60 kHz (2022) | Hacker News Reader

60 kHz (2022)

ben.page

250 pointsjer0me150 comments

> I’m not particularly patriotic, but this kind of thing feels particularly American.

Maybe that tinge of patriotism is why Americans don't even bother to see if something isn't an American invention - https://en.wikipedia.org/wiki/Time_from_NPL_(MSF) - they'll just claim it anyways since they barely read outside their borders.

Radio 4 would also like a word: https://en.wikipedia.org/wiki/Greenwich_Time_Signal

>The first radio time signal, sent by telegraphic code, was broadcast in September 1903 by the United States Navy. Most sources list Navesink, New Jersey as the site of this broadcast, but the reference clock was located at the United States Naval Observatory (USNO) in Washington, DC. The first regularly scheduled time broadcasts began on August 9, 1904* from the Navy Yard in Boston. By the end of 1905, the Navy had transmitted time signals from stations in several other cities, including Norfolk, Newport, Cape Cod, Key West, Portsmouth, and Mare Island in California

(PDF) https://tf.nist.gov/general/pdf/2131.pdf

*Another source said August 9, 1905

And before radio, between 1880-1927, time was pumped throughout Paris in the form of compressed air using a network of pneumatic tubes.

Yes but it's not "particularly American".

"In November 1898, an optical instrument maker and inventor named Sir Howard Grubb addressed the Royal Dublin Society and proposed the concept of a radio controlled clock."

It was already used in telegraph transmission.

America just implemented first.

Radio 4 is particularly interesting, as it carries additional 25bps data [0] using for radio teleswitch operation [1] - a service whose days are numbered. Quite fun to receive this signal, as it's trivial to build a 198KHz receiver and to recover the data stream (+ time signal) using a signal, e.g. mix it with a 200KHz signal and process the resultant 2Khz audio tone.

[0] https://www.bbc.co.uk/rd/publications/rdreport_1984_19

[1] https://en.wikipedia.org/wiki/Radio_teleswitch

Radio 4 is also the station that if there is no communication with mainland UK, and Radio 4 no longer broadcasting, submarine commanders were to assume the country was attacked and destroyed.

https://en.m.wikipedia.org/wiki/Letters_of_last_resort

The US Bill of Rights is copied almost word-for-word from English legislation: https://en.wikipedia.org/wiki/Bill_of_Rights_1689

Inspired by, certainly. The founders were not ignorant and were aware of precedent.

But calling it "almost copied word-for-word" is not justifiable. On a trivial basis, it's literally not word-for-word in any way. On a more serious basis, there are significant changes in the laws, and enshrining something in an Act which can be changed by future Parliaments is a lot different that enshrining something into a Constitution which is much harder to change.

In fairness, the United States is a breakaway region of Great Britain.

Afaik, not Great Britain which is Scotland, Wales and England combined. It was part of the British Empire when it broke away.

A copy of the Magna Carta was in the National Archives for a while, and John Locke was a notable influence on founders such as Jefferson. Nihil novi sub sole.

I saw it there the day before yesterday!

Cool—I saw it once, and then it was gone a few years later. Maybe being serviced.

Oh dear. Where is it now?

I was going to remark on this as well, but my observation is different: It strikes me as a very (old-school) American thing indeed. But not a modern American thing, if it was a modern American thing, it'd be privately owned, for profit with continually degrading quality and multiple incompatible "service providers" competing to trick people into their particular walled garden..

NPL - the National Physics Laboratory in Teddington, London, also invented packet switching, the foundational technology for the internet.

https://en.wikipedia.org/wiki/Packet_switching

inventing a solution to a problem, only in america

It’s like apple pie then

Existed everywhere in the world since radios became common.

I have an old solar powered Casio g-shock multi-band watch and it gets signals from transmitters located in US, Germany, UK, 2X Japan and China. I have never needed to put watch on time, or change batteries. https://gshock.casio.com/intl/technology/radio/

These are indeed very cool!

If for some reason you are a few standard deviations more paranoid about not having the correct time than the average person, they now apparently have models that can get the current time via GPS, time beacon, or Bluetooth from a connected smartphone :)

https://gshock.casio.com/us/technology/3way/

WWVB also broadcasts on 60KHz and a number of other frequencies. WWV (time signal on different frequency) was started a few years before the one you mention. Though I’m not sure it’s really worth arguing about… not sure who was the first radio time signal.

https://en.m.wikipedia.org/wiki/Radio_clock

> 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"?

US seems to be the first to pioneer this according to my very cursory research: https://timeandnavigation.si.edu/multimedia-asset/us-navy-wi...

I stand corrected, it seems to indeed have been the US Navy that pioneered time signals. France followed up a few years later.

