date:20140206


Tom Harris celephi...@gmail.com said:
 I'm just surprised that you get such results with a cheap transformer. 

I think you are missing the decimal point.  (Or maybe I'm not being nutty 
enough.)

I'm counting cycles and grabbing the time with a PC running Linux.

I haven't carefully looked at the error budget.  60 Hz is 16.6 ms per cycle.  
I'm pretty sure the clock on that PC is good to a fraction of a ms.  It's not 
good to the microsecond level.  As tvb said, the time from the power grid 
wanders over seconds during the day.  That's hundreds of cycles, so a tiny 
fraction of a cycle is lost in the noise.

There is also noise on the PPS capture path - interrupts disabled and cache 
loads and such.  I don't have good numbers for the 60 Hz case, but should 
have some data on the 1 PPS path as used by ntpd.  I'll see if I can come up 
with an interesting graph.


One thing that is interesting.  If the measurement system misses a pulse 
(interrupts disabled for too long or whatever), there is an obvious big 
glitch in the frequency.  A missing pulse turns 60 Hz into 59.9 Hz.  It's 
rare that I see anything that far off.   As you can see from the graph, the 
frequency usually doesn't change much on the scale of 10s of seconds, but 
there is a lot of noise at the 0.01 Hz level.  I don't know if that's from 
the capture system or in the raw data.

Similarly, if noise on the hardware turns into an extra pulse, that stands 
out in the other direction.  So I'm pretty sure the pulse count is correct.


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Re: [time-nuts] MC100LVEL34

2014-02-06 Thread John C. Westmoreland, P.E.

Hello John M.,

Thanks for the plot.  Did you take that out past 1MHz - I assume it stayS
'flat' - maybe not.

What explains that little spike at 10kHz for the AD9511?  Interesting
artifact.

Thanks,
John W.


On Thu, Feb 6, 2014 at 12:44 AM, John Miles j...@miles.io wrote:

 (Different John here)  Some quick and dirty residual PN measurements made
 on
 the 100EL family versus some newer clock distribution chips from Analog
 Devices:
 http://www.ke5fx.com/100EL_vs_AD.png

 These may not be directly applicable to 100LVEL parts and shouldn't be
 taken
 as gospel in any case, because real-world results are dependent on signal
 levels and power supply contributions.  But the overall trend of lower 1/f
 noise than CMOS with similar broadband floors will probably hold for all of
 the current-generation fast ECL parts.  More data would be good to have.

 -- john, KE5FX
 Miles Design LLC

  Hello John,
 
  Did you happen to do any phase noise measurements?
 
  Thanks,
  John W.

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Re: [time-nuts] MC100LVEL34

2014-02-06 Thread John Miles

There were quite a few spurs in those tests due to a wide-open layout with
cables running everywhere.  That bump was just a case where the software
didn't get rid of them all.

You can assume they'll be reasonably flat past 1 MHz.  That's as far as
those plots went.

-- john, KE5FX
Miles Design LLC


 -Original Message-
 From: time-nuts-boun...@febo.com [mailto:time-nuts-
 boun...@febo.com] On Behalf Of John C. Westmoreland, P.E.
 Sent: Thursday, February 06, 2014 1:06 AM
 To: Discussion of precise time and frequency measurement
 Subject: Re: [time-nuts] MC100LVEL34
 
 Hello John M.,
 
 Thanks for the plot.  Did you take that out past 1MHz - I assume it stayS
 'flat' - maybe not.
 
 What explains that little spike at 10kHz for the AD9511?  Interesting
 artifact.
 
 Thanks,
 John W.
 

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Re: [time-nuts] MC100LVEL34

2014-02-06 Thread John C. Westmoreland, P.E.

John,

OK - no problem there - in fact - that's kindof good.

Thanks For The Help,
John W.


On Thu, Feb 6, 2014 at 1:13 AM, John Miles j...@miles.io wrote:

 There were quite a few spurs in those tests due to a wide-open layout with
 cables running everywhere.  That bump was just a case where the software
 didn't get rid of them all.

 You can assume they'll be reasonably flat past 1 MHz.  That's as far as
 those plots went.

 -- john, KE5FX
 Miles Design LLC


  -Original Message-
  From: time-nuts-boun...@febo.com [mailto:time-nuts-
  boun...@febo.com] On Behalf Of John C. Westmoreland, P.E.
  Sent: Thursday, February 06, 2014 1:06 AM
  To: Discussion of precise time and frequency measurement
  Subject: Re: [time-nuts] MC100LVEL34
 
  Hello John M.,
 
  Thanks for the plot.  Did you take that out past 1MHz - I assume it stayS
  'flat' - maybe not.
 
  What explains that little spike at 10kHz for the AD9511?  Interesting
  artifact.
 
  Thanks,
  John W.
 

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Re: [time-nuts] clock and cannon at noon story

2014-02-06 Thread David Malone

I think a version of this story is included in Derek Howse's
Greenwich Time and Longitude book, in relation to the shutting
down of the telegraph-based time service from Greenwich. See
here, on page 115:

https://archive.org/details/GreenwichTime

He even gives a reference for the story.

David.
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[time-nuts] A Lady Heather question...

2014-02-06 Thread Michael Baker


Hello, Time-Nutters--

I have been trying to figure out how to tell
LH to display the GPS birds signal strength
vs EL and AZ. I have a note that says the
command for this is SAS but when I enter
/ followed by SAS, the ADEV lists go away
but after a few seconds, the ADEV list starts
back up again.

I do not see the command SAS listed anywhere,
so I have no idea who passed that on to me
or where it came from. A year or so ago I
managed to get the signal strength vs AZ/EL
display running but have lost track of how
to do it.

What am I doing wrong?

Where is the command SAS listed?

Thanks!

Mike Baker
---

--
 
“The duty of a Patriot is to protect his

country from its government.” – Thomas Paine

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[time-nuts] How I got my FE-5680A to lock in Sydney, Australia

Hi again folks,

You may (or may not) recall that a month or so ago, I asked for any information 
that might be available regarding how to fix a ‘used’ FE-5680A rubidium module 
from China (via ebay) which was tested by the supplier in China as working OK, 
but would not seem to lock up to rubidium here in Sydney. There wasn’t a great 
deal of info available, it seems, so I kept on checking ideas myself – mostly 
with no luck. The module would never lock, but kept cycling back and forth 
between about 9.999770MHz and 10.36MHz – ‘searching’ for a lock, but never 
finding it.

Anyway, a couple of days ago I was reading more about the operation of rubidium 
vapour oscillators, and noticed that the ‘filter cell’ is very sensitive to 
magnetic fields – hence the mu-metal shielding case, and also for the 
‘C-tuning’ coil. And I wondered if the main reason why the FE-5680A  had 
apparently worked in China, but wouldn’t lock up in Sydney (Australia) might be 
caused by the fact that Quangzhou (China) is in the northern hemisphere while 
I’m ‘down under’ in the southern hemisphere – where the earth’s field is 
presumably somewhat different, in terms of both strength and direction.

So I decided to test this in a crude way, by inverting the FE-5680A and seeing 
what happened. And – lo and behold – it locked up within 2.5 minutes, and 
stayed locked until I turned off the power and let it go cold again. The next 
morning I applied power again, and within 3 minutes it locked up again with no 
problems. And it’s been locked up now for over 48 hours...

So it seems that the different magnetic field here may have been the problem – 
either that, or it may have received a ‘jolt’ in transit, which prevented in 
from locking unless it was inverted.

But how do I tell which of these explanations is right, without ‘opening her 
up’ again and looking for some kind of subtle physical fault?

Another idea: perhaps the mu-metal shield case had acquired a small dose of 
magnetisation in transit (via a physical shock, or from a strong field metal 
detector). I guess in this case that I would have to remove the two halves of 
the case, and bake them in a furnace to demagnetise them again.

Or should I just run the FE-5680A upside down permanently – the simple but 
‘crude’ answer?

