Prototype of my next project - a PTP clock with a 1,000,000fps, 1us display, with a true displayed accuracy of better than 500ns with respect to PTP time. No, I don't know why this is useful. Maybe some high speed photography setup with a need for absolute […]
[Original post on nonexistent.ca]
One news item, that nobody reported on last year is, that we now have three optical transitions measured to just 1e-16 (88Sr+), 1.8e-16 (87Sr) and 1.9e-16 (171Yb).
This means, that we now have three atom species that can be used for optical clocks, whose uncertainty is below what the […]
Today in things I have not done in a long time: Giving presentations on atomic clocks.
#timenuts #AtomicClocks
You might have heard, that CGPM will vote on whether to (de facto) abolish leapseconds in October, due to the technical problems it causes, each time we have a leapsecond. And because of the prospect of the first ever negative leapsecond […]
[Original post on society.oftrolls.com]
Coming back to OSHW atomic clocks. After thinking for a while. I think the cheapest option is to build a 87 Rb vapor cell coherent population trapping clock. I.e. one that shines a laser onto a vapor cell, which is modulated with half the hyperfine splitting.
The only special part needed would […]
A photo of a PCB bristling with SMA ports in the omnivise. A port on the left and a port on the bottom are connected to the NanoVNA, which is showing an S11 plot. The plot shows a bandpass response.
Finally back to #timenuts stuff! GNSS distribution amplifier seems to be working as designed. S11 seems much higher than expected at only around -5 to -10dB. The filter is meant to be internally matched, as is the amplifier stage so not sure what is going on […]
[Original post on nonexistent.ca]
So far we've only synchronized the PHC on the NIC - the system can observe this clock, and it can be used to precisely timestamp network packets - but it is not coupled to the system's timekeeping yet.
In order to do that, we need a second control loop. In my current setup, that role is taken […]
A diagram showing the components and control loops of a Linux system using a PHC to synchronize to GNSS.
While I wait for the distribution amp PCBs to arrive, let's talk about how we make use of the UTC-aligned PPS from GNSS to keep accurate time.
In order to achieve network time synchronization on the order of nanoseconds, it's essential that timestamping […]
[Original post on nonexistent.ca]
A 3D rendering of a PCB bristling with 5 SMA connectors.
Now that I have two working platforms to run my timing experiments with, I'll need some tools to set that up.
First on the block is a 4-way distribution amplifier for GNSS (GPS, etc.), so that I can use the same antenna to feed multiple receivers with an […]
[Original post on nonexistent.ca]
The BananaPi F3 board sits on the bench, with a timing-nic PCB installed in its miniPCIe slot. Minigrabbers can be seen supplying power, and another timing-nic PCB sits above on the bench.
Time testing platform #2 - BananaPi F3. This one is intriguing for a few reasons. It's one of the few modern SBCs with miniPCIe, it's a desktop-tier RISC-V (8 cores! they're pretty slow, though) which I don't yet have in my stable, and it's considerably […]
[Original post on nonexistent.ca]
The test setup again, this time with two tiny blue wires criss-crossed over the EEPROM, and the 8P8C breakout attached with a Cat5e cable connected.
A terminal window showing 3 panes. Left half is a log generated by `ts2phc` on the test platform indicating that the incoming PPS pulses are consistently only a few ns offset from the PHC. Right top shows the output of `chronyc sources` on another machine, indicating it is synchronized via PTP with the test machine, and a confidence of +/- 166us. Several internet-based servers show current offsets < 5ms, indicating agreement. Right bottom shows the `cgps` output indicating the module has NO FIX, but can see 4 GPS and 1 Beidou satellites and is confident enough to produce a time output.
Today on adventures in precision time:
* 🛠️ Fixed the DO/DI design error with some bodge wires
* ✨ Amazingly to me, the `eeupdate64e` tool immediately worked to write both the flash image and the eeprom settings (mostly MAC address). `nvmupdate64e` didn't […]
[Original post on nonexistent.ca]
