date:20141209

Hi

 On Dec 8, 2014, at 10:35 PM, Brooke Clarke bro...@pacific.net wrote:
 
 Hi Rich:
 
 Did you use the 723 or . . . .?
 As far as I know the 723 is supposed to have low noise.

There are more modern parts with lower close in noise. Linear Technology has a 
number of them. Your filter caps take out the broadband stuff, close in is all 
that really matters.

Bob

 
 Mail_Attachment --
 Have Fun,
 
 Brooke Clarke
 http://www.PRC68.com
 http://www.end2partygovernment.com/2012Issues.html
 http://www.prc68.com/I/DietNutrition.html
 Richard (Rick) Karlquist wrote:
 
 
 On 12/8/2014 4:53 PM, Bert Kehren via time-nuts wrote:
 We solved that problem by attaching the regulators to the FRK back plate
 which is with fan control is kept within 0.01C. We did not do it for that
 purpose but found that we needed some more heat in order to keep the fan in 
 an
  optimum fan speed. Rb, OCXO and Fan power transistor are on the back
 plate.  Works for us.
 Bert Kehren
 
 
 When I designed the E1938A, I chose a reasonable looking voltage
 reference IC and put it inside the oven.  I figured that was
 the end of it as far as tempco was concerned.  It was, but it
 turned out that the *noise* of the reference was unacceptable
 and of course the oven does nothing to fix that.  I had to
 switch to a lower noise reference.
 
 Rick Karlquist N6RK
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Re: [time-nuts] Did a member of time-nuts buy this?

Hi

 On Dec 9, 2014, at 6:10 AM, Mike Monett timen...@binsamp.e4ward.com wrote:
 
 Hi Bob, I have been having problems posting this. If other versions
 show up, please disregard.
 
 I have some questions for you.
 
 Hi
 
 If you toss a Rb into the GPSDO mix things can get quite good.
 The Rb *should* be better than an OCXO in the  1,000 second
 range.
 
 It's crossover with the GPS ADEV will be further out than the
 OCXO's. The gotcha with both the OCXO and Rb is their temperature
 dependance. Some / many / all of the lower cost Rb's are not much
 better than a good double oven OCXO in terms of raw temperature
 performance. The approach they use to correct this does not help
 their ADEV at all. Yes, you can disable the correction and put the
 whole thing in a temperature controlled environment.
 
 What does the temperature controller do that degrades the ADEV? Can
 anything be done to modify it to improve the performance?

On the lightweight Rb’s they feed the correction into a DDS. The DDS steps are 
big enough to show up above the ADEV. You get a “hump” in the ADEV as a result. 
The solution is to disconnect the temperature sensor that feeds the correction 
circuit. 

 
 Lots of details to take care of. If you get them all right, you'll
 beat any / all of the older Cs standards.
 
 Is there a list anywhere of all the details that need to be
 addressed?

Well, there’s this list :)

The things that need to be done are a “that depends” based on the approach you 
take. A full listing of all you might do down all of the roads you could take 
would be a wall full of books.


 How about words or phrases that can be used to search
 google and the archives?

GPSDO is a good place to start.

 
 One very cute addition would be to pull down the NIST GPS data and
 use it to correct your system on an hourly / daily basis. If you
 do that with common view satellites, you most certainly will beat
 a surplus grade Cs standard.
 
 How can we do this?

First step is to be able to extract timing data from individual sat’s. Not all 
GPS modules do this correctly. 

 The NIST archives state
 
 The archive is only updated once every 24 hours, so data are not
 available for today's date.

Thus the “daily” statement. There has been discussion on the list that 
interchange with other list members at a more rapid rate might make sense. 
Given the floor of most setups, daily updates are not a bad thing. 

 Data from the previous day are added to
 the archive at about 1600 UTC.
 
 http://www.nist.gov/pml/div688/grp40/gpsarchive.cfm
 
 Is there another page that has current data? If so, how do we
 incorporate it into the GPSDO?

1) Measure your local time offset by GPS sat number every hour and save the 
data.

2) When NIST posts there data, pull it down.

3) Compare your data to theirs

4) Do a fit

5) Feed that into your control loop equation. 

The missing element is the per sat data….

Bob

 
 Bob
 
 Thanks,
 
 Mike
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Re: [time-nuts] PRS-45A is alive!

2014-12-09 Thread Dave Martindale

One zero-effort way to do this: a portable GFCI.

I have several GFCIs (Ground Fault Circuit Interrupters) designed for
portable use.  They may be in the form of an extension cord with the GFI
electronics in the male plug, or a short cord with the electronics in the
middle of the length, or a small block that plugs into an outlet, with a
female outlet that a device plugs into.  All of these portable GFCIs
require line power to remain in the on position.  If the AC is
interrupted briefly, the GFCI drops out and stays off until manually reset.

This must be by design, because it is different from the behaviour of GFCI
outlets, and GFCI circuit breakers.  It mimics the behaviour of latching
magnetic contactors (relays) used on large AC-powered tools.  I use the
portable GFCIs to get the same shut-off-and-stay-off feature for small shop
tools that are equipped only with an ordinary switch.  A portable GFCI
should work just as well for electronics that you want to stay off until
manually reset.

- Dave

On Tue, Dec 9, 2014 at 1:24 AM, wb6bnq wb6...@cox.net wrote:

 Hi Bob,

 I think using a latching relay is a very good idea and prudent.  Besides
 while it is reacquiring lock you would probably be busy resetting VCR's and
 so forth.

 BillWB6BNQ


 Bob Stewart wrote:

   Hi Pete,
 I don't have any way of knowing.  I've asked the seller if he has a copy
 of the control software, and I don't like to go back with a bunch of petty
 questions like that.  The next issue is adapting some serial port software
 i wrote to the protocol in the manual Magnus sent to see if I can pull the
 status codes out.  That would probably tell me something.
 I have some tests I want to run immediately on my GPSDO and the KS to
 settle the question of which one can't keep time.  After that, I'll power
 it down, lift its skirts and take some pics.  It's pretty simple on the
 surface: a Cs Beam Tube, a main board, a microwave package with MTI 5Mhz
 OCXO, and the HV and LV power supplies.
 I don't intend to keep this thing running 24/7, but I have a question:
  Here in Houston, we have the occasional large thunderstorm and resulting
 short power outages.  So, should I put a latching relay in the power stream
 to keep it off if I lose power?  The budget is now officially busted, and a
 UPS is not going to happen for awhile.  Santa's sleigh is now officially
 out of gas.
 Bob
  From: Pete Lancashire p...@petelancashire.com
 To: Bob Stewart b...@evoria.net; Discussion of precise time and
 frequency measurement time-nuts@febo.com Sent: Monday, December 8,
 2014 11:46 PM
 Subject: Re: [time-nuts] PRS-45A is alive!
   Love to have known how long it was off, and how much of that 16
 minutes was getting the tube degassed.

 -pete



 On Mon, Dec 8, 2014 at 7:11 PM, Bob Stewart b...@evoria.net wrote:


 Well, it's alive, and I even have 10MHz coming from it.  It took about
 16 minutes to go to lock.  Is that good, or doesn't matter?  Now I've got
 to put together a serial cable and see if I can talk to it and find out how
 it thinks it's doing.  But, this is good!


 www.evoria.net/AE6RV/PRS-45A/2014-12-08%2020.51.33.jpg

 Hope you enjoy the wall decorations.  =)

 Bob - AE6RV
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Re: [time-nuts] 10MHz LTE-Lite - PPS accuracy?

2014-12-09 Thread Dave Martindale

In my case, the LTE-Lite had been operating for at least a week before I
made my accumulate mode measurement, and the Thunderbolt had been
operating for at least a month.  But both antennas were in poor locations -
not bad enough to lose lock any time I was watching, but nowhere close to a
clear view of most of the sky.  I never saw the 1 PPS disappear while I was
watching it.

I wonder if your LTE-Lite ever finished its survey and switched into
1D/position hold mode?  A GPS operating in 3D mode can indeed fail to get a
position fix with 5 satellites being received, if they have bad geometry
(e.g. all are in the same plane in space) because the solution will have
horrible DOP values.  But a timing-mode GPS in position hold mode knows its
own (antenna) position, and only needs one visible satellite to continue to
provide timing outputs.

We don't know how the LTE-Lite's disciplining algorithm is tuned.  If
frequency stability was considered to be more important that timing, the
algorithm may limit the maximum frequency offset that can be used to
correct a timing error.  Watching the scope output in real time, I can see
the time offset between the two 1 PPS pulses change with time, but it
always changes rather slowly, so the maximum frequency difference I've seen
is quite small.  (I no longer have the equipment set up, so I can't provide
a quantitative number).

- Dave

On Tue, Dec 9, 2014 at 5:13 AM, David J Taylor 
david-tay...@blueyonder.co.uk wrote:

 I work with Said at Jackson Labs.  I've been reading the time-nuts
 discussion for a few years, but rarely chime in.  I saw this discussion and
 wanted to make a couple points.

 * The LTE Lite time accuracy specification corresponds with the Skytraq GPS
 receiver's specs page which I have attached.  The specification is for the
 output directly from the GPS receiver available on the LTE Lite Eval
 Board's JP1 connector pin 12.  This specification assumes optimal antenna
 placement and thermal conditions, and position hold mode. It is also an RMS
 (1-sigma) measurement not a peak-to-peak measurement.

 * The GPSDO-generated 1PPS on the LTE Lite Eval Board's J1 connector has a
 phase offset to the GPS raw 1PPS that is shown in the PJLTS message (2nd
 field).  The GPSDO functions to drive this phase offset to zero.  But at a
 given time--especially shortly after power up--the offset may 100 ns or
 more.

 Keith
 ==

 Keith,

 Thanks very much for chiming in, as it has resolved what we are seeing,
 particularly your second comment.

 One thing I do notice is that the device appears less sensitive than some
 other GPS devices I have.  Perhaps sensitive isn't the correct word, but
 looking at the NMEA output it seems to indicate bursts of no/invalid
 position a lot more often than I would expect.  This is shown by the all
 the signal strength bars being grey rather than some of them being blue.
 I've also seen times when five or more satellites are above strength 29,
 and yet there is no position shown.  This also seems to stop the generation
 of the PPS output, which would be not so good when driving an NTP server.

 I am wondering whether this is due to overly stringent criteria being set
 for a position found, at least for my location and antenna location, and
 if this is the case, whether there is any chance of relaxing those
 criteria. I'm guessing not, as the device will not accept any serial input.

