Hal writes:
It might be possible to avoid hanging bridges by dithering
the sawtooth. I'm thinking of something like a heater under
the xtal for the GPS unit that gets driven by a medium
frequency - slow relative to the normal sawtooth but fast
relative to the PLL time constant. This somehow
-Ursprüngliche Nachricht- Von: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] Im Auftrag von Brooke Clarke
Gesendet: Dienstag, 19. Dezember 2006 20:05
An: time-nuts@febo.com
Betreff: Re: [time-nuts] LPRO-101 with Brooks Shera's GPS
locking circuit
Hi Brendan:
It's my take
In message [EMAIL PROTECTED], Ulrich Bangert writes:
a) that for most of us a GPSD Rb is of little to no use compared to a
good GPSD xtal oscillator
... if your hold-over requirement is trivial.
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
[EMAIL PROTECTED] | TCP/IP since
At 10:25 AM 12/20/2006, you wrote:
Hello folks,
The controller's task is to always pour just enough fluid from the
second pot into the first pot to keep the fluid level constant despite
the fluid lost through the small hole. One refinement of the model is
that we also consider that the amount of
Yes, agreed!
-Ursprüngliche Nachricht-
Von: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] Im Auftrag von Poul-Henning Kamp
Gesendet: Mittwoch, 20. Dezember 2006 16:43
An: Discussion of precise time and frequency measurement
Betreff: Re: [time-nuts] LPRO-101 with Brooks Shera's GPS
Hello folks,
i like to play the bad boy again: My claim is
a) that for most of us a GPSD Rb is of little to no
use compared to a good GPSD xtal oscillator
Ulrich,
That's a rather general statement, but I understand what
you mean. Consider, instead of a bold general assertion
which can be
In the matter of lifetime (outside of MTBF issues), is it correct that
Rb has a built-in life limiting mechanism (the lamp wears out), where Qz
does not? If so, Rb oscillators will eventually fail but one might hope
a Qz oscillator may not.
Didier
Tom Van Baak wrote:
Hello folks,
i like to
In message [EMAIL PROTECTED], Tom Van Baak writes:
Warm-up time --
Many Rb will lock in 5 minutes, typically. Some Qz
take much longer to get on-frequency from cold start.
This can simplify the initial loop locking algorithm.
Initial capture is best done with a looser timeconstant in
Tom Van Baak wrote:
Hal writes:
It might be possible to avoid hanging bridges by dithering
the sawtooth. I'm thinking of something like a heater under
the xtal for the GPS unit that gets driven by a medium
frequency - slow relative to the normal sawtooth but fast
relative to the PLL time
My original Question has sparked off quite an interesting discussion and
I learnt a lot
Since it seems that the Brooks Shera Project is not the optimum way of
GPS disciplining a Rubidium Oscillator can anyone here point me in the
direction of other DIY projects (or even ideas) that might yield a
Hi Brendan:
It's my take that there are two aspects of the Brooks (no relation)
design that need to be addressed for optimum operation:
1. the filter time constants of the stock design are not correct for a
Rb oscillator, and that can be fixed by getting a custom PIC from Brooks.
2. the TIC
On Tue, 2006-12-19 at 11:05 -0800, Brooke Clarke wrote:
Hi Brendan:
Keep in mind that this design does work and that the above items relate
to optimization not bug fixes.
I currently have the Brooks Shera design disciplining my LPRO-101
without any mods and using the ADC connected directly
Hi Brendan:
It's interesting that the PRS10 can time stamp the 1 PPS input with a
resolution of 10 ns. I wonder how they do that.
