Re: [time-nuts] Improving the stability of crystal oscillators

[Don Collie]

s been achieved.
Objects of intermediate size like some ECDLs routinely achieve a
stability of 0.01C or better when a Peltier cooler is used.

Bruce

- Original Message - 
From: "Bruce Griffiths" <[EMAIL PROTECTED]>
To: "Don Collie" <[EMAIL PROTECTED]>
Sent: Wednesday, October 17, 2007 4:35 PM
Subject: Re: [time-nuts] Improving the stability of crystal oscillators


> Don Collie wrote:
>> Dear Dr Bruce,
>>I am partially depantsed [*only* partially]. Do I have your
>> permission to respond to your points on group? This way either you, or
>> I will be fully depantsed.
>> All the best,...Don.
>>
>>
> Don
>
> That would perhaps be a good idea in that it may be educational to
> others and any delusions etc may be cured.
>
> Bruce 


___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Bruce Griffiths]

Don Collie wrote:
> Hi Hal,
> I was thinking of attaching a temparature sensor [AKA Star Treck] to the 
> cold side of a Peltier [what`s the other type? Are they available/better?] 
> pile. and driving the pile from the output of some sort of servo loop to 
> maintain a temparature of ,say , 0 Degree C.
>  If you wanted a double oven, you could heatsink a small oven, 
> containing the crystal, the oscillator, and buffer[s] to this, and use a 
> second servo loop to raise the temparature of this to 25 Degrees C working 
> against the Peltier. In this way, you could maintain the crystal, and 
> circuitry at 25 Deg C., over an ambient temparature of 0 to ,say 70 Deg C.
> Yes, you can cut a crystal to have an inversion temp at 25Deg C. [well 
> certainly with an AT cut - I`m not sure about the SC cut.]
> Cheers,Don C.
>
> - Original Message - 
>   
Don

With such a wide swing in the temperature differeence across the Peltier
stack, you will need to adjust the PID loop parameters to maintain
optimum control.
A fixed set of parameters is only useful for a temperature range of up
to 10C. The Peltier stack performance varies significantly with the
temperature difference across the stack.
Consequently you also need to sense the peltier device heatsink temperature.

Bruce

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[John Franke]

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

This is something I have thought about but never did any experimentation. 
With the low cost and increased availability of thermoelectric coolers, I am 
interested in pursuing this concept.  The unfortunate thing is that the 
crystals are ground for 25C or the higher turnover temperature point.  If 
someone has a crystal that has drifted, it may be a good candidate for 
experimentation.  Another thought would be to let the crystal operate at its 
natural frequency, divide it down to 1 or ten Hz and then phase lock a more 
convenient crystal frequency to the low pulse rate.  The idea is to save an 
otherwise aged and well performing crystal.

John  WA4WDL

- Original Message - 
From: "Tom Van Baak" <[EMAIL PROTECTED]>
To: "Discussion of precise time and frequency measurement" 

Sent: Monday, October 15, 2007 10:12 PM
Subject: Re: [time-nuts] Improving the stability of crystal oscillators


> As far as I can tell, temperature curve plots for quartz typically
> show both an upper and a lower turnover point (for example,
> see the pages below). Since the upper is well above maximum
> ambient, it makes sense that this point is used in O[ven]CXO.
>
> The question is -- does anyone know if the lower turnover point
> (LTP) is ever used? I ask because I heard that a quartz oscillator
> might have slightly better short-term stability at the LTP compared
> to the UTP. If so, this might argue for the extra trouble of using
> TEC for cooling in some low-noise applications.
>
> /tvb
>
> http://www.ieee-uffc.org/freqcontrol/tutorials/vig3/vig3_files/slide0164.htm
> http://www.ieee-uffc.org/freqcontrol/tutorials/vig3/vig3_files/slide0306.htm
>
>
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to 
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
> 



___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Don Collie]

Hi Rick,
Perhaps I should have said : "Temperature at which the lowest change of 
frequency with temperature occurs".
What cut of crystal is used in these high quality crystal references, 
please?
Cheers,Don C.

- Original Message - 
From: "Richard (Rick) Karlquist" <[EMAIL PROTECTED]>
To: "Don Collie" <[EMAIL PROTECTED]>; "Discussion of precise time and 
frequency measurement" 
Sent: Tuesday, October 16, 2007 2:54 PM
Subject: Re: [time-nuts] Improving the stability of crystal oscillators


> Don Collie wrote:
>
>> Yes, you can cut a crystal to have an inversion temp at 25Deg C. 
>> [well certainly with an AT cut - I`m not sure about the SC cut.]
>> Cheers,Don C.
>
> The AT cut has an inflection point at 25 degrees C.  You cannot
> get a "turnover" (which is what I think you mean an "inversion")
> at the inflection point.
>
> As SC cut inventor Jack Kusters explained to me, the "true" SC cut
> has an inflection point temperature of around 85 degrees C.  You can get
> a turnover above or below this, depending on minor angle changes.
> Some crystal fabs make a so called "fake SC" cut where they attempt
> to change the inflection point.  However, when this is done the stress
> compensation is degraded or lost.
>
> Rick Karlquist N6RK
>
>
> -- 
> No virus found in this incoming message.
> Checked by AVG Free Edition. Version: 7.5.488 / Virus Database: 
> 269.14.12/1072 - Release Date: 10/15/2007 5:55 PM
> 


___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Tom Van Baak]

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

As far as I can tell, temperature curve plots for quartz typically
show both an upper and a lower turnover point (for example,
see the pages below). Since the upper is well above maximum
ambient, it makes sense that this point is used in O[ven]CXO.

The question is -- does anyone know if the lower turnover point
(LTP) is ever used? I ask because I heard that a quartz oscillator
might have slightly better short-term stability at the LTP compared
to the UTP. If so, this might argue for the extra trouble of using
TEC for cooling in some low-noise applications.

/tvb

http://www.ieee-uffc.org/freqcontrol/tutorials/vig3/vig3_files/slide0164.htm
http://www.ieee-uffc.org/freqcontrol/tutorials/vig3/vig3_files/slide0306.htm


___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Richard (Rick) Karlquist]

Don Collie wrote:

> Yes, you can cut a crystal to have an inversion temp at 25Deg C. [well 
> certainly with an AT cut - I`m not sure about the SC cut.]
> Cheers,Don C.

The AT cut has an inflection point at 25 degrees C.  You cannot
get a "turnover" (which is what I think you mean an "inversion")
at the inflection point.

As SC cut inventor Jack Kusters explained to me, the "true" SC cut
has an inflection point temperature of around 85 degrees C.  You can get
a turnover above or below this, depending on minor angle changes.
Some crystal fabs make a so called "fake SC" cut where they attempt
to change the inflection point.  However, when this is done the stress
compensation is degraded or lost.

Rick Karlquist N6RK

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Don Collie]

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

Hi Hal,
I was thinking of attaching a temparature sensor [AKA Star Treck] to the 
cold side of a Peltier [what`s the other type? Are they available/better?] 
pile. and driving the pile from the output of some sort of servo loop to 
maintain a temparature of ,say , 0 Degree C.
 If you wanted a double oven, you could heatsink a small oven, 
containing the crystal, the oscillator, and buffer[s] to this, and use a 
second servo loop to raise the temparature of this to 25 Degrees C working 
against the Peltier. In this way, you could maintain the crystal, and 
circuitry at 25 Deg C., over an ambient temparature of 0 to ,say 70 Deg C.
Yes, you can cut a crystal to have an inversion temp at 25Deg C. [well 
certainly with an AT cut - I`m not sure about the SC cut.]
Cheers,Don C.

- Original Message - 
From: "Hal Murray" <[EMAIL PROTECTED]>
To: "Discussion of precise time and frequency measurement" 

Sent: Tuesday, October 16, 2007 5:49 AM
Subject: Re: [time-nuts] Improving the stability of crystal oscillators


> ); SAEximRunCond expanded to false
> Errors-To: [EMAIL PROTECTED] RETRY
>
>
>> The resonator inversion temperature occurs at 70-80 degrees Celsius,
>> depending on the cut angles.
>
> Is there something magic about quartz that has a turnover in the region 
> that
> just happens to be handy for OCXOs?  Or is it the other way around: people
> chose the cut angle to get a temperature that works well for ovens?
>
> Could I cut a crystal with a temperature at (say) 0C or something handy 
> for
> Peltiers?
>
>
> -- 
> These are my opinions, not necessarily my employer's.  I hate spam.
>
>
>
>
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to 
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>
>
> -- 
> No virus found in this incoming message.
> Checked by AVG Free Edition.
> Version: 7.5.488 / Virus Database: 269.14.12/1072 - Release Date: 
> 10/15/2007 5:55 PM
> 


___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Bruce Griffiths]

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

Hal

For a summary of the state of the art in Peltier devices etc see:
ARTI Report No. 10120-01THERMOELECTRIC TECHNOLOGY ASSESSMENT
Final Report May 2007 Dr. Bao Yang

A COP up to 6 or so can be achieved at around room temperature.
Nanostructured materials have been used to reduce thermal conduction
(via phonon scattering) whilst retaining high electrical conduction
(minimal electron scattering).
There are no known theoretical limits to the figure of merit attainable.
However dont expect nanostructured Peltier devices to be readily
available for some time.

Bruce

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Enrico Rubiola]

> Is there something magic about quartz that has a turnover in the  
> region that
> just happens to be handy for OCXOs?  Or is it the other way around:  
> people
> chose the cut angle to get a temperature that works well for ovens?

First, better heat-only than heat-cool or cool-only because of
- efficiency
- temperature stability
(see my recent mail "against" the Peltier cell)

Second, think about the inside of an instrument.  Think about a heat- 
only
control.  Account for some 5 degrees minimum difference between the  
quartz
and its environment.  70-80 degrees Celsius is the most comfortable  
temperature.
Physicists designed the resonator for the inversion temperature to be  
75 deg Celsius.
That's it.


> Could I cut a crystal with a temperature at (say) 0C or something  
> handy for
> Peltiers?

Probably yes, if it made sense.



Very best


















Enrico Rubiola
professor of electronics

web:http://rubiola.org
e-mail: [EMAIL PROTECTED]

FEMTO-ST Institute
32 av. de l'Observatoire
25044 Besancon, FRANCE
voice:  +33(0)381.853940 (E.Rubiola)
voice:  +33(0)381.853999 (switchboard)
fax:+33(0)381.853998


___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Hal Murray]

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


> The resonator inversion temperature occurs at 70-80 degrees Celsius,
> depending on the cut angles. 

Is there something magic about quartz that has a turnover in the region that 
just happens to be handy for OCXOs?  Or is it the other way around: people 
chose the cut angle to get a temperature that works well for ovens?

Could I cut a crystal with a temperature at (say) 0C or something handy for 
Peltiers?


-- 
These are my opinions, not necessarily my employer's.  I hate spam.