I’m not sure if this FE-5680A has the ‘C-tuning’ gizmo fitted, or wired up. Am 
I right in thinking that another approach might be to try varying the tuning 
via the RS-232C serial port? Does this work via the C-tuning coil anyway, or by 
tweaking the DDS?

I hope a much more experienced time nut can provide a few answers, please.

Jim Rowe
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Re: [time-nuts] 60 Hz power glitch, US West coast (Silicon Valley)

 The software is a simple python hack.  It runs on Linux.
  http://www.megapathdsl.net/~hmurray/time-nuts/60Hz/pps.py

Sigh.  That's not the right code.  I've deleted it to avoid confusion.

The code I was trying to point to is:
  http://www.megapathdsl.net/~hmurray/time-nuts/60Hz/60Hz.py


-- 
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[time-nuts] Rb as source for ADEV?

I'm getting a little more familiar with ADEV and OADEV now.  With a little help 
from Tom, I've put together gnuplot scripts and his software to get a decent 
plot.  But, as some time-nuts have pointed out, my measurements are of one part 
of my system being compared to another.  Would I learn anything useful by 
hooking my Rb standard up to my 5335A and comparing that to the OCXO?  How long 
should I let the Rb heat up before starting the test?  I'm a bit uncertain 
about the result of comparing a stable clock of questionable accuracy to an 
accurate clock of questionable stability.  Hopefully I said that right.

thanks,

Bob - AE6RV
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Re: [time-nuts] Rb as source for ADEV?

Hi Bob,

Short-term measurements like that do a good job using a OCXO and TIC to reveal 
TIC and GPS resolution limits. It's a useful exercise, but it usually doesn't 
tell you anything about the OCXO itself.

Long-term measurements like that do a superb job using GPS to measure the 
long-term stability and frequency drift rate of the OCXO (or Rb). This, because 
for intervals of days to weeks to months you can't beat GPS as an inexpensive 
ultimate time/frequency standard. And for those long intervals, the TIC 
resolution is usually more than enough.

Just collect the raw phase data and raw DAC data. In a few weeks you'll be able 
to make some really nice plots.

Also consider freezing the DAC for a week (unlocked) and compare that data with 
your locked data. You can then make plots that look like: 
http://leapsecond.com/pages/gpsdo/

On Rb -- since you're now a time nut, do not let the Rb warm up at all -- the 
data get you the first hour or first day will be just as interesting as the 
data you collect the next month.

On ADEV -- I know the source code calls them adev and oadev, but you should 
just call it ADEV. No one uses the old back-to-back formula anymore; the 
overlapping formula is the default. And then plot using the all or many tau 
method I mentioned.

/tvb

- Original Message - 
From: Bob Stewart b...@evoria.net
To: Discussion of precise time and frequency measurement time-nuts@febo.com
Sent: Thursday, February 06, 2014 2:23 PM
Subject: [time-nuts] Rb as source for ADEV?


I'm getting a little more familiar with ADEV and OADEV now. With a little help 
from Tom, I've put together gnuplot scripts and his software to get a decent 
plot. But, as some time-nuts have pointed out, my measurements are of one part 
of my system being compared to another. Would I learn anything useful by 
hooking my Rb standard up to my 5335A and comparing that to the OCXO? How long 
should I let the Rb heat up before starting the test? I'm a bit uncertain about 
the result of comparing a stable clock of questionable accuracy to an accurate 
clock of questionable stability. Hopefully I said that right.

thanks,

Bob - AE6RV



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Re: [time-nuts] Rb as source for ADEV?

2014-02-06 Thread Bob Camp

Hi

Your Rb should be good to about 10 ppt at  1 second. Thats 10 ps. Your OCXO 
might be good to 1 to 10 ppt at 1 second that’s 1 to 10 ps. Your 5334 has a 
measurement resolution of 2 ns single shot (which is what matters in this 
case), that’s 2000 ps. You would like to have a resolution 5X better than the 
thing you are trying to measure. 

Your counter gate time error in ppt scales directly as tau. It’s always 2 ns, 
but at 10s tau it’s going to be 200 ppt not 2,000 ppt. Your Rb ADEV likely 
scales as square root of tau. At 100 seconds it’s 1 ppt, which would be 100 ps. 
You still aren’t there yet.  Who knows what the OCXO is doing, let’s say it’s 
= 10 ppt. Still not there.

At 10,000 seconds the Rb might get to 0.1 ppt. That would be 1,000 ps.  Your 
counter still isn’t there. Who knows what the OCXO is doing at 10,000 seconds. 
The counter might follow the OCXO. 

———

Simple answer - doing this directly with a counter is not the best approach. 

Bob

On Feb 6, 2014, at 5:23 PM, Bob Stewart b...@evoria.net wrote:

 I'm getting a little more familiar with ADEV and OADEV now.  With a little 
 help from Tom, I've put together gnuplot scripts and his software to get a 
 decent plot.  But, as some time-nuts have pointed out, my measurements are of 
 one part of my system being compared to another.  Would I learn anything 
 useful by hooking my Rb standard up to my 5335A and comparing that to the 
 OCXO?  How long should I let the Rb heat up before starting the test?  I'm a 
 bit uncertain about the result of comparing a stable clock of questionable 
 accuracy to an accurate clock of questionable stability.  Hopefully I said 
 that right.
 
 thanks,
 
 Bob - AE6RV
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Re: [time-nuts] Rb as source for ADEV?

 Simple answer - doing this directly with a counter is not the best approach. 

Most of us work with what we have. I think it's pretty cool what Bob is doing 
with a 5335A. Someday he may buy or build something better. Your best may not 
be his best, or my best. What is best at one tau is not at another. Time-nuts 
has never been about being best (otherwise we all loose to USNO); it's about 
learning and exploring this interesting field of time  frequency with what we 
have at home, whether it's the ADEV of 60 Hz or ADEV of a 5335A/GPSDO, etc.

/tvb

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Re: [time-nuts] A Lady Heather question...

2014-02-06 Thread Azelio Boriani

Use:
S A S   signal
S A Ddata
S A E elevation
S A A azimuth
S A W
S A C to clear the view

On Thu, Feb 6, 2014 at 10:22 PM, Michael Baker mp...@clanbaker.org wrote:
 Hello, Time-Nutters--

 I have been trying to figure out how to tell
 LH to display the GPS birds signal strength
 vs EL and AZ. I have a note that says the
 command for this is SAS but when I enter
 / followed by SAS, the ADEV lists go away
 but after a few seconds, the ADEV list starts
 back up again.

 I do not see the command SAS listed anywhere,
 so I have no idea who passed that on to me
 or where it came from. A year or so ago I
 managed to get the signal strength vs AZ/EL
 display running but have lost track of how
 to do it.

 What am I doing wrong?

 Where is the command SAS listed?

 Thanks!

 Mike Baker
 ---

 --
  The duty of a Patriot is to protect his
 country from its government. - Thomas Paine

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Re: [time-nuts] Rb as source for ADEV?

2014-02-06 Thread Richard Karlquist


On 2014-02-06 15:13, Tom Van Baak wrote:

On ADEV -- I know the source code calls them adev and oadev, but you
should just call it ADEV. No one uses the old back-to-back formula
anymore; the overlapping formula is the default. And then plot using
the all or many tau method I mentioned.

/tvb



I never knew about these different versions of ADEV.
Can you point me to any reference?

Rick
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[time-nuts] West coast power: Flex Alert

California Energy Officials Urge Less Gas and Electricity Use Tonight
  http://blogs.kqed.org/newsfix/2014/02/06/california-electricity/

Energy officials are asking state residents to conserve gas and electricity 
until 10 o'clock tonight.

The California Independent System Operator issued a statewide Flex Alert this 
afternoon, saying the cold snap in parts of the Midwest and East is causing a 
natural gas shortage here.

---

Anybody want to predict what will happen to clocks?


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Re: [time-nuts] Rb as source for ADEV?