http://www.thinksrs.com/downloads/PDFs/Catalog/PRS10c.pdf
When I picked up my PRS10 at the factory during the tour I learned that
the 10 MHz oscillator in the
Magnus Danielson wrote:
From: Brooke Clarke [EMAIL PROTECTED]
Subject: Re: [time-nuts] LPRO-101 with Brooks Shera's GPS locking circuit
Date: Tue, 19 Dec 2006 13:42:28 -0800
Message-ID: [EMAIL PROTECTED]
Hi Brendan:
It's interesting that the PRS10 can time stamp the 1 PPS input
From: Magnus Danielson [EMAIL PROTECTED]
Subject: Re: [time-nuts] LPRO-101 with Brooks Shera's GPS locking circuit
Date: Tue, 19 Dec 2006 23:00:55 +0100 (CET)
Message-ID: [EMAIL PROTECTED]
From: Brooke Clarke [EMAIL PROTECTED]
Subject: Re: [time-nuts] LPRO-101 with Brooks Shera's GPS locking
From: Dr Bruce Griffiths [EMAIL PROTECTED]
Subject: Re: [time-nuts] LPRO-101 with Brooks Shera's GPS locking circuit
Date: Wed, 20 Dec 2006 11:24:42 +1300
Message-ID: [EMAIL PROTECTED]
Magnus Danielson wrote:
From: Brooke Clarke [EMAIL PROTECTED]
Subject: Re: [time-nuts] LPRO-101 with Brooks
In message [EMAIL PROTECTED], Magnus Danielson wri
tes:
It actually uses the CPU builtin counter, which
will do for the purpose. They could have spent a little more and got better
single shot resolution out of it, but I suspect they didn't see the need.
They are limited by digital noise inside
From: Poul-Henning Kamp [EMAIL PROTECTED]
Subject: Re: [time-nuts] LPRO-101 with Brooks Shera's GPS locking circuit
Date: Tue, 19 Dec 2006 23:17:03 +
Message-ID: [EMAIL PROTECTED]
In message [EMAIL PROTECTED], Magnus Danielson wri
tes:
It actually uses the CPU builtin counter, which
Noise like the oncore sawtooth isn't always a bad thing.
I was going to comment on that area... Thanks for the reminder.
The problem is that the sawtooth isn't noise in the normal Gaussian sense.
If you happen to hit a long/wide hanging bridge, the resulting offset may get
past your PLL
Hal Murray wrote:
Noise like the oncore sawtooth isn't always a bad thing.
I was going to comment on that area... Thanks for the reminder.
The problem is that the sawtooth isn't noise in the normal Gaussian sense.
If you happen to hit a long/wide hanging bridge, the resulting offset
[EMAIL PROTECTED] wrote:
Hi Bruce,
would you have pointers to good temperature sensing circuits with sub
millidegree resolution?
thanks,
Said
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[EMAIL PROTECTED] wrote:
Hi Bruce,
would you have pointers to good temperature sensing circuits with sub
millidegree resolution?
thanks,
Said
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Hi Bruce,
great ideas, thanks!
Said
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[EMAIL PROTECTED] wrote:
Hi Bruce,
great ideas, thanks!
Said
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Said
Attached circuit illustrates how a PT100 may be interfaced to a single
2006 02:00
An: Brooks Shera; Discussion of precise time and frequency measurement
Betreff: Re: [time-nuts] LPRO-101 with Brooks Shera's GPS
locking circuit
Brooks Shera wrote:
- Original Message -
From: Ulrich Bangert [EMAIL PROTECTED]
To: 'Discussion of precise time
In message [EMAIL PROTECTED], Ulrich Bangert writes:
ONE SIMPLE RULE applies to this question despite the fact that some math
for drawing tau-sigma-diagrams is indispensable.
Ulrich,
The real challenge is to build an algorithm which finds this point dynamically.
--
Poul-Henning Kamp |
In message [EMAIL PROTECTED], Ulrich Bangert writes:
Poul,
i appreciate your comments always a lot! But dynamical methods are
especially usefull when the input parameters are subject of change,
aren't they?
They are also very useful for amateur projects where the users do
not have the necessary
From: Poul-Henning Kamp [EMAIL PROTECTED]
Subject: Re: [time-nuts] LPRO-101 with Brooks Shera's GPS locking circuit
Date: Sat, 16 Dec 2006 15:56:32 +
Message-ID: [EMAIL PROTECTED]
In message [EMAIL PROTECTED], Ulrich Bangert writes:
Poul,
i appreciate your comments always a lot
In message [EMAIL PROTECTED], Magnus Danielson writes:
The way you do this is by measuring the ADEV between your two sources
and how it changes with changes in your timeconstant.
