> I’m not particularly patriotic, but this kind of thing feels particularly American.
??? America has no doubt done some very remarkable things (the moon landing, the first backward compatible color TV standard), but I don't think this is a notable example of that.
I think everyone in Europe was familiar with even wristwatches getting the time from "airwaves". At least in Germany, watches were a very common thing since the 80s (I think everyone old enough vividly remembers the many Junghans commercials on TV). The corresponding signal has been broadcast for many decades earlier, as it's no surprise that railroad and airplane networks were in need of a common time: https://en.wikipedia.org/wiki/DCF77
> But we had a problem, and we solved it with technology. And none of that fancy newfangled technology — we solved it using solid technology, the kind that you can touch with your hands and that buzzes in the airwaves.
There wasn't much "newfangled technology" around at the time. We essentially solved it using the simplest method there was at the time, at least I find it a bit hard to come up with a simpler one.
Also, what would be an example of technology that you can't either "touch with your hands" or that does "buzz in airwaves"?
> Radio time signals for setting chronometers were sent from stations such as NAA in Arlington, Virginia, which began broadcasting in 1913. The time was supplied from a direct communication line with the clocks of the U.S. Naval Observatory in Washington, D.C. In combination with another low-frequency installation mounted on the Eiffel Tower in Paris, the towers had the range to cover the North Atlantic Ocean and the eastern United States.
So I looked up the Eiffel tower.
> The Eiffel Tower time signal broadcasts began on May 23, 1910
Also, same source starts with the 1898 proposal of time sync via radio being made by an Irish bloke.
> I don’t know who had the first system accessible to civilians, but at this point we’d just be arguing details.
Agreed. Even non-civilian, and whoever came first, the timeline of things across various countries, I don't think the core point of TFA holds water: it's not a "particularly American" thing, it just made sense out of engineering requirements: time sync was transmitted over telegraph wires, and telegraph went wireless; the leap is not exactly surprising.
I can touch microprocessors, and lasers are buzzing in airwaves. It’s the same electromagnetic radiation as what we know as radio, just
at much, much higher frequencies.
But this was asked in the context of solving this problem, in the 1950s.
Sure, but trench soldiers used to build their own radios. A soldier today stationed in the middle of a war isn't likely to assemble their own laser emitter.
No you can't, you're just touching the box they come in.
You can touch copper cables and wires, vacuum tubes, resistors, capacitors, breadboards, and (large!) printed circuit boards among other "basic" electronic components. You can't touch microprocessors, it's even stated on the tin they are microscopic in scale; you can't touch that in any meaningful way.
> I think everyone in Europe was familiar with even wristwatches getting the time from "airwaves". At least in Germany, watches were a very common thing since the 80s
Not the 80s. The first radio controlled wristwatch came out in 1990 (Junghans Mega 1).
Sorry, I mistranslated “clock” (hence why I differentiated “wristwatch” in the sentence before). We owned a Funkuhr-Wecker in the 80s, so, an alarm clock synchronizing to DCF77, in the 80s. The wristwatches came a bit later, yeah (not that I’d have known without looking it up whether that was earlier or later than 1990).
I wondered about its American origins too. I vaguely remember a little detail in the novel Cryptonomicon where one of the characters (a Lieutenant in the Imperial Japanese Army during WWII) sets his watch with a radio time signal. So that got me thinking that maybe the idea arose in different places.
Also I was wondering about the “forever” wording. I imagine the signal is very robust, but couldn’t American politics just one day decide that it’s not worth it to broadcast the time by radio signal anymore?
> Official Notice: Commencing from 0000 Coordinated Universal Time (UTC) on April 7, 2024, the southern antenna of WWVB has been rendered non-operational due to damage sustained from wind gusts exceeding 90 MPH. Please be advised that WWVB continues to function at a diminished overall power, utilizing only its northern antenna.
> Update 20 May 2024: The components necessary for the refurbishment of the southern antenna’s triatic are currently being manufactured and shipped. The projected timeline for the completion of these repairs is tentatively set for the latter part of June 2024. We would like to emphasize that this is an estimated timeline and may be subject to alterations based on a variety of factors. We greatly appreciate your understanding and patience during this process.
Can someone using WWVB radio clocks describe what the current situation is? Is the second working antenna strong enough to provide signals throughout the US / North America?
Are WWVB radio clocks popular at all?
Here in Europe, DCF77-based clocks are popular, especially with respect to automatic summer time adaption and (less obvious) leap second HANDLING. It would be very noticeable eventually if the DCF77 signal had severe issues.
Also, I'm very surprised about the abysmal historical uptime of Wwvb. It lists thirteen downtimes of more than 5 minutes each in 2023 alone.
Given that most clocks listen for it about once per day, if that, to save battery, and in my experience even then only manage to catch the signal every couple of days, high continuous availability doesn't really seem to be a concern.
the bandwidth is just enough to broadcast a single digit of binary every second.