 You will have gathered that my main interest is time rather than
 frequency, and it seems that other GPS devices give PPS outputs which are
 nearer to UTC but they have considerably more jitter.  I'm only seeing this
 on the 'scope - likely my PCs would bother with a microsecond either way.


 Cheers,
 David
 --
 SatSignal Software - Quality software written to your requirements
 Web: http://www.satsignal.eu
 Email: david-tay...@blueyonder.co.uk
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Re: [time-nuts] PRS-45A is alive!

Bob
That is one nice looking unit. Most Cs's that we get have had there days.
This one looks really good physically. The fact that it warmed and locked
in 16 minutes means it did not need to pump down very much. Heck a small RB
takes 15 minutes to hit lock and it has a much smaller mass to heat up.
Congratulations on a great buy.
Regards
Paul
WB8TSL

On Tue, Dec 9, 2014 at 8:29 AM, Dave Martindale dave.martind...@gmail.com
wrote:

 One zero-effort way to do this: a portable GFCI.

 I have several GFCIs (Ground Fault Circuit Interrupters) designed for
 portable use.  They may be in the form of an extension cord with the GFI
 electronics in the male plug, or a short cord with the electronics in the
 middle of the length, or a small block that plugs into an outlet, with a
 female outlet that a device plugs into.  All of these portable GFCIs
 require line power to remain in the on position.  If the AC is
 interrupted briefly, the GFCI drops out and stays off until manually reset.

 This must be by design, because it is different from the behaviour of GFCI
 outlets, and GFCI circuit breakers.  It mimics the behaviour of latching
 magnetic contactors (relays) used on large AC-powered tools.  I use the
 portable GFCIs to get the same shut-off-and-stay-off feature for small shop
 tools that are equipped only with an ordinary switch.  A portable GFCI
 should work just as well for electronics that you want to stay off until
 manually reset.

 - Dave

 On Tue, Dec 9, 2014 at 1:24 AM, wb6bnq wb6...@cox.net wrote:

  Hi Bob,
 
  I think using a latching relay is a very good idea and prudent.  Besides
  while it is reacquiring lock you would probably be busy resetting VCR's
 and
  so forth.
 
  BillWB6BNQ
 
 
  Bob Stewart wrote:
 
Hi Pete,
  I don't have any way of knowing.  I've asked the seller if he has a copy
  of the control software, and I don't like to go back with a bunch of
 petty
  questions like that.  The next issue is adapting some serial port
 software
  i wrote to the protocol in the manual Magnus sent to see if I can pull
 the
  status codes out.  That would probably tell me something.
  I have some tests I want to run immediately on my GPSDO and the KS to
  settle the question of which one can't keep time.  After that, I'll
 power
  it down, lift its skirts and take some pics.  It's pretty simple on the
  surface: a Cs Beam Tube, a main board, a microwave package with MTI 5Mhz
  OCXO, and the HV and LV power supplies.
  I don't intend to keep this thing running 24/7, but I have a question:
   Here in Houston, we have the occasional large thunderstorm and
 resulting
  short power outages.  So, should I put a latching relay in the power
 stream
  to keep it off if I lose power?  The budget is now officially busted,
 and a
  UPS is not going to happen for awhile.  Santa's sleigh is now officially
  out of gas.
  Bob
   From: Pete Lancashire p...@petelancashire.com
  To: Bob Stewart b...@evoria.net; Discussion of precise time and
  frequency measurement time-nuts@febo.com Sent: Monday, December 8,
  2014 11:46 PM
  Subject: Re: [time-nuts] PRS-45A is alive!
Love to have known how long it was off, and how much of that 16
  minutes was getting the tube degassed.
 
  -pete
 
 
 
  On Mon, Dec 8, 2014 at 7:11 PM, Bob Stewart b...@evoria.net wrote:
 
 
  Well, it's alive, and I even have 10MHz coming from it.  It took about
  16 minutes to go to lock.  Is that good, or doesn't matter?  Now I've
 got
  to put together a serial cable and see if I can talk to it and find
 out how
  it thinks it's doing.  But, this is good!
 
 
  www.evoria.net/AE6RV/PRS-45A/2014-12-08%2020.51.33.jpg
 
  Hope you enjoy the wall decorations.  =)
 
  Bob - AE6RV
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Re: [time-nuts] PRS-45A is alive!

2014-12-09 Thread Bert Kehren via time-nuts

16 Minutes is normal. First FTS tubes do not leak as much as the old HP  
tubes. Second the seller most likely did run a test which means the tube was  
pumped down. 
Unless there is software that tells beam current the only way I know to get 
 some idea of health of tube is as I mentioned before measure the beam 
current. I  have probably done it at least a hundred times, made a connector 
adapter.
Bert Kehren
 
 
In a message dated 12/8/2014 10:15:08 P.M. Eastern Standard Time,  
b...@evoria.net writes:

Well,  it's alive, and I even have 10MHz coming from it.  It took about 16  
minutes to go to lock.  Is that good, or doesn't matter?  Now I've  got to 
put together a serial cable and see if I can talk to it and find out  how it 
thinks it's doing.  But, this is  good!


www.evoria.net/AE6RV/PRS-45A/2014-12-08%2020.51.33.jpg

Hope  you enjoy the wall decorations.  =)

Bob -  AE6RV
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Re: [time-nuts] Beaglebone NTP server

2014-12-09 Thread Frister

Thanks for pointing this out David,
Compiling an new kernel was holding me back. I followed your instructions and
everything works beautiful. The PI that is running the PPS timekeeping with NTP
is serving as a VLF receiver as well. Taxing the poor CPU, but with
kernel PPS support
the NTP daemon has become way happier! (see attachment)

73, Frits W1FVB


On 12/8/14, David J Taylor david-tay...@blueyonder.co.uk wrote:
 From: Chris Albertson

 Really?   The PPS to GPIO interface is handles in user space?  It is not
 interrupt driven?
 In the implementations I've seen the critical real time work is done inside
 the PPS interrupt handler and then of course ntpd runs in userland and can
 take as much time as it needs
 =

 Folkert's solution was very helpful, but there is now kernel-mode PPS
 support for a GPIO pin the current Raspberry Pi Linux - see:

   http://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html#easy

 I'm running that on a couple of systems here.

 Cheers,
 David
 --
 SatSignal Software - Quality software written to your requirements
 Web: http://www.satsignal.eu
 Email: david-tay...@blueyonder.co.uk

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[time-nuts] LM 723 Ckt Wanted.

2014-12-09 Thread Perry Sandeen via time-nuts

List,
Many, many years ago I think it was in EDN magazine that a circuit was 
published that used two LM 723 regulators.
One was used as a heater circuit and the other as a voltage regulator.
I lost my paper copy in moving and found that that particular circuit is behind 
a paywall.
If anyone has this circuit I'd appreciate a copy.
TIA
Regards,
PerriersandeenpaXXyatXXyahoo.com
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[time-nuts] Simple xtal oven for accurate clocks II

2014-12-09 Thread Perry Sandeen via time-nuts

List, 
This TL 431 temperature regulator circuit might be useful.
www.techlib.com/electronics/ovenckts.htm
Regards,
PerriersandeenpaXXyatXXyahoo.com
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Re: [time-nuts] Did a member of time-nuts buy this?

2014-12-09 Thread Bert Kehren via time-nuts

With the exception of the HP 5065 where the Rb cell actually is the ADEV  
contributor as Corby has repeatedly demonstrated with tests and if you check 
the  filter time constant.  Most Rb's  will be well served with a  cleanup 
OCXO. 
The PRS 10 has good performance as is,  but is limited by DAC  resolution 
to 1 E-12 in frequency resolution/accuracy.
In the popular FE5680 and 5650 we use a separate cleanup circuit using a  
Morion and on FRK's use the modified internal loop with HP 10811, M 1000  and 
Oscilloquartz 8600 deactivating the internal OCXO.
Going the extra mile gives you the best of both and you do not have to  
compromize.
Bert Kehren
 
 
In a message dated 12/9/2014 7:40:56 A.M. Eastern Standard Time,  
kb...@n1k.org writes:

Hi

  On Dec 9, 2014, at 6:10 AM, Mike Monett timen...@binsamp.e4ward.com  
wrote:
 
 Hi Bob, I have been having problems posting this. If  other versions
 show up, please disregard.
 
 I have some  questions for you.
 
 Hi
 
 If you toss a  Rb into the GPSDO mix things can get quite good.
 The Rb *should*  be better than an OCXO in the  1,000 second
 range.
  
 It's crossover with the GPS ADEV will be further out than  the
 OCXO's. The gotcha with both the OCXO and Rb is their  temperature
 dependance. Some / many / all of the lower cost Rb's  are not much
 better than a good double oven OCXO in terms of raw  temperature
 performance. The approach they use to correct this  does not help
 their ADEV at all. Yes, you can disable the  correction and put the
 whole thing in a temperature controlled  environment.
 
 What does the temperature controller do that  degrades the ADEV? Can
 anything be done to modify it to improve the  performance?

On the lightweight Rb’s they feed the correction into a  DDS. The DDS steps 
are big enough to show up above the ADEV. You get a “hump”  in the ADEV as 
a result. The solution is to disconnect the temperature sensor  that feeds 
the correction circuit. 

 
 Lots of details  to take care of. If you get them all right, you'll
 beat any / all  of the older Cs standards.
 
 Is there a list anywhere of all  the details that need to be
 addressed?

Well, there’s this list  :)

The things that need to be done are a “that depends” based on the  
approach you take. A full listing of all you might do down all of the roads  
you 
could take would be a wall full of books.


 How about words  or phrases that can be used to search
 google and the  archives?

GPSDO is a good place to start.

 
 One  very cute addition would be to pull down the NIST GPS data and
 use  it to correct your system on an hourly / daily basis. If you
 do  that with common view satellites, you most certainly will beat
 a  surplus grade Cs standard.
 
 How can we do this?

First  step is to be able to extract timing data from individual sat’s. Not 
all GPS  modules do this correctly. 

 The NIST archives state
  
 The archive is only updated once every 24 hours, so data are  not
 available for today's date.

Thus the “daily” statement.  There has been discussion on the list that 
interchange with other list members  at a more rapid rate might make sense. 
Given the floor of most setups, daily  updates are not a bad thing. 

 Data from the previous day are added  to
 the archive at about 1600 UTC.
 
  http://www.nist.gov/pml/div688/grp40/gpsarchive.cfm
 
 Is there  another page that has current data? If so, how do we
 incorporate it  into the GPSDO?

