Re: [time-nuts] High accuracy temp controller ckt

[Dr. David Kirkby]

On Fri, 12 Jul 2019 at 06:03, Perry Sandeen via time-nuts <
time-nuts@lists.febo.com> wrote:

> Yo Bubba Dudes!,
> This may not be too germain to the present discussion of temperature
> controllers but if anyone is interested I have a PDF copy of:
> A versatile thermoelectric temperature controller with10 mK reproducibility
> and 100 mK absolute accuracy
> by K. G. Libbrechta and A. W. LibbrechtDepartment of Physics, California
> Institute ofTechnology, Pasadena, California 91125, USA
>  Received 4 September 2009; accepted 23 November 2009; published online28
> December 2009
> If interested send me an email and I'll attach a copy
> Regards,
> Perrier


I  would appreciate a copy.

I  have recently assembled some reasonably low temperature coefficient (5
ppm/deg C) resistors in a reasonably well insulated box to try to make a
resistor that should be stable over short time periods to allow it to be
used as a transfer standard. But I am seriously considering having another
attempt at this, but putting the resistor in an oven.

Dave.
-- 
Dr. David Kirkby,
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Re: [time-nuts] High accuracy temp controller ckt

[Tom Van Baak]

Thanks Perry for that offer. I think the PDF is available several places 
on the web, including the author's own website:


https://www.its.caltech.edu/~atomic/publist/tempcontroller.pdf

In addition there's a "comment on" the paper here:

https://aip.scitation.org/doi/pdf/10.1063/1.3534845?class=pdf

Followed by a "Response to a comment on" paper here:

https://www.its.caltech.edu/~atomic/publist/response.pdf

I would suggest reading all three papers together.


The author has a lot of interesting (but non time-nut) papers:

http://www.its.caltech.edu/~atomic/publist/kglpub.htm
https://www.its.caltech.edu/~atomic/

/tvb

On 7/11/2019 8:59 PM, Perry Sandeen via time-nuts wrote:

Yo Bubba Dudes!,
This may not be too germain to the present discussion of temperature 
controllers but if anyone is interested I have a PDF copy of:
A versatile thermoelectric temperature controller with10 mK reproducibility
and 100 mK absolute accuracy
by K. G. Libbrechta and A. W. LibbrechtDepartment of Physics, California 
Institute ofTechnology, Pasadena, California 91125, USA
  Received 4 September 2009; accepted 23 November 2009; published online28 
December 2009
If interested send me an email and I'll attach a copy
Regards,
Perrier
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Re: [time-nuts] Thunderbolt E

[Steve65]

I'm not going to buy one, but . . . what does a new-from-Trimble 
Thunderbolt E cost?


Steve, K8JQ


On 7/11/2019 6:06 PM, Bob kb8tq wrote:

Hi

There is nothing on the spec sheet that leaps out as “obviously better” than the
T-Bolt’s that we all know and love. Indeed you *will* get support, a warranty, 
and
a unit that has 10 to 20 years less wear and tear.

Bob


On Jul 11, 2019, at 3:22 PM, Chris Burford  wrote:

I'm on the fence on purchasing a new Thunderbolt E from Trimble and wanted to 
hear from current or past owners.

I have a couple of the eBay x-telecom patchwork quilt GPSDO units which seem to 
do an OK job. Is there anything else besides a warranty and better performance 
specs that the Thunderbolt offers? My intention is to use the Thunderbolt as a 
backup reference to my PRS10.

Thanks.


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Re: [time-nuts] Thunderbolt E

[Bob kb8tq]

Hi

There is nothing on the spec sheet that leaps out as “obviously better” than 
the 
T-Bolt’s that we all know and love. Indeed you *will* get support, a warranty, 
and
a unit that has 10 to 20 years less wear and tear. 

Bob

> On Jul 11, 2019, at 3:22 PM, Chris Burford  wrote:
> 
> I'm on the fence on purchasing a new Thunderbolt E from Trimble and wanted to 
> hear from current or past owners.
> 
> I have a couple of the eBay x-telecom patchwork quilt GPSDO units which seem 
> to do an OK job. Is there anything else besides a warranty and better 
> performance specs that the Thunderbolt offers? My intention is to use the 
> Thunderbolt as a backup reference to my PRS10.
> 
> Thanks.
> 
> 
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Re: [time-nuts] Used Hydrogen Maser, and Mercury Stored-Ion Clocks

[Demetrios Matsakis via time-nuts]

For what it’s worth, the mercury ion clocks were shipped to the US Naval 
Observatory.  HP shortly thereafter did a market survey and concluded there was 
not enough profit in it.   They did allow Len and Robin to give short-answer 
support, and the project fell to me.   I found the clocks were not performing 
well due to sudden vacuum-contamination events.   Len, Robin, and I published 
our data in the proceedings of the 1995 Frequency Control Symposium.  At about 
the same time, JPL came up with a second generation design.   They kept 
improving it, and 20 years later this is now the Deep Space Atomic Clock, which 
was just launched.  See https://www.nasa.gov/mission_pages/tdm/clock/index.html 
  and 
https://en.wikipedia.org/wiki/Deep_Space_Atomic_Clock 


As for costs for an unit that is not space-qualified, I would guess you still 
need a lab with PhD’s and skilled technicians because I doubt much of the 
hardware is commercially available.

