"Stable" time references

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

No.

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

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" :> ]

For simple time transfer applications, the only thing you need is a common signal source, this might be a local analog TV transmitter, some Loran-C type LF transmitter or a pulsar in the sky.

In addition to this, you need some means to communicate the difference from the reference pulse from the reference source (atomic clock) to your local clock.

Without exaggerating too much, you could use a local homing pigeon nest, transport one pigeon to the atomic clock site, attach the time difference to the pigeon, let the pigeon return to the nest and read out the time difference. There might be some more cost effective ways of doing this :-)