1) Measure your local time offset by GPS sat number  every hour and save 
the data.

2) When NIST posts there data, pull it  down.

3) Compare your data to theirs

4) Do a fit

5) Feed  that into your control loop equation. 

The missing element is the per  sat data….

Bob

 
 Bob
 
  Thanks,
 
 Mike
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Re: [time-nuts] Beaglebone NTP server

2014-12-09 Thread David J Taylor


Thanks for pointing this out David,
Compiling an new kernel was holding me back. I followed your instructions 
and
everything works beautiful. The PI that is running the PPS timekeeping with 
NTP

is serving as a VLF receiver as well. Taxing the poor CPU, but with
kernel PPS support
the NTP daemon has become way happier! (see attachment)

73, Frits W1FVB
==

Oh, yes!  That's much better, Frits!  Delighted to have helped!

(Although it now shows up an hourly periodicity - any idea what might be 
causing that?)


73,
David GM8ARV
--
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-tay...@blueyonder.co.uk 


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Re: [time-nuts] 10MHz LTE-Lite - PPS accuracy?

2014-12-09 Thread David J Taylor


From: Dave Martindale

In my case, the LTE-Lite had been operating for at least a week before I
made my accumulate mode measurement, and the Thunderbolt had been
operating for at least a month.  But both antennas were in poor locations -
not bad enough to lose lock any time I was watching, but nowhere close to a
clear view of most of the sky.  I never saw the 1 PPS disappear while I was
watching it.

I wonder if your LTE-Lite ever finished its survey and switched into
1D/position hold mode?  A GPS operating in 3D mode can indeed fail to get a
position fix with 5 satellites being received, if they have bad geometry
(e.g. all are in the same plane in space) because the solution will have
horrible DOP values.  But a timing-mode GPS in position hold mode knows its
own (antenna) position, and only needs one visible satellite to continue to
provide timing outputs.

We don't know how the LTE-Lite's disciplining algorithm is tuned.  If
frequency stability was considered to be more important that timing, the
algorithm may limit the maximum frequency offset that can be used to
correct a timing error.  Watching the scope output in real time, I can see
the time offset between the two 1 PPS pulses change with time, but it
always changes rather slowly, so the maximum frequency difference I've seen
is quite small.  (I no longer have the equipment set up, so I can't provide
a quantitative number).

- Dave
===

Dave,

Thanks for that background.  I'm sure Said must be on holiday (or unwell) 
otherwise he would have chipped in!


Mine did finish the survey - eventually - and I saw this as the positions 
which were emitted being identical, and also that the survey light was 
extinguished.  But at the moment the Lock OK light is out, and the survey 
light is out.  Four satellites are showing at strength 27 or above, but no 
position is being emitted.  PPS is present, about 170 ns late compared to 
the Rapco 1904M.  The other GPS receivers are showing normal lock and a 
positional output.


I suspect you are correct about the algorithms - the device being optimised 
for frequency rather than timing.


Cheers,
David
--
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-tay...@blueyonder.co.uk 


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Re: [time-nuts] Linear voltage regulator hints...


Hittite introduced a low noise reference a
few years ago, but it was only low noise when
filtered with a big cap.  IOW, the cap did
all the heavy lifting and the IC was nothing
special.  Good marketing, bad engineering.

Rick

On 12/9/2014 4:30 AM, Bob Camp wrote:

Hi


On Dec 8, 2014, at 10:35 PM, Brooke Clarke bro...@pacific.net wrote:

Hi Rich:

Did you use the 723 or . . . .?
As far as I know the 723 is supposed to have low noise.


There are more modern parts with lower close in noise. Linear Technology has a 
number of them. Your filter caps take out the broadband stuff, close in is all 
that really matters.

Bob



Mail_Attachment --
Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
http://www.prc68.com/I/DietNutrition.html
Richard (Rick) Karlquist wrote:



On 12/8/2014 4:53 PM, Bert Kehren via time-nuts wrote:

We solved that problem by attaching the regulators to the FRK back plate
which is with fan control is kept within 0.01C. We did not do it for that
purpose but found that we needed some more heat in order to keep the fan in an
  optimum fan speed. Rb, OCXO and Fan power transistor are on the back
plate.  Works for us.
Bert Kehren



When I designed the E1938A, I chose a reasonable looking voltage
reference IC and put it inside the oven.  I figured that was
the end of it as far as tempco was concerned.  It was, but it
turned out that the *noise* of the reference was unacceptable
and of course the oven does nothing to fix that.  I had to
switch to a lower noise reference.

Rick Karlquist N6RK
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Re: [time-nuts] Linear voltage regulator hints...


I don't remember, but it wasn't a 723.

Rick

On 12/8/2014 7:35 PM, Brooke Clarke wrote:

Hi Rich:

Did you use the 723 or . . . .?
As far as I know the 723 is supposed to have low noise.

Mail_Attachment --
Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
http://www.prc68.com/I/DietNutrition.html
Richard (Rick) Karlquist wrote:



On 12/8/2014 4:53 PM, Bert Kehren via time-nuts wrote:

We solved that problem by attaching the regulators to the FRK back plate
which is with fan control is kept within 0.01C. We did not do it for
that
purpose but found that we needed some more heat in order to keep the
fan in an
  optimum fan speed. Rb, OCXO and Fan power transistor are on the back
plate.  Works for us.
Bert Kehren



When I designed the E1938A, I chose a reasonable looking voltage
reference IC and put it inside the oven.  I figured that was
the end of it as far as tempco was concerned.  It was, but it
turned out that the *noise* of the reference was unacceptable
and of course the oven does nothing to fix that.  I had to
switch to a lower noise reference.

Rick Karlquist N6RK
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Re: [time-nuts] Linear voltage regulator hints...

Hi Bob,
I can't speak for Dan, but since he hasn't responded, I can speak a bit about 
the issue.  As you know, my GPSDO uses a constant voltage TIC and the PWM 
output from a dsPIC33 to perform the DAC function.  During testing we've found 
that one critical point is that the PWM voltage from the PIC changes with 
temperature.  Dan managed to solve that for us by buffering the PWM with a 125 
gate powered by a stable voltage.  So, the temperature sensitivity issue is 
essentially solved.  I would guess that he's looking around for a canned 
solution rather than using a good reference with an op-am.  

We need very stable voltages for both 2.5 and 3.3 unless I revisit the TIC's RC 
to make it useable at 3.3.  On my prototype, I'm using an ADR-291G as a VREF 
for the ADC on the PIC.  I had originally used LF33 regulators for the board 
voltage, but recently switched to using another ADR-291G with an op-amp and a 
suitable divider to get 3.3V to power the rest of the board, including the 125 
gate.  My prototype board was made with through-hole components, but I'm about 
convinced to do the next board on SMT.  Good regulators would have been nice, 
but it sounds like we're going to be using references and op-amps to get what 
we need.

Here's an overnight ADEV plot against the new Cs of where we are in the 
project.  Red is ADEV.  Green is the TIC.  Blue is the output of the GPSDO to 
Channel A and the Cs to Channel B of my 5335A measuring TI, using the 1PPS from 
my GPSDO to trigger the external gate.  I see that the Cs phase has drifted 
down slightly vs my GPSDOe.  I wonder if this is an indication of a calibration 
problem with the Cs or some subtle issue on my board?  This test will run 
throughout the day, so maybe that question will be answered.

http://evoria.net/AE6RV/PRS-45A/GPSDOe.vs.Cs.12.9.14.10:19.png


Bob

  From: Bob Camp kb...@n1k.org
 To: Discussion of precise time and frequency measurement time-nuts@febo.com 
 Sent: Monday, December 8, 2014 6:48 PM
 Subject: Re: [time-nuts] Linear voltage regulator hints...
   
Hi

Hopefully the issue  (and question) is about stability of the EFC voltage. Any 
decent OCXO should have a voltage stability that’s well below it’s temperature 
stability when run off of a fairly standard regulator. As an example, An OCXO 
that does 5x10^-9 over 0 to 70 C probably has a voltage stability below 
5x10^-10 for a 1% change. One percent is more than what a modern regulator 
should be moving when running an OCXO.  

Bob

 On Dec 8, 2014, at 7:33 PM, Dave M dgmin...@mediacombb.net wrote:
 
 Dan Kemppainen wrote:
 Hi,
 
 In playing with some oscillators and a GPSDO here, I think I'm seeing
 a voltage sensitivity issue.
 
 So, I started looking at the output voltage of various regulators vs.
 temp. Using standard LM/UA type linear regulators and some LDO's, they
 all appear to be pretty sensitive to temperature. (millivolt / few
 degrees Fahrenheit sort of sensitivity). Most of the datasheets seem
 to ignore temp sensitivity. Almost like they are so bad they don't
 want to publish it...
 
 Does anyone have hints on TO-220 or D-Pak type regulators that have
 really good temp coefficients and good line regulation? A few PPM/Deg
 C might be nice, if possible. Or am I into a 'roll you own' type
 design...
 Dan
 
 
 
 Yes, in order to get low PPM stability, you are going to roll your own. No 
 3-terminal regulator or reference that I know of can run an OXCO (heater and 
 oscillator).
 What are your voltage and current requirements?
 
 Dave M 
 
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Re: [time-nuts] PRS-45A is alive!

Hi Bert,
Thanks for the comments.  I did learn today that this was a recent pull, so 
that explains why it came up well.  I hope you'll understand my reluctance to 
start making adapters and doing direct measurements on the thing.  One of my 
next steps is to get it to talk to me.  Unfortunately, I'm out of serial ports, 
so I've got to wait till this evening until I can rewire my GPSDO to accept a 
USB adapter to free up my RS-232.

Bob

  From: Bert Kehren via time-nuts time-nuts@febo.com
 To: time-nuts@febo.com 
 Sent: Tuesday, December 9, 2014 8:20 AM
 Subject: Re: [time-nuts] PRS-45A is alive!
   
16 Minutes is normal. First FTS tubes do not leak as much as the old HP  
tubes. Second the seller most likely did run a test which means the tube was  
pumped down. 
Unless there is software that tells beam current the only way I know to get 
 some idea of health of tube is as I mentioned before measure the beam 
current. I  have probably done it at least a hundred times, made a connector 
adapter.
Bert Kehren
 
 
In a message dated 12/8/2014 10:15:08 P.M. Eastern Standard Time,  
b...@evoria.net writes:

Well,  it's alive, and I even have 10MHz coming from it.  It took about 16  
minutes to go to lock.  Is that good, or doesn't matter?  Now I've  got to 
put together a serial cable and see if I can talk to it and find out  how it 
thinks it's doing.  But, this is  good!


www.evoria.net/AE6RV/PRS-45A/2014-12-08%2020.51.33.jpg

Hope  you enjoy the wall decorations.  =)

Bob -  AE6RV
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Re: [time-nuts] PRS-45A is alive!