Demetrios Matsakis, as of this Saturday a USNO retiree, and as of August 1 a 
consultant for Masterclock.

> FWIW, about 20 years ago, Len Cutler and Robin Giffard of 5071A fame
> built several Hg ion clocks to be shipped to some govt customer I
> don't remember.  One of the clocks was dropped by the shipping company
> UPS or FedEX) and destroyed.  Only then did Len learn that HP was
> self insured, probably as part of a package deal to get a low
> corporate shipping rate.  HP products were packed extremely well, so
> the only real risk was the unit getting stolen.  I vaguely remember
> Len saying they were out $10K, which was probably just the cost of
> parts.  Nevertheless, it didn't seem like building an Hg clock was
> all that big of a project.  Way simpler than the 5071A.
> Now a days, the electronics would be considerably easier and cheaper. 
> The mechanical parts would all be CNC'ed by an online machine shop.
> 
> Rick N6RK
> 

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[time-nuts] Thunderbolt E

[Chris Burford]

I'm on the fence on purchasing a new Thunderbolt E from Trimble and 
wanted to hear from current or past owners.


I have a couple of the eBay x-telecom patchwork quilt GPSDO units which 
seem to do an OK job. Is there anything else besides a warranty and 
better performance specs that the Thunderbolt offers? My intention is to 
use the Thunderbolt as a backup reference to my PRS10.


Thanks.


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Re: [time-nuts] Sawtooth correction

[Art Sepin]

Hi,

We have a TM1 Eval Kit with User's Guide. It has not been powered on for about 
13 years. We'll check it out this week to see if it's operational.

Art

-Original Message-
From: time-nuts  On Behalf Of Jerry via 
time-nuts
Sent: Wednesday, July 10, 2019 9:03 PM
To: time-nuts@lists.febo.com
Cc: gsteinb...@aol.com
Subject: [time-nuts] Sawtooth correction

Recent postings on 'sawtooth' hardware correction; several years ago SigNav 
Australia (no longer is business) had a timing product called TM3-02 that 
claimed to "Eliminate sawtooth correction" via some technology they had 
developed.
 
     
https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fweb.archive.org%2Fweb%2F20091123094332%2Fhttp%3A%2F%2Fwww.signav.com.au%2Fdata=01%7C01%7Cart%40synergy-gps.com%7Cf0a6ce1359cb439c035a08d705be9fa6%7Cc81f9fdec0e04d8c95779afaa0cad9ed%7C1sdata=7C4hAeLzeJGdN1WAQ3WxdmyIZVtZka4svBC54IPSrnk%3Dreserved=0
 
     
https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fweb.archive.org%2Fweb%2F20091013133934%2Fhttp%3A%2F%2Fwww.signav.com.au%2Ffiles%2Fbrochures%2FBrochure%2520TM3-02%2520module.pdfdata=01%7C01%7Cart%40synergy-gps.com%7Cf0a6ce1359cb439c035a08d705be9fa6%7Cc81f9fdec0e04d8c95779afaa0cad9ed%7C1sdata=A5mE8BMY%2BEgY5d3S3AO8n3z%2BR0XJz%2FSlG2ZpP150eu8%3Dreserved=0
 
Any of our Australian contingent remenber this company? Did anyone on the list 
test one of these things?

 I belive Synergy was a US distributor - maybe Art can chime in with some 
details.

Jerry
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Re: [time-nuts] Advantages of GNSS ???

[Bob kb8tq]

Hi


> On Jul 11, 2019, at 9:37 AM, Leo Bodnar  wrote:
> 
>> Well part of it comes from designing, testing, and manufacturing a few 
>> thousand OCXO designs over the years. We likely built 10’s of millions of 
>> OCXO’s over the time I was doing / managing that. 
> It might be just my personal opinion but credential swinging is better left 
> out of technical discussion.
>>> - high-Q crystals require SC-cut 
>> ... An SC has a lower Q than an AT of similar size
>> and design up to the point acoustic Q losses completely take over. 
>> If you are talking about sub 20 MHz OCXO’s with “doable” crystal 
>> package sizes, the AT will have the higher Q by a significant margin. 
> 
> Could you please back up this claim with verifiable facts?