I'd be interested in some more context on this. I think it's pretty clear that you can encode more than 1bps in a 60kHz signal, but I'm curious how the encoding was chosen. There's some more detail on it here:
The WWVB 60 kHz carrier, which has a normal ERP of 70 kW, is reduced in power at the start of each UTC second by 17 dB (to 1.4 kW ERP). It is restored to full power some time during the second. The duration of the reduced power encodes one of three symbols:
If power is reduced for one-fifth of a second (0.2 s), this is a data bit with value zero.
If power is reduced for one-half of a second (0.5 s), this is a data bit with value one.
If power is reduced for four-fifths of a second (0.8 s), this is a special non-data "mark", used for framing.
This is apparently the IRIG H encoding, which dates to the 50s and is probably designed to be easily decoded. By what, I wonder?
I can't say why you were downvoted but that's still pretty slow for relays.
One bit per second seems more like it's aimed at casual human decoding. Especially because each digit is encoded separately, even for the hours. Also for plain old range purposes, one transmission per minute is about as wide as you can go before things get silly.
The signal is not 60 kHz wide. It is at 60 kHz. A pure carrier with no modulation has the inverse of infinite bandwidth. (Assuming perfect transmitters, which can't really exist, of course.) The faster you modulate the signal, the more it spreads out across the spectrum. The frequency-time tradeoff.
The time signals run at the low end of longwave. That spans from about 40 to 120 kHz or so. There is about 100 kHz of spectrum down there. Though broadcasting a broadband longwave signal like that would be an imposing task. To cover a large area with AM broadcast (maybe 5 - 10 kHz) uses 1 - 2 megawatt transmitters in Europe. To cover the continent with a 100 kHz broadband digital signal would probably take 10 - 50 megawatts, maybe with 3 transmitter sites. Though I think it could be done. Could fit maybe a megabit a sec in there.
Something less ambitious maybe. A few hundred bytes a second? A kilohertz or so of spectrum used. It could work inside elevators, deep underground in parking garages, and so on. Digital alert stream for emergencies, time signal, etc.? Would not be much more complicated than the time signal transmitters, just with a more sophisticated modulation.
There is also an antenna issue with regards to resonance. If the signal spreads to wide, the antenna and associated tuning equipment are going to suffer RF losses, reflections and likely heating.
That is why the 17khz naval CW station has a limitation on cw speed.
These days though, a more popular idea seem to be to piggy back onto GNSS signals, which are also broadly available (no idea how well they compare in practice to low frequency time beacons), and for which importantly many mobile devices already have a receiver built-in:
The US also already has pretty good coverage with the NOAA weather radio system, which supports a digital, zone-based alerting system for both weather and other hazards. That has the big advantage of being regionally steerable.
In fact, I can't imagine many events other than weather (which is usually localized) that warrant such a low-entropy signal on a nationwide basis, and everything I can imagine has very limited actionability. ("Asteroid inbound, prepare to hide in the basement for a few thousand years"?)
As mentioned somewhere else, these time signals also carry information about DST and adapt for leap seconds, both of which GPS doesn't do as far as I know. I remember that earlier versions of Android always set the phone clock to GPS which was then off by a number of seconds.
GPS navigation messages do include information about leap seconds and other stuff necessary to convert between GPS time and UTC. See GPS Interface Specification IS-GPS-200, 30.3.3.6.2 - UTC and GPS Time
> These days though, a more popular idea seem to be to piggy back onto GNSS signals, which are also broadly available (no idea how well they compare in practice to low frequency time beacons), and for which importantly many mobile devices already have a receiver built-in
GPS chips are very very power intensive as the compute power involved to decode a signal out of something that would normally be way below the noise threshold is still very high, despite some two decades worth of optimization. And they're pretty useless outside of direct line of sight towards the sky.
> In fact, I can't imagine many events other than weather (which is usually localized) that warrant such a low-entropy signal on a nationwide basis, and everything I can imagine has very limited actionability. ("Asteroid inbound, prepare to hide in the basement for a few thousand years"?)
It's a trigger signal for a low-power receiver that can then turn on a higher-bandwidth (and thus, higher power) device to detect what is actually going on. Say you're a country at war like Ukraine - have the "emergency bit" on nationwide during Russian air raids so that receivers can listen for area-specific signals and blare horns if affected.
No matter what, we have to prepare for war, and that includes having robust technology that is hard to take out on the sender side (which cellphone stations aren't, they're easy targets in a cyber war!) and, most importantly, can be stored in everyone's garden shed and live on a single battery for years.
>Say you're a country at war like Ukraine - have the "emergency bit" on nationwide during Russian air raids so that receivers can listen for area-specific signals and blare horns if affected.
And what would prevent Russia from continuously broadcasting this emergency bit to cause chaos?
> And what would prevent Russia from continuously broadcasting this emergency bit to cause chaos?
So what, all that would do in my scenario is drain the batteries of the civilian populations' alarms a bit faster as they'd keep their more power-intensive CPU awake.