Hi Dave,
I'll have to look into this.  If it's a GFCI, I don't understand why it would 
dropout on power loss.  But I'll take your word for it.
Bob

  From: Dave Martindale dave.martind...@gmail.com
 To: Discussion of precise time and frequency measurement time-nuts@febo.com 
 Sent: Tuesday, December 9, 2014 7:29 AM
 Subject: Re: [time-nuts] PRS-45A is alive!

One zero-effort way to do this: a portable GFCI.

I have several GFCIs (Ground Fault Circuit Interrupters) designed for
portable use.  They may be in the form of an extension cord with the GFI
electronics in the male plug, or a short cord with the electronics in the
middle of the length, or a small block that plugs into an outlet, with a
female outlet that a device plugs into.  All of these portable GFCIs
require line power to remain in the on position.  If the AC is
interrupted briefly, the GFCI drops out and stays off until manually reset.

This must be by design, because it is different from the behaviour of GFCI
outlets, and GFCI circuit breakers.  It mimics the behaviour of latching
magnetic contactors (relays) used on large AC-powered tools.  I use the
portable GFCIs to get the same shut-off-and-stay-off feature for small shop
tools that are equipped only with an ordinary switch.  A portable GFCI
should work just as well for electronics that you want to stay off until
manually reset.

- Dave

On Tue, Dec 9, 2014 at 1:24 AM, wb6bnq wb6...@cox.net wrote:

 Hi Bob,

 I think using a latching relay is a very good idea and prudent.  Besides
 while it is reacquiring lock you would probably be busy resetting VCR's and
 so forth.

 BillWB6BNQ

 Bob Stewart wrote:

  Hi Pete,
 I don't have any way of knowing.  I've asked the seller if he has a copy
 of the control software, and I don't like to go back with a bunch of petty
 questions like that.  The next issue is adapting some serial port software
 i wrote to the protocol in the manual Magnus sent to see if I can pull the
 status codes out.  That would probably tell me something.
 I have some tests I want to run immediately on my GPSDO and the KS to
 settle the question of which one can't keep time.  After that, I'll power
 it down, lift its skirts and take some pics.  It's pretty simple on the
 surface: a Cs Beam Tube, a main board, a microwave package with MTI 5Mhz
 OCXO, and the HV and LV power supplies.
 I don't intend to keep this thing running 24/7, but I have a question:
  Here in Houston, we have the occasional large thunderstorm and resulting
 short power outages.  So, should I put a latching relay in the power stream
 to keep it off if I lose power?  The budget is now officially busted, and a
 UPS is not going to happen for awhile.  Santa's sleigh is now officially
 out of gas.
 Bob
      From: Pete Lancashire p...@petelancashire.com
 To: Bob Stewart b...@evoria.net; Discussion of precise time and
 frequency measurement time-nuts@febo.com Sent: Monday, December 8,
 2014 11:46 PM
 Subject: Re: [time-nuts] PRS-45A is alive!
  Love to have known how long it was off, and how much of that 16
 minutes was getting the tube degassed.

 -pete

 On Mon, Dec 8, 2014 at 7:11 PM, Bob Stewart b...@evoria.net wrote:

 Well, it's alive, and I even have 10MHz coming from it.  It took about
 16 minutes to go to lock.  Is that good, or doesn't matter?  Now I've got
 to put together a serial cable and see if I can talk to it and find out how
 it thinks it's doing.  But, this is good!

 www.evoria.net/AE6RV/PRS-45A/2014-12-08%2020.51.33.jpg

 Hope you enjoy the wall decorations.  =)

 Bob - AE6RV
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Re: [time-nuts] PRS-45A is alive!

Thanks Paul.  It does seem too good to be true, and it certainly came at the 
right time in my GPSDO development effort.
Bob

  From: paul swed paulsw...@gmail.com
 To: Discussion of precise time and frequency measurement time-nuts@febo.com 
 Sent: Tuesday, December 9, 2014 8:04 AM
 Subject: Re: [time-nuts] PRS-45A is alive!

Bob
That is one nice looking unit. Most Cs's that we get have had there days.
This one looks really good physically. The fact that it warmed and locked
in 16 minutes means it did not need to pump down very much. Heck a small RB
takes 15 minutes to hit lock and it has a much smaller mass to heat up.
Congratulations on a great buy.
Regards
Paul
WB8TSL

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Re: [time-nuts] Linear voltage regulator hints...

2014-12-09 Thread Dan Kemppainen


Hi All,

Thanks for the responses. I had a feeling the answer wouldn't be good, 
but was hoping someone would have a suggestion. There are currently a 
bunch of regulators in the 'system'. If there were some really good 
regulator out there, the shotgun approach would apply...


Of course it is difficult to provide a good reference and pass 
transistor on the same die, but it was worth asking.



Bert,

The thought of temp control of the regulators crossed my mind. Not 
planning on going there unless I need to. But it was a thought, maybe if 
all else fails...



Bob,

 There are more modern parts with lower close in noise. Linear 
Technology has a number of them. Your filter caps take out the broadband 
stuff, close in is all that really matters.



Got any hints on which ones? Maybe a nice quiet regulator can be 
'disciplined' with a better reference.


Thanks,
Dan

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Re: [time-nuts] Beaglebone NTP server

2014-12-09 Thread Bob Darlington

Hourly cron jobs, perhaps?

-Bob

On Tue, Dec 9, 2014 at 8:04 AM, David J Taylor 
david-tay...@blueyonder.co.uk wrote:

 Thanks for pointing this out David,
 Compiling an new kernel was holding me back. I followed your instructions
 and
 everything works beautiful. The PI that is running the PPS timekeeping
 with NTP
 is serving as a VLF receiver as well. Taxing the poor CPU, but with
 kernel PPS support
 the NTP daemon has become way happier! (see attachment)

 73, Frits W1FVB
 ==

 Oh, yes!  That's much better, Frits!  Delighted to have helped!

 (Although it now shows up an hourly periodicity - any idea what might be
 causing that?)

 73,
 David GM8ARV

 --
 SatSignal Software - Quality software written to your requirements
 Web: http://www.satsignal.eu
 Email: david-tay...@blueyonder.co.uk
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Re: [time-nuts] Beaglebone NTP server

2014-12-09 Thread Graham / KE9H

For those of you that have gotten the BeagleBone Black up and
running as an ntp server with the 1PPS signal input in kernel space,
what gpio input pin is being used?

I guess I am asking if the kernel pps-gpio has a specific preferred pin,
or whether it can be mapped to any available gpio pin.

Thanks,
--- Graham / KE9H

==

On Tue, Dec 9, 2014 at 11:18 AM, Bob Darlington rdarling...@gmail.com
wrote:

 Hourly cron jobs, perhaps?

 -Bob

 On Tue, Dec 9, 2014 at 8:04 AM, David J Taylor 
 david-tay...@blueyonder.co.uk wrote:

  Thanks for pointing this out David,
  Compiling an new kernel was holding me back. I followed your instructions
  and
  everything works beautiful. The PI that is running the PPS timekeeping
  with NTP
  is serving as a VLF receiver as well. Taxing the poor CPU, but with
  kernel PPS support
  the NTP daemon has become way happier! (see attachment)
 
  73, Frits W1FVB
  ==
 
  Oh, yes!  That's much better, Frits!  Delighted to have helped!
 
  (Although it now shows up an hourly periodicity - any idea what might be
  causing that?)
 
  73,
  David GM8ARV
 
  --
  SatSignal Software - Quality software written to your requirements
  Web: http://www.satsignal.eu
  Email: david-tay...@blueyonder.co.uk
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Re: [time-nuts] Linear voltage regulator hints...

2014-12-09 Thread Didier Juges

Voltage References are usually not able to deliver much more than a few 10mA. 

Having a stable reference means no big temperature gradient on the die, so that 
precludes a big pass transistor.

Most likely, you will have to roll your own.

Using TL431 types of shunt regulator with a single bipolar transistor yields a 
simple and high performing regulator (at least much higher than most 3 terminal 
series regulators) particularly if you use the Linear Tech equivalent part 
(forgot the part number at the moment, but look for shunt regulators)

Didier KO4BB


On December 8, 2014 4:59:24 PM CST, Bob Camp kb...@n1k.org wrote:
Hi

As with anything else it’s a matter of “what’s in your wallet”. 

The parts you are after are called voltage references rather than
voltage regulators. You can get them well down into the low ppm’s / C
or lower. The cutoff is more a function of “do you want to spend $100
or not” rather than a specific level you simply can’t get to. 

Bob

 On Dec 8, 2014, at 1:18 PM, Dan Kemppainen d...@irtelemetrics.com
wrote:
 
 Hi,
 
 In playing with some oscillators and a GPSDO here, I think I'm seeing
a voltage sensitivity issue.
 
 So, I started looking at the output voltage of various regulators vs.
temp. Using standard LM/UA type linear regulators and some LDO's, they
all appear to be pretty sensitive to temperature. (millivolt / few
degrees Fahrenheit sort of sensitivity). Most of the datasheets seem to
ignore temp sensitivity. Almost like they are so bad they don't want to
publish it...
 
 Does anyone have hints on TO-220 or D-Pak type regulators that have
really good temp coefficients and good line regulation? A few PPM/Deg C
might be nice, if possible. Or am I into a 'roll you own' type
design...
 
 Dan
 
 
 
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Re: [time-nuts] Beaglebone NTP server

2014-12-09 Thread Dan Drown

If you're using the pps-gpio module, the hardware can support up to  
Two Interrupt Inputs per Bank.  So if you're not using the gpio for  
anything else, any of the gpio should work.


If you want to use the timer hardware (and pps-dmtimer module), each  
timer has an assigned pin.


Quoting Graham / KE9H ke9h.gra...@gmail.com:

For those of you that have gotten the BeagleBone Black up and
running as an ntp server with the 1PPS signal input in kernel space,
what gpio input pin is being used?

I guess I am asking if the kernel pps-gpio has a specific preferred pin,
or whether it can be mapped to any available gpio pin.