Order up a few 5 MHz 3rd overtones in HC-40 packages and see what you get.
You also could send in an RFQ for a batch of each to any of the people who make 
them
and see what comes back. 

Bob

> 
> Leo
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Re: [time-nuts] AN/URQ-10A standard docs

[paul swed]

The URQ 10 was a reference that drove a distribution system that then
provided the receivers and transmitters with a very stable reference. These
were used with the T827 and R1051 synthesized radios. If the radio was off
by 1 hz something was wrong. If the signal wasn't heard it wasn't there.
Not because the radio was off frequency. On the ship I was on we had 3 HF
2KW +transmitters and 20 R1051s. Circa 1973. A r1051 at the time was
$27,000.
These radios did have a oven reference that was ok nothing like the URQ10.
One of the maintenance procedures was to zero beat the internal to the
external reference every month.
Just in case the URQ 10s went missing.
Thats my bit of history.
Regards
Paul
WB8TSL

On Thu, Jul 11, 2019 at 8:00 AM Hal Murray  wrote:

>
> scmcgr...@gmail.com said:
> > The USS Iowa Radio room team was looking for URQ/10’s to restore the
> ships
> > radio systems a while back
>
> What was it used for?
>
> I'm guessing for tweaking the frequency of radios as their crystals
> drift.
> How many radios does a WW II battleship have?  How many after various
> upgrades?  (The URQ/10 manual said 1966.)
>
> Does it matter if a radar set drifts off frequency?  I'm assuming that the
> transmit and receive side would be locked together.
>
> --
> These are my opinions.  I hate spam.
>
>
>
>
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Re: [time-nuts] Advantages of GNSS ???

[Leo Bodnar]

> Well part of it comes from designing, testing, and manufacturing a few 
> thousand OCXO designs over the years. We likely built 10’s of millions of 
> OCXO’s over the time I was doing / managing that. 
It might be just my personal opinion but credential swinging is better left out 
of technical discussion.
> > - high-Q crystals require SC-cut 
> ... An SC has a lower Q than an AT of similar size
> and design up to the point acoustic Q losses completely take over. 
> If you are talking about sub 20 MHz OCXO’s with “doable” crystal 
> package sizes, the AT will have the higher Q by a significant margin. 

Could you please back up this claim with verifiable facts?

Leo
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Re: [time-nuts] Advantages of GNSS ???

[Bob kb8tq]

Hi 

Well part of it comes from designing, testing, and manufacturing a few 
thousand OCXO designs over the years. We likely built 10’s of millions of 
OCXO’s over the time I was doing / managing that. 

> On Jul 11, 2019, at 3:56 AM, Leo Bodnar  wrote:
> 
> Hello, /
> 
> Why would you not want high drive level for best close-in noise?  This is at 
> odds with general thinking in the industry.
> Close-in in this context means from 0.1Hz to 1/f knee which is 1-100kHz 
> depending on the design of the sustaining amplifier.
> 
> There are few reasons why low phase noise "practical" oscillators are built 
> as OCXOs:
> 
> On one hand:
> - close-in noise depends on 1/f knee frequency  

That is a quick approximation. There always will be a bit more to it. 

> - lowering knee frequency requires high-Q resonators

That does help, but it’s far from the whole story

> - for classic 1MHz..100MHz range this means crystals

There are other exotic things you could do. Cost wise they get a bit crazy. 
There are materials other than quartz that give you higher Q. In some
cases *much* higher Q without a massive cost penalty. 

> - high-Q crystals require SC-cut 

Actually not so much. An SC has a lower Q than an AT of similar size
and design up to the point acoustic Q losses completely take over. 
If you are talking about sub 20 MHz OCXO’s with “doable” crystal 
package sizes, the AT will have the higher Q by a significant margin. 

> 
> On the other hand:
> - phase noise density is measured as a ratio referred to carrier level

True, that’s how it’s defined

> - increasing carrier level improves phase noise figure

Which is often how you get good phase noise far removed, since your circuit
does not have issues as you increase the drive level. (if properly designed) 

> - increasing carrier level necessitates increasing drive level

To the degree that “carrier level” in this case is defined to be exactly the 
same as drive level. 

> - maintaining reasonable ageing rate at higher drive levels requires SC-cut 
> crystals

Not so much. Indeed there are a number of cuts that do well. The SC’s claim to 
fame is 
immunity to acceleration / stress effects in a single plane. (SC = Stress 
Compensated ).
 
A side effect of the design is a shallow turn point at higher temperatures. 
There are other 
cuts that share this characteristic. Things like the FC do get used in OCXO’s. 

> 
> Having established that SC-cut is preferred:
> - SC-cut has high temperature turning point.  Its room temperature tempco is 
> much worse than AT-cut's one making it mostly unusable as XO or TCXO

Depends on the XO, They get built into down hole gear as an XO. There are other 
“un heated”
SC based applications. 