DCF77 is a natural for this because it already includes a phase-modulated signal (as well as the 1bps amplitude-modulation). At the moment it's a 512-bit pseudo random sequence, but could obviously carry a data stream instead.
Alternatively, it would be fun to see how much noise you can put into the signal and still decode it. Maybe using the knowledge of its structure, kind of how (I believe?) GPS reception works.
GPS is spread spectrum. It's modulated using a pseudo random sequence and then demodulated using the same sequence. All the same theory still applies but it's just a different way of using the spectrum, instead of a fixed band the bandwidth is "spread" across a broader band in a way that allows all these different signals to be multiplexed. Specifically with GPS IIRC the phase of the pseudo random sequence is also conveying timing information because of how it relates to the precise clock on the satellites. Spread spectrum can be a little more resilient to certain kinds of noise, e.g. if you have noise just at one frequency now you've reduced the impact of that noise.
It's fun with software radio to take a long recording of a chunk of spectrum and do the fourier transform and plot it. There will be clear lines indicating carriers, even ones too faint to be heard over the static. Software can do the same trick for decoding a modulation (at the expense of latency in decoding). Modern tech allows a further neat hack here. If you have a very stable local clock (which any modern digital device does) you can correct for frequency errors in the transmission. Once the clocks are synced, you know exactly when the next symbol should be. And you know how much the transmitter frequency as actually received, is varying from what it should be. And since a convolutional coding with a pseudorandom number might be used, you also know what the next symbol will be (only a small number are valid in any state). With all that together, in effect, the decoder knows when and where the signal will be, and at least part of what it will look like, before it receives it. So it can be compared with what is actually received, making it possible to pick it up well below the noise floor. Just add some error correcting codes for robustness.
Amateurs have successfully communicated data between California and New Zealand on longwave using only 1 watt of radiated power at the transmitter. (But the baudrate for that is measured in hours per bit. And the receiving antenna was considerable.)
Could we have something like an AM broadcast, but then the receiver “upsampling” the data? Maybe using some ML?
For example, if you have an AM channel that always transmits some song from a list, then you might not even need to receive the whole song. Or maybe you can have a model that’s good at upsampling those types of songs/data?
This is pretty much what audio compression, like a MP3 file, does: it figures out how to encode perceptually-identical (or close) stuff more densely and remove redundant information.
Every time you listen to "HD Radio" you're doing exactly this.
Yes, but modern ML techniques (particularly with neural networks) are much more impressive at recovering signal with even less information than things like MP3. An example of this in the visual domain is upscaling. So it’s not a bad question at all.
I extremely dislike the Hutter Prize. I think it's generally agreed that intelligence compresses the model better & therefore it's reasonable to assume that the better the compression, the more intelligence you have (at least for now where we are with AI, this seems to be a roughly reasonable assumption). My problem with the Hutter prize is that it makes the leap to say that lossless compression is this when everything about AI is choosing how much error you're willing to tolerate. In other words, intelligence is linked to lossy compression, not lossless - a competition for lossless compression doesn't do anything more than get us better lossless compressors / decompressors.
AM broadcast uses a "band" around the carrier. Whatever tricks you use Shannon's law is going to determine the upper limit of how much data you can carry which depends on the bandwidth and the signal to noise ratio. ML makes no difference from a theoretical perspective. Compression just reduces the bandwidth you'll need assuming your data compresses (with whatever method you choose, ML can be part of that)...
I guess my usual experience is that AM transmissions sound pretty horrible, especially compared to FM
So, my question is more like, can we just upgrade the equipment and keep the channels? And can AM be used more like for signal/indexing rather than full data dump? (eg. instead of transmitting the whole song, transmitting just an id of the song)
AM sounds bad because it’s amplitude modulated. So variation in amplitude (i.e. signal strength) results in noise when decoding. FM however is not sensitive to this issue because its frequency modulated - slight variations in signal strength have no effect on the encoded signal.
And yes, we can always upgrade the equipment. That’s what we did when we transitioned TV to digital signals and FM to digital FM - we reserved some bandwidth for over-the-air while freeing up the rest to be used for other purposes. But it’s an expensive proposition and one that happens rarely (in fact those are the only two times I’m aware of it, they happened at basically the same time, took forever, & there was insane opposition to it).
The limit is Shannon's law which depends on bandwidth and signal to noise. A more advanced modulation technique can get more "information" through up to that limit. A song for this matter can just be considered information as well. So the answer is almost certainly yes, one can get more out of existing channels by upgrading the equipment assuming the current equipment doesn't approach the theoretical limit which is almost certainly the case for this "old" technology we're talking about.
An FM radio channel has a bandwidth of 200Khz. AM radio has a bandwidth of of 10Khz. That's a big part of the reason why AM sounds horrible compared to FM. The way noise impacts AM and FM is also different, especially given human perception. IIRC both these methods were picked for practical reasons not necessarily any optimal criteria. AM is fairly crude, there's only so much you can change the amplitude for any practical purpose. Changing the frequency makes it easier to use more bandwidth so it was a natural evolution. Depending on how you're modulating the amplitude (the naive old school radio IIRC is just using the signal you're transmitting to modulate it) you can make the bandwidth larger or smaller. Random e.g. something like Ethernet on copper can be viewed as a very very fast, high bandwidth, AM. All these things boil down to the same Shannon law just with somewhat different efficiencies depending on how well you can control the frequency domain.