Thanks,
--- Graham / KE9H

==

On Tue, Dec 9, 2014 at 11:18 AM, Bob Darlington rdarling...@gmail.com
wrote:


Hourly cron jobs, perhaps?

-Bob

On Tue, Dec 9, 2014 at 8:04 AM, David J Taylor 
david-tay...@blueyonder.co.uk wrote:

 Thanks for pointing this out David,
 Compiling an new kernel was holding me back. I followed your instructions
 and
 everything works beautiful. The PI that is running the PPS timekeeping
 with NTP
 is serving as a VLF receiver as well. Taxing the poor CPU, but with
 kernel PPS support
 the NTP daemon has become way happier! (see attachment)

 73, Frits W1FVB
 ==

 Oh, yes!  That's much better, Frits!  Delighted to have helped!

 (Although it now shows up an hourly periodicity - any idea what might be
 causing that?)

 73,
 David GM8ARV

 --
 SatSignal Software - Quality software written to your requirements
 Web: http://www.satsignal.eu
 Email: david-tay...@blueyonder.co.uk
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Re: [time-nuts] Linear voltage regulator hints...

2014-12-09 Thread ed breya

I'd recommend going with what Bob Stewart mentioned, using separate 
gates as buffers, operated from a better-grade reference, to shift 
from the noisier and driftier logic supplies, into the more critical 
circuits. It's simple, and can be powered from a modest reference circuit.


If the logic circuits themselves need better supply noise and tempco 
performance, don't use any kind of three-terminal regulators - use a 
good opamp driving a pass transistor. Use a reference IC that has a 
buried zener for lowest noise - this eliminates all the low voltage 
references and three-terminal etc regulators that use band-gap 
references. The down side is that the good kind of reference ICs will 
need a higher (like 10V and up) operating voltage than may be 
available, so that complicates it.


For a system using a conventional PC-style supply, with +5V and +12V 
available, an LM399, for example, could run from the +12V, along with 
the opamp circuitry, while the pass transistor could feed from the 
+5V, dropping to the +3.3V or whatever low logic supply is needed. 
For modest current requirement, use only an NPN pass transistor in 
emitter-follower mode. For higher currents, add another NPN 
emitter-follower in front of it for more drive - its collector can be 
supplied from the +12V via some limiting R, to ensure enough 
overhead. The opamp and associated network resistors, of course, 
should have performance commensurate with the reference, and 
sufficient for the application. Since there's also plenty of digital 
and PS noise around, a lot of bypassing in the right spots should help a lot.


Ed

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Re: [time-nuts] Linear voltage regulator hints...

Hi


 On Dec 9, 2014, at 11:31 AM, Bob Stewart b...@evoria.net wrote:
 
 Hi Bob,
 I can't speak for Dan, but since he hasn't responded, I can speak a bit about 
 the issue.  As you know, my GPSDO uses a constant voltage TIC and the PWM 
 output from a dsPIC33 to perform the DAC function.  During testing we've 
 found that one critical point is that the PWM voltage from the PIC changes 
 with temperature.  Dan managed to solve that for us by buffering the PWM with 
 a 125 gate powered by a stable voltage.  So, the temperature sensitivity 
 issue is essentially solved.  I would guess that he's looking around for a 
 canned solution rather than using a good reference with an op-am.  
 
 We need very stable voltages for both 2.5 and 3.3 unless I revisit the TIC's 
 RC to make it useable at 3.3.  

Most TIC’s are “radiometric” devices. If you feed all of the parts with the 
same voltage, the first order drift cancels out. Yes there are always second 
order effects. For what we do, a simple regulator is probably good enough.

 On my prototype, I'm using an ADR-291G as a VREF for the ADC on the PIC.  I 
 had originally used LF33 regulators for the board voltage, but recently 
 switched to using another ADR-291G with an op-amp and a suitable divider to 
 get 3.3V to power the rest of the board, including the 125 gate.  My 
 prototype board was made with through-hole components, but I'm about 
 convinced to do the next board on SMT.  Good regulators would have been nice, 
 but it sounds like we're going to be using references and op-amps to get what 
 we need.

On the DAC out of the control loop, a stable reference may be useful. The same 
is true of a quiet one. With PWM(s) that means feeding the final gate(s) with a 
stable source. Since they likely pull  2 ma, a voltage reference should be 
fine.  

 
 Here's an overnight ADEV plot against the new Cs of where we are in the 
 project.  Red is ADEV.  Green is the TIC.  Blue is the output of the GPSDO to 
 Channel A and the Cs to Channel B of my 5335A measuring TI, using the 1PPS 
 from my GPSDO to trigger the external gate.  I see that the Cs phase has 
 drifted down slightly vs my GPSDOe.  I wonder if this is an indication of a 
 calibration problem with the Cs or some subtle issue on my board?  

Looks perfectly normal to me. Your Cs is sensitive to magnetic field. Have you 
“zeroed” it out? No of course not, nobody does. (almost nobody …). 

Bob

 This test will run throughout the day, so maybe that question will be 
 answered.
 
 http://evoria.net/AE6RV/PRS-45A/GPSDOe.vs.Cs.12.9.14.10:19.png
 
 
 Bob
 
  From: Bob Camp kb...@n1k.org
 To: Discussion of precise time and frequency measurement time-nuts@febo.com 
 Sent: Monday, December 8, 2014 6:48 PM
 Subject: Re: [time-nuts] Linear voltage regulator hints...
 
 Hi
 
 Hopefully the issue  (and question) is about stability of the EFC voltage. 
 Any decent OCXO should have a voltage stability that’s well below it’s 
 temperature stability when run off of a fairly standard regulator. As an 
 example, An OCXO that does 5x10^-9 over 0 to 70 C probably has a voltage 
 stability below 5x10^-10 for a 1% change. One percent is more than what a 
 modern regulator should be moving when running an OCXO.  
 
 Bob
 
 On Dec 8, 2014, at 7:33 PM, Dave M dgmin...@mediacombb.net wrote:
 
 Dan Kemppainen wrote:
 Hi,
 
 In playing with some oscillators and a GPSDO here, I think I'm seeing
 a voltage sensitivity issue.
 
 So, I started looking at the output voltage of various regulators vs.
 temp. Using standard LM/UA type linear regulators and some LDO's, they
 all appear to be pretty sensitive to temperature. (millivolt / few
 degrees Fahrenheit sort of sensitivity). Most of the datasheets seem
 to ignore temp sensitivity. Almost like they are so bad they don't
 want to publish it...
 
 Does anyone have hints on TO-220 or D-Pak type regulators that have
 really good temp coefficients and good line regulation? A few PPM/Deg
 C might be nice, if possible. Or am I into a 'roll you own' type
 design...
 Dan
 
 
 
 Yes, in order to get low PPM stability, you are going to roll your own. No 
 3-terminal regulator or reference that I know of can run an OXCO (heater and 
 oscillator).
 What are your voltage and current requirements?
 
 Dave M 
 
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Re: [time-nuts] Linear voltage regulator hints...

Hi

 On Dec 9, 2014, at 11:57 AM, Dan Kemppainen d...@irtelemetrics.com wrote:
 
 Hi All,
 
 Thanks for the responses. I had a feeling the answer wouldn't be good, but 
 was hoping someone would have a suggestion. There are currently a bunch of 
 regulators in the 'system'. If there were some really good regulator out 
 there, the shotgun approach would apply...
 
 Of course it is difficult to provide a good reference and pass transistor on 
 the same die, but it was worth asking.
 
 
 Bert,
 
 The thought of temp control of the regulators crossed my mind. Not planning 
 on going there unless I need to. But it was a thought, maybe if all else 
 fails...
 
 
 Bob,
 
  There are more modern parts with lower close in noise. Linear Technology 
  has a number of them. Your filter caps take out the broadband stuff, close 
  in is all that really matters.
 
 
 Got any hints on which ones? Maybe a nice quiet regulator can be 
 'disciplined' with a better reference.

http://www.linear.com/product/LTC6655

I believe that if you are trying to regulate the entire OCXO supply, you are 
doing the wrong thing and chasing the wrong problem ….

Bob

 
 Thanks,
 Dan
 
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[time-nuts] PRS-45A

Subject changed, as I inadvertently stole Dan's thread.

Hi Bob Camp,
You wrote: Looks perfectly normal to me. Your Cs is sensitive to magnetic 
field. Have you “zeroed” it out? No of course not, nobody does. (almost nobody 
…). 

What does it mean to zero out the magnetic field for a Cs?  Sounds like I 
need to align something to local magnetic north.  What?  I suspect that 
figuring out a way to mount it to the wall (no rack system here) is going to be 
my next priority.  It can't safely live on my bench or the floor with all those 
perforations in the case covers.

The people at Symmetricom indicated I should be able to download the monitor 
software, but the registration process seems to take some time.  Hopefully that 
gets resolved soon.
Having this thing hooked up just for this short time has pointed out some 
problems that I couldn't see without a reference that I trusted.

Bob


  
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Re: [time-nuts] Linear voltage regulator hints...

2014-12-09 Thread Magnus Danielson


Hi,

On 12/09/2014 10:30 PM, ed breya wrote:

I'd recommend going with what Bob Stewart mentioned, using separate
gates as buffers, operated from a better-grade reference, to shift from
the noisier and driftier logic supplies, into the more critical
circuits. It's simple, and can be powered from a modest reference circuit.


I've used this technique myself with great success. Nice way to convert 
dirty supply digital bits into benign noise supplies digital bits.



If the logic circuits themselves need better supply noise and tempco
performance, don't use any kind of three-terminal regulators - use a
good opamp driving a pass transistor. Use a reference IC that has a
buried zener for lowest noise - this eliminates all the low voltage
references and three-terminal etc regulators that use band-gap
references. The down side is that the good kind of reference ICs will
need a higher (like 10V and up) operating voltage than may be available,
so that complicates it.


One should not trust the transition levels of logic to do any sine to 
square shaping. Most of that should have already been done before it 
meets the inherent comparator level of a logic gate. That you have 
sensitivity to power supply traceable to gate comparator voltage is a 
sign that you need to shape up first. Only once you have jolly good 
slew-rate you can hit a logical gate for further shaping, and that's 
when swapping power-supply using the above trick should be a trivial 
exercise .


Cheers,
Magnus
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Re: [time-nuts] Beaglebone NTP server

2014-12-09 Thread Paul

On Tue, Dec 9, 2014 at 12:59 PM, Graham / KE9H ke9h.gra...@gmail.com
wrote:

 I guess I am asking if the kernel pps-gpio has a specific preferred pin,
 or whether it can be mapped to any available gpio pin.


