Re: [time-nuts] E1938 oven design

[Bob kb8tq]

Hi

I certainly saw the “positive gain at this setting” going to “negative gain at 
that setting” result on a lot 
of OCXO designs. I never had the patience (or a stable enough system) to get 
into the millions 
or even 100K’s on a single oven.  As a practical result, a gain of -500 is not 
really any better or worse
than a gain of +500. It *can* be a bit confusing to set up though ….

Bob
 
> On Jun 11, 2017, at 1:43 PM, Richard (Rick) Karlquist  
> wrote:
> 
> 
> 
> On 6/11/2017 8:59 AM, Attila Kinali wrote:
> 
>>> The exact insulation is relatively unimportant.
>>> We even tried still air using a knife edge
>>> cradle.  Didn't make much difference.
> 
> 
>> What is a knife edge cradle?
> 
> We wanted to test still air as insulation.
> We couldn't just replace the insulation with
> "nothing".  There had to be some kind of mechanical
> support to keep the oven mass suspended inside the
> outer case.  Our ME built a skeleton framework
> made of plastic to support it.  In order to minimize
> conduction thru the plastic, he designed in knife
> edges where the plastic came into contact with the
> oven mass.
> 
> 
>> One big question remains: How did you set the ratio
>> between face and rim heater? Was it determined at design
>> time and then just set the same for all units or was
>> it part of the production test?
> 
> During proof of concept phase in R, I peaked up the
> thermal gain on each unit by trial and error.  I could
> usually get a run with positive thermal gain, then
> increment the ratio, and get a run with negative
> thermal gain.  I could then interpolate to get the
> ratio that should give "infinite" gain.  Maybe one
> or two more runs after that would get me to where
> the gain passed through infinity at some ambient
> temperature, and was well into the millions over the
> whole range.  At extremely high thermal gain, the
> gain is not constant over ambient temperature.
> 
> I collected data on a number of units and then used
> the average ratio as the production setting.  I
> checked production units from time to time and they
> typically ran well in the 100's of thousands for gain.
> 
> This compromise was workable because we individually
> programmed the oven set point to the exact turnover
> temperature.  This is a lot easier because it doesn't
> require environmental chamber runs.  The E1983A software that
> I "leaked" to the time-nuts community I believe has a
> command that can be used to search for the turnover.
> 
> 
> Rick N6RK
> 
>>  Attila Kinali
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Re: [time-nuts] E1938 oven design

[Richard (Rick) Karlquist]

On 6/11/2017 8:59 AM, Attila Kinali wrote:


The exact insulation is relatively unimportant.
We even tried still air using a knife edge
cradle.  Didn't make much difference.




What is a knife edge cradle?


We wanted to test still air as insulation.
We couldn't just replace the insulation with
"nothing".  There had to be some kind of mechanical
support to keep the oven mass suspended inside the
outer case.  Our ME built a skeleton framework
made of plastic to support it.  In order to minimize
conduction thru the plastic, he designed in knife
edges where the plastic came into contact with the
oven mass.



One big question remains: How did you set the ratio
between face and rim heater? Was it determined at design
time and then just set the same for all units or was
it part of the production test?


During proof of concept phase in R, I peaked up the
thermal gain on each unit by trial and error.  I could
usually get a run with positive thermal gain, then
increment the ratio, and get a run with negative
thermal gain.  I could then interpolate to get the
ratio that should give "infinite" gain.  Maybe one
or two more runs after that would get me to where
the gain passed through infinity at some ambient
temperature, and was well into the millions over the
whole range.  At extremely high thermal gain, the
gain is not constant over ambient temperature.

I collected data on a number of units and then used
the average ratio as the production setting.  I
checked production units from time to time and they
typically ran well in the 100's of thousands for gain.

This compromise was workable because we individually
programmed the oven set point to the exact turnover
temperature.  This is a lot easier because it doesn't
require environmental chamber runs.  The E1983A software that
I "leaked" to the time-nuts community I believe has a
command that can be used to search for the turnover.