This problem of cramming the most bits into a given channel is something people have been working on for a long time. Some coverage of this here: https://en.wikipedia.org/wiki/Modulation
That's how we got from 300bps modems to 56k modems over the same phone lines way back and how we push more out of radio spectrum today.
How gratuitous with modern tech. FM needs tens of decibels of signal to noise ratio to sound reasonable, especially if you want stereo. But a digital signal could fit perfect audio into that range at less than one bit per Hz, which would let it tolerate radio noise that's as strong as the actual signal.
One thing you forgot to mention is that in contrast to an FM receiver, or even more a digital one, AM receivers are incredibly easy to build even with very basic "household items", which I believe is at least part of the motivation to provide emergency services and similar broadcasts over AM.
Since the equivalent European signal I'm familiar with only covers a single timezone, with unified DST rules, I'm curious:
Do these usually have an adjustment button for a time zone offset? And how do they handle DST – do they have an "I'm in Arizona (but not in the Navajo Nation), leave me on standard time" switch?
They usually have an offset and a DST option. So in Arizona you'd choose -7/Off, and never touch it again. In Colorado you'll have to toggle DST twice a year manually, because it doesn't know the rules for when it starts/ends.
Modern watches too, e.g. Casio digital watches marketed as integrating their "Wave Ceptor"/"Multi-Band 6" feature[1].
I still use a 17-year-old (batch code[2] 202A327G) G-Shock GW-530A (predecessor of this active offering[3]) that syncs with WWVB every morning several hours before dawn.
In fact there are lower-frequency signals that carry more data, generally used for submarine communication - the wikipedia article says "uo tp 300bps" using VLF (30KHz or so).
Fun fact: sound cards in PC's are now fast enough that it's possible to receive many of these signals (including WWWV, DCF77 and MSF) directly with a sound card - basically connect a long wire (or tuned circuir) to the sound card input and do a bit of DSP. Sampling at 192KHz makes reception of any of these easy.
More likely a radio nerd, John Alvin Pierce, that was just really good at radio and obsessed with oscillators (https://ieeexplore.ieee.org/document/60675) that inspired a group of distinguished government-employed engineers and scientists.
In fairness, there _might_ be a pocket-protector in this picture of them but it's a bit blurry. Actually, yes, there definitely is. No cigarettes, however:
It's kind of baffling that in 2024 there are appliances that exist for which I have to manually set the time, or at least have to go through some cumbersome IoT set-up process, that most likely is absolute garbage security-wise if it isn't actively acting against my interests (like those fridges that only work with first-party water filters).
Maybe I'm under-thinking this, but couldn't my Wi-Fi router just broadcast the current time (and time zone) every minute or so in an unencrypted fashion to all devices within range?
That would have absolutely been myself, wardriving at 16 (back in the early aughts). Sending nonsensical print jobs and then setting everyone’s clocks to 4:20.
It is baffling that in 2024 that my appliances don't have a battery backup for the time. It costs less than 50 cents and requires the battery be changed no more than every 20 years.
But still every time the power goes out I need to reset my clocks.
It could – but it could just as easily (either accidentally or on purpose) broadcast the wrong time, greatly annoying everybody within broadcast distance.
Of course the same is also possible for WWVB, but at least there, I suspect that some agencies might take objection and convince you to stop sooner or later.
> appliances that exist for which I have to manually set the time
I've never owned an electric oven that could configure its own time. Anytime there's a power cut, I have to do some crazy dance - which usually involves digging out the oven's manual. It's the same for microwave ovens. I don't know why they don't at least store the time in a scrap of NVRAM, like a PC motherboard.
I have thought that Matter should have a time broadcast message that can be sent over Wifi, Bluetooth, and Thread. Which should be enough to set the time for any Wifi device that doesn't need NTP, and low-power devices with Bluetooth and Thread.
One problem is that need to pair with Wifi, Bluetooth, and Thread. The other problem is the cost to add time sync. And probably couldn't remove the UI for setting the clock because need it for people without technology.
""I’m not particularly patriotic, but this kind of thing feels particularly American. Perhaps my imagination of American innovation is still set in the era of lunar missions and radio.""
Yes. From the first trans continental train, telegraph, up through landing on the moon. It does inspire a lot of patriotism, it was very 'can-do' time. Very innovative, huge public works. The old technology is still amazing.
I remember my dad getting a solar-powered wristwatch that could tune in to the Western European equivalent of WWVB (DCF77, located in Germany) and adjust itself (respecting DST!) when I was a teenager.
Not that I'd regularly suffer from empty watch batteries or horribly incorrect time on my quartz watch, but I always found that extremely neat :)
If I think about time an American nowadays the first thing that comes into my mind is GPS.