I.e. out of your TIC. The trouble is that you do not get one result but
several. Either you just drive the
From: Poul-Henning Kamp [EMAIL PROTECTED]
Subject: Re: [time-nuts] LPRO-101 with Brooks Shera's GPS locking circuit
Date: Sat, 16 Dec 2006 17:06:00 +
Message-ID: [EMAIL PROTECTED]
In message [EMAIL PROTECTED], Magnus Danielson writes:
The way you do this is by measuring the ADEV between
You still want to produce some form of quality measure for the ADEV
shape in order to form some form of control loop.
Suppose I build I good GPSDO. How do I determine how good it is? (or even
if it is any good)
How much do I learn by just plotting the control voltage?
How much do I learn
. Dezember 2006 20:52
An: Magnus Danielson
Cc: time-nuts@febo.com
Betreff: Re: [time-nuts] LPRO-101 with Brooks Shera's GPS
locking circuit
In message [EMAIL PROTECTED],
Magnus Danielson writes:
You still want to produce some form of quality measure for the ADEV
shape in order to form
In message [EMAIL PROTECTED], Hal Murray writes:
You still want to produce some form of quality measure for the ADEV
shape in order to form some form of control loop.
Suppose I build I good GPSDO. How do I determine how good it is? (or even
if it is any good)
Since you pretty much know
Hal Murray wrote:
You still want to produce some form of quality measure for the ADEV
shape in order to form some form of control loop.
Suppose I build I good GPSDO. How do I determine how good it is? (or even
if it is any good)
How much do I learn by just plotting the control
Hi Ulrich,
good details on how to set the time constant for best GPSDO performance etc!
Some issues you did not mention are but that are essential to get a good
GPSDO are:
* Aging compensation
* Temperature compensation
* fault recovery, such as mechanical shock to
[EMAIL PROTECTED] wrote:
Hi Ulrich,
good details on how to set the time constant for best GPSDO performance etc!
Some issues you did not mention are but that are essential to get a good
GPSDO are:
* Aging compensation
* Temperature compensation
* fault
Hi Bruce,
would you have pointers to good temperature sensing circuits with sub
millidegree resolution?
thanks,
Said
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von Tom Van Baak
Gesendet: Freitag, 15. Dezember 2006 08:23
An: Discussion of precise time and frequency measurement
Betreff: Re: [time-nuts] LPRO-101 with Brooks Shera's GPS
locking circuit
Tom
A TIC with 0.5ns jitter at 1 second isn't actually too much
in the way
of overkill
Hi Ulrich:
I think the answer is what other low cost options are available? I
would like to have a more modern TIC capability to add to the clock I'm
working on. But although there's been a lot of discussion about
different ways of making TIC measurements, it's not clear to me how to
do it
Brooke Clarke wrote:
Hi Ulrich:
I think the answer is what other low cost options are available? I
would like to have a more modern TIC capability to add to the clock I'm
working on. But although there's been a lot of discussion about
different ways of making TIC measurements, it's not
- Original Message -
From: Ulrich Bangert [EMAIL PROTECTED]
To: 'Discussion of precise time and frequency measurement'
time-nuts@febo.com
Sent: Friday, December 15, 2006 05:47
Subject: Re: [time-nuts] LPRO-101 with Brooks Shera's GPS locking circuit
...
I second Bruces's opinion
Brooks Shera wrote:
- Original Message -
From: Ulrich Bangert [EMAIL PROTECTED]
To: 'Discussion of precise time and frequency measurement'
time-nuts@febo.com
Sent: Friday, December 15, 2006 05:47
Subject: Re: [time-nuts] LPRO-101 with Brooks Shera's GPS locking circuit
Tom Van Baak wrote:
On the subject of Brooks Shera's design, the one thing that troubles me is
the
use of a 24 MHz oscillator to count the width of the 1PPS signal.
This yields a precision of 4.16e-8, but does it really?
No, with averaging it's much better than that.
