[time-nuts] rapid startup GPSDO

[Luis Cupido]

Jim,

The implementation I've done on "reflock II"
(on a MAXII CPLD form Altera
http://www.qsl.net/ct1dmk/reflock.html )
Had fast aqs time in mind(*).
It captures in few 1pps pulses
and could stabilize to about 1% of dac range
in quite less then 60s.

How slower you need it to be in addition to the
above timings depends on how much you want to average
the 1pps. Having it fast it would obviously
track the 1pps jitter.

'how good you need' -> 'how slow it has to be'

These timings are off course after your GPS starts
producing good enough 1pps pulses.

Luis Cupido.
CT1DMK.

P.S. Super cheap approach is the reflockI
(on a $5 CPLD) for which I made also a 1pps code.
(but a few less specs and addons than II)

(*) uW Radio ham application where you arrive on the top
of the hill and switch all equipment on and can be making
contacts minutes after having better than 1e-8(1e-9).


jimlux wrote:
> Is there some (inexpensive) GPSDO that has a "time from power on in an 
> unknown location to reasonably stable" in the <5 minute category?
> 
> Frequency accuracy in the 1E-9 range would be fine.
> 
> A regular old GPS has a Time to First Fix well under that, and it should 
> be cranking out 1pps pulses with 1E-7 or 1E-8  precision pretty 
> quickly.. Would it be fair to say that after 100 seconds, one could 
> theoretically have driven that down another factor of 10?
> 
> As I understand it, a thunderbolt needs some number of hours after turn 
> on to stabilize, but just how bad is it after, say, 5 minutes.
> 
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