What WWVB or DCF77 (and JJY) was back then is now GPS timing capabilities.
Much higher precision but of course a higher complexity for the receiver. [1]
I don't know about WWVB and JJY but the German DFC77 is not only AM modulated but FM too allowing for a better accuracy.
Slightly tangent: being substantively patriotic is cool. It should be cool. America has done some incredible things like this and I’m sure it’s not just Americans that find it cool.
I think there are a lot of countries that have done some really remarkable things. I’m American, and I’m generally very proud of my country. If I were, say, French, Swedish or Japanese, I’d feel the same way.
Obviously none of those countries - or any country - is perfect, and all have some distinctly dark chapters in their past, but there’s something inspiring about a society organizing itself to accomplish generally good things.
I honestly think pride only makes sense if the place feels more than home to you; the people always were more important than some man-made borders and identities.
Can confirm, it's a great way to get started with radio stuff. Since I live in Europe, I did this with the German DCF77 signal. The frequency is low enough that you can do direct sampling with a 192ksps sound card or with an RP2040.
A nice thing about DCF77 is that once you manage to receive the amplitude modulated signal, you can move onto decoding the slightly more advanced spread-spectrum phase modulated signal, which carries (almost) the same data.
You can start by buying a time signal receiver module, and once you confirm that the module can receive the signal, cut off the ferrite antenna and use it with your own receiver.
Sadly, WWVB is damaged. At midnight on April 7, 2024, WWVB's south antenna was disabled due to damage sustained during high winds. WWVB now broadcasts exclusively from the north antenna, at a reduced power of 30kW. This situation is expected to continue "indefinitely", presumably because of a lack of budget for repairs.
Update 20 May 2024: The components necessary for the refurbishment of the southern antenna’s triatic are currently being manufactured and shipped. The projected timeline for the completion of these repairs is tentatively set for the latter part of June 2024. We would like to emphasize that this is an estimated timeline and may be subject to alterations based on a variety of factors. We greatly appreciate your understanding and patience during this process.
For those looking to hear what this sounds like without buying any radio gear, there are many public kiwisdr sites that can hear 60khz. It's a matter of choosing AM decoding and tuning to the particular frequency.
I have a friend with a 300' longwire antenna. A few weeks ago, after we were done repairing an old receiver that included VLF, he tuned in WWVB for me... checking it off my bucket list. It was interesting to hear the beeps of different lengths.
It came in surprisingly clear, in our Chicago suburb, especially since this was after the antenna issue on their end.
I wear a Citizen “AT” [1] wristwatch daily. It not only keeps perfect time, because of its daily sync at 2am to WWVB, but it also never needs a battery change since it self charges from light. These two features make it the perfect zero maintenance timepiece IMHO, and it looks stylish too.
Great watches, I'm a bit sad my Garmin Instinct spoiled more classic wristwatches for me — with GPS and a lot of sensors, and an actually functional flashlight, I cannot imagine giving up that valuable wristspace for a bit of added beauty (fortunately it looks decent with an aftermarket strap).
60 kHz is “long wave”, a frequency so low you could almost still hear. It's just thrice the upper limit of ~20 kHz for the human ear.
I love how my wristwatch eats sunlight at day (solar-powered) and drinks radio waves at night. Never has to change a battery and shows time as accurately as any internet-connected device that listens to NTP.
For the makers here, you can purchase cheap small modules that interface to any microcontroller, including most popular ones like AVR (Arduino), ESP32, etc. so that they can receive and decode time signals from WWVB or the European equivalent DCF77. Just search for "WWVB (or DCF77) module" at the usual online shops.
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[ 2.9 ms ] story [ 203 ms ] thread??? America has no doubt done some very remarkable things (the moon landing, the first backward compatible color TV standard), but I don't think this is a notable example of that.
I think everyone in Europe was familiar with even wristwatches getting the time from "airwaves". At least in Germany, watches were a very common thing since the 80s (I think everyone old enough vividly remembers the many Junghans commercials on TV). The corresponding signal has been broadcast for many decades earlier, as it's no surprise that railroad and airplane networks were in need of a common time: https://en.wikipedia.org/wiki/DCF77
> But we had a problem, and we solved it with technology. And none of that fancy newfangled technology — we solved it using solid technology, the kind that you can touch with your hands and that buzzes in the airwaves.
There wasn't much "newfangled technology" around at the time. We essentially solved it using the simplest method there was at the time, at least I find it a bit hard to come up with a simpler one.
Also, what would be an example of technology that you can't either "touch with your hands" or that does "buzz in airwaves"?
I don’t know who had the first system accessible to civilians, but at this point we’d just be arguing details.
> Radio time signals for setting chronometers were sent from stations such as NAA in Arlington, Virginia, which began broadcasting in 1913. The time was supplied from a direct communication line with the clocks of the U.S. Naval Observatory in Washington, D.C. In combination with another low-frequency installation mounted on the Eiffel Tower in Paris, the towers had the range to cover the North Atlantic Ocean and the eastern United States.