Rick N6RK



Attila Kinali


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Re: [time-nuts] E1938 oven design

[Attila Kinali]

On Thu, 8 Jun 2017 16:17:20 -0700
"Richard (Rick) Karlquist"  wrote:

> We were stuck under 1,000 for a long time
> using only face heaters.  I still remember the
> day that I rigged up the first crude rim header
> by winding a piece of magnet wire around the rim
> and holding it in place with 5 min epoxy.  I
> didn't know what else to try.  This seemed like
> a Hail Mary play at the time, until I
> measured the gain.  We instantly went to gains
> above 20,000.  It seemed high at the time but
> it was only the beginning.
> 
> The exact insulation is relatively unimportant.
> We even tried still air using a knife edge
> cradle.  Didn't make much difference.

What is a knife edge cradle?

One big question remains: How did you set the ratio
between face and rim heater? Was it determined at design
time and then just set the same for all units or was
it part of the production test?

Attila Kinali
-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] E1938 oven design

[Richard (Rick) Karlquist]

Yes, that's right.  The copper oven mass
has two pieces:  a main piece and a lid.
The main piece has a wall around the outside
into which the cover fits, using an O-ring.
In the center, there is a cylindrical cavity
into which the crystal mounts.  It is like
a 10811 crystal, except the height is reduced.
In retrospect, there is no reason why the
10811 crystal shouldn't have been that size.
It is potted into the cavity, therefore, it
doesn't use the famous flat head 4-40 screw
welded to the can as in the 10811.  Thermistors
are potted into holes drilled in the cavity
wall.  The lid has screws that screw into
the cavity wall.

The main piece holds a circular PC board
containing the bridge oscillator circuit.
It has a big hole in the middle for the
crystal cavity.  The production people
immediately named it the "donut board."
And the finished oscillator is the "hockey
puck".

Summarizing, the crystal is very well thermally
connected to the copper oven mass.

There are 3 flex circuit heaters.  One for
the lid, one for the other face of the
main piece, and one that goes around the
outside.  The two face heaters are operated
together as one heater.  The ratio of heat
to the faces vs the outside rim is adjusted
for maximum thermal gain.  The rim heater is
the difference between under 1,000 gain and
over 1,000,000 gain.

We were stuck under 1,000 for a long time
using only face heaters.  I still remember the
day that I rigged up the first crude rim header
by winding a piece of magnet wire around the rim
and holding it in place with 5 min epoxy.  I
didn't know what else to try.  This seemed like
a Hail Mary play at the time, until I
measured the gain.  We instantly went to gains
above 20,000.  It seemed high at the time but
it was only the beginning.

The exact insulation is relatively unimportant.
We even tried still air using a knife edge
cradle.  Didn't make much difference.

Rick N6RK

On 6/8/2017 1:27 PM, Attila Kinali wrote:

On Wed, 7 Jun 2017 14:21:52 -0700
"Richard (Rick) Karlquist"  wrote:



The crystal case is well connected to the oven mass and gets
heated by conduction.  I don't think radiation is a player.


Do I interpret the papers correctly, that the oven mass is
a closed can, with the crystal holder "molded" into it?
Then wrapped around it are the face and the rim heaters,
and outside those comes the insulation and the outer can?

Attila Kinali


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[time-nuts] E1938 oven design (was: Poor man's oven)

[Attila Kinali]

On Wed, 7 Jun 2017 14:21:52 -0700
"Richard (Rick) Karlquist"  wrote:


> The crystal case is well connected to the oven mass and gets
> heated by conduction.  I don't think radiation is a player.

Do I interpret the papers correctly, that the oven mass is
a closed can, with the crystal holder "molded" into it?
Then wrapped around it are the face and the rim heaters,
and outside those comes the insulation and the outer can?

Attila Kinali

-- 
You know, the very powerful and the very stupid have one thing in common.
They don't alters their views to fit the facts, they alter the facts to
fit the views, which can be uncomfortable if you happen to be one of the
facts that needs altering.  -- The Doctor
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Re: [time-nuts] E1938 info regarding LEDs, push button switch and EFC voltage notation

[Azelio Boriani]

You can find schematics and various info here:




On Thu, May 11, 2017 at 3:47 PM, James Robbins  wrote:
> 1.  I have just acquired an E1938 and powered it up.  It seems to work.   I
> see that it has 4 blinking board LEDs (green, red, yellow, yellow) and a
> pushbutton switch at the end of the board opposite to the DB25 connector.
> Can anyone point me to either the schematic for the board or what these LEDs
> and pushbutton show or do?
>
>
>
> 2.  Also, there is an "EFC" voltage ("3.69v") marked in magic marker on top
> of the can.  Can anyone point me to where I can learn what, if anything,
> this voltage notation should be used for?
>
>
>
> Many thanks.
>
>
>
> Jim Robbins
>
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[time-nuts] E1938 info regarding LEDs, push button switch and EFC voltage notation