___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Enrico Rubiola]

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

Dear all,

the major problem for the use of a Peltier cell with
a quartz oscillator is that the cell maximum operating
temperature is of the order of 80 degrees Celsius.
This is due to the low melting point of the metal pairs
suitable to produce the Peltier effect (reversed thermocouple).

The resonator inversion temperature occurs at 70-80
degrees Celsius, depending on the cut angles.



A more general problem is that
a good temperature controlled oven has high thermal
resistance, limited by the dissipation inside the oven.
Unfortunately, the Peltier cell has low thermal resistance,
which means poor isolation from the oven.

This problem is made worse by the joule effect, which
always go with the Peltier effect.  For this reason, the
temperature fluctuations of the Peltier heat sink tend
to be larger than the environment fluctuations (unless
you use water cooling!).  Thus, the thermal fluctuations
propagating through the Peltier cell tend to be an amplified
version of the environment fluctuation.
This phenomenon is dramatic when the Peltier cools down,
and a minor problem when the Peltier cell heats up.

Very best,

Enrico




On 13 Oct 2007, at 22:13 , Don Collie wrote:

> ); SAEximRunCond expanded to false
> Errors-To: [EMAIL PROTECTED] RETRY
>
> Has anyone concidered using a small Peltier pile to maintain the  
> crystal`s
> temparature. I understand that these devices will heat or cool, so  
> it would
> be possible to maintain the crystal temparature at , say, 25 degrees
> celcius, over a range of ambient temparatures
> [perhaps 0 to 70  degrees]. There would be several advantages in this
> approach.
> Cheers!,Don Collie jnr.
>
>
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/ 
> time-nuts
> and follow the instructions there.

Enrico Rubiola
professor of electronics

web:http://rubiola.org
e-mail: [EMAIL PROTECTED]

FEMTO-ST Institute
32 av. de l'Observatoire
25044 Besancon, FRANCE
voice:  +33(0)381.853940 (E.Rubiola)
voice:  +33(0)381.853999 (switchboard)
fax:+33(0)381.853998


___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[SAIDJACK]

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

 
In a message dated 10/14/2007 23:07:04 Pacific Daylight Time,  
[EMAIL PROTECTED] writes:

>Thermal transients propagate into the ground on a different  law,  
>Gauss' Error Function.
>If the ground is cleared of  trees, one hundred years later at a depth  
>of 100 metres  or
>so there will be a record of the change in average soil  temperature.
>The Cave was Saltpetre Cave in Carter Caves  Park.
>Just thought you might like to know.
>Neville  Michie



Hi Neville,
 
your post made me remember stuff from my University days!
 
Gauss' Error Function is also used to calculate diffusion depth of  
semiconductors.
 
HP/Agilent makes a semiconductor tester to measure this depth.
 
One interesting fact I remember from this: the form of the diffusion  profile 
depends on the speed (time) of the actual diffusion process into the  bulk 
material.
 
I bet there is a nice analog to temperature transients progressing through  
soil.
 
I love it when micro and macro effects show mathematical  similarities.
 
bye,
Said 



** See what's new at http://www.aol.com
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Neville Michie]

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

Enough speculation on ground temperatures.
The attenuation of cyclic variations of surface temperature die away
at an exponential rate with depth.
The thermal diffusivity of soils does vary but not so you can not  
generalise.
For daily changes, the temperature variation is attenuated to 1% of  
the surface swing between
0.3 and 0.6 metres.
For the annual swing, the distances are about 20 times greater.
I once was investigating a limestone cave climate, and I was  
delighted by
a pure sine wave of temperature that showed up on a data logger after  
a year
of measureing the temperature of the cave roof. It would not have  
been noticed except
that the logger was a high resolution model.
It was about 15 metres underground.
Higher frequencies have much higher attenuation, so the harmonics of  
daily and
annual  cycles are quickly lost.
Thermal transients propagate into the ground on a different law,  
Gauss' Error Function.
If the ground is cleared of trees, one hundred years later at a depth  
of 100 metres or
so there will be a record of the change in average soil temperature.
The Cave was Saltpetre Cave in Carter Caves Park.
Just thought you might like to know.
Neville Michie





On 15/10/2007, at 1:18 PM, Hal Murray wrote:

>
>> I've heard there is some depth that building foundations need to  
>> be so
>> they  don't get winter frost heave that might be on the order of a
>> couple of feet,  but that's far different from an constant  
>> temperature
>> depth.
>
> That depends on where you live.
>
>> I'm guessing that 10 or 15 feet may be required to get fractional
>> degree temp  stability where I am.  The Wisconsin data was in loam
>> which I think means a  fairly good insulator.  They had the widest
>> temperature variation (15 c delta @  120 cm down).  I've got sand and
>> clay after the first foot or so which may be a  better thermal
>> conductor implying less variation.
>
> The math is the same as for skin depth on RF on metal.  The  
> temperature
> fluctuation decays exponentially with depth.  Lower frequencies  
> (years vs
> days) go deeper.
>
>
>
>
> -- 
> These are my opinions, not necessarily my employer's.  I hate spam.
>
>
>
>
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/ 
> time-nuts
> and follow the instructions there.


___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Hal Murray]

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


> I've heard there is some depth that building foundations need to be so
> they  don't get winter frost heave that might be on the order of a
> couple of feet,  but that's far different from an constant temperature
> depth.

That depends on where you live.

> I'm guessing that 10 or 15 feet may be required to get fractional
> degree temp  stability where I am.  The Wisconsin data was in loam
> which I think means a  fairly good insulator.  They had the widest
> temperature variation (15 c delta @  120 cm down).  I've got sand and
> clay after the first foot or so which may be a  better thermal
> conductor implying less variation. 

The math is the same as for skin depth on RF on metal.  The temperature 
fluctuation decays exponentially with depth.  Lower frequencies (years vs 
days) go deeper.




-- 
These are my opinions, not necessarily my employer's.  I hate spam.




___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Brooke Clarke]

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

Hi Bruce:

All the papers are for depths on the order of a few feet, aimed at plant 
growth, nevertheless in all cases the temperature was changing by at least 1 
deg c at the deepest depth recorded.

I've heard there is some depth that building foundations need to be so they 
don't get winter frost heave that might be on the order of a couple of feet, 
but that's far different from an constant temperature depth.

I'm guessing that 10 or 15 feet may be required to get fractional degree temp 
stability where I am.  The Wisconsin data was in loam which I think means a 
fairly good insulator.  They had the widest temperature variation (15 c delta @ 
120 cm down).  I've got sand and clay after the first foot or so which may be a 
better thermal conductor implying less variation.

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


Bruce Griffiths wrote:
> ); SAEximRunCond expanded to false
> Errors-To: [EMAIL PROTECTED] RETRY
> 
> Brooke Clarke wrote:
> 
>>Hi Bruce:
>>
>>Details on your experiment please.
>>Hole/pipe diameter, material?
>>Depth?
>>Delta T at different depths vs surface ambient?
>>Soil type?
>>
>>
>>Have Fun,
>>
>>Brooke Clarke
>>  
> 
> Brooke
> 
> Unable as yet to find my data, it was published in some very obscure
> publication if I remember correctly.
> However there was extensive series of records kept in England from the
> time of Lord Kelvin.
> 
> More recent data is available from the US forest service among others:
> http://ncrs.fs.fed.us/pubs/rn/rn_nc032.pdf
> Above is for Wisconsin, not directly applicable to California.
> http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?letter=.&classic=YES&bibcode=1952AuSRA...5..303W&page=&type=SCREEN_VIEW&data_type=PDF_HIGH&send=GET&filetype=.pdf
> 
> Above paper by CSIRO is for an Australian site.
> Analysis is fairly comprehensive.
> 
> http://www.mmm.ucar.edu/mm5/lsm/soil.pdf
> 
> http://www.ias.ac.in/epsci/mar2002/Esb1439.pdf
> 
> Bruce
> 
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
> 

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Magnus Danielson]

From: "John Miles" <[EMAIL PROTECTED]>
Subject: Re: [time-nuts] Improving the stability of crystal oscillators
Date: Sun, 14 Oct 2007 14:15:10 -0700
Message-ID: <[EMAIL PROTECTED]>

> ); SAEximRunCond expanded to false
> Errors-To: [EMAIL PROTECTED] RETRY
> 
> 
> > The required depth depends on the soil diffusivity and the temperature
> > stability required.
> > It is instructive to install thermometers at depth intervals of a foot
> > or so and record the temperature fluctuations experienced by each
> > thermometer.
> > This was first done around 1860 by Forbes.
> > I repeated the experiment in 1966.
> 
> There was an interesting bit in the last Agilent Measurement Journal about a
> product that uses an ordinary communications-grade fiber as a thermometer.
> >From what I remember, they send a laser pulse down the fiber, then look at
> the backscatter, correlating time-of-flight with the Raman-scattering lines
> (Stokes and anti-Stokes).  One of those spectral lines is
> temperature-dependent while the other isn't, so by recording the separation,
> they end up with is a graph of temperature versus distance along the fiber,
> gathering up to a few kilometers' worth of data with what looked like
> sub-meter resolution.
> 
> No doubt this effect is old hat to physicists on the list, but I'd never
> heard how it worked before.  So if you buried a fiber like this, you'd
> presumably get a great picture of what happens with temperature at various
> depths.  Plotting the temperature-versus-distance on a waterfall display
> gives a nice diurnal picture.  The article used it to study water
> temperature along the course of a stream, but you could think of plenty of
> other uses for 2D remote temperature sensing.

Bell Labs have made measures on soil temperature at different deps and also
fiber-delay as it varies with temperature. As it happends, the delay is part
due to fiber length change due to temperature and most part due to change of
delay due to change in dielectrics which converts into changes in the wave-
equation.

It naturally depends on temperature, laser wavelength and accumulates over
distance. I haven't seen any paper on non-chromatic delay shifts, but I haven't
looked too closely.

Cheers,
Magnus

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[John Miles]

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


> The required depth depends on the soil diffusivity and the temperature
> stability required.
> It is instructive to install thermometers at depth intervals of a foot
> or so and record the temperature fluctuations experienced by each
> thermometer.
> This was first done around 1860 by Forbes.
> I repeated the experiment in 1966.

There was an interesting bit in the last Agilent Measurement Journal about a
product that uses an ordinary communications-grade fiber as a thermometer.
>From what I remember, they send a laser pulse down the fiber, then look at
the backscatter, correlating time-of-flight with the Raman-scattering lines
(Stokes and anti-Stokes).  One of those spectral lines is
temperature-dependent while the other isn't, so by recording the separation,
they end up with is a graph of temperature versus distance along the fiber,
gathering up to a few kilometers' worth of data with what looked like
sub-meter resolution.

No doubt this effect is old hat to physicists on the list, but I'd never
heard how it worked before.  So if you buried a fiber like this, you'd
presumably get a great picture of what happens with temperature at various
depths.  Plotting the temperature-versus-distance on a waterfall display
gives a nice diurnal picture.  The article used it to study water
temperature along the course of a stream, but you could think of plenty of
other uses for 2D remote temperature sensing.