Hi Tom,

If I understand you right, the only thing I need from the adev program is the 
OADEV values and those are the new ADEV?  Here's the plot for the past 24 hours 
using 0 for bins.  It takes a few seconds to run, doesn't it?  


Thanks for the ideas on what to measure.  I'm going to replace the EFC divider 
with low temp coeff resistors and do a software bug fix, and hopefully that 
will be the end of fiddling with this thing and I'll be able to get some really 
long runs in.


http://www.evoria.net/AE6RV/GPSstd_PLL/Plots/ADEV.2.6.png

thanks for all the help,


Bob






 From: Tom Van Baak t...@leapsecond.com
To: Discussion of precise time and frequency measurement time-nuts@febo.com 
Sent: Thursday, February 6, 2014 5:13 PM
Subject: Re: [time-nuts] Rb as source for ADEV?
 

Hi Bob,

Short-term measurements like that do a good job using a OCXO and TIC to reveal 
TIC and GPS resolution limits. It's a useful exercise, but it usually doesn't 
tell you anything about the OCXO itself.

Long-term measurements like that do a superb job using GPS to measure the 
long-term stability and frequency drift rate of the OCXO (or Rb). This, 
because for intervals of days to weeks to months you can't beat GPS as an 
inexpensive ultimate time/frequency standard. And for those long intervals, 
the TIC resolution is usually more than enough.

Just collect the raw phase data and raw DAC data. In a few weeks you'll be 
able to make some really nice plots.

Also consider freezing the DAC for a week (unlocked) and compare that data 
with your locked data. You can then make plots that look like: 
http://leapsecond.com/pages/gpsdo/

On Rb -- since you're now a time nut, do not let the Rb warm up at all -- the 
data get you the first hour or first day will be just as interesting as the 
data you collect the next month.

On ADEV -- I know the source code calls them adev and oadev, but you should 
just call it ADEV. No one uses the old back-to-back formula anymore; the 
overlapping formula is the default. And then plot using the all or many 
tau method I mentioned.

/tvb

- Original Message - 
From: Bob Stewart b...@evoria.net
To: Discussion of precise time and frequency measurement time-nuts@febo.com
Sent: Thursday, February 06, 2014 2:23 PM
Subject: [time-nuts] Rb as source for ADEV?


I'm getting a little more familiar with ADEV and OADEV now. With a little help 
from Tom, I've put together gnuplot scripts and his software to get a decent 
plot. But, as some time-nuts have pointed out, my measurements are of one part 
of my system being compared to another. Would I learn anything useful by 
hooking my Rb standard up to my 5335A and comparing that to the OCXO? How long 
should I let the Rb heat up before starting the test? I'm a bit uncertain 
about the result of comparing a stable clock of questionable accuracy to an 
accurate clock of questionable stability. Hopefully I said that right.

thanks,

Bob - AE6RV



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Re: [time-nuts] How I got my FE-5680A to lock in Sydney, Australia


On 06/02/14 22:32, Jamieson (Jim) Rowe wrote:

Hi again folks,

You may (or may not) recall that a month or so ago, I asked for any information 
that might be available regarding how to fix a ‘used’ FE-5680A rubidium module 
from China (via ebay) which was tested by the supplier in China as working OK, 
but would not seem to lock up to rubidium here in Sydney. There wasn’t a great 
deal of info available, it seems, so I kept on checking ideas myself – mostly 
with no luck. The module would never lock, but kept cycling back and forth 
between about 9.999770MHz and 10.36MHz – ‘searching’ for a lock, but never 
finding it.

Anyway, a couple of days ago I was reading more about the operation of rubidium 
vapour oscillators, and noticed that the ‘filter cell’ is very sensitive to 
magnetic fields – hence the mu-metal shielding case, and also for the 
‘C-tuning’ coil. And I wondered if the main reason why the FE-5680A  had 
apparently worked in China, but wouldn’t lock up in Sydney (Australia) might be 
caused by the fact that Quangzhou (China) is in the northern hemisphere while 
I’m ‘down under’ in the southern hemisphere – where the earth’s field is 
presumably somewhat different, in terms of both strength and direction.

So I decided to test this in a crude way, by inverting the FE-5680A and seeing 
what happened. And – lo and behold – it locked up within 2.5 minutes, and 
stayed locked until I turned off the power and let it go cold again. The next 
morning I applied power again, and within 3 minutes it locked up again with no 
problems. And it’s been locked up now for over 48 hours...

So it seems that the different magnetic field here may have been the problem – 
either that, or it may have received a ‘jolt’ in transit, which prevented in 
from locking unless it was inverted.

But how do I tell which of these explanations is right, without ‘opening her 
up’ again and looking for some kind of subtle physical fault?

Another idea: perhaps the mu-metal shield case had acquired a small dose of 
magnetisation in transit (via a physical shock, or from a strong field metal 
detector). I guess in this case that I would have to remove the two halves of 
the case, and bake them in a furnace to demagnetise them again.

Or should I just run the FE-5680A upside down permanently – the simple but 
‘crude’ answer?

I’m not sure if this FE-5680A has the ‘C-tuning’ gizmo fitted, or wired up. Am 
I right in thinking that another approach might be to try varying the tuning 
via the RS-232C serial port? Does this work via the C-tuning coil anyway, or by 
tweaking the DDS?

I hope a much more experienced time nut can provide a few answers, please.


The magnetic shield can loose it's shielding capabilities.
C-field tuning doesn't really change the opportunity for locking, unless 
your oscillator is on the edge of the locking range, so trimming the 
oscillator might work. Putting the oscillator upside-down might be the 
2G shift needed. This only tells you that you may consider trimming the 
oscillator.


If you have a strong signal, it's usually the crystal oscillator that is 
too far off the mark for being pulled in. Measure the frequency as it 
tries to lock-in. If the sweeps is too high or too low then you need to 
look at that oscillator.


Cheers,
Magnus
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[time-nuts] BC637PCI and OCXO

2014-02-06 Thread d0ct0r



Hello,

Does anybody seen any links to the information how to implement external 
OCXO to Symmetricom PCI TFP BC635/BC637 ?



--
WBW,

V.P.
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Re: [time-nuts] Rb as source for ADEV?

Thanks for the correction.  Averaging Time, τ, tau it is.

Bob

 From: Tom Van Baak t...@leapsecond.com
To: Discussion of precise time and frequency measurement time-nuts@febo.com 
Sent: Thursday, February 6, 2014 9:31 PM
Subject: Re: [time-nuts] Rb as source for ADEV?

 Hi Tom,

 If I understand you right, the only thing I need from the adev program is 
 the OADEV values and those are the new
 ADEV? Here's the plot for the past 24 hours using 0 for bins. It takes a 
 few seconds to run, doesn't it? 

Yes, just grab the code for calc_adev() in 
http://leapsecond.com/tools/adev_lib.c and always set ovlp = 1. Either way, 
it's ADEV; it's just that the overlap method gives better results (smaller 
error bars).

 http://www.evoria.net/AE6RV/GPSstd_PLL/Plots/ADEV.2.6.png

Suggestion: do not label the x-axis time in seconds. This gives the 
impression that the axis is some sort of elapsed time. Better wording might be 
integration time, or sampling interval, or averaging time, or tau, or 
sampling interval, tau.

/tvb

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Re: [time-nuts] Rb as source for ADEV?

On 07/02/14 04:22, Tom Van Baak wrote:

I never knew about these different versions of ADEV.
Can you point me to any reference?

Rick

Hi Rick,

There are a couple of separate issues regarding ADEV.

1)
In old literature ADEV was computed using adjacent segments of data. This is about all you could do
with a HP 5360A computing counter. Once real computers got into the game, it was possible to use
the overlapping version of ADEV, which milks more information from the data
set. You can see the two different formulas for computing it at: http://www.wriley.com/paper2ht.htm

See calc_adev() source code at: http://leapsecond.com/tools/adev_lib.c

Really, the only thing the overlapping version does is use a stride of 1
instead of tau. This is possible when you have the whole data set in memory. The more
primitive back-to-back ADEV could be computed as a summing sum, requiring no data storage
at all (typical of 60's and 70's instruments).