The provided-with-stock-dtb pin is: 0x40 which is P9 pin 15.
I use the only free pin on P8 or P9: 0x7c which is P8 pin 26

There are various maps/charts/lists around with the pins.  Just decompile
/lib/firmware/BB-BONE-GPS-00A0.dtbo and fiddle if you want a different
pin.  The Debian relases come with dtc, I don't know about Angstrom.

e.g.
http://www.embedded-things.com/bbb/beaglebone-black-pin-mux-spreadsheet/
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Re: [time-nuts] Linear voltage regulator hints...

Hi Ed,
I just wanted to clarify this, so that credit goes where it's due.  Dan is 
helping me with my GPSDO project, and he was the one who came up with the idea 
of putting the 125 gate on with a good power source.  Left to myself, I'd still 
be trying to figure out how to cancel the thermal noise.

Bob

  From: ed breya e...@telight.com
 To: time-nuts@febo.com 
 Sent: Tuesday, December 9, 2014 3:30 PM
 Subject: Re: [time-nuts] Linear voltage regulator hints...

I'd recommend going with what Bob Stewart mentioned, using separate 
gates as buffers, operated from a better-grade reference, to shift 
from the noisier and driftier logic supplies, into the more critical 
circuits. It's simple, and can be powered from a modest reference circuit.

If the logic circuits themselves need better supply noise and tempco 
performance, don't use any kind of three-terminal regulators - use a 
good opamp driving a pass transistor. Use a reference IC that has a 
buried zener for lowest noise - this eliminates all the low voltage 
references and three-terminal etc regulators that use band-gap 
references. The down side is that the good kind of reference ICs will 
need a higher (like 10V and up) operating voltage than may be 
available, so that complicates it.

For a system using a conventional PC-style supply, with +5V and +12V 
available, an LM399, for example, could run from the +12V, along with 
the opamp circuitry, while the pass transistor could feed from the 
+5V, dropping to the +3.3V or whatever low logic supply is needed. 
For modest current requirement, use only an NPN pass transistor in 
emitter-follower mode. For higher currents, add another NPN 
emitter-follower in front of it for more drive - its collector can be 
supplied from the +12V via some limiting R, to ensure enough 
overhead. The opamp and associated network resistors, of course, 
should have performance commensurate with the reference, and 
sufficient for the application. Since there's also plenty of digital 
and PS noise around, a lot of bypassing in the right spots should help a lot.

Ed

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Re: [time-nuts] Linear voltage regulator hints...


On 12/9/2014 1:30 PM, ed breya wrote:


buried zener for lowest noise - this eliminates all the low voltage
references and three-terminal etc regulators that use band-gap
references. The down side is that the good kind of reference ICs will
need a higher (like 10V and up) operating voltage than may be available,
so that complicates it.


Great post, Ed.  I might add that my understanding of band gap
regulators is that they rely on amplifying a small DC difference
in voltage between two transistors.  This also amplifies the SUM
of the noise of the respective inputs, which jacks up the noise to
much more than a good zener.  Because of physics, no band gap
reference will ever be low noise.

Rick Karlquist N6RK
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Re: [time-nuts] Linear voltage regulator hints...




On 12/9/2014 3:02 PM, Bob Camp wrote:
 Here's an overnight ADEV plot against the new Cs of where we are in 
the project.  Red is ADEV.  Green is the TIC.  Blue is the output of the 
GPSDO to Channel A and the Cs to Channel B of my 5335A measuring TI, 
using the 1PPS from my GPSDO to trigger the external gate.  I see that 
the Cs phase has drifted down slightly vs my GPSDOe.  I wonder if this 
is an indication of a calibration problem with the Cs or some subtle 
issue on my board?


Looks perfectly normal to me. Your Cs is sensitive to magnetic field. Have you 
“zeroed” it out? No of course not, nobody does. (almost nobody …).

Bob


This reminds me of the great CBT demagnetizer debate at HP.
Even Len Cutler didn't think this was necessary, at least
in the 5071, and possibly the 5061.  When Len says something
is overkill, you can be sure of it.  Anyway, we still had
to support a CBT demagnetizer for customers who wanted it.
The customer (with money to spend) is always right.  The
5071 measures the C-field with a Zeeman line measurement
and adjusts it if necessary.

Rick Karlquist N6RK
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Re: [time-nuts] PRS-45A

Hi

Somewhere in / on the beast there should be a magnetic field adjustment. You 
play with it (within reason) to get the thing “on frequency”. The real question 
being: do you care that it’s 1x10^-13 off frequency? In most cases, the answer 
is no and you move on. 

Yes, if you are going to do the adjustment thing, figure out a fixed location 
before you go to all the trouble. Also let it sit for a bit to “settle in” to 
the local mag field. I would not play with any adjustments for a week. 

Bob

 On Dec 9, 2014, at 6:22 PM, Bob Stewart b...@evoria.net wrote:
 
 Subject changed, as I inadvertently stole Dan's thread.
 
 Hi Bob Camp,
 You wrote: Looks perfectly normal to me. Your Cs is sensitive to magnetic 
 field. Have you “zeroed” it out? No of course not, nobody does. (almost 
 nobody …). 
 
 What does it mean to zero out the magnetic field for a Cs?  Sounds like I 
 need to align something to local magnetic north.  What?  I suspect that 
 figuring out a way to mount it to the wall (no rack system here) is going to 
 be my next priority.  It can't safely live on my bench or the floor with all 
 those perforations in the case covers.
 
 The people at Symmetricom indicated I should be able to download the monitor 
 software, but the registration process seems to take some time.  Hopefully 
 that gets resolved soon.
 Having this thing hooked up just for this short time has pointed out some 
 problems that I couldn't see without a reference that I trusted.
 
 Bob
 
 
 
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Re: [time-nuts] Linear voltage regulator hints...

Hi

 On Dec 9, 2014, at 6:57 PM, Richard (Rick) Karlquist rich...@karlquist.com 
 wrote:
 
 
 
 On 12/9/2014 3:02 PM, Bob Camp wrote:
 Here's an overnight ADEV plot against the new Cs of where we are in the 
 project.  Red is ADEV.  Green is the TIC.  Blue is the output of the GPSDO to 
 Channel A and the Cs to Channel B of my 5335A measuring TI, using the 1PPS 
 from my GPSDO to trigger the external gate.  I see that the Cs phase has 
 drifted down slightly vs my GPSDOe.  I wonder if this is an indication of a 
 calibration problem with the Cs or some subtle issue on my board?
 
 Looks perfectly normal to me. Your Cs is sensitive to magnetic field. Have 
 you “zeroed” it out? No of course not, nobody does. (almost nobody …).
 
 Bob
 
 This reminds me of the great CBT demagnetizer debate at HP.
 Even Len Cutler didn't think this was necessary, at least
 in the 5071, and possibly the 5061.  When Len says something
 is overkill, you can be sure of it.  Anyway, we still had
 to support a CBT demagnetizer for customers who wanted it.
 The customer (with money to spend) is always right.  The
 5071 measures the C-field with a Zeeman line measurement
 and adjusts it if necessary.

… and it seems to do *something* roughly every 24 hours …. That might include 
“react to the heating turning off in the building ..”.

Bob

 
 Rick Karlquist N6RK
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Re: [time-nuts] PRS-45A

2014-12-09 Thread Magnus Danielson

Hi,

This most likely has the C-field servo:ed. It is most probably best to
keep it in auto-mode.

Cheers,
Magnus

On 12/10/2014 01:11 AM, Bob Camp wrote:

Somewhere in / on the beast there should be a magnetic field adjustment. You
play with it (within reason) to get the thing “on frequency”. The real question
being: do you care that it’s 1x10^-13 off frequency? In most cases, the answer
is no and you move on.

Yes, if you are going to do the adjustment thing, figure out a fixed location
before you go to all the trouble. Also let it sit for a bit to “settle in” to
the local mag field. I would not play with any adjustments for a week.

Bob

On Dec 9, 2014, at 6:22 PM, Bob Stewart b...@evoria.net wrote:

Subject changed, as I inadvertently stole Dan's thread.

Hi Bob Camp,
You wrote: Looks perfectly normal to me. Your Cs is sensitive to magnetic field.
Have you “zeroed” it out? No of course not, nobody does. (almost nobody …).

What does it mean to zero out the magnetic field for a Cs? Sounds like I
need to align something to local magnetic north. What? I suspect that figuring out a
way to mount it to the wall (no rack system here) is going to be my next priority. It
can't safely live on my bench or the floor with all those perforations in the case covers.

The people at Symmetricom indicated I should be able to download the monitor
software, but the registration process seems to take some time. Hopefully that
gets resolved soon.
Having this thing hooked up just for this short time has pointed out some
problems that I couldn't see without a reference that I trusted.

Bob

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[time-nuts] Another GPSDO

I think I have finally graduated to Junior Time Nut. I now have three
GPSDO's. The trusty Z3801A I have had for years. The LTE-Lite is
recent. The Lucent 2-box unit just arrived today. Maybe I'll finally
know what time it is :-)

This Lucent is much smaller than I thought it would be. Slightly wider
than the Z3801A, but much shorter. Smaller is good.

Now I need to find a 24 VDC supply and an empty space to put the new GPSDO.


Joe Gray
W5JG
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Re: [time-nuts] PRS-45A

Thanks Bob,
I got the Monitor software just now.  The unit has 92,902 hours on it, which is 
a bit over 10.6 years.  I need to head out the door, but here are a few values 
from the screen.  I'll figure out how to get a status log out of it later.
Clock Servo:Ramsey Error 0 mvRabi Error -1 mvOCXO CV 3151 mvDeviation 194
Zeeman Servo:Ramsey Error 0 mvRabi eError -28 mvC Field CV -32 mv
Cesium Oven 4.80 VEM Voltage 8.00 VIon Pump 23 uAC-Field 19.10 mAIonizer 0.87 
VMass Spec 14.10 V
The monitor checks every 10 seconds, so these are a bit dynamic.  So, is this 
in good health, or do I need to worry?
Bob

  From: Bob Camp kb...@n1k.org
 To: Bob Stewart b...@evoria.net; Discussion of precise time and frequency 
measurement time-nuts@febo.com 
 Sent: Tuesday, December 9, 2014 6:11 PM
 Subject: Re: [time-nuts] PRS-45A
   
Hi

Somewhere in / on the beast there should be a magnetic field adjustment. You 
play with it (within reason) to get the thing “on frequency”. The real question 
being: do you care that it’s 1x10^-13 off frequency? In most cases, the answer 
is no and you move on. 