Auftrag von Tom Van Baak
Gesendet: Donnerstag, 14. Dezember 2006 07:47
An: Discussion of precise time and frequency measurement
Betreff: Re: [time-nuts] LPRO-101 with Brooks Shera's GPS
locking circuit
On the subject of Brooks Shera's design, the one thing that
troubles
me
But is it really an improvement that you get out of it? The answer is
NO! He, why not? The answer is: Because you have to PAY the increase in
precision with the increase in observation time. For every increase of
10 in precision you need to increase the observation time by 10!
Ulrich,
On Thu, December 14, 2006 23:07, Dr Bruce Griffiths said:
Thus devising inexpensive phase detectors/TICs with subnanosecond
performance allows one to take advantage of improvements in GPS timing
receiver performance when they occur.
The possibility of utilising GPS carrier phase tracking
[EMAIL PROTECTED] wrote:
On Thu, December 14, 2006 23:07, Dr Bruce Griffiths said:
Thus devising inexpensive phase detectors/TICs with subnanosecond
performance allows one to take advantage of improvements in GPS timing
receiver performance when they occur.
The possibility of utilising
[EMAIL PROTECTED] wrote:
On Thu, December 14, 2006 23:07, Dr Bruce Griffiths said:
Thus devising inexpensive phase detectors/TICs with subnanosecond
performance allows one to take advantage of improvements in GPS timing
receiver performance when they occur.
The possibility of utilising
From: Dr Bruce Griffiths [EMAIL PROTECTED]
Subject: Re: [time-nuts] LPRO-101 with Brooks Shera's GPS locking circuit
Date: Fri, 15 Dec 2006 12:55:19 +1300
Message-ID: [EMAIL PROTECTED]
Björn
Bruce,
You will need a dual frequency receiver to more accurately correct for the
ionospheric delay
From: [EMAIL PROTECTED]
Subject: Re: [time-nuts] LPRO-101 with Brooks Shera's GPS locking circuit
Date: Fri, 15 Dec 2006 00:21:25 +0100 (CET)
Message-ID: [EMAIL PROTECTED]
On Thu, December 14, 2006 23:07, Dr Bruce Griffiths said:
Thus devising inexpensive phase detectors/TICs
On Fri, December 15, 2006 0:55, Dr Bruce Griffiths said:
Björn
You will need a dual frequency receiver to more accurately correct for the
ionospheric delay.
Sure, that is an improvement. But how large is really the time rate of
change of the ionosphere? (Depends on the solar activity
Tom
A TIC with 0.5ns jitter at 1 second isn't actually too much in the way
of overkill when the PPS signal has 2ns of jitter.
Bruce,
Can you clarify about the jitter, though. The TIC jitter
that was quoted (500 ps) is the single-shot resolution
for the 53131A. The 2 ns M12+ jitter is an
Hi I am looking for info on using the Brooks Shera GPS-VCXO Controller
with an EFRATOM LPRO-101?
I currently have it locking an old and unknown single oven Xtal
oscillator this is working as well but I hope to replace this with the
LPRO-101
Has anyone any suggestions as to how best to choose
-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf
Of Richard H McCorkle
Sent: Wednesday, December 13, 2006 4:44 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] LPRO-101 with Brooks Shera's GPS locking circuit
Hi Brendan,
I would contact Brooks
the one thing that troubles me is the use of a 24 MHz oscillator to
count the width of the 1PPS signal. This yields a precision of
4.16e-8
Question: Why not multiply the VCXO or OCXO output by 5 or 10 and run
that into 24 or 32 bit counter? OR just sample the counter on every
10th PPS?
PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf
Of Dr Bruce Griffiths
Sent: Wednesday, December 13, 2006 7:52 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] LPRO-101 with Brooks Shera's GPS locking circuit
The Brooks Shera circuit relies on the 24 MHz
I'm sure Brooks Shera can describe the nuances of his GPS locking circuit
far better than I can; but that said, the 24MHz oscillator is not used to
directly count the 1PPS signals. It is used over a 30 second measurement
interval, yielding a precision of about 1.4nS per count. Also the digital
On the subject of Brooks Shera's design, the one thing that troubles me is
the
use of a 24 MHz oscillator to count the width of the 1PPS signal.
This yields a precision of 4.16e-8, but does it really?
No, with averaging it's much better than that.
This oscillator is uncontrolled and any
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