If you read up, you discover that the overlapping trick only came in as
an inspiration for ADEV with a pair of articles from J.J. Snyder which
took inspiration from ways to get laser frequency estimates quickly. The
overlapping technique came to be introduced alongside the tau
pre-filtering for the modified Allan Deviation, as can be found in the
original MDEV article.

2)
Regardless of back-to-back or overlap, there's also the question of how many
points to plot. Again, in the early days, because both computation and plotting
was very time consuming, people tended to plot only a few points per decade.
Maybe tau 1,10,100,1000 or 1,2,5,10,20,50, or 1,2,4,8,16,32, etc. To make it
look more like a graph they would connect the dots with lines (and guessing).
These days, calculating ADEV is so fast there's no need to even draw the lines;
just compute ADEV for every tau you can imagine and the dots connect themselves
due to their density.

Stable32 has an all tau option in which case ADEV is computed for every possible tau. E.g., 1 to 100,000.
However, it turns out this is overkill. Not so much for small tau (say 1 to 100), but once you get up to the thousands
or tens of thousands there's usually no significant difference between using tau N and N+1. And it can actually take a
lot of time to compute ADEV hundreds of thousands of times. So we are now in the era of many tau which
computes lots of tau *per decade*. Think of it as a logarithmic sweep of tau instead of a linear sweep. For large data
sets this is orders of magnitude faster than all tau, yet it still fills in all the gaps in the plot with
real points, not extrapolated lines. Note that Timelab does many tau by default.

3)
And the third issue is, of course, what child in the ADEV family to use: ADEV,
MDEV, TDEV, HDEV, etc.

Actually, it's not that simple. You actually have a wider palette of
selections to choose from:

Frequency or time stability - ADEV vs TDEV - a scaling issue

Pre-filtering - ADEV vs MDEV - a tau-averaging filter allows better
noise separation

Derivate processing - ADEV vs HDEV - 2nd vs 3rd phase derivate, higher
derivates will surpress more systematic frequency drift components

Degrees of Freedom processing - non-overlapping, overlapping, total, theo

In principle you can choose algorithm from the full combinatorial
matrix, but all the slots isn't filled in, as there is no point in doing
non-overlapping MDEV and TDEVs, since overlapping is so simple and gives
so good performance. There is no point in doing non-filtered TDEV, as
MDEV gives better analysis than ADEV. The scaling is trivial for both.
This is to show that the progress of development in these various fields
have been on-going. TOTAL and Theo is better in general, but might be
more processing than it is worth.

I've tried to convey this on the ADEV wikipedia page, but I'm sure it
can be improved.

Dr. Allan makes the point that one should be using MDEV rather than
ADEV, as MDEV was what he wanted ADEV to do, but could not originally,
so he was so happy to fix it. I agree with his motivation and analysis.

Anyway, what is the problem you are trying to solve? The correct
answer depends from case to case.

Cheers,
Magnus
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Re: [time-nuts] How I got my FE-5680A to lock in Sydney, Australia

2014-02-06 Thread Ed Palmer


Hi Jim,

On 2/6/2014 3:32 PM, Jamieson (Jim) Rowe wrote:

Hi again folks,

You may (or may not) recall that a month or so ago, I asked for any information 
that might be available regarding how to fix a ‘used’ FE-5680A rubidium module 
from China (via ebay) which was tested by the supplier in China as working OK, 
but would not seem to lock up to rubidium here in Sydney. There wasn’t a great 
deal of info available, it seems, so I kept on checking ideas myself – mostly 
with no luck. The module would never lock, but kept cycling back and forth 
between about 9.999770MHz and 10.36MHz – ‘searching’ for a lock, but never 
finding it.

Anyway, a couple of days ago I was reading more about the operation of rubidium 
vapour oscillators, and noticed that the ‘filter cell’ is very sensitive to 
magnetic fields – hence the mu-metal shielding case, and also for the 
‘C-tuning’ coil. And I wondered if the main reason why the FE-5680A  had 
apparently worked in China, but wouldn’t lock up in Sydney (Australia) might be 
caused by the fact that Quangzhou (China) is in the northern hemisphere while 
I’m ‘down under’ in the southern hemisphere – where the earth’s field is 
presumably somewhat different, in terms of both strength and direction.

So I decided to test this in a crude way, by inverting the FE-5680A and seeing 
what happened. And – lo and behold – it locked up within 2.5 minutes, and 
stayed locked until I turned off the power and let it go cold again. The next 
morning I applied power again, and within 3 minutes it locked up again with no 
problems. And it’s been locked up now for over 48 hours...


My first thought was to make a typical 'down-under' joke and suggest you 
run the 5680A upside down, but you beat me to it! :)



So it seems that the different magnetic field here may have been the problem – 
either that, or it may have received a ‘jolt’ in transit, which prevented in 
from locking unless it was inverted.

But how do I tell which of these explanations is right, without ‘opening her 
up’ again and looking for some kind of subtle physical fault?

Another idea: perhaps the mu-metal shield case had acquired a small dose of 
magnetisation in transit (via a physical shock, or from a strong field metal 
detector). I guess in this case that I would have to remove the two halves of 
the case, and bake them in a furnace to demagnetise them again.


My very limited knowledge regarding mu-metal is that it is so 
magnetically 'soft' that it can't be magnetized.  If it was somehow 
magnetized, inverting the unit wouldn't make any difference, would it?



Or should I just run the FE-5680A upside down permanently – the simple but 
‘crude’ answer?


I don't believe for a second (pun intended) that the earth's magnetic 
field has any effect on the locking of your 5680A.  It's just not strong 
enough.  The same applies to the C-field which can only nudge the 
frequency one way or another by a small amount.


Since flipping the unit DID make a difference, my money would be on a 
trivial, boring mechanical issue inside the unit.  Could be a bad solder 
joint, broken wire, floating piece of debris, or something like that.  
Worst case might be a broken glue joint somewhere in the physics 
package.  That could be ugly.  I would definitely open it up and see if 
anything falls out.



I’m not sure if this FE-5680A has the ‘C-tuning’ gizmo fitted, or wired up. Am 
I right in thinking that another approach might be to try varying the tuning 
via the RS-232C serial port? Does this work via the C-tuning coil anyway, or by 
tweaking the DDS?


The RS-232 commands affect the DDS - assuming your unit does have one.  
It will have no effect on the locking, only on the output frequency.


A few years ago I bought a dead Datum SLCR Rb standard.  It's a cousin 
to the LPRO.  I thought I'd learn some things by trying to fix it.  The 
problem was intermittent.  I tore it apart and found that one of the 
legs of the crystal had never been soldered!  Never overlook the obvious.



I hope a much more experienced time nut can provide a few answers, please.


Maybe the blind leading the blind is a closer description.

Ed


Jim Rowe


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Re: [time-nuts] Rb as source for ADEV?

On 07/02/14 04:31, Tom Van Baak wrote:

Hi Tom,

If I understand you right, the only thing I need from the adev program is the
OADEV values and those are the new
ADEV? Here's the plot for the past 24 hours using 0 for bins. It takes a few
seconds to run, doesn't it?

Yes, just grab the code for calc_adev() in
http://leapsecond.com/tools/adev_lib.c and always set ovlp = 1. Either way,
it's ADEV; it's just that the overlap method gives better results (smaller
error bars).

http://www.evoria.net/AE6RV/GPSstd_PLL/Plots/ADEV.2.6.png

Suggestion: do not label the x-axis time in seconds. This gives the impression that the axis is some sort of elapsed time.
Better wording might be integration time, or sampling interval, or averaging time, or tau,
or sampling interval, tau.

Averaging time is unfortunate in several aspects, part for it not being
averaging being done and part for the fact that averaging is a separate
processing step that can be done, and you can make a plot orthogonal to
the ADEV plot with various degrees of averaging-pre-filter.