Yes, if you are going to do the adjustment thing, figure out a fixed location 
before you go to all the trouble. Also let it sit for a bit to “settle in” to 
the local mag field. I would not play with any adjustments for a week. 

Bob



 On Dec 9, 2014, at 6:22 PM, Bob Stewart b...@evoria.net wrote:
 
 Subject changed, as I inadvertently stole Dan's thread.
 
 Hi Bob Camp,
 You wrote: Looks perfectly normal to me. Your Cs is sensitive to magnetic 
 field. Have you “zeroed” it out? No of course not, nobody does. (almost 
 nobody …). 
 
 What does it mean to zero out the magnetic field for a Cs?  Sounds like I 
 need to align something to local magnetic north.  What?  I suspect that 
 figuring out a way to mount it to the wall (no rack system here) is going to 
 be my next priority.  It can't safely live on my bench or the floor with all 
 those perforations in the case covers.
 
 The people at Symmetricom indicated I should be able to download the monitor 
 software, but the registration process seems to take some time.  Hopefully 
 that gets resolved soon.
 Having this thing hooked up just for this short time has pointed out some 
 problems that I couldn't see without a reference that I trusted.
 
 Bob
 
 
 
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Re: [time-nuts] Another GPSDO

Joe since the lucents are most likely NOS you will need to let it cook in
30 days. I now have two units and they do match up well to the 3801. But
they did need to age. Just a heads up.
It is nice to see them line up pretty well.
Regards
Paul
WB8TSL

On Tue, Dec 9, 2014 at 7:37 PM, Joseph Gray jg...@zianet.com wrote:

 I think I have finally graduated to Junior Time Nut. I now have three
 GPSDO's. The trusty Z3801A I have had for years. The LTE-Lite is
 recent. The Lucent 2-box unit just arrived today. Maybe I'll finally
 know what time it is :-)

 This Lucent is much smaller than I thought it would be. Slightly wider
 than the Z3801A, but much shorter. Smaller is good.

 Now I need to find a 24 VDC supply and an empty space to put the new GPSDO.


 Joe Gray
 W5JG
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Re: [time-nuts] PRS-45A

Hi

 On Dec 9, 2014, at 7:45 PM, Bob Stewart b...@evoria.net wrote:
 
 Thanks Bob,
 
 I got the Monitor software just now.  The unit has 92,902 hours on it, which 
 is a bit over 10.6 years.

So as usual I owe PHK another beer. He guessed that one right. 

  I need to head out the door, but here are a few values from the screen.  
 I'll figure out how to get a status log out of it later.
 
 Clock Servo:
 Ramsey Error 0 mv

servo looks fine

 Rabi Error -1 mv
 OCXO CV 3151 mv

OCXO tune at 3.1V which would be fine on a 5V tune part. 

 Deviation 194
 
 Zeeman Servo:
 Ramsey Error 0 mv
 Rabi eError -28 mv
 C Field CV -32 mv
 
 Cesium Oven 4.80 V
 EM Voltage 8.00 V
 Ion Pump 23 uA

don’t know what this model normally reads. Others may have some input here. 

 C-Field 19.10 mA
 Ionizer 0.87 V
 Mass Spec 14.10 V
 
 The monitor checks every 10 seconds, so these are a bit dynamic.  So, is this 
 in good health, or do I need to worry?

The simple fact that it’s up and running  in 16 minutes is a major “one up” 
compared to  90% of the under $4K Cs’s on eBay. Best bet is you will get a few 
years out of it. One approach is to keep it turned off most of the time. 

Bob

 
 Bob
 
 From: Bob Camp kb...@n1k.org
 To: Bob Stewart b...@evoria.net; Discussion of precise time and frequency 
 measurement time-nuts@febo.com 
 Sent: Tuesday, December 9, 2014 6:11 PM
 Subject: Re: [time-nuts] PRS-45A
 
 Hi
 
 Somewhere in / on the beast there should be a magnetic field adjustment. You 
 play with it (within reason) to get the thing “on frequency”. The real 
 question being: do you care that it’s 1x10^-13 off frequency? In most cases, 
 the answer is no and you move on. 
 
 Yes, if you are going to do the adjustment thing, figure out a fixed location 
 before you go to all the trouble. Also let it sit for a bit to “settle in” to 
 the local mag field. I would not play with any adjustments for a week. 
 
 Bob
 
 
 
  On Dec 9, 2014, at 6:22 PM, Bob Stewart b...@evoria.net wrote:
  
  Subject changed, as I inadvertently stole Dan's thread.
  
  Hi Bob Camp,
  You wrote: Looks perfectly normal to me. Your Cs is sensitive to magnetic 
  field. Have you “zeroed” it out? No of course not, nobody does. (almost 
  nobody …). 
  
  What does it mean to zero out the magnetic field for a Cs?  Sounds like I 
  need to align something to local magnetic north.  What?  I suspect that 
  figuring out a way to mount it to the wall (no rack system here) is going 
  to be my next priority.  It can't safely live on my bench or the floor with 
  all those perforations in the case covers.
  
  The people at Symmetricom indicated I should be able to download the 
  monitor software, but the registration process seems to take some time.  
  Hopefully that gets resolved soon.
  Having this thing hooked up just for this short time has pointed out some 
  problems that I couldn't see without a reference that I trusted.
  
  Bob
 
  
  
  
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[time-nuts] Nortel Trimble GPSDO

Did I miss the discussion, or hasn't anyone mentioned this unit on
ebay? With a timing antenna, it looks like a good deal.

Nortel Trimble NTBW50AA GPSTM 10MHz Oscillator GPSDO + Antenna Acc. Thunderbolt
Item 301424570443


Joe Gray
W5JG
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Re: [time-nuts] Another GPSDO

Paul,

Thanks for the info. I have been following most of the discussion on
these units. I have even saved several posts, so that I could
reference them once I had one of these.

I do plan on letting it cook for quite some time. I will certainly
check it via serial port to make sure everything is OK before the 30
day warranty is up.

I just dug up some SMA to BNC pigtails I still need to find a 24 VDC
supply (I think I have one), make a power cable, move some things to
make a space for this thing, etc.

Joe Gray
W5JG


On Tue, Dec 9, 2014 at 6:22 PM, paul swed paulsw...@gmail.com wrote:
 Joe since the lucents are most likely NOS you will need to let it cook in
 30 days. I now have two units and they do match up well to the 3801. But
 they did need to age. Just a heads up.
 It is nice to see them line up pretty well.
 Regards
 Paul
 WB8TSL

 On Tue, Dec 9, 2014 at 7:37 PM, Joseph Gray jg...@zianet.com wrote:

 I think I have finally graduated to Junior Time Nut. I now have three
 GPSDO's. The trusty Z3801A I have had for years. The LTE-Lite is
 recent. The Lucent 2-box unit just arrived today. Maybe I'll finally
 know what time it is :-)

 This Lucent is much smaller than I thought it would be. Slightly wider
 than the Z3801A, but much shorter. Smaller is good.

 Now I need to find a 24 VDC supply and an empty space to put the new GPSDO.


 Joe Gray
 W5JG
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Re: [time-nuts] Linear voltage regulator hints...

2014-12-09 Thread Vasco Soares


Hi All,

Take a look on the low noise 1.5A LDO regulator LT1963 and 500 mA LT1763. 
Voltage regulation depend on how good is the circuit behaviour with respect 
to Noise, PSRR, Line regulation and Load regulation. For instance some LT 
regulators like LT1117, 1085 and 1086 have  1% of Line and Load regulation 
but have worst noise specs than LT1963, LT1763, MCP1825, MCP1826.


Regards,
Vasco Soares



- Original Message - 
From: Dan Kemppainen d...@irtelemetrics.com

To: time-nuts@febo.com
Sent: Tuesday, December 09, 2014 4:57 PM
Subject: Re: [time-nuts] Linear voltage regulator hints...



Hi All,

Thanks for the responses. I had a feeling the answer wouldn't be good, but 
was hoping someone would have a suggestion. There are currently a bunch of 
regulators in the 'system'. If there were some really good regulator out 
there, the shotgun approach would apply...


Of course it is difficult to provide a good reference and pass transistor 
on the same die, but it was worth asking.



Bert,

The thought of temp control of the regulators crossed my mind. Not 
planning on going there unless I need to. But it was a thought, maybe if 
all else fails...



Bob,

 There are more modern parts with lower close in noise. Linear
Technology has a number of them. Your filter caps take out the broadband 
stuff, close in is all that really matters.



Got any hints on which ones? Maybe a nice quiet regulator can be 
'disciplined' with a better reference.


Thanks,
Dan

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Re: [time-nuts] Linear voltage regulator hints...

2014-12-09 Thread Alex Pummer

about linear regulators: 
http://www.analog.com/static/imported-files/tutorials/MT-087.pdf

73
Alex


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[time-nuts] up converting 10MHz to 20MHz

2014-12-09 Thread lincoln

Hello,
I'm having a dumb idea, I have an MCU that uses a 20 MHz VC-TCXO. The 
micro, among other things, runs a loop and correct the oscillator by using a 
1pps from a gps. I have a 10 MHz mv200 that I would like to try to use. I've 
got the control voltage handled but i will need to multiply its output up to 20 
MHz. What would be the most kosher way do do this? I was having a look at 
Cypress's CY22381 because I have the programmer but the chips are not widely 
distributed. But nether are mv200's Silicon labs also make all kinds of clock 
chips as well.

What do you guys think? What would be the best way to scale up by X 2? lowish 
phase noise / jitter is important, low power is not. 

Thank you,
Lincoln
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Re: [time-nuts] Beaglebone NTP server

2014-12-09 Thread Frister

Hi David,
Yes, You mean the hourly dips? That is caused by the the VLF receive
software that
is running on the same PI. It makes hourly recordings of DC to 24 Khz
with a USB soundcard. The CPU is running at max capacity most of the
time.

Perhaps it is now time for a dedicated PI, that only has the task of
playing Stratum One.