-- john, KE5FX


___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Richard (Rick) Karlquist]

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


Neon John wrote:

> Nah, not for this application.  A Peltier module typically has a COP of 1.  
> That is,
> it moves a watt of energy for each watt consumed.   Thus, for each watt 
> moved, two
> watts have to be dissipated to air.
> 
> I can't imagine a well-insulated quartz oscillator needing more than a watt 
> or two of
> cooling at the most.  A heat sink capable of handling 4-5 watts should do the 
> job
> just fine.
> 
> Don:  I've seen peltier-controlled "ambient" ovens before but I can't recall 
> the
> details.  I'm fairly sure one was a Fluke precision voltage transfer standard 
> in
> which the zener reference diode was controlled to a constant temperature.

The problem with Peltier coolers is that they have low thermal 
resistance to ambient.  This makes them suitable only for
non critical ovens.

Rick Karlquist N6RK

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Bruce Griffiths]

Brooke Clarke wrote:
> Hi Bruce:
>
> Details on your experiment please.
> Hole/pipe diameter, material?
> Depth?
> Delta T at different depths vs surface ambient?
> Soil type?
>
>
> Have Fun,
>
> Brooke Clarke
>   
Brooke

Unable as yet to find my data, it was published in some very obscure
publication if I remember correctly.
However there was extensive series of records kept in England from the
time of Lord Kelvin.

More recent data is available from the US forest service among others:
http://ncrs.fs.fed.us/pubs/rn/rn_nc032.pdf
Above is for Wisconsin, not directly applicable to California.
http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?letter=.&classic=YES&bibcode=1952AuSRA...5..303W&page=&type=SCREEN_VIEW&data_type=PDF_HIGH&send=GET&filetype=.pdf

Above paper by CSIRO is for an Australian site.
Analysis is fairly comprehensive.

http://www.mmm.ucar.edu/mm5/lsm/soil.pdf

http://www.ias.ac.in/epsci/mar2002/Esb1439.pdf

Bruce

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Bruce Griffiths]

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

Brooke Clarke wrote:
> Hi Bruce:
>
> Details on your experiment please.
> Hole/pipe diameter, material?
> Depth?
> Delta T at different depths vs surface ambient?
> Soil type?
>
>
> Have Fun,
>
> Brooke Clarke
>   
Booke

I will try to find the data, but it was 41 years ago and may take some time.
Location was Palmerston North NZ.
Not sure of soil type, however flat region not too far (within 1km or
so) from a river.

If I remember correctly an access shaft was dug and thermometers were
inserted into the soil at the sides of the hole.
The leads were bought to the surface and the shaft/hole carefully
backfilled and left to settle for some weeks.

All measurements were logged manually.

Bruce

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Brooke Clarke]

Hi Bruce:

Details on your experiment please.
Hole/pipe diameter, material?
Depth?
Delta T at different depths vs surface ambient?
Soil type?


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


Bruce Griffiths wrote:
> ); SAEximRunCond expanded to false
> Errors-To: [EMAIL PROTECTED] RETRY
> 
> Brooke Clarke wrote:
> 
>>Hi Bruce:
>>
>>I've also looked into drilling a hole (garden hose, 90 deg fitting & pipe 
>>with 
>>end smashed flat to make a nozzle will easily drill as deep as the pipe is 
>>long).  Then using a short length of capped copper pipe at the bottom and the 
>>rest PVC.
>>
>>Like I think here in California wine country 4 feet would be plenty deep.  
>>But 
>>this method only works at your home location.  Not too good for a clock that 
>>will be sent to someone else.
>>
>>I think the long time constant method can be done in a few cubic inches.
>>
>>Have Fun,
>>
>>Brooke Clarke
>>  
> 
> Brooke
> 
> The required depth depends on the soil diffusivity and the temperature
> stability required.
> It is instructive to install thermometers at depth intervals of a foot
> or so and record the temperature fluctuations experienced by each
> thermometer.
> This was first done around 1860 by Forbes.
> I repeated the experiment in 1966.
> 
> Bruce
> 
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
> 

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Bruce Griffiths]

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

Brooke Clarke wrote:
> Hi Bruce:
>
> I've also looked into drilling a hole (garden hose, 90 deg fitting & pipe 
> with 
> end smashed flat to make a nozzle will easily drill as deep as the pipe is 
> long).  Then using a short length of capped copper pipe at the bottom and the 
> rest PVC.
>
> Like I think here in California wine country 4 feet would be plenty deep.  
> But 
> this method only works at your home location.  Not too good for a clock that 
> will be sent to someone else.
>
> I think the long time constant method can be done in a few cubic inches.
>
> Have Fun,
>
> Brooke Clarke
>   
Brooke

The required depth depends on the soil diffusivity and the temperature
stability required.
It is instructive to install thermometers at depth intervals of a foot
or so and record the temperature fluctuations experienced by each
thermometer.
This was first done around 1860 by Forbes.
I repeated the experiment in 1966.

Bruce

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Don Collie]

Thanks for that John. I`ve always wanted to play arround with one of these 
[Peltier] modules. They can now be bought quite cheaply. I envisage a double 
oven, with the inner oven heated [to 25 degrees], by conventional means, 
while the Peltier pile cools the inner oven. This way you could use
a precision temparature regulator for the inner oven, while the outer "oven" 
would only have to cool. You wouldn`t be talking too many pumped watts, 
here.
FWIW etc.,...Don C.


- Original Message - 
From: "Neon John" <[EMAIL PROTECTED]>
To: "Discussion of precise time and frequency measurement" 

Sent: Sunday, October 14, 2007 11:19 AM
Subject: Re: [time-nuts] Improving the stability of crystal oscillators


> ); SAEximRunCond expanded to false
> Errors-To: [EMAIL PROTECTED] RETRY
>
> Nah, not for this application.  A Peltier module typically has a COP of 1. 
> That is,
> it moves a watt of energy for each watt consumed.   Thus, for each watt 
> moved, two
> watts have to be dissipated to air.
>
> I can't imagine a well-insulated quartz oscillator needing more than a 
> watt or two of
> cooling at the most.  A heat sink capable of handling 4-5 watts should do 
> the job
> just fine.
>
> Don:  I've seen peltier-controlled "ambient" ovens before but I can't 
> recall the
> details.  I'm fairly sure one was a Fluke precision voltage transfer 
> standard in
> which the zener reference diode was controlled to a constant temperature.
>
> The advantage of using room temperature, e.g., 70 deg F, is that under 
> most
> conditions, the peltier module is doing little to nothing, perhaps just 
> ridding the
> ovenized unit of the few milliwatts dissipated in the circuit itself.
>
> I've used multiple cascaded modules to cool a nuclear detector (Silicon 
> surface
> barrier diode) to reduce its noise. Not as good as LN2 but much cheaper to 
> operate.
>
> John
>
> On Sat, 13 Oct 2007 13:26:52 -0700, Brooke Clarke <[EMAIL PROTECTED]> 
> wrote:
>
>>Hi Don:
>>
>>They are very inefficient to the point that a system that's supposed to 
>>cool
>>something may heat it because of all the heat generated by the module.
>>
>>It takes a huge amount of heat sinking or liquid cooling to get them to 
>>work.
>
>>Don Collie wrote:
>>> ); SAEximRunCond expanded to false
>>> Errors-To: [EMAIL PROTECTED] RETRY
>>>
>>> Has anyone concidered using a small Peltier pile to maintain the 
>>> crystal`s
>>> temparature. I understand that these devices will heat or cool, so it 
>>> would
>>> be possible to maintain the crystal temparature at , say, 25 degrees
>>> celcius, over a range of ambient temparatures
>>> [perhaps 0 to 70  degrees]. There would be several advantages in this
>>> approach.
> --
> John De Armond
> See my website for my current email address
> http://www.neon-john.com
> http://www.johndearmond.com <-- best little blog on the net!
> Tellico Plains, Occupied TN
> I like you ... you remind me of me when I was young and stupid.
>
>
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to 
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>
>
> -- 
> No virus found in this incoming message.
> Checked by AVG Free Edition.
> Version: 7.5.488 / Virus Database: 269.14.9/1069 - Release Date: 
> 10/13/2007 7:26 PM
> 


___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Brooke Clarke]

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

Hi Dick:

 From what I can Google he built maybe the first parametric amplifier but 
haven't come across details on the crystal temp stabilization.  Do you have 
info about that?

Because of the year involved I think he must have just used the long time 
constant to slow down the changes, or was he actually using the time of day as 
a function of frequency?

Have Fun,

Brooke Clarke, N6GCE
http://www.PRC68.com
http://www.precisionclock.com
http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Cam


Richard W. Solomon wrote:
> ); SAEximRunCond expanded to false
> Errors-To: [EMAIL PROTECTED] RETRY
> 
> Sam Harris (SK) did that over 40 years ago. It provided a stable
> reference for his pioneering work in Moonbounce Communication.
> 
> 73, Dick, W1KSZ/7
> 
> -Original Message-
> 
>>From: Bruce Griffiths <[EMAIL PROTECTED]>
>>Sent: Oct 13, 2007 2:44 PM
>>To: Discussion of precise time and frequency measurement 
>>Subject: Re: [time-nuts] Improving the stability of crystal oscillators
>>
>>Brooke Clarke wrote:
>>
>>>Hi:
>>>
>>>Something I've been thinking about is attaching a large thermal mass of 
>>>aluminum to the crystal and it's oscillator then surrounding that with 
>>>insulation.  Then surround that with a thin copper layer.  Temperature 
>>>sensors 
>>>on the copper and aluminum.  If the thermal time constant could be made very 
>>>close to 24 hours, or integer multiples of that, it might be possible to 
>>>predict the inner temperature allowing compensation.
>>>
>>>Has this already been done?
>>>
>>>  
>>
>>Brooke
>>
>>Why stop there?
>>Try burying the oscillator under 6ft or so of soil.
>>The daily temperature fluctuations at this depth are very small.
>>
>>Bruce
>>
>>___
>>time-nuts mailing list -- time-nuts@febo.com
>>To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>and follow the instructions there.
> 
> 
> 
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
> 

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Bill Powell]

I doug up and included below a time-nuts email from a couple of years 
ago on improving oscillator stability, with some thoughts from Jack 
Kusters, Tom Clark, and Brooke Clarke.

Also, there's a good history of high precision oscillators at:

http://www.ieee-uffc.org/fc_history/norton.html

Regards,
Bill Powell
af4jg



FROM: 
<[EMAIL PROTECTED]>
 | Save Address

DATE:   Wed, 26 Oct 2005 13:20:14 -0700
TO:   <[EMAIL PROTECTED]>,  SUBJECT:   
RE: [time-nuts] Xtal Oscillator Aging

Hi,

 I posed this question to Jack Kusters, now retired
from HP/Agilent.  He and Charles Adams commercialized
the SC-cut crystal for HP in the 10811A oscillator.  He
gave me permission to post his response on the reflector.