I don’t know who had the first system accessible to civilians, but at this point we’d just be arguing details.

From the link:

> 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.

Nice find!

This turns out to be quite an interesting rabbit hole.

It's definitely earlier than I would have guessed regardless.

> 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?

>what would be an example of technology that you can't either "touch with your hands" or that does "buzz in airwaves"?

Microprocessors and lights/lasers respectively, among I'm certain countless other examples.

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.

I don’t think anybody at that time could have built a laser emitter, even. Not sure why you would want to, to solve that problem, even today.

I feel like the point of my question was lost.

>I can touch microprocessors,

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.

We could argue about that, but let me rephrase then:

What technology that you can neither touch, nor that buzzes in airwaves, could they have used to solve this problem back then?

Digital communications is America’s gift to the world, look up Claude Shannon

AC motor, steam, diesel, jet engines are european "gifts to the world",

yet it would be cringe to write sentence like "I’m not particularly patriotic, but this kind of thing feels particularly European"

I think the Englishman George Boole deserves significant credit as well.

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:

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?

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.

The agency running the German equivalent to WWVB, DCF77, has looked into piggybacking an emergency warning signal onto unused bits of the time signal:

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"?)

> 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.

> a more popular idea seem to be to piggy back onto GNSS signals

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.

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

Yes, the GPS signal in a way is primarily a very precise time signal :) It’s a TDOA system!

I was referring to piggying back an emergency signal onto that!

Yes, it is needed to compute a location. More accurate time = more accurate location.

If we could have have 58 kHz to 62, that's 4 kHz. Enough for a 300 baud modem to work, which is 300 times faster than 1 bit per second.

We need to know the signal to noise ratio. Not just the bandwidth. 4khz is enough to carry much higher rates on residential phone lines...

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.

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.)

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.

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?

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.

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.

> An FM radio channel has a bandwidth of 200Khz.

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.

You might be interested in Digital Radio Mondiale: https://en.wikipedia.org/wiki/Digital_Radio_Mondiale

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.

Sure-- as we've discussed endlessly here: compression and ML are really very close cousins. I never said it was a bad question.

You can even win a prize for that https://en.m.wikipedia.org/wiki/Hutter_Prize.

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.

By "atomic" clocks (for example https://www.amazon.com/Crosse-Technology-WT-3129B-Atomic-Ana...), and older brands of watches.

I think there are also older industrial applications using this technology to syncronize.

> ...and older brands of watches.

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/

I love these clocks! I've had a few in every house I've lived in, from all along the West Coast and Midwest.

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.

You shouldn't have to toggle DST manually; it's encoded at :57-58.

That said, my clock stopped syncing for some reason, so ...

The one remaining clock I have took a hard fall, and no longer syncs.

Oh, is there no “DST in effect” flag in the signal?

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.

The time code format does include a DST bit.

https://www.nist.gov/pml/time-and-frequency-division/time-di...

Not every region of the continental US respects DST.

I know, but if it does, it switches on the same day as all the others, which could be encoded in the signal, and it seems like it is [1].

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_...

Wow, added to wish list!

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.

[0] https://en.wikipedia.org/wiki/Communication_with_submarines

> By what, I wonder?

At that length of symbol encoding, by hand. :)

> This is apparently the IRIG H encoding, which dates to the 50s and is probably designed to be easily decoded. By what, I wonder?

Wonder no more! This technology is used in wall clocks, weather stations, and even wrist-watches.

They're usually marketed as "atomic clocks".

For those of us that are visual or audio learners: https://www.youtube.com/watch?v=V0CWj9DwRBY

And a "coverage map" https://www.nist.gov/pml/time-and-frequency-division/time-di...

Reminds me of encodings for IR remote controls such as RC5

Relays maybe?

EDIT: Not sure why I was downvoted. Relays seem like period-accurate technology (happy to be corrected), and they’re comparably slow.

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.

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.

[1] https://www.hopf.com/dcf77-gps_en.php#chapter3

There are several of these stations, they are maintained and operated by NIST. Two of them were almost shut down recently due to budget concerns:

https://www.radioworld.com/global/why-wwv-and-wwvh-still-mat...

In April one of the two WWVB antennas failed (broke) because of 90mph winds.

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.

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.

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.

[1] https://www.citizenwatch.com/us/en/collection/mens-atomic-ti...

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).

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.

Important to note the update:

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.

This looks like a great candidate for crowd funding.

yes, in this case I'd say a good crowd funding platform is the IRS.

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.

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.

You can also pick "timecode" from the extensions menu in the KiwiSDR interface and actually decode the time signal live on the receiver.

