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    Wait you’re telling me that we’ve been blasting the current time via radio waves across the continent since 1963 and I still have to reprogram my oven’s clock when I lose power???

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      Yes, because the oven company built it as cheap as possible.

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        You should be thankful that your microwave/oven clock keeps time as well as it does. I bought an alarm clock that manages to lose three minutes a month. What’s more, it was a brand name (Sony), Googling reveals everyone has this problem, and the clock is especially designed to be “extra automatic timekeeping” by having a battery backup in case of power outages, automatically calculating DST, and having sliders to choose the time zone. Yet they couldn’t afford to use a crystal oscillator.

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          Any appliance connected to the grid has no excuse to fail at timekeeping. The power company takes great pains to average sixty cycles/second. Picking off and counting the signal is a simple circuit and easy enough for a four-bit processor.

          Some of these clocks are probably using tuning-fork style 32768 Hz crystal oscillators as found in wristwatches. They have a bit of a parabolic temperature dependence. In the original wrist-mounted application they do better, “ovenized” at about 98.6° F for living persons.

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            Yup, this is known as TEC (Time Error Correction). Unfortunately due to cost-cutting a great many clocks and other electronics that run solely or primarily off of AC power no longer plug directly into the power line but use an off-the-shelf AC-DC wall wart (internally or externally) - or, increasingly, a USB plug - and so can no longer avail themselves of the mains frequency for tracking time.

            Power companies have been trying to weasel out of this responsibility for a couple of decades now as it simplifies things and reduces costs on their end. I wouldn’t be surprised to see TEC go sometime in the next ten years, tbh.

            My Sony radio alarm clock did not have that excuse.

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        We bought atomic wall clocks for a school, and despite paying for a “name brand” (I don’t mind calling them out, it was La Crosse) we found that more than half wouldn’t synchronize (ever) due to not having a powerful enough receiver. WWVB is a 60KHz signal, so it should have no problem with wall penetration (and this was in the Midwest so not so far from Fort Collins, though you really should be able to get a signal anywhere in the continental US after the power boost in the 90s) - this had to be an issue with the receivers, though they were “functional” in that when we left them leaning against a window overnight they would finally synchronize.

        The school is on a decent-sized plot of land and set back from the street. This same uWWVB link had been posted a few months earlier and it occurred to me that I could probably get away with making my own WWVB signal and blasting its signal building-wide (NTP-backed, though) to get these clocks to actually show the right time. I seriously thought about it for a while and wrote the firmware for the system (rust on STM32 w/ an ESP8266 carrier board for wi-fi) but never ended up deploying it. I still think about it from time-to-time, especially when the precariousness of WWVB’s funding or its potential sunsetting make the news (which I was shocked to learn could even really be a possibility).

        Nowadays there are little modules for tinkerers that come paired with a tuned antenna and are set up to receive from WWVB in the USA, MSF in the UK, and JJY-60 in Japan readily available yet it seems that atomic time gets less love than ever before. I was on the market for a replacement alarm clock (see my comment elsewhere in this thread) and didn’t end up finding a good atomic option, so I’m probably going to finally build my own.

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          There are mobile phone apps that use the speaker to generate EM signals that approximate different radio sync signals. Fun fact: if you’re my age you won’t hear it, but if you’re a young whippersnapper like my coworkers you will.

          I got a ferro-magnetic bar with a purchase of a radio-synced wristwatch which really helps getting a signal from DCF77.

          My newest used watch (a Casio) has both “6 band” radio sync (works signals from the US, Japan, Germany and China) as well as an NTP-like sync via Bluetooth from a mobile. Being within a second or so of UTC gives me a warm fuzzy feeling.

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            Stories with similar links:

            1. μWWVB: A Tiny WWVB Station (2016) authored by anishathalye 4 years ago | 17 points | 1 comment