[James Robbins]

1.  I have just acquired an E1938 and powered it up.  It seems to work.   I
see that it has 4 blinking board LEDs (green, red, yellow, yellow) and a
pushbutton switch at the end of the board opposite to the DB25 connector.
Can anyone point me to either the schematic for the board or what these LEDs
and pushbutton show or do?  

 

2.  Also, there is an "EFC" voltage ("3.69v") marked in magic marker on top
of the can.  Can anyone point me to where I can learn what, if anything,
this voltage notation should be used for?

 

Many thanks.

 

Jim Robbins

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Re: [time-nuts] E1938 PIC hex files?

[Richard H McCorkle]

Hi Dan,

If the 1938 was purchased through Fluke1 he is usually very good
about replacing bad items he sells to Time-Nuts. You might want
to contact him about a replacement unit or perhaps getting a
pre-programmed PIC from a different unit to try.

Richard


 I am beginning to think that the PIC in my Chinese Ebay 1938 is dead or
 at least injured.  Does anyone have the hex files for this one?  Blank
 PIC16C74As can be had and it may be worth my trying to program a new
 one.  Nothing else seems to make it work and as the PIC seems to be
 asleep, I'm not sure that attempting to talk to it with the serial
 program is going to help me much, but I will try.

 The part number is: E1938-80002


 Dan

 ac6ao



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Re: [time-nuts] E1938 PIC hex files?

[Robert Atkinson]

Pics have pretty good copy protection. I'd be surprised if Agilent haven't 
protected the pic in the E1938. Many pics (AFIK thisincludes the 'C74) scramble 
the data on reading a copy protected chip. This allows the verification of a 
chip without revealing the code. A known good chip is a starting point. 
fortuntly HP socketed the PLCC pic. Know you need a time nut with a good E1938, 
a PicStart Plus ( or similar programmer) and a PLCC adaptor. I have the latter 
two but no E1938.

Robert G8RPI.

--- On Sat, 13/6/09, Richard H McCorkle mccor...@ptialaska.net wrote:

 From: Richard H McCorkle mccor...@ptialaska.net
 Subject: Re: [time-nuts] E1938 PIC hex files?
 To: dan...@verizon.net, Discussion of precise time and frequency 
 measurement time-nuts@febo.com
 Date: Saturday, 13 June, 2009, 7:16 AM
 Hi Dan,
 
 If the 1938 was purchased through Fluke1 he is usually very
 good
 about replacing bad items he sells to Time-Nuts. You might
 want
 to contact him about a replacement unit or perhaps getting
 a
 pre-programmed PIC from a different unit to try.
 
 Richard
 
 
  I am beginning to think that the PIC in my Chinese
 Ebay 1938 is dead or
  at least injured.  Does anyone have the hex files
 for this one?  Blank
  PIC16C74As can be had and it may be worth my trying to
 program a new
  one.  Nothing else seems to make it work and as
 the PIC seems to be
  asleep, I'm not sure that attempting to talk to it
 with the serial
  program is going to help me much, but I will try.
 
  The part number is: E1938-80002
 
 
  Dan
 
  ac6ao
 
 
 
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[time-nuts] E1938 PIC hex files?

[Dan Rae]

I am beginning to think that the PIC in my Chinese Ebay 1938 is dead or 
at least injured.  Does anyone have the hex files for this one?  Blank 
PIC16C74As can be had and it may be worth my trying to program a new 
one.  Nothing else seems to make it work and as the PIC seems to be 
asleep, I'm not sure that attempting to talk to it with the serial 
program is going to help me much, but I will try.


The part number is: E1938-80002


Dan

ac6ao



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[time-nuts] E1938 question

[Dan Rae]

I have one of the Chinese E1938 modules I bought about a month ago.  I 
just tried it out on the bench, and have not had much luck with it.  The 
5 Volt supply never goes above 50 mA or so, none of the heaters seem to 
be powered looking at the hockey puck D-sub connector pins.  The four 
leds up by the PIC (?) seem to flash once on switch on and then pulse 
about once a second.  The other led which seems to be on the 5 V supply 
is on.  It does oscillate, but very low since it never warms up.