The MDEV uses a tau averaging for a tau observation time.

The tau is really the observation time, and ADEV is the frequency
stability for that observation time, that is the RMS relative frequency
noise when observing it tau seconds later. Similarly the TDEV is the
time stability in RMS s for the observation time tau.

ADEV also rises for long taus on oscillators, where you expect even
better averaging to keep it going further down.

The field is confused enough, so I want to avoid this confusion.

Cheers,
Magnus
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Re: [time-nuts] BC637PCI and OCXO


On 07/02/14 00:18, d0ct0r wrote:


Hello,

Does anybody seen any links to the information how to implement external
OCXO to Symmetricom PCI TFP BC635/BC637 ?


As I recall it, it's fairly straigh-forward to output the EFC and input 
the clock frequency. I also recall that there is a API for changing the 
PI-filtering parameters.


Cheers,
Magnus

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Re: [time-nuts] Rb as source for ADEV?

 Averaging time is unfortunate in several aspects, part for it not being 
 averaging being done and part for the fact that averaging is a separate 
 processing step that can be done, and you can make a plot orthogonal to 
 the ADEV plot with various degrees of averaging-pre-filter.

I agree.

 The MDEV uses a tau averaging for a tau observation time.
 
 The tau is really the observation time, and ADEV is the frequency 
 stability for that observation time, that is the ROMS relative frequency 
 noise when observing it tau seconds later. Similarly the TDEV is the 
 time stability in RMS s for the observation time tau.

The phrase observation time is probably no better than averaging time for 
the x-axis label; they both give the impression of elapsed time to newcomers. 
Both observation and averaging connote run time or elapsed time or 
experiment duration. I would stay away from the word time on the ADEV x-axis 
completely. Using the word interval (as in sampling interval) is good; the 
least likely to be confused with elapsed time. Also, it's always nice to add 
tau to the axis label since that letter is universally associated with 
sampling in TF metrology.

Stable32 uses Averaging Time, tau, Seconds. TimeLab avoids the issue by not 
having labels.

/tvb

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Re: [time-nuts] How I got my FE-5680A to lock in Sydney, Australia

2014-02-06 Thread Tom Harris

I got into trouble once when we got a centrifuge from the US (I'm in
Australia) and it didn't work and I suggested to the Yanks that they should
have made it revolve in the opposite direction for working S on the
equator. The idiots tried this by rewiring the motor and the basket (the
large heavy casting that holds stuff to be centrifuged) promply unscrewed
itself and nearly came off the shaft. 30Kg of steel about 500mm in diameter
spinning at 5000rpm careening round the lab would not be much fun. I never
thought that there could actually be a real reason why things stuff up
across the equator.

Actually the vertical component of the magnetic field here has the opposite
sense, which is why compasses made for Europe are unusable in Australia,
the card just tries to align itself at 45 deg to the horizontal and refuses
to work as it fouls the internals of the mount, so this might make sense.


Tom Harris celephi...@gmail.com


On 7 February 2014 08:32, Jamieson (Jim) Rowe jimr...@optusnet.com.auwrote:

 Hi again folks,

 You may (or may not) recall that a month or so ago, I asked for any
 information that might be available regarding how to fix a 'used' FE-5680A
 rubidium module from China (via ebay) which was tested by the supplier in
 China as working OK, but would not seem to lock up to rubidium here in
 Sydney. There wasn't a great deal of info available, it seems, so I kept on
 checking ideas myself - mostly with no luck. The module would never lock,
 but kept cycling back and forth between about 9.999770MHz and 10.36MHz
 - 'searching' for a lock, but never finding it.

 Anyway, a couple of days ago I was reading more about the operation of
 rubidium vapour oscillators, and noticed that the 'filter cell' is very
 sensitive to magnetic fields - hence the mu-metal shielding case, and also
 for the 'C-tuning' coil. And I wondered if the main reason why the FE-5680A
  had apparently worked in China, but wouldn't lock up in Sydney (Australia)
 might be caused by the fact that Quangzhou (China) is in the northern
 hemisphere while I'm 'down under' in the southern hemisphere - where the
 earth's field is presumably somewhat different, in terms of both strength
 and direction.

 So I decided to test this in a crude way, by inverting the FE-5680A and
 seeing what happened. And - lo and behold - it locked up within 2.5
 minutes, and stayed locked until I turned off the power and let it go cold
 again. The next morning I applied power again, and within 3 minutes it
 locked up again with no problems. And it's been locked up now for over 48
 hours...

 So it seems that the different magnetic field here may have been the
 problem - either that, or it may have received a 'jolt' in transit, which
 prevented in from locking unless it was inverted.

 But how do I tell which of these explanations is right, without 'opening
 her up' again and looking for some kind of subtle physical fault?

 Another idea: perhaps the mu-metal shield case had acquired a small dose
 of magnetisation in transit (via a physical shock, or from a strong field
 metal detector). I guess in this case that I would have to remove the two
 halves of the case, and bake them in a furnace to demagnetise them again.

 Or should I just run the FE-5680A upside down permanently - the simple but
 'crude' answer?

 I'm not sure if this FE-5680A has the 'C-tuning' gizmo fitted, or wired
 up. Am I right in thinking that another approach might be to try varying
 the tuning via the RS-232C serial port? Does this work via the C-tuning
 coil anyway, or by tweaking the DDS?

 I hope a much more experienced time nut can provide a few answers, please.

 Jim Rowe
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Re: [time-nuts] Rb as source for ADEV?


Bob Camp li...@rtty.us:
 Offset the local reference one hertz or so and let the 5334 do its thing. 

Any hints on how to get a good oscillator that's off by 1 Hz from 10 MHz?

How did you pick 1 Hz?  Is 10 Hz offset better?  How about 0.1 Hz?


-- 
These are my opinions.  I hate spam.



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Re: [time-nuts] Rb as source for ADEV?

I think I see the problem.  I was wondering about using the 1PPS output from my 
Rb in a test.  Cobbling all that together would be a quick bit of work for you, 
but I spent my life in IT.  I'm good with a soldering iron, but I readily admit 
my shortcomings at hardware tinkering.


Bob





 From: Bob Camp li...@rtty.us
To: Tom Van Baak t...@leapsecond.com; Discussion of precise time and 
frequency measurement time-nuts@febo.com 
Sent: Thursday, February 6, 2014 7:43 PM
Subject: Re: [time-nuts] Rb as source for ADEV?
 

Hi

My intent was certainly not to stop anybody from doing anything with what they 
have. My concern is that this is a lot of work for modest return. A simple 
single mixer setup for  $20 would dramatically change things….

$3 mini circuits double balanced mixer
$3 op amps x 2
+/- 15 V supply you already have (hopefully).
$5 for a piece of perf board
$3 for 3 BNC connectors. 
$3 left over for resistors and capacitors. 
snip

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Re: [time-nuts] Rb as source for ADEV?


On 07/02/14 03:47, Hal Murray wrote:


Bob Camp li...@rtty.us:

Offset the local reference one hertz or so and let the 5334 do it’s thing.


Any hints on how to get a good oscillator that's off by 1 Hz from 10 MHz?

How did you pick 1 Hz?  Is 10 Hz offset better?  How about 0.1 Hz?


Higher beat frequency is better for avoiding flicker noise.
Higher beat frequency is better for producing events at higher rate, 
shorter tau.
Lower beat frequency is better for the time-resolution gain 
(beat/nominal frequency relationship).

Higher beat frequency is better for avoiding injection locking.
Higher beat frequency makes it easier to make a good noise reduction 
filter which is stable.


There is more, but that should give you a rough hint. Let me know if you 
need more detailed knowledge on these.


Cheers,
Magnus
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Re: [time-nuts] Rb as source for ADEV?


On 07/02/14 01:09, Richard Karlquist wrote:

On 2014-02-06 15:13, Tom Van Baak wrote:

On ADEV -- I know the source code calls them adev and oadev, but you
should just call it ADEV. No one uses the old back-to-back formula
anymore; the overlapping formula is the default. And then plot using
the all or many tau method I mentioned.