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 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 :)

WWVB data transmission format is described here:

https://www.nist.gov/system/files/documents/2017/05/09/NIST-...

The WWVB transmitter sometimes has surprisingly long propagation: https://blog.jgc.org/2021/07/receiving-wwvb-time-signal-in-p... and https://blog.jgc.org/2023/03/wave-ok-wwvb-time-signal-sets-m...

I can picture a room full of engineers in ties, wearing pocket protectors full of implements, chain smoking cigarettes while coming up with this one.

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:

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/

Quick image link fix...spaces in URL broke auto-hyperlinking:

https://www.ncbi.nlm.nih.gov/core/lw/2.0/html/tileshop_pmc/t...

Damn, he's got two pocket protectors!

I can picture a black woman at a desk in a nicely pressed dress coming up with this one on pencil and paper.

https://en.wikipedia.org/wiki/Hidden_Figures

Decoding these signals should be a fun 1st project for Software Defined Radio. Google search shows several projects which did just that.

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.

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.

If you go below 300 Hz, you are probably into some hardcore top secret stuff: https://en.wikipedia.org/wiki/Communication_with_submarines

Assuming salt water, a 1024 Kb message should take around 3 hours to transmit.

This got me thinking of this video:

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.

I'm currently reading (1954) The Time Regulation Institute [1], which has as plot element a series of fines for people not having their clocks set correctly.

Upon my walls hang two "atomic clocks," identical, which utilize this 60 kHz signal to set each time. For some reason, they are consistantly not set to the same time! In Tanpınar's world, the fines would be laughably immense, updated daily, and intentionally frustrating!

In my present realtime world, it is just mildly frustrating.

Thanks for the background/technical information =D

[1]: https://en.wikipedia.org/wiki/The_Time_Regulation_Institute

I see there are cheap indoor wall clocks that are syncd with WWVB. But can't find anything that use gps instead. I am wondering why? Are the receivers too power hungry or the signals just too weak? I'd think going with a gps time sync would be a more future proof design.

I like the topic very much, but why did this very basic blog post get so many upvotes?

It introduces something new that tickles our curiosity. Not everything needs to be a long read. I do like short posts.

Could someone please explain why the low frequency means the bandwidth is limited to 1 bps? Why can't the signal be turned on and off more times per second to transmit at a higher rate?

Earlier this week I purchased a Casio Waveceptor watch. It features the ability to synchronize with this radio signal. I'm very happy with it. I was also happy with an early-2000s model for several years prior. The older one's receiver seemed to become unreliable after about a decade, possibly due to changes in the wireless spectrum over time. Overall, it was quite a reliable watch and so I have good confidence in this product line.

American patriotism set aside, I share the author's enthusiasm for these types of technology! The post's main focus on how we stand on the shoulders of giants is so true! It makes me happy and proud as well.

Another fascinating technology that we take for granted, is the possibility to travel with 280km/h in a train and still be able to receive digital bits and bytes. What kind of witchcraft would our grand-grand-grandparents have called that?

""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.

Not to mention the voyager missions.. still zooming out into interstellar space..

1 bps on a 60 kHz carrier? That is certainly not the maximum possible data rate.

There are AM stations broadcasting at only two or three times that frequency that broadcast voice and music.

Perhaps they meant that it is the most practical for small receivers like watches.

BBC R4 Longwave is at 198 kHz (formerly 200 kHz). The transmitter at Droitwich has been broadcasting voice and music since 1934.

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.

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.

Well said. I couldn’t agree more.

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.

Blind patriotism isn‘t cool. Most of those inventions were invented by multicultural people, so it has really not so much to do with the country.

This is completely incorrect. Time synchronization across the entire US is done via GPS, not radio signals.

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?

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.

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.

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.

> 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.

NTP (https://en.wikipedia.org/wiki/Network_Time_Protocol) can be run on any OpenWRT router. Too bad it isn't a standard feature of every router and appliance.

Yes but then that would require consensus on protocol, encoding/decoding, etc., aka the things large companies are the worst at aligning on.

Plus you have to defend yourself from the neighborhood kid who thinks that it'd be a laugh riot to randomize everyone's clocks at 5:15 in the morning.

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.

I'm in my mid 30s and I still regularly tell unattended Google Homes and Alexa's to set an alarm for 4 AM.

I'm not that malicious, I just like picking up friends' unattended phones and snapping a goofy selfie for them to discover later.

There is only one government

Well said. Simple, solid technology for the benefit of everyone.

Can you use this in basically the lower 48 with a long antenna?

Free RTC L48?

I looked into getting a wristwatch that uses this.

Wonderful post, thank you.

Pretty sure there’ll be lots of comments on this to do with bandwidth and speed of light.

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