Is there any point in my trying to go any further with this?  It seems 
pretty dead to me, the PIC maybe?   :^(


Nice museum piece perhaps, but a bit expensive for only that...

Dan

ac6ao




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Re: [time-nuts] E1938 question

[Bruce Griffiths]

Dan Rae wrote:
 I have one of the Chinese E1938 modules I bought about a month ago. 
 I just tried it out on the bench, and have not had much luck with it. 
 The 5 Volt supply never goes above 50 mA or so, none of the heaters
 seem to be powered looking at the hockey puck D-sub connector pins. 
 The four leds up by the PIC (?) seem to flash once on switch on and
 then pulse about once a second.  The other led which seems to be on
 the 5 V supply is on.  It does oscillate, but very low since it never
 warms up.

 Is there any point in my trying to go any further with this?  It seems
 pretty dead to me, the PIC maybe?   :^(

 Nice museum piece perhaps, but a bit expensive for only that...

 Dan

 ac6ao




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You did connect the 12V supply as well?
The output signal level is only about  +4dBm.


Bruce


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Re: [time-nuts] E1938 question

[Bruce Griffiths]

Dan Rae wrote:
 I have one of the Chinese E1938 modules I bought about a month ago. 
 I just tried it out on the bench, and have not had much luck with it. 
 The 5 Volt supply never goes above 50 mA or so, none of the heaters
 seem to be powered looking at the hockey puck D-sub connector pins. 
 The four leds up by the PIC (?) seem to flash once on switch on and
 then pulse about once a second.  The other led which seems to be on
 the 5 V supply is on.  It does oscillate, but very low since it never
 warms up.

 Is there any point in my trying to go any further with this?  It seems
 pretty dead to me, the PIC maybe?   :^(

 Nice museum piece perhaps, but a bit expensive for only that...

 Dan

 ac6ao




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When operating correctly:

1) The green power led near the heater PMOSFETS should be on continuously


2) The green led at the other end of the board should flash at 1Hz.

3) The oven takes several minutes to warm up and the outer oven shell
should be noticeably warm.

If other LEDs are flashing the PIC may be locked in the wrong mode.
This state can sometimes be cleared by resetting the PIC by powering it
down and restarting.

Bruce

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Re: [time-nuts] E1938 question

[Bruce Griffiths]

Dan Rae wrote:
 I have one of the Chinese E1938 modules I bought about a month ago. 
 I just tried it out on the bench, and have not had much luck with it. 
 The 5 Volt supply never goes above 50 mA or so, none of the heaters
 seem to be powered looking at the hockey puck D-sub connector pins. 
 The four leds up by the PIC (?) seem to flash once on switch on and
 then pulse about once a second.  The other led which seems to be on
 the 5 V supply is on.  It does oscillate, but very low since it never
 warms up.

 Is there any point in my trying to go any further with this?  It seems
 pretty dead to me, the PIC maybe?   :^(

 Nice museum piece perhaps, but a bit expensive for only that...

 Dan

 ac6ao




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Have you checked that the outputs of all the regulators on the board are OK.
In particular the -5V rail used by the heater PMOSFET driver opamps?

Bruce

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Re: [time-nuts] E1938 question

[Bruce Griffiths]

Dan Rae wrote:
 I have one of the Chinese E1938 modules I bought about a month ago. 
 I just tried it out on the bench, and have not had much luck with it. 
 The 5 Volt supply never goes above 50 mA or so, none of the heaters
 seem to be powered looking at the hockey puck D-sub connector pins. 
 The four leds up by the PIC (?) seem to flash once on switch on and
 then pulse about once a second.  The other led which seems to be on
 the 5 V supply is on.  It does oscillate, but very low since it never
 warms up.

 Is there any point in my trying to go any further with this?  It seems
 pretty dead to me, the PIC maybe?   :^(

 Nice museum piece perhaps, but a bit expensive for only that...

 Dan

 ac6ao




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You can also try pushing the PIC reset button near the front of the board.

