Re: [time-nuts] Determination of the placement of the first pps
Not to mention the solar noon varies by +/- 15min over the year (don't ask
me how this is called...old knowledge from my high school days)
Analemma: It's the figure 8 you see on globes in the middle of the Pacific
Ocean.
It's caused by the Earth's orbit not being circular and the axis of rotation
not being perpendicular to the orbit plane.
http://en.wikipedia.org/wiki/Analemma
--
These are my opinions, not necessarily my employer's. I hate spam.
The Earth's rotation is always refferenced to a larger reference frame
of distant stars, not the sun. If you try and use the Sun, I think
there are smaller effects like the Earth and Moon revolve around a
common center and then there is Jupiter. So they use stars.
The next question is "which stars" and I think measurements are good
enough that the question of "Which Stars?" matters. Makes sense when
you remember that a nano second is about a foot and all stars are
moving quite fast relative to each other.
On Mon, Jan 23, 2012 at 11:39 AM, Hal Murray hmurray@megapathdsl.net wrote:
Not to mention the solar noon varies by +/- 15min over the year (don't ask
me how this is called...old knowledge from my high school days)
Analemma: It's the figure 8 you see on globes in the middle of the Pacific
Ocean.
It's caused by the Earth's orbit not being circular and the axis of rotation
not being perpendicular to the orbit plane.
http://en.wikipedia.org/wiki/Analemma
--
These are my opinions, not necessarily my employer's. I hate spam.
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.
--
Chris Albertson
Redondo Beach, California
In message CABbxVHtyRBAQY8tLVDxxsVKjMLVF8LzgCn1q266yBMY9f13Bsw@mail.gmail.com
, Chris Albertson writes:
The Earth's rotation is always refferenced to a larger reference frame
of distant stars, not the sun.
It's actually distant quarsars, and the point being that they are so
far away that any cross-field motion they might or might not have
would not represent a parallax error in our measurements of their
posisiton.
The measurements are done with VLBI, which is a good google search
to learn more about this.
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
Is this, in any way, related to the fact the Earth has a Moon?
Ideally, the Earth rotates around the Sun and the Moon rotates around the
Earth. However, is it better described as the 'center of mass' of the
Earth/Moon rotates around the Sun? Not to mention all those other
confounding variables such as other planets and moons?
Also, getting back to the placement of the 'first pps', is there a way to
'sync' the 1 PPS output of an FE-5680A to an external signal, such as a GPS
receiver or TBolt? I would think that might be possible given their
original purpose.
Thanks in advance.
Joe
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Hal Murray
Sent: Monday, January 23, 2012 1:39 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Determination of the placement of the first pps
Not to mention the solar noon varies by +/- 15min over the year (don't ask
me how this is called...old knowledge from my high school days)
Analemma: It's the figure 8 you see on globes in the middle of the Pacific
Ocean.
It's caused by the Earth's orbit not being circular and the axis of rotation
not being perpendicular to the orbit plane.
http://en.wikipedia.org/wiki/Analemma
--
These are my opinions, not necessarily my employer's. I hate spam.
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.
On 1/23/12 5:50 PM, J. L. Trantham wrote:
Is this, in any way, related to the fact the Earth has a Moon?
Ideally, the Earth rotates around the Sun and the Moon rotates around the
Earth. However, is it better described as the 'center of mass' of the
Earth/Moon
barycenter is the term
rotates around the Sun? Not to mention all those other
confounding variables such as other planets and moons?
Well, yes.. there are fairly sophisticated numerical integration
programs that figure all this stuff out, if you're interested.
On Mon, Jan 23, 2012 at 5:50 PM, J. L. Trantham jltran@att.net wrote:
Is this, in any way, related to the fact the Earth has a Moon?
is there a way to
'sync' the 1 PPS output of an FE-5680A to an external signal, such as a GPS
receiver or TBolt? I would think that might be possible given their
original purpose.
The 1PPS is not in the units specs. It is just by luck that it works.
However we could adjust the phase of the 1PPS by running the unit
fast or slow for some period of time and then going back to exact
10MHz. But that method could take a LONG time, like tens of thousands
of seconds. Better I think to test the phase and if it is "off" by
more than say, 0.01 second to just power the unit off and restart and
see what luck gives you. I bet 100 power cycles is faster than
moving the phase by 0.5 seconds.