So I looked up the Eiffel tower.
> The Eiffel Tower time signal broadcasts began on May 23, 1910
https://tf.nist.gov/general/pdf/2131.pdf
Also, same source starts with the 1898 proposal of time sync via radio being made by an Irish bloke.
> I don’t know who had the first system accessible to civilians, but at this point we’d just be arguing details.
Agreed. Even non-civilian, and whoever came first, the timeline of things across various countries, I don't think the core point of TFA holds water: it's not a "particularly American" thing, it just made sense out of engineering requirements: time sync was transmitted over telegraph wires, and telegraph went wireless; the leap is not exactly surprising.
This turns out to be quite an interesting rabbit hole.
It's definitely earlier than I would have guessed regardless.
Microprocessors and lights/lasers respectively, among I'm certain countless other examples.
But this was asked in the context of solving this problem, in the 1950s.
I feel like the point of my question was lost.
No you can't, you're just touching the box they come in.
You can touch copper cables and wires, vacuum tubes, resistors, capacitors, breadboards, and (large!) printed circuit boards among other "basic" electronic components. You can't touch microprocessors, it's even stated on the tin they are microscopic in scale; you can't touch that in any meaningful way.
What technology that you can neither touch, nor that buzzes in airwaves, could they have used to solve this problem back then?
yet it would be cringe to write sentence like "I’m not particularly patriotic, but this kind of thing feels particularly European"
Not the 80s. The first radio controlled wristwatch came out in 1990 (Junghans Mega 1).
Also I was wondering about the “forever” wording. I imagine the signal is very robust, but couldn’t American politics just one day decide that it’s not worth it to broadcast the time by radio signal anymore?
https://www.radioworld.com/global/why-wwv-and-wwvh-still-mat...
https://www.nist.gov/pml/time-and-frequency-division/time-di...
> Official Notice: Commencing from 0000 Coordinated Universal Time (UTC) on April 7, 2024, the southern antenna of WWVB has been rendered non-operational due to damage sustained from wind gusts exceeding 90 MPH. Please be advised that WWVB continues to function at a diminished overall power, utilizing only its northern antenna.
> Update 20 May 2024: The components necessary for the refurbishment of the southern antenna’s triatic are currently being manufactured and shipped. The projected timeline for the completion of these repairs is tentatively set for the latter part of June 2024. We would like to emphasize that this is an estimated timeline and may be subject to alterations based on a variety of factors. We greatly appreciate your understanding and patience during this process.
Can someone using WWVB radio clocks describe what the current situation is? Is the second working antenna strong enough to provide signals throughout the US / North America?
Are WWVB radio clocks popular at all?
Here in Europe, DCF77-based clocks are popular, especially with respect to automatic summer time adaption and (less obvious) leap second HANDLING. It would be very noticeable eventually if the DCF77 signal had severe issues.
Also, I'm very surprised about the abysmal historical uptime of Wwvb. It lists thirteen downtimes of more than 5 minutes each in 2023 alone.
I'd be interested in some more context on this. I think it's pretty clear that you can encode more than 1bps in a 60kHz signal, but I'm curious how the encoding was chosen. There's some more detail on it here:
https://en.wikipedia.org/wiki/WWVB#Modulation_format
The WWVB 60 kHz carrier, which has a normal ERP of 70 kW, is reduced in power at the start of each UTC second by 17 dB (to 1.4 kW ERP). It is restored to full power some time during the second. The duration of the reduced power encodes one of three symbols:
If power is reduced for one-fifth of a second (0.2 s), this is a data bit with value zero.
If power is reduced for one-half of a second (0.5 s), this is a data bit with value one.
If power is reduced for four-fifths of a second (0.8 s), this is a special non-data "mark", used for framing.
This is apparently the IRIG H encoding, which dates to the 50s and is probably designed to be easily decoded. By what, I wonder?
At that length of symbol encoding, by hand. :)
EDIT: Not sure why I was downvoted. Relays seem like period-accurate technology (happy to be corrected), and they’re comparably slow.
One bit per second seems more like it's aimed at casual human decoding. Especially because each digit is encoded separately, even for the hours. Also for plain old range purposes, one transmission per minute is about as wide as you can go before things get silly.
The time signals run at the low end of longwave. That spans from about 40 to 120 kHz or so. There is about 100 kHz of spectrum down there. Though broadcasting a broadband longwave signal like that would be an imposing task. To cover a large area with AM broadcast (maybe 5 - 10 kHz) uses 1 - 2 megawatt transmitters in Europe. To cover the continent with a 100 kHz broadband digital signal would probably take 10 - 50 megawatts, maybe with 3 transmitter sites. Though I think it could be done. Could fit maybe a megabit a sec in there.
Something less ambitious maybe. A few hundred bytes a second? A kilohertz or so of spectrum used. It could work inside elevators, deep underground in parking garages, and so on. Digital alert stream for emergencies, time signal, etc.? Would not be much more complicated than the time signal transmitters, just with a more sophisticated modulation.
