[ntp:questions] Re: Using a Radio for setting a PC clock.
Richard B. Gilbert
rgilbert88 at comcast.net
Sat Jun 4 17:23:36 UTC 2005
arupkgeorge at coolgoose.com wrote:
>Is there any way in which an ordinary radio can be used for
>synchronising the clock of a PC? I have read in a Japaneese site that
>by connecting the audio out of a radio to the mic in of a sound card,
>some sort of timing information can be extracted and it can be used for
>setting a PC's Clock. If some one knows about this please clarify.
>Please provide some links, if there is any?
There are a couple of ways to do this! The so called "Atomic'"
wristwatches and clocks use a 60KHz signal broadcast by WWVB in Fort
Collins, Colorado. The modulation can be decoded by some very simple
circuitry that plugs into a serial port and a small program (radioclkd)
by Jonathan Buzzard.
ntpd includes a driver for decoding the HF signal broadcast by WWV (also
in Fort Collins). This requires a short-wave receiver capable of
receiving one or more of the frequencies: 2.5MHz, 5MHZ, 10MHz, 15MHz or
20MHz. You plug the receiver audio output into the audio input on your
computer. I recall reading a message from Professor Mills that this
driver was no longer maintainable; using wording from which I infer that
it has been hacked too often by too many people to the point where it is
impossible to fix a bug without introducing at least one more bug!
It might work for your particular combination of hardware, O/S, and
software or, it might not. If it doesn't, don't expect a fix any time
soon unless you do it yourself.
Frankly, I don't think it's worth the effort unless you have no other
means of getting the time. HF radio propagation is such that there are
places in the US where reception is poor to non-existent for many hours
of the day. VLF radio propagation isn't so great either; the "atomic"
clocks and wrist watches that use it typically synch up once per day,
late at night, and free run the rest of the time. If you are close
enough to Fort Collins, this may not be a problem for you. If you live
in New Jersey I can practically guarantee that you will have problems.
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