/tvb



I never knew about these different versions of ADEV.
Can you point me to any reference?


Hopefully this is a good start:
https://en.wikipedia.org/wiki/Allan_variance

In the references I also put NIST SP 1065:
http://tf.nist.gov/timefreq/general/pdf/2220.pdf

Cheers,
Magnus
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Re: [time-nuts] Rb as source for ADEV?

 Hi Tom,

 If I understand you right, the only thing I need from the adev program is the 
 OADEV values and those are the new
 ADEV? Here's the plot for the past 24 hours using 0 for bins. It takes a 
 few seconds to run, doesn't it? 

Yes, just grab the code for calc_adev() in 
http://leapsecond.com/tools/adev_lib.c and always set ovlp = 1. Either way, 
it's ADEV; it's just that the overlap method gives better results (smaller 
error bars).

 http://www.evoria.net/AE6RV/GPSstd_PLL/Plots/ADEV.2.6.png

Suggestion: do not label the x-axis time in seconds. This gives the 
impression that the axis is some sort of elapsed time. Better wording might be 
integration time, or sampling interval, or averaging time, or tau, or 
sampling interval, tau.

/tvb


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Re: [time-nuts] Rb as source for ADEV?

 I never knew about these different versions of ADEV.
 Can you point me to any reference?
 
 Rick

Hi Rick,

There are a couple of separate issues regarding ADEV.

1)
In old literature ADEV was computed using adjacent segments of data. This is 
about all you could do with a HP 5360A computing counter. Once real computers 
got into the game, it was possible to use the overlapping version of ADEV, 
which milks more information from the data set. You can see the two different 
formulas for computing it at: http://www.wriley.com/paper2ht.htm

See calc_adev() source code at: http://leapsecond.com/tools/adev_lib.c

Really, the only thing the overlapping version does is use a stride of 1 
instead of tau. This is possible when you have the whole data set in memory. 
The more primitive back-to-back ADEV could be computed as a summing sum, 
requiring no data storage at all (typical of 60's and 70's instruments).

2)
Regardless of back-to-back or overlap, there's also the question of how many 
points to plot. Again, in the early days, because both computation and plotting 
was very time consuming, people tended to plot only a few points per decade. 
Maybe tau 1,10,100,1000 or 1,2,5,10,20,50, or 1,2,4,8,16,32, etc. To make it 
look more like a graph they would connect the dots with lines (and guessing). 
These days, calculating ADEV is so fast there's no need to even draw the lines; 
just compute ADEV for every tau you can imagine and the dots connect themselves 
due to their density.

Stable32 has an all tau option in which case ADEV is computed for every 
possible tau. E.g., 1 to 100,000. However, it turns out this is overkill. Not 
so much for small tau (say 1 to 100), but once you get up to the thousands or 
tens of thousands there's usually no significant difference between using tau N 
and N+1. And it can actually take a lot of time to compute ADEV hundreds of 
thousands of times. So we are now in the era of many tau which computes lots 
of tau *per decade*. Think of it as a logarithmic sweep of tau instead of a 
linear sweep. For large data sets this is orders of magnitude faster than all 
tau, yet it still fills in all the gaps in the plot with real points, not 
extrapolated lines. Note that Timelab does many tau by default.

3)
And the third issue is, of course, what child in the ADEV family to use: ADEV, 
MDEV, TDEV, HDEV, etc.

Does all this make sense? I can post graphic examples of all these issues if 
you're interested.

Thanks,
/tvb

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Re: [time-nuts] Rb as source for ADEV?

2014-02-06 Thread Bob Camp

Hi

My intent was certainly not to stop anybody from doing anything with what they 
have. My concern is that this is a lot of work for modest return. A simple 
single mixer setup for  $20 would dramatically change things….

$3 mini circuits double balanced mixer
$3 op amps x 2
+/- 15 V supply you already have (hopefully).
$5 for a piece of perf board
$3 for 3 BNC connectors. 
$3 left over for resistors and capacitors. 

Offset the local reference one hertz or so and let the 5334 do it’s thing. Your 
resolution is now plenty good enough to see what’s happening. 

Circuit:

Mixer driven by your two sources
L/C filter between the mixer output and a positive gain op amp (OP-37 or 
similar)
Op amp set up with enough gain to give you 28V p-p when the mixer is saturated 
(OP-27 or similar)
Next op amp run as an inverter / limiter and driving the counter, use diodes in 
the feedback path to do the limiting. 

Not the most elegant circuit. Not the highest resolution possible.  Cheap / 
easy to build / simple to troubleshoot. Used a *lot* of times by a *lot* of 
people. 

If you want to get fancy terminate the mixer in 500 ohms at audio and 50 ohms 
at RF. Fancier still is to do some single pole R-C high pass / low pass in 
front of the first op-amp. Neither one adds much cost. They do make it slightly 
harder to build. 

To totally blow the budget go with an RPD-1 mixer rather than one of the simple 
ones. Termination would then be 500 ohms at RF and 5K at audio.  

Bob

Yes, I’m assuming you get the mixer at the hamfest / 20 piece price rather than 
just ordering one at a time from Mine Circuits.



On Feb 6, 2014, at 6:52 PM, Tom Van Baak t...@leapsecond.com wrote:

 Simple answer - doing this directly with a counter is not the best approach. 
 
 Most of us work with what we have. I think it's pretty cool what Bob is doing 
 with a 5335A. Someday he may buy or build something better. Your best may not 
 be his best, or my best. What is best at one tau is not at another. Time-nuts 
 has never been about being best (otherwise we all loose to USNO); it's about 
 learning and exploring this interesting field of time  frequency with what 
 we have at home, whether it's the ADEV of 60 Hz or ADEV of a 5335A/GPSDO, etc.
 
 /tvb
 
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Re: [time-nuts] Rb as source for ADEV?

2014-02-06 Thread Mark Spencer

To add a bit to this discussion I recently switched from using from using 
HP5370B's for long term data collection to HP5335's.   For plotting the long 
term drift of two of my more stable OCXO's versus a GPSDO  the 5335's combined 
with Timelab work fine for my limited needs.   Just for grins I compared the 
same sources using both the 5370B's and the 5335's at the same time and 
overlaid the ADEV plots, IIRC the results were identical for Tau's of approx 
2,000 seconds and higher.   
 
At times I also compare the OCXO's to one of my better Rb's (while also 
comparing the OCXO's to the GPSDO) to provide a bit of a sanity check that the 
GPSDO is behaving itself.    I also wrote data collection routines using that 
time stamp all of the data I collect which makes later comparisions 
considerably easier.
 
Regards
Mark S  
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Re: [time-nuts] How I got my FE-5680A to lock in Sydney, Australia


Hi Ed,

Thanks for those suggestions -- much appreciated. I guess you're right -- if 
the case was magnetised, inverting the unit wouldn't make any difference. So 
presumably, the problem is due to a dry joint or similar problem inside, as 
you suggest, or perhaps the local magnetic field after all (I do have quite 
a bit of electrical wiring and electronic gear in my work room).


All the best,

Jim Rowe


-Original Message- 
From: Ed Palmer

Sent: Friday, February 07, 2014 1:54 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] How I got my FE-5680A to lock in Sydney, Australia

Hi Jim,

On 2/6/2014 3:32 PM, Jamieson (Jim) Rowe wrote:

Hi again folks,

You may (or may not) recall that a month or so ago, I asked for any 
information that might be available regarding how to fix a ‘used’ FE-5680A 
rubidium module from China (via ebay) which was tested by the supplier in 
China as working OK, but would not seem to lock up to rubidium here in 
Sydney. There wasn’t a great deal of info available, it seems, so I kept 
on checking ideas myself – mostly with no luck. The module would never 
lock, but kept cycling back and forth between about 9.999770MHz and 
10.36MHz – ‘searching’ for a lock, but never finding it.