Jim Johnson
[EMAIL PROTECTED]

===

Hi Jim,

In addition to everything Tom Clark said (I agree in general with his
explanation), there is another aging mechanism associated with
stress.  When the crystal blank is manufactured, it is sawn, lapped,
ground, etched, and otherwise abused.  All of this produces stress in
the blank. In addition, there are mounting stresses that arise because
of the way the blank is mounted on its header, surface stresses that
develop because the electrode material when evaporated and then
condensed on the surface shrinks as it cools.

All of these result in long-term aging as these stresses need to
equilibrate out.  In addition, there are other stress related mechanisms
that may result in either long- or short- term aging.  The quartz
material is anisotropic, the mounts, electrode material are isotropic.

So, lets assume that we've had the crystal at an elevated, constant
temperature.  Over a period of time, all stresses, material, mount,
electrode, cracks, etc. equilibrate to their lowest energy level and it
appears that aging has stopped.

Now, take it down in temperature.  The anisotropic quartz and the
isotropic mount and electrode, have different contraction rates, so the
overall system now has a new set of stresses.

Let the unit come to full equilibrium at the new, lower
temperature.  Now take it up in temperature to where it was before.  Now
we see a whole new set of aging and stress relief.  The only virtue is
that aging due to cracks and material stress from manufacturing
processes should be mostly gone, so the unit should come to equilibrium
much faster.

One further comment, glass sealed crystals are not necessarily the best
way to seal a crystal.  It takes heat from a source sufficiently
elevated in temperature to melt the glass.  This tends to cause
contaminents to migrate from the area being sealed to a cooler spot in
the package, usually the crystal.  Contaminents come from gasses from
the torch or from junk trapped in the glass.

The cleanest mount one can do is a cold-weld seal under proper conditions.
For example, the HP crystals were put into a vacuum furnace, heated to
300+ deg-C overnite at 10E-7 torr with the can stored next to the
crystal.  After reducing the temperature to about 80-84 deg-C, the
crystal was frequency plated to within several parts in 10E7.  After
that, the mount was placed in the can, the temperature raised up to
about 150 deg-C, stabilised in temperature and vacuum, then cold-welded.

Done properly, there is essentially no contamination inside the crystal
assembly, most of the other stresses are gone, and the typical HP SC-cut
would reach an aging rate of better than 1E-7 per day, within the first
5 days.

Best regards,
Jack Kusters

==

-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf Of Tom Clark, W3IWI
Sent: Sunday, October 23, 2005 9:21 PM
To: time-nuts@febo.com
Subject: [time-nuts] Xtal Oscillator Aging


  Brooke (no relation) commented

Hi Richard:

>
> It's my understanding that this optimization can be done by changing
> the oscillator power level at the crystal.
>
> In the case of the 32768 Hz watch crystal, it must be run a very low
> power and it has a very low aging rate when compared to higher
> frequency crystals that are typically run at higher power levels.  I
> think this is related to the crystal throwing off atoms, so more power
> means more acceleration and more atoms thrown off.
>
> Have Fun,
>
> Brooke Clarke, N6GCE


  It has nothing to do with "throwing off atoms". A Xtal is actually a
  mechanical oscillator, with the quartz slab vibrating (in either its
  fundamental mode, or on an odd overtone); quartz is a piezo-electric
  material so the voltage across the pins of the xtal has a direct
  connection to the mechanical vibration. When an xtal oscillator starts
  up, the associated amplifier generates noise, which then starts the
  xtal vibrating, which generates signal at the right frequency and a
  feedback loop is set up. When you crank up the power to the mechanical
  resonator, the signal increases with

Re: [time-nuts] Improving the stability of crystal oscillators

[Brooke Clarke]

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

Hi Bruce:

I've also looked into drilling a hole (garden hose, 90 deg fitting & pipe with 
end smashed flat to make a nozzle will easily drill as deep as the pipe is 
long).  Then using a short length of capped copper pipe at the bottom and the 
rest PVC.

Like I think here in California wine country 4 feet would be plenty deep.  But 
this method only works at your home location.  Not too good for a clock that 
will be sent to someone else.

I think the long time constant method can be done in a few cubic inches.

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


Bruce Griffiths wrote:
> ); SAEximRunCond expanded to false
> Errors-To: [EMAIL PROTECTED] RETRY
> 
> Brooke Clarke wrote:
> 
>>Hi:
>>
>>Something I've been thinking about is attaching a large thermal mass of 
>>aluminum to the crystal and it's oscillator then surrounding that with 
>>insulation.  Then surround that with a thin copper layer.  Temperature 
>>sensors 
>>on the copper and aluminum.  If the thermal time constant could be made very 
>>close to 24 hours, or integer multiples of that, it might be possible to 
>>predict the inner temperature allowing compensation.
>>
>>Has this already been done?
>>
>>  
> 
> Brooke
> 
> Why stop there?
> Try burying the oscillator under 6ft or so of soil.
> The daily temperature fluctuations at this depth are very small.
> 
> Bruce
> 
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
> 

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Richard W. Solomon]

Sam Harris (SK) did that over 40 years ago. It provided a stable
reference for his pioneering work in Moonbounce Communication.

73, Dick, W1KSZ/7

-Original Message-
>From: Bruce Griffiths <[EMAIL PROTECTED]>
>Sent: Oct 13, 2007 2:44 PM
>To: Discussion of precise time and frequency measurement 
>Subject: Re: [time-nuts] Improving the stability of crystal oscillators
>
>Brooke Clarke wrote:
>> Hi:
>>
>> Something I've been thinking about is attaching a large thermal mass of 
>> aluminum to the crystal and it's oscillator then surrounding that with 
>> insulation.  Then surround that with a thin copper layer.  Temperature 
>> sensors 
>> on the copper and aluminum.  If the thermal time constant could be made very 
>> close to 24 hours, or integer multiples of that, it might be possible to 
>> predict the inner temperature allowing compensation.
>>
>> Has this already been done?
>>
>>   
>Brooke
>
>Why stop there?
>Try burying the oscillator under 6ft or so of soil.
>The daily temperature fluctuations at this depth are very small.
>
>Bruce
>
>___
>time-nuts mailing list -- time-nuts@febo.com
>To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>and follow the instructions there.


___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Tim Shoppa]

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

"Don Collie" <[EMAIL PROTECTED]> wrote:
> Has anyone concidered using a small Peltier pile to maintain the crystal`s 
> temparature. I understand that these devices will heat or cool, so it would 
> be possible to maintain the crystal temparature at , say, 25 degrees 
> celcius, over a range of ambient temparatures
> [perhaps 0 to 70  degrees]. There would be several advantages in this 
> approach.
> Cheers!,Don Collie jnr. 

Overall, the Petier devices don't heat or cool, just heat :-).

I don't know about crystal oven applications, but condensation on
the cold side has ruled out several applications for Peltiers
at my day job.

Tim.

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Bruce Griffiths]

Brooke Clarke wrote:
> Hi Don:
>
> They are very inefficient to the point that a system that's supposed to cool 
> something may heat it because of all the heat generated by the module.
>
> It takes a huge amount of heat sinking or liquid cooling to get them to work.
>
> Have Fun,
>
> Brooke Clarke
>   
Brooke

The answer depends on how much heat has to be pumped.

Peltier heat pumps are quite effective as long as the amount of heat to
be pumped is relatively small.
With a 70W module a water cooled or blown heatsink is advisable.
With a 1W module an aircooled heatsink is adequate.
Small Peltier heatpump have been used to stabilise the temperature of 
photodiodes etc (HP used them in the 8153 light wave multimeter optical
detector heads).
They have also been successfully used to stabilise the temperature of a
baseplate with devices dissipating 10W or so attached to the baseplate.
Peltier modules are also used in small aerogel insulated refrigerators
and in drink coolers.

One potential problem is that low power peltier modules are very small
so that a high thermal conductivity heat spreader is desirable to
improve the temperature uniformity.
Single stage peltier modules are quite thin so that a thick low thermal
resistance heat-spreader/spacer is required to allow a sufficiently
thick layer on insulation to be used.

Bruce


___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Neon John]

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

Nah, not for this application.  A Peltier module typically has a COP of 1.  
That is,
it moves a watt of energy for each watt consumed.   Thus, for each watt moved, 
two
watts have to be dissipated to air.

I can't imagine a well-insulated quartz oscillator needing more than a watt or 
two of
cooling at the most.  A heat sink capable of handling 4-5 watts should do the 
job
just fine.

Don:  I've seen peltier-controlled "ambient" ovens before but I can't recall the
details.  I'm fairly sure one was a Fluke precision voltage transfer standard in
which the zener reference diode was controlled to a constant temperature.

The advantage of using room temperature, e.g., 70 deg F, is that under most
conditions, the peltier module is doing little to nothing, perhaps just ridding 
the
ovenized unit of the few milliwatts dissipated in the circuit itself.

I've used multiple cascaded modules to cool a nuclear detector (Silicon surface
barrier diode) to reduce its noise. Not as good as LN2 but much cheaper to 
operate.

John 

On Sat, 13 Oct 2007 13:26:52 -0700, Brooke Clarke <[EMAIL PROTECTED]> wrote:

>Hi Don:
>
>They are very inefficient to the point that a system that's supposed to cool 
>something may heat it because of all the heat generated by the module.
>
>It takes a huge amount of heat sinking or liquid cooling to get them to work.

>Don Collie wrote:
>> ); SAEximRunCond expanded to false
>> Errors-To: [EMAIL PROTECTED] RETRY
>> 
>> Has anyone concidered using a small Peltier pile to maintain the crystal`s 
>> temparature. I understand that these devices will heat or cool, so it would 
>> be possible to maintain the crystal temparature at , say, 25 degrees 
>> celcius, over a range of ambient temparatures
>> [perhaps 0 to 70  degrees]. There would be several advantages in this 
>> approach.
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com <-- best little blog on the net!
Tellico Plains, Occupied TN
I like you ... you remind me of me when I was young and stupid.


___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Bruce Griffiths]

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

Brooke Clarke wrote:
> Hi:
>
> Something I've been thinking about is attaching a large thermal mass of 
> aluminum to the crystal and it's oscillator then surrounding that with 
> insulation.  Then surround that with a thin copper layer.  Temperature 
> sensors 
> on the copper and aluminum.  If the thermal time constant could be made very 
> close to 24 hours, or integer multiples of that, it might be possible to 
> predict the inner temperature allowing compensation.
>
> Has this already been done?
>
>   
Brooke

Why stop there?
Try burying the oscillator under 6ft or so of soil.
The daily temperature fluctuations at this depth are very small.

