We'll, if you need millisecond accuracy its OK. But if you running real
clocks - rubidium or cesium, WWV is just not good enough.
If you look around, you can pick up a OEM GPS receiver board for under
$40. You can also find cheap patch antennas for $9/10 - at TAPR. Put
the receiver in a case of your choice, provide 5 volts to run it - use a
MAX232 IC to convert TTL to RS232 and you can have microsecond or better
accuracy say for under $100 max. The old Motorola Oncore VPs are still
useful and will keep you within +/- 55 nS of UTC. The M12 I believe
was +/- 15 nS. I believe Garmin has a GPS18 which is a senor type unit,
the Receiver is built into the antenna and it provides time under 1 uS.
The unit is terminated into RS232 or USB, cost you $79.
There was also a group purchase on this list for the Trimble Thunderbolt
and I see them on Ebay for $130, which is good, thats a real GPS DO.
Justin Pinnix wrote:
Hi Nuts,
Most of you have probably seen this before, but I ran across a great
1975-vintage paper on how to synchronize your clocks and frequency standards
to WWV's HF broadcasts. The equipment needs are very basic - a clock, a
radio, and an oscilloscope. The procedure is simple and far more reliable
than the tone-detection method I attempted earlier.
NBS Technical Note 668 - The Use of National Bureau of Standards High
Frequency Broadcasts for Time and Frequency Calibrations (
http://tf.nist.gov/timefreq/general/pdf/453.pdf)
Yes, I realize that GPS is literally a million times more accurate, but if
all you need is milliseconds, this will do the job cheaper than a GPSDO or
it could serve as a backup. Plus it's a lot of fun to stare at the traces.
They are quite hypnotic.
Thanks,
-JP
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