That is why the 17khz naval CW station has a limitation on cw speed.
https://www.ptb.de/cms/en/presseaktuelles/journals-magazines...
These days though, a more popular idea seem to be to piggy back onto GNSS signals, which are also broadly available (no idea how well they compare in practice to low frequency time beacons), and for which importantly many mobile devices already have a receiver built-in:
https://defence-industry-space.ec.europa.eu/galileo-emergenc...
The US also already has pretty good coverage with the NOAA weather radio system, which supports a digital, zone-based alerting system for both weather and other hazards. That has the big advantage of being regionally steerable.
In fact, I can't imagine many events other than weather (which is usually localized) that warrant such a low-entropy signal on a nationwide basis, and everything I can imagine has very limited actionability. ("Asteroid inbound, prepare to hide in the basement for a few thousand years"?)
Don’t all GNSS systems provide a highly accurate time signal (maybe needed for computing the distance to satellite)? I know GPS does at least.
I was referring to piggying back an emergency signal onto that!
GPS chips are very very power intensive as the compute power involved to decode a signal out of something that would normally be way below the noise threshold is still very high, despite some two decades worth of optimization. And they're pretty useless outside of direct line of sight towards the sky.
> In fact, I can't imagine many events other than weather (which is usually localized) that warrant such a low-entropy signal on a nationwide basis, and everything I can imagine has very limited actionability. ("Asteroid inbound, prepare to hide in the basement for a few thousand years"?)
It's a trigger signal for a low-power receiver that can then turn on a higher-bandwidth (and thus, higher power) device to detect what is actually going on. Say you're a country at war like Ukraine - have the "emergency bit" on nationwide during Russian air raids so that receivers can listen for area-specific signals and blare horns if affected.
No matter what, we have to prepare for war, and that includes having robust technology that is hard to take out on the sender side (which cellphone stations aren't, they're easy targets in a cyber war!) and, most importantly, can be stored in everyone's garden shed and live on a single battery for years.
And what would prevent Russia from continuously broadcasting this emergency bit to cause chaos?
So what, all that would do in my scenario is drain the batteries of the civilian populations' alarms a bit faster as they'd keep their more power-intensive CPU awake.
Amateurs have successfully communicated data between California and New Zealand on longwave using only 1 watt of radiated power at the transmitter. (But the baudrate for that is measured in hours per bit. And the receiving antenna was considerable.)
For example, if you have an AM channel that always transmits some song from a list, then you might not even need to receive the whole song. Or maybe you can have a model that’s good at upsampling those types of songs/data?
Every time you listen to "HD Radio" you're doing exactly this.
So, my question is more like, can we just upgrade the equipment and keep the channels? And can AM be used more like for signal/indexing rather than full data dump? (eg. instead of transmitting the whole song, transmitting just an id of the song)
And yes, we can always upgrade the equipment. That’s what we did when we transitioned TV to digital signals and FM to digital FM - we reserved some bandwidth for over-the-air while freeing up the rest to be used for other purposes. But it’s an expensive proposition and one that happens rarely (in fact those are the only two times I’m aware of it, they happened at basically the same time, took forever, & there was insane opposition to it).
An FM radio channel has a bandwidth of 200Khz. AM radio has a bandwidth of of 10Khz. That's a big part of the reason why AM sounds horrible compared to FM. The way noise impacts AM and FM is also different, especially given human perception. IIRC both these methods were picked for practical reasons not necessarily any optimal criteria. AM is fairly crude, there's only so much you can change the amplitude for any practical purpose. Changing the frequency makes it easier to use more bandwidth so it was a natural evolution. Depending on how you're modulating the amplitude (the naive old school radio IIRC is just using the signal you're transmitting to modulate it) you can make the bandwidth larger or smaller. Random e.g. something like Ethernet on copper can be viewed as a very very fast, high bandwidth, AM. All these things boil down to the same Shannon law just with somewhat different efficiencies depending on how well you can control the frequency domain.
This problem of cramming the most bits into a given channel is something people have been working on for a long time. Some coverage of this here: https://en.wikipedia.org/wiki/Modulation
That's how we got from 300bps modems to 56k modems over the same phone lines way back and how we push more out of radio spectrum today.
How gratuitous with modern tech. FM needs tens of decibels of signal to noise ratio to sound reasonable, especially if you want stereo. But a digital signal could fit perfect audio into that range at less than one bit per Hz, which would let it tolerate radio noise that's as strong as the actual signal.
I think there are also older industrial applications using this technology to syncronize.
Do these usually have an adjustment button for a time zone offset? And how do they handle DST – do they have an "I'm in Arizona (but not in the Navajo Nation), leave me on standard time" switch?
As I understand it, the US switches at the same day across the country (for the states that do have it), so that should theoretically be possible.
So instead of a switch to “add an hour”, there could be one that says “add an hour if the signal says DST is currently in effect”.
