3 ms·

WWVB, operating from Fort Collins transmits its time code signal at a rate of 1 bit/second at 60 kHz using carrier power modulation. This translates to a wave l

WWVB, operating from Fort Collins transmits its time code signal at a rate of 1 bit/second at 60 kHz using carrier power modulation. This translates to a wave length of 5 km yet your cheap "atomic clock" is able to detect and sync to the signal with a short folded quarter wave antenna that fits inside the clock or inside of your wrist watch. Coverage is over most of the continental US

LeoPanthera 9y ago
The iPhone app "Clock Wave" is able to generate and transmit this signal from the speaker (!) in your iPhone, so you can accurately set radio-controlled clocks and watches if you cannot receive the real thing. It can simulate the five major time transmitters around the world. I'm always amazed that it works at all.
- matthewmcg 9y ago
  This page has a good explanation of a similar application: http://www.jrcomputing.com.au/Set_Watch/Set_Watch_Auto.html http://www.jrcomputing.com.au/Set_Watch/Set_Watch_Auto.html The app has the phone's audio output circuit send a modulated 20KHz tone to the headphones or speaker. This incidentally results in faint EM emission at the third harmonic (60KHz) which can be detected by the watch at short range. You can call this the "Part 15 loophole" [1]. [1]: https://www.gpo.gov/fdsys/pkg/CFR-2016-title47-vol1/xml/CFR-2016-title47-vol1-sec15-5.xml https://www.gpo.gov/fdsys/pkg/CFR-2016-title47-vol1/xml/CFR-...
- jlgaddis 9y ago
  Is it actually receiving WWVB, et al., or jusy synchronizing with, for example, an NTP server and then using that to generate an audio signal you can "manually" sync with?
  - sizzzzlerz 9y ago
    I don't think the iPhone nor any Android phone have the necessary circuitry to receive the WWVB signal directly. THey do, however, keep time sync with NTP or some NTP-like service over the wireless network or wifi. That should keep it's knowledge of time accurate to a second or two.
  - LeoPanthera 9y ago
    It simply broadcasts the time on your iPhone (the source of which is usually time.apple.com) as a WWVB-compatible radio signal.

LeoPanthera 9y ago

The iPhone app "Clock Wave" is able to generate and transmit this signal from the speaker (!) in your iPhone, so you can accurately set radio-controlled clocks and watches if you cannot receive the real thing. It can simulate the five major time transmitters around the world. I'm always amazed that it works at all.

matthewmcg 9y ago
This page has a good explanation of a similar application: http://www.jrcomputing.com.au/Set_Watch/Set_Watch_Auto.html http://www.jrcomputing.com.au/Set_Watch/Set_Watch_Auto.html The app has the phone's audio output circuit send a modulated 20KHz tone to the headphones or speaker. This incidentally results in faint EM emission at the third harmonic (60KHz) which can be detected by the watch at short range. You can call this the "Part 15 loophole" [1]. [1]: https://www.gpo.gov/fdsys/pkg/CFR-2016-title47-vol1/xml/CFR-2016-title47-vol1-sec15-5.xml https://www.gpo.gov/fdsys/pkg/CFR-2016-title47-vol1/xml/CFR-...
jlgaddis 9y ago
Is it actually receiving WWVB, et al., or jusy synchronizing with, for example, an NTP server and then using that to generate an audio signal you can "manually" sync with?
- sizzzzlerz 9y ago
  I don't think the iPhone nor any Android phone have the necessary circuitry to receive the WWVB signal directly. THey do, however, keep time sync with NTP or some NTP-like service over the wireless network or wifi. That should keep it's knowledge of time accurate to a second or two.
- LeoPanthera 9y ago
  It simply broadcasts the time on your iPhone (the source of which is usually time.apple.com) as a WWVB-compatible radio signal.