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Most Stable Raspberry Pi? Better NTP with Thermal Management

austinsnerdythings.com

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Re: Most Stable Raspberry Pi? Better NTP with Thermal Management

#91

Post by drob518 »

auspiv wrote: post #65

Austin from austinsnerdythings.com here! Posted this last night and went to sleep. Definitely didn't expect to wake up to it #1 on HN this morning! Some notes that weren't included in this post: I do have my LEA-M8T generating time pulses at 16 Hz, with a dpoll of -4 in the chrony config. The poll interval of 16 seconds means it gets 256 samples which also improved the stability. I do also have that mentioned BH3SAP…

First: cool project.

Second: Is the Pi in an enclosure? You’ll get even more consistency if it is (vs a bare PCB). Even if it’s thin and metal it’ll insulate the system from things like your home heater or AC cycling.

Re: Most Stable Raspberry Pi? Better NTP with Thermal Management

#92

Post by ProllyInfamous »

dfc wrote: post #54

The transmission site for WWVB has hundreds of water bottles to insulate the equipment from temperature swings. https://jila.colorado.edu/news-events/articles/spare-time

I do this same trick in an insulated utility shed, storing water beneath a desk to prevent overnight freezing within.

Works about as good as a heated rock in your sleeping bag.

Re: Most Stable Raspberry Pi? Better NTP with Thermal Management

#93

Post by gorgoiler »

What sorts of cool things can you do with perfectly synchronized clocks? The one that springs to mind might be catching a bullet or “catching” a light pulse, perhaps? Triangulating lightning strikes, or other EM events? Maybe some kind of TEMPEST hackery?

I’d love to have a highly precise clock but I’d also like to be able to do something with it!

Re: Most Stable Raspberry Pi? Better NTP with Thermal Management

#95

Post by protocolture »

mort96 wrote: post #21

What's the point in reading posts like this when the solution "they" came up with is basically, "tell Claude to make a script which does whatever"? I read blog posts to read thoughts from people, not computers

Theres vastly more interesting information in the article than any comment complaining about it.

Re: Most Stable Raspberry Pi? Better NTP with Thermal Management

#96

Post by tw1984 »

auspiv wrote: post #71
tw1984 wrote: post #45

some ideas - 1. using a second hand single frequency Ublox LEA-M8T GNSS receiver is not a good idea in 2025 when a dual frequency GNSS receiver chip can be purchased online for as little as $20-30. buy one of those ublox ZED-F9P receivers with the 2018/2019 firmware, they get you the exact same timing performance as ZED-F9T with QEerr support. PPS jitter is going to drop from 20ns to less than 2ns after qErr compensa…

1 - I like to consider myself an expert eBay-er (my ebay account can legally buy alcohol in the US, and I am myself only 36 years old) but I have not found any ZED-F9P for less than $90 ish. I am aware of the Quactel (sp) modules, and am considering a set for some RTK experiments. Is that what you're referring to? 2 - I've thought about replacing with ocxo but the pads are tiny. My soldering skills aren't nearly as g…

there are good deals on ebay atm. e.g. brand new ublox zed-f9p dev board pin compatible with the M8T receiver you are using. it also comes with dual frequency antenna. it is not a second hand chip, but a brand new module ready to be plugged into your system.

www.ebay.com/itm/277500530946

I usually buy my second hand electronics stuff from www.goofish.com, the home base of all those "From China" ebay vendors.

Re: Most Stable Raspberry Pi? Better NTP with Thermal Management

#97

Post by nerdralph »

easygenes wrote: post #51

You can go further and replace the cheap Pi oscillator crystal with a proper TCXO, as others using them for NTD have done and documented: https://raspberrypi.stackexchange.com/questions/74482/switch... That should give you 4-5x less drift than his results (though you could pair the techniques for even better figures)

And TCXOs are surprisingly cheap. Less than $2 when I looked at some of Abracon's offerings.

Re: Most Stable Raspberry Pi? Better NTP with Thermal Management

#98

Post by timeinput »

auspiv wrote: post #86
easygenes wrote: post #51

You can go further and replace the cheap Pi oscillator crystal with a proper TCXO, as others using them for NTD have done and documented: https://raspberrypi.stackexchange.com/questions/74482/switch... That should give you 4-5x less drift than his results (though you could pair the techniques for even better figures)

Believe me, I have read that post/comment quite a few times. There are actually Pi 4 hats for sale for audiophiles (that seem to believe that you need 54000000.000 MHz system clock or whatever it is for Pi4 (Pi3 is 19.2 MHz) for optimal audio) that have an OCXO on them. But in another comment I said I'm not sure my soldering skills are that good.

I mean you made an OCXO in a way. Why bother buying one? If you cold more tightly couple the temperature of the CPU and the crystal you'd be set.

Re: Most Stable Raspberry Pi? Better NTP with Thermal Management

#99

Post by wpm »

auspiv wrote: post #86
easygenes wrote: post #51

You can go further and replace the cheap Pi oscillator crystal with a proper TCXO, as others using them for NTD have done and documented: https://raspberrypi.stackexchange.com/questions/74482/switch... That should give you 4-5x less drift than his results (though you could pair the techniques for even better figures)

Believe me, I have read that post/comment quite a few times. There are actually Pi 4 hats for sale for audiophiles (that seem to believe that you need 54000000.000 MHz system clock or whatever it is for Pi4 (Pi3 is 19.2 MHz) for optimal audio) that have an OCXO on them. But in another comment I said I'm not sure my soldering skills are that good.

Adafruit sells a DS3231 module with standard 2.54mm pin headers. I'm using one on a Beaglebone Black that I setup as my NTP/PTP server (using work based on your work from 2021, so thank you!). No soldering required.

https://www.analog.com/en/products/ds3231.html

https://www.adafruit.com/product/3013

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