Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

60 kHz (2022)

ben.page

Post reply on HN
Print view View original

11–20 of 161 posts

Re: 60 kHz (2022)

#11

Post by anyfoo »

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…

Relays maybe?

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

Re: 60 kHz (2022)

#12

Post by retrac »

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 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.

Re: 60 kHz (2022)

#13

Post by frankus »

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?

Re: 60 kHz (2022)

#14

Post by Dalewyn »

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…

>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.

Re: 60 kHz (2022)

#15

Post by erikpukinskis »

khaki54 wrote: post #7

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.

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

Re: 60 kHz (2022)

#16

Post by FrustratedMonky »

""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.

Re: 60 kHz (2022)

#17

Post by [deleted] »

aeonik wrote: post #4
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…

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

[deleted]

Re: 60 kHz (2022)

#18

Post by wglb »

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…

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.

Re: 60 kHz (2022)

#19

Post by joshellington »

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…

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

Re: 60 kHz (2022)

#20

Post by wglb »

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…

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.

Post reply on HN