Maybe the answer is to wire up a few decade divers and divide the
10MHz to 1pps yourself. Thenyou can let a known good PPS reset your
counters and get the phase correct instantly
--
Chris Albertson
Redondo Beach, California
Thanks Chris.
It seems such a logical feature to have, I would think it would have been
included perhaps by a serial command. My old CS clocks have this feature
though I have never taken the time to sync them.
Joe
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Chris Albertson
Sent: Tuesday, January 24, 2012 12:34 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Determination of the placement of the first pps
On Mon, Jan 23, 2012 at 5:50 PM, J. L. Trantham jltran@att.net wrote:
Is this, in any way, related to the fact the Earth has a Moon?
is there a way to
'sync' the 1 PPS output of an FE-5680A to an external signal, such as
a GPS receiver or TBolt? I would think that might be possible given
their original purpose.
The 1PPS is not in the units specs. It is just by luck that it works.
However we could adjust the phase of the 1PPS by running the unit fast or
slow for some period of time and then going back to exact 10MHz. But that
method could take a LONG time, like tens of thousands
of seconds. Better I think to test the phase and if it is "off" by
more than say, 0.01 second to just power the unit off and restart and
see what luck gives you. I bet 100 power cycles is faster than
moving the phase by 0.5 seconds.
Maybe the answer is to wire up a few decade divers and divide the 10MHz to
1pps yourself. Thenyou can let a known good PPS reset your counters and get
the phase correct instantly
--
Chris Albertson
Redondo Beach, California
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.
Thanks.
As I was re-reading the postings, I noted additional information in an
earlier post that pretty much answered the question though the term
'barycenter' is new to me.
Joe
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Jim Lux
Sent: Tuesday, January 24, 2012 12:06 AM
To: time-nuts@febo.com
Subject: Re: [time-nuts] Determination of the placement of the first pps
On 1/23/12 5:50 PM, J. L. Trantham wrote:
Is this, in any way, related to the fact the Earth has a Moon?
Ideally, the Earth rotates around the Sun and the Moon rotates around
the Earth. However, is it better described as the 'center of mass' of
the Earth/Moon
barycenter is the term
rotates around the Sun? Not to mention all those other
confounding variables such as other planets and moons?
Well, yes.. there are fairly sophisticated numerical integration
programs that figure all this stuff out, if you're interested.
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.
On 01/24/2012 12:42 PM, J. L. Trantham wrote:
Thanks Chris.
It seems such a logical feature to have, I would think it would have been
included perhaps by a serial command. My old CS clocks have this feature
though I have never taken the time to sync them.
"Jumping" the PPS into about the right phase is done within a second and
is well worth the effort. I use this myself and it works well.
Forcing "sync" on atomic clocks is badly needed. The frequency steering
range is small so frequency limit sideways would take ages.
Cheers,
Magnus
Joe
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Chris Albertson
Sent: Tuesday, January 24, 2012 12:34 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Determination of the placement of the first pps
On Mon, Jan 23, 2012 at 5:50 PM, J. L. Tranthamjltran@att.net wrote:
Is this, in any way, related to the fact the Earth has a Moon?
is there a way to
'sync' the 1 PPS output of an FE-5680A to an external signal, such as
a GPS receiver or TBolt? I would think that might be possible given
their original purpose.
The 1PPS is not in the units specs. It is just by luck that it works.
However we could adjust the phase of the 1PPS by running the unit fast or
slow for some period of time and then going back to exact 10MHz. But that
method could take a LONG time, like tens of thousands
of seconds. Better I think to test the phase and if it is "off" by
more than say, 0.01 second to just power the unit off and restart and
see what luck gives you. I bet 100 power cycles is faster than
moving the phase by 0.5 seconds.
Maybe the answer is to wire up a few decade divers and divide the 10MHz to
1pps yourself. Thenyou can let a known good PPS reset your counters and get
the phase correct instantly
Magnus,
How did you 'jump' the PPS on the FE-5680A? Is it a serial command? How do
you 'sync' it to the external PPS from say a TBolt?
Joe
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Magnus Danielson
Sent: Tuesday, January 24, 2012 12:51 PM
To: time-nuts@febo.com
Subject: Re: [time-nuts] Determination of the placement of the first pps
On 01/24/2012 12:42 PM, J. L. Trantham wrote:
Thanks Chris.
It seems such a logical feature to have, I would think it would have
been included perhaps by a serial command. My old CS clocks have this
feature though I have never taken the time to sync them.
"Jumping" the PPS into about the right phase is done within a second and is
well worth the effort. I use this myself and it works well.