Bruce

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

[time-nuts] Improving the stability of crystal oscillators

[Brooke Clarke]

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

Hi:

Something I've been thinking about is attaching a large thermal mass of 
aluminum to the crystal and it's oscillator then surrounding that with 
insulation.  Then surround that with a thin copper layer.  Temperature sensors 
on the copper and aluminum.  If the thermal time constant could be made very 
close to 24 hours, or integer multiples of that, it might be possible to 
predict the inner temperature allowing compensation.

Has this already been done?

-- 
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

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Brooke Clarke]

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

Hi Don:

They are very inefficient to the point that a system that's supposed to cool 
something may heat it because of all the heat generated by the module.

It takes a huge amount of heat sinking or liquid cooling to get them to work.

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


Don Collie wrote:
> ); SAEximRunCond expanded to false
> Errors-To: [EMAIL PROTECTED] RETRY
> 
> Has anyone concidered using a small Peltier pile to maintain the crystal`s 
> temparature. I understand that these devices will heat or cool, so it would 
> be possible to maintain the crystal temparature at , say, 25 degrees 
> celcius, over a range of ambient temparatures
> [perhaps 0 to 70  degrees]. There would be several advantages in this 
> approach.
> Cheers!,Don Collie jnr. 
> 
> 
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
> 

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

[time-nuts] Improving the stability of crystal oscillators

[Don Collie]

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

Has anyone concidered using a small Peltier pile to maintain the crystal`s 
temparature. I understand that these devices will heat or cool, so it would 
be possible to maintain the crystal temparature at , say, 25 degrees 
celcius, over a range of ambient temparatures
[perhaps 0 to 70  degrees]. There would be several advantages in this 
approach.
Cheers!,Don Collie jnr. 


___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[fre_eng]

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

I used to use the clipon posistors to stabilise my crystals (the Murata 
BM500N previously mentioned) but after seeing some results on what 
temperature they really stabilise at versus what they should stabilise at i 
moved on to the heater controller design by John Hazell at 

http://www.microwaves.dsl.pipex.com/mk2/mk2.pdf 

note in recent iterations the crystal is embedded in the aluminium block 

After using the calibration technique he mentions to operate the crystal at 
the "knee" point oscillators have had adequate stability for 134GHz local 
oscillator usage 

Dave 

 

> Message: 1
> Date: Wed, 10 Oct 2007 10:14:28 -0700 (PDT)
> From: Tom Clifton <[EMAIL PROTECTED]>
> Subject: [time-nuts] Improving the stability of crystal oscillators
> To: time-nuts@febo.com
> Message-ID: <[EMAIL PROTECTED]>
> Content-Type: text/plain; charset=iso-8859-1 
> 
> While the website is not explicitly about frequency
> measurement, there is an interesting bit on improving 
> the stability of crystal oscillators with external
> heater controllers.  While it may not be suitable for
> long term high stability control it might be suitable
> for many other purposes. 
> 
> http://www.qrss.thersgb.net/Crystal-Ovens.html 
> 
> The main page is also a good read: 
> 
> http://www.qrss.thersgb.net/Receiving-QRSS.html#Introduction
 


___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[SAIDJACK]

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

 
In a message dated 10/11/2007 11:52:37 Pacific Daylight Time,  
[EMAIL PROTECTED] writes:

>Maybe Vectron has figured out something we didn't think of  or
>has sufficiently difference constraints that a vacuum  makes
>sense for them.

>Rick Karlquist  N6RK



Hi Rick,
 
they get 0.2ppm with it over -45C to 85C, I think that's a pretty  acceptable 
performance in a small DIP-8 can which is not much bigger than a  penny 
really, including all the circuitry!
 
Probably the best insulator to use in that small of a case, where you only  
have a millimeter or two between the crystal blank and the housing. Any other  
material would probably have much less insulation.
 
One interesting fact to mention is the +85C upper limit, there are very few  
OCXO's out there that run their crystals over 90C as would be required. Most  
seem to run between 80C and 90C and it get's really expensive if one looks for 
 an OCXO that is speced to operate above +75C.
 
Then again the DIP-8 is still vapor-ware...
 
bye,
Said



** See what's new at http://www.aol.com
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[SAIDJACK]

 
In a message dated 10/11/2007 14:31:04 Pacific Daylight Time,  
[EMAIL PROTECTED] writes:

>The  lack of radiation shields and an isothermal block enclosing  the
>oscillator components within the vacuum will surely reduce  the
>performance somewhat.

>Bruce



Hi Bruce,
 
yes I would agree, the spec of 2E-07 is not that great by itself.
 
But if we look at their market which seems to be space/military/Telecom  
mostly for this part, then it starts to make sense. Not many DIP size OCXO's 
out  
there, Micro Crystal makes one as well.
 
I wonder how expensive these parts will be. If they are in the $30 to $75  
range they could be a good match for a lot of apps.
 
Nice building blocks nonetheless, and their phase noise is very acceptable  
for the size as well. No ADEV specs unfortunately.
 
bye,
Said



** See what's new at http://www.aol.com
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Magnus Danielson]

From: Bruce Griffiths <[EMAIL PROTECTED]>
Subject: Re: [time-nuts] Improving the stability of crystal oscillators
Date: Fri, 12 Oct 2007 10:08:34 +1300
Message-ID: <[EMAIL PROTECTED]>

Hej Bruce and Neville,

> Neville Michie wrote:
> >
> > If you use a transistor as a heater, the full supply voltage is  
> > across the
> > element all the time, so heating is proportional to the current flowing.
> >
> > Neville
> >   
> Neville
> 
> However using a transistor has the disadvantage of a small area heat
> source rather than the large area heat source possible with a heater
> winding.
> Using a small area heat source produces significant temperature gradients.

Using a single transistor yes. Spread out transistors can provide significantly
less gradients.

Cheers,
Magnus

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[christopher hoover]

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

Rick Karlquist N6RK wrote:
> If you want to "soup up" at 10811 oven, externally wire in a
> larger capacitor in parallel and change the resistors to increase
> the gain.  The 10811 designers did the best they could with
> what they had to work with, but you don't want to blindly 
> copy them in new applications.

That would be an interesting experiment.  Hmmm ...

I suppose we can presume that the 10811 tempco wasn't good enough
for the requirements for the Z3801A, given that in that application
the 10811 was placed inside of another oven.

I now have both a Z3801A and a Z3815A w/E1938A.  But I
haven't yet compared them head to head.

Tom: I presume the Z3801A is included in your GPSDO comparison
project.  Is the Z3815A included, too?  What's your status? 
 
-ch



___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Rick Karlquist]

We went through this tradeoff on the E1938A.  Resistive heaters
can be distributed.  However, it is very inefficient to drive
them with transistors, because then you waste a lot of power
heating the transistors, which is waste heat if resistive heating
is used.  Prior to the 10544, they just put up with this.  The
10544 used a switching regulator for up the efficiency, but it
put a 1 kHz spur on the oscillator.  The 10811 used two transistors
on opposite sides to try to sort of distribute the heat.  On
the E1938A, we looked at an array of small surface mount transistors
to have the best of both worlds.  However, this turned out not to
be manufacturable and we settled for resistive heaters (back to
1970!).

Rick Karlquist N6RK


Bruce Griffiths wrote:
> ); SAEximRunCond expanded to false
> Errors-To: [EMAIL PROTECTED] RETRY
>
> Neville Michie wrote:
>>
>> If you use a transistor as a heater, the full supply voltage is
>> across the
>> element all the time, so heating is proportional to the current flowing.
>>
>> Neville
>>
> Neville
>
> However using a transistor has the disadvantage of a small area heat
> source rather than the large area heat source possible with a heater
> winding.
> Using a small area heat source produces significant temperature gradients.
>
> Bruce
>
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>
>



___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Bruce Griffiths]

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

[EMAIL PROTECTED] wrote:
> Hi Rick,
>  
> thanks for the pointers to the E1938A oven quality.
>  
> Today there are some interesting new technologies which allow small double,  
> or even tripple (not sure if that makes sense) ovens to be built. Vectron for 
>  
> example just had a lead-article in RFDesign magazine  introducing their  
> newest evacuated OCXO's.
>  
>_http://rfdesign.com/vlf_to_uhf/time_and_frequency/709RFDF1.pdf_ 
> (http://rfdesign.com/vlf_to_uhf/time_and_frequency/709RFDF1.pdf) 
>  
> They claim stabilities on the order of 2E-07 over a very wide temp  range of 
> -40 to +85C in a DIP14 can.
>  
> The 1/2 size DIP8 can is supposed to be available end of the year with  
> similar performance.
>  
> Those small cans and wide operating ranges should make it possible to build  
> a nice small and inexpensive oven. If one can get a true thermal gain of  
> 1000+, then that would theoretically mean stabilities approaching 2E-010  
> over 
> temperature. That's 1.6E-012 per degree Celcius.
>  
> bye,
> Said
>   
Said

The lack of radiation shields and an isothermal block enclosing the
oscillator components within the vacuum will surely reduce the
performance somewhat.

Bruce

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Bruce Griffiths]

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

Neville Michie wrote:
>
> If you use a transistor as a heater, the full supply voltage is  
> across the
> element all the time, so heating is proportional to the current flowing.
>
> Neville
>   
Neville

However using a transistor has the disadvantage of a small area heat
source rather than the large area heat source possible with a heater
winding.
Using a small area heat source produces significant temperature gradients.

Bruce

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Neville Michie]

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


On 11/10/2007, at 10:23 PM, Bruce Griffiths wrote:


> If one uses resistive heating then some linearisation improves the
> performance as the heat from the heating element is proportional to  
> the
> square of the voltage across the heating element.
>

If you use a transistor as a heater, the full supply voltage is  
across the
element all the time, so heating is proportional to the current flowing.

Neville

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Brooke Clarke]

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

Hi Tom:

Very interesting.  How about  building a circuit to drive those GR crystals?

The same man is the inventor of all four of the early GR patents, James Kilton 
Clapp, of   "Clapp Oscillator" fame.
http://en.wikipedia.org/wiki/Clapp_oscillator
In the 1930s GR patents he's showing an inductor in series with the crystal and 
Wiki dates the "Clapp Oscillator" 1948 where a capacitor is in series.

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

Tom Van Baak wrote:
> 
> Maybe because it was written back in 1930's, but one of the better
> discussions of quartz temperature control, including considerations
> of insulation and isothermal layers (attenuation and conduction)
> are in the patents for the old double oven General Radio frequency
> standard:
> 
> http://www.leapsecond.com/museum/gr676b-50kc/
> http://www.leapsecond.com/museum/gr676b-50kc/US1967185.pdf
> 
> /tvb
> 
> 
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
> 

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Rick Karlquist]

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

At HP, in the 90's, we did a lot of brainstorming about vacuum ovens.
This never seemed to make sense to us.  If you actually
achieve high amounts of thermal resistance, then you can't
get the heat out of the oven.  And if you don't, why bother
with a vacuum.  Also, a vacuum only helps if you do everything
else you need to do to make a true Dewar (thermos bottle), like
having mirrored surfaces, etc.  Finally, having a vacuum means
that nothing that outgasses can be used in the oscillator.
Maybe Vectron has figured out something we didn't think of or
has sufficiently difference constraints that a vacuum makes
sense for them.