Bruce

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[time-nuts] E1938

[Jeroen Bastemeijer]

); SAEximRunCond expanded to false
Errors-To: [EMAIL PROTECTED] RETRY

Dear All,

After some shipping time, my E1938 arrived today! :-)  :-)  :-)

Thank you Rick!

First thing was examining the board, oscillator and the HP-test 
notes/labels. Most of the specs mentioned there are logical and numbers 
are very reasonable. ;-) However, one spec drew my attention: Hz off 
freq. after warm up: -2,94. Does anyone know what it means? Is this the 
offset after warm-up without EFC applied?

The unit hasn't been powered up. Whit the hardware at hand I first want 
to read some docs to be sure about what I'm doing. For comparison, what 
other numbers are around for the Hz off freq. after warm up-spec?

Final result of the HP-test was: PASS. So, I assume this number is OK. 
What is your opinion? Looking forward to your reactions.

73 Jeroen PE1RGE

-- 
Ing. Jeroen Bastemeijer

Delft University of Technology
Department of Electrical Engineering
Electronic Instrumentation Laboratory
Mekelweg 4, Room 13.090
2628 CD Delft
The Netherlands

Phone: +31.15.27.86542
Fax: +31.15.27.85755
E-mail: [EMAIL PROTECTED]
GPS: Lat N52.2 Lon E4.37157 Alt 46.2m


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Re: [time-nuts] E1938

[Richard (Rick) Karlquist]

The labels may or may not be significant.  If the frequency
is indeed -2.94 Hz at 2.5V EFC, you could probably get it back
to 10 MHz by increasing the EFC voltage.  You can also decrease
the bridge capacitor to bring the frequency up if necessary.
The factory was supposed to choose the capacitor to get 10 MHz
in the center of the EFC range.  If this is not correct, the
oscillator is usually perfectly OK , and they just
goofed on the capacitor.  The capacitor installation process
had a lot of problems.  Should be safe to power it up and see
what the status is.

Rick N6RK

Jeroen Bastemeijer wrote:
 ); SAEximRunCond expanded to false
 Errors-To: [EMAIL PROTECTED] RETRY
 
 Dear All,
 
 After some shipping time, my E1938 arrived today! :-)  :-)  :-)
 
 Thank you Rick!
 
 First thing was examining the board, oscillator and the HP-test 
 notes/labels. Most of the specs mentioned there are logical and numbers 
 are very reasonable. ;-) However, one spec drew my attention: Hz off 
 freq. after warm up: -2,94. Does anyone know what it means? Is this the 
 offset after warm-up without EFC applied?
 
 The unit hasn't been powered up. Whit the hardware at hand I first want 
 to read some docs to be sure about what I'm doing. For comparison, what 
 other numbers are around for the Hz off freq. after warm up-spec?
 
 Final result of the HP-test was: PASS. So, I assume this number is OK. 
 What is your opinion? Looking forward to your reactions.
 
 73 Jeroen PE1RGE
 

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Re: [time-nuts] E1938

[Brooke Clarke]

); SAEximRunCond expanded to false
Errors-To: [EMAIL PROTECTED] RETRY

Hi Rick:

If the aging drift is up in frequency then there might be an advantage in 
starting at the low end of the window.  Any idea of how these age?

Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.precisionclock.com
http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Cam


Richard (Rick) Karlquist wrote:
 ); SAEximRunCond expanded to false
 Errors-To: [EMAIL PROTECTED] RETRY
 
 The labels may or may not be significant.  If the frequency
 is indeed -2.94 Hz at 2.5V EFC, you could probably get it back
 to 10 MHz by increasing the EFC voltage.  You can also decrease
 the bridge capacitor to bring the frequency up if necessary.
 The factory was supposed to choose the capacitor to get 10 MHz
 in the center of the EFC range.  If this is not correct, the
 oscillator is usually perfectly OK , and they just
 goofed on the capacitor.  The capacitor installation process
 had a lot of problems.  Should be safe to power it up and see
 what the status is.
 
 Rick N6RK
 
 Jeroen Bastemeijer wrote:
 
); SAEximRunCond expanded to false
Errors-To: [EMAIL PROTECTED] RETRY

Dear All,

After some shipping time, my E1938 arrived today! :-)  :-)  :-)

Thank you Rick!