Forcing "sync" on atomic clocks is badly needed. The frequency steering
range is small so frequency limit sideways would take ages.
Cheers,
Magnus
Joe
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com]
On Behalf Of Chris Albertson
Sent: Tuesday, January 24, 2012 12:34 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Determination of the placement of the first
pps
On Mon, Jan 23, 2012 at 5:50 PM, J. L. Tranthamjltran@att.net wrote:
Is this, in any way, related to the fact the Earth has a Moon?
is there a way to
'sync' the 1 PPS output of an FE-5680A to an external signal, such as
a GPS receiver or TBolt? I would think that might be possible given
their original purpose.
The 1PPS is not in the units specs. It is just by luck that it works.
However we could adjust the phase of the 1PPS by running the unit
fast or slow for some period of time and then going back to exact
10MHz. But that method could take a LONG time, like tens of thousands
of seconds. Better I think to test the phase and if it is "off" by
more than say, 0.01 second to just power the unit off and restart and
see what luck gives you. I bet 100 power cycles is faster than
moving the phase by 0.5 seconds.
Maybe the answer is to wire up a few decade divers and divide the
10MHz to 1pps yourself. Thenyou can let a known good PPS reset your
counters and get the phase correct instantly
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.
On 01/24/2012 08:07 PM, J. L. Trantham wrote:
Magnus,
How did you 'jump' the PPS on the FE-5680A? Is it a serial command? How do
you 'sync' it to the external PPS from say a TBolt?
I was not talking about the 5680 specific. Sorry for the unclarity.
Cheers,
Magnus
Darn.
I was hoping for that feature. I still think it should be there.
Joe
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Magnus Danielson
Sent: Tuesday, January 24, 2012 1:19 PM
To: time-nuts@febo.com
Subject: Re: [time-nuts] Determination of the placement of the first pps
On 01/24/2012 08:07 PM, J. L. Trantham wrote:
Magnus,
How did you 'jump' the PPS on the FE-5680A? Is it a serial command? How
do
you 'sync' it to the external PPS from say a TBolt?
I was not talking about the 5680 specific. Sorry for the unclarity.
Cheers,
Magnus
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.
On 01/25/2012 02:41 AM, J. L. Trantham wrote:
Darn.
I was hoping for that feature. I still think it should be there.
Indeed. Should be in there somewhere...
Didn't see these link hit the list:
http://pastebin.com/S8UcnCMZ
http://www.dd1us.de/Downloads/precise%20reference%20frequency%20rev%200_7.pdf
http://vk2xv.djirra.com/tech_rubidium.htm
Looking at the last one it says:
"NOTE: Although this unit is marked with both 10MHz and 1pps, research
on the 'net seems to indicate that the '1pps' output has only a period
of exactly 1 second when the frequency is set to 223 Hz (8.388608Mhz).
According to those sources the '1pps' will have a period of 0.8388608
seconds when the output frequency is set to 10MHz. This should be easy
to verify. In any case I have no need for a 1pps output - I use a GPS
module to get a 1pps signal which also has the advantage of being
in-phase with real time seconds. "
Now... to speed-adjust the PPS phase, use the DDS and steer it
intentionally of frequence with sufficient delta frequence for suitable
time and you should home in pretty quickly.
Hunting some more:
http://www.qsl.net/zl1bpu/PROJ/Ruby.htm
"Without modification the units have just one output - 1pps (1 Hz).
There is a simple modification to extract 8388.608 kHz, which is of
course 223 Hz, and this frequency is used, through binary division, to
generate the 1pps output. The 8388.608 kHz output is generated by a
32-bit Direct Digital Synthesizer chip (AD9830). This output can be
steered to any other frequency within the operating range, by
interacting with the controlling microcontroller, with three provisos:
- The unit has a peaked filter at the synthesizer output, and so the
level at other frequencies varies wildly. This can be corrected with
minor modifications. - When operating at any other frequency than 8388.608kHz, the 1pps
output is of course incorrect. - The synthesizer operating frequency can be set to within ±5 mHz
(milliHertz) of the requested frequency,
- but ONLY if the calculations, on which the command sent to it
is based, correctly use 32-bit maths. "
Which is a confirmation...
http://www.leapsecond.com/museum/fei5650a/
http://www.ko4bb.com/dokuwiki/doku.php?id=precision_timing:rubidium_oscillators
So, this would work for the 50,255+ MHz based FE 5680A. For 60 MHz
variants it works a little different, but it has two MCUs sitting there,
so some use for theme should there be.
