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60 kHz (2022)

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Re: 60 kHz (2022)

#31

Post by anyfoo »

Dalewyn wrote: post #27
anyfoo wrote: post #21

Earlier quoted context omitted.

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.

>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 micro scopic 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?

Re: 60 kHz (2022)

#32

Post by anyfoo »

pavel_lishin wrote: post #24
anyfoo wrote: post #21

Earlier quoted context omitted.

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.

Re: 60 kHz (2022)

#33

Post by someguydave »

anyfoo wrote: post #2

> 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 sin…

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

Re: 60 kHz (2022)

#35

Post by lxgr »

retrac wrote: post #12
tkzed49 wrote: post #6

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 powe…

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 s…

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"?)

Re: 60 kHz (2022)

#36

Post by alright2565 »

frankus wrote: post #13

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…

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.

Re: 60 kHz (2022)

#37

Post by lxgr »

frankus wrote: post #13

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…

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.

Re: 60 kHz (2022)

#38

Post by lxgr »

Eduard wrote: post #26
dfc wrote: post #9

Earlier quoted context omitted.

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...

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…

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.

Re: 60 kHz (2022)

#39

Post by lxgr »

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 :)

Re: 60 kHz (2022)

#40

Post by lxgr »

anaidioschrono wrote: post #30
wglb wrote: post #18

Earlier quoted context omitted.

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.

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?

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