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60 kHz (2022)

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Re: 60 kHz (2022)

#101

Post by new299 »

tanepiper wrote: post #97

> 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

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

Re: 60 kHz (2022)

#102

Post by denton-scratch »

metaphor wrote: post #45
mmastrac wrote: post #22

Earlier quoted context omitted.

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.n…

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!

Re: 60 kHz (2022)

#103

Post by denton-scratch »

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…

> 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.

Re: 60 kHz (2022)

#104

Post by nicbou »

anArbitraryOne wrote: post #69

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.

Re: 60 kHz (2022)

#105

Post by zh3 »

tanepiper wrote: post #97

> 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

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

Re: 60 kHz (2022)

#106

Post by zh3 »

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…

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

Re: 60 kHz (2022)

#107

Post by zh3 »

lxgr wrote: post #35
retrac wrote: post #12

Earlier quoted context omitted.

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…

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.

Re: 60 kHz (2022)

#108

Post by kqbx »

vzaliva wrote: post #56

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.

Re: 60 kHz (2022)

#109

Post by misstuned »

bb88 wrote: post #72

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.

Re: 60 kHz (2022)

#110

Post by meindnoch »

mschuster91 wrote: post #96
lxgr wrote: post #35

Earlier quoted context omitted.

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…

> 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…

>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?

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