4 ms·
> The only big problems I can think of are devices that use the frequency as a reference, such as motors and clocks. This was my March mindfuck: That there ar
by rrr_oh_man 2y ago
> The only big problems I can think of are devices that use the frequency as a reference, such as motors and clocks.
This was my March mindfuck:
That there are periods every couple weeks when the WHOLE ELECTRICITY GRID of a country is run with higher/lower frequency for a period of time to get your Chinese oven clocks back into sync.
- lxgr 2y agoLong-term grid frequency stability is something you take for granted, until it suddenly fails, like in most of Europe back in 2018, due to a political disagreement between Serbia and Kosovo: https://www.reuters.com/article/idUSL5N1QP2FF/ https://www.reuters.com/article/idUSL5N1QP2FF/ I also find it quite funny that our cheap oven clock is probably among the most precise (non-internet connected) ones in our apartment :)
- Scoundreller 2y agoWWVB de-rating has got us all a bit down in North America. Lots of consumer level “atomic clock accuracy” devices just don’t update any more. https://www.watchuseek.com/threads/wwvb-operating-with-reduced-power.5564472/ https://www.watchuseek.com/threads/wwvb-operating-with-reduc...
- toomuchtodo 2y agoIt’s a shame there aren’t more time tower sites broadcasting in a distributed manner for redundancy.
- Taniwha 2y agoNoted my car got time from GPS the other day and it got me thinking, why aren't there unencrypted packets on all wifi that distribute NTP time so my oven/microwave/alarm/etc can grab it from any wifi it can see (even if it's not paired to them) - bonus points if APs also hand out local TZ data
- joha4270 2y agoPhone networks can already do this. And its true broadcast, you can decode it passively without ever connecting to the network, so no SIM/transmission required. I have no idea this is actually enabled in networks in practice, but the specification exists.
- cesarb 2y agoAnd in my experience, it's often wrong on some towers. I can't enable the setting on my phone to automatically set the time from the network, because if I do, it gets several minutes out of sync with the real time, which breaks TOTP generation.
- lxgr 2y agoYeah, a large German cell provider had their time off by a couple of minutes some years back, which made the news as it resulted in people's alarms ringing late and them being late to work/school etc. Hopefully modern phones prioritize GPS or NTP derived time and timezone information over NITZ (which is how networks provide it). At least Android has the capability to do so, but it's ultimately up to device manufacturers, as far as I understand [1]. [1] https://source.android.com/docs/core/connect/time https://source.android.com/docs/core/connect/time
- toomuchtodo 2y agoCould the detection and reporting of this inaccuracy be crowdsourced, either with mobile devices or perhaps SDRs? Fetch tower time, fetch real time over GNSS or NTP, report delta with tower ID and drift to a central server? Perhaps even include a map, like the map of GPS error rates derived from ADS-B data feeds. Related: https://news.ycombinator.com/item?id=39771354 https://news.ycombinator.com/item?id=39771354
- lxgr 2y agoI'm almost certain that at least Apple already has such a database on the operator level, i.e. a list of MNCs and the (non-)trustworthiness of NITZ. I vaguely remember seeing some carrier settings keys to that extent somewhere.
- smallmancontrov 2y agoLike the 6 independent 24-satellite (plus spare) constellations that constantly orbit Earth and output synchronized beacons accurate to nanoseconds?
- toomuchtodo 2y agoHow effective is receiving precision time from a GNSS constellation within structures, urban areas, and other challenging SNR envs? Another comment mentions cell towers broadcast this unencrypted and without the need for service, so perhaps the solution is to instead require strong SLAs around that service, with the gov potentially paying for that service level? https://news.ycombinator.com/item?id=40388421 https://news.ycombinator.com/item?id=40388421
- smallmancontrov 2y agoYep, reception is a real problem with straight GNSS. WWVB suffered from it too, and cellular (which is locked to GPS) is a big upgrade. I suppose that now the thing to do is wait for the $0.10 cellular clock chip that makes it easy.
- toomuchtodo 2y agoMy interest is as a bit of a precision time enthusiast and an advocate of public goods. We’re awash in “good time”, GNSS, RF, NTP over IP, cellular, but it still feels like there is a gap to fill to make precision time super cheap and ubiquitous. Getting time over mains power or other previously convenient but potentially low precision sources should be over, but getting precision time should be as easy and reliable as mains power. Thanks for riffing with me!
- lxgr 2y agoI feel like once you're concerned about SLAs for precision timekeeping, you need to start worrying about spoofing as well, which is tricky to combat in an inherently unidirectional protocol. Galileo has an interesting signal authentication service [1], but even that is subject to replay attacks by definition (although you can't skip ahead a receiver's time). In comparison, networked bidirectional protocols like NTP are almost trivially secure-able, by including a challenge in the request and a cryptographic signature over the response. [1] https://berthub.eu/articles/posts/galileos-authentication-algorithm-part-1/ https://berthub.eu/articles/posts/galileos-authentication-al...
- eternityforest 2y agoIt's probably about time for an update that can work with more compact receivers. Governments(Or an industry group, or really anyone) could publish digitally signed timestamps every second with a a key that doesn't change, and you could have a BLE profile for sharing them.
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- AdamH12113 2y agoIt's surprisingly hard to keep a clock accurate over time. Typical crystal oscillators can gain or lose seconds per day. If you want to do better than that, you either need internet access (for NTP), a radio receiver of some kind (for atomic clock broadcasts, GPS, etc.), or a significantly more expensive oscillator. Having a frequency reference with perfect long-term accuracy that any electrically-powered clock can use for free is pretty convenient! I've often wondered how hard it would be to make portable battery-powered clocks use 60 Hz noise as a timekeeping source. Maybe I should make a project out of it.
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- rrr_oh_man 2y ago> Typical crystal oscillators can gain or lose seconds per day. Are you sure? I only owned a quartz watch when I was a kid, but all sources I find on the web say even the lowest quality quartz watch movements are accurate to +- 20-30 seconds a month. For comparison: my several decades old manual Poljot loses some seconds per day.
- AdamH12113 2y agoThe Casio G-Shock I got in the 90s was ~66 ppm fast, which worked out to ~5 seconds/day. There are cheap crystals on Digi-Key with ~10 ppm accuracy, which is around 0.86 seconds/day. But crystals drift with age (and a tiny bit with temperature). Perhaps watches have improved since I last looked, but I would want to measure the actual real-world accuracy before believing anything better than 1 second/day.
- crote 2y agoYeah, that sounds about right. Crystal oscillators typically have an accuracy of about 20ppm, which is 1.73 seconds per day. Keep in mind that those number are a guaranteed worst-case performance - real-world performance is often much better.
- agos 2y agohow more expensive is a "more expensive" oscillator?
- Taniwha 2y agoThere used to be a local hydro generation that fed the local city, they had 2 clocks on the wall, one on the local grid and one on the national one - some time late at night they'd speed up/slow down the local grid to keep the clocks in sync