Rick Karlquist N6RK



[EMAIL PROTECTED] wrote:

> Today there are some interesting new technologies which allow small
> double,
> or even tripple (not sure if that makes sense) ovens to be built. Vectron
> for
> example just had a lead-article in RFDesign magazine  introducing their
> newest evacuated OCXO's.
>
>_http://rfdesign.com/vlf_to_uhf/time_and_frequency/709RFDF1.pdf_
> (http://rfdesign.com/vlf_to_uhf/time_and_frequency/709RFDF1.pdf)
>
> They claim stabilities on the order of 2E-07 over a very wide temp  range
> of
> -40 to +85C in a DIP14 can.
>
> The 1/2 size DIP8 can is supposed to be available end of the year with
> similar performance.
>
> Those small cans and wide operating ranges should make it possible to
> build
> a nice small and inexpensive oven. If one can get a true thermal gain of
> 1000+, then that would theoretically mean stabilities approaching 2E-010
> over
> temperature. That's 1.6E-012 per degree Celcius.
>
> bye,
> Said
>


___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[SAIDJACK]

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

 
In a message dated 10/11/2007 09:12:44 Pacific Daylight Time,  
[EMAIL PROTECTED] writes:

>Your  last statement is not generally true.  The block cannot be  well
>insulated because of the thermal overhead of the oven circuitry  (the
>heat has to escape).  I explained in my 1997 FCS paper how to  achieve
>the isothermal condition, which is achieved by symmetry rather  than
>high amounts of insulation.  The E1938A oven works quite well  if the
>insulation is omitted or replaced by poor insulation, except  that it
>consumes more power.

>Rick Karlquist  N6RK



Hi Rick,
 
thanks for the pointers to the E1938A oven quality.
 
Today there are some interesting new technologies which allow small double,  
or even tripple (not sure if that makes sense) ovens to be built. Vectron for  
example just had a lead-article in RFDesign magazine  introducing their  
newest evacuated OCXO's.
 
   _http://rfdesign.com/vlf_to_uhf/time_and_frequency/709RFDF1.pdf_ 
(http://rfdesign.com/vlf_to_uhf/time_and_frequency/709RFDF1.pdf) 
 
They claim stabilities on the order of 2E-07 over a very wide temp  range of 
-40 to +85C in a DIP14 can.
 
The 1/2 size DIP8 can is supposed to be available end of the year with  
similar performance.
 
Those small cans and wide operating ranges should make it possible to build  
a nice small and inexpensive oven. If one can get a true thermal gain of  
1000+, then that would theoretically mean stabilities approaching 2E-010  over 
temperature. That's 1.6E-012 per degree Celcius.
 
bye,
Said



** See what's new at http://www.aol.com
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Richard (Rick) Karlquist]

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

The 10811 has an ANALOG oven control loop.  The gain is set
to be just below the oscillation point.  This is due to the
stability limits dictated by the oven mass and (believe it
or not) the size of integrator capacitor that can physically
fit.  If you want to "soup up" at 10811 oven, externally wire
in a larger capacitor in parallel and change the resistors to
increase the gain.  The 10811 designers did the best they
could with what they had to work with, but you don't want to
blindly copy them in new applications.

BTW, do not use a "metalized" plastic integrator capacitor.
Must be "foil" type.

I am extremely happy with the PII^2D control loop on the E1938A
(I didn't design it, only tested it).  I can't imagine anything
being better.

Rick Karlquist N6RK

Bruce Griffiths wrote:
>
> 
> If a purely proportional control loop has such great performance why
> does the 10811A use a PI temperature controller and the E1938A use a
> PII^2 D controller?
> 
> Surely the finite offset between the setpoint and actual temperature
> achieved by a proportional controller is a source of long term
> temperature instability?
> If one uses resistive heating then some linearisation improves the
> performance as the heat from the heating element is proportional to the
> square of the voltage across the heating element.
> 
> A state space controller may give improved performance but PI(10811A),
> PID and PII^2 D(E1938A) controllers seem to work well when used to
> regulate crystal oscillator temperatures.
> 
> Bruce
> 
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
> 
> 

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Richard (Rick) Karlquist]

Neville Michie wrote:

> I am not trying to start an argument, but I would like to point out  
> that PID controllers are only
> good at controlling a certain class of system.

> The thermal block controllers work well because of the dominant  
> integrating effect of the block,
> the time delay for a heat front to propagate through the block is the  
> only concern for instability.
> When instability is a problem I relocate the thermistor closer to the  
> heater, giving a marginal degree of under-
> control.
> Because the block is well insulated it soon becomes very close to  
> isothermal.
> cheers, Neville Michie

I would like to point out that the E1938A uses a PID controller and
has a *transient* thermal gain of many 1000's not to mention a static
gain that has in some cases exceeded 1,000,000 for a single oven.

Your last statement is not generally true.  The block cannot be well
insulated because of the thermal overhead of the oven circuitry (the
heat has to escape).  I explained in my 1997 FCS paper how to achieve
the isothermal condition, which is achieved by symmetry rather than
high amounts of insulation.  The E1938A oven works quite well if the
insulation is omitted or replaced by poor insulation, except that it
consumes more power.

Rick Karlquist N6RK

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Bruce Griffiths]

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

Neville Michie wrote:
> Hi All,
> I am not trying to start an argument, but I would like to point out  
> that PID controllers are only
> good at controlling a certain class of system.
> For a system that has a coal truck that must dump its coal down a  
> hole, the system has mass, velocity
> and distance, all the qualities to get a perfectly damped system with  
> PID control.
> For thermal control, the function is more likely to be a Bessel  
> Function, and a Z transform filter
> is more likely to find a match.
> In any case, PID controllers are often to be found in totally  
> unsuitable situations giving worse control
> than even a bang-bang controller.
> The thermal block controllers work well because of the dominant  
> integrating effect of the block,
> the time delay for a heat front to propagate through the block is the  
> only concern for instability.
> When instability is a problem I relocate the thermistor closer to the  
> heater, giving a marginal degree of under-
> control.
> Because the block is well insulated it soon becomes very close to  
> isothermal.
> cheers, Neville Michie
>
>
>
>   
Neville

If a purely proportional control loop has such great performance why
does the 10811A use a PI temperature controller and the E1938A use a
PII^2 D controller?

Surely the finite offset between the setpoint and actual temperature
achieved by a proportional controller is a source of long term
temperature instability?
If one uses resistive heating then some linearisation improves the
performance as the heat from the heating element is proportional to the
square of the voltage across the heating element.

A state space controller may give improved performance but PI(10811A),
PID and PII^2 D(E1938A) controllers seem to work well when used to
regulate crystal oscillator temperatures.

Bruce

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Tom Van Baak]

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

Maybe because it was written back in 1930's, but one of the better
discussions of quartz temperature control, including considerations
of insulation and isothermal layers (attenuation and conduction)
are in the patents for the old double oven General Radio frequency
standard:

http://www.leapsecond.com/museum/gr676b-50kc/
http://www.leapsecond.com/museum/gr676b-50kc/US1967185.pdf

/tvb


___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Neville Michie]

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

Hi All,
I am not trying to start an argument, but I would like to point out  
that PID controllers are only
good at controlling a certain class of system.
For a system that has a coal truck that must dump its coal down a  
hole, the system has mass, velocity
and distance, all the qualities to get a perfectly damped system with  
PID control.
For thermal control, the function is more likely to be a Bessel  
Function, and a Z transform filter
is more likely to find a match.
In any case, PID controllers are often to be found in totally  
unsuitable situations giving worse control
than even a bang-bang controller.
The thermal block controllers work well because of the dominant  
integrating effect of the block,
the time delay for a heat front to propagate through the block is the  
only concern for instability.
When instability is a problem I relocate the thermistor closer to the  
heater, giving a marginal degree of under-
control.
Because the block is well insulated it soon becomes very close to  
isothermal.
cheers, Neville Michie



On 11/10/2007, at 3:08 PM, Bruce Griffiths wrote:

> Neville Michie wrote:
>> I have made several ovens for oscillators over the years.
>> The recipe is:
>> get a piece of aluminium big enough to contain the oscillator,
>> voltage regulator and first stage amplifier.
>> With a mill remove the shapes of each component.
>> Bolt a large power transistor, large power fets are best, to the
>> outside of the block as a heater, and it is run
>> off the unregulated input power. Judicious selection of a component
>> decides the start-up current.
>> Make a plate to cover the excavation for the components, and bolt it
>> down.
>> The circuit can be made with discrete transistors in the most
>> unstable looking amplifier ever seen,
>> alternating NPN and PNP transistors, connected directly to each other
>> with load resistors.
>> The main temperature sensor is a resistor bridge with a high value
>> glass encapsulated thermistor.
>> These are available a several trade houses. The amplifier is also
>> temperature sensitive, but is within the thermal loop.
>> The thermistor bridge gives a very large signal ~ 50mV per degree.
>> Gain may have to be backed off if thermal
>> oscillations do not die down, but the metal block acts as an
>> integrator and the circuits are very easy to get
>> high gain and sensitivity.
>> The whole block is packed in two inches of foam insulation, my 1MHz
>> oscillator only draws about 80 mA at 12 volts.
>> The temperature is set to 40 C.
>> The stability of the oscillator is very good, but as I have not yet
>> got a disciplined oscillator going I dont know which is drifting,
>> the HP 10811 in my frequency counter or the 1MHz oscillator. After a
>> year, the difference is currently 0.3 ppm.
>> cheers Neville Michie
>>
>>
> Neville
>
> A correctly tuned PID control loop should allow even tighter  
> temperature
> control.
> A "boostrapped" oven like that used by Wenzel should be even better.
>
> (http://www.wenzel.com/documents/Sub-pico%20Multiplier.pdf).
>
>
> Despite Wenzel's claims this type of oven isn't new it was used for
> portable standard cell enclosures decades ago.
>
> Bruce
>
>
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/ 
> time-nuts
> and follow the instructions there.