[1] https://en.wikipedia.org/wiki/WWVB#Amplitude-modulated_time_...
https://www.nist.gov/pml/time-and-frequency-division/time-di...
That said, my clock stopped syncing for some reason, so ...
Modern watches too, e.g. Casio digital watches marketed as integrating their "Wave Ceptor"/"Multi-Band 6" feature[1].
I still use a 17-year-old (batch code[2] 202A327G) G-Shock GW-530A (predecessor of this active offering[3]) that syncs with WWVB every morning several hours before dawn.
[1] https://en.wikipedia.org/wiki/Casio_Wave_Ceptor
[2] https://shockbase.org/watches/batchcode.php
[3] https://www.casio.com/us/watches/gshock/product.GW-M530A-1/
Wonder no more! This technology is used in wall clocks, weather stations, and even wrist-watches.
They're usually marketed as "atomic clocks".
Fun fact: sound cards in PC's are now fast enough that it's possible to receive many of these signals (including WWWV, DCF77 and MSF) directly with a sound card - basically connect a long wire (or tuned circuir) to the sound card input and do a bit of DSP. Sampling at 192KHz makes reception of any of these easy.
[0] https://en.wikipedia.org/wiki/Communication_with_submarines
In fairness, there _might_ be a pocket-protector in this picture of them but it's a bit blurry. Actually, yes, there definitely is. No cigarettes, however:
https://www.ncbi.nlm.nih.gov/core/lw/2.0/html/tileshop_pmc/t... on image to zoom&p=PMC3&id=4487279_jres.119.004f7.jpg
[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4487279/
https://www.ncbi.nlm.nih.gov/core/lw/2.0/html/tileshop_pmc/t...
Maybe I'm under-thinking this, but couldn't my Wi-Fi router just broadcast the current time (and time zone) every minute or so in an unencrypted fashion to all devices within range?
But still every time the power goes out I need to reset my clocks.
Of course the same is also possible for WWVB, but at least there, I suspect that some agencies might take objection and convince you to stop sooner or later.
I've never owned an electric oven that could configure its own time. Anytime there's a power cut, I have to do some crazy dance - which usually involves digging out the oven's manual. It's the same for microwave ovens. I don't know why they don't at least store the time in a scrap of NVRAM, like a PC motherboard.
One problem is that need to pair with Wifi, Bluetooth, and Thread. The other problem is the cost to add time sync. And probably couldn't remove the UI for setting the clock because need it for people without technology.
Yes. From the first trans continental train, telegraph, up through landing on the moon. It does inspire a lot of patriotism, it was very 'can-do' time. Very innovative, huge public works. The old technology is still amazing.
https://www.youtube.com/watch?v=IbUhA6Vt6Sk
"We just lost the most powerful longwave transmitter in Europe, and why that's kind of a big deal" (2023)
Slight Technology Connection vibes, really fascinating stuff.
Not that I'd regularly suffer from empty watch batteries or horribly incorrect time on my quartz watch, but I always found that extremely neat :)
I don't know about WWVB and JJY but the German DFC77 is not only AM modulated but FM too allowing for a better accuracy.
[1] https://www.hopf.com/dcf77-gps_en.php#chapter3
https://www.nist.gov/system/files/documents/2017/05/09/NIST-...
Free RTC L48?
I think there are a lot of countries that have done some really remarkable things. I’m American, and I’m generally very proud of my country. If I were, say, French, Swedish or Japanese, I’d feel the same way.
Obviously none of those countries - or any country - is perfect, and all have some distinctly dark chapters in their past, but there’s something inspiring about a society organizing itself to accomplish generally good things.
A nice thing about DCF77 is that once you manage to receive the amplitude modulated signal, you can move onto decoding the slightly more advanced spread-spectrum phase modulated signal, which carries (almost) the same data.
You can start by buying a time signal receiver module, and once you confirm that the module can receive the signal, cut off the ferrite antenna and use it with your own receiver.
Here's a nice article on which I based my own project: https://hal.science/hal-02182845/
Using the same setup (ferrite stick -> discrete transistor amplifier -> RP2040) I also managed to receive the polish AM station at 225kHz.
Update 20 May 2024: The components necessary for the refurbishment of the southern antenna’s triatic are currently being manufactured and shipped. The projected timeline for the completion of these repairs is tentatively set for the latter part of June 2024. We would like to emphasize that this is an estimated timeline and may be subject to alterations based on a variety of factors. We greatly appreciate your understanding and patience during this process.
http://kiwisdr.com/public/
Many of these have user limits and time limits as well. Note that you can also hear WWVB on 2.5mhz, 5mhz, 10mhz, and 15mhz.
It came in surprisingly clear, in our Chicago suburb, especially since this was after the antenna issue on their end.
[1] https://www.citizenwatch.com/us/en/collection/mens-atomic-ti...
I love how my wristwatch eats sunlight at day (solar-powered) and drinks radio waves at night. Never has to change a battery and shows time as accurately as any internet-connected device that listens to NTP.