First thing was examining the board, oscillator and the HP-test 
notes/labels. Most of the specs mentioned there are logical and numbers 
are very reasonable. ;-) However, one spec drew my attention: Hz off 
freq. after warm up: -2,94. Does anyone know what it means? Is this the 
offset after warm-up without EFC applied?

The unit hasn't been powered up. Whit the hardware at hand I first want 
to read some docs to be sure about what I'm doing. For comparison, what 
other numbers are around for the Hz off freq. after warm up-spec?

Final result of the HP-test was: PASS. So, I assume this number is OK. 
What is your opinion? Looking forward to your reactions.

73 Jeroen PE1RGE

 
 
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Re: [time-nuts] E1938

[Brooke Clarke]

Hi Rick:

I've heard that but it's not clear to me which oscillators are in the non aging 
catagory.  For example what about the HP 10811 or the Stanford Research SC 10?

The plot on Brooks Shrea's web page for his GPSDO shows linear aging on his 
Austron 1250. See:  http://www.rt66.com/%7Eshera/index_fs.htm

Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.precisionclock.com
http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Cam


Rick Karlquist wrote:
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 This question keeps coming up in relation to various crystal
 oscillators.  Basically, if you have a really good process,
 which HP had for the E1938A, there will be no bias in favor
 of aging in any particular direction.  If there was any
 bias, the cause of it would be investigated and then eliminated.
 The main source of aging that remains is believed to be microcracks.
 These can increase or decrease frequency.
 
 Now if you are talking about colorburst crystals, they usually age down
 because crud from the package deposits on the crystal to
 a greater extent than dirt on the crystal flying away.
 
 Rick N6RK
 
 
 
 
 Brooke Clarke wrote:
 
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Hi Rick:

If the aging drift is up in frequency then there might be an advantage in
starting at the low end of the window.  Any idea of how these age?

Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.precisionclock.com
http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Cam


Richard (Rick) Karlquist wrote:

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The labels may or may not be significant.  If the frequency
is indeed -2.94 Hz at 2.5V EFC, you could probably get it back
to 10 MHz by increasing the EFC voltage.  You can also decrease
the bridge capacitor to bring the frequency up if necessary.
The factory was supposed to choose the capacitor to get 10 MHz
in the center of the EFC range.  If this is not correct, the
oscillator is usually perfectly OK , and they just
goofed on the capacitor.  The capacitor installation process
had a lot of problems.  Should be safe to power it up and see
what the status is.

Rick N6RK

Jeroen Bastemeijer wrote:


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Dear All,

After some shipping time, my E1938 arrived today! :-)  :-)  :-)

Thank you Rick!

First thing was examining the board, oscillator and the HP-test
notes/labels. Most of the specs mentioned there are logical and numbers
are very reasonable. ;-) However, one spec drew my attention: Hz off
freq. after warm up: -2,94. Does anyone know what it means? Is this the
offset after warm-up without EFC applied?

The unit hasn't been powered up. Whit the hardware at hand I first want
to read some docs to be sure about what I'm doing. For comparison, what
other numbers are around for the Hz off freq. after warm up-spec?

Final result of the HP-test was: PASS. So, I assume this number is OK.
What is your opinion? Looking forward to your reactions.

73 Jeroen PE1RGE



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Re: [time-nuts] E1938

[Rick Karlquist]

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No oscillators are in the non aging category.  However, the E1938
and 10811 are in the RANDOM aging category.  As I previously said,
the direction of the aging is random.  Now you have brought up the
so called disciplined oscillator concept.  This concept admits that
the direction and slope of aging is random between oscillators,
but maintains that an individual oscillator has a known direction
and slope that can be taken out.  This is an extension of the
initial fallacy.  Oscillators can initially age in one direction
for a while and then change directions.  Also, the slope may be
fairly constant, allowing disciplining. or it may gradually decrease.
However, it is also a fallacy to think that the aging will
asymptotically approach zero if you wait long enough.  There are
now extremely old 10811's, and you will find that their aging
is nothing special.

The discipling concept with frequent GPS updates only assumes that
aging characteristics won't change abruptly.  That is the one
assumption that is probably fairly safe.  However, all oscillators
exhibit frequency jumps, that will only be made up after the
time constant of the GPS loop has time to track them out.

When reading papers on discipled oscillators, pay no attention
to anecdotal data.  The only data that counts is on large numbers
of oscillators over large spans of time.