If anyone is interested:
https://pivlf.wordpress.com/


73, Frits W1FVB



On 12/9/14, David J Taylor david-tay...@blueyonder.co.uk wrote:
 Thanks for pointing this out David,
 Compiling an new kernel was holding me back. I followed your instructions
 and
 everything works beautiful. The PI that is running the PPS timekeeping with

 NTP
 is serving as a VLF receiver as well. Taxing the poor CPU, but with
 kernel PPS support
 the NTP daemon has become way happier! (see attachment)

 73, Frits W1FVB
 ==

 Oh, yes!  That's much better, Frits!  Delighted to have helped!

 (Although it now shows up an hourly periodicity - any idea what might be
 causing that?)

 73,
 David GM8ARV
 --
 SatSignal Software - Quality software written to your requirements
 Web: http://www.satsignal.eu
 Email: david-tay...@blueyonder.co.uk

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-- 
vbradio.wordpress.com
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Re: [time-nuts] Linear voltage regulator hints...

2014-12-09 Thread Didier Juges

That seems to be generally true, but as always there are outliers.

The LT1034 bandgap reference has 6uVp-p of low frequency noise at 2.5V,
which compares favorably with the 20uVp-p of noise at 6.95V of the LM399.
Of course, for many applications, you will have to amplify the 2V reference
to what you need, which will bring up additional noise while the 6.95V of
the LM399 may be closer to what you need.

Of course, the tempco of the LT1034 does not even get close to that of the
LM399, but it is not thermostatically regulated and draws considerably
lower power. You can't have everything :)

I observe that the LT1034 has two outputs, the high quality 2.5V and a
lower quality 7V.

http://www.linear.com/parametric/Shunt_Voltage_References

Didier KO4BB


On Tue, Dec 9, 2014 at 5:51 PM, Richard (Rick) Karlquist 
rich...@karlquist.com wrote:

 On 12/9/2014 1:30 PM, ed breya wrote:

  buried zener for lowest noise - this eliminates all the low voltage
 references and three-terminal etc regulators that use band-gap
 references. The down side is that the good kind of reference ICs will
 need a higher (like 10V and up) operating voltage than may be available,
 so that complicates it.


 Great post, Ed.  I might add that my understanding of band gap
 regulators is that they rely on amplifying a small DC difference
 in voltage between two transistors.  This also amplifies the SUM
 of the noise of the respective inputs, which jacks up the noise to
 much more than a good zener.  Because of physics, no band gap
 reference will ever be low noise.

 Rick Karlquist N6RK

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Re: [time-nuts] Did a member of time-nuts buy this?

2014-12-09 Thread Angus

On Sun, 7 Dec 2014 19:34:02 -0500, you wrote:

On Dec 7, 2014, at 7:15 PM, Angus not.ag...@btinternet.com wrote:

On Sat, 6 Dec 2014 11:47:10 -0500, you wrote:

I am looking forward to long term data on the Lucent unit. GPSDO's are
getting closer and closer to Cesium. Having worked for 18 month on two
GPSDO
projects we find that the limiting factors are the Cesium Standards.
Working
presently on a Cesium GPSDO. Short term OCXO, medium Rb and long term
Cesium. With Cesium may be able to use 14 day filter. Will find out. If we
do
not see an improvement we will most likely retire our Cesium units.
Bert Kehren

Hi Bert,

Out of curiosity, what Rb are you using, and how does it respond to
air pressure changes?

Properly identifying / measuring pressure induced drift is not as easy as one
might think. The tweak and see approach seems to be the best bet. Hmm I
wonder who originally suggested that . oh, yea it was Angus.

That depends a lot on the Rb. With a temperature controlled LPRO it's
easy - just logging air pressure against frequency get you most of the
way. With the LPRO's I've tested that gets the variation with pressure
to down under +/- 2E-13, some well under, over 60mbars pressure range.
I have one that had almost no residual left after correction, though
the others had a little. Getting past that is harder.

There is also some time lag - looked like something around 3/4Hr, but
with GPS as my reference and air pressure moving so slowly, it was
hard to tell.

Of course the lower the numbers, the more error sources start to
become significant, but since the LPRO's I've test are all around
8E-14/mbar, it's not exactly hard to measure. It is time consuming
though, since it normally took 3-6 weeks to do each test, depending on
the weather.

Interestingly, the both the FE5680A's I tested had similar responses
to pressure variations - very variable compared to the LPRO's, so
impossible to correct simply and well. Seeing the comments about the
temp correction in FE5680A's causing problems, I did wonder if that
might be part of the problem, but have not got around to testing that
yet.

Angus.

Bob

Combining temp control, air pressure compensation and drift
compensation can give very good results with the right Rb.

Angus.

In a message dated 12/6/2014 10:46:57 A.M. Eastern Standard Time,
kb...@n1k.org writes:

Hi
On Dec 6, 2014, at 10:35 AM, Magnus Danielson
mag...@rubidium.dyndns.org wrote:

Bob,

On 12/06/2014 04:16 PM, Bob Camp wrote:
Hi

On Dec 6, 2014, at 9:54 AM, Dr. David Kirkby (Kirkby Microwave Ltd)
drkir...@kirkbymicrowave.co.uk wrote:

I see this cesium reference on eBay, where apparently someone returned
it due to the fact it had a bad tube.

http://www.ebay.com/itm/HP-Agilent-5061A-Cesium-Beam-Frequency-Standard-FOR-PARTS-REPAIR-/141483787108

I'm wondering if it was someone on this list. It is likely to be
practical to replace the tube?

New tubes for Cs standards are in the $20K range. Getting a modern one
re-tubed with a high performance tube is $32K.

The stock of ?new old stock? tubes is long gone. About the only tubes
you see are pulls from used gear. The question with them (as with any Cs)
is just how many years (or months) is left on the tube. You physically
move
Cs from one end of the tube to the other when you operate the device. One
you have exhausted the pre-loaded stock, the tube is dead. It?s also coated

all over the inside with surplus Cs. Since signal to noise ratio is very
important, the drop in Cs at end of life and crud on the inside leads to
degradation in the performance towards the end of the tube life. Even if
the
tube works, it may (or may not) be useful in a given application.

For many applications, GPSDO?s are the more useful device. Their
performance rivals that of most of the older Cs standards. They are way
cheaper,
and they don?t wear out. Indeed, if you have a 5071A with a high
performance tube in it, a GPSDO is not going to match it?s performance.
I?ve
replaced two tubes in one of those, so they are correct when they talk
about the
projected life of the tube.

The other subtle issue with Cs standards is shipping. If you are going
to do it ?right? it?s a major pain. Sending one back for re-tube does
require you to do all the formal shipping nuttiness. That may or may not
be an
issue on the surplus market
.

Well, there is one use-case for a cesium, which is the validation of GPS
receivers. Rubidiums do help to some degree. Comparing two GPS clocks with
their highly systematic sources, so you can't get useful differences that
way for the stability of the produced signal.

Unless you are making a GPS receiver from scratch (which you might be),
there is a certain ?trust factor? that comes into using a GPS for timing.
Since you can?t play with the firmware, you trust that the guy

Re: [time-nuts] up converting 10MHz to 20MHz

2014-12-09 Thread Dave M


lincoln wrote:

Hello,
I'm having a dumb idea, I have an MCU that uses a 20 MHz VC-TCXO. The
micro, among other things, runs a loop and correct the oscillator by
using a 1pps from a gps. I have a 10 MHz mv200 that I would like to
try to use. I've got the control voltage handled but i will need to
multiply its output up to 20 MHz. What would be the most kosher way
do do this? I was having a look at Cypress's CY22381 because I have
the programmer but the chips are not widely distributed. But nether
are mv200's Silicon labs also make all kinds of clock chips as well.

What do you guys think? What would be the best way to scale up by X
2? lowish phase noise / jitter is important, low power is not.

Thank you,
Lincoln


A couple ways to go on a doubler.
Minicircuits makes a line of frequency doublers, such as the SK-2, RK-2, 
RK-3, etc.  You could also roll your own using a balun and a diode bridge 
(http://www.techlib.com/files/diodedbl.pdf).  Insertion loss is pretty hefty 
in both solutions, so you''ll need to follow with a 10-15db amp.


Dave M 



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Re: [time-nuts] Nortel Trimble GPSDO

Time-nuts miss an ebay opportunity? Can't imagine that.
I suspect we are all very happy with the brand new lucents.
I was lucky that a fellow Time-nut clued me in. I had seen the posts and
ignored them as Just another GPSDO.
Regards
Paul
WB8TSL

On Tue, Dec 9, 2014 at 8:53 PM, Joseph Gray jg...@zianet.com wrote:

 Did I miss the discussion, or hasn't anyone mentioned this unit on
 ebay? With a timing antenna, it looks like a good deal.

 Nortel Trimble NTBW50AA GPSTM 10MHz Oscillator GPSDO + Antenna Acc.
 Thunderbolt
 Item 301424570443


 Joe Gray
 W5JG
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Re: [time-nuts] Another GPSDO

Yes its pretty easy to get going especially with the details and help of
fellow Time-nuts. Good luck.

On Tue, Dec 9, 2014 at 9:13 PM, Joseph Gray jg...@zianet.com wrote:

 Paul,

 Thanks for the info. I have been following most of the discussion on
 these units. I have even saved several posts, so that I could
 reference them once I had one of these.

 I do plan on letting it cook for quite some time. I will certainly
 check it via serial port to make sure everything is OK before the 30
 day warranty is up.

 I just dug up some SMA to BNC pigtails I still need to find a 24 VDC
 supply (I think I have one), make a power cable, move some things to
 make a space for this thing, etc.

 Joe Gray
 W5JG


 On Tue, Dec 9, 2014 at 6:22 PM, paul swed paulsw...@gmail.com wrote:
  Joe since the lucents are most likely NOS you will need to let it cook in
  30 days. I now have two units and they do match up well to the 3801. But
  they did need to age. Just a heads up.
  It is nice to see them line up pretty well.
  Regards
  Paul
  WB8TSL
 
  On Tue, Dec 9, 2014 at 7:37 PM, Joseph Gray jg...@zianet.com wrote:
 
  I think I have finally graduated to Junior Time Nut. I now have three
  GPSDO's. The trusty Z3801A I have had for years. The LTE-Lite is
  recent. The Lucent 2-box unit just arrived today. Maybe I'll finally
  know what time it is :-)
 
  This Lucent is much smaller than I thought it would be. Slightly wider
  than the Z3801A, but much shorter. Smaller is good.
 
  Now I need to find a 24 VDC supply and an empty space to put the new
 GPSDO.
 
 
  Joe Gray
  W5JG
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Re: [time-nuts] Nortel Trimble GPSDO