Cheers,
Magnus
Yikes, please delete that pastebin link. That was just my initial try at a FAQ. A significantly updated and more current version of the FE-5680A FAQ is located at http://www.ko4bb.com/dokuwiki/doku.php?id=precision_timing:fe5860a_faq
Scott's utility seems to be able to dump the FEI unit serial number, and perhaps the included options. If my guess is correct, all three of the units I have are equipped only with "Option 2" which is the RS-232 port. But there are many possible varieties of 5680 units out there, and some of them may have the 1 PPS behavior you mention while others do not- I have no information on that.
-------Original Message-------
From: Magnus Danielson magnus@rubidium.dyndns.org
Didn't see these link hit the list:
http://pastebin.com/S8UcnCMZ
http://www.dd1us.de/Downloads/precise%20reference%20frequency%20rev%200_7.pdf
http://vk2xv.djirra.com/tech_rubidium.htm
Hi
Based on the number of units that come in with the "1 pps output" missing,
I'd bet the $40 FE5680's were used only for the 10 MHz output.
Bob
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Magnus Danielson
Sent: Tuesday, January 24, 2012 10:14 PM
To: time-nuts@febo.com
Subject: Re: [time-nuts] Determination of the placement of the first pps
On 01/25/2012 02:41 AM, J. L. Trantham wrote:
Darn.
I was hoping for that feature. I still think it should be there.
Indeed. Should be in there somewhere...
Didn't see these link hit the list:
http://pastebin.com/S8UcnCMZ
http://www.dd1us.de/Downloads/precise%20reference%20frequency%20rev%200_7.pd
f
http://vk2xv.djirra.com/tech_rubidium.htm
Looking at the last one it says:
"NOTE: Although this unit is marked with both 10MHz and 1pps, research
on the 'net seems to indicate that the '1pps' output has only a period
of exactly 1 second when the frequency is set to 223 Hz (8.388608Mhz).
According to those sources the '1pps' will have a period of 0.8388608
seconds when the output frequency is set to 10MHz. This should be easy
to verify. In any case I have no need for a 1pps output - I use a GPS
module to get a 1pps signal which also has the advantage of being
in-phase with real time seconds. "
Now... to speed-adjust the PPS phase, use the DDS and steer it
intentionally of frequence with sufficient delta frequence for suitable
time and you should home in pretty quickly.
Hunting some more:
http://www.qsl.net/zl1bpu/PROJ/Ruby.htm
"Without modification the units have just one output - 1pps (1 Hz).
There is a simple modification to extract 8388.608 kHz, which is of
course 223 Hz, and this frequency is used, through binary division, to
generate the 1pps output. The 8388.608 kHz output is generated by a
32-bit Direct Digital Synthesizer chip (AD9830). This output can be
steered to any other frequency within the operating range, by
interacting with the controlling microcontroller, with three provisos:
- The unit has a peaked filter at the synthesizer output, and so the
level at other frequencies varies wildly. This can be corrected with
minor modifications. - When operating at any other frequency than 8388.608kHz, the 1pps
output is of course incorrect. - The synthesizer operating frequency can be set to within ±5 mHz
(milliHertz) of the requested frequency,
- but ONLY if the calculations, on which the command sent to it
is based, correctly use 32-bit maths. "
Which is a confirmation...
http://www.leapsecond.com/museum/fei5650a/
http://www.ko4bb.com/dokuwiki/doku.php?id=precision_timing:rubidium_oscillat
ors
So, this would work for the 50,255+ MHz based FE 5680A. For 60 MHz
variants it works a little different, but it has two MCUs sitting there,
so some use for theme should there be.
Cheers,
Magnus
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.
Magnus,
Thanks for the research. Now that I have read your information, I am going
to have to go back and 'measure' the PPS output on my unit. I just
'eyeballed' the '1 PPS' and it seemed close to 1 second.
It would be nice to find a serial command that would allow placing the 1 PPS
at any arbitrary point in phase to match GPS.
My impression of reading the posts about the FE-5680A is that the 1 PPS is
likely there, just not easily documented.
Joe
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Bob Camp
Sent: Wednesday, January 25, 2012 11:43 AM
To: 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] Determination of the placement of the first pps
Hi
Based on the number of units that come in with the "1 pps output" missing,
I'd bet the $40 FE5680's were used only for the 10 MHz output.
