lot of embedded stuff, down to even MCUs like STM32.
Even if you want a NIC with a stable oscillator or GPS inputs to act as a grandmaster, you can buy an E810 with the necessary hardware from eBay etc. for a few hundred or DIY something yourself much cheaper.
GNSS time is still cooler because you can have extremely accurate time and a reading of your position without the broadcasting satellites knowing you're there.
With GNSS+PPS and a hardware timer latch you can easily sync internal microcontroller timers to 2 to 3-digits nanoseconds against the global standard with a tightly controlled loop. But cannot get better than the PPS signal itself (roughly 30-100nS).
Everything below needs that a huge amount of engineering. CERN&friends developed the "White Rabbit" (https://ohwr.org/projects/white-rabbit/) system for this. This allows sub-Nanoseconds syncing of netwoked devices.
I've wondered if you could have an array of "firecrackers", each timed very precisely, with perfect spatial knowledge of each, and synchronize their ignition to produce arbitrary shaped pressure waves.
When you drive through the Texas Pandhandle at night, squaremiles of electric windmills blink together – like fireflies stirring across flatlines of [L]one-star horizon.
They've been simultaneous for decades... and remains a breathtaking detour (if you're out there, schedule night-travel).
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I like the similar project which uses GPS signal offsets, captured on a RaspberryPi, to then broadcast (e.g:) a local-network-timeserver.
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[ 3.4 ms ] story [ 46.0 ms ] threadEven if you want a NIC with a stable oscillator or GPS inputs to act as a grandmaster, you can buy an E810 with the necessary hardware from eBay etc. for a few hundred or DIY something yourself much cheaper.
> 2Way
Does that mean you won't get to know the time unless you let them spy on your physical location too? That's what the diagram implies: https://www.gps.gov/sites/default/files/2025-06/CGSICMeeting...
GNSS time is still cooler because you can have extremely accurate time and a reading of your position without the broadcasting satellites knowing you're there.
Everything below needs that a huge amount of engineering. CERN&friends developed the "White Rabbit" (https://ohwr.org/projects/white-rabbit/) system for this. This allows sub-Nanoseconds syncing of netwoked devices.
They've been simultaneous for decades... and remains a breathtaking detour (if you're out there, schedule night-travel).
----
I like the similar project which uses GPS signal offsets, captured on a RaspberryPi, to then broadcast (e.g:) a local-network-timeserver.
Wouldn't that require a 200 MHz wide RF channel? Unless there is some kind of encoding or compression I guess.