Rick


Brooke Clarke wrote:
 Hi Rick:

 I've heard that but it's not clear to me which oscillators are in the non
 aging
 catagory.  For example what about the HP 10811 or the Stanford Research SC
 10?

 The plot on Brooks Shrea's web page for his GPSDO shows linear aging on
 his
 Austron 1250. See:  http://www.rt66.com/%7Eshera/index_fs.htm

 Have Fun,

 Brooke Clarke
 http://www.PRC68.com
 http://www.precisionclock.com
 http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Cam


 Rick Karlquist wrote:
 ); SAEximRunCond expanded to false
 Errors-To: [EMAIL PROTECTED] RETRY

 This question keeps coming up in relation to various crystal
 oscillators.  Basically, if you have a really good process,
 which HP had for the E1938A, there will be no bias in favor
 of aging in any particular direction.  If there was any
 bias, the cause of it would be investigated and then eliminated.
 The main source of aging that remains is believed to be microcracks.
 These can increase or decrease frequency.

 Now if you are talking about colorburst crystals, they usually age down
 because crud from the package deposits on the crystal to
 a greater extent than dirt on the crystal flying away.

 Rick N6RK




 Brooke Clarke wrote:

); SAEximRunCond expanded to false
Errors-To: [EMAIL PROTECTED] RETRY

Hi Rick:

If the aging drift is up in frequency then there might be an advantage
 in
starting at the low end of the window.  Any idea of how these age?

Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.precisionclock.com
http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Cam


Richard (Rick) Karlquist wrote:

); SAEximRunCond expanded to false
Errors-To: [EMAIL PROTECTED] RETRY

The labels may or may not be significant.  If the frequency
is indeed -2.94 Hz at 2.5V EFC, you could probably get it back
to 10 MHz by increasing the EFC voltage.  You can also decrease
the bridge capacitor to bring the frequency up if necessary.
The factory was supposed to choose the capacitor to get 10 MHz
in the center of the EFC range.  If this is not correct, the
oscillator is usually perfectly OK , and they just
goofed on the capacitor.  The capacitor installation process
had a lot of problems.  Should be safe to power it up and see
what the status is.

Rick N6RK

Jeroen Bastemeijer wrote:


); SAEximRunCond expanded to false
Errors-To: [EMAIL PROTECTED] RETRY

Dear All,

After some shipping time, my E1938 arrived today! :-)  :-)  :-)

Thank you Rick!

First thing was examining the board, oscillator and the HP-test
notes/labels. Most of the specs mentioned there are logical and
 numbers
are very reasonable. ;-) However, one spec drew my attention: Hz off
freq. after warm up: -2,94. Does anyone know what it means? Is this
 the
offset after warm-up without EFC applied?

The unit hasn't been powered up. Whit the hardware at hand I first
 want
to read some docs to be sure about what I'm doing. For comparison,
 what
other numbers are around for the Hz off freq. after warm up-spec?

Final result of the HP-test was: PASS. So, I assume this number is OK.
What is your opinion? Looking forward to your reactions.

73 Jeroen PE1RGE



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Re: [time-nuts] E1938 phase noise

[John Ackermann N8UR]

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Richard (Rick) Karlquist said the following on 08/28/2007 12:27 AM:
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 E1938A phase noise should be similar to 10811,
 possibly even a little better far out.
 
 Short term stability should be similar to 10811
 except down around 1 second, where the AFC circuit
 degrades it a little to 10^11 or so.
 
 The phase noise was very repeatable.

I'm on vacation now and away from the lab, but when I get back I'll do a
phase noise run against a Wenzel ULN and report the results.

John

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Re: [time-nuts] E1938 phase noise

[Richard (Rick) Karlquist]

); SAEximRunCond expanded to false
Errors-To: [EMAIL PROTECTED] RETRY

E1938A phase noise should be similar to 10811,
possibly even a little better far out.

Short term stability should be similar to 10811
except down around 1 second, where the AFC circuit
degrades it a little to 10^11 or so.

The phase noise was very repeatable.

Rick N6RK

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Re: [time-nuts] E1938 phase noise

[SAIDJACK]

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Hi Rick,
 
thanks so much for providing us with the info, and units!
 
I got mine locked to GPS already as of 30 minutes ago.
 
Said



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