Anyway, a couple of days ago I was reading more about the operation of 
rubidium vapour oscillators, and noticed that the ‘filter cell’ is very 
sensitive to magnetic fields – hence the mu-metal shielding case, and also 
for the ‘C-tuning’ coil. And I wondered if the main reason why the 
FE-5680A  had apparently worked in China, but wouldn’t lock up in Sydney 
(Australia) might be caused by the fact that Quangzhou (China) is in the 
northern hemisphere while I’m ‘down under’ in the southern hemisphere – 
where the earth’s field is presumably somewhat different, in terms of both 
strength and direction.


So I decided to test this in a crude way, by inverting the FE-5680A and 
seeing what happened. And – lo and behold – it locked up within 2.5 
minutes, and stayed locked until I turned off the power and let it go cold 
again. The next morning I applied power again, and within 3 minutes it 
locked up again with no problems. And it’s been locked up now for over 48 
hours...


My first thought was to make a typical 'down-under' joke and suggest you
run the 5680A upside down, but you beat me to it! :)

So it seems that the different magnetic field here may have been the 
problem – either that, or it may have received a ‘jolt’ in transit, which 
prevented in from locking unless it was inverted.


But how do I tell which of these explanations is right, without ‘opening 
her up’ again and looking for some kind of subtle physical fault?


Another idea: perhaps the mu-metal shield case had acquired a small dose 
of magnetisation in transit (via a physical shock, or from a strong field 
metal detector). I guess in this case that I would have to remove the two 
halves of the case, and bake them in a furnace to demagnetise them again.


My very limited knowledge regarding mu-metal is that it is so
magnetically 'soft' that it can't be magnetized.  If it was somehow
magnetized, inverting the unit wouldn't make any difference, would it?

Or should I just run the FE-5680A upside down permanently – the simple but 
‘crude’ answer?


I don't believe for a second (pun intended) that the earth's magnetic
field has any effect on the locking of your 5680A.  It's just not strong
enough.  The same applies to the C-field which can only nudge the
frequency one way or another by a small amount.

Since flipping the unit DID make a difference, my money would be on a
trivial, boring mechanical issue inside the unit.  Could be a bad solder
joint, broken wire, floating piece of debris, or something like that.
Worst case might be a broken glue joint somewhere in the physics
package.  That could be ugly.  I would definitely open it up and see if
anything falls out.

I’m not sure if this FE-5680A has the ‘C-tuning’ gizmo fitted, or wired 
up. Am I right in thinking that another approach might be to try varying 
the tuning via the RS-232C serial port? Does this work via the C-tuning 
coil anyway, or by tweaking the DDS?


The RS-232 commands affect the DDS - assuming your unit does have one.
It will have no effect on the locking, only on the output frequency.

A few years ago I bought a dead Datum SLCR Rb standard.  It's a cousin
to the LPRO.  I thought I'd learn some things by trying to fix it.  The
problem was intermittent.  I tore it apart and found that one of the
legs of the crystal had never been soldered!  Never overlook the obvious.


I hope a much more experienced time nut can provide a few answers, please.


Maybe the blind leading the blind is a closer description.

Ed


Jim Rowe


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Re: [time-nuts] How I got my FE-5680A to lock in Sydney, Australia


Hi Tom,

Thanks for your comment, which seems to confirm that the earth's magnetic 
field (plus the fields associated with my other gear might well be 
associated with the problem. Perhaps I'd be better off getting hold of a 
soft steel box to put the complete FE-5680A into, along with its mu-metal 
shield case...


Best regards,

Jim Rowe


-Original Message- 
From: Tom Harris

Sent: Friday, February 07, 2014 2:31 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] How I got my FE-5680A to lock in Sydney, Australia

I got into trouble once when we got a centrifuge from the US (I'm in
Australia) and it didn't work and I suggested to the Yanks that they should
have made it revolve in the opposite direction for working S on the
equator. The idiots tried this by rewiring the motor and the basket (the
large heavy casting that holds stuff to be centrifuged) promply unscrewed
itself and nearly came off the shaft. 30Kg of steel about 500mm in diameter
spinning at 5000rpm careening round the lab would not be much fun. I never
thought that there could actually be a real reason why things stuff up
across the equator.

Actually the vertical component of the magnetic field here has the opposite
sense, which is why compasses made for Europe are unusable in Australia,
the card just tries to align itself at 45 deg to the horizontal and refuses
to work as it fouls the internals of the mount, so this might make sense.


Tom Harris celephi...@gmail.com


On 7 February 2014 08:32, Jamieson (Jim) Rowe 
jimr...@optusnet.com.auwrote:



Hi again folks,

You may (or may not) recall that a month or so ago, I asked for any
information that might be available regarding how to fix a 'used' FE-5680A
rubidium module from China (via ebay) which was tested by the supplier in
China as working OK, but would not seem to lock up to rubidium here in
Sydney. There wasn't a great deal of info available, it seems, so I kept 
on

checking ideas myself - mostly with no luck. The module would never lock,
but kept cycling back and forth between about 9.999770MHz and 10.36MHz
- 'searching' for a lock, but never finding it.

Anyway, a couple of days ago I was reading more about the operation of
rubidium vapour oscillators, and noticed that the 'filter cell' is very
sensitive to magnetic fields - hence the mu-metal shielding case, and also
for the 'C-tuning' coil. And I wondered if the main reason why the 
FE-5680A
 had apparently worked in China, but wouldn't lock up in Sydney 
(Australia)

might be caused by the fact that Quangzhou (China) is in the northern
hemisphere while I'm 'down under' in the southern hemisphere - where the
earth's field is presumably somewhat different, in terms of both strength
and direction.

So I decided to test this in a crude way, by inverting the FE-5680A and
seeing what happened. And - lo and behold - it locked up within 2.5
minutes, and stayed locked until I turned off the power and let it go cold
again. The next morning I applied power again, and within 3 minutes it
locked up again with no problems. And it's been locked up now for over 48
hours...

So it seems that the different magnetic field here may have been the
problem - either that, or it may have received a 'jolt' in transit, which
prevented in from locking unless it was inverted.

But how do I tell which of these explanations is right, without 'opening
her up' again and looking for some kind of subtle physical fault?

Another idea: perhaps the mu-metal shield case had acquired a small dose
of magnetisation in transit (via a physical shock, or from a strong field
metal detector). I guess in this case that I would have to remove the two
halves of the case, and bake them in a furnace to demagnetise them again.

Or should I just run the FE-5680A upside down permanently - the simple but
'crude' answer?

I'm not sure if this FE-5680A has the 'C-tuning' gizmo fitted, or wired
up. Am I right in thinking that another approach might be to try varying
the tuning via the RS-232C serial port? Does this work via the C-tuning
coil anyway, or by tweaking the DDS?

I hope a much more experienced time nut can provide a few answers, please.

Jim Rowe
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Re: [time-nuts] housing multiple GPS timing receivers in the same box.

2014-02-06 Thread Alex Pummer


Hi
where is a good source of GPS receiver modules I need one which has 
10kHz output to phase lock a quartz oscillator


Thank you in advance
Alex

On 2/4/2014 9:32 AM, Brian Lloyd wrote:

Get a signal splitter from minicircuits specifically designed with a
passband tailored for GPS that has DC pass-through to power the antenna and
LNA. If you can't find one that has DC pass-through then you will need to
add a power injector to power the antenna/LNA.

Here: http://www.minicircuits.com/pages/npa/ZAPD-2DC+.pdf


On Tue, Feb 4, 2014 at 7:08 AM, mike cook michael.c...@sfr.fr wrote:


Hi,
   Till now I have been putting receivers in individual boxes. So to limit
the growing number of boxes, I want to put two Resolution-T SMT receivers
in one box, sharing power and antenna inputs. My question is  How best can
I share the antenna input, minimizing any interference between the
receivers? . Will any interference matter? For example, I can easily
connect three bits of shielded coax in a Y , but will probably get
reflections from each receiver. As the cables will only be about 15cm long,
would it matter? How about the DC antenna supply? The antenna DC will NOT
be powering an antenna as it passes through a DC blocked splitter used to
share an antenna between most of my receivers. I might be able squeeze a
Mini-Circuits splitter in the box and DC-block both outputs but that may be
overkill.  What discrete circuitry might be a replacement? Will the Y do
it?