Bob
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Magnus Danielson
Sent: Tuesday, January 24, 2012 10:14 PM
To: time-nuts@febo.com
Subject: Re: [time-nuts] Determination of the placement of the first pps
On 01/25/2012 02:41 AM, J. L. Trantham wrote:
Darn.
I was hoping for that feature. I still think it should be there.
Indeed. Should be in there somewhere...
Didn't see these link hit the list:
http://pastebin.com/S8UcnCMZ
http://www.dd1us.de/Downloads/precise%20reference%20frequency%20rev%200_7.pd
f
http://vk2xv.djirra.com/tech_rubidium.htm
Looking at the last one it says:
"NOTE: Although this unit is marked with both 10MHz and 1pps, research on
the 'net seems to indicate that the '1pps' output has only a period of
exactly 1 second when the frequency is set to 223 Hz (8.388608Mhz).
According to those sources the '1pps' will have a period of 0.8388608
seconds when the output frequency is set to 10MHz. This should be easy to
verify. In any case I have no need for a 1pps output - I use a GPS module to
get a 1pps signal which also has the advantage of being in-phase with real
time seconds. "
Now... to speed-adjust the PPS phase, use the DDS and steer it intentionally
of frequence with sufficient delta frequence for suitable time and you
should home in pretty quickly.
Hunting some more:
http://www.qsl.net/zl1bpu/PROJ/Ruby.htm
"Without modification the units have just one output - 1pps (1 Hz).
There is a simple modification to extract 8388.608 kHz, which is of course
223 Hz, and this frequency is used, through binary division, to generate the
1pps output. The 8388.608 kHz output is generated by a 32-bit Direct Digital
Synthesizer chip (AD9830). This output can be steered to any other frequency
within the operating range, by interacting with the controlling
microcontroller, with three provisos:
- The unit has a peaked filter at the synthesizer output, and so the level
at other frequencies varies wildly. This can be corrected with minor
modifications. - When operating at any other frequency than 8388.608kHz, the 1pps output
is of course incorrect. - The synthesizer operating frequency can be set to within ±5 mHz
(milliHertz) of the requested frequency,
- but ONLY if the calculations, on which the command sent to it is
based, correctly use 32-bit maths. "
Which is a confirmation...
http://www.leapsecond.com/museum/fei5650a/
http://www.ko4bb.com/dokuwiki/doku.php?id=precision_timing:rubidium_oscillat
ors
So, this would work for the 50,255+ MHz based FE 5680A. For 60 MHz variants
it works a little different, but it has two MCUs sitting there, so some use
for theme should there be.
Cheers,
Magnus
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.
time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to
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and follow the instructions there.
Hi Joe,
On 01/25/2012 08:04 PM, J. L. Trantham wrote:
Magnus,
Thanks for the research. Now that I have read your information, I am going
to have to go back and 'measure' the PPS output on my unit. I just
'eyeballed' the '1 PPS' and it seemed close to 1 second.
Good luck. Hopefully I put you onto a working solution.
It would be nice to find a serial command that would allow placing the 1 PPS
at any arbitrary point in phase to match GPS.
My impression of reading the posts about the FE-5680A is that the 1 PPS is
likely there, just not easily documented.
Well, being lazy enough not to go into the lab and open up my 5680 I
went hunting the web and it seems like there was more out there than we
seems to have been piecing together.
Seems like a bit of more systematic research needs to be done. There are
obviously at least two basic models, one older with 50,255+ MHz
oscillators and various add-on boards and secondly the 60 MHz + DDS
variant. Reverse-engineering the schematics and functions has only
partly been done, but I haven't seen any systematic schematic popping
out of the work.
There is already plenty of information available, but it is not
coordinated and systematically done to the level that most aspects can
be written down in a service type of document.
Cheers,
Magnus
I'm sure people will figure out all these undocumented features. But
there is a danger is using any of them because some day your Rb
oscillator will fail and you will need to replace it. You can't count
on the replacement unit to have the same set of undocumented features.
I do intend to lock mine to a T-Bolt. but I'll phase lock the 10MHz
signals not the PPS.
I think I can send both 10MHz to the 74HCT9046 a uPwill read the
74HCT9046 and then send rs-232 commands to adjust the fe5680 to reduce
the phase or frequency error
The uP might also check the temperature of the FE5680 and keep a table
of DDS words vs. temperature and use this table for hold over when the
GPS is disconnected. I don't know. First steps first need to play
with 74HCT9046 and need to write fe5680 library for Arduino.
