"Stable" time references

[[email protected]]

Ok, Which horse do you use for a NIST?

One that can turn a 12-foot diameter mill wheel 144 times in an hour,
at a pull force of 180 pounds.
http://en.wikipedia.org/wiki/Horsepower#History_of_the_unit

Matt Roberds

 

[Shaun]

"Don Y" wrote in message
Hi,

I need a relatively stable timebase against which to calibrate
my own *local* timebase.

Assume *my* environment is reasonably well controlled (temp, etc.).

Also, assume I can make measurements over VERY long periods of
time (24/7/365 duty).

Ideally, I would like the choice of reference to be something
that user could trade cost/convenience/performance.


To that end, I've got a few basic ideas:
- local XTAL (too easy to "pull", no real advantage over TCXO)
- local TCXO (overkill -- hard to make this "optional")
- external PPS input from GPS (requires view of sky, expensive)
- network time service (hole in firewall, latency issues)
- LFC (low accuracy but dirt cheap, LONG integration periods)

To be clear, I am calibrating *time* -- beyond that is my own
concern.

Any other ideas I should entertain?

Thx,



All you need is a decent shortwave radio with a decent antenna that can pick
up 5000 Hz, 10,000, 15,000, 20,000 Hz. Depending on the time of year;
different frequencies will travel to you home local. The atomic clock in
Bolder Colorado transmits the time on these frequencies, one second ticks.
You will have to compensate for your distance away from Boulder Colorado of
course to get a precise time. There are also some digital clocks that pick
up 60 Khz which is a sync frequency also for the atomic clock in Boulder
Colorado.

Shaun

--

 

[Don Y]

Is the Loran-C navigation system at 100 kHz still working in the USA ?
No.

It should solve the location and propagation delay issues, however,

There are still environmental factors that affect the signal.
But, some of these can be mitigated depending on usage patterns.

you would need some means of telling when (ToD) the transmission code
sequence for each transmitter started.

I'm not interested in time-of-day. The LORAN beacons would be
most effective as frequency references. I.e., using the GRI
as a reference. Or, time between pulses. Or, counting 100KHz
cycles within the modulated envelope.

[But, I've never looked into the accuracy of these aspects
of the signal -- usually more involved with finding the correct
zero-crossing to track, noting envelope polarity, TD's, blink
codes, ECD, etc. You know, the "good stuff" :> ]