Someone must have already succeeded with this type of config.

Thanks in advance  for your input.

Regards,
Mike


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Re: [time-nuts] BC637PCI and OCXO

Hi Vlad,

There was discussion about that board on the list some years ago. Google for: 
site:febo.com BC637PCI

See, for example, 
http://www.febo.com/pipermail/time-nuts/2008-October/033730.html

/tvb

- Original Message - 
From: d0ct0r t...@patoka.org
To: time-nuts@febo.com
Sent: Thursday, February 06, 2014 3:18 PM
Subject: [time-nuts] BC637PCI and OCXO


 
 Hello,
 
 Does anybody seen any links to the information how to implement external 
 OCXO to Symmetricom PCI TFP BC635/BC637 ?
 
 
 -- 
 WBW,
 
 V.P.


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Re: [time-nuts] How I got my FE-5680A to lock in Sydney, Australia


Hi Magnus,

Thanks for those suggestions also. So if I understand you right, I'd be 
better off trying to tweak the oscillator tuning -- using the trimcap?  Or 
did you mean via the RS-232C 'offset adjustment' command?


Regards,

Jim Rowe


-Original Message- 
From: Magnus Danielson

Sent: Friday, February 07, 2014 2:36 PM
To: time-nuts@febo.com
Subject: Re: [time-nuts] How I got my FE-5680A to lock in Sydney, Australia

On 06/02/14 22:32, Jamieson (Jim) Rowe wrote:

Hi again folks,

You may (or may not) recall that a month or so ago, I asked for any 
information that might be available regarding how to fix a ‘used’ FE-5680A 
rubidium module from China (via ebay) which was tested by the supplier in 
China as working OK, but would not seem to lock up to rubidium here in 
Sydney. There wasn’t a great deal of info available, it seems, so I kept 
on checking ideas myself – mostly with no luck. The module would never 
lock, but kept cycling back and forth between about 9.999770MHz and 
10.36MHz – ‘searching’ for a lock, but never finding it.


Anyway, a couple of days ago I was reading more about the operation of 
rubidium vapour oscillators, and noticed that the ‘filter cell’ is very 
sensitive to magnetic fields – hence the mu-metal shielding case, and also 
for the ‘C-tuning’ coil. And I wondered if the main reason why the 
FE-5680A  had apparently worked in China, but wouldn’t lock up in Sydney 
(Australia) might be caused by the fact that Quangzhou (China) is in the 
northern hemisphere while I’m ‘down under’ in the southern hemisphere – 
where the earth’s field is presumably somewhat different, in terms of both 
strength and direction.


So I decided to test this in a crude way, by inverting the FE-5680A and 
seeing what happened. And – lo and behold – it locked up within 2.5 
minutes, and stayed locked until I turned off the power and let it go cold 
again. The next morning I applied power again, and within 3 minutes it 
locked up again with no problems. And it’s been locked up now for over 48 
hours...


So it seems that the different magnetic field here may have been the 
problem – either that, or it may have received a ‘jolt’ in transit, which 
prevented in from locking unless it was inverted.


But how do I tell which of these explanations is right, without ‘opening 
her up’ again and looking for some kind of subtle physical fault?


Another idea: perhaps the mu-metal shield case had acquired a small dose 
of magnetisation in transit (via a physical shock, or from a strong field 
metal detector). I guess in this case that I would have to remove the two 
halves of the case, and bake them in a furnace to demagnetise them again.


Or should I just run the FE-5680A upside down permanently – the simple but 
‘crude’ answer?


I’m not sure if this FE-5680A has the ‘C-tuning’ gizmo fitted, or wired 
up. Am I right in thinking that another approach might be to try varying 
the tuning via the RS-232C serial port? Does this work via the C-tuning 
coil anyway, or by tweaking the DDS?


I hope a much more experienced time nut can provide a few answers, please.


The magnetic shield can loose it's shielding capabilities.
C-field tuning doesn't really change the opportunity for locking, unless
your oscillator is on the edge of the locking range, so trimming the
oscillator might work. Putting the oscillator upside-down might be the
2G shift needed. This only tells you that you may consider trimming the
oscillator.

If you have a strong signal, it's usually the crystal oscillator that is
too far off the mark for being pulled in. Measure the frequency as it
tries to lock-in. If the sweeps is too high or too low then you need to
look at that oscillator.

Cheers,
Magnus
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Re: [time-nuts] Rb as source for ADEV?

On 07/02/14 05:27, Tom Van Baak wrote:

I agree.

The MDEV uses a tau averaging for a tau observation time.

The tau is really the observation time, and ADEV is the frequency
stability for that observation time, that is the ROMS relative frequency
noise when observing it tau seconds later. Similarly the TDEV is the
time stability in RMS s for the observation time tau.

The phrase observation time is probably no better than averaging time for the x-axis label; they both give the impression of elapsed time
to newcomers. Both observation and averaging connote run time or elapsed time or experiment duration. I would stay away from the word
time on the ADEV x-axis completely. Using the word interval (as in sampling interval) is good; the least likely to be confused
with elapsed time. Also, it's always nice to add tau to the axis label since that letter is universally associated with sampling in TF metrology.

Stable32 uses Averaging Time, tau, Seconds. TimeLab avoids the issue by not
having labels.

Observation time is better, but it needs to be used properly not to be
confused with measurement time. You can never make a single term become
completely unambiguous from all interpretations, rather you pick one and
define what it means and stick with it.

Observation period is what I've used in the ADEV wiki. Avoids time as
it is often confused for elapsed measurement time.

Stable32 and SP 1065 (both by W. Riley) uses the loose term Averaging
time, as that is what it was called initially, before the analysis
became more complex and they needed to separate terms.

Cheers,
Magnus

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Re: [time-nuts] BC637PCI and OCXO

2014-02-06 Thread Alex Pummer


Hi Magnus,
I could help you with that,
I also looking for a GPS module which has a 10kHz output,
To lock to the 1pps is a bit complicated, one would need a crystal 
oscillator with very good short-time stability, with a 10kHz is just an 
analog PLL, for what would you use the output -- what frequency do you need?

Regards
Alex
73
KJ6UHN

On 2/6/2014 8:05 PM, Magnus Danielson wrote:

On 07/02/14 00:18, d0ct0r wrote:


Hello,

Does anybody seen any links to the information how to implement external
OCXO to Symmetricom PCI TFP BC635/BC637 ?


As I recall it, it's fairly straigh-forward to output the EFC and 
input the clock frequency. I also recall that there is a API for 
changing the PI-filtering parameters.


Cheers,
Magnus

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Re: [time-nuts] Lady Heather command question

2014-02-06 Thread Michael Baker


Thank you Azelio, for your response to my question
regarding how to get Lady Heather to display the
signal-strengths vs AZ and EL.

I have been trying to figure out how to get LH to display
the signal strength diagram. I have been entering
'SAS' ret into the command line. LH responds by
clearing off the ADEV lists but then starts the ADEV lists
all over again.

Where do the SAS, SAD, SAE, SAA, SAW, SAC commands
and their function explanation appear?
I do not see them listed anywhere.

What is the correct procedure for entering the commands?

Are you saying I should enter ' SAS/SAD/SAE/SAA ' (ret)...?

In other words, enter all the commands in sequence separated
by the forward slash (/)...?

Thanks--

Mike Baker
**


Azelio Boriani said:
Use:
S A S signal
S A D data
S A E elevation
S A A azimuth
S A W
S A C to clear the view

--
 
“The duty of a Patriot is to protect his

country from its government.” – Thomas Paine

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Re: [time-nuts] BC637PCI and OCXO