rapid startup GPSDO
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.
After a forced cold start in an unknown location, the TB will still be searching for satellites after five minutes.
If you move it and don't clear the incorrect location, I don't know how long it will take to realise it is wrong (if it ever does).
Dave
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On Behalf Of jimlux
Sent: 14 July 2010 14:43
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] rapid startup GPSDO
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.
time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Trimble Thunderbolt: I once forgot the minus sign keying in
latitude for the stored position, and it ran for days.
I wondered why I was having trouble seeing the satellites. :)
David C. Partridge wrote:
After a forced cold start in an unknown location, the TB will still be searching for satellites after five minutes.
If you move it and don't clear the incorrect location, I don't know how long it will take to realise it is wrong (if it ever does).
Dave
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.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Luis Cupido wrote:
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).
that's precisely the sort of application I'm looking at..
Wheels stopped to on-the-air in <20 minutes.
Hi
I would guess that a fairly simple TCXO / fast lock GPS combo would get you pretty close.
Bob
On Jul 14, 2010, at 12:13 PM, jimlux wrote:
Luis Cupido wrote:
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).
that's precisely the sort of application I'm looking at..
Wheels stopped to on-the-air in <20 minutes.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
(*) 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).
that's precisely the sort of application I'm looking at..
Wheels stopped to on-the-air in <20 minutes.
Then... Look no further ;-) Reflock to 1pps is your thing.
Take a look of all variants by VE1ALQ and G8ACE
(there is also a japanese variation... can't recall).
all those variants may use my reflockI 1pps CPLD config.
Luis Cupido.