___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Bruce Griffiths]

Neville Michie wrote:
> I have made several ovens for oscillators over the years.
> The recipe is:
> get a piece of aluminium big enough to contain the oscillator,  
> voltage regulator and first stage amplifier.
> With a mill remove the shapes of each component.
> Bolt a large power transistor, large power fets are best, to the  
> outside of the block as a heater, and it is run
> off the unregulated input power. Judicious selection of a component  
> decides the start-up current.
> Make a plate to cover the excavation for the components, and bolt it  
> down.
> The circuit can be made with discrete transistors in the most  
> unstable looking amplifier ever seen,
> alternating NPN and PNP transistors, connected directly to each other  
> with load resistors.
> The main temperature sensor is a resistor bridge with a high value  
> glass encapsulated thermistor.
> These are available a several trade houses. The amplifier is also  
> temperature sensitive, but is within the thermal loop.
> The thermistor bridge gives a very large signal ~ 50mV per degree.  
> Gain may have to be backed off if thermal
> oscillations do not die down, but the metal block acts as an  
> integrator and the circuits are very easy to get
> high gain and sensitivity.
> The whole block is packed in two inches of foam insulation, my 1MHz  
> oscillator only draws about 80 mA at 12 volts.
> The temperature is set to 40 C.
> The stability of the oscillator is very good, but as I have not yet  
> got a disciplined oscillator going I dont know which is drifting,
> the HP 10811 in my frequency counter or the 1MHz oscillator. After a  
> year, the difference is currently 0.3 ppm.
> cheers Neville Michie
>   
>
Neville

A correctly tuned PID control loop should allow even tighter temperature
control.
A "boostrapped" oven like that used by Wenzel should be even better.

(http://www.wenzel.com/documents/Sub-pico%20Multiplier.pdf).


Despite Wenzel's claims this type of oven isn't new it was used for
portable standard cell enclosures decades ago.

Bruce


___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Neville Michie]

I have made several ovens for oscillators over the years.
The recipe is:
get a piece of aluminium big enough to contain the oscillator,  
voltage regulator and first stage amplifier.
With a mill remove the shapes of each component.
Bolt a large power transistor, large power fets are best, to the  
outside of the block as a heater, and it is run
off the unregulated input power. Judicious selection of a component  
decides the start-up current.
Make a plate to cover the excavation for the components, and bolt it  
down.
The circuit can be made with discrete transistors in the most  
unstable looking amplifier ever seen,
alternating NPN and PNP transistors, connected directly to each other  
with load resistors.
The main temperature sensor is a resistor bridge with a high value  
glass encapsulated thermistor.
These are available a several trade houses. The amplifier is also  
temperature sensitive, but is within the thermal loop.
The thermistor bridge gives a very large signal ~ 50mV per degree.  
Gain may have to be backed off if thermal
oscillations do not die down, but the metal block acts as an  
integrator and the circuits are very easy to get
high gain and sensitivity.
The whole block is packed in two inches of foam insulation, my 1MHz  
oscillator only draws about 80 mA at 12 volts.
The temperature is set to 40 C.
The stability of the oscillator is very good, but as I have not yet  
got a disciplined oscillator going I dont know which is drifting,
the HP 10811 in my frequency counter or the 1MHz oscillator. After a  
year, the difference is currently 0.3 ppm.
cheers Neville Michie



On 11/10/2007, at 9:24 AM, Didier Juges wrote:

> I bought 10kohm nominal NTC thermistors  from Digikey, P/N 490-4653- 
> ND. They
> are very small, 1/10th of an inch long or so.
>
> I have used those (or similar parts) in projects both at home and  
> at work
> (in military equipment...) for about 15 years.
>
> Didier KO4BB
>
>> -Original Message-
>> From: [EMAIL PROTECTED]
>> [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED]
>> Sent: Wednesday, October 10, 2007 1:17 PM
>> To: time-nuts@febo.com
>> Subject: Re: [time-nuts] Improving the stability of crystal
>> oscillators
>>
>> In a message dated 10/10/2007 11:13:21 Pacific Daylight Time,
>> [EMAIL PROTECTED]
>> writes:
>>
>>> We  first built a small proportional heater circuit that we
>> could shove
>>> in  next to the crystal, and that worked OK.  We finally found a
>>> source for thermistors spot welded to a spring clip that
>> would mount
>>> snugly directly to the crystal case.  With 12 volts applied, these
>>> heated the crystals very nicely.  With the heaters, we were able  to
>>> keep the systems running year round with about 1/10 the
>> service  calls.
>>
>> Hi John,
>>
>> interesting anecdote!
>>
>> Would you know if the thermistors are still available? Who made   
>> them?
>>
>> Thanks
>> Said
>>
>>
>>
>>
>>
>>
>>
>>
>> ** See what's new at
>> http://www.aol.com ___
>> time-nuts mailing list -- time-nuts@febo.com To unsubscribe,
>> go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>
>
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/ 
> time-nuts
> and follow the instructions there.


___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Didier Juges]

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

I bought 10kohm nominal NTC thermistors  from Digikey, P/N 490-4653-ND. They
are very small, 1/10th of an inch long or so.

I have used those (or similar parts) in projects both at home and at work
(in military equipment...) for about 15 years.

Didier KO4BB

> -Original Message-
> From: [EMAIL PROTECTED] 
> [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED]
> Sent: Wednesday, October 10, 2007 1:17 PM
> To: time-nuts@febo.com
> Subject: Re: [time-nuts] Improving the stability of crystal 
> oscillators
> 
> In a message dated 10/10/2007 11:13:21 Pacific Daylight Time, 
> [EMAIL PROTECTED]
> writes:
> 
> >We  first built a small proportional heater circuit that we 
> could shove 
> >in  next to the crystal, and that worked OK.  We finally found a  
> >source for thermistors spot welded to a spring clip that 
> would mount  
> >snugly directly to the crystal case.  With 12 volts applied, these  
> >heated the crystals very nicely.  With the heaters, we were able  to 
> >keep the systems running year round with about 1/10 the 
> service  calls.
> 
> Hi John,
>  
> interesting anecdote!
>  
> Would you know if the thermistors are still available? Who made  them?
>  
> Thanks
> Said
> 
> 
> 
> 
> 
> 
> 
> 
> ** See what's new at 
> http://www.aol.com ___
> time-nuts mailing list -- time-nuts@febo.com To unsubscribe, 
> go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.


___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Magnus Danielson]

From: [EMAIL PROTECTED]
Subject: Re: [time-nuts] Improving the stability of crystal oscillators
Date: Wed, 10 Oct 2007 14:17:24 EDT
Message-ID: <[EMAIL PROTECTED]>

John,

> In a message dated 10/10/2007 11:13:21 Pacific Daylight Time, [EMAIL 
> PROTECTED]  
> writes:
> 
> >We  first built a small proportional heater circuit that we could shove
> >in  next to the crystal, and that worked OK.  We finally found a  source
> >for thermistors spot welded to a spring clip that would mount  snugly
> >directly to the crystal case.  With 12 volts applied, these  heated the
> >crystals very nicely.  With the heaters, we were able  to keep the
> >systems running year round with about 1/10 the service  calls.
> 
> Hi John,
>  
> interesting anecdote!

Agree!

Thanks!

Cheers,
Magnus

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Brooke Clarke]

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

Hi Brian:

I used to use "Balco" (as far as I can remember) positive coefficient resistors 
that had specs similar to the Digikey units you linked to.  These were only 
available in values under 200 Ohms and have a positive linear coefficient.

The more common negative coefficient type like:

have a much larger change with temperature and so are a very common way to 
sense a set point.  When a resistor with the same value is used to make a half 
bridge the voltage change around the balance point is nearly linear.

There's a way  to fit a third order polynomial to the data and once you have 
the coefficients it's only a linear equation to solve for converting resistance 
back to temperature.

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


[EMAIL PROTECTED] wrote:
> ); SAEximRunCond expanded to false
> Errors-To: [EMAIL PROTECTED] RETRY
> 
> Try DigiKey pn:  235-1123-ND  for a simple PTC Thermistor that can be
> soldered to the xtal case if one were so inclined. Do so at your own
> risk to the xtal!
> 
> -Brian
> 
> 
> -- Original message --
> From: John Ackermann N8UR <[EMAIL PROTECTED]>
> 
>>[EMAIL PROTECTED] said the following on 10/10/2007 02:17 PM:
>>
>>>In a message dated 10/10/2007 11:13:21 Pacific Daylight Time, [EMAIL 
>>>PROTECTED]  
>>>writes:
>>>
>>>
We  first built a small proportional heater circuit that we could shove
in  next to the crystal, and that worked OK.  We finally found a  source
for thermistors spot welded to a spring clip that would mount  snugly
directly to the crystal case.  With 12 volts applied, these  heated the
crystals very nicely.  With the heaters, we were able  to keep the
systems running year round with about 1/10 the service  calls.
>>>
>>>Hi John,
>>> 
>>>interesting anecdote!
>>> 
>>>Would you know if the thermistors are still available? Who made  them?
>>
>>We bought them as a replacement part from Yaesu USA.  This data is 10
>>years or more old, but here you go:
>>
>>Part Name Yaesu Part Number   Murata Part Number
>>Posistor  G9090019PTH507A01BG330N020
>>
>>They used to be about $7.00 each.  Yaesu's parts-order phone number at
>>the time was (800) 255-9237.  I'm not sure if there's another source for
>>the Murata part; back then, we couldn't find one.
>>
>>Amazingly, I still have a web page documenting all that we learned about
>>those cursed radios, including the schematic of our original homebrew
>>heater design: http://www.febo.com/hamdocs/d4art.html.  The quality of
>>the heater schematic isn't very good, but it's all I have.
>>
>>John
>>
>>___
>>time-nuts mailing list -- time-nuts@febo.com
>>To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>and follow the instructions there.
> 
> 
> 
> 
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
> 

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[GandalfG8]

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

In a message dated 10/10/2007 19:34:55 GMT Daylight Time, [EMAIL PROTECTED]  
writes:

We  bought them as a replacement part from Yaesu USA.  This data is  10
years or more old, but here you go:

Part NameYaesu  Part NumberMurata Part Number
Posistor G9090019PTH507A01BG330N020
-



I don't know if this is the same part, Ebay Ref...110177471348, but this  
seller has been selling these two at a time for quite a while.
Might be ok if you just want a couple to play with, probably not ideal for  
planning a production run:-)
 
regards
 
Nigel
GM8PZR



   
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[John Ackermann N8UR]

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

[EMAIL PROTECTED] said the following on 10/10/2007 02:39 PM:

> BTW: I wonder how much effect thermistor and resistor-bridge aging as well  
> as opamp offset drift has on the long term aging of typical OCXO's since it 
> will  shift the temperature setpoint of the crystal.
>  
> I think this is an issue that's not receiving a lot of attention in the  
> literature..

More anecdotes.  I have a bunch of old Sulzer 2.5 and 5 oscillators.  As
Tom will happily tell you, one of these guys that still works well can
be one of the best pieces of quartz you'll ever find (and a great toilet
flush detector!).  But most of mine are a bit flaky, and the thermistors
seem to be the main problem.  Each unit has at least two -- one is
inside the inner oven and is part of a bridge that drives the "TEMP"
meter position; it's supposed to read 0 when the oven is at temperature.
 Another is part of the bridge that sets the oven temperature; there are
hand-chosen components designed to work with the thermistor to drive the
heater to the right temperature.  I've seen units where one or both was
so far off, you couldn't really tell what the oven was doing.  In at
least one case, there was an open that drove the oven full blast
continuously.

