At 08:21 AM 04/01/2013, you wrote:
>* I originally wrote "one second per month" but I'm not 100% sure that
>was correct. (It may have been 30+ years ago). I know it was very
>accurate indeed once trimmed. The tech was surprised when I told him
>how much adjustment I wanted. He had a frequency meter calibrated in
>seconds per xxx error and my claimed drift matched what he measured
>almost exactly. As you'd expect - but he can't have met many engineers
>:-).

It's interesting that you can buy 0.1ppm (commercial temp range)
TCXO (not OCXO, so only a few mA @ 3.3V) oscillators for $35 or so:

http://www.conwin.com/datasheets/tx/tx350.pdf

That should be a few seconds per year, but the initial calibration
is only +/-1ppm (about 30 seconds per year).

or maybe one of the new < 150mW atomic clocks for about +16dB$

--sp



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