> - High temperature turning point requires oven

Depending on the application and temperature spec. There *are* indeed low phase 
noise / SC based
room temperature oscillators sold for some “interesting” applications. There’s 
a list member who has
posted about their experience doing so. 



The bigger problem is that your approximation that drive always improves phase 
noise falls
apart as you get closer to carrier. There are a lot of things that drive this. 
If they didn’t, the design 
task would simply be to have a low noise follower amp. There have been designs 
published in a 
lot of places for amps that are 50 db better than the noise of any OCXO at 1 Hz 
offset. 

Bob

> 
> Leo
> 
>>> From: Bob kb8tq 
>> It depends a lot on the offset you are looking at. For close in phase noise, 
>> you probably don’t 
>> want high drive. If you are only after phase noise past 10KHz, you may not 
>> want / need
>> an OCXO in the first place. Selecting crystals (like one in a hundred) for 
>> very high drive /
>> low phase noise setups *is* done. It’s just not very practical. 
>> 
>>> On Jul 10, 2019, at 3:49 AM, Leo Bodnar  wrote:
>>> It depends whether OCXO is designed for long term stability and low ageing 
>>> or low phase noise.
>>> Low ageing requires low drive but low phase noise needs as much drive as 
>>> humanely possible - often approaching mW levels.
> 
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Re: [time-nuts] Sawtooth correction

[Azelio Boriani]

>From the block diagram of the TM3-02 I can say that it is like the
TBolt, it has the disciplined oscillator in the receive chain so no
need to correct for the sawtooth.

On Thu, Jul 11, 2019 at 7:14 AM Jerry via time-nuts
 wrote:
>
> Recent postings on 'sawtooth' hardware correction; several years ago SigNav 
> Australia (no longer is business) had a timing product called TM3-02 that 
> claimed to "Eliminate sawtooth correction" via some technology they had 
> developed.
>
>  https://web.archive.org/web/20091123094332/http://www.signav.com.au/
>
>  
> https://web.archive.org/web/20091013133934/http://www.signav.com.au/files/brochures/Brochure%20TM3-02%20module.pdf
>
> Any of our Australian contingent remenber this company? Did anyone on the 
> list test one of these things?
>
>  I belive Synergy was a US distributor - maybe Art can chime in with some 
> details.
>
> Jerry
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Re: [time-nuts] verifying synchronization with PPS

[Gabs Ricalde]

On Wed, Jul 10, 2019 at 8:00 PM folkert  wrote:
>
> > Folkert van Heusden has a driver for NTP which includes PPS output:
> >  https://vanheusden.com/time/rpi_gpio_ntp/
> > Perhaps this might help?
>
> Indeed I did! :-)
>
> But please note that the jitter is high, iirc around 18ms.
> Personally I would use https://github.com/mlichvar/pps-gpio-poll.git and
> then patch it toggle an other gpio-pin.
>

I did something similar using an early version of that PPS driver:
https://lists.febo.com/pipermail/time-nuts_lists.febo.com/2018-April/092234.html

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Re: [time-nuts] Advantages of GNSS ???

[Leo Bodnar]

Hello,

Why would you not want high drive level for best close-in noise?  This is at 
odds with general thinking in the industry.
Close-in in this context means from 0.1Hz to 1/f knee which is 1-100kHz 
depending on the design of the sustaining amplifier.

There are few reasons why low phase noise "practical" oscillators are built as 
OCXOs:

On one hand:
- close-in noise depends on 1/f knee frequency  
- lowering knee frequency requires high-Q resonators
- for classic 1MHz..100MHz range this means crystals
- high-Q crystals require SC-cut 

On the other hand:
- phase noise density is measured as a ratio referred to carrier level
- increasing carrier level improves phase noise figure
- increasing carrier level necessitates increasing drive level
- maintaining reasonable ageing rate at higher drive levels requires SC-cut 
crystals

Having established that SC-cut is preferred:
- SC-cut has high temperature turning point.  Its room temperature tempco is 
much worse than AT-cut's one making it mostly unusable as XO or TCXO
- High temperature turning point requires oven

Leo

>> From: Bob kb8tq 
> It depends a lot on the offset you are looking at. For close in phase noise, 
> you probably don’t 
> want high drive. If you are only after phase noise past 10KHz, you may not 
> want / need
> an OCXO in the first place. Selecting crystals (like one in a hundred) for 
> very high drive /
> low phase noise setups *is* done. It’s just not very practical. 
> 
> > On Jul 10, 2019, at 3:49 AM, Leo Bodnar  wrote:
> > It depends whether OCXO is designed for long term stability and low ageing 
> > or low phase noise.
> > Low ageing requires low drive but low phase noise needs as much drive as 
> > humanely possible - often approaching mW levels.

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