Someday I'd like to build a test fixture that would allow measuring the
crystal turning point and setting the ovens back to optimal temperature...

So, aging of these parts can certainly be an issue.

John

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[wa1zms]

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

Try DigiKey pn:  235-1123-ND  for a simple PTC Thermistor that can be
soldered to the xtal case if one were so inclined. Do so at your own
risk to the xtal!

-Brian


-- Original message --
From: John Ackermann N8UR <[EMAIL PROTECTED]>
>
> [EMAIL PROTECTED] said the following on 10/10/2007 02:17 PM:
> > In a message dated 10/10/2007 11:13:21 Pacific Daylight Time, [EMAIL 
> > PROTECTED]  
> > writes:
> > 
> >> We  first built a small proportional heater circuit that we could shove
> >> in  next to the crystal, and that worked OK.  We finally found a  source
> >> for thermistors spot welded to a spring clip that would mount  snugly
> >> directly to the crystal case.  With 12 volts applied, these  heated the
> >> crystals very nicely.  With the heaters, we were able  to keep the
> >> systems running year round with about 1/10 the service  calls.
> > 
> > Hi John,
> >  
> > interesting anecdote!
> >  
> > Would you know if the thermistors are still available? Who made  them?
> 
> We bought them as a replacement part from Yaesu USA.  This data is 10
> years or more old, but here you go:
> 
> Part Name Yaesu Part Number   Murata Part Number
> Posistor  G9090019PTH507A01BG330N020
> 
> They used to be about $7.00 each.  Yaesu's parts-order phone number at
> the time was (800) 255-9237.  I'm not sure if there's another source for
> the Murata part; back then, we couldn't find one.
> 
> Amazingly, I still have a web page documenting all that we learned about
> those cursed radios, including the schematic of our original homebrew
> heater design: http://www.febo.com/hamdocs/d4art.html.  The quality of
> the heater schematic isn't very good, but it's all I have.
> 
> John
> 
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.



___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[SAIDJACK]

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

 
In a message dated 10/10/2007 11:34:43 Pacific Daylight Time, [EMAIL PROTECTED] 
 
writes:

>heater design: http://www.febo.com/hamdocs/d4art.html.  The  quality of
>the heater schematic isn't very good, but it's all I  have.

>John


Thanks John!
 
BTW: I wonder how much effect thermistor and resistor-bridge aging as well  
as opamp offset drift has on the long term aging of typical OCXO's since it 
will  shift the temperature setpoint of the crystal.
 
I think this is an issue that's not receiving a lot of attention in the  
literature..
 
Said



** See what's new at http://www.aol.com
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[John Ackermann N8UR]

[EMAIL PROTECTED] said the following on 10/10/2007 02:17 PM:
> In a message dated 10/10/2007 11:13:21 Pacific Daylight Time, [EMAIL 
> PROTECTED]  
> writes:
> 
>> We  first built a small proportional heater circuit that we could shove
>> in  next to the crystal, and that worked OK.  We finally found a  source
>> for thermistors spot welded to a spring clip that would mount  snugly
>> directly to the crystal case.  With 12 volts applied, these  heated the
>> crystals very nicely.  With the heaters, we were able  to keep the
>> systems running year round with about 1/10 the service  calls.
> 
> Hi John,
>  
> interesting anecdote!
>  
> Would you know if the thermistors are still available? Who made  them?

We bought them as a replacement part from Yaesu USA.  This data is 10
years or more old, but here you go:

Part Name   Yaesu Part Number   Murata Part Number
PosistorG9090019PTH507A01BG330N020

They used to be about $7.00 each.  Yaesu's parts-order phone number at
the time was (800) 255-9237.  I'm not sure if there's another source for
the Murata part; back then, we couldn't find one.

Amazingly, I still have a web page documenting all that we learned about
those cursed radios, including the schematic of our original homebrew
heater design: http://www.febo.com/hamdocs/d4art.html.  The quality of
the heater schematic isn't very good, but it's all I have.

John

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[SAIDJACK]

In a message dated 10/10/2007 11:13:21 Pacific Daylight Time, [EMAIL PROTECTED] 
 
writes:

>We  first built a small proportional heater circuit that we could shove
>in  next to the crystal, and that worked OK.  We finally found a  source
>for thermistors spot welded to a spring clip that would mount  snugly
>directly to the crystal case.  With 12 volts applied, these  heated the
>crystals very nicely.  With the heaters, we were able  to keep the
>systems running year round with about 1/10 the service  calls.

Hi John,
 
interesting anecdote!
 
Would you know if the thermistors are still available? Who made  them?
 
Thanks
Said








** See what's new at http://www.aol.com
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[John Ackermann N8UR]

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

This is getting off topic (because it's far to practical!) but hanging
heaters on crystals is a time-honored activity for hams.  Many of the
surplus FM rigs for VHF and UHF that we obtained from the likes of
Motorola, GE, RCA, etc. that were made B.S. (before synthesizers) had
ovens, or later "channel elements" that were actually TCXOs.  This was
particularly necessary for UHF systems that operated in rugged
environments.  But most ham-grade gear didn't have anything like this.

I spent quite a bit of time 15 years ago building a packet radio network
 that linked Columbus, Dayton, and Cincinnati Ohio using UHF (440 MHz)
19.2 kbps data radios made by Kantronics, a company with limited RF
experience.  The data transmission scheme we used required a frequency
tolerance of about +/- 2 kHz at 440 MHz (i.e., about 5x10e-6).  The
standard crystals could almost maintain that tolerance in a nicely
regulated room, but we had these radios out in transmitter shacks in the
middle of corn fields, and with wide temperature swings the radio links
would die completely.

We first built a small proportional heater circuit that we could shove
in next to the crystal, and that worked OK.  We finally found a source
for thermistors spot welded to a spring clip that would mount snugly
directly to the crystal case.  With 12 volts applied, these heated the
crystals very nicely.  With the heaters, we were able to keep the
systems running year round with about 1/10 the service calls.

The original crystals (designed for room temperature) worked OK and we
could warp them onto frequency even with the heaters installed, but we
noticed what seemed to be accelerated aging; after a couple of years,
the crystals could no longer be brought onto frequency.  Later, we
ordered some crystals designed for higher temperature (I think it was
something like 50 degrees C) and those were both easier to trim, and
didn't seem to suffer the rapid aging.

That network is now dead and gone, victim of single-source components
(Kantronics stopped making or supporting the radios, and some of the
transistors became Unobtanium) as well as the death of traditional
packet radio in the face of the internet.  Sigh...

John

Brooke Clarke said the following on 10/10/2007 01:52 PM:

> Hi Tom:
> 
> That's a cleaver improvement to a non ovenized crystal.  Usually crystals are 
> ground to have a temp vs freq turnover point occur at a specified 
> temperature. 
>   The common one is to be on frequency at room temperature.  So if a room 
> temperature crystal is heated it's no longer operating at the turnover 
> temperature and so there is a steep delta frequency vs. temperature slope.  
> Did 
>   you get a crystal cut for your heater temperature or somehow match the 
> heaters temperature to a turnover point on your crystal?
> 
> I spent many many hours adjusting the oven temperature of a Gibbs frequency 
> standard to get it right on the turnover point.
> 
> Since the improvement in frequency stability depends on minimizing the 
> temperature excursions it's good to have as much gain as possible in the 
> heater 
> feedback circuitry.  This was done for the HP E1938 10 MHz oscillator, see:
> http://www.prc68.com/I/HPE1938.shtml
> and the paper: The Theory Of Zero Gradient Crystal Ovens, R.K. Karlquist, 
> L.S. 
> Cutler, E.M. Ingman, J.L. Johnson, T. Parisek
> 
> Have Fun,
> 
> Brooke Clarke, N6GCE
> http://www.PRC68.com
> http://www.precisionclock.com
> http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Cam
> 
> 
> Tom Clifton wrote:
>> ); SAEximRunCond expanded to false
>> Errors-To: [EMAIL PROTECTED] RETRY
>>
>> While the website is not explicitly about frequency
>> measurement, there is an interesting bit on improving 
>> the stability of crystal oscillators with external
>> heater controllers.  While it may not be suitable for
>> long term high stability control it might be suitable
>> for many other purposes.
>>
>> http://www.qrss.thersgb.net/Crystal-Ovens.html
>>
>> The main page is also a good read:
>>
>> http://www.qrss.thersgb.net/Receiving-QRSS.html#Introduction

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Improving the stability of crystal oscillators

[Brooke Clarke]

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

Hi Tom:

That's a cleaver improvement to a non ovenized crystal.  Usually crystals are 
ground to have a temp vs freq turnover point occur at a specified temperature. 
  The common one is to be on frequency at room temperature.  So if a room 
temperature crystal is heated it's no longer operating at the turnover 
temperature and so there is a steep delta frequency vs. temperature slope.  Did 
  you get a crystal cut for your heater temperature or somehow match the 
heaters temperature to a turnover point on your crystal?

I spent many many hours adjusting the oven temperature of a Gibbs frequency 
standard to get it right on the turnover point.

Since the improvement in frequency stability depends on minimizing the 
temperature excursions it's good to have as much gain as possible in the heater 
feedback circuitry.  This was done for the HP E1938 10 MHz oscillator, see:
http://www.prc68.com/I/HPE1938.shtml
and the paper: The Theory Of Zero Gradient Crystal Ovens, R.K. Karlquist, L.S. 
Cutler, E.M. Ingman, J.L. Johnson, T. Parisek

Have Fun,

Brooke Clarke, N6GCE
http://www.PRC68.com
http://www.precisionclock.com
http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Cam


Tom Clifton wrote:
> ); SAEximRunCond expanded to false
> Errors-To: [EMAIL PROTECTED] RETRY
> 
> While the website is not explicitly about frequency
> measurement, there is an interesting bit on improving 
> the stability of crystal oscillators with external
> heater controllers.  While it may not be suitable for
> long term high stability control it might be suitable
> for many other purposes.
> 
> http://www.qrss.thersgb.net/Crystal-Ovens.html
> 
> The main page is also a good read:
> 
> http://www.qrss.thersgb.net/Receiving-QRSS.html#Introduction
> 
> 
> 
> 
> 
>
> 
> Need a vacation? Get great deals
> to amazing places on Yahoo! Travel.
> http://travel.yahoo.com/
> 
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
> 

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

[time-nuts] Improving the stability of crystal oscillators

[Tom Clifton]

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

While the website is not explicitly about frequency
measurement, there is an interesting bit on improving 
the stability of crystal oscillators with external
heater controllers.  While it may not be suitable for
long term high stability control it might be suitable
for many other purposes.

http://www.qrss.thersgb.net/Crystal-Ovens.html

The main page is also a good read:

http://www.qrss.thersgb.net/Receiving-QRSS.html#Introduction





   

Need a vacation? Get great deals
to amazing places on Yahoo! Travel.
http://travel.yahoo.com/

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.