On Wed, Jan 25, 2012 at 11:19 AM, Magnus Danielson
magnus@rubidium.dyndns.org wrote:
Hi Joe,
On 01/25/2012 08:04 PM, J. L. Trantham wrote:
Magnus,
Thanks for the research. Now that I have read your information, I am
going
to have to go back and 'measure' the PPS output on my unit. I just
'eyeballed' the '1 PPS' and it seemed close to 1 second.
Good luck. Hopefully I put you onto a working solution.
It would be nice to find a serial command that would allow placing the 1
PPS
at any arbitrary point in phase to match GPS.
My impression of reading the posts about the FE-5680A is that the 1 PPS is
likely there, just not easily documented.
Well, being lazy enough not to go into the lab and open up my 5680 I went
hunting the web and it seems like there was more out there than we seems to
have been piecing together.
Seems like a bit of more systematic research needs to be done. There are
obviously at least two basic models, one older with 50,255+ MHz oscillators
and various add-on boards and secondly the 60 MHz + DDS variant.
Reverse-engineering the schematics and functions has only partly been done,
but I haven't seen any systematic schematic popping out of the work.
There is already plenty of information available, but it is not coordinated
and systematically done to the level that most aspects can be written down
in a service type of document.
Cheers,
Magnus
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--
Chris Albertson
Redondo Beach, California
On Wed, 25 Jan 2012 20:19:16 +0100
Magnus Danielson magnus@rubidium.dyndns.org wrote:
Reverse-engineering the schematics and functions has only
partly been done, but I haven't seen any systematic schematic popping
out of the work.
Now that i have received my units, i thought could help with the
schematics. But having had a look at mine, i dont think it's worth
the effort. The PCB has at least 4 layers, more likely 6. I don't
think it's 8 as the PCB looks cost optimized.
A few distinct subsystems can be identified by their position, but
their connections and the connections within are hard to get. It would
take countless hours with good measurement equipment to get anything
halfway usable.
I'd rather say, save the time, buy another spare unit if you think
one of those you have is going to fail.
For those who wants to open their unit here a few hints:
-
Unscrew the unit from it's base plate
They are either Torx or Hex. But this doesn't matter at this size,
the difference is hard to tell and is very small anyways.
I used a T6 Torx screw driver, as that was what i had at
hand that did fit. Be carefull, the screws are cheap and very
soft. It's easy to rip the torx/hex bit apart. Apply ample pressure
to your screw driver. -
Unscrew all screws that you can see from outside
- two in the center of the bottom plate
- two underneath the DB-9 connector
- two on the side of the DB-9
- two on the sides
These are Philips-1 and Philips-2 screws
-
There is a screw under each lable at the top
-
After this, you can take the unit apart. The heat spreader in the middle
comes out together with the PCB -
Do NOT force the PCB out. If you need to, wiggle gently. If you have
to use force, you've forgotten a screw. -
The two screws that you see on the PCB stay there (they hold the PCB
on the head spreader). I do not recommend to unscrew them. -
Take lots of pictures while you are at it :-)
If possible, i'd be interested in two Revision markings on the PCB.
Mine has a sticker at the bottom, that reads "RevF".
Then there is a PCB number on the top side, at the edge near the
reference crystal (that with the PTC soldered to it). My unit reads there
"217421-30352" "Rev G"
Attila Kinali
--
Why does it take years to find the answers to
the questions one should have asked long ago?
On Thu, 26 Jan 2012 00:21:46 +0100
Attila Kinali attila@kinali.ch wrote:
- Do NOT force the PCB out. If you need to, wiggle gently. If you have
to use force, you've forgotten a screw.
Additional note: wiggle holding the heat spreader, not the PCB.
If possible, i'd be interested in two Revision markings on the PCB.
Mine has a sticker at the bottom, that reads "RevF".
Then there is a PCB number on the top side, at the edge near the
reference crystal (that with the PTC soldered to it). My unit reads there
"217421-30352" "Rev G"
And a correction: the sticker reads "406" "RevF".
I think the sticker denotes the what population option was choosen,
while the PCB marking denotes the type and revision of the PCB.
Additonal note to self: do not take any device apart, when already
being half asleep. Also do not try to write emails and trying to make
any sense.
^^;
Attila Kinali
--
Why does it take years to